Minimizing cell delay variation in CRMA/ATM interworking

In wide area networks, ATM is emerging as the predominant technology which provides flexible transmission and switching mechanism to accommodate a large variety of services. Though ATM can be used for LAN/MANs, at present it does not provide economical solution for LAN/MAN. A simple Cyclic-Reservation Multiple-Access (CRMA) protocol proposed in [1] can be used as a media access protocol for high-speed LAN and MAN on slotted unidirectional bus structure. While there is a need for interconnection of existing LAN/MAN networks, the evolution of new LAN/MAN protocols will depend on how easily and efficiently the protocol can interwork with the ATM. Under the normal CRMA protocol, ATM stations located in the CRMA network will experience large Cell Delay Variation (CDV) due to variable cycle lengths during access within the CRMA network. Also due to the cancellation mechanism incorporated within the CRMA protocol, the CDV increases. The CRMA access mechanism also forms bursts during access. This paper proposes a novel mechanism that minimizes the CDV in CRMA/ATM interworking by embedding fixed length cycles for the ATM traffic in the normal CRMA cycles of variable length. Another novel scheme is used which allocates CRMA slots uniformly to the ATM traffic within the fixed length cycles, thereby smoothing the ATM traffic. The simulation results show that the proposed scheme reduces the CDV and burstiness of ATM traffic to a great extent without significantly affecting the delay performance of the CRMA traffic. (C) 1997 Elsevier Science B.V.