Network Address Translation

Network Address Translation, defined in the Internet Standard RFC 1631, allows your Intranet to use addresses that are different from what the outside Internet thinks you are using. As an example of something similar, consider a company telephone system with several hundred telephone extensions. Each telephone has its own internal "extension" number, which it uses to call others in the company. When it calls someone on the outside, however, the outside sees the number of the "trunk" line that the system uses and not the extension number of the user's telephone. The actual connection between the outside trunk and the inside user is maintained temporarily by the telephone system.

Our NAT products do the same thing for your Internet communication. You assign IP Addresses to your internal users, and when they want to connect to the outside Internet, our NATs create a temporary connection, just like the telephone system would. And, like the telephone system, the outside doesn't care what sort of internal numbering scheme you create for your users. The only IP Address that matters is the one seen from the outside.

Why Should I Care?

In the early days of the Internet, when just the Universities and the government were using it, 4 billion IP Addresses were considered to be vastly more than we would ever need. In fact, this is true. However, this false sense of wealth resulted in the dispensing of huge blocks of addresses to those that asked. For example, consider:

MIT has 16,843,008 registered IP Addresses.
USC has 16,911,360.
General Electric has 17,206,528.
IBM has 17,542,656.
AT&T has 19,800,320.

The list could go on and on. Had those in charge foreseen the present situation, they would have been more careful in issuing IP Addresses.

Of course, they didn't and they weren't, and now we are nearly out of IP Addresses, just when we're beginning to connect everyone to the net. When we're out, all of this fun will come to a halt. What can we do? Here are a few possibilities:

Redesign IP with a bigger address field. We're doing exactly that, but it won't help us for at least three years.
Take back those vast quantities of addresses that we gave away so long ago. This will never happen. It can't happen.
Figure out a way to stretch what we have as long as we can. That's what Network Address Translation is all about.

We were one of the first to produce Network Address Translators, delivering our first in November of 1994. We were the first to permit many users to share a single external IP Address at the same time.