Subject: [MMUSIC] 0.0.0.0 address in draft-rescorla-mmusic-ice-trickle-01

From: Matthew Kaufman <[email-masked]>
Date: Thu, 25 Oct 2012 15:40:22 -0700

"In some cases, agents may choose to just send an offer that the remote 
party would reject as invalid unless it supports trickling. One such 
example would be an offer with no ICE candidates and an invalid default 
address (e.g. 0.0.0.0)."

Is there in fact evidence that some/most/all existing SDP-parsing SIP 
applications will in fact reject c= (and a=rtcp) lines that contain 
0.0.0.0 with an appropriate SDP-rejecting answer, rather than just 
answering affirmatively and attempting to send the media packets there?

If we can't confirm this to be the case, this is an inappropriate 
"negotiation" mechanism and the spec needs to get a little more concrete 
about it.

Matthew Kaufman

---

From: "Dan Wing" <[email-masked]>
Date: Thu, 25 Oct 2012 18:03:43 -0700

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf
> Of Matthew Kaufman
> Sent: Thursday, October 25, 2012 3:40 PM
> To: [email-masked]
> Subject: [MMUSIC] 0.0.0.0 address in draft-rescorla-mmusic-ice-trickle-
> 01
> 

By my read, they violate the last paragraph of RFC3264 Section 8.4,
http://tools.ietf.org/html/rfc3264#section-8.4, which says:

   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.

-d

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