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

Yoshifumi Nishida <nishida@sfc.wide.ad.jp> Fri, 21 April 2017 09:01 UTC

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From: Yoshifumi Nishida <nishida@sfc.wide.ad.jp>
Date: Fri, 21 Apr 2017 02:00:57 -0700
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To: Joe Touch <touch@isi.edu>
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Subject: Re: [multipathtcp] Consensus call on potential MPTCP proxy work
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Hi Joe,

On Tue, Apr 18, 2017 at 6:18 PM, Joe Touch <touch@isi.edu>; wrote:
>
> On 4/18/2017 6:12 PM, Yoshifumi Nishida wrote:
>
> Hi Joe,
>
> On Tue, Apr 18, 2017 at 2:56 PM, Joe Touch <touch@isi.edu>; wrote:
>
>>
>>
>> On 4/18/2017 2:44 PM, Yoshifumi Nishida wrote:
>> > Hi Joe,
>> >
>> > It's not tunneling. The proxy converts a tcp connection into a mptcp
>> > connection and converts it back to a tcp connection (if necessary)
>> > So, it won't be tcp over tcp.
>> OK, but that's not proxying either.
>>
>> That's (at best) connection hijacking.
>>
>
> I won't deny it as I'm not 100% sure whether proxy is a good name or not.
> But, I am thinking you might want to call NAT hijacking as well.
>
> Yes, but we do know what a NAT is responsible for - i.e., it is 1:1
> translation of only addresses and ports.
>
> Doing more than that has never been part of an IETF standard, AFAICT - for
> many reasons.
>

I am not very sure how 1 TCP: 1 MPTCP translations is complicated yet.
So, I don't have a reason to stop people exploring.


> > MPTCP will convey control data for application (proxy) in payload.
>> > But, MPTCP of course doesn't care the contents of payload.
>> > It just carries data and app will parse the data. Putting data in SYN
>> > is trying to reduce the latency and no other meaning as far as I
>> > understand.
>>
>> MPTCP is TCP. Putting the data in the SYN of a TCP connection is
>> hazardous. The goal is irrelevant.
>
>
> In TCP, we already have a precedence such as TFO.
>
>
> Sorry, to be more clear:
>     Data in the SYN has been part of TCP since it was standardized.
>
> Using the SYN data as control information is the hazardous part.
>
> I think what the solution does won't exceed what TFO does.
>
> TFO changes when the SYN data is delivered, based on the fact that past
> cookie information "accelerates" the 3WHS.
>
> It does not put control plane information in the data area of the SYN.
>

In my view, TFO relies on the info from past connections and we somehow
believe it's valid and not staled. But, it's still external info because it
is from the outside of the current connection.
This case relies on other type of external info and when we believe the
info, we will send data in SYN. I personally don't see big differences.

--
Yoshi