Subject: [ipcdn] pktcSigDevCodecTable request for clarification

From: "David De Reu" <[email-masked]>
Date: Fri, 21 Jan 2005 10:27:12 +0100

Dear all,

Some MTA vendors are a bit puzzled regarding what to include in the
pktcSigDevCodecTable table. On their and my own behalf, I would like to
request some clarification.

More specifically, there actually are two types of codecs:

- First, the "real" voice codecs, like the ones listed in the PktcCodecType
TEXTUAL-CONVENTION (PCMA, PCMU, G.729... etc)

- Second, supplementary "codecs", for example for DTMF relay (RFC 2833). In
(Euro-)PacketCable/IPCablecom, this is the "telephone-event" "codec". Other,
proprietary solutions for DTMF relay exist as well, by the way, so this is
not limited to "telephone-event" alone.

>From a signaling point of view (NCS and SDP in our case), the "codecs" of
the second type, are treated as all other codecs. However in practice they
cannot be used for the entire call, they have to be used in conjunction with
a "real" codec.

The question now is: do the codecs of the second type have to be included in
the pktcSigDevCodecTable, or is this table just intended for "real" codecs?
Either way, a clarification of some sort in the DESCRIPTION clause would be
helpful to implementors (and testers, as a matter of fact). If they are to
be included, currently the only way is to use "other (1)" as the type, which
is of course allowed but not very informative.

This leads me to my second point: if things like "telephone-event" are
supposed to be included in the pktcSigDevCodecTable, then I at least suggest
extending the PktcCodecType with something like "telephoneEvent (15)".

Any feedback would be appreciated.

Regards,

David

_____________________________________________________
David De Reu
tComLabs
Stapelplein 70/004 – 9000 Ghent – Belgium
Tel: +32 9 269 22 91 – Fax: +32 9 329 31 74
www.tComLabs.com
_____________________________________________________

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