Valentin Nechayev wrote:
>>>>>> Paul Kyzivat <[EMAIL PROTECTED]> wrote:
>
>> Right. Lets take an example:
>> Assume call is initially To: sip:[EMAIL PROTECTED]
>> Alice forwards it to sip:[EMAIL PROTECTED] by putting that into the R-URI.
>> (To
>> URI is unchanged.)
>> The call then arrives at the softswitch for biloxy.com. The softswitch
>> then rewrites the R-URI with the contact for Bob's device:
>> sip:bobphone.biloxy.com.
>> When the invite reaches the phone, it tries to use the To-uri to figure out
>> which line the call was addressed to. But it is expecting it to be either
>> sip:[EMAIL PROTECTED] or sip:[EMAIL PROTECTED] It is not expecting
>> sip:[EMAIL PROTECTED] and so can't figure out which line was intended.
>
> This example shows only that any approach has its limited usage
> scope and won't work when is used in inappropriate way.
Yes. There are *some* ways in which To might be productively used.
But not the ways I hear of it being used.
> And the
> main point is final UA ignorance of target.
Its a problem not just for the final target - but rather for any element
that is more than one translation away from the source.
> If this were, for
> example, Bob's call center which proceeds secretary service for its
> subscribers including Alice, it can use any header field to detect
> what target was original to this request - if it sees Alice in
> h_To, it would accept calls as targeted to Alice, use Alice's
> incoming voicemail pool and even greet as "Alice enterprises,
> please leave your message after beep". But you explicitly denied
> its intelligence to distinguish calls using h_To, and that's your
> choice, not its.
The same problem can occur here, if the call was first sent to Charlie,
was then forwarded to Alice, who then forwarded it to Bob for answering
services.
The only reliable usage I have been able to imagine for To is to
recognize that actual recipient is not who the caller intended to reach.
That can indeed condition a different greeting than if the call had
actually been intended for the recipient. But that greeting cannot use
that to figure out who the actual recipient was.
Paul
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