A Multi-Class MAC for time-slotted WDM Optical Packet Ring
Résumé
In this paper we present an approach for supporting best effort traffic on an ECOFRAME ring network which has been dimensioned primarily for Guaranteed Traffic. This approach is reservation based, and is combined within the ECOFRAME MAC with the opportunistic access method used for Guaranteed traffic. The reservation method is intended to both protect the Guaranteed traffic and allocate fair shares of the excess resources to the competing Best Effort traffic flows. We analyze the performance of the proposed approach on 2 simple scenarios, i.e. a "concentration" scenario where all stations send the same amount of traffic to a Hub on the ring, and an "any-to-any" scenario where each station sends the same amount of traffic to each other station on the ring. The maximum amount of BE traffic that can be supported without degrading the QoS offered to Guaranteed traffic is derived using simple queueing models. The simple scenarios are then simulated, with the modified MAC, and compared to the theoretical results. The obtained simulation results show that Guaranteed traffic is very well protected, and that spare resources are indeed fairly shared. However, the reservation approach fails to meet the maximum utilization in the any-to-any scenario due to the fact that it forbids spatial reuse for BE traffic.
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