Re: [multipathtcp] rfc6824bis - RST after MP_FASTCLOSE retransmission

Alan Ford <alan.ford@gmail.com> Thu, 01 June 2017 07:37 UTC

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From: Alan Ford <alan.ford@gmail.com>
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Date: Thu, 1 Jun 2017 08:37:29 +0100
Cc: Christoph Paasch <cpaasch@apple.com>, =?utf-8?Q?Fran=C3=A7ois_Finfe?= <francois.finfe@tessares.net>, multipathtcp@ietf.org
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To: Olivier.Bonaventure@uclouvain.be
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Subject: Re: [multipathtcp] rfc6824bis - RST after MP_FASTCLOSE retransmission
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Hi Olivier,

> For MPTCP, a possible modification to rfc6824bis could be
> 
>   o  If Host A does not receive a TCP RST in reply to its MP_FASTCLOSE
>      after one retransmission timeout (RTO) (the RTO of the subflow
>      where the MPTCP_RST has been sent), it SHOULD retransmit the
>      MP_FASTCLOSE.  The number of retransmissions SHOULD be limited to
>      avoid this connection from being retained for a long time, but
>      this limit is implementation specific.  A RECOMMENDED number is 3.
> 
> We could add. a sentence like : After 3 retransmission of the MP_FASTCLOSE without any TCP RST in response, Host A MAY send a TCP RST when it releases the state for this MPTCP connection.


In essence, you are saying that when we give up retransmitting MP_FASTCLOSE, just throw a TCP RST down that subflow anyway, it won’t do any harm, and may help clear up state. That seems like a safe addition to me.

Best regards,
Alan