Coupled Multipath-Aware Congestion Control

Document Type Replaced Internet-Draft (individual)
Last updated 2010-08-25 (latest revision 2010-03-08)
Replaced by draft-ietf-mptcp-congestion
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


Often endpoints are connected by multiple paths, but communications are usually restricted to a single path per connection. Resource usage within the network would be more efficient were it possible for these multiple paths to be used concurrently. Multipath TCP is a proposal to achieve multipath transport in TCP. New congestion control algorithms are needed for multipath transport protocols such as Multipath TCP, as single path algorithms have a series of issues in the multipath context. One of the prominent problems is that running existing algorithms such as TCP New Reno independently on each path would give the multipath flow more than its fair share at a bottleneck link traversed by more than one of its subflows. Further, it is desirable that a source with multiple paths available will transfer more traffic using the least congested of the paths, hence achieving resource pooling. This would increase the overall utilization of the network and also its robustness to failure. This document presents a congestion control algorithm which couples the congestion control algorithms running on different subflows by linking their increase functions, and dynamically controls the overall aggresiveness of the multipath flow. The result is a practical algorithm that is fair to TCP at bottlenecks while moving traffic away from congested links.


Costin Raiciu (
Mark Handley (
Damon Wischik (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)