From nobody Tue Apr 11 03:03:38 2023 Return-Path: X-Original-To: tsvwg@ietfa.amsl.com Delivered-To: tsvwg@ietfa.amsl.com Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id BA26DC14CF09 for ; Tue, 11 Apr 2023 03:03:37 -0700 (PDT) X-Virus-Scanned: amavisd-new at amsl.com X-Spam-Flag: NO X-Spam-Score: -1.997 X-Spam-Level: X-Spam-Status: No, score=-1.997 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_ZEN_BLOCKED_OPENDNS=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001, URIBL_DBL_BLOCKED_OPENDNS=0.001, URIBL_ZEN_BLOCKED_OPENDNS=0.001] autolearn=ham autolearn_force=no Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=ifi.uio.no Received: from mail.ietf.org ([50.223.129.194]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Txaxw0FuNybR for ; Tue, 11 Apr 2023 03:03:32 -0700 (PDT) Received: from mail-out02.uio.no (mail-out02.uio.no [IPv6:2001:700:100:8210::71]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 783DFC14CE42 for ; Tue, 11 Apr 2023 03:03:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=ifi.uio.no; s=key2103; h=To:References:Message-Id:Content-Transfer-Encoding:Cc:Date: In-Reply-To:From:Subject:Mime-Version:Content-Type:Sender:Reply-To:Content-ID :Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To: Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe :List-Post:List-Owner:List-Archive; bh=JjpincyXGnHpVkrYuzDbNFhMM1O3j4KsTFzARry82Lg=; b=Bk6a2g4sBIDHT4q4AgJEAuhYH3 OBEsZ+2kfyyYTniYY4vB7b5+d9ZMGTqAcmp03uiQ5T7ieoDzhPm/oqebLD2gy1svF359OH7xvMfVe pPZhDYFuA/GboSDdo2TLBsgIPpgf3dEbQuT+PIx36rlekdgJ6NSjgRU5kAhx7BT+fRZZNz37gLP0Z uqRuACSql0C3hknF0aB/+Ys+S6/boejJfBay6YHsa902dvY0WLFRICQjXbnTOW88kQxOI0E21GsU8 v/vbIk6OlJRT+2oGSNTxkstkQFJLQCs7NdduxRxl1aT9Xu7o/r76HT2vHn7dJNKiY320YztKs0TZT iopoz2Sg==; Received: from mail-mx03.uio.no ([129.240.10.15]) by mail-out02.uio.no with esmtps (TLS1.2) tls TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1pmAqX-00Cmvp-1t; Tue, 11 Apr 2023 12:03:29 +0200 Received: from 178.165.194.79.wireless.dyn.drei.com ([178.165.194.79] helo=smtpclient.apple) by mail-mx03.uio.no with esmtpsa (TLS1.2:ECDHE-ECDSA-AES256-GCM-SHA384:256) user michawe (Exim 4.96) (envelope-from ) id 1pmAq6-0009Xz-1D; Tue, 11 Apr 2023 12:03:29 +0200 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.120.41.1.1\)) From: Michael Welzl In-Reply-To: Date: Tue, 11 Apr 2023 12:02:00 +0200 Cc: "tsvwg@ietf.org" Content-Transfer-Encoding: quoted-printable Message-Id: References: <78604000-0F5E-4E09-8CC3-0BEB06ABC5CF@ifi.uio.no> To: Michael Tuexen X-Mailer: Apple Mail (2.3696.120.41.1.1) X-UiO-SPF-Received: Received-SPF: neutral (mail-mx03.uio.no: 178.165.194.79 is neither permitted nor denied by domain of ifi.uio.no) client-ip=178.165.194.79; envelope-from=michawe@ifi.uio.no; helo=smtpclient.apple; X-UiO-Spam-info: not spam, SpamAssassin (score=-5.0, required=5.0, autolearn=disabled, AWL=0.001, TVD_RCVD_IP=0.001, UIO_MAIL_IS_INTERNAL=-5) X-UiO-Scanned: 51E230D16BC658B99C13F4EF77D7556147C34B2B X-UiOonly: D23FB211C722EDB2600DAA6CED6C2D695D7B7783 Archived-At: Subject: Re: [tsvwg] Adoption call fordraft-tuexen-tsvwg-sctp-zero-checksum - to conclude 25th April 2023 X-BeenThere: tsvwg@ietf.org X-Mailman-Version: 2.1.39 Precedence: list List-Id: Transport Area Working Group List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 11 Apr 2023 10:03:37 -0000 > On Apr 11, 2023, at 11:47 AM, Michael Tuexen = wrote: >=20 >> On 11. Apr 2023, at 11:28, Michael Welzl wrote: >>=20 >> Hi, >>=20 >> I have now read this document and support progressing it: it looks = genuinely useful to me. >>=20 >> I was just wondering if the receiver-side behavior should include a = statement about the possibility of simply ignoring the checksum? The = way section 4.3 is written, it doesn=E2=80=99t exclude this, but I guess = that the SCTP base RFCs prescribe that the checksum *must* be calculated = and checked. So, why not relax this? With or without negotiation of = "Zero Checksum Acceptable=E2=80=9D, a receiver could probably always = locally decide: =E2=80=9CI see that this is going over DTLS, so I will = ignore the SCTP checksum." > Right now the idea is to accept packets > * which contain the correct CRC32c, or > * which contain an incorrect CRC32c of zero, it this support was = announced during the handshake. > Just ignoring the checksum would also accept packets which contain an = invalid checksum different > from zero. This is currently not allowed. >=20 > Your proposal would be something like 'Any Checksum Acceptable' = instead of 'Zero Checksum Acceptable'. > Could be done, but do you gain anything? If the sender is not aware of this new mechanism and inserts a correct = (zero or not) SCTP checksum, the receiver could nevertheless skip doing = the calculation. > The implementation on the receiver side done in a way that you don't = do any computation if > you receive zero as the CRC32c and after looking up the association, = you determine that > the end point has sent initially the Zero Checksum Acceptable. > If you know that the Zero Checksum Acceptable feature is used always, = you can skip the lookup > part. What I=E2=80=99m proposing is to allow the receiver to not even do a = checksum calculation even if the peer doesn=E2=80=99t use Zero Checksum = Acceptable and/or isn=E2=80=99t aware of this feature. I don=E2=80=99t know if specifying this matters, as it=E2=80=99s purely = a local implementation decision anyway. I guess a receiver = implementation could just decide that the checksum is assumed-correct in = some cases, as the chance of a CRC below being right but the SCTP CRC = being wrong is truly miniscule... Never mind, then. Probably not worth adding words for it. Cheers, Michael >=20 > Best regards > Michael >>=20 >> A nit - though, not being a native speaker, I don=E2=80=99t even know = if this really is a mistake: "This is in particular important for = computational limited end points using SCTP encapsulated in DTLS.=E2=80=9D= >> I believe that =E2=80=9Ccomputationally=E2=80=9D should be used here = instead of =E2=80=9Ccomputational". >>=20 >> Cheers, >> Michael >>=20 >>=20 >>> On Apr 11, 2023, at 10:31 AM, Gorry Fairhurst = wrote: >>>=20 >>> This email now marks the start of a WG adoption call for: Zero = Checksum for the Stream Control Transmission Protocol = (draft-tuexen-tsvwg-sctp-zero-checksum-02). This draft was discussed at = the recent TSVWG meeting. >>>=20 >>> Abstract: >>>=20 >>> The Stream Control Transmission Protocol (SCTP) uses a 32-bit >>> checksum in the common header of each packet to provide some level = of >>> data integrity. When the lower layer used by SCTP provides already >>> the same or a higher level of data integrity, computing this = checksum >>> does not provide any additional protection, but does require >>> computing resources. This document provides a simple extension to >>> SCTP allowing to save these computing resources by using the = constant >>> 0 as the checksum in a backwards compatible way. >>>=20 >>> Please read this draft, and send any comments/concerns to either the = TSVWG or to the chairs . Notes of support to = progress this work, and volunteers to review the drafts will also be = very welcome at this stage. >>>=20 >>> All participants, should disclose any relevant intellectual property = rights (IPR) under [RFC8179]. >>>=20 >>>=20 >>> Best wishes, >>> Gorry and Marten >>> (tsvwg co-chairs) >>>=20 >>>=20 >>=20 >=20