Subject: RE: Clarification regarding RTP

From: "Ramana Divvi" <[email-masked]>
Date: Mon, 6 Jan 2003 15:34:07 +0530

Hi 
I have very basic doubt ( please don't laugh at me).
How will we know , UDP is carrying RTP payload?.
Is there any reserved port numbers for this case?

Thanks in advance.
With Kind Regards,
Ramana.

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From: Stephen Casner <[email-masked]>
Date: Mon, 6 Jan 2003 12:01:10 -0800 (PST)

> Is there any reserved port numbers for this case?

The UDP port numbers used with RTP are assigned dynamically.  See
Section 7 of RFC 1890, which is being revised in Section 8 of
draft-ietf-avt-profile-new-12, for an explanation.

If your question is in regard to RTP header compression, Section 3.1
of RFC 2508 explains that the compressor must decide heuristically
whether a UDP stream carries RTP.

In other cases, the UDP port numbers are learned from the signaling
protocol that sets up the session between/among the endpoints.

These questions regarding RTP would be more appropriately directed to
the [email-masked] mailing list of the Audio/Video Transport working
group.

Please be sure to read carefully the documents I have mentioned, and
the references they point to where appropriate, before asking further
questions.  For example, your first question was answered in the
document you were reading (RFC 2507).  Section 5.3.2 says: "Data field
is explained in section 12", and Section 12 explains the use and gives
a pointer to RFC 2508, same as I did in my first reply.

                                                        -- Steve