Fast TCP Matt Weaver CS622 Fall 2007

FAST TCP: Motivation, Architecture, Algorithms, Performance David X. Wei, Student Member, IEEE, Cheng Jin, Steven H. Low, Senior Member, IEEE, and Sanjay Hegde 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance

FAST TCP: Motivation, Architecture, Algorithms, Performance Abstract FAST TCP is a congestion control algorithm that attempts to solve the problems of congestion control. This paper covers: The algorithm itself. Performance metrics 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 3

FAST TCP: Motivation, Architecture, Algorithms, Performance Background “Congestion control is a distributed algorithm to share network resources among competing users.” A difficult problem to solve... Resource needs vary, depending on time of day. Available resources is usually static. 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 4

FAST TCP: Motivation, Architecture, Algorithms, Performance FAST is a recursive acronym: FAST AQM Scalable TCP AQM: Active Queue Management TCP: Transmission Control Protocol (duh) 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 5

FAST TCP: Motivation, Architecture, Algorithms, Performance Current Issues As congestion is monitored, current algorithms slow down monitoring as packets are dropped, the average sending rate depends on low loss probability. High data transmission rates are required for low loss. Usually lower than WiFi can support. 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 6

FAST TCP: Motivation, Architecture, Algorithms, Performance Solution FAST TCP uses queues to store a constant number of packets. If too few packets are queued, the sending rate increases. If too few, the rate decreases. 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 7

FAST TCP: Motivation, Architecture, Algorithms, Performance Congestion Control Current TCP congestion control algorithm (aka Reno). At the packet level, linear increase by one packet per roundtrip time (RTT) is too slow, and multiplicative decrease per loss event is too drastic. At the flow level, maintaining large average congestion windows requires an extremely small equilibrium loss probability. At the packet level, oscillation in congestion window is unavoidable because TCP uses a binary congestion signal (packet loss). At the flow level, the dynamics is unstable, leading to severe oscillations that can only be reduced by the accurate estimation of packet loss probability and a stable design of the flow dynamics. 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 8

FAST TCP: Motivation, Architecture, Algorithms, Performance Motivations Two levels of design: The flow level (macroscopic) covers: QoS Stability etc Packet level (microscopic) covers: The same goals, but focused on end to end. Reno suffered because higher level control was considered after the micro level. 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 9

FAST TCP: Motivation, Architecture, Algorithms, Performance Calculations Congestion and utility: U calculates utility for each stakeholder (user) at a given flow. 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 10

FAST TCP: Motivation, Architecture, Algorithms, Performance Calculations Equilibrium (FAST): Equilibrium (Reno): 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 11

FAST TCP: Motivation, Architecture, Algorithms, Performance Calculations “A key departure of our model from those in the literature is that we assume that a source’s send rate, defined as xi(t) :=wi(t)=Ti(t), cannot exceed the throughput it receives. “ 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 12

FAST TCP: Motivation, Architecture, Algorithms, Performance Dynamic Structure The weakness of current schemes versus FAST is shown for large window sizes. 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 13

FAST TCP: Motivation, Architecture, Algorithms, Performance Equilibrium Equilibrium measures congestion consistency. 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 14

FAST TCP: Motivation, Architecture, Algorithms, Performance Differences Though all of the aforementioned algorithms look different at the packet level, they actually have similar structures at the flow and equilibrium levels. 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 15

FAST TCP: Motivation, Architecture, Algorithms, Performance Performance Test 1 To test performance, packet data is pushed through a semi-articial network. Identical sender and receiver boxes, running dummynet on FreeBSD. Emulated router. Dummynet running: Paths with RTTs of 50, 100, 150, and 200ms. Second path with a bottleneck capacity of 8M/s and a buffer size of 2,000 packets shared by all the delay pipes. 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 16

FAST TCP: Motivation, Architecture, Algorithms, Performance Results Dynamic state I: Small flows, large windows Dynamic state II: Larger flows 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 17

FAST TCP: Motivation, Architecture, Algorithms, Performance Dynamic State I 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 18

FAST TCP: Motivation, Architecture, Algorithms, Performance Throughput kbps Queue(avg) # of pkts FAST vs Reno I Sec 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 19

FAST TCP: Motivation, Architecture, Algorithms, Performance Dynamic State II 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 20

FAST TCP: Motivation, Architecture, Algorithms, Performance Dynamic State II 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 21

FAST TCP: Motivation, Architecture, Algorithms, Performance FAST vs Reno II 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 22

FAST TCP: Motivation, Architecture, Algorithms, Performance BIC 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 23

FAST TCP: Motivation, Architecture, Algorithms, Performance Performance Test 2 Dummynet tests are limited to a single bottleneck and the same protocols. NS-2 Simulation run in lab: Same algorithm. Noise added to eliminate phase artifacts. 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 24

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FAST TCP: Motivation, Architecture, Algorithms, Performance 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 26

FAST TCP: Motivation, Architecture, Algorithms, Performance 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 27

FAST TCP: Motivation, Architecture, Algorithms, Performance 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 28

FAST TCP: Motivation, Architecture, Algorithms, Performance 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 29

FAST TCP: Motivation, Architecture, Algorithms, Performance 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 30

FAST TCP: Motivation, Architecture, Algorithms, Performance Conclusion Because of the use of queues, FAST TCP can handle lower transmission rates. The paper also covers some simulated scenarios (too lengthy to cover properly here). 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 31

FAST TCP: Motivation, Architecture, Algorithms, Performance Caveat Emptor Possibly biased research: Jin Cheng, Steve Low, and David Wei (the authors) patented and market the FAST TCP algorithm. FAST TCP implementation sold as FastSoft Aria (a 1 U rack mountable hardware solution). http://www.fastsoft.com/ Ao Tang proposed that these measurements were somewhat misleading in another paper. 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 32

FAST TCP: Motivation, Architecture, Algorithms, Performance Other CC Algorithms BIC TCP Compound TCP CUBIC H-TCP High Speed TCP HSTCP-LP Hybla New Reno Tahoe TCP-Illinois TCP-LP TCP-SACK TCP-Veno Westwood Westwood+ XCP YeAH-TCP 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 33

FAST TCP: Motivation, Architecture, Algorithms, Performance Related Work Tang, A., Wang, J., Low, S. H., and Chiang, M. 2007. Equilibrium of heterogeneous congestion control: existence and uniqueness. IEEE/ACM Trans. Netw. 15, 4 (Aug. 2007), 824-837. DOI= http://dx.doi.org/10.1109/TNET.2007.893885 Ma, J., Ruutu, J., and Wu, J. 2000. An enhanced TCP mechanism—fast-TCP in IP networks with wireless links. Wirel. Netw. 6, 5 (Nov. 2000), 375-379. DOI= http://dx.doi.org/10.1023/A:1019118421144 Gu, Y., Hong, X., and Grossman, R. L. 2004. Experiences in Design and Implementation of a High Performance Transport Protocol. In Proceedings of the 2004 ACM/IEEE Conference on Supercomputing (November 06 - 12, 2004). Conference on High Performance Networking and Computing. IEEE Computer Society, Washington, DC, 22. DOI= http://dx.doi.org/10.1109/SC.2004.24 Grieco, L. A. and Mascolo, S. 2004. Performance evaluation and comparison of Westwood+, New Reno, and Vegas TCP congestion control. SIGCOMM Comput. Commun. Rev. 34, 2 (Apr. 2004), 25-38. DOI= http://doi.acm.org/10.1145/997150.997155 24/11/2018 FAST TCP: Motivation, Architecture, Algorithms, Performance 34