> On 12/28/12 8:45 AM, Theo Zourzouvillys wrote:
> > On Tue, Dec 18, 2012 at 4:24 PM, Paul Kyzivat <[email protected]>
> wrote:
> >> I don't think so. But maybe others will find a justification for
> doing so.
> >
> > I don't think it is valid - although it's totally underspecified.
> >
> > user=phone implies the user portion is a tel URI, and
> > tel:anonymous.invalid;phone-context=+1 isn't legitimate - so i can
> see
> > why a parser would fail it, as even if it was matching a
> > local-phone-number only hex digits would be allowed.
> 
> Yeah, that makes some sense.
> 
> 3261 is indeed underspecified about this. What it says is:
> 
>           The user URI parameter exists to
>           distinguish telephone numbers from user names that happen to
>           look like telephone numbers.  If the user string contains a
>           telephone number formatted as a telephone-subscriber, the
> user
>           parameter value "phone" SHOULD be present.
> 
> It doesn't ever say the flip of that: "If the user parameter value
> "phone" is present, the user string (SHOULD/MUST?) be formatted as a
> telephone-subscriber".
> 
> If that is not so, then the parameter doesn't have a lot of value.

I agree that RFC 3261 is underspecified.  RFC 2543 was a little more clear.

"If the host is an Internet telephony gateway, the user field
 MAY also encode a telephone number using the notation of
 telephone-subscriber (Fig. 4). The telephone number is a special
 case of a user name and cannot be distinguished by a BNF. Thus,
 a URL parameter, user, is added to distinguish telephone numbers
 from user names. The phone identifier is to be used when
 connecting to a telephony gateway. Even without this parameter,
 recipients of SIP URLs MAY interpret the pre-@ part as a phone
 number if local restrictions on the name space for user name
 allow it."


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