1. Stallings W (2000) Local and metropolitan area network. Prentice Hall, Upper Saddle River
2. Comar DE (2000) Internetworking with TCP/IP: principles, protocols, and architecture, 4th edn. Prentice-Hall, Upper Saddle River
3. RFC (1812) Requirements for IP version 4 routers.
http://www.cis.ohio-state.edu/cgi-bin/rfc/ rfc1812.html#sec-2.2.3
4. Sangoma Technologies.
http://www.sangoma.com/x25.htm