INFOCOM 2003

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A Receiver-Driven Bandwidth Sharing System (BWSS) for TCP

Puneet Mehra, Avideh ZakhorUC Berkeley, USA

Christophe De VleeschouwerUniversité Catholique de Louvain,

Belgium

INFOCOM 2003

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Talk Outline

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

INFOCOM 2003

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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 2003

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Example Situation

Internet

User’s PC

FTP

P2PVIDEO

BottleneckAccess

Link

=

High RTT

Med. RTT

Low RTT

Congestion

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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 2003

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Talk Outline

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

INFOCOM 2003

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BWSS Overview

FCS1

Flow ControlSystem

FCSn

Flow ControlSystem

TRASTRAS

TargetRate

AllocationSub-

System

TargetRate

AllocationSub-

System

CalculationSub-System

Internet

BWSSBandwidth Sharing System

UserPreferences Receiver

Tn

T1

R1

R1

Rn

Rn

W1 & d1

Sender1

Sendern

For the receiver: = system target bit-rate

For the n th connection:W n = Advertised Windowdn = Delay in ACK packetsTn = Target RateRn = Measured Rate

Wn & dn

INFOCOM 2003

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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

T1

User Prefs.

σ

Tn

INFOCOM 2003

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BWSS Overview

FCS1

Flow ControlSystem

FCSn

Flow ControlSystem

TRASTRAS

TargetRate

AllocationSub-

System

TargetRate

AllocationSub-

System

CalculationSub-System

Internet

BWSSBandwidth Sharing System

UserPreferences Receiver

Tn

T1

R1

R1

Rn

Rn

W1 & d1

Sender1

Sendern

For the receiver: = system target bit-rate

For the n th connection:W n = Advertised Windowdn = Delay in ACK packetsTn = Target RateRn = Measured Rate

Wn & dn

INFOCOM 2003

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Flow Control System (FCS)

MeasureBit-rate and RTT

CalculateTarget Rate

- Measured Rate

AdaptReceiver Window

ACK Delay

W i

Ri

Ti

Wi = Advertised Windowdi = Delay in ACK packetsTi = Target RateRi = Measured Rate

FCS

di

dRTT

MSSwR

w – TCP window

d – delay in ACKs

RTT – Flow RTT

MSS – TCP MSS

wR

RTw

anddRTT

MSS

w

R

/

INFOCOM 2003

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BWSS Overview

FCS1

Flow ControlSystem

FCSn

Flow ControlSystem

TRASTRAS

TargetRate

AllocationSub-

System

TargetRate

AllocationSub-

System

CalculationSub-System

Internet

BWSSBandwidth Sharing System

UserPreferences Receiver

Tn

T1

R1

R1

Rn

Rn

W1 & d1

Sender1

Sendern

For the receiver: = system target bit-rate

For the n th connection:W n = Advertised Windowdn = Delay in ACK packetsTn = Target RateRn = Measured Rate

Wn & dn

INFOCOM 2003

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σ – Calculation Subsystem

Goal: Choose σ to maximize link utilization. U = Σi Ri (σ)

Approach: Iteratively increase/decrease σ and measure the impact on utilization

R1

RN

σ

T1 = R1

σ UW2W1

Link Capacity

T2 = R2

T1 = R1

T2 != R2

T2 = R2

INFOCOM 2003

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BWSS Overview

FCS1

Flow ControlSystem

FCSn

Flow ControlSystem

TRASTRAS

TargetRate

AllocationSub-

System

TargetRate

AllocationSub-

System

CalculationSub-System

Internet

BWSSBandwidth Sharing System

UserPreferences Receiver

Tn

T1

R1

R1

Rn

Rn

W1 & d1

Sender1

Sendern

For the receiver: = system target bit-rate

For the n th connection:W n = Advertised Windowdn = Delay in ACK packetsTn = Target RateRn = Measured Rate

Wn & dn

INFOCOM 2003

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Talk Outline

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

INFOCOM 2003

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Example of User Preferences

Time 0: Min. Rate = 0 Kb/sweights = 1,2,3 for S0-S2Priority -> S0 (max), S2(min)

Time 300: Min Rate = 600 Kb/s

TCP BWSS

INFOCOM 2003

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Network-Congestion Example

Priorities: increasing from S0-S2Min Rate:S0,S2 – 600Kb/sS1 – 100 Kb/s

Time 400s to 1200s700Kb/s Interfering TCP trafficS2 limited to 300Kb/s

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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 2003

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Talk Outline

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

INFOCOM 2003

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BWSS Implementation

Internet

User’s PC

ETH0

BWSSUser-space shared

librarysetsockopt()

No Kernel Mods!

APP_1 APP_nAPP_2

Invisible to Apps

INFOCOM 2003

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Experimental Setup

Internet

ftp14.freebsd.org

ftp12.freebsd.org

ftp13.freebsd.org

Host PC running Linux 2.4.8 kernel

AT&T Cable modem connection

INFOCOM 2003

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Experiment 1 – User Preferences

BWSS allows flexible allocation of B/W

Standard TCP

Weighted Fair SharingRatios: 3,2,1

Minimum Rate of 100Kb/sPriorities: Blue, green, red

INFOCOM 2003

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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 2003

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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]