TCP-FIT: An Improved TCP Congestion Control

1. Jingyuan Wang, Jiangtao Wen, Jun Zhang and Yuxing Han Tsinghua National Laboratory for Information Science and Technology
2.  Introduction  Background and Motivation  The TCP-FIT Algorithm  Experimental Results  Conclusion
3.  TCP ◦ The Transmission Control Protocol  TCP Reno/ TCP New Reno ◦ Pros  Reliable  Sequential ◦ Cons  Wireless network  high Bandwidth Delay Product (BDP)
4.  Recent development ◦ Wireless  TCP Westwood  TCP Veno ◦ BDP  TCP Compound  TCP CUBIC  FAST TCP  TCP-FIT ◦ Inspired by parallel TCP
5.  Introduction  Background and Motivation  The TCP-FIT Algorithm  Experimental Results  Conclusion
6.  What is a Congestion Algorithm?  Classification ◦ Loss-based ◦ Delay-based ◦ Hybrid
7.  Loss-Based ◦ TCP Reno, TCP CUBIC ◦ TCP BIC , High Speed TCP  Definition  Assumption ◦ Constraints  In wireless scenarios  In BDP scenarios
8.  Delay-Based ◦ TCP Vegas and FAST TCP  Definition  Assumption ◦ Queuing delay = RTT – Propagation delay. ◦ Pros  Resilient -> good ◦ Cons  bandwidth starvation
9.  Hybrid TCP ◦ Veno, TCP Westwood, TCP Illinois, H-TCP and Fusion TCP ◦ Compound TCP  Cons ◦ Poor in BDP-wireless-hybrid scenarios
10.  TCP-FIT ◦ Parallel TCP ◦ E.g. GridFTP and E-MulTCP ◦ Pros:  Utilization  Good in wireless and BDP ◦ Cons:  Compatibility  Fairness
11.  Introduction  Background and Motivation  The TCP-FIT Algorithm  Experimental Results  Conclusion
12.  Notation of parameter ◦ : Size of congestion window  � ◦ : RTT time ◦ : PLR, Packet Loss Rate ◦ : Throughput of the network ◦ : Propagation delay ◦ : Queuing delay
13.  Object ◦ achieve N times throughput of the TCP Reno ◦ meanwhile maintain fairness  TCP Reno ◦ AIMD  : ← + 1  : ← − 1 2
14.  MulTCP ◦ : ← + ◦ : ← − 1 2  Proposed Method ◦ : ← + ◦ : ← − 2 3+1
15.  Assumption: one loss adjustment is enough ◦ Based on AIMD ◦ = − 2 3+1 ◦ + = 2� ◦ We get ◦ = 3+1 3 �
16.  In a certain length of time( we set it as k*RTT time ) ◦ ∆ = 1 − � + � 𝑘𝑘 � � 2 3+1  Then ◦ ̇ = ∆ ̇ = 𝑇𝑇 − 𝑋𝑋 � 2 3+1 � 3+1 3 �  Let ̇ = 0 then we get = 32 2 � 2 ( = � 𝑇𝑇 ) ◦ = 1 𝑇𝑇 3 2 1
17.  The is adjusted adaptively. Update of is ◦ 𝑖𝑖+1 = 1, 𝑖𝑖 + − −𝑡𝑡 𝑖𝑖  The equilibrium of is ◦ = � −𝑡𝑡 = 𝑇𝑇 ◦ (denote α as α = (𝑡𝑡 − 𝑡𝑡 )/𝑡𝑡 ) ◦ (Easy to know = = + = 𝑡𝑡 + ) ◦ = 2 3 1
18.  Network Utilization ◦ = 1 𝑇𝑇 3 2 1 vs = 1 𝑇𝑇 3 2 1  Fairness ◦ RTT-fairness  η = 𝑖𝑖 = 1 vs η = 𝑖𝑖 = + 𝑖𝑖+ ( = = + ) ◦ Inter-fairness  = 𝑇𝑇∗−𝑇𝑇′ 𝑇𝑇∗
19.  Introduction  Background and Motivation  The TCP-FIT Algorithm  Experimental Results  Conclusion
20.  BDP Scenarios
21.  Wireless Scenarios
22.  Inter-fairness
23.  RTT-fairness
24.  Cons: ◦ a low speed ADSL network with large bandwidth variations ◦ Due to simplistic model of bandwidth estimation compared with FAST.
25. Thank you