Re: TDMPW and MeGaCo/SDP

Hello Javi and Albrecht,

I think its safe to say that there's really no normative (or informative 
description for that matter) of how TDMoIP (as defined by Y.1453) can be 
described by SDP. Given that TDMoIP is essentially a new payload format 
then an approach as suggested by Javi of the dynamic payload is probably 
the way to go. However as Albrecht points out there are other parameters 
that either need to be provisioned or signalled. Some of these are 
probably available in RFC3108 i.e. the SBC parameter for nx64. Other 
parameters are defined in H.248.1 Annex C. These would be available in 
SDP using H.248.15 "SDP H.248 package attribute".

Regards, Christian


On 2/02/2011 3:50 AM, Javi wrote:
> El 01/02/2011 15:11, Schwarz, Albrecht (Albrecht) escribió:
>> /To H.248 Media Descriptor for IP bearer:/
>>
>>    *
>>       /your proposal would be insufficient, Y.1453 defines not a
>>       single, but multiple possible modes of TDMoIP interworking! /
>>    *
>>       /See § 7.2/Y.1453 concerning information elements for TDMoIP
>>       control (=> ´correspondent SDP must be defined if the Y.1453
>>       provisioning approach would be replaced by an SDP-based
>>       signalling approach (for TDMoIP IWFs embedded in H.248 MGs or
>>       SIP VoiceGateways)./
>>
>
> I agree. could you propose an possible example of SDP descriptions for 
> TDMPWs?
>
>> /
>> /To H.248 Media Descriptor for TDM bearer:/
>>
>>    *
>>       /the MUX approach is just an option!/
>>    *
>>       /alternatives, e.g., the "the group-and-member scheme (addrtype
>>       is "GRP")" as proposed by Tom in his SDP-TDM draft
>>       (http://www.watersprings.org/pub/id/draft-taylor-mmusic-sdp-tdm-01.txt)/
>>
>> /
>
> Is GRP suitable for MeGaCo?:
>
>     The NUL scheme is suitable for use with media gateway control, since
>     other means are available (as mentioned above) for designating the
>     TDM circuit.
> If NUL is useful for MeGaCo, I assumed GRP is for SIP only.
>
> Version "01" removed Nx64 services:
>
> 1.4 Changes From The Previous Version
> The main change from the previous version has been to limit the
> scope of the present document by placing greater reliance on the
> Megaco/H.248 multiplex concept. This has meant the removal of wideband
> or aggregated N x 64 kbit/s service from the scope of thedocument
>
>>
>>     ------------------------------------------------------------------------
>>     *From:* Javi Muñoz [mailto:[email protected]]
>>     *Sent:* Dienstag, 1. Februar 2011 14:07
>>     *To:* [email protected]
>>     *Subject:* Re: [Megaco] TDMPW and MeGaCo/SDP
>>
>>     H.248 MUX termination (N x B channels) is a good choice at ISDN
>>     termination.
>>
>>     But, at IP side, we still need to describe TDMoIP in SDP. For
>>     instance, we may propose any like this:
>>
>>     m=audio <puerto> RTP/AVP <PT_dinámico>
>>     a=rtpmap:<PT_dinámico> TDMoIP/8000
>>
>>
>>
>>
>>
>>     El 31/01/2011 16:54, Schwarz, Albrecht (Albrecht) escribió:
>>>     /Just some high-level indications:/
>>>     //
>>>     /Multirate means effectively N-out-of-K (with K = 24 or 30
>>>     dependent on ANSI /ETSI markets; and 1 < N <= K)./
>>>     /That's a first requirement./
>>>     /Secondly, the selection of channels may be random, they must
>>>     not be in consecutive order (e.g., think about the permutations
>>>     for N = 5)./
>>>     /Thirdly, there could be a dependency of the choosen CESoIP
>>>     emulation service to the H.248 connection model./
>>>     //
>>>     /Possible solution: H.248 MUX termination ... at the high-level .../
>>>     //
>>>
>>>         ------------------------------------------------------------------------
>>>         *From:* Javi [mailto:[email protected]]
>>>         *Sent:* Montag, 31. Januar 2011 11:47
>>>         *To:* [email protected]
>>>         *Subject:* Re: [Megaco] TDMPW and MeGaCo/SDP
>>>
>>>         I agree, TDMoIP is an option only.
>>>
>>>         But, if it is used, MGC would use SDP at Local/Remote MeGaCo
>>>         descriptors. How may be that SDP description for TDMoIP?
>>>
>>>>         However, there was never any H.248 Profile standardized
>>>>         with /*multirate*/ support, at least to my knowledge.
>>>>         (I'm aware of vendor specific profile, but that are
>>>>         proprietary solutions.)
>>>>
>>>
>>>         I would be interested to know any of that proprietary
>>>         solutions. May you indicate me any?
>>>
>>>>
>>>>         __
>>>>         /*Y.2262 PSTN/ISDN emulation and simulation, Appendix IV
>>>>         Examples of emulation of PSTN and N-ISDN bearer services
>>>>         *(This appendix does not form an integral part of this
>>>>         Recommendation)
>>>>
>>>>         Examples for the emulation of PSTN and N-ISDN bearer
>>>>         services are provided:
>>>>
>>>>         1) Monorate bearer services (= 1 × 64-kbit/s digital bearer
>>>>         in PSTN/ISDN)
>>>>         • ITU-T Recommendations I.231.2 and I.231.3 may be emulated
>>>>         by a single RTP
>>>>         session, with or without RTP control protocol (RTCP), using
>>>>         an RTP profile according
>>>>         to IETF RFC 3551.
>>>>         • ITU-T Recommendation I.231.1 may be emulated by a single
>>>>         RTP session, with or
>>>>         without RTCP, using RTP clearmode according to IETF RFC 4040.
>>>>
>>>>         2) Multirate bearer services (= N × 64-kbit/s digital
>>>>         bearer in PSTN/ISDN; N greater than one)
>>>>         • ITU-T Recommendations I.231.4 to I.231.10 may be emulated
>>>>         by TDMoIP described
>>>>         in ITU-T Recommendation Y.1453.
>>>>
>>>>         /
>>>>         > -----Original Message-----
>>>>         > From: [email protected]
>>>>         > [mailto:[email protected]] On Behalf Of Javi
>>>>         > Sent: Samstag, 29. Januar 2011 02:13
>>>>         > To: [email protected]
>>>>         > Subject: [Megaco] TDMPW and MeGaCo/SDP
>>>>         >
>>>>         > Assuming the next situation:
>>>>         >
>>>>         > ISDN Terminal 1 - MG1 - [IP network] - MG2 - ISDN Terminal 2
>>>>         >
>>>>         > where the MGs (Media Gateway) are controlled by a MGC
>>>>         (Media Gateway
>>>>         > Controller) via MeGaCo[H.248.1].
>>>>         >
>>>>         > [ITU-T Y.2262 / Annex IV] proposses that MGs may transport
>>>>         > ISDN B-channels over the IP network:
>>>>         >
>>>>         > + By a single RTP session (when monochannels ISDN services)
>>>>         >
>>>>         > + Or by TDMoIP (= UDP TDMPWs), when multichannels ISDN
>>>>         services.
>>>>         >
>>>>         >
>>>>         > How may MGC indicate to the MG that it uses PWs at the IP
>>>>         termination?
>>>>         >
>>>>         > It may be done by MeGaCo, using SDP[RFC4566] at Local/Remote
>>>>         > descriptors. However, how may be that SDP description of
>>>>         TDMPWs?
>>>>         >
>>>>         > Thanks,
>>>>         >
>>>>         > Javier Muñoz
>>>>         >
>>>>         >
>>>>         > _______________________________________________
>>>>         > Megaco mailing list
>>>>         > [email protected]
>>>>         > https://www.ietf.org/mailman/listinfo/megaco
>>>>         >
>>>
>>
>
>
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