GeoPriv R. Marshall, Ed. Internet-Draft TCS Intended status: Informational
September 5,October 11, 2007 Expires: March 8,April 13, 2008 Requirements for a Location-by-Reference Mechanism draft-ietf-geopriv-lbyr-requirements-00draft-ietf-geopriv-lbyr-requirements-01 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 have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on March 8,April 13, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document defines terminology and provides requirements relating to aLocation-by-Reference approach to handling location information within SIPsignaling and other Internet messaging. The key for a Location-by-Reference mechanism is the Location URI, which is a reference to a location, and is used by either an end-device or a middlebox to represent a location, and is used as a key by a dereferencing protocol to get a usable form of location. An example application for which the Location-by-Reference mechanism is used is emergency call routing with voice-over-IP (VoIP) and general Internet multimedia systems, where Internet protocols are used end-to-end.Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Terminology . . . . . . . . . . . . . . . . . . . 54 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 65 3.1. Definition ofTerms . . . . . . . . . . . . . . . . . . . 6 4. Basic Actors .. . . . . . . 5 4. Basic Actors . . . . . . . . . . . . . . . . . 8 5. High-Level Requirements for a Location Configuration Protocol. . . . . . . . 6 5. High-Level Requirements . . . . . . . . . . . . . . . . . . . 10 6. High-Level8 5.1. Requirements for a Location DereferenceConfiguration Protocol . . . 8 5.2. Requirements for a Location Dereference Protocol . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 1211 7. SecurityIANA Considerations . . . . . . . . . . . . . . . . . . . 14 8. IANA Considerations. . 12 8. Acknowledgements . . . . . . . . . . . . . . . . . . . 15 9. Acknowledgements. . . . 13 9. References . . . . . . . . . . . . . . . . . . . 16 10. References. . . . . . . 14 9.1. Normative References . . . . . . . . . . . . . . . . . . . 17 10.1. Normative14 9.2. Informative References . . . . . . . . . . . . . . . . . . 14 Appendix A. Change log . 17 10.2. Informative References. . . . . . . . . . . . . . . . . . 17. . 15 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 1816 Intellectual Property and Copyright Statements . . . . . . . . . . 1917 1. Introduction Location-based services rely on ready access to location information, which can be through a direct,direct or indirect mechanism. While there is already a direct mechanism which exists to provide location as part of the SIP signaling protocol, an alternative mechanism has been developed for handling location indirectly, via a location reference, a reference which points to the actual location information. This reference is called the location URI, and is used by the Location-by- Reference mechanism. Since possessing the location URI alone is insufficient to perform location-based routing,mechanism we call Location-by-Reference, or LbyR. Each of the actions by which a location URI mustcan be dereferenced. Once the actual location informationused is returnedrepresented by specific individual protocol. For example, a Location Configuration Protocol, is used by a device or middlebox to acquire a location recipient, itwhich already exists (examples of this protocol include DHCP, LLDP-MED, and HELD [I-D.ietf-geopriv-http-location-delivery]). The location configuration protocol problem statement and requirements document can thenbe used as input to some location-based service, such asfound in the case of routing a VoIP-based emergency call. This document lists a set[I-D.ietf-geopriv-l7-lcp-ps]. The action of requirements for a Location-by-Reference (LbyR) mechanism, using a location URI within the SIP protocol for the purpose of executing a location-based service routing request. There are a variety of actions in which a location URI can be used. Included in this list is the action of 'location configuration', or the acquisition of the location into an end device or middlebox, 'location conveyance', which is the shuttling of location between SIP signaling nodes, and, 'location dereferencing', which we define as the action of exchanging a location URI for the actual location information it points to at a dereference server, which we call a Location Information Server, or LIS. Each of these actions are represented by specific individual protocols. A Location Configuration Protocol (LCP), is used by a device or middlebox to acquire a location which already exists (examples of this protocol include DHCP, LLDP-MED, and HELD). By conveyance protocol, we mean a protocol which transportsconveying a location URI along from node to node according to specific rules (e.g., SIP).in SIP, for example, is known as a conveyance protocol. A Location Dereferencing Protocol (LDP),location dereferencing protocol, is used by a client to resolve a location URI in exchange for location information at a LIS. Though conveyance of a location URI may be discussed in general terms, any requirements for conveyance using LbyR are not included, and are considered out of scope. In our SIP example, the LbyR is setup, instead of having a content identifier (cid:) pointing to a location object within a SIP body, to have a location URI carried in the SIP Geolocation header. In constrast to LbyR, a direct access to location is equivalent to havingfrom a location object included along with the signaling,dereference server (e.g., a PIDF-LO), is referred to as the Location-by-Value (LbyV) mechanism, and is treated as out of scope for this document. A separate draft document exists which describes, for both LbyR and LbyV scenarios, a way to convey location within SIP [I-D.ietf-sip-location-conveyance].LIS). The structure of this document first defines terminologyterminology, or points to the appropriate draft where defined, in Section 3. Then a short discussion on the basic elements which show LbyR. This section on actors, Section 4 includes a basic LbyRmodel, and describes the steps which the LbyR mechanism takes. Requirements are outlined separately for the configuration step (LCP), (Section 5),location configuration, Section 5.1, followed by those for a dereferencing protocol, Section 5.2. Location-by-Value, called LbyV, in contrast to LbyR, is a direct location conveyance approach and includes the location object, e.g., a PIDF-LO [RFC4119] in the SIP signaling. Location conveyance is out of scope for this document (see [I-D.ietf-sip-location-conveyance] for an additional listexplanation of requirements targeted toward the dereferencing step (LDP) (Section 6).conveyance of location including both LbyR and LbyV scenarios. Location determination, which may include the processes of manual provisioning, automated measurements, or location transformations, (e.g., geo-coding), are beyond the scope of this document. A detailed discussion of Identity information related to the caller, subscriber, or device, as associated to location or location URI, is also out of scope. 2. Requirements Terminology 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 RFC 2119 [RFC2119]. This document outlines only requirements for an LbyR mechanism which is used by two different protocols, a Location Configuration Protocol, and a Location Derferencing Protocol. Each of these protocols has its own unique client and server interactions, and the requirements here are not intended to state what either an LCP or LDP host client or server is expected to do, but rather which requirements must be met by both the LCP and LDP interface protocols. 3. Terminology 3.1. Definition of Terms Several of the terms presented below are based on Geopriv Requirements [RFC3693], and in some cases, extended to include additional language to support the LbyR model. Civic location: A described location based on some understood location reference system, such a jurisdictions or postal delivery grid. A street address valid within the USPS system is a common example. Coordinate location: A reference to a geographic point which is able to be located as described by a set of defined coordinates within a geographic coordinate system, such as latitude and longitude, within the WGS-84 datum. For example, 2-D geographic location is defined as an (x,y) coordinate value pair according to the distance north or south of the equator and east or westthis document. A detailed discussion of Identity information related to the prime meridian. A coordinate location may be absolute,caller, subscriber, or may havedevice, as associated uncertainty relatedto it's exact position, depending on how it is represented. Location: Either a geographic coordinate or feature representation based on a specific coordinate reference system,location or by other identifiable informationlocation URI, is also out of scope. 2. Requirements Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 3. Terminology This document reuses the terminology of [RFC3693], such as a street numberLocation Server (LS), Location Recipient (LR), Rule Maker (RM), Target, Location Generator (LG), Location Object (LO), and street name within a civic, postal, or abstract location reference system. Location-by-Value:Using Protocol: 3.1. Terms Location-by-Value (LbyV): The mechanism of representing location either in configuration or conveyance protocols, (i.e., the actual included location value is included). Location-by-Reference:value). Location-by-Reference (LbyR): The mechanism of representing location either in configuration, conveyance, andor in dereferencing protocols as an identifier which refers to a fully specified location, (i.e., a pointer to the actual location value). Location Configuration Protocol (LCP):Protocol: A protocol which is used by a client to acquire either location or a location URI from a location configuration server (e.g., (LIS)),server, based on information unique to the client. Location Dereference Protocol (LDP): A protocol which is used by a client to query a location dereference server (e.g., (LIS)), based on location URI input and which returns location information (e.g., a PIDF-LO). Location Information Server (LIS): The entity which receives a client request for either location or a location reference. In the latter case, also performs the dereference function for a Location Refernce Identifier, in the context of the Location-by- Reference model. May also be referred to as a Location Information Server (LIS). In the SIP Presence architecture, the LIS may be referred to as a Presence Server (PS). In this document the LIS is an instance of an LS. Location Object (LO): An object conveying location information (and possibly privacy rules) to which Geopriv security mechanisms and privacy rules are to be applied. Location Recipient (LR): The entity that receives location information. It may have asked for this location explicitly (by sending a query containing an location URI to a location configuration server), or it may receive this location asynchronously. Location Server (LS): The entity toLocation Dereference Protocol: A protocol which is used by a client to query a LG publisheslocation objects, the recipient of queries fromdereference server, based on location receivers,URI input and the entity that applies rules designed by the rule maker.which returns location information. Location URI: An identifier which serves as a pointer to a location record on a remote host (e.g., LIS). Used within an Location-by- Reference (LbyR) mechanism. Amechanism, a location URI is provided by a location configuration server, based on a client request,and is the inputused as input by thea dereference protocol to retrieve the associatedlocation from a dereference server. It is assumed that a LIS can function both as a configuration server and dereference server. 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, end device, or other entity whose location is communicated by a Geopriv Location Object. Using Protocol: A protocol (e.g., SIP) which carries a Location Object or an Location Reference Identifier.4. Basic Actors LbyR with Location Subscription The LbyR mechanism can be used via a normal query/response mode, or alternatively, by using a subscription model to get updated location.In mobile wireless networks it is not efficient for the end host to periodically query the LIS for up-to-date location information. This is especially the case when power is a constraint or a location update is not immediately needed. Furthermore, the end host might want to delegate the task of retrieving and publishing location information to a third party, such as to a presence server. Finally, in some deployments, the network operator may not want to make location information widely available. These use scenarios motivated the introduction of the LbyR concept. Depending on the type of reference, such as HTTP/HTTPS or SIP Presence URI, different operations can be performed. While an HTTP/ HTTPS URI can be resolved to location information, a SIP Presence URI provides further benefits from the SUBSCRIBE/NOTIFY concept that can additionally be combined with location filters [I-D.ietf-geopriv-loc-filters]. +-----------+ Geopriv +-----------+ | | LDP (3)Location | Location | | LIS +---------------+ Recipient | | | Dereference | | +-----+-----+ Protocol (3) +----+------+ | -- | Geopriv -- | GeoprivLocation -- | LCPConfiguration -- | (1)Protocol -- | (1) -- Geopriv | -- Using Protocol | -- (e.g., SIP) +-----+-----+ -- (2) | Target / |-- | End Host + | | +-----------+ Figure 1: Shows the assumed communication model for both a layer 7 (L7) LCPlocation configuration protocol and LDP:a dereference protocol: Note that there is no requirement for using the same protocol in (1) and (3). The following list describes the location subscription approach: 1. The end host discovers the LIS. 2. The target (end host) sends a request to the LIS asking for a location URI, as shown in (1) of Figure 1. 3. The LIS responds to the request and includes a location object along with a subscription URI. 4. The Target puts the subscription URI into a SIP message and forwards it to a Location Recipient via a using protocol, as shown in (2) of Figure 1. The Location Recipient subscribes to the obtained subscription URI (see (3) of Figure 1) and potentially uses a location filter (see [I-D.ietf-geopriv-loc-filters]) to limit the notification rate. 5. If the Target moves outside a certain area, indicated by a location filter, the Location Recipient will receive a notification. Note that the Target may also act in the role of the Location Recipient whereby it would subscribe to its own location information. For example, the Target obtains a subscription URI from the Geopriv L7 LCP protocol.Location Configuration Protocol. It subscribes to the URI in order to obtain its current location information. A service boundary indicates the bounded extent up to which the device can move without the need to have an updated location, since a re-query with any location within the boundary would result in the same answer returned from a location-based service. For LbyR, the LIS needs to maintain a list of randomized location URIs for each host, timing out each of these URIs after the reference expires. Location URIs need to expire to prevent the recipient of such a URI from being able to (in some cases) permanently track a host. Furthermore, an expiration mechanism also offers garbage collection capability for the LIS. Location URIs must be designed to prevent adversaries from obtaining a known Target's location. There are at least two approaches: The location URI contains a random component which helps obscure sequential updates to location, yet still allows any holder of the location URI to obtain location information. Alternatively, the location URI can remain public and the LIS performs access control via a separate authentication mechanism, such as HTTP digest or TLS client side authentication, when resolving the reference to a location object. 5. High-Level Requirements This document outlines only requirements for an LbyR mechanism which is used by two different protocols, a location configuration protocol, and a location dereferencing protocol. Each of these protocols has its own unique client and server interactions, and the requirements here are not intended to state what a client or server is expected to do, but rather which requirements must be met by either the configuration or dereferencing protocol itself. 5.1. Requirements for a Location Configuration Protocol Below, we summarize high-level design requirements needed for a location-by-reference mechanism as used within the LCP.location configuration protocol. C1. Location URI support - LCP:support: The configuration protocol MUST support a location reference in URI form. Motivation: It is helpful to have a consistent form of key for the LbyR mechanism. C2. Location URI expiration: The LCP MUST support the ability to specify to the server, the lengthlifetime of time thata location URI willSHOULD be valid.indicated. Motivation: Location URIs are not intended to represent a location forever, and the identifier eventually may need to be recycled, or may be subject to a specific window of validity, after which the location reference fails to yield a location, or the location is determined to be kept confidential. A configurable carried in the LCP for a location URI ensures that the location reference becomes invalid based on some internal LIS settings.C3. Location URI cancellation: The LCP MUSTlocation configuration protocol SHOULD support the ability to request a cancellation of a specific location URI. Motivation: If the client determines that in its best interest to destroy the ability for a location URI to effectively be used to dereference a location, then there has toshould be a way to nullify the location URI. (This may be accomplished by setting the C2 configurable to 'expire=now', for example.)C4. Random Generated: The location URI MUST be hard to guess, i.e., it MUST contain a cryptographically random component. Motivation: There is some benefit to the client if the location URI is generated in an obscured manner so that its sequence, for example in the case of a client's location update, can't be easy guessed. C5. Identity Protection - LCP :Protection: The location URI MUST NOT contain any information that identifies the user, device or address of record within the URI form. Motivation: It is important to protect caller identity or contact address from being included in the form of the location URI itself when it is generated. C6. Reuse flag default: The LCP MUST support the default condition of a requested location URI being repeatedly reused. Motivation: The requestor ofindicator: There SHOULD be a location URI, shouldn't need to specify any special flag in orderway to receiveallow a location URI which can later be used repeatedly, such as for an updated location. C7. One-time-use: The LCP MUST support the ability for theclient to requestcontrol whether a 'one-time-use'location URI (e.g., via a reuse flag setting).can be resolved once or multiple times. Motivation: The client requesting a location URI may request a location URI which has a 'one-time-use' only characteristic, as opposed to a location URI having multiple reuse capability. 6. High-LevelC7. Location timestamp: There SHOULD be a way to allow a client to determine whether the dereferenced location information refers to the location of the Target at the time when the location URI was created or when it was dereferenced. Motivation: It is important to distinguish between an original and an updated location. 5.2. Requirements for a Location Dereference Protocol Below, we summarize high-level design requirements needed for a location-by-reference mechanism.mechanism as used within the location dereference protocol. D1. Location URI support - LDP:support: The LDPlocation dereference protocol MUST support a location reference in URI form. Motivation: It is required that there be consistency of use between location URI formats used in an LCPconfiguration protocol and those used by a LDP.dereference protocol. D2. Location URI expiration status: The LDPlocation dereference protocol MUST support a message indicating that for a location URI which is no longer valid, that the location URI has expired. Motivation: Location URIs are expected to expire, based on LCPlocation configuration protocol parameters, and it is therefore useful to convey the expired status of the location URI in the LDP.location dereference protocol. D3. Authentication: The LDPlocation dereference protocol MUST support either client-side and server-side authentication between client and server.authentication. Motivation: It is reasonable to expect implementations of authentication to vary. Some implementations may choose to implement both client-side and server-side authentication, might implement one only, or may implement neither. D4. Dereferenced Location Form: Location URI dereferencingThe dereferenced location MUST result in a well-formed PIDF-LO. Motivation: This is in order to ensure both interoperation consistancy andthat adequate privacy rules can be adhered to, since the PIDF-LO format comprises the necessary structures to maintain location privacy. D5. Repeated use: The LDP MUST support the ability for the same location URI to be resolved more than once, based on server settings and LCP parameters. Motivation: According to LCP parameters, there may or may not be a limit on the number of dereferencing actions at the dereference server. D6. Updated location: The LDP MUST support the ability for the same location URI to be resolved into a continuum of location values (e.g., location updates). Motivation: A location URI when reused may not always result in the same location value, but may be a mixture of unchanged and changed location values. D7. Location form:D5. Repeated use: The LDPlocation dereference protocol MUST support dereferencedthe ability for the same location in both coordinateURI to be resolved more than once, based on server settings and civic forms.configuration server parameters. Motivation: It is important that the LDP not limit which type of location gets dereferenced, sinceAccording to configuration server parameters, it is assumed that some dereference servers may provide coordinate form of location only, others may provide civic only, while somemay provide both formsbe necessary to have a limit on the number of location. 7.dereferencing attempts. 6. Security Considerations The LbyR mechanism currently addresses security issues as follows. A location URI, regardless of its randomized construction, if public, implies no safeguard against anyone being able to dereference and get the location. The randomization of a location URI in its naming,naming does help prevent some potential guessing, according to some defined pattern. In the instance of one-time- use location URIs, which function similarly to a pawn ticket, the argument can be made that with a pawn ticket, possession implies permission, and location URIs which are public are protected only by privacy rules enforced at the dereference server. Additional security issues will be discussed in a separatethe geopriv document. 8.draft, draft-barnes-geopriv-lo-sec-00.txt. 7. IANA Considerations This document does not require actions by the IANA. 9.8. Acknowledgements IWe would like to thank the IETF GEOPRIV working group chairs, Andy Newton, Allison Mankin and Randall Gellens, for creating the design team which initiated this requirements work. IWe'd also wouldlike to thank Andrew Newton;those design team participants for their inputs, comments, and reviews. The design team included the following folks: Richard Barnes; Martin Dawson; Henning Schulzrinne; Marc Linsner; Brian Rosen;Keith Drage; Randall Gellens; Ted Hardie; Cullen Jennings; Marc Linsner; Rohan Mahy; Allison Mankin; Roger Marshall; Andrew Newton; Jon Peterson; James M. Polk; James Winterbottom; Martin Thomson;Brian Rosen; John Schnizlein; Henning Schulzrinne; Barbara Stark; Jon Peterson; Allison Mankin; Randall Gellens; Cullen Jennings; Richard Barnes; Keith Drage; Rohan Mahy; andHannes Tschofenig, for their individual contributionsTschofenig; Martin Thomson; and comments. 10.James Winterbottom. 9. References 10.1.9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 10.2.9.2. Informative References [I-D.ietf-geopriv-http-location-delivery] Barnes, M., Winterbottom, J., Thomson, M., and B. Stark, "HTTP Enabled Location Delivery (HELD)", draft-ietf-geopriv-http-location-delivery-01draft-ietf-geopriv-http-location-delivery-02 (work in progress), JulySeptember 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-04draft-ietf-geopriv-l7-lcp-ps-05 (work in progress), AugustSeptember 2007. [I-D.ietf-geopriv-loc-filters] Mahy, R., "A Document Format for Filtering and Reporting Location Notications in the Presence Information Document Format Location Object (PIDF-LO)", draft-ietf-geopriv-loc-filters-01 (work in progress), March 2007. [I-D.ietf-sip-location-conveyance] Polk, J. and B. Rosen, "Location Conveyance for the Session Initiation Protocol", draft-ietf-sip-location-conveyance-08 (work in progress), July 2007. [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. Appendix A. Change log Changes to this draft in comparison to the -00 version: 1. Shortened Abstract and Introduction. 2. LDP term gone. Expansion of Location Dereferencing Protocol, deletion of "LDP" acronym throughout, since LDP stands for Label Distribution Protocol elsewhere in the IETF. 3. LCP term is also gone. LCP is used as Link Control Protocol elsewhere (IETF). 4. Reduced the number of terms in the doc. Referenced other drafts or RFCs for repeated terms. 5. Requirement C2. changed to indicate that the URI has a lifetime. 6. C3. Softened by changing from a MUST to a SHOULD. 7. C6. Reworded for clarity. 8. C7. Changed the MUST to a SHOULD to reflect a more appropriate level. 9. D6. Replaced the text to make it clearer. 10. D7. Deleted the requirement since it wasn't an appropriate task for the protocol. 11. Referenced Richard's security document 12. Cleaned up some text. Author's Address Roger Marshall (editor) TeleCommunication Systems, Inc. 2401 Elliott Avenue 2nd Floor Seattle, WA 98121 US Phone: +1 206 792 2424 Email: firstname.lastname@example.org URI: http://www.telecomsys.com Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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