ECRIT H. Schulzrinne
Internet-Draft Columbia University
Intended status: Experimental H. Tschofenig
Expires: January 11, 2013 Nokia Siemens Networks
July 10, 2012
Synchronizing Location-to-Service Translation (LoST) Protocol based
Service Boundaries and Mapping Elements
draft-ietf-ecrit-lost-sync-18.txt
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 is used to encapsulate information about
service boundaries is defined in the LoST protocol specification 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. In any case, this document can also be
used without the LoST protocol even though the format of the
<mapping> element is re-used from the LoST specification.
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."
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This Internet-Draft will expire on January 11, 2013.
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
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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.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. A Motivating Example . . . . . . . . . . . . . . . . . . . . . 6
4. Querying for Mappings with a <getMappingsRequest> /
<getMappingsResponse> Exchange . . . . . . . . . . . . . . . . 12
4.1. Behavior of the LoST Sync Destination . . . . . . . . . . 12
4.2. Behavior of the LoST Sync Source . . . . . . . . . . . . . 12
4.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 13
5. Pushing Mappings via <pushMappings> and
<pushMappingsResponse> . . . . . . . . . . . . . . . . . . . . 15
5.1. Behavior of the LoST Sync Source . . . . . . . . . . . . . 15
5.2. Behavior of the LoST Sync Destination . . . . . . . . . . 15
5.3. Example . . . . . . . . . . . . . . . . . . . . . . . . . 16
6. Transport . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7. RelaxNG . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8. Operational Considerations . . . . . . . . . . . . . . . . . . 23
9. Security Considerations . . . . . . . . . . . . . . . . . . . 24
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
10.1. Media Type Registration . . . . . . . . . . . . . . . . . 25
10.2. LoST Sync Relax NG Schema Registration . . . . . . . . . . 26
10.3. LoST Synchronization Namespace Registration . . . . . . . 27
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
12.1. Normative References . . . . . . . . . . . . . . . . . . . 29
12.2. Informative References . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30
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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 multiple 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 Uniform Resource Identifier
(URI) or set of URIs for a given service. A service boundary may
consist of several non-contiguous geometric shapes.
RFC 5222 [RFC5222] not only defines the term but it also specifies
the data structure itself: the <mapping> element.
This document re-uses this existing data structure and defines an
XML-based protocol to exchange authoritative service boundaries
between two entities (the LoST Sync source and the LoST Sync
destination). This protocol can be used with and without the actual
LoST protocol.
The rest of the document is structured as follows: Section 3 starts
with an example usage of the LoST protocol. In Section 4, Section 5,
Section 6, and Section 7 we describe the protocol semantics,
transport considerations and the schema. Finally, we conclude with
operational and security considerations in Section 8, and in
Section 9.
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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', 'authoritative mapping server', and 'ESRP'.
Throughout this document we use the term LoST Sync source and LoST
Sync destination to denote the protocol end points of the exchange.
The protocol is referred 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 the [RFC5582]. There, LoST servers act
in different roles that cooperate to provide an ubiquitous, globally
scalable and resilient mapping service. In the LoST mapping
architecture, LoST servers can peer, i.e., have an on-going 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 deployent 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'
whereby the former two cover the entire country expect for Vienna,
which is covered by a separate LoST server. There may be other
caching LoST servers run by ISPs, universities, and 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 configuration of these nodes would therefore be as follows:
Forest Guide Austria: This forest guide would contain mappings for
the three authoritative mapping servers (East, West and Vienna)
describing what area they are responsible for. Note that each
mapping would contain a service URN and these mappings point to
LoST servers rather than to PSAPs or ESRPs.
LoST Server 'East': This LoST server would contain all the mappings
to PSAPs covering one half 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). Such a mapping could
have the following structure:
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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 it 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 above-shown mapping is what is the LoST server "east-
austria.lost-example.com" provides to the Austrian Forest Guide.
LoST Server 'West': This LoST server would contain all the mappings
to PSAPs covering the other half of the country.
LoST Server 'Vienna': This LoST server would contain all the
mappings to PSAPs in the area of Vienna.
Forest Guide Finland: In our example we assume that Finland would
deploy 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 FG would distribute 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 could be run
between the two Forest Guides. Thereby, the three mappings stored in
the Austria FG 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
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in Austria would be responsible to maintain 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 and those are best
described by the exchange between two nodes as shown in Figure 5 and
Figure 6. The protocol exchange always runs between a LoST Sync
source and a LoST Sync destination. Node A in the examples of
Figure 5 and Figure 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.
The <pushMappingsRequest> exchange allows a LoST Sync source to push
mappings to 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.
No publish/subscribe mechanism is defined in this document that would
allow Node B to tell Node A about what mappings it is interested in
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nor a mechanism for learning to which 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.
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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. A mechanisms that is suitable when no mappings are available on
the LoST Sync destination is to submit an empty
<getMappingsRequest> message, as shown in Figure 7. The intent
by the LoST Sync destination thereby is to retrieve all mappings
from the LoST Sync source. Note that the request does not
propagate further to other nodes.
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
when to poll for updated mapping information is outside the scope
of this document. The <getMappingsRequest> message with one or
multiple <exists> child element(s) allows to reduce the number of
returned mappings to those that have been updated and also to
those that are missing.
In response to 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 multiple <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'
attribut 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>,
<serverTimeout> errors, defined in [RFC5222], are utilized by this
specification. Neither the <redirect> nor the <warnings> messages
are reused by this message.
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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 <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 mapping that
matched 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"
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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@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
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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.
The LoST Sync source SHOULD keep track of which LoST Sync destination
it has pushed mapping elements. 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 containing
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" attribute. Figure 10 shows an example
request where the mapping with the source="nj.us.example",
sourceId="123", lastUpdated="2008-11-01T01:00:00Z", expires="2008-11-
01T01:00:00Z" is requested to be deleted. Note that the 'expires'
attribute is required per 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 which peers it has distributed this update to 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
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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.
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.
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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">
<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>
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<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>
<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 operation 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 that a mapping could not be deleted as requested the
following error response might be returned instead.
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<?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
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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.
When using HTTP-over-TLS [RFC2818], LoST Sync messages use the POST
method. Request 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 indicates that the request itself failed or
was redirected; these responses do not contain any LoST Sync XML
elements.
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7. RelaxNG
Note: In order to avoid copying pattern definitions from the LoST
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>
</define>
<define name="pushMappingsResponse">
<element name="pushMappingsResponse">
<ref name="extensionPoint"/>
</element>
</define>
<define name="getMappingsRequest">
<element name="getMappingsRequest">
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<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">
<element name="notDeleted">
<ref name="basicException"/>
<oneOrMore>
<ref name="mapping"/>
</oneOrMore>
</element>
</define>
</grammar>
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8. Operational Considerations
When different LoST servers use the mechanism described in this
document to synchronize their mapping data then it is important to
ensure that loops are avoided. 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 would push this new mapping to B and
C. When B obtained this new mapping it would find out that it has to
distribute it to its peer C. C would also want to distribute the
mapping to 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.
It is important that implementations MUST NOT modify mappings they
receive. An entity acting maliciously would, however, intentially
modify mappings or inject bogus mappings. To avoid the possibility
of an untrustworthy member claiming a coverage region that it is not
authorized for, authoritative mapping server 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 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 digitially signed, they cannot be modified by
intermediate LoST servers.
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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 toolkits. 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 network internal mappings
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 an 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 unusal 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 RFCXXXX is applicable. In addition, as this media type
uses the "+xml" convention, it shares the same security
considerations as described in [RFC3023], Section 10. [NOTE TO
IANA/RFC-EDITOR: Please replace XXXX with the RFC number of this
specification.]
Interoperability considerations: None
Published specification: RFCXXXX [NOTE TO IANA/RFC-EDITOR: Please
replace XXXX with the RFC number of this specification.]
Applications which use this media type: Emergency and Location-based
Systems
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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
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
Please register the schema defined in this document 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).
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Relax NG Schema: The Relax NG schema to be registered is contained
in Section 7.
10.3. LoST Synchronization Namespace Registration
Please register the namespace defined in this document 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).
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]">RFCXXXX
[NOTE TO IANA/RFC-EDITOR:
Please replace XXXX with the RFC number of this
specification.]</a>.</p>
</body>
</html>
END
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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
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication",
RFC 2617, June 1999.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media
Types", RFC 3023, January 2001.
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", BCP 13, RFC 4288, December 2005.
[RFC5222] Hardie, T., Newton, A., Schulzrinne, H., and H.
Tschofenig, "LoST: A Location-to-Service Translation
Protocol", RFC 5222, August 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[W3C.REC-xmldsig-core-20020212]
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
[RFC5582] 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
US
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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