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