RFC 6739: Synchronizing Service Boundaries and <mapping> Elements Based on the Location-to-Service Translation (LoST) Protocol

This RFC was updated

Internet Engineering Task Force (IETF) H. Schulzrinne
Request for Comments: 6739 Columbia University
Category: Experimental H. Tschofenig
ISSN: 2070-1721 Nokia Siemens Networks
 October 2012


 Synchronizing Service Boundaries and <mapping> Elements Based on the
 Location-to-Service Translation (LoST) Protocol

Abstract

 The Location-to-Service Translation (LoST) protocol is an XML-based
 protocol for mapping service identifiers and geodetic or civic
 location information to service URIs and service boundaries. In
 particular, it can be used to determine the location-appropriate
 Public Safety Answering Point (PSAP) for emergency services.

 The <mapping> element in the LoST protocol specification encapsulates
 information about service boundaries and circumscribes the region
 within which all locations map to the same service Uniform Resource
 Identifier (URI) or set of URIs for a given service.

 This document defines an XML protocol to exchange these mappings
 between two nodes. This mechanism is designed for the exchange of
 authoritative <mapping> elements between two entities. Exchanging
 cached <mapping> elements, i.e., non-authoritative elements, is
 possible but not envisioned. Even though the <mapping> element
 format is reused from the LoST specification, the mechanism in this
 document can be used without the LoST protocol.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for examination, experimental implementation, and
 evaluation.

 This document defines an Experimental Protocol for the Internet
 community. 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). Not
 all documents approved by the IESG are a candidate for any level of
 Internet Standard; see 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/rfc6739.



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Copyright Notice

 Copyright (c) 2012 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.

Table of Contents

 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
 3. A Motivating Example . . . . . . . . . . . . . . . . . . . . . 4
 4. Querying for Mappings with a
 <getMappingsRequest>/<getMappingsResponse> Exchange . . . . . 9
 4.1. Behavior of the LoST Sync Destination . . . . . . . . . . 9
 4.2. Behavior of the LoST Sync Source . . . . . . . . . . . . . 10
 4.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 10
 5. Pushing Mappings via <pushMappings> and
 <pushMappingsResponse> . . . . . . . . . . . . . . . . . . . . 12
 5.1. Behavior of the LoST Sync Source . . . . . . . . . . . . . 12
 5.2. Behavior of the LoST Sync Destination . . . . . . . . . . 13
 5.3. Example . . . . . . . . . . . . . . . . . . . . . . . . . 14
 6. Transport . . . . . . . . . . . . . . . . . . . . . . . . . . 16
 7. RELAX NG . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
 8. Operational Considerations . . . . . . . . . . . . . . . . . . 19
 9. Security Considerations . . . . . . . . . . . . . . . . . . . 20
 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
 10.1. Media Type Registration . . . . . . . . . . . . . . . . . 21
 10.2. LoST Sync RELAX NG Schema Registration . . . . . . . . . . 22
 10.3. LoST Synchronization Namespace Registration . . . . . . . 22
 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23
 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
 12.1. Normative References . . . . . . . . . . . . . . . . . . . 24
 12.2. Informative References . . . . . . . . . . . . . . . . . . 24









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1. Introduction

 Since the early days of emergency services, there has been a desire
 to route emergency calls to Public Safety Answering Points (PSAPs)
 that are nearest to the location of the emergency caller. For this
 purpose each PSAP discloses one or more service boundaries so that
 this information can be used to select the appropriate PSAP and to
 route the call to it. RFC 5222 [RFC5222] defines this data structure
 in the following way:

 A service boundary circumscribes the region within which all
 locations map to the same service URI or set of URIs for a given
 service. A service boundary may consist of several non-contiguous
 geometric shapes.

 RFC 5222 [RFC5222] also specifies the data structure itself as the
 <mapping> element.

 This document reuses this existing data structure and defines an XML-
 based protocol to exchange authoritative service boundaries between
 two entities, namely, the LoST Sync source and the LoST Sync
 destination. This protocol can be used whether or not the LoST
 protocol is used for querying for service boundary information.

 The rest of the document is structured as follows. Section 3 starts
 with an example usage of the LoST protocol. In Sections 4, 5, 6, and
 7, we describe the protocol semantics, transport considerations, and
 the schema. Finally, we conclude with operational, security, and
 IANA considerations in Sections 8, 9, and 10.

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].

 This document reuses terminology introduced by the mapping
 architecture document [RFC5582], such as 'coverage region', 'forest
 guide', 'mapping', and 'authoritative mapping server'. This document
 also uses the term 'ESRP', defined in [RFC5012].

 Throughout this document, we use the terms 'LoST Sync source' and
 'LoST Sync destination' to denote the protocol endpoints of the
 exchange. The protocol is referred to as 'LoST Sync' within the
 text.






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3. A Motivating Example

 The LoST Sync mechanism can, for example, be used in the LoST
 architecture, as specified in [RFC5582]. There, LoST servers
 cooperate to provide an ubiquitous, globally scalable, and resilient
 mapping service. In the LoST mapping architecture, LoST servers can
 peer, i.e., have an ongoing data exchange relationship. Peering
 relationships are set up manually, based on local policies. A LoST
 server may peer with any number of other LoST servers. Forest guides
 peer with other forest guides; authoritative mapping servers peer
 with forest guides and other authoritative servers, either in the
 same cluster or above or below them in the tree. Authoritative
 mapping servers push coverage regions "up" the tree, i.e., from child
 nodes to parent nodes. The child informs the parent of the
 geospatial or civic region that it covers for a specific service.

 Consider a hypothetical deployment of LoST in two countries, for
 example, Austria and Finland. Austria, in our example, runs three
 authoritative mapping servers labeled as 'East', 'West', and
 'Vienna', where the former two cover the entire country except for
 Vienna, which is covered by a separate LoST server. There may be
 other caching LoST servers run by ISPs, universities, and Voice
 Service Providers (VSPs), but they are not relevant for this
 illustration. Finland, on the other hand, decided to only deploy a
 single LoST server that also acts as a forest guide. For this
 simplistic illustration, we assume that only one service is
 available, namely 'urn:service:sos' since otherwise the number of
 stored mappings would have to be multiplied by the number of used
 services.

 Figure 1 shows the example deployment.




















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 +---LoST-Sync-->\\ //<--LoST-Sync----+
 | ----- |
 | |
 \/ \/
 ----- -----
 // \\ // \\
 / \ / \
 | Forest | | Forest |
 | Guide | | Guide |
 | Austria | | Finland
 \ / \ /
 +--------->\\ //<--------+ \\ //
 | ----- | -----
 | /\ | |
 LoST | LoST //------\\
 Sync LoST Sync |Co-Located|
 | Sync | | LoST |
 \/ | \/ | Server |
 //----\\ \/ //----\\ \\------//
 | LoST | //----\\ | LoST |
 | Server | | LoST | | Server |
 | 'East' | | Server | |'Vienna'|
 \\----// | 'West' | \\----//
 \\----//

 Figure 1: LoST Deployment Example

 The nodes are configured as follows:

 Forest Guide Austria: This forest guide contains mappings for the
 three authoritative mapping servers (East, West, and Vienna)
 describing the area for which they are responsible. Note that
 each mapping contains a service URN, and these mappings point to
 LoST servers rather than to PSAPs or Emergency Services Routing
 Proxies (ESRPs).

 LoST Server 'East': This LoST server contains all the mappings to
 PSAPs covering the eastern part of the country.

 Additionally, the LoST server aggregates all the information it
 has and provides an abstracted view towards the forest guide
 indicating that it is responsible for a certain area (for a given
 service and for a given location profile). For our example, the
 structure of a mapping is shown below:







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 <mapping
 xmlns="urn:ietf:params:xml:ns:lost1"
 xmlns:gml="http://www.opengis.net/gml"
 expires="2009-01-01T01:44:33Z"
 lastUpdated="2009-12-01T01:00:00Z"
 source="east-austria.lost-example.com"
 sourceId="e8b05a41d8d1415b80f2cdbb96ccf109">
 <displayName xml:lang="en">LoST Server 'East'</displayName>
 <service>urn:service:sos</service>
 <serviceBoundary profile="geodetic-2d">
 <gml:Polygon srsName="urn:ogc:def::crs:EPSG::4326">
 <gml:exterior>
 <gml:LinearRing>
 <gml:pos> ... </gml:pos>
 ..... list of coordinates for
 boundary of LoST server 'East'
 <gml:pos> ... </gml:pos>
 </gml:LinearRing>
 </gml:exterior>
 </gml:Polygon>
 </serviceBoundary>
 <uri/>
 </mapping>

 Figure 2: Forest Guide Austria Mapping XML Snippet

 Note that the XML code snippet in Figure 2 serves illustrative
 purposes only and does not validate. As can be seen in this
 example, the <uri> element is absent, and the 'source' attribute
 identifies the LoST server, namely "east-austria.lost-
 example.com".

 The mapping shown above is what is the LoST server "east-
 austria.lost-example.com" provides to the Austrian forest guide.

 LoST Server 'West': This LoST server contains all the mappings to
 PSAPs covering the western half of the country.

 LoST Server 'Vienna': This LoST server contains all the mappings to
 PSAPs for the city of Vienna.

 Forest Guide Finland: In our example, we assume that Finland deploys
 a single ESRP for the entire country as their IP-based emergency
 services solution. There is only a single LoST server, and it is
 co-located with the forest guide, as shown in Figure 1. The
 mapping data this forest guide (FG) then distributes via LoST Sync
 is shown in Figure 3.




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 <mapping xmlns="urn:ietf:params:xml:ns:lost1"
 expires="2007-01-01T01:44:33Z"
 lastUpdated="2006-11-01T01:00:00Z"
 source="finland.lost-example.com"
 sourceId="7e3f40b098c711dbb6060800200c9a66">
 <displayName xml:lang="en">Finland ESRP</displayName>
 <service>urn:service:sos</service>
 <serviceBoundary profile="civic">
 <civicAddress
 xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
 <country>FI</country>
 </civicAddress>
 </serviceBoundary>
 <uri/>
 </mapping>

 Figure 3: Forest Guide Finland Mapping XML Snippet

 An example mapping stored at the co-located LoST server is shown
 in Figure 4.

 <mapping xmlns="urn:ietf:params:xml:ns:lost1"
 expires="2007-01-01T01:44:33Z"
 lastUpdated="2006-11-01T01:00:00Z"
 source="finland.lost-example.com"
 sourceId="7e3f40b098c711dbb6060800200c9a66">
 <displayName xml:lang="en">Finland ESRP</displayName>
 <service>urn:service:sos</service>
 <serviceBoundary profile="civic">
 <civicAddress
 xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
 <country>FI</country>
 </civicAddress>
 </serviceBoundary>
 <uri>sip:esrp@finland-example.com</uri>
 <uri>xmpp:esrp@finland-example.com</uri>
 <serviceNumber>112</serviceNumber>
 </mapping>

 Figure 4: Forest Guide Finland / Co-Located LoST Server Mapping
 XML Snippet

 The LoST Sync mechanism described in this document can be run between
 the two forest guides. That way, the three mappings stored in the FG
 Austria are sent to the FG Finland, and a single mapping in the FG
 Finland is sent to the FG Austria. Additionally, the three Austrian
 LoST servers could utilize LoST Sync to inform the Austrian FG about
 their boundaries. These three authoritative mapping servers in



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 Austria would be responsible for maintaining their own mapping
 information. Since the amount of data being exchanged is small and
 the expected rate of change is low, the nodes are configured to
 always exchange all their mapping information whenever a change
 happens.

 This document defines two types of exchanges, which are best
 described by the exchange between two nodes as shown in Figures 5 and
 6. The protocol exchange always runs between a LoST Sync source and
 a LoST Sync destination. Node A in the examples of Figures 5 and 6
 has mappings that Node B is going to retrieve. Node A acts as the
 source for the data and Node B is the destination.

 The <getMappingsRequest> request allows a LoST Sync source to request
 mappings from a LoST Sync destination.

 +---------+ +---------+
 | Node B | | Node A |
 | acting | | acting |
 | as | | as |
 | LoST | | LoST |
 | Sync | | Sync |
 | Dest. | | Source |
 +---------+ +---------+
 | |
 | |
 | |
 | <getMappingsRequest> |
 |----------------------------->|
 | |
 | <getMappingsResponse> |
 |<-----------------------------|
 | |
 | |
 | |

 Figure 5: Querying for Mappings with a <getMappingsRequest> Message

 Note that in the exchange illustrated in Figure 5, Node B is issuing
 the first request and plays the role of the HTTPS client, and Node A
 plays the role of the HTTPS server.

 In Figure 6, the <pushMappingsRequest> exchange allows a LoST Sync
 source to push mappings to a LoST Sync destination. In this example,
 we assume that Node A has been configured maintain state about the
 mappings it had pushed to Node B.





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 This document does not define a publish/subscribe mechanism. Such a
 mechanism would allow Node B to tell Node A what mappings it is
 interested in. This document also does not define a mechanism for
 nodes to find out to which other entities mappings have to be pushed.

 +---------+ +---------+
 | Node A | | Node B |
 | acting | | acting |
 | as | | as |
 | LoST | | LoST |
 | Sync | | Sync |
 | Source | | Dest. |
 +---------+ +---------+
 | |
 | |
 | |
 | <pushMappingsRequest> |
 |----------------------------->|
 | |
 | <pushMappingsResponse> |
 |<-----------------------------|
 | |
 | |
 | |

 Figure 6: Pushing Mappings with a <pushMappingsRequest> Message

 Node A issuing the first request in Figure 6 plays the role of the
 HTTPS client, and Node B plays the role of the HTTPS server.

4. Querying for Mappings with a <getMappingsRequest>/
 <getMappingsResponse> Exchange

4.1. Behavior of the LoST Sync Destination

 A LoST Sync destination has two ways to retrieve <mapping> elements
 from a LoST Sync source.

 1. When the Lost Sync destination does not have any mappings, it
 submits an empty <getMappingsRequest> message, as shown in
 Figure 7. This indicates that it wishes to retrieve all mappings
 from the LoST Sync source. Note that the request does not
 propagate further to other nodes.








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 2. In case a LoST Sync destination node has already obtained
 mappings in previous exchanges, then it may want to check whether
 these mappings have been updated in the meanwhile. The policy
 regarding when to poll for updated mapping information is outside
 the scope of this document. The <getMappingsRequest> message
 with one or more <exists> child element(s) allows the source to
 only return mappings that are missing at the destination or have
 been updated.

 After issuing the <getMappingsRequest> message, the LoST Sync
 destination waits for the <getMappingsResponse> message. In case of
 a successful response, the LoST Sync destination stores the received
 mappings and determines which mappings to update.

4.2. Behavior of the LoST Sync Source

 When a LoST Sync source receives an empty <getMappingsRequest>
 message, then all locally available mappings MUST be returned.

 When a LoST Sync source receives a <getMappingsRequest> message with
 one or more <exists> child element(s), then it MUST consult with the
 local mapping database to determine whether any of the mappings of
 the client is stale and whether there are mappings locally that the
 client does not yet have. The former can be determined by finding
 mappings corresponding to the 'source' and 'sourceID' attributes
 where a mapping with a more recent 'lastUpdated' date exists.

 Processing a <getMappingsRequest> message MAY lead to a successful
 response in the form of a <getMappingsResponse> or an <errors>
 message. Only the <badRequest>, <forbidden>, <internalError>, and
 <serverTimeout> errors, defined in [RFC5222], are used by this
 specification. Neither the <redirect> nor the <warnings> messages
 are reused by this message.

4.3. Examples

 The first example shows an empty <getMappingsRequest> message that
 would retrieve all locally stored mappings at the LoST Sync source.

 <?xml version="1.0" encoding="UTF-8"?>
 <getMappingsRequest xmlns="urn:ietf:params:xml:ns:lostsync1"/>

 Figure 7: Example of Empty <getMappingsRequest> Message

 A further example request is shown in Figure 8, and the corresponding
 response is depicted in Figure 9. In this example, the
 <getMappingsRequest> element contains information about the mapping
 that is locally available to the client inside the



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 <mapping-fingerprint> element (with
 source="authoritative.bar.example",
 sourceId="7e3f40b098c711dbb6060800200c9a66", and lastUpdated="2006-
 11-01T01:00:00Z"). The query asks for mappings that are more recent
 than the available one as well as any missing mapping.

 <?xml version="1.0" encoding="UTF-8"?>
 <getMappingsRequest xmlns="urn:ietf:params:xml:ns:lostsync1">
 <exists>
 <mapping-fingerprint source="authoritative.bar.example"
 sourceId="7e3f40b098c711dbb6060800200c9a66"
 lastUpdated="2006-11-01T01:00:00Z">
 </mapping-fingerprint>
 </exists>
 </getMappingsRequest>

 Figure 8: Example <getMappingsRequest> Message

 The response to the above request is shown in Figure 9. A more
 recent mapping was available with the identification of
 source="authoritative.bar.example" and
 sourceId="7e3f40b098c711dbb6060800200c9a66". Only one missing
 mapping, with source "authoritative.foo.example", was found and
 returned.

 <?xml version="1.0" encoding="UTF-8"?>
 <sync:getMappingsResponse
 xmlns:sync="urn:ietf:params:xml:ns:lostsync1"
 xmlns="urn:ietf:params:xml:ns:lost1"
 xmlns:gml="http://www.opengis.net/gml">

 <mapping source="authoritative.bar.example"
 sourceId="7e3f40b098c711dbb6060800200c9a66"
 lastUpdated="2008-11-26T01:00:00Z"
 expires="2009-12-26T01:00:00Z">
 <displayName xml:lang="en">Leonia Police Department
 </displayName>
 <service>urn:service:sos.police</service>
 <serviceBoundary
 profile="urn:ietf:params:lost:location-profile:basic-civic">
 <civicAddress
 xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
 <country>US</country>
 <A1>NJ</A1>
 <A3>Leonia</A3>
 <PC>07605</PC>
 </civicAddress>
 </serviceBoundary>



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 <uri>sip:police@leonianj2.example.org</uri>
 <serviceNumber>911</serviceNumber>
 </mapping>

 <mapping expires="2009-01-01T01:44:33Z"
 lastUpdated="2008-11-01T01:00:00Z"
 source="authoritative.foo.example"
 sourceId="7e3f40b098c711dbb606011111111111">
 <displayName xml:lang="en">New York City Police Department
 </displayName>
 <service>urn:service:sos.police</service>
 <serviceBoundary profile="geodetic-2d">
 <gml:Polygon srsName="urn:ogc:def::crs:EPSG::4326">
 <gml:exterior>
 <gml:LinearRing>
 <gml:pos>37.775 -122.4194</gml:pos>
 <gml:pos>37.555 -122.4194</gml:pos>
 <gml:pos>37.555 -122.4264</gml:pos>
 <gml:pos>37.775 -122.4264</gml:pos>
 <gml:pos>37.775 -122.4194</gml:pos>
 </gml:LinearRing>
 </gml:exterior>
 </gml:Polygon>
 </serviceBoundary>
 <uri>sip:nypd@example.com</uri>
 <uri>xmpp:nypd@example.com</uri>
 <serviceNumber>911</serviceNumber>
 </mapping>

 </sync:getMappingsResponse>

 Figure 9: Example <getMappingsResponse> Message

5. Pushing Mappings via <pushMappings> and <pushMappingsResponse>

5.1. Behavior of the LoST Sync Source

 When a LoST Sync source obtains new information that is of interest
 to its peers, it may push the new mappings to its peers.
 Configuration settings at both peers decide whether this
 functionality is used and what mappings are pushed to which other
 peers. New mappings may arrive through various means, such as a
 manual addition to the local mapping database, or through the
 interaction with other entities. Deleting mappings may also trigger
 a protocol interaction.






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 The LoST Sync source SHOULD keep track of which LoST Sync destination
 it has pushed <mapping> elements to. If it does not keep state
 information, then it always has to push the complete data set. As
 discussed in Section 5.1 of [RFC5222], <mapping> elements are
 identified by the 'source', 'sourceID', and 'lastUpdated' attributes.
 A mapping is considered the same if these three attributes match.

 A <pushMappings> request sent by a LoST Sync source MUST contain one
 or more <mapping> elements.

 To delete a mapping, the content of the mapping is left empty, i.e.,
 the <mapping> element only contains the 'source', 'sourceID',
 'lastUpdated', and 'expires' attributes. Figure 10 shows an example
 request where the mapping with the source="nj.us.example",
 sourceId="123", lastUpdated="2008-11-01T01:00:00Z", and
 expires="2008-11-01T01:00:00Z" is requested to be deleted. Note that
 the 'expires' attribute is required per the schema definition but
 will be ignored in processing the request on the receiving side. A
 sync source may want to delete the mapping from its internal mapping
 database but has to remember the peers to which it has distributed
 this update unless it has other ways to ensure that databases do not
 get out of sync.

5.2. Behavior of the LoST Sync Destination

 When a LoST Sync destination receives a <pushMappingsRequest>
 message, then the cache with the existing mappings is inspected to
 determine whether the received mapping should lead to an update of an
 already existing mapping, should create a new mapping in the cache,
 or should be discarded.

 If a newly received mapping has a more recent time in its
 'lastUpdated' attribute, it MUST update an existing mapping that has
 matching 'source' and 'sourceID' attributes.

 If the received mapping does not match with any existing mapping
 based on the 'source' and 'sourceId', then it MUST be added to the
 local cache as an independent mapping.

 If a <pushMappingsRequest> message with an empty <mapping> element is
 received, then a corresponding mapping has to be determined based on
 the 'source' and the 'sourceID'.

 If no mapping can be identified, then an <errors> response MUST be
 returned that contains the <notDeleted> child element. The
 <notDeleted> element MAY contain a 'message' attribute with an error
 description used for debugging purposes. The <notDeleted> element
 MUST contain the <mapping> element(s) that caused the error.



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 The response to a <pushMappingsRequest> request is a
 <pushMappingsResponse> message. With this specification, a
 successful response message returns no additional elements, whereas
 an <errors> response is returned in the response message if the
 request failed. Only the <badRequest>, <forbidden>, <internalError>,
 or <serverTimeout> errors defined in Section 13.1 of [RFC5222] are
 used. The <redirect> and <warnings> messages are not used for this
 query/response.

 If the set of nodes that are synchronizing their data does not form a
 tree, it is possible that the same information arrives through
 several other nodes. This is unavoidable but generally only imposes
 a modest overhead. (It would be possible to create a spanning tree
 in the same fashion as IP multicast, but the complexity does not seem
 warranted, given the relatively low volume of data.)

5.3. Example

 An example is shown in Figure 10. Imagine a LoST node that obtained
 two new mappings identified as follows:

 o source="authoritative.example"
 sourceId="7e3f40b098c711dbb6060800200c9a66"
 lastUpdated="2008-11-26T01:00:00Z"

 o source="authoritative.example"
 sourceId="7e3f40b098c711dbb606011111111111"
 lastUpdated="2008-11-01T01:00:00Z"

 These two mappings have to be added to the peer's mapping database.

 Additionally, the following mapping has to be deleted:

 o source="nj.us.example"
 sourceId="123"
 lastUpdated="2008-11-01T01:00:00Z"

 <?xml version="1.0" encoding="UTF-8"?>
 <sync:pushMappings
 xmlns:sync="urn:ietf:params:xml:ns:lostsync1"
 xmlns="urn:ietf:params:xml:ns:lost1"
 xmlns:gml="http://www.opengis.net/gml">









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 <mapping source="authoritative.example"
 sourceId="7e3f40b098c711dbb6060800200c9a66"
 lastUpdated="2008-11-26T01:00:00Z"
 expires="2009-12-26T01:00:00Z">
 <displayName xml:lang="en">Leonia Police Department
 </displayName>
 <service>urn:service:sos.police</service>
 <serviceBoundary
 profile="urn:ietf:params:lost:location-profile:basic-civic">
 <civicAddress
 xmlns="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr">
 <country>US</country>
 <A1>NJ</A1>
 <A3>Leonia</A3>
 <PC>07605</PC>
 </civicAddress>
 </serviceBoundary>
 <uri>sip:police@leonianj.example.org</uri>
 <serviceNumber>911</serviceNumber>
 </mapping>

 <mapping expires="2009-01-01T01:44:33Z"
 lastUpdated="2008-11-01T01:00:00Z"
 source="authoritative.example"
 sourceId="7e3f40b098c711dbb606011111111111">
 <displayName xml:lang="en">New York City Police Department
 </displayName>
 <service>urn:service:sos.police</service>
 <serviceBoundary profile="geodetic-2d">
 <gml:Polygon srsName="urn:ogc:def::crs:EPSG::4326">
 <gml:exterior>
 <gml:LinearRing>
 <gml:pos>37.775 -122.4194</gml:pos>
 <gml:pos>37.555 -122.4194</gml:pos>
 <gml:pos>37.555 -122.4264</gml:pos>
 <gml:pos>37.775 -122.4264</gml:pos>
 <gml:pos>37.775 -122.4194</gml:pos>
 </gml:LinearRing>
 </gml:exterior>
 </gml:Polygon>
 </serviceBoundary>
 <uri>sip:nypd@example.com</uri>
 <uri>xmpp:nypd@example.com</uri>
 <serviceNumber>911</serviceNumber>
 </mapping>






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 <mapping source="nj.us.example"
 sourceId="123"
 lastUpdated="2008-11-01T01:00:00Z"
 expires="2008-11-01T01:00:00Z"/>

 </sync:pushMappings>

 Figure 10: Example <pushMappingsRequest> Message

 In response, the peer performs the necessary operations and updates
 its mapping database. In particular, it will check whether the other
 peer is authorized to perform the update and whether the elements and
 attributes contain values that it understands. In our example, a
 positive response is returned as shown in Figure 11.

 <?xml version="1.0" encoding="UTF-8"?>
 <pushMappingsResponse xmlns="urn:ietf:params:xml:ns:lostsync1" />

 Figure 11: Example <pushMappingsResponse>

 In case a mapping could not be deleted as requested, the following
 error response might be returned instead.

 <?xml version="1.0" encoding="UTF-8"?>
 <errors xmlns="urn:ietf:params:xml:ns:lost1"
 xmlns:sync="urn:ietf:params:xml:ns:lostsync1"
 source="nodeA.example.com">

 <sync:notDeleted
 message="Could not delete the indicated mapping."
 xml:lang="en">

 <mapping source="nj.us.example"
 sourceId="123"
 lastUpdated="2008-11-01T01:00:00Z"
 expires="2008-11-01T01:00:00Z"/>
 </sync:notDeleted>
 </errors>

 Figure 12: Example <errors> Message

6. Transport

 LoST Sync needs an underlying protocol transport mechanism to carry
 requests and responses. This document uses HTTPS as a transport to
 exchange XML documents. No fallback to HTTP is provided.





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 When using HTTP over Transport Layer Security (TLS) [RFC2818], LoST
 Sync messages use the POST method. Requests MUST use the Cache-
 Control response directive "no-cache".

 All LoST Sync responses, including those indicating a LoST warning or
 error, are carried in 2xx responses, typically 200 (OK). 3xx, 4xx,
 and 5xx HTTP response codes indicate that the request itself failed
 or was redirected; these responses do not contain any LoST Sync XML
 elements.

7. RELAX NG

 Note: In order to avoid copying pattern definitions from the LoST
 Regular Language for XML Next Generation (RELAX NG) schema [RFC5222]
 to this document, we include it as "lost.rng" (XML syntax) in the
 RELAX NG schema below.

 <?xml version="1.0" encoding="utf-8"?>

 <grammar ns="urn:ietf:params:xml:ns:lostsync1"
 xmlns="http://relaxng.org/ns/structure/1.0"
 xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
 datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">

 <include href="lost.rng"/>

 <start combine="choice">

 <a:documentation> Location-to-Service Translation (LoST)
 Synchronization Protocol</a:documentation>

 <choice>
 <ref name="pushMappings"/>
 <ref name="pushMappingsResponse"/>
 <ref name="getMappingsRequest"/>
 <ref name="getMappingsResponse"/>
 </choice>
 </start>


 <define name="pushMappings">
 <element name="pushMappings">
 <oneOrMore>
 <ref name="mapping"/>
 </oneOrMore>

 <ref name="extensionPoint"/>
 </element>



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 </define>

 <define name="pushMappingsResponse">
 <element name="pushMappingsResponse">
 <ref name="extensionPoint"/>
 </element>
 </define>

 <define name="getMappingsRequest">
 <element name="getMappingsRequest">
 <choice>
 <ref name="exists"></ref>
 <ref name="extensionPoint"/>
 </choice>
 </element>
 </define>

 <define name="exists">
 <element name="exists">
 <oneOrMore>
 <element name="mapping-fingerprint">
 <attribute name="source">
 <data type="token"/>
 </attribute>
 <attribute name="sourceId">
 <data type="token"/>
 </attribute>
 <attribute name="lastUpdated">
 <data type="dateTime"/>
 </attribute>
 <ref name="extensionPoint"/>
 </element>
 </oneOrMore>
 </element>
 </define>

 <define name="getMappingsResponse">
 <element name="getMappingsResponse">
 <oneOrMore>
 <ref name="mapping"/>
 </oneOrMore>
 <ref name="extensionPoint"/>
 </element>
 </define>

 <!-- error messages -->

 <define name="notDeleted">



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 <element name="notDeleted">
 <ref name="basicException"/>
 <oneOrMore>
 <ref name="mapping"/>
 </oneOrMore>
 </element>
 </define>
 </grammar>

8. Operational Considerations

 It is important to avoid loops when more than two LoST servers use
 the mechanism described in this document. The example shown in
 Figure 13 with three LoST servers A, B, and C (each of them acts as a
 sync source and a sync destination) illustrates the challenge in more
 detail. A and B synchronize data between each other; the same is
 true for A and C, and B and C, respectively.

 A -------- B
 \ /
 \ /
 \ /
 \ /
 C

 Figure 13: Synchronization Configuration Example

 Now, imagine that server A adds a new mapping. This mapping is
 uniquely identified by the combination of "source", "sourceid", and
 "last updated". Assume that A wants to push this new mapping to B
 and C. When B obtains this new mapping, it determines that it has to
 distribute it to its peer C. C also needs to distribute the mapping
 to its peer B. If the original mapping with the "source",
 "sourceid", and "last updated" is not modified by either B or C, then
 these two servers would recognize that they already possess the
 mapping and can ignore the update.

 Implementations MUST NOT modify mappings they receive. An entity
 acting maliciously would, however, intentionally modify mappings or
 inject bogus mappings. To avoid the possibility of an untrustworthy
 member claiming a coverage region for which it is not authorized,
 authoritative mapping servers MUST sign mappings they distribute
 using an XML digital signature [W3C.REC-xmldsig-core-20020212]. A
 recipient MUST verify that the signing entity is indeed authorized to
 speak for that region. In many cases, this will require an out-of-
 band agreement to be in place to agree on specific entities to take
 on this role. Determining who can speak for a particular region is
 inherently difficult unless there is a small set of authorizing



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 entities that participants in the mapping architecture can trust.
 Receiving systems should be particularly suspicious if an existing
 coverage region is replaced by a new one that contains a different
 value in the <uri> element. When mappings are digitally signed, they
 cannot be modified by intermediate LoST servers.

9. Security Considerations

 This document defines a protocol for exchange of authoritative
 mapping information between two entities. Hence, the protocol
 operations described in this document require authentication of
 neighboring nodes.

 The LoST Sync client and servers MUST implement TLS and use TLS.
 Which version(s) ought to be implemented will vary over time and
 depend on the widespread deployment and known security
 vulnerabilities at the time of implementation. At the time of this
 writing, TLS version 1.2 [RFC5246] is the most recent version but has
 very limited actual deployment and might not be readily available in
 implementation tool kits. TLS version 1.0 [RFC2246] is the most
 widely deployed version and will give the broadest interoperability.

 Mutual authentication between the LoST Sync source and the LoST Sync
 destination is not necessarily required in all deployments unless an
 emergency service authority wants to enforce access control prior to
 the distribution of their <mapping> elements. This may, for example,
 be the case when certain emergency services networks distribute
 internal mappings that are not meant for public distribution.

 An additional threat is caused by compromised or misconfigured LoST
 servers. A denial of service could be the consequence of an injected
 mapping. If the mapping data contains a URL that does not exist,
 then emergency services for the indicated area are not reachable. If
 all mapping data contains URLs that point to a single PSAP (rather
 than a large number of PSAPs), then this PSAP is likely to experience
 overload conditions. If the mapping data contains a URL that points
 to a server controlled by the adversary itself, then it might
 impersonate PSAPs.

 Section 8 discusses this security threat and mandates signed
 mappings. For unusual changes to the mapping database, approval by a
 system administrator of the emergency services infrastructure (or a
 similar expert) may be required before any mappings are installed.








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10. IANA Considerations

10.1. Media Type Registration

 This specification requests the registration of a new media type
 according to the procedures of RFC 4288 [RFC4288] and guidelines in
 RFC 3023 [RFC3023].

 Type name: application

 Subtype name: lostsync+xml

 Required parameters: none

 Optional parameters: charset

 Same as charset parameter of application/xml as specified in RFC
 3023 [RFC3023].

 Encoding considerations: Identical to those of "application/xml" as
 described in [RFC3023], Section 3.2.

 Security considerations: This content type is designed to carry LoST
 Synchronization protocol payloads, and the security considerations
 section of RFC 6739 is applicable. In addition, as this media
 type uses the "+xml" convention, it shares the same security
 considerations as described in [RFC3023], Section 10.

 Interoperability considerations: None

 Published specification: RFC 6739

 Applications that use this media type: Emergency and Location-based
 Systems

 Additional information:

 Magic number(s): None

 File extension(s): .lostsyncxml

 Macintosh file type code(s): 'TEXT'

 Person & email address to contact for further information:
 Hannes Tschofenig <Hannes.Tschofenig@gmx.net>

 Intended usage: LIMITED USE




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 Restrictions on usage: None

 Author: Hannes Tschofenig <Hannes.Tschofenig@gmx.net>

 Change controller:

 This specification is a work item of the IETF ECRIT working group,
 with mailing list address <ecrit@ietf.org>.

 Change controller:

 The IESG <iesg@ietf.org>

10.2. LoST Sync RELAX NG Schema Registration

 The schema defined in this document has been registered under the XML
 schema registry at
 http://www.iana.org/assignments/xml-registry/schema.html

 URI: urn:ietf:params:xml:schema:lostsync1

 Registrant Contact: IETF ECRIT Working Group, Hannes Tschofenig
 (Hannes.Tschofenig@gmx.net).

 RELAX NG Schema: The RELAX NG schema that has been registered is
 contained in Section 7.

10.3. LoST Synchronization Namespace Registration

 The namespace defined in this document has been registered under the
 XML namespace registry at
 http://www.iana.org/assignments/xml-registry/ns.html

 URI: urn:ietf:params:xml:ns:lostsync1

 Registrant Contact: IETF ECRIT Working Group, Hannes Tschofenig
 (Hannes.Tschofenig@gmx.net).














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 XML:

 BEGIN
 <?xml version="1.0"?>
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
 "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml">
 <head>
 <meta http-equiv="content-type"
 content="text/html;charset=iso-8859-1"/>
 <title>LoST Synchronization Namespace</title>
 </head>
 <body>
 <h1>Namespace for LoST server synchronization</h1>
 <h2>urn:ietf:params:xml:ns:lostsync1</h2>
 <p>See <a href="[URL of published RFC]">RFC 6739
 </a>.</p>
 </body>
 </html>

 END

11. Acknowledgments

 Robins George, Cullen Jennings, Karl Heinz Wolf, Richard Barnes,
 Mayutan Arumaithurai, Alexander Mayrhofer, and Andrew Newton provided
 helpful input. Jari Urpalainen assisted with the RELAX NG schema.
 We would also like to thank our document shepherd Roger Marshall for
 his help with the document.

 We would like to particularly thank Andrew Newton for his timely and
 valuable review of the XML-related content.

 We would like to thank Robert Sparks, Barry Leiba, Stephen Farrell,
 Brian Haberman, Pete Resnick, and Sean Turner for their AD reviews.
 We would also like to thank Bjoern Hoehrmann for his media type
 review, Julian Reschke and Martin Duerst for their applications area
 reviews, and Wassim Haddad for his Gen-ART review.













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12. References

12.1. Normative References

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

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

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

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

 [] Freed, N. and J. Klensin, "Media Type Specifications and
 Registration Procedures", BCP 13, RFC 4288, December 2005.

 [] Hardie, T., Newton, A., Schulzrinne, H., and H.
 Tschofenig, "LoST: A Location-to-Service Translation
 Protocol", RFC 5222, August 2008.

 [] Dierks, T. and E. Rescorla, "The Transport Layer Security
 (TLS) Protocol Version 1.2", RFC 5246, August 2008.

 []
 Eastlake, D., Reagle, J., Solo, D., Hirsch, F., and T.
 Roessler, "XML-Signature Syntax and Processing", World
 Wide Web Consortium, Second Edition, REC-xmldsig-core-
 20020212, June 2008.

12.2. Informative References

 [] Schulzrinne, H. and R. Marshall, "Requirements for
 Emergency Context Resolution with Internet Technologies",
 RFC 5012, January 2008.

 [] Schulzrinne, H., "Location-to-URL Mapping Architecture and
 Framework", RFC 5582, September 2009.












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Authors' Addresses

 Henning Schulzrinne
 Columbia University
 Department of Computer Science
 450 Computer Science Building
 New York, NY 10027
 USA

 Phone: +1 212 939 7004
 EMail: hgs+ecrit@cs.columbia.edu
 URI: http://www.cs.columbia.edu


 Hannes Tschofenig
 Nokia Siemens Networks
 Linnoitustie 6
 Espoo 02600
 Finland

 Phone: +358 (50) 4871445
 EMail: Hannes.Tschofenig@gmx.net
 URI: http://www.tschofenig.priv.at




























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