ECRIT                                                    J. Winterbottom
Internet-Draft                               Winterb Consulting Services
Updates: RFC6881, RFC5985                                  H. Tschofenig
(if approved)
Intended status: Standards Track                                L. Liess
Expires: October 7, 2015                                Deutsche Telekom
                                                           April 5, 2015

           A Routing Request Extension for the HELD Protocol


   In many circumstances public LoST servers or a distributed network of
   forest guides linking public LoST servers is not available.  The
   general ECRIT calling models breakdown without publically accessible
   LoST servers.  Sometimes location servers may have access to
   emergency routing information.  This document defines an extension to
   the HELD protocol so a location request can include a request for
   routing information and allowing the subsequent location response to
   include routing information.

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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 7, 2015.

Copyright Notice

   Copyright (c) 2015 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
   ( in effect on the date of

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   publication of this document.  Please review these documents
   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  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Mechanism  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   5.  HELD Schema Extension  . . . . . . . . . . . . . . . . . . . .  8
   6.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   7.  Privacy Considerations . . . . . . . . . . . . . . . . . . . . 10
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
     9.1.  URN sub-namespace registration for
           'urn:ietf:params:xml:ns:geopriv:held:ri' . . . . . . . . . 10
     9.2.  XML Schema Registration  . . . . . . . . . . . . . . . . . 11
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 12
     11.2. Informative References . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13

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1.  Introduction

   The general ECRIT calling models described in [RFC6443] and
   [RFC6881]require a local LoST server or network of forest guides in
   order to determine the address of the PSAP in the best position to
   handle a call.  Networks of forest guides have not eventuated and
   while PSAPs are moving towards IP networks, LoST server deployment is
   not ubiquitous.  Some regions and countries have expressed reluctance
   to deploy LoST servers making aspects of the current ECRIT
   architecture hard to realize.

   Evolving architectures in Europe to address regulatory requirements,
   such as [M493], couple location and routing information in the access
   network whilst using a softswitch-centric approach to emergency call
   processing.  This document describes adding an extension to the HELD
   protocol [RFC5985] so that a location information server can provide
   emergency routing information in the absence of a LoST server or
   network of forest guides.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

   The terms LIS, ESRP, VSP and PSAP are used as defined in [RFC6443].

   The term "Access Network Provider" is used as defined in [RFC5687]
   and incompasses both the Internet Access Provider (IAP) and Internet
   Service Provider (ISP).

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3.  Motivation

   The Internet emergency calling architecture specified in [RFC6881]
   describes two main models for emergency call processing.  The first
   is a device-centric model, where a device obtains location
   information using a location configuration protocol, such a HELD
   [RFC5985], and then proceeds to determine the address of the next hop
   closer to the local PSAP using LoST [RFC5222].  Figure 1 shows this
   model in a simplified form.

        +---Location Request---+
        |         (1)          |
    +---+----+             +---V---+
    |        |<--Location--|  LIS  |
    | Caller |    (2)      +-------+             +--------+
    |        |                                   | ESRP/  |
    |        |----Find Service-------+           |  PSAP  |
    +------^-+     (3)               |           +--------+
       |   |                +--------V----+          ^
       |   +-----Service----| LoST Server |          |
       |         (4)        +-------------+      +---+---+
       +-------------Call Initiation------------>|  VSP  |
                        (5)                      +-------+

             Figure 1: Device-Centric Emergency Services Model

   The second approach is a softswitch-centric model, where a device
   initiates and emergency call and the serving softswitch detects that
   the call is an emergency and initiates retrieving the caller's
   location from a Location Information Server (LIS) using HELD
   [RFC5985] with identity extensions [RFC6155] [RFC6915] and then
   determining the route to the local PSAP using LoST [RFC5222].
   Figure 2 shows the high-level protocol interactions.

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                               +---Location Request---+
                               |         (2)          |
                           +---V---+                  |
                           |  LIS  |                  |
                           +----+--+             +----+----+
                                |                |         |
                                +----Location--->|  Soft   |
    +--------+                          (3)      | Switch  |
    | Caller |------Call Initiation------------> |         |
    +--------+          (1)                      +-+-^---+-+
                    +-------------+                | |   |
                    | LoST Server |<-Find Service--+ |   |
                    +------+------+     (4)          |   |
                           |                         |   |
                           +----------Service--------+   |
                                       (5)               |
                             +-----------+               |
                             | ESRP/PSAP |<------Call----+
                             +-----------+       (6)

                Figure 2: Softswitch-Centric Calling Model

   In the softswitch-centric model when a VSP receives an emergency call
   it performs two tasks.  The first task is to determine the correct
   LIS to ask for location information, this is done using a combination
   of reverse DNS lookup described in [RFC7216] to acquire the serving
   domain name and then using [RFC5986] to determine the LIS URI.  Once
   the location is obtained from the LIS, the VSP determines the LoST
   server associated with the domain serving the caller and queries it
   for the correct PSAP address.

   LoST server discovery is a domain based activity, similar to the LIS
   discovery technique.  However, unlike the LIS that is a domain bound
   service, a LoST server is a geographically bound service.  This means
   that for a domain that spans multiple geographic regions the LoST
   server determined may not be able to provide a route to the necessary
   PSAP.  When this occurs, the contacted LoST server invokes the help
   of other LoST servers and this requires the deployment of forest

   At the time of writing, several countries have expressed a reluctance
   to deploy public LoST servers.  In countries amenable to the use of
   LoST and forest guides no public forest guides have been deployed.
   There appears little interest from the public sector in establishing
   a global forest guide network.  These issues pose threats to both the
   device-centric and the softswitch-centric calling approaches in terms
   of them operating everywhere.

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   The device-centric and softswitch-centric calling models both involve
   the notion of a LIS bound to the serving access network.  In many
   cases the LIS already knows the destination PSAP URI for any given
   location.  In [RFC6881] for example, the LIS validates civic
   locations using a location validation procedure based on the LoST
   protocol [RFC5222].  The LoST validation request is similar to a LoST
   routing request and provides the LIS with the same PSAP routing
   information that a routing request would.  In other cases, the LIS
   knows the correct PSAP for a given location at provisioning time, or
   the access network might always route to the same emergency provider.
   Irrespective of the way in which the LIS learns the PSAP URI for a
   location, the LIS will, in a great many cases, already have this

   This document specifies an extension to the HELD protocol so that
   emergency routing information can be requested from the LIS at the
   same time that location information is requested.  The document
   updates [RFC6881] by requiring devices and softswitches that
   understand this specification to always request routing information
   to avoid the risk of query failure where no LoST server or forest
   guide network is deployed.

4.  Mechanism

   The mechanism consists of adding an element to the HELD
   locationRequest and an element to the locationResponse.

   The request element indicates that the requestor wants the LIS to
   provide routing information based on the location of the end-device.
   If the routing request is sent with no attribute then URIs for
   urn:service:sos are returned.  If the requestor wants routing
   information for a specific service then they may include an optional
   service URN.  If a service is specified, and the LIS does not
   understand the requested service then URIs for urn:service:sos are

   If the LIS understands the routing request and has routing
   information for the location then it includes the information in a
   routingInformation element returned in the locationResponse.  How the
   LIS obtains this information is left to implementation, one possible
   option is that the LIS acquires it from a LoST server, other
   possibilities are described in Section 3.

   A LIS that does not understand the routing request element ignores it
   and returns location as normal.

   A LIS that does support the routing request element SHALL support

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   returning URIs for urn:service:sos

   A LIS that does understand the routing request element but can't
   obtain any routing information for the end-device's location SHALL
   only return location information.

   A LIS that understands the routing request element but not the
   specified service URN, returns the routing URIs for the
   urn:service:sos service.

   The routing information in the location response consists of a
   service element identified by a service name.  The service name is a
   urn and might contain a general emergency service urn such as
   urn:service:sos or might contain a specific service urn depending on
   what was requested and what the LIS is able to provide.  A list of
   one or more service destinations is provided for the service name.
   Each destination is expressed as a URI and each URI scheme should
   only appear once in this list.  The routing URIs are intended to be
   used at the time they are received.  To avoid any risks of using
   stale routing URIs the values MUST NOT be cached by the receiving

   The LoST Protocol [RFC5222] defines a <mapping> element that
   describes a service region and associated service URLs.  Reusing this
   element from LoST to provide the routing URIs was considered.
   However, this would have meant that several of the mandatory
   components in the <mapping> element would have had to contain
   ambiguous or misleading values.  Specifically, the "source" attribute
   is required to contain a LoST application unique string for the
   authoritative server.  However, in the situations described in this
   specification there may not be an authoritative LoST server, so any
   value put into this attribute would be misleading.  In addition to
   this, routing information received in the manner described in this
   specification should not be cached by the receiver, so detailing when
   the routing information expires or was last updated is irrelevant.

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5.  HELD Schema Extension

   This section describes the schema extension to HELD.

   <?xml version="1.0"?>
     elementFormDefault="qualified" attributeFormDefault="unqualified">

     <xs:element name="requestRoutingInformation">
        <xs:complexType name="empty">
           <xs:attribute name="service" type="xs:anyUri"
               use="optional" default="urn:service:sos"/>

     <xs:complexType name="service">
          <xs:restriction base="xs:anyType">
                <xs:element name="dest" type="xs:anyURI"
                <xs:any namespace="##other" processContents="lax"
                       minOccurs="0" maxOccurs="unbounded"/>
             <xs:attribute name="serviceUri" type="xs:anyURI"

     <xs:element name="routingInformation" type="ri:riType"/>
        <xs:complexType name="riType">
            <xs:restriction base="xs:anyType">
               <xs:element name="service" type="ri:service"/>
               <xs:any namespace="##other" processContents="lax"
                       minOccurs="0" maxOccurs="unbounded"/>
             <xs:anyAttribute namespace="##any" processContents="lax"/>

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6.  Examples

   Figure 3 illustrates a <locationRequest> example that contains IP
   flow information in the request.

   <locationRequest xmlns="urn:ietf:params:xml:ns:geopriv:held"


           <flow xmlns="urn:ietf:params:xml:ns:geopriv:held:flow"
                 layer4="tcp" layer3="ipv4">

                    Figure 3: Example Location Request.

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   Figure 4 illustrates the <locationResponse> message containing two
   location URIs: a HTTPS and a SIP URI.  Additionally, the response
   contains routing information.

   <locationResponse xmlns="urn:ietf:params:xml:ns:geopriv:held">
         <locationUriSet expires="2006-01-01T13:00:00.0Z">

           <service serviceUri="urn:service:sos">


                    Figure 4: Example Location Response

7.  Privacy Considerations

   This document makes no changes that require privacy considerations
   beyond those already described in [RFC5985] and [RFC6155].

8.  Security Considerations

   This document imposes no additional security considerations beyond
   those already described in [RFC5985] and [RFC6155].

9.  IANA Considerations

9.1.  URN sub-namespace registration for

   This document calls for IANA to register a new XML namespace, as per
   the guidelines in [RFC3688].

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   URI:  urn:ietf:params:xml:ns:geopriv:held:ri

   Registrant Contact:  IETF, ECRIT working group (,
      James Winterbottom (


    <?xml version="1.0"?>
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
    <html xmlns="" xml:lang="en">
       <title>HELD Routing Information Extensions</title>
      <h1>Additional Element for HELD Routing Information</h1>
      [[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX
        with the RFC number for this specification.]]
      <p>See <a href="[[RFC URL]]">RFCXXXX</a>.</p>

9.2.  XML Schema Registration

   This section registers an XML schema as per the procedures in

   URI:  urn:ietf:params:xml:schema:geopriv:held:ri

   Registrant Contact:  IETF, ECRIT working group, (,
      James Winterbottom (

      The XML for this schema can be found as the entirety of Section 5
      of this document.

10.  Acknowledgements

   We would like to thank Wilfried Lange for sharing his views with us.
   We would also like to thank Bruno Chatras for his early review
   comments and Bernd Henschel for his support.  Thanks to Roger
   Marshall and Randy Gellens for their helpful suggestions.

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11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              January 2004.

   [RFC5222]  Hardie, T., Newton, A., Schulzrinne, H., and H.
              Tschofenig, "LoST: A Location-to-Service Translation
              Protocol", RFC 5222, August 2008.

   [RFC5687]  Tschofenig, H. and H. Schulzrinne, "GEOPRIV Layer 7
              Location Configuration Protocol: Problem Statement and
              Requirements", RFC 5687, March 2010.

   [RFC5985]  Barnes, M., "HTTP-Enabled Location Delivery (HELD)",
              RFC 5985, September 2010.

   [RFC6443]  Rosen, B., Schulzrinne, H., Polk, J., and A. Newton,
              "Framework for Emergency Calling Using Internet
              Multimedia", RFC 6443, December 2011.

   [RFC6881]  Rosen, B. and J. Polk, "Best Current Practice for
              Communications Services in Support of Emergency Calling",
              BCP 181, RFC 6881, March 2013.

11.2.  Informative References

   [M493]     European Telecommunications Standards Institute,
              "Functional architecture to support European requirements
              on emergency caller location determination and transport",
              ES 203 178, V 1.0.5, December 2014.

   [RFC5986]  Thomson, M. and J. Winterbottom, "Discovering the Local
              Location Information Server (LIS)", RFC 5986,
              September 2010.

   [RFC6155]  Winterbottom, J., Thomson, M., Tschofenig, H., and R.
              Barnes, "Use of Device Identity in HTTP-Enabled Location
              Delivery (HELD)", RFC 6155, March 2011.

   [RFC6915]  Bellis, R., "Flow Identity Extension for HTTP-Enabled
              Location Delivery (HELD)", RFC 6915, April 2013.

   [RFC7216]  Thomson, M. and R. Bellis, "Location Information Server

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              (LIS) Discovery Using IP Addresses and Reverse DNS",
              RFC 7216, April 2014.

Authors' Addresses

   James Winterbottom
   Winterb Consulting Services
   Gwynneville, NSW  2500

   Phone: +61 448 266004

   Hannes Tschofenig
   Halls in Tirol  6060


   Laura Liess
   Deutsche Telekom Networks
   Deutsche Telekom Allee 7
   Darmstadt, Hessen  64295


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