LAN-ATM internetworking over a priority-based slotted-ring network

Bandwidth-intensive and delay-sensitive applications demand ATM technology to be brought into every desktop. However, it is very costly in terms of both hardware and software to replace a traditional LAN such as Ethernet and token ring by an ATM network. Therefore, internetworking LANs with an ATM backbone network is considered a cost-effective and most promising solution for bringing ATM into the mainstream. To sustain delay-sensitive applications (e.g., video or voice) and loss-sensitive applications (e.g., data transfer), this paper presents a slotted-ring network (SRN) with spatial reuse. A simple priority-based access protocol, called the check request before send (CRBS), for providing nonpreemptive multipriority services over SRN is described. SRN provides communication among an ATM switch, ATM stations, and internetworking units connected to legacy LANs. Any node of SRN in the CRBS protocol determines whether it can use a slot, without requiring any authorization or an exchange of message with the other nodes. The CRBS protocol reduces the unfairness features associated with any slotted-ring network. An analytical model is presented to analyze the CRBS protocol under Poisson input traffic and uniform output traffic. Extensive simulations are run to assess the performance of the CRBS protocol for two classes of cells with priorities 0 and 1. The analytical performance results are shown to be close to those obtained by simulations.