Subject: [Sip] IANA registries and question raised in IESG review of answermode

From: Dean Willis <[email-masked]>
Date: Wed, 24 Oct 2007 14:39:07 -0500

A question about IANA registry came up during review of draft-ietf- 
sip-answermode.

The draft currently defines two new header fields, "Answer-Mode" and  
"Priv-Answer-Mode".

Each header field can take the values "Auto" or "Manual".

Either value can be further modified by adding a ";require". For  
example:

     Answer-Mode: Manual;require

We have an IANA registry of header fields, as well as one of  
parameters to header fields. This is at:

http://www.iana.org/assignments/sip-parameters

and the specific registry of interest is:

Registry Name: Header Field Parameters and Parameter Values
Reference: [RFC3968]
Registration Procedures: Published RFC (A standards-track RFC is NOT  
required)

which has columns like:

                                                Predefined
Header Field                  Parameter Name     Values     Reference
----------------------------  ---------------   ---------   ---------
Accept                        q                    No       [RFC3261]

So far , so good. The draft-ietf-sip-anwermode text currently adds  
four rows:

                                                Predefined
Header Field                  Parameter Name     Values     Reference
----------------------------  ---------------   ---------   -------
Answer-Mode                   Auto                 No       [This doc]
Answer-Mode                   Manual               No       [This doc]
Priv-Answer-Mode              Auto                 No       [This doc]
Priv-Answer-Mode              Manual               No       [This doc]

Let's go back and consider the example:

Answer-Mode: Manual;require

The "require" is not a full parameter of Answer-Mode. That is, it  
makes no sense to say:

Answer-Mode: require

So, where do we IANA register the "require"? O
We could do something like:

                                                Predefined
Header Field                  Parameter Name     Values     Reference
----------------------------  ---------------   ---------   -------
Answer-Mode                   Auto                 No       [This doc]
Answer-Mode                   Manual               No       [This doc]
Answer-Mode                   Auto;require         No       [This doc]
Answer-Mode                   Manual;require       No       [This doc]
Priv-Answer-Mode              Auto                 No       [This doc]
Priv-Answer-Mode              Manual               No       [This doc]
Priv-Answer-Mode              Auto;require         No       [This doc]
Priv-Answer-Mode              Manual;require       No       [This doc]

We could also ignore the registration problem for "require" (which is  
what I did in the draft), add a new registry, or restructure the  
existing registry.

Or it could be that the syntax used in Answer-Mode is just broken and  
requires revision.

One suggestion I've received was to restructure to something like the  
following:

                                                Predefined
Header Field                  Parameter Name     Values     Reference
----------------------------  ---------------   ---------   -------
Answer-Mode                   Auto                 No       [This doc]
Answer-Mode                   Manual               No       [This doc]
Answer-Mode                   Privauto             No       [This doc]
Answer-Mode                   Privmanual           No       [This doc]

Anybody have a great idea here?

--
Dean

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