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Versions: (draft-rosen-ecrit-data-only-ea) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16

ECRIT                                                           B. Rosen
Internet-Draft                                             NeuStar, Inc.
Intended status: Experimental                             H. Schulzrinne
Expires: April 28, 2011                                      Columbia U.
                                                           H. Tschofenig
                                                  Nokia Siemens Networks
                                                        October 25, 2010


 Common Alerting Protocol (CAP) based Data-Only Emergency Alerts using
                 the Session Initiation Protocol (SIP)
                  draft-ietf-ecrit-data-only-ea-01.txt

Abstract

   The Common Alerting Protocol (CAP) is a document format for
   exchanging emergency alerts and public warnings.  CAP is mainly used
   for conveying alerts and warnings between authorities and from
   authorities to citizen/individuals.  This document describes how
   data-only emergency alerts allow devices to issue alerts using the
   CAP document format.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 28, 2011.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Architectural Overview . . . . . . . . . . . . . . . . . . . .  5
   4.  Protocol Specification . . . . . . . . . . . . . . . . . . . .  7
     4.1.  CAP Transport  . . . . . . . . . . . . . . . . . . . . . .  7
     4.2.  Profiling of the CAP Document Content  . . . . . . . . . .  7
   5.  Example  . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
     6.1.  Forgery  . . . . . . . . . . . . . . . . . . . . . . . . . 10
     6.2.  Replay Attack  . . . . . . . . . . . . . . . . . . . . . . 10
     6.3.  Injecting False Alerts . . . . . . . . . . . . . . . . . . 11
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
     7.1.  Registration of the
           'application/common-alerting-protocol+xml' MIME type . . . 12
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 14
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 15
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17























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1.  Introduction

   The Common Alerting Protocol (CAP) [cap] is an XML document format
   for exchanging emergency alerts and public warnings.  CAP is mainly
   used for conveying alerts and warnings between authorities and from
   authorities to citizen/individuals.  This document describes how
   data-only emergency calls are able to utilize the same CAP document
   format.

   Data-only emergency alerts are similar to regular emergency calls in
   the sense that they require emergency call routing functionality and
   may even have the same location requirements.  On the other hand, the
   initial communication interaction will not lead to the establishment
   of a voice or video channel.

   Based on the deployment experience with non-IP based systems we
   distinguish between two types of environments, namely (1) data-only
   emergency alerts that are targeted directly to a recipient
   responsible for evaluating the alerts and for taking the necessary
   steps, including triggering an emergency call towards a Public Safety
   Answering Point (PSAP) and (2) alerts that are targeted to a Service
   URN as used for regular IP-based emergency calls where the recipient
   is not known to the originator.  We describe these two cases in more
   detail in Section 3.



























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2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

   This document utilizes terminology introduced in
   [I-D.ietf-atoca-requirements].











































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3.  Architectural Overview

   This section illustrates two envisioned usage modes; targeted and
   location-based emergency alert routing.  Figure 1 shows a deployment
   variant where a sensor, as the author and originator of the alert, is
   pre-configured (using techniques outside the scope of this document)
   to issue an alert to a receiver or an aggregator, a special form of
   mediator, that processes these messages and performs whatever steps
   are necessary to appropriately react on the alert.  For example, a
   security firm may use different sensor inputs to dispatch their
   security staff to a building they protect.



    +------------+              +------------+
    | Sensor     |              | Aggregator |
    |            |              |            |
    +---+--------+              +------+-----+
        |                              |
     Sensors                           |
     trigger                           |
     emergency                         |
     alert                             |
        |        MESSAGE with CAP      |
        |----------------------------->|
        |                              |
        |                           Aggregator
        |                           processes
        |                           emergency
        |                           alert
        |        200 (OK)              |
        |<-----------------------------|
        |                              |
        |                              |

                Figure 1: Targeted Emergency Alert Routing

   In Figure 2 a scenario is shown whereby the alert is routed using
   location information and the Service URN.  In case the LoST
   resolution is done at an emergency services routing proxy rather than
   at the entity issuing the alert since it may not know the address of
   the receiver.  A possible receiver is a PSAP and the recipient of the
   alert may be call taker.  In the generic case, there is very likely
   no prior relationship between the originator and the receiver, e.g.
   PSAP.  A PSAP, for example, is likely to receive and accept alerts
   from entities it cannot authorize.  This scenario corresponds more to
   the classical emergency services use case and the description in
   [I-D.ietf-ecrit-phonebcp] is applicable.



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                           +-----------+                  +----------+
      +--------+           | SIP Proxy |                  | PSAP as  |
      | Sensor |           | as Relay  |                  | Receiver |
      +---+----+           +---+-------+                  +---+------+
          |                    |                              |
       Sensors                 |                              |
       trigger                 |                              |
       emergency               |                              |
       alert                   |                              |
          |                    |                              |
          |                    |                              |
          | MESSAGE with CAP   |                              |
          | (including Service URN,                           |
          | such as urn:service:sos)                          |
          |------------------->|                              |
          |                    |                              |
          |              SIP Proxy performs                   |
          |              emergency alert                      |
          |              routing                              |
          |                    |  MESSAGE with CAP            |
          |                    |  (including identity info)   |
          |                    |----------------------------->|
          |                    |                              |
          |                    |                           PSAP
          |                    |                           processes
          |                    |                           emergency
          |                    |                           alert
          |                    |        200 (OK)              |
          |                    |<-----------------------------|
          |                    |                              |
          |  200 (OK)          |                              |
          |<-------------------|                              |
          |                    |                              |
          |                    |                              |

             Figure 2: Location-Based Emergency Alert Routing















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4.  Protocol Specification

4.1.  CAP Transport

   Since alerts structured via CAP require a "push" medium, they SHOULD
   be sent via the SIP MESSAGE.  The MIME type is set to 'application/
   common-alerting-protocol+xml'.

      Alternatively, the SIP PUBLISH mechanism or other SIP messages
      could be used.  However, the usage of SIP MESSAGE is a simple
      enough approach from an implementation point of view.

4.2.  Profiling of the CAP Document Content

   The usage of CAP MUST conform to the specification provided with
   [cap].  For the usage with SIP the following additional requirements
   are imposed:

   sender:  When the CAP was created by a SIP-based entity then the
      element MUST be populated with the SIP URI of that entity.


   incidents:  The <incidents> element MUST be present whenever there is
      a possibility that alert information needs to be updated.  The
      initial message will then contain an incident identifier carried
      in the <incidents> element.  This incident identifier MUST be
      chosen in such a way that it is unique for a given <sender,
      expires, incidents> combination.  Note that the <expires> element
      is optional and may not be present.


   scope:  The value of the <scope> element MUST be set to "private" as
      the alert is not meant for public consumption.  The <addresses>
      element is, however, not used by this specification since the
      message routing is performed by SIP and the respective address
      information is already available in the geolocation header.
      Populating location information twice into different parts of the
      message can quickly lead to inconsistency.


   parameter:  The <parameter> element MAY contain additional
      information specific to the sensor.


   area:  It is RECOMMENDED to omit this element when constructing a
      message.  In case that the CAP message already contained an <area>
      element then the specified location information MUST be copied
      into the PIDF-LO structure of the geolocation header element.



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5.  Example

   Figure 3 shows a CAP document indicating a BURLARY alert issued by a
   sensor with the identity 'sensor1@domain.com'.  The location of the
   sensor can be obtained from the attached geolocation information
   provided via the geolocation header contained in the SIP MESSAGE
   structure.  Additionally, the sensor provided some data long with the
   alert message using proprietary information elements only to be
   processed by the receiver, a SIP entity acting as an aggregator.
   This example reflects the description in Figure 1.



   MESSAGE sip:aggregator@domain.com SIP/2.0
   Via: SIP/2.0/TCP sensor1.domain.com;branch=z9hG4bK776sgdkse
   Max-Forwards: 70
   From: sip:sensor1@domain.com;tag=49583
   To: sip:aggregator@domain.com
   Call-ID: asd88asd77a@1.2.3.4
   Geolocation: <cid:abcdef@domain.com>
     ;routing-allowed=yes
   Supported: geolocation
   Accept: application/pidf+xml, application/common-alerting-protocol+xml
   CSeq: 1 MESSAGE
   Content-Type: multipart/mixed; boundary=boundary1
   Content-Length: ...

   --boundary1

   Content-Type: common-alerting-protocol+xml
   Content-ID: <abcdef2@domain.com>
  <?xml version="1.0" encoding="UTF-8"?>

  <alert xmlns="urn:oasis:names:tc:emergency:cap:1.1">
    <identifier>S-1</identifier>
    <sender>sip:sensor1@domain.com</sender>
    <sent>2008-11-19T14:57:00-07:00</sent>
    <status>Actual</status>
    <msgType>Alert</msgType>
    <scope>Private</scope>
    <incidents>abc1234</incidents>
    <info>
        <category>Security</category>
        <event>BURGLARY</event>
        <urgency>Expected</urgency>
        <certainty>Likely</certainty>
        <severity>Moderate</severity>
        <senderName>SENSOR 1</senderName>



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        <parameter>
          <valueName>SENSOR-DATA-NAMESPACE1</valueName>
          <value>123</value>
        </parameter>
        <parameter>
          <valueName>SENSOR-DATA-NAMESPACE2</valueName>
          <value>TRUE</value>
        </parameter>
    </info>
   </alert>

   --boundary1

   Content-Type: application/pidf+xml
   Content-ID: <abcdef2@domain.com>
   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:cl="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
          xmlns:gml="http://www.opengis.net/gml"
          entity="pres:sensor1@domain.com">
        <tuple id="12345">
         <dm:device id="sensor1">
          <gp:geopriv>
            <gp:location-info>
              <gml:location>
                <gml:Point srsName="urn:ogc:def:crs:EPSG::4326">
                  <gml:pos>32.86726 -97.16054</gml:pos>
                </gml:Point>
               </gml:location>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>yes
              </gp:retransmission-allowed>
              <gp:retention-expiry>2010-07-30T20:00:00Z
              </gp:retention-expiry>
            </gp:usage-rules>
            <gp:method>802.11</gp:method>
           </gp:geopriv>
          <dm:deviceID>mac:1234567890ab</dm:deviceID>
          <dm:timestamp>2010-07-28T20:57:29Z</dm:timestamp>
         </dm:device>
        </tuple>
      </presence>

   --boundary1--

               Figure 3: Example Message conveying an Alert



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6.  Security Considerations

   This section discusses security considerations when using SIP to make
   data-only emergency alerts utilizing CAP.  Location specific threats
   are not unique to this document and the discussion in
   [I-D.ietf-ecrit-trustworthy-location].

6.1.  Forgery

   Threat:

      An adversary could forge or alter a CAP document to report false
      emergency alarms.


   Countermeasures:

      To avoid this kind of attack, the entities must assure that proper
      mechanisms for protecting the CAP documents are employed, e.g.,
      signing the CAP document itself.  Section 3.3.2.1 of [cap]
      specifies the signing of CAP documents.  This does not protect
      against a legitimate sensor sending phrank alerts after being
      compromised.

6.2.  Replay Attack

   Threat:

      An adversary could eavesdrop alerts and reply them at a later
      time.


   Countermeasures:

      A CAP document contains the mandatory <identifier>, <sender>,
      <sent> elements and an optional <expire> element.  These
      attributes make the CAP document unique for a specific sender and
      provide time restrictions.  An entity that has received a CAP
      message already within the indicated timeframe is able to detect a
      replayed message and, if the content of that message is unchanged,
      then no additional security vulnerability is created.
      Additionally, it is RECOMMENDED to make use of SIP security
      mechanisms, such as SIP Identity [RFC4474], to tie the CAP message
      to the SIP message.







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6.3.  Injecting False Alerts

   Threat:

      When an entity receives a CAP message it has to determine whether
      the entity distributing the CAP messages is genuine to avoid
      accepting messages that are injected by adversaries.  In scenario


   Countermeasures:

      For some types of data-only emergency calls author/originator and
      the receiver/recipient have a relationship with each other and
      hence it is possible (using cryptographic techniques) to verify
      whether a message was indeed issued by an authorized entity.
      Figure 1 is such an environment.  Standard SIP security mechanisms
      can be re-used for this purpose.  For example, identity based
      access control is a viable approach utilizing the asserted
      identity of the alert originator using P-Asserted-Identity
      [RFC3325] or SIP Identity [RFC4474].

      There are, however, other types of data-only emergency calls where
      there is no such relationship between the author/originator and
      the receiver/recipient.  Incoming alerts need to be treated more
      carefully than multi-media emergency calls that contain additional
      information, such as audio, to allow a call taker to sort out
      phrank calls.
























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7.  IANA Considerations

7.1.  Registration of the 'application/common-alerting-protocol+xml'
      MIME type

   To:  ietf-types@iana.org


   Subject:  Registration of MIME media type application/ common-
      alerting-protocol+xml


   MIME media type name:  application


   MIME subtype name:  common-alerting-protocol+xml


   Required parameters:  (none)


   Optional parameters:  charset; Indicates the character encoding of
      enclosed XML.  Default is UTF-8 [RFC3629].


   Encoding considerations:  Uses XML, which can employ 8-bit
      characters, depending on the character encoding used.  See RFC
      3023 [RFC3023], Section 3.2.


   Security considerations:  This content type is designed to carry
      payloads of the Common Alerting Protocol (CAP).


   Interoperability considerations:  This content type provides a way to
      convey CAP payloads.


   Published specification:  RFC XXX [Replace by the RFC number of this
      specification].


   Applications which use this media type:  Applications that convey
      alerts and warnings according to the CAP standard.







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   Additional information:  OASIS has published the Common Alerting
      Protocol at http://www.oasis-open.org/committees/
      documents.php&wg_abbrev=emergency


   Person & email address to contact for further information:  Hannes
      Tschofenig, Hannes.Tschofenig@nsn.com


   Intended usage:  Limited use


   Author/Change controller:  IETF SIPPING working group


   Other information:  This media type is a specialization of
      application/xml RFC 3023 [RFC3023], and many of the considerations
      described there also apply to application/
      common-alerting-protocol+xml.
































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8.  Acknowledgments

   The authors would like to thank the participants of the Early Warning
   adhoc meeting at IETF#69 for their feedback.  Additionally, we would
   like to thank the members of the NENA Long Term Direction Working
   Group for their feedback.













































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9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", March 1997.

   [cap]      Jones, E. and A. Botterell, "Common Alerting Protocol v.
              1.1", October 2005.

   [RFC3265]  Roach, A., "Session Initiation Protocol (SIP)-Specific
              Event Notification", RFC 3265, June 2002.

   [RFC3903]  Niemi, A., "Session Initiation Protocol (SIP) Extension
              for Event State Publication", RFC 3903, October 2004.

   [RFC3023]  Murata, M., St. Laurent, S., and D. Kohn, "XML Media
              Types", RFC 3023, January 2001.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [I-D.ietf-ecrit-trustworthy-location]
              Tschofenig, H., Schulzrinne, H., and B. Aboba,
              "Trustworthy Location Information",
              draft-ietf-ecrit-trustworthy-location-01 (work in
              progress), October 2010.

9.2.  Informative References

   [I-D.ietf-ecrit-phonebcp]
              Rosen, B. and J. Polk, "Best Current Practice for
              Communications Services in support of Emergency Calling",
              draft-ietf-ecrit-phonebcp-15 (work in progress),
              July 2010.

   [I-D.ietf-atoca-requirements]
              Schulzrinne, H., Norreys, S., Rosen, B., and H.
              Tschofenig, "Requirements, Terminology and Framework for
              Exigent Communications", draft-ietf-atoca-requirements-00
              (work in progress), September 2010.

   [RFC4474]  Peterson, J. and C. Jennings, "Enhancements for
              Authenticated Identity Management in the Session
              Initiation Protocol (SIP)", RFC 4474, August 2006.

   [RFC3325]  Jennings, C., Peterson, J., and M. Watson, "Private
              Extensions to the Session Initiation Protocol (SIP) for



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              Asserted Identity within Trusted Networks", RFC 3325,
              November 2002.

















































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Authors' Addresses

   Brian Rosen
   NeuStar, Inc.
   470 Conrad Dr
   Mars, PA  16046
   US

   Phone:
   Email: br@brianrosen.net


   Henning Schulzrinne
   Columbia University
   Department of Computer Science
   450 Computer Science Building
   New York, NY  10027
   US

   Phone: +1 212 939 7004
   Email: hgs+ecrit@cs.columbia.edu
   URI:   http://www.cs.columbia.edu


   Hannes Tschofenig
   Nokia Siemens Networks
   Linnoitustie 6
   Espoo  02600
   Finland

   Phone: +358 (50) 4871445
   Email: Hannes.Tschofenig@gmx.net
   URI:   http://www.tschofenig.priv.at


















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