IPv6 Options for Congestion Measurement

Internet-Draft	CM	March 2024
Shi, et al.	Expires 5 September 2024	[Page]

Abstract

The Congestion Measurement enables precise congestion control, aids in effective load balancing, and simplifies network debugging by accurately reflecting the degree of congestion across network paths. This document outlines how Congestion Measurement Data-Fields are encapsulated in IPv6.¶

Status of This Memo

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This Internet-Draft will expire on 5 September 2024.¶

Copyright Notice

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶

1. Introduction

[I-D.draft-shi-ippm-congestion-measurement-data] defines data fields of Congestion Measurement which enables sender to obtain the degree of congestion across the path. This document defines the IPv6 encapsulation of the Congestion Measurement Data-Fields.¶

1.1. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

2. Congestion Measurement Option

One IPv6 header option, Congestion Measurement Option is defined to carry the Congestion Measurement Data-Fields.¶

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                |Opt Type = TBD1|  Opt Data Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
.                                                               .
.        Congestion Measurement Data-Fields (Variable)          .
.                                                               .
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: Congestion Measurement Option

where:¶

Opt Type: Type value is TBD1, an 8-bit unsigned integer. Identifier of the type of this Congestion Measurement Option.¶
Opt Data Len: An 8-bit unsigned integer. Length of the Option Data field of this option, that is, length of the Congestion Measurement Data-Fields.¶
Congestion Measurement Data-Fields: Option-Type-specific data. It carries the data fields for Congestion Measurement as specified in [I-D.draft-shi-ippm-congestion-measurement-data].¶

2.1. Congestion Measurement Hop-by-hop Options Header (HBH)

The Congestion Measurement option can be carried in the IPv6 Hop-by-Hop Options Header. In this case, each node along the path can inspect the Congestion Info Data field if they are configured the support this option. If the U bit of Congestion Measurement Data-Fields is set, intermediate nodes will modify the Congestion Info Data field accordingly.In theory, the presence of the Hop-by-Hop Option should not affect the traffic throughput both on nodes that do not recognize this Option and on the nodes that support it. However, in a real implementation, a packet with a Hop-by-hop Option may be skipped or processed in the slow path. Proposals to mitigate the problem are out of the scope for this document.¶

2.2. Congestion Measurement Destination Options Header (DOH)

The Congestion Measurement option can be carried in the IPv6 Destination Options Header. In this case, it is usually processed by the destination node. Note that, if there is also a Routing Header (RH), any visited destination in the route list can process it. If the U bit of Congestion Measurement Data-Fields is set, intermediate nodes will modify the Congestion Info Data field accordingly.¶

Table 1
Value	Description	Reference
TBD1	Congestion Measurement Option	Section 2

5. References

5.1. Normative References

[RFC2119]: Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/rfc/rfc2119>.
[RFC8174]: Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

5.2. Informative References

[I-D.draft-shi-ippm-congestion-measurement-data]: Shi, H., Zhou, T., and Z. Li, "Data Fields for Congestion Measurement", Work in Progress, Internet-Draft, draft-shi-ippm-congestion-measurement-data-00, 3 March 2024, <https://datatracker.ietf.org/doc/html/draft-shi-ippm-congestion-measurement-data-00>.