As others have suggested, you almost certainly need to find a way to authenticate the address before presenting it to the PSTN.

One solution to that and your other problems, would be to use the P-Asserted-Identity header for this purpose. (draft-ietf-sip-asserted-identity-02.txt). In addition to providing a way to solve the authentication problem, it permits you to have multiple asserted identities. So your caller could have both a sip: address and a tel: address. Presumably the gateway would use the tel: address, while a sip UAS might prefer to present the sip: address to the callee.

Of course this won't work in isolation - it will only work in a deployment where all the parties agree to use P-Asserted-Identity.

Paul

Maria Yndefors wrote:
Hi!
The caller presentation is a widly used service in the PSTN network, and
ofcource IP telephony users will want to have the same service even if they
are calling from the IP world to the PSTN. Yes, the gateway will have some
numberseries, and also each user of the IP telephony network will have its
own phonenumber, so that they can be reach from the PSTN. We don't want to
present the gateway number to the called party, but the actual number where
the caller can be reached.

We are developing a gateway and I am interested in how others have solved
this problem.

Regards Maria

-----Original Message-----
From: James Undery [mailto:[EMAIL PROTECTED]]
Sent: Thursday, December 19, 2002 2:44 PM
To: Maria Yndefors
Subject: RE: [Sip-implementors] phone number to be contacted at


This is exactly the complexity I means, in reality a SIP UA won't have a
phone number and the callee will see the gateway as the caller-id. Unless
you've got gateway controlling a range of number and a proxy the otherside
handling the location within that range you wouldn't be able to call from
the PSTN. The otherway round you'd need an extension on the gateway so that
you could tell it which of its numbers to use. (You'd have to see gateway
vendors about this if it exists.)

James


-----Original Message-----
From: Maria Yndefors [mailto:[EMAIL PROTECTED]]
Sent: 19 December 2002 13:33
To: James Undery; Sip-Implementors
Subject: RE: [Sip-implementors] phone number to be contacted at


Hi!
Thanks for answering, the thing is that the useragent might
not put its
phonenumber in the From, it will perhaps put maria@e-horizon, and not
[EMAIL PROTECTED], otherwise other IP phone also will
have call
[EMAIL PROTECTED] when they call back to
[EMAIL PROTECTED], why
should a IP phone have to use the phonenumber when it could
just use the
more simpler [EMAIL PROTECTED], So what I'm looking for is
some alternate
From field, to put the phonenumber in.

/Maria


-----Original Message-----
From: James Undery [mailto:[EMAIL PROTECTED]]
Sent: Thursday, December 19, 2002 2:15 PM
To: Maria Yndefors; Sip-Implementors
Subject: RE: [Sip-implementors] phone number to be contacted at


Hi,

I guess no one answered as you've more or less answered it
your self, the
From header would be used if anything was (if it was a tel uri or
equivalent). As you can probably guess though this is far
more complex than
that as the gateway is likely to present it's own number due
to regulations
about tracability and the possibility for spoofing.

James

-----Original Message-----
From: Maria Yndefors [mailto:[EMAIL PROTECTED]]
Sent: 19 December 2002 13:05
To: Sip-Implementors
Subject: [Sip-implementors] phone number to be contacted at


Hi!
I have asked similar question before but I did not get an
answer so I will
try again.

When an useragent calls through a gateway out to the PSTN it
will send a sip
address with user@host in the From header field (the same
address it used to
register itslef with), What header field could be used if the
UA would like
to send its phonenumber, so that it can be displayed to the
called party.

Thanks and Regards
Maria



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