Subject: [MMUSIC] Question about the use of 0.0.0.0 and 0:0:0:0:0:0:0:0 in RFC 3264 (Offer/Answer)

From: "Barany, Pete" <[email-masked]>
Date: Thu, 20 May 2004 07:17:47 -0700

Hi,

In Section 8.4 of RFC 3264 "An Offer/Answer Model with the Session
Description Protocol (SDP)", the following statement is made:

-->BEGIN

RFC 2543 [10] specified that placing a user on hold was accomplished
by setting the connection address to 0.0.0.0.  Its usage for putting
a call on hold is no longer recommended, since it doesn't allow for
RTCP to be used with held streams, doesn't work with IPv6, and breaks
with connection oriented media.  However, it can be useful in an
initial offer when the offerer knows it wants to use a particular set
of media streams and formats, but doesn't know the addresses and
ports at the time of the offer.  Of course, when used, the port
number MUST NOT be zero, which would specify that the stream has been
disabled.  An agent MUST be capable of receiving SDP with a
connection address of 0.0.0.0, in which case it means that neither
RTP nor RTCP should be sent to the peer.

-->END

Question:
The statement "An agent MUST be capable of receiving SDP with a
Connection address of 0.0.0.0, in which case it means that neither
RTP nor RTCP should be sent to the peer."

Does this apply also to IPv6 (0:0:0:0:0:0:0:0, or in abbreviated
format ::)? There is some mention about putting a call on hold early
in the paragraph above and how this doesn't work for IPv6 ...
therefore, this is the cause of my confusion. Thnx.

- Pete

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From: Jonathan Rosenberg <[email-masked]>
Date: Thu, 20 May 2004 11:52:09 -0400

It doesn't apply to 0:0:0:0:0:0:0:0.

In other words, a v6 host shouldn't generate this as a technique for 
putting a call on hold (or for any other purpose). There is no defined 
behavior for how to react if you received such a thing.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                600 Lanidex Plaza
Chief Technology Officer                    Parsippany, NJ 07054-2711
dynamicsoft
[email-masked]                     FAX:   (973) 952-5050
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From: Paul Kyzivat <[email-masked]>
Date: Thu, 20 May 2004 12:07:03 -0400

> therefore, this is the cause of my confusion. Thnx.

It never said that, so I don't suppose you can assume it, even though I 
would expect most implementors would consider it a no-brainer to do this.

OTOH, if you want to use this mechanism for hold, why not just use the 
IPv4 form? Even if you otherwise would use an IPv6 address, this doesn't 
have to.

	Paul