Intelligent Grouping of TCP Flows for Coordinated Congestion Management

Venkatesh PrabhakarRajeev Gopalakrishna

Hoi Chang

Motivation and Goals

To coordinate TCP flows and make them more reactive to current network states

MotivationMotivation

GoalsGoals To dynamically identify and group flows with common points of congestion

To coordinate the congestion control for each group in a network friendly manner

Coordinated Congestion Management

NeedNeed Provide fairness among flows Better utilize network bandwidth

MechanismsMechanisms Group related flows together Make the flows in a group react to

congestion in a similar manner

Real traces of PING RTTs

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

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

Related work TCP-Int TCP-Ensemble TCP Fast Start Congestion Manager (CM)

DrawbackDrawbackCan only coordinate flows between the sameend hosts.

Our approachOur approachCoordinate flows that share common points ofcongestion.

Intelligent grouping of TCP flows

TCP process startsTCP process starts

No grouping of flowsNo grouping of flows

Coordinate flows on a group basis Coordinate flows on a group basis

End of correlation period reachedEnd of correlation period reached

Correlate RTTs of flowsCorrelate RTTs of flows

Regroup flows based on pastRegroup flows based on pastand current correlationshipsand current correlationships

• Dynamically Dynamically group/regroup group/regroup flows based on their flows based on their (dynamic) RTT (dynamic) RTT correlationshipcorrelationship

• Coordinate flows on a Coordinate flows on a

groupgroup basisbasis

Correlating different TCP flows

RTTsof twodiff.TCPflows

Time

...

current correlation time periodprev. period

RTTsofflowRED

RTTs of flow BLUE

x

xx

x

Correlation formula:Correlation formula:

correlation coeff: r = SR,B/(SR,B SR,B)where Su,v = (u - u’)(v - v’)

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.

Simulation

Source

Destination 1

Destination 2

Congestion sink

3Mb 5ms

10Mb 5ms

6Mb 5ms

6Mb 5ms

Major bottleneck at 1st hop

Another bottleneck bet’n router and dest2

2nd bottleneck starts 50 sec later

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.