RE: [Megaco] Local/Remote descriptors and Permanent terminations
"David Barr"<david.barr@nortelnetworks.com> Wed, 03 April 2002 14:19 UTC
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From: David Barr <david.barr@nortelnetworks.com>
To: 'Carl Rutter' <crutter@telica.com>, 'Pauls Markus' <Markus.Pauls@icn.siemens.de>, "'megaco@ietf.org'" <megaco@ietf.org>
Subject: RE: [Megaco] Local/Remote descriptors and Permanent terminations
Date: Wed, 03 Apr 2002 14:52:25 +0100
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In making a decision please consider the following: With silence suppression, there are actually 2 separate things we need to achieve: (A) To have a way for the MGC to "hint" to the MG that it wants silence suppression to be used or not. (B) To have a way for the two MGs to negotiate whether silence suppression should be used or not. If one of the MGs cannot support silence suppression, then the peer-MG must not send silence-packets, regardless of what the "hint" from the MGC was. For (B), the SDP exchange between MGs is used to negotiate silence suppression capability. For G.711, payload-type 13 on the media line of the returned Local descriptor is typically used to indicate a MG's ability to do silence suppression. Now, whatever method is chosen for (A) should not conflict with what is currently done for (B), especially if the underspecified Local descriptor from MGC to MG is used to convey the "hint" from the MGC. Dave. -----Original Message----- From: Carl Rutter [mailto:crutter@telica.com] Sent: Wednesday, April 03, 2002 1:53 PM To: Carl Rutter; 'Pauls Markus'; 'megaco@ietf.org' Subject: RE: [Megaco] Local/Remote descriptors and Permanent terminations One more comment, sorry for so many. Would be really need to specify the 13 if we had the SilSup parameter? Carl -----Original Message----- From: Carl Rutter Sent: Wednesday, April 03, 2002 7:52 AM To: 'Pauls Markus'; megaco@ietf.org Cc: Carl Rutter Subject: RE: [Megaco] Local/Remote descriptors and Permanent terminations Yea, for overspecification I see your point. m=audio 4444 RTP/AVP 0 18 13 a=fmtp:18 annexb=no a=fmtp:0 silSup=yes makes sense, but still seems kind of awkward in that we have different ways of implementing Silent Suppression based on the payload. It would be nice to have a common parameter among the payloads that had more than just an ON/OFF option to provide future flexibility like they thought of in RFC3018: silenceSupp: <silenceSuppEnable> <silenceTimer> <suppPref> <sidUse> <fxnslevel> So from the discussions I've read, Silent Suppression should: 1) Be implemented in SDP 2) Enabled/Disabled on a per payload type 3) Should have more than just and On/Off option 4) Be backward compatable to allow support for the Annex option with the compressed vocoders 5) Be consistant among Payload types I guess if we gave up on #3 and #5 we could implement Pauls suggestion. Not sure the logistics of how thats done?? Are we getting close? Carl -----Original Message----- From: Pauls Markus [mailto:Markus.Pauls@icn.siemens.de] Sent: Wednesday, April 03, 2002 2:49 AM To: megaco@ietf.org Cc: 'Carl Rutter' Subject: RE: [Megaco] Local/Remote descriptors and Permanent terminations Suppose you have the following SDP: m=audio 4444 RTP/AVP 0 18 a=fmtp:18 annexb=no // G.729, Silence Suppression off (see draft-ietf-avt-rtp-mime-05) a=silenceSupp: on - - - - (that means the GW may either use G.711 µ-law or G.729) The silenceSupp attribute is not specific for a payload type, the fmtp attribute is. So which one has precedence in this case? In my opinion you should have the ability to switch on silence suppression depending on the payload type. If you want to use it with G.711, it does not mean that you want it with G.729. Beyond that I believe generally it is more suited to an ephemeral termination. Therefore it should be expressed by means of SDP. However, if you want to transport the comfort noise payload (according to draft-ietf-avt-rtp-cn-05), you should add the payload type 13 to the SDP media line as well (IMO). From my point of view the SDP should therefore look something like this: m=audio 4444 RTP/AVP 0 18 13 a=fmtp:18 annexb=no a=fmtp:0 silSup=yes where this PCMU specific parameter silSup must still be defined (for PCMA as well). Any comment is appreciated. Kind regards Markus Pauls ________________________________________________________ Markus Pauls SIEMENS Information and Communication Networks ICN WN CC NA B13 Tel.: +49 89 722 62937 Hofmannstr. 51 Fax: +49 89 722 44176 81359 Munich Email: markus.pauls@icn.siemens.de Germany -----Original Message----- From: Carl Rutter [mailto:crutter@telica.com] Sent: Wednesday, April 03, 2002 3:36 AM To: Chuong N. Nguyen Cc: megaco@ietf.org Subject: RE: [Megaco] Local/Remote descriptors and Permanent terminations You bring up a good point, Is/Should Silient Suppression be tied to the TDM package or SDP TDM, if in fact its really more applicable to the Ephemral side. If no can think of a good reason then your right it would make more sense to be in the SDP. For now we could use 0 13 for G711 and long-term use the ATM approach for SDP. Trying to drive towards closure as we have a need to implement this. Yea, the hairpinning would be in the MG Switch. Comments? Carl -----Original Message----- From: megaco-admin@ietf.org [mailto:megaco-admin@ietf.org]On Behalf Of Chuong N. Nguyen Sent: Tuesday, April 02, 2002 8:05 PM Cc: megaco@ietf.org Subject: Re: [Megaco] Local/Remote descriptors and Permanent terminations That is what I initially thought silence suppression was about. But then I was told differently. It could be applied to TDM. If not, then why are we discussing adding silence suppresion to the TDM package? By the way, I thought TDM-TDM calls are being made at the Gwy too. Aren't you guys doing that now? Carl Rutter wrote: I can't think of an application where you'd want to do that. Silence suppression really wouldn't make sense for a TDM-TDMwhich is hairpined at the CO. The DS0 is dedicated. The advantage of Silent suppression it to limit the RTP traffic on the IP side, which you wouldn't have in that case.Maybe if you wanted to inject Comfort Noise instead of backgroundnoice in the TDM-TDM call??Carl -----Original Message----- From: megaco-admin@ietf.org [mailto:megaco-admin@ietf.org]On Behalf Of Chuong N. Nguyen Sent: Tuesday, April 02, 2002 7:16 PM To: megaco@ietf.org Subject: Re: [Megaco] Local/Remote descriptors and Permanent terminations Tom-PT Taylor wrote: I've had a message pointing out the existence of draft-ietf-avt-rtp-cn-05.txt. Specifying this payload type as well as G.711 would indicate the use of silence suppression implicitly. That covers RTP transport. For ATM we have the a=silenceSupp attribute defined in RFC 3108. Do we need anything for TDM? What if someone wanted to make a TDM-TDM, hairpin call? Would silenceSupp be used for such a call? If yes, then what? -- Alcatel USA, Inc Internet: Chuong.Nguyen@usa.alcatel.com 1000 Coit Road Plano, Texas 75075 Phone: (972) 519-4613 **** The opinions expressed are not those of Alcatel USA, Inc **** -- Alcatel USA, Inc Internet: Chuong.Nguyen@usa.alcatel.com 1000 Coit Road Plano, Texas 75075 Phone: (972) 519-4613 **** The opinions expressed are not those of Alcatel USA, Inc **** _______________________________________________ Megaco mailing list Megaco@ietf.org https://www1.ietf.org/mailman/listinfo/megaco
- [Megaco] Local/Remote descriptors and Permanent t… Rajesh N
- RE: [Megaco] Local/Remote descriptors and Permane… Tom-PT Taylor
- RE: [Megaco] Local/Remote descriptors and Permane… Madhu Babu Brahmanapally
- Re: [Megaco] Local/Remote descriptors and Permane… Chuong N. Nguyen
- RE: [Megaco] Local/Remote descriptors and Permane… Tom-PT Taylor
- Re: [Megaco] Local/Remote descriptors and Permane… Chuong N. Nguyen
- RE: [Megaco] Local/Remote descriptors and Permane… Carl Rutter
- Re: [Megaco] Local/Remote descriptors and Permane… Chuong N. Nguyen
- RE: [Megaco] Local/Remote descriptors and Permane… Carl Rutter
- Re: [Megaco] Local/Remote descriptors and Permane… Chuong N. Nguyen
- RE: [Megaco] Local/Remote descriptors and Permane… Tom-PT Taylor
- RE: [Megaco] Local/Remote descriptors and Permane… Carl Rutter
- Re: [Megaco] Local/Remote descriptors and Permane… Chuong N. Nguyen
- RE: [Megaco] Local/Remote descriptors and Permane… Carl Rutter
- Re: [Megaco] Local/Remote descriptors and Permane… Chuong N. Nguyen
- RE: [Megaco] Local/Remote descriptors and Permane… Carl Rutter
- RE: [Megaco] Local/Remote descriptors and Permane… Carl Rutter
- Re: [Megaco] Local/Remote descriptors and Permane… Chuong N. Nguyen
- RE: [Megaco] Local/Remote descriptors and Permane… Pauls Markus
- RE: [Megaco] Local/Remote descriptors and Permane… Carl Rutter
- RE: [Megaco] Local/Remote descriptors and Permane… Carl Rutter
- RE: [Megaco] Local/Remote descriptors and Permane… Tom-PT Taylor
- RE: [Megaco] Local/Remote descriptors and Permane… David Barr
- Re: [Megaco] Local/Remote descriptors and Permane… Terry L Anderson