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Recent Congestion Control Research at UCLA

TCP Libra - RTT-Fairness for TCP Authors: Gustavo Marfia*, Claudio E. Palazzi**, G. Pau*, Mario Gerla*, M. Y. Sanadidi*, Marco Roccetti** NRL – UCLA* Universita` di Bologna**. Recent Congestion Control Research at UCLA. TCP Evaluation Suite

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Recent Congestion Control Research at UCLA

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  1. TCP Libra - RTT-Fairness for TCP Authors: Gustavo Marfia*, Claudio E. Palazzi**, G. Pau*, Mario Gerla*, M. Y. Sanadidi*, Marco Roccetti** NRL – UCLA* Universita` di Bologna** Recent Congestion Control Research at UCLA TCP Evaluation Suite Authors: Hideyuki Shimonishi*, Tutomu Murase*, Cesar Marcondes**, M.Y. Sanadidi**, Mario Gerla**, Padmanabhan Vasu** NEC Japan* NRL – UCLA** Presenter: Cesar Marcondes PhD Candidate CS/UCLA Chicago, July 24 2007 IRTF/ICCRG Meeting

  2. Recent Congestion Control Research at UCLA TCP Libra - RTT-Fairness for TCP Authors: Gustavo Marfia*, Claudio E. Palazzi**, G. Pau*, Mario Gerla*, M. Y. Sanadidi*, Marco Roccetti** NRL – UCLA* Universita` di Bologna** Presenter: Cesar Marcondes PhD Candidate CS/UCLA Chicago, July 24 2007 IRTF/ICCRG Meeting

  3. RTT fairness: TCP sessions share same bottleneck => same bandwidth Not true with TCP NewReno, bandwidth share is RTT-biased TCP RTT-bias first recognized by Floyd et al, SIGCOMM 1991 Simple solution was proposed, but proved unstable (Henderson et al) Research community never lost interest in the RTT-fairness problem FAST BIC (Improving RTT-unfairness) Hybla Motivation & Previous Work IRTF/ICCRG Meeting Chicago July 24 2007

  4. Other Challenges: Scalability: TCP NewReno doesn’t scale to Gbps Friendliness: Compatible TCP NewReno performance (Co-existence) Stability: Lack of Control Theoretical Proofs of Congestion Control Protocols Stability Libra Algorithm Solutions Scalability: The congestion window initially grows proportional to the narrow link capacity Friendliness: A parallel Libra goal Stability: The congestion window growth slows down as the MAX RTT is approached (avoid heavy congestion in the network) Beyond RTT-Fairness IRTF/ICCRG Meeting Chicago July 24 2007

  5. Libra Congestion Control Algorithm Fairness Control T0,controls Thrput Variance & Convergence ------------ T1 controls RTT-fairness • Derived directly from Fluid model: • On a successful transmission: • On a packet loss: Scalability Control C representsEstimated Capacity and the PenaltyFunction is based on queueing delay IRTF/ICCRG Meeting Chicago July 24 2007

  6. Perfect-RTT Fairness Libra-RTT Fairness Linear-RTT Fairness Perfect-RTT Fairness • Protocols with “perfect” RTT fairness: • But Hybla has narrower stability region • Delay based protocols (Vegas, Fast) have co-existence problems with TCP Reno • Libra's perfect fairness can be tuned by T1 Linear-RTT Fairness Libra-RTT Fairness IRTF/ICCRG Meeting Chicago July 24 2007

  7. DumbBell Topology • Based on BIC original Test Simulation Suite • 4 forward + 4 backward regular long-lived TCP Sack flows • 25 TCP flows in both directions, window limited to 64 segments • Web traffic in both directions (20-50% of bandwidth) • Studied Connections: • Short RTT conn: 21 ms • Long RTT conn: 119ms IRTF/ICCRG Meeting Chicago July 24 2007

  8. DumbBell Topology Results Pipe Size Buffer Small Buffer • Studied Flows Achieved Jain Index while competing with cross-traffic • TCP Libra obtained the best Jain’s Index • specially on small buffers Jain’s Index IRTF/ICCRG Meeting Chicago July 24 2007

  9. Parking Lot Topology • Parking lot topology • Flows 1 and 2: 180ms • Flows 3 and 4: 90ms • Flows 5 through 8: 30ms • 2 buffer sizes: • 375 and 2250 pkts • Jain’s Index IRTF/ICCRG Meeting Chicago July 24 2007

  10. Parking Topology Results 50% (even) SACK + 50% (odd) Other TCP SACK Only Point of View when Competing with Other Protocols Same Experiment #1 Different Protocols Jain Index Computed over Flows 1-4 Same Experiment #1 Different Protocols Jain Index Computed over Flows 1-8 Buffer Size = Pipe Size = 2250 pkts Buffer Size = 375 pkts • TCP Libra obtained optimal RTT-Fairness among flows utilizing the same number of congested queues • FAST shows unfriendliness • by reducing flows 2 and 4 • BIC couldn’t reach good utilization • Libra balancea: • RTT-FairnessandFriendliness • Improved RTT-Fairness of SACK !! IRTF/ICCRG Meeting Chicago July 24 2007

  11. The main contribution of this work is to propose a stable solution to an old problem RTT-fairness (Floyd et al 1991) A complete proof of the stability bound for a simple case may be found in recent publication at IFIP/Networking 2007 TCP Libra proves to have an excellent trade-off between fairness, efficiency and friendliness http://www.tcplibra.org/ Conclusion IRTF/ICCRG Meeting Chicago July 24 2007

  12. Recent Congestion Control Research at UCLA TCP Evaluation Suite Authors: Hideyuki Shimonishi*, Cesar Marcondes**, M.Y. Sanadidi**, Mario Gerla**, Padmanabhan Vasu** NEC Japan* NRL – UCLA** Presenter: Cesar Marcondes PhD Candidate CS/UCLA Chicago, July 24 2007 IRTF/ICCRG Meeting

  13. TCP NewReno well-known doesn’t scale to Gbps Many New Congestion Control Proposed (ARENO, Westwood, BIC, FAST, HTCP, STCP) However, there is a need of a standard TCP Evaluation Suite for general use Lack of Meaningful Qualitative Comparison between Proposals Motivation • How do they behave differently • Resource fairness vs throughput fairness • Efficiency and throughput • Fairness and friendliness • How do they co-exist with Reno • Can we have reasonable scenario for migration ? IRTF/ICCRG Meeting Chicago July 24 2007

  14. TCP Evaluation Suite • Reproducible simulation experiments for different set of protocols • Pre-configured Environment to be used in Simulation • Core Network Size / Link Delay / Workload (Flow Size) / Start time Equal • Configurable (Example) • Parking Lot Topology • 4 core routers w/ 2MB • Links delays 15 ms (exponential) • Short Lived Flow 1MB/1sec (pareto/exponential) • Long Lived Flow 4.7GB/2min (fixed/exponential) IRTF/ICCRG Meeting Chicago July 24 2007

  15. After several simulations using different seeds we have the following results: RENO + RENO (today) RENO + HS (2008) HS + HS (2012) TReno_iReno+Reno is the throughput of Reno flow i in the first SET where all flow use Reno (RENO+RENO) Where TReno_iHS+Reno is the throughput of Reno flow i in the second SET in which half of the flows use high-speed protocols RENO + HS). Where TiHS+HS and TiReno+Reno are the throughput of flow i in the third SET where all flows use high-speed protocols (HS+HS) and the first SET where all flows use Reno (RENO+RENO), respectively Qualitative TCP Evaluation Comparison IRTF/ICCRG Meeting Chicago July 24 2007

  16. Qualitative Comparison with TCP NewReno and Congestion Window Dynamics Details Sorted by Flow RTT Sorted by Link Utilization Sorted by Number of Hops Long-Lived Flow 1 Queue Fluctuation (10ms) Cumulative Packet Losses IRTF/ICCRG Meeting Chicago July 24 2007

  17. The suite is available for download http://netlab.cs.ucla.edu/tcpsuite/ Topology generator Flow generator Workload generator New set of metrics allow qualitative comparison with the current state of the network It is also possible to investigate individual flow dynamics and queues reproducibly Please submit YOUR scenario Library for public sharing ! Scenario library Link A-B BW Delay Link A-B BW Delay Tcl scripts for NS2 Log data Questions, comments, contributions, to: cesar@cs.ucla.edu,h-shimonishi@cd.jp.nec.com Plotting tools IRTF/ICCRG Meeting Chicago July 24 2007

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