On Apr 18, 2008, at 9:32 AM, Hadriel Kaplan wrote:
>
>> -----Original Message-----
>> From: Dean Willis [mailto:[EMAIL PROTECTED]
>>
>> Proxies that recurse on 302 responses should be taken out and burned
>> anyhow. It's just a tragically stupid thing to do in most cases. In
>> the scenarios we're talking about, which probably involve a
>> transition
>> from a "no charge" IP call to a potentially very expensive (like, up
>> to $25 a minute for some premium services) PSTN call, the user REALLY
>> needs to be able to make a decision.
>
> I think that's a great utopian view, but in the real world that
> would be impractical. A great many SIP UA's are ultimately just TDM
> gateways, providing POTS-type interfaces into the home, or PBX phone
> lines into the office, etc. Afaik there is no way for them to
> indicate this redirection to the human, or have a way to be told yes/
> no by the human. Some people handle this type of thing with an app-
> server b2bua where it plays out a message and takes in DTMF to make
> the decision, but I think that's uncommon.
IMHO, the right thing for a POTS terminal to do on a 302 response is
probably either indicate an error condition to the user or use a voice
app to inform the user if no GUI is available.
>
> I think/hope in the common case, if a call goes from one provider to
> another, the second provider will not recurse it outside of its
> domain and will pass it back upstream to the calling provider to
> decide. I think that because often the billing model between them
> seems to dictate that. I have no doubt some cases will occur to
> validate your concern, but I think market forces will "correct" them
> naturally over time. Providers have plenty of natural motivation
> not to piss off their customers and regulators.
In some sectors, providers have financial incentives to do just the
opposite. Lots of US carriers made money charging victims that had
been tricked into calling those expensive Carribbean premium lines.
See:
http://www.scambusters.org/ScamBusters8.html
While this has gotten better recently (which could be your market
forces at work), I have been in many discussions around 3GPP and OMA
where people expressed concerns that 302 handling could engender a new
wave of such problems.
That's partly why I think that anything doing a retargeting needs to
inform the calling party about the retargeting operation. I'm still
liking a new provisional response as a way to do this, especially with
Identity in responses. This would allow the call to be dropped quickly
(and before sending media) if the connected identity is unanticipated.
--
Dean
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