There are two cases:
The gateway is part of an enterprise telephony system
The gateway is part of a service provider's internal network
Considering each of them separately:
When the gateway is part of an enterprise telephony system,
then the line that the gateway is connected to has a phone
number. The PSTN will put this number in the CallerId field.
It doesn't matter what the UA sends. This is what James said.
When the gateway is part of service provider's internal network,
the PSTN will most likely assert an identity using one of the
mechanisms that are in process now (P-Asserted-Identity). It
doesn't matter what the UA tries to do with its fields, the identity
must be what the service provider asserts.
There is a complication to the first case, which is where there
is a PRI or CAS trunk. In this case the gateway needs to assert
a number which would be within the range(s) of the numbers
assigned to the trunk. Here there is the exact problem
you are worried about -- the gateway needs to know the phone
number to assert on the trunk. Our current solution is a B2BUA that
rewrites the From, mapping a user name to a phone number.
Brian
> -----Original Message-----
> From: Maria Yndefors [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, December 19, 2002 8:57 AM
> To: Sip-Implementors
> Subject: RE: [Sip-implementors] phone number to be contacted at
>
>
> 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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