One document matched: draft-rosen-ecrit-data-only-ea-00.xml
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<rfc category="exp" docName="draft-rosen-ecrit-data-only-ea-00.txt" ipr="trust200902">
<front>
<title abbrev="Data-Only Emergency Alerts">Common Alerting Protocol (CAP) based Data-Only
Emergency Alerts using the Session Initiation Protocol (SIP)</title>
<author initials="B." surname="Rosen" fullname="Brian Rosen">
<organization>NeuStar, Inc. </organization>
<address>
<postal>
<street>470 Conrad Dr</street>
<city>Mars</city>
<region> PA </region>
<code>16046 </code>
<country>US </country>
</postal>
<phone> </phone>
<email>br@brianrosen.net
</email>
</address>
</author>
<author initials="H." surname="Schulzrinne" fullname="Henning Schulzrinne">
<organization abbrev="Columbia U.">Columbia University</organization>
<address>
<postal>
<street>Department of Computer Science</street>
<street>450 Computer Science Building</street>
<city>New York</city>
<region>NY</region>
<code>10027</code>
<country>US</country>
</postal>
<phone>+1 212 939 7004</phone>
<email>hgs+ecrit@cs.columbia.edu</email>
<uri>http://www.cs.columbia.edu</uri>
</address>
</author>
<author initials="H." surname="Tschofenig" fullname="Hannes Tschofenig">
<organization>Nokia Siemens Networks</organization>
<address>
<postal>
<street>Linnoitustie 6</street>
<city>Espoo</city>
<code>02600</code>
<country>Finland</country>
</postal>
<phone>+358 (50) 4871445</phone>
<email>Hannes.Tschofenig@gmx.net</email>
<uri>http://www.tschofenig.priv.at</uri>
</address>
</author>
<date year="2009"/>
<area>RAI</area>
<workgroup>ECRIT</workgroup>
<keyword>Internet-Draft</keyword>
<keyword>CAP</keyword>
<keyword>Common Alerting Protocol</keyword>
<keyword>Data-Only Emergency Alerts</keyword>
<abstract>
<t>The Common Alerting Protocol (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 alerts allow to utilize the same CAP document format.</t>
</abstract>
</front>
<middle>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section anchor="introduction" title="Introduction">
<t>The Common Alerting Protocol (CAP) <xref target="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 may be similar to regular emergency calls in the sense that they
have the same emergency call routing and location requirements; they do, however, not lead
to the establishment of a voice channel. There are, however, data-only emergency alerts that
are targeted directly to a dedicated entity responsible for evaluating the alerts and for
taking the necessary steps, including triggering an emergency call towards a Public Safety
Answering Point (PSAP).</t>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section anchor="terminology" title="Terminology">
<t>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 <xref target="RFC2119"/>.</t>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section title="Architectural Overview">
<t>This section illustrates two envisioned usage modes; targeted and location-based emergency alert routing. <xref target="targeted"/>
shows a deployment variant where a device is pre-configured (using techniques outside the scope of this document) to issue an alert to
an aggregator that processes these messages and performs whatever steps are necessary to appropriately react on the alert. In many cases
the device has the address of the aggregator pre-configured and corresponding security mechanisms are in place to ensure that only
alert from authorized devices are processed.</t>
<t> <figure anchor="targeted" title="Targeted Emergency Alert Routing">
<artwork xml:space="preserve">
<![CDATA[
+--------+ +------------+
| Device | | Aggregator |
+---+----+ +------+-----+
| |
Sensors |
trigger |
emergency |
alert |
| MESSAGE with CAP |
|----------------------------->|
| |
| Aggregator
| processes
| emergency
| alert
| 200 (OK) |
|<-----------------------------|
| |
| |
]]></artwork>
</figure>
</t>
<t>
In <xref target="location"/> a scenario is shown whereby the alert is routed
using location information and the Service URN. In this case the device issuing the alert may not
know
the message recipient (in case the LoST resolution is done at an emergency services routing proxy rather
than at the end host). In any case, a trust relationship between the alert-issuing device and the PSAP
cannot be assumed, i.e., the PSAP is likely to receive alerts from entities it cannot authorize.
This scenario corresponds more to the classical emergency services classical and the description
in <xref target="I-D.ietf-ecrit-phonebcp"/> is applicable.
</t>
<t>
<figure anchor="location" title="Location-Based Emergency Alert Routing">
<artwork xml:space="preserve">
<![CDATA[
+-------+
+--------+ | SIP | +------+
| Device | | Proxy | | PSAP |
+---+----+ +---+---+ +---+--+
| | |
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) | |
|<-------------------| |
| | |
| | |
]]></artwork>
</figure>
</t>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section title="Protocol Specification">
<section title="CAP Transport">
<t>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'.</t>
<t>
<list style="empty">
<t>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. </t>
</list>
</t>
</section>
<section title="Profiling of the CAP Document Content">
<t>The usage of CAP MUST conform to the specification provided with <xref target="cap"/>.
For the usage with SIP the following additional requirements are imposed: </t>
<t><list
style="hanging">
<t hangText="sender:">When the CAP was created by a SIP-based entity then the element
MUST be populated with the SIP URI of that entity. <vspace blankLines="1"/></t>
<t hangText="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 combination.</t>
<t hangText="scope:">The value of the <scope> element MUST be set to
private as the alert is not meant for public consumption.<vspace blankLines="1"/> </t>
<t hangText="parameter:">The <parameter> element MAY contain additional
information specific to the sensor. <vspace blankLines="1"/></t>
<t hangText="area:">For geodetic information the polygon and circle location shapes are
available. The ability to conveying a structured format of civic location information
is missing and hence civic information is encoded as a text string in the
<areaDesc> element.</t>
</list></t>
<t>[Editor's Note: The usage of a number of CAP elements is unclear and/or insufficient and
requires further discussion with the authors of the CAP specification. Based on the
outcome of these discussions more fields might require profiling.]</t>
</section>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section anchor="example" title="Example">
<t><xref target="warning1"/> shows a CAP document indicating a BURLARY alert issued by
sensor1@example.com indicating that the alert was issued from the civic address NATURAL
HISTORY MUSEUM, BURGRING 7, 1010 VIENNA, AUSTRIA. Additionally, the sensor provided some
additional data long with the alert message using non-standardized information elements. </t>
<t>
<figure anchor="warning1" title="Example for an alert triggered by a sensor">
<artwork>
<![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<alert xmlns="urn:oasis:names:tc:emergency:cap:1.1">
<identifier>S-1</identifier>
<sender>sensor1@example.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>
<area>
<areaDesc>NATURAL HISTORY MUSEUM,
BURGRING 7, 1010 VIENNA, AUSTRIA
</areaDesc>
</area>
<parameter>
<valueName>SENSOR-DATA-NAMESPACE1</valueName>
<value>123</value>
</parameter>
<parameter>
<valueName>SENSOR-DATA-NAMESPACE2</valueName>
<value>TRUE</value>
</parameter>
</info>
</alert>
]]></artwork>
</figure>
</t>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section anchor="sec-cons" title="Security Considerations">
<t> This section discusses security considerations when using SIP to make data-only emergency
alerts utilizing CAP. </t>
<section anchor="sec-cons-forged-assn" title="Forgery">
<t>
<list style="hanging">
<t hangText="Threat:">
<vspace blankLines="1"/> An adversary could forge or alter a CAP document to report
false emergency alarms.<vspace blankLines="1"/> </t>
<t hangText="Countermeasures:">
<vspace blankLines="1"/> 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 <xref target="cap"/> specifies the signing of CAP
documents. This does not protect against a legitimate sensor sending phrank alerts
after being compromised.</t>
</list>
</t>
</section>
<section anchor="sec-cons-replay-attack" title="Replay Attack">
<t>
<list style="hanging">
<t hangText="Threat:">
<vspace blankLines="1"/> Theft of CAP documents described in this document and replay
of it at a later time.<vspace blankLines="1"/> </t>
<t hangText="Countermeasures:">
<vspace blankLines="1"/> 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, to tie the CAP message to the SIP
message.</t>
</list>
</t>
</section>
<section anchor="sec-cons-authorization" title="Injecting False Alerts">
<t>
<list style="hanging">
<t hangText="Threat:">
<vspace blankLines="1"/> 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. <vspace blankLines="1"/></t>
<t hangText="Countermeasures:">
<vspace blankLines="1"/>For some types of data-only emergency calls the entity issuing
the alert and the entity consuming the alert have a relationship with each other and
hence it is possible (using cryptographic authentication ) to verify whether a message
was indeed issued by an authorized entity. There are, however, other types of
data-only emergency calls where there is no such relationship between the sender and
the consumer. In that case incoming alerts need to be treated more carefully, as the
possibilities to place phrank calls are higher than with regular emergency calls that
at least setup an audio channel. </t>
</list>
</t>
</section>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section title="IANA Considerations">
<section title="Registration of the 'application/common-alerting-protocol+xml' MIME type">
<t>
<list style="hanging">
<t hangText="To:"> ietf-types@iana.org<vspace blankLines="1"/> </t>
<t hangText="Subject:">Registration of MIME media type application/
common-alerting-protocol+xml<vspace blankLines="1"/></t>
<t hangText="MIME media type name:"> application <vspace blankLines="1"/></t>
<t hangText="MIME subtype name:">common-alerting-protocol+xml <vspace blankLines="1"/></t>
<t hangText="Required parameters:"> (none)<vspace blankLines="1"/> </t>
<t hangText="Optional parameters:"> charset; Indicates the character encoding of
enclosed XML. Default is UTF-8 <xref target="RFC3629"/>.<vspace blankLines="1"/></t>
<t hangText="Encoding considerations:"> Uses XML, which can employ 8-bit characters,
depending on the character encoding used. See RFC 3023 <xref target="RFC3023"/>,
Section 3.2.<vspace blankLines="1"/></t>
<t hangText="Security considerations:"> This content type is designed to carry payloads
of the Common Alerting Protocol (CAP). <vspace blankLines="1"/></t>
<t hangText="Interoperability considerations:"> This content type provides a way to
convey CAP payloads.<vspace blankLines="1"/> </t>
<t hangText="Published specification:"> RFC XXX [Replace by the RFC number of this
specification]. <vspace blankLines="1"/></t>
<t hangText="Applications which use this media type:"> Applications that convey alerts
and warnings according to the CAP standard.<vspace blankLines="1"/></t>
<t hangText="Additional information:"> OASIS has published the Common Alerting Protocol
at http://www.oasis-open.org/committees/documents.php&wg_abbrev=emergency <vspace blankLines="1"/></t>
<t hangText="Person & email address to contact for further information:"> Hannes
Tschofenig, Hannes.Tschofenig@nsn.com <vspace blankLines="1"/></t>
<t hangText="Intended usage:"> Limited use <vspace blankLines="1"/></t>
<t hangText="Author/Change controller:"> IETF SIPPING working group <vspace blankLines="1"/></t>
<t hangText="Other information:"> This media type is a specialization of application/xml
RFC 3023 <xref target="RFC3023"/>, and many of the considerations described there also
apply to application/common-alerting-protocol+xml. <vspace blankLines="1"/></t>
</list>
</t>
</section>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section title="Acknowledgments">
<t>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. </t>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
</middle>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<back>
<references title="Normative References">
<reference anchor="RFC2119">
<front>
<title abbrev="RFC Key Words">Key words for use in RFCs to Indicate Requirement Levels</title>
<author fullname="Scott Bradner" initials="S." surname="Bradner">
<organization>Harvard University</organization>
</author>
<date month="March" year="1997"/>
</front>
<format octets="4723" target="ftp://ftp.isi.edu/in-notes/rfc2119.txt" type="TXT"/>
</reference>
<reference anchor="cap">
<front>
<title>Common Alerting Protocol v. 1.1 </title>
<author fullname="Elysa Jones" initials="E." surname="Jones">
<organization>Warning Systems, Inc</organization>
</author>
<author fullname="Art Botterell" initials="A." surname="Botterell">
<organization>Individual</organization>
</author>
<date month="October" year="2005"/>
</front>
<format
target="http://www.oasis-open.org/apps/org/workgroup/emergency/download.php/14205/emergency-CAPv1.1-Committee%20Specification.pdf"
type="PDF"/>
</reference> &RFC3265; &RFC3903; &RFC3023; &RFC3629; </references>
<references title="Informative References"> &I-D.ietf-ecrit-phonebcp; </references>
</back>
</rfc>
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