Geopriv J. Winterbottom Internet-Draft M. Thomson Expires: September 6, 2007 Andrew Corporation H. Tschofenig Siemens Networks GmbH & Co KG March 5, 2007 GEOPRIV PIDF-LO Usage Clarification, Considerations and Recommendations draft-ietf-geopriv-pdif-lo-profile-06.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 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 September 6, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Winterbottom, et al. Expires September 6, 2007 [Page 1] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 Abstract The Presence Information Data Format Location Object (PIDF-LO) specification provides a flexible and versatile means to represent location information. There are, however, circumstances that arise when information needs to be constrained in how it is represented so that the number of options that need to be implemented in order to make use of it are reduced. There is growing interest in being able to use location information contained in a PIDF-LO for routing applications. To allow successfully interoperability between applications, location information needs to be normative and more tightly constrained than is currently specified in the PIDF-LO. This document makes recommendations on how to constrain, represent and interpret locations in a PIDF-LO. It further recommends a subset of GML that MUST be implemented by applications involved in location based routing. Winterbottom, et al. Expires September 6, 2007 [Page 2] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Using Location Information . . . . . . . . . . . . . . . . . . 6 3.1. Single Civic Location Information . . . . . . . . . . . . 8 3.2. Civic and Geospatial Location Information . . . . . . . . 8 3.3. Manual/Automatic Configuration of Location Information . . 9 4. Geodetic Coordinate Representation . . . . . . . . . . . . . . 10 5. Geodetic Shape Representation . . . . . . . . . . . . . . . . 11 5.1. Polygon Restrictions . . . . . . . . . . . . . . . . . . . 12 5.2. Complex Shape Examples . . . . . . . . . . . . . . . . . . 12 5.2.1. Polygon Representation and Usage . . . . . . . . . . . 12 5.2.2. Prism Representation and Usage . . . . . . . . . . . . 14 5.2.3. Arc Band Respresentation and Usage . . . . . . . . . . 16 5.2.4. Ellipsoid Representation and Usage . . . . . . . . . . 18 5.3. Emergency Shape Representations . . . . . . . . . . . . . 20 6. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 22 7. Security Considerations . . . . . . . . . . . . . . . . . . . 23 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26 10.1. Normative references . . . . . . . . . . . . . . . . . . . 26 10.2. Informative References . . . . . . . . . . . . . . . . . . 26 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27 Intellectual Property and Copyright Statements . . . . . . . . . . 28 Winterbottom, et al. Expires September 6, 2007 [Page 3] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 1. Introduction The Presence Information Data Format Location Object (PIDF-LO) [2] is the IETF recommended way of encoding location information and associated privacy policies. Location information in a PIDF-LO may be described in a geospatial manner based on a subset of GMLv3, or as civic location information [4]. A GML profile for expressing geodetic shapes in a PIDF-LO is described in [6]. Uses for PIDF-LO are envisioned in the context of numerous location based applications. This document makes recommendations for formats and conventions to make interoperability less problematic. Winterbottom, et al. Expires September 6, 2007 [Page 4] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [1]. The definition for "Target" is taken from [5]. In this document a "discrete location" is defined as a place, point, area or volume in which a Target can be found. It must be described with sufficient precision to address the requirements of an intended application. The term "location complex" is used to describe location information represented by a composite of both civic and geodetic information. An example of a location complex might be a geodetic polygon describing the perimeter of a building and a civic element representing the floor in the building. Winterbottom, et al. Expires September 6, 2007 [Page 5] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 3. Using Location Information The PIDF format provides for an unbounded number of tuples. The geopriv element resides inside the status component of a tuple, hence a single PIDF document may contain an arbitrary number of location objects some or all of which may be contradictory or complementary. The actual location information is contained inside a element, and there may be one or more actual locations described inside the element. Graphically, the structure of the PIDF-LO can be depicted as follows: PIDF document tuple 1 status geopriv location-info civicAddress geodetic location... usage-rules geopriv 2 geopriv 3 . . . tuple 2 tuple 3 All of these potential sources and storage places for location lead to confusion for the generators, conveyors and users of location information. Practical experience within the United States National Emergency Number Association (NENA) in trying to solve these ambiguities led to a set of conventions being adopted. These rules do not have any particular order, but should be followed by creators and users of location information contained in a PIDF-LO to ensure that a consistent interpretation of the data can be achieved. Rule #1: A geopriv element MUST describe a discrete location. Winterbottom, et al. Expires September 6, 2007 [Page 6] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 Rule #2: Where a discrete location can be uniquely described in more than one way, each location description SHOULD reside in a separate tuple. Rule #3: Providing more than one location in a single presence document (PIDF) MUST only be done if all objects describe the same location. This may occur if a Target's location is determined using a series of different techniques. Rule #4: Providing more than one location in a single element SHOULD be avoided where possible. Rule #5: When providing more than one location in a single element the locations MUST be provided by a common source at the same time and by the same method. Rule #6: Providing more than one location in a single element SHOULD only be done if they form a complex to describe the same location. For example, a geodetic location describing a point, and a civic location indicating the floor in a building. Rule #7: Where a location complex is provided in a single element, the coarse location information MUST be provided first. For example, a geodetic location describing an area, and a civic location indicating the floor should be represented with the area first followed by the civic location. Rule #8: Where a PIDF document contains more than one tuple containing a status element with a geopriv location element , the priority of tuples SHOULD be based on tuple position within the PIDF document. That is to say, the tuple with the highest priority location occurs earliest in the PIDF document. Rule #9: Where multiple PIDF documents can be sent or received together, say in a multi-part MIME body, and current location information is required by the recipient, then document selection SHOULD be based on document order, with the first document be considered first. The following examples illustrate the application of these rules. Winterbottom, et al. Expires September 6, 2007 [Page 7] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 3.1. Single Civic Location Information Jane is at a coffee shop on the ground floor of a large shopping mall. Jane turns on her laptop and connects to the coffee-shop's WiFi hotspot, Jane obtains a complete civic address for her current location, for example using the DHCP civic mechanism defined in [3]. A Location Object is constructed consisting of a single PIDF document, with a single geopriv tuple, and a single location residing in the element. This document is unambiguous, and should be interpreted consistently by receiving nodes if sent over the network. 3.2. Civic and Geospatial Location Information Mike is visiting his Seattle office and connects his laptop into the Ethernet port in a spare cube. In this case the location is a geodetic location, with the altitude represented as a building floor number. Mike's main location is the point specified by the geodetic coordinates. Further, Mike is on the second floor of the building located at these coordinates. Applying rules #6 and #7 are applied, the PIDF-LO document creates a complex as shown below. -43.5723 153.21760 2 2003-06-22T20:57:29Z Winterbottom, et al. Expires September 6, 2007 [Page 8] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 3.3. Manual/Automatic Configuration of Location Information Loraine has a predefined civic location stored in her laptop, since she normally lives in Sydney, the address is for her Sydney-based apartment. Loraine decides to visit sunny San Francisco, and when she gets there she plugs in her laptop and makes a call. Loraine's laptop receives a new location from the visited network in San Francisco. As this system cannot be sure that the pre-existing, and new location, describe the same place, Loraine's computer generates a new PIDF-LO and will use this to represent Loraine's location. If Loraine's computer were to add the new location to her existing PIDF location document (breaking rule #3), then the correct information may still be interpreted by location recipient providing Loraine's system applies rule #9. In this case the resulting order of location information in the PIDF document should be San Francisco first, followed by Sydney. Since the information is provided by different sources, rule #8 should also be applied and the information placed in different tuples with the tuple containing the San Francisco location first. Winterbottom, et al. Expires September 6, 2007 [Page 9] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 4. Geodetic Coordinate Representation The geodetic examples provided in RFC 4119 [2] are illustrated using the gml:location element which uses the gml:coordinates elements (inside the gml:Point element) and this representation has several drawbacks. Firstly, it has been deprecated in later versions of GML (3.1 and beyond) making it inadvisable to use for new applications. Secondly, the format of the coordinates type is opaque and so can be difficult to parse and interpret to ensure consistent results, as the same geodetic location can be expressed in a variety of ways. The PIDF-LO Geodetic Shapes specification [6] provides a specific GML profile for expressing commonly used shapes using simple GML representations. The shapes defined in [6] are the recommended shapes to ensure interoperability between location based applications. Winterbottom, et al. Expires September 6, 2007 [Page 10] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 5. Geodetic Shape Representation The cellular mobile world today makes extensive use of geodetic based location information for emergency and other location-based applications. Generally these locations are expressed as a point (either in two or three dimensions) and an area or volume of uncertainty around the point. In theory, the area or volume represents a coverage in which the user has a relatively high probability of being found, and the point is a convenient means of defining the centroid for the area or volume. In practice, most systems use the point as an absolute value and ignore the uncertainty. It is difficult to determine if systems have been implemented in this manner for simplicity, and even more difficult to predict if uncertainty will play a more important role in the future. An important decision is whether an uncertainty area should be specified. The PIDF-LO Geodetic Shapes specification [6] defines eight shape types most of which are easily translated into shapes definitions used in other applications and protocols, such as Open Mobile Alliance (OMA) Mobile Location Protocol (MLP). For completeness the shapes defined in [6] are listed below: o Point (2d or 3d) o Polygon (2d) o Circle (2d) o Ellipse (2d) o Arc band (2d) o Sphere (3d) o Ellipsoid (3d) o Prism (3d) The GeoShape specification [6] also describes a standard set of coordinate reference systems (CRS), unit of measure (UoM) and conventions relating to lines and distances. GeoShape mandates the use the WGS-84 Coordinate reference system and restricts usage to EPSG-4326 for two dimensional (2d) shape representations and EPSG- 4979 for three dimensional (3d) volume representations. Distance and heights are expressed in meters using EPSG-9001. It is RECOMMENDED that where uncertainty is included, a confidence of Winterbottom, et al. Expires September 6, 2007 [Page 11] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 68% (or one standard deviation) is used. Specifying a convention for confidence enables better use of uncertainty values. 5.1. Polygon Restrictions The Polygon shape type defined in [6] intentionally does not place any constraints on the number of vertices that may be included to define the bounds of the Polygon. This allows arbitrarily complex shapes to be defined and conveyed in a PIDF-LO. However where location information is to be used in real-time processing applications, such as location dependent routing, having arbitrarily complex shapes consisting of tens or even hundreds of points could result in significant performance impacts. To mitigate this risk it is recommended that Polygons be restricted to a maximum of 15 discrete points (16 including the repeated point) when the location information is intended for use in real-time applications. This limit of 15 points is chosen to allow moderately complex shape definitions while at the same time enabling interoperation with other location transporting protocols such as those defined in 3GPP ([7]) and OMA where the 15 point limit is already imposed. Polygons are defined with the minimum distance between two adjacent vertices (geodesic). A connecting line SHALL NOT cross another connecting line of the same Polygon. Polygons SHOULD be defined with the upward normal pointing up, this is accomplished by defining the vertices in counter-clockwise direction. Points specified in a polygon must be coplanar, and it is recommended that where points are specified in 3 dimensions that all points maintain the same altitude. 5.2. Complex Shape Examples This section provides some examples of where some of the more complex shapes are used, how they are determined, and how they are represented in a PIDF-LO. Complete details on all of the Geoshape types are provided in [6]. 5.2.1. Polygon Representation and Usage The polygon shape may be used to represent a building outline or coverage area. The first and last points of the polygon must be the same to form a closed shape. For example looking at the octagon below with vertices, A,H,G,F,E,D,C,B,A. The resulting polygon will be defined with 9 points, with the first and last points both having the coordinates of point A. Winterbottom, et al. Expires September 6, 2007 [Page 12] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 B-------------C / \ / \ / \ A D | | | | | | | | H E \ / \ / \ / G--------------F Winterbottom, et al. Expires September 6, 2007 [Page 13] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 43.311 -73.422 43.211 -73.422 43.111 -73.322 43.111 -73.222 43.211 -73.122 43.311 -73.122 43.411 -73.222 43.411 -73.322 43.311 -73.422 2007-06-22T20:57:29Z 5.2.2. Prism Representation and Usage A prsim may be used to represent a section of a building or range of floors of building. The prism extrudes a polygon by providing a height element. It consists of a base made up of coplanar 3 points defined in 3 dimensions all at the same altitude. The prism is then an extrusion from this base to the value specified in the height element. If the height is negative, then the prism is extruded from the top down, while a positive height extrudes from the bottom up. The first and last points of the polygon must be the same to form a closed shape. For example looking at the cube below. If the prism is extruded from Winterbottom, et al. Expires September 6, 2007 [Page 14] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 the bottom up, then the polygon forming the base of the prism is defined with the points A, B, C, D, A. The height of the prism is the distance between point A and point E in meters. The resulting PIDF-LO is provided below. G-----F /| /| / | / | H--+--E | | C--|--B | / | / |/ |/ D-----A Winterbottom, et al. Expires September 6, 2007 [Page 15] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 42.556844 -73.248157 36.6 42.656844 -73.248157 36.6 42.656844 -73.348157 36.6 42.556844 -73.348157 36.6 42.556844 -73.248157 36.6 2.4 2007-06-22T20:57:29Z 5.2.3. Arc Band Respresentation and Usage The arc band shape type is commonly generated in wireless systems where timing advance or code offsets sequences are used to compensate for distances between handsets and the access point. The arc band is represented as two radii emanating from a central point, and two angles which represent the starting angle and the opening angle of the arc. In a cellular environment the central point is nominally Winterbottom, et al. Expires September 6, 2007 [Page 16] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 the location of the cell tower, the two radii are determined by the extent of the timing advance, and the two angles are generally provisioned information. For example, Paul is using a cellular wireless device and is 7 timing advance symbols away from the cell tower. For a GSM-based network this would place Paul roughly between 3,594 meters and 4,148 meters from the cell tower, providing the inner and outer radius values. If the start angle is 20 degrees from north, and the opening angle is 120 degrees, an arc band representing Paul's location would look similar to the figure below. N ^ ,.__ | a(s) / `-. | 20 / `-. |--. / `. | `/ \ | /__ \ | . `-. \ | . `. \ |. \ \ . ---c-- a(o) -- | | --> |. / 120 ' | E | . / ' | . / ; .,' / r(i)`. / (3594m) `. / `. ,' `. ,' r(o)`' (4148m) The resulting PIDF-LO is reflected below. Winterbottom, et al. Expires September 6, 2007 [Page 17] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 -43.5723 153.21760 3594 4148 20 20 2003-06-22T20:57:29Z An important note to make on the arc band is that the center point used in the definition of the shape is not included in resulting enclosed area, and that Target may be anywhere in the defined area of the arc band. 5.2.4. Ellipsoid Representation and Usage The ellipsoid is the volume most commonly produced by GPS systems. It is used extensively in navigation systems and wireless location networks. The ellipsoid is constructed around a central point specified in three dimensions, and three axies perpendicular to one Winterbottom, et al. Expires September 6, 2007 [Page 18] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 another are extended outwards from this point. These axies are defined as the semi-major (M) axis, the semi-minor (m) axis, and the vertical (v) axis respectively. An angle is used to express the orientation of the ellipsoid. The orientation angle is measured in degrees from north, and represents the direction of the semi-major axis from the center point. \ _.-\""""^"""""-._ .' \ | `. / v m \ | \ | | | -c ----M---->| | | \ / `._ _.' `-...........-' A PIDF-LO containing an ellipsoid would like something like the sample below. Winterbottom, et al. Expires September 6, 2007 [Page 19] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 42.5463 -73.2512 26.3 7.7156 3.31 28.7 90 2003-06-22T20:57:29Z 5.3. Emergency Shape Representations In some parts of the world cellular networks constraints are placed on the shape types that can be used to represent the location of an emergency caller. These restrictions, while to some extend are artificial, may pose significant interoperability problems in emergency networks were they to be unilaterally lifted. The largest impact likely being on Public Safety Answer Point (PSAP) where multiple communication networks report emergency data. Wholesale swap-out or upgrading of this equipment is deemed to be complex and costly and has resulted in a number of countries, most notably the Winterbottom, et al. Expires September 6, 2007 [Page 20] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 United States, to adopt migratory standards towards emergency IP telephony support. Where these migratory standards are implemented restrictions on acceptable geodetic shape types to represent the location of an emergency caller may exist. Conversion from one shape type to another should be avoided to eliminate the introduction of errors in reported location. In North America the migratory VoIP emergency services standard (i2) [8] reuses the NENA E2 interface [9] which restriction geodetic shape representation to a point, a point with an uncertain circle, a point with an altitude and an uncertainty circle. The NENA recommended shapes can be represented in a PIDF-LO using the GeoShape Point, GeoShape Circle, and GeoShape Sphere definitions respectively. Winterbottom, et al. Expires September 6, 2007 [Page 21] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 6. Recommendations As a summary, this document gives a few recommendations on the usage of location information in PIDF-LO. Nine rules specified in Section 3 give guidelines on avoiding ambiguity in PIDF-LO interpretations when multiple locations may be provided to a Target or location recipient. It is recommended that only the shape types and shape representations described in [6] be used to express geodetic locations for exchange between general applications. By standardizing geodetic data representation interoperability issues are mitigated. It is recommended that GML Polygons be restricted to a maximum of 16 points when used in location-dependent routing and other real-time applications to mitigate possible performance issues. This allows for interoperability with other location protocols where this restriction applies. Geodetic location may require restricted shape definitions in regions where migratory emergency IP telephony implementations are deployed. Where the acceptable shape types are not understood restrictions to Point, Circle and Sphere representations should be used to accommodate most existing deployments. Conversions from one geodetic shape type to another should be avoided where data is considered critical and the introduction of errors considered unacceptable. In the absence of any application specific knowledge shapes and volumes should assumed to have a corresponding confidence value of 68% when associated representing a Target's location. Winterbottom, et al. Expires September 6, 2007 [Page 22] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 7. Security Considerations The primary security considerations relate to how location information is conveyed and used, which are outside the scope of this document. This document is intended to serve only as a set of guidelines as to which elements MUST or SHOULD be implemented by systems wishing to perform location dependent routing. The ramification of such recommendations is that they extend to devices and clients that wish to make use of such services. Winterbottom, et al. Expires September 6, 2007 [Page 23] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 8. IANA Considerations This document does not introduce any IANA considerations. Winterbottom, et al. Expires September 6, 2007 [Page 24] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 9. Acknowledgments The authors would like to thank the GEOPRIV working group for their discussions in the context of PIDF-LO, in particular Carl Reed, Ron Lake, James Polk and Henning Schulzrinne. Furthermore, we would like to thank Jon Peterson as the author of PIDF-LO and Nadine Abbott for her constructive comments in clarifying some aspects of the document. Winterbottom, et al. Expires September 6, 2007 [Page 25] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 10. References 10.1. Normative references [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", March 1997. [2] Peterson, J., "A Presence-based GEOPRIV Location Object Format", RFC 4119, December 2005. [3] Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration Information", RFC 4676, October 2006. [4] Thomson, M. and J. Winterbottom, "Revised Civic Location Format for PIDF-LO", draft-ietf-geopriv-revised-civic-lo-05 (work in progress), February 2007. [5] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J. Polk, "Geopriv Requirements", RFC 3693, February 2004. [6] Thomson, M. and C. Reed, "GML 3.1.1 PIDF-LO Shape Application Schema for use by the Internet Engineering Task Force (IETF)", Candidate OpenGIS Implementation Specification 06-142, Version: 0.0.9, December 2006. 10.2. Informative References [7] "3GPP TS 23.032 V6.0.0 3rd Generation Partnership Project; Technical Specification Group Code Network; Universal Geographic Area Description (GAD)". [8] "abbrev"i2">NENA VoIP-Packet Technical Committee, Interim VoIP Architecture for Enhanced 9-1-1 Services (i2), NENA 08-001, Dec 2005". [9] "NENA Standard for the Implementation of the Wireless Emergency Service Protocol E2 Interface, NENA 05-001, Dec 2003". [10] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host Configuration Protocol Option for Coordinate-based Location Configuration Information", RFC 3825, July 2004. Winterbottom, et al. Expires September 6, 2007 [Page 26] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 Authors' Addresses James Winterbottom Andrew Corporation Wollongong NSW Australia Email: james.winterbottom@andrew.com Martin Thomson Andrew Corporation Wollongong NSW Australia Email: martin.thomson@andrew.com Hannes Tschofenig Siemens Networks GmbH & Co KG Otto-Hahn-Ring 6 Munich, Bavaria 81739 Germany Email: Hannes.Tschofenig@siemens.com Winterbottom, et al. Expires September 6, 2007 [Page 27] Internet-Draft GEOPRIV PIDF-LO Profile March 2007 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. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Winterbottom, et al. Expires September 6, 2007 [Page 28]