[multipathtcp] Offload MPTCP Proxy (was RE: potential MPTCP proxy charter item)

<mohamed.boucadair@orange.com> Mon, 07 November 2016 15:03 UTC

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From: mohamed.boucadair@orange.com
To: "Olivier.Bonaventure@uclouvain.be" <Olivier.Bonaventure@uclouvain.be>, Mirja Kühlewind <mirja.kuehlewind@tik.ee.ethz.ch>, Alan Ford <alan.ford@gmail.com>
Thread-Topic: Offload MPTCP Proxy (was RE: [multipathtcp] potential MPTCP proxy charter item)
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Date: Mon, 07 Nov 2016 15:03:49 +0000
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Subject: [multipathtcp] Offload MPTCP Proxy (was RE: potential MPTCP proxy charter item)
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Hi Olivier,

I'm not sure it is that clear we need to systematically include MP_CAPABLE option in the SYN to the ultimate server. I see some value there...but also some side effects. I'm reiterating what I already said in this thread: 

(+) I see "a big benefit" for some operators to offload the MTPCP proxies if the server is MPTCP-capable.
(-) I don’t see "a big benefit" for the client from a QoE perspective, because they already have the MPTCP experience with the network assistance (network aggregation, path resiliency). 
(-) I don’t see "a big benefit" for the client if the MPTCP-capable server decides to use a given path to place data, while that path is subject to a data volume quota. This means that the client will be mono-path quickly if an MPTCP-capable server adopts some traffic distribution schemes.
That said, I have no problem to leave this as a configurable parameter. A configuration knob can be supported to instruct the MCP about the behavior to follow. Also, a white list of servers can be provided to the MCP. 

This is exactly the kind of technical considerations for which we need a formal WG document so that we can record the WG decision.


> -----Message d'origine-----
> De : Olivier Bonaventure [mailto:Olivier.Bonaventure@uclouvain.be]
> Envoyé : dimanche 6 novembre 2016 22:12
> À : Mirja Kühlewind; BOUCADAIR Mohamed IMT/OLN; Alan Ford
> Cc : multipathtcp@ietf.org
> Objet : Re: [multipathtcp] potential MPTCP proxy charter item
> It's clear that the MCP should send the MP_CAPABLE option in the SYN
> towards the destination server and fallback to TCP is this fails. Since
> there are some middleboxes that continue to silently drop the MP_CAPABLE
> option, the MCP should be able to maintain a list of destination servers
> where it had to fallback to regular TCP (e.g. after n retransmissions of
> the SYN with MP_CAPABLE as suggested in RFC6824) and no attempt to use
> MPTCP for these destinations. This cache should be reset on a regular
> basis to probe again the destination servers.