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 discusses the use of Explicit Congestion Notification (ECN) mechanisms in the TCP/IP protocol. The first part proposes new guidelines for TCP’s response to ECN mechanisms (e.g., Source Quench packets, ECN fields in packet headers). Next, using simulations, we explore the benefits and drawbacks of ECN in TCP/IP networks. Our simulations use RED gateways modified to set an ECN bit in the IP packet header as an indication of congestion, with Reno-style TCP modified to respond to ECN as well as to packet drops as indications of congestion. The simulations show that one advantage of ECN mechanisms is in avoiding unnecessary packet drops, and therefore avoiding unnecessary delay for packets from low-bandwidth delay-sensitive TCP connections. A second advantage of ECN mechanisms is in networks (generally LANs) where the effectiveness of TCP retransmit timers is limited by the coarse granularity of the TCP clock. The paper also discusses some implementation issues concerning specific ECN mechanisms in TCP/IP networks.

Abstract not found

The congestion control algorithm embedded in the 4.3-Tahoe BSD TCP implementation has dramatically improved congestion control over the Internet. However, several recent simulation studies on the dynamics of this algorithm has revealed that the algorithm exhibits clear oscillatory patterns in sending window size, round trip delay and bottleneck queue length. In this paper, we present a new congestion signal scheme and a dual traffic adjustment strategy. Simulation results show that our modifications can eliminate the periodic packet losses and substantially reduce the traffic oscillation.

The Fuzzball is an operating system and applications library designed for the PDP11 family of computers. It was intended as a development platform and research pipewrench for the DARPA/NSF Internet, but has occasionally escaped to earn revenue in commercial service. It was designed, implemented and evolved over a seventeen-year era spanning the development of the ARPANET and TCP/IP protocol suites and can today be found at Internet outposts from Hawaii to Italy standing watch for adventurous applications and enduring experiments. This paper describes the Fuzzball and its applications, including a description of its novel congestion avoidance/control and timekeeping mechanisms.<E-110> Keywords: protocol testing, network testing, performance evaluation, Internet architecture, TCP/IP protocols, congestion control, internetwork time synchronization.<E-132> 1. Introduction<E-128> The Fuzzball is a software package consisting of a fast, compact operating system, support for the DARPA/...

Most of the end-to-end congestion control schemes are "voluntary" in nature and critically depend on end-user cooperation. We show that in the presence of selfish users, all such schemes will inevitably lead to a congestion collapse. Router and switch mechanisms such as service disciplines and buffer management policies determine the sharing of resources during congestion. We show, using a game-theoretic approach, that all currently proposed mechanisms, either encourage the behaviour that leads to congestion or are oblivious to it. We propose a class of service disciplines called the Diminishing Weight Schedulers (DWS) that punish misbehaving users and reward congestion avoiding well behaved users. We also propose a sample service discipline called the Rate Inverse Scheduling (RIS) from the class of DWS schedulers. With DWS schedulers deployed in the network, max-min fair rates constitute a unique Nash and Stackelberg Equilibrium. We show that RIS solves the problems of excessive congestion due to unresponsive flows, aggressive versions of TCP, multiple parallel connections and is also fair to TCP.

In this paper, we propose router mechanisms to regulate unresponsive best-effort traffic. By unresponsive traffic, we mean flows that do not reduce their sending rate in response to congestion. The goal of the proposed mechanisms is to drop undeliverable packets as close to the periphery of the network as possible. The key ideas of our approach are: (1) edge routers keep track of incoming flows and their arrival rates; (2) core routers use RED for queue management and generate rate-limited source quenches on packet drops to advice sources to reduce their sending rates; and (3) edge routers snoop on source quenches passing through them and use them to control per-flow regulators. Regulators adjust their maximum sending rate using a multiplicative-decrease, additive-increase discipline. A decrease is triggered by the arrival of a source quench; an increase is triggered by non-arrival of source quenches for a time period. We examine the impact of these mechanisms for a variety of simulate...

Most of the end-to-end congestion control schemes are "voluntary" in nature and critically depend on enduser cooperation. We show that in the presence of selfish users, all such schemes will inevitably lead to a congestion collapse. Router and switch mechanisms such as service disciplines and buffer management policies determine the sharing of resources during congestion. We show, using a Game Theoretic approach, that all the currently proposed mechanisms, either encourage the behaviour that leads to congestion ("Evil behaviour") or are oblivious to it. We propose a sample...

In this thesis, we propose router mechanisms to regulate unresponsive best-effort traffic. By unresponsive traffic, we mean flows that do not reduce their sending rate in response to congestion. The goal of the proposed mechanisms is to drop undeliverable packets (packets that are dropped somewhere in the network before they reach their destination) as close to the periphery of the network as possible. The key ideas of our approach are: (1) edge routers keep track of incoming flows and their arrival rates; (2) non-edge routers use RED (Random Early Detection) for queue management and generate rate-limited source quenches on packet drops to advise sources to reduce their sending rates; and (3) edge routers snoop on source quenches passing through them and use them to control per-flow regulators. Regulators adjust their maximum sending rate using a multiplicative-decrease, additive-increase discipline. A decrease is triggere...

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