Re: [MMUSIC] Data channel dcsa attribute usage and IANA

Christer Holmberg <> Wed, 28 August 2019 16:24 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 76405120241 for <>; Wed, 28 Aug 2019 09:24:51 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -2.002
X-Spam-Status: No, score=-2.002 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (1024-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id uhvuEgu0rpIX for <>; Wed, 28 Aug 2019 09:24:49 -0700 (PDT)
Received: from ( []) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id B1602120108 for <>; Wed, 28 Aug 2019 09:24:48 -0700 (PDT)
ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901;; cv=none; b=d+XcIQi7Lzc9Bz/FAlaHxmCbiBZd1uyPgRYne3uw6KM2S8t8F/bBgaMZdtTBqHGdG899UVY3ssGbyRCh2ziNPwm8MOUrfUa68OEgXjJi24r6chcET3Qngy0oluPQBgI4TDoK4efjgSqR++wGeEVjI+Nfn2TrX/p+KW809/6jIpk/93+r+ZTtYaN2S7lsjjRE0h9PvsCO9PUZXIw6nmhwBHml/Tlhdna2A/FnkGAN71s2M6CrYboFeSQrpADVdzH7Maeb4uSnyadqLx59hxbJGJRI6wcSOWQN7jKW2ibMirMZrkHIUvx4+vx7vfd3PMjzPj3qjtMpKwOJIqz92MgP4A==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed;; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=MrmUuslHW+sePufUBvcGrnhean1rQzeImu1k8ZG9IHE=; b=in32d+5wC0V9z3js/3O/FGLrbHxLxIOSImobWod/ZXZSwivl3mYfNp1K297zPEkkJAr0WlkaqMQO5XyBdL2YhAz8nRKzbQakTOxVp4FvvLEcfuYaPpLCQMEJCzGTufnSQGnuu3+86q3Q3HSNh5oO5mR8aRbo2FgBg/Ytz7vK7VzGuLhqOZzsHChYsgt/+ggHZOWWKV3dLljLG6rEa9sndCR1SdTzVCtBc3wZYT1YhDjXTMcZKBVHXgs7Bkdphuq1pmQHRV2+wYoRIUfeNHduMCYCwWgeArvApNCtb29Jc7zgMvZwo2ugRnXImN/UocflrdTbVJP8wfOeHIuyNb2XHg==
ARC-Authentication-Results: i=1; 1; spf=pass; dmarc=pass action=none; dkim=pass; arc=none
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=MrmUuslHW+sePufUBvcGrnhean1rQzeImu1k8ZG9IHE=; b=jwC6/03peQQbob+Yh5aRz48lEtXE9tlTqgvTkOEnKmDTm21mz/FWShS0kme2ZsptMcmVxi79iL6BXk1xTq4G7JAyUTCnqXAT0d/s/+4braKs40wVRPpHGQpMGFUK38d+meaoP+VoGh3HVZtMIgjymuY0PZDEUYgwQ4zHIJK6+Fw=
Received: from ( by ( with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2220.13; Wed, 28 Aug 2019 16:24:46 +0000
Received: from ([fe80::f0a1:2199:7816:ff8d]) by ([fe80::f0a1:2199:7816:ff8d%6]) with mapi id 15.20.2220.013; Wed, 28 Aug 2019 16:24:46 +0000
From: Christer Holmberg <>
To: Paul Kyzivat <>, "" <>
Thread-Topic: [MMUSIC] Data channel dcsa attribute usage and IANA
Date: Wed, 28 Aug 2019 16:24:46 +0000
Message-ID: <>
References: <> <> <> <>
In-Reply-To: <>
Accept-Language: en-US
Content-Language: fi-FI
authentication-results: spf=none (sender IP is );
x-originating-ip: []
x-ms-publictraffictype: Email
x-ms-office365-filtering-correlation-id: f7c5f61d-b634-413e-d8ae-08d72bd43dc6
x-microsoft-antispam: BCL:0; PCL:0; RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600166)(711020)(4605104)(1401327)(2017052603328)(7193020); SRVR:HE1PR07MB3067;
x-ms-traffictypediagnostic: HE1PR07MB3067:
x-microsoft-antispam-prvs: <>
x-ms-oob-tlc-oobclassifiers: OLM:10000;
x-forefront-prvs: 014304E855
x-forefront-antispam-report: SFV:NSPM; SFS:(10009020)(4636009)(376002)(346002)(366004)(39860400002)(396003)(136003)(51444003)(199004)(189003)(76116006)(66556008)(71200400001)(2906002)(66946007)(71190400001)(64756008)(305945005)(66446008)(66066001)(5660300002)(86362001)(81156014)(8936002)(8676002)(7736002)(81166006)(52536014)(14454004)(6116002)(3846002)(66476007)(76176011)(7696005)(476003)(55016002)(9686003)(99286004)(6506007)(26005)(33656002)(74316002)(44832011)(478600001)(110136005)(25786009)(53936002)(102836004)(256004)(14444005)(186003)(486006)(446003)(11346002)(316002)(6436002)(2501003)(2171002); DIR:OUT; SFP:1101; SCL:1; SRVR:HE1PR07MB3067;; FPR:; SPF:None; LANG:en; PTR:InfoNoRecords; A:1; MX:1;
received-spf: None ( does not designate permitted sender hosts)
x-ms-exchange-senderadcheck: 1
x-microsoft-antispam-message-info: AKYZsVVFnyI5GcWPg7+z2EJnp8JE+KKW7xPqLMHZqKP+Zn74YvCsdA5YCDcmqD1yqIzbBQSjVZ4cB7V+e3JDNKr/r8mkhizdyxcJgwwsAB6VK4UM9mtO464CZdelAYa4gb36nttiJ6pVgvbm36Xq+Y0mhFXDeYI/FyUWkRNiV8KcO5XTpLrr5+4zA65B7zf5fXegW3aiVAKbJTdPMgKBZZBBheAaB24cGnzJPP2xyYTR+a5+RA3V1ZCPp4MsPrdWUtF++r0OmbRqt/ahwKT6aJF6nrVXLY5/a7TDrRnEEvzMF7/qcvwjTA8cVMNvoZNJctYPIter/3+b9VuiSygI4ckja1g6SqUyKGWDudyI16PBPaxxE1RjrOrkNbMaKqi2LE4GUnpqkoj4L7F2T19dXvNbg8pLr6O8RWWOtDrtEJY=
x-ms-exchange-transport-forked: True
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: base64
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: f7c5f61d-b634-413e-d8ae-08d72bd43dc6
X-MS-Exchange-CrossTenant-originalarrivaltime: 28 Aug 2019 16:24:46.4148 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 92e84ceb-fbfd-47ab-be52-080c6b87953f
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: ge+ebe41QjxwozEduvfVcXc6+oXedPrvFRq7esRnb8H/t9VWjgzuW+08ZE+75uCtnyAu1qK1bpaGX57rgQCKDo16piYyrNthmvrQRmfM/aU=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR07MB3067
Archived-At: <>
Subject: Re: [MMUSIC] Data channel dcsa attribute usage and IANA
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Multiparty Multimedia Session Control Working Group <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Wed, 28 Aug 2019 16:24:52 -0000


>>>> Section 7.2 of draft-ietf-mmusic-msrp-usage-data-channel updates the 
>>>> IANA registry for the SDP ‘setup’ attribute, by indicating that it 
>>>> can be used inside an SDP ‘dcsa’ attribute.
>>>> Do we really need to update the IANA registry for all SDP attributes 
>>>> that can be included in an ‘dcsa’ attribute???
>>> I think so. Look at RFC4566bis for the revised attribute registry.
>>> The way to avoid this would be to remove "Usage Level" from the 
>>> registry and thus force people to consult the defining documents for 
>>> the attribute in order to learn this. But it is seriously late in the cycle to update 4566bis.
>> I think it can be seen in two different ways, that have no impact on 4566bis.
>> 1) If the usage level is "media", that doesn't change inside a dcsa 
>> attribute. From an SDP perspective it is still "media", as it is part 
>> of an m= line. If you place a "session" level attribute inside a dcsa 
>> attribute that changes, but I don't think we do that; or
>> 2) From an SDP perspective, only the dcsa attribute is used. What's inside is "application specific", and has nothing to do with SDP.
> I think you are mixing two things here:
> - what currently is required based on the specs as written (including 4566bis);
>- what would be the ideal way for it to work.
> Based on the current specs I think the registry must be updated. And I think that was always expected during the development of the dcsa attribute.

draft-mmusic-data-channel-sdpneg doesn't say anything (unless I've missed it) about updating the IANA registry, so I am not sure what specs you are referring to.

>What is most important is that people have a well defined way to determine whether an attribute can be used in dcsa in a particular case. 

Sure, but that is defined in the data channel usage specs (e.g., the MSRP usage spec and the T.140 usage spec).

>If they are expected to find this in a document defining the attribute, then the document had better provide an answer.

We are not updating the documents defining the attributes.

>If you feel a change is needed to 4566bis then we will have to figure out if and how to accomplish that. It is already at the editor.

I don't think a change is needed for 4566bis.  But, if an IANA registry update is required for attributes used with dcsa I think it should be said in draft-mmusic-data-channel-sdpneg (unless it's already there and I've missed it...)