Subject: [Sipping] draft-ietf-sipping-nat-scenarios, TURN and RTCP

From: Frank Shearar <[email-masked]>
Date: Fri, 18 Jun 2010 10:24:25 +0200

draft-ietf-sipping-nat-scenarios-13 section 5.2.2.2 TURN Solution shows 
a user agent sending two Alloc Reqs to a TURN server for its two media 
ports (RTP + RTCP). The TURN server returns (message (3)) STUN-PUB-2 for 
the first Alloc Req and (message (7)) STUN-PUB-3 for the second Alloc Req.

Surely STUN-PUB-2 is not necessarily the same as STUN-PUB-3?

I would imagine that in most environments it would be, but if it's not a 
MUST, what does one do in the SDP, given that "a=rtcp:$STUN-PUB-3.port" 
defines the port that RTCP will use, but not the address?

frank

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From: Simon Perreault <[email-masked]>
Date: Fri, 18 Jun 2010 08:20:18 -0400

> defines the port that RTCP will use, but not the address?

Yes, this is important.

Assuming that this exchange implicitly uses the EVEN-PORT and
RESERVATION-TOKEN attributes, I think it should be made explicit in the
text.

i.e. Message (1) contains an EVEN-PORT attribute with the R flag set to
1. Message (3) contains a RESERVATION-TOKEN attribute, which is echoed
in message (5).

Simon
-- 
NAT64/DNS64 open-source --> http://ecdysis.viagenie.ca
STUN/TURN server        --> http://numb.viagenie.ca
vCard 4.0               --> http://www.vcarddav.org

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From: Frank Shearar <[email-masked]>
Date: Mon, 21 Jun 2010 15:22:50 +0200

> defines the port that RTCP will use, but not the address?

It occurs to me that if $STUN-PUB-2.address != $STUN-PUB-3.address then 
the user agent could
* repeatedly ask for TURN bindings until it gets a pair with the same 
address or
* elect to multiplex RTP and RTCP over the same port, and abandon the 
TURN binding for RTCP.
* ???

frank