Switching Technologies

With the advent of faster computer networks and a far more stable infrastructure has come the need for a quicker way to “switch” this information around. Two of the best known methods for doing so are ATM and Frame Relay. Within the confines of this article we will discuss just what they are and where they fit in.

The Internet as we know it today has grown in leaps and bounds from when it first really became popular back in 1994. Back then a 14.4K modem was pretty happening. Well times have changed and technology has certainly evolved since then. Presently most of us have high speed modems whether they be DSL or broadband cable modems. These modems transmit and receive data that your computer generates on your behalf. This is done in a very orderly fashion by your operating system. Seen as most of us use one version or another of Microsoft Windows we can map how our computer generates this information by mapping it to the OSI Reference Model. Almost each layer of this communications model has some information added to it by your computer’s operating system.

Let's think of this from the top on down. At the application layer Internet Explorer would make a HTTP GET request for your home page. There would be nothing for the presentation layer or session layer to add. Next your computer would generate a TCP header and the network layer an IP header. After that your Data Link Layer would put this information in a logical format and put the MAC information at the front of this frame. Lastly, it would be sent out via the NIC card at the physical layer. Bearing this trickling down of bytes from the application layer on down, we realize that each packet will likely not always be the same size. That is no problem for the computer, but it does present a problem if you want to switch this information around faster. The various shapes and sizes of Ethernet packets presents a challenge if we want to speed things up. Being predictable is not always a bad thing. Knowing that a computer will always generate a certain frame size will certainly help in efforts to design a faster way of switching these now uniform size packets.