Carrier Ethernet and the New OSI
Tom Nolle, Founder and President, CIMI Corporation
A Webtorials Brief
Published September 2008, Posted September 2008
Back in the mid-1970s, the organization then known as the CCITT (now the ITU-T) formulated a rather revolutionary thing called the "Basic Reference Model for Open Systems Interconnect," better known as the OSI model. This model created a seven-layer architecture that has been used ever since to describe network protocols and networks themselves.
Despite the longevity of the references to the OSI model, the conception of the OSI model has changed over the years. Some "layers" have been added, and some donít seem to be getting used very much. Most recently, there is talk about concepts like "virtual networks" and "abstract topologies" that donít clearly relate to the old OSI concepts. To make matters worse, the Internetís evolution, based on TCP/IP, never strictly followed the old OSI model at all. A reasonable person might ask whether people who talk about "Layer One" or "Layer Three" arenít blowing kisses at an old friend instead of recognizing the relevance of the original OSI model.
Are they? What is the real value of layered architectures today, the real role of layered protocols, and the relationship between protocols, services, networks, and users? Weíre proposing to look at these questions here.
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