Re: [multipathtcp] Options or Payload?

Joe Touch <touch@ISI.EDU> Tue, 10 November 2009 03:03 UTC

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Date: Mon, 09 Nov 2009 19:04:08 -0800
From: Joe Touch <touch@ISI.EDU>
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To: "Ford, Alan" <alan.ford@roke.co.uk>
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Cc: multipathtcp@ietf.org
Subject: Re: [multipathtcp] Options or Payload?
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Ford, Alan wrote:
> We had considered that, however the main reason against this was whether
> certain middleboxes would split and coalesce TCP payloads thus breaking
> the placement of the extended options - the TCP payload is essentially
> no longer a continuous stream.
> 
> Wes Eddy proposed a "Long Options Option"
> (http://tools.ietf.org/id/draft-eddy-tcp-loo-04.txt) which seemed to be
> a possible way of doing a very similar thing, by negotiating to ensure
> that long options would work along a path. Although, this draft is now
> expired, and I'm not sure why it was dropped. Anyone know?

Same problems.

Joe

>> -----Original Message-----
>> From: Yoshifumi Nishida [mailto:nishida@sfc.wide.ad.jp]
>> Sent: 10 November 2009 01:35
>> To: Ford, Alan
>> Cc: multipathtcp@ietf.org
>> Subject: Re: [multipathtcp] Options or Payload?
>>
>>
>> Hello,
>> How about having a simple option which indicates the offset for real
> tcp
>> payload?
>> For example, if mptcp packets conveys 10 bytes control info in the
> payload,
>> set
>> offset to 10 in the option.
>>
>> Thanks,
>> --
>> Yoshifumi Nishida
>> nishida@sfc.wide.ad.jp
>>
>> From: "Ford, Alan" <alan.ford@roke.co.uk>
>> Subject: [multipathtcp] Options or Payload?
>> Date: Tue, 10 Nov 2009 00:58:48 -0000
>> Message-ID:
>> <2181C5F19DD0254692452BFF3EAF1D6808D7BB51@rsys005a.comm.ad.roke.co.uk>
>>
>>  > Hi all,
>>  >
>>  > One of the big issues to be raised during yesterday's MPTCP session
> was
>>  > the question of whether TCP Options are really the right place to
> be
>>  > doing this. This is not the first time this has come up but
> deserves
>>  > further exploration.
>>  >
>>  > Specifically, instead of doing this with TCP Options, the same
>>  > instructions could be included in the payload. Similar to TLS, the
> data
>>  > could be chunked and each chunk has a data sequence and length
> header.
>>  > These can be interspersed with control blocks to signal addresses,
>>  > security of joining subflows to connections, and connection close.
> A
>>  > simple 2-octet TCP option would still be used in the initial SYN to
>>  > signal MPTCP capability.
>>  >
>>  > This has the benefit that it would allow the signalling to have
>>  > reliability, and we wouldn't be hit with option space limits, and
> thus
>>  > be potentially able to do better security algorithms. It would also
> give
>>  > us greater freedom in signals for future extensibility (for
> example, if
>>  > we wanted to signal ports for additional subflows, not just
> addresses).
>>  >
>>  > On the downside, there may be cases where this could confuse
>>  > middleboxes, e.g. expecting HTTP on port 80 and finding this kind
> of
>>  > data instead. However, since a TCP option would be used at the
> start to
>>  > identify capability, if this were dropped by a middlebox/proxy then
>>  > MPTCP would not be used.
>>  >
>>  > What do people think is the best approach?
>>  >
>>  > Regards,
>>  > Alan
>>  >
>>  > _______________________________________________
>>  > multipathtcp mailing list
>>  > multipathtcp@ietf.org
>>  > https://www.ietf.org/mailman/listinfo/multipathtcp
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