Subject: [SIP] Call redirected (302) to more expensive destination.

From: "Mathieu Gervais" <[email-masked]>
Date: Wed, 11 Oct 2000 18:17:56 EDT

Hi,

Scenario :

   Caller A calls Callee B, but B User Agent redirects, with a 302, Caller A 
to another destination which is (way) more expensive for A. Because 302 is 
handled kind of automatically, the user A is not really asked if he still 
wants to try to reach B (at higher cost).

(Someone that doesn't want to talk to you could easily redirect all your 
calls to an expensive destination, or something like that)

Does this scenario makes sense? If yes, what do people think about this 
problem?

I guess that the user agent of A can inform him where it is getting 
redirected, and give him a little delay to cancel the call before doing 
automatic redirection, but what if A does not look at the "screen", or just 
does not have an idea that it's going to be a more expensive address to 
contact?

thanks,

Mathieu

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From: [email-masked]
Date: Thu, 12 Oct 2000 09:06:54 +0530

I would say automatic call-redirection on a 302 response is something that
the endclient can always decide
to accept/reject. This seems to be an endpoint descision related issue -
since the redirection comes back to him.

Matheiu>(Someone that doesn't want to talk to you could easily redirect all
your
Matheiu> calls to an expensive destination, or something like that)

In the case of 302, the client shouls decide in consultation with the user
whether
to reissue an INVITE to the new destination. That should be all.

I doubt if should at all handle things like if the user missed seeing the
address
of the redirected call.

Regds
Arjun

"Mathieu Gervais" <[email-masked]> on 10/12/2000 03:47:56 AM

Please respond to [email-masked]

To:   [email-masked]
cc:

Subject:  [SIP] Call redirected (302) to more expensive destination.

Hi,

Scenario :

   Caller A calls Callee B, but B User Agent redirects, with a 302, Caller
A
to another destination which is (way) more expensive for A. Because 302 is
handled kind of automatically, the user A is not really asked if he still
wants to try to reach B (at higher cost).

thanks,

Mathieu

---

From: Jonathan Rosenberg <[email-masked]>
Date: Thu, 12 Oct 2000 01:45:08 -0400

> -----Original Message-----
> From: Mathieu Gervais [mailto:[email-masked]]
> Sent: Wednesday, October 11, 2000 6:18 PM

Its only going to be a problem in cases where there is recursion; that is,
where proxies in the network act on redirect responses and try the addresses
listed in the Contact headers. When there is no recursion, the originating
UA will see exactly where they have been redirected to, and so its no
problem if the GUI can show such a thing. It could still be a problem for
standalone phones with no UI, gateways, and other such PSTNish devices.

The caller preferences spec:
http://www.ietf.org/internet-drafts/draft-ietf-sip-callerprefs-02.txt

 has a way to allow an originating UA to request that there be no recursion:

Request-Disposition: no-recurse

which can help solve this problem to some degree. Its still an issue for UIs
that can't show redirections. Such devices should probably consider
redirects to phone numbers as call failures. 

Even that doesn't completely solve the problem, since there is nothing, in
theory, that would prevent a proxy somewhere along the line from proxying a
request to a destination that is some far away phone number. In practice, I
doubt this would happen. Gateways don't just accept random calls, terminate
them, and send a bill off to someone. Typically, termination services are
arranged on a bilateral basis. This will require a proxy at the interface
between them to do accouting and authorization. So, a call routed from a
caller to domain A, which then forwards the call to a number in Zimbabwe,
would be routed by domain A through this proxy and be counted amongst the
calls billed to domain A. Serves as a good incentive not to do such bad
things.

-Jonathan R.

---
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
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