Re: [Sip-implementors] Doubt on CPC parameter

[Paul Kyzivat]

The point here is that cpc is a parameter related to phone numbers, not 
general sip addresses. So while the following *could* be valid, you 
shouldn't count on it:

	From: <sip:pkyzivat;[EMAIL PROTECTED]>;tag=1928301774

Paul

Brett Tate wrote:
cpc parameter is to be defined as tel uri 
parameter, neither as sip uri parameter
nor as any header parameter.
So, I think, the correct answer is putting 
it in the user part of sip uri like:

From: <sip:+17005554141;[EMAIL PROTECTED]>;tag=1928301774

This issue is explained in detail in the 
section 19.1.6, RFC 3261.
The sip-uri parameter setting user=phone is also needed.

<sip:+17005554141;[EMAIL PROTECTED];user=phone>

In my understanding, user=phone is not necessarily 
needed.  Probably, it is RECOMMENDED to be put in 
sip URI when user part includes tel URI.  Even without 
user parameter, user part is syntactically correct
and can still be interpreted as E.164 number under 
the designated domain.

User parameter MAY be required to be interpreted 
as E.164, depending on the policies and the 
implementations.  But, I assume, the domain which 
can handle E.164 number SHOULD be able to recognize 
and, if it is possible, interpret user part as 
E.164 even without user=phone.


The following text from RFC 3261 section 19.1.1
hopefully clarifies emphasis level.
 "If the user string contains a telephone number 
  formatted as a telephone-subscriber, the user
  parameter value "phone" SHOULD be present.  
  Even without this parameter, recipients of SIP 
  and SIPS URIs MAY interpret the pre-@ part as a 
  telephone number if local restrictions on the
  name space for user name allow it."

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