Inferring the extent of network address port translation at public/private internet boundaries

This technical report describes a relatively simple method for inferring the percentage of public/private internet boundaries that utilize network address port translation (NAPT, often colloquially referred to as NAT). Estimates were obtained from the IP address/port pairs seen in the server logs of three well-used, online game servers between May 2001 and June 2002. The report concludes that NAPT may be in use at approximately 17 to 25% of public/private internet access boundaries in the online gaming community. Estimates of NAT deployment can help provide context for discussions about the need for IPV6 and other techniques for scaling the Internet.