One document matched: draft-rosen-ecrit-premature-disconnect-rqmts-00.xml

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<front>
    <title abbrev="Abandoned Call/PrematureDisconnect">
       Requirements for handling abandoned calls and premature disconnects in emergency calls on the Internet
    </title>
    <author fullname="Brian Rosen" initials="B.R" surname="Rosen">
      <organization>NeuStar</organization>

      <address>
        <postal>
          <street>470 Conrad Dr.</street>
          <city>Mars</city>
          <region>PA</region>
          <code>16046</code>
          <country>US</country>
        </postal>
        <phone>+1 724 382 1051</phone>
        <email>br@brianrosen.net</email>
      </address>
    </author>
    <date month="July" day="28" year="2008" />
    <area>RAI</area>
    <workgroup>ecrit</workgroup>
    <keyword>I-D</keyword>
    <keyword>Internet-Draft</keyword>
    <keyword>geopriv</keyword>
    <keyword>location</keyword>
    <abstract>
      <t>
The -phonebcp draft currently requires endpoints to disable sending a BYE on an emergency call.  Insufficient justification
and lack of attention to the entire problem has caused comment on that section of the document.  This document attempts to define the
problem and the requirements to controlling disconnect on emergency calls.
      </t>
    </abstract>
</front>
<middle>
 
<section title="Problem Statement">
<t><xref target="I-D.ietf-ecrit-phonebcp"/> currently disallows sending of BYE by the calling UA.  This requirement has generated a request for
additional capability, and has also caused some to question why it is needed, and how the mechanisms interact with current and future 
emergency call systems.  There are two aspects of handing emergency calls that give rise to the discussion.</t>
<section title="Premature disconnect">
<t>Occasionally, when on an emergency call, a caller hangs up the call before the call taker is finished acquiring enough 
information. Emergency calls are stressful, and mistakes are easily made. A mechanism is needed to re-establish communication 
between the caller and the call taker when this happens. The PSTN has a feature available, "Called Party Hold" which is used 
in some jurisdictions to meet this requirement. When CPH is engaged, if the user hangs up, the call is not torn down, 
but instead is maintained despite the "on hook" condition. The call taker has a mechanism (called "Ringback" which is different 
than call-back) to ring the user's telephone. If the handset is picked up, since the call is still active and resources 
maintained, the caller and the call taker are readily reconnected. Called Party Hold is a feature that has long been 
available in wireline networks, but is not currently implemented in wireless networks.  Some jurisdictions are desirous 
of maintaining the current PSAP call disconnect control capability, while other jurisdictions would like to gain 
access to those capabilities. Still, in other jurisdictions, the function may not be needed or desired.</t> 
</section>
<section title="Abandoned Call">
<t>It is not uncommon for an emergency call to be cancelled before it reaches a call taker. Abandoned, in this context, 
means that the call is terminated before the call taker answers it.  While it can be that the user is fully aware that 
the call is being cancelled, and considers the cancellation the most appropriate solution, abandoned calls are problematic 
to PSAPs because they don't know why the call was abandoned. Unfortunately, what looks like an abandoned call 
can be a more serious circumstance such as a hostage situation. In some jurisdictions, the PSAP dispatches a police unit 
to all logged abandoned calls.  In such jurisdictions, dispatch could be avoided for true inadvertent calling 
if the call went through, and the call taker was able to assess the actual situation. Other jurisdictions do not have the 
resources and may not respond to abandoned calls at all. Sometimes, application of the function depends on conditions.
For example, in a mass calling event, an Interactive Media Response unit may be used to answer calls.
Abandoning a call answered by a machine may be appropriate. Even if jurisdictions respond to abandoned calls by 
dispatching emergency personnel in normal situations, they may not in this situation.</t>
<t>Retaining the connection is extremely important when there is no callback information (e.g., uninitialized phone) 
or the caller has call termination features active (such as call forwarding, do not disturb) and the PSAP is unable to callback.</t> 
</section>
</section>
<section title="Requirements for Premature Disconnect">
<t><list style="hanging">
<t hangText="PD-1"> It must be possible to have the PSAP rapidly re-establish communications with a caller that 
attempts to prematurely disconnect from the call.</t>
<t hangText="  Rationale:"> Time is paramount when handling emergency calls. Keeping resources active and available 
until the call taker determines the call can be terminated saves valuable time.</t>
<t hangText="PD-2"> It must be possible for the PSAP to know when the user has attempted to prematurely disconnect</t>
<t hangText="  Rationale:"> Knowledge of the device state (and caller action) gives valuable information to the call 
taker which may influence how the call will be managed going forward.</t>
<t hangText="PD-3"> Reconnecting the caller must work reasonably reliably under congestion conditions.</t>  
<t hangText="  Rationale:"> PSAPs require robust mechanisms to perform their tasks.</t>
<t hangText="PD-4"> When PD-1 is enforced, the PSAP must be able to cause alerting at an endpoint which 
has attempted to prematurely disconnect from the emergency call</t>
<t hangText="  Rationale:"> The user believes they have disconnected.  The ability to alert is needed to 
encourage the user to reconnect.</t>
<t hangText="PD-5"> When PD-1 is enforced,the caller must not be able to place another call until the PSAP 
allows the call to be released.</t>
<t hangText="  Rationale:"> Priority must be given to the PSAP until such time the call taker determines the call can be terminated.</t>
<t hangText="PD-6"> All Media and signaling streams flowing between the caller and call taker must be maintained to the 
extent needed for rapid reconnection.</t> 
<t hangText="  Rationale:"> Media and signaling resources must be available as soon as the user re-answers.</t>
<t hangText="PD-7"> Control of premature disconnect is not needed in all jurisdictions. It must be possible to not 
invoke the function and allow premature disconnect to terminate the call as if no special features were present.</t>
<t hangText="  Rationale:"> This reflects the current situation.</t>
</list></t>
</section>
    
<section title="Requirements for Abandoned Call">
<t><list style="hanging">
<t hangText="AC-1"> It must be possible for the PSAP, or the network that serves it, to have abandoned calls complete and stay connected.</t>
<t hangText="  Rationale:"> PSAPs cannot distinguish between calls which are appropriately abandoned and calls that 
need response but were cut short. Controls to limit abandonment are needed for those PSAPs who would otherwise respond to all abandoned calls.</t> 
<t hangText="AC-2"> AC-1 shall be applied at the earliest possible time in the call establishment process.</t>
<t hangText="  Rationale:"> Disallowing call abandonment early minimizes the chances of abandoned calls.</t>
<t hangText="AC-3"> Control of abandoned call is not needed in all jurisdictions.  It must be possible to not invoke the 
function and allow calls to be abandoned as if no special features were present. Enabling or disabling must be dynamic, 
so that it can be enforced or not depending on requirements at the PSAP.</t>
<t hangText="  Rationale:"> This reflects the current situation.</t></list></t>  
</section>
    

<section title="IANA Considerations">
<t>There are no IANA Considerations for this document</t>
</section>

<section title="Security Considerations">
<t>If these features can be enabled by entities other than PSAPs, the entity may gain more control over the end device.  Failures of various
kinds may prohibit callers from being able to disconnect.</t>
</section>

<section title="Acknowledgments">
<t>
Thanks to Guy Caron, Theresa Reese, John Hearty and other members of the NENA i2.5 working group for their comments and suggestions on this draft.
</t>
</section>
  </middle>

  <back>
    <references title="Informative References">
      &draft-ietf-ecrit-phonebcp;
    </references>
  </back>
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