-  
iptables-1.2.6 by Paul Russell. 
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Linux netfilter Hacking HOWTO by Paul Russell. 
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iproute2 by Alexey Kuznetsov. 
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Advance routing Linux HOWTO. 
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HTB queueing discipline implementation by Martin Devera. 
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Linux-Advance Networking Overview by Saravanan Radhakrishnan. 
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monitor.pl by Stef Coene. 
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netcat by Hobbit.