rfc9665.original.xml   rfc9665.xml 
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<front> <front>
<title abbrev='Service Registration Protocol'>Service Registration Protocol <title abbrev="Service Registration Protocol">Service Registration Protocol
for DNS-Based Service Discovery</title> for DNS-Based Service Discovery</title>
<author initials="T" surname="Lemon" fullname="Ted Lemon"> <seriesInfo name="RFC" value="9665"/>
<author initials="T." surname="Lemon" fullname="Ted Lemon">
<organization>Apple Inc.</organization> <organization>Apple Inc.</organization>
<address> <address>
<postal> <postal>
<street>One Apple Park Way</street> <street>One Apple Park Way</street>
<city>Cupertino</city> <city>Cupertino</city>
<region>California</region> <region>CA</region>
<code>95014</code> <code>95014</code>
<country>USA</country> <country>United States of America</country>
</postal> </postal>
<email>mellon@fugue.com</email> <email>mellon@fugue.com</email>
</address> </address>
</author> </author>
<author initials='S' surname='Cheshire' fullname='Stuart Cheshire'> <author initials="S." surname="Cheshire" fullname="Stuart Cheshire">
<organization>Apple Inc.</organization> <organization>Apple Inc.</organization>
<address> <address>
<postal> <postal>
<street>One Apple Park Way</street> <street>One Apple Park Way</street>
<city>Cupertino</city> <city>Cupertino</city>
<region>California</region> <region>CA</region>
<code>95014</code> <code>95014</code>
<country>USA</country> <country>United States of America</country>
</postal> </postal>
<phone>+1 408 974 3207</phone> <phone>+1 408 974 3207</phone>
<email>cheshire@apple.com</email> <email>cheshire@apple.com</email>
</address> </address>
</author> </author>
<date>March 4, 2024</date> <date month="October" year="2024"/>
<area>Internet</area> <area>INT</area>
<workgroup>Internet Engineering Task Force</workgroup> <workgroup>dnssd</workgroup>
<keyword>Multicast DNS</keyword> <keyword>Multicast DNS</keyword>
<keyword>DNS-Based Service Discovery</keyword> <keyword>DNS-Based Service Discovery</keyword>
<keyword>DNS Update</keyword> <keyword>DNS Update</keyword>
<keyword>SIG(0)</keyword> <keyword>SIG(0)</keyword>
<abstract>
<t>
The Service Registration Protocol for DNS-Based Service Discovery uses t
he standard DNS Update mechanism to enable DNS-Based
Service Discovery using only unicast packets. This makes it possible to
deploy DNS Service Discovery without multicast,
which greatly improves scalability and improves performance on networks
where multicast service is not an optimal choice,
particularly IEEE 802.11 (Wi&nbhy;Fi) and IEEE 802.15.4 networks. DNS&n
bhy;SD Service registration
uses public keys and SIG(0) to allow services to defend their registrati
ons.
<abstract>
<t>The Service Registration Protocol (SRP) for DNS-based Service Discovery
(DNS-SD)
uses the standard DNS Update mechanism to enable DNS-SD using only unica
st packets. This makes it possible to
deploy DNS-SD without multicast, which greatly improves
scalability and improves performance on networks where multicast
service is not an optimal choice, particularly IEEE 802.11
(Wi-Fi) and IEEE 802.15.4 networks. DNS-SD Service
registration uses public keys and SIG(0) to allow services to defend
their registrations.
</t> </t>
</abstract> </abstract>
<note removeInRFC="true">
<name>About This Document</name>
<t>
The latest revision of this draft can be found at <eref target="https://
dnssd-wg.github.io/draft-ietf-dnssd-srp/draft-ietf-dnssd-srp.html"/>.
Status information for this document may be found at <eref target="https
://datatracker.ietf.org/doc/draft-ietf-dnssd-srp/"/>.
</t>
<t>
Discussion of this document takes place on the
DNS-SD Working Group mailing list (<eref target="mailto:dnssd@ietf.org"/
>),
which is archived at <eref target="https://mailarchive.ietf.org/arch/bro
wse/dnssd/"/>.
Subscribe at <eref target="https://www.ietf.org/mailman/listinfo/dnssd/"
/>.
</t>
<t>Source for this draft and an issue tracker can be found at
<eref target="https://github.com/dnssd-wg/draft-ietf-dnssd-srp"/>.</t>
</note>
</front> </front>
<middle> <middle>
<section> <section>
<name>Introduction</name> <name>Introduction</name>
<t> <t>
DNS-SD (see <xref target="RFC6763"></xref>) is a component of Zero Confi
<xref target="RFC6763">DNS-Based Service Discovery</xref> is a component guration Networking
of Zero Configuration Networking (see <xref target="RFC6760"/>, <xref target="ZC"/>, and <xref target="I-
<xref target="RFC6760"/> <xref target="ZC"/> <xref target="I-D.cheshire- D.cheshire-dnssd-roadmap"/>).</t>
dnssd-roadmap"/>.</t>
<t> <t>
This document describes an enhancement to <xref target="RFC6763">DNS-Bas This document describes an enhancement to DNS-SD that
ed Service Discovery</xref> (DNS&nbhy;SD) that allows servers to register the services they offer using the DNS protocol
allows servers to register the services they offer using the DNS protocol rather than using Multicast DNS (mDNS) (see <xref target="RFC6762"></xref>). T
rather than using <xref target="RFC6762">Multicast here is already a large installed base of DNS&nbhy;SD clients that can discover
DNS</xref> (mDNS). There is already a large installed base of DNS&nbhy;S services using the DNS
D clients that can discover services using the DNS protocol (e.g., Android, Windows, Linux, Apple).</t>
protocol (e.g. Android, Windows, Linux, Apple).</t>
<t> <t>
This document is intended for three audiences: implementors of software that provides services that should be advertised This document is intended for three audiences: implementors of software that provides services that should be advertised
using DNS&nbhy;SD, implementors of DNS servers that will be used in cont exts where DNS&nbhy;SD registration is needed, and using DNS&nbhy;SD, implementors of DNS servers that will be used in cont exts where DNS&nbhy;SD registration is needed, and
administrators of networks where DNS&nbhy;SD service is required. The d ocument is expected to provide sufficient administrators of networks where DNS&nbhy;SD is required. The document is expected to provide sufficient
information to allow interoperable implementation of the registration pr otocol.</t> information to allow interoperable implementation of the registration pr otocol.</t>
<t> <t>
DNS-Based Service Discovery (DNS&nbhy;SD) allows services to advertise t
he fact that they provide service, and to provide <!--[rfced] Should "services" be "servers" here to match previous,
similar text? And perhaps avoiding the two "provide" uses so
close together would be helpful for the reader?
Original:
DNS-Based Service Discovery (DNS-SD) allows services to advertise
the fact that they provide service, and to provide the
information required to access that service.
Perhaps:
DNS-SD allows servers to advertise the fact that they provide
service and to share the information required to access that
service.
-->
DNS&nbhy;SD allows services to advertise the fact that they provide serv
ice and to provide
the information required to access that service. DNS&nbhy;SD clients ca n then discover the set of services of a particular the information required to access that service. DNS&nbhy;SD clients ca n then discover the set of services of a particular
type that are available. They can then select a service from among thos e that are available and obtain the information type that are available. They can then select a service from among thos e that are available and obtain the information
required to use it. Although DNS Service Discovery (DNS-SD) using the D required to use it. Although DNS-SD using the DNS protocol (as opposed
NS protocol (as opposed to mDNS) can be more efficient and versatile, it is to mDNS) can be more efficient and versatile, it is
not common in practice, because of the difficulties associated with upda not common in practice because of the difficulties associated with updat
ting authoritative DNS services with service ing authoritative DNS services with service
information.</t> information.</t>
<t> <t>
Existing practice for updating DNS zones is to either manually enter new The existing practice for updating DNS zones is either to manually enter
data, or else use DNS Update new data or to use a DNS Update
<xref target="RFC2136"/>. Unfortunately DNS Update requires either that t (see <xref target="RFC2136"/>). Unfortunately, a DNS Update requires eithe
he authoritative DNS server automatically trust r:</t>
updates, or else that the DNS Update requestor have some kind of shared s <ul>
ecret or public key that is known to the DNS server <li>that the authoritative DNS server automatically trust
and can be used to authenticate the update. Furthermore, DNS Update can updates or</li>
be a fairly chatty process, requiring multiple <li>that the DNS Update requestor have some kind of shared secret or publ
round trips with different conditional predicates to complete the update ic key that is known to the DNS server
process.</t> and can be used to authenticate the update.</li></ul>
<t>Furthermore, the DNS Update can be a fairly chatty process, requiring
multiple
roundtrips with different conditional predicates to complete the update p
rocess.</t>
<t> <t>
The Service Registration Protocol (SRP) adds a set of default heuristics The Service Registration Protocol (SRP) adds a set of default heuristics
for processing DNS updates that eliminates the need for DNS update for processing DNS updates that eliminates the need for DNS-update-conditional p
conditional predicates: instead, the SRP registrar (a DNS server that sup redicates. Instead, the SRP registrar (a DNS server that supports SRP updates) h
ports SRP updates) has a set of default predicates as a set of default predicates
that are applied to the update, and the update either succeeds entirely, that are applied to the update; and the update either succeeds entirely o
or fails in a way that allows the requestor to know r fails in a way that allows the requestor to know
what went wrong and construct a new update.</t> what went wrong and construct a new update.</t>
<t> <t>
SRP also adds a feature called First-Come, First-Served (FCFS) Naming, wh SRP also adds a feature called "First Come, First Served Naming" (or "FCF
ich allows the requestor to claim a name that is S Naming"), which allows the requestor to:</t>
not yet in use, and, using SIG(0) <xref target="RFC2931"/>, to authentica <ul><li>claim a name that is
te both the initial claim and subsequent not yet in use, and</li>
updates. This prevents name conflicts, since a second SRP requestor attem <li>using SIG(0) (<xref target="RFC2931"/>), authenticate both the initia
pting to claim the same name will not possess the l claim and subsequent
SIG(0) key used by the first requestor to claim it, and so its claim will updates.</li></ul>
be rejected and the second requestor will have to <t>This prevents name conflicts, since a second SRP requestor attempting
to claim the same name will not possess the
SIG(0) key used by the first requestor to claim it: so its claim will be
rejected, and the second requestor will have to
choose a new name.</t> choose a new name.</t>
<t> <t>
It is important to understand that "authenticate" here just means that we can tell that an update came from the same source It is important to understand that "authenticate" here just means that we can tell that an update came from the same source
as the original registration. We have not established trust. This has imp ortant implications for what we can and can't do as the original registration. We have not established trust. This has imp ortant implications for what we can and can't do
with data the client sends us. You will notice as you read this document that we only support adding a very restricted set with data the client sends us. You will notice as you read this document that we only support adding a very restricted set
of records, and the content of those records is further constrained.</t> of records, and the content of those records is further constrained.</t>
<t> <t>
The reason for this is precisely that we have not established trust. So w The reason for this is precisely that we have not established trust. So,
e can only publish information that we feel safe in we can only publish information that we feel safe in
publishing even though we do not have any basis for trusting the requesto publishing even though we do not have any basis for trusting the requesto
r. We reason that mDNS <xref target="RFC6762"/> r. We reason that mDNS (<xref target="RFC6762"/>)
allows arbitrary hosts on a single IP link to advertise services <xref ta allows arbitrary hosts on a single IP link to advertise services (<xref t
rget="RFC6763"/>, relying on whatever service is arget="RFC6763"/>), relying on whatever service is
advertised to provide authentication as a part of its protocol rather tha n in the service advertisement.</t> advertised to provide authentication as a part of its protocol rather tha n in the service advertisement.</t>
<t> <t>
This is considered reasonably safe because it requires physical presence on the network in order to advertise. An off-network This is considered reasonably safe because it requires physical presence on the network in order to advertise. An off-network
mDNS attack is simply not possible. Our goal with this specification is t o impose similar constraints. Because of this you will mDNS attack is simply not possible. Our goal with this specification is t o impose similar constraints. Therefore, you will
see in <xref target="add_validation"/> that a very restricted set of reco rds with a very restricted set of relationships are see in <xref target="add_validation"/> that a very restricted set of reco rds with a very restricted set of relationships are
allowed. You will also see in <xref target="source_validation"/> that we give advice on how to prevent off-network attacks.</t> allowed. You will also see in <xref target="source_validation"/> that we give advice on how to prevent off-network attacks.</t>
<t> <t>
This leads us to the disappointing observation that this protocol is not a mechanism for adding arbitrary information to This leads us to the disappointing observation that this protocol is not a mechanism for adding arbitrary information to
DNS zones. We have not evaluated the security properties of adding, for e xample, an SOA record, an MX record, or a CNAME DNS zones. We have not evaluated the security properties of adding, for e xample, an SOA record, an MX record, or a CNAME
record, and so these are forbidden. A future protocol specification might include analyses for other records, and extend record; therefore, these are forbidden. A future protocol specification m ight include analyses for other records and extend
the set of records that can be registered here. Or it might require estab lishment of trust, and add an authorization model the set of records that can be registered here. Or it might require estab lishment of trust, and add an authorization model
to the authentication model we now have. But this is work for a future do cument.</t> to the authentication model we now have. But this is work for a future do cument.</t>
<t> <t>
Finally, SRP adds the concept of a 'lease,' similar to leases in Dynamic Finally, SRP adds the concept of a "lease", similar to leases in DHCP
Host Configuration Protocol (<xref target="RFC8415"/>). The SRP registration itself has a lease that
<xref target="RFC8415"/>. The SRP registration itself has a lease which may be on the order of an hour; if the requestor
may be on the order of an hour; if the requestor
does not renew the lease before it has elapsed, the registration is remov ed. The claim on the name can have a longer does not renew the lease before it has elapsed, the registration is remov ed. The claim on the name can have a longer
lease, so that another requestor cannot claim the name, even though the r egistration has expired.</t> lease so that another requestor cannot claim the name, even though the re gistration has expired.</t>
<t> <t>
The Service Registration Protocol for DNS&nbhy;SD (SRP), specified in th The SRP for DNS-SD specified in this document provides a reasonably secu
is document, provides a reasonably secure mechanism re mechanism
for publishing this information. Once published, these services can be for publishing this information. Once published, these services can be
readily discovered by DNS&nbhy;SD clients using readily discovered by DNS-SD clients using
standard DNS lookups.</t> standard DNS lookups.</t>
<t> <t>
The DNS&nbhy;SD specification (<xref target="RFC6763" section="10" secti The DNS-SD specification (see <xref target="RFC6763" section="10" sectio
onFormat="comma"/>, “Populating the DNS with nFormat="of"/> briefly discusses ways that servers can publish their information
Information”), briefly discusses ways that servers can publish their inf in the DNS namespace. In the case of
ormation in the DNS namespace. In the case of
mDNS, it allows servers to publish their information on the local link, using names in the ".local" namespace, which makes mDNS, it allows servers to publish their information on the local link, using names in the ".local" namespace, which makes
their services directly discoverable by peers attached to that same loca l link.</t> their services directly discoverable by peers attached to that same loca l link.</t>
<t> <t>
RFC6763 also allows clients to discover services using <xref target="RFC RFC 6763 also allows clients to discover services using the DNS protocol
1035">the DNS protocol</xref>. This can be done by (see <xref target="RFC1035"></xref>). This can be done by
having a system administrator manually configure service information in having a system administrator manually configure service information in
the DNS, but manually populating DNS authoritative the DNS; however, manually populating DNS authoritative
server databases is costly and potentially error-prone, and requires a k server databases is costly and potentially error-prone and requires a kn
nowledgeable network administrator. Consequently, owledgeable network administrator. Consequently,
although all DNS&nbhy;SD client implementations of which we are aware su although all DNS-SD client implementations of which we are aware support
pport DNS&nbhy;SD using DNS queries, in practice it DNS-SD using DNS queries, in practice, it
is used much less frequently than mDNS.</t> is used much less frequently than mDNS.</t>
<t> <t>
The <xref target="RFC8766">Discovery Proxy</xref> provides one way to au The Discovery Proxy (see <xref target="RFC8766"></xref>) provides one wa
tomatically populate the DNS y to automatically populate the DNS
namespace, but is only appropriate on networks where services are easily namespace but is only appropriate on networks where services are easily
advertised using mDNS. This document describes a advertised using mDNS. The present document describes a
solution more suitable for networks where multicast is inefficient, or w solution more suitable for networks where multicast is inefficient or wh
here sleepy devices are common, by supporting both ere sleepy devices are common by supporting both the
offering of services, and discovery of services, using unicast.</t> offering of services and the discovery of services using unicast.</t>
</section> </section>
<section> <section>
<name>Conventions and Terminology Used in This Document</name> <name>Conventions and Terminology Used in This Document</name>
<t> <t>
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOU The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQU
LD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", IRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
"MAY", and "OPTIONAL" in this document are to be interpreted as described NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>
in BCP 14 <xref target="RFC2119"/> RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
<xref target="RFC8174"/> when, and only when, they appear in all capital "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to
s, as shown here. be interpreted as
</t> described in BCP&nbsp;14 <xref target="RFC2119"/> <xref target="RFC8174"/>
when, and only when, they appear in all capitals, as shown here.
</t>
</section> </section>
<section> <section>
<name>Service Registration Protocol</name> <name>Service Registration Protocol</name>
<t> <t>
Services that implement SRP use DNS Update <xref target="RFC2136"/> <xre Services that implement SRP use DNS Update (see <xref target="RFC2136"/>
f target="RFC3007"/> to publish service information and <xref target="RFC3007"/>) to publish service information
in the DNS. Two variants exist, one for full-featured hosts, and one fo in the DNS. Two variants exist: one for full-featured hosts and one for
r devices designed for "Constrained-Node Networks" devices designed for Constrained-Node Networks (CNNs)
<xref target="RFC7228"/>. An SRP registrar is most likely an authoritati (<xref target="RFC7228"/>). An SRP registrar is most likely an authorita
ve DNS server, or else is updating an authoritative tive DNS server or is updating an authoritative
DNS server. There is no requirement that the server that is receiving SRP updates be the same server that is answering DNS server. There is no requirement that the server that is receiving SRP updates be the same server that is answering
queries that return records that have been registered.</t> queries that return records that have been registered.</t>
<section> <section>
<name>Protocol Variants</name> <name>Protocol Variants</name>
<section> <section>
<name>Full-featured Hosts</name> <name>Full-Featured Hosts</name>
<t> <t>
Full-featured hosts either are configured manually with a registrati on domain, or discover the default registration Full-featured hosts either are configured manually with a registrati on domain or discover the default registration
domain as described in <xref target="RFC6763" section="11" sectionFor mat="of"/>. If this process does not produce a domain as described in <xref target="RFC6763" section="11" sectionFor mat="of"/>. If this process does not produce a
default registration domain, the Service Registration protocol is not default registration domain, the SRP is not discoverable on the local
discoverable on the local network using this network using this
mechanism. Other discovery mechanisms are possible, but are out of sc mechanism. Other discovery mechanisms are possible, but they are out
ope for this document.</t> of scope for this document.</t>
<t> <t>
Manual configuration of the registration domain can be done either b Manual configuration of the registration domain can be done either:<
y querying the list of available registration /t>
domains ("r._dns&nbhy;sd._udp") and allowing the user to select one <ul><li>by querying the list of available registration
from the UI, or by any other means appropriate to domains ("r._dns&nbhy;sd._udp") and allowing the user to select one
the particular use case being addressed. Full-featured devices cons from the UI or</li>
truct the names of the SRV, TXT, and PTR records <li>by any other means appropriate to
describing their service(s) as subdomains of the chosen service regi the particular use case being addressed.</li></ul>
stration domain. For these names they then discover <t>Full-featured devices construct the names of the SRV, TXT, and PTR
the zone apex of the closest enclosing DNS zone using SOA queries <x records
ref target="RFC8765" section="6.1"/>. Having describing their service or services as subdomains of the chosen ser
vice registration domain. For these names, they then discover
the zone apex of the closest enclosing DNS zone using SOA queries (s
ee <xref target="RFC8765" section="6.1"/>). Having
discovered the enclosing DNS zone, they query for the "_dnssd&nbhy;s rp._tcp.&lt;zone&gt;" SRV record to discover the discovered the enclosing DNS zone, they query for the "_dnssd&nbhy;s rp._tcp.&lt;zone&gt;" SRV record to discover the
server to which they can send SRP updates. Hosts that support SRP U pdates using TLS use the server to which they can send SRP updates. Hosts that support SRP U pdates using TLS use the
"_dnssd&nbhy;srp&nbhy;tls._tcp.&lt;zone&gt;" SRV record instead.</t> "_dnssd&nbhy;srp&nbhy;tls._tcp.&lt;zone&gt;" SRV record instead.</t>
<t> <t>
Examples of full-featured hosts include devices such as home computer s, laptops, powered peripherals with network Examples of full-featured hosts include devices such as home computer s, laptops, powered peripherals with network
connections such as printers, home routers, and even battery-operated connections (such as printers, home routers, and even battery-operate
devices such as mobile phones that have d devices such as mobile phones that have
long battery lives. long battery lives).
</t> </t>
</section> </section>
<section> <section>
<name>Constrained Hosts</name> <name>Constrained Hosts</name>
<t> <t>
For devices designed for Constrained-Node Networks <xref target="RFC 7228"/> some simplifications are available. Instead of For devices designed for CNNs (<xref target="RFC7228"/>), some simpl ifications are available. Instead of
being configured with (or discovering) the service registration doma in, the special-use domain name (see being configured with (or discovering) the service registration doma in, the special-use domain name (see
<xref target="RFC6761"/>) "default.service.arpa" is used. The detai <xref target="RFC6761"/>) "default.service.arpa" is used. The detai
ls of how SRP registrar(s) are discovered will be specific ls of how SRP registrars are discovered will be specific
to the constrained network, and therefore we do not suggest a specif to the constrained network; therefore, we do not suggest a specific
ic mechanism here.</t> mechanism here.</t>
<t> <t>
SRP requestors on constrained networks are expected to receive from SRP requestors on constrained networks are expected to receive, from
the network a list of SRP registrars with which to register. the network, a list of SRP registrars with which to register.
It is the responsibility of a Constrained-Node Network supporting SR It is the responsibility of a CNN supporting SRP to provide one or m
P to provide one or more registrar addresses. It is ore registrar addresses. It is
the responsibility of the registrar supporting a Constrained-Node Ne the responsibility of the registrar supporting a CNN to handle the u
twork to handle the updates appropriately. In some pdates appropriately. In some
network environments, updates may be accepted directly into a local "default.service.arpa" zone, which has only local network environments, updates may be accepted directly into a local "default.service.arpa" zone, which has only local
visibility. In other network environments, updates for names ending in "default.service.arpa" may be rewritten by the registrar visibility. In other network environments, updates for names ending in "default.service.arpa" may be rewritten by the registrar
to names with broader visibility.</t> to names with broader visibility.</t>
</section> </section>
<section> <section>
<name>Why two variants?</name> <name>Why two variants?</name>
<t> <t>
The reason for these different variants is that low-power devices th at typically use Constrained-Node Networks may have The reason for these different variants is that low-power devices th at typically use CNNs may have
very limited battery storage. The series of DNS lookups required to discover an SRP registrar and then communicate with very limited battery storage. The series of DNS lookups required to discover an SRP registrar and then communicate with
it will increase the energy required to advertise a service; for low -power devices, the additional flexibility this it will increase the energy required to advertise a service; for low -power devices, the additional flexibility this
provides does not justify the additional use of energy. It is also fairly typical of such networks that some network provides does not justify the additional use of energy. It is also fairly typical of such networks that some network
service information is obtained as part of the process of joining th e network, and so this can be relied upon to provide service information is obtained as part of the process of joining th e network; thus, this can be relied upon to provide
nodes with the information they need.</t> nodes with the information they need.</t>
<t> <t>
Networks that are not constrained networks can have more complicated topologies at the IP layer. Nodes connected Networks that are not constrained can have more complicated topologi es at the IP layer. Nodes connected
to such networks can be assumed to be able to do DNS-SD service regi stration domain discovery. Such networks are to such networks can be assumed to be able to do DNS-SD service regi stration domain discovery. Such networks are
generally able to provide registration domain discovery and routing. This creates the possibility of off-network generally able to provide registration domain discovery and routing. This creates the possibility of off-network
spoofing, where a device from a foreign network registers a service o n the local network in order to attack devices spoofing, where a device from a foreign network registers a service o n the local network in order to attack devices
on the local network. To prevent such spoofing, TCP is required for s uch networks. on the local network. To prevent such spoofing, TCP is required for s uch networks.
</t> </t>
</section> </section>
</section> </section>
<section> <section>
<name>Protocol Details</name> <name>Protocol Details</name>
<t> <t>
We will discuss several parts to this process: how to know what to pub We will discuss several parts to this process:</t>
lish, how to know where to publish it (under what
name), how to publish it, and how to secure its publication. In <xref
target="maintenance"/>, we specify how to maintain
the information once published.</t>
<section> <ul>
<name>What to publish</name> <li>how to know what to publish (see <xref target="what"/>),</li>
<li>how to know where to publish it (under what name) (see <xref target="where
"/>),</li>
<li>how to publish it (see <xref target="how"/>),</li>
<li>how to secure its publication (see <xref target="how-to-secure"/>), and</li>
<li>how to maintain
the information once published (see <xref target="maintenance"/>).</li
></ul>
<section anchor="what">
<name>What to Publish</name>
<t> <t>
SRP Updates are sent by SRP requestors to SRP registrars. Three typ es of instructions appear in an SRP update: Service SRP Updates are sent by SRP requestors to SRP registrars. Three typ es of instructions appear in an SRP update: Service
Discovery instructions, Service Description instructions, and Host De scription instructions. These instructions are made Discovery instructions, Service Description instructions, and Host De scription instructions. These instructions are made
up of DNS Update RRs that are either adds or deletes. The types of re cords that are added, updated and removed in each up of DNS Update Resource Records (RRs) that are either adds or delet es. The types of records that are added, updated, and removed in each
of these instructions, as well as the constraints that apply to them, are described in <xref target="server_behavior"/>. of these instructions, as well as the constraints that apply to them, are described in <xref target="server_behavior"/>.
An SRP Update is a DNS Update message that is constructed so as to me et the constraints described in that section. The An SRP Update is a DNS Update message that is constructed so as to me et the constraints described in that section. The
following is a brief overview of what is included in a typical SRP Up date: following is a brief overview of what is included in a typical SRP Up date:
</t> </t>
<ul spacing="compact"> <ul spacing="normal">
<li> <li>
PTR Resource Record (RR) for services, which map from a generic se PTR RR for services, which map from a generic service type (or sub
rvice type (or subtype) name to a specific type) name to a specific
Service Instance Name.</li> Service Instance Name (<xref target="RFC6763" section="4.1" sectio
nFormat="of"/>).</li>
<li> <li>
For any Service Instance Name (<xref target="RFC6763" section="4.1" For any Service Instance Name, an SRV RR, one or more
sectionFormat="comma"/>), an SRV RR, one or more TXT RRs, and a KEY RR. Although, in principle, DNS-SD Service Descr
TXT RRs, and a KEY RR. Although in principle DNS-SD Service Descrip iption records can include other record types with
tion records can include other record types with the same Service Instance Name, in practice, they rarely do. SRP do
the same Service Instance Name, in practice they rarely do. SRP doe es not permit other record types. The KEY RR is used
s not permit other record types. The KEY RR is used to support FCFS naming and has no specific meaning for DNS-SD looku
to support FCFS naming, and has no specific meaning for DNS-SD look ps. SRV records for all services described in an
ups. SRV records for all services described in an
SRP update point to the same hostname.</li> SRP update point to the same hostname.</li>
<li> <li>
There is never more than one hostname in a single SRP update. The h ostname has one or more address RRs (AAAA or A) and There is never more than one hostname in a single SRP update. The h ostname has one or more address RRs (AAAA or A) and
a KEY RR (used for FCFS naming). Depending on the use case, an SRP requestor may be required to suppress some a KEY RR (used for FCFS naming). Depending on the use case, an SRP requestor may be required to suppress some
addresses that would not be usable by hosts discovering the servic e through the SRP registrar. The exact address addresses that would not be usable by hosts discovering the servic e through the SRP registrar. The exact address
record suppression behavior required may vary for different types of SRP requestors. An example of such advice can be record suppression behavior required may vary for different types of SRP requestors. An example of such advice can be
found in <xref target="RFC8766" section="5.5.2" sectionFormat="of" />. found in <xref target="RFC8766" section="5.5.2" sectionFormat="of" />.
</li> </li>
</ul> </ul>
<t> <t>
<xref target="RFC6763"/> describes the details of what each of these <xref target="RFC6763"/> describes the details of what each of these
types of RR mean, with the exception of types of RRs mean, with the exception of
the KEY RR, which is defined in <xref target="RFC2539"/>. These RFCs the KEY RR, which is defined in <xref target="RFC2539"/>. These RFCs
should be considered the definitive source for should be considered the definitive sources for
information about what to publish; the reason for summarizing this h ere is to provide the reader with enough information information about what to publish; the reason for summarizing this h ere is to provide the reader with enough information
about what will be published that the service registration process c an be understood at a high level without first about what will be published that the service registration process c an be understood at a high level without first
learning the full details of DNS&nbhy;SD. Also, the "Service Instan ce Name" is an important aspect of FCFS learning the full details of DNS-SD. Also, the "Service Instance Na me" is an important aspect of FCFS
naming, which we describe later on in this document.</t> naming, which we describe later on in this document.</t>
</section> </section>
<section> <section anchor="where">
<name>Where to publish it</name> <name>Where to Publish It</name>
<t> <t>
Multicast DNS uses a single namespace, ".local", which is valid on t Multicast DNS (mDNS) uses a single namespace that is valid on the lo
he local link. This convenience is not available for cal link called ".local". This convenience is not available for
DNS&nbhy;SD using the DNS protocol: services must exist in some spec DNS-SD using the DNS protocol: services must exist in some specific
ific DNS namespace that is chosen either by the DNS namespace that is chosen either by the
network operator, or automatically.</t> network operator or automatically.</t>
<t> <t>
As described above, full-featured devices are responsible for knowin g the domain in which to register their services. As described above, full-featured devices are responsible for knowin g the domain in which to register their services.
Such devices MAY optionally support configuration of a registration d Such devices <bcp14>MAY</bcp14> optionally support configuration of a
omain by the operator of the device. However, registration domain by the operator of the device. However,
such devices MUST support registration domain discovery as described such devices <bcp14>MUST</bcp14> support registration domain discover
in <xref target="RFC6763" section="11" sectionFormat="of"/>, y as described in <xref target="RFC6763" section="11" sectionFormat="of"/>.
"Discovery of Browsing and Registration Domains".
</t> </t>
<t> <t>
Devices made for Constrained-Node Networks register in the special u Devices made for CNNs register in the special-use domain name (<xref
se domain name <xref target="RFC6761"/> target="RFC6761"/>)
"default.service.arpa", and let the SRP registrar handle rewriting t "default.service.arpa" and let the SRP registrar handle rewriting th
hat to a different domain if necessary.</t> at to a different domain if necessary.</t>
</section> </section>
<section> <section anchor="how">
<name>How to publish it</name> <name>How to Publish It</name>
<t> <t>
It is possible to issue a DNS Update that does several things at onc It is possible to issue a DNS Update that does several things at onc
e; this means that it's possible to do all the work of e: meaning that it's possible to do all the work of
adding a PTR resource record to the PTR RRset on the Service Name, a adding a PTR RR to the PTR RRset on the Service Name and creating or
nd creating or updating the Service Instance Name and updating the Service Instance Name and
Host Description, in a single transaction.</t> Host Description in a single transaction.</t>
<t> <t>
An SRP Update takes advantage of this: it is implemented as a single DNS Update message that contains a service's Service An SRP Update takes advantage of this: it is implemented as a single DNS Update message that contains a service's Service
Discovery records, Service Description records, and Host Description records.</t> Discovery records, Service Description records, and Host Description records.</t>
<t> <t>
Updates done according to this specification are somewhat different than regular DNS Updates as defined in Updates done according to this specification are somewhat different than regular DNS Updates as defined in
<xref target="RFC2136"/>. The <xref target="RFC2136"/> update proces s can involve many update attempts: you might first <xref target="RFC2136"/> where the update process could involve many update attempts. You might first
attempt to add a name if it doesn't exist; if that fails, then in a s econd message you might update the name if it does attempt to add a name if it doesn't exist; if that fails, then in a s econd message you might update the name if it does
exist but matches certain preconditions. Because the registration pr otocol uses a single transaction, some of this exist but matches certain preconditions. Because the registration pr otocol described in this document uses a single transaction, some of this
adaptability is lost.</t> adaptability is lost.</t>
<t> <t>
In order to allow updates to happen in a single transaction, SRP Upd ates do not include update prerequisites. The In order to allow updates to happen in a single transaction, SRP Upd ates do not include update prerequisites. The
requirements specified in <xref target="server_behavior"/> are impli cit in the processing of SRP Updates, and so there is requirements specified in <xref target="server_behavior"/> are impli cit in the processing of SRP Updates; thus, there is
no need for the SRP requestor to put in any explicit prerequisites.< /t> no need for the SRP requestor to put in any explicit prerequisites.< /t>
<section> <section>
<name>How the DNS&nbhy;SD Service Registration process differs from D NS Update as specified in RFC2136</name> <name>How the DNS-SD Service Registration Process Differs from the DN S Update Specified in RFC 2136</name>
<t> <t>
DNS&nbhy;SD Service Registration is based on standard RFC2136 DNS DNS-SD Service Registration is based on the standard DNS Update sp
Update, with some differences:</t> ecified in <xref target="RFC2136"/>, with some differences:</t>
<ul spacing="compact"> <ul spacing="normal">
<li> <li>
It implements first-come first-served name allocation, protected using SIG(0) <xref target="RFC2931"/>.</li> It implements FCFS name allocation, protected using SIG(0) (<xref target="RFC2931"/>).</li>
<li> <li>
It enforces policy about what updates are allowed.</li> It enforces policy about what updates are allowed.</li>
<li> <li>
It optionally performs rewriting of "default.service.arpa" to som e other domain.</li> It optionally performs rewriting of "default.service.arpa" to som e other domain.</li>
<li> <li>
It optionally performs automatic population of the address-to-nam e reverse mapping domains.</li> It optionally performs automatic population of the address-to-nam e reverse mapping domains.</li>
<li> <li>
An SRP registrar is not required to implement general DNS Update prerequisite processing.</li> An SRP registrar is not required to implement general DNS Update prerequisite processing.</li>
<li> <li>
Constrained-Node SRP requestors are allowed to send updates to th e generic domain "default.service.arpa."</li> Constrained-Node SRP requestors are allowed to send updates to th e generic domain "default.service.arpa.".</li>
</ul> </ul>
</section> </section>
<section> <section>
<name>Retransmission Strategy</name> <name>Retransmission Strategy</name>
<t>The DNS protocol, including DNS updates, can operate over UDP or T CP. When using UDP, reliable <t>The DNS protocol, including DNS updates, can operate over UDP or T CP. When using UDP, reliable
transmission must be guaranteed by retransmitting if a DNS UDP mess age is not acknowledged in a transmission must be guaranteed by retransmitting if a DNS UDP mess age is not acknowledged in a
reasonable interval. <xref target="RFC1035" section="4.2.1" section Format="of"/> provides some reasonable interval. <xref target="RFC1035" section="4.2.1" section Format="of"/> provides some
guidance on this topic, as does <xref target="RFC1536" section="1" sectionFormat="of"/>. guidance on this topic, as does <xref target="RFC1536" section="1" sectionFormat="of"/>.
<xref target="RFC8085" section="3.1.3" sectionFormat="of"/> also pr ovides useful guidance that <xref target="RFC8085" section="3.1.3" sectionFormat="of"/> also pr ovides useful guidance that
is particularly relevant to DNS.</t> is particularly relevant to DNS.</t>
</section> </section>
<section> <section>
<name>Successive Updates</name> <name>Successive Updates</name>
<t>Service Registration Protocol does not require that every update c <t>SRP does not require that every update contain the same informatio
ontain the same information. n.
When an SRP requestor needs to send more than one SRP update to the When an SRP requestor needs to send more than one SRP update to the
SRP registrar, it MUST send SRP registrar, it <bcp14>MUST</bcp14> send
these sequentially: until an earlier update has been successfully a cknowledged, the requestor these sequentially: until an earlier update has been successfully a cknowledged, the requestor
MUST NOT begin sending a subsequent update.</t> <bcp14>MUST NOT</bcp14> begin sending a subsequent update.</t>
</section> </section>
</section> </section>
<section anchor="how-to-secure"> <section anchor="how-to-secure">
<name>How to secure it</name> <name>How to Secure It</name>
<t> <t>
DNS update as described in <xref target="RFC2136"/> is secured using A DNS update, as described in <xref target="RFC2136"/>, is secured u
Secret Key Transaction Signatures, sing secret key transaction signatures
<xref target="RFC8945"/>, which uses a secret key shared between the (<xref target="RFC8945"/>) that uses a secret key shared between the
DNS Update requestor (which issues the update) and DNS Update requestor (which issues the update) and
the server (which authenticates it). This model does not work for a utomatic service registration.</t> the server (which authenticates it). This model does not work for a utomatic service registration.</t>
<t> <t>
The goal of securing the DNS&nbhy;SD Registration Protocol is to pro vide the best possible security given the constraint The goal of securing the DNS-SD Registration Protocol is to provide the best possible security given the constraint
that service registration has to be automatic. It is possible to la yer more operational security on top of what we that service registration has to be automatic. It is possible to la yer more operational security on top of what we
describe here, but FCFS naming is already an improvement over the se curity of mDNS.</t> describe here, but FCFS naming is already an improvement over the se curity of mDNS.</t>
<section anchor="fcfs"> <section anchor="fcfs">
<name>First-Come First-Served Naming</name> <name>FCFS Naming</name>
<t> <t>
First-Come First-Serve naming provides a limited degree of securit
y: a server that registers its service using <!--[rfced] To what does "that" refer in this sentence?
DNS&nbhy;SD Registration protocol is given ownership of a name for
an extended period of time based on a lease Original:
As long as the registration service remembers the name and the key
used to register that name, no other server can add or update the
information associated with that.
Perhaps:
As long as the registration service remembers the name and the key
used to register that name, no other server can add or update the
information associated with them.
Perhaps:
As long as the registration service remembers the name and the key
used to register that name, no other server can add or update the
information associated with that pair.
-->
FCFS naming provides a limited degree of security. A server that r
egisters its service using the
DNS-SD Registration Protocol is given ownership of a name for an e
xtended period of time based on a lease
specific to the key used to authenticate the DNS Update, which may be longer than the lease associated with the specific to the key used to authenticate the DNS Update, which may be longer than the lease associated with the
registered records. As long as the registration service remembers the name and registered records. As long as the registration service remembers the name and
the key used to register that name, no other server can add or upd ate the information associated with that. If the the key used to register that name, no other server can add or upd ate the information associated with that. If the
server fails to renew its service registration before the KEY leas e (<xref target="I-D.ietf-dnssd-update-lease" server fails to renew its service registration before the KEY leas e (see <xref target="RFC9664"
section="4"/>) expires, its name is no longer protected. FCFS nam ing is used to protect both the Service Description section="4"/>) expires, its name is no longer protected. FCFS nam ing is used to protect both the Service Description
and the Host Description.</t> and the Host Description.</t>
</section> </section>
</section> </section>
<section> <section>
<name>SRP Requestor Behavior</name> <name>SRP Requestor Behavior</name>
<section> <section>
<name>Public/Private key pair generation and storage</name> <name>Public/Private Key Pair Generation and Storage</name>
<t> <t>
The requestor generates a public/private key pair (See <xref target The requestor generates a public/private key pair (see <xref target
="rsa"/>). This key pair MUST be stored in stable ="rsa"/>). This key pair <bcp14>MUST</bcp14> be stored in stable
storage; if there is no writable stable storage on the SRP requesto storage; if there is no writable stable storage on the SRP requesto
r, the SRP requestor MUST be pre-configured with a r, the SRP requestor <bcp14>MUST</bcp14> be preconfigured with a
public/private key pair in read-only storage that can be used. Thi public/private key pair in read-only storage that can be used. Thi
s key pair MUST be unique to the device. A device s key pair <bcp14>MUST</bcp14> be unique to the device. A device
with rewritable storage SHOULD retain this key indefinitely. When with rewritable storage <bcp14>SHOULD</bcp14> retain this key indef
the device changes ownership, it may be appropriate initely. When the device changes ownership, it may be appropriate
for the former owner to erase the old key pair, which would then re quire the new owner to install a new for the former owner to erase the old key pair, which would then re quire the new owner to install a new
one. Therefore, the SRP requestor on the device SHOULD provide a me one. Therefore, the SRP requestor on the device <bcp14>SHOULD</bcp1
chanism to erase the key, for example as the 4> provide a mechanism to erase the key (for example, as the
result of a "factory reset," and to generate a new key.</t> result of a "factory reset") and to generate a new key.</t>
<t> <t>
The policy described here for managing keys assumes that the keys a re only used for SRP. If a key that is used for SRP The policy described here for managing keys assumes that the keys a re only used for SRP. If a key that is used for SRP
is also used for other purposes, the policy described here is likel is also used for other purposes, the policy described here is likel
y to be insufficient. The policy stated here is NOT y to be insufficient. The policy stated here is <bcp14>NOT
RECOMMENDED in such a situation: a policy appropriate to the full s RECOMMENDED</bcp14> in such a situation: a policy appropriate to th
et of uses for the key must be chosen. Specifying e full set of uses for the key must be chosen. Specifying
such a policy is out of scope for this document.</t> such a policy is out of scope for this document.</t>
<t> <t>
When sending DNS updates, the requestor includes a KEY record conta ining the public portion of the key in each Host When sending DNS updates, the requestor includes a KEY record conta ining the public portion of the key in each Host
Description Instruction and each Service Description Instruction. Each KEY record MUST contain the same public key. Description Instruction and each Service Description Instruction. Each KEY record <bcp14>MUST</bcp14> contain the same public key.
The update is signed using SIG(0), using the private key that corre sponds to the public key in the KEY record. The The update is signed using SIG(0), using the private key that corre sponds to the public key in the KEY record. The
lifetimes of the records in the update is set using the EDNS(0) Upd lifetimes of the records in the update is set using the Extension M
ate Lease option echanisms for DNS (EDNS(0)) Update Lease option
<xref target="I-D.ietf-dnssd-update-lease"/>.</t> (see <xref target="RFC9664"/>).</t>
<t> <t>
The format of the KEY resource record in the SRP Update is defined in <xref target="RFC3445"/>. Because the KEY RR The format of the KEY resource record in the SRP Update is defined in <xref target="RFC3445"/>. Because the KEY RR
used in TSIG is not a zone-signing key, the flags field in the KEY RR MUST be all zeroes.</t> used in TSIG is not a zone-signing key, the flags field in the KEY RR <bcp14>MUST</bcp14> be all zeroes.</t>
<t> <t>
The KEY record in Service Description updates MAY be omitted for br evity; if it is omitted, the SRP registrar MUST behave The KEY record in Service Description updates <bcp14>MAY</bcp14> be omitted for brevity; if it is omitted, the SRP registrar <bcp14>MUST</bcp14> be have
as if the same KEY record that is given for the Host Description is also given for each Service Description for which as if the same KEY record that is given for the Host Description is also given for each Service Description for which
no KEY record is provided. Omitted KEY records are not used when c omputing the SIG(0) signature.</t> no KEY record is provided. Omitted KEY records are not used when c omputing the SIG(0) signature.</t>
</section> </section>
<section> <section>
<name>Name Conflict Handling</name> <name>Name Conflict Handling</name>
<t> <t>
Both Host Description RR adds and Service Description RR adds can h ave names that result in name conflicts. Adds for both Host Description RRs and Service Description RRs can have names that result in name conflicts.
Service Discovery record adds cannot have name conflicts. If any Ho st Description or Service Description record Service Discovery record adds cannot have name conflicts. If any Ho st Description or Service Description record
is found by the SRP registrar to have a conflict with an existing n ame, the registrar will respond to the SRP Update is found by the SRP registrar to have a conflict with an existing n ame, the registrar will respond to the SRP Update
with a YXDomain RCODE (<xref target="RFC2136" section="2.2" section Format="of"/>). In this case, the with a YXDomain RCODE (<xref target="RFC2136" section="2.2" section Format="of"/>). In this case, the
requestor MUST choose a new name or give up.</t> requestor <bcp14>MUST</bcp14> choose a new name or give up.</t>
<t> <t>
There is no specific requirement for how this is done; typically, h There is no specific requirement for how this is done. Typically, h
owever, the requestor will append a number to the owever, the requestor will append a number to the
preferred name. This number could be sequentially increasing, or co preferred name. This number could be sequentially increasing or cou
uld be chosen randomly. One existing implementation ld be chosen randomly. One existing implementation
attempts several sequential numbers before choosing randomly. So fo attempts several sequential numbers before choosing randomly. For i
r instance, it might try host.default.service.arpa, nstance, it might try host.default.service.arpa,
then host-1.default.service.arpa, then host-2.default.service.arpa, then host-31773.default.service.arpa.</t> then host-1.default.service.arpa, then host-2.default.service.arpa, then host-31773.default.service.arpa.</t>
</section> </section>
<section> <section>
<name>Record Lifetimes</name> <name>Record Lifetimes</name>
<t> <t>
The lifetime of the <xref target="RFC6763">DNS&nbhy;SD PTR, SRV, A, The lifetime of the DNS-SD PTR, SRV, A, AAAA, and TXT records (see
AAAA and TXT records</xref> uses the LEASE field <xref target="RFC6763"></xref>) uses the LEASE field
of the Update Lease option, and is typically set to two hours. Thi of the Update Lease option and is typically set to two hours. Thus
s means that if a device is disconnected from the , if a device is disconnected from the
network, it does not appear in the user interfaces of devices looki ng for services of that type for too long.</t> network, it does not appear in the user interfaces of devices looki ng for services of that type for too long.</t>
<t> <t>
The lifetime of the KEY records is set using the KEY-LEASE field of The lifetime of the KEY records is set using the KEY-LEASE field of
the Update Lease Option, and SHOULD be set to a the Update Lease Option and <bcp14>SHOULD</bcp14> be set to a
much longer time, typically 14 days. The result of this is that ev much longer time, typically 14 days. The result being that even th
en though a device may be temporarily unplugged, ough a device may be temporarily unplugged --
disappearing from the network for a few days, it makes a claim on i disappearing from the network for a few days -- it makes a claim on
ts name that lasts much longer.</t> its name that lasts much longer.</t>
<t> <t>
This means that even if a device is unplugged from the network for a few days, and its services are not available for Therefore, even if a device is unplugged from the network for a few days, and its services are not available for
that time, no other device can come along and claim its name the mo ment it disappears from the network. In the event that time, no other device can come along and claim its name the mo ment it disappears from the network. In the event
that a device is unplugged from the network and permanently discard ed, then its name is eventually cleaned up and made that a device is unplugged from the network and permanently discard ed, then its name is eventually cleaned up and made
available for re-use.</t> available for reuse.</t>
</section> </section>
<section> <section>
<name>Compression in SRV records</name> <name>Compression in SRV Records</name>
<t> <t>
Although <xref target="RFC2782"/> requires that the target name in the SRV record not be compressed, an SRP requestor Although <xref target="RFC2782"/> requires that the target name in the SRV record not be compressed, an SRP requestor
MAY compress the target in the SRV record. The motivation for <em>n <bcp14>MAY</bcp14> compress the target in the SRV record. The motiv
ot</em> compressing in <xref target="RFC2782"/> ation for <em>not</em> compressing in <xref target="RFC2782"/>
is not stated, but is assumed to be because a caching resolver that is not stated but is assumed to be because a caching resolver that
does not understand the format of the SRV record does not understand the format of the SRV record
might store it as binary data and thus return an invalid pointer in response to a query. This does not apply in the might store it as binary data and thus return an invalid pointer in response to a query. This does not apply in the
case of SRP: an SRP registrar needs to understand SRV records in or der to validate the SRP Update. Compression of the case of SRP. An SRP registrar needs to understand SRV records in or der to validate the SRP Update. Compression of the
target can save space in the SRP Update, so we want clients to be a ble to assume that the registrar will handle target can save space in the SRP Update, so we want clients to be a ble to assume that the registrar will handle
this. Therefore, SRP registrars MUST support compression of SRV RR this. Therefore, SRP registrars <bcp14>MUST</bcp14> support compres
targets.</t> sion of SRV RR targets.</t>
<t> <t>
Note that this does not update <xref target="RFC2782"/>: DNS server
s still MUST NOT compress SRV record targets. The <!--[rfced] How might we clarify "this" for the ease of the reader
(especially as this sentence is the first of the paragraph)?
Original:
Note that this does not update [RFC2782]: DNS servers still MUST
NOT compress SRV record targets.
-->
Note that this does not update <xref target="RFC2782"/>: DNS server
s still <bcp14>MUST NOT</bcp14> compress SRV record targets. The
requirement to accept compressed SRV records in updates only applie s to SRP registrars, and SRP registrars that are requirement to accept compressed SRV records in updates only applie s to SRP registrars, and SRP registrars that are
also DNS servers still MUST NOT compress SRV record targets in DNS also DNS servers still <bcp14>MUST NOT</bcp14> compress SRV record
responses. We note also that targets in DNS responses. We note also that
<xref target="RFC6762"/> recomments that SRV records be compressed <xref target="RFC6762"/> recommends that SRV records be compressed
in mDNS messages, so <xref target="RFC2782"/> does in mDNS messages, so <xref target="RFC2782"/> does
not apply to mDNS messages.</t> not apply to mDNS messages.</t>
<t> <t>
In addition, we note that an implementor of an SRP requestor might update existing code that creates SRV records In addition, we note that an implementor of an SRP requestor might update existing code that creates SRV records
or compresses DNS messages so that it compresses the target of an S RV record. Care must be taken if such code is or compresses DNS messages so that it compresses the target of an S RV record. Care must be taken if such code is
used both in requestors and in DNS servers that the code only compr esses in the case where a requestor is generating used both in requestors and in DNS servers that the code only compr esses in the case where a requestor is generating
an SRP update.</t> an SRP update.</t>
</section> </section>
<section anchor="remove"> <section anchor="remove">
<name>Removing published services</name> <name>Removing Published Services</name>
<section anchor="zero-lease"> <section anchor="zero-lease">
<name>Removing all published services</name> <name>Removing All Published Services</name>
<t> <t>
To remove all the services registered to a particular host, the S RP requestor transmits an SRP update for that host To remove all the services registered to a particular host, the S RP requestor transmits an SRP update for that host
with an Update Lease option that has a LEASE value of zero. If th e registration is to be permanently removed, with an Update Lease option that has a LEASE value of zero. If th e registration is to be permanently removed,
KEY-LEASE SHOULD also be zero. Otherwise, it SHOULD be set to the same value it had previously; this holds the name KEY-LEASE <bcp14>SHOULD</bcp14> also be zero. Otherwise, it <bcp1 4>SHOULD</bcp14> be set to the same value it had previously; this holds the name
in reserve for when the SRP requestor is once again able to provi de the service.</t> in reserve for when the SRP requestor is once again able to provi de the service.</t>
<t> <t>
SRP requestors are normally expected to remove all service instan ces when removing a host. However, in some cases an SRP SRP requestors are normally expected to remove all service instan ces when removing a host. However, in some cases, an SRP
requestor may not have retained sufficient state to know that som e service instance is pointing to a host that it is requestor may not have retained sufficient state to know that som e service instance is pointing to a host that it is
removing. This method of removing services is intended for the c ase where the requestor is going offline and does removing. This method of removing services is intended for the c ase where the requestor is going offline and does
not want its services advertised. Therefore, it is sufficient for not want its services advertised. Therefore, it is sufficient for
the requestor to send the the requestor to send the Host Description Instruction (see <xref target="hdi">
<xref target="hdi">Host Description Instruction</xref>. </xref>).
</t> </t>
<t> <t>
To support this, when removing services based on the lease time b eing zero, an SRP registrar MUST remove all service To support this, when removing services based on the lease time b eing zero, an SRP registrar <bcp14>MUST</bcp14> remove all service
instances pointing to a host when a host is removed, even if the SRP requestor doesn't list them explicitly. If the instances pointing to a host when a host is removed, even if the SRP requestor doesn't list them explicitly. If the
KEY lease time is nonzero, the SRP registrar MUST NOT delete the KEY records for these SRP requestors. KEY lease time is nonzero, the SRP registrar <bcp14>MUST NOT</bcp 14> delete the KEY records for these SRP requestors.
</t> </t>
</section> </section>
<section> <section>
<name>Removing some published services</name> <name>Removing Some Published Services</name>
<t>
In some use cases a requestor may need to remove some specific se
rvice, without removing its other services. This can
be accomplished in one of two ways. To simply remove a specific s
ervice, the requestor sends a valid SRP Update where
the <xref target="servdis">Service Discovery Instruction</xref> c
ontains a single Delete an RR from an RRset
(<xref target="RFC2136" section="2.5.4" sectionFormat="comma"/>)
update that deletes the PTR record whose target is
the service instance name. The <xref target="servdesc">Service De
scription Instruction</xref> in this case contains
a single Delete all RRsets from a Name (<xref target="RFC2136" se
ction="2.5.3" sectionFormat="comma"/>) update to
the service instance name.
</t>
<t> <t>
The second alternative is used when some service is being replace In some use cases, a requestor may need to remove a specific serv
d by a different service with a different service ice without removing its other services. This can
be accomplished in one of two ways:</t>
<ol><li>To simply remove a specific service, the requestor sends a valid SRP Upd
ate where
the Service Discovery Instruction (see <xref target="servdis"></x
ref>) contains a single "Delete An RR From An RRset" update
(<xref target="RFC2136" section="2.5.4" sectionFormat="of"/>) tha
t deletes the PTR record whose target is
the service instance name. In this case, the Service Description
Instruction (see <xref target="servdesc"></xref>) contains
a single "Delete All RRsets From A Name" update (<xref target="RF
C2136" section="2.5.3" sectionFormat="of"/>) to
the service instance name. </li>
<li>
This alternative is used when some service is being replaced by a
different service with a different service
instance name. In this case, the old service is deleted as in the first alternative. The new service is added, just instance name. In this case, the old service is deleted as in the first alternative. The new service is added, just
as it would be in an update that wasn't deleting the old service. Because both the removal of the old service and as it would be in an update that wasn't deleting the old service. Because both the removal of the old service and
the add of the new service consist of a valid Service Discovery I nstruction and a valid Service Description the add of the new service consist of a valid Service Discovery I nstruction and a valid Service Description
Instruction, the update as a whole is a valid SRP Update, and wil Instruction, the update as a whole is a valid SRP Update and will
l result in the old service being removed and the result in the old service being removed and the
new one added, or, to put it differently, in the old service bein new one added; or, to put it differently, the update will result
g replaced by the new service. in the old service being replaced by the new service.
</t> </li></ol>
<t> <t>
It is perhaps worth noting that if a service is being updated wit hout the service instance name changing, that will It is perhaps worth noting that, if a service is being updated wi thout the service instance name changing, that situation will
look very much like the second alternative above. The difference is that because the target for the PTR record in look very much like the second alternative above. The difference is that because the target for the PTR record in
the Service Discovery Instruction is the same for both the Delete the Service Discovery Instruction is the same for both the "Delet
An RR From An RRset update and the Add To An RRSet e An RR From An RRset" update and the "Add
update, there is no way to tell whether they were intended to be To An RRset" update (<xref target="RFC2136" section="2.5.1" secti
one or two Instructions. The same would be true of onFormat="of"/>), there is no way to tell whether they were intended to be one o
r two Instructions. The same would be true of
the Service Description Instruction. the Service Description Instruction.
</t> </t>
<t> <t>
Whichever of these two alternatives is used, the host lease will be updated with the lease time provided in the SRP Whichever of these two alternatives is used, the host lease will be updated with the lease time provided in the SRP
update. In neither of these cases is it permissible to delete the host. All services must point to a host. If a host update. In neither of these cases is it permissible to delete the host. All services must point to a host. If a host
is to be deleted, this must be done using the method described in <xref target="zero-lease"/>, which deletes the is to be deleted, this must be done using the method described in <xref target="zero-lease"/>, which deletes the
host and all services that have that host as their target. host and all services that have that host as their target.
</t> </t>
</section> </section>
</section> </section>
skipping to change at line 541 skipping to change at line 595
<section anchor="server_behavior"> <section anchor="server_behavior">
<name>Validation and Processing of SRP Updates</name> <name>Validation and Processing of SRP Updates</name>
<section anchor="add_validation"> <section anchor="add_validation">
<name>Validation of DNS Update Add and Delete RRs</name> <name>Validation of DNS Update Add and Delete RRs</name>
<t> <t>
The SRP registrar first validates that the DNS Update is a syntactica lly and semantically valid DNS Update according to The SRP registrar first validates that the DNS Update is a syntactica lly and semantically valid DNS Update according to
the rules specified in <xref target="RFC2136"/>.</t> the rules specified in <xref target="RFC2136"/>.</t>
<t> <t>
SRP Updates consist of a set of <em>instructions</em> that together a dd or remove one or more services. Each instruction SRP Updates consist of a set of <em>instructions</em> that together a dd or remove one or more services. Each instruction
consists of some combination of delete updates and add updates. When an instruction contains a delete and an add, the consists of some combination of delete updates and add updates. When an instruction contains a delete and an add, the
delete MUST precede the add.</t> delete <bcp14>MUST</bcp14> precede the add.</t>
<t> <t>
The SRP registrar checks each instruction in the SRP Update to see th at it is either a Service Discovery Instruction, a The SRP registrar checks each instruction in the SRP Update to see th at it is either a Service Discovery Instruction, a
Service Description Instruction, or a Host Description Instruction. Order matters in DNS updates. Specifically, Service Description Instruction, or a Host Description Instruction. Order matters in DNS updates. Specifically,
deletes must precede adds for records that the deletes would affect; deletes must precede adds for records that the deletes would affect;
otherwise the add will have no effect. This is the otherwise, the add will have no effect. This is the
only ordering constraint; aside from this constraint, updates may app only ordering constraint: aside from this constraint, updates may app
ear in whatever order is convenient when ear in whatever order is convenient when
constructing the update.</t> constructing the update.</t>
<t> <t>
Because the SRP Update is a DNS update, it MUST contain a single ques Because the SRP Update is a DNS update, it <bcp14>MUST</bcp14> contai
tion that indicates the zone to be updated. n a single question that indicates the zone to be updated.
Every delete and update in an SRP Update MUST be within the zone that Every delete and update in an SRP Update <bcp14>MUST</bcp14> be withi
is specified for the SRP Update.</t> n the zone that is specified for the SRP Update.</t>
<section anchor="servdis"> <section anchor="servdis">
<name>Service Discovery Instruction</name> <name>Service Discovery Instruction</name>
<t>An instruction is a Service Discovery Instruction if it contains< <t>An instruction is a Service Discovery Instruction if it:</t>
/t>
<ul spacing="compact"> <!-- [rfced] FYI - we updated the list as follows for clarity. Please let us
<li>exactly one "Add to an RRSet" (<xref target="RFC2136" section=" know if there are any objections.
2.5.1" sectionFormat="comma"/>) or exactly one
"Delete an RR from an RRSet" (<xref target="RFC2136" section="2.5 Original:
.4" sectionFormat="comma"/>) RR update,</li> An instruction is a Service Discovery Instruction if it contains
<li>which updates a PTR RR,</li>
<li>the target of which is a Service Instance Name</li> * exactly one "Add to an RRSet" ([RFC2136], Section 2.5.1) or
<li><t>for which name a Service Description Instruction is present exactly one "Delete an RR from an RRSet" ([RFC2136],
in the SRP Update, and:</t> Section 2.5.4) RR update,
* which updates a PTR RR,
* the target of which is a Service Instance Name
* for which name a Service Description Instruction is present in the
SRP Update, and:
- if the RR Update is an "Add to an RRSet" instruction, that
Service Description Instruction contains an "Add to an RRset"
RR update for the SRV RR describing that service and no other
"Delete from an RRset" instructions for that Service Instance
Name; or
- if the RR Update is a "Delete an RR from an RRSet" instruction,
that Service Description Instruction contains a "Delete from an
RRset" RR update and no other "Add to an RRset" instructions
for that Service Instance Name.
* and contains no other add or delete RR updates for the same name
as the PTR RR Update.
Current:
An instruction is a Service Discovery Instruction if it:
* Contains exactly one "Add to an RRSet" (Section 2.5.1 of
[RFC2136]) or exactly one "Delete an RR from an RRSet"
(Section 2.5.4 of [RFC2136]) RR update, which updates a PTR RR;
the target of which is a Service Instance Name for which name a
Service Description Instruction is present in the SRP Update.
Additionally:
- If the RR Update is an "Add to an RRSet" instruction, that
Service Description Instruction contains an "Add to an RRset"
RR update for the SRV RR describing that service and no other
"Delete from an RRset" instructions for that Service Instance
Name.
- If the RR Update is a "Delete an RR from an RRSet" instruction,
that Service Description Instruction contains a "Delete from an
RRset" RR update and no other "Add to an RRset" instructions
for that Service Instance Name.
* Contains no other add or delete RR updates for the same name as
the PTR RR Update.
-->
<ul spacing="normal">
<li><t>Contains exactly one "Add To An RRset" RR update (<xref
target="RFC2136" section="2.5.1" sectionFormat="of"/>) or
exactly one "Delete An RR From An RRset" RR update (<xref target="R
FC2136"
section="2.5.4" sectionFormat="of"/>), which updates a
PTR RR; the target of which is a Service Instance Name for which
name a Service Description Instruction is present in the SRP
Update. Additionally:</t>
<ul spacing="compact"> <ul spacing="compact">
<li>if the RR Update is an "Add to an RRSet" instruction, that <li>If the RR Update is an "Add To An RRset" instruction,
Service Description Instruction contains an "Add to that Service Description Instruction contains an "Add To An
an RRset" RR update for the SRV RR describing that service an RRset" RR update for the SRV RR describing that service and
d no other "Delete from an RRset" instructions for no other "Delete From An RRset" instructions for that
that Service Instance Name; or</li> Service Instance Name.</li>
<li>if the RR Update is a "Delete an RR from an RRSet" instruct <li>If the RR Update is a "Delete An RR From An RRset"
ion, that Service Description Instruction contains instruction, that Service Description Instruction contains a
a "Delete from an RRset" RR update and no other "Add to an RR "Delete From An RRset" RR update and no other "Add To An
set" instructions for that Service Instance RRset" instructions for that Service Instance
Name.</li></ul></li> Name.</li></ul></li>
<li>and contains no other add or delete RR updates for the same nam <li>Contains no other add or delete RR updates for the same name
e as the PTR RR Update.</li> as the PTR RR Update.</li>
</ul> </ul>
<t> <t>
Note that there can be more than one Service Discovery Instruction Note that there can be more than one Service Discovery
for the same name if the SRP requestor is Instruction for the same name if the SRP requestor is
advertising more than one service of the same type, or is changing advertising more than one service of the same type or is
the target of a PTR RR. This is also true for SRP changing the target of a PTR RR. This is also true for SRP
subtypes (<xref target="RFC6763" section="7.1"/>). For each such PT subtypes (<xref target="RFC6763" section="7.1"
R RR add or delete, the above constraints must be sectionFormat="of"/>). For each such PTR RR add or delete, the
met.</t> above constraints must be met.</t>
</section> </section>
<section anchor="servdesc"> <section anchor="servdesc">
<name>Service Description Instruction</name> <name>Service Description Instruction</name>
<t>An instruction is a Service Description Instruction if, for the a <t>An instruction is a Service Description Instruction if, for the
ppropriate Service Instance Name, the following are true:</t> appropriate Service Instance Name, the following are true:</t>
<ul spacing="compact"> <ul spacing="normal">
<li>
It contains exactly one "Delete all RRsets from a name" update fo
r the service instance name
(<xref target="RFC2136" section="2.5.3" sectionFormat="comma"/>),
</li>
<li>
It contains zero or one "Add to an RRset" SRV RR,</li>
<li> <li>
It contains zero or one "Add to an RRset" KEY RR that, if present It contains exactly one "Delete All RRsets From A Name" update
, contains the public key corresponding to the private key for the service instance name (see <xref target="RFC2136"
that was used to sign the message (if present, the KEY MUST match section="2.5.3" sectionFormat="of"/>).</li>
the KEY RR given in the Host Description),</li>
<li> <li>
It contains zero or more "Add to an RRset" TXT RRs,</li> It contains zero or one "Add To An RRset" SRV RR.</li>
<li> <li>
If there is one "Add to an RRset" SRV update, there MUST be at le It contains zero or one "Add To An RRset" KEY RR that, if
ast one "Add to an RRset" TXT update.</li> present, contains the public key corresponding to the private
key that was used to sign the message (if present, the KEY
<bcp14>MUST</bcp14> match the KEY RR given in the Host
Description).</li>
<li> <li>
The target of the SRV RR Add, if present points to a hostname for It contains zero or more "Add To An RRset" TXT RRs.</li>
which there is a Host Description Instruction in
the SRP Update, or</li>
<li> <li>
If there is no "Add to an RRset" SRV RR, then either:</li> If there is one "Add To An RRset" SRV update, there
<li><ul> <bcp14>MUST</bcp14> be at least one "Add To An RRset" TXT
<li>the name to which the "Delete all RRsets from a name" applies update.</li>
does not exist, or</li> <li>
<li>there is an existing KEY RR on that name, which matches the k
ey with which the SRP Update was <t>The target of the SRV RR Add, if present, points to a
signed.</li></ul></li> hostname for which there is a Host Description Instruction in
the SRP Update; or if there is no "Add To An RRset" SRV RR,
then either:</t>
<ul spacing="normal">
<li>the name to which the "Delete All RRsets From A Name"
applies does not exist, or</li>
<li>there is an existing KEY RR on that name that matches
the key with which the SRP Update was signed.</li></ul></li>
<li> <li>
No other resource records on the Service Instance Name are modifi No other resource records on the Service Instance Name are
ed.</li> modified.</li>
</ul> </ul>
<t>An SRP registrar MUST correctly handle compressed names in the SRV target.</t> <t>An SRP registrar <bcp14>MUST</bcp14> correctly handle compressed n ames in the SRV target.</t>
</section> </section>
<section anchor="hdi"> <section anchor="hdi">
<name>Host Description Instruction</name> <name>Host Description Instruction</name>
<t>An instruction is a Host Description Instruction if, for the appr <t>An instruction is a Host Description Instruction if, for the appr
opriate hostname, it contains</t> opriate hostname, it contains the following:</t>
<ul spacing="compact"> <ul spacing="normal">
<li>
exactly one "Delete all RRsets from a name" RR,</li>
<li> <li>
one or more "Add to an RRset" RRs of type A and/or AAAA,</li> exactly one "Delete All RRsets From A Name" RR,</li>
<li> <li>
exactly one "Add to an RRset" RR that adds a KEY RR that contains one or more "Add To An RRset" RRs of type A and/or AAAA, and </li
the public key corresponding to the private key >
that was used to sign the message,</li>
<li> <li>
Host Description Instructions do not modify any other resource re exactly one "Add To An RRset" RR that adds a KEY RR that
cords.</li> contains the public key corresponding to the private key that
</ul> was used to sign the message</li>
</ul>
<t>Host Description Instructions do not modify any other resource rec
ords.</t>
<t> <t>
A and/or AAAA records that are not of sufficient scope to be validl A and/or AAAA records that are not of sufficient scope to be
y published in a DNS zone MAY be ignored by the validly published in a DNS zone <bcp14>MAY</bcp14> be ignored by
SRP registrar, which could result in a host description effectively the SRP registrar, which could result in a host description
containing zero reachable addresses even when it effectively containing zero reachable addresses even when it
contains one or more addresses.</t> contains one or more addresses.</t>
<t> <t>
For example, if a link-scope address or IPv4 autoconfiguration addr ess is provided by the SRP requestor, the SRP For example, if a link-scope address or IPv4 autoconfiguration addr ess is provided by the SRP requestor, the SRP
registrar could not publish this in a DNS zone. However, in some si tuations, the registrar might make the records registrar could not publish this in a DNS zone. However, in some si tuations, the registrar might make the records
available through a mechanism such as an advertising proxy only on the specific link from which the SRP update available through a mechanism such as an advertising proxy only on the specific link from which the SRP update
originated; in such a situation, locally-scoped records are still v alid.</t> originated. In such a situation, locally scoped records are still v alid.</t>
</section> </section>
</section> </section>
<section> <section>
<name>Valid SRP Update Requirements</name> <name>Valid SRP Update Requirements</name>
<t> <t>
An SRP Update MUST contain exactly one Host Description Instruction. In addition, there MUST NOT be any Service An SRP Update <bcp14>MUST</bcp14> contain exactly one Host Descriptio n Instruction. In addition, there <bcp14>MUST NOT</bcp14> be any Service
Description Instruction to which no Service Discovery Instruction poi nts. A DNS Update that contains any additional Description Instruction to which no Service Discovery Instruction poi nts. A DNS Update that contains any additional
adds or deletes that cannot be identified as Service Discovery, Servi ce Description or Host Description Instructions is adds or deletes that cannot be identified as Service Discovery, Servi ce Description, or Host Description Instructions is
not an SRP Update. A DNS update that contains any prerequisites is no t an SRP Update.</t> not an SRP Update. A DNS update that contains any prerequisites is no t an SRP Update.</t>
<t>An SRP Update MUST include an EDNS(0) Update Lease option <t>An SRP Update <bcp14>MUST</bcp14> include an EDNS(0) Update Lease op
<xref target="I-D.ietf-dnssd-update-lease"/>. The LEASE time specifie tion
d in the Update Lease option MUST be less than (see <xref target="RFC9664"/>). The LEASE time specified in the Updat
e Lease option <bcp14>MUST</bcp14> be less than
or equal to the KEY-LEASE time. A DNS update that does not include th e Update Lease option, or that includes a or equal to the KEY-LEASE time. A DNS update that does not include th e Update Lease option, or that includes a
KEY-LEASE value that is less than the LEASE value, is not an SRP upda te.</t> KEY-LEASE value that is less than the LEASE value, is not an SRP upda te.</t>
<t>When an SRP registrar receives a DNS Update that is not an SRP updat <t>When an SRP registrar receives a DNS Update that is not an SRP
e, it MAY update, it <bcp14>MAY</bcp14> process the update as regular updates
process the update as regular RFC2136 updates, including access contr described in <xref target="RFC2136" format="default"/>, including
ol checks and constraint access control checks and constraint checks, if supported. Otherwise,
checks, if supported. Otherwise the SRP registrar MUST reject the DNS the SRP registrar <bcp14>MUST</bcp14> reject the DNS Update with the
Update with the Refused RCODE.</t> Refused RCODE.</t>
<t> <t>
If the definitions of each of these instructions are followed careful ly and the update requirements are validated If the definitions of each of these instructions are followed careful ly and the update requirements are validated
correctly, many DNS Updates that look very much like SRP Updates neve rtheless will fail to validate. For example, a DNS correctly, many DNS Updates that look very much like SRP Updates neve rtheless will fail to validate. For example, a DNS
update that contains an Add to an RRset instruction for a Service Nam e and an Add to an RRset instruction for a Service update that contains an "Add To An RRset" instruction for a Service N ame and an Add to an RRset instruction for a Service
Instance Name, where the PTR record added to the Service Name does no t reference the Service Instance Name, is not a Instance Name, where the PTR record added to the Service Name does no t reference the Service Instance Name, is not a
valid SRP Update message, but may be a valid RFC2136 update.</t> valid SRP Update message but may be a valid update as described in <x ref target="RFC2136" format="default"/>.</t>
</section> </section>
<section> <section>
<name>FCFS Name And Signature Validation</name> <name>FCFS Name and Signature Validation</name>
<!--[rfced] For the ease of the reader, might we clarify what "these
conditions" are?
Original:
Assuming that a DNS Update message has been validated with these
conditions and is a valid SRP Update, the SRP registrar checks that
the name in the Host Description Instruction exists.
Perhaps:
Assuming that a DNS Update message has been validated with an FCFS name
and signature and is a valid SRP Update, the SRP registrar checks that
the name in the Host Description Instruction exists.
-->
<t> <t>
Assuming that a DNS Update message has been validated with these cond itions and is a valid SRP Update, the SRP registrar Assuming that a DNS Update message has been validated with these cond itions and is a valid SRP Update, the SRP registrar
checks that the name in the Host Description Instruction exists. If so, then the registrar checks to see if the KEY checks that the name in the Host Description Instruction exists. If so, then the registrar checks to see if the KEY
record on that name is the same as the KEY record in the Host Descrip tion Instruction. The registrar performs the same record on that name is the same as the KEY record in the Host Descrip tion Instruction. The registrar performs the same
check for the KEY records in any Service Description Instructions. F or KEY records that were omitted from Service check for the KEY records in any Service Description Instructions. F or KEY records that were omitted from Service
Description Instructions, the KEY from the Host Description Instructi on is used. If any existing KEY record Description Instructions, the KEY from the Host Description Instructi on is used. If any existing KEY record
corresponding to a KEY record in the SRP Update does not match the KE Y record in the SRP Update (whether provided corresponding to a KEY record in the SRP Update does not match the KE Y record in the SRP Update (whether provided
or taken from the Host Description Instruction), then the SRP registr or taken from the Host Description Instruction), then the SRP registr
ar MUST reject the SRP Update with the YXDomain ar <bcp14>MUST</bcp14> reject the SRP Update with the YXDomain
RCODE.</t> RCODE.</t>
<!--[rfced] Please review this transition sentence. Because it is
placed at the beginning of a new paragraph, the "Otherwise" might
be a bit jarring to the reader. (Our suggestion is likely weak,
but for demonstrative purposes...)
Original:
Otherwise, the SRP registrar validates the SRP Update using SIG(0)
against the public key in the KEY record of the Host Description
Instruction.
Perhaps:
If the above steps are not taken, the SRP registrar validates the
SRP Update using SIG(0) against the public key in the KEY record of
the Host Description Instruction.
-->
<t> <t>
Otherwise, the SRP registrar validates the SRP Update using SIG(0) ag ainst the public key in the KEY record of the Host Otherwise, the SRP registrar validates the SRP Update using SIG(0) ag ainst the public key in the KEY record of the Host
Description Instruction. If the validation fails, the registrar MUST Description Instruction. If the validation fails, the registrar <bcp
reject the SRP Update with the Refused RCODE. 14>MUST</bcp14> reject the SRP Update with the Refused RCODE.
Otherwise, the SRP Update is considered valid and authentic, and is p Otherwise, the SRP Update is considered valid and authentic and is pr
rocessed according to the method described in ocessed according to the method described in
RFC2136.</t> <xref target="RFC2136" format="default"/>.</t>
<t> <t>
KEY record updates omitted from Service Description Instruction are p KEY record updates omitted from Service Description Instruction are p
rocessed as if they had been explicitly present: rocessed as if they had been explicitly present.
every Service Description that is updated MUST, after the SRP Update After the SRP Update has been applied, every Service Description that
has been applied, have a KEY RR, and it must be the is updated <bcp14>MUST</bcp14> have a KEY RR: and it must be the
same KEY RR that is present in the Host Description to which the Serv ice Description refers.</t> same KEY RR that is present in the Host Description to which the Serv ice Description refers.</t>
<t> <t>
<xref target="RFC3445"/> states that the flags field in the KEY RR MU <xref target="RFC3445"/> states that the flags field in the KEY RR <b
ST be zero except for bit 7, which can cp14>MUST</bcp14> be zero except for bit 7, which can
be one in the case of a zone key. However, the SRP registrar MUST NOT be one in the case of a zone key. However, the SRP registrar <bcp14>M
validate the flags field.</t> UST NOT</bcp14> validate the flags field.</t>
</section> </section>
<section> <section>
<name>Handling of Service Subtypes</name> <name>Handling of Service Subtypes</name>
<t> <t>
SRP registrars MUST treat the update instructions for a service type and all its subtypes as atomic. That is, when a SRP registrars <bcp14>MUST</bcp14> treat the update instructions for a service type and all its subtypes as atomic. That is, when a
service and its subtypes are being updated, whatever information appe ars in the SRP Update is the entirety of service and its subtypes are being updated, whatever information appe ars in the SRP Update is the entirety of
information about that service and its subtypes. If any subtype appea red in a previous update but does not appear in information about that service and its subtypes. If any subtype appea red in a previous update but does not appear in
the current update, then the SRP registrar MUST remove that subtype. the current update, then the SRP registrar <bcp14>MUST</bcp14> remove that subtype.
</t> </t>
<t> <t>
Similarly, there is no mechanism for deleting subtypes. A delete of a service deletes all of its subtypes. To delete an Similarly, there is no mechanism for deleting subtypes. A delete of a service deletes all of its subtypes. To delete an
individual subtype, an SRP Update must be constructed that contains t he service type and all subtypes for that service individual subtype, an SRP Update must be constructed that contains t he service type and all subtypes for that service
except for the one to be deleted. except for the one to be deleted.
</t> </t>
</section> </section>
<section> <section>
<name>SRP Update response</name> <name>SRP Update Response</name>
<t> <t>
The status that is returned depends on the result of processing the u The status that is returned depends on the result of processing the u
pdate, and can be either NoError, ServFail, Refused pdate and can be either NoError, ServFail, Refused,
or YXDomain: all other possible outcomes will already have been accou or YXDomain. All other possible outcomes will already have been accou
nted for when applying the constraints that nted for when applying the constraints that
qualify the update as an SRP Update. The meanings of these responses are explained in <xref target="RFC2136" qualify the update as an SRP Update. The meanings of these responses are explained in <xref target="RFC2136"
section="2.2"/>.</t> section="2.2"/>.</t>
<t> <t>
In the case of a response other than NoError, <xref target="RFC2136" section="3.8"/> specifies that the server is permitted In the case of a response other than NoError, <xref target="RFC2136" section="3.8"/> specifies that the server is permitted
to respond either with no RRs or to copy the RRs sent by the client into the response. The SRP Requestor MUST NOT attempt to respond either with no RRs or to copy the RRs sent by the client into the response. The SRP requestor <bcp14>MUST NOT</bcp14> attempt
to validate any RRs that are included in the response. It is possible that a future SRP extension may include per-RR to validate any RRs that are included in the response. It is possible that a future SRP extension may include per-RR
indications as to why the update failed, but at present this is not s indications as to why the update failed, but at the time of writing t
pecified, so if a client were to attempt to validate his is not specified. So, if a client were to attempt to validate
the RRs in the response, it might reject such a response, since it w the RRs in the response, it might reject such a response since it wo
ould contain RRs, but probably not a set of RRs uld contain RRs but probably not a set of RRs
identical to what was sent in the SRP Update.</t> identical to what was sent in the SRP Update.</t>
</section> </section>
<section> <section>
<name>Optional Behavior</name> <name>Optional Behavior</name>
<t> <t>
The SRP registrar MAY add a Reverse Mapping (<xref target="RFC1035" s The SRP registrar <bcp14>MAY</bcp14> add a Reverse Mapping (see <xref
ection="3.5"/>, <xref target="RFC3596" section="2.5"/>) target="RFC1035" section="3.5"/> and <xref target="RFC3596" section="2.5"/>)
that corresponds to the Host Description. This is not required becau that corresponds to the Host Description. This is not required becau
se the Reverse Mapping serves no protocol function, se the reverse mapping serves no protocol function,
but it may be useful for debugging, e.g. in annotating network packet but it may be useful for debugging, e.g., in annotating network packe
traces or logs. In order for the registrar to do t traces or logs. In order for the registrar to do
a reverse mapping update, it must be authoritative for the zone that a reverse mapping update, it must be authoritative for the zone that
would need to be updated, or have credentials to do would need to be updated or have credentials to do
the update. The SRP requestor MAY also do a reverse mapping update i the update. The SRP requestor <bcp14>MAY</bcp14> also do a reverse m
f it has credentials to do so.</t> apping update if it has credentials to do so.</t>
<t> <t>
The SRP registrar MAY apply additional criteria when accepting update The SRP registrar <bcp14>MAY</bcp14> apply additional criteria when a
s. In some networks, it may be possible to do ccepting updates. In some networks, it may be possible to do
out-of-band registration of keys, and only accept updates from pre-re out-of-band registration of keys and only accept updates from preregi
gistered keys. In this case, an update for a key stered keys. In this case, an update for a key
that has not been registered SHOULD be rejected with the Refused RCOD that has not been registered <bcp14>SHOULD</bcp14> be rejected with t
E.</t> he Refused RCODE.</t>
<t> <t>
There are at least two benefits to doing this rather than simply usin There are at least two benefits to doing this rather than simply using
g normal SIG(0) DNS updates. First, the same normal SIG(0) DNS updates:</t>
<ol><li>The same
registration protocol can be used in both cases, so both use cases ca n be addressed by the same SRP requestor registration protocol can be used in both cases, so both use cases ca n be addressed by the same SRP requestor
implementation. Second, the registration protocol includes maintenan implementation.</li>
ce functionality not present with normal DNS <li>The registration protocol includes maintenance functionality not
updates.</t> present with normal DNS
updates.</li></ol>
<t> <t>
Note that the semantics of using SRP in this way are different than f Note that the semantics of using SRP in this way are different than f
or typical RFC2136 implementations: the KEY used or typical implementations described in <xref target="RFC2136" format="default"/
to sign the SRP Update only allows the SRP requestor to update record >. The KEY used
s that refer to its Host Description. RFC2136 to sign the SRP Update only allows the SRP requestor to update record
implementations do not normally provide a way to enforce a constraint s that refer to its Host Description.
of this type.</t> Implementations specific to <xref target="RFC2136" format="default"/>
do not normally provide a way to enforce a constraint of this type.</t>
<t> <t>
The SRP registrar could also have a dictionary of names or name patte rns that are not permitted. If such a list is used, The SRP registrar could also have a dictionary of names or name patte rns that are not permitted. If such a list is used,
updates for Service Instance Names that match entries in the dictiona ry are rejected with a Refused RCODE.</t> updates for Service Instance Names that match entries in the dictiona ry are rejected with a Refused RCODE.</t>
</section> </section>
</section> </section>
</section> </section>
<section> <section>
<name>TTL Consistency</name> <name>TTL Consistency</name>
<t> <t>
All RRs within an RRset are required to have the same TTL All RRs within an RRset are required to have the same TTL
(<xref target="RFC2181" section="5.2" sectionFormat="comma"> Clarificatio ns to the DNS Specification</xref>). (see <xref target="RFC2181" section="5.2" sectionFormat="of"/>).
In order to avoid inconsistencies, SRP places restrictions on TTLs sent b y requestors and requires that SRP registrars enforce In order to avoid inconsistencies, SRP places restrictions on TTLs sent b y requestors and requires that SRP registrars enforce
consistency.</t> consistency.</t>
<t> <t>
Requestors sending SRP Updates MUST use consistent TTLs in all RRs within the SRP Update.</t> Requestors sending SRP Updates <bcp14>MUST</bcp14> use consistent TTLs in all RRs within the SRP Update.</t>
<t> <t>
SRP registrars MUST check that the TTLs for all RRs within the SRP Update SRP registrars <bcp14>MUST</bcp14> check that the TTLs for all RRs within
are the same. If they are not, the SRP the SRP Update are the same. If they are not, the SRP
update MUST be rejected with a Refused RCODE.</t> update <bcp14>MUST</bcp14> be rejected with a Refused RCODE.</t>
<t> <t>
Additionally, when adding RRs to an RRset, for example when processing Se rvice Discovery records, the SRP registrar MUST use the Additionally, when adding RRs to an RRset (for example, when processing S ervice Discovery records), the SRP registrar <bcp14>MUST</bcp14> use the
same TTL on all RRs in the RRset. How this consistency is enforced is up to the implementation.</t> same TTL on all RRs in the RRset. How this consistency is enforced is up to the implementation.</t>
<t> <t>
TTLs sent in SRP Updates are advisory: they indicate the SRP requestor's guess as to what a good TTL would be. SRP registrars may TTLs sent in SRP Updates are advisory: they indicate the SRP requestor's guess as to what a good TTL would be. SRP registrars may
override these TTLs. SRP registrars SHOULD ensure that TTLs are reasonab le: neither too long nor too short. The TTL SHOULD NOT override these TTLs. SRP registrars <bcp14>SHOULD</bcp14> ensure that TT Ls are reasonable: neither too long nor too short. The TTL <bcp14>SHOULD NOT</b cp14>
ever be longer than the lease time (<xref target="stale"/>). Shorter TTL s will result in more frequent data refreshes; ever be longer than the lease time (<xref target="stale"/>). Shorter TTL s will result in more frequent data refreshes;
this increases latency on the DNS-SD client side, increases load on any c aching resolvers and on the authoritative server, this increases latency on the DNS-SD client side, increases load on any c aching resolvers and on the authoritative server,
and also increases network load, which may be an issue for constrained ne tworks. Longer TTLs will increase the likelihood and also increases network load, which may be an issue for constrained ne tworks. Longer TTLs will increase the likelihood
that data in caches will be stale. TTL minimums and maximums SHOULD be c onfigurable by the operator of the SRP registrar. that data in caches will be stale. TTL minimums and maximums <bcp14>SHOU LD</bcp14> be configurable by the operator of the SRP registrar.
</t> </t>
</section> </section>
<section anchor="maintenance"> <section anchor="maintenance">
<name>Maintenance</name> <name>Maintenance</name>
<section anchor="stale"> <section anchor="stale">
<name>Cleaning up stale data</name> <name>Cleaning Up Stale Data</name>
<t>Because the DNS&nbhy;SD registration protocol is automatic, and not ma <t>Because the DNS-SD registration protocol is automatic and not managed
naged by humans, by humans,
some additional bookkeeping is required. When an update is constructe d by the SRP requestor, some additional bookkeeping is required. When an update is constructe d by the SRP requestor,
it MUST include an EDNS(0) Update Lease Option <xref target="I-D.ietf- dnssd-update-lease"/>. it <bcp14>MUST</bcp14> include an EDNS(0) Update Lease Option (see <xr ef target="RFC9664"/>).
The Update Lease Option contains two lease times: the Lease Time and t he KEY The Update Lease Option contains two lease times: the Lease Time and t he KEY
Lease Time.</t> Lease Time.</t>
<t>These leases are promises, similar to <xref target="RFC2131">DHCP leas <t>Similar to DHCP leases (see <xref target="RFC2131"></xref>), these lea
es</xref>, ses are promises from the SRP requestor that it will send a new update for the s
from the SRP requestor that it will send a new update for the service ervice registration before the
registration before the
lease time expires. The Lease time is chosen to represent the time af ter the lease time expires. The Lease time is chosen to represent the time af ter the
update during which the registered records other than the KEY record c an be assumed update during which the registered records other than the KEY record c an be assumed
to be valid. The KEY lease time represents the time after the update during to be valid. The KEY lease time represents the time after the update during
which the KEY record can be assumed to be valid.</t> which the KEY record can be assumed to be valid.</t>
<t>The reasoning behind the different lease times is discussed in the sec <t>The reasoning behind the different lease times is discussed in <xref t
tion on FCFS naming arget="fcfs" format="default"/>. SRP registrars may be configured with limits f
(<xref target="fcfs"/>). SRP registrars may be configured with limits or these values. At the time of writing, a default limit of two hours for
for these values. A default limit of two hours for the Lease and 14 days for the SIG(0) KEY are thought to be good choice
the Lease and 14 days for the SIG(0) KEY are currently thought to be g s. Constrained devices with limited
ood choices. Constrained devices with limited
battery that wake infrequently are likely to request longer leases; re gistrars that support such devices may need to set battery that wake infrequently are likely to request longer leases; re gistrars that support such devices may need to set
higher limits. SRP requestors that are going to continue to use names higher limits. SRP requestors that are going to continue to use names
on which they hold leases SHOULD update well before on which they hold leases <bcp14>SHOULD</bcp14> update well before
the lease ends, in case the registrar is unavailable or under heavy lo the lease ends in case the registrar is unavailable or under heavy loa
ad.</t> d.</t>
<t> <t>
The lease time applies specifically to the host. All service instances, and all service entries for such service The lease time applies specifically to the host. All service instances, and all service entries for such service
instances, depend on the host. When the lease on a host expires, the ho instances, depend on the host. When the lease on a host expires, the ho
st and all services that reference it MUST be st and all services that reference it <bcp14>MUST</bcp14> be
removed at the same time&mdash;it is never valid for a service instance removed at the same time: it is never valid for a service instance to r
to remain when the host it references has been emain when the host it references has been
removed. If the KEY record for the host is to remain, the KEY record fo removed. If the KEY record for the host is to remain, the KEY record fo
r any services that reference it MUST also r any services that reference it <bcp14>MUST</bcp14> also
remain. However, the service PTR record MUST be removed, since it has n remain. However, the service PTR record <bcp14>MUST</bcp14> be removed
o key associated with it, and since it is never since it has no key associated with it and since it is never
valid to have a service PTR record for which there is no service instan ce on the target of the PTR record. valid to have a service PTR record for which there is no service instan ce on the target of the PTR record.
</t> </t>
<t> <t>
SRP registrars MUST also track a lease time per service instance. The r SRP registrars <bcp14>MUST</bcp14> also track a lease time per service
eason for doing this is that a requestor may instance. The reason being that a requestor may
re-register a host with a different set of services, and not remember t re-register a host with a different set of services and not remember th
hat some different service instance had previously at some different service instance had previously
been registered. In this case, when that service instance lease expires been registered. In this case, when that service instance lease expires
, the SRP registrar MUST remove the service , the SRP registrar <bcp14>MUST</bcp14> remove the service
instance (although the KEY record for the service instance SHOULD be re instance (although the KEY record for the service instance <bcp14>SHOUL
tained until the KEY lease on that service D</bcp14> be retained until the KEY lease on that service
expires). This is beneficial because otherwise if the SRP requestor con expires). This is beneficial because, otherwise, if the SRP requestor c
tinues to renew the host, but never mentions the ontinues to renew the host but never mentions the
stale service again, the stale service will continue to be advertised. stale service again, the stale service will continue to be advertised.
</t> </t>
<t>The SRP registrar MUST include an EDNS(0) Update Lease option in the <t>The SRP registrar <bcp14>MUST</bcp14> include an EDNS(0) Update Lease option in the
response if the lease time proposed by the requestor has been shortene d or lengthened by the registrar. The requestor response if the lease time proposed by the requestor has been shortene d or lengthened by the registrar. The requestor
MUST check for the EDNS(0) Update Lease option in the response and MUS T use the lease <bcp14>MUST</bcp14> check for the EDNS(0) Update Lease option in the r esponse and <bcp14>MUST</bcp14> use the lease
times from that option in place of the options that it sent to the reg istrar when times from that option in place of the options that it sent to the reg istrar when
deciding when to renew its registration. The times may be shorter or longer than deciding when to renew its registration. The times may be shorter or longer than
those specified in the SRP Update; the SRP requestor must honor them i n either case.</t> those specified in the SRP Update: the SRP requestor must honor them i n either case.</t>
<t>SRP requestors SHOULD assume that each lease ends N seconds after the <!-- [rfced] In Section 5.1, we see both "N" and "'n'". Please review
update was first and let us know if/how we may update for uniformity.
transmitted, where N is the lease duration. SRP Registrars SHOULD ass
ume that each lease
ends N seconds after the update that was successfully processed was re
ceived. Because
the registrar will always receive the update after the SRP requestor s
ent it, this avoids the
possibility of misunderstandings.</t>
<t>SRP registrars MUST reject updates that do not include an Original "N":
EDNS(0) Update Lease option. DNS authoritative servers that allow bot SRP requestors SHOULD assume that each lease ends N seconds after the
h SRP and non-SRP DNS updates MAY accept updates that don't include update was first transmitted, where N is the lease duration.
leases, but SHOULD differentiate between SRP Updates and
other updates, and MUST reject updates that would otherwise be SRP Upd
ates
if they do not include leases.</t>
<t>Lease times have a completely different function than TTLs. On an aut Original "'n'":
horitative The lease time is never sent as a TTL; its
DNS server, the TTL on a resource record is a constant: whenever that sole purpose is to determine when the authoritative DNS server will
RR is served in delete stale records. It is not an error to send a DNS response with
a DNS response, the TTL value sent in the answer is the same. The lea a TTL of 'n' when the remaining time on the lease is less than 'n'.
se time is never -->
sent as a TTL; its sole purpose is to determine when the authoritative
DNS server will <t>SRP requestors <bcp14>SHOULD</bcp14> assume that each lease ends N
delete stale records. It is not an error to send a DNS response with seconds after the update was first transmitted (where N is the lease
a TTL of 'n' when duration). SRP registrars <bcp14>SHOULD</bcp14> assume that each lease
the remaining time on the lease is less than 'n'.</t> ends N seconds after the update that was successfully processed was
received. Because the registrar will always receive the update after
the SRP requestor sent it, this avoids the possibility of
misunderstandings.</t>
<t>SRP registrars <bcp14>MUST</bcp14> reject updates that do not
include an EDNS(0) Update Lease option. DNS authoritative servers
that allow both SRP and non-SRP DNS updates <bcp14>MAY</bcp14> accept
updates that don't include leases, but they <bcp14>SHOULD</bcp14>
differentiate between SRP Updates and other updates and
<bcp14>MUST</bcp14> reject updates that would otherwise be SRP Updates
if they do not include leases.</t>
<t>Lease times have a completely different function than TTLs. On an
authoritative DNS server, the TTL on a resource record is a
constant. Whenever that RR is served in a DNS response, the TTL value
sent in the answer is the same. The lease time is never sent as a
TTL; its sole purpose is to determine when the authoritative DNS
server will delete stale records. It is not an error to send a DNS
response with a TTL of 'n' when the remaining time on the lease is
less than 'n'.</t>
</section> </section>
</section> </section>
<section> <section>
<name>Security Considerations</name> <name>Security Considerations</name>
<section anchor="source_validation"> <section anchor="source_validation">
<name>Source Validation</name> <name>Source Validation</name>
<t>SRP Updates have no authorization semantics other than <t>SRP Updates have no authorization semantics other than
FCFS. This means that if an attacker from outside of the administrati FCFS. Thus, if an attacker from outside the administrative
ve domain of the SRP registrar knows the registrar's IP address, it can, i
domain of the SRP registrar knows the registrar's IP address, it can in n principle, send updates to the registrar
principle send updates to the registrar that will be processed successfully. Therefore, SRP registrars <bcp14
that will be processed successfully. SRP Registrars SHOULD therefore >SHOULD</bcp14> be configured to reject updates
be configured to reject updates
from source addresses outside of the administrative domain of the regis trar.</t> from source addresses outside of the administrative domain of the regis trar.</t>
<t>For TCP updates, the initial SYN-SYN+ACK handshake prevents updates be ing forged by an off-network attacker. In order to <t>For TCP updates, the initial SYN-SYN+ACK handshake prevents updates be ing forged by an off-network attacker. In order to
ensure that this handshake happens, SRP registrars relying on three-way ensure that this handshake happens, SRP registrars relying on three-way
-handshake validation MUST NOT accept TCP Fast Open -handshake validation <bcp14>MUST NOT</bcp14> accept TCP Fast Open payloads
<xref target="RFC7413"/> payloads. If the network infrastructure allow (see <xref target="RFC7413"/>). If the network infrastructure allows i
s it, an SRP registrar MAY accept TCP Fast Open payloads if all such packets t, an SRP registrar <bcp14>MAY</bcp14> accept TCP Fast Open payloads if all such
packets
are validated along the path, and the network is able to reject this ty pe of spoofing at all ingress points.</t> are validated along the path, and the network is able to reject this ty pe of spoofing at all ingress points.</t>
<t>For UDP updates from constrained devices, spoofing would have to be pr evented with appropriate source address filtration <t>For UDP updates from constrained devices, spoofing would have to be pr evented with appropriate source address filtration
on routers <xref target="RFC2827"/>. This would ordinarily be accomplis on routers (<xref target="RFC2827"/>). This would ordinarily be accompl
hed by measures such as are described in ished by measures such as those described in
<xref target="RFC7084" section="4.5" sectionFormat="of"/>. For example, (<xref target="RFC7084" section="4.5" sectionFormat="of"/>). For exampl
a stub router <xref target="I-D.ietf-snac-simple"/> e, a stub router (<xref target="I-D.ietf-snac-simple"/>)
for a constrained network might only accept UDP updates from source add for a constrained network might only accept UDP updates from source add
resses known to be on-link on that stub network, and might resses known to be on-link on that stub network and might
further validate that the UDP update was actually received on the stub network interface and not the interface connected to further validate that the UDP update was actually received on the stub network interface and not the interface connected to
the adjacent infrastructure link.</t> the adjacent infrastructure link.</t>
</section> </section>
<section> <section>
<name>Other DNS updates</name> <name>Other DNS Updates</name>
<t>Note that these rules only apply to the validation of SRP Updates. <t>Note that these rules only apply to the validation of SRP Updates.
A server that accepts updates from SRP A server that accepts updates from SRP
requestors may also accept other DNS updates, and those DNS updates may be validated requestors may also accept other DNS updates, and those DNS updates may be validated
using different rules. However, in the case of a DNS server that acce pts SRP using different rules. However, in the case of a DNS server that acce pts SRP
updates, the intersection of the SRP Update rules and updates, the intersection of the SRP Update rules and
whatever other update rules are present must be considered very careful ly.</t> whatever other update rules are present must be considered very careful ly.</t>
<t>For example, a normal, authenticated DNS update to any RR that was add <t>For example, a normal authenticated DNS update to any RR that was adde
ed using SRP, but that is authenticated using a d using SRP, but that is authenticated using a
different key, could be used to override a promise made by the SRP regi different key, could be used to override a promise made by the SRP regi
strar to an SRP requestor, by replacing all or part of strar to an SRP requestor by replacing all or part of
the service registration information with information provided by an au thenticated DNS update requestor. An implementation the service registration information with information provided by an au thenticated DNS update requestor. An implementation
that allows both kinds of updates SHOULD NOT allow DNS Update requestor s that are using different authentication and that allows both kinds of updates <bcp14>SHOULD NOT</bcp14> allow DNS U pdate requestors that are using different authentication and
authorization credentials to update records added by SRP requestors.</t > authorization credentials to update records added by SRP requestors.</t >
</section> </section>
<section> <section>
<name>Risks of allowing arbitrary names to be registered in SRP updates</ name> <name>Risks of Allowing Arbitrary Names to be Registered in SRP Updates</ name>
<t>It is possible to set up SRP updates for a zone that is used for non-D NSSD services. For example, imagine that you set <t>It is possible to set up SRP updates for a zone that is used for non-D NSSD services. For example, imagine that you set
up SRP service for example.com. SRP hosts can now register names like " www" or "mail" or "smtp" in this domain. In addition, up SRP service for example.com. SRP hosts can now register names like " www" or "mail" or "smtp" in this domain. In addition,
SRP updates using FCFS naming can insert names that are obscene or offe nsive into the zone. There is no simple solution to SRP updates using FCFS naming can insert names that are obscene or offe nsive into the zone. There is no simple solution to
these problems. We have two recommendations to address this problem, ho these problems. However, we have two recommendations to address this pr
wever:</t> oblem:</t>
<ul spacing="compact"> <ul spacing="normal">
<li>Do not provide SRP service in organization-level zones. Use subdoma <li>Do not provide SRP service in organization-level zones. Use subdoma
ins of the organizational domain for DNS service ins of the organizational domain for DNS-SD. This does not prevent registering
discovery. This does not prevent registering names as mentioned abov names as mentioned above but does ensure that genuinely important names
e, but does ensure that genuinely important names are not accidentally reserved for SRP clients. So, for example, the z
are not accidentally reserved for SRP clients. So for example, the zo one "dnssd.example.com" could be used instead of
ne "dnssd.example.com" could be used instead of "example.com" for SRP updates. Because of the way that DNS-browsing d
"example.com" for SRP updates. Because of the way that DNS browsing d omains are discovered, there is no need for the
omains are discovered, there is no need for the DNSSD discovery zone that is updated by SRP to have a user-friendly or
DNSSD discovery zone that is updated by SRP to have a user-friendly o important-sounding name.</li>
r important-sounding name.</li>
<li>Configure a dictionary of names that are prohibited. Dictionaries o f common obscene and offensive names are no doubt <li>Configure a dictionary of names that are prohibited. Dictionaries o f common obscene and offensive names are no doubt
available, and can be augmented with a list of typical "special" name available and can be augmented with a list of typical "special" names
s like "www", "mail", "smtp" and so on. Lists of like "www", "mail", "smtp", and so on. Lists of
names are generally available, or can be constructed manually.</li> names are generally available or can be constructed manually.</li>
</ul> </ul>
</section> </section>
<section> <section>
<name>Security of local service discovery</name> <name>Security of Local Service Discovery</name>
<t>Local links can be protected by managed services such as RA Guard <xre <t>Local links can be protected by managed services such as Router Advert
f target="RFC6105"/>, but multicast services like isement Guard (see <xref target="RFC6105"/>), but multicast services like
DHCP <xref target="RFC2131"/>, DHCPv6 <xref target="RFC8415"/> and IPv6 DHCP, DHCPv6, and IPv6 Neighbor Discovery (see <xref target="RFC2131"/>
Neighbor Discovery <xref target="RFC4861"/> are , <xref target="RFC8415"/>, and <xref target="RFC4861"/>, respectively) are,
in most cases not authenticated and can't be controlled on unmanaged ne in most cases, not authenticated and can't be controlled on unmanaged n
tworks, such as home networks and small-office etworks, such as home networks and small office
networks where no network management staff are present. In such situati ons, the SRP service has comparatively fewer networks where no network management staff are present. In such situati ons, the SRP service has comparatively fewer
potential security exposures and hence is not the weak link. This is di scussed in more detail in potential security exposures and, hence, is not the weak link. This is discussed in more detail in
<xref target="how-to-secure"/>.</t> <xref target="how-to-secure"/>.</t>
<t>The fundamental protection for networks of this type is the user's cho ice of what devices to add to the network. Work is <t>The fundamental protection for networks of this type is the user's cho ice of what devices to add to the network. Work is
being done in other working groups and standards bodies to improve the state of the art for network on-boarding and device being done in other working groups and standards bodies to improve the state of the art for network on-boarding and device
isolation (e.g., <xref target="RFC8520"/> provides a means for constrai ning what behaviors are allowed for a device in an isolation (e.g., <xref target="RFC8520"/> provides a means for constrai ning what behaviors are allowed for a device in an
automatic way), but such work is out of scope for this document.</t> automatic way), but such work is out of scope for this document.</t>
</section> </section>
<section> <section>
<name>SRP Registrar Authentication</name> <name>SRP Registrar Authentication</name>
<t>This specification does not provide a mechanism for validating respons es from SRP Registrars to <t>This specification does not provide a mechanism for validating respons es from SRP registrars to
SRP requestors. In principle, a KEY RR could be used by SRP requestors. In principle, a KEY RR could be used by
a non-constrained SRP requestor to validate responses from the registra r, but this is not required, a non-constrained SRP requestor to validate responses from the registra r, but this is not required,
nor do we specify a mechanism for determining which key to use.</t> nor do we specify a mechanism for determining which key to use.</t>
<t>In addition, for DNS-over-TLS connections, out-of-band key pinning as described in <t>In addition, for DNS-over-TLS connections, out-of-band key pinning as described in
<xref target="RFC7858" section="4.2" sectionFormat="comma"/> could be u <xref target="RFC7858" section="4.2" sectionFormat="of"/> could be used
sed for authentication of the SRP registrar, for authentication of the SRP registrar,
e.g. to prevent man-in-the-middle attacks. However the use of such keys e.g., to prevent man-in-the-middle attacks. However, the use of such ke
is impractical for an unmanaged service ys is impractical for an unmanaged service
registration protocol, and hence is out of scope for this document.</t> registration protocol; hence, it is out of scope for this document.</t>
</section> </section>
<section anchor="rsa"> <section anchor="rsa">
<name>Required Signature Algorithm</name> <name>Required Signature Algorithm</name>
<t> <t>
For validation, SRP registrars MUST implement the ECDSAP256SHA256 signa For validation, SRP registrars <bcp14>MUST</bcp14> implement the ECDSAP
ture algorithm. SRP registrars SHOULD implement the 256SHA256 signature algorithm. SRP registrars <bcp14>SHOULD</bcp14> implement t
algorithms specified in <xref target="RFC8624" section="3.1" sectionFor he
mat="comma"/>, in the validation column of the algorithms that are specified in <xref target="RFC8624" section="3.1" s
table, that are numbered 13 or higher and have a "MUST", "RECOMMENDED", ectionFormat="of"/>, in the validation column of the
or "MAY" designation in the validation column of table, that are numbered 13 or higher, and that have a "<bcp14>MUST</bc
p14>", "<bcp14>RECOMMENDED</bcp14>", or "<bcp14>MAY</bcp14>" designation in the
validation column of
the table. the table.
SRP requestors MUST NOT assume that any algorithm numbered lower than 1 3 is SRP requestors <bcp14>MUST NOT</bcp14> assume that any algorithm number ed lower than 13 is
available for use in validating SIG(0) signatures.</t> available for use in validating SIG(0) signatures.</t>
</section> </section>
</section> </section>
<section> <section>
<name>Privacy Considerations</name> <name>Privacy Considerations</name>
<t> <t>
Because DNS-SD SRP Updates can be sent off-link, the privacy implications Because DNS-SD SRP Updates can be sent off-link, the privacy implications
of SRP are different than for multicast DNS of SRP are different than for mDNS
responses. Host implementations that are using TCP SHOULD also use TLS i responses. Host implementations that are using TCP <bcp14>SHOULD</bcp14>
f available. SRP Registrar implementations MUST offer also use TLS if available. SRP registrar implementations <bcp14>MUST</bcp14> o
ffer
TLS support. The use of TLS with DNS is described in <xref target="RFC78 58"/>. Because there is no mechanism for sharing TLS support. The use of TLS with DNS is described in <xref target="RFC78 58"/>. Because there is no mechanism for sharing
keys, validation of DNS-over-TLS keys is not possible; DNS-over-TLS is us ed only as described in keys, validation of DNS-over-TLS keys is not possible; DNS-over-TLS is us ed only as described in
<xref target="RFC7858" section="4.1" sectionFormat="comma"/> <xref target="RFC7858" section="4.1" sectionFormat="of"/>.
</t> </t>
<t> <t>
Hosts that implement TLS support SHOULD NOT fall back to TCP; since SRP r egistrars are required to support Hosts that implement TLS support <bcp14>SHOULD NOT</bcp14> fall back to T CP. Since SRP registrars are required to support
TLS, it is entirely up to the host implementation whether to use it. TLS, it is entirely up to the host implementation whether to use it.
</t> </t>
<t> <t>
Public keys can be used as identifiers to track hosts. SRP registrars MAY elect not to return KEY records for queries for Public keys can be used as identifiers to track hosts. SRP registrars <bc p14>MAY</bcp14> elect not to return KEY records for queries for
SRP registrations. To avoid DNSSEC validation failures, an SRP registrar that signs the zone for DNSSEC but refuses to return SRP registrations. To avoid DNSSEC validation failures, an SRP registrar that signs the zone for DNSSEC but refuses to return
a KEY record MUST NOT store the KEY record in the zone itself. Because th a KEY record <bcp14>MUST NOT</bcp14> store the KEY record in the zone its
e KEY record isn't in the zone, the nonexistance of elf. Because the KEY record isn't in the zone, the nonexistence of
the KEY record can be validated. If the zone is not signed, the server MA the KEY record can be validated. If the zone is not signed, the server <b
Y instead return a negative non-error response cp14>MAY</bcp14> instead return a negative non-error response
(either NXDOMAIN or no data). (either NXDOMAIN or no data).
</t> </t>
</section> </section>
<section> <section>
<name>Domain Name Reservation Considerations</name> <name>Domain Name Reservation Considerations</name>
<t>This section specifies considerations for systems involved in domain na me resolution when resolving queries for names <t>This section specifies considerations for systems involved in domain na me resolution when resolving queries for names
ending with '.service.arpa.'. Each item in this section addresses some a ending with ".service.arpa.". Each item in this section addresses some a
spect of the DNS or the process of resolving domain spect of the DNS or the process of resolving domain
names that would be affected by this special-use allocation. Detailed ex names that would be affected by this special-use allocation. Detailed ex
planations of these items can be found in Section 5 planations of these items can be found in <xref target="RFC6761" sectionFormat="
of <xref target="RFC6761"/>.</t> of" section="5"/>.</t>
<section> <section>
<name>Users</name> <name>Users</name>
<t>The current proposed use for 'service.arpa' does not require special k <t>The current proposed use for "service.arpa" does not require special k
nowledge on the part of the user. While the nowledge on the part of the user. While the
'default.service.arpa.' subdomain is used as a generic name for registr "default.service.arpa." subdomain is used as a generic name for registr
ation, users are not expected to see this name in ation, users are not expected to see this name in
user interfaces. In the event that it does show up in a user interface, user interfaces. In the event that it does show up in a user interface,
it is just a domain name, and requires no special it is just a domain name and requires no special
treatment by the user. Users are not expected to see this name in user interfaces, although it's certainly possible that treatment by the user. Users are not expected to see this name in user interfaces, although it's certainly possible that
they might. If they do, they are not expected to treat it specially.</t > they might. If they do, they are not expected to treat it specially.</t >
</section> </section>
<section> <section>
<name>Application Software</name> <name>Application Software</name>
<t> <t>
Application software does not need to handle subdomains of 'service.arp Application software does not need to handle subdomains of "service.arp
a' specially. 'service.arpa' SHOULD NOT be treated a" specially. "service.arpa" <bcp14>SHOULD NOT</bcp14> be treated
as more trustworthy than any other insecure DNS domain, simply because as more trustworthy than any other insecure DNS domain, simply because
it is locally-served (or for any other reason). It it is locally served (or for any other reason). It
is not possible to register a PKI certificate for a subdomain of 'servi is not possible to register a PKI certificate for a subdomain of "servi
ce.arpa.' because it is a locally-served domain ce.arpa." because it is a locally served domain
name. So no such subdomain can be considered as uniquely identifying a name. So, no such subdomain can be considered to be uniquely identifyin
particular host, as would be required for such a g a particular host, as would be required for such a
PKI cert to be issued. If a subdomain of 'service.arpa.' is returned by PKI certificate to be issued. If a subdomain of "service.arpa." is retu
an API or entered in an input field of an rned by an API or entered in an input field of an
application, PKI authentication of the endpoint being identified by the name will not be possible. Alternative methods application, PKI authentication of the endpoint being identified by the name will not be possible. Alternative methods
and practices for authenticating such endpoints are out of scope for th is document.</t> and practices for authenticating such endpoints are out of scope for th is document.</t>
</section> </section>
<section> <section>
<name>Name Resolution APIs and Libraries</name> <name>Name Resolution APIs and Libraries</name>
<t>Name resolution APIs and libraries MUST NOT recognize names that end i n '.service.arpa.' as special and MUST NOT treat <t>Name resolution APIs and libraries <bcp14>MUST NOT</bcp14> recognize n ames that end in "service.arpa." as special and <bcp14>MUST NOT</bcp14> treat
them as having special significance, except that it may be necessary th at such APIs not bypass the locally configured them as having special significance, except that it may be necessary th at such APIs not bypass the locally configured
recursive resolvers.</t> recursive resolvers.</t>
<t>One or more IP addresses for recursive DNS servers will usually be sup plied to the client through router advertisements <t>One or more IP addresses for recursive DNS servers will usually be sup plied to the client through router advertisements
or DHCP. For an administrative domain that uses subdomains of 'service or DHCP. For an administrative domain that uses subdomains of "service
.arpa.', the recursive resolvers provided by that .arpa.", the recursive resolvers provided by that
domain will be able to answer queries for subdomains of 'service.arpa.' domain will be able to answer queries for subdomains of "service.arpa."
; other (non-local) resolvers will not, or they . Other (non-local) resolvers will not, or they
will provide answers that are not correct within that administrative do main.</t> will provide answers that are not correct within that administrative do main.</t>
<t>A host that is configured to use a resolver other than one that has be <t>A host that is configured to use a resolver other than one that has be
en provided by the local network may be unable to en provided by the local network may not be able to
resolve, or may receive incorrect results for, subdomains of 'service.a resolve or may receive incorrect results for subdomains of "service.arp
rpa.'. In order to avoid this, it is permissible a.". In order to avoid this, it is permissible
that hosts use the resolvers that are locally provided for resolving 's that hosts use the resolvers that are locally provided for resolving "s
ervice.arpa.', even when they are configured to ervice.arpa.", even when they are configured to
use other resolvers.</t> use other resolvers.</t>
</section> </section>
<section> <section>
<name>Caching DNS Servers</name> <name>Caching DNS Servers</name>
<!-- [rfced] In the following text, before the two numbered points,
the text reads "There are three considerations". Should we update
"three" to "two", or is there another point that the text is
missing?
Current:
There are three considerations for caching DNS servers that follow
this specification:
1. For correctness, recursive resolvers at sites using
'service.arpa.' must, in practice, transparently support DNSSEC
queries: queries for DNSSEC records and queries with the DNSSEC
OK (DO) bit set (Section 3.2.1 of [RFC4035]). DNSSEC validation
is a Best Current Practice ([RFC9364]): although validation is not
required, a caching recursive resolver that does not validate
answers that can be validated may cache invalid data. In turn,
this would prevent validating stub resolvers from successfully
validating answers. Hence, as a practical matter, recursive
resolvers at sites using 'service.arpa' should do DNSSEC
validation.
2. Unless configured otherwise, recursive resolvers and DNS proxies
MUST behave as described in Locally Served Zones (Section 3 of
[RFC6303]). That is, queries for 'service.arpa.' and subdomains
of 'service.arpa.' MUST NOT be forwarded, with one important
exception: a query for a DS record with the DO bit set MUST
return the correct answer for that question, including correct
information in the authority section that proves that the record
is nonexistent.
So, for example, a query for the NS record for 'service.arpa.'
MUST NOT result in that query being forwarded to an upstream
cache nor to the authoritative DNS server for '.arpa.'. However,
as necessary to provide accurate authority information, a query
for the DS record MUST result in forwarding whatever queries are
necessary. Typically, this will just be a query for the DS
record since the necessary authority information will be included
in the authority section of the response if the DO bit is set.
-->
<t>There are three considerations for caching DNS servers that <t>There are three considerations for caching DNS servers that
follow this specification:</t> follow this specification:</t>
<ol>
<li>For correctness, recursive resolvers at sites using 'service.arpa.' <!--[rfced In the following, is the intention to talk about the
must in practice transparently support DNSSEC document status of RFC 9365 or to talk about the concept of
queries: queries for DNSSEC records and queries with the DNSSEC OK ( DNSSEC validation as being a best current practice in the general
DO) bit set (<xref target="RFC4035" section="3.2.1" sense?
sectionFormat="of"/>). DNSSEC validation is a Best Current Practice
<xref target="RFC9364"/>: although validation is Original:
not required, a caching recursive resolver that does not validate an DNSSEC validation is a Best Current Practice [RFC9364]:
swers that can be validated may cache invalid data.
This, in turn, would prevent validating stub resolvers from successf Perhaps A:
ully validating answers. Hence, as a practical "DNS Security Extensions (DNSSEC)" is a Best Current Practice
matter, recursive resolvers at sites using 'service.arpa' should do ([RFC9364]) that describes DNSSEC validation:
DNSSEC validation.</li>
Perhaps B:
DNSSEC (see [RFC9364]) validation is a best current practice:
-->
<ol spacing="normal">
<li>For correctness, recursive resolvers at sites using
'service.arpa.' must, in practice, transparently support DNSSEC
queries: queries for DNSSEC records and queries with the DNSSEC OK
(DO) bit set (<xref target="RFC4035" section="3.2.1"
sectionFormat="of"/>). DNSSEC validation is a Best Current Practice
(<xref target="RFC9364"/>): although validation is not required, a
caching recursive resolver that does not validate answers that can
be validated may cache invalid data. In turn, this would prevent
validating stub resolvers from successfully validating
answers. Hence, as a practical matter, recursive resolvers at sites
using "service.arpa" should do DNSSEC validation.</li>
<li> <li>
<t>Unless configured otherwise, recursive resolvers and DNS proxies M <t>Unless configured otherwise, recursive resolvers and DNS
UST behave as described in Locally Served Zones, proxies <bcp14>MUST</bcp14> behave as described in Locally Served
<xref target="RFC6303" section="3" sectionFormat="of"/>. That is, Zones (<xref target="RFC6303" section="3" sectionFormat="of"/>).
queries for 'service.arpa.' and subdomains of That is, queries for "service.arpa." and subdomains of
'service.arpa.' MUST NOT be forwarded, with one important exceptio "service.arpa." <bcp14>MUST NOT</bcp14> be forwarded, with one
n: a query for a DS record with the DO bit set MUST important exception: a query for a DS record with the DO bit set
return the correct answer for that question, including correct info <bcp14>MUST</bcp14> return the correct answer for that question,
rmation in the authority section that proves that including correct information in the authority section that proves
the record is nonexistent.</t> that the record is nonexistent.</t>
<t>So, for example, a query for the NS record for 'service.arpa.' M
UST NOT result in that query being forwarded to an <!--[rfced] Is this text redundant (with two uses of necessary)? Does our
upstream cache nor to the authoritative DNS server for '.arpa.'. H suggestion change your intended meaning?
owever, as necessary to provide accurate
authority information, a query for the DS record MUST result in for Original:
warding whatever queries are necessary; However, as necessary to provide accurate authority information, a
typically, this will just be a query for the DS record, since the n query for the DS record MUST result in forwarding whatever queries are
ecessary authority information will be included necessary; typically, ...
in the authority section of the response if the DO bit is set.</t>
Perhaps:
However, to provide accurate authority information, a
query for the DS record MUST result in forwarding whatever queries are
necessary.
-->
<t>So, for example, a query for the NS record for "service.arpa."
<bcp14>MUST NOT</bcp14> result in that query being forwarded to an
upstream cache nor to the authoritative DNS server for ".arpa.".
However, as necessary to provide accurate authority information, a
query for the DS record <bcp14>MUST</bcp14> result in forwarding
whatever queries are necessary. Typically, this will just be a
query for the DS record since the necessary authority information
will be included in the authority section of the response if the
DO bit is set.</t>
</li> </li>
</ol> </ol>
</section> </section>
<section> <section>
<name>Authoritative DNS Servers</name> <name>Authoritative DNS Servers</name>
<t>No special processing of 'service.arpa.' is required for authoritative <t>No special processing of "service.arpa." is required for authoritative
DNS server implementations. It is possible that an DNS server implementations. It is possible that an
authoritative DNS server might attempt to check the authoritative serve authoritative DNS server might attempt to check the authoritative serve
rs for 'service.arpa.' for a delegation beneath that rs for "service.arpa." for a delegation beneath that
name before answering authoritatively for such a delegated name. In su ch a case, because the name always has only local name before answering authoritatively for such a delegated name. In su ch a case, because the name always has only local
significance, there will be no such delegation in the 'service.arpa.' z significance, there will be no such delegation in the "service.arpa." z
one, and so the server would refuse to answer one; therefore, the server would refuse to answer
authoritatively for such a zone. A server that implements this sort of authoritatively for such a zone. A server that implements this sort of
check MUST be configurable so that either it does check <bcp14>MUST</bcp14> be configurable so that either it does
not do this check for the 'service.arpa.' domain or it ignores the resu not do this check for the "service.arpa." domain or it ignores the resu
lts of the check.</t> lts of the check.</t>
</section> </section>
<section> <section>
<!--[rfced] We are having trouble parsing this sentence. Is there text
missing?
Original:
The operator for the DNS servers authoritative for 'service.arpa.' in
the global DNS will configure any such servers as described in Section
9.
Perhaps:
The operator for the DNS servers that are authoritative for "service.arpa." in
the global DNS will configure any such servers as described in Section
9.
-->
<name>DNS Server Operators</name> <name>DNS Server Operators</name>
<t>DNS server operators MAY configure an authoritative server for 'servic <t>DNS server operators <bcp14>MAY</bcp14> configure an authoritative ser
e.arpa.' for use with SRP. The operator for the ver for "service.arpa." for use with SRP. The operator for the
DNS servers authoritative for 'service.arpa.' in the global DNS will co DNS servers authoritative for "service.arpa." in the global DNS will co
nfigure any such servers as described in nfigure any such servers as described in
<xref target="delegation"/>.</t> <xref target="delegation"/>.</t>
</section> </section>
<section> <section>
<name>DNS Registries/Registrars</name> <name>DNS Registries/Registrars</name>
<t>'service.arpa.' is a subdomain of the 'arpa' top-level domain, which i <t>"service.arpa." is a subdomain of the "arpa" top-level domain, which i
s operated by IANA under the authority of the s operated by IANA under the authority of the
Internet Architecture Board according to the rules established in [RFC3 Internet Architecture Board (IAB) according to the rules established in
172]. There are no other DNS registrars for <xref target="RFC3172" format="default"/>. There are no other DNS registrars f
'.arpa'.</t> or
".arpa".</t>
</section> </section>
</section> </section>
<section anchor="delegation"> <section anchor="delegation">
<name>Delegation of 'service.arpa.'</name> <name>Delegation of "service.arpa."</name>
<t>In order to be fully functional, the owner of the 'arpa.' zone must add <t>In order to be fully functional, the owner of the "arpa." zone must add
a delegation of 'service.arpa.' in the '.arpa.' a delegation of "service.arpa." in the ".arpa."
zone <xref target="RFC3172"/>. This delegation is to be set up as was don zone (see <xref target="RFC3172"/>). This delegation is to be set up as w
e for 'home.arpa', as a result of the as done for "home.arpa", as a result of the
specification in <xref target="RFC8375" section="7" sectionFormat="of"/>. This is currently the responsibility of the IAB specification in <xref target="RFC8375" section="7" sectionFormat="of"/>. This is currently the responsibility of the IAB
<xref target="IAB-ARPA"/></t> (see <xref target="IAB-ARPA"/>).</t>
</section> </section>
<section> <section>
<name>IANA Considerations</name> <name>IANA Considerations</name>
<section> <section>
<name>Registration and Delegation of 'service.arpa' as a Special-Use Doma
in Name</name> <!--[rfced] We have some questions about Section 10.1 in the IANA
<t>IANA is requested to record the domain name 'service.arpa.' in the Spe Considerations:
cial-Use Domain Names registry
<xref target="SUDN"/>. IANA is requested, with the approval of IAB, to a) We see the title of the section is related to the first paragraph
implement the delegation requested in only. May we move the second paragraph to its own subsection? If so,
please let us know how you would like the text to appear using
Old/New.
Original:
10.1. Registration and Delegation of 'service.arpa' as a Special-Use
Domain Name
IANA is requested to record the domain name 'service.arpa.' in the
Special-Use Domain Names registry [SUDN]. IANA is requested, with
the approval of IAB, to implement the delegation requested in
Section 9.
IANA is further requested to add a new entry to the "Transport-
Independent Locally-Served Zones" subregistry of the "Locally-Served
DNS Zones" registry [LSDZ]. The entry will be for the domain
'service.arpa.' with the description "DNS-SD Service Registration
Protocol Special-Use Domain", and listing this document as the
reference.
b) The first paragraph of Section 10.1 mentions Section 9, which
states:
Original:
9. Delegation of 'service.arpa.'
In order to be fully functional, the owner of the 'arpa.' zone must
add a delegation of 'service.arpa.' in the '.arpa.' zone [RFC3172].
This delegation is to be set up as was done for 'home.arpa', as a
result of the specification in Section 7 of [RFC8375]. This is
currently the responsibility of the IAB [IAB-ARPA]
Should Section 9 be updated as follows since this action has been
taken? Also, please review whether this information actually belongs
in the IANA section. If so, please let us know (using old/new) how to
update.
9. Delegation of "service.arpa."
The owner of the 'arpa.' zone, at the time of writing the IAB [IAB-ARPA],
has added a delegation of 'service.arpa.' in the '.arpa.' zone
[RFC3172], following the guidance provided in Section 7 of [RFC8375].
-->
<name>Registration and Delegation of "service.arpa" as a Special-Use Doma
in Name</name>
<t>IANA has recorded the domain name "service.arpa." in the "Special-Use
Domain Names" registry
(see <xref target="SUDN"/>). IANA has implemented the delegation reques
ted in
<xref target="delegation"/>.</t> <xref target="delegation"/>.</t>
<t>IANA is further requested to add a new entry to the "Transport-Indepen <t>IANA has also added a new entry to the "Transport-Independent Locally-
dent Locally-Served Zones" subregistry of Served Zones Registry" registry of
the "Locally-Served DNS Zones" registry <xref target="LSDZ"/>. The ent the "Locally-Served DNS Zones" group (see <xref target="LSDZ"/>). The
ry will be for the domain 'service.arpa.' with the entry is for the domain "SERVICE.ARPA" with the
description "DNS&nbhy;SD Service Registration Protocol Special-Use Doma description "DNS-SD Service Registration Protocol Special-Use Domain" a
in", listing this document as the reference.</t> nd lists this document as the reference.</t>
</section> </section>
<section anchor="subdomains"> <section anchor="subdomains">
<name>Subdomains of 'service.arpa.'</name> <name>Subdomains of "service.arpa."</name>
<t>This document only makes use of the 'default.service.arpa' subdomain o
f 'service.arpa.' Other subdomains are reserved for <t>This document only makes use of the "default.service.arpa" subdomain o
future use by DNS-SD or related work. The IANA is requested to create a f "service.arpa." Other subdomains are reserved for
registry, the "service.arpa Subdomain" registry. future use by DNS-SD or related work. IANA has created the "service.arp
The IETF shall have change control for this registry. New entries may b a Subdomain" registry (see <xref target="SUB"/>).
e added either as a result of Standards Action The IETF has change control for this registry. New entries may be added
<xref target="RFC8126" section="4.9"/> or with IESG approval <xref targ either as a result of Standards Action
et="RFC8126" section="4.10"/>, provided that a (<xref target="RFC8126" section="4.9" sectionFormat="of"/>) or with IES
specification exists <xref target="RFC8126" section="4.6"/>. G Approval (<xref target="RFC8126" section="4.10" sectionFormat="of"/>), provide
d that a
specification exists (<xref target="RFC8126" section="4.6"/>).
</t> </t>
<t> <t>
The IANA shall group the "service.arpa Subdomain" registry with the "Lo IANA has grouped the "service.arpa Subdomain" registry with the "Locall
cally-Served DNS Zones" registry. y-Served DNS Zones" group.
The registry shall be a table with three columns: the subdomain name ( The registry is a table with three columns: the subdomain name (expres
expressed as a fully-qualified domain sed as a fully qualified domain
name), a brief description of how it is used, and a reference to the do cument that describes its use in detail. name), a brief description of how it is used, and a reference to the do cument that describes its use in detail.
</t> </t>
<t> <t>
This registry shall begin as the following table: This initial contents of this registry are as follows:
</t> </t>
<table> <table>
<thead> <thead>
<tr> <tr>
<th>Subdomain Name</th> <th>Subdomain Name</th>
<th>Description</th> <th>Description</th>
<th>reference</th> <th>Reference</th>
</tr> </tr>
</thead> </thead>
<tbody> <tbody>
<tr> <tr>
<td>default.service.arpa.</td> <td>default.service.arpa.</td>
<td>Default domain for SRP updates</td> <td>Default domain for SRP updates</td>
<td>[THIS DOCUMENT]</td> <td>RFC 9665</td>
</tr> </tr>
</tbody> </tbody>
</table> </table>
</section> </section>
<section> <section>
<name>Service Name registrations</name> <name>Service Name Registrations</name>
<t>IANA is requested to add two new entries to the Service Names and Port <t>IANA has added two new entries to the "Service Name and Transport Prot
Numbers registry. The following sections ocol Port Number Registry" (see <xref target="PORT"/>). The following subsection
s
contain tables with the fields required by <xref target="RFC6335" secti on="8.1.1" sectionFormat="of"/>.</t> contain tables with the fields required by <xref target="RFC6335" secti on="8.1.1" sectionFormat="of"/>.</t>
</section>
<section> <section>
<name>'dnssd-srp' Service Name</name> <name>'dnssd-srp' Service Name</name>
<table> <table>
<thead><tr><td>Field Name</td><td>Value</td></tr></thead> <thead><tr><th>Field Name</th><th>Value</th></tr></thead>
<tbody> <tbody>
<tr><td> Service Name </td><td> dnssd-srp </td></tr> <tr><td> Service Name </td><td> dnssd-srp </td></tr>
<tr><td> Transport Protocol </td><td> TCP </td></tr> <tr><td> Transport Protocol </td><td> tcp </td></tr>
<tr><td> Assignee </td><td> IESG &lt;iesg@ietf.org&gt; </td></tr> <tr><td> Assignee </td><td> IESG &lt;iesg@ietf.org&gt; </td></tr>
<tr><td> Contact </td><td> IETF Chair &lt;chair@ietf.org &gt; </td></tr> <tr><td> Contact </td><td> IETF Chair &lt;chair@ietf.org &gt; </td></tr>
<tr><td> Description </td><td> DNS-SD Service Registration <tr><td> Description </td><td> DNS-SD Service Discovery
</td></tr> </td></tr>
<tr><td> Reference </td><td> this document <tr><td> Reference </td><td> RFC 9665
</td></tr> </td></tr>
<tr><td> Port Number </td><td> None </td></tr> <tr><td> Port Number </td><td> None </td></tr>
<tr><td> Service Code </td><td> None </td></tr> <tr><td> Service Code </td><td> None </td></tr>
</tbody> </tbody>
</table> </table>
</section> </section>
<section> <section>
<name>'dnssd-srp-tls' Service Name</name> <name>'dnssd-srp-tls' Service Name</name>
<table> <table>
<thead><tr><td>Field Name</td><td>Value</td></tr></thead> <thead><tr><th>Field Name</th><th>Value</th></tr></thead>
<tbody> <tbody>
<tr><td> Service Name </td><td> dnssd-srp-tls </td></tr> <tr><td> Service Name </td><td> dnssd-srp-tls </td></tr>
<tr><td> Transport Protocol </td><td> TCP <tr><td> Transport Protocol </td><td> tcp
</td></tr> </td></tr>
<tr><td> Assignee </td><td> IESG <tr><td> Assignee </td><td> IESG &lt;iesg@ietf.org&gt;
</td></tr> </td></tr>
<tr><td> Contact </td><td> IETF Chair <tr><td> Contact </td><td> IETF Chair&lt;chair@ietf.org&
</td></tr> gt; </td></tr>
<tr><td> Description </td><td> DNS-SD Service Registration ( <tr><td> Description </td><td> DNS-SD Service Discovery (TLS
TLS) </td></tr> ) </td></tr>
<tr><td> Reference </td><td> this document <tr><td> Reference </td><td> RFC 9665
</td></tr> </td></tr>
<tr><td> Port Number </td><td> None </td></tr> <tr><td> Port Number </td><td> None </td></tr>
<tr><td> Service Code </td><td> None </td></tr> <tr><td> Service Code </td><td> None </td></tr>
</tbody> </tbody>
</table> </table>
</section> </section>
</section>
<section> <section>
<name>Anycast Address</name> <name>Anycast Address</name>
<t>IANA is requested to allocate an IPv6 Anycast address from the IPv6 Sp <t>IANA has allocated an IPv6 Anycast address from the "IANA IPv6 Special
ecial-Purpose Address Registry, similar to the Port -Purpose Address Registry" (see <xref target="IPv6"/>), similar to the Port
Control Protocol anycast address, 2001:1::1. The value TBD is to be rep Control Protocol anycast address: 2001:1::1. The purpose of this alloca
laced with the actual allocation in the table that tion is to provide a fixed anycast address that can be commonly used as a destin
follows. The purpose of this allocation is to provide a fixed anycast a ation for
ddress that can be commonly used as a destination for SRP updates when no SRP registrar is explicitly configured. The initial
SRP updates when no SRP registrar is explicitly configured. The values values for the registry are as follows:</t>
for the registry are:</t>
<table> <table>
<thead> <thead>
<tr><td>Attribute</td> <td>value</td></tr> <tr><th>Attribute</th> <th>Value</th></tr>
</thead> </thead>
<tbody> <tbody>
<tr><td>Address Block</td> <td>2001:1::TBD/128</td></t r> <tr><td>Address Block</td> <td>2001:1::3/128</td></tr>
<tr><td>Name</td> <td>DNS-SD Service Registra tion Protocol Anycast Address</td></tr> <tr><td>Name</td> <td>DNS-SD Service Registra tion Protocol Anycast Address</td></tr>
<tr><td>RFC</td> <td>[this document]</td></t <tr><td>RFC</td> <td>RFC 9665</td></tr>
r> <tr><td>Allocation Date</td> <td>2024-04</td></tr>
<tr><td>Allocation Date</td> <td>[date of allocation]</t
d></tr>
<tr><td>Termination Date</td> <td>N/A</td></tr> <tr><td>Termination Date</td> <td>N/A</td></tr>
<tr><td>Source</td> <td>True</td></tr> <tr><td>Source</td> <td>True</td></tr>
<tr><td>Destination</td> <td>True</td></tr> <tr><td>Destination</td> <td>True</td></tr>
<tr><td>Forwardable</td> <td>True</td></tr> <tr><td>Forwardable</td> <td>True</td></tr>
<tr><td>Global</td> <td>True</td></tr> <tr><td>Globally Reachable</td> <td>True</td></
<tr><td>Reserved-by-protocol</td> <td>False</td></tr> tr>
<tr><td>Reserved-by-Protocol</td> <td>False</td></tr>
</tbody> </tbody>
</table> </table>
</section> </section>
</section> </section>
<section>
<name>Implementation Status</name>
<t>[Note to the RFC Editor: please remove this section prior to publicatio
n.]</t>
<t>
This section records the status of known implementations of the protocol
defined by this specification at the time of
posting of this Internet-Draft, and is based on a proposal described in R
FC 7942. The description of implementations in
this section is intended to assist the IETF in its decision processes in
progressing drafts to RFCs. Please note that the
listing of any individual implementation here does not imply endorsement
by the IETF. Furthermore, no effort has been spent
to verify the information presented here that was supplied by IETF contri
butors. This is not intended as, and must not be
construed to be, a catalog of available implementations or their features
. Readers are advised to note that other
implementations may exist.
</t>
<t>
According to RFC 7942, "this will allow reviewers and working groups to a
ssign due consideration to documents that have the
benefit of running code, which may serve as evidence of valuable experime
ntation and feedback that have made the implemented
protocols more mature. It is up to the individual working groups to use
this information as they see fit".
</t>
<t>
There are two known independent implementations of SRP requestors:
</t>
<ul>
<li>SRP Client for OpenThread: https://github.com/openthread/openthread/p
ull/6038</li>
<li>mDNSResponder open source project: https://github.com/Abhayakara/mdns
responder</li>
</ul>
<t>
There are two related implementations of an SRP registrar. One acts as a
DNS Update proxy, taking an SRP Update and applying it
to the specified DNS zone using DNS update. The other acts as an Advertis
ing Proxy
<xref target="I-D.ietf-dnssd-advertising-proxy"/>. Both are included in t
he mDNSResponder open source project mentioned above.
</t>
</section>
<section>
<name>Acknowledgments</name>
<t>Thanks to <contact fullname="Toke Høiland-Jørgensen"/>, Jonathan Hui, E
sko Dijk, Kangping Dong and Abtin Keshavarzian for
their thorough technical reviews. Thanks to Kangping and Abtin as well fo
r testing the document by doing an independent
implementation. Thanks to Tamara Kemper for doing a nice developmental ed
it, Tim Wattenberg for doing an SRP requestor
proof-of-concept implementation at the Montreal Hackathon at IETF 102, an
d Tom Pusateri for reviewing during the hackathon
and afterwards. Thanks to Esko for a really thorough second last call rev
iew. Thanks also to Nathan Dyck, Gabriel
Montenegro, Kangping Dong, Martin Turon, and Michael Cowan for their deta
iled second last call reviews. Thanks to Patrik
Fältström, Dhruv Dhody, David Dong, Joey Salazar, Jean-Michel Combes, and
Joerg Ott for their respective directorate
reviews. Thanks to Paul Wouters for a <em>really</em> detailed IESG revie
w! Thanks also to the other IESG members who
provided comments or simply took the time to review the document.</t>
</section>
</middle> </middle>
<back> <back>
<displayreference target="I-D.cheshire-dnssd-roadmap" to="ROADMAP"/> <displayreference target="I-D.cheshire-dnssd-roadmap" to="ROADMAP"/>
<displayreference target="I-D.ietf-dnssd-advertising-proxy" to="AP"/> <displayreference target="I-D.ietf-snac-simple" to="SNAC-SIMPLE"/>
<!-- <displayreference target="I-D.ietf-dnssd-hybrid" to="I-D.ietf-dnssd-hyb rid"/> appears to not work in xml2rfc 2.6.2 -->
<references> <references>
<name>References</name>
<references>
<name>Normative References</name> <name>Normative References</name>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-
D.ietf-dnssd-update-lease.xml"/> <!-- [I-D.ietf-dnssd-update-lease] companion document RFC 9664-->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <reference anchor="RFC9664" target="https://www.rfc-editor.org/info/rfc966
.1035.xml" /> 4">
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <front>
.1536.xml" /> <title>An EDNS(0) Option to Negotiate Leases on DNS Updates</title>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <author fullname="Stuart Cheshire" initials="S." surname="Cheshire">
.2119.xml" /> <organization>Apple Inc.</organization>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC </author>
.2136.xml" /> <author fullname="Ted Lemon" initials="T." surname="Lemon">
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <organization>Apple Inc</organization>
.2181.xml" /> </author>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <date month="October" year="2024"/>
.2539.xml" /> </front>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <seriesInfo name="RFC" value="9664"/>
.2782.xml" /> <seriesInfo name="DOI" value="10.17487/RFC9664"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC </reference>
.2931.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.103
.3172.xml"/> 5.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.153
.3445.xml"/> 6.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.211
.3596.xml"/> 9.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.213
.4035.xml"/> 6.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.218
.6303.xml"/> 1.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.253
.6763.xml"/> 9.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.278
.7858.xml" /> 2.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.293
.8085.xml" /> 1.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.317
.8126.xml"/> 2.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC
.8174.xml"/> <!-- [rfced] Normative reference RFC 3445 has been obsoleted by
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC RFC 4033. We will update to the latter unless we hear objection.
.8375.xml"/> -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC
.8624.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.344
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC 5.xml"/>
.8765.xml" /> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.359
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC 6.xml"/>
.9364.xml" /> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.403
5.xml"/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.630
3.xml"/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.676
3.xml"/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.785
8.xml" />
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.808
5.xml" />
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.812
6.xml"/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.817
4.xml"/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.837
5.xml"/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.862
4.xml"/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.876
5.xml" />
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.936
4.xml" />
</references> </references>
<references> <references>
<name>Informative References</name> <name>Informative References</name>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.213
.2131.xml" /> 1.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.282
.2827.xml" /> 7.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.300
.3007.xml" /> 7.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.486
.4861.xml" /> 1.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.610
.6105.xml" /> 5.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.633
.6335.xml" /> 5.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.676
.6760.xml" /> 0.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.676
.6761.xml" /> 1.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.676
.6762.xml" /> 2.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.708
.7084.xml" /> 4.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.722
.7228.xml" /> 8.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.741
.7413.xml" /> 3.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.841
.8415.xml" /> 5.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.852
.8520.xml" /> 0.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.876
.8766.xml" /> 6.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.894
.8945.xml" /> 5.xml" />
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-
D.cheshire-dnssd-roadmap.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-
D.ietf-dnssd-advertising-proxy.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-
D.ietf-snac-simple.xml"/>
<reference anchor="SUDN" target="https://www.iana.org/assignments/special- <!-- [I-D.cheshire-dnssd-roadmap] IESG state: Expired as of 07/15/24-->
use-domain-names/special-use-domain-names.xhtml"> <xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D.c
heshire-dnssd-roadmap.xml"/>
<!-- [I-D.ietf-snac-simple] IESG state: I-D Exists as of 07/15/24-->
<xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D.i
etf-snac-simple.xml"/>
<reference anchor="SUDN" target="https://www.iana.org/assignments/special-
use-domain-names">
<front> <front>
<title>Special-Use Domain Names Registry</title> <title>Special-Use Domain Names</title>
<author/> <author>
<date month="July" year="2012"/> <organization>IANA</organization>
</author>
</front> </front>
</reference> </reference>
<reference anchor="LSDZ" target="https://www.iana.org/assignments/locally- served-dns-zones/locally-served-dns-zones.xhtml"> <reference anchor="LSDZ" target="https://www.iana.org/assignments/locally- served-dns-zones">
<front> <front>
<title>Locally-Served DNS Zones Registry</title> <title>Locally-Served DNS Zones</title>
<author/> <author>
<date month="July" year="2011"/> <organization>IANA</organization>
</author>
</front>
</reference>
<reference anchor="SUB" target="https://www.iana.org/assignments/locally-s
erved-dns-zones/locally-served-dns-zones">
<front>
<title>service.arpa Subdomain</title>
<author>
<organization>IANA</organization>
</author>
</front>
</reference>
<reference anchor="PORT" target="https://www.iana.org/assignments/service-names-
port-numbers">
<front>
<title>Service Name and Transport Protocol Port Number Registry</title
>
<author>
<organization>IANA</organization>
</author>
</front>
</reference>
<reference anchor="IPv6" target="https://www.iana.org/assignments/iana-ipv
6-special-registry">
<front>
<title>IANA IPv6 Special-Purpose Address Registry</title>
<author>
<organization>IANA</organization>
</author>
</front> </front>
</reference> </reference>
<reference anchor="IAB-ARPA" target="https://www.iab.org/documents/corresp ondence-reports-documents/2017-2/iab-statement-on-the-registration-of-special-us e-names-in-the-arpa-domain/"> <reference anchor="IAB-ARPA" target="https://www.iab.org/documents/corresp ondence-reports-documents/2017-2/iab-statement-on-the-registration-of-special-us e-names-in-the-arpa-domain/">
<front> <front>
<title>Internet Architecture Board statement on the registration of sp ecial use names in the ARPA domain</title> <title>Internet Architecture Board statement on the registration of sp ecial use names in the ARPA domain</title>
<author/> <author/>
<date month="March" year="2017"/> <date month="March" year="2017"/>
</front> </front>
</reference> </reference>
<reference anchor="ZC"> <reference anchor="ZC">
<front> <front>
<title>Zero Configuration Networking: The Definitive Guide</title> <title>Zero Configuration Networking: The Definitive Guide</title>
<author initials="S." surname="Cheshire" fullname="Stuart Cheshire"/>
<author initials="D.H." surname="Steinberg" fullname="Daniel H. Steinb erg"/> <author initials="D.H." surname="Steinberg" fullname="Daniel H. Steinb erg"/>
<author initials="S." surname="Cheshire" fullname="Stuart Cheshire"/>
<date year="2005" month="December"/> <date year="2005" month="December"/>
</front> </front>
<seriesInfo name="O'Reilly Media, Inc." value=""/> <refcontent>O'Reilly Media, Inc.</refcontent>
<seriesInfo name="ISBN" value="0-596-10100-7"/> <seriesInfo name="ISBN" value="9780596101008"/>
</reference> </reference>
</references> </references>
</references>
<!--[rfced] Might this be an agreeable update to the title of
Appendix A (to avoid double -ing words in the beginning?)?
Original:
Appendix A. Testing Using Standard DNS Servers Compliant with RFC
2136
Perhaps:
Appendix A. Testing the Use of Standard DNS Servers Compliant with RFC
2136
Perhaps:
Appendix A. Testing Standard DNS Servers Compliant with RFC 2136
-->
<section> <section>
<name>Testing using standard RFC2136-compliant DNS servers</name> <name>Testing Using Standard DNS Servers Compliant with RFC 2136</name>
<t> <t>
It may be useful to set up an authoritative DNS server for testing that does not implement SRP. This can be done by configuring the It may be useful to set up an authoritative DNS server for testing that does not implement SRP. This can be done by configuring the
server to listen on the anycast address, or advertising it in the _dnssd &nbhy;srp._tcp.&lt;zone&gt; SRV and server to listen on the anycast address or by advertising it in the _dns sd&nbhy;srp._tcp.&lt;zone&gt; SRV and
_dnssd&nbhy;srp&nbhy;tls._tcp.&lt;zone&gt; record. It must be configure d to be authoritative for _dnssd&nbhy;srp&nbhy;tls._tcp.&lt;zone&gt; record. It must be configure d to be authoritative for
"default.service.arpa", and to accept updates from hosts on local networ "default.service.arpa" and to accept updates from hosts on local network
ks for names under "default.service.arpa" s for names under "default.service.arpa"
without authentication, since such servers will not have support for FCF without authentication since such servers will not have support for FCFS
S authentication (<xref target="fcfs"/>).</t> authentication (<xref target="fcfs"/>).</t>
<t> <t>
An authoritative DNS server configured in this way will be able to succe ssfully accept and process SRP Updates from requestors that send SRP An authoritative DNS server configured in this way will be able to succe ssfully accept and process SRP Updates from requestors that send SRP
updates. However, no prerequisites will be applied, and this means that updates. However, no prerequisites will be applied; this means that the
the test server will accept internally test server will accept internally
inconsistent SRP Updates, and will not stop two SRP Updates, sent by dif inconsistent SRP Updates and will not stop two SRP Updates sent by diffe
ferent services, that claim the same name(s), rent services that claim the same name or names
from overwriting each other.</t> from overwriting each other.</t>
<t> <t>
Since SRP Updates are signed with keys, validation of the SIG(0) algorit hm used by the requestor can be done by manually Since SRP Updates are signed with keys, validation of the SIG(0) algorit hm used by the requestor can be done by manually
installing the requestor's public key on the DNS server that will be rec eiving the updates. The key can then be used to installing the requestor's public key on the DNS server that will be rec eiving the updates. The key can then be used to
authenticate the SRP update, and can be used as a requirement for the up date. An example configuration for testing SRP authenticate the SRP update and can be used as a requirement for the upd ate. An example configuration for testing SRP
using BIND 9 is given in <xref target="bind-example"/>.</t> using BIND 9 is given in <xref target="bind-example"/>.</t>
</section> </section>
<section> <section>
<name>How to allow SRP requestors to update standard RFC2136-compliant ser vers</name> <name>How to Allow SRP Requestors to Update Standard Servers Compliant wit h RFC 2136</name>
<t> <t>
Ordinarily SRP Updates will fail when sent to an RFC 2136-compliant serv Ordinarily, SRP Updates will fail when sent to a server compliant with <
er that does not implement SRP because the zone xref target="RFC2136"/> that does not implement SRP because the zone
being updated is "default.service.arpa", and no DNS server that is not a being updated is "default.service.arpa" and because no DNS server that i
n SRP registrar would normally be configured to be s not an SRP registrar would normally be configured to be
authoritative for "default.service.arpa". Therefore, a requestor that s ends an SRP Update can tell that the receiving server authoritative for "default.service.arpa". Therefore, a requestor that s ends an SRP Update can tell that the receiving server
does not support SRP, but does support RFC2136, because the RCODE will e does not support SRP but does support <xref target="RFC2136"/> because t
ither be NotZone, NotAuth or Refused, or because he RCODE will either be NotZone, NotAuth, or Refused or because
there is no response to the update request (when using the anycast addre there is no response to the update request (when using the anycast addre
ss)</t> ss).</t>
<t> <t>
In this case a requestor MAY attempt to register itself using regular RF C2136 DNS updates. To do so, it must discover the In this case, a requestor <bcp14>MAY</bcp14> attempt to register itself using regular DNS updates described in <xref target="RFC2136"/>. To do so, it mu st discover the
default registration zone and the DNS server designated to receive updat es for that zone, as described earlier, using the default registration zone and the DNS server designated to receive updat es for that zone, as described earlier, using the
_dns&nbhy;update._udp SRV record. It can then send the update to the po rt and host pointed to by the SRV record, and is _dns&nbhy;update._udp SRV record. It can then send the update to the po rt and host pointed to by the SRV record, and it is
expected to use appropriate prerequisites to avoid overwriting competing records. Such updates are out of scope for SRP, expected to use appropriate prerequisites to avoid overwriting competing records. Such updates are out of scope for SRP,
and a requestor that implements SRP MUST first attempt to use SRP to reg and a requestor that implements SRP <bcp14>MUST</bcp14> first attempt to
ister itself, and only attempt to use RFC2136 use SRP to register itself and only attempt to use backwards capability with <x
backwards compatibility if that fails. Although the owner name for the ref target="RFC2136"/>
SRV record specifies the UDP protocol for updates, if that fails. Although the owner name for the SRV record specifies UDP
it is also possible to use TCP, and TCP SHOULD be required to prevent sp for updates,
oofing.</t> it is also possible to use TCP, and TCP <bcp14>SHOULD</bcp14> be require
d to prevent spoofing.</t>
</section> </section>
<section anchor="bind-example"> <section anchor="bind-example">
<name>Sample BIND9 configuration for default.service.arpa.</name> <name>Sample BIND9 Configuration for "default.service.arpa."</name>
<figure title="Zone Configuration in named.conf"><artwork><![CDATA[
<figure title="Zone Configuration in named.conf">
<artwork><![CDATA[
zone "default.service.arpa." { zone "default.service.arpa." {
type primary; type primary;
file "/etc/bind/primary/service.db"; file "/etc/bind/primary/service.db";
allow-update { key demo.default.service.arpa.; }; allow-update { key demo.default.service.arpa.; };
}; };]]></artwork>
]]></artwork></figure> </figure>
<figure title="Example Zone file"><artwork><![CDATA[
<figure title="Example Zone File">
<artwork><![CDATA[
$ORIGIN . $ORIGIN .
$TTL 57600 ; 16 hours $TTL 57600 ; 16 hours
default.service.arpa IN SOA ns3.default.service.arpa. default.service.arpa IN SOA ns3.default.service.arpa.
postmaster.default.service.arpa. ( postmaster.default.service.arpa. (
2951053287 ; serial 2951053287 ; serial
3600 ; refresh (1 hour) 3600 ; refresh (1 hour)
1800 ; retry (30 minutes) 1800 ; retry (30 minutes)
604800 ; expire (1 week) 604800 ; expire (1 week)
3600 ; minimum (1 hour) 3600 ; minimum (1 hour)
) )
skipping to change at line 1367 skipping to change at line 1739
$ORIGIN default.service.arpa. $ORIGIN default.service.arpa.
$TTL 300 ; 5 minutes $TTL 300 ; 5 minutes
ns3 AAAA 2001:db8:0:1::1 ns3 AAAA 2001:db8:0:1::1
$TTL 3600 ; 1 hour $TTL 3600 ; 1 hour
demo AAAA 2001:db8:0:2::1 demo AAAA 2001:db8:0:2::1
KEY 0 3 13 ( KEY 0 3 13 (
qweEmaaq0FAWok5//ftuQtZgiZoiFSUsm0srWREdywQU qweEmaaq0FAWok5//ftuQtZgiZoiFSUsm0srWREdywQU
9dpvtOhrdKWUuPT3uEFF5TZU6B4q1z1I662GdaUwqg== 9dpvtOhrdKWUuPT3uEFF5TZU6B4q1z1I662GdaUwqg==
); alg = ECDSAP256SHA256 ; key id = 15008 ); alg = ECDSAP256SHA256 ; key id = 15008
AAAA ::1 AAAA ::1
]]></artwork></figure> ]]></artwork>
</figure>
</section> </section>
<section numbered="false">
<name>Acknowledgments</name>
<t>Thanks to <contact fullname="Toke Høiland-Jørgensen"/>, <contact
fullname="Jonathan Hui"/>, <contact fullname="Esko Dijk"/>, <contact
fullname="Kangping Dong"/>, and <contact fullname="Abtin Keshavarzian"/>
for their thorough technical reviews. Thanks to <contact
fullname="Kangping"/> and <contact fullname="Abtin"/> as well for
testing the document by doing an independent implementation. Thanks to
<contact fullname="Tamara Kemper"/> for doing a nice developmental edit,
<contact fullname="Tim Wattenberg"/> for doing an SRP requestor
proof-of-concept implementation at the Montreal Hackathon at IETF 102,
and <contact fullname="Tom Pusateri"/> for reviewing during the
hackathon and afterwards. Thanks to <contact fullname="Esko"/> for a
really thorough second Last Call review. Thanks also to <contact
fullname="Nathan Dyck"/>, <contact fullname="Gabriel Montenegro"/>,
<contact fullname="Kangping Dong"/>, <contact fullname="Martin Turon"/>,
and <contact fullname="Michael Cowan"/> for their detailed second last
call reviews. Thanks to <contact fullname="Patrik Fältström"/>, <contact
fullname="Dhruv Dhody"/>, <contact fullname="David Dong"/>, <contact
fullname="Joey Salazar"/>, <contact fullname="Jean-Michel Combes"/>, and
<contact fullname="Joerg Ott"/> for their respective directorate
reviews. Thanks to <contact fullname="Paul Wouters"/> for a
<em>really</em> detailed IESG review! Thanks also to the other IESG
members who provided comments or simply took the time to review the
document.</t>
</section>
</back> </back>
</rfc>
<!-- Keep this comment at the end of the file <!-- [rfced] We had some questions about abbreviations:
Local variables:
mode: sgml a) Should "DNSSD" (in "non-DNSSD services" and "DNSSD discovery zone")
fill-column:132 be updated to "DNS-SD" (hyphen) or "dnssd" (lowercase) to match prior
sgml-omittag:t usage in the document?
sgml-shorttag:t
sgml-namecase-general:t b) Is the "Service" (or "Service Description") redundant here and in
sgml-general-insert-case:lower similar cases throughout the document (as SD = Service Discovery)?
sgml-minimize-attributes:nil That is, just examples below, more cases exist.
sgml-always-quote-attributes:t
sgml-indent-step:2 Original:
sgml-indent-data:t DNS-SD Service registration uses public keys and SIG(0) to allow
sgml-parent-document:nil services to defend their registrations.
sgml-exposed-tags:nil
sgml-local-catalogs:nil Original:
sgml-local-ecat-files:nil Although in principle DNS-SD Service Description records can
End: include other record types with the same Service Instance Name, in
--> practice they rarely do.
c) For "TSIG", would you like us to expand to "transaction signature"
upon first usage to match RFC 8945?
Original:
The format of the KEY resource record in the SRP Update is defined in
[RFC3445]. Because the KEY RR used in TSIG is not a zone-signing
key, the flags field in the KEY RR MUST be all zeroes.
d) Throughout the document, "SRP update" is used, and there is only
one instance of "SRV update". We wanted to make sure that "SRV" was
indeed intended and not "SRP".
Original:
* If there is one "Add to an RRset" SRV update, there MUST be at
least one "Add to an RRset" TXT update.
e) We have updated to use the abbreviation CNN for Constrained-Node
Network (to match its use in RFC 7228). Please review and let us know
any objections. Further, please review uses of "constrained network"
and let us know if any of these should be updated to CNN as well.
-->
<!-- [rfced] We had some questions regarding capitalization of certain terms:
a) We see instances of "Anycast" (capitalized) and "anycast"
(lowercase) throughout the document, but we are unsure if certain
instances are part of proper names while other instances are more
generic. Please let us know if these need to be made more consistent
or if they are accurate as they currently are. We've listed a few
instances below.
Anycast vs. anycast:
IPv6 Anycast address
Port Control Protocol anycast address
fixed anycast address
anycast address
b) We see the following similar terms. Please review and let us know
if/how to make these terms consistent.
service instance name
Service Instance Name
"Service Instance Name"
service instance
Service Name
c) We see the following similar terms. Please let us know how to
update for consistency.
BIND 9 vs. BIND9
d) We have updated the quoted terms that correspond to Sections 2.5.1
- 2.5.4 of RFC 2136 to appear consistently in double quotes and with
capitalization that matches those section titles. Please let us know
any objections.
We further wondered if the following update should be made:
Original:
The target of the SRV RR Add...
Perhaps:
The "Add To An RRset" SRV update
Please review other terms similar to these titles if they exist and
let us know if any further changes should be made.
e) The NoError status names are in all caps in Section 2.2 of RFC
2136. Should the following updates be made to match?
ServFail to SERVFAIL
Refused to REFUSED
YXDomain to YXDOMAIN
f) Regarding the terms “Service Description”, Service Discovery, and
“Host Description”.
- We see both Instruction and instruction when following these terms.
If/How may we make this uniform?
- Should “instruction” or the like should be inserted after instances
of these terms? Sometimes they are followed by "record" or "update",
if they appear without a label, might this be confusing to the reader?
Example:
The KEY record in Service Description updates MAY be omitted for
brevity; if it is omitted, the SRP registrar MUST behave as if the
same KEY record that is given for the Host Description is also given
for each Service Description for which no KEY record is provided.
g) Please review the following similar terms and let us know if/how
they should be made uniform with regard to quotes and ending with a
period (note that this term would have IANA implications):
"default.service.arpa"
"default.service.arpa."
host.default.service.arpa
host-1.default.service.arpa
host-2.default.service.arpa
host-31773.default.service.arpa. (at end of sentence)
".service.arpa."
"service.arpa"
"service.arpa."
Further note that we have updated from single to double quotes around
terms that were quoted in the original consistently. Please review
and let us know if further updates are necessary.
h) Please review the following for the use of quotes and consistent
use of SRV record. Please let us know if/how to update.
"_dnssd-srp._tcp.<zone>" SRV record vs. _dnssd-srp._tcp.<zone> SRV
"_dnssd-srp-tls._tcp.<zone>" SRV record vs. _dnssd-srp-tls._tcp.<zone> record
_dns-update._udp SRV
-->
<!-- [rfced] Please review each artwork element in Appendix C in case
they should be tagged as sourcecode or another element.
-->
<!-- [rfced] Please review the "Inclusive Language" portion of the
online Style Guide
<https://www.rfc-editor.org/styleguide/part2/#inclusive_language>
and let us know if any changes are needed.
Note that our script did not flag any words in particular, but this
should still be reviewed as a best practice.
-->
</rfc>
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