Re: [sipcore] 4244bis and privacy

["Ian Elz" <[e-mail]>]

Mary,

I am a little concerned about one answer that you gave:


If you have a Privacy header with a value of "none" and a H-I entry with
Privacy header parameter with value "history" what is the privacy of the
individual H-I entry?
[MB] We did not explicitly address the "none" in RFC 4244, but the
general statement is the privacy headers at the request level override
any at the hi-entry level. [/MB]
 
This means that if privacy is required for an individual H-I entry but
the originating user included "Privacy:none" in the request then there
is no option to include the real URI in the H-I entry.

This occurs as RFC3323 states in section 4.3: "However, if the Privacy
header value of 'none' is specified in a message, privacy services MUST
NOT perform any privacy function and MUST NOT remove or modify the
Privacy header."

The only option for an intermediate node including a H-I entry where
"Privacy:none" is specified and privacy for the H-I URI is required is
to include an anonymous entry or not include the H-I entry.

In your previous response you stated that we would violate RFC3323 if we
specified additional behaviour for privacy explicitly stated with a URI
-n the H-I entry. I don't believe that this is the case as RFC3323 only
considered privacy in a two party scenario and did not consider third
party identities being included in a message between two parties. H-I is
not the only case where this occurs as the Referred-By header when
included in the INVITE (or other request) which results from the REFER
has the same issue.

RFC4244 was the first time that there was a recognition that privacy for
these individual third party identities may be required. To allow this
explicit statement of privacy to be overridden by a generic statement
which is applicable to a different user is counterintuitive.

The original Privacy header is usually included by or on behalf of the
originating user and should not be allowed to specify the privacy of the
original called user, e.g. the 800 number, and prevent this identity
being presented if this user does not have the same level of privacy.

The real issue with the 800 scenario is as you have stated is that the
answerer will not know the original called identity and will not be able
to correctly handle the call. As more generic call centres are used
which will answer calls on behalf of many different organizations using
CTI and the original called identity to have to implement a generic
system asking the caller who he originally called appear unprofessional,
is inefficient and unproductive.

We have an opportunity to allow presentation of specific identities and
to solve this particular problem so we should take it.

I hope that we can get some wider discussion on this issue so a more
general consensus can be obtained.

Regards

Ian



-----Original Message-----
From: Mary Barnes [mailto:[e-mail]] 
Sent: 24 June 2009 17:27
To: Ian Elz
Cc: Christer Holmberg; Hans Erik van Elburg; Shida Schubert;
[e-mail]; Francois Audet
Subject: RE: 4244bis and privacy

Hi Ian,

Responses inline below [MB].

Mary. 

-----Original Message-----
From: Ian Elz [mailto:[e-mail]]
Sent: Wednesday, June 24, 2009 10:37 AM
To: Barnes, Mary (RICH2:AR00)
Cc: Christer Holmberg; Hans Erik van Elburg; Shida Schubert;
[e-mail]; Audet, Francois (SC100:3055)
Subject: RE: 4244bis and privacy

Mary,

I was not proposing that we change the handling of H-I which is based
upon local policy. If that causes an issue for a network operator then
they can modify their local policy accordingly or arrange with the proxy
vendor to modify their equipment to be more flexible with regards to
policy.

Can you clarify for me:

If you have a Privacy header with either "session" or "header" doe this
impact the H-I entries or will only a value of "history" impact the H-I
entries?
[MB] Yes, both "session" and "header" level privacy, consistent with RFC
3323, mandate that entries be anonymized or dropped, with the latter
being the recommendation for "session" level privacy. RFC 4244 mandated
that they be dropped and 4244bis recommends they be anonymized. The
original intent for the value of "history" was for the tagging of the
individual entries, but you end up getting the header level
functionality as well. [/MB] 

If you have a Privacy header with a value of "none" and a H-I entry with
Privacy header parameter with value "history" what is the privacy of the
individual H-I entry?
[MB] We did not explicitly address the "none" in RFC 4244, but the
general statement is the privacy headers at the request level override
any at the hi-entry level. [/MB]

>From reading RFC4244 a Privacy header with value "history" will
effectively make all H-I entries private and there is currently no
option to  include a H-I Privacy header parameter with value "none".
[MB] Correct, per my comment above. [/MB]

H-I at present allows the inclusion of Privacy header parameters to
explicitly express privacy for an individual H-I entry but a single node
which includes a header "Privacy: history" makes all H-I entries private
even if this is not the requirements for the specific URI.
[MB] Correct, but the only node that should add the header is a node
which is responsible for the domain associated with the Request URI in
the incoming request or is authorized to do so. [/MB]

I will admit that having worked in a telephony environment for a long
time I am used to having privacy of identities set on a per number basis
and the relative inflexibility of the IETF Privacy header is relatively
restrictive as to specifying which identities may be presented and which
not.
[MB] Yes, this is an entirely different paradigm.  I developed telephony
s/w for over a decade and this is entirely different - it provides a lot
more flexibility, which makes things far, far less deterministic than
what you have in telephony switches where your routing and translations
are configured for the most part, with just a few capabilities for
controlling the privacy and it's a closed network.  

With RFC4244/4244bis, there MUST be a mechanism at the UAS or end
application that can handle a request that doesn't have the appropriate
information either because nodes didn't support History-Info or some
random node in the network applied privacy (which I think is highly
unlikely) - this is normative per section 5 of RFC 4244.  So, the worst
case scenario I see for this 800 service  (which will get to the right
UAS but without the exact 800 number that was dialed) is that it goes to
a default ACD group/customer service agent, etc. who then needs to
gather the appropriate information and in my experience this is often an
IVR system these days.  So, the service is not broken when privacy is
applied in an undesireable manner, it's just not optimal.  This is
something that should be addressed in the target-uri draft which has all
the details of how specific services use History-Info.
One other thing to consider is that most networks that are emulating
telephony type features use B2BUAs, which follow the UAS/UAC rules for
the header rather than the proxy rules, noting that the UAC can set the
Privacy header to whatever value it sees as appropriate for the request.
[/MB]


Regards 

Ian

-----Original Message-----
From: Mary Barnes [mailto:[e-mail]]
Sent: 24 June 2009 15:48
To: Ian Elz
Cc: Christer Holmberg; Hans Erik van Elburg; Shida Schubert;
[e-mail]; Francois Audet
Subject: RE: 4244bis and privacy

Hi Ian,

I do not believe we should do the "override" behavior as I think that
violates RFC 3323, as the "history" is really a subset of the cases
whereby a UAC or proxy would add "session" or "header" to the request.
And, the latter two cases have the same (undesireable) result.   I agree
this impacts your services, but we can't mandate that proxies provide
information that might violate their local policies and indeed a proxy's
local policies can result in the information being anonymized (or
removed if they can't anonymize) even in the "none" case. 

I do believe it's reasonable that we strongly recommend that the request
level (versus specific hi-entries) not be used and if it is used, the
consequence is that some services will not have the information they
need - this was the gist of my previous response (to which I did not get
any additional feedback). Now, we could add some text that the "none"
case SHOULD be used (e.g., added by first hop proxy) if it is desired
that the information not be subject to privacy restrictions. I do not
think it is then particularly useful to add logic around the proxy then
being able to tag the entries within their domain as subject to privacy.
I think that conflicts with the intent of the request level "none".
However, as I mention above, per the current text, a proxy can (based on
local policy) remove entries - so a proxy can capture hi within their
domain and not forward any of that information to the next hop in
another domain - you already have that functionality.  But, I think this
introduces the general problem that you might be impacting other
services further down the line, which I thought was the problem you were
wanting to solve - not specifically your example service but, for
example, in the case that someone is debugging and they want the entire
history, so depending upon the service, this is also undesirable
behavior.  


Regards,
Mary. 

-----Original Message-----
From: Ian Elz [mailto:[e-mail]]
Sent: Wednesday, June 24, 2009 2:57 AM
To: Barnes, Mary (RICH2:AR00)
Cc: Christer Holmberg; Hans Erik van Elburg; Shida Schubert;
[e-mail]; Audet, Francois (SC100:3055)
Subject: RE: 4244bis and privacy


 Mary,

[I have added the list to this thread for wider comment.]

In the previous discussions I commented that in RFC4424 that a Privacy
header with value "history" effectively makes all H-I entries private
with the result that the H-I entries may be removed.

There has now been a comprehensive discussion on indication of the
initial 'target' to the final recipient for call handling purposes.

The main use case related to a freephone example where the answering
location may be a call centre where the original freephone number may be
required for correct call handling.

If you now consider the following example (modified from Francois' text
in the latest draft - excuse any errors that I may have inserted)

INVITE sip:sip:[e-mail];user=phone;p=x
Privacy: history
History-Info:
<sip:[e-mail];user=phone;p=x>;index=1;rt;aor         (1)
History-Info: <sip:[e-mail]>;index=1.1;mp;aor
(2)
History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc
(3)

In this case due to the Privacy header all of the H-I entries are
considered private and the [phone] will not be delivered to the
final destination with the result that call handling may not be correct.
The Privacy header may have been inserted by any of the nodes which
routed the message and inserted a H-I entry.

If however the H-I was allowed to include a header parameter of
"?Privacy=none" in the H-I entry and that an explicit H-I entry privacy
value would be considered to have precedence over a Privacy header with
a value of "history" then the mapping of the [phone] could be
explicitly specified as not private and may be passed on.

Thus when the mapping from sip:[e-mail] to
sip:[e-mail] when H-I entry (2) above is included could
also insert the Privacy header parameter in H-I entry (1).

Thus the message would appear as follows:

INVITE sip:sip:[e-mail]; user=phone;p=x
Privacy: history
History-Info:
<sip:[e-mail]?Privacy=none;user=phone;p=x>;index=1;rt;ao
r
History-Info: <sip:[e-mail]>;index=1.1;mp;aor
History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc

This would result in all the H-I entries except (1) being considered
private with the result that the =1800... Number is passed for call
handling purposes.

This change is backward compatible with the existing implementation as
any node using the existing functionality as defined in RFC4244 will
continue to be supported.

The alternative is to remove the ability to include the value "history"
in the Privacy header and only allow this value in the Privacy header
parameter. This alternative is not backward compatible.

Without this change a single node in the message path which includes a
header "Privacy: history" will prevent delivery of the aor and thus
prevent proper call handling.

Ian Elz



-----Original Message-----
From: Christer Holmberg
Sent: 23 June 2009 19:40
To: 'Mary Barnes'; Francois Audet; Hans Erik van Elburg; Shida Schubert
Cc: Ian Elz
Subject: RE: 4244bis and privacy

 
Hi,

I include Ian, so he can comment to your resposne himself.

Regards,

Christer


-----Original Message-----
From: Mary Barnes [mailto:[e-mail]]
Sent: Tuesday, June 23, 2009 9:40 PM
To: Christer Holmberg; Francois Audet; Hans Erik van Elburg; Shida
Schubert
Subject: RE: 4244bis and privacy

Here was the thread of response and the last comment was from Ian that
he would consider the response:
http://www.ietf.org/mail-archive/web/sip/current/msg26948.html

And, there was not agreement on the "none" but rather to qualify the
SHOULD NOT forward.  However, in the sipcore-4244bis-00, rather than
changing the text such that the headers SHOULD be removed, we recommend
that they be anonymized (in section 4.3.3.3.1).  That is entirely
consistent with RFC 3324 and thus we have removed the recommendations to
remove the headers entirely. However, that changed never got done in
section 3.2, so we would need to change this:
   "Thus, the History- Info header
   SHOULD NOT be included in Requests where the requestor has indicated
   a priv-value of Session- or Header-level privacy."

But, I'm really beginning to be of the mindset that we should just
remove all the subsections of section 3 (i.e., leave the text in the
upper level section), so we don't have to keep worrying about
consistency.

So, lets either fixt the text in 3.2 or remove altogether and then I
think we are really at the point of needing to submit this version so
folks that actually have an interest in it can review the updated
document. 

Mary. 

-----Original Message-----
From: Christer Holmberg [mailto:[e-mail]]
Sent: Tuesday, June 23, 2009 1:10 PM
To: Barnes, Mary (RICH2:AR00); Audet, Francois (SC100:3055); Hans Erik
van Elburg; Shida Schubert
Subject: 4244bis and privacy


Hi,

Below is a comment/proposal which one of my collegues (Ian Elz) gave on
the list a while ago, when the first version of 4244bis was submitted,
but was not incorporated. Do you think it would be useful?

-------

While the HI approach to target may solve the problem of being able to
deliver the target URI to the final destination there is no guarantee
that it will actually be delivered.

The problem arises with how Privacy is defined for HI.

4424 defines a new Privacy value "history" which may be placed in either
the Privacy header or as a header parameter to the HI entry.

If one node uses the former option "Privacy: history" then this will
make all headers private and will result in all HI entries being removed
or made anonymous when the message containing the HI is delivered to the
user.

There is a simple solution to this and that is to also allow the use of
the "none" Privacy value as a header parameter in the HI entry. This
would explicitly state that no privacy is required to the HI entry and
this would override a "history" value in the Privacy header.

I pointed this out to Mary when the 4424bis draft was first published
but the change has not been made in the latest draft.

The change is backward compatible and would not cause an issue with any
existing implementations.

------

Regards,

Christer