SV: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03
"Gunnar Hellstrom" <gunnar.hellstrom@omnitor.se> Sat, 24 June 2006 23:02 UTC
Received: from [127.0.0.1] (helo=stiedprmman1.va.neustar.com) by megatron.ietf.org with esmtp (Exim 4.43) id 1FuH9L-0004Gg-5Y; Sat, 24 Jun 2006 19:02:47 -0400
Received: from [10.91.34.44] (helo=ietf-mx.ietf.org) by megatron.ietf.org with esmtp (Exim 4.43) id 1FuH9K-0004Gb-8q for mmusic@ietf.org; Sat, 24 Jun 2006 19:02:46 -0400
Received: from pne-smtpout1-sn2.hy.skanova.net ([81.228.8.83]) by ietf-mx.ietf.org with esmtp (Exim 4.43) id 1FuH9I-0005hc-7b for mmusic@ietf.org; Sat, 24 Jun 2006 19:02:46 -0400
Received: from my (213.64.228.153) by pne-smtpout1-sn2.hy.skanova.net (7.2.072.1) id 449A7EFE00065EBC; Sun, 25 Jun 2006 01:02:39 +0200
From: Gunnar Hellstrom <gunnar.hellstrom@omnitor.se>
To: Colin Perkins <csp@csperkins.org>, Cullen Jennings <fluffy@cisco.com>, arnoud@annies.nl
Subject: SV: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03
Date: Sun, 25 Jun 2006 01:00:44 +0200
Message-ID: <NEEHLBJFCFOHFBNEOLMJAEKMCCAA.gunnar.hellstrom@omnitor.se>
MIME-Version: 1.0
Content-Type: text/plain; charset="Windows-1252"
X-Priority: 3 (Normal)
X-MSMail-Priority: Normal
X-Mailer: Microsoft Outlook IMO, Build 9.0.6604 (9.0.2911.0)
In-reply-to: <AE07A18A-F9DE-4961-A9ED-FDDB37CB43B2@cisco.com>
Importance: Normal
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165
Content-Transfer-Encoding: quoted-printable
X-Spam-Score: 0.0 (/)
X-Scan-Signature: 8353da2fde044920180672209f5bf8a0
Cc: IETF MMUSIC WG <mmusic@ietf.org>, Gonzalo Camarillo <Gonzalo.Camarillo@ericsson.com>, degodefroi@gmail.com
X-BeenThere: mmusic@ietf.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Multiparty Multimedia Session Control Working Group <mmusic.ietf.org>
List-Unsubscribe: <https://www1.ietf.org/mailman/listinfo/mmusic>, <mailto:mmusic-request@ietf.org?subject=unsubscribe>
List-Post: <mailto:mmusic@ietf.org>
List-Help: <mailto:mmusic-request@ietf.org?subject=help>
List-Subscribe: <https://www1.ietf.org/mailman/listinfo/mmusic>, <mailto:mmusic-request@ietf.org?subject=subscribe>
Errors-To: mmusic-bounces@ietf.org
Hi, You want a more stringent text for the "txp" parameter. The current one in -03 is: ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ txp: This indicates that the media stream is originated from a textphone, and it requires special behavior from the receiving application. A typical use case for this is a connection where one endpoint is an analog textphone of a kind that cannot handle two-way simultaneous text communication, and the other one is a native IP based real time text capable terminal. The human users normally need to apply formal turn-taking habits, and need to figure out to what extent it is possible to interrupt the other party if the need arises. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ I looked back into the earlier discussion. I had a proposed line about that the application should give an indication to the user. That was deleted with the motivation that application actions should not be documented in this draft. However, I see no other use of the "txp" parameter ( and also the "user-floor" parameter ) than to convey it clearly to the user because it requires different behaviour from the user. So, I suggest to modify the wording to clearly indicate that "txp" is only sent from a party knowing that its real-time text presentation capability is limited. And I suggest to enter a few words of the intended usage of the parameter. This is new text proposal: ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ txp: This indicates that the media stream is originated from a textphone that is incapable of handling simultaneous two-way communication. This limitation requires special behavior from the user of a terminal receiving the indication. The indication should be used for an indication in the user interface. A typical use case is a connection where one endpoint is an analog textphone of a kind that cannot handle two-way simultaneous text communication, and the other one is a native IP based real time text capable terminal. The human user need to change behaviour when this indication is received, and apply formal turn-taking habits. They may also need to figure out to what extent it is possible to interrupt the other party if the need arises. +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ The earlier discussion indicated that there are too many variations in capability to handle simultaneity and two-way communication in legacy textphones for it to be realistic to give detailed info with txp subparameters. So, I prefer to just indicate "txp" for all. I would appreciate very much to get comments on the procedures described below in proposed V.151 Annex D2 as well. Regards Gunnar -----Ursprungligt meddelande----- Från: Cullen Jennings [mailto:fluffy@cisco.com] Skickat: den 24 juni 2006 21:56 Till: Colin Perkins Kopia: Gunnar Hellstrom; Jani Hautakorpi (JO/LMF); IETF MMUSIC WG; degodefroi@gmail.com; Gonzalo Camarillo Ämne: Re: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 Ok, I just entered proper comments in tracker, bit more inline here. On Jun 20, 2006, at 3:29 PM, Colin Perkins wrote: > Hi, > > Just following up on this... did we ever get agreement on the right > way to proceed? If an updated draft is needed, I'd like to get it > in before the deadline. Cullen? Jani? > > Colin > > > > > On 18 May 2006, at 22:25, Gunnar Hellstrom wrote: >> Hi, >> I agree that the content parameters "txp" and "user-floor" >> indicate similar functionality. >> >> But I see nothing wrong in having them both in the specification >> anyway. I've no problem with one, both, or three but it needs to be clear what implementers need to do. >> >> The txp parameter value may be used to invoke some automated >> mechanism in a text capable gateway to support conversion between >> full duplex simultaneous multimedia communication and half-duplex >> turn-taking, alternating text - voice communication in PSTN. But >> it can also be used just as a warning to the IP user to be aware >> of possible limitations in simultanity and duplex use of media. >> >> We could go deeper in specifying exactly what limitations are >> valid at each moment, but I doubt that any manufacturer want to >> refine their gateway designs to that degree. >> If we want to go deeper, we could use the following parameters: >> >> - voice-text-alternating ( in fact influencing two media ) >> >> - half-duplex ( when strictly only one >> direction at a time can be used ) >> >> - half-duplex-interruptable ( when only one direction at a >> time should be used for contents, but it is possible to send an >> indication that the other party want the turn. ) >> >> >> I think that txp is enough. >> >> I just participate in a discussion where we have tried to meet >> requirements to keep gateway resources low by allowing it to set >> up a real-time text connection between a PSTN gateway and an IP >> terminal only when there are indications that text will be used. >> It is a compromise that may be needed in reality. I agree this is needed - just want it to be clear. >> >> In the draft document from that discussion, we use both the >> a=content:txp parameter, and the following parmeters from RFC 3840 >> and 3841. >> >> Contact: duplex="half", >> >> Contact: <uri>;text >> >> Accept-Contact: *;text;require >> >> Accept-Contact: *;text It seems like the 3840 style stuff may be the way you want to signal this. >> >> >> I would appreciate very much to get comments on the parameter >> values and logic we have drafted. >> >> ----------------------Proposed alternative to ITU-T V.151 Annex D, >> using caller and callee capabilities and preferences and media- >> contents to control gateway - IP text capable terminal >> communication-------------------------------------------------------- >> ---------------- >> >> Alternative proposal for V.151 Annex D. >> ANNEX D2 >> >> Interworking IP Text Devices with V.151 Gateways. >> Connect text channel when usage of real-time text is likely. >> >> >> >> D.1 Introduction >> Some non-Gateway IP devices in the network not having a means of >> modulating or demodulating PSTN textphone signals, such as IVR >> systems, voicemail systems, IP phones, Multimedia telephones or >> other devices, may support the transmission of real-time text over >> IP networks and, ideally, interwork with V.151-compliant Gateways >> in order to provide a means through which users of PSTN textphone >> devices can communicate with those IP devices. This class of >> devices is referred to herein as an "IP Text Device” (ITD). This >> Annex defines the procedures that may be used in order to allow >> for such interworking between V.151 Gateways and ITDs. The main >> principle is to use RFC 4103 as the default text transport method >> between gateways and ITD:s, and open text channels only when it is >> likely that the text channel will be used. >> >> D.2 Exchanging capabilities and opening media streams >> When establishing a call, an ITD may advertise support for real- >> time text in accordance with IETF RFC 4103. >> >> In general, ITDs also transmit text characters when communicating >> with other ITDs using RFC 4103, which specifies the establishment >> of a separate RTP stream specifically for transmitting text >> characters. However, since V.151 PSTN gateway devices interleave >> audio and text data when used for Gateway - to - gateway >> operation, V.151 gateways need to support both RFC 4103 to >> interwork with ITDs and RFC 4351 for communicating with other PSTN >> gateways. >> >> As such, V.151 gateways are Recommended to indicate support for >> both transport methods initially when exchanging capability >> information. However, relatively few calls use real-time text in >> the PSTN, and therefore it may be desirable for the gateway to not >> open the text channel until either party in the call explicitly >> acts to use real-time text. >> >> According to normal procedures in IP multimedia systems, it is >> allowable to indicate capability for other transport protocols for >> real-time text as well as RFC 4103 and connect such alternatives. >> >> ---- >> >> D.2.2 SDP based systems >> Similar logic follows for SDP-based systems. >> >> In SIP-based systems, the terminal and gateway shall announce >> support for text in the Contact field according to RFC 3840, and >> may indicate preference for text according to RFC 3841. >> >> Contact: <uri>;text >> >> A calling SIP terminal who does not put priority to text may >> indicate an interest to use text by: >> >> Accept-Contact: *;text >> >> A calling SIP terminal who want to put priority to establishing a >> text connection shall indicate that by: >> >> Accept-Contact: *;text;require >> >> Most commonly, PSTN text telephones support alternating text and >> audio during the call, but not simultaneous text and audio. If the >> gateway only supports alternating text and audio during the PSTN >> text session, it may be beneficial to make the ITD user aware of >> this limitation. It is proposed to use the Duplex parameter of RFC >> 3840 for this purpose. >> >> Contact: duplex="half" >> >> There is a parameter also for use in the text media description: >> >> a=content:txp >> >> It should be used to indicate to the ITD user that the text >> channel is half duplex and turn-taking habits should be used. >> >> >> >> Note that while the use of RFC 2198 redundancy or other fault >> tolerance scheme is not shown in the abbreviated examples below, >> appropriate mechanisms should be employed to protect the >> transmission of the text stream in accordance with the text >> transport specifications. >> >> >> >> D.2.2.1 Call from PSTN >> Consider the following abbreviated example SDP that might be found >> in an offer sent by a V.151 Gateway not offering RFC 4103 support >> initially, but indicating text support and that the text support >> is alternating with audio: >> >> Contact: <uri>;text;duplex="half" >> >> m=audio 7200 RTP/AVP 0 98 >> >> a=rtpmap:98 t140c/8000 >> >> a=fmtp:98 cps=20 >> >> If the gateway at that time already knows that text will be needed >> in the call, a requirement for text shall be included, and a media >> line for text. The decision to include text when offering the call >> may be because textphone tones have already been detected on the >> PSTN line, the gateway may be configured to be a dedicated text >> gateway, or it may be known by subscription or any other external >> means that either user has preference for text. >> >> Accept-Contact: *;text;require >> >> Contact: <uri>;text;duplex="half" >> >> m=audio 7200 RTP/AVP 0 98 >> >> a=rtpmap:98 t140c/8000 >> >> a=fmtp:98 cps=20 >> >> m=text 7202 RTP/AVP 99 >> >> a=rtpmap:99 t140/1000 >> >> a=content:txp >> >> >> >> If the answering device is an ITD, with no specific indication >> that text would be used, it would accept only the G.711 audio. >> >> Contact: <uri>;text >> >> m=audio 7200 RTP/AVP 0 >> >> >> >> If the answering device is an ITD where the user has indicated a >> preference for text, it would accept the text/t140 medium and >> optionally G.711 audio. >> >> Contact: <uri>;text >> >> m=audio 7200 RTP/AVP 0 >> >> m=text 7202 RTP/AVP 99 >> >> a=rtpmap:99 t140/1000 >> >> Note that this response is only possible when the gateway had >> included text/140 in the offer. For other cases, the terminal >> needs to do a reinvite to add text to the call. >> >> D.2.2.2 Call from IP terminal >> A calling ITD could give a strong indication that it requires text >> support in the call by an INVITE according to this example: >> >> Contact: <sip:terminal@host.example.com>;text >> >> Accept-Contact: *;text;require >> >> m=audio 7200 RTP/AVP 0 >> >> m=text 7202 RTP/AVP 99 >> >> a=rtpmap:99 t140/1000 >> >> >> >> The network would make efforts to connect to a text capable >> gateway, that may acknowledge the text channel initially, because >> of the indication that text is required. The gateway should also >> start text channel connection procedures on the PSTN side. >> >> Contact: <gwy-uri>;text;duplex="half" >> >> m=audio 7200 RTP/AVP 0 >> >> m=text 7202 RTP/AVP 99 >> >> a=rtpmap:99 t140/1000 >> >> a=fmtp:99 cps=20 >> >> a=content:txp >> >> >> >> If on the other hand, the ITD user is not depending on text, but >> want to have it available for occasional use, the ITD can be >> configured to make its INVITE as follows: >> >> >> >> Contact: <sip:terminal@host.example.com>;text >> >> Accept-Contact: *;text >> >> m=audio 7200 RTP/AVP 0 >> >> m=text 7202 RTP/AVP 99 >> >> a=rtpmap:99 t140/1000 >> >> a=fmtp:99 >> >> >> >> The network would try to connect to a text capable gateway, but >> may connect through a non capable. The gateway may decide to not >> acknowledge the text channel initially, but indicates its text >> capability in the Contact header. >> >> Contact: <gwy-uri>;text;duplex="half" >> >> m=audio 7200 RTP/AVP 0 >> >> >> >> D.2.2.3 Text channel establishment during a call >> If at a later stage in the call, either party in the call starts >> text activity, and no text channel was set up initially, a text >> channel should be added to the session by a REINVITE. . >> >> This is an example of how it would be expressed from the gateway, >> >> Contact: <uri>;text;duplex="half" >> >> m=audio 7200 RTP/AVP 0 >> >> m=text 7202 RTP/AVP 99 >> >> a=rtpmap:99 t140/1000 >> >> a=fmtp:99 cps=20 >> >> a=content:txp >> >> The other party should answer with a similar sdp. >> >> >> >> If instead it is the ITD user who starts text activity, a text >> channel should be added to the session by a REINVITE from the ITD >> according to the following example. . >> >> Contact: <uri>;text >> >> m=audio 7200 RTP/AVP 0 >> >> m=text 7202 RTP/AVP 99 >> >> a=rtpmap:99 t140/1000 >> >> a=fmtp:99 cps=20 >> >> >> >> The gateway should answer with >> >> Contact: <uri>;text;duplex="half" >> >> m=audio 7200 RTP/AVP 0 >> >> m=text 7202 RTP/AVP 99 >> >> a=rtpmap:99 t140/1000 >> >> a=fmtp:99 cps=20 >> >> a=content:txp >> >> . >> >> The line "a=content:txp" is sent from the gateway as an indication >> that half duplex procedures should be applied by the users in the >> text stream. >> >> D.3 Procedure for terminals including both RFC 4103 and RFC 4351 >> support >> In the case when a terminal implements both RFC 4103 and RFC 4351 >> for text transport, the following procedures should be applied in >> the terminal. >> >> When establishing a call, an ITD may advertise support for ToIP in >> accordance with Annex B or Annex C, with one notable important >> exception: the ITD shall not include a list of supported >> modulations. Absence of the list of modulations shall be used as >> an indicator to the V.151 Gateway that the remote side is an ITD. >> >> Further, ITD devices shall not utilize SSEs in order to control >> state transition to ToIP. Rather, once a media flow is >> established to transport T.140 characters, either the Gateway or >> the ITD may transmit text immediately and without further >> negotiation. Payload type switching is used to transition between >> AUDIO and Text Relay modes. >> >> D.4 State transition and text handling >> The following description assumes that a V.151-compliant Gateway >> is in communication with an ITD and media flows have been >> established to transport text over IP in accordance with RFC 4103. >> >> When the gateway compliant to this annex detects a PSTN textphone >> that it supports using text relay, it shall autonomously connect >> to the textphone. After connection on the PSTN side, the gateway >> shall open the text channel to the ITD. It shall decode the >> characters received and transmit those to the ITD, giving proper >> respect to the maximum character-per-second (CPS) parameter >> advertised by the ITD. Determining the type of PSTN textphone >> device in use is the responsibility of the Gateway and the ITD >> need not concern itself with what kind of PSTN textphone device is >> connected to the Gateway. >> >> Likewise, when the ITD first has characters to send to the Gateway >> using text/140 payload type, the ITD opens the text channel if it >> was not opened before. Then the ITD transmits the characters to >> the Gateway. The Gateway shall perform a probing, as necessary, to >> determine the type of PSTN device connected, if any. While >> probing, the Gateway shall buffer any characters received and >> transmit those when probing completes and the gateway is connected >> to the text phone. The size of the character buffer is a matter >> of implementation, but should support the reception and buffering >> of characters for at least 60 seconds at the specified maximum >> character-per-second (CPS) value signaled to the ITD. >> >> If the Gateway does not support the modulation used by the PSTN >> textphone device, the Gateway may transmit the received textphone >> signals via VBD or the audio stream, depending on the capabilities >> of the ITD. Further, the Gateway may simply discard characters >> received from the ITD or transmit them to the PSTN textphone >> device using a pre-provisioned modulation. >> >> >> / >> >> Gunnar >> --------------------------------------------------------------------- >> -------- >> Gunnar Hellström, Omnitor >> gunnar.hellstrom@omnitor.se <mailto:gunnar.hellstrom@omnitor.se> >> Mob: +46 708 204 288 >> Phone: +46 8 556 002 03 >> www.omnitor.se <http://www.omnitor.se> >> >> >> -----Original Message----- >> From: Jani Hautakorpi (JO/LMF) [mailto:jani.hautakorpi@ericsson.com] >> Sent: Wednesday, May 17, 2006 10:12 AM >> To: Cullen Jennings >> Cc: gunnar.hellstrom@omnitor.se; degodefroi@gmail.com; Gonzalo >> Camarillo; IETF MMUSIC WG >> Subject: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 >> >> >> Hi Cullen, >> >> Cullen Jennings wrote: >> > I was just reviewing this document and I can't figure out the >> > difference from user-floor and txp from the point of view >> describing >> > the content. >> >> Actually, there are no major differences between them, but Gunnar >> Hellstrom and Arnoud van Wijk (in the cc:) really wanted a value that >> was "txp". Gunnar and Arnoud can explain this better, but the main >> reason is that this way they can refer to and further describe the >> usage >> of "txp" from some other draft, e.g. ietf-draft-sipping-toip. >> >> > It seems like this might be better to indicate that the >> > content type was "simplex" as normal media is assumed to be >> "duplex". >> >> This is a matter of naming. Personally I believe that "user-floor" is >> more descriptive than "simplex", because there can also be such >> one-way >> media that doesn't require user level floor control. What do you >> think? >> >> > I'm not sure I like what I am proposing here but I think we need to >> > improve on the definition for these two. The current description >> of txt >> > does not seem to match the requirements for it on the email >> list and >> > the definition of user-floor I have no idea when to add to a >> stream. >> >> I would say that "txp" is exactly what was described on the mmusic's >> mailing list, please see the "[MMUSIC] I-D ACTION: >> draft-ietf-mmusic-sdp-media-content-01.txt" thread, starting 18th >> Feb. >> >> Regarding the addition of "user-floor" to media stream: The device >> that >> needs to add this value knows it by itself. For example, a new >> walkie-talkie type of device can know that it requires user level >> floor >> control. But of course we can try to elaborate this on the draft, >> if you >> want. >> >> > It also might be nice to provide more guidance on what is >> appropriate >> > to signal with "content" and what is not. For example, I would >> not want >> > people signaling the mpeg profile using this. I think what we >> want to >> > do here is something like signal the "semantic content" of the >> stream >> > such that an application that is offered multiple streams can >> pick the >> > right stream or map the streams to the users preferences. Would >> it be >> > possible to add more text about what would not be appropriate >> to use >> > this registry for. >> >> I really can't see how somebody could try to signal the mpeg profile >> with this draft, because it just doesn't have enough features for >> signaling such information. I feel that the possible use scenarios >> are >> already quite limited, and it's hard for me to invent how anybody >> could >> misuse this draft. But, if you (or somebody else) can come up with >> some >> valid, non-appropriate use cases, I'm happy to add them to the draft. >> >> >> -- >> Jani >> >> _______________________________________________ >> mmusic mailing list >> mmusic@ietf.org >> https://www1.ietf.org/mailman/listinfo/mmusic >> >> >> _______________________________________________ >> mmusic mailing list >> mmusic@ietf.org >> https://www1.ietf.org/mailman/listinfo/mmusic _______________________________________________ mmusic mailing list mmusic@ietf.org https://www1.ietf.org/mailman/listinfo/mmusic
- [MMUSIC] hautokorpi-mmusic-sdp-media-content-01 Cullen Jennings
- [MMUSIC] hautokorpi-mmusic-sdp-media-content-01 Marc Manthey
- Re: [MMUSIC] hautokorpi-mmusic-sdp-media-content-… Jani Hautakorpi (JO/LMF)
- [MMUSIC] ietf-mmusic-sdp-media-content-03 Cullen Jennings
- [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 Jani Hautakorpi (JO/LMF)
- RE: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 Gunnar Hellstrom
- Re: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 Colin Perkins
- Re: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 Cullen Jennings
- SV: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 Gunnar Hellstrom
- RE: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 Arnoud van Wijk
- Re: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 Cullen Jennings
- SV: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 Gunnar Hellstrom
- SV: [MMUSIC] Re: ietf-mmusic-sdp-media-content-03 Gunnar Hellstrom