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Performance Evaluation of TCP over Multiple Paths in Fixed Robust Routing

Performance Evaluation of TCP over Multiple Paths in Fixed Robust Routing. Wenjie Chen, Yukinobu Fukushima , Takashi Matsumura, Yuichi Nishida, and Tokumi Yokohira The Graduate School of Natural Science and Technology, Okayama University, Japan. Background.

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Performance Evaluation of TCP over Multiple Paths in Fixed Robust Routing

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  1. Performance Evaluation of TCP over Multiple Paths in Fixed Robust Routing Wenjie Chen, Yukinobu Fukushima, Takashi Matsumura, Yuichi Nishida, and Tokumi Yokohira The Graduate School of Natural Science and Technology, Okayama University, Japan CQR 2011

  2. Background • Penetration of bandwidth-consuming applications(e.g., P2P file sharing and video streaming) Traffic patterns in ISP networks become variable • Need for ISP networks to accommodate those variable traffic patterns • Routing for variable traffic patterns • Dynamic routing • Increases operational complexity • Can lead to route instability • Fixed robust routing [1, 3] • Low operational complexity • No route instability (static routing) [1] M. Kodialam, T. V. Lakshman, and S. Sengupta, “Maximum throughput routing of traffic in the hose model,” in Proceedings of IEEE INFOCOM2006, pp. 1–11, Apr. 2006. [3] V. Tabatabaee, A. Kashyap, B. Bhattacharjee, R. J. La, and M. A. Shayman, “Robust routing with unknown traffic matrices,” in Proceedings of IEEE INFOCOM 2007, pp. 2436–2440, May 2007. CQR 2011

  3. Fixed Robust Routing • Tries to achieve the best worst-case performance (e.g., maximum link load), given variable traffic patterns • Traffic patterns are assumed to vary within the region specified by some traffic variation models (e.g., hose model) • Performs multipath routing • Traffic of every source-destination pair is routed on multiple paths Multipath routing causes out-of-order packet arrivalsTCP performance may be degraded CQR 2011

  4. Research Objective • Investigation of TCP performance over general fixed robust routing • Proposal of fixed robust routing algorithm that tries to improve TCP performance in addition to decreasing maximum link load CQR 2011

  5. Formulation of Fixed Robust Routing Problem [3] Linear semi-infinite programming problem(convertible to polynomial size linear programming problem [3]) Output Input : Maximum link load subject to : Fraction of traffic of the corresponding (i, j) pair routed on path p : Candidate paths of every (i, j) pair : capacity of link l : Set of paths routed on link l : Set of all links in the network : Set of traffic matricesthat follow hose and pipe traffic model Path 1 Node i Node j Path 2 Path 3 [3] V. Tabatabaee, A. Kashyap, B. Bhattacharjee, R. J. La, and M. A. Shayman, “Robust routing with unknown traffic matrices,” in Proceedings of IEEE INFOCOM 2007, pp. 2436–2440, May 2007. CQR 2011

  6. Performance Degradation of TCP over Fixed Robust Routing 4 3 Shorter Path 2 Packets on shorter path overtake preceding packets on longer path Source Destination 1 Longer Path Source Destination Out-of-order packet arrivals at destination host 1 2 Source host receives three duplicated Acks and decreases its congestionwindow size 3 4 2 3 Reception of three duplicated Acks 4 TCP throughput is degraded 1 Time Time CQR 2011

  7. Evaluation of TCP Performance over Fixed Robust Routing: Simulation model Bandwidth: 100 [Mbps] Propagation delay: 2.0 + d [ms] for L 2.0 [ms] for S • Two kinds of path between R1 and R2 • L (Long path): 2.0 + d [ms] • S (Short path): 2.0 [ms] • Combination of paths: SLLL, SSLL, SSSL • One TCP connection for every end-host pair (Si , Di) • Si ’s data transmission rate: 20 [Mbps] D1 S1 D2 S2 S3 D3 R1 R2 S4 D4 Bandwidth: 50 [Mbps] Propagation delay: 0.2 [ms] S5 D5 CQR 2011

  8. Evaluation of TCP Performance over Fixed Robust Routing: Result • Larger delay difference more candidates for overtaking packet • Higher ratio of shorter path higher probability of three out-of-order packet arrivals Lower TCP throughput 100 SLLL 80 60 SSLL Total throughput [Mbps] SSSL 40 20 0 0 0.4 1.6 0.8 1.2 2.0 2.4 2.8 d (delay difference between path L and path S) [ms] CQR 2011

  9. Proposal of Fixed Robust Routing Taking Account of TCP Performance (1/2): Basic Strategy Our proposed fixed robust routing selects such candidate paths ( ) that avoid TCP performance degradation as much as possible subject to Linear semi-infinite programming problem Output Input : Maximum link load : Fraction of traffic of the corresponding (i, j) pair routed on path p : Candidate paths of every (i, j) pair : capacity of link l : Set of paths routed on link l : Set of all links in the network : Set of traffic matrices that follow hose and pipe traffic model CQR 2011

  10. Proposal of Fixed Robust Routing Taking Account of TCP Performance (2/2): Algorithm MDD-LF (Minimum Delay Difference with Limited Fraction) Step. 1 Selection of candidate paths of every source-destination pair Step. 1.1 We select Kshortest hop paths Step. 1.2 From the Kpaths, we select Mpathswith the minimum delay differencebetween the shortest and the longest delay paths Step. 2. We solve the formulated problem and obtain maximum link load (t) and fraction (xp) of traffic routed on every path. When solving the problem, we bound fraction of traffic routed on the shortest delay path by α Path 1, 15ms Path 2, 8ms Path 3, 3ms Node i Node j Path 4, 14ms Path 5, 10ms

  11. Simulation Model 2.8ms • One TCP connection for every node-pair (Ri , Rj) • Source host’s data transmission rate: 10 [Mbps] • Parameter settings in MDD-LF • K = 5 • M = 2 • α = 0.25 • Comparison: k-shortest • A straightforward fixed robust routing algorithm that selects M (= 2) shortest hop paths as candidate paths for every node-pair Link bandwidth: 1 [Gbps] 1.4ms 9.1ms 11.2ms 3.5ms 3.5ms 4.7ms 1.4ms 7.0ms 3.5ms 1.4ms R4 3.5ms 3.5ms 0.7ms [2%] 3.5ms 2.8ms 5.6ms 2.8ms 8.4ms 8.4ms 4.9ms CQR 2011

  12. Evaluation Results Compared to k-shortest, MDD-LF: 27% higher throughput Candidate path selection policy of MDD-LF is effective for improving TCP throughput Compared to k-shortest, MDD-LF: 2.3 times higher load MDD-LF tends to select longer hop paths than k-shortest 1 10 0.8 8 0.6 6 Maximum link load Average Throughput [Mbps] 0.4 4 0.2 2 0 0 k-shortest k-shortest MDD-LF MDD-LF CQR 2011

  13. Conclusions and Future Work • Conclusions • Investigation of TCP throughput over fixed robust routing • Larger delay difference • Higher ratio of shorter path • Proposal of fixed robust routing algorithm that tries to improve TCP throughput • MDD-LF: 27% higher throughput but 2.3 times higher load • Future work • Performance evaluation of our proposed algorithm in detail • Modification of our proposed algorithm • Selection of link-disjoint paths as candidate paths Lower TCP throughput CQR 2011

  14. Number of Candidates for Overtaking packets d = 1.0 Average packet transmission interval Source Destination 100 1 0.4 SLLL 80 2 60 SSLL 3 Total throughput [Mbps] 2 SSSL 40 4 3 # of candidates for overtaking packets 20 1 1 2 3 4 5 6 0 4 0 0 0.4 1.6 0.8 1.2 2.0 2.4 2.8 d (delay difference between path L and path S) [ms] Time Time CQR 2011

  15. Evaluation of TCP Performance over Fixed Robust Routing: Result • Larger delay difference more candidates for overtaking packet • Higher ratio of shorter path higher probability of three out-of-order packet arrivals • SLLL: 0.012 • SSLL: 0.063 • SSSL: 0.11 Lower TCP throughput 100 SLLL 80 60 SSLL Total throughput [Mbps] SSSL 40 20 0 0 0.4 1.6 0.8 1.2 2.0 2.4 2.8 d (delay difference between path L and path S) [ms] CQR 2011

  16. Traffic Variation Models Assumed in Fixed Robust Routing ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Hose traffic model Pipe traffic model : Upper bound on traffic volume that enters the network at node i (e.g., bandwidth of external ingress link of node i) t11 t12 t1n t21 t2n t22 T = : Upper bound on traffic volume that leaves the network at node j (e.g., bandwidth of external egress link of node j) t21 t2n t22 : Upper bound on traffic volume from node i to node j (The value is determined based on traffic histories or service level agreement) t11 t12 t1n t2n t21 t22 T = t21 t2n t22 CQR 2011

  17. Evaluation Results Compared to k-shortest, MDD: 22% higher throughput MDD-LF: 27% higher throughput candidate path selection policy of MDD and MDD-LD are effective for improving TCP throughput Compared to k-shortest, MDD: 1.7 times higher load MDD-LF: 2.3 times higher load MDD and MDD-LF tend to select longer hop paths than k-shortest 1 10 0.8 8 0.6 6 Maximum link load Average Throughput [Mbps] 0.4 4 0.2 2 0 0 MDD k-shortest MDD k-shortest MDD-LF MDD-LF CQR 2011

  18. Evaluation of TCP Performance over Fixed Robust Routing: Result • Larger delay difference more candidates for overtaking packet • Higher ratio of shorter path higher probability of three out-of-order packet arrivals • SLLL: 0.012 • SSLL: 0.063 • SSSL: 0.11 Lower TCP throughput 100 SLLL 80 60 SSLL Total throughput [Mbps] SSSL 40 20 Average packet transmission interval 0 0 0.4 1.6 0.8 1.2 2.0 2.4 2.8 d (delay difference between path L and path S) CQR 2011

  19. Proposal of Fixed Robust Routing Taking Account of TCP Performance (2/2): Algorithm MDD (Minimum Delay Difference) and MDD-LF (MDD with Limited Fraction) Step. 1 Selection of candidate paths of every source-destination pair Step. 1.1 We select Kshortest hop paths Step. 1.2 From the Kpaths, we select Mpaths with the minimum delay difference between the shortest and the longest delay paths Step. 2. We solve the formulated problem and obtain maximum link load (t) and fraction (xp) of traffic routed on every path. In MDD-LF, we bound fraction of traffic routed on the shortest delay path by α Path 1, 15ms Path 2, 8ms Path 3, 3ms Node i Node j Path 4, 14ms Path 5, 10ms

  20. Simulation Model 2.8ms • One TCP connection for every node-pair (Ri , Rj) • Each source host’s data transmission rate: 10 [Mbps] • Parameter settings in MDD and MDD-LF • K = 5 • M = 2 • α = 0.25 • Comparison: k-shortest • A straightforward fixed robust routing that selects M (= 2) shortest hop paths as candidate paths for every node-pair Link bandwidth: 1 [Gbps] 1.4ms 9.1ms 11.2ms 3.5ms 3.5ms 4.7ms 1.4ms 7.0ms 3.5ms 1.4ms R4 3.5ms 3.5ms 0.7ms [2%] 3.5ms 2.8ms 5.6ms 2.8ms 8.4ms 8.4ms 4.9ms CQR 2011

  21. Conclusions and Future Work • Conclusions • Investigation of TCP throughput over fixed robust routing • Larger delay difference • Higher ratio of shorter path • Proposal of fixed robust routing algorithms that try to improve TCP throughput • MDD: 22% higher throughput but 1.7times higher load • MDD-LF: 27% higher throughput but 2.3 times higher load • Future work • Performance evaluation of our proposed algorithms in detail • Modification of our proposed algorithms • Selection of link-disjoint paths as candidate paths Lower TCP throughput CQR 2011

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