Re: [multipathtcp] High-level design decisions /architecture

[Joe Touch <[e-mail]>]

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Ford, Alan wrote:
...
>> We have an awful lot of TCP options that are only valid in the
>> SYN-SYN/ACK exchange and only 40 bytes to put them all. What's wrong
>> with starting all TCP connections in non-MP mode and allowing the
>> connection's initiator to request MPTCP starting with any packet that
>> expects an ACK?
> 
> We had began with assuming that a connection was either MPTCP or regular
> TCP from the start, so endpoints would know whether they could make use
> of Multipath immediately and start more subflows immediately.
> 
> I'm intrigued with your suggestion, though. I see your point that there
> may not be any critical reason why this information should be known at
> the beginning of a session. I can't immediately think of any technical
> reason why doing it later in a session wouldn't work. But it would need
> further thought.

TCP negotiates all options during the SYN - that's the only 'handshake'
there is. TCP does not define option negotiation after connection
establishment.

I.e., you can decide to start the separate connections later, but you
need to negotiate support for the option during the SYN.

Joe
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