QoS-aware routing in ATM and IP-over-ATM

Abstract

This paper analyzes the performance of some dynamic routing algorithms for ATM and IP-over-ATM networks. The main algorithm, named AR-DLCP (Alternate Routing — Distributed Least Congested Path), is based on a distributed computation, where the “best” route is chosen node-by-node in the call set-up phase, by taking decisions on the basis of a cost function, composed of a local part and an aggregate part. The local cost is constructed for each outgoing link on the basis of the knowledge of the current and the maximum number of connections that the link can support, while still ensuring the required Quality-of-Service at the cell level. The aggregate cost is aimed at reflecting the congestion situation of a node and is computed through an information exchange mechanism among adjacent nodes. In a fully connected core network, only direct and two-hop paths are considered; in the general meshed topology case, paths are organized in a two-level hierarchy. Static and dynamic trunk reservation schemes that guarantee enough bandwidth to direct paths are discussed. The performance of the two alternatives is evaluated by simulation under various traffic load situations. In particular, AR-DLCP is compared with other algorithms already in the literature as DLCP, Learning Automata and RTNR (Real Time Network Routing). In the general topology case, the algorithm is also combined with a bandwidth allocation mechanism and IP routing, by taking into account the presence of best-effort traffic, in an IP-over-ATM context.