Knowledgebase: General Networking
NAT: Overview
Posted by Adrien de Croy (Import) on 30 January 2004 05:25 PM
Network Address Translation protocol or NAT as it is more commonly termed, is a technology that has been implemented for use by WinGate's Extended Networking Services, as a client connectivity method in WinGate.

In simple terms NAT works by taking any data destined for the Internet from the client machine (regardless of the application it is using) and sends it to a Gateway server such as WinGate.

WinGate will take this data packet, store the details of what client machine it came from, and then re-append the address details of the packet with the details of its own external location so that it can preform the Internet request on behalf of the client.

When the response data comes back in from the Internet, the WinGate machine “translates” the address back into the private IP address of the original client machine and forwards the data back to the appropriate client.

The concept of NAT technology use in proxy server solutions, was developed around the realisation that the Internet, using the current Ip version 4 addressing scheme, would run out of IP addresses to allocate to every machine that needed to access the Internet.

NAT was offered as one solution to this dilemma by creating a proxy server solution, which could easily handle the translation between Private and Public addresses. This meant that large networks needing Internet access could use private IP addresses and only require to have one external IP address to the Internet.

To read more about private versus public Ip addresses and how they are used in WinGate you can click here.

WinGate implemented NAT technology as part of its Extended Networking service and it offers the following benefits:

  • Little client configuration required, no additional software needed.
  • Works at a packet level so there is greater performance with through put and speed
  • Because it works at packet level all tcp/ip internet applications on the client machine will use it. Applications don’t have to be configured individually, such as with the straight proxy method of connection where a proxy server is specified on an application by application basis.
  • Hides Internal users from direct contact with the Internet at large, reducing the security risk
NAT does have several disadvantages with its use:
  • Client machines have no way of identifying themselves individually on the Internet if required.
  • Inability of Internet application servers running behind a NAT server to receive communications on a predefined port number.
  • Can be a problem in some instances where an Internet server only allow 1 connection from a particular IP at anyone time. If multiple clients attempt to connect to the server from behind NAT then only one will be allowed to connect as they will all appear to be connecting from the same external IP address.(A common problem with some Internet Gaming server scenarios).
WinGate’s implementation of NAT has expanded its functionality through the use of transparent redirection, which essentially takes all client traffic that is connecting via NAT and redirects it through the appropriate Proxy service to take advantage of the features only offered by the Proxy.
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