INFOCOM A Receiver-Driven Bandwidth Sharing System (BWSS) for TCP Puneet Mehra, Avideh Zakhor UC Berkeley, USA Christophe De Vleeschouwer Université Catholique de Louvain, Belgium

INFOCOM Talk Outline Motivation & Goals BWSS Overview NS-2 Simulations Internet Experiments Related Work Conclusion

INFOCOM Motivation Most traffic on Internet is TCP HTTP, FTP, P2P,… In many cases access links are bottleneck Limited Bandwidth (B/W) eg: DSL/Cable < 1.5Mbps User run many apps that compete for B/W Problem: TCP shares bottleneck B/W according to RTT Not fair to flows w/ large RTT Doesn’t consider application needs or user prefs!

INFOCOM Example Situation High RTT Med. RTT Low RTT Congestion

INFOCOM Goal & Approach Goal: Let user control application B/W allocations User preferences dictate bandwidth allocation Approach: limit throughput of low-priority flows to provide additional B/W for high-priority ones Ensure full utilization of access link Don’t change TCP/senders or routers  easily deployable!

INFOCOM Talk Outline Motivation & Goals BWSS Overview NS-2 Simulations Internet Experiments Related Work Conclusion

INFOCOM BWSS Overview

INFOCOM Target Rate Allocation Subsystem Some apps need minimum guaranteed rate(video), others don’t (ftp) User assigns each flow: Priority, minimum rate and weight Bandwidth allocation algorithm: Satisfy minimum rate in decreasing order of priority Remaining B/W shared according to weight T1T1 User Prefs. σ TnTn

INFOCOM BWSS Overview

INFOCOM Flow Control System (FCS) w – TCP window d – delay in ACKs RTT – Flow RTT MSS – TCP MSS

INFOCOM BWSS Overview

INFOCOM σ – Calculation Subsystem Goal: Choose σ to maximize link utilization. U = Σ i R i (σ) Approach: Iteratively increase/decrease σ and measure the impact on utilization R1R1 RNRN σ T 1 = R 1 σ U W2W2 W1W1 Link Capacity T 2 = R 2 T 1 = R 1 T 2 != R 2 T 2 = R 2

INFOCOM BWSS Overview

INFOCOM Talk Outline Motivation & Goals BWSS Overview NS-2 Simulations Internet Experiments Related Work Conclusion

INFOCOM Example of User Preferences Time 0: Min. Rate = 0 Kb/s weights = 1,2,3 for S0-S2 Priority -> S0 (max), S2(min) Time 300: Min Rate = 600 Kb/s TCP BWSS

INFOCOM Network-Congestion Example Priorities: increasing from S0-S2 Min Rate: S0,S2 – 600Kb/s S1 – 100 Kb/s Time 400s to 1200s 700Kb/s Interfering TCP traffic S2 limited to 300Kb/s

INFOCOM Multimedia Streaming Example S0 – Ftp traffic. Low Priority Min Rate = 700Kb/s S1 – Streaming at 450Kb/s High Priority 300Kb/s UDP flow (400s-1000s)

INFOCOM Talk Outline Motivation & Goals BWSS Overview NS-2 Simulations Internet Experiments Related Work Conclusion

INFOCOM BWSS Implementation ETH0 BWSS User-space shared library setsockopt() No Kernel Mods! APP_1APP_nAPP_2 Invisible to Apps

INFOCOM Experimental Setup Host PC running Linux kernel AT&T Cable modem connection

INFOCOM Experiment 1 – User Preferences BWSS allows flexible allocation of B/W Standard TCP Weighted Fair Sharing Ratios: 3,2,1 Minimum Rate of 100Kb/s Priorities: Blue, green, red

INFOCOM Related Work Network-Modifying Solutions Router Scheduling Policies WFQ, W2FQ: allow B/W allocation Require infrastructure changes  little deployment Network Appliances – PacketShaper Placed at network ingress  does traffic management Not easy to manage individual preferences End-Host solution Modify receiver’s window [Spring et al, 2000] Prioritize short-lived flows over longer ones Focus: reduce queuing delay for interactive apps (telnet)

INFOCOM Conclusions BWSS allows user to allocate link B/W Flexible B/W allocation model Adapts to changing network conditions No changes to TCP/senders/routers Implemented as shared library  easily deployable Enables efficient video streaming over TCP Simulations show better performance than standard TCP Additional Internet experiments validate [TCP Based Video Streaming using Receiver-Driven Bandwidth Sharing, Packet Video 2003, To appear]