Internet Engineering Task Force (IETF) M. Barnes, Ed. Request for Comments: 5985 Polycom Category: Standards Track September 2010 ISSN: 2070-1721 HTTP-Enabled Location Delivery (HELD) Abstract This document defines a Layer 7 Location Configuration Protocol (L7 LCP) and describes the use of HTTP and HTTP/TLS as transports for the L7 LCP. The L7 LCP is used for retrieving location information from a server within an access network. It includes options for retrieving location information in two forms: by value and by reference. The protocol is an extensible application-layer protocol that is independent of the session layer. Status of This Memo This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc5985. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Barnes Standards Track [Page 1] RFC 5985 HELD September 2010 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3 3. Overview and Scope . . . . . . . . . . . . . . . . . . . . . . 4 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 5 4.1. Device Identifiers, NAT and VPNs . . . . . . . . . . . . . 6 4.1.1. Devices and VPNs . . . . . . . . . . . . . . . . . . . 6 4.1.2. LIS Handling of NATs and VPNs . . . . . . . . . . . . 7 4.2. Location by Value . . . . . . . . . . . . . . . . . . . . 7 4.3. Location by Reference . . . . . . . . . . . . . . . . . . 8 5. Protocol Description . . . . . . . . . . . . . . . . . . . . . 8 5.1. Location Request . . . . . . . . . . . . . . . . . . . . . 9 5.2. Location Response . . . . . . . . . . . . . . . . . . . . 9 5.3. Indicating Errors . . . . . . . . . . . . . . . . . . . . 9 6. Protocol Parameters . . . . . . . . . . . . . . . . . . . . . 10 6.1. "responseTime" Parameter . . . . . . . . . . . . . . . . . 10 6.2. "locationType" Parameter . . . . . . . . . . . . . . . . . 11 6.2.1. "exact" Attribute . . . . . . . . . . . . . . . . . . 13 6.3. "code" Parameter . . . . . . . . . . . . . . . . . . . . . 13 6.4. "message" Parameter . . . . . . . . . . . . . . . . . . . 14 6.5. "locationUriSet" Parameter . . . . . . . . . . . . . . . . 14 6.5.1. "locationURI" Parameter . . . . . . . . . . . . . . . 14 6.5.2. "expires" Parameter . . . . . . . . . . . . . . . . . 15 6.6. "Presence" Parameter (PIDF-LO) . . . . . . . . . . . . . . 16 7. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 16 8. HTTP Binding . . . . . . . . . . . . . . . . . . . . . . . . . 20 9. Security Considerations . . . . . . . . . . . . . . . . . . . 22 9.1. Assuring That the Proper LIS Has Been Contacted . . . . . 23 9.2. Protecting Responses from Modification . . . . . . . . . . 23 9.3. Privacy and Confidentiality . . . . . . . . . . . . . . . 23 10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 10.1. Examples of HTTPS Messages . . . . . . . . . . . . . . . . 25 10.2. Example of a Simple Location Request . . . . . . . . . . . 26 10.3. An Example of a Location Request for Multiple Location Types . . . . . . . . . . . . . . . . . . . . . . . . . . 27 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28 11.1. URN Sub-Namespace Registration for urn:ietf:params:xml:ns:geopriv:held . . . . . . . . . . . 28 11.2. XML Schema Registration . . . . . . . . . . . . . . . . . 29 11.3. MIME Media Type Registration for 'application/held+xml' . 29 11.4. Error Code Registry . . . . . . . . . . . . . . . . . . . 30 12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 32 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 32 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 33 14.1. Normative References . . . . . . . . . . . . . . . . . . . 33 14.2. Informative References . . . . . . . . . . . . . . . . . . 34 Barnes Standards Track [Page 2] RFC 5985 HELD September 2010 Appendix A. HELD Compliance to IETF LCP Requirements . . . . . . 36 A.1. L7-1: Identifier Choice . . . . . . . . . . . . . . . . . 36 A.2. L7-2: Mobility Support . . . . . . . . . . . . . . . . . . 36 A.3. L7-3: ASP and Access Network Provider Relationship . . . . 37 A.4. L7-4: Layer 2 and Layer 3 Provider Relationship . . . . . 37 A.5. L7-5: Legacy Device Considerations . . . . . . . . . . . . 37 A.6. L7-6: VPN Awareness . . . . . . . . . . . . . . . . . . . 38 A.7. L7-7: Network Access Authentication . . . . . . . . . . . 38 A.8. L7-8: Network Topology Unawareness . . . . . . . . . . . . 38 A.9. L7-9: Discovery Mechanism . . . . . . . . . . . . . . . . 39 A.10. L7-10: PIDF-LO Creation . . . . . . . . . . . . . . . . . 39 1. Introduction The location of a Device is information that is useful for a number of applications. The L7 Location Configuration Protocol (LCP) problem statement and requirements document [RFC5687] provides some scenarios in which a Device might rely on its access network to provide location information. The Location Information Server (LIS) service applies to access networks employing both wired technology (e.g., DSL, cable) and wireless technology (e.g., WiMAX) with varying degrees of Device mobility. This document describes a protocol that can be used to acquire Location Information (LI) from a LIS within an access network. This specification identifies two types of location information that may be retrieved from the LIS. Location may be retrieved from the LIS by value; that is, the Device may acquire a literal location object describing the location of the Device. The Device may also request that the LIS provide a location reference in the form of a Location URI or set of Location URIs, allowing the Device to distribute its LI by reference. Both of these methods can be provided concurrently from the same LIS to accommodate application requirements for different types of location information. This specification defines an extensible XML-based protocol that enables the retrieval of LI from a LIS by a Device. This protocol can be bound to any session-layer protocol, particularly those capable of MIME transport. This document describes the use of HTTP and HTTP/TLS as transports for the protocol. 2. Conventions and Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. Barnes Standards Track [Page 3] RFC 5985 HELD September 2010 This document uses the terms (and their acronym forms): Access Provider (AP), Location Information (LI), Location Object (LO), Device, Target, Location Generator (LG), Location Recipient (LR), and Rule Maker (RM) and Rule Holder (RH) as defined in GEOPRIV Requirements [RFC3693]. The terms Location Information Server (LIS), Access Network, Access Provider (AP), and Access Network Provider are used in the same context as defined in the L7 LCP Problem statement and Requirements document [RFC5687]. The usage of the terms Civic Location/Address and Geodetic Location follows the usage in many of the referenced documents. In describing the protocol, the terms "attribute" and "element" are used according to their context in XML. The term "parameter" is used in a more general protocol context and can refer to either an XML "attribute" or "element". 3. Overview and Scope This document describes an interface between a Device and a Location Information Server (LIS). This document assumes that the LIS is present within the same administrative domain as the Device (e.g., the access network). The LIS exists because not all Devices are capable of determining LI, and because, even if a Device is able to determine its own LI, it may be more efficient with assistance. This document does not specify how LI is determined. An Access Provider (AP) operates the LIS so that Devices (and Targets) can retrieve their LI. This document assumes that the Device and Access Provider have no prior relationship other than what is necessary for the Device to obtain network access. This document is based on the attribution of the LI to a Device and not specifically a person (end user) or Target, based on the premise that location determination technologies are generally designed to locate a Device and not a person. It is expected that, for most applications, LI for the Device can be used as an adequate substitute for the end user's LI. Since revealing the location of the Device almost invariably reveals some information about the location of the user of the Device, the same level of privacy protection demanded by a user is required for the Device. This approach may require either some additional assurances about the link between Device and target, or an acceptance of the limitation that unless the Device requires active user authentication, there is no guarantee that any particular individual is using the Device at that instant. The following diagram shows the logical configuration of some of the functional elements identified in [RFC3693] and the LIS defined in [RFC5687]. It also shows where this protocol applies, with the Rule Barnes Standards Track [Page 4] RFC 5985 HELD September 2010 Maker and Target represented by the role of the Device. Note that only the interfaces relevant to the Device are identified in the diagram. +---------------------------------------------+ | Access Network Provider | | | | +--------------------------------------+ | | | Location Information Server | | | | | | | | | | | | | | | | | | | +------|-------------------------------+ | +----------|----------------------------------+ | | HELD | Rule Maker - - _ +-----------+ +-----------+ o - - | Device | | Location | This document (RFC 5985) defines HELD messages. Barnes Standards Track [Page 17] RFC 5985 HELD September 2010 Barnes Standards Track [Page 18] RFC 5985 HELD September 2010 Barnes Standards Track [Page 19] RFC 5985 HELD September 2010 8. HTTP Binding This section describes the use of HTTP [RFC2616] and HTTP over TLS [RFC2818] as transport mechanisms for the HELD protocol, which a conforming LIS and Device MUST support. Although HELD uses HTTP as a transport, it uses a strict subset of HTTP features, and due to the restrictions of some features, a LIS is not a fully compliant HTTP server. It is intended that a LIS can easily be built using an HTTP server with extensibility mechanisms and that a HELD Device can trivially use existing HTTP libraries. This subset of requirements helps implementors avoid ambiguity with the many options that the full HTTP protocol offers. A Device that conforms to this specification MAY choose not to support HTTP authentication [RFC2617] or cookies [RFC2965]. Because the Device and the LIS may not necessarily have a prior relationship, the LIS SHOULD NOT require a Device to authenticate, either using the above HTTP authentication methods or TLS client authentication. Unless all Devices that access a LIS can be expected to be able to authenticate in a certain fashion, denying access to location information could prevent a Device from using location-dependent services, such as emergency calling. Extensions to this protocol might result in the addition of request parameters that a LIS might use to decide to request Device authentication. A HELD request is carried in the body of an HTTP POST request. The Device MUST include a Host header in the request. Barnes Standards Track [Page 20] RFC 5985 HELD September 2010 The MIME type of HELD request and response bodies is "application/held+xml". LIS and Device MUST provide this value in the HTTP Content-Type and Accept header fields. If the LIS does not receive the appropriate Content-Type and Accept header fields, the LIS SHOULD fail the request, returning a 406 (not acceptable) response. HELD responses SHOULD include a Content-Length header. Devices MUST NOT use the "Expect" header or the "Range" header in HELD requests. The LIS MAY return 501 (not implemented) errors if either of these HTTP features are used. In the case that the LIS receives a request from the Device containing an If-* (conditional) header, the LIS SHOULD return a 412 (precondition failed) response. The POST method is the only method REQUIRED for HELD. If a LIS chooses to support GET or HEAD, it SHOULD consider the kind of application doing the GET. Since a HELD Device only uses a POST method, the GET or HEAD MUST be either an escaped URL (e.g., somebody found a URL in protocol traces or log files and fed it into their browser) or somebody doing testing/debugging. The LIS could provide information in the HELD response indicating that the URL corresponds to a LIS server and only responds to HELD POST requests, or the LIS could instead try to avoid any leak of information by returning a very generic HTTP error message such as 404 (not found). The LIS populates the HTTP headers of responses so that they are consistent with the contents of the message. In particular, the "CacheControl" header SHOULD be set to disable caching of any PIDF-LO document or Location URIs by HTTP intermediaries. Otherwise, there is the risk of stale locations and/or the unauthorized disclosure of the LI. This also allows the LIS to control any caching with the HELD "expires" parameter. The HTTP status code MUST indicate a 2xx series response for all HELD locationResponse and HELD error messages. The LIS MAY redirect a HELD request. A Device MUST handle redirects by using the Location header provided by the server in a 3xx response. When redirecting, the Device MUST observe the delay indicated by the Retry-After header. The Device MUST authenticate the server that returns the redirect response before following the redirect, if a Device requires that the server is authenticated. A Device SHOULD authenticate the LIS indicated in a redirect. The LIS SHOULD support persistent connections and request pipelining. If pipelining is not supported, the LIS MUST NOT allow persistent connections. The Device MUST support termination of a response by the closing of a connection. Barnes Standards Track [Page 21] RFC 5985 HELD September 2010 Implementations of HELD that implement HTTP transport MUST implement transport over TLS [RFC2818]. TLS provides message integrity and confidentiality between the Device and LIS. The Device MUST implement the server authentication method described in Section 3.1 of [RFC2818], with an exception in how wildcards are handled. The leftmost label MAY contain the wildcard string "*", which matches any single domain name label. Additional characters in this leftmost label are invalid (that is, "f*.example.com" is not a valid name and does not match any domain name). The Device uses the URI obtained during LIS discovery to authenticate the server. The details of this authentication method are provided in Section 3.1 of HTTPS [RFC2818]. When TLS is used, the Device SHOULD fail a request if server authentication fails, except in the event of an emergency. 9. Security Considerations HELD is a location acquisition protocol whereby the client requests its location from a LIS. Specific requirements and security considerations for location acquisition protocols are provided in [RFC5687]. An in-depth discussion of the security considerations applicable to the use of Location URIs and by-reference provision of LI is included in [RFC5808]. By using the HELD protocol, the client and the LIS expose themselves to two types of risk: Accuracy: The client receives incorrect location information. Privacy: An unauthorized entity receives location information. The provision of an accurate and privacy- and confidentiality- protected location to the requestor depends on the success of five steps: 1. The client must determine the proper LIS. 2. The client must connect to the proper LIS. 3. The LIS must be able to identify the Device by its identifier (IP address). 4. The LIS must be able to return the desired location. 5. HELD messages must be transmitted unmodified between the LIS and the client. Barnes Standards Track [Page 22] RFC 5985 HELD September 2010 Of these, only steps 2, 3, and 5 are within the scope of this document. Step 1 is based on either manual configuration or on the LIS discovery defined in [RFC5986], in which appropriate security considerations are already discussed. Step 4 is dependent on the specific positioning capabilities of the LIS and is thus outside the scope of this document. 9.1. Assuring That the Proper LIS Has Been Contacted This document assumes that the LIS to be contacted is identified either by an IP address or a domain name, as is the case for a LIS discovered as described in LIS Discovery [RFC5986]. When the HELD transaction is conducted using TLS [RFC5246], the LIS can authenticate its identity, either as a domain name or as an IP address, to the client by presenting a certificate containing that identifier as a subjectAltName (i.e., as an iPAddress or dNSName, respectively). In the case of the HTTP binding described above, this is exactly the authentication described by TLS [RFC2818]. If the client has external information as to the expected identity or credentials of the proper LIS (e.g., a certificate fingerprint), these checks MAY be omitted. Any binding of HELD MUST be capable of being transacted over TLS so that the client can request the above authentication, and a LIS implementation for a binding MUST include this feature. Note that in order for the presented certificate to be valid at the client, the client must be able to validate the certificate. In particular, the validation path of the certificate must end in one of the client's trust anchors, even if that trust anchor is the LIS certificate itself. 9.2. Protecting Responses from Modification In order to prevent that response from being modified en route, messages must be transmitted over an integrity-protected channel. When the transaction is being conducted over TLS (a required feature per Section 9.1), the channel will be integrity protected by appropriate ciphersuites. When TLS is not used, this protection will vary depending on the binding; in most cases, without protection from TLS, the response will not be protected from modification en route. 9.3. Privacy and Confidentiality Location information returned by the LIS must be protected from access by unauthorized parties, whether those parties request the location from the LIS or intercept it en route. As in Section 9.2, transactions conducted over TLS with appropriate ciphersuites are protected from access by unauthorized parties en route. Conversely, in most cases, when not conducted over TLS, the response will be accessible while en route from the LIS to the requestor. Barnes Standards Track [Page 23] RFC 5985 HELD September 2010 Because HELD is an LCP and identifies clients and targets by IP addresses, a requestor is authorized to access location for an IP address only if it is the holder of that IP address. The LIS MUST verify that the client is the target of the returned location, i.e., the LIS MUST NOT provide location to other entities than the target. Note that this is a necessary, but not sufficient, criterion for authorization. A LIS MAY deny requests according to any local policy. A prerequisite for meeting this requirement is that the LIS must have some assurance of the identity of the client. Since the target of the returned location is identified by an IP address, simply sending the response to this IP address will provide sufficient assurance in many cases. This is the default mechanism in HELD for assuring that location is given only to authorized clients; LIS implementations MUST support a mode of operation in which this is the only client authentication. Using IP return routability as an authenticator means that location information is vulnerable to exposure through IP address spoofing attacks. A temporary spoofing of an IP address could mean that when a Device requests a Location Object or Location URI, it receives another Device's location because the attacker is able to receive packets sent to the spoofed address. In addition, in cases where a Device drops off the network for various reasons, the re-use of the Device's IP address could result in another Device receiving the original Device's location rather than its own location. These exposures are limited by the following: o Location URIs MUST have a limited lifetime, as reflected by the value for the "expires" element in Section 6.5.2. The lifetime of Location URIs necessarily depends on the nature of the access. o The LIS and network SHOULD be configured so that the LIS is made aware of Device movement within the network and addressing changes. If the LIS detects a change in the network that results in it no longer being able to determine the location of the Device, then all Location URIs for that Device SHOULD be invalidated. The above measures are dependent on network configuration, which SHOULD be considered. For instance, in a fixed Internet access, providers may be able to restrict the allocation of IP addresses to a single physical line, ensuring that spoofing is not possible; in such an environment, additional measures may not be necessary. Barnes Standards Track [Page 24] RFC 5985 HELD September 2010 10. Examples The following sections provide examples of basic HTTP/HTTPS, a simple location request, and a location request for multiple location types, along with the relevant location responses. To focus on important portions of messages, the examples in Sections 10.2 and 10.3 do not show HTTP/HTTPS headers or the XML prologue. In addition, sections of XML not relevant to the example are replaced with comments. 10.1. Examples of HTTPS Messages The examples in this section show complete HTTP/HTTPS messages that include the HELD request or response document. This example shows the most basic request for a LO. The POST includes an empty "locationRequest" element. POST /location HTTP/1.1 Host: lis.example.com:49152 Content-Type: application/held+xml;charset=utf-8 Content-Length: 87 Since the above request does not include a "locationType" element, the successful response to the request may contain any type of location. The following shows a response containing a minimal PIDF-LO. HTTP/1.1 200 OK Server: Example LIS Date: Tue, 10 Jan 2006 03:42:29 GMT Expires: Tue, 10 Jan 2006 03:42:29 GMT Cache-control: private Content-Type: application/held+xml;charset=utf-8 Content-Length: 856 Barnes Standards Track [Page 25] RFC 5985 HELD September 2010 -34.407 150.88001 2006-01-11T03:42:28+00:00 Wiremap 2006-01-10T03:42:28+00:00 The error response to the request is an error document. The following response shows an example error response. HTTP/1.1 200 OK Server: Example LIS Expires: Tue, 10 Jan 2006 03:49:20 GMT Cache-control: private Content-Type: application/held+xml;charset=utf-8 Content-Length: 182 Unable to determine location 10.2. Example of a Simple Location Request The location request shown below doesn't specify any location types or response time. The example response to this location request contains a list of Location URIs. https://ls.example.com:9768/357yc6s64ceyoiuy5ax3o sip:9769+357yc6s64ceyoiuy5ax3o@ls.example.com Barnes Standards Track [Page 26] RFC 5985 HELD September 2010 An error response to this location request is shown below: Location not available 10.3. An Example of a Location Request for Multiple Location Types The following Location Request message includes a request for geodetic, civic, and any Location URIs. geodetic civic locationURI The corresponding Location Response message includes the requested location information, including two Location URIs. https://ls.example.com:9768/357yc6s64ceyoiuy5ax3o sip:9769+357yc6s64ceyoiuy5ax3o@ls.example.com: -34.407242 150.882518 30 Barnes Standards Track [Page 27] RFC 5985 HELD September 2010 AU NSW Wollongong Gwynneville Northfield Avenue University of Wollongong 2 Andrew Corporation 2500 39 WS-183 U40 false 2007-05-25T12:35:02+10:00 Wiremap 2007-05-24T12:35:02+10:00 11. IANA Considerations IANA has made the registrations detailed in the following sections. 11.1. 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", per the guidelines in [RFC3688]. URI: urn:ietf:params:xml:ns:geopriv:held Registrant Contact: IETF, GEOPRIV working group, (geopriv@ietf.org), Mary Barnes (mary.ietf.barnes@gmail.com). Barnes Standards Track [Page 28] RFC 5985 HELD September 2010 XML: BEGIN HELD Messages

Namespace for HELD Messages

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

See RFC 5985

END 11.2. 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), Mary Barnes (mary.ietf.barnes@gmail.com). Schema: The XML for this schema can be found as the entirety of Section 7 of this document. 11.3. 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 Same as the charset parameter of "application/xml" as specified in RFC 3023 [RFC3023], Section 3.2. Barnes Standards Track [Page 29] RFC 5985 HELD September 2010 Encoding considerations: Same as the encoding considerations of "application/xml" as specified in 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. Interoperability considerations: This content type provides a basis for a protocol. There are multiple interoperable implementations of this protocol. Published specification: RFC 5985 Applications which use this media type: Location information providers and consumers. Additional Information: Magic Number(s): (none) File extension(s): .heldxml Macintosh File Type Code(s): "TEXT" Person & email address to contact for further information: Mary Barnes Intended usage: LIMITED USE Author/Change controller: The IETF 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. 11.4. Error Code Registry As defined in this document, IANA created a new registry for the HELD protocol including an initial registry for error codes. The error codes are included in HELD error messages as described in Section 6.3 and defined in the schema in the 'codeType' token in the XML schema in Section 7. The following is a summary of the registry: Related Registry: Geopriv HELD Registries, Error codes for HELD Defining RFC: RFC 5985 Barnes Standards Track [Page 30] RFC 5985 HELD September 2010 Registration/Assignment Procedures: Following the policies outlined in [RFC5226], the IANA policy for assigning new values for the Error codes for HELD is Standards Action: Values are assigned only for Standards Track RFCs approved by the IESG. Registrant Contact: IETF, GEOPRIV working group, (geopriv@ietf.org), Mary Barnes (mary.ietf.barnes@gmail.com). This section registers the following eight initial error codes as described in Section 6.3: requestError: This code indicates that the request was badly formed in some fashion. xmlError: This code indicates that the XML content of the request was either badly formed or invalid. generalLisError: This code indicates that an unspecified error occurred at the LIS. locationUnknown: This code indicates that the LIS could not determine the location of the Device. unsupportedMessage: This code indicates that the request was not supported or understood by the LIS. This error code is used when a HELD request contains a document element that is not supported by the receiver. timeout: This code indicates that the LIS could not satisfy the request within the time specified in the "responseTime" parameter. cannotProvideLiType: This code indicates that the LIS 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". notLocatable: This code indicates that the LIS is unable to locate the Device and that the Device MUST NOT make further attempts to retrieve LI from this LIS. This error code is used to indicate that the Device is outside the access network served by the LIS; for instance, the VPN and NAT scenarios discussed in Section 4.1.2. Barnes Standards Track [Page 31] RFC 5985 HELD September 2010 12. Contributors James Winterbottom, Martin Thomson and Barbara Stark are the authors of the original document, from which this WG document was derived. Their contact information is included below. They made additional contributions to the WG document, including the XML schema. James Winterbottom Andrew Andrew Building (39) University of Wollongong Northfields Avenue Wollongong, NSW 2522 AU Phone: +61 2 4221 2938 EMail: james.winterbottom@andrew.com URI: http://www.andrew.com/ Martin Thomson Andrew Andrew Building (39) University of Wollongong Northfields Avenue Wollongong, NSW 2522 AU Phone: +61 2 4221 2915 EMail: martin.thomson@andrew.com URI: http://www.andrew.com/ Barbara Stark BellSouth Room 7A43 725 W Peachtree St. Atlanta, GA 30308 US EMail: barbara.stark@att.com 13. Acknowledgements The author and contributors would like to thank the participants in the GEOPRIV WG and the following people for their constructive input and feedback on this document (in alphabetical order): Nadine Abbott, Bernard Aboba, Eric Arolick, Richard Barnes (in particular, the security considerations section), Peter Blatherwick, Ben Campbell, Barnes Standards Track [Page 32] RFC 5985 HELD September 2010 Guy Caron, Eddy Corbett, Martin Dawson, Lisa Dusseault, Robins George, Jerome Grenier, Ted Hardie, Cullen Jennings, Neil Justusson, Tat Lam, Marc Linsner, Patti McCalmont, Alexey Melnikov, Roger Marshall, Tim Polk, Perry Prozeniuk, Carl Reed, Julian Reschke, Eric Rescorla, Dan Romascanu, Brian Rosen, John Schnizlein, Shida Schubert, Henning Schulzrinne, Ed Shrum, Doug Stuard, Hannes Tschofenig, and Karl Heinz Wolf. 14. References 14.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [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. [RFC2965] Kristol, D. and L. Montulli, "HTTP State Management Mechanism", RFC 2965, October 2000. [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. [RFC5491] Winterbottom, J., Thomson, M., and H. Tschofenig, "GEOPRIV Presence Information Data Format Location Object (PIDF-LO) Usage Clarification, Considerations, and Recommendations", RFC 5491, March 2009. [RFC5646] Phillips, A. and M. Davis, "Tags for Identifying Languages", BCP 47, RFC 5646, September 2009. [RFC5986] Thomson, M. and J. Winterbottom, "Discovering the Local Location Information Server (LIS)", RFC 5986, September 2010. [W3C.REC-xmlschema-1-20041028] Thompson, H., Mendelsohn, N., Beech, D., and M. Maloney, "XML Schema Part 1: Structures Second Edition", World Wide Web Consortium Recommendation REC-xmlschema-1-20041028, October 2004, . Barnes Standards Track [Page 33] RFC 5985 HELD September 2010 [W3C.REC-xmlschema-2-20041028] Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes Second Edition", World Wide Web Consortium Recommendation REC-xmlschema-2-20041028, October 2004, . 14.2. Informative References [LLDP-MED] TIA, "ANSI/TIA-1057 Link Layer Discovery Protocol - Media Endpoint Discovery". [LOC-CONVEY] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance for the Session Initiation Protocol", Work in Progress, July 2010. [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, September 1981. [RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., Leach, P., Luotonen, A., and L. Stewart, "HTTP Authentication: Basic and Digest Access Authentication", RFC 2617, June 1999. [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media Types", RFC 3023, January 2001. [RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J. Polk, "Geopriv Requirements", RFC 3693, February 2004. [RFC3825] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host Configuration Protocol Option for Coordinate-based Location Configuration Information", RFC 3825, July 2004. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [RFC4479] Rosenberg, J., "A Data Model for Presence", RFC 4479, July 2006. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. Barnes Standards Track [Page 34] RFC 5985 HELD September 2010 [RFC5687] Tschofenig, H. and H. Schulzrinne, "GEOPRIV Layer 7 Location Configuration Protocol: Problem Statement and Requirements", RFC 5687, March 2010. [RFC5808] Marshall, R., "Requirements for a Location-by-Reference Mechanism", RFC 5808, May 2010. Barnes Standards Track [Page 35] RFC 5985 HELD September 2010 Appendix A. HELD Compliance to IETF LCP Requirements This appendix describes HELD's compliance to the requirements specified in [RFC5687]. A.1. L7-1: Identifier Choice "The L7 LCP MUST be able to carry different identifiers or MUST define an identifier that is mandatory to implement. Regarding the latter aspect, such an identifier is only appropriate if it is from the same realm as the one for which the location information service maintains identifier to location mapping." COMPLY HELD uses the IP address of the location request message as the primary source of identity for the requesting Device or target. This identity can be used with other contextual network information to provide a physical location for the Target for many network deployments. There may be network deployments where an IP address alone is insufficient to identify a Target in a network. However, any necessary identity extensions for these networks is beyond the scope of this document. 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 determining the location based on the identity of the serving base station), 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. Barnes Standards Track [Page 36] RFC 5985 HELD September 2010 A.3. L7-3: ASP and Access Network Provider Relationship "The design of the L7 LCP MUST NOT assume a business or trust relationship between the Application Service Provider (ASP) and the Access Network Provider. Requirements for resolving a reference to location information are not discussed in this document." COMPLY HELD describes a location acquisition protocol between a Device and a LIS. In the context of HELD, the LIS is within the Access Network. Thus, HELD is independent of the business or trust relationship between the Application Service Provider (ASP) and the Access Network Provider. Location acquisition using HELD is subject to the restrictions described in Section 9. 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. HELD is a webservices protocol which can be bound to transports other than HTTP, such as BEEP. Using a protocol such as BEEP 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. A.5. L7-5: Legacy Device Considerations "The design of the GEOPRIV Layer 7 Location Configuration Protocol MUST consider legacy residential NAT Devices and Network Termination Equipment (NTE) in an DSL environment that cannot be upgraded to support additional protocols, for example to pass additional information through DHCP." Barnes Standards Track [Page 37] RFC 5985 HELD September 2010 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. 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 from 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 endpoint and the LIS. There is no requirement for the endpoint to authenticate with the LIS. 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." Barnes Standards Track [Page 38] RFC 5985 HELD September 2010 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. A.9. L7-9: Discovery Mechanism "The L7 LCP MUST define a single mandatory to implement discovery mechanism." COMPLY HELD uses the discovery mechanism in [RFC5986]. A.10. L7-10: PIDF-LO Creation "When a LIS creates a PIDF-LO per RFC 4119 then it MUST put the element into the element of the presence document (see RFC 4479). This ensures that the resulting PIDF-LO document, which is subsequently distributed to other entities, conforms to the rules outlined in [now RFC 5941]." COMPLY HELD protocol overview (Section 4) describes the requirements on the LIS in creating the PIDF-LO and prescribes that the PIDF-LO generated by the LIS MUST conform to [RFC5491]. Author's Address Mary Barnes (editor) Polycom EMail: mary.ietf.barnes@gmail.com Barnes Standards Track [Page 39]