• RFC 1349 - Type of Service in the Internet Protocol Suite - RFC describing some changes and clarifications of the TOS field in the IP header.
• RFC 1812 - Requirements for IP Version 4 Routers - This RFC specifies how routers on the Internet should behave and how they are expected to handle different situations. Very interesting reading.
• RFC 2401 - Security Architecture for the Internet Protocol - This is an RFC talking about the IPSEC implementation and standardisation. Well worth reading if you are working with IPSEC.
• RFC 2474 - Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers - In this document you will find out how the DiffServ works, and you will find much needed information about the TCP/IP protocol additions/changes needed for the DiffServ protocol to work.
• RFC 2638 - A Two-bit Differentiated Services Architecture for the Internet - This RFC describes a method of implementing two different differentiated service architecture into one. Both where described originally by D. Clark and van Jacobsen at the Munich IETH meeting 1997.
• RFC 2960 - Stream Control Transmission Protocol - This is a relatively new protocol developed by several large telecoms companies to complement UDP and TCP as a layer 3 protocol with higher reliability and resilience.
• RFC 3168 - The Addition of Explicit Congestion Notification (ECN) to IP - This RFC defines how ECN is to be used on a technical level and how it should be implemented in the TCP and IP protocols. Written by K. Ramakrishnan, S. Floyd and D. Black.
• RFC 3260 - New Terminology and Clarifications for Diffserv - This memo captures Diffserv working group agreements concerning new and improved terminology, and provides minor technical clarifications.
• RFC 3286 - An Introduction to the Stream Control Transmission Protocol - RFC introducing the Stream Control Transmission Protocol, a relatively new layer 3 protocol in the TCP/IP stack. Developed by several large telecom companies.
• ip_dynaddr.txt - from the 2.4.14 kernel. A really short reference to the ip_dynaddr settings available via sysctl and the proc file system.
• iptables.8 - The iptables 1.3.1 man page. This is an HTMLized version of the man page which is an excellent reference when reading/writing iptables rule-sets. Always have it at hand.
• Ipsysctl tutorial - Another tutorial I have written about the IP System Control in Linux. A try to make a complete listing of all the IP variables that can be set on the fly in Linux.
• Policy Routing Using Linux - This is an excellent book that has now been opened up on the Internet regarding Policy routing in Linux. It is well written and most definitely worth buying. Written by Matthew G. Marsh.
• Security-Enhanced Linux - The official site of the Security-Enhanced Linux (SELinux) system developed as a proof of concept by the National Security Agency (NSA). SELinux is a fine grained Mandatory Access Control system, which lets you have a much higher control on who can do what and what processes has what privileges, et cetera.
• Firewall rules table - A small PDF document gracefully given to this project by Stuart Clark, which gives a reference form where you can write all of the information needed for your firewall, in a simple manner.
• http://l7-filter.sourceforge.net/ - The l7-filter project is basically a set of patches and files to make iptables and netfilter able to handle layer 7 filtering, mainly for QoS and traffic accounting. It works less reliably for filtering however, since it will allow the first couple of packets through before actually blocking traffic.
• http://www.netfilter.org/ - The official Netfilter and iptables site. It is a must for everyone wanting to set up iptables and Netfilter in linux.
• http://www.insecure.org/nmap/ - Nmap is one of the best, and most known, port scanners available. It is very useful when debugging your firewall scripts. Take a closer look at it.
• http://www.netfilter.org/documentation/index.html#FAQ - The official Netfilter Frequently Asked Questions. Also a good place to start at when wondering what iptables and Netfilter is about.
• http://www.netfilter.org/unreliable-guides/packet-filtering-HOWTO/index.html - Rusty Russells Unreliable Guide to packet filtering. Excellent documentation about basic packet filtering with iptables written by one of the core developers of iptables and Netfilter.
• http://www.netfilter.org/unreliable-guides/NAT-HOWTO/index.html - Rusty Russells Unreliable Guide to Network Address Translation. Excellent documentation about Network Address Translation in iptables and Netfilter written by one of the core developers, Rusty Russell.
• http://www.netfilter.org/unreliable-guides/netfilter-hacking-HOWTO/index.html - Rusty Russells Unreliable Netfilter Hacking HOW-TO. One of the few documentations on how to write code in the Netfilter and iptables user-space and kernel space code-base. This was also written by Rusty Russell.
• http://www.linuxguruz.org/iptables/ - Excellent link-page with links to most of the pages on the Internet about iptables and Netfilter. Also maintains a list of iptables scripts for different purposes.
• Policy Routing using Linux - The best book I have ever read on Policy routing nad linux. This is an absolute must when it comes to routing in linux. Written by Matthew G. Marsh.
• Implementing Quality of Service Policies with DSCP - A link about the cisco implementation of DSCP. This shows some classes used in DSCP, and so on.
• IETF SIP Working Group - SIP is one of the "next big things" it seems. Basically it is the defacto standards for Internet telephony today. It is horribly complex as you can see from the amount of documentation on the working groups homepage, and should hopefully be able to cope with pretty much any needs of session initiation in the future. It is used mainly to setup peer to peer connections between known users, for example to connect to user@example.org and setup a phone connection to that user. This is the IETF Working group handling all SIP work.