[RAI] RFC 3427bis - grandfathering in existing P-headers that are in the IETF process?

[Dan York <dyork at voxeo.com>]

In RFC 3427bis ( http://tools.ietf.org/html/draft-peterson-rai-rfc3427bis-01 
 ), it states very clearly that P-headers are deprecated and NOT to  
be registered.  For instance, section 4 makes this VERY clear statement:

  New proposals to document SIP headers of an experimental or private  
nature, however,
   shall not use the "P-" prefix.

While I am fine with that for new headers being created, what about  
those headers that are already deployed in actual usage and are being  
documented in the existing RFC 3427 process?  And what about existing  
headers in usage that have never been documented but might be under  
this simpler process?

For instance, for about the past year I have been working P-Charge- 
Info through the process and am at the point in RFC 3427 where I need  
to "request expert review" from the SIPPING chairs after having gone  
through multiple rounds of review on the SIPPING mailing list:

  http://tools.ietf.org/html/draft-york-sipping-p-charge-info-06

Under a literal reading of RFC 3427bis, I would not be able to  
register this header.  Yet this header has been in common usage for at  
this point 3 or 4 years and is already in usage in various equipment  
and applications.  I do not see the vendors of the equipment nor the  
carriers using it changing their software/firmware at this point  
purely because we are changing course on the use of "P-".

I would note that RFC 3427 is not 100% consistent on this point.  
Section 4 states clearly "New proposals... shall not use the P- prefix."

However, in the very next paragraph, the usage is "discouraged" but by  
implication would seem to be permitted:

   The use of any
   header field name prefix ("P-" or "X-" or what have you) to  
designate
   headers of limited applicability is discouraged.

And in Section 6, IANA Considerations, it says that "new registrations  
of Informational headers **need not** begin..." :

   Standard headers and messages MUST NOT begin with the leading
   characters "P-".  Existing "P-" header registrations are considered
   grandfathered, but new registrations of Informational headers need
   not begin with the leading characters "P-".  Short forms of headers
   MUST only be assigned to standards track headers.

Personally, I think the guidance in Section 6 is appropriate.  For  
*Informational* headers, the leading "P-" prefix should be allowed,  
although discouraged, to accommodate existing P-headers that may be in  
common usage but may perhaps have never been documented because of the  
steps involved with the existing RFC 3427 process.

My suggestion would be to ease the text in section 4 to be something  
more like:

   New proposals to document SIP headers of an experimental or  
private nature, however,
   are discouraged from using the "P-" prefix.

My 2 cents,
Dan

--
Dan York, Director of Conversations
Voxeo Corporation   http://www.voxeo.com  dyork at voxeo.com
Phone: +1-407-455-5859    Skype: danyork
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