Subject: [Sipping] draft-ietf-sip-isup-02 and sip URL

From: Terry L Anderson <[email-masked]>
Date: Wed, 25 Jul 2001 13:05:41 -0400

The 02 draft corrects the use of user=phone in the sip URL examples
using a local-phone-number, but I notice 2 other issues.

It states that ';user=phone' is added only when the '+' is not present.
But RFC 2543 suggests that when the telephone-subscriber option is used
'user=phone' should always be added since the case cannot be
distinguished by BNF (although it allows interpreting the user part as a
phone number even without it).  All the examples in the callflows draft
include it even with global numbers (those with '+').  Seems like the
sip-isup draft should suggest always using it rather than just with
local numbers.

In addition, the local number example does not include an area-specifier
('phone-context=xxx').  SIP refers to RFC2806 for the syntax of
telephone-subscriber (so the syntax for this part of the sip URL is the
same as for the tel URL).  RFC 2806 states in one place:
    "Not all numbers are valid within all numbering areas. The <area-
   specifier> parameter, which is MANDATORY for local numbers, is used
   to indicate the locale within which this number is valid, or to
   qualify the phone number so that it may be used unambiguously. " (my
emphasis)
yet in another:
    "If local phone numbers are used, the document in which they are
    present SHOULD contain an indication of the context in which they
    are intended to be used, and an appropriate <area-specifier> SHOULD
    be present in the URL."

So it is contradictory whether the area-specifier is required or
recommended.
What is common practice in the SIP community?  Do we require it or not?
I see that phone-context was removed from the flows in the call-flows
example draft between 03 and 04 and the description changed to make it
optional.  Does this mean the SIP community accepts the second excerpt
above rather than the first?  And that it should NOT normally be used?

--
Waiting for the other shoe to drop but hoping its a one legged man.
------------------------------------------------------------
Terry L Anderson              mailto:[email-masked]
Tel:908.582.7013   Fax:908.582.6729
Lucent Technologies/INS/Voice Over IP Access Networks
Rm 2B-121, 600 Mountain Av, Murray Hill, NJ 07974
http://its.lucent.com/~tla (Lucent internal) http://www.gti.net/tla