Admission control for hard real-time connections in ATM LANs

Abstract

A connection admission control (CAC) algorithm must efficiently determine if a new connection can be admitted by verifying that its QoS requirements can be met without violating those of previously admitted connections. In hard real-time systems, the QoS requirements are specified in terms of end-to-end cell deadlines and no cell loss due to buffer overflow. To achieve these objectives a CAC algorithm must account for the traffic characteristics of connections. Furthermore, arbitrary topology of the network may lead to cyclic dependencies among various connections. An efficient CAC algorithm is presented that addresses these issues. The algorithm uses a traffic descriptor called the 'maximum traffic rate function' to effectively compute bounds on end-to-end delays of connections and buffer requirements within the network. The work differs from most previous work in that it does not require traffic restoration inside the network.