ECRIT K. Wolf Internet-Draft nic.at Intended status: Experimental August 6, 2010 Expires: February 7, 2011 LoST Service List Boundary Extension draft-ietf-ecrit-lost-servicelistboundary-04 Abstract LoST maps service identifiers and location information to service contact URIs. If a LoST client wants to discover available services for a particular location, it will perform a query to the LoST server. However, the LoST server, in its response, does not provide context information, that is, it does not provide any additional information about the geographical region for which the returned list of services is considered valid within. Therefore, this document proposes a Service List Boundary that returns a local context along with the list of services returned, in order to assist the client to not miss a change in available services when moving. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on February 7, 2011. 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 Wolf Expires February 7, 2011 [Page 1] Internet-Draft serviceListBoundary August 2010 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. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Wolf Expires February 7, 2011 [Page 2] Internet-Draft serviceListBoundary August 2010 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. LoST Extensions . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Extensions to . . . . . . . . . . 5 3.2. Retrieving the via . . . . . . . . . . . . . . . . . 8 3.3. . . . . . . . . . . . . . . . . . . 9 3.4. Implementation Considerations . . . . . . . . . . . . . . 10 3.4.1. Server Side . . . . . . . . . . . . . . . . . . . . . 10 3.4.2. Client Side . . . . . . . . . . . . . . . . . . . . . 10 4. Security & Privacy Considerations . . . . . . . . . . . . . . 11 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 5.1. Relax NG Schema Registration . . . . . . . . . . . . . . . 11 5.2. Namespace Registration . . . . . . . . . . . . . . . . . . 14 6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 15 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 7.1. Normative References . . . . . . . . . . . . . . . . . . . 15 7.2. Informative References . . . . . . . . . . . . . . . . . . 16 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16 Wolf Expires February 7, 2011 [Page 3] Internet-Draft serviceListBoundary August 2010 1. Introduction Location based service providers as well as Public Safety Answering Points (PSAPs) only serve a specific geographic region. Therefore the LoST protocol [RFC5222] defines the Service Boundary, which indicates the service region for a specific service URL. However, not all services are available everywhere. Clients can discover available services for a particular location by the query in LoST. The LoST server returns a list of services that are available at this particular location. But the server does not inform the client as to the extent of coverage for which geographical region the returned Service List is valid. This may lead to the situation where a client initially discovers all available services by the query, and then moves to a different location (while refreshing the service mappings), but without noticing the availability of other services. The following imaginary example illustrates the problem for emergency calling: The client is powered-up, does location determination (resulting in location A) and performs an initial query with location A requesting urn:services:sos. The LoST server returns the following list of services: urn:service:sos.police urn:service:sos.ambulance urn:service:sos.fire The client does the initial LoST mapping and discovers the dialstrings for each service. Then the client moves, refreshing the individual service mappings when necessary as told by the Service Boundary. However, when arriving in location B (close to a mountain), service sos.mountainrescue is available, which was not available in location A. Nevertheless, the client does not detect this, because only the mapping of the initially discovered services (police, ambulance, fire) are refreshed. Consequently, the dialstring for the mountain rescue is not known by the client. Hence, the client is unable to recognize an emergency call when the user enters the dialstring of the mountain rescue and thus the emergency call may fail altogether. Note that the Service Boundary (service region for an individual service) cannot be considered as an indicator for the region a specific Service List is valid for. The Service List may even change within the Service Boundary of another service. For example, the ambulance mapping is valid for a whole state, but for a part of the state there is an additional mountain rescue service. Wolf Expires February 7, 2011 [Page 4] Internet-Draft serviceListBoundary August 2010 Consequently, there are two ways to tackle this issue: o clients continuously poll for the Service List, although it may not have changed o a boundary information (telling the client that the Service List does not change inside this area) Since the LoST protocol employs the Service Boundary concept in order to avoid having clients continuously trying to refresh the mapping of a specific service, a Service List Boundary mechanism would provide similar advantages for Service Lists. 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 RFC 2119 [RFC2119]. 3. LoST Extensions This chapter describes the necessary extensions to the LoST protocol in order to support the proposed Service List Boundary in a similar way as the . Extensions defined in this document are declared in the new XML namespace urn:ietf:params:xml:ns:lost1:slb. 3.1. Extensions to The query may contain an additional element to additionally request the boundary for the Service List based on the location provided, with the resulting location for the list presented either by value or by reference. In the example below the value of 'type' attribute of the element is set to "value": Wolf Expires February 7, 2011 [Page 5] Internet-Draft serviceListBoundary August 2010 AT Lower Austria Bruck an der Leitha Wolfsthal Hauptplatz 1 2412 urn:service:sos A with the addition of one elemenents is shown below: Wolf Expires February 7, 2011 [Page 6] Internet-Draft serviceListBoundary August 2010 urn:service:sos.ambulance urn:service:sos.fire urn:service:sos.gas urn:service:sos.mountain urn:service:sos.poison urn:service:sos.police AT Lower Austria This response above indicates that the Service List is valid for Lower Austria. The request needs to be repeated by the client only when moving out of Lower Austria. However, the mappings of the services itself may have other service boundaries. Additionally, the 'expires' attribute indicates the absolute time when this Service List becomes invalid. The response MAY contain multiple elements for alternative representation, each representing the boundary in a specific location profile. However, multiple locations inside a serviceListBoundary element are considered to be additive. The boundary can also be requested by reference when setting the value of the 'type' attribute of the element to "reference" (which is the default in case the attribute is omitted). Then the response contains a element with a 'serviceListKey' attribute (described in Section 3.2), as shown below. Wolf Expires February 7, 2011 [Page 7] Internet-Draft serviceListBoundary August 2010 urn:service:sos.ambulance urn:service:sos.fire urn:service:sos.gas urn:service:sos.mountain urn:service:sos.poison urn:service:sos.police 3.2. Retrieving the via In order to retrieve the boundary corresponding a specific 'serviceListKey', the client issues a request to the server identified in the 'source' attribute of the element, similar to the request. An example is shown below: The LoST server response is shown below: Wolf Expires February 7, 2011 [Page 8] Internet-Draft serviceListBoundary August 2010 AT Lower Austria The 'serviceListKey' uniquely identifies a Service List Boundary as the 'key' does for the Service Boundary (see Section 5.6 in RFC 5222). Therefore the 'serviceListKey' is a random token with at least 128 bits of entropy and can be assumed globally unique. Whenever the boundary changes, a new 'serviceListKey' MUST be assigned. Note: since LoST does not define an attribute to indicate which location profile the clients understands in a request, this document also does not define one for the request. 3.3. The Service List Boundary information that gets returned indicates the geographic region in which all the service identifiers returned from a element are the same, within a query. A Service List Boundary may consist of geometric shapes (both in civic and geodetic location format), and may be non-contiguous, like the Service Boundary. The mapping of the specific services within the Service List Boundary may be different at different locations. The server MAY return the boundary information in multiple location profiles, but MUST use at least one profile that the client used in the request in order to ensure that the client is able to process the boundary information. There is no need to include boundary information to a . The request is purely for diagnostic purposes and does not contain location information at all, Wolf Expires February 7, 2011 [Page 9] Internet-Draft serviceListBoundary August 2010 so no boundary information is reasonable. Also note that the Service List Boundary is optional and the LoST server may return it or not based on its local policy - like it is the case with the Service Boundary. However, especially for emergency services, the Service List Boundary might be crucial to ensure that moving clients do not miss changes in the available services. 3.4. Implementation Considerations The subsections below discuss implementation issues for the LoST server and client for the Service List Boundary support. 3.4.1. Server Side The mapping architecture and framework [RFC5582] describes that each tree announces its coverage region (for one type of service, e.g. sos.police) to one or more forest guides. Forest guides peer with each other and synchronize their data. Hence, a forest guide has sufficient knowledge (it knows all the services and their coverage regions) to answer a query and additionally add the or as well. The calculation of the largest possible area for which the Service List stays the same might be a complex task. An alternative would be to return smaller areas that are easier to compute. In such a case some unneeded queries to the LoST server are the consequence, but still the main purpose of the Service List Boundary is achieved: Never miss a change of available services. Thus, the server operator may specify a reasonable trade-off between the effort to generate the boundary information and the saved queries to the LoST server. For example, in some countries the offered services may differ in adjacent counties (or districts, cantons, states, ...). Their borders may be suitable as Service List Boundary as well, even though some adjacent counties offer the same services. Other countries might have different structures and the generation of the Service List Boundary might follow other rules as long as it is ensured that a client is able to notice any change in the Service List when moving. 3.4.2. Client Side A mobile client that already implements LoST and evaluates the has almost everything that is needed to make use of Wolf Expires February 7, 2011 [Page 10] Internet-Draft serviceListBoundary August 2010 the Service List Boundary. Since the integration into LoST follows the concept of the (and also makes use of the same location profiles), just the additional needs to be evaluated. Whenever moving outside a Service List Boundary, the client performs a new query with the new location information in order to determine a change in available services. 4. Security & Privacy Considerations Security considerations for LoST are discussed in [RFC5222]. This document extends LoST to also carry Service List Boundaries (and requests for them). These Service List Boundaries are calculated by the server based on the individual Service Boundaries and sent to clients in case the local policy allows this. Therefore it is generally considered to have the same level of sensitivity as for the Service Boundary and thus the same access control and confidentiality requirements as the base LoST protocol. As a result, the security measures incorporated in the base LoST specification provide sufficient protection for LoST messages that use the Service List Boundary extension. 5. IANA Considerations This document requests two actions by IANA: an XML schema registration and namespace registration, according to the description in the following sections. 5.1. Relax NG Schema Registration This document requests registration of the following Relax NG Schema to the IETF XML Registry [RFC3688]: URI: urn:ietf:params:xml:schema:lost1:slb Registrant Contact: IETF ECRIT Working Group, Karl Heinz Wolf (karlheinz.wolf@nic.at) Relax NG Schema: BEGIN true Wolf Expires February 7, 2011 [Page 12] Internet-Draft serviceListBoundary August 2010 value reference reference Wolf Expires February 7, 2011 [Page 13] Internet-Draft serviceListBoundary August 2010 END 5.2. Namespace Registration This document requests registration of the following namespace (below the LoST namespace defined in [RFC5222]) to the IETF XML Registry [RFC3688]: URI: urn:ietf:params:xml:ns:lost1:slb Registrant Contact: IETF ECRIT Working Group, Karl Heinz Wolf (karlheinz.wolf@nic.at) XML: Wolf Expires February 7, 2011 [Page 14] Internet-Draft serviceListBoundary August 2010 BEGIN LoST Service List Boundary Namespace

Namespace for the LoST Service List Boundary

urn:ietf:params:xml:ns:lost1:slb

See RFCXXXX.

END 6. Acknowledgement The author would like to thank Henning Schulzrinne for the discussion on the draft and Martin Thomson, Richard Barnes and Roger Marshall for their valuable input and text suggestions during the WGLC. Further thanks go to Joshua Bell from the Applications Area Review Team for his help with Relax NG. 7. References 7.1. Normative References [RFC5222] Hardie, T., Newton, A., Schulzrinne, H., and H. Tschofenig, "LoST: A Location-to-Service Translation Protocol", RFC 5222, August 2008. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004. Wolf Expires February 7, 2011 [Page 15] Internet-Draft serviceListBoundary August 2010 7.2. Informative References [RFC5582] Schulzrinne, H., "Location-to-URL Mapping Architecture and Framework", RFC 5582, September 2009. Author's Address Karl Heinz Wolf nic.at GmbH Karlsplatz 1/2/9 Wien A-1010 Austria Phone: +43 1 5056416 37 Email: karlheinz.wolf@nic.at URI: http://www.nic.at/ Wolf Expires February 7, 2011 [Page 16]