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Receiver Driven Bandwidth Sharing for TCP. Authors: Puneet Mehra, Avideh Zakor and Christophe De Vlesschouwer University of California Berkeley. Presented at: INFOCOM 2003 . Twenty-Second Annual Joint Conference of the IEEE Computer and Communications Societies. Overview of the Presentation.

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receiver driven bandwidth sharing for tcp

Receiver Driven Bandwidth Sharing for TCP

Authors: Puneet Mehra, Avideh Zakor and Christophe De Vlesschouwer

University of California Berkeley.

Presented at: INFOCOM 2003. Twenty-Second Annual Joint Conference of the IEEE Computer and Communications Societies.

overview of the presentation
Overview of the Presentation
  • Motivation
  • Goals
  • Proposed Method
  • NS-2 Simulations
  • Conclusion
motivation
Motivation
  • Most Internet traffic is TCP
    • HTTP, FTP, P2P, Multimedia streaming…
  • 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 with large RTT
    • Doesn’t consider application needs or user prefs!
example

Congestion

Example:

FTP

Low RTT

INTERNET

P2P

Video traffic

Med. RTT

High RTT

goals
Goals
  • Achieve full utilization of the receiver’s access link (bottleneck).
  • Satisfy user preferences:

-priorities assigned to each flow.

  • Approach: limit throughput of low-priority flows to provide additional B/W for high-priority ones
overview of the presentation6
Overview of the Presentation
  • Motivation
  • Goals
  • Proposed Method
  • NS-2 Simulations
  • Conclusion
system overview
System Overview

User

Preferences

W1 & d1

R1

T1

TRAS

Target Rate Allocation Sub-System

FCS1

Flow Control System

Sender1

.

.

.

.

.

.

Internet

Wn & dn

σ

Tn

FCSn

Flow Control System

σ

Calculation

Sub-System

Rn

R1

Sendern

Rn

For the receiverσ= system target bit-rate

For the nth connectionWn= Advertised Windowdn = Delay in ACK packetsTn= Target RateRn = Measured Rate

BWSSBandwidth Sharing System

system overview8
System Overview…
  • Band-Width Sharing System (BWSS) consists of:

a) Flow Control System (FCS)

b) Target Rate Allocation Sub-system (TRAS)

c) σ Calculation Sub-system.

flow control system
Flow Control System

For the nth connectionW = Advertised Windowd = Delay in ACK packetsR = Measured RateP = Packet size in bitsTi= Target Ratemi = minimum bandwidthwi= weight

Measure

Bit-rate and RTT

R1

Adapt

Receiver Window / ACK Delay

Calculate

Target Rate – Measured Rate

W1

T1

d1

FCS1

Flow Control System

flow control system10
Flow Control System…

Ri < Ti : search for the smallest Wi to achieve (1- α )Ti =< Ri =< (1+ α )Ti

If Ri > (1+α)*Ti then delay the ACKs as decreasing Wi is ineffective.

Aim to minimize delay : otherwise results in unresponsiveness & instability in TCP flow.

example11
Example

After fast recovery

Receiver’s advertised window

Window size limits the data rate :

Max Window size = min (cwndmax, receiver’s adv. window)

Slide borrowed from Dr. Nitin Vaidya’s TCP tutorial

rtt and bandwidth estimation
RTT and Bandwidth estimation
  • TCP timestamp option to estimate RTT.
  • Bandwidth estimation relies on exponentially weighted moving average

R  α*R + (1-α)*Rø

  • Ø – bandwidth estimation period, tradeoff between accuracy of estimation and time for convergence.
target rate allocation system

σ

User Prefs.

Tn

Target Rate Allocation System

T1

  • Some apps need minimum guaranteed rate(video), others don’t (ftp)
  • User assigns each flow:
    • Priority (pi), minimum rate (mi) and weight (wi)
  • Bandwidth allocation algorithm:
    • Satisfy minimum rate in decreasing order of priority
    • Remaining B/W shared according to weight

Prevents starvation of low priority connection

calculation subsystem
σ – Calculation Subsystem

R1

σ

U = Σi Ri

RN

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

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

σ < σideal implies under-utilization of the link.

If σ > σideal , does it affect the system ?

overview of the presentation15
Overview of the Presentation
  • Motivation
  • Goals
  • Proposed Method
  • NS-2 Simulations
  • Conclusion
slide16

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

slide17

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

slide18

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)
overview of the presentation19
Overview of the Presentation
  • Motivation
  • Goals
  • Proposed Method
  • NS-2 Simulations
  • Conclusion
conclusion
Conclusion
  • BWSS allows user to allocate link B/W
    • Flexible B/W allocation model
    • Adapts to changing network conditions
    • No changes to TCP/senders/routers
  • Observation:

- works only if desired rate is achievable under flow’s cwnd

- What was receiver window advertisement actually designed for??

observation tcp window management

Data1 win4

2

Ack1 win4

4

3 4 5 6

DATA3 ~ 6 win4

8

Ack6 win2

9

DATA10 ~11 win4

10 11

Observation: TCP window management

sender

receiver

1

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