LoST-based Discovery of Servers Distributing Alerts
draft-rosen-atoca-server-discovery-00.txt

Abstract

The Common Alerting Protocol (CAP) is an XML document format for exchanging emergency alerts and public warnings. Different organizations issue alerts for specific geographic regions. The Location-to-Service Translation (LoST) protocol provides a way to discover servers that distribute these alerts for a geographical region. This document defines the Service Uniform Resource Names (URN)s for warnings in the same way as they have been defined with RFC 5031 for citizen-to-authority emergency services. Additionally, this document suggests to use LoST for the discovery of servers distributing alerts.

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Table of Contents

1.  Introduction
2.  Terminology
3.  Protocol Semantics
4.  Examples
5.  Security Considerations
6.  IANA Considerations
    6.1.  Sub-Services for the 'warning' Service
    6.2.  Initial IANA Registration
7.  Acknowledgments
8.  References
    8.1.  Normative References
    8.2.  Informative References
§  Authors' Addresses

1.  Introduction

The Common Alerting Protocol (CAP) is an XML document format for exchanging emergency alerts and public warnings. Different organizations issue alerts for specific geographical regions. The Location-to-Service Translation (LoST) protocol provides a way to discover servers that distribute these alerts for a geographical region. This document defines the Service Uniform Resource Names (URN)s for warnings in the same way as they have been defined with RFC 5031 for citizen-to-authority emergency services. Additionally, this document suggests to use LoST for the discovery of servers distributing alerts.

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] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

3.  Protocol Semantics

This document makes use of LoST, RFC 5222 [RFC5222] (Hardie, T., Newton, A., Schulzrinne, H., and H. Tschofenig, “LoST: A Location-to-Service Translation Protocol,” August 2008.). However, instead of performing a translation from location information and a Service URN to a PSAP URI (plus supplementary information), as used with [I‑D.ietf‑ecrit‑phonebcp] (Rosen, B. and J. Polk, “Best Current Practice for Communications Services in support of Emergency Calling,” January 2010.) for the citizen-to-authority emergency services use case, the LoST client asks the LoST server for a URI to receive further information on how to obtain warning alerts. In a response the URIs in the <uri> element MUST be from the following format: sip, xmpp or http. The SIP URI MUST subsequently be used with [I‑D.rosen‑sipping‑cap] (Rosen, B., Schulzrinne, H., and H. Tschofenig, “Session Initiation Protocol (SIP) Event Package for the Common Alerting Protocol (CAP),” July 2009.). An XMPP URI MUST be used as described in [XEP‑0127] (Saint-Andre, P. and B. Fletcher, “Common Alerting Protocol (CAP) Over XMPP,” December 2004.). An HTTP URI MUST be used with GeoRSS ([Reference to be added.]).

In a LoST response the optional <serviceNumber> element is not used by this specification. In mapping citizen-to-authority services, receiving multiple mappings is an exception. However, since many organizations may provide warnings for the same area, this is likely to be more common for alerts. As such, the extensions defined in [I‑D.forte‑ecrit‑lost‑extensions] (Forte, A. and H. Schulzrinne, “Location-to-Service Translation Protocol (LoST) Extensions,” March 2009.) (e.g., the ability to limit the number of returned mappings) are useful in this context.

4.  Examples

Figure 1 (A <findService> geodetic query) shows a regular LoST query including geodetic location information with the Service URN pointing to 'urn:service:warning'. The semantic of the query is: "I am at location (point,"37.775 -122.422"). Please give me a URI where I can obtain information for warnings under the category 'urn:service:warning'.

   <?xml version="1.0" encoding="UTF-8"?>
   <findService
     xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:p2="http://www.opengis.net/gml"
     serviceBoundary="value"
     recursive="true">

     <location id="6020688f1ce1896d" profile="geodetic-2d">
       <p2:Point id="point1" srsName="urn:ogc:def:crs:EPSG::4326">
          <p2:pos>37.775 -122.422</p2:pos>
       </p2:Point>
     </location>
     <service>urn:service:warning</service>

   </findService>

In response to the query in Figure 1 (A <findService> geodetic query) the LoST server returns a regular LoST response, as shown in Figure 2 (A <findServiceResponse> geodetic answer). The returned mapping information indicates that the URIs (sip:alerts@example.com and xmpp:alerts@example.com) can be contacted to subscribe to warning events. The service boundary indicates that subsequent requests to the same service will lead to the same response for the geodetic region indicated by the polygon in the <serviceBoundary> element.

   <?xml version="1.0" encoding="UTF-8"?>
   <findServiceResponse xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:p2="http://www.opengis.net/gml">
     <mapping
       expires="2007-01-01T01:44:33Z"
       lastUpdated="2006-11-01T01:00:00Z"
       source="authoritative.example"
       sourceId="7e3f40b098c711dbb6060800200c9a66">
       <displayName xml:lang="en">
         Austrian Early Warning Center
       </displayName>
       <service>urn:service:warning</service>
       <serviceBoundary profile="geodetic-2d">
         <p2:Polygon srsName="urn:ogc:def::crs:EPSG::4326">
           <p2:exterior>
             <p2:LinearRing>
               <p2:pos>37.775 -122.4194</p2:pos>
               <p2:pos>37.555 -122.4194</p2:pos>
               <p2:pos>37.555 -122.4264</p2:pos>
               <p2:pos>37.775 -122.4264</p2:pos>
               <p2:pos>37.775 -122.4194</p2:pos>
             </p2:LinearRing>
           </p2:exterior>
         </p2:Polygon>
       </serviceBoundary>
       <uri>sip:alerts@example.com</uri>
       <uri>xmpp:alerts@example.com</uri>
     </mapping>
     <path>
       <via source="resolver.example"/>
       <via source="authoritative.example"/>
     </path>
     <locationUsed id="6020688f1ce1896d"/>
   </findServiceResponse>

Figure 3 (Example of <ListServicesByLocation> query) shows a <ListServicesByLocation> query asking for the services that are available at a given location; in this example at a point (-34.407 150.883).

   <?xml version="1.0" encoding="UTF-8"?>
   <listServicesByLocation
     xmlns="urn:ietf:params:xml:ns:lost1"
     xmlns:p2="http://www.opengis.net/gml"
     recursive="true">
     <location id="3e19dfb3b9828c3" profile="geodetic-2d">
       <p2:Point srsName="urn:ogc:def:crs:EPSG::4326">
         <p2:pos>-34.407 150.883</p2:pos>
       </p2:Point>
     </location>
     <service>urn:service:warning</service>
   </listServicesByLocation>

Figure 4 (Example of <listServicesByLocationResponse>) lists a possible response to the <ListServicesByLocation> query with 6 subservices being offered for the indicated geographical region.

   <?xml version="1.0" encoding="UTF-8"?>
   <listServicesByLocationResponse
    xmlns="urn:ietf:params:xml:ns:lost1">
    <serviceList>
     urn:service:warning.geo
     urn:service:warning.met
     urn:service:warning.safety
     urn:service:warning.security
     urn:service:warning.rescue
     urn:service:warning.fire
    </serviceList>
    <path>
     <via source="resolver.example"/>
     <via source="authoritative.example"/>
    </path>
    <locationUsed id="3e19dfb3b9828c3"/>
   </listServicesByLocationResponse>

5.  Security Considerations

The security considerations of RFC 5031 [RFC5031] (Schulzrinne, H., “A Uniform Resource Name (URN) for Emergency and Other Well-Known Services,” January 2008.), RFC 5222 [RFC5222] (Hardie, T., Newton, A., Schulzrinne, H., and H. Tschofenig, “LoST: A Location-to-Service Translation Protocol,” August 2008.) and [I‑D.rosen‑sipping‑cap] (Rosen, B., Schulzrinne, H., and H. Tschofenig, “Session Initiation Protocol (SIP) Event Package for the Common Alerting Protocol (CAP),” July 2009.) are relevant to this document. This document does not introduce new security vulnerabilities.

6.  IANA Considerations

6.1.  Sub-Services for the 'warning' Service

This section defines the service registration within the IANA registry defined in Section 4.1 of [RFC5031] (Schulzrinne, H., “A Uniform Resource Name (URN) for Emergency and Other Well-Known Services,” January 2008.), using the top-level service label 'warning'.

The 'warning' service type describes services providing public safety alerts, i.e., alerts that can warn members of the public about dangers to life, health and property. Additional sub-services can be added after expert review and must be of general public interest and have a similar emergency nature. The expert is designated by the ECRIT working group, its successor, or, in their absence, the IESG. The expert review should only approve early warning based emergency services that are offered widely and in different countries, with approximately the same caller expectation in terms of services rendered. The 'warning' service is not meant to be used by non-emergency services related information.

The warning classification (including description) in the list below is taken from the CAP specification [cap] (Jones, E. and A. Botterell, “Common Alerting Protocol v. 1.1,” October 2005.):

'urn:service:warning':

The generic 'warning' service denotes a generic early warning message of any type encompassing all of the services listed below.

'urn:service:warning:geo':

Geophysical (inc. landslide)

'urn:service:warning:met':

Meteorological (inc. flood)

'urn:service:warning:safety':

General emergency and public safety

'urn:service:warning:security':

Law enforcement, military, homeland and local/private security

'urn:service:warning:rescue':

Rescue and recovery

'urn:service:warning:fire':

Fire suppression and rescue

'urn:service:warning:health':

Medical and public health

'urn:service:warning:env':

Pollution and other environmental

'urn:service:warning:transport':

Public and private transportation

'urn:service:warning:infra':

Utility, telecommunication, other non-transport infrastructure

'urn:service:warning:cbrne':

Chemical, Biological, Radiological, Nuclear or High-Yield Explosive threat or attack

6.2.  Initial IANA Registration

The following table contains the initial IANA registration for early warning services.

Service                   Reference  Description
------------------------------------------------------------------------
warning                   RFC TBD    Early Warning Services
warning.geo               RFC TBD    Geophysical (inc. landslide)
warning.met               RFC TBD    Meteorological (inc. flood)
warning.safety            RFC TBD    General emergency and public safety
warning.security          RFC TBD    Law enforcement, military,
                                     homeland and local/private security
warning.rescue            RFC TBD    Rescue and recovery
warning.fire              RFC TBD    Fire suppression and rescue
warning.health            RFC TBD    Medical and public health
warning.env               RFC TBD    Pollution and other environmental
warning.transport         RFC TBD    Public and private transportation
warning.infra             RFC TBD    Utility, telecommunication, other
                                     non-transport infrastructure
warning.cbrne             RFC TBD    Chemical, Biological,
                                     Radiological, Nuclear or High-Yield
                                     Explosive threat or attack

7.  Acknowledgments

We would also like to thank the participants of the Early Warning Adhoc meeting at IETF#69.

8.  References

8.1. Normative References

8.2. Informative References

Authors' Addresses