25 years of TCP/IP

Some of us have been around long enough to remember when there was no Internet. Also, we were around before there was TCP/IP. This year we are hearing quite a bit – even in the popular press – about 2008 being the 25th anniversary of the Internet and TCP/IP. For instance, NPR has a great interview with Vinton Cerf, who, along with Robert Kahn, “invented” the protocol. Cerf discussed the original scope of the project as defined for Defense Advanced Research Projects Agency (DARPA), and, in particular, gives a great explanation for the layperson what distinguished TCP (Transmission Control Protocol) from IP (Internet Protocol). With this in mind, it seems appropriate to take a look back to reminisce – for those who remember – and to educate – for those who don’t – concerning this evolution.

The first point is that TCP/IP was far from being the first packet switching protocol in existence. At the inception of TCP/IP, X.25 networks were already widely used, especially outside the United States. The major change, and one that would continue to be an issue for the next several years, is the fact that IP is a connectionless protocol while X.25 (and, later, frame relay and ATM) are connection-oriented. As a connectionless protocol, the delivery of data is not guaranteed at the IP layer; hence, the addition of TCP to ensure that all of the packets are delivered – and that they are delivered in the proper order. (It’s also worth pointing out that the equivalent of IP was available in X.25 in the form of single-packet “datagrams.”)

Nevertheless, we need to cognizant that even though TCP/IP is now a de-facto standard for most communications – corporate and otherwise – it was not an instant “slam-dunk” success that was the obvious choice for all networks.

Next time, we look at where TCP/IP is now and why it requires a whole new generation of WAN firewalls.