An Evaluation of Fairness Among Heterogeneous TCP Variants Over 10Gbps High-speed Networks

1. An Evaluation of Fairness Among Heterogeneous TCP Variants Over 10Gbps High-speed Networks • Lin Xue*, Suman Kumar', Cheng Cui* and Seung-Jong Park* • *School of Electrical Engineering and Computer Science, Center for Computation & Technology, Louisiana State University, USA • 'Department of Computer Science, Troy University, USA Introduction and Background • 10Gbps Testbed Setup • CRON (http://www.cron.loni.org) • Cyber-infrastructure of Reconfigurable Optical Networks • Experimental networking testbed for 10Gbps high-speed networks • Heterogeneous TCP variants • Traditional network is rapidly evolving into a heterogeneous one. • According to a recent study on 5000 most popular web servers[1]: • Components • Hardware • Cisco N5000 switch • with 48 X 10Gbps ports • High-end servers with 10GE NICs • 10Gbps hardware emulators • Software • Emulab-based interface & controller • 10Gbps software emulators • (optimized 10Gbps Dummynet ) • Fairness Problem for heterogeneous TCP flows • Every TCP employs its own congestion control mechanism. • Fairness among heterogeneous TCP variants depends on router parameters such as queue management schemes and buffer size[2] High-speed TCP congestion control variants • Experimental Design • Dumbbell Topology • 2 10Gbps Linux Router • (4X10Gbps NICs) • 3 X 10Gbps links (120ms delay) • 3 senders and 3 receivers running heterogeneous TCP flows • Software • OS: Optimized Ubuntu 64bit & FreeBSD 64bit • Measurement S/W : Zero-copy Iperf • TCP variants: TCP-SACK, HSTCP, CUBIC, etc. • Patched Queue Management schemes: Drop-tail, RED, CHOKe, etc. Queue Management Schemes Evaluation of Fairness Among Heterogeneous TCP Variants • Loss Synchronization Effect • AQM schemes make de-synchronization of TCP flows • Very small buffer sizes (e.g. 1% BDP) create TCP loss synchronization • Homogeneous TCP vs. Heterogeneous TCP • Fairness index for buffer size = 20% BDP, RTT = 120ms Buffer Size = 20% de-synchronization • Fairness for Heterogeneous TCP flows • Three scenarios • 1 TCP-SACK, 1 CUBIC, and 1 HSTCP flow • 10 TCP-SACK, 10 CUBIC, and 10 HSTCP flow • 10 TCP-SACK, 10 CUBIC, and 10 HSTCP flow with short-lived TCP flows • Active queue management schemes (e.g. RED, CHOKe) perform better fairness than Drop-tail for large buffer sizes • All three queue management schemes show same fairness behavior for small buffer sizes • Short-lived TCP flows improve fairness in heterogeneous TCP networks Buffer Size = 1% synchronization • Throughput for Heterogeneous TCP flows • Tradeoff between fairness and throughput • Drop-tail performs the best among three queue management schemes • References • [1] P. Yang, W. Luo, L. Xu, J. Deogun, and Y. Lu, “Tcp congestion avoidance algorithm identification,” in Distributed Computing Systems (ICDCS), 2011 31st International Conference on. IEEE, 2011, pp. 310–321. • [2] Ao Tang; Xiaoliang Wei; Low, S.H.; Mung Chiang; , "Equilibrium of Heterogeneous Congestion Control: Optimality and Stability," Networking, IEEE/ACM Transactions on , vol.18, no.3, pp.844-857, June 2010 10 TCP-SACK, 10 CUBIC, and 10 HSTCP flow 10 TCP-SACK, 10 CUBIC, and 10 HSTCP flow with short-lived TCP flows 1 TCP-SACK, 1 CUBIC, and 1 HSTCP flow