Analysis of practical backoff protocols for contention resolution with multiple servers
- Univ. of Warwick, Coventry (United Kingdom)
- Sandia National Lab., Albuquerque, NM (United States)
Backoff protocols are probably the most widely used protocols for contention resolution in multiple access channels. In this paper, we analyze the stochastic behavior of backoff protocols for contention resolution among a set of clients and servers, each server being a multiple access channel that deals with contention like an Ethernet channel. We use the standard model in which each client generates requests for a given server according to a Bemoulli distribution with a specified mean. The client-server request rate of a system is the maximum over all client-server pairs (i, j) of the sum of all request rates associated with either client i or server j. Our main result is that any superlinear polynomial backoff protocol is stable for any multiple-server system with a sub-unit client-server request rate. We confirm the practical relevance of our result by demonstrating experimentally that the average waiting time of requests is very small when such a system is run with reasonably few clients and reasonably small request rates such as those that occur in actual ethernets. Our result is the first proof of stability for any backoff protocol for contention resolution with multiple servers. Our result is also the first proof that any weakly acknowledgment based protocol is stable for contention resolution with multiple servers and such high request rates. Two special cases of our result are of interest. Hastad, Leighton and Rogoff have shown that for a single-server system with a sub-unit client-server request rate any modified superlinear polynomial backoff protocol is stable. These modified backoff protocols are similar to standard backoff protocols but require more random bits to implement. The special case of our result in which there is only one server extends the result of Hastad, Leighton and Rogoff to standard (practical) backoff protocols. Finally, our result applies to dynamic routing in optical networks.
- Research Organization:
- Sandia National Laboratory
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 416841
- Report Number(s):
- CONF-960121--
- Country of Publication:
- United States
- Language:
- English
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