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</o:shapelayout></xml><![endif]--></head><body lang=EN-GB link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Hi,<o:p></o:p></p><p class=MsoNormal>This starts a WG last call for the MPTCP WG’s congestion control draft, <a href="http://tools.ietf.org/wg/mptcp/draft-ietf-mptcp-congestion/">http://tools.ietf.org/wg/mptcp/draft-ietf-mptcp-congestion/</a> <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Since we are near the IETF, we will run until 22<sup>nd</sup> April. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thank-you to Michael Tüxen and Michael Welzl for reviewing it from an ICCRG perspective, also Howard Tripp’s review, and to Costin for updating it.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Best wishes,<o:p></o:p></p><p class=MsoNormal>Phil & Yoshifumi. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>--<o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>Abstract<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> Often endpoints are connected by multiple paths, but communications<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> are usually restricted to a single path per connection. Resource<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> usage within the network would be more efficient were it possible for<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> these multiple paths to be used concurrently. Multipath TCP is a<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> proposal to achieve multipath transport in TCP.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> New congestion control algorithms are needed for multipath transport<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> protocols such as Multipath TCP, as single path algorithms have a<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> series of issues in the multipath context. One of the prominent<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> problems is that running existing algorithms such as TCP New Reno<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> independently on each path would give the multipath flow more than<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> its fair share at a bottleneck link traversed by more than one of its<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> subflows. Further, it is desirable that a source with multiple paths<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> available will transfer more traffic using the least congested of the<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> paths, hence achieving resource pooling. This would increase the<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> overall efficiency of the network and also its robustness to failure.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> This document presents a congestion control algorithm which couples<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> the congestion control algorithms running on different subflows by<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> linking their increase functions, and dynamically controls the<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> overall aggresiveness of the multipath flow. The result is a<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> practical algorithm that is fair to TCP at bottlenecks while moving<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> traffic away from congested links.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>