Re: [multipathtcp] Some questions for proxy work

Joe Touch <touch@isi.edu> Thu, 27 April 2017 17:21 UTC

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To: mohamed.boucadair@orange.com, Yoshifumi Nishida <nishida@sfc.wide.ad.jp>, multipathtcp <multipathtcp@ietf.org>
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From: Joe Touch <touch@isi.edu>
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Date: Thu, 27 Apr 2017 10:17:41 -0700
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Subject: Re: [multipathtcp] Some questions for proxy work
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On 4/27/2017 1:04 AM, mohamed.boucadair@orange.com wrote:
>
> Some folks might say we can use routing techniques or bundling IP
> tunnels here. But, I guess we'll need to handle reorder packets and
> proper congestion controls across multiple paths.*//*
>
> [Med] Yes, MPTCP will need to be reinvented at the bundling tunnel level.
>
You have it backwards.

MPTCP reinvents existing channel bonding mechanisms, but with additional
constraints.

E.g.:
    - reordering by one MPTCP proxy-proxy connection might be undermined
by later reordering over a subsequent multipath sub-path
        it's more efficient to let the final hop reorder everything, and
there's no way that a MPTCP proxy knows it's the last hop

    - retransmission might be less efficient and incur higher delays
than FEC, e.g., which some channel bonding systems implement

Joe