ECRIT H. Schulzrinne
Internet-Draft Columbia University
Intended status: Standards Track H. Tschofenig
Expires: July 28, 2009 Nokia Siemens Networks
January 24, 2009
Synchronizing Location-to-Service Translation (LoST) Protocol based
Service Boundaries and Mapping Elements
draft-ietf-ecrit-lost-sync-02.txt
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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 main data structure, the XML <mapping> element, used for
encapsulating information about service boundaries is defined in the
LoST protocol specification and circumscribes the region within which
all locations map to the same service URI or set of URIs for a given
service.
This document defines an XML protocol to exchange these mappings
between two nodes. As motived in the Location-to-URL Mapping
Architecture document this mechanism is useful for the
synchronization of top-level LoST Forest Guides. This document is,
however, even useful in a deployment that does not make use of the
LoST protocol but purely wants to distribute service boundaries.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Distributing Mappings via <pushMappings> and
<pushMappingsResponse> . . . . . . . . . . . . . . . . . . . . 6
4. Synchronizing Mapping Stores via <getMappings> and
<getMappingsResponse> . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
6.1. LoST Synchronization Namespace Registration . . . . . . . 13
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
8. RelaxNG . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
9.1. Normative References . . . . . . . . . . . . . . . . . . . 18
9.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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1. Introduction
The LoST (Location-to-Service Translation) protocol [RFC5222] maps
service identifiers and geodetic or civic location information to
service URIs. As specified in the LoST architecture description
[I-D.ietf-ecrit-mapping-arch], there are a variety of LoST servers
that cooperate to provide an ubiquitous, globally scalable and
resilient mapping service. The LoST protocol specification only
describes the protocol used for individual seeker-originated queries.
This document allow forest guides, resolver clusters and
authoritative servers to synchronize their database of mappings.
In the LoST architecture, servers can peer, i.e., have an on-going
data exchange relationship. Peering relationships are set up
manually, based on local policies. A server can peer with any number
of other servers. Forest guides peer with other forest guides;
resolvers peer with forest guides and other resolvers (in the same
cluster); authoritative mapping servers peer with forest guides and
other authoritative servers, either in the same cluster or above or
below them in the tree. If the type of LoST role does not matter, we
refer to LoST protocol participants as LoST nodes.
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.
The coverage regions of different authoritative servers can overlap.
This should only happen if the authoritative servers are
misconfigured or if there is a political dispute that involves
competing claims for the same region. A server MUST detect such
colliding claims and implement a policy to resolve the collision,
either through an automated policy mechanism or manual intervention.
This extension defines two new requests, <pushMappings> and
<getMappings>, that allow peering servers to exchange mappings.
These requests are used for all peering relationships and always
contain mapping entries, but naturally the content of the data
exchanged differs. <pushMappings> allows a peer to send newer
mappings to another peer; with a <getMappings> query, a node can
obtain mappings that are newer than those it already has.
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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 [I-D.ietf-ecrit-mapping-arch].
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3. Distributing Mappings via <pushMappings> and <pushMappingsResponse>
When a LoST node obtains new information that is of interest to its
peers, it pushes the new mappings to its peers. This information
might arrive through non-LoST means, such as a manual addition to the
local mappings database, or through another LoST node, via a
<pushMappings> request or a <getMappingsResponse> described later.
Each peer keeps track of which peer it has exchanged which mapping
elements with. 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. Nodes never push the same information to the same
peer twice.
To delete a mapping, the content of the mapping is left empty. The
node can delete the mapping from its internal mapping database, but
has to remember which peers it has distributed this update to. The
'expires' attribute is required, but ignored. If the querier
attempts to delete a non-existent mapping, the query is silently
ignored.
The response to a <pushMappings> request is a <pushMappingsResponse>
message. Currently, 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.)
A newly received mapping M' replaces an existing mapping M if all of
the following conditions hold:
1. M'.source equals M.source, ignoring case
2. M'.sourceID' equals M.sourceID, ignoring case
3. M'.lastUpdated greater or equal to M.lastUpdated
An example is shown in Figure 1. Image a LoST node that obtained two
new mappings identified as follows:
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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, it determines that 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:pushMappingsRequest
xmlns:sync="urn:ietf:params:xml:ns:lost-sync1"
xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:p2="http://www.opengis.net/gml";>
<sync:mappings>
<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 at leonianj.example.org</uri>
<serviceNumber>911</serviceNumber>
</mapping>
<mapping expires="2009-01-01T01:44:33Z"
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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">
<p2:Polygon srsName="urn:ogc:def::crs:EPSG::4326">
<p2:exterior>
<p2:LinearRing>
<p2:pos>37.775 -122.4194</p2:pos>
<p2:pos>37.555 -122.4194</p2:pos>
<p2:pos>37.555 -122.4264</p2:pos>
<p2:pos>37.775 -122.4264</p2:pos>
<p2:pos>37.775 -122.4194</p2:pos>
</p2:LinearRing>
</p2:exterior>
</p2:Polygon>
</serviceBoundary>
<uri>sip:nypd at example.com</uri>
<uri>xmpp:nypd at 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:mappings>
</sync:pushMappingsRequest>
Figure 1: Example <pushMappings>
In response, the peer performs the necessary operation and updates
its mapping database. In particular, it will check whether the
querier 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 2.
<?xml version="1.0" encoding="UTF-8"?>
<pushMappingsResponse xmlns="urn:ietf:params:xml:ns:lost1:sync" />
Figure 2: Example <pushMappingsResponse>
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4. Synchronizing Mapping Stores via <getMappings> and
<getMappingsResponse>
Instead of pushing mappings to another LoST node, a LoST client can
declare all the mappings it has, via a sequence of <m> elements in
the <getMappings>, and then obtain any missing or outdated mappings
in the <getMappingsResponse>. Specifying the existing mappings
avoids retransmitting data that the querier has already stored.
If the <getMappings> query has no attributes, the
<getMappingsResponse> contains all mappings that are either newer
than the <m> elements or not contained in the sequence of <m>
elements. The querier can restrict the mappings returned by adding
'source' and 'sourceId' attributes to the <getMappings> query. Only
the combinations
o source
o source, sourceID
are allowed.
If the 'source' attribute is specified, only mappings with that
particular source attribute are considered. Similarly, the
'sourceId' attribute restricts mappings to those matching the
attribute from the 'source' named.
<m> elements MUST only contain the 'source', 'sourceId' and
'lastUpdated' attributes that are not contained in the <GetMappings>
element itself. Extra attributes that do not match the values of the
<getMappings> attributes are silently ignored. (This structure
reduces the query size for the common case that there are many
mappings from the same source.)
Processing a <getMappings> message may lead to a successful response
in the form of a &tl;getMappingsResponse> or an <errors> message.
Only the <badRequest>, <forbidden>, <internalError>, <serverTimeout>
errors defined in [RFC5222] are used. Neither the <redirect> nor the
<warnings> messages are used for this query.
An example request is shown in Figure 3, the corresponding response
in Figure 4. In this example a LoST node requests a specific mapping
for source="authoritative.bar.example" and
sourceId="7e3f40b098c711dbb6060800200c9a66" that is fresher than
"2006-11-01T01:00:00Z". Additionally, all mappings that match
source="authoritative.foo.example" are requested.
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<?xml version="1.0" encoding="UTF-8"?>
<getMappingsRequest xmlns="urn:ietf:params:xml:ns:lost-sync1">
<m source="authoritative.bar.example"
sourceId="7e3f40b098c711dbb6060800200c9a66"
lastUpdated="2006-11-01T01:00:00Z"/>
<m source="authoritative.foo.example"/>
</getMappingsRequest>
Figure 3: Example <getMappings> request
The response is shown in Figure 4. 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:lost-sync1"
xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:p2="http://www.opengis.net/gml";>
<sync:mappings>
<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>
<uri>sip:police at leonianj2.example.org</uri>
<serviceNumber>911</serviceNumber>
</mapping>
<mapping expires="2009-01-01T01:44:33Z"
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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">
<p2:Polygon srsName="urn:ogc:def::crs:EPSG::4326">
<p2:exterior>
<p2:LinearRing>
<p2:pos>37.775 -122.4194</p2:pos>
<p2:pos>37.555 -122.4194</p2:pos>
<p2:pos>37.555 -122.4264</p2:pos>
<p2:pos>37.775 -122.4264</p2:pos>
<p2:pos>37.775 -122.4194</p2:pos>
</p2:LinearRing>
</p2:exterior>
</p2:Polygon>
</serviceBoundary>
<uri>sip:nypd at example.com</uri>
<uri>xmpp:nypd at example.com</uri>
<serviceNumber>911</serviceNumber>
</mapping>
</sync:mappings>
</sync:getMappingsResponse>
Figure 4: Example <getMappingsResponse>
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5. Security Considerations
The LoST security considerations are discussed in [RFC5222]. The
operations described in this document involve mutually-trusting LoST
nodes. These nodes need to authenticate each other, using mechanisms
such as HTTP Digest [RFC2617], HTTP Basic [RFC2617] over TLS
[RFC5246] or TLS client and server certificates. Nodes implementing
LoST MUST implement HTTP Basic authentication over TLS and MAY
implement other authentication mechanisms.
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6. IANA Considerations
6.1. LoST Synchronization Namespace Registration
URI: urn:ietf:params:xml:ns:lost1:sync
Registrant Contact: IETF ECRIT Working Group, Henning Schulzrinne
(hgs@cs.columbia.edu).
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:lost1:sync</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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7. Acknowledgments
Robins George, Cullen Jennings and Andrew Newton provided helpful
input. Jari Urpalainen assisted with the Relax NG schema. We would
also like to thank our PROTO shepherd Roger Marshall for his help
with the document.
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8. RelaxNG
<?xml version="1.0" encoding="utf-8"?>
<grammar ns="urn:ietf:params:xml:ns:lost-sync1"
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="getMappings"/>
<ref name="getMappingsResponse"/>
</choice>
</start>
<define name="pushMappings">
<element name="pushMappings">
<element name="mappings">
<oneOrMore>
<ref name="mapping"/>
</oneOrMore>
</element>
<ref name="extensionPoint"/>
</element>
</define>
<define name="pushMappingsResponse">
<element name="pushMappingsResponse">
<ref name="extensionPoint"/>
</element>
</define>
<define name="getMappings">
<element name="getMappings">
<choice>
<ref name="ScopeSource"/>
<ref name="ScopeSourceId"/>
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</choice>
<oneOrMore>
<element name="m">
<choice>
<ref name="ScopeSource"/>
<ref name="ScopeSourceId"/>
<ref name="ScopeLastUpdated"/>
</choice>
</element>
</oneOrMore>
<ref name="extensionPoint"/>
</element>
</define>
<define name="getMappingsResponse">
<element name="getMappingsResponse">
<element name="mappings">
<oneOrMore>
<ref name="mapping"/>
</oneOrMore>
</element>
<ref name="extensionPoint"/>
</element>
</define>
<define name="ScopeSource">
<attribute name="source">
<data type="token"/>
</attribute>
</define>
<define name="ScopeSourceId">
<attribute name="source">
<data type="token"/>
</attribute>
<attribute name="sourceId">
<data type="token"/>
</attribute>
</define>
<define name="ScopeLastUpdated">
<attribute name="source">
<data type="token"/>
</attribute>
<attribute name="sourceId">
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<data type="token"/>
</attribute>
<attribute name="lastUpdated">
<data type="dateTime"/>
</attribute>
</define>
</grammar>
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9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[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.
9.2. Informative References
[I-D.ietf-ecrit-mapping-arch]
Schulzrinne, H., "Location-to-URL Mapping Architecture and
Framework", draft-ietf-ecrit-mapping-arch-03 (work in
progress), September 2007.
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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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