Techniques for the planning of multi-service telecommunications networks over a multi-period scenario are proposed, based on routing optimisation to reduce network cost by removing DWDM transmission systems. A model of a medium-size national network is optimised using the various techniques, and the results presented in terms of the total number of DWDM systems required and the amount of wavelength-hops (giving an indication toward the number of optical transponders required). Traffic is taken as a mix between unprotected and 1+1 SNCP optical path protected demands. Traffic growth is applied over the 5 year planning horizon to give a tenfold increase in total traffic volume for the final year. A greenfield situation is assumed, yet since deployment occurs over several years, a present value calculation is used to estimate total cost, assuming that transponders and systems are only installed when they are due to be 'lit'.

In wireless ATM networks, user connections need to be rerouted during handoff as mobile users move among base stations. The rerouting of connections must be done quickly with minimal disruption to traffic. In addition, the resulting routes must be optimal. A reasonable approach is to implement handoff in two phases. In the first phase connections are rapidly rerouted and in the second phase a periodic route optimization procedure is executed. The route optimization should impose minimal signaling and processing load on the ATM switches. In this paper, we propose and study a periodic execution of route optimization for a two-phase handoff scheme. We study two types of execution: non-adaptive and adaptive. For the adaptive optimization, we consider two adaptation schemes that are dependent on network conditions. A simulation model is developed to study system performance. The adaptive route optimization is shown to minimize signaling and processing load while maximizing utilization of reserved resources.

Supporting mobility in wireless ATM networks poses a number of technical issues. An important issue is the ability to reroute on-going virtual connections during handoff as mobile users move among base stations. We propose a two-phase inter-switch handoff scheme using permanent virtual paths reserved between adjacent mobility enhanced switches (MES). The virtual paths are used in the first phase to rapidly reroute user connections. In the second phase, a distributed optimization process is initiated to optimally reroute handoff connections. The proposed handoff scheme yields small handoff latency and optimal routes while decreasing system cost and complexity. The paper also describes wireless control and ATM signaling capabilities required for supporting this scheme. Specific ATM UNI/NNI protocol extensions are presented. Using analysis, we calculate and study the bandwidth requirement for the reserved virtual paths. We also study the second-phase optimization process overhead as well as the effect of other system design parameters.

The paper studies the performance of computing environment design alternatives for an application workload associated with a large software product generation process. A number of configurations based on shared memory multiprocessor computing platforms and network file servers are considered in the study. The various computing environment configurations are differentiated based on the location of the devices that provide physical storage for the input and output files of the software product generation process, and the characteristics of the computing platforms that are used to provide compute and file services. The evaluation of the design alternatives is based on a multiclass priority queuing network model that is used to analyze system performance under various load conditions, identify potential bottlenecks and study design tradeoffs.

The paper describes the network design and analysis of a multi-protocol application environment characterized by a client/server architecture, integration of legacy and distributed database structures, frame relay wide area network, and token ring local area networks. Detailed workload characterization and performance modeling of the application environment is presented, and network design issues are addressed. The model is used to study network performance under various load conditions, identify bottlenecks and compare design alternatives.

The performance of a network based computing system that consists of a number of clients and a server, interconnected by a local area network, is studied. Each client represents a diskless or swapful workstation, or an X terminal, and generates application workload using either a conventional UNIX file system or the Network File System (NFS). To characterize the application workload and the effect of the protocol (login, rlogin, NFS), the user interface (workstation, X terminal) and its configuration (memory size, disk storage), a series of measurement experiments was performed in a controlled environment. During each experiment the traffic on the network and the activity on the various system resources were monitored. The measurements obtained are used to parameterize a queuing network model of the system, which is then used to project the performance of the system under various load conditions, to identify system bottlenecks, and to compare design alternatives.>

The performance analysis of a system in which storage is provided by a file server node on a network of client processors is discussed. The server controls a hierarchy of storage devices, and provides all the necessary file management functions. The clients are large mainframe systems that have their own local storage devices. The movement of files among the various storage levels is managed by a hierarchical storage management system. A closed queuing network model of the client-server storage system is used to analyze the performance of the system for various file movement criteria and to study the tradeoffs between recalling a file and accessing it by a distributed file system. Several network topologies (Ethernet, token ring, channel-to-channel) and their effect on performance are considered.>