Re: [multipathtcp] Timestamp option for Multipath TCP

Alan Ford <> Wed, 29 March 2017 03:16 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 7C0F9129445 for <>; Tue, 28 Mar 2017 20:16:53 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -2.698
X-Spam-Status: No, score=-2.698 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_FROM=0.001, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_LOW=-0.7, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (2048-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id tSi_yitOV_fp for <>; Tue, 28 Mar 2017 20:16:51 -0700 (PDT)
Received: from ( [IPv6:2607:f8b0:4003:c06::234]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 0F5D5128DE5 for <>; Tue, 28 Mar 2017 20:16:47 -0700 (PDT)
Received: by with SMTP id r203so1658832oib.3 for <>; Tue, 28 Mar 2017 20:16:47 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to; bh=0ECs3cN5q9xvDallRHSWCZ3kP9q7TTjJLrbXz5zWaug=; b=nsjXFfeaanGkvfBX7zpfTGeI+9ggkViST0H14yJhM0KwoY8UaIiJLkDI8ZFjTXXiPg jFjUqsvYot7OBCoVF88Ia54moCbkrhQcHabvZiXTS/iz+lF9OmYqMqD4BShTmELef3qq X4LS2gxEtVu6wqmnJwHgWhY5PV6IbNdlgLtAjcc1Io+10y889leLAiLuO+FSoKKPucso nNjwGrlVTSP6Gi3to3kmc2DnVF4jYMJU3zTXXxKhjSsTEZpUWrm1a/bY8A3Kft9suCUb sCNwdok8hlAT/lEUkKo9SrOT2MfK8XdVtdIfleAu3ARpwr0sD6KojobH51Hfp7dZTtAg LYIw==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to; bh=0ECs3cN5q9xvDallRHSWCZ3kP9q7TTjJLrbXz5zWaug=; b=sA803/InOmRY08hEbWecM47pDhsZUdGB1H8tAumB0TsULyEIABKJbj/A8iuyEvoWyT HKW7q6KBXcwDPkWnafUU8UisLEXTQvz6QKC6YFLgrPrbxKoBC5VUzhFyuAUvcLzjTt+0 gJWDrKgSqGLAOSTToBgudyW245FaWhrgmRVZzMJlowjrG8xgn+mJsr/Iy96rZYGMX359 h+NVz3hotwCLqlqX3hMs3rnKmJdQDH1/bkP8imbUvv27EwMqE/4o97Rhq9/FJlSgrdM5 C0Xxv3chIkW28OY2675ow/Mue4U+GgLw33dMRZtAewNWRSoDsQaUmF/KNZ4tEAf/rG2X rrxw==
X-Gm-Message-State: AFeK/H1UraG5PNBAFDixVARwD3Qeugo6z/NFuiqC5Pnpxar53ux/bbMbBUXuhxLDSox5eb9NgkKDXgBH54zU3Q==
X-Received: by with SMTP id x140mr14416610oif.205.1490757406444; Tue, 28 Mar 2017 20:16:46 -0700 (PDT)
MIME-Version: 1.0
References: <>
In-Reply-To: <>
From: Alan Ford <>
Date: Wed, 29 Mar 2017 03:16:35 +0000
Message-ID: <>
To:, multipathtcp <>
Content-Type: multipart/alternative; boundary=001a11c17e88a85370054bd601a9
Archived-At: <>
Subject: Re: [multipathtcp] Timestamp option for Multipath TCP
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: Multi-path extensions for TCP <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Wed, 29 Mar 2017 03:16:53 -0000

Hi Olivier,

Are these really mutually exclusive options? Relaxing the 7323 requirement
seems the right thing to do anyway; adding an option is a nice extra for
people that need TS for measurements other than PAWS.

But we could in theory put timestamp negotiation in MP_CAPABLE so we define
what it means for one end to require timestamps, and then use regular TCP
timestamps - no need for it to be a MPTCP option.

Or we could say that MP_CAPABLE + Timestamp = TS required. Then that makes
it negotiable; 6824bis would be changing the semantics of the presence of
today's TS option.


On Thu, 23 Mar 2017 at 09:34, Olivier Bonaventure <> wrote:

> Hello,
> The standard timestamp option for TCP is defined in RFC7323. It is
> widely implemented and used. It has two main objectives :
> - timing measurements
> - protection agains wrapped sequence numbers
> Given the importance of the second utilisation, RFC7323 has mandated the
> presence of a timestamp option in each segment once negotiated in the
> three-way handshake. For Multipath TCP, the DSN option already protects
> us from PAWS problems and it should not be mandatory to include
> timestamps in each packet sent over a Multipath TCP connection. Given
> the length of the timestamp and DSN options these two options already
> consume a large number of bytes and could limit the number of SACK
> blocks that can be placed inside acknowledgements.
> I will only be able to attend the Chicago meeting remotely, but I would
> like to start a discussion on the utilisation of timestamps by Multipath
> TCP on the list. I see two possibilities, but there are possibly more :
> 1. Ask for a revision of RFC7323 that allows timestamp options to be
> optional in packets of Multipath TCP connections
> 2. Define a new Multipath TCP option to carry timestamps. The
> utilisation of this option would be included in Multipath TCP and thus
> no option besides MP_CAPABLE would need to be included in the SYN.
> Do you have any opinion on these two possibilities ?
> Thanks
> Olivier
> _______________________________________________
> multipathtcp mailing list