: Cx Interface Compatibility Issues and IETF Last Call

In recent discussion, issues have arisen about compatibility of the 
Diameter SIP Application with the Cx interface in 3GPP.

In the IETF it is common to work on standardization of new protocols in   
scenarios where existing protocols are widely deployed.  This is not only
appropriate, but in many cases necessary. There is a saying that "we can  
only standardize something we know how to do" -- so that standards 
often benefit from the experience of previous efforts. 

However, in these situations the new protocol needs to overcome 
significant hurdles in order to succeed.  If the existing protocol 
is widely deployed, interoperable and thought to function well, these 
hurdles may be particularly difficult to overcome. 

However, we need to distinguish between barriers that exist within
the marketplace and those that we establish within the IETF process
to ensure the technical quality of documents.  In terms of the IETF 
process, the determinant of further progress is WG consensus 
(AAA WG last call) and IETF consensus (IETF Last Call). 

The primary goal in the development of the Diameter SIP application
within the AAA WG is to produce a specification that is technically
sound, and that is backwards compatible with the RADIUS protocol,
the Digest Authentication draft in particular.  The AAA WG charter
does not mention backwards compatibility with the Cx interface
as a requirement for the Diameter SIP application. 

As a result, I believe that Cx interface compatibility is not a 
requirement for the Diameter SIP application to successfully complete 
AAA WG last call and advance to IETF last call.  However, I do believe 
that issue Cx interface compatibility is an important concern that needs 
to be considered by the IETF community at large, as part of the IETF Last 
Call process.  As described in RFC 20206, community consensus needs to be 
demonstrated in IETF Last Call in order to allow a specification to move 
forward on the standards track. 

If participants in the IETF community have a concern about whether
the Diameter SIP application is appropriate for consideration as an IETF 
Proposed Standard, they should make those concerns known by posting their 
opinions to the IETF Mailing list in response to the IETF Last Call 
notice.  If those concerns are serious, the respondents can indicate that 
they believe the Diameter SIP specification should be rejected as 
unsuitable the IETF Proposed Standard designation.  The IESG will gauge 
consensus on the IETF mailing list, and based on the opinions expressed, 
will make a determination fo whether the Diameter SIP application will be 
published as an IETF Proposed Standard.