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

Recent Congestion Control Research at UCLA Presenter: Cesar Marcondes PhD Candidate CS/UCLA Chicago, July IRTF/ICCRG Meeting Presenter: Cesar Marcondes PhD Candidate CS/UCLA Chicago, July IRTF/ICCRG Meeting 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**

IRTF/ICCRG Meeting Chicago July Motivation & Previous Work  RTT fairness:  TCP sessions share same bottleneck => same bandwidth  Not true with TCP NewReno, bandwidth share is RTT-biased  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

IRTF/ICCRG Meeting Chicago July Beyond RTT-Fairness  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  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)

IRTF/ICCRG Meeting Chicago July  Derived directly from Fluid model:  On a successful transmission:  On a packet loss:  Derived directly from Fluid model:  On a successful transmission:  On a packet loss: Libra Congestion Control Algorithm Fairness Control T 0, controls Thrput Variance & Convergence T 1 controls RTT-fairness Scalability Control C represents Estimated Capacity and the Penalty Function is based on queueing delay

IRTF/ICCRG Meeting Chicago July Linear-RTT Fairness Perfect-RTT FairnessLibra-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 Perfect-RTT Fairness Libra-RTT Fairness

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

IRTF/ICCRG Meeting Chicago July 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  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 Parking Topology Results 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 = 375 pkts Buffer Size = Pipe Size = 2250 pkts TCP Libra obtained optimal RTT- Fairness among flows utilizing the same number of congested queues 50% (even) SACK + 50% (odd) Other TCP SACK Only Point of View when Competing with Other Protocols  FAST shows unfriendliness  by reducing flows 2 and 4  BIC couldn’t reach good utilization  Libra balancea:  RTT-Fairness and Friendliness  Improved RTT-Fairness of SACK !!

IRTF/ICCRG Meeting Chicago July Conclusion  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  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 

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

IRTF/ICCRG Meeting Chicago July Motivation  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  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 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 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)  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 Qualitative TCP Evaluation Comparison  After several simulations using different seeds we have the following results:  RENO + RENO (today)  RENO + HS (2008)  HS + HS (2012)  After several simulations using different seeds we have the following results:  RENO + RENO (today)  RENO + HS (2008)  HS + HS (2012)  T Reno_i Reno+Reno is the throughput of Reno flow i in the first SET where all flow use Reno (RENO+RENO)  Where T Reno_i HS+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 T i HS+HS and T i Reno+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

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

IRTF/ICCRG Meeting Chicago July The suite is available for download Topology generator Flow generator Workload generator Link A-B BW Delay Scenario library Tcl scripts for NS2 Log data Plotting tools 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 ! Questions, comments, contributions, to: