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 Node

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 modified. 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 SMURPH language by Pawel Gburzynski. I highly recommend this package for anybody doing simulation of computer communication networks.

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 pages.

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