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72
FAST TCP: Motivation, Architecture, Algorithms, Performance
, 2004
"... We describe FAST TCP, a new TCP congestion control algorithm for highspeed longlatency networks, from design to implementation. We highlight the approach taken by FAST TCP to address the four difficulties, at both packet and flow levels, which the current TCP implementation has at large windows. W ..."
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Cited by 369 (18 self)
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We describe FAST TCP, a new TCP congestion control algorithm for highspeed longlatency networks, from design to implementation. We highlight the approach taken by FAST TCP to address the four difficulties, at both packet and flow levels, which the current TCP implementation has at large windows. We describe the architecture and characterize the equilibrium and stability properties of FAST TCP. We present experimental results comparing our first Linux prototype with TCP Reno, HSTCP, and STCP in terms of throughput, fairness, stability, and responsiveness. FAST TCP aims to rapidly stabilize highspeed longlatency networks into steady, efficient and fair operating points, in dynamic sharing environments, and the preliminary results are promising.
A Duality Model of TCP and Queue Management Algorithms
 IEEE/ACM Trans. on Networking
, 2002
"... We propose a duality model of congestion control and apply it to understand the equilibrium properties of TCP and active queue management schemes. Congestion control is the interaction of source rates with certain congestion measures at network links. The basic idea is to regard source rates as p ..."
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Cited by 307 (37 self)
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We propose a duality model of congestion control and apply it to understand the equilibrium properties of TCP and active queue management schemes. Congestion control is the interaction of source rates with certain congestion measures at network links. The basic idea is to regard source rates as primal variables and congestion measures as dual variables, and congestion control as a distributed primaldual algorithm carried out over the Internet to maximize aggregate utility subject to capacity constraints. The primal iteration is carried out by TCP algorithms such as Reno or Vegas, and the dual iteration is carried out by queue management such as DropTail, RED or REM. We present these algorithms and their generalizations, derive their utility functions, and study their interaction.
Internet Congestion Control.
 IEEE Control Systems Magazine,
, 2002
"... Abstract This article reviews the current TCP congestion control protocols and overviews recent advances that have brought analytical tools to this problem. We describe an optimizationbased framework that provides an interpretation of various flow control mechanisms, in particular, the utility bei ..."
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Cited by 194 (25 self)
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Abstract This article reviews the current TCP congestion control protocols and overviews recent advances that have brought analytical tools to this problem. We describe an optimizationbased framework that provides an interpretation of various flow control mechanisms, in particular, the utility being optimized by the protocol's equilibrium structure. We also look at the dynamics of TCP and employ linear models to exhibit stability limitations in the predominant TCP versions, despite certain builtin compensations for delay. Finally, we present a new protocol that overcomes these limitations and provides stability in a way that is scalable to arbitrary networks, link capacities, and delays.
One More Bit Is Enough
 in Proceedings of ACM SIGCOMM
, 2005
"... Achieving efficient and fair bandwidth allocation while minimizing packet loss and bottleneck queue in high bandwidthdelay product networks has long been a daunting challenge. Existing endtoend congestion control (e.g., TCP) and traditional congestion notification schemes (e.g., TCP+AQM/ ECN) have ..."
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Cited by 67 (1 self)
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Achieving efficient and fair bandwidth allocation while minimizing packet loss and bottleneck queue in high bandwidthdelay product networks has long been a daunting challenge. Existing endtoend congestion control (e.g., TCP) and traditional congestion notification schemes (e.g., TCP+AQM/ ECN) have significant limitations in achieving this goal. While the XCP protocol addresses this challenge, it requires multiple bits to encode the congestionrelated information exchanged between routers and endhosts. Unfortunately, there is no space in the IP header for these bits, and solving this problem involves a nontrivial and timeconsuming standardization process. In this paper, we design and implement a simple, lowcomplexity protocol, called Variablestructure congestion Control Protocol (VCP), that leverages only the existing two ECN bits for network congestion feedback, and yet achieves comparable performance to XCP, i.e., high utilization, negligible packet loss rate, low persistent queue length, and reasonable fairness. On the downside, VCP converges significantly slower to a fair allocation than XCP. We evaluate the performance of VCP using extensive ns2 simulations over a wide range of network scenarios and find that it significantly outperforms many recentlyproposed TCP variants, such as HSTCP, FAST, and CUBIC. To gain insight into the behavior of VCP, we analyze a simplified fluid model and prove its global stability for the case of a single bottleneck shared by synchronous flows with identical roundtrip times. 1.
Understanding XCP: Equilibrium and fairness
 in Proc. IEEE INFOCOM, 2005
"... Abstract—We prove that the XCP equilibrium solves a constrained maxmin fairness problem by identifying it with the unique solution of a hierarchy of optimization problems, namely those solved by maxmin fair allocation, but solved by XCP under an additional constraint. This constraint is due to the ..."
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Cited by 56 (4 self)
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Abstract—We prove that the XCP equilibrium solves a constrained maxmin fairness problem by identifying it with the unique solution of a hierarchy of optimization problems, namely those solved by maxmin fair allocation, but solved by XCP under an additional constraint. This constraint is due to the “bandwidth shuffling ” necessary to obtain fairness. We describe an algorithm to compute this equilibrium and derive a lower and upper bound on link utilization. While XCP reduces to maxmin allocation at a single link, its behavior in a network can be very different. We illustrate that the additional constraint can cause flows to receive an arbitrarily small fraction of their maxmin fair allocations. We confirm these results using ns2 simulations. Index Terms—Congestion control, maxmin, optimization.
Fast tcp: From theory to experiments
 IEEE Network
, 2005
"... he congestion control algorithm in the current TCP has performed remarkably well and is generally believed to have prevented severe congestion as the Internet scaled up by six orders of magnitude in size, speed, load, and connectivity in the last 15 years. It is also well known, however, that as ban ..."
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Cited by 48 (9 self)
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he congestion control algorithm in the current TCP has performed remarkably well and is generally believed to have prevented severe congestion as the Internet scaled up by six orders of magnitude in size, speed, load, and connectivity in the last 15 years. It is also well known, however, that as bandwidthdelay product continues to grow, the current TCP implementation will eventually become a performance bottleneck. In this article we describe a different congestion control algorithm for TCP, called FAST [1]. FAST TCP has three key differences. First, it is an equationbased algorithm and hence eliminates packetlevel oscillations. Second, it uses queuing delay as the primary measure of congestion, which can be more reliably measured by end hosts than loss probability in fast longdistance networks. Third, it has stable flow dynamics and achieves weighted proportional fairness in equilibrium that does not penalize long flows, as the current congestion control algorithm does. Alternative approaches are described in [2–6]. The details of the architecture, algorithms, extensive experimental evaluations of FAST TCP, and comparison with other TCP variants can be found in [1, 7]. In this article we highlight the motivation, background theory, implementation, and our first major experimental results. The scientific community is singular in its urgent need for efficient highspeed data transfer. We explain why this community has been driving the development and deployment of ultrascale networking. The design of FAST TCP builds on an emerging theory that allows us to understand the equilibrium and stability properties of large networks under endtoend control. It provides a framework to understand issues, clarify ideas, and suggest directions, leading to a more robust and better performing design. We summarize this theory and explain FAST TCP. We report the results of our first global experiment and conclude the article.
Modeling and stability of FAST TCP
 In IMA Volumes in Mathematics and its Applications, Volume 143: Wireless Communications
, 2006
"... Abstract — We introduce a discretetime model of FAST TCP that fully captures the effect of selfclocking, and compare it with the traditional continuoustime model. While the continuoustime model predicts instability for homogeneous sources sharing a single link when feedback delay is large, exper ..."
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Cited by 32 (8 self)
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Abstract — We introduce a discretetime model of FAST TCP that fully captures the effect of selfclocking, and compare it with the traditional continuoustime model. While the continuoustime model predicts instability for homogeneous sources sharing a single link when feedback delay is large, experiments suggest otherwise. Using the discretetime model, we prove that FAST TCP is locally asymptotically stable in general networks when all sources have a common roundtrip feedback delay, no matter how large the delay is. We also prove global stability for a single bottleneck link in the absence of feedback delay. The techniques developed here are new and applicable to other protocols.
Methodological Frameworks for Largescale Network Analysis and Design
 ACM SIGCOMM Computer Communications Review
, 2004
"... This paper emphasizes the need for methodological frameworks for analysis and design of large scale networks which are independent of specific design innovations and their advocacy, with the aim of making networking a more systematic engineering discipline. Networking problems have largely confounde ..."
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Cited by 24 (6 self)
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This paper emphasizes the need for methodological frameworks for analysis and design of large scale networks which are independent of specific design innovations and their advocacy, with the aim of making networking a more systematic engineering discipline. Networking problems have largely confounded existing theory, and innovation based on intuition has dominated design. This paper will illustrate potential pitfalls of this practice. The general aim is to illustrate universal aspects of theoretical and methodological research that can be applied to network design and verification. The issues focused on will include the choice of models, including the relationship between flow and packet level descriptions, the need to account for uncertainty generated by modelling abstractions, and the challenges of dealing with network scale. The rigorous comparison of proposed schemes will be illustrated using various abstractions. While standard tools from robust control theory have been applied in this area, we will also illustrate how networkspecific challenges can drive the development of new mathematics that expand their range of applicability, and how many enormous challenges remain.
Equilibrium and fairness of networks shared by TCP
, 2005
"... It has been proved theoretically that a network with heterogeneous congestion control algorithms that react to different congestion signals can have multiple equilibrium points. In this paper, we demonstrate this experimentally using TCP Reno and Vegas/FAST. We also show that any desired interproto ..."
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Cited by 17 (10 self)
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It has been proved theoretically that a network with heterogeneous congestion control algorithms that react to different congestion signals can have multiple equilibrium points. In this paper, we demonstrate this experimentally using TCP Reno and Vegas/FAST. We also show that any desired interprotocol fairness is in principle achievable by an appropriate choice of Vegas/FAST parameter, and that intraprotocol fairness among flows within each protocol is unaffected by the presence of the other protocol except for a reduction in effective link capacities. Dummynet experiments and ns2 simulations are presented to verify these results. 1
The case for delaybased congestion control
 IEEE Annual Workshop on Computer Communications
, 2003
"... We argue that, in the absence of explicit feedback, delaybased algorithms become the preferred approach for endtoend congestion control as networks scale up in capacity. Their advantage is small at low speed but decisive at high speed. The distinction between packetlevel and flowlevel problems of ..."
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Cited by 9 (0 self)
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We argue that, in the absence of explicit feedback, delaybased algorithms become the preferred approach for endtoend congestion control as networks scale up in capacity. Their advantage is small at low speed but decisive at high speed. The distinction between packetlevel and flowlevel problems of the current TCP exposes the difficulty of lossbased algorithms at large congestion windows. 1