This paper presents Random Early Detection (RED) gate-ways for congestion avoidance in packet-switched networks. The gateway detects incipient congestion by com-puting the average queue size. The gateway could notify connections of congestion either by dropping packets ar-riving at the gateway or by setting a bit in packet headers. When the average queue size exceeds a preset threshold,the gateway drops or marks each arriving packet with a certain probability, where the exact probability is a func-tion of the average queue size. RED gateways keep the average queue size low while allowing occasional bursts of packets in the queue. During congestion, the probability that the gateway notifies a particular connection to reduce its window is roughly proportional to that connection's share of the bandwidth throughthe gateway. RED gateways are designed to accompany a transport-layer congestion control protocol such as TCP.The RED gateway has no bias against bursty traffic and avoids the global synchronization of many connectionsdecreasing their window at the same time. Simulations of a TCP/IP network are used to illustrate the performance of RED gateways.

This paper presents a control-theoretic approach to reactive flow control in networks that do not reserve bandwidth. We assume a round-robin-like queue service discipline in the output queues of the network’s switches, and propose deterministic and stochastic models for a single conversation in a network of such switches. These models motivate the Packet-Pair rate probing technique, and a provably stable rate-based flow control scheme. A Kalman state estimator is derived from discrete-time state space analysis, but there are difficulties in using the estimator in practice. These difficulties are overcome by a novel estimation scheme based on fuzzy logic. We then present a technique to extract and use additional information horn the system to develop a continuous-time system model. This is used to design a wuisnt of the control law that is also provably stable, and, in addition, takes control action as rapidly as possible. Finally, practical issues such as correcting parameter drift and cmmlination with window flow control are described.

In this paper, we characterize wide-area network applications that use the TCP transport protocol. We also describe a new way to model the wide-area traffic generated by a stub network. We believe the traffic model presented here will be useful in studying congestion control, routing algorithms, and other resource management schemes for existing and future networks. Our model is based on trace analysis of TCP/IP widearea internetwork traffic. We collected the TCP/IP packet headers of USC, UCB, and Bellcore networks at the point they connect with their respective regional access networks. We then wrote a handful of programs to analyze the traces. Our model characterizes individual TCP conversations by the distributions of: number of bytes transferred, duration, number of packets transferred, packet size, and packet interarrival time. Our trace analysis shows that both interactive and bulk transfer traffic from all sites reflect a large number of short conversations. Similarly, it shows that a very large percentage of traffic is bidirectional, even for bulk transfer. We observed that interactive applications send significantly different amounts of data in each direction of a conversation, and that interarrival times for interactive applications closely follow a constant plus exponential model. Half of the conversations are directed to a handful of networks, but the other half are directed to hundreds of networks. Many of these observations contradict commonly held beliefs regarding wide-area traffic.

As the speed and complexity of computer networks evolve, sharing network resources becomes increasingly important. Thus, the issue of how to allocate the available bandwidth among the multitude of users needs to be addressed. Such allocation needs to be in some sense efficient and fair to different users. In this work the so-called maxmin fairness is chosen as the optimality criterion. A new distributed and asynchronous algorithm is suggested. The algorithm is shown to converge to the optimal rate allocation in a network with general topology under dynamic changes in the set of network users, individual user load and occasional route changes. An upper bound on convergence time is given. The algorithm is shown to be well-behaved in transience. Unlike previous work, the algorithm takes bandwidth consumed by feedback traffic into account. Further, an extension of the algorithm is suggested to address the problem of policing misbehaved users.

This paper presents the packet-pair rate-based feedback flow control scheme. This scheme is designed for networks where individual connections do not reserve bandwidth and for the available bitrate (best-effort) component of integrated networks. We assume a round-robin-like queue service discipline in the output queues of the network's switches, and propose a linear stochastic model for a single conversation in a network of such switches. These model motivates the Packet-Pair rate probing technique, which forms the basis for provably stable discrete and continuous time rate-based flow control schemes. We present a novel state estimation scheme based on fuzzy logic. We then address several practical concerns: dealing with system startup, retransmission and timeout strategy, and dynamic setpoint probing. We present a finite state machine as well as source code for a model implementation. The dynamics of a single source, the interactions of multiple sources, and the behavior of packet-pai...

Current developments in technologies and markets stress the importance of exible and robust performance optimisation and congestion control. In intelligent networks, congestion control has traditionally taken a purely technical view and focused on protecting individual nodes from harmful overloads. We take a pro t oriented, network wide view and develop a congestion control mechanism to ensure real time performance under pro t maximisation. Numerical studies in a simulator show that the proposed mechanism is robust and, in particular in overloaded states, provides a substantial improvement in comparison to conventional load control mechanisms.

Traffic measurement and analysis are crucial to the design, operation and maintenance of wide-area networks based on Internet Protocol. This paper has outlined some important issues in real time traffic measurement and analysis. Firstly we give a brief survey on the related work of Internet traffic measurement, and then we focus on the general measurement methodologies. At last we present several visualizing results of our analysis upon some TCP traffic data.