Subject: [SIP] E.164 request-uri domain's.

From: "Fairlie-Cuninghame, Robert" <[email-masked]>
Date: Sat, 2 Jun 2001 08:26:21 -0700

Hi,

We have had this discussion quite a few times but I thought I would throw in
a new idea.

When building a request-uri containing an E.164 number which does not
"belong" or is associated with a particular domain name then the most
desirable action is to place a tel: URL in the outbound request-uri.
However, if a tel URL cannot be generated or received for whatever reason,
then a SIP url must be used instead and a domain name must selected for the
url.

The easiest option is to simply place the outbound proxy/destination's
address or hostname in the host portion. Eg "sip:+12135551234@<proxy
hostname>;user=phone". I remember that some people had some academic
objections to this approach because the request-uri referred to an
"intermediate destination" rather than the final destination. I personally
believe that it is 
a)	easy to ignore the domain name for the telephone subscriber case at
a proxy (that is you simply treat a "user=phone" request-uri as a simple
telephone number (ala tel URL) if the domain name is that of the proxy's).
With the new loop detection rules I don't believe this creates any problems.
This removes the objection  due to the "intermediate destination" concept.
b)	A proxy worth the disk sectors it is written on should be able to
route a call of this form.

Firstly, do people who previously had objections to this approach still have
their objections?

Alternatively, for E.164 numbers what do people think about allowing
"sip:+12135551234@e164;user=phone"? e164 is the domain stem used by ENUM for
doing DNS lookups of E.164 numbers. In this case the host name of the sip
URL correctly indicates that domain of the user portion.

Cheers,

Robert.

---

From: Dean Willis <[email-masked]>
Date: Sun, 03 Jun 2001 11:43:16 -0500

This is basically how the phone, proxy, and gateway connecting my desk 
to the PSTN work.

--
Dean

Fairlie-Cuninghame, Robert wrote:

> Hi,
> 
> We have had this discussion quite a few times but I thought I would 
> throw in a new idea.
> 
> However, if a tel URL cannot be generated or received for whatever 
> reason, then a SIP url must be used instead and a domain name must 
> selected for the url.
> 
> "intermediate destination" rather than the final destination. I 
> personally believe that it is
> 
>    1. easy to ignore the domain name for the telephone subscriber case 
>       at a proxy (that is you simply treat a "user=phone" request-uri as 
>       a simple telephone number (ala tel URL) if the domain name is that 
>       of the proxy's). With the new loop detection rules I don't believe 
>       this creates any problems. This removes the objection  due to the 
>       "intermediate destination" concept.
>    2. A proxy worth the disk sectors it is written on should be able to 
> Firstly, do people who previously had objections to this approach still 
> have their objections?
> 
> "sip:+12135551234@e164;user=phone"? e164 is the domain stem used by ENUM 
> for doing DNS lookups of E.164 numbers. In this case the host name of 
> the sip URL correctly indicates that domain of the user portion.
> 
> Cheers,
> 
> Robert.

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