Subject: RE: [Ecrit] Issue 30: Requirements regarding Emergency Identifiers

From: "Stark, Barbara" <[email-masked]>
Date: Wed, 18 Jan 2006 13:31:53 -0600

My recommendation for emergency IDs would be that only recognition of
the "home" emergency number(s) and the global SIP URI is required (MUST
or SHALL), for UAs. For dialing plans intended to be local in the US,
this would include 911. Dialing plans that are local in an EU country
would include 112. I do not believe, however, that a US dialing plan
must include 112 as an emergency ID, in all VoIP scenarios. 

As I look at some of our potential hosted enterprise implementations,
3-digit extension dialing is a supported option. I do not believe that
it is reasonable to restrict enterprises in the US from ever using "112"
as an extension, just because it is the EU emergency number.

If ecrit wants to recommend that UAs SHOULD recognize 911 and 112 or any
of the others, that would probably be ok. But not MUST or SHALL.

While it may be useful to provide a means (DNS, etc.) of sending a VoIP
end device local emergency numbers, I, personally, would not trust the
behavior of such a device in handling those numbers and would prefer
that any device I was using not make use of such information.
 - Does the device incorporate this info into its dialing plan, or does
it examine the digits, once it determines the last digit has been
entered (e.g., timeout, matched dial string, "#", or user pressed
"send")?
 - If the device does not incorporate the local emergency number(s) into
its dialing plan, how do I know there isn't something in the dialing
plan that would prevent the emergency number from ever being dialed?
 - If the device does incorporate the local emergency number(s) into its
dialing plan, does it put them at the beginning or the end?
 - If it places them at the beginning, how do I know there isn't now a
part of my regular dialing plan that I can no longer call?
 - If it places it at the end, how do I know there isn't a part of my
regular dialing plan that will keep the emergency number from being
dialed?

I have a colleague with a son who lives in Australia. The son maintains
a VoIP account from a US VoIP provider. The son does this so that he can
call US destinations (such as his father) for just the monthly cost of
the account. He does NOT expect or want to use an Australian dial plan
from this phone, and he knows that today he cannot use it to call for
emergency services. One aspect of many US dial plans is that "00" is
used to indicate the caller wants to be routed to an international
operator. No other digits are expected after "00", so the VoIP device
can be set to immediately recognize the string after the 2nd "0", and
send the SIP Invite. The emergency number there in Australia is "000".
Under the existing dialing plan defined in the ATA, "000" can never be
dialed. If this ATA claimed to support being sent (e.g., DNS) local
emergency numbers, I would not be able to predict its behavior when
trying to dial "000", unless there were some very detailed rules
written.
---------------------------------------------------
On a slightly different note relating to emergency IDs, I think the
overall solution needs to accept that location-aware VoIP end devices
may be improperly configured (possibly by the end user playing around
with things), and may not recognize emergency numbers, and therefore
would not attach the location. In this case, the proxy would recognize
the emegency number. My reading of current expectations is that the VoIP
service would then use sort of a "best guess" of the user's location
(e.g., a saved emergency address on file). It might be useful to
recommend that a server which recognizes an emergency call should send
the VoIP end device a request for location (OPTIONS request?), just in
case the device does know the location, but didn't know it was an
emergency call.

Barbara

Barbara Stark
BellSouth Science & Technology

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From: Henning Schulzrinne <[email-masked]>
Date: Wed, 18 Jan 2006 16:56:53 -0500

> case the device does know the location, but didn't know it was an

Unfortunately, this clearly has privacy implications. How do you prevent 
  any party I might be calling from sending a "send me your location" 
request?