NAT/Firewall Traversal: Issues and Solutions

Overview

Network Address Translators (NATs) and Firewalls are increasingly used in all type of networks because of various reasons. However, NATs and firewalls are limiting some kind of communications and they are known to cause problems for applications that carry IP addresses in the payload which are mainly related to multimedia communications and Voice over IP. Nowadays there are many techniques and solutions are used to allow those increasingly popular applications to work through NATs and Firewalls. Examples of such applications are NAT/Firewall NSLP, STUN, Application Level Gateways, CODO, etc. This paper takes a look on a few exscinding and proposed solutions and studies their features, advantages and shortcomes.