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[AVT] Re: Clearmode / VoIP Media Gateways supporting ISDN data

I don't get to agree with Leslie much, so I want to take this opportunity... to agree. :-)

64 kbit Unrestricted service is pretty much what it says it is: Unrestricted 64 kbit/s synchronous digital service with 8 kHz integrity. Which means to me that I can transmit anything I want to over it.

It is being used (or has been used) to carry:
* Audio (as pointed out by Leslie at 7 kHz)
* Higher rate Audio (15 kHz at n x 64 kbit/s)
* Video (H.320 at n x 64 bkit/s where each channel is
signaled independently)
* PPP (with IP on top).
* X.25/LAPB
* Subrate asynch or sync rate adapted to 64 kbit/s
(V.110, V.120, T-Link, DMI Mode 2/3, X.25)
* Group 4 Fax

As for Multirate service (n x 64 kbit/s with 8 kHz integrity), the only public service I was aware of as of 1996 was the H0 (384 kbit/s), and H11 (1536 kbit/s) and possibly H12 (1920 kbit/s) rates, although there could be more by now.

I believe that if this will work at all over IP, then it needs something similar to RTP. Sticking 125 usec samples into UDP probably won't work. :-)

Some coordination with pwe3 wg might be needed, but there isn't necessarily complete overlap. Also, I learned through painful experience that just because the Q.931 signaling (Bearer Capability) said 64 kbit/s unrestricted didn't necessarily mean that the service actually supported 64 kbit/s unrestricted. Things have no doubt improved, but in the mid-'90s calls signaled as 64 kbit/s rate adapted to 56 kbit/s from US to Australia showed up in Australia as 64 kbit/s unrestricted.

Chip

At 08:04 PM 10/21/2002, Leslie Graf wrote:
Collegues,
Just to add to what Steve has correctly stated. This TMR calue is used for the 7kHZ ausio service where no network fallback is permited.. This is certainly not a data service.
Regards Leslie

steve.norreys@bt.com wrote:

> Gents
>
> Just because the call is marked as "64Kbits/s unrestricted" does not mean
> that this is a data call in the IP sense of a data call. Some customers use
> this TMR to transfer real time data between applications in different
> networks. That the TMR does not tell you of the type of application that is
> using this "media" so it would be prudent to use RTP when interworking ISUP
> to SIP networks.
>
> Regards
>
> Steve Norreys acd
>
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> -----Original Message-----
> From: Chong, Koan S, ALVAP [mailto:kschong@att.com]
> Sent: 15 October 2002 15:44
> To: tsg11bicc
> Subject: FW: Clearmode / VoIP Media Gateways supporting ISDN data
>
> Please look at the questions at the end of the attached email.
> Regards,
> Koan
>
> -----Original Message-----
> From: Kreuter Ruediger [mailto:ruediger.kreuter@siemens.com]
> Sent: Tuesday, October 15, 2002 8:45 AM
> To: avt@ietf.org
> Cc: 'danny@tcb.net'; Chong, Koan S, ALVAP
> Subject: Clearmode / VoIP Media Gateways supporting ISDN data
>
> Hi,
>
> in August I published draft-kreuter-avt-rtp-clearmode-00.txt
> with the intention to drive a IANA registration for a Codec
> that can be used to support ISDN data connections via RTP.
> The main application for that are VoIP media gateways
> replacing a TDM network.
>
> This registration will have an influence on all VoIP media
> gateways and related softswitches in the converged network
> market, at least in interworking cases. Therefore I would
> like to get some comments by suppliers of such gear.
> Do you agree with this draft (besides from typos :-) ?
> Are there concurrent solutions in the market/field ?
>
> *********************************************************
>
> Another topic to be discussed,
> is a discussion input for a "Coding of SDP Media Description
> Lines from TMR/USI", in case of "Call Interworking from BICC/
> ISUP to SIP" (ITU, Study Group 11, WP3, Meetings of BICC/SIP
> interworking in Ottawa, Canada, 9th - 13th September 2002).
>
> This ITU standardization input, recommends to use UDP for
> Nx64kbit/s unrestricted connections. ("64kbit/s unrestricted"
> or "transparent mode" are synonyms for "clearmode")
> In SDP this would look like:
>
> b=AS:64
> m=data <port> udp
>
> This approach leads to two questions:
>
> Is it a good idea to transport ISDN data in VoIP networks
> directly on top of UDP instead of RTP ?
> This would enforce to rebuild all features which currently
> are based on RTP/RTCP parameters; e.g. synchronization
> (time stamps) or statistics & billing (RTCP sender/receiver
> reports).
>
> And is it necessary to support Nx64kbit/s (with N>1)
> within draft-kreuter-avt-rtp-clearmode-00.txt ?
> That is, is TDM:Nx64kbit/s visible to a VoIP media
> gateway ?
> In that case an additional parameter describing the
> size of N would be needed, and an algorithm describing
> the packetization in case of N>1.
>
> Any opinions according this topic ?
>
> Regards
>
> Ruediger Kreuter
> ruediger.kreuter@siemens.com
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