Re: [MMUSIC] Draft LS response to 3GPP re: use of .invalid vs. 0.0.0.0in SDP connection addresses

["Philip Hodges" <philip.hodges at ericsson.com>]

Hi Jean-Francois,
so in short:

.invalid TLD may be used (i.e. it is not a violation) but due to
existing implementations not currently supporting this MMUSIC recommends
keeping to 0.0.0.0. 

cheers,
Phil Hodges
Ericsson
Mobile: +61404069546
 
 

-----Original Message-----
From: mmusic-bounces at ietf.org [mailto:mmusic-bounces at ietf.org] On Behalf
Of Jean-Francois Mule
Sent: Thursday, 7 August 2008 9:04 AM
To: mmusic at ietf.org
Subject: [MMUSIC] Draft LS response to 3GPP re: use of .invalid vs.
0.0.0.0in SDP connection addresses

   Based on the list discussion and wg session last Friday, this is what
we plan to send in response to the 3GPP LS.

Comments welcome on the mmusic list.
Thanks,
Joerg and Jean-Francois.



   The IETF MMUSIC working group would like to thank 3GPP for the
liaison statement referenced under
https://datatracker.ietf.org/liaison/449/.  3GPP asked for IETF feedback
on whether the .invalid TLD may be used to indicate an unspecified IPv4
connection address in SDP.

   The working group has discussed the question on its mailing list and
also during its recent meeting on August 1 2008 at IETF#72 in Dublin,
Ireland.  The MMUSIC chairs specifically requested feedback from IETF
participants on both what is allowed or recommended by IETF RFCs, and
the experience of SDP implementations. 

   We note that several IETF participants clarified that the question
should be taken in the context of SDP use for an H.248-based protocol
specification.  While the feedback we received is mostly coming from SIP
SDP IPv4 implementers, this may be relevant feedback if SDP is to be
re-used between H.248 connections and SIP dialogs, or if
interoperability with IPV4 SIP implementations is important.

   Based on the input we received, we would like to recommend that 3GPP
continues to use the 0.0.0.0 IPv4 address to indicate an invalid
connection address in SDP connection lines with IPv4 addresses:
   - while the SDP aBNF allows .invalid (RFC 4566), the SDP offer/answer
RFC has a normative requirement for implementations to support 0.0.0.0
as a connection address to indicate that neither RTP nor RTCP should be
sent to the peer (RFC 3264, section 8.4).  Note that the use of port 0
has a special meaning per RFC 3264 section 5.1 for unicast streams.
  - feedback received on the IETF MMUSIC mailing list from several SIP
implementers indicate that only 0.0.0.0 is supported by IPv4-only
endpoints.
  
  We would appreciate if you could let us know what the additional
discussions in 3GPP conclude for the benefit of the working group
participants.

Regards,
Joerg Ott and Jean-Francois Mule
MMUSIC co-chairs
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