On 8/23/2010 6:39 PM, John Kristoff wrote:
A few classes ago I had a student tell me they had an instructor spend two full classes (out of 10) on Token Ring.
There's a serious need to cover such a construct, but also to introduce it in the context of modern systems: Probably none of what is sold today as ethernet is actually the original ethernet protocol or even close to it. What is sold today is a the ethernet *interface* and some other protocol under it. This difference between the interface and the infrastructure under it that provides service to it is a fundamental construct that is often missed. Standardized interfaces let technology adapt underneath it. So, for example, IBM published the API for netbios, without publishing the protocol. That let some of us build alternative protocols that satisfied the API but ran over TCP. (See RFC 1001, 1002 for the standardized version.) Much of what is sold today as ethernet has a protocol under it that is contention-free. The different Token Ring schemes provide that in a distributed manner.[1] d/ [1] Though my own focus was on email, my CS prof was Dave Farber, so I had to absorb more about TR than I would have wanted. One of the interesting metricts for TR is delay-time per node. The Irvine Ring introduced one bit-time delay. Scaled great. The IBM TR introduced one full packet-time. Didn't scale well. -- Dave Crocker Brandenburg InternetWorking bbiw.net