Subject: [Sip] Location-conveyance: ISSUE #2 - emergency calls

From: "Drage, Keith \(Keith\)" <[email-masked]>
Date: Fri, 27 Apr 2007 02:32:48 +0200

(As SIP WG chair)

During the review of the WGLC comments, we have identified some issues
where we need consensus calls on the list. These are in one call per
message.

There is an amount of text (primarily section 6) within
draft-ietf-sip-location-conveyance related to emergency calls. It is
proposed to remove this text on the basis that there are charter items
within the IETF ECRIT working group that fully specify this application
of location conveyance to this particular purpose. The editor's will
make sure that all the removed text is reflected in appropriately in the
concerned ECRIT documents.

We will assume that this removal represents WG consensus unless we hear
otherwise from the WG in 7 calendar days from the posting of this
message.

Regards

Keith

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---

From: Ted Hardie <[email-masked]>
Date: Thu, 26 Apr 2007 20:52:29 -0700

>concerned ECRIT documents.

I don't think we can answer this question without the actual bits to
be removed.  Can you cite in more detail?

I'd also like to point out that section 6 has a number of  elements
where the baseline assumption of SIP and ECRIT may differ.  This,
for example:

    Thus S/MIME protection of location MUST NOT
   be used.  TLS protection of location SHOULD be used, however, if
   establishment of the TLS connection fails, the call set-up
   operation, including location conveyance, MUST be retried without
   TLS.

The context in SIP and the larger document here makes it clear
that "S/MIME protection of location" means encrypting the location,
rather than signing it.  But location signing is a topic of interest to
ECRIT, and the resulting baseline assumptions may be different.
Increased clarity on exactly what is meant will hopefully result,
but remember this will end up in some document with a bunch of
other context to it.

I also believe that this section:

  Both the "retransmission-allowed" and "routing-query-allowed" SHOULD
   be set to "yes".  Querying for routing may be performed by proxies
   providing a routing service for emergency calls even if
   retransmission-allowed or routing-query-allowed is set to "no" or is
   not present.  Proxies routing on the location MUST set the
   "message-routed-on-this-uri" parameter.

would have to be substantially re-written to fit into phonebcp (presuming
that is where it lands).  To make sense there, I believe it would have to repeat
context from location-conveyance (even with the existing normative
reference).  That's always an invitation to things getting out of synch
in the future, and has to be considered.

Put another way, I don't think you're going to be able to just shift
the text en masse and be done.
			
			regards,
					Ted

---

From: Richard Barnes <[email-masked]>
Date: Fri, 27 Apr 2007 11:40:30 -0400

Ted,

I think the proposal was to remove Section 6 entirely, and any other 
bits of emergency-specific text elsewhere, from the location conveyance 
document to phonebcp/framework.  In terms of the other bits, I only see 
two non-normative mentions after a brief scan:
-- Last paragraph of Section 1
-- Last sentence of Section 4.3

Hope this helps to clarify,
--Richard

---

From: Ted Hardie <[email-masked]>
Date: Fri, 27 Apr 2007 10:38:32 -0700

At 11:40 AM -0400 4/27/07, Richard Barnes wrote:
>Ted,
>
>I think the proposal was to remove Section 6 entirely, and any other bits of emergency-specific text elsewhere, from the location conveyance document to phonebcp/framework.  In terms of the other bits, I only see two non-normative mentions after a brief scan:

So, this text:

   In this document, we frequently refer to the "emergency case".  This
   refers to a specific, important use of sip location conveyance where
   the location of the caller is used to determine which Public Safety
   Answering Point (PSAP) should receive an emergency call request for
   help (e.g. a call to 1-1-2 or 9-1-1).  This is an example of
   location-based routing.  The location conveyed is also used by the
   PSAP to dispatch first responders to the caller's location.  There
   are special security considerations which make the emergency case
   unique, compared to a normal location conveyance within SIP.

>-- Last sentence of Section 4.3

The last sentence of this:

   A location recipient would need to dereference the sips-URI in the
   Geolocation header to retrieve Alice's location.  If the
   atlanta.example.com domain chooses to implement location conveyance
   and delivery in this way (i.e. location-by-reference), it is
   RECOMMENDED that entities outside this domain be able to reach the
   dereferencing LIS server, otherwise this model of implementation is
   only viable within the atlanta.example.com domain.  This will likely
   not suit some services already being considered in the IETF at the
   time of this writing, such as emergency calling.

And section 6, which I talked about in my first message.

Having reviewed this again, I don't believe that it is appropriate to
remove the text in Section 1, since the emergency use case was and
is an important driver for both location based routing and location
conveyance.  Removing that context doesn't help the reader.  An
additional pointer there to the ECRIT documents and a statement
that the full context is in them might be valuable as a way of pointing
out that the location-conveyance draft will not provide that.

I think much the same is true for the last sentence in 4.3; replacing
it with a statement like "For special considerations relevant to
dereferencing location in emergency call situations, see [CITATION]"
would be better.

I believe the issues in Section 6 could be covered in the ECRIT phonebcp
document, but I continue to believe that they will need to be re-written
to fit into that document.

I assume that any change to this text will require an update to the
Security Considerations, which currently have this:

    UAC implementations MUST make such capabilities
   conditional on explicit user permission, and SHOULD alert a user
   that location is being conveyed.  Emergency calls have their own
   rules in this regard, as detailed in Section 6.  Proxies inserting
   location for location-based routing are unable to meet this
   requirement, and such use is NOT RECOMMENDED.  Proxies conveying
   location using this extension MUST have the permission of the target
   to do so. 

				regards,
					Ted Hardie

---

From: "Brian Rosen" <[email-masked]>
Date: Fri, 27 Apr 2007 14:29:05 -0400

See In line

> be removed.  Can you cite in more detail?
We'll make a list as we go through the text, but the goal is to remove any
reference to emergency call.

> but remember this will end up in some document with a bunch of
We will rewrite this text to discuss the general issue of security in
location based routing while not having any specific text that is peculiar
to emergency calls.

We would then have in ecrit documents specific advise for emergency call use
of location conveyance.

> in the future, and has to be considered.
I would prefer to rewrite this text to better work in generalized location
based routing, and then have minimal additional text in ecrit documents that
expand on that.

The "Querying for routing..." sentence can reasonably be rewritten in ecrit
documents.  The other two sentances in the cited text probably should remain
as general advice for any location based routing scenario.

> the text en masse and be done.

Well, do you agree with the principal, while reserving the right to comment
on the specifics?

---

From: "Brian Rosen" <[email-masked]>
Date: Fri, 27 Apr 2007 14:39:31 -0400

In line

>    unique, compared to a normal location conveyance within SIP.
We will rewrite this text to say that emergency call routing is a use case
for this document.  Something like:
  A specific, important use of sip location conveyance is in emergency 
  calls (citizen to authority, for example a call to 1-1-2 or 9-1-1) where
  the location of the caller is used to determine which Public Safety
  Answering Point (PSAP) should receive an emergency call request for
  help.  This is an example of location-based routing.  The location 
  conveyed is also used by the PSAP to dispatch first responders to the 
  caller's location.
>    time of this writing, such as emergency calling.
I think we should leave this.

> dereferencing location in emergency call situations, see [CITATION]"
I'd rather not have a normative reference to ecrit documents hold up this
document.

> to fit into that document.
Yes, of course

>    location using this extension MUST have the permission of the target
Yes, a rewrite of this text is in order

---

From: Ted Hardie <[email-masked]>
Date: Fri, 27 Apr 2007 12:16:58 -0700

>I'd rather not have a normative reference to ecrit documents hold up this

Well, if the dereferencing model is different for emergency services than
for the other uses covered in 4.3 and you expect someone to understand
both in order to deploy this, I think your choices are repeat the considerations
here or put in a pointer.  I don't really see that this can be an informative
reference, since you have to follow it in order to get the deployment
right for the relevant use case.

				regards,
					Ted Hardie

---

From: Hannes Tschofenig <[email-masked]>
Date: Sat, 28 Apr 2007 09:54:40 +0200

Hi Ted,

> be removed.  Can you cite in more detail?
I would imagine that at least Section 6 "Special Considerations for 
Emergency Calls" would go away.
Additionally, the security consideration section might also be affected.

> the text en masse and be done.

I agree that a simple copy-and-paste operation from the SIP Location 
Conveyance document to the Phone BCP is not sufficient.

I do, however, believe that it is better not to speak about emergency 
services in this document since we already have the Phone BCP. With the 
same argument I would like to remove Section 5.3 "Emergency Shape 
Representations" from draft-ietf-geopriv-pdif-lo-profile-06.txt.

Ciao
Hannes