Recommendations on Queue Management and Congestion Avoidance in the Internet
01 Apr 1998-Vol. 2309, pp 1-17
TL;DR: This memo presents a strong recommendation for testing, standardization, and widespread deployment of active queue management in routers, to improve the performance of today's Internet.
Abstract: This memo presents two recommendations to the Internet community concerning measures to improve and preserve Internet performance. It presents a strong recommendation for testing, standardization, and widespread deployment of active queue management in routers, to improve the performance of today's Internet. It also urges a concerted effort of research, measurement, and ultimate deployment of router mechanisms to protect the Internet from flows that are not sufficiently responsive to congestion notification.
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04 Mar 1999
TL;DR: In this paper, the authors propose the ratio between the worst possible Nash equilibrium and the social optimum as a measure of the effectiveness of the system and derive upper and lower bounds for this ratio in a model in which several agents share a very simple network.
Abstract: In a system in which noncooperative agents share a common resource, we propose the ratio between the worst possible Nash equilibrium and the social optimum as a measure of the effectiveness of the system. Deriving upper and lower bounds for this ratio in a model in which several agents share a very simple network leads to some interesting mathematics, results, and open problems.
1,958 citations
Cites background from "Recommendations on Queue Management..."
...It is worth mentioning that when s2=s1 >the probabilities given above are outside the interval [0; 1 ]. Therefore, both agents have pure strategies and the coordination ratio is 1....
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...Game-theoretic aspects of the Internet have also been considered by researchers associated with the Internet Society [ 1 ,12], with an eye towards designing variants of the Internet Protocols which are more resilient to video-like...
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...Internet users and service providers act selshly and spontaneously, without an authority that monitors and regulates network operation in order to achieve some \social optimum" such as minimum total delay [ 1 ]....
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...Finally, it would be extremely interesting, once the relative quality of the Nash equilibria in such situations is better understood, to employ such understanding in the design of improved protocols [ 1 ]....
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TL;DR: It is argued that router mechanisms are needed to identify and restrict the bandwidth of selected high-bandwidth best-effort flows in times of congestion, and several general approaches are discussed for identifying those flows suitable for bandwidth regulation.
Abstract: This paper considers the potentially negative impacts of an increasing deployment of non-congestion-controlled best-effort traffic on the Internet. These negative impacts range from extreme unfairness against competing TCP traffic to the potential for congestion collapse. To promote the inclusion of end-to-end congestion control in the design of future protocols using best-effort traffic, we argue that router mechanisms are needed to identify and restrict the bandwidth of selected high-bandwidth best-effort flows in times of congestion. The paper discusses several general approaches for identifying those flows suitable for bandwidth regulation. These approaches are to identify a high-bandwidth flow in times of congestion as unresponsive, "not TCP-friendly", or simply using disproportionate bandwidth. A flow that is not "TCP-friendly" is one whose long-term arrival rate exceeds that of any conformant TCP in the same circumstances. An unresponsive flow is one failing to reduce its offered load at a router in response to an increased packet drop rate, and a disproportionate-bandwidth flow is one that uses considerably more bandwidth than other flows in a time of congestion.
1,787 citations
TL;DR: The degradation in network performance due to unregulated traffic is quantified and it is proved that if the latency of each edge is a linear function of its congestion, then the total latency of the routes chosen by selfish network users is at most 4/3 times the minimum possible total latency.
Abstract: We consider the problem of routing traffic to optimize the performance of a congested network. We are given a network, a rate of traffic between each pair of nodes, and a latency function for each edge specifying the time needed to traverse the edge given its congestion; the objective is to route traffic such that the sum of all travel times---the total latency---is minimized.In many settings, it may be expensive or impossible to regulate network traffic so as to implement an optimal assignment of routes. In the absence of regulation by some central authority, we assume that each network user routes its traffic on the minimum-latency path available to it, given the network congestion caused by the other users. In general such a "selfishly motivated" assignment of traffic to paths will not minimize the total latency; hence, this lack of regulation carries the cost of decreased network performance.In this article, we quantify the degradation in network performance due to unregulated traffic. We prove that if the latency of each edge is a linear function of its congestion, then the total latency of the routes chosen by selfish network users is at most 4/3 times the minimum possible total latency (subject to the condition that all traffic must be routed). We also consider the more general setting in which edge latency functions are assumed only to be continuous and nondecreasing in the edge congestion. Here, the total latency of the routes chosen by unregulated selfish network users may be arbitrarily larger than the minimum possible total latency; however, we prove that it is no more than the total latency incurred by optimally routing twice as much traffic.
1,703 citations
01 Jul 1997
TL;DR: A performance model for the TCP Congestion Avoidance algorithm that predicts the bandwidth of a sustained TCP connection subjected to light to moderate packet losses, such as loss caused by network congestion is analyzed.
Abstract: In this paper, we analyze a performance model for the TCP Congestion Avoidance algorithm. The model predicts the bandwidth of a sustained TCP connection subjected to light to moderate packet losses, such as loss caused by network congestion. It assumes that TCP avoids retransmission timeouts and always has sufficient receiver window and sender data. The model predicts the Congestion Avoidance performance of nearly all TCP implementations under restricted conditions and of TCP with Selective Acknowledgements over a much wider range of Internet conditions.We verify the model through both simulation and live Internet measurements. The simulations test several TCP implementations under a range of loss conditions and in environments with both drop-tail and RED queuing. The model is also compared to live Internet measurements using the TReno diagnostic and real TCP implementations.We also present several applications of the model to problems of bandwidth allocation in the Internet. We use the model to analyze networks with multiple congested gateways; this analysis shows strong agreement with prior work in this area. Finally, we present several important implications about the behavior of the Internet in the presence of high load from diverse user communities.
1,580 citations
28 Aug 2000
TL;DR: A mechanism for equation-based congestion control for unicast traffic that refrains from reducing the sending rate in half in response to a single packet drop, and uses both simulations and experiments over the Internet to explore performance.
Abstract: This paper proposes a mechanism for equation-based congestion control for unicast traffic. Most best-effort traffic in the current Internet is well-served by the dominant transport protocol, TCP. However, traffic such as best-effort unicast streaming multimedia could find use for a TCP-friendly congestion control mechanism that refrains from reducing the sending rate in half in response to a single packet drop. With our mechanism, the sender explicitly adjusts its sending rate as a function of the measured rate of loss events, where a loss event consists of one or more packets dropped within a single round-trip time. We use both simulations and experiments over the Internet to explore performance.
1,458 citations
Cites background from "Recommendations on Queue Management..."
...From [2], a TCPcompatible flow is defined as a flow that, in steady-state, uses no more bandwidth than a conformant TCP running under comparable conditions....
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References
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TL;DR: Red gateways are designed to accompany a transport-layer congestion control protocol such as TCP and have no bias against bursty traffic and avoids the global synchronization of many connections decreasing their window at the same time.
Abstract: The authors present random early detection (RED) gateways for congestion avoidance in packet-switched networks. The gateway detects incipient congestion by computing the average queue size. The gateway could notify connections of congestion either by dropping packets arriving at the gateway or by setting a bit in packet headers. When the average queue size exceeds a present threshold, the gateway drops or marks each arriving packet with a certain probability, where the exact probability is a function 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 through the 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 connections decreasing their window at the same time. Simulations of a TCP/IP network are used to illustrate the performance of RED gateways. >
6,198 citations
01 Aug 1988
TL;DR: The measurements and the reports of beta testers suggest that the final product is fairly good at dealing with congested conditions on the Internet, and an algorithm recently developed by Phil Karn of Bell Communications Research is described in a soon-to-be-published RFC.
Abstract: In October of '86, the Internet had the first of what became a series of 'congestion collapses'. During this period, the data throughput from LBL to UC Berkeley (sites separated by 400 yards and three IMP hops) dropped from 32 Kbps to 40 bps. Mike Karels1 and I were fascinated by this sudden factor-of-thousand drop in bandwidth and embarked on an investigation of why things had gotten so bad. We wondered, in particular, if the 4.3BSD (Berkeley UNIX) TCP was mis-behaving or if it could be tuned to work better under abysmal network conditions. The answer to both of these questions was “yes”.Since that time, we have put seven new algorithms into the 4BSD TCP: round-trip-time variance estimationexponential retransmit timer backoffslow-startmore aggressive receiver ack policydynamic window sizing on congestionKarn's clamped retransmit backofffast retransmit Our measurements and the reports of beta testers suggest that the final product is fairly good at dealing with congested conditions on the Internet.This paper is a brief description of (i) - (v) and the rationale behind them. (vi) is an algorithm recently developed by Phil Karn of Bell Communications Research, described in [KP87]. (viii) is described in a soon-to-be-published RFC.Algorithms (i) - (v) spring from one observation: The flow on a TCP connection (or ISO TP-4 or Xerox NS SPP connection) should obey a 'conservation of packets' principle. And, if this principle were obeyed, congestion collapse would become the exception rather than the rule. Thus congestion control involves finding places that violate conservation and fixing them.By 'conservation of packets' I mean that for a connection 'in equilibrium', i.e., running stably with a full window of data in transit, the packet flow is what a physicist would call 'conservative': A new packet isn't put into the network until an old packet leaves. The physics of flow predicts that systems with this property should be robust in the face of congestion. Observation of the Internet suggests that it was not particularly robust. Why the discrepancy?There are only three ways for packet conservation to fail: The connection doesn't get to equilibrium, orA sender injects a new packet before an old packet has exited, orThe equilibrium can't be reached because of resource limits along the path. In the following sections, we treat each of these in turn.
5,620 citations
"Recommendations on Queue Management..." refers background or methods in this paper
...RED estimates the average queue size, either in the forwarding path using a simple exponentially weighted moving average (such as presented in Appendix A of [ Jacobson88 ]), or in the background (i.e., not in the forwarding path) using a similar...
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...Beginning in 1986, Jacobson developed the congestion avoidance mechanisms that are now required in TCP implementations [ Jacobson88 , HostReq89]....
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TL;DR: It is demonstrated that Ethernet LAN traffic is statistically self-similar, that none of the commonly used traffic models is able to capture this fractal-like behavior, and that such behavior has serious implications for the design, control, and analysis of high-speed, cell-based networks.
Abstract: Demonstrates that Ethernet LAN traffic is statistically self-similar, that none of the commonly used traffic models is able to capture this fractal-like behavior, that such behavior has serious implications for the design, control, and analysis of high-speed, cell-based networks, and that aggregating streams of such traffic typically intensifies the self-similarity ("burstiness") instead of smoothing it. These conclusions are supported by a rigorous statistical analysis of hundreds of millions of high quality Ethernet traffic measurements collected between 1989 and 1992, coupled with a discussion of the underlying mathematical and statistical properties of self-similarity and their relationship with actual network behavior. The authors also present traffic models based on self-similar stochastic processes that provide simple, accurate, and realistic descriptions of traffic scenarios expected during B-ISDN deployment. >
5,567 citations
TL;DR: In this article, a fair gateway queueing algorithm based on an earlier suggestion by Nagle is proposed to control congestion in datagram networks, based on the idea of fair queueing.
Abstract: We discuss gateway queueing algorithms and their role in controlling congestion in datagram networks. A fair queueing algorithm, based on an earlier suggestion by Nagle, is proposed. Analysis and s...
2,639 citations
01 Oct 1989
TL;DR: This RFC is an official specification for the Internet community that incorporates by reference, amends, corrects, and supplements the primary protocol standards documents relating to hosts.
Abstract: This RFC is an official specification for the Internet community It
incorporates by reference, amends, corrects, and supplements the
primary protocol standards documents relating to hosts [STANDARDS-
TRACK]
1,675 citations