The paper presents a model of a network with multiple controls that are hierarchically arranged in time, based on the time constants of events they control. The authors model the network with such hierarchical controls as a closed multi-chain queueing network and use a quasi static approximation based on a hierarchical decomposition technique to solve the model. They determine the blocking probability at the call level and burst level, as well as the waiting time distribution for bursts that are blocked. They investigate the trade off in performance that can be achieved at different levels in the hierarchical control model.>

The authors examine the networking environment of the future, pose the technical questions that need to be addressed to provide service assurance, and propose a set of strategies for congestion avoidance. Congestion avoidance is recommended instead of congestion control, which has very limited value in a high-speed network, where the latency in detecting congestion and reacting to it may make the control ineffective. The proposed solution consists of enforcing rate-control at the network edges, bandwidth reservation for continuous bit oriented (CBO) traffic using a unique two-queue strategy, and a scheduler-based packet cross-connect system. Simulation results of a Q+ model of an access node are presented that quantify the performance of this solution and compare it to existing congestion control mechanisms. The results demonstrate that it is possible to meet the differing needs of traffic types needing datagram transport and those needing virtual-circuit transport by using an intelligent scheduling strategy and a meaningful packet transport protocol.>

The authors propose a congestion control strategy called distributed source control (DSC), designed to address the integration of diverse traffic types in broadband packet networks. DSC is a rate-based network access control implemented at the asynchronous transfer mode (ATM) layer as a feedforward control, in conjunction with an adaptive end-to-end control between network edges. The authors examine the performance of high-speed data traffic such as large file transfers, still images, and document retrievals. The authors study DSC's integrability with real-time traffic such as voice and video. With the help of a simulation model of a broadband packet network (150 Mb/s), the authors quantify the improvement in network performance due to DSC. An analytic model for an access node under DSC is developed, and guidelines for sizing of buffers in the switch and for choosing the end-to-end window size are provided.>

A multidimensional approach to congestion control in integrated broadband networks is described, and a framework for a congestion control strategy that is applicable to virtual-circuit-based services as well as connectionless services is developed. The proposed congestion control strategy is based on a set of temporal controls, classification of services is based on their traffic characteristics and quality of service (QOS) requirements, and partitioning of the control space is based on the reaction time of the controls and the network time constants. The congestion control framework is simple, scales as the delay-bandwidth product increases, and is well suited for the asynchronous transfer mode that is being promoted as the underlying transport for B-ISDN.>

The authors propose a congestion control strategy called distributed source control (DSC), which is designed to address the integration of these diverse traffic types in broadband packet networks. An examination is made of the performance of high-speed continuous-stream data traffic such as large-file transfer and still-image and document retrievals, which are projected to be high runners in future networks and for which congestion control in broadband systems is a serious problem. Their integrability with real-time traffic such as voice and video is studied. With the help of a simulation model of a 150-Mb/s broadband packet network, the improvements in the performance of the different traffic types by using DSC are quantified. The authors also provide guidelines for sizing buffers in the switch and recommend a call-acceptance policy for these traffic types in the network.>

With the advent of high-speed networks, there has been a tendency to simplify flow/congestion control functions at lower levels of the OSI model and relegate them to higher levels. This paper shows that a class of traffic, namely host-to-host file transfers, can experience severe degradation in performance due to lack of proper control in such networks. A simple distributed rate-based flow control scheme is proposed which solves the problem without affecting the performance of the network. The scheme is easily implemented, with control totally distributed and managed by the sources. The rate is negotiated at call setup time and entails very little overhead. A detailed simulation model is built to quantify the problems and verify the solution.>