RFC 6356 on Coupled Congestion Control for Multipath Transport Protocols

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        RFC 6356

        Title:      Coupled Congestion Control for Multipath 
                    Transport Protocols 
        Author:     C. Raiciu, M. Handley,
                    D. Wischik
        Status:     Experimental
        Stream:     IETF
        Date:       October 2011
        Mailbox:    costin.raiciu@cs.pub.ro, 
                    m.handley@cs.ucl.ac.uk, 
                    d.wischik@cs.ucl.ac.uk
        Pages:      12
        Characters: 27961
        Updates/Obsoletes/SeeAlso:   None

        I-D Tag:    draft-ietf-mptcp-congestion-07.txt

        URL:        http://www.rfc-editor.org/rfc/rfc6356.txt

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 standard TCP
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, achieving a property called "resource pooling" where a bundle
of links effectively behaves like one shared link with bigger
capacity.  This would increase the overall efficiency of the network
and also its robustness to failure.

This document presents a congestion control algorithm that couples
the congestion control algorithms running on different subflows by
linking their increase functions, and dynamically controls the
overall aggressiveness of the multipath flow.  The result is a
practical algorithm that is fair to TCP at bottlenecks while moving
traffic away from congested links.  This document defines an Experimental 
Protocol for the Internet community.

This document is a product of the Multipath TCP Working Group of the IETF.

EXPERIMENTAL: This memo defines an Experimental Protocol for the
Internet community.  It does not specify an Internet standard of any
kind. Discussion and suggestions for improvement are requested.
Distribution of this memo is unlimited.

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