Wayne Hayes's work in Computer Communications Networks
As a student with Mart L.
Molle, I invented, coded, and tested
(via simulation) SHEP, the Switched Half-duplex
Ethernet Protocol. At the 20th Annual Local
Computer Networks Conference in Minneapolis, Minnesota Oct 17-18 1995,
I presented the following paper describing the protocol.
Solving Capture in Switched Two-Node Ethernets by Changing Only One
Wayne Hayes and Mart L. Molle
It is well known that the Ethernet medium access control protocol can
cause significant short-term unfairness through a mechanism known as
the Capture Effect, and that this unfairness condition is worst in
heavily loaded Ethernets with a small number of active nodes. Recently,
Ramakrishnan and Yang proposed Capture Avoidance Binary Exponential
Backoff (CABEB) to provide 1-packet-per-turn round robin service
in the important special case of
a 2-node collision domain. In this paper, we introduce an equal
time round-robin scheme, in which only one node needs to be
In our scheme, the modified node maintains a local copy of
the attempts counter of the other node. It uses this information
to trigger switching its medium access policy between the two
extremes of aggressively persistent and completely passive.
As a result, the modified node can control the actions
of the other node in such a way that both enjoy fair, low delay,
round-robin access to the shared channel.
Click here for a compressed postscript copy of
the paper, and the talk.
The code used for this (and other) simulations was written in the
by Pawel Gburzynski. I
highly recommend this package for anybody doing simulation of computer
The code I wrote in SMURPH was also an integral part of Mart's
work on the BLAM
Ethernet protocol, which is likely to become part of the new Ethernet
standard. Following this link also leads to many other interesting Ethernet
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