Re: [multipathtcp] Consensus call on potential MPTCP proxy work

Joe Touch <> Wed, 19 April 2017 18:17 UTC

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Subject: Re: [multipathtcp] Consensus call on potential MPTCP proxy work
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On 4/18/2017 10:26 PM, wrote:
> As explained in my previous message, there is no layered congestion
> control. All packets are transported over plain TCP: no encap, no tunnel.
I did say "if"; I now understand better what you're trying to do, but
there are plenty of parts still not addressed:

>  I really reiterate my comment to read
Here's what those slides do not explain:

- is this system 1:1 per client TCP connection, or are you expecting a
single MPTCP between proxies to support multiples?
- what is the congestion control interaction? I.e., does the client
think the RTT is to the proxy (which will work), or to the TCP receiver
past the end of the MPTCP connection?
    NOTE: if the latter, then you still end up with layered congestion
- what is the proxy relaying?
    is it TCP data, or is it somehow trying to tunnel and reconstitute
the entire packet?
    NOTE: if it reconstitutes the packet, what happens when you get an
option you don't understand? E.g., EDO?

There are still plenty of more concerns with this system. Overall, you
*still* appear to be doing one of two things:

    a) acting like a conventional application-layer proxy, which would
be fine but would not require any new RFCs
    b) tunneling - or acting exactly like you're tunneling, by
reconstituting packets on the other end - a TCP connection over TCP,
which is a bad idea

So which is it? Or is it something else?