Re: [multipathtcp] when and how is data-ACK responded?

"Sargent, Matthew T. (GRC-LCA0)[Peerless Technologies]" <matthew.t.sargent@nasa.gov> Fri, 24 March 2017 12:52 UTC

Return-Path: <matthew.t.sargent@nasa.gov>
X-Original-To: multipathtcp@ietfa.amsl.com
Delivered-To: multipathtcp@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 4F8581296CF for <multipathtcp@ietfa.amsl.com>; Fri, 24 Mar 2017 05:52:34 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -4.302
X-Spam-Level:
X-Spam-Status: No, score=-4.302 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_MED=-2.3, RP_MATCHES_RCVD=-0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=nasa.gov
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id x9j-tLc-mHel for <multipathtcp@ietfa.amsl.com>; Fri, 24 Mar 2017 05:52:33 -0700 (PDT)
Received: from ndjsvnpf104.ndc.nasa.gov (NDJSVNPF104.ndc.nasa.gov [198.117.1.154]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id E3EB31296CC for <multipathtcp@ietf.org>; Fri, 24 Mar 2017 05:52:32 -0700 (PDT)
X-Comment: SPF check N/A for local connections - client-ip=198.117.1.197; helo=ndjsppt103.ndc.nasa.gov; envelope-from=matthew.t.sargent@nasa.gov; receiver=multipathtcp@ietf.org
DKIM-Filter: OpenDKIM Filter v2.11.0 ndjsvnpf104.ndc.nasa.gov 073C043690A8
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nasa.gov; s=letsgomars; t=1490359952; bh=CPtlGBohxwCIVCTOkM998ODXqwcAdm8fpLE24SpPKuE=; h=From:To:CC:Subject:Date:References:In-Reply-To:From; b=Txl38ZsQk9TidePnLs5rq+Ywv9eT9kL6kGVR6jgDa/EwLAf/jRhIHrE8cw8jncx3v q9RGhMeq2Vb+cdSWOrcl6brUoFJGVMzKbM1FwLZhuRaJeD3UWBhsDSiuW/XxQIYwvL w3qU6PTu5nEql9Owb/f8gDTrKoVYkpc5XGo1Nad99XGUG3DsGLDUBFxibgGDCNAZWC +jAKgNcWLnFT1y4myGIVFPT75OWZIejEN1IcUjVNBFre/yDvZ0JZF1UEwxFJCzWhM4 27DgsMasAwe4OwABb3uYHedwVX8D/go9fGR74N0zcgwxf3XmycB6dWSuVFYIsBWL/x bxs/ksSGf4y3g==
Received: from ndjsppt103.ndc.nasa.gov (ndjsppt103.ndc.nasa.gov [198.117.1.197]) by ndjsvnpf104.ndc.nasa.gov (Postfix) with ESMTP id 073C043690A8; Fri, 24 Mar 2017 07:52:32 -0500 (CDT)
Received: from pps.filterd (ndjsppt103.ndc.nasa.gov [127.0.0.1]) by ndjsppt103.ndc.nasa.gov (8.16.0.20/8.16.0.20) with SMTP id v2OCpEk7022283; Fri, 24 Mar 2017 07:52:32 -0500
Received: from ndjscht113.ndc.nasa.gov (ndjscht113-pub.ndc.nasa.gov [198.117.1.213]) by ndjsppt103.ndc.nasa.gov with ESMTP id 29d1c9gmt7-1; Fri, 24 Mar 2017 07:52:31 -0500
Received: from NDJSMBX102.ndc.nasa.gov ([169.254.5.32]) by NDJSCHT113.ndc.nasa.gov ([198.117.1.183]) with mapi id 14.03.0319.002; Fri, 24 Mar 2017 07:52:31 -0500
From: "Sargent, Matthew T. (GRC-LCA0)[Peerless Technologies]" <matthew.t.sargent@nasa.gov>
To: =?utf-8?B?546L5biF?= <13211134@bjtu.edu.cn>
CC: multipathtcp <multipathtcp@ietf.org>
Thread-Topic: [multipathtcp] when and how is data-ACK responded?
Thread-Index: AQHSpGggFWEUs6QOSU+4npqCGpgiB6GkRgAA
Date: Fri, 24 Mar 2017 12:52:30 +0000
Message-ID: <5D0D0E88-2EF1-41DF-8B06-0A76AD6DACA7@nasa.gov>
References: <22f85d56.40512.15afefe044a.Coremail.13211134@bjtu.edu.cn>
In-Reply-To: <22f85d56.40512.15afefe044a.Coremail.13211134@bjtu.edu.cn>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [139.88.44.39]
Content-Type: text/plain; charset="utf-8"
Content-ID: <52BAEA22633566478DE42598725A83F6@mail.nasa.gov>
Content-Transfer-Encoding: base64
MIME-Version: 1.0
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-03-24_11:, , signatures=0
Archived-At: <https://mailarchive.ietf.org/arch/msg/multipathtcp/mxpZAAjkfVilB9gwwEukdbyI-FY>
Subject: Re: [multipathtcp] when and how is data-ACK responded?
X-BeenThere: multipathtcp@ietf.org
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: Multi-path extensions for TCP <multipathtcp.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/multipathtcp>, <mailto:multipathtcp-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/multipathtcp/>
List-Post: <mailto:multipathtcp@ietf.org>
List-Help: <mailto:multipathtcp-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/multipathtcp>, <mailto:multipathtcp-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 24 Mar 2017 12:52:34 -0000

Hi Wang,

> On Mar 24, 2017, at 2:25 AM, 王帅 <13211134@bjtu.edu.cn> wrote:
> 
> Hi,
> 
>    Data-ACK is independent with subflow-ACK which is responded by TCP layer, but when and how is data-ACK responded? I wonder whether discontinuous segments in data-level will trigger duplicate ACK, so fast retransmission will happen.If not, how to avoid this problem?


From Section 3 of RFC 6824:
Therefore, an MPTCP implementation receiving a duplicate ACK that contains an MPTCP option MUST NOT treat it as a signal of congestion.

My reading on this is that an MPTCP implementation will have the logic built in to avoid the behavior you are describing. Could anyone confirm or correct this?

Thanks,
Matt