A ReceiverDriven Bandwidth Sharing System BWSS for TCP

1
A Receiver-Driven Bandwidth Sharing System (BWSS)
for TCP

• Puneet Mehra, Avideh Zakhor
• UC Berkeley, USA
• Christophe De Vleeschouwer
• Université Catholique de Louvain, Belgium

2
Talk Outline

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

3
Motivation

• Most traffic on Internet is TCP
• HTTP, FTP, P2P,
• In many cases access links are bottleneck
• Limited Bandwidth (B/W) eg DSL/Cable lt 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
• Doesnt consider application needs or user prefs!

4
Example Situation
Low RTT
Med. RTT
High RTT
Congestion
5
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
• Dont change TCP/senders or routers ? easily
  deployable!

6
Talk Outline

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

7
BWSS Overview
8
Target Rate Allocation Subsystem
T1

• Some apps need minimum guaranteed rate(video),
  others dont (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

9
BWSS Overview
10
Flow Control System (FCS)
11
BWSS Overview
12
s Calculation Subsystem
R1
s
RN

• Goal Choose s to maximize link utilization. U
  Si Ri (s)
• Approach Iteratively increase/decrease s and
  measure the impact on utilization

T2 ! R2
T2 R2
T1 R1
T2 R2
Link Capacity
T1 R1
U
s
W1
W2
13
BWSS Overview
14
Talk Outline

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

15
Example of User Preferences
Time 0 Min. Rate 0 Kb/s weights 1,2,3 for
S0-S2 Priority -gt S0 (max), S2(min) Time 300
Min Rate 600 Kb/s
TCP
BWSS
16
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
17
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)

18
Talk Outline

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

19
BWSS Implementation
BWSS User-space shared library setsockopt() No
Kernel Mods!
ETH0
Invisible to Apps
20
Experimental Setup
ATT Cable modem connection
Host PC running Linux 2.4.8 kernel
21
Experiment 1 User Preferences
Standard TCP
Minimum Rate of 100Kb/s Priorities Blue, green,
red
Weighted Fair Sharing Ratios 3,2,1

• BWSS allows flexible allocation of B/W

22
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 receivers window Spring et al, 2000
• Prioritize short-lived flows over longer ones
• Focus reduce queuing delay for interactive apps
  (telnet)

23
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