Hi,

> > > > 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."
> 
Probably, this is what my understanding came from.
My last SHOULD may be too strong, though.
Thank you for the clarification.

New tel URI format, currently developped in 2806bis(-05 version),
is more restricted than it is in RFC 2806.
Revised draft requires "+" sign or globally unique phone-context
parameter. This makes it easier to distinguish tel URI format from 
others without help of user parameter.

Anyway, I hope that the implementation can
- send with user=phone, if user part denotes tel URI, and
- accept even without user=phone, if configuration allows.
along with the principle;
"Be liberal in what you accept, and conservative in what you send." 

Regards,
Takuya

--------
Takuya Sawada
KDDI Corporation (KDDI)
Garden Air Tower, 3-10-10, Iidabashi, 
Chiyoda-ku, Tokyo 102-8460, Japan
Tel: +81-3-6678-2997
Fax: +81-3-6678-0286
[EMAIL PROTECTED]
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