Providing deterministic delay guarantees in ATM networks

Abstract

B-ISDN is expected to carry various types of traffic for which stringent quality of service (QoS) requirements must be met. In particular, per-packet (per-cell) delay guarantees are an important QoS requirement for real-time applications. Although several methods have been proposed to provide delay guarantees in packet-switching networks, they are either too complex for ATM networks which allow only very simple operations to achieve high bandwidths (hence, high-speed switching and routing), or too inefficient (in using network resources) to be cost effective. In this paper, we propose a cell-multiplexing scheme for the real-time communication service in ATM networks. The proposed scheme achieves an efficiency close to that of packet-by-packet generalized processor sharing, and incurs an implementation cost similar to that of rate controlled static priority queueing. It employs the leaky bucket model as the input traffic description model and regulates the input traffic at the user network interface to follow the input traffic specification. Inside the network, it consists of two components, traffic controller and scheduler. The function of the traffic controller is to shape real-time traffic to have the same input pattern at every switch along the path. The end-to-end delay is bounded by the scheduler which employs a nonpreemptive rate-monotonic priority scheduling policy at each switch on the path. The proposed scheme is compared to three other popular schemes with MPEG-coded movie clips. Finally, we present a hardware implementation of the proposed scheme based on a systolic array priority queue.