Real ops talking to future ops
dhc2 at dcrocker.net
Tue Aug 24 15:11:21 UTC 2010
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
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
 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.
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