Re: [MMUSIC] Starting shepherd's review of draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments

Christer Holmberg <christer.holmberg@ericsson.com> Thu, 07 November 2019 18:04 UTC

Return-Path: <christer.holmberg@ericsson.com>
X-Original-To: mmusic@ietfa.amsl.com
Delivered-To: mmusic@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id DE4FD1200B9 for <mmusic@ietfa.amsl.com>; Thu, 7 Nov 2019 10:04:12 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.9
X-Spam-Level:
X-Spam-Status: No, score=-1.9 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, HTML_MESSAGE=0.001, HTTPS_HTTP_MISMATCH=0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=ericsson.com
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 3tgU9TzeQo_B for <mmusic@ietfa.amsl.com>; Thu, 7 Nov 2019 10:04:08 -0800 (PST)
Received: from EUR01-HE1-obe.outbound.protection.outlook.com (mail-he1eur01on0619.outbound.protection.outlook.com [IPv6:2a01:111:f400:fe1e::619]) (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 146101208C3 for <mmusic@ietf.org>; Thu, 7 Nov 2019 10:04:07 -0800 (PST)
ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=kNmKBxJWL4IbKyZ7XBfR9qMZ/5t4rpRpQ+ol/w2JAhQHsEtUhHNdqNyWiDnmswrgvGrHRwCMBl5H917svAm4QITzufnB5PsyDspcW43LCpCE/YmvCab8k63AgV9etznKl6swiKaCZun4jPoWtuGuJ75Rqg6O3191B5E/chc62EqNy0ln8PMYwlRAUsENokkaWXSVDW1gqP8R5hX58+hCG0J0UrZ9sOBwuJRH5+XNRMiITC3snzxe+OAp6YJihnhooB0Sq8OSo7GOCEqhxfhc/asLaFc0CNUyzR8p4gFbuAzzQhogelZ6x4lyDOIqYsNWCITzWsoUfmdwCEX5EkITVA==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=86Af6p3AO0IJU/s4ctbKE3a2C/xSXQ8tuWFG1eX49iQ=; b=CHlZizuDJglox3GJBxJOxO1aBMJ2N7Ta/9oboXUaiuR4Ly66Esmzx69Eo0RmwLDyBHssdvi/Q6jPqUoB8RTK1+WtrzSzP4DduVVF1rnqs0r8XIuKCTQ1uFKhx1roP+VcxWK4YkzHU0oc9So2Hto55FRtPkxTK3sOZdNsqKANPUCrWKKMb21iALWJ1bMEbfbvgAgDKHmh14IKX1olthcY8tXthgmwnaFGs7F+WyRgQcJNoYRNrKsopJHKUU/jcttM0vB0jtAVxgHGVlTd41/vTHuY6MnF4UnVa9ntM0QPlbtEDf6ND8zRK/ZRbvUzH0wfmJ/S2nd3qsujkC2n9OAlGQ==
ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=ericsson.com; dmarc=pass action=none header.from=ericsson.com; dkim=pass header.d=ericsson.com; arc=none
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ericsson.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=86Af6p3AO0IJU/s4ctbKE3a2C/xSXQ8tuWFG1eX49iQ=; b=JOR3mc3d6+xHxckG2qbm6H5VrDakLG68zzjDzBQ2bhFXablMOlSj0T6SbChx7EMCcBNbB4JB5yEAVQGqaK5Fwt/jelDkrCL9YiDY7UGWxUMqjnCdk1HY9FsfBs3BjRhglzDg/SiWgnBQSpBWtHDYPsBxpRh6WyC1QTfz93N1nCY=
Received: from VI1PR07MB3167.eurprd07.prod.outlook.com (10.175.243.17) by VI1PR07MB3358.eurprd07.prod.outlook.com (10.175.243.148) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2430.16; Thu, 7 Nov 2019 18:04:05 +0000
Received: from VI1PR07MB3167.eurprd07.prod.outlook.com ([fe80::41a:f6a0:9660:bc09]) by VI1PR07MB3167.eurprd07.prod.outlook.com ([fe80::41a:f6a0:9660:bc09%3]) with mapi id 15.20.2430.020; Thu, 7 Nov 2019 18:04:04 +0000
From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Gunnar Hellström <gunnar.hellstrom@omnitor.se>, Bo Burman <bo.burman@ericsson.com>, "mmusic (mmusic@ietf.org)" <mmusic@ietf.org>
Thread-Topic: [MMUSIC] Starting shepherd's review of draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments
Thread-Index: AQHVk909yEtpzH2MKEqkZmDSG+/rpKd9K6IAgACj3A+AAHGsCYAAFbG3gAA2oYCAAOw63YAACpyAgABNzID//+A1AIAABXdggAA6m4D///0IgIAAE/54
Date: Thu, 07 Nov 2019 18:04:04 +0000
Message-ID: <VI1PR07MB3167CF5169E2A7723BC5AA3693780@VI1PR07MB3167.eurprd07.prod.outlook.com>
References: <31B83060-1653-48A1-AB78-9D2418B49CC6@ericsson.com> <5742e425-788d-7d10-0e68-0a75bea74f3a@omnitor.se> <HE1PR07MB31619BBC3A73260C14CC693693790@HE1PR07MB3161.eurprd07.prod.outlook.com> <VI1P193MB06698D287FB68B4DDE435E98FB790@VI1P193MB0669.EURP193.PROD.OUTLOOK.COM> <HE1PR07MB31610CA6717330B5823EC72F93790@HE1PR07MB3161.eurprd07.prod.outlook.com> <c45c5029-72b2-d25f-4a3f-bc1d1c445a1f@omnitor.se> <HE1PR07MB3161BB6FFAC11E637111E0D193780@HE1PR07MB3161.eurprd07.prod.outlook.com> <f79712fd-84fd-3289-f7cb-97e547b2537d@omnitor.se> <FC883EE8-E05F-4E3E-ABF9-A1E94EB61F52@ericsson.com> <169e65c6-207f-3ccd-6c2c-9268d425e2fb@omnitor.se> <HE1PR07MB32593108119FAE1F07C2D7478D780@HE1PR07MB3259.eurprd07.prod.outlook.com> <E6D08311-B137-4583-9AAD-74C1BA728CFB@ericsson.com>, <3d0479a3-3221-bcc0-d9f6-b7a3d292ffbc@omnitor.se>
In-Reply-To: <3d0479a3-3221-bcc0-d9f6-b7a3d292ffbc@omnitor.se>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
authentication-results: spf=none (sender IP is ) smtp.mailfrom=christer.holmberg@ericsson.com;
x-originating-ip: [2001:14bb:80:e328:bd07:7d33:14e0:ff88]
x-ms-publictraffictype: Email
x-ms-office365-filtering-correlation-id: d7245b0b-36b4-478b-e53b-08d763ace065
x-ms-traffictypediagnostic: VI1PR07MB3358:
x-ms-exchange-purlcount: 1
x-ms-exchange-transport-forked: True
x-microsoft-antispam-prvs: <VI1PR07MB335844845E0F144C40F091D593780@VI1PR07MB3358.eurprd07.prod.outlook.com>
x-ms-oob-tlc-oobclassifiers: OLM:10000;
x-forefront-prvs: 0214EB3F68
x-forefront-antispam-report: SFV:NSPM; SFS:(10009020)(4636009)(136003)(376002)(39860400002)(366004)(346002)(396003)(13464003)(199004)(189003)(446003)(6436002)(30864003)(66574012)(966005)(11346002)(71190400001)(476003)(71200400001)(6306002)(229853002)(14454004)(2906002)(46003)(54896002)(236005)(44832011)(486006)(9686003)(55016002)(5660300002)(7696005)(478600001)(81166006)(81156014)(8676002)(8936002)(86362001)(76176011)(66556008)(14444005)(52536014)(561944003)(76116006)(66946007)(99286004)(66476007)(64756008)(66446008)(33656002)(6506007)(53546011)(606006)(256004)(74316002)(110136005)(25786009)(7736002)(6116002)(186003)(102836004)(6246003)(316002); DIR:OUT; SFP:1101; SCL:1; SRVR:VI1PR07MB3358; H:VI1PR07MB3167.eurprd07.prod.outlook.com; FPR:; SPF:None; LANG:en; PTR:InfoNoRecords; A:1; MX:1;
received-spf: None (protection.outlook.com: ericsson.com does not designate permitted sender hosts)
x-ms-exchange-senderadcheck: 1
x-microsoft-antispam: BCL:0;
x-microsoft-antispam-message-info: CJ5pwWH92+MuJ1tnZegEMYTkB7YXS/GoeL5rQCL8F8yfxwilS6X0HJflSyBYs/A5fyADT3BxECPIJglaMmng6evyit+JzKGkkwO4/gNdxZ8PyFA4GgLwmFJG8d+e/pLdOh3vZYbfJITOnTdmcJMm+DdiYFuaJLWaIDB/gBz0z5DvzM5rUbaEe1Bab/XXKDz0xjYNsax5VLHAgDRLKwbOgN08bgSnsN24MWZojyAb26/aBO9vzZ+S+gZ0Qm9KZ9KqcVdizgS2AUABk7qaSchsfSMg8tvt95E8x7hm6V3xk6ZxXLJd3lcb/yHxsEZV/GhzCmo1MdQTxFWsqP7MvLbZjipwGZcquC+yx0hGOv/8KPdupfLqOiVJK6uat6VL2m96A21ZB8f3JW+gjfcbSOEYdkN//oA/ygXC5SXvcVyFZq8DcwIK0vb3ujsYzoB1AaiG8gEKGJq6h/mXp41Q/2mByYu/+shWc3ljBNTaz565W0Y=
Content-Type: multipart/alternative; boundary="_000_VI1PR07MB3167CF5169E2A7723BC5AA3693780VI1PR07MB3167eurp_"
MIME-Version: 1.0
X-OriginatorOrg: ericsson.com
X-MS-Exchange-CrossTenant-Network-Message-Id: d7245b0b-36b4-478b-e53b-08d763ace065
X-MS-Exchange-CrossTenant-originalarrivaltime: 07 Nov 2019 18:04:04.5394 (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: eCNvZTC9uZt4SiZrPK3oPw07cn3TFLLnPRtkTmugQLEVgZrbsrWEJsbHbAcXZXogwXfjN4qKCcI1P2ZTyNbiFwNWz6S500gyGF0u0CukmTQ=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR07MB3358
Archived-At: <https://mailarchive.ietf.org/arch/msg/mmusic/M2hZq5BVUUs4sCCC9IQwyE9xBcI>
Subject: Re: [MMUSIC] Starting shepherd's review of draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments
X-BeenThere: mmusic@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Multiparty Multimedia Session Control Working Group <mmusic.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/mmusic>, <mailto:mmusic-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/mmusic/>
List-Post: <mailto:mmusic@ietf.org>
List-Help: <mailto:mmusic-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/mmusic>, <mailto:mmusic-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 07 Nov 2019 18:04:13 -0000

Hi,

I guess we can reference RFC 1459 - how often does that happen nowadays? :)

Regards,

Christer
________________________________
From: Gunnar Hellström <gunnar.hellstrom@omnitor.se>
Sent: Thursday, November 7, 2019 6:51:19 PM
To: Christer Holmberg <christer.holmberg@ericsson.com>; Bo Burman <bo.burman@ericsson.com>; mmusic (mmusic@ietf.org) <mmusic@ietf.org>
Subject: Re: [MMUSIC] Starting shepherd's review of draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments

Hi,

I am sorry, I have not yet found a reference for the common look of
messages with a leading source label that I called "IRC style".

Anyone knows?

Regards

Gunnar

Den 2019-11-07 kl. 16:01, skrev Christer Holmberg:
> Hi,
>
> I have updated the pull request based on Bo's technical comments. Please take a look.
>
> https://protect2.fireeye.com/v1/url?k=e0987931-bc4c728f-e09839aa-86742d02e7e2-df3d38683e05ec32&q=1&e=9c7cc8f6-262c-4fc4-a624-42d361ef532b&u=https%3A%2F%2Fgithub.com%2Fcdh4u%2Fdraft-datachannel-t140%2Fpull%2F52
>
> Gunnar, which RFC should I add as reference for the IRC labels?
>
> Regards,
>
> Christer
>
>
>
> On 07/11/2019, 15.34, "Bo Burman" <bo.burman@ericsson.com> wrote:
>
>      Yes, I agree that should resolve the  issue I had with the text.
>      Thanks,
>      /Bo
>
>      > -----Original Message-----
>      > From: Gunnar Hellström <gunnar.hellstrom@omnitor.se>
>      > Sent: den 7 november 2019 14:13
>      > To: Christer Holmberg <christer.holmberg@ericsson.com>; Bo Burman
>      > <bo.burman@ericsson.com>; mmusic (mmusic@ietf.org)
>      > <mmusic@ietf.org>
>      > Subject: Re: [MMUSIC] Starting shepherd's review of draft-ietf-mmusic-t140-
>      > usage-data-channel-07 - Bo's technical comments
>      >
>      > Hi,
>      >
>      > Christer, I accept your proposal below. With the remaining text it should be
>      > apparent for all that the solution has limitations.
>      >
>      > I hope also Bo thinks that the issues are solved now.
>      >
>      > Regards
>      >
>      > Gunnar
>      >
>      >
>      > Den 2019-11-07 kl. 14:06, skrev Christer Holmberg:
>      > > Hi,
>      > >
>      > >>> In the first paragraph we say that one needs to use separate data
>      > >>> channels, so it sounds strange to then have a note saying that is not true.
>      > Also, the way you suggest the text makes it look like you are defining a
>      > mechanism for using a single channel.
>      > >> Yes, I realized the conflict and tried to avoid it by the words
>      > >> "limited functionality multi-party RTT presentation in one display area",
>      > and "This presentation style does not meet all RTT requirements".
>      > >>
>      > >> But maybe that was not obvious. So, I accept your proposal below with
>      > >> some modifications
>      > >>
>      > >>> Maybe something like this:
>      > >>>
>      > >>> "The usage of a single T.140 data channel, without any protocol
>      > extensions, would require the conference server to only forward
>      > >>>   real-time text from one source at any given time, and e.g., include IRC
>      > style text labels in the real-time text in order for the receiver
>      > >>>   to separate real-time text from different sources. The procedures of
>      > such mechanism is outside the scope of this document."
>      > >> Yes, quite good, I suggest a few modifications to:
>      > >>
>      > >> "The usage of a single T.140 data channel, without any protocol
>      > >> extensions, would require the conference server to only forward
>      > >> real-time text from one source at any given time, and e.g., include
>      > >> IRC style text labels in the real-time text in order for the receiver to
>      > present real-time text from different sources separated. The procedures of
>      > such mechanisms cause functional limitations and are outside the scope of
>      > this document."
>      > > I am ok to replace 'separate' with 'present', but with the modification to the
>      > last sentence you would still have the question what those 'functional
>      > limitations' are,  and we would need to include additional text...
>      > >
>      > > So, I suggest that we remove the text about functional limitations.
>      > >
>      > > Regards,
>      > >
>      > > Christer
>      > >
>      > >
>      > >
>      > >
>      > >
>      > > From: Gunnar Hellström mailto:gunnar.hellstrom@omnitor.se
>      > > Sent: Wednesday, November 6, 2019 9:44 PM
>      > > To: Christer Holmberg mailto:christer.holmberg@ericsson.com; Bo Burman
>      > > mailto:bo.burman=40ericsson.com@dmarc.ietf.org; mmusic
>      > > (mailto:mmusic@ietf.org) mailto:mmusic@ietf.org
>      > > Subject: Re: [MMUSIC] Starting shepherd's review of
>      > > draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments
>      > >
>      > > Hi,
>      > > Even if I accepted to delete the last sentence in section 5 on multi-party, I
>      > want to propose a solution that might better address the original issue 5.
>      > >
>      > > So, this is a proposal for new wording of the last sentence in 5, as a solution
>      > on issue 5:
>      > > "Conference mixers that use a single T.140 data channel
>      > >     to transmit real-time text towards clients might however without any
>      > protocol extensions produce a limited functionality multi-party RTT
>      > presentation in one display area. Only one source at a time can be presented
>      > in real-time, but switch of source of text to display in real-time can be made
>      > automatically by the mixer and at suitable points in the text streams. Sources
>      > could be identified by inline text labels in IRC style. This presentation style
>      > does not meet all RTT requirements and if used, should be a temporary
>      > fallback method for conference-unaware clients."
>      > >
>      > > This wording is a self sustained description on what is possible and would
>      > also match better the recently revived work on multi-party rtt.
>      > >
>      > > Regards
>      > >
>      > > Gunnar
>      > >
>      > >
>      > >
>      > > Den 2019-11-06 kl. 17:29, skrev Christer Holmberg:
>      > > Bo, are you ok with the proposals?
>      > >
>      > > Regards,
>      > >
>      > > Christer
>      > >
>      > >
>      > > From: Gunnar Hellström mailto:gunnar.hellstrom@omnitor.se
>      > > Sent: Wednesday, November 6, 2019 5:16 PM
>      > > To: Christer Holmberg mailto:christer.holmberg@ericsson.com; Bo Burman
>      > > mailto:bo.burman=40ericsson.com@dmarc.ietf.org; mmusic
>      > > (mailto:mmusic@ietf.org) mailto:mmusic@ietf.org
>      > > Cc: 'mailto:mmusic-chairs@tools.ietf.org'
>      > > mailto:mmusic-chairs@tools.ietf.org
>      > > Subject: SV: [MMUSIC] Starting shepherd's review of
>      > > draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments
>      > >
>      > > Christer,
>      > > I agree with your proposals.
>      > >
>      > > Regards
>      > > Gunnar
>      > >
>      > > ----------------------------------------------------------------------
>      > > Gunnar Hellström
>      > > Omnitor
>      > > mailto:gunnar.hellstrom@omnitor.se
>      > > +46 708 20 42 88
>      > >
>      > > Från: Christer Holmberg mailto:christer.holmberg@ericsson.com
>      > > Skickat: den 6 november 2019 09:58:30
>      > > Till: Gunnar Hellström mailto:gunnar.hellstrom@omnitor.se; Bo Burman
>      > > mailto:bo.burman=40ericsson.com@dmarc.ietf.org; mmusic
>      > > (mailto:mmusic@ietf.org) mailto:mmusic@ietf.org
>      > > Kopia: 'mailto:mmusic-chairs@tools.ietf.org'
>      > > mailto:mmusic-chairs@tools.ietf.org
>      > > Ämne: Re: [MMUSIC] Starting shepherd's review of
>      > > draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments
>      > >
>      > > Hi,
>      > >
>      > > ---
>      > > 3) In section 4.2.1, it says that “If the 'fmtp' attribute is not included, it
>      > indicates that no maximum character transmission rate is indicated.  It does
>      > not mean that the default value of 30 applies”; >why is this deviation from
>      > RFC 4103 chosen? Does it introduce a risk for interoperability problems with
>      > systems that also doesn’t use fmtp but interprets it as maximum 30 cps?
>      > > Gunnar?
>      > > [GH] I don't know why this deviation was chosen. But I have not
>      > commented it. You are right that it may introduce an increased risk for
>      > interoperability problems. But RFC 4103 has a precaution. In chapter 6, where
>      > the cps is introduced, it is said:
>      > > "
>      > >     receivers of text/t140 MUST be designed so they can handle temporary
>      > >     reception of characters at a higher rate than this parameter
>      > >     specifies.  As a result malfunction due to buffer overflow is avoided
>      > >     for text conversation with human input."
>      > >
>      > > (the reason for this note is for backward compatibility with RFC 2793,
>      > > the obsoleted predecessor of RFC 4103, so it is not exactly our case, but still
>      > valid.) We have discussed the risk that implementations may not implement
>      > setting or reading the dcsa attributes because of the complexity to do so
>      > alongside with the WebRTC API. That situation may cause a situation where a
>      > sent cps parameter is not obeyed. So the case is quite similar to the case in
>      > RFC 4103, and applications would be required to prepare for handling
>      > temporary reception at high rates.
>      > > The intention of T.140 is to handle real-time text conversation between
>      > humans. Huge cut and paste chunks of text cannot be required to be
>      > handled rapidly. The highest speed human interaction would be with speech-
>      > to-text applications. A very rapid speaker may produce 200 words per
>      > minute. That is 17 characters per second. The speech-to-text applications
>      > often makes corrections by long backspaces and resendings. That may add 10
>      > characters per second in the total. That results in a practical need of up to 27
>      > characters per second for one stream.
>      > > This calculation shows that for two-party calls, it would not hurt to use the
>      > same convention regarding cps default as RFC 4103 (30).
>      > > For centralized conference solutions with just one data channel from the
>      > conference server discussed in section 5.5, the need would be a multiple of
>      > that rate (27) corresponding to the number of simultaneous text senders. In
>      > well managed conferences this multiple is very close to one.
>      > > The figures above are extremes. Currently most use of RTT is typing at
>      > maximum speeds of about 7 characters per second.
>      > > Leaving the default to unrestricted might attract some misuse by
>      > implementations or users trying to use the T.140 data channel for data
>      > transmission of data totally different from the intended real-time text.
>      > > Conclusion after all this discussion:
>      > > Neither leaving the default to unlimited, nor changing to a default of 30 cps
>      > as in RFC 4103 seems very critical. Any solution will do.
>      > >
>      > > [Christer] I am pretty sure IESG would ask about this too, I suggest that we
>      > change the default to 30 cps.
>      > >
>      > > ---
>      > > ​5) In section 5.5, in the note, it says ‘…with limitations in real-time
>      > performance and presentation style’; I think it would be helpful to briefly
>      > elaborate on what type of limitations would be >expected and why.
>      > > I think it is explained in the other text of the section. For example, using a
>      > single data channel without any protocol extensions would not allow to
>      > separate the sources etc.
>      > > [GH] I think we can offer a bit more text at the end of the note to clarify.
>      > How about this:
>      > > "T.140 shows two examples of presentation layout for real-time text, one
>      > being column oriented, with one column per participant, another being
>      > arranged in one column with labels identifying the beginning of text from
>      > each participant and text from a number of participants received and placed
>      > in places corresponding to these different participants. With a conference
>      > mixer using one text stream and not applying any presentation protocol
>      > extension would only be able to produce a string for presentation in one
>      > column, including a source label in the beginning of text from one participant
>      > and only show text in real time from one participant at a time, shifting real-
>      > time presented participant at suitable points in the text stream. (end of
>      > phrase, end of sentence, line separator, long delay etc.). This presentation
>      > style may not be preferred by the user and it may cause delay before
>      > presentation of text from other than the currently presenting participant."
>      > > Pew, maybe too long and detailed....
>      > >
>      > > [Christer] Or, could we simply remove the last sentence ("Conference
>      > mixers that...")? The 1st paragraph already says why separate channels are
>      > needed, and the note says that future extensions may allow usage of a single
>      > channel, so I think it is pretty clear that using a single channel without any
>      > such extensions would come with limitations.
>      > >
>      > > ---
>      > >
>      > > 6) In section 6, bullet “If the gateway detects or suspects loss of data on the
>      > RTP stream…”; shouldn’t it await possible redundancy first and missing text
>      > marker is inserted only when the used >redundancy is not capable to repair
>      > the loss?
>      > > Gunnar?
>      > > [GH]The intention was that it would mean "after using possibly received
>      > redundant data".   You could interpret "loss of data" to mean that (instead of
>      > "loss of packets"), but let me try an improvement: "If the gateway detects or
>      > suspects loss of data on the RTP stream, after use of possibly received
>      > redundant data, …"
>      > >
>      > > [Christer] What about?
>      > >
>      > >
>      > > "If the gateway detects or suspects loss of data on the RTP stream, and the
>      > lost data has not been retrieved using a redundancy mechanism, the
>      > gateway SHOULD insert the T.140 missing text marker [T140ad1] in the data
>      > sent on the outgoing T.140 data channel."
>      > > ---
>      > >
>      > > 12) In section 11.1, in the [T140ad1] reference, is “aEUR” really part of the
>      > name? The name I find listed on the ITU-T web is “ITU-T T.140 (1998) Add. 1
>      > (02/2000)”, and the title in the document >itself seems to be “Protocol for
>      > multimedia application text conversation; Addendum 1”.
>      > > Interesting. There is no "aEUR" in the XML file, so this seems to be
>      > something created by XML2RFC.
>      > >
>      > > The intended title is:
>      > >
>      > >     Recommendation ITU-T.140 – Addendum 1  (02/2000), "Protocol for
>      > multimedia application text conversation"
>      > >
>      > > I will fix it.
>      > > [GH] I chased a number of such occurrences earlier. I think it was because
>      > your editor inserted an unusual slanting quotation mark. Note that there is
>      > also a double quotation mark on the third line of the same reference.
>      > >
>      > > [Christer] I will double check.
>      > >
>      > > ---
>      > >
>      > > Regards,
>      > >
>      > > Christer
>      > >
>      > >
>      > --
>      >
>      > + + + + + + + + + + + + + +
>      >
>      > Gunnar Hellström
>      > Omnitor
>      > gunnar.hellstrom@omnitor.se
>      > +46 708 204 288
>
>
>
--

+ + + + + + + + + + + + + +

Gunnar Hellström
Omnitor
gunnar.hellstrom@omnitor.se
+46 708 204 288