Re: [AVT] rtpmap and fmtp for telephone-event
"Tom-PT Taylor" <taylor@nortel.com> Wed, 27 September 2006 04:45 UTC
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Date: Wed, 27 Sep 2006 00:39:31 -0400
From: Tom-PT Taylor <taylor@nortel.com>
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To: Murat Artun <artunmurat@gmail.com>
Subject: Re: [AVT] rtpmap and fmtp for telephone-event
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The key passage is in section 2.5.1.1 of 2833bis:
The sender SHOULD indicate what events it supports, using the
optional "events" parameter associated with the telephone-events
media type. If the sender receives an "events" parameter from the
receiver, it MUST restrict the set of events it sends to those listed
in the received "events" parameter. For backward compatibility, if
no "events" parameter is received, the sender SHOULD assume support
for the DTMF events 0-15 but for no other events.
So it is possible for the IP phone to omit the fmtp, but there should be
a very good reason for doing so. And as you say, if the fmtp attribute
isn't there, the other end has good reason to expect support of DTMF
tone events.
Murat Artun wrote:
> Hello,
>
> Both in RFC2833 and draft-ietf-avt-rfc2833bis-15 it was specified that
> SDP usage is recommended for telephone-event payload format, or I have
> interpreted it to be so. In RFC 2833 it was said that: "Receivers MAY
> indicate which named events they can handle, for example, by using the
> Session Description Protocol (RFC 2327 [7])." In addition, latest
> draft indicates in section "Relationship to SDP" that mapping is
> recommended.
>
> Considering these, can we say that it is possible for an IP phone that
> announces a codec type specification for the telephone-event omits
> using fmtp? If this is possible, will the other IP phone which
> receives this SDP, interpret it as to be that the remote end is ready
> to receive only 0-15?
>
> Thanks.
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- [AVT] rtpmap and fmtp for telephone-event Murat Artun
- Re: [AVT] rtpmap and fmtp for telephone-event Tom-PT Taylor