What Are Differences Between NAT and Proxy?
Both NAT and proxy provide Internet access through private IP addresses.
These two technologies differ in their positions in the TCP/IP protocol stack. NAT works at the network layer while proxy at the application layer. NAT is transparent to various applications, whereas proxy must resort to the IP address of the proxy server specified in application programs. For example, to access a web page by using NAT, no configuration is required in the browser. To access a web page by using a proxy, you must specify the IP address of the proxy in the browser. If the proxy supports only HTTP, only web servers can be accessed through the proxy, but not FTP. In terms of Internet access, NAT delivers higher scalability than proxy, because NAT is not targeted at applications.
However, NAT cannot provide user name- and password-based authentication. The proxy supports authentication. In this way, only the users that are authenticated on the basis of their user names and passwords are allowed to access the Internet.