Re: [multipathtcp] charter discussion

Olivier Bonaventure <> Fri, 07 April 2017 19:04 UTC

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From: Olivier Bonaventure <>
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Date: Fri, 7 Apr 2017 15:54:38 +0200
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Subject: Re: [multipathtcp] charter discussion
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> Regarding the charter discussions that happened at the mptcp session on
> Thursday March 30, I asked a question but I could not understand the
> answer, let me ask it again.
> In chairs slides page 12, TCP SYN shown in Option 1 and Option 2
> actually were different although the slides seems to show that they are
> the same.

Option 2 is SOCKS. Option 1 places control information in the SYN and 
SYN+AC while SOCKS places this information in the bytestream.

> In Option 1, if the proxy sends TCP SYN than is it OK in a conversation
> the destination does not know who the source is?

This is common with proxies. SOCKS and HTTP proxies for example often 
use their own address to contact
remote servers and not the client address. draft-plain-mode proposes a 
method to allow the proxy to learn the client address and thus use it to 
reach the final detaintion

> In Option 2, if TCP SYN sent was the original TCP SYN from the source then
> how come the TCP-ACK goes through the proxy?

Option 2 is SOCKS, thus the proxy uses its own address as a source to 
contact the final server.

> A node sending a packet without its address as source address means it
> is router, right?

The node could have a pool of addresses like a CG-NAT