Subject: [Sipping] calling number blocking at sip/isup gateway

From: Juha Heinanen <[email-masked]>
Date: Wed, 23 Jan 2002 20:14:20 +0200

i didn't find from draft-ietf-sipping-isup-00.txt, how should sip
originated invite look like in order to prevent the called pstn party
from seeing the calling sip party's number in the from field of the
invite.

can a proxy add something to the invite on behalf of the calling sip
user in order to get the calling number blocked by the sip/isup gw?

-- juha

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From: Dean Willis <[email-masked]>
Date: Wed, 23 Jan 2002 22:59:26 -0600

I suggest that if you don't want your From field displayed as a phone number, 
set it to something like "anonymous".

--
Dean

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From: Juha Heinanen <[email-masked]>
Date: Thu, 24 Jan 2002 07:54:56 +0200

Dean Willis writes:

 > I suggest that if you don't want your From field displayed as a phone
 > number, set it to something like "anonymous".

won't work, because pstn needs to know the actual from number.  there
needs to be something in the sip headers that tells the sip/isup gw that
when this call is routed to the pstn, presentation of the calling party
number will be "restricted".  further, it must be possible for the proxy
to add this "something", where proxy is not allowed to touch the from
field.

-- juha

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From: "Dean Willis" <[email-masked]>
Date: Thu, 24 Jan 2002 01:02:28 -0600

The PSTN isn't allowed to know my phone number when I don't want it
displayed. In fact, I may not even HAVE a phone number. For example, I place
calls quite frequently from my SIP phone through a PSTN gateway. Try
translating [email-masked] into a phone number . . .

Although from what you're saying, I suspect you would be more satisfied with
the approach in the "privacy" draft, which for some reason assumes that
non-local proxies can be trusted to protect confidential information. See
draft-ietf-sip-privacy. In this methodology, one would use the
remote-party-ID as the source of the calling-party identifier, and use the
"privacy" header value to populate the presentation flag. Scares me badly.

--
Dean

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From: Juha Heinanen <[email-masked]>
Date: Thu, 24 Jan 2002 10:07:10 +0200

> translating [email-masked] into a phone number . . .

i'm quite sure that in that case your calling number will be a number of
your gateway.  my understanding is that the laws and accounting require
pstn to always have a calling party number.  now the question just is,
will this number be displayed to the called number or is displaying of
the number restricted.

the reason why i wan't the proxy to be able to restrict the display is
local law here in finland that gives the caller the right to ask the
phone company not to diaply the calling number even if callers terminal
is so stupid that it can't ask it itself or the caller so lazy that he
doesn't want to configure his terminal to do so.

by the way, i would not blame the caller fro lazyness if he doesn't read
the privacy i-d, since it is pretty complicated document.  i'll try to
read it again and figure out what i must do, if my sip customer asks for
non-display of his number.  what i need to do may depend on if the call
gets routed to another sip phone or to pstn.  so i'm back to square one,
i.e., still don't know how to interpret the privacy i-d.

-- juha

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From: Dean Willis <[email-masked]>
Date: Thu, 24 Jan 2002 02:32:15 -0600

> i.e., still don't know how to interpret the privacy i-d.

Well, that's a darned good question, considering that we're basically in the 
process of last-calling the privacy draft in the SIP WG. If this part of it 
doesn't make sense to a casual reader, we may have an issue with the draft. 
Please feel free to make suggestions on clarifying anything that needs it.

Actually, I'm considering making a couple of suggestions on improving the 
utility of the draft, such as allowing for the representation of multiple 
identities, and providing transitive "vouching" for an 
authenticable/authenticated identity.  

Perhaps we need also to consider a means of distinguishing a specific 
identity as the preferred e.164 number so that gateways know which identity 
to map into ISUP. 

--
Dean

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From: Juha Heinanen <[email-masked]>
Date: Thu, 24 Jan 2002 19:26:30 +0200

> "privacy" header value to populate the presentation flag. Scares me badly.

ok, i tried again and still can't figure out how my proxy can tell to a
trusted sip/isup gw that the calling user doesn't want his/her phone
number to be shown to the called pstn user.  i would like to be able to
do something simple in the proxy, like adding a header

Anonymity: from

to the invite, but that kind of thing is not available.  my suggestion
is that the authors of the privacy i-d and the sip-isup i-d figure it
out how to map isup Calling party indicator "Address presentation
restricted" to/from sip.  before that is done, i would not vote going
forward with either i-d.

-- juha

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From: Flemming Andreasen <[email-masked]>
Date: Thu, 24 Jan 2002 12:53:03 -0500

Juha Heinanen wrote:

> number to be shown to the called pstn user.

You simply include "privacy=uri" with that Remote-Party-ID, e.g

        Remote-Party-ID: "John Doe" <sip:[email-masked]>;party=calling;
                            id-type=subscriber;privacy=uri;screen=yes

>  i would like to be able to
> to the invite, but that kind of thing is not available.

The Anonymity header currently only controls IP-address privacy. What you want is
privacy for the Remote-Party-ID information, so you simply add the corresponding
privacy indication to the Remote-Party-ID in question.

>  my suggestion
> restricted" to/from sip.

See above - you can already do it.

-- Flemming

> before that is done, i would not vote going
> forward with either i-d.
>
> -- juha
>

--
Flemming Andreasen
Cisco Systems

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From: Juha Heinanen <[email-masked]>
Date: Thu, 24 Jan 2002 21:03:19 +0200

>                             id-type=subscriber;privacy=uri;screen=yes

in this example, the sip/isup gw will use one of its own phone numbers as
the calling party number and that number needs privacy, not the original
from uri sip:[email-masked].  

in this application i don't care what the from url actually is.  why do
i still need to include it in the Remote-Party-ID?  to me it is
redundant information.  what happens if Remote-Party-ID doesn't match
the from irl? that is why i feel that this is an overkill.

-- juha

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From: Flemming Andreasen <[email-masked]>
Date: Thu, 24 Jan 2002 14:12:15 -0500

> from uri sip:[email-masked].

Fine - just use the gw number instead then.

> i still need to include it in the Remote-Party-ID?

You do not necessarily include the From URL in the Remote-Party-ID. What you
include is identity information for the calling party which may or may not be
the same (if you want privacy, you obviously don't include your real identity
in the From header field, since the From header field cannot be changed). You
can put anyting you want in a From URL, but not in a Remote-Party-Id.

> to me it is
> the from irl?

Nothing since there is no such requirement. In fact, if you have requested
privacy, you are almost guaranteed that the two will be different.

-- Flemming

> that is why i feel that this is an overkill.
>
> -- juha

--
Flemming Andreasen
Cisco Systems

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From: Juha Heinanen <[email-masked]>
Date: Thu, 24 Jan 2002 21:28:21 +0200

> Fine - just use the gw number instead then.

but my proxy that would need to insert the Remote-Party-ID on behalf of
the UA, doesn't know what the gw number will be.

 > privacy, you are almost guaranteed that the two will be different.

i'm talkigng about the case where the UA doesn't understand the privacy
stuff (like no UA that i have seen doesn't) and i have to in the proxy
indicate the privacy requirement to the isup gw.  then the from field
will include the real calling party number and the addr-spec in the
Remote-Party-ID has no function.

-- juha

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From: Flemming Andreasen <[email-masked]>
Date: Thu, 24 Jan 2002 15:02:13 -0500

> the UA, doesn't know what the gw number will be.

Are you simply talking about the sip/isup gw simply inserting it's own phone
number in the ISUP message ? If so, I'm not sure why we are talking about SIP or
the privacy draft for that matter.

> Remote-Party-ID has no function.

In this specific scenario, where you assume that the From header field can be
trusted and the message will never be forwarded to an untrusted entity, then yes,
you can argue that there is redundant information present. That's the price you
pay for using something that's a little more generic and hence applicable to more
scenarios than exactly what you are describing (some people would like it to be
much more generic). There's always a trade-off here, however I dont' see a problem
in this case.

-- Flemming

--
Flemming Andreasen
Cisco Systems