Packet Switching Portal

Packet Switching Portal

I've been in the computer networking field for more years than some of you readers are alive. I know, that makes me sound ancient. Well, at the pace that technology changes, I am ancient. But ancient people can be wise. And my wisdom tells me that no matter what technologies come and go, packet switching will be part of the networking scene in one form or another, and it will also be one of the foundational topics of any computer networking course.

In this portal, I will bring together the basic concepts in packet switching - concepts that I have taught for years in computer networking courses and concepts that are still essential in understanding new technologies - with several packet switching protocols and technologies. Some of the packet switching technologies that will be explored in this portal are ancient and outmoded - maybe even more ancient than my experience in the networking field. Nevertheless, they are still part of the standard curriculum in many computer networking courses. In particular, I'm thinking of X.25. Did any of you recently use an X.25 network? Would you know how to access one? Does your network service provider or your phone company offer access to one? How much X.25 equipment was sold in the last year?

I'm not going to provide the answers to those questions. But because X.25 embodies so many important concepts in computer networking, it is still taught in many networking courses and included in many newly published computer networking textbooks - and is included in this portal, even though it is a very old technology and even though its popularity has been overshadowed by much newer and faster technologies. And, by the way, it is still in use for some appropriate applications.

The first chapter in this portal will discuss the concepts of packet switching and contrast them with circuit switching, the form of switching that is used in classic telephony. This comparison is important, because it helps explain the development of packet switching, and why it was an innovation.

We will then look at two kinds of packet switching: virtual circuit packet switching and datagram delivery. An IP network, which everyone uses when they use the Internet, is a packet switching network of the datagram delivery type, though often people (among those who do know something about computer networks) don't think of IP as a packet switching protocol (while those who don't know about computer networks don't think about IP at all - they just use it). Since, in the interest of bit-conservation, this portal will recycle bits when it is appropriate, I will incorporate an interactive applet, written by two of my students, which demonstrates the difference between virtual circuit packet switching and datagram delivery. All recycled materials will be credited on the References, Links, and Credits page.

There is a multi-chapter unit on X.25 followed by a multi-chapter unit on Frame Relay. Next, I will briefly explain ATM's position in the family of packet switching technologies, and link you to the ATM portal. Similarly, I will place MPLS into the packet switching space, and link you to the IP/MPLS portal. If you do work your way through all of the topics, you should not only be familiar with each of the protocols, but you should be able to compare them and understand how each one contributed to later developments. And, perhaps most important, you should have a good grasp of packet switching concepts so that you'll be ready to learn about - or even develop - new and improved packet switching protocols.

Thank you for visiting RAD University. We hope that this portal will be helpful and fun, and we welcome your comments.

Debby Koren, "Dean" RAD University