Registered payload types for G.723.1/G.729

Stephen Casner casner at CISCO.COM
Wed Feb 23 21:20:54 EST 2000


On Wed, 23 Feb 2000, Chip Sharp wrote:
> At 01:11 PM 2/23/00 -0800, Hutton, Charles wrote:
> >I have the same concerns for G.729E.
>
> I'd recommend that as SG16 defines new encoding types that it register them
> with IANA.
>
> Theoretically, someone could register your codepoints for a different
> algorithm.

No.  As I mentioned in my previous response, the registration policy
has been revised.  There will be no more assignments of static payload
type numbers because mechanisms are now in place in various control
protocols to dynamically define payload type number bindings for each
session.  It should be clear that static assignments cannot continue
indefinitely in a small number space.  This rationale is explained
further in section 3 of the draft revision of RFC 1890, which is

http://www.ietf.org/internet-drafts/draft-ietf-avt-profile-new-08.txt

My understanding is that H.245 provides a means to define dynamic
payload types as part of the capability exchange using OIDs.  This is
necessary for non-standard encodings, for example.  It should be used
for future standard encodings as well to dynamically map from a larger
encoding name space to the small payload type number space.

In addition to whatever namespace(s) may be needed for ITU protocols,
several IETF protocols use the MIME namespace, including the "rtpmap"
attribute used for dynamic payload type mapping in SDP.  A few weeks
ago, the IETF AVT working group sent a liaison statement to SG16 (or
at least attempted to) via Joerg Ott to the Rapporteur of ITU SG16
Q.13 to describe the procedure for defining new RTP payload formats.
In particular, we encourage the registration of new payload formats in
the MIME namespace according to the procedures in

http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-mime-01.txt

I don't know the details of G.729E.  If it requires a different
payload format than G.729, then I would encourage you to let AVT
review the payload format specification and that you register the
payload format in the MIME namespace.
                                                        -- Steve



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