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
Blogs: http://blogs.voxeo.com http://www.disruptivetelephony.com
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