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GEOPRIV WG                                               J. Winterbottom
Internet-Draft                                                M. Thomson
Intended status: Standards Track                                  Andrew
Expires: September 3, 2007                                      B. Stark
                                                               BellSouth
                                                           March 2, 2007


                 HTTP Enabled Location Delivery (HELD)
            draft-winterbottom-http-location-delivery-05.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
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   This Internet-Draft will expire on September 3, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).












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Abstract

   A Geopriv using protocol is described that is used for retrieving
   location information from a server within an access network.  The
   protocol includes options for retrieving location information either
   by-value or by-reference.  The protocol supports mobile and nomadic
   devices through Location URIs.  The protocol is an application-layer
   protocol that is independent of session-layer; an HTTP, web services
   binding is specified.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.1.  Exclusions . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.2.  Device or Target . . . . . . . . . . . . . . . . . . . . .  6
     1.3.  The Bigger Picture . . . . . . . . . . . . . . . . . . . .  6
   2.  Conventions used in this document  . . . . . . . . . . . . . .  8
     2.1.  GEOPRIV Terminology  . . . . . . . . . . . . . . . . . . .  8
   3.  HELD Overview  . . . . . . . . . . . . . . . . . . . . . . . . 10
     3.1.  Requesting Location Information Directly . . . . . . . . . 10
       3.1.1.  Shaping the PIDF-LO  . . . . . . . . . . . . . . . . . 11
     3.2.  Requesting a Location URI  . . . . . . . . . . . . . . . . 11
       3.2.1.  Establishing a Location Server Context . . . . . . . . 12
   4.  Protocol Description . . . . . . . . . . . . . . . . . . . . . 14
     4.1.  Protocol Binding . . . . . . . . . . . . . . . . . . . . . 15
     4.2.  Location Request . . . . . . . . . . . . . . . . . . . . . 15
     4.3.  Contexts . . . . . . . . . . . . . . . . . . . . . . . . . 16
       4.3.1.  Creating Contexts  . . . . . . . . . . . . . . . . . . 16
       4.3.2.  Updating Contexts  . . . . . . . . . . . . . . . . . . 17
       4.3.3.  Terminating Contexts . . . . . . . . . . . . . . . . . 17
     4.4.  Combined Context and Location Requests . . . . . . . . . . 18
     4.5.  Indicating Errors  . . . . . . . . . . . . . . . . . . . . 18
   5.  Protocol Parameters  . . . . . . . . . . . . . . . . . . . . . 19
     5.1.  "responseTime" Parameter . . . . . . . . . . . . . . . . . 20
     5.2.  "assert" Parameter . . . . . . . . . . . . . . . . . . . . 20
       5.2.1.  "method" Parameter . . . . . . . . . . . . . . . . . . 20
       5.2.2.  "timestamp" Parameter  . . . . . . . . . . . . . . . . 20
       5.2.3.  "expires" Parameter  . . . . . . . . . . . . . . . . . 21
       5.2.4.  "exact" Parameter  . . . . . . . . . . . . . . . . . . 21
     5.3.  "locationType" Parameter . . . . . . . . . . . . . . . . . 21
       5.3.1.  "exact" Parameter  . . . . . . . . . . . . . . . . . . 22
     5.4.  "profile" Parameter  . . . . . . . . . . . . . . . . . . . 22
       5.4.1.  "presentity" Parameter . . . . . . . . . . . . . . . . 23
       5.4.2.  "retentionExpiry" Parameter  . . . . . . . . . . . . . 23
       5.4.3.  "retentionInterval" Parameter  . . . . . . . . . . . . 23
       5.4.4.  "retransmission" Parameter . . . . . . . . . . . . . . 24
       5.4.5.  "rulesetURI" Parameter . . . . . . . . . . . . . . . . 24



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     5.5.  "signed" Parameter . . . . . . . . . . . . . . . . . . . . 24
     5.6.  "lifetime" Parameter . . . . . . . . . . . . . . . . . . . 24
     5.7.  "rules" Parameter  . . . . . . . . . . . . . . . . . . . . 24
       5.7.1.  "rulesetURI" Parameter . . . . . . . . . . . . . . . . 25
       5.7.2.  Common Policy "ruleset" Parameter  . . . . . . . . . . 25
     5.8.  "code" Parameter . . . . . . . . . . . . . . . . . . . . . 25
     5.9.  "message" Parameter  . . . . . . . . . . . . . . . . . . . 27
     5.10. "context" Parameter  . . . . . . . . . . . . . . . . . . . 27
       5.10.1. "locationURI" Parameter  . . . . . . . . . . . . . . . 27
       5.10.2. "password" Parameter . . . . . . . . . . . . . . . . . 27
       5.10.3. "expires" Parameter  . . . . . . . . . . . . . . . . . 28
     5.11. "location" Parameter . . . . . . . . . . . . . . . . . . . 28
   6.  XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 29
   7.  HTTP Binding . . . . . . . . . . . . . . . . . . . . . . . . . 35
     7.1.  HTTP Binding WSDL  . . . . . . . . . . . . . . . . . . . . 35
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 38
     8.1.  Return Routability . . . . . . . . . . . . . . . . . . . . 38
     8.2.  Transaction Layer Security . . . . . . . . . . . . . . . . 39
     8.3.  Veracity of Asserted LI  . . . . . . . . . . . . . . . . . 39
   9.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
     9.1.  Simple HTTP Binding Example Messages . . . . . . . . . . . 40
     9.2.  Location Request Examples  . . . . . . . . . . . . . . . . 42
     9.3.  Context Creation and Update Examples . . . . . . . . . . . 44
     9.4.  Sample LG WSDL Document  . . . . . . . . . . . . . . . . . 48
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 49
     10.1. IANA Registry for HELD Result Codes  . . . . . . . . . . . 49
     10.2. URN Sub-Namespace Registration for
           urn:ietf:params:xml:ns:geopriv:held  . . . . . . . . . . . 49
     10.3. XML Schema Registration  . . . . . . . . . . . . . . . . . 50
     10.4. URN Sub-Namespace Registration for
           urn:ietf:params:xml:ns:geopriv:held:http . . . . . . . . . 50
     10.5. MIME Media Type Registration for 'application/held+xml'  . 51
   11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 53
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 54
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 54
     12.2. Informative References . . . . . . . . . . . . . . . . . . 55
   Appendix A.  HELD Compliance to IETF LCP requirements  . . . . . . 58
     A.1.  L7-1: Identifier Choice  . . . . . . . . . . . . . . . . . 58
     A.2.  L7-2: Mobility Support . . . . . . . . . . . . . . . . . . 58
     A.3.  L7-3: Layer 7 and Layer 2/3 Provider Relationship  . . . . 59
     A.4.  L7-4: Layer 2 and Layer 3 Provider Relationship  . . . . . 59
     A.5.  L7-5: Legacy Device Considerations . . . . . . . . . . . . 60
     A.6.  L7-6: VPN Awareness  . . . . . . . . . . . . . . . . . . . 60
     A.7.  L7-7: Network Access Authentication  . . . . . . . . . . . 60
     A.8.  L7-8: Network Topology Unawareness . . . . . . . . . . . . 61
   Appendix B.  HELD Compliance to NENA Location Acqusition
                Requirements  . . . . . . . . . . . . . . . . . . . . 62
     B.1.  DA1  . . . . . . . . . . . . . . . . . . . . . . . . . . . 62



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     B.2.  DA2  . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
     B.3.  DA3  . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
     B.4.  DA4  . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
     B.5.  DA5  . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
     B.6.  DA6  . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
     B.7.  DA7  . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
     B.8.  DA8  . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
     B.9.  DA9  . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
     B.10. DA10 . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
     B.11. DA11 . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
     B.12. DA12 . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
     B.13. Rep1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
     B.14. Rep2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
     B.15. Rep3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
     B.16. Rep4 . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
     B.17. LocSec1  . . . . . . . . . . . . . . . . . . . . . . . . . 66
     B.18. LocSec2  . . . . . . . . . . . . . . . . . . . . . . . . . 67
     B.19. LocSec3  . . . . . . . . . . . . . . . . . . . . . . . . . 67
     B.20. LocSec4  . . . . . . . . . . . . . . . . . . . . . . . . . 67
     B.21. LocSec5  . . . . . . . . . . . . . . . . . . . . . . . . . 68
     B.22. LocSec6  . . . . . . . . . . . . . . . . . . . . . . . . . 68
     B.23. LocSec7  . . . . . . . . . . . . . . . . . . . . . . . . . 68
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 69
   Intellectual Property and Copyright Statements . . . . . . . . . . 70



























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1.  Introduction

   The location of a Device is information that is useful for a number
   of applications.  A Device might be able to determine this
   information using its own resources, but more often than not, the
   Device must rely on its access network to provide this information.
   This document describes a protocol that can be used to acquire
   Location Information (LI) from a service within an access network.

   This specification identifies two methods for acquiring LI.  Location
   may be retrieved from a Location Generator (LG) by-value, that is,
   the Device may acquire LI directly.  Alternatively, the Device may
   request that the LG provide a location URI so that LI can be
   distributed by-reference.  Both of these methods are compatible, and
   both can be provided concurrently from the same LG so that
   application needs can be addressed individually.

   This specification defines an XML-based protocol that enables the
   retrieval of LI from a LG.  This protocol can be bound to any
   session-layer protocol, particularly those capable of MIME transport;
   an HTTP binding is included as a minimum requirement.

1.1.  Exclusions

   This document defines a protocol for configuration purposes; that is,
   a protocol for requesting (and receiving) the information necessary
   to use LI.  This document does not define a Geopriv Using Protocol.
   The LG is assumed to be present within the same administrative domain
   as the Device (the access network), which limits the security threats
   that this protocol is exposed to.

   This document does not specify how LI is derived.  Determination of
   the physical location of a network termination point is dependent on
   the type of access network and the capabilities of networking
   equipment.  The specific methods that could be used are innumerable,
   therefore this is left to individual network and equipment
   implementations.

   Providing LI by-reference implies that a server is able to provide
   the Device with a public, globally-routable URI.  How this URI is
   provided is not covered by this specification.  This includes any
   interactions between the LG and LS necessary to facilitate the
   provision of a Location URI.

   This document does not define how an LG is discovered or configured.
   Service discovery techniques are described in
   [I-D.thomson-geopriv-lis-discovery].




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1.2.  Device or Target

   LI provided for the Device is often represented as the location of a
   user.  However, in this document LI is attributed to a Device and not
   a person.  Primarily, this is because location determination
   technologies are generally designed to locate a Device and not a
   person.  In addition to this, unless the Device requires active user
   authentication, there is no guarantee that any particular individual
   is using the Device at that instant.  Thus, if any claim of veracity
   is to be made for LI, the distinction between Target and Device must
   be made explicit.

   This distinction should not lead to the impression that the location
   of the Device does not impact the privacy constraints required by
   this protocol.  Revealing the location of the Device almost
   invariably reveals some information about the location of the user of
   the Device, therefore the same level of privacy protection demanded
   by a user is required for the Device.

   It is expected that, for most applications, this distinction will be
   unnecessary: LI for the Device will be used as an adequate substitute
   for the user's LI.  This requires either some additional assurances
   about the link between Device and Target, or an acceptance of the
   aforementioned limitations.

   This document assumes that the Device is responsible for the protocol
   interactions described and that it does so with the authority of the
   Target and Rule Maker (RM).

1.3.  The Bigger Picture

   This document describes an interface between a Device and a Location
   Generator (LG).  Detailing the interactions between these two
   entities requires a wider understanding of other interested parties.

   For the Device, the most important consideration is the Target.  In
   some cases, this is the same as the Device, but it is more likely to
   be a human user.  The foundation of this protocol is that the Target
   is able to direct the dissemination of LI, that is, the Target
   provides authorization policies and otherwise controls how LI is
   granted to Location Recipients (LRs).  This extends to when a
   Location Server (LS) is employed to provide a Location URI; the LS
   cannot provide LI to an LR without express permission from the
   Target.

   The LG exists as an access network service.  An Access Provider (AP)
   operates this service so that Devices (and Targets) can retrieve LI.
   The LG exists because not all Devices are capable of determining LI,



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   and because, even if a Device is able to determine its own LI, it may
   be more efficient with assistance.

   The following diagram shows one possible configuration of the roles
   identified in [RFC3693] and where this protocol applies.

                          +-----------+         +-----------+
                          | Location  |         | Location  |
                          | Generator | - - - - | Server    |
                          |           |         |           |
                          +-----------+         +-----------+
                                |                     |
                               HELD                   |
                                |                     |
       Rule Maker - _     +-----------+         +-----------+
           o          - - | Device    |         | Location  |
          <U\             |           | - - - - | Recipient |
          / \       _ - - |           |         |           |
         Target - -       +-----------+         +-----------+

                        Figure 1: Significant Roles






























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2.  Conventions used in this document

   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 [RFC2119].

   This specification provides an XML Schema
   [W3C.REC-xmlschema-1-20041028].  The schema definition is normative.

2.1.  GEOPRIV Terminology

   This document uses the terms (and their acronym forms) Location
   Information (LI), Location Object (LO), Device, Target, Access
   Provider (AP), Location Server (LS), Location Generator (LG),
   Location Recipient (LR), Rule Maker (RM), Rule Holder (RH) and Using
   Protocol as defined in [RFC3693].

   For convenience, abbreviated versions of RFC 3693 [RFC3693]
   definitions are included:

   Access Provider (AP):  An organization that provides physical network
      connectivity to its customers or users, e.g., through digital
      subscriber lines, cable TV plants, Ethernet, leased lines or radio
      frequencies.  Examples of such organizations include
      telecommunication carriers, municipal utilities, larger
      enterprises with their own network infrastructure, and government
      organizations such as the military.

   Civic Location/Address:  A location expressed in a form that is
      defined by civic demarcations.  Civic addresses can be specialized
      for jurisdictional (general use) or postal (message delivery)
      purposes, or they can apply to either.

   Device:  The technical device whereby the location is tracked as a
      proxy for the location of a Target.

   Geodetic Location:  A location expressed in coordinate form.

   Location Generator (LG):  The entity that initially determines or
      gathers the location of the Target.

   Location Information (LI):  The data that describes the location of a
      Device.  Note that the term LI does not include the representation
      of this data.







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   Location Object (LO):  An object conveying Location Information (and
      possibly privacy rules) to which Geopriv security mechanisms and
      privacy rules are to be applied [from 3693]; this is a specific
      by-value representation of Location Information (LI).  In this
      document, LO refers to PIDF-LO [RFC4119].

   Location Server (LS):  The LS is an element that receives
      publications of Location Objects from Location Generators and may
      receive subscriptions from Location Recipients.  The LS applies
      the rules (which it learns from the Rule Holder) to LOs it
      receives from LGs, and then notifies LRs of resulting LOs as
      necessary.

      In some specifications the Location Server is referred to as a
      Location Information Server or LIS.  Note that in this context,
      the Location Server is distinct from what is alternatively
      referred to as a Registrar in other contexts.

   Location Recipient (LR):  The entity that receives Location
      Information (LI).

   Rule Holder (RH):  The entity that provides the rules associated with
      a particular target for the distribution of Location Information
      (LI).

   Rule Maker (RM):  The authority that creates rules governing access
      to location information for a target (typically, this it the
      Target themselves).

   Target:  A person or other entity whose location is communicated by a
      Location Object (LO).

   Using Protocol:  A protocol that carries a Location Object.


















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3.  HELD Overview

   The HELD protocol facilitates retrieval of LI either by-value, as a
   PIDF-LO document, or by-reference, as a Location URI.

   This section describes how HELD can be used within a larger framework
   that moves LI from a source (the LG) to a destination (the LR).

3.1.  Requesting Location Information Directly

   Where a Device requires LI directly, it can request that the LG
   create a PIDF-LO document.  The Device is then able to use the
   provided PIDF-LO document as it is required, using the appropriate
   application protocol.  Figure 2 illustrates how this usage of HELD
   fits within the model presented in [RFC3693].

     +-----------+              +----------+              +-----------+
     | Location  |   Location   | Device   |   Location   | Location  |
     | Generator |----Object--->| (Target) |----Object--->| Recipient |
     |           |              | (LS, RH) |              |           |
     +-----------+              +----------+              +-----------+

                  Figure 2: Simple Location Request Model

   In this model, the Device in this scenario acts as a Location Server
   (LS) and Rule Holder (RH); it is responsible for making authorization
   decisions about which Location Recipients are given LOs.

   The LG needs to uniquely identify the Device within the access
   network.  The source address of the request message is sufficient in
   most cases.  Once the Device is identified, the LG uses network
   domain-specific information to determine the location of the Device.

   An LI request does not need to include any identification information
   other than return addressing.  In fact, the HTTP binding (Section 7)
   includes the option for a GET request.  Return routability also
   addresses a number of security concerns, see Section 8.

   The response from the LG is a PIDF-LO document [RFC4119], unless
   there were errors in processing the request.

   The interface between Device (acting as LS) and Location Recipient
   (LR) is application-specific and outside the scope of this
   specification.







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3.1.1.  Shaping the PIDF-LO

   A Device can include additional information in an LI request that
   controls how the LG populates the fields in a PIDF-LO document.
   Related to privacy, a presentity URI and usage rules can be
   specified.  The Device can also include a location estimate, or
   request a specific type of location information, including a request
   for a signed PIDF-LO.

   When requesting LI, the Device can include a presentity URI for the
   Target and a ruleset reference.  The LG incorporates this information
   in the PIDF-LO document, or modifies the document accordingly.

   LI contained within a PIDF-LO document can be either geodetic
   (coordinates using latitude and longitude or some other coordinate
   system) or civic (street or postal addresses).  The Device can
   request that the LG provide a specific type of LI, including whether
   a jurisdictional or postal civic address is required.

   If a Device is capable of providing its own location it can include
   this in a request.  The LG is then able to include this LI in the
   returned PIDF-LO.  The type of LI is inferred from the request when
   LI is provided.

   The PIDF-LO document generated by an LG MUST follow the rules in
   [I-D.ietf-geopriv-pdif-lo-profile].  The LI sent in a request MUST
   follow the subset of those rules relating to the construction of the
   "location-info" element.

3.2.  Requesting a Location URI

   Requesting LI directly does not always address the requirements of an
   application.  A Location URI is a URI [RFC3986] of any scheme, which
   a Location Recipient (LR) can use to retrieve LI.  A Device can
   request a Location URI instead of LI.

   Figure 3 illustrates how this usage of HELD fits within the model
   presented in [RFC3693].  The first aspect of the diagram shows how
   the Device acts as an agent for the Target and retrieves a Location
   URI, which it then provides to the Location Recipient.  The second
   aspect has the Device acting as an agent for the Rule Maker; the
   Device forwards rules to the LG, which forwards them to the LS.









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      +-----------+    Location    +--------------+
      | Location  |------URI------>| Device       |
      | Generator |                | (Target)     |
      |           |<-----Rules-----| (Rule Maker) |
      +-----------+                +--------------+
           |                              |
       LO & Rules                    Location URI
           |                              |
           V                              V
      +----------+                  +------------+
      | Location |     Location     | Location   |
      | Server   |------Object----->| Recipient  |
      |          |                  |            |
      +----------+                  +------------+

                    Figure 3: Location URI Usage Model

   Note that the Location Server takes the role of a (Private) Rule
   Holder when the rules are provided by-value.  The rules may also be
   provided to the LG and LS by-reference, in which case, a Public Rule
   Holder is required; the Public Rule Holder is not shown in this
   diagram.

   The interface between Device (acting as LS) and Location Recipient
   (LR) is application-specific and outside the scope of this
   specification.  Also, any interface between Device (acting as RM) and
   a Public Rule Holder is not relevant to this specification.

   The merits and drawbacks of using a Location URI approach are
   discussed in [I-D.marshall-geopriv-lbyr-requirements].

3.2.1.  Establishing a Location Server Context

   A Location URI is allocated for a Device by the LS.  If the LS is to
   be able to service queries for location directed at the Location URI,
   it must maintain certain information.  When the LG receives a request
   for a Location URI, it requests that the LS allocate a URI for a
   particular Device.  As a part of providing a Location URI, the LS
   also creates a _context_, which contains the information that it
   requires to properly service requests to the URI.

   This document does not make any normative statements about the
   interface between the LG and LS.  Any assumptions that are made about
   the nature of this interface are stated where necessary.

   A context contains sufficient information for the LS to identify the
   Device to the LG, so that LI can be generated as required, which
   could be on a per-request basis.  The context also includes



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   instructions from the Device on how the PIDF-LO is to be generated,
   as described in Section 3.1.1.

   The context contains an authorization policy that describes to whom,
   and how, LI is granted.  This is a common-policy document
   [I-D.ietf-geopriv-common-policy] that is provided by the Device in
   the context creation request, either directly, or by reference.












































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4.  Protocol Description

   As discussed in Section 3, this protocol provides two basic
   functions: LI request and Location URI request.  Messages are defined
   as XML documents.

   The Location Request message is described in Section 4.2.  A Location
   Request from a Device results in a PIDF-LO document in case of
   success, or an error message.

   In requesting a Location URI, the Device requests that a context be
   created on the LS.  The parameters for the create context request are
   described in Section 4.3.1.  The response to a context creation
   request includes Location URIs and a password that can be used to
   update the information contained in the context.  The details stored
   by the LS can be updated at any time after creation using the update
   context request, described in Section 4.3.2.

   Table 1 shows the basic set of messages supported by this protocol
   and their respective responses, successful or otherwise.

   +------------+------------------+-------------------+---------------+
   | Operation  | Request Message  | Successful        | Error         |
   |            |                  | Response          | Response      |
   +------------+------------------+-------------------+---------------+
   | Request    | locationRequest  | PIDF-LO document  | error         |
   | Location   | (Section 4.2)    | [RFC4119]         | (Section 4.5) |
   |            |                  |                   |               |
   | Create     | createContext    | contextResponse   | error         |
   | Context    | (Section 4.3.1)  |                   | (Section 4.5) |
   |            |                  |                   |               |
   | Update     | updateContext    | contextResponse   | error         |
   | Context    | (Section 4.3.2)  |                   | (Section 4.5) |
   +------------+------------------+-------------------+---------------+

                         Table 1: HELD Operations

   A MIME type "application/held+xml" is registered in Section 10.5 to
   distinguish HELD messages from other XML document bodies.  This
   specification follows the recommendations and conventions described
   in [RFC3023], including the naming convention of the type ('+xml'
   suffix) and the usage of the 'charset' parameter.

   Section 5 contains a more thorough description of the protocol
   parameters, valid values, and how each should be handled.  Section 6
   contains a more specific definition of the structure of these
   messages in the form of an XML Schema [W3C.REC-xmlschema-1-20041028].




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4.1.  Protocol Binding

   The HELD protocol is an application-layer protocol that is defined
   independently of any lower layers.  This means that any protocol can
   be used to transport this protocol providing that it can provide a
   few basic features:

   o  The protocol must have acknowledged delivery.

   o  The protocol must be able to correlate a response with a request.

   o  The protocol must provide authentication, privacy and protection
      against modification.

   Candidate protocols that could be used to address these purposes
   include: TCP [RFC0793], TLS [RFC2246], SASL [RFC2222], HTTP
   [RFC2616], SIP [RFC3261], BEEP [RFC3080] and SOAP
   [W3C.REC-soap12-part1-20030624] [W3C.REC-soap12-part2-20030624].
   This document includes a binding that uses a combination of HTTP, TLS
   and TCP in Section 7.

4.2.  Location Request

   A location request is sent from the Device to the LG when it requires
   LI.  This request can be very simple, including no parameters; in
   fact, the HTTP binding includes a GET request that does not include a
   message body.

   A Device MAY make an assertion about its own location as part of a
   location request.  Devices that have some means of acquiring LI,
   either from embedded technology like Global Positioning System (GPS)
   receivers or from user input, can use this to convey that information
   to the LG.  The "assert" element can be used to convey this
   information.

   The type of LI that a Device requests is determined by the type of LI
   that is included in the "assert" element.  When asserted LI is not
   provided, the Device MAY specify the type of location requested using
   the "locationType" element.

   LI provided by the Device is potentially more precise than that
   provided by the LG, therefore the LG MAY use this information to
   create a response.  The LG SHOULD validate the LI provided for
   accuracy and precision before using this information.

   The Device MAY specify a "profile" element that instructs the LG on
   how to construct the LO.  Alternatively, if the Device has created a
   profile in an LS context, the Device can provide a "context" element



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   so that the LG can retrieve the profile from the LS.

   The location request is made by sending a document formed of a
   "locationRequest" element.  The successful response to a location
   request is a PIDF-LO document, unless the request fails, in which
   case the LG SHOULD provide an error indication document.

4.3.  Contexts

   A context is established by the LS in order to provide a Location
   URI.  The context includes information necessary to identify the
   Device and determine its location when an LR requests an LO using the
   Location URI.

4.3.1.  Creating Contexts

   The Device uses the "createContext" message to request that the LG,
   and the LS, assign a Location URI.  This establishes a context at the
   LS.

   The LS MUST maintain the information provided in the create context
   request.  The create context request includes a time limit, which
   sets the maximum time that this context can be maintained.

   The response to a create context request contains information that
   the Device can use to identify a context.  A set of Location URIs are
   included, each one MUST uniquely identify the context; that is, the
   LS MUST be able to identify a context based on a single Location URI.
   A Device can distribute a Location URI to an LR to allow it retrieve
   LI from the LS.

   A Location URI MUST NOT contain any information that could be used to
   identify the Device or Target.  It is RECOMMENDED that a Location URI
   contain a public address for the LS and a random sequence of
   characters that the LS can use to identify a particular context.  The
   presentity identifier included in a PIDF-LO document SHOULD NOT be
   used for either part or the entirety of a Location URI.

   The response to a create context request MUST include the time when
   the LS will terminate the context.  The LS MUST NOT respond to any
   queries to the context beyond this time.  A response to a context
   creation also includes a password that the Device uses to identify
   itself when updating the context at any time before the context
   expiry time.







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4.3.2.  Updating Contexts

   A Device can update any of the information it has provided for a
   context at any time.  The update context request includes the same
   information as the create context request with the addition of
   information that identifies an existing context.

   A Device uses any one of the Location URIs provided to uniquely
   identify a context when updating context information.  The context
   password MUST be provided when updating context information.

   If a Device includes an authorization policy (or ruleset) in an
   update context request, the LS MUST refresh any stored copy of the
   authorization policy.  This is especially important for authorization
   policies that are provided by-reference; the LS MUST update the
   authorization policy, even if the URI has not changed.  Updated
   authorization policies MUST be processed by the LG and LS before any
   subsequent requests from LRs are accepted; the LG and LS MAY defer
   processing of the authorization policy until after a response is sent
   to the Device.

   The update context request is constructed using the "updateContext"
   element.  A successful response is the "contextResponse" element,
   which is the same as the response to a create context response.

   The update context request can also indicate that data can be removed
   by the context by specifying a _nil_ value for any of the parameters,
   using the "xsi:nil" attribute.  This applies to the profile
   (Section 5.4) element.

   The response to an update context request is identical in form to the
   create context response, with updated information about the context.
   The Location URIs MUST be the same as those in the response to the
   initial create context request, but the password and expiry time MAY
   be changed.

4.3.3.  Terminating Contexts

   The update context request can be used to instruct the LS to
   terminate a context.  The "lifetime" element in the request is set to
   a zero duration.  Once the context has been terminated, or it has
   expired, Location URIs that reference that context can no longer be
   used and the Device MUST NOT use the Location URIs or password
   relating to that context.

   The LS MAY terminate a context without notifying the Device.  The LS
   SHOULD terminate contexts if it, or the LG, detect that any
   information relating to the Device changes in a way that invalidates



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   the context.

   When the Device requests that a context be terminated, the LG
   responds with a "contextResponse" message that does not include any
   context information; this message MUST include the HELD "201"
   response code.

4.4.  Combined Context and Location Requests

   HELD supports an optimization that allows for the creation or update
   of a context while simultaneously requesting location information.
   The optional "location" attribute on the "createContext" or
   "updateContext" request can be used to request that the LG include a
   PIDF-LO in the "contextResponse".  This PIDF-LO is formed according
   to the profile details associated with the context.

4.5.  Indicating Errors

   In the event of an error, the LG SHOULD respond to the Device with an
   error document.  The error response applies to all request types and
   SHOULD also be sent in response to any unrecognized request.

   An error indication document consists of an "error" element.  The
   "error" element MUST include a "code" attribute that indicates the
   type of error.  A set of predefined error codes are included in
   Section 5.8.

   Error responses MAY also include a "message" attribute that can
   include additional information.  This information SHOULD be for
   diagnostic purposes only, and MAY be in any language.  The language
   of the message SHOULD be indicated with an "xml:lang" attribute.




















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5.  Protocol Parameters

   This section describes, in detail the parameters that are used for
   this protocol.  Table 2 lists the top-level components used within
   the protocol and where they are used.

   +------------------------+-------------+-------------+--------------+
   | Parameter              |   Location  |    Create   |    Update    |
   |                        |   Request   |   Context   |    Context   |
   +------------------------+-------------+-------------+--------------+
   | responseTime           |   Request   |   Request   |    Request   |
   | (Section 5.1)          |             |             |              |
   |                        |             |             |              |
   | assert (Section 5.2)   |   Request   |             |              |
   |                        |             |             |              |
   | exact (assert)         |   Request   |             |              |
   | (Section 5.2.4)        |             |             |              |
   |                        |             |             |              |
   | locationType           |   Request   |             |              |
   | (Section 5.3)          |             |             |              |
   |                        |             |             |              |
   | exact (locationType)   |   Request   |             |              |
   | (Section 5.3.1)        |             |             |              |
   |                        |             |             |              |
   | profile (Section 5.4)  |   Request   |   Request   |    Request   |
   |                        |             |             |              |
   | signed (Section 5.5)   |   Request   |             |              |
   |                        |             |             |              |
   | lifetime (Section 5.6) |             |   Request   |    Request   |
   |                        |             |             |              |
   | rules (Section 5.7)    |             |   Request   |    Request   |
   |                        |             |             |              |
   | code (Section 5.8)     |    Error    |   Error &   |    Error &   |
   |                        |             |   Response  |   Response   |
   |                        |             |             |              |
   | message (Section 5.9)  |    Error    |   Error &   |    Error &   |
   |                        |             |   Response  |   Response   |
   |                        |             |             |              |
   | context (Section 5.10) |   Request   |   Response  |   Request &  |
   |                        |             |             |   Response   |
   |                        |             |             |              |
   | location               |             |   Request   |    Request   |
   | (Section 5.11)         |             |             |              |
   +------------------------+-------------+-------------+--------------+

                     Table 2: Message Parameter Usage





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5.1.  "responseTime" Parameter

   The "responseTime" attribute indicates to the LG how long the Device
   is prepared to wait for a response.  This attribute MAY be added to
   any request message, although it is primarily used with the location
   request.  The value of this attribute is indicative only, the LG is
   under no obligation to strictly adhere to the time limit implied; any
   enforcement of the time limit is left to the Device.

   This attribute MAY be either a duration value as defined in XML
   Schema [W3C.REC-xmlschema-2-20041028], or a decimal seconds value,
   which may include a decimal point.  It is RECOMMENDED that systems
   support millisecond precision for this parameter.

   The LG SHOULD provide the most accurate LI that can be determined
   within the specified interval.  This parameter could be used as input
   when selecting the method of location determination, where multiple
   such methods exist.  If this parameter is absent, then the LG SHOULD
   return the most precise LI it is capable of determining.

5.2.  "assert" Parameter

   The "assert" element allows a Device to provide LI to the LG as part
   of a location request.  Two types of content are allowed: a geodetic
   structure made up of a Geography Markup Language (GML) geometry
   object, "_Geometry" as defined by [OGC.GML-3.1.1]; and a civic
   address structure, "civicAddress" as defined by
   [I-D.ietf-geopriv-revised-civic-lo].  The contents of this element
   SHOULD follow the rules in [I-D.ietf-geopriv-pdif-lo-profile].

   When used in combination with the "context" element, this LI MAY be
   used by the LS for requests to Location URIs for that context.

   This element is mutually exclusive with the "locationType" parameter,
   defined in Section 5.3.  The type of LI requested is implied by the
   types included in the assertion.

5.2.1.  "method" Parameter

   The "method" attribute SHOULD be attached to the "assert" element to
   indicate the means by which the LI was derived.  This attribute
   follows the rules of the similarly named method element of the
   PIDF-LO.

5.2.2.  "timestamp" Parameter

   The "timestamp" attribute SHOULD be attached to the "assert" element
   to indicate when the LI was generated.



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5.2.3.  "expires" Parameter

   The "expires" attribute MAY be attached to the "assert" element to
   indicate when the included LI is no longer valid.  The LG SHOULD set
   the "retention-expires" element in the returned PIDF-LO to no later
   than this time if it uses the LI.  This attribute SHOULD NOT be
   included unless this time is definite.

5.2.4.  "exact" Parameter

   When the "exact" attribute is set to "true", it indicates to the LG
   that the contents of the "assert" parameter MUST be strictly
   followed.  The default value of "false" allows the LG the option of
   ignoring these values.

   This attribute indicates that the asserted LI MUST be included in the
   PIDF-LO response.  If the LG cannot do this for any reason, which is
   usually because it determines that the LI was inaccurate or
   insufficiently precise, the LG MUST indicate an error.

5.3.  "locationType" Parameter

   The "locationType" element is included in a location request.  It
   contains a list of LI types that are requested by the Device.  The
   following list describes the possible values:

   any:  The LG SHOULD attempt to provide LI in all forms available to
      it.  This value MUST be assumed as the default if no
      "locationType" is specified.  The LG SHOULD return location
      information in a form that is suited for routing and responding to
      an emergency call in its jurisdiction.

   geodetic:  The LG SHOULD return a geodetic location for the Target.

   civic:  The LG SHOULD return a civic address for the Target.  Any
      type of civic address may be returned.  The LG SHOULD ignore this
      value if a request for jurisdictional or postal civic address has
      been made and can be satisfied.

   jurisdictionalCivic:  The LG SHOULD return a jurisdictional civic
      address for the Target.

   postalCivic:  The LG SHOULD return a postal civic address for the
      Target.

   The "locationType" element is mutually exclusive with the "assert"
   element, defined in Section 5.2.




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   The LG SHOULD return the requested location type or types.  The LG
   MAY provide additional location types, or it MAY provide alternative
   types if the request cannot be satisfied for a requested location
   type.  If the "exact" attribute is present and set to "true" in a
   location request, then a successful LG response MUST provide the
   requested location type only, with no additional location
   information.  The "exact" attribute has no effect when this element
   is set to "any".

   The "SHOULD"-strength requirement on this parameter is included to
   allow for soft-failover.  This enables a fixed client configuration
   that prefers a specific location type without causing location
   requests to fail when that location type is unavailable.  Unless the
   "exact" attribute is set, the LG MUST provide LI in any available
   form if it is unable to comply with the request.

   For example, a notebook computer could be configured to retrieve
   civic addresses, which is usually available from typical home or work
   situations.  However, when using a wireless modem, the LG might be
   unable to provide a civic address.

5.3.1.  "exact" Parameter

   When the "exact" attribute is set to "true", it indicates to the LG
   that the contents of the "locationType" parameter MUST be strictly
   followed.  The default value of "false" allows the LG the option of
   ignoring these values.

   A value of "true" indicates that the LG MUST provide a PIDF-LO that
   includes LI of the requested type or types.  The LG MUST provide the
   requested types only and these types SHOULD be specified in the same
   order as they were requested.  The LG SHOULD handle an exact request
   that includes a "locationType" element set to "any" as if the "exact"
   attribute were set to "false".

5.4.  "profile" Parameter

   The "profile" element contains a presentity identifier [RFC2778] and
   GEOPRIV usage rules [RFC4119] information.  All fields are optional
   within this element, but when these fields are included, the LG MUST
   use these parameters when constructing the PIDF-LO document.

   This element MAY be included in location requests, create context
   requests and update context requests.  When included in a location
   request, the profile is used immediately; when used in create context
   or update context requests, the profile is stored on the LS and is
   provided to the LG when the LS responds to requests from LRs.




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5.4.1.  "presentity" Parameter

   The "presentity" element contains a presentity identifier that the LG
   SHOULD include in the "pres" attribute of the PIDF-LO document.

   The LG MAY require authentication of the presentity through any
   means; the LG SHOULD ignore this parameter if authentication
   information is not present or authentication information cannot be
   verified.

5.4.2.  "retentionExpiry" Parameter

   The "retentionExpiry" element contains an absolute "dateTime"
   [W3C.REC-xmlschema-2-20041028] value for the "retention-expires"
   element of the PIDF-LO usage rules.  This element is mutually
   exclusive with the "retentionInterval" element.

   The LG MAY use a different value than that specified (or the
   suggested default) as circumstances dictate, but MUST NOT use a value
   later than specified.  If this value indicates a time that has
   already passed, the request MUST be rejected with an error.  See
   retentionInterval (Section 5.4.3) for more details.

5.4.3.  "retentionInterval" Parameter

   The "retentionInterval" element contains a time duration value that
   is specified in the same fashion as the responseTime attribute
   (Section 5.1).

   This value MUST be added to the time at which the PIDF-LO document is
   created to set the value of the "retention-expires" element.  This
   element enables the Target to set an interval over which a LR can
   retain a LO, rather than an absolute time.  This element is mutually
   exclusive with the "retentionExpires" element.

   If neither "retentionExpiry" nor "retentionInterval" are specified,
   the LG SHOULD provide a default value for the "retention-expires"
   element of the generated PIDF-LO document.  The default for this
   value SHOULD be 24 hours from the receipt of the location request as
   defined in [RFC4119].

   The LG MAY use a different value than that specified (or the
   suggested default) as circumstances dictate, but MUST NOT use a value
   larger than specified.







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5.4.4.  "retransmission" Parameter

   The "retransmission" element contains a boolean value that MUST be
   included in the "retransmission-allowed" element of the generated
   PIDF-LO usage rules.  When this element is not provided, the LG MUST
   set the "retransmission-allowed" element to "false".

5.4.5.  "rulesetURI" Parameter

   The "rulesetURI" element contains a URI value that MUST be included
   in the "ruleset-reference" element of the generated PIDF-LO usage
   rules.

   This datum is only used to construct the usage rules in the PIDF-LO
   document.  Within the context of a profile, this ruleset is not
   applied by either LG or LS, and the LS does not apply the rules found
   at the URI.

5.5.  "signed" Parameter

   The "signed" attribute indicates whether the Device requires a
   digitally signed PIDF-LO.  When present and set to "true", the LG
   MUST provide a PIDF-LO document that is signed according to
   [I-D.thomson-geopriv-location-dependability].

5.6.  "lifetime" Parameter

   The "lifetime" element specifies the maximum time that a context
   should be maintained by the LS.  This parameter MUST be included in
   the context creation request to indicate to the LS the latest time
   that the context is allowed to be retained.  The parameter MAY be
   included in context update requests to modify this time; when
   included in an update request with a zero value, it indicates that
   the context MUST be removed immediately.

   The "lifetime" element is a duration value that is specified in the
   same fashion as the "responseTime" attribute.

   This value MUST be added to the current time when received by the LS
   to determine the time at which the context expires.  An LS MAY use
   any value less than or equal to this value, but MUST NOT use a longer
   value.  The actual expiry time of the context MUST be indicated in
   the context response.

5.7.  "rules" Parameter

   The "rules" element contains the authorization policy of the Target
   that dictates how and to whom LI is provided by the LS.  This policy



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   MUST be applied by the LS when providing LI to LRs.

   Authorization policies MUST conform to
   [I-D.ietf-geopriv-common-policy].  If the authorization policy is
   invalid, cannot be retrieved, or is otherwise not understood by the
   LS, the LG SHOULD fail the request.  Note that this implies that the
   LS SHOULD attempt to retrieve an authorization policy that is
   provided by-reference at the time of a create context request;
   however, an LS MAY choose to do this later, if the requested response
   time might be exceeded.

   In the absence of an authorization policy, the LS MUST NOT provide LI
   to any LR.  Note that in certain jurisdictions an LS might be
   required to provide LI to specific parties irrespective of the
   authorization policy, as mandated by legislation; for example,
   emergency services in some countries.

5.7.1.  "rulesetURI" Parameter

   The "rulesetURI" element contains a URI that references the Target's
   authorization policy.  This URI should reference a document of type
   "application/auth-policy+xml" as defined in
   [I-D.ietf-geopriv-common-policy].

   It is RECOMMENDED that a ruleset URI use the "https" scheme.  It is
   anticipated that, to improve responsiveness and reduce network usage,
   an LS could cache an authorization policy, consistent with the rules
   specified by the Rule Holder.  For instance, the Rule Holder could
   specified retention times using the "Expires" header in HTTP
   [RFC2616].  The impact of changes to authorization policies are
   discussed in Section 4.3.2.

5.7.2.  Common Policy "ruleset" Parameter

   The "ruleset" element, which is in the
   "urn:ietf:params:xml:ns:common-policy" namespace
   [I-D.ietf-geopriv-common-policy], allows for providing an
   authorization policy directly as part of a request.

5.8.  "code" Parameter

   All responses, except a PIDF-LO document, MUST contain a response
   code.  The "code" attribute applies to the "error" and
   "contextResponse" messages.

   The following response codes follow a three decimal form similar to
   that in HTTP [RFC2616] and SIP [RFC3261]:




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   200 (Success):  This code indicates that the request was successful.
      This code MUST not be used for an error response.

   201 (Context Terminated):  This code indicates that the request to
      terminate a context was successful.

   400 (Request Error):  This code indicates that the request was badly
      formed in some fashion.

   401 (XML Error):  This code indicates that the XML content of the
      request was either badly formed or invalid.

   402 (Authentication Error):  This code indicates that the request
      either did not contain authentication information, or the
      authentication provided was not accepted.

   403 (Asserted Location Error):  This code indicates that the LI that
      was asserted in the request was not acceptable to the LG.  This
      code is used when the "exact" attribute on the "assert" parameter
      is set to "true".

   404 (Context Not Found):  This code indicates that the context
      identified in the request was not found.  This code MAY also be
      used if the password provided was incorrect.

   500 (General LG Error):  This code indicates that an unspecified
      error occurred at the LG.

   501 (Location Unknown):  This code indicates that the LG could not
      determine the location of the Device.

   502 (Unsupported Message):  This code indicates that the request was
      not supported or understood by the LG.

   503 (Timeout):  This code indicates that the LG could not satisfy the
      request within the time specified in the "requestTime" parameter.

   504 (Cannot Provide LI Type):  This code indicates that the LG was
      unable to provide LI of the type or types requested.  This code is
      used when the "exact" attribute on the "locationType" parameter is
      set to "true".

   Additional response codes within the x00 to x79 range MUST be
   specified in published RFCs; the range from x80 to x99 is reserved
   for private usage.






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5.9.  "message" Parameter

   The "contextResponse" and "error" messages MAY include a "message"
   attribute to convey some additional, human-readable information about
   the result of the request.  This message MAY be included in any
   language, which SHOULD be indicated by the "xml:lang", attribute.

5.10.  "context" Parameter

   The "context" element includes information that is used to identify a
   context and control access to it.  The context is identified by one
   or more Location URIs and a Device is granted a password which MUST
   be provided when accessing the context to update the information
   contained.

   When a context is created, the LG provides a "contextResponse"
   message that contains the "context" element.  This element contains
   all of the Location URIs that can be used for the context, a
   password, and an expiry time.

   To update the details in a context, or reuse profile information
   stored in the context, the Device provides a "context" element.  When
   identifying a context in this manner, the Device MUST provide only
   one Location URI and the password.

5.10.1.  "locationURI" Parameter

   The "locationURI" element includes a single Location URI.  Each
   Location URI is allocated by the LS so that it is able to uniquely
   identify the context.

   A "contextResponse" message contains any number of "locationURI"
   elements.  It is RECOMMENDED that the LS allocate a Location URI for
   all schemes that it supports and that no scheme is present twice.

   All "updateContext" request messages MUST contain only one
   "locationURI" element, which is all that is necessary to uniquely
   identify a context.  The Device MAY select any of the Location URIs
   provided by the LS.  Location URIs do not change over the lifetime of
   a context.

5.10.2.  "password" Parameter

   The "password" element carries a password that is used to access the
   context after it has been created.  The LS generates this value when
   creating a context and the Device MUST use the exact same value when
   it wishes to access the context.  This value acts as a shared secret
   between Device and LS.



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   The value of the password MAY be updated in the response to any
   "updateContext" message.

   This element MAY contain any valid XML character data, within the
   constraints of the XML Schema "token" type.

5.10.3.  "expires" Parameter

   The "expires" attribute indicates the time at which the context
   created by the LS will expire.  This attribute is included in the
   "contextResponse" message only.

   Responses to create and update context requests MUST include the
   expiry time of the context.  If the LS has expired a context in
   response to an update context request, this value SHOULD include a
   time in the past to avoid problems that could be caused by a slow
   clock in the Device.

5.11.  "location" Parameter

   The "location" parameter is a boolean attribute associated with the
   "createContext" or "updateContext" message.  The default for this
   attribute is "false".

   This parameter, when present and set to "true" indicates that the LG
   SHOULD include a PIDF-LO document in the "contextResponse" message.
   The success of any request that includes this parameter MUST NOT be
   affected by any error in providing a location; thus, if the LG is
   unable to include a PIDF-LO, it is only omitted from the response.
   If a "contextResponse" does not include a PIDF-LO, the Device can
   determine the reasons for failure by sending a separate
   "locationRequest".

   Note: The schema does not include an explicit particle for the
   "presence" element.  This is because the "any" construct used to
   allow for extensions would conflict with any optional element, due to
   the Unique Particle Attribution schema rule.














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6.  XML Schema

   This section gives the XML Schema Definition
   [W3C.REC-xmlschema-1-20041028] of the "application/held+xml" format.
   This is presented as a formal definition of the "application/
   held+xml" format.  Note that the XML Schema definition is not
   intended to be used with on-the-fly validation of the presence XML
   document.

   <?xml version="1.0"?>
   <xs:schema
       targetNamespace="urn:ietf:params:xml:ns:geopriv:held"
       xmlns:xs="http://www.w3.org/2001/XMLSchema"
       xmlns:held="urn:ietf:params:xml:ns:geopriv:held"
       xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
       xmlns:ca="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
       xmlns:cp="urn:ietf:params:xml:ns:common-policy"
       xmlns:gml="http://www.opengis.net/gml"
       xmlns:xml="http://www.w3.org/XML/1998/namespace"
       elementFormDefault="qualified"
       attributeFormDefault="unqualified">

     <xs:annotation>
       <xs:documentation source="http://www.ietf.org/rfc/rfcXXXX.txt">
   <!-- [[NOTE TO RFC-EDITOR: Please replace above URL with URL of
          published RFC and remove this note.]] -->
         This document defines HELD messages.
       </xs:documentation>
     </xs:annotation>

     <xs:import namespace="http://www.w3.org/XML/1998/namespace"/>
     <xs:import namespace="urn:ietf:params:xml:ns:pidf:geopriv10"/>
     <xs:import
         namespace="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"/>
     <xs:import namespace="urn:ietf:params:xml:ns:common-policy"/>
     <xs:import namespace="http://www.opengis.net/gml"/>

     <!-- Context Information -->
     <xs:complexType name="returnContextType">
       <xs:complexContent>
         <xs:restriction base="xs:anyType">
           <xs:sequence>
             <xs:element name="locationURI" type="xs:anyURI"
                         maxOccurs="unbounded"/>
             <xs:element name="password" type="xs:token"/>
           </xs:sequence>
           <xs:attribute name="expires" type="xs:dateTime"
                         use="required"/>



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         </xs:restriction>
       </xs:complexContent>
     </xs:complexType>

     <xs:complexType name="usesContextType">
       <xs:complexContent>
         <xs:restriction base="xs:anyType">
           <xs:sequence>
             <xs:element name="locationURI" type="xs:anyURI"/>
             <xs:element name="password" type="xs:token"/>
           </xs:sequence>
         </xs:restriction>
       </xs:complexContent>
     </xs:complexType>

     <!-- Duration Type -->
     <xs:simpleType name="durationType">
       <xs:union>
         <xs:simpleType>
           <xs:restriction base="xs:decimal">
             <xs:minInclusive value="0.0"/>
           </xs:restriction>
         </xs:simpleType>
         <xs:simpleType>
           <xs:restriction base="xs:duration">
             <xs:minInclusive value="PT0S"/>
           </xs:restriction>
         </xs:simpleType>
       </xs:union>
     </xs:simpleType>

     <xs:complexType name="pidfloProfileType">
       <xs:complexContent>
         <xs:restriction base="xs:anyType">
           <xs:sequence>
             <xs:element name="presentity" type="xs:anyURI"
                         nillable="true" minOccurs="0"/>
             <xs:choice minOccurs="0">
               <xs:element name="retentionExpiry" type="xs:dateTime"
                           nillable="true"/>
               <xs:element name="retentionInterval"
                           type="held:durationType" nillable="true"/>
             </xs:choice>
             <xs:element name="retransmission" type="xs:boolean"
                         minOccurs="0" nillable="true"/>
             <xs:element name="rulesetURI" type="xs:anyURI"
                         minOccurs="0" nillable="true"/>
           </xs:sequence>



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         </xs:restriction>
       </xs:complexContent>
     </xs:complexType>

     <xs:complexType name="rulesType">
       <xs:choice minOccurs="0">
         <xs:element name="rulesetURI" type="xs:anyURI"/>
         <xs:element ref="cp:ruleset"/>
       </xs:choice>
     </xs:complexType>

     <!-- Location Type -->
     <xs:simpleType name="locationTypeBase">
       <xs:union>
         <xs:simpleType>
           <xs:restriction base="xs:token">
             <xs:enumeration value="any"/>
           </xs:restriction>
         </xs:simpleType>
         <xs:simpleType>
           <xs:list>
             <xs:simpleType>
               <xs:restriction base="xs:token">
                 <xs:enumeration value="civic"/>
                 <xs:enumeration value="geodetic"/>
                 <xs:enumeration value="postalCivic"/>
                 <xs:enumeration value="jurisdictionalCivic"/>
               </xs:restriction>
             </xs:simpleType>
           </xs:list>
         </xs:simpleType>
       </xs:union>
     </xs:simpleType>

     <xs:complexType name="locationTypeType">
       <xs:simpleContent>
         <xs:extension base="held:locationTypeBase">
           <xs:attribute name="exact" type="xs:boolean"
                         use="optional" default="false"/>
         </xs:extension>
       </xs:simpleContent>
     </xs:complexType>

     <!-- Location Assertion -->
     <xs:complexType name="locationAssertionType">
       <xs:complexContent>
         <xs:restriction base="xs:anyType">
           <xs:choice>



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             <xs:element ref="ca:civicAddress"/>
             <xs:sequence>
               <xs:element ref="gml:_Geometry"/>
               <xs:element ref="ca:civicAddress" minOccurs="0"/>
             </xs:sequence>
           </xs:choice>
           <xs:attribute name="method" type="xs:token"/>
           <xs:attribute name="timestamp" type="xs:dateTime"/>
           <xs:attribute name="expires" type="xs:dateTime"/>
           <xs:attribute name="exact" type="xs:boolean"
                         use="optional" default="false"/>
         </xs:restriction>
       </xs:complexContent>
     </xs:complexType>

     <!-- Response code -->
     <xs:simpleType name="codeType">
       <xs:restriction base="xs:nonNegativeInteger">
         <xs:pattern value="[0-5][0-9][0-9]"/>
       </xs:restriction>
     </xs:simpleType>

     <!-- Message Definitions -->
     <xs:complexType name="baseRequestType">
       <xs:complexContent>
         <xs:restriction base="xs:anyType">
           <xs:sequence/>
           <xs:attribute name="responseTime" type="held:durationType"
                         use="optional"/>
         </xs:restriction>
       </xs:complexContent>
     </xs:complexType>

     <xs:complexType name="baseResponseType">
       <xs:complexContent>
         <xs:restriction base="xs:anyType">
           <xs:sequence/>
           <xs:attribute name="code" type="held:codeType"
                         use="required"/>
           <xs:attribute name="message" type="xs:token"
                         use="optional"/>
           <xs:attribute ref="xml:lang" use="optional"/>
         </xs:restriction>
       </xs:complexContent>
     </xs:complexType>

     <xs:element name="error" type="held:baseResponseType"/>




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     <!-- Create Context -->
     <xs:complexType name="createContextType">
       <xs:complexContent>
         <xs:extension base="held:baseRequestType">
           <xs:sequence>
             <xs:element name="lifetime" type="held:durationType"/>
             <xs:element name="profile" type="held:pidfloProfileType"
                         minOccurs="0"/>
             <xs:element name="rules" type="held:rulesType"
                         minOccurs="0"/>
             <xs:any namespace="##other" processContents="lax"
                     minOccurs="0" maxOccurs="unbounded"/>
           </xs:sequence>
           <xs:attribute name="location" type="xs:boolean"
                         default="false"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>

     <xs:element name="createContext" type="held:createContextType"/>

     <!-- Context Response -->
     <xs:complexType name="contextResponseType">
       <xs:complexContent>
         <xs:extension base="held:baseResponseType">
           <xs:sequence>
             <xs:element name="context" type="held:returnContextType"
                         minOccurs="0"/>
             <xs:any namespace="##other" processContents="lax"
                     minOccurs="0" maxOccurs="unbounded"/>
           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>

     <xs:element name="contextResponse"
                 type="held:contextResponseType"/>

     <!-- Update Context -->
     <xs:complexType name="updateContextType">
       <xs:complexContent>
         <xs:extension base="held:baseRequestType">
           <xs:sequence>
             <xs:element name="context" type="held:usesContextType"/>
             <xs:element name="lifetime" type="held:durationType"
                         minOccurs="0"/>
             <xs:element name="profile" type="held:pidfloProfileType"
                         minOccurs="0"/>



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             <xs:element name="rules" type="held:rulesType"
                         minOccurs="0"/>
             <xs:any namespace="##other" processContents="lax"
                     minOccurs="0" maxOccurs="unbounded"/>
           </xs:sequence>
           <xs:attribute name="location" type="xs:boolean"
                         default="false"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>

     <xs:element name="updateContext" type="held:updateContextType"/>

     <!-- ... response to updateContext is contextResponse -->

     <!-- Location Request -->
     <xs:complexType name="locationRequestType">
       <xs:complexContent>
         <xs:extension base="held:baseRequestType">
           <xs:sequence>
             <xs:choice minOccurs="0">
               <xs:element name="locationType"
                           type="held:locationTypeType"/>
               <xs:element name="assert"
                           type="held:locationAssertionType"/>
             </xs:choice>
             <xs:choice minOccurs="0">
               <xs:element name="context" type="held:usesContextType"/>
               <xs:element name="profile"
                           type="held:pidfloProfileType"/>
             </xs:choice>
             <xs:any namespace="##other" processContents="lax"
                     minOccurs="0" maxOccurs="unbounded"/>
           </xs:sequence>
           <xs:attribute name="signed" type="xs:boolean"
                         use="optional"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>

     <xs:element name="locationRequest"
                 type="held:locationRequestType"/>

   </xs:schema>







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7.  HTTP Binding

   This section defines an HTTP [RFC2616] binding for this protocol,
   which all conforming implementations MUST support.  This binding
   takes the form of a Web Service (WS) that can be described by the Web
   Services Description Language (WSDL) document in Section 7.1.

   The three request messages are carried in this binding as the body of
   an HTTP POST request.  The MIME type of both request and response
   bodies should be "application/held+xml", except that a PIDF-LO
   document SHOULD have the MIME type "application/pidf+xml".

   The LG populates the HTTP headers so that they are consistent with
   the contents of the message.  In particular, the "Expires" and cache
   control headers are used to control the caching of any PIDF-LO
   document.  The HTTP status code SHOULD have the same first digit as
   any "contextResponse" or "error" body included, and it SHOULD
   indicate a 2xx series response when a PIDF-LO document is included.

   This binding also includes a default behaviour, which is triggered by
   a GET request, or a POST with no request body.  If either of these
   queries are received, the LG MUST attempt to provide a PIDF-LO
   document, as if the request was a location request.

   This binding MUST use TLS as described in [RFC2818].  TLS provides
   message integrity and privacy between Device and LG.  The LG MUST use
   the server authentication method described in [RFC2818]; the Device
   MUST fail a request if server authentication fails, except in the
   event of an emergency.

7.1.  HTTP Binding WSDL

   The following WSDL 2.0 [W3C.CR-wsdl20-20060106] document describes
   the HTTP binding for this protocol.  Actual service instances MUST
   provide a "service" with at least one "endpoint" that implements the
   "heldHTTP" binding.  A service description document MAY include this
   schema directly or by using the "import" or "include" directives.

   <?xml version="1.0"?>
   <wsdl:definitions
       xmlns:wsdl="http://www.w3.org/2005/05/wsdl"
       xmlns:whttp="http://www.w3.org/2005/05/wsdl/http"
       xmlns:held="urn:ietf:params:xml:ns:geopriv:held"
       xmlns:pidf="urn:ietf:params:xml:ns:pidf"
       xmlns:heldhttp="urn:ietf:params:xml:ns:geopriv:held:http"
       targetNamespace="urn:ietf:params:xml:ns:geopriv:held:http"
       type="http://www.w3.org/2005/05/wsdl/http">




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     <wsdl:documentation>
       This document describes the basic HELD web service.
       Please refer to RFCXXXX for details.
   [[NOTE TO RFC-EDITOR: Please replace XXXX with the RFC number
     for this specification and remove this note.]]
     </wsdl:documentation>

     <wsdl:types>
       <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
         <xsd:import namespace="urn:ietf:params:xml:ns:geopriv:held"
                     schemaLocation="held.xsd"/>
         <xsd:import namespace="urn:ietf:params:xml:ns:pidf"/>
       </xsd:schema>
     </wsdl:types>

     <wsdl:interface name="held">

       <wsdl:operation name="createContext" method="POST">
         <wsdl:input message="held:createContext"/>
         <wsdl:output message="held:contextResponse"/>
         <wsdl:fault message="held:error"/>
       </wsdl:operation>

       <wsdl:operation name="updateContext" method="POST">
         <wsdl:input message="held:updateContext"/>
         <wsdl:output message="held:contextResponse"/>
         <wsdl:fault message="held:error"/>
       </wsdl:operation>

       <wsdl:operation name="locationRequest" method="POST">
         <wsdl:input message="held:locationRequest"/>
         <wsdl:output ref="pidf:presence"/>
         <wsdl:fault message="held:error"/>
       </wsdl:operation>

       <wsdl:operation
           name="getLocation" method="GET"
           pattern="http://www.w3.org/2004/08/wsdl/out-only">
         <wsdl:output ref="pidf:presence"/>
         <wsdl:fault message="held:error"/>
       </wsdl:operation>

     </wsdl:interface>

     <wsdl:binding name="heldHTTP" whttp:defaultMethod="POST">
     <wsdl:operation ref="heldhttp:createContext"
           whttp:inputSerialization="application/held+xml"
           whttp:outputSerialization="application/held+xml"



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           whttp:faultSerialization="application/held+xml"/>
       <wsdl:operation ref="heldhttp:updateContext"
           whttp:inputSerialization="application/held+xml"
           whttp:outputSerialization="application/held+xml"
           whttp:faultSerialization="application/held+xml"/>
       <wsdl:operation
           ref="heldhttp:locationRequest"
           whttp:inputSerialization="application/held+xml"
           whttp:outputSerialization="application/pidf+xml"
           whttp:faultSerialization="application/held+xml"/>
       <wsdl:operation
           ref="heldhttp:getLocation"
           whttp:method="GET"
           whttp:inputSerialization="application/held+xml"
           whttp:outputSerialization="application/pidf+xml"
           whttp:faultSerialization="application/held+xml"/>
     </wsdl:binding>

   </wsdl:definitions>
































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8.  Security Considerations

   The threat model for this protocol assumes that the LG exists within
   the same administrative domain as the Device.  The LG requires access
   to network information so that it can determine LI.  Therefore, the
   LG can use network information to protect against a number of the
   possible attacks.

   Specific requirements and security considerations ofr location
   acquisition protocols provided in [I-D.ietf-geopriv-l7-lcp-ps].

   An in-depth discussion of the security considerations applicable to
   the use of Location URIs and by-reference provision of LI is included
   in [I-D.marshall-geopriv-lbyr-requirements].

8.1.  Return Routability

   It is RECOMMENDED that Location Generators use return routability
   rather than requiring Device authentication.  Device authentication
   SHOULD NOT be required due to the administrative challenge of issuing
   and managing of client credentials, particularly when networks allow
   visiting users to attach devices.  However, the LG MAY require any
   form of authentication as long as these factors are considered.

   Addressing information used in a request to the LG is used to
   determine the identity of the Device, and to address a response.
   This ensures that a Device can only request its own LI.

   A temporary spoofing of IP address could mean that a device could
   request a Location URI that would result in another Device's
   location.  One or more of the follow approaches are RECOMMENDED to
   limit this exposure:

   o  Location URIs SHOULD have a limited lifetime, that is, the LG
      SHOULD enforce a maximum value for the lifetime element
      (Section 5.6).

   o  The network SHOULD have mechanisms that protect against IP address
      spoofing.

   o  The LG SHOULD ensure that requests can only originate from within
      its administrative domain.

   o  The LG and network SHOULD be configured so that the LG is made
      aware of Device movement within the network and addressing
      changes.  If the LG and LS detect a change in the network that
      invalidates a context, the context MUST be terminated.




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   The above measures are dependent on network configuration and SHOULD
   be considered with circumstances in mind.  For instance, in a fixed
   internet access providers may be able to restriction the allocation
   of IP addresses to a single physical line, ensuring that spoofing is
   not possible; in such an environment, the other measures are not
   necessary.

8.2.  Transaction Layer Security

   All bindings for this protocol MUST ensure that messages are
   adequately protected against eavesdropping and modification.
   Bindings MUST also provide a means of authenticating the LG.

   It is RECOMMENDED that all bindings also use TLS [RFC2246].

   For the HTTP binding, TLS MUST be used.  TLS provides protection
   against eavesdropping and modification.  The server authentication
   methods described in HTTP on TLS [RFC2818] MUST be used.

8.3.  Veracity of Asserted LI

   The assert element (Section 5.2) allows a Device the ability to
   provide LI.  However, if an LG uses asserted LI, it is the LG that
   becomes responsible for the veracity of that information.  Therefore,
   when the Device provides LI in a request, the LG MUST NOT use this
   information unless it can ensure its accuracy.  This prevents the
   fraudulent provision of LI that could be caused by the LG accepting
   LI without any checks.

   It is unlikely that an LG is able to verify Device-provided LI beyond
   any uncertainty.  The ability of an LG to verify LI is limited by its
   own capacity to determine the location of the Device.  The LG SHOULD
   indicate the source of LI using the PIDF-LO "method" parameter so
   that users of LI can make appropriate judgments on its veracity.

















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9.  Examples

9.1.  Simple HTTP Binding Example Messages

   The examples in this section show a complete HTTP message that
   includes the HELD request or response document.

   This example shows the most basic request for a LO.  This uses the
   GET feature described by the HTTP binding.  This example assumes that
   the LG service exists at the URL "https://lg.example.com/location".

GET /location HTTP/1.1
Host: lg.example.com
Accept: application/pidf+xml,application/held+xml,application/xml;q=0.8,
    text/xml;q=0.7
Accept-Charset: UTF-8,*


   The GET request is exactly identical to a minimal POST request that
   includes an empty "locationRequest" element.

POST /location HTTP/1.1
Host: lg.example.com
Accept: application/pidf+xml,application/held+xml,application/xml;q=0.8,
    text/xml;q=0.7
Accept-Charset: UTF-8,*
Content-Type: application/held+xml
Content-Length: 87

<?xml version="1.0"?>
<locationRequest xmlns="urn:ietf:params:xml:ns:geopriv:held"/>




















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   The successful response to either of these requests is a PIDF-LO
   document.  The following response shows a minimal PIDF-LO response.

   HTTP/1.x 200 OK
   Server: Example LG
   Date: Tue, 10 Jan 2006 03:42:29 GMT
   Expires: Tue, 10 Jan 2006 03:42:29 GMT
   Cache-control: private
   Content-Type: application/pidf+xml
   Content-Length: 594

   <?xml version="1.0"?>
   <presence xmlns="urn:ietf:params:xml:ns:pidf"
             entity="pres:3650n87934c@ls.example.com">
     <tuple id="3b650sf789nd">
     <status>
      <geopriv xmlns="urn:ietf:params:xml:ns:pidf:geopriv10">
        <location-info>
          <Point xmlns="http://www.opengis.net/gml"
                 srsName="urn:ogc:def:crs:EPSG::4326">
            <pos>-34.407 150.88001</pos>
          </Point>
        </location-info>
        <usage-rules>
          <retention-expires>
            2006-01-11T03:42:28+00:00</retention-expires>
        </usage-rules>
      </geopriv>
     </status>
     <timestamp>2006-01-10T03:42:28+00:00</timestamp>
     </tuple>
   </presence>

   The error response to either of these requests is an error document.
   The following response shows an example error response.

   HTTP/1.x 500 Server Error
   Server: Example LG
   Date: Tue, 10 Jan 2006 03:49:20 GMT
   Expires: Tue, 10 Jan 2006 03:49:20 GMT
   Cache-control: private
   Content-Type: application/held+xml
   Content-Length: 135

   <?xml version="1.0"?>
   <error xmlns="urn:ietf:params:xml:ns:geopriv:held" code="501"
          message="Unable to determine location"/>




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   Note:  To focus on important portions of messages, all examples
      following this note do not show HTTP headers or the XML prologue.
      In addition, sections of XML not relevant to the example are
      replaced with comments.

9.2.  Location Request Examples

   The location request shown below specifies location types and
   provides a profile that the LG applies to the PIDF-LO document.  The
   request specifies that a response is desired within 10.5 seconds.

   <locationRequest xmlns="urn:ietf:params:xml:ns:geopriv:held"
                    responseTime="PT10.5S" signed="false">
     <locationType exact="true">
       jurisdictionalCivic
       geodetic
     </locationType>
     <profile>
       <presentity>pres:user@example.com</presentity>
       <retentionInterval>1800</retentionInterval>
       <retransmission>false</retransmission>
       <rulesetURI>https://example.com/~user/ruleset.xml</rulesetURI>
     </profile>
   </locationRequest>



























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   The response to this location request is the following PIDF-LO
   document, which shows how the profile values are applied.

   <presence xmlns="urn:ietf:params:xml:ns:pidf"
             entity="pres:user@example.com">
     <tuple id="dtnv49a3c08ud35q">
     <status>
      <geopriv xmlns="urn:ietf:params:xml:ns:pidf:geopriv10">
        <location-info>
          <civicAddress
              xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
            <!-- Jurisdictional Civic LI here -->
          </civicAddress>
          <Point xmlns="http://www.opengis.net/gml">
            <!-- Geodetic LI here -->
          </Point>
        </location-info>
        <usage-rules>
          <retransmission-allowed>false</retransmission-allowed>
          <retention-expires>
            2006-01-11T03:42:28+00:00</retention-expires>
          <ruleset-reference>
            https://example.com/~user/ruleset.xml
          </ruleset-reference>
        </usage-rules>
      </geopriv>
     </status>
     <timestamp>2006-01-10T03:42:28+00:00</timestamp>
     </tuple>
   </presence>





















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   The following location request includes a location assertion that
   includes a user-provided civic address.  This message also requests
   that the LG retrieve profile information from a context that exists
   on an LS.

   <locationRequest xmlns="urn:ietf:params:xml:ns:geopriv:held"
                    responseTime="2">
     <assert method="Manual" exact="true">
       <civicAddress
           xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
           xml:lang="en-AU">
         <!-- civic address contents -->
       </civicAddress>
     </assert>
     <context>
       <locationURI>
         https://ls.example.com:9768/357yc6s64ceyoiuy5ax3o
       </locationURI>
       <password>vs76e8cae9873a079888p9y4txwa</password>
     </context>
   </locationRequest>

   Since this request includes the "exact" parameter set to "true", any
   successful response MUST include the provided LI.

9.3.  Context Creation and Update Examples

   The following create context request shows the simplest form of this
   message, which sets a two hour lifetime on the context and includes a
   "rulesetURI" element for the LS.

   <createContext xmlns="urn:ietf:params:xml:ns:geopriv:held">
     <lifetime>PT2H</lifetime>
     <rules>
       <rulesetURI>
         https://www.example.com/~user/privacy/ruleset.xml
       </rulesetURI>
     </rules>
   </createContext>












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   The following more complex create context request includes additional
   information.  This includes a profile that sets the presentity and
   some of the "usage-rules" components in the PIDF-LO that the LS
   serves.

   <createContext xmlns="urn:ietf:params:xml:ns:geopriv:held">
     <lifetime>PT2H</lifetime>
     <profile>
       <presentity>pres:user@example.com</presentity>
       <retentionExpiry>2006-01-13T12:00:00+00:00</retentionExpiry>
       <retransmission>false</retransmission>
     </profile>
     <rules>
       <rulesetURI>
         https://www.example.com/~user/privacy/ruleset.xml
       </rulesetURI>
     </rules>
   </createContext>

   A typical successful response to this message provides several
   Location URIs in different schemes (in this case: "https" and
   "sips"), the exact context expiry time, and a password that can be
   used to update the context.

   <contextResponse xmlns="urn:ietf:params:xml:ns:geopriv:held"
                    code="200" message="OK">
     <context expires="2006-01-11T05:38:01+00:00">
       <locationURI>
         https://ls.example.com:9768/357yc6s64ceyoiuy5ax3o
       </locationURI>
       <locationURI>
         sips://ls.example.com:9769/357yc6s64ceyoiuy5ax3o
       </locationURI>
       <password>38cdj38mjcd-0-=54821kj28mp1qms.1</password>
     </context>
   </contextResponse>

   If any aspect of the data stored in a context changes, a
   "contextUpdate" request is sent to the LG to request that it update
   the information.  This request includes the information necessary to
   access a context (the location URI and password) and only the
   information that has changed.









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   The following request demonstrates how information stored in a
   context could be updated.  For the context previously created, this
   provides the "retentionInterval" element, which overrides a
   previously configured "retentionExpiry" value.

   <updateContext xmlns="urn:ietf:params:xml:ns:geopriv:held"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
     <context>
       <locationURI>
         https://ls.example.com:9768/357yc6s64ceyoiuy5ax3o
       </locationURI>
       <password>38cdj38mjcd-0-=54821kj28mp1qms.1</password>
     </context>
     <profile>
       <retentionInterval>600</retentionInterval>
     </profile>
   </updateContext>

   To indicate success, the LG provides a "contextResponse" identical in
   form to the original request.

   The following request shows that a context lifetime can be extended
   or shortened by the Device by updating a context with a new
   "lifetime" element.  The following message requests that the LS
   maintain the context for two hours beyond the current time.

   <updateContext xmlns="urn:ietf:params:xml:ns:geopriv:held">
     <context>
       <locationURI>
         https://ls.example.com:9768/357yc6s64ceyoiuy5ax3o
       </locationURI>
       <password>38cdj38mjcd-0-=54821kj28mp1qms.1</password>
     </context>
     <lifetime>PT2H</lifetime>
   </updateContext>
















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   The response to a request to extend the context includes the new
   expiry time of the context, if it has changed.

   <contextResponse xmlns="urn:ietf:params:xml:ns:geopriv:held"
                    code="200" message="OK">
     <context expires="2006-01-11T05:39:46+00:00">
       <locationURI>
         https://ls.example.com:9768/357yc6s64ceyoiuy5ax3o
       </locationURI>
       <locationURI>
         sips://ls.example.com:9769/357yc6s64ceyoiuy5ax3o
       </locationURI>
       <password>38cdj38mjcd-0-=54821kj28mp1qms.1</password>
     </context>
   </contextResponse>

   A zero value for the "lifetime" element terminates the context.  The
   following request terminates the context.

   <updateContext xmlns="urn:ietf:params:xml:ns:geopriv:held">
     <context>
       <locationURI>
         https://ls.example.com:9768/357yc6s64ceyoiuy5ax3o
       </locationURI>
       <password>38cdj38mjcd-0-=54821kj28mp1qms.1</password>
     </context>
     <lifetime>PT0S</lifetime>
   </updateContext>

   The response to a message that requests the termination of a context
   appears as follows.

   <contextResponse xmlns="urn:ietf:params:xml:ns:geopriv:held"
                    code="201" message="Context removed"/>

















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9.4.  Sample LG WSDL Document

   The following WSDL document demonstrates how a WSDL document can be
   created for a specific service, in this case, a service at the URI
   "https://lg.example.com/location".

   <?xml version="1.0"?>
   <wsdl:definitions
       xmlns:wsdl="http://www.w3.org/2005/05/wsdl"
       xmlns:heldhttp="urn:ietf:params:xml:ns:geopriv:held:http"
       targetNamespace="http://lg.example.com/ws/held">

     <wsdl:import
         namespace="urn:ietf:params:xml:ns:geopriv:held:http"/>

     <wsdl:service name="sample-held-svc" interface="heldhttp:held">
       <wsdl:endpoint name="sample-held-ep"
                      binding="heldhttp:heldHTTP"
                      address="https://lg.example.com/location"/>
     </wsdl:service>

   </wsdl:definitions>





























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10.  IANA Considerations

   According to the guidelines in [RFC3688], this document calls for an
   IANA registry for result codes and registers an XML namespace and
   schema.  It also registers the "application/held+xml" MIME type.

10.1.  IANA Registry for HELD Result Codes

   IANA will establish and maintain a registry of HELD result codes.
   Additional values are registered based on the "specification
   required" option in [RFC3688].

   Specifications MUST specify the following information when
   registering new values in this registry:

   Code Value:  A three-digit value from 000 to 679.  The last 20 codes
      in each block of 100 (from x80 to x99) are reserved for private or
      experimental use and cannot be registered.

   Short Message:  A brief message that describes the general reason for
      the code.

   Publication:  A reference to any relevant publication or
      specification.

   Description and Usage:  A longer description of the code and the
      circumstances where it applies.  This description does not need to
      be exhaustive.

   The values in Section 5.8 are pre-registered in this registry.

10.2.  URN Sub-Namespace Registration for
       urn:ietf:params:xml:ns:geopriv:held

   This section registers a new XML namespace,
   "urn:ietf:params:xml:ns:geopriv:held", as per the guidelines in
   [RFC3688].

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

      Registrant Contact: IETF, GEOPRIV working group,
      (geopriv@ietf.org), Martin Thomson (martin.thomson@andrew.com).

      XML:







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         BEGIN
           <?xml version="1.0"?>
           <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
             "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
           <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
             <head>
               <title>HELD Messages</title>
             </head>
             <body>
               <h1>Namespace for HELD Messages</h1>
               <h2>urn:ietf:params:xml:ns:geopriv:held</h2>
   [[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>
             </body>
           </html>
         END

10.3.  XML Schema Registration

   This section registers an XML schema as per the guidelines in
   [RFC3688].

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

   Registrant Contact:  IETF, GEOPRIV working group, (geopriv@ietf.org),
      Martin Thomson (martin.thomson@andrew.com).

   Schema:  The XML for this schema can be found as the entirety of
      Section 6 of this document.

10.4.  URN Sub-Namespace Registration for
       urn:ietf:params:xml:ns:geopriv:held:http

   This section registers a new XML namespace,
   "urn:ietf:params:xml:ns:geopriv:held:http", as per the guidelines in
   [RFC3688].

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

      Registrant Contact: IETF, GEOPRIV working group,
      (geopriv@ietf.org), Martin Thomson (martin.thomson@andrew.com).

      XML:







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         BEGIN
           <?xml version="1.0"?>
           <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
             "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
           <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
             <head>
               <title>HELD HTTP Binding WS</title>
             </head>
             <body>
               <h1>Namespace for HELD HTTP Binding WS</h1>
               <h2>urn:ietf:params:xml:ns:geopriv:held:http</h2>
   [[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>
             </body>
           </html>
         END

10.5.  MIME Media Type Registration for 'application/held+xml'

   This section registers the "application/held+xml" MIME type.

   To:  ietf-types@iana.org

   Subject:  Registration of MIME media type application/held+xml

   MIME media type name:  application

   MIME subtype name:  held+xml

   Required parameters:  (none)

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

   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
      protocol data related to the location of an entity, which could
      include information that is considered private.  Appropriate
      precautions should be taken to limit disclosure of this
      information.






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   Interoperability considerations:  This content type provides a basis
      for a protocol

   Published specification:  RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please
      replace XXXX with the RFC number for this specification.]]

   Applications which use this media type:  Location information
      providers and consumers.

   Additional Information:  Magic Number(s): (none)
      File extension(s): .xml
      Macintosh File Type Code(s): (none)

   Person & email address to contact for further information:  Martin
      Thomson <martin.thomson@andrew.com>

   Intended usage:  LIMITED USE

   Author/Change controller:  This specification is TBD

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




























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11.  Acknowledgements

   The authors would like to thank the following people for their
   contribution to this document (in alphabetical order): Nadine Abbott,
   Guy Caron, Martin Dawson, Jerome Grenier, Neil Justusson, Tat Lam,
   Patti McCalmont, Perry Prozeniuk, John Schnizlein, Henning
   Schulzrinne, Ed Shrum, and Hannes Tschofenig.












































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12.  References

12.1.  Normative References

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

   [RFC2246]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
              RFC 2246, January 1999.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

   [RFC3275]  Eastlake, D., Reagle, J., and D. Solo, "(Extensible Markup
              Language) XML-Signature Syntax and Processing", RFC 3275,
              March 2002.

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

   [RFC3693]  Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and
              J. Polk, "Geopriv Requirements", RFC 3693, February 2004.

   [RFC4119]  Peterson, J., "A Presence-based GEOPRIV Location Object
              Format", RFC 4119, December 2005.

   [I-D.ietf-geopriv-revised-civic-lo]
              Thomson, M. and J. Winterbottom, "Revised Civic Location
              Format for PIDF-LO",
              draft-ietf-geopriv-revised-civic-lo-05 (work in progress),
              February 2007.

   [I-D.ietf-geopriv-pdif-lo-profile]
              Tschofenig, H., "GEOPRIV PIDF-LO Usage Clarification,
              Considerations and Recommendations",
              draft-ietf-geopriv-pdif-lo-profile-05 (work in progress),
              October 2006.

   [I-D.thomson-geopriv-lis-discovery]
              Thomson, M. and J. Winterbottom, "Discovering the Local
              Location Information Server (LIS)",
              draft-thomson-geopriv-lis-discovery-00 (work in progress),
              February 2007.

   [I-D.marshall-geopriv-lbyr-requirements]



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              Marshall, R., "Requirements for a Location-by-Reference
              Mechanism used in Location  Configuration and Conveyance",
              draft-marshall-geopriv-lbyr-requirements-00 (work in
              progress), February 2007.

   [I-D.ietf-geopriv-l7-lcp-ps]
              Tschofenig, H. and H. Schulzrinne, "GEOPRIV Layer 7
              Location Configuration Protocol; Problem Statement and
              Requirements", draft-ietf-geopriv-l7-lcp-ps-00 (work in
              progress), January 2007.

   [I-D.ietf-geopriv-common-policy]
              Schulzrinne, H., "Common Policy: A Document Format for
              Expressing Privacy Preferences",
              draft-ietf-geopriv-common-policy-11 (work in progress),
              August 2006.

   [W3C.REC-xmlschema-2-20041028]
              Biron, P. and A. Malhotra, "XML Schema Part 2: Datatypes
              Second Edition", World Wide Web Consortium
              Recommendation REC-xmlschema-2-20041028, October 2004,
              <http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>.

   [OGC.GML-3.1.1]
              Cox, S., Daisey, P., Lake, R., Portele, C., and A.
              Whiteside, "Geographic information - Geography Markup
              Language (GML)", OpenGIS 03-105r1, April 2004,
              <http://portal.opengeospatial.org/files/
              ?artifact_id=4700>.

   [NENA_TID]
              National Emergency Number Association (NENA), "NENA
              Recommended Method(s) for Location Determination to
              Support IP-Based Emergency Services Technical Information
              Document", NENA VoIP Location Working Group 08-505 Issue
              1, December 2006,
              <http://www.nena.org/media/files/08-505_20061221.pdf>.

   [I-D.thomson-geopriv-location-dependability]
              Thomson, M. and J. Winterbottom, "Digital Signature
              Methods for Location Dependability", February 2007.

12.2.  Informative References

   [RFC0793]  Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, September 1981.

   [RFC2222]  Myers, J., "Simple Authentication and Security Layer



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              (SASL)", RFC 2222, October 1997.

   [RFC2778]  Day, M., Rosenberg, J., and H. Sugano, "A Model for
              Presence and Instant Messaging", RFC 2778, February 2000.

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

   [RFC3080]  Rose, M., "The Blocks Extensible Exchange Protocol Core",
              RFC 3080, March 2001.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [W3C.REC-xmlschema-1-20041028]
              Maloney, M., Thompson, H., Mendelsohn, N., and D. Beech,
              "XML Schema Part 1: Structures Second Edition", World Wide
              Web Consortium Recommendation REC-xmlschema-1-20041028,
              October 2004,
              <http://www.w3.org/TR/2004/REC-xmlschema-1-20041028>.

   [W3C.REC-soap12-part1-20030624]
              Mendelsohn, N., Gudgin, M., Moreau, J., Hadley, M., and H.
              Nielsen, "SOAP Version 1.2 Part 1: Messaging Framework",
              World Wide Web Consortium Recommendation REC-soap12-part1-
              20030624, June 2003,
              <http://www.w3.org/TR/2003/REC-soap12-part1-20030624>.

   [W3C.REC-soap12-part2-20030624]
              Gudgin, M., Hadley, M., Nielsen, H., Moreau, J., and N.
              Mendelsohn, "SOAP Version 1.2 Part 2: Adjuncts", World
              Wide Web Consortium Recommendation REC-soap12-part2-
              20030624, June 2003,
              <http://www.w3.org/TR/2003/REC-soap12-part2-20030624>.

   [W3C.CR-wsdl20-20060106]
              Chinnici, R., Moreau, J., Ryman, A., and S. Weerawarana,
              "Web Services Description Language (WSDL) Version 2.0 Part
              1: Core Language", W3C CR CR-wsdl20-20060106,
              January 2006.

   [I-D.winterbottom-geopriv-held-identity-extensions]



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              Winterbottom, J. and M. Thomson, "HELD End-Point identity
              Extensions",
              draft-winterbottom-geopriv-held-identity-extensions-00
              (work in progress), October 2006.

   [I-D.thomson-geopriv-held-capabilities]
              Thomson, M. and J. Winterbottom, "Device Capability
              Negotiation for Device-Based Location Determination and
              Location Measurements in HELD",
              draft-thomson-geopriv-held-capabilities-01 (work in
              progress), February 2007.

   [I-D.thomson-geopriv-held-beep]
              Thomson, M. and J. Winterbottom, "A BEEP Binding for the
              HELD Protocol", February 2007.




































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Appendix A.  HELD Compliance to IETF LCP requirements

   This appendix describes HELD's compliance to the requirements
   specified in the [I-D.ietf-geopriv-l7-lcp-ps].  In addition to the
   LCP requirements specified by the IETF, HELD has independently been
   assessed against and found to comply with all the NENA requirements
   for a location acqusition protocol defined in [NENA_TID].

A.1.  L7-1: Identifier Choice

   "The LIS MUST be presented with a unique identifier of its own
   addressing realm associated in some way with the physical location of
   the end host."

   COMPLY

   The identifier used may be the source address of the request packet
   and/or additional client identifier values relevant to the scope of
   the access network provided within the request.  Mapping an IP
   address into lower-level attachment data is access network dependent
   and is the responsibility the LIS.  HELD can however be used to
   provide assistence to the LIS through the inclusion of identity
   extensions such as those defined in
   [I-D.winterbottom-geopriv-held-identity-extensions].

A.2.  L7-2: Mobility Support

   "The GEOPRIV Layer 7 Location Configuration Protocol MUST support a
   broad range of mobility from devices that can only move between
   reboots, to devices that can change attachment points with the impact
   that their IP address is changed, to devices that do not change their
   IP address while roaming, to devices that continuously move by being
   attached to the same network attachment point."

   COMPLY

   Mobility support is inherently a characteristic of the access network
   technology and HELD is designed to be access network agnostic.
   Consequently HELD complies with this requirement.  In addition HELD
   provides specific support for mobile environments by providing an
   optional responseTime attribute in location request messages.
   Wireless networks often have several different mechanisms at their
   disposal for position determination (e.g.  Assisted GPS versus
   location based on serving base station identity), each providing
   different degrees of accuracy and taking different amounts of time to
   yield a result.  The responseTime parameter provides the LIS with a
   criterion which it can use to select a location determination
   technique.



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   HELD also supports an extension mechanism that allows location
   measurement capabilities to be exchanged between the end-point and
   the LIS.  This mechanism allows for a greater number of location
   determination techniques to be used by both the end-point and the
   LIS.  The specification describing this capability is provided in
   [I-D.thomson-geopriv-held-capabilities].

A.3.  L7-3: Layer 7 and Layer 2/3 Provider Relationship

   "The design of the GEOPRIV Layer 7 Location Configuration Protocol
   MUST NOT assume a business or trust relationship between the provider
   of application layer (e.g., SIP, XMPP, H.323) provider and the access
   network provider operating the LIS."

   COMPLY

   HELD describes a location acquisition protocol and has no
   dependencies on how location is used once it has been acquired.
   Location acquisition using HELD is subject to the restrictions
   described in Section 8.

A.4.  L7-4: Layer 2 and Layer 3 Provider Relationship

   "The design of the GEOPRIV Layer 7 Location Configuration Protocol
   MUST assume that there is a trust and business relationship between
   the L2 and the L3 provider.  The L3 provider operates the LIS and
   needs to obtain location information from the L2 provider since this
   one is closest to the end host.  If the L2 and L3 provider for the
   same host are different entities, they cooperate for the purposes
   needed to determine end system locations."

   COMPLY

   HELD was specifically designed with this model in mind and readily
   allows itself to chaining requests between operators without a change
   in protocol being required.  Examples of how HELD can be used in this
   manner are provided in detail in [NENA_TID].  HELD is a webservices
   protocol it can be bound to transports other than HTTP, for example a
   BEEP binding for HELD, [I-D.thomson-geopriv-held-beep].  Using a
   transport like BEEP for HELD offers the option of high request
   throughput over a dedicated connection between an L3 provider and an
   L2 provider without incurring the serial restriction imposed by HTTP.
   This is less easy to do with protocols that do not decouple
   themselves from the transport.







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A.5.  L7-5: Legacy Device Considerations

   "The design of the GEOPRIV Layer 7 Location Configuration Protocol
   MUST consider legacy residential NAT devices and NTEs in an DSL
   environment that cannot be upgraded to support additional protocols,
   for example to pass additional information through DHCP."

   COMPLY

   HELD is an application protocol and operates on top of IP.  A HELD
   request from a host behind a residential NAT will traverse the NAT
   acquiring the external address of the home router.  The location
   provided to the host therefore will be the address of the home router
   in this circumstance.  No changes are required to the home router in
   order to support this function, HELD was designed specifically to
   address this deployment scenario.  Examples of how HELD can be used
   in this type of network environment are provided in [NENA_TID].

A.6.  L7-6: VPN Awareness

   "The design of the GEOPRIV Layer 7 Location Configuration Protocol
   MUST assume that at least one end of a VPN is aware of the VPN
   functionality.  In an enterprise scenario, the enterprise side will
   provide the LIS used by the client and can thereby detect whether the
   LIS request was initiated through a VPN tunnel."

   COMPLY

   HELD does not preclude a LIS on the far end of a VPN tunnel being
   aware that the client request is occurring over that tunnel.  It also
   does not preclude a client device from accessing a LIS serving the
   local physical network and subsequently using the location
   information with an application that is accessed over a VPN tunnel.

A.7.  L7-7: Network Access Authentication

   "The design of the GEOPRIV Layer 7 Location Configuration Protocol
   MUST NOT assume prior network access authentication."

   COMPLY

   HELD makes no assumptions about prior network access authentication.
   HELD strongly recommends the use of TLS with server-side certificates
   for communication between the end-point and the LIS.  There is no
   requirement for the end-point to authenticate with the LIS.






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A.8.  L7-8: Network Topology Unawareness

   "The design of the GEOPRIV Layer 7 Location Configuration Protocol
   MUST NOT assume end systems being aware of the access network
   topology.  End systems are, however, able to determine their public
   IP address(es) via mechanisms such as STUN or NSIS NATFW NSLP."

   COMPLY

   HELD makes no assumption about the network topology.  HELD doesn't
   require that the device know its external IP address, except where
   that is required for discovery of the LIS.  LIS disocvery techniques
   available to a HELD client are described in
   [I-D.thomson-geopriv-lis-discovery].  In certain network environments
   an end-point maybe able to ascertain information about the topology
   of the access network which may assist the LIS in location
   determination.  HELD provides support for extensions that allow this
   information to be communicated to the LIS when it is available.

































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Appendix B.  HELD Compliance to NENA Location Acqusition Requirements

   This section details how HELD complies to each of the requirements
   provided in section 4 of [NENA_TID].

B.1.  DA1

   "The access network shall provide a mechanism for determination and
   acquisition of location information, and support queries for
   location."

   COMPLY

   HELD provides location acqusition functionality.  A LIS may use any
   means to obtain measurements from the network to assist with location
   determination.

B.2.  DA2

   "The location estimate used shall be that associated with the
   physically (wire, fiber, air) connected network."

   COMPLY

   HELD is designed to support the acquisition of location information
   determined on the basis of the physical access network with which the
   device is associated.  HELD does not preclude any specific technology
   used by that access.

B.3.  DA3

   "Location may be requested at any time.  Location information must be
   associated with the device at the time the location is requested."

   COMPLY

   HELD location requests can be made at any time to the identified LIS
   serving the access network.  It is the responsibility of the LIS to
   use the IP address and/or other identifiers included in the location
   request and determine the current location of the Target.  Where more
   than one determination technology is available, the requesting entity
   may specify a response time to assist the LIS in selecting the
   appropriate location determination technology to use.  The HELD
   protocol does not impose any physical constraints that prevent the
   LIS from reassessing the location at the time of each request.






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B.4.  DA4

   "Location acquisition should be provided by a consistent method
   across all network configurations."

   COMPLY

   HELD requires an end-point to be able to discover the LIS in the
   local access network.  Once the LIS is known HELD is access network
   agnostic and can be used in the same way in any network topology.

B.5.  DA5

   "Location determination and acquisition mechanisms must be applicable
   to emergency calling, and may also be applicable to a wide range of
   value-added location-based services."

   COMPLY

   HELD has specific semantics defined for obtaining locations suitable
   for routing emergency calls.  In particular, HELD provides a rich set
   of location request options so that an application can retrieve
   location information in the form most suitable for its purpose.

B.6.  DA6

   "Location determination and acquisition techniques shall support both
   NENA i2 and i3 network architectures."

   COMPLY

   HELD provides all of the functions necessary to support emergency
   calling applications.  HELD has a specific semantic for requesting
   location information suitable to inclusion in emergency calling
   applications.  Location information acquired using HELD is contained
   in a PIDF-LO the form required by both the NENA i2 and i3
   architectures.  It also supports location by reference mechanisms for
   out-of-band mid-call location updates as required, for example, for
   mobile wireless networks.

B.7.  DA7

   "When measurement based-location determination mechanisms fail, the
   most accurate location information available should be provided.
   Examples include: For mobile, the Wireless Service Provider might
   provide tower or Access Point location, last known fix, etc.  For
   wireline, a LIS might provide a civic location that defines the
   serving area of an access point, e.g., the State of Texas."



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   Not Applicable

   HELD is a location acqusition protocol and will return the location
   determined by the LIS.  HELD does not preclude the LIS from applying
   any arbitrarily sophisticated set of location determination
   techniques and associated fallback policy appropriate to the access
   technology it supports.

B.8.  DA8

   "Location determination and acquisition must provide minimal impact
   to call setup time in the event that location is not known ahead of
   time."

   COMPLY

   HELD allows a location to be requested at any time, including prior
   to or during a call.  Where time is of the essence the requesting
   entity can provide a response time indicating to the LIS that
   location is needed in the period specified.  This allows the LIS to
   select the most accurate location determination technology available
   to it that can yield a location in the allotted time.  This is of
   particular importance in wireless networks where the most accurate
   location determination techniques may take 10s of seconds.

B.9.  DA9

   "Where a device is not location aware the IP Access network should
   have the ability to provide a location estimate on behalf of the
   device."

   COMPLY

   In order to support this functionality the requesting node must have
   a pre-existing trust relationship with the LIS, and HELD identity
   extensions as described in
   [I-D.winterbottom-geopriv-held-identity-extensions].  Where these
   requirements are satisfied, the LIS may provide a HELD response to
   the requesting device that has the same form as if the target device
   had been the requestor.  If the traffic volume between the trusted
   node and the LIS is likely to be high, the HELD BEEP binding
   [I-D.thomson-geopriv-held-beep] may be used.

B.10.  DA10

   "Location acquisition methods should not require modification of
   hardware/firmware in home-routers or modems."




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   COMPLY

   This requirement is essentially the same as Appendix A.5.  HELD is an
   application protocol and operates on top of IP.  A HELD request from
   a host behind a residential NAT will traverse the NAT acquiring the
   external address of the home router.  The location provided to the
   host therefore will be the address of the home router in this
   circumstance.  No changes are required to the home router in order to
   support this function, HELD was designed specifically to address this
   deployment scenario.

B.11.  DA11

   "A location determination method must exist that does not require
   network hardware replacement."

   Not Applicable

   HELD is a location acquisition protocol and does not directly specify
   how location is determined in the network.  However, HELD does not
   require additions to or replacement of existing network server
   implementations because it is not defined as an extension to any
   existing non-location service protocol.

B.12.  DA12

   "The location acquisition protocol shall allow the requesting device
   to specify a response time requirement to the LIS when requesting
   location information.  The response time is expressed as the maximum
   time that the requesting node is prepared to wait for location
   information.  The LIS is required to provide the most accurate
   location fix it can within the specified response time."

   COMPLY

   HELD has an explicit "responseTime" parameter that can be used with
   any request to the LIS.  This parameter provides an indication to the
   LIS of how long the requesting node is prepared to wait for location,
   allowing the LIS to select the appropriate location determination
   technology to invoke particularly where it may need to trade off the
   accuracy of the result to meet the time constraint.

B.13.  Rep1

   "Location information may be provided as location-by-value or
   location-by-reference and the form is subject to the nature of the
   request."




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   COMPLY

   HELD supports requesting either a location reference in the form a
   location URI and/or a literal location.  Literal locations are
   provided as a PIDF-LO.

B.14.  Rep2

   "Location determination and acquisition mechanisms must support all
   location information fields defined within a PIDF-LO."

   COMPLY

   HELD provides location information in the form of a PIDF-LO,
   consequently all PIDF-LO fields are implicitly supported.

B.15.  Rep3

   "Location acquisition mechanisms must allow for easy backwards
   compatibility as the representation of location information evolves."

   COMPLY

   HELD provides location as a PIDF-LO, any changes made to the PIDF-LO
   definition are made independently and without impact to the HELD
   definition.

B.16.  Rep4

   "All representations of location shall include the ability to carry
   altitude and/or floor designation.  This requirement does not imply
   altitude and/or floor designation is always used or supplied."

   COMPLY

   The PIDF-LO has explicit support for both civic and geodtic location
   types and consequently provides support for encoding both altitude
   and building floor values.  Since HELD provides location as a
   PIDF-LO, any location that can be expressed in a PIDF-LO is
   compatible with HELD.  HELD recommends that PIDF-LOs be constructed
   in accordance with the rules laid out in
   [I-D.ietf-geopriv-pdif-lo-profile].

B.17.  LocSec1

   "Location information shall only be provided to authenticated and
   authorized network devices.  The degree of authentication and
   authorization required may vary depending on the network."



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   COMPLY

   A LIS generally authenticates a Target using HELD to request its own
   location implicitly.  Authentication is based on the IP address of
   the source request packet, inband indentifiers, and return
   routability.  Where this level of authentication is not deemed
   sufficient other authentications mechanisms can be used, such as
   client-side certificates, shared-secret keys and HTTP digest.

B.18.  LocSec2

   "Location determination and acquisition methods should preserve
   privacy of location information, subject to local laws and
   regulations."

   COMPLY

   This requirement is of particular significance where the acqusition
   protocol is also being used as a dereference protocol for a location
   URI.  HELD supports this function by allowing a Target to provide
   access rules to the LIS.  The Target may provide either an explicit
   set of rules defined using common policy syntax as described in
   [I-D.ietf-geopriv-common-policy], or the Target may provide a ruleset
   URI allowing the LIS to retrieve the ruleset from a third-party.  LIS
   operators are also able to provide a default set of overiding
   policies to support, for example, emergency services.  How these
   additional rules are provisioned and applied is a matter of LIS
   implementation and is outside the scope of any location acquisition
   protocol.

B.19.  LocSec3

   "The location or location estimate of a caller should be dependable."

   COMPLY

   HELD supports this through two mechanisms.  The first is a "signed"
   attribute that can be included with a location request.  This allows
   the user to explicitly request a signed location object.  The second
   is through location assertion.  This allows an end-point to proffer a
   location to the LIS, and for the LIS to assert this location against
   the location that the LIS would provide.  The assert function is
   described in more detail in Section 5.2.

B.20.  LocSec4

   "The location acquisition protocol must support authentication of the
   Location Information Server, integrity protection of the Location



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   Information, and protection against replay."

   COMPLY

   HELD recommends the use of TLS with server-side certificates for LIS
   authentication to requesting nodes where considered necessary.  TLS
   when used in this fashion mitigates the risks of impersonation of the
   LIS.  TLS also provides confidentiality and replay protection for
   requests and location information.

B.21.  LocSec5

   "The location source shall be identified and should be authenticated.
   This includes manually entered location."

   COMPLY

   HELD provides a "signed" attribute that can be used to request a
   signed location object as described in Section 5.5.  For Target
   provided locations, be for manually entered or device-determined
   location, HELD provides the location assertion function, which when
   combined with the "signed" attribute provides location source
   identification and authentication.

B.22.  LocSec6

   "Where a location is acquired and cached prior to an emergency call,
   it should be refreshed at regular intervals to ensure that it is as
   current as possible, in the event location information cannot be
   obtained in real time."

   COMPLY

   HELD supports the ability to request location at any time.

B.23.  LocSec7

   "Where location by-reference is used the appropriate privacy policies
   must be implemented and enforced by the LIS operator."

   COMPLY

   HELD allows a Target to provide access rules ot the LIS.  The Target
   may provide either an explicit set of rules defined using common
   policy syntax as described in [I-D.ietf-geopriv-common-policy], or
   the Target may provide a ruleset URI allowing the LIS to retrieve the
   ruleset from a third-party.




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Authors' Addresses

   James Winterbottom
   Andrew
   PO Box U40
   Wollongong University Campus, NSW  2500
   AU

   Phone: +61 2 4221 2938
   Email: james.winterbottom@andrew.com
   URI:   http://www.andrew.com/


   Martin Thomson
   Andrew
   PO Box U40
   Wollongong University Campus, NSW  2500
   AU

   Phone: +61 2 4221 2915
   Email: martin.thomson@andrew.com
   URI:   http://www.andrew.com/


   Barbara Stark
   BellSouth
   Room 7A41
   725 W Peachtree St.
   Atlanta, GA  30308
   US

   Email: barbara.stark@bellsouth.com



















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