Intelligent Grouping of TCP Flows for Coordinated Congestion Management

1
Intelligent Grouping of TCP Flows for Coordinated
Congestion Management

• Venkatesh Prabhakar
• Rajeev Gopalakrishna
• Hoi Chang

2
Motivation and Goals
Motivation
To coordinate TCP flows and make them more
reactive to current network states
Goals
To dynamically identify and group flows with
common points of congestion To coordinate the
congestion control for each group in a network
friendly manner
3
Coordinated Congestion Management

• Need
• Provide fairness among flows
• Better utilize network bandwidth
• Mechanisms
• Group related flows together
• Make the flows in a group react to congestion in
  a similar manner

4
Real traces of PING RTTs

• Ping from the home PC thru AOL
• Flows 40, 50, and 55 same flows
• Flows 10, 20, 25, and 30
• web sites in California

• Ping from the CS Dept
• Flow 50 www.umass.edu
• Flow 55 www.cs.umass.edu
• Flow 40 www.mit.edu

5
Related work

• TCP-Int
• TCP-Ensemble
• TCP Fast Start
• Congestion Manager (CM)

Drawback
Can only coordinate flows between the same end
hosts.
Our approach
Coordinate flows that share common points
of congestion.
6
Intelligent grouping of TCP flows

• Dynamically group/regroup
• flows based on their
• (dynamic) RTT
• correlationship
• Coordinate flows on a group
• basis

7
Correlating different TCP flows
Correlation formula
correlation coeff r SR,B/?(SR,B ?
SR,B) where Su,v ?(u - u)(v - v)
RTTs of flow RED
RTTs of flow BLUE
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Coordinating flows within a group

• React to available bandwidth
• Upon receipt of a fast ack, increase the cwnd of
  all other flows in the same group based on a
  threshold scheme.
• React to congestion
• Upon packet loss for a flow, decrease the
  cwnd/ssthresh of all other flows in the same
  group accordingly.

9
Simulation
Congestion sink
Destination 1
10Mb 5ms
6Mb 5ms
3Mb 5ms
Source
6Mb 5ms
Destination 2
10
Major bottleneck at 1st hop
11
Another bottleneck betn router and dest2
12
2nd bottleneck starts 50 sec later
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Conclusion

• Achieved dynamic grouping of TCP flows which
  shared common points of congestion.
• Achieved fairness among TCP flows in each group
  by coordinating their congestion control.