Subject: RE: [Sipping] SIP URL's with telephony numbers

From: "Michael O'Doherty" <[email-masked]>
Date: Wed, 28 Nov 2001 14:54:04 -0000

Firstly using 'user =' as a hint is fine - I think we can consider this one
closed !

A quick comment on one of things that was mentioned:

>This is a really, really bad thing. As Ben has said, only the owner of the
>domain in the URI can interpret the user part. Interpreting the user part
>outside of that domain is just going to be trouble. 

I think in practice there will likely be scenarios where it is done whether
we like it or not - for example an outbound proxy that wants to bar all
calls to a particular username at a particular domain or a proxy which is
doing some sort of legal intercept and which wants to catch all calls going
to a particular username at a particular domain. Or to take a telephone
number example, an outbound proxy which wants to allow normal telephone
numbers but bar premium telephone numbers.

---

From: Ben Campbell <[email-masked]>
Date: Wed, 28 Nov 2001 09:12:27 -0600

Michael O'Doherty wrote:

> Firstly using 'user =' as a hint is fine - I think we can consider this 
> one closed !
> 
> I think in practice there will likely be scenarios where it is done 
> whether we like it or not - for example an outbound proxy that wants to 
> bar all calls to a particular username at a particular domain or a proxy 
> which is doing some sort of legal intercept and which wants to catch all 
> calls going to a particular username at a particular domain. Or to take 
> a telephone number example, an outbound proxy which wants to allow 
> normal telephone numbers but bar premium telephone numbers.
> 

Your first two examples just requires a URL match, not an 
interpretation. The last one can only really be done at the destination 
domain (e.g. the domain of the gateway) or with tel urls.

And as people design each of those scenarios, they should use care not 
to attempt to interpret URLs that don't belong to their domain. You 
simply _cannot_ depend on a URL pointing to a domain that you do not 
control to mean what you think it means. (Unless you have some sort of 
agreement with that domain that includes URL interpretation.)

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