Strategies for Dynamic Network Management

We study management of transport networks based on virtual paths, i.e. rearrangable end-to-end transport network \highways". Among its main advantages are found cost savings, network operation simpli cation and enhanced network management capabilities. Virtual paths networks are readily implemented in any network using the synchronous digital hierarchy and/or the asynchronous transfer mode. Algorithms for virtual path designs are reviewed and found to have a few shortcomings. A new algorithm is therefore proposed and it is found to compare favourably with the algorithm providing the most similar features. Applying the proposed algorithm to a large number of networks, we discuss operational considerations associated with recon gurable networks and investigate simple tra c estimation procedures and their performance in this context. Finally, the choice of recon guration parameters such as updating frequency, and the impact of network design time are examined. 1 Recon gurable Virtual Path Networks for ATM 1.1 Description We are concerned with the part of a telecommunications network that often is referred to as the \transit network", gure 1, i.e. the part that carries calls between subscribers that belong to di erent local switching centres. It consists of transit switching systems interconnected by high capacity links, e.g. coaxial cables, micro wave links, satellite links or optical bres. For a number of reasons it may be desirable to enhance a basic, physical network by creating a higher layer which is logically independent of the underlying physical network. Such a network is formed by reserving a certain amount of transmission capacity on a series of links and cross connecting the reserved channels through possible, intermediate transit nodes. The combination of reserved capacities on links and possible cross connections is called a virtual path (VP). Referring to gure 1, a VP between nodes T1 and T4 could e.g. be formed by reserving equal amounts of transmission capacity on links L1, L3 and L5 and cross connecting the reserved channels through T2 and T5. Two nodes being interconnected by a VP is, from the point of view of acceptance, routing and establishment of calls, essentially identical to having a single, direct route between them to which they have exclusive access. Figure 2 shows how the physical transit network of gure 1 can be transformed into a fully interconnected logical transit network by means of VPs. The process of creating and/or rearranging a (logical) network of VPs between a number of end nodes, i.e. partitioning the transmission capacities of the links between VPs, is called capacity management [10], bandwidth management [21], bandwidth switching [1] or bandwidth control [30] and is performed at a network management centre. Since the The work reported herein was partly carried out at the Teletra c Research Centre, The University of Adelaide, G.P.O. Box 498, Adelaide, South Australia 5001, Australia.