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Re: [Ecrit] PSAP Call Backs
Hi,
I get a bit nervous when I read SP-36, and compare it with what is desired
for users of relay services.
USA has just put regulations and technology in place for calling via relay
services to emergency services. The number that accompanies the call is
intended to be usable for call-back. The call-back MUST be taken through a
relay service, because the user need to use sign language or real-time text.
In Sweden, we have made plans and brief trials for a system with similar
goals as the one in USA, and Europe is on the same way.
The relay service is invoked in a call to the end user's number by a routing
evaluation that takes the call through a service instead of directly to the
user. It is done in one way in USA, but there are other optional ways to do
the same thing that seem to collide with the wording of som of the
requirements here.
The current wording of SP-36 can give the impression that that kind of
routing would not be allowed for the call-back.
"SP-36 Call backs to the Contact: header URI recieved within 30
minutes of an emergency call must reach the device regardless of call
features or services that would normally cause the call to be routed
to some other entity."
I see similar risks in interpretation of this requirement, where I have
picked out the dangerous requirements:
"13. Disabling of features
ED-70/SP-39 User Agents and proxies MUST disable outgoing call
features such as
--
o Call Transfer
o Three Way Call
--
when an emergency call is established. Also see ED-77 in Section 14.
ED-71/SP-40 The emergency dial strings SHOULD NOT be permitted in
Call Forward numbers or speed dial lists.
ED-72/SP-41 The User Agent and Proxies SHOULD disable the following
incoming call features on call backs from the PSAP:
--
o Call Forward (all kinds)"
--
These operations may be essential for bringing in relay services and other
kind of supporting services in the call. I have raised this question before
and got an answer that was meant to take my fears away, referring to that
this has always been so in PSTN. I am still afraid that we make a lot of
good supporting actions impossible by these statements and would like to see
them deleted.
Regarding SP-36, I suggest rewording to:
"SP-36 Call backs to the Contact: header URI recieved within 30
minutes of an emergency call must include call
features or services that would normally be included in calls routed
to the device."
----
And 39 - 40 - 41 to:
SP-39 User Agents and proxies MUST disable outgoing call features
such as
o Call Waiting
o Flash hold
o Outbound Call Blocking
when an emergency call is established. Also see ED-77 in Section 14.
SP-41 The User Agent and Proxies SHOULD disable the following
incoming call features on call backs from the PSAP:
o Call Waiting
o Do Not Disturb
I understand that there is a conflict between some traditions in this area,
and the new need for invoking supporting services, and look forward to a
discussion on what we lose and gain by the changes I propose.
Gunnar
-----Original Message-----
From: ecrit-bounces at ietf.org [mailto:ecrit-bounces at ietf.org] On Behalf Of
Tschofenig, Hannes (NSN - FI/Espoo)
Sent: Wednesday, December 31, 2008 11:21 AM
To: ECRIT
Subject: [Ecrit] PSAP Call Backs
Hi all,
In the last few months we have seen increased interest in the topic of PSAP
call backs.
Section 10 of http://tools.ietf.org/html/draft-ietf-ecrit-phonebcp-06
says:
SP-36 Call backs to the Contact: header URI recieved within 30
minutes of an emergency call must reach the device regardless of call
features or services that would normally cause the call to be routed
to some other entity.
More importantly, Section 13 says:
ED-73 Call backs SHOULD be determined by retaining the domain of the
PSAP which answers an outgoing emergency call and instantiating a
timer which starts when the call is terminated. If a call is
received from the same domain and within the timer period, sent to
the Contact: or AoR used in the emergency call, it should be assumed
to be a call back. The suggested timer period is 5 minutes.
http://tools.ietf.org/id/draft-patel-ecrit-sos-parameter-01.txt proposed
another solution based on marking the callback using the "sos" URI
parameter.
http://tools.ietf.org/wg/ecrit/draft-ietf-ecrit-local-emergency-rph-name
space/ proposes another solution by utilizing the Resource Priority Header.
So, here are my high-level questions:
A) Do you think that you understand the requirements that lead to a need for
a technical solution?
B) Do you believe that more work beyond the mechanism described in Phone BCP
is needed?
Ciao
Hannes
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