Slot pre-using in IEEE 802.6 metropolitan area networks

The authors deal with a new technique that is fully compatible with the IEEE 802.6 MAN standard and allows for multiple use of a slot for segment transmissions. In particular, this technique increases the efficiency of the distributed-queue dual-bus (DQDB) protocol by allowing pre-use of slots traveling along the bus before they are taken as determined by normal DQDB operation. These slots may be captured by nodes wishing to transmit their queued-arbitrated segments addressed to neighbors. The proposed technique is particularly well suited for the case when information transfer between neighboring nodes is more likely than that between remote ones. Simulation was used to study the throughput, delay, and fairness performance. It is demonstrated that the resulting extension of DQDB, which is called SP-DQDB (slot pre-use DQDB), may be much more efficient than DQDB in several different environments