Re: [multipathtcp] WG Last Call for draft-ietf-mptcp-rfc6824bis

[<[e-mail]>]

In-line

-----Original Message-----
From: [e-mail] [mailto:[e-mail]] 
Sent: 15 July 2018 15:12
To: Eardley,PL,Philip,TUD1 R <[e-mail]>
Cc: [e-mail]
Subject: Re: [multipathtcp] WG Last Call for draft-ietf-mptcp-rfc6824bis

Hello Phil,

some replies to your comments inline:

On 14/06/18 - 10:55:37, [e-mail] wrote:
> A few comments as I work through the document, basically minor so far
> 
> Section 3.1
> << Given the SYN exchange is different between v1 and v0
>    the exchange cannot be immediately downgraded, and therefore if the
>    far end has requested a lower version then the initiator SHOULD
>    respond with an ACK without any MP_CAPABLE option, to fall back to
>    regular TCP.>>
> I think it should say "to ensure the exchange cannot..."

I'm not sure where you would put the "to ensure the exchange cannot..."?

However, reading through this paragraph, I think the SHOULD should rather be a MUST, no? Because, if conflicting versions are being requested we anyways can't do MPTCP.

[phil] re-reading, I think I mis-interpreted the phrase "Given the SYN exchange is different between v1 and v0  the exchange cannot be immediately downgraded". -- I think you're saying "A downgrade attack is not immediately possible because the SYN exchange is different in v0 and v1". I don't understand - the downgrade attack is possible, in what sense isn't it immediately possible" ? 

Re SHOULD vs MUST. Are there circumstances when you might want to use mptvp v0 rather than use tcp?. Perhaps where an operator has control of both end points (even in a proxy scenario)