6 jul 2008 kl. 16.19 skrev Iñaki Baz Castillo:

> Hi, I understand that the use of "tel" URI could be cool when the
> INVITE is received by a PSTN gateway (so an URI domain makes no sense
> at all) but I wonder who should create this tel URI.
>
> For example, I consider very very difficult that a phone could handle
> "tel" URI's since it cannot know when the call is for a PSTN number, a
> private extension or an outbound call to other SIP domain, so IMHO a
> final UA should always use SIP/SIPS URI's and not "tel".
>
> But when the UA sends an INVITE to its proxy like:
>  INVITE sip:[EMAIL PROTECTED] SIP/2.0
> the proxy can detect that it's a PSTN number and convert it to "tel"
> URI before forward it to a PSTN gateway:
>  INVITE tel:0034999000111 SIP/2.0
>
> Is it correct? Note that I'm trying to imagine a real and feasible
> bahaviour. Please, don't suggest me that the phone could handle "tel"
> URI's since it's just an impossible dream, isn't?
>
I think your examples are correct.

Let's add a phone call from PSTN to a SIP UA. The gateway could then  
use a TEL uri in
the From: header since the call is not from someone in a domain the  
gateway controls.
The SIP UA needs to be able to send a call back to a Tel: uri in order  
to reply,
if this turns up as a missed call, or something that you want to add  
to a phone book.

So while I agree with you that the phone can't make decisions on  
whether a given sequence is a telephone
number or not, I still think it has to be able to handle a tel: uri.

/O
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