Re: [tcpm] WG status update

  Dear Richard;

Thank you for looking at TCP-Rehash.
Please see my comments inline.

Regards,
Bruno Mongazon

Le 10/11/2010 13:51, Scheffenegger, Richard a écrit :
> Hi Bruno,
>
> After a casual look, it appears to me that a lightweight implementation of MP-TCP can have the same benefits, but does not require the opaque exchange of IPv4 addresses...

Yes an idea would be to have TCP-Rehash == lightweigth MPTCP
There are a few design diffferences that need to be looked at.

> Your use case - that the old L3 address is already no longer available at the time of the rehash - may need to be looked at in MPTCP though (iirc, they do a graceful session setup first (thus can work with NAT mostly), and move data transport only after the successful establishment of the 2nd L3 connectivity, and only then tear down the original L3 connectivity).

Right but... there is no real constraint on old address availability, 
thus the old address might still be available.
A key difference between TCP-Rehash and MPTCP is the session setup. With 
TCP-Rehash there is no setup, it is a straight move. If it fails, the 
connection is broken, this would happen anyway if L3 address changes and 
there is no "move" mechanism. Doing so is just opportunistic but 
deterministic. MPTCP is more complex since a new connection is setup 
before the old connection is being "moved".
 From design perspective, would it be that complex for MPTCP to handle 
rehash design ?

NAT is a different story (orthogonal i would say) and issue.

> Perhaps the effort would be better placed on making sure that such light-weight MPTCP implementations remain feasible, instead of defining an alternate method that is addressing only this one aspect, but incompatible with MPTCP otherwise?

To be honest i have both TCP-Rehash and MPTCP linux kernel source 
code... my intention is not to define an alternate method ! Rather i 
posted the TCP-Rehash draft with the intention to provide some 
additional work on the topic. Convergence and collaboration is of course 
to be considered. I think my work, although it was not disclosed, 
started sometimes ago, almost at early MPTCP.

Please let me know, if from the design point of view, the WG would 
consider the opportunity to have a lightweight MPTCP that would look 
like TCP-Rehash.

> Richard Scheffenegger
>
>
>
>> -----Original Message-----
>> From: Bruno Mongazon-Cazavet
>> [mailto:bruno.mongazon-cazavet@alcatel-lucent.com]
>> Sent: Mittwoch, 10. November 2010 08:54
>> To: Eddy, Wesley M. (GRC-MS00)[ASRC AEROSPACE CORP]
>> Cc: tcpm@ietf.org
>> Subject: Re: [tcpm] WG status update
>>
>>
>>    Le 10/11/2010 01:54, Eddy, Wesley M. (GRC-MS00)[ASRC
>> AEROSPACE CORP] a écrit :
>>> Hi, for those of you who aren't in Beijing, here's a
>> snapshot of the TCPM WG status.
>>
>> Hi,
>>
>> I have posted a 00 draft that might be of interest for your working
>> group. I don't see any mention in your snapshot.
>> http://www.ietf.org/id/draft-mongazon-tcpm-tcp-rehash-00.txt
>>
>> I will not be in Beijing to present it but i hope to be in
>> Prague to do so.
>> I would appreciate the working group can look at it and let
>> me know if
>> it could be of any interest and how i shall pursue my contribution.
>>
>> I have done a Linux kernel implementation of the draft and be
>> ready for
>> a demo in Prague.
>>
>> Best Regards,
>> Bruno.
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