Design and implementation of a network address translator

Abstract

A continuously increasing demand for Internet Protocol (IP) Addresses was something that was not considered at the time when the Internet was first designed. The argument was actually quite the opposite and most experts pooh-poohed the idea of the internet ever growing to beyond 100,000 networks. However, the 100,000th network was connected to the internet in 1996 (Tanenbaum 2003). The Explosive growth of the Internet has resulted in a shortage of the number of available IP Addresses. As this growth continues the shortage will increase and a new form of Internet Addressing will need to be established. The current form, IPv6 has been under development for some time now and has not gathered wide industry support. Obviously a temporary solution must be established to overcome the shortage of IP Addresses in the immediate future until permanent solutions can be achieved. On the other hand the TCP Protocol was established as an end-to-end connection for reliable communication and makes use of its own 16-bit port number. This allows for up to 65,535 unique port numbers for TCP communication. Most hosts never maintain 65,535 end-to-end connections and this allows for a technology called Network Address Translation (NAT) to save on the number of IP Addresses required on the Internet by multiplexing many IP Sources onto one or more IP Addresses using unique TCP port numbers for each data stream. The ultimate aim of this project is to produce a small prototype Network Address Translator and discuss further improvements necessary for its use in a production environment.