A Distributed Traffic Control Scheme for Large-Scale Multi-Stage ATM Switcliing Systems

摘要

This paper describes a distributed traffic con- trol scheme for large multi-stage ATM switching systems. When a new virtual circuit is to be added from some source line- interface unit (LU) to a destination LU, the system must find an optimal path through the system to accommodate the new circuit. Conventional systems have a central control processor and control lines to manage the bandwidth of all the links in the systems. The central control processor handles all the virtual circuits, but have trouble doing this when the switching system becomes large because of the limited ability of the central pro- cessor to handle the number of virtual circuits. A large switching system with Tbit/s-class throughput requires a distributed traffic control scheme. In our proposed switching system, each port of the basic switches has its own traffic monitor. Operation, admin- istration, and maintenance (OAM) cells that are defined inside the system carry the path-congestion information to the LUs, enabling each LU to route new virtual circuits independently. A central control processor and control lines are not required. The performance of the proposed system depends on the interval be- tween OAM cells. This paper shows how an optimal interval can be determined in order to maximize the bandwidth for user cells. This traffic control scheme will suit future Tbit/s ATM switching systems.