A distributed real-time MAC protocol for WDM-based LANs

Abstract

In this paper, we consider the problem of developing a MAC layer protocol to support real-time as well as non-real-time packet streams in Broadcast and Select WDM optical networks having rapidly tunable transmitters. We propose a MAC layer protocol which is the best-effort in nature and has two phases: demand notification phase and packet transmission phase. In the demand notification phase, a token circulates among the nodes in a round robin manner gathering the demand information of the traffic on each node. This information is recorded in the local status tables of each node. An algorithm is run on all the nodes in a distributed manner in order to resolve the contention for each channel. The contention resolution algorithm gives due weightage to both the real-time deadline of the streams of traffic and tuning time of the transmitter. In the proposed protocol, the traffic streams on any node are not bound to a physical channel and can use any channel onto which a receiver on the destination node is tuned. Also, the protocol attempts to overlap the transmitter tuning with the packet transmission in order to minimize the channel idle time due to transmitter tuning. We demonstrate the effectiveness of the proposed protocol through extensive simulation studies.