GEOPRIV WG M. Barnes, Ed.
Internet-Draft Nortel
Intended status: Standards Track
Expires: June 19, 2009
December 16, 2008
HTTP Enabled Location Delivery (HELD)
draft-ietf-geopriv-http-location-delivery-11.txt
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Abstract
A Layer 7 Location Configuration Protocol (L7 LCP) is described that
is used for retrieving location information from a server within an
access network. The protocol includes options for retrieving
location information in two forms: by value and by reference. The
protocol is an extensible application-layer protocol that is
independent of session-layer. This document describes the use of
HyperText Transfer Protocol (HTTP) and HTTP over Transport Layer
Security (HTTP/TLS) as transports for the protocol.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions & Terminology . . . . . . . . . . . . . . . . . . 4
3. Overview and Scope . . . . . . . . . . . . . . . . . . . . . . 5
4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Device Identifiers, NAT and VPNs . . . . . . . . . . . . . 7
4.1.1. Devices and VPNs . . . . . . . . . . . . . . . . . . . 7
4.1.2. LIS Handling of NATs and VPNs . . . . . . . . . . . . 8
4.2. Location by Value . . . . . . . . . . . . . . . . . . . . 8
4.3. Location by Reference . . . . . . . . . . . . . . . . . . 9
5. Protocol Description . . . . . . . . . . . . . . . . . . . . . 9
5.1. Delivery Protocol . . . . . . . . . . . . . . . . . . . . 10
5.2. Location Request . . . . . . . . . . . . . . . . . . . . . 10
5.3. Location Response . . . . . . . . . . . . . . . . . . . . 10
5.4. Indicating Errors . . . . . . . . . . . . . . . . . . . . 11
6. Protocol Parameters . . . . . . . . . . . . . . . . . . . . . 11
6.1. "responseTime" Parameter . . . . . . . . . . . . . . . . . 12
6.2. "locationType" Parameter . . . . . . . . . . . . . . . . . 12
6.2.1. "exact" Attribute . . . . . . . . . . . . . . . . . . 14
6.3. "code" Parameter . . . . . . . . . . . . . . . . . . . . . 14
6.4. "message" Parameter . . . . . . . . . . . . . . . . . . . 15
6.5. "locationUriSet" Parameter . . . . . . . . . . . . . . . . 15
6.5.1. "locationURI" Parameter . . . . . . . . . . . . . . . 15
6.5.2. "expires" Parameter . . . . . . . . . . . . . . . . . 16
6.6. "Presence" Parameter (PIDF-LO) . . . . . . . . . . . . . . 16
7. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8. HTTP/HTTPS Binding . . . . . . . . . . . . . . . . . . . . . . 20
9. Security Considerations . . . . . . . . . . . . . . . . . . . 21
9.1. Assuring that the proper LIS has been contacted . . . . . 22
9.2. Protecting responses from modification . . . . . . . . . . 22
9.3. Privacy and Confidentiality . . . . . . . . . . . . . . . 22
10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
10.1. HTTPS Example Messages . . . . . . . . . . . . . . . . . . 24
10.2. Simple Location Request Example . . . . . . . . . . . . . 26
10.3. Location Request Example for Multiple Location Types . . . 27
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
11.1. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:held . . . . . . . . . . . 28
11.2. XML Schema Registration . . . . . . . . . . . . . . . . . 29
11.3. MIME Media Type Registration for 'application/held+xml' . 29
11.4. Error code Registry . . . . . . . . . . . . . . . . . . . 30
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 31
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 31
14. Changes since last Version . . . . . . . . . . . . . . . . . . 32
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 38
15.1. Normative References . . . . . . . . . . . . . . . . . . . 38
15.2. Informative References . . . . . . . . . . . . . . . . . . 38
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Appendix A. HELD Compliance to IETF LCP requirements . . . . . . 40
A.1. L7-1: Identifier Choice . . . . . . . . . . . . . . . . . 40
A.2. L7-2: Mobility Support . . . . . . . . . . . . . . . . . . 40
A.3. L7-3: ASP and Access Network Provider Relationship . . . . 41
A.4. L7-4: Layer 2 and Layer 3 Provider Relationship . . . . . 41
A.5. L7-5: Legacy Device Considerations . . . . . . . . . . . . 41
A.6. L7-6: VPN Awareness . . . . . . . . . . . . . . . . . . . 42
A.7. L7-7: Network Access Authentication . . . . . . . . . . . 42
A.8. L7-8: Network Topology Unawareness . . . . . . . . . . . . 42
A.9. L7-9: Discovery Mechanism . . . . . . . . . . . . . . . . 43
A.10. L7-10: PIDF-LO Creation . . . . . . . . . . . . . . . . . 43
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 43
Intellectual Property and Copyright Statements . . . . . . . . . . 45
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1. Introduction
The location of a Device is information that is useful for a number
of applications. The L7 Location Configuration Protocol (LCP)
problem statement and requirements document
[I-D.ietf-geopriv-l7-lcp-ps] provides some scenarios in which a
Device might rely on its access network to provide location
information. The Location Information Server (LIS) service applies
to access networks employing both wired technology (e.g. DSL, Cable)
and wireless technology (e.g. WiMAX) with varying degrees of Device
mobility. This document describes a protocol that can be used to
acquire Location Information (LI) from a LIS within an access
network.
This specification identifies two types of location information that
may be retrieved from the LIS. Location may be retrieved from the
LIS by value, that is, the Device may acquire a literal location
object describing the location of the Device. The Device may also
request that the LIS provide a location reference in the form of a
location URI or set of location URIs, allowing the Device to
distribute its LI by reference. Both of these methods can be
provided concurrently from the same LIS to accommodate application
requirements for different types of location information.
This specification defines an extensible XML-based protocol that
enables the retrieval of LI from a LIS by a Device. This protocol
can be bound to any session-layer protocol, particularly those
capable of MIME transport. This document describes the use of
HyperText Transfer Protocol (HTTP) and HTTP over Transport Layer
Security (HTTP/TLS) as transports for the protocol.
2. Conventions & 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 [RFC2119].
This document uses the terms (and their acronym forms) Access
Provider (AP), Location Information (LI), Location Object (LO),
Device, Target, Location Generator (LG), Location Recipient (LR),
Rule Maker (RM) and Rule Holder (RH) as defined in RFC 3693, GEOPRIV
Requirements [RFC3693] . The terms Location Information Server
(LIS), Access Network, Access Provider (AP) and Access Network
Provider are used in the same context as defined in the L7 LCP
Problem statement and Requirements document
[I-D.ietf-geopriv-l7-lcp-ps]. The usage of the terms, Civic
Location/Address and Geodetic Location follows the usage in many of
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the referenced documents.
In describing the protocol, the terms "attribute" and "element" are
used according to their context in XML. The term "parameter" is used
in a more general protocol context and can refer to either an XML
"attribute" or "element".
3. Overview and Scope
This document describes an interface between a Device and a Location
Information Server (LIS). This document assumes that the LIS is
present within the same administrative domain as the Device (e.g.,
the access network). An Access Provider (AP) operates the LIS so
that Devices (and Targets) can retrieve their LI. The LIS exists
because not all Devices are capable of determining LI, and because,
even if a device is able to determine its own LI, it may be more
efficient with assistance. This document does not specify how LI is
determined.
This document is based on the attribution of the LI to a Device and
not specifically a person (end user) or Target, based on the premise
that location determination technologies are generally designed to
locate a device and not a person. It is expected that, for most
applications, LI for the device can be used as an adequate substitute
for the end user's LI. Since revealing the location of the device
almost invariably reveals some information about the location of the
user of the device, the same level of privacy protection demanded by
a user is required for the device. This approach may require either
some additional assurances about the link between device and target,
or an acceptance of the limitation that unless the device requires
active user authentication, there is no guarantee that any particular
individual is using the device at that instant.
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The following diagram shows the logical configuration of some of the
functional elements identified in [RFC3693] and the LIS defined in
[I-D.ietf-geopriv-l7-lcp-ps] and where this protocol applies, with
the Rule Maker and Target represented by the role of the Device.
Note that only the interfaces relevant to the Device are identified
in the diagram.
+---------------------------------------------+
| Access Network Provider |
| |
| +--------------------------------------+ |
| | Location Information Server | |
| | | |
| | | |
| | | |
| | | |
| +------|-------------------------------+ |
+----------|----------------------------------+
|
|
HELD
|
Rule Maker - _ +-----------+ +-----------+
o - - | Device | | Location |
<U\ | | - - - - | Recipient |
/ \ _ - - | | APP | |
Target - - +-----------+ +-----------+
Figure 1: Significant Roles
The interface between the Location Recipient (LR) and the Device
and/or LIS is application specific, as indicated by the APP
annotation in the diagram and it is outside the scope of the
document. An example of an APP interface between a device and LR can
be found in the SIP Location Conveyance document
[I-D.ietf-sip-location-conveyance].
4. Protocol Overview
A device uses the HELD protocol to retrieve its location either
directly in the form of a PIDF-LO document (by value) and indirectly
as a Location URI (by reference). The security necessary to ensure
the accuracy, privacy and confidentiality of the device's location is
described in the Security Considerations (Section 9).
As described in the L7 LCP problem statement and requirements
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[I-D.ietf-geopriv-l7-lcp-ps], the Device MUST first discover the URI
for the LIS for sending the HELD protocol requests. The URI for the
LIS SHOULD be obtained from an authorized and authenticated entity.
The details for ensuring that an appropriate LIS is contacted are
provided in Section 9 and in particular Section 9.1. The LIS
discovery protocol details are out of scope of this document and are
specified in [I-D.ietf-geopriv-lis-discovery]. The type of URI
provided by LIS discovery is RECOMMENDED not be a general HTTP URI.
The LIS requires an identifier for the Device in order to determine
the appropriate location to include in the location response message.
In this document, the IP address of the Device, as reflected by the
source IP address in the location request message, is used as the
identifier. Other identifiers are possible, but are beyond the scope
of this document.
4.1. Device Identifiers, NAT and VPNs
Use of the HELD protocol is subject to the viability of the
identifier used by the LIS to determine location. This document
describes the use of the source IP address sent from the Device as
the identifier used by the LIS. When Network Address Translation
(NAT), a Virtual Private Network (VPN) or other forms of address
modification occur between the Device and the LIS the location
returned could be inaccurate.
Not all cases of NATs introduce inaccuracies in the returned
location. For example, a NAT used in a residential Local Area
Network (LAN) is typically not a problem. The external IP address
used on the Wide Area Network (WAN) side of the NAT is an acceptable
identifier for all of the devices in the residence, on the LAN side
of the NAT, since the covered geographical area is small.
On the other hand, if there is a VPN between the Device and the LIS,
for example for a teleworker, then the IP address seen by a LIS
inside the enterprise network might not be the right address to
identify the location of the Device. Section 4.1.2 provides
recommendations to address this issue.
4.1.1. Devices and VPNs
To minimize the impact of connections or tunnels setup for security
purposes or to traverse middleboxes, Devices that connect to servers
such as VPN servers, SOCKS servers and HTTP proxy servers should
perform their HELD query to the LIS prior to establishing a
connection to other servers. It is RECOMMENDED that discovery
[I-D.ietf-geopriv-lis-discovery] and an initial query are performed
before establishing any connections to other servers. If a Device
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performs the HELD query after establishing a connection to another
server, the Device may receive inaccurate location information.
Devices that establish VPN connections for use by other devices
inside a LAN or other closed network could serve as a LIS, that
implements the HELD protocol, for those other Devices. Devices
within the closed network are not necessarily able to detect the
presence of the VPN. In this case, a VPN device should provide the
address of the LIS server it provides, in response to discovery
queries, rather than passing such queries through the VPN tunnel.
Otherwise, the other devices would be totally unaware that they could
receive inaccurate location information.
It could also be useful for a VPN device to serve as a LIS for other
location configuration options such as Dynamic Host Configuration
Protocol (DHCP)[RFC3825] or Link Layer Discovery Protocol - Media
Endpoint Discovery (LLDP-MED) [LLDP-MED]. For this case, the VPN
device that serves as a LIS may first acquire its own location using
HELD.
4.1.2. LIS Handling of NATs and VPNs
In the cases where the Device connects to the LIS through a VPN or a
NAT that serves a large geographic area or multiple geographic
locations (for example, a NAT used by an enterprise to connect their
private network to the Internet), the LIS might not be able to return
an accurate LI. If the LIS cannot determine LI for the device, it
should provide an error response to the requesting device. The LIS
needs to be configured to recognize identifiers that represent these
conditions.
LIS operators have a large role in ensuring the best possible
environment for location determination. The LIS operator needs to
ensure that the LIS is properly configured with identifiers that fall
within NATs and VPNs. In order to serve a Device on a remote side of
a NAT or VPN a LIS needs to have a presence on the side of the NAT or
VPN nearest the Device.
4.2. Location by Value
Where a Device requires LI directly, it can request that the LIS
create a PIDF-LO document. This approach fits well with a
configuration whereby the device directly makes use of the provided
PIDF-LO document. The details on the information that may be
included in the PIDF-LO MUST follow the subset of those rules
relating to the construction of the "location-info" element in the
PIDF-LO Usage Clarification, Considerations and Recommendations
document [I-D.ietf-geopriv-pdif-lo-profile]. Further detail is
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included in the detailed protocol section of this document Section 6
4.3. Location by Reference
Requesting location directly does not always address the requirements
of an application. A Device can request a location URI instead of
literal location. A Location URI is a URI [RFC3986] of any scheme,
which a Location Recipient (LR) can use to retrieve LI. A location
URI provided by a LIS can be assumed to be globally-addressable; that
is, anyone in possession of the URI can access the LIS.
However, possession of the URI does not in any way suggest that the
LIS indiscriminately reveals the location associated with the
location URI. The specific requirements associated with the
dereference of the location are specified in
[I-D.ietf-geopriv-lbyr-requirements]. The location dereference
protocol details are out of scope of this document and are specified
in [I-D.winterbottom-geopriv-deref-protocol].
It should also be noted that while the lybr requirements document
specifies a requirement that a client SHOULD be able to cancel
location references, the protocol specified in this document does not
provide that functionality. The mechanism to provide this support in
the protocol requires explicit management of Target state on the LIS.
It is anticipated that extensions to HELD may support that
requirement.
5. Protocol Description
As discussed in Section 4, this protocol provides for the retrieval
of the device's location in the form of a PIDF-LO document and/or
Location URI(s) from a LIS. Three messages are defined to support
the location retrieval: locationRequest, locationResponse and error.
Messages are defined as XML documents.
The Location Request (locationRequest) message is described in
Section 5.2. A Location Request message from a Device indicates
whether location in the form of a PIDF-LO document (with specific
type(s) of location) and/or Location URI(s) should be returned. The
LIS replies with a locationResponse message, including a PIDF-LO
document and/or one or more Location URIs in case of success. In the
case of an error, the LIS replies with an error message.
A MIME type "application/held+xml" is registered in Section 11.3 to
distinguish HELD messages from other XML document bodies. This
specification follows the recommendations and conventions described
in [RFC3023], including the naming convention of the type ('+xml'
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suffix) and the usage of the 'charset' parameter.
Section 6 contains a more thorough description of the protocol
parameters, valid values, and how each should be handled. Section 7
contains a more specific definition of the structure of these
messages in the form of an XML Schema [W3C.REC-xmlschema-1-20041028].
5.1. Delivery Protocol
The HELD protocol is an application-layer protocol specified by an
XML document. The HELD protocol is defined independently of any
lower layers used to transport messages from one host to another.
This means that any protocol can be used to transport this protocol
providing that it can provide a few basic features:
o The HELD protocol doesn't provide any mechanisms that enable
detection of missing messages and retransmission, thus the
protocol must have acknowledged delivery.
o The HELD protocol is a request/response protocol, thus the
protocol must be able to correlate a response with a request.
o The HELD protocol RECOMMENDS that the underlying transport provide
authentication, confidentiality, and protection against
modification per Section 9.3.
This document describes the use of a combination of HTTP [RFC2616],
TLS [RFC4346] and TCP [RFC0793] in Section 8.
5.2. Location Request
A location request message is sent from the Device to the LIS when
the Device requires its own LI. The type of LI that a Device
requests is determined by the type of LI that is included in the
"locationType" element.
The location request is made by sending a document formed of a
"locationRequest" element. The LIS uses the source IP address of the
location request message as the primary source of identity for the
requesting device or target. It is anticipated that other Device
identities may be provided through schema extensions.
The LIS MUST ignore any part of a location request message that it
does not understand, except the document element.
5.3. Location Response
A successful response to a location request MUST contain a PIDF-LO
and/or location URI(s). The response SHOULD contain location
information of the requested "locationType". The cases whereby a
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different type of location information MAY be returned are described
in Section 6.2.
5.4. Indicating Errors
If the LIS is unable to provide location information based on the
received locationRequest message, it MUST return an error message.
The LIS may return an error message in response to requests for any
"locationType".
An error indication document consists of an "error" element. The
"error" element MUST include a "code" attribute that indicates the
type of error. A set of predefined error codes are included in
Section 6.3.
Error responses MAY also include a "message" attribute that can
include additional information. This information SHOULD be for
diagnostic purposes only, and MAY be in any language. The language
of the message SHOULD be indicated with an "xml:lang" attribute.
6. Protocol Parameters
This section describes in detail the parameters that are used for
this protocol. Table 1 lists the top-level components used within
the protocol and where they are mandatory or optional for each of the
messages.
+----------------+----------------+----------------+----------------+
| Parameter | Location | Location | Error |
| | Request | Response | |
+----------------+----------------+----------------+----------------+
| responseTime | o | | |
| (Section 6.1) | | | |
| locationType | o | | |
| (Section 6.2) | | | |
| code | | | m |
| (Section 6.3) | | | |
| message | | | o |
| (Section 6.4) | | | |
| locationUriSet | | o | |
| (Section 6.5) | | | |
| Presence | | o | |
| (PIDF-LO) | | | |
| (Section 6.6) | | | |
+----------------+----------------+----------------+----------------+
Table 1: Message Parameter Usage
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6.1. "responseTime" Parameter
The "responseTime" attribute MAY be included in a location request
message. The "responseTime" attribute includes a time value
indicating to the LIS how long the Device is prepared to wait for a
response or a purpose for which the Device needs the location.
In the case of emergency services, the purpose of obtaining the LI
could be either for routing a call to the appropriate PSAP or
indicating the location to which responders should be dispatched.
The values defined for the purpose, "emergencyRouting" and
"emergencyDispatch", will likely be governed by jurisdictional
policies, and should be configurable on the LIS.
The time value in the "responseTime" attribute is expressed as a non-
negative integer in units of milliseconds. The time value is
indicative only and the LIS is under no obligation to strictly adhere
to the time limit implied; any enforcement of the time limit is left
to the requesting Device. The LIS should provide the most accurate
LI that can be determined within the specified interval for the
specific service.
The LIS may use the value of the time in the "responseTime" attribute
as input when selecting the method of location determination, where
multiple such methods exist. If the "responseTime" attribute is
absent, then the LIS should return the most precise LI it is capable
of determining, with the time interval being implementation
dependent.
6.2. "locationType" Parameter
The "locationType" element MAY be included in a location request
message. It contains a list of LI types that are requested by the
Device. The following list describes the possible values:
any: The LIS SHOULD attempt to provide LI in all forms available to
it.
geodetic: The LIS SHOULD return a geodetic location for the Target.
civic: The LIS SHOULD return a civic address for the Target.
locationURI: The LIS SHOULD return a set of location URIs for the
Target.
The LIS SHOULD return the requested location type or types. The
location types the LIS returns also depend on the setting of the
optional "exact" attribute. If the "exact" attribute is set to
"true" then the LIS MUST return either the requested location type or
provide an error response. The "exact" attribute does not apply (is
ignored) for a request for a location type of "any". Further detail
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of the "exact" attribute processing is provided in the following
Section 6.2.1.
In the case of a request for specific locationType(s) and the "exact"
attribute is false, the LIS MAY provide additional location types, or
it MAY provide alternative types if the request cannot be satisfied
for a requested location type. The "SHOULD"-strength requirements on
this parameter for specific location types are included to allow for
soft-failover. This enables a fixed client configuration that
prefers a specific location type without causing location requests to
fail when that location type is unavailable. For example, a notebook
computer could be configured to retrieve civic addresses, which is
usually available from typical home or work situations. However,
when using a wireless modem, the LIS might be unable to provide a
civic address and thus provides a geodetic address.
The LIS SHOULD return location information in a form that is suited
for routing and responding to an emergency call in its jurisdiction,
specifically by value. The LIS MAY alternatively or additionally
return a location URI. If the "locationType" element is absent, a
location URI MUST be assumed as the default. A location URI provided
by the LIS is a reference to the most current available LI and is not
a stable reference to a specific location.
It should be noted that the protocol does not support a request to
just receive one of a subset of location types. For example, in the
case where a Device has a preference for just "geodetic" or "civic",
it is necessary to make the request without an "exact" attribute,
including both location types. In this case, if neither is available
a LIS SHOULD return a locationURI if available.
The LIS SHOULD provide the locations in the response in the same
order in which they were included in the "locationType" element in
the request. Indeed, the primary advantage of including specific
location types in a request when the "exact" attribute is set to
"false" is to ensure that one receives the available locations in a
specific order. For example, a locationRequest for "civic" could
yield any of the following location types in the response:
o civic
o civic, geodetic
o civic, locationURI
o civic, geodetic, locationURI
o civic, locationURI, geodetic
o geodetic, locationURI (only if civic is not available)
o locationURI, geodetic (only if civic is not available)
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o geodetic (only if civic is not available)
o locationURI (only if civic is not available)
For the example above, if the "exact" attribute was "true", then the
only possible response is either a "civic" location or an error
message.
6.2.1. "exact" Attribute
The "exact" attribute MAY be included in a location request message
when the "locationType" element is included. When the "exact"
attribute is set to "true", it indicates to the LIS that the contents
of the "locationType" parameter MUST be strictly followed. The
default value of "false" allows the LIS the option of returning
something beyond what is specified, such as a set of location URIs
when only a civic location was requested.
A value of "true" indicates that the LIS MUST provide a location of
the requested type or types or MUST provide an error. The LIS MUST
provide the requested types only. The LIS MUST handle an exact
request that includes a "locationType" element set to "any" as if the
"exact" attribute were set to "false".
6.3. "code" Parameter
All "error" responses MUST contain a response code. All errors are
application-level errors, and MUST only be provided in successfully
processed transport-level responses. For example where HTTP/HTTPS is
used as the transport, HELD error messages MUST be accompanied by a
200 OK HTTP/HTTPS response.
The value of the response code MUST be one of the following tokens:
requestError: This code indicates that the request was badly formed
in some fashion (other than the XML content).
xmlError: This code indicates that the XML content of the request
was either badly formed or invalid.
generalLisError: This code indicates that an unspecified error
occurred at the LIS.
locationUnknown: This code indicates that the LIS could not
determine the location of the Device.
unsupportedMessage: This code indicates that an element in the XML
document for the request, was not supported or understood by the
LIS. This error code is used when a HELD request contains a
document element that is not supported by the receiver.
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timeout: This code indicates that the LIS could not satisfy the
request within the time specified in the "responseTime" parameter.
cannotProvideLiType: This code indicates that the LIS was unable to
provide LI of the type or types requested. This code is used when
the "exact" attribute on the "locationType" parameter is set to
"true".
notLocatable: This code indicates that the LIS is unable to locate
the Device, and that the Device MUST NOT make further attempts to
retrieve LI from this LIS. This error code is used to indicate
that the Device is outside the access network served by the LIS;
for instance, the VPN and NAT scenarios discussed in
Section 4.1.2.
6.4. "message" Parameter
The "error" message MAY include a "message" attribute to convey some
additional, human-readable information about the result of the
request. This message MAY be included in any language, which SHOULD
be indicated by the "xml:lang", attribute. The default language is
assumed to be English.
6.5. "locationUriSet" Parameter
The "locationUriSet" element, received in a "locationResponse"
message MAY contain any number of "locationURI" elements. It is
RECOMMENDED that the LIS allocate a Location URI for each scheme that
it supports and that each scheme is present only once. URI schemes
and their secure variants, such as http and https, MUST be regarded
as two separate schemes.
If a "locationUriSet" element is received in a "locationResponse"
message, it MUST contain an "expires" attribute, which defines the
length of time for which the set of "locationURI" elements are valid.
6.5.1. "locationURI" Parameter
The "locationURI" element includes a single Location URI. In order
for a URI of any particular scheme to be included in a response,
there MUST be a specification that defines how that URI can be used
to retrieve location information. The details of the protocol for
dereferencing must meet the location dereference protocol
requirements as specified in [I-D.ietf-geopriv-lbyr-requirements] and
are outside the scope of this base HELD specification.
Each Location URI that is allocated by the LIS is unique to the
device that is requesting it. At the time the location URI is
provided in the response, there is no binding to a specific location
type and the location URI is totally independent of the specific type
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of location it might reference. The specific location type is
determined at the time of dereference.
A "locationURI" SHOULD NOT contain any information that could be used
to identify the Device or Target. Thus, it is RECOMMENDED that the
"locationURI" element contain a public address for the LIS and an
anonymous identifier, such as a local identifier or unlinked
pseudonym. Further guidelines to ensure the privacy and
confidentiality of the information contained in the
"locationResponse" message, including the "locationURI", are included
in Section 9.3.
6.5.2. "expires" Parameter
The "expires" attribute is only included in a "locationResponse"
message when a "locationUriSet" element is included. The "expires"
attribute indicates the date/time at which the Location URIs provided
by the LIS will expire. The "expires" attribute does not define the
length of time a location received by dereferencing the location URI
will be valid. The "expires" attribute is RECOMMENDED not to exceed
24 hours and SHOULD be a minimum of 30 minutes.
Location responses that contain a "locationUriSet" element MUST
include the expiry time in the "expires" attribute. If a Device
dereferences a location URI after the expiry time, the dereference
SHOULD fail.
6.6. "Presence" Parameter (PIDF-LO)
A single "presence" parameter MAY be included in the
"locationResponse" message when specific locationTypes (e.g.,
"geodetic" or "civic") are requested or a "locationType" of "any" is
requested. The LIS MUST follow the subset of the rules relating to
the construction of the "location-info" element in the PIDF-LO Usage
Clarification, Considerations and Recommendations document
[I-D.ietf-geopriv-pdif-lo-profile] in generating the PIDF-LO for the
presence parameter.
Note that the presence parameter is not explicitly shown in the XML
schema in Section 7 for a location response message, due to XML
schema constraints, since PIDF is already defined and registered
separately. Thus, the "##other" namespace serves as a placeholder
for the presence parameter in the schema.
7. XML Schema
This section gives the XML Schema Definition
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[W3C.REC-xmlschema-1-20041028], [W3C.REC-xmlschema-2-20041028] of the
"application/held+xml" format. This is presented as a formal
definition of the "application/held+xml" format. Note that the XML
Schema definition is not intended to be used with on-the-fly
validation of the presence XML document. Whitespaces are included in
the schema to conform to the line length restrictions of the RFC
format without having a negative impact on the readability of the
document. Any conforming processor should remove leading and
trailing white spaces.
<?xml version="1.0"?>
<xs:schema
targetNamespace="urn:ietf:params:xml:ns:geopriv:held"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:held="urn:ietf:params:xml:ns:geopriv:held"
xmlns:xml="http://www.w3.org/XML/1998/namespace"
elementFormDefault="qualified"
attributeFormDefault="unqualified">
<xs:annotation>
<xs:documentation>
This document (RFC xxxx) defines HELD messages.
<!-- [[NOTE TO RFC-EDITOR: Please replace XXXX
with the RFC number for this specification.]] -->
</xs:documentation>
</xs:annotation>
<xs:import namespace="http://www.w3.org/XML/1998/namespace"
schemaLocation="http://www.w3.org/2001/xml.xsd"/>
<!-- Return Location -->
<xs:complexType name="returnLocationType">
<xs:complexContent>
<xs:restriction base="xs:anyType">
<xs:sequence>
<xs:element name="locationURI" type="xs:anyURI"
maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="expires" type="xs:dateTime"
use="required"/>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
<!-- responseTime Type -->
<xs:simpleType name="responseTimeType">
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<xs:union>
<xs:simpleType>
<xs:restriction base="xs:token">
<xs:enumeration value="emergencyRouting"/>
<xs:enumeration value="emergencyDispatch"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType>
<xs:restriction base="xs:nonNegativeInteger">
<xs:minInclusive value="0"/>
</xs:restriction>
</xs:simpleType>
</xs:union>
</xs:simpleType>
<!-- Location Type -->
<!-- Location Type -->
<xs:simpleType name="locationTypeBase">
<xs:union>
<xs:simpleType>
<xs:restriction base="xs:token">
<xs:enumeration value="any"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType>
<xs:restriction base="held:locationTypeList">
<xs:minLength value="1"/>
</xs:restriction>
</xs:simpleType>
</xs:union>
</xs:simpleType>
<xs:simpleType name="locationTypeList">
<xs:list>
<xs:simpleType>
<xs:restriction base="xs:token">
<xs:enumeration value="civic"/>
<xs:enumeration value="geodetic"/>
<xs:enumeration value="locationURI"/>
</xs:restriction>
</xs:simpleType>
</xs:list>
</xs:simpleType>
<xs:complexType name="locationTypeType">
<xs:simpleContent>
<xs:extension base="held:locationTypeBase">
<xs:attribute name="exact" type="xs:boolean"
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use="optional" default="false"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
<!-- Message Definitions -->
<xs:complexType name="baseRequestType">
<xs:complexContent>
<xs:restriction base="xs:anyType">
<xs:sequence/>
<xs:attribute name="responseTime" type="held:responseTimeType"
use="optional"/>
<xs:anyAttribute namespace="##any" processContents="lax"/>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
<xs:complexType name="errorType">
<xs:complexContent>
<xs:restriction base="xs:anyType">
<xs:sequence/>
<xs:attribute name="code" type="xs:token"
use="required"/>
<xs:attribute name="message" type="xs:string"
use="optional"/>
<xs:attribute ref="xml:lang" use="optional"/>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
<xs:element name="error" type="held:errorType"/>
<!-- Location Response -->
<xs:complexType name="locationResponseType">
<xs:complexContent>
<xs:restriction base="xs:anyType">
<xs:sequence>
<xs:element name="locationUriSet"
type="held:returnLocationType"
minOccurs="0"/>
<xs:any namespace="##other" processContents="lax"
minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
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<xs:element name="locationResponse"
type="held:locationResponseType"/>
<!-- Location Request -->
<xs:complexType name="locationRequestType">
<xs:complexContent>
<xs:extension base="held:baseRequestType">
<xs:sequence>
<xs:element name="locationType"
type="held:locationTypeType"
minOccurs="0"/>
<xs:any namespace="##other" processContents="lax"
minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:element name="locationRequest"
type="held:locationRequestType"/>
</xs:schema>
8. HTTP/HTTPS Binding
This section describes the use of HTTP [RFC2616] and HTTPS [RFC2818]
as transport mechanisms for the HELD protocol, which all conforming
implementations MUST support.
The request is carried in the body of an HTTP/HTTPS POST request.
The MIME type of both request and response bodies should be
"application/held+xml". This should be reflected in the HTTP
Content-Type and Accept header fields.
The LIS populates the HTTP/HTTPS headers so that they are consistent
with the contents of the message. In particular, the cache control
header SHOULD be set to disable the HTTP/HTTPS caching of any PIDF-LO
document or Location URIs. Otherwise, there is the risk of stale
locations and/or the unauthorized disclosure of the LI. This also
allows the LIS to control any caching with the "expires" parameter.
The HTTP/HTTPS status code MUST indicate a 2xx series response for
all HELD locationResponse and error messages.
The use of HTTP/HTTPS also includes a default behaviour, which is
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triggered by a GET request, or a POST with no request body. If
either of these queries are received, the LIS MUST attempt to provide
either a PIDF-LO document or a Location URI, as if the request was a
location request.
Implementation of HELD that implement HTTP transport MUST implement a
transport over HTTPS [RFC2818]. TLS provides message integrity and
confidentiality between Device and LIS. The LIS MUST implement the
server authentication method described in [RFC2818]. The device uses
the URI obtained during LIS discovery to authenticate the server.
The details of this authentication method are provided in section 3.1
of [RFC2818]. When TLS is used, the Device SHOULD fail a request if
server authentication fails, except in the event of an emergency.
9. Security Considerations
HELD is a location acquisition protocol whereby the a client requests
its location from a LIS. Specific requirements and security
considerations for location acquisition protocols are provided in
[I-D.ietf-geopriv-l7-lcp-ps]. An in-depth discussion of the security
considerations applicable to the use of Location URIs and by
reference provision of LI is included in
[I-D.ietf-geopriv-lbyr-requirements].
By using the HELD protocol, the client and the LIS expose themselves
to two types of risk:
Accuracy: Client receives incorrect location information
Privacy: An unauthorized entity receives location information
The provision of an accurate and privacy/confidentiality protected
location to the requestor depends on the success of five steps:
1. The client must determine the proper LIS.
2. The client must connect to the proper LIS.
3. The LIS must be able to identify the device by its identifier
(IP Address).
4. The LIS must be able to return the desired location.
5. HELD messages must be transmitted unmodified between the LIS
and the client.
Of these, only the second, third and the fifth are within the scope
of this document. The first step is based on either manual
configuration or on the LIS discovery defined in
[I-D.ietf-geopriv-lis-discovery], in which appropriate security
considerations are already discussed. The fourth step is dependent
on the specific positioning capabilities of the LIS, and is thus
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outside the scope of this document.
9.1. Assuring that the proper LIS has been contacted
This document assumes that the LIS to be contacted is identified
either by an IP address or a domain name, as is the case for a LIS
discovered as described in LIS Discovery
[I-D.ietf-geopriv-lis-discovery]. When the HELD transaction is
conducted using TLS [RFC4346], the LIS can authenticate its identity,
either as a domain name or as an IP address, to the client by
presenting a certificate containing that identifier as a
subjectAltName (i.e., as an iPAddress or dNSName, respectively). In
the case of the HTTP binding described above, this is exactly the
authentication described by TLS [RFC2818]. Any binding of HELD MUST
be capable of being transacted over TLS so that the client can
request the above authentication, and a LIS implementation for a
binding MUST include this feature. Note that in order for the
presented certificate to be valid at the client, the client must be
able to validate the certificate. In particular, the validation path
of the certificate must end in one of the client's trust anchors,
even if that trust anchor is the LIS certificate itself.
9.2. Protecting responses from modification
In order to prevent that response from being modified en route,
messages must be transmitted over an integrity-protected channel.
When the transaction is being conducted over TLS (a required feature
per Section 9.1), the channel will be integrity protected by
appropriate ciphersuites. When TLS is not used, this protection will
vary depending on the binding; in most cases, without protection from
TLS, the response will not be protected from modification en route.
9.3. Privacy and Confidentiality
Location information returned by the LIS must be protected from
access by unauthorized parties, whether those parties request the
location from the LIS or intercept it en route. As in Section 9.2,
transactions conducted over TLS with appropriate ciphersuites are
protected from access by unauthorized parties en route. Conversely,
in most cases, when not conducted over TLS, the response will be
accessible while en route from the LIS to the requestor.
Because HELD is an LCP and identifies clients and targets by IP
addresses, a requestor is authorized to access location for an IP
address only if it is the holder of that IP address. The LIS MUST
verify that the client is the target of the returned location, i.e.,
the LIS MUST NOT provide location to other entities than the target.
Note that this is a necessary, but not sufficient criterion for
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authorization. A LIS MAY deny requests according to any local
policy.
A prerequisite for meeting this requirement is that the LIS must have
some assurance of the identity of the client. Since the target of
the returned location is identified by an IP address, simply sending
the response to this IP address will provide sufficient assurance in
many cases. This is the default mechanism in HELD for assuring that
location is given only to authorized clients; LIS implementations
MUST support a mode of operation in which this is the only client
authentication.
Using IP return routability as an authenticator means that location
information is vulnerable to exposure through IP address spoofing
attacks. A temporary spoofing of IP address could mean that a device
could request a Location Object or Location URI that would result in
another Device's location. In addition, in cases where a Device
drops off the network for various reasons, the re-use of the Device's
IP address could result in another Device receiving the original
Device's location rather than its own location. These exposures are
limited by the following:
o Location URIs MUST have a limited lifetime, as reflected by the
value for the expires element in Section 6.5.2. The lifetime of
location URIs necessarily depends on the nature of the access.
o The LIS and network SHOULD be configured so that the LIS is made
aware of Device movement within the network and addressing
changes. If the LIS detects a change in the network that results
in it no longer being able to determine the location of the
Device, then all location URIs for that Device SHOULD be
invalidated.
The above measures are dependent on network configuration, which
SHOULD be considered. For instance, in a fixed internet access,
providers may be able to restrict the allocation of IP addresses to a
single physical line, ensuring that spoofing is not possible; in such
an environment, additional measures may not be necessary.
10. Examples
The following sections provide basic HTTP/HTTPS examples, a simple
location request example and a location request for multiple location
types example along with the relevant location responses. To focus
on important portions of messages, the examples in Section 10.2 and
Section 10.3 do not show HTTP/HTTPS headers or the XML prologue. In
addition, sections of XML not relevant to the example are replaced
with comments.
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10.1. HTTPS Example Messages
The examples in this section show complete HTTP/HTTPS messages that
include the HELD request or response document.
This example shows the most basic request for a LO. The POST
includes an empty "locationRequest" element.
POST /location HTTPS/1.1
Host: lis.example.com:49152
Content-Type: application/held+xml
Content-Length: 87
<?xml version="1.0"?>
<locationRequest xmlns="urn:ietf:params:xml:ns:geopriv:held"/>
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Since the above request does not include a "locationType" element,
the successful response to the request may contain any type of
location. The following shows a response containing a minimal
PIDF-LO.
HTTPS/1.1 200 OK
Server: Example LIS
Date: Tue, 10 Jan 2006 03:42:29 GMT
Expires: Tue, 10 Jan 2006 03:42:29 GMT
Cache-control: private
Content-Type: application/held+xml
Content-Length: 594
<?xml version="1.0"?>
<locationResponse xmlns="urn:ietf:params:xml:ns:geopriv:held">
<presence xmlns="urn:ietf:params:xml:ns:pidf"
entity="pres:3650n87934c@ls.example.com">
<tuple id="b650sf789nd">
<status>
<geopriv xmlns="urn:ietf:params:xml:ns:pidf:geopriv10">
<location-info>
<Point xmlns="http://www.opengis.net/gml"
srsName="urn:ogc:def:crs:EPSG::4326">
<pos>-34.407 150.88001</pos>
</Point>
</location-info>
<usage-rules>
<retention-expiry>
2006-01-11T03:42:28+00:00</retention-expiry>
</usage-rules>
<method>Wiremap</method>
</geopriv>
</status>
<timestamp>2006-01-10T03:42:28+00:00</timestamp>
</tuple>
</presence>
</locationResponse>
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The error response to the request is an error document. The
following response shows an example error response.
HTTPS/1.1 200 OK
Server: Example LIS
Expires: Tue, 10 Jan 2006 03:49:20 GMT
Cache-control: private
Content-Type: application/held+xml
Content-Length: 135
<?xml version="1.0"?>
<error xmlns="urn:ietf:params:xml:ns:geopriv:held"
code="locationUnknown"
message="Unable to determine location"/>
10.2. Simple Location Request Example
The location request shown below doesn't specify any location types
or response time.
<locationRequest xmlns="urn:ietf:params:xml:ns:geopriv:held"/>
The example response to this location request contains a list of
Location URIs.
<locationResponse xmlns="urn:ietf:params:xml:ns:geopriv:held">
<locationUriSet expires="2006-01-01T13:00:00">
<locationURI>https://ls.example.com:9768/357yc6s64ceyoiuy5ax3o
</locationURI>
<locationURI>sip:9769+357yc6s64ceyoiuy5ax3o@ls.example.com
</locationURI>
</locationUriSet>
</locationResponse>
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An error response to this location request is shown below:
<error xmlns="urn:ietf:params:xml:ns:geopriv:held"
code="locationUnknown"
message="Location not available"/>
10.3. Location Request Example for Multiple Location Types
The following Location Request message includes a request for
geodetic, civic and any Location URIs.
<locationRequest xmlns="urn:ietf:params:xml:ns:geopriv:held">
<locationType exact="true">
geodetic
civic
locationURI
</locationType>
</locationRequest>
The corresponding Location Response message includes the requested
location information, including two location URIs.
<locationResponse xmlns="urn:ietf:params:xml:ns:geopriv:held">
<locationUriSet expires="2006-01-01T13:00:00">
<locationURI>https://ls.example.com:9768/357yc6s64ceyoiuy5ax3o
</locationURI>
<locationURI>sip:9769+357yc6s64ceyoiuy5ax3o@ls.example.com:
</locationURI>
</locationUriSet>
<presence xmlns="urn:ietf:params:xml:ns:pidf:geopriv10"
entity="pres:ae3be8585902e2253ce2@10.102.23.9">
<tuple id="lisLocation">
<status>
<geopriv>
<location-info>
<gs:Circle
xmlns:gs="http://www.opengis.net/pidflo/1.0"
xmlns:gml="http://www.opengis.net/gml"
srsName="urn:ogc:def:crs:EPSG::4326">
<gml:pos>-34.407242 150.882518</gml:pos>
<gs:radius uom="urn:ogc:def:uom:EPSG::9001">30
</gs:radius>
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</gs:Circle>
<ca:civicAddress
xmlns:ca="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
xml:lang="en-au">
<ca:country>AU</ca:country>
<ca:A1>NSW</ca:A1>
<ca:A3>Wollongong</ca:A3>
<ca:A4>Gwynneville</ca:A4>
<ca:STS>Northfield Avenue</ca:STS>
<ca:LMK>University of Wollongong</ca:LMK>
<ca:FLR>2</ca:FLR>
<ca:NAM>Andrew Corporation</ca:NAM>
<ca:PC>2500</ca:PC>
<ca:BLD>39</ca:BLD>
<ca:SEAT>WS-183</ca:SEAT>
<ca:POBOX>U40</ca:POBOX>
</ca:civicAddress>
</location-info>
<usage-rules>
<retransmission-allowed>false</retransmission-allowed>
<retention-expiry>2007-05-25T12:35:02+10:00
</retention-expiry>
</usage-rules>
<method>Wiremap</method>
</geopriv>
</status>
<timestamp>2007-05-24T12:35:02+10:00</timestamp>
</tuple>
</presence>
</locationResponse>
11. IANA Considerations
This document requires several IANA registrations detailed in the
following sections.
11.1. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:held
This section registers a new XML namespace,
"urn:ietf:params:xml:ns:geopriv:held", per the guidelines in
[RFC3688].
URI: urn:ietf:params:xml:ns:geopriv:held
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Registrant Contact: IETF, GEOPRIV working group,
(geopriv@ietf.org), Mary Barnes (mary.barnes@nortel.com).
XML:
BEGIN
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<title>HELD Messages</title>
</head>
<body>
<h1>Namespace for HELD Messages</h1>
<h2>urn:ietf:params:xml:ns:geopriv:held</h2>
[NOTE TO IANA/RFC-EDITOR: Please replace XXXX
with the RFC number for this specification.]
<p>See RFCXXXX</p>
</body>
</html>
END
11.2. XML Schema Registration
This section registers an XML schema as per the guidelines in
[RFC3688].
URI: urn:ietf:params:xml:schema:geopriv:held
Registrant Contact: IETF, GEOPRIV working group, (geopriv@ietf.org),
Mary Barnes (mary.barnes@nortel.com).
Schema: The XML for this schema can be found as the entirety of
Section 7 of this document.
11.3. MIME Media Type Registration for 'application/held+xml'
This section registers the "application/held+xml" MIME type.
To: ietf-types@iana.org
Subject: Registration of MIME media type application/held+xml
MIME media type name: application
MIME subtype name: held+xml
Required parameters: (none)
Optional parameters: charset
Indicates the character encoding of enclosed XML. Default is
UTF-8.
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Encoding considerations: Uses XML, which can employ 8-bit
characters, depending on the character encoding used. See RFC
3023 [RFC3023], section 3.2.
Security considerations: This content type is designed to carry
protocol data related to the location of an entity, which could
include information that is considered private. Appropriate
precautions should be taken to limit disclosure of this
information.
Interoperability considerations: This content type provides a basis
for a protocol
Published specification: RFC XXXX [NOTE TO IANA/RFC-EDITOR: Please
replace XXXX with the RFC number for this specification.]
Applications which use this media type: Location information
providers and consumers.
Additional Information: Magic Number(s): (none)
File extension(s): .xml
Macintosh File Type Code(s): (none)
Person & email address to contact for further information: Mary
Barnes <mary.barnes@nortel.com>
Intended usage: LIMITED USE
Author/Change controller: The IETF
Other information: This media type is a specialization of
application/xml [RFC3023], and many of the considerations
described there also apply to application/held+xml.
11.4. Error code Registry
This document requests that the IANA create a new registry for the
HELD protocol including an initial registry for error codes. The
error codes are included in HELD error messages as described in
Section 6.3 and defined in the schema in the 'codeType' token in the
XML schema in (Section 7)
The following summarizes the requested registry:
Related Registry: Geopriv HELD Registries, Error codes for HELD
Defining RFC: RFC XXXX [NOTE TO IANA/RFC-EDITOR: Please replace XXXX
with the RFC number for this specification.]
Registration/Assignment Procedures: Following the policies outlined
in [RFC5226], the IANA policy for assigning new values for the
Error codes for HELD shall be Specification Required: values and
their meanings must be documented in an RFC or in some other
permanent and readily available reference, in sufficient detail
that interoperability between independent implementations is
possible.
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Registrant Contact: IETF, GEOPRIV working group, (geopriv@ietf.org),
Mary Barnes (mary.barnes@nortel.com).
This section pre-registers the following seven initial error codes as
described above in Section 6.3:
requestError: This code indicates that the request was badly formed
in some fashion.
xmlError: This code indicates that the XML content of the request
was either badly formed or invalid.
generalLisError: This code indicates that an unspecified error
occurred at the LIS.
locationUnknown: This code indicates that the LIS could not
determine the location of the Device.
unsupportedMessage: This code indicates that the request was not
supported or understood by the LIS. This error code is used when
a HELD request contains a document element that is not supported
by the receiver.
timeout: This code indicates that the LIS could not satisfy the
request within the time specified in the "responseTime" parameter.
cannotProvideLiType: This code indicates that the LIS was unable to
provide LI of the type or types requested. This code is used when
the "exact" attribute on the "locationType" parameter is set to
"true".
notLocatable: This code indicates that the LIS is unable to locate
the Device, and that the Device MUST NOT make further attempts to
retrieve LI from this LIS. This error code is used to indicate
that the Device is outside the access network served by the LIS;
for instance, the VPN and NAT scenarios discussed in
Section 4.1.2.
12. Contributors
James Winterbottom, Martin Thomson and Barbara Stark are the authors
of the original document, from which this WG document was derived.
Their contact information is included in the Author's address
section. In addition, they also contributed to the WG document,
including the XML schema.
13. Acknowledgements
The author/contributors would like to thank the participants in the
GEOPRIV WG and the following people for their constructive input and
feedback on this document (in alphabetical order): Nadine Abbott,
Eric Arolick, Richard Barnes (in particular the security section),
Peter Blatherwick, Ben Campbell, Guy Caron, Eddy Corbett, Martin
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Dawson, Lisa Dusseault, Jerome Grenier, Ted Hardie, Cullen Jennings,
Neil Justusson, Tat Lam, Marc Linsner, Patti McCalmont, Roger
Marshall, Perry Prozeniuk, Carl Reed, Julian Reschke, Eric Rescorla,
Brian Rosen, John Schnizlein, Shida Schubert, Henning Schulzrinne, Ed
Shrum, Doug Stuard, Hannes Tschofenig and Karl Heinz Wolf.
14. Changes since last Version
NOTE TO THE RFC-Editor: Please remove this section prior to
publication as an RFC.
Changes from WG 10 to 11 (Post-2nd WGLC):
1) Added additional text around the scope and applicability of the
URI returned from LIS Discovery (section 4).
2) Removed HTTP GET - will always use POST.
3) Removed sentence wrt mobile devices in section 6.2.
4) Added specific recommendation for minimum value for expires in
section 6.5.2 (30 Minutes).
5) Remove reference to RFC 3704 (for IP address spoofing) in section
9.3 (bullet 2).
6) Clarified that both HTTP and HTTPS are allowed - changed last
bullet in section 5.1 from REQUIRES to RECOMMENDS.
7) Clarification wrt "presence" parameter in section 6.6 - a "single"
presence parameter may be included.
Changes from WG 09 to 10 (2nd WGLC):
1) Updated text for Devices and VPNs (section 4.1.1) to include
servers such as HTTP and SOCKs, thus changed the text to be generic
in terms of locating LIS before connecting to one of these servers,
etc.
2) Fixed (still buggy) HTTP examples.
3) Added text explaining the whitespaces in XML schema are for
readability/document format limitations and that they should be
handled via parser/schema validation.
4) Miscellaneous editorial nits
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Changes from WG 08 to 09 (Post-IETF LC: continued resolution of sec-
dir and gen-art review comments, along with apps-area feedback):
1) Removed heldref/heldrefs URIs, including fixing examples (which
were buggy anyways).
2) Clarified text for locationURI - specifying that the deref
protocol must define or appropriately restrict and clarifying that
requirements for deref must be met and that deref details are out of
scope for this document.
3) Clarified text in security section for support of both HTTP/HTTPS.
4) Changed definition for Location Type to force the specification of
at least one location type.
Changes from WG 07 to 08 (IETF LC: sec-dir and gen-art review
comments):
1) Fix editorial nits: rearranging sections in 4.1 for readibility,
etc.
2) Added back text in Device and VPN section referencing DHCP and
LLDP-MED when a VPN device serves as a LIS.
3) Clarified the use of both HTTP and HTTPS.
4) Defined two URIs related to 3 respectively - divided IANA
registrations into sub-sections to accomodate this change. (Note:
LIS Discovery will now define that URI, thus this document defines
the one associatied with a Location reference).
5) Clarified the description of the location URI in Protocol Overview
and Protocol parameter sections. Note that these sections again
reference location dereference protocol for completeness and
clarification of issues that are out of scope for this base document.
6) Defined new error code: notLocatable.
7) Clarifications and corrections in security section.
8) Clarified text for locationType, specifically removing extra text
from "any" description and putting that in a separate paragraph.
Also, provided an example.
9) Added boundaries for "expires" parameter.
10) Clarified that the HELD protocol as defined by this document does
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not allow for canceling location references.
Changes from WG 06 to 07 (PROTO review comments):
1) Fix nits: remove unused references, move requirements to
Informational References section, fix long line in ABNF, fix ABNF
(quotes around '?'), add schemaLocation to import namespace in XML
schema.
2) Remove text in Device and VPN section referencing DHCP and LLDP-
MED when a VPN device serves as a LIS, per Issue 1 resolution at
IETF-71. (Editorial oversight in producing version 06).
Changes from WG 05 to 06 (2nd WGLC comments):
1) Updated security section based on WG feedback, including
condensing section 10.1.1 (Assuring the proper LIS has been
contacted), restructuring sections by flattening, adding an
additional step to the list that had been in the Accuracy section and
removing summary section.
2) Changed URI schema to "helds" to address concerns over referential
integrity and for consistency with mandate of TLS for HELD.
3) Editorial clarifications including fixing examples to match HELD
URI definition (e.g., adding port, adding randomness to URI examples,
etc.)
4) Updated references removing unused references and moving
requirements docs to Informational Reference section to avoid
downrefs.
Changes from WG 04 to 05 (WGLC comments):
1) Totally replaced the security section with the details provided by
Richard Barnes so that we don't need a reference to the location
security document.
2) Fixed error codes in schema to allow extensibility. Change the
IANA registration to be "specification required".
3) Cleaned up the HELD: URI description, per comments from Martin and
James and partially addressing HELD-04 Issue 1. Put the definition
in a separate section and clarified the applicability (to also
include being a results of the discovery process) and fixed examples.
4) Updated the LocationURI section to be more accurate, address
HELD-04 Issue 3, and include the reference to the new HELD:URI
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section. Also, fixed an error in the doc in that the top level parm
in the locationResponse is actually locationUriSet, which contains
any number of locationURI elements and the "expires" parameter. So,
Table 1 was also updated and a new section for the LocationURISet was
added that includes the subsections for the "locationURI" and
"expires". And, then clarified that "expires" applies to
"locationURISet" and not per "locationURI".
5) Editorial nits: pointed out offline by Richard (e.g., by-value ->
by value, by-reference -> by reference, etc.) and onlist by James and
Martin. Please refer to the diff for a complete view of editorial
changes.
6) Added text in HTTP binding section to disable HTTP caching
(HELD-04 Issue 5 on the list).
Changes from WG 03 to 04:
1) Terminology: clarified in terminology section that "attribute" and
"element" are used in the strict XML sense and "parameter" is used as
a general protocol term Replaced term "HTTP delivery" with "HTTP
transport". Still have two terms "HTTP transport" and "HTTP
binding", but those are consistent with general uses of HTTP.
2) Editorial changes and clarifications: per Roger Marshall's and
Eric Arolick's comments and subsequent WG mailing list discussion.
3) Changed normative language for describing expected and recommended
LIS behaviors to be non-normative recommendations in cases where the
protocol parameters were not the target of the discussion (e.g., we
can't prescribe to the LIS how it determines location or what it
defines to be an "accurate" location).
4) Clarified responseTime attribute (section 6.1). Changed type from
"decimal" to "nonNegativeInteger" in XML schema (section 7)
5) Updated Table 1 in section 6 to only include top-level parameters
and fixed some errors in that table (i.e., code for locationResponse)
and adding PIDF-LO to the table. Added a detailed section describing
PIDF-LO (section 6.6), moving some of the normative text in the
Protocol Overview to this section.
6) Added schema and description for locationURI to section 6.5.
Added IANA registration for HELD: URI schema.
7) Added IANA registry for error codes.
Changes from WG 02 to 03:
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1) Added text to address concern over use of IP address as device
identifier, per long email thread - changes to section 3 (overview)
and section 4 (protocol overview).
2) Removed WSDL (section 8 updated, section 8.1 and 10.4 removed)
3) Added extensibility to baseRequestType in the schema (an oversight
from previous edits), along with fixing some other nits in schema
(section 7)
4) Moved discussion of Location URI from section 5.3 (Location
Response) to where it rightly belonged in Section 6.5 (Location URI
Parameter).
5) Clarified text for "expires" parameter (6.5.1) - it's an optional
parm, but required for LocationURIs
6) Clarified responseTime parameter: when missing, then the LCS
provides most precise LI, with the time required being implementation
specific.
7) Clarified that the MUST use in section 8 (HTTP binding) is a MUST
implement.
8) Updated references (removed unused/added new).
Changes from WG 01 to 02:
1) Updated Terminology to be consistent with WG agreements and other
documents (e.g., LCS -> LIS and removed duplicate terms). In the
end, there are no new terms defined in this document.
2) Modified definition of responseTime to reflect WG consensus.
3) Removed jurisdictionalCivic and postalCivic locationTypes (leaving
just "civic").
4) Clarified text that locationType is optional. Fixed table 1 and
text in section 5.2 (locationRequest description). Text in section
6.2 (description of locationType element) already defined the default
to be "any".
5) Simplified error responses. Separated the definition of error
response type from the locationResponse type thus no need for
defining an error code of "success". This simplifies the schema and
processing.
6) Updated schema/examples for the above.
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7) Updated Appendix A based on updates to requirements document,
specifically changes to A.1, A.3 and adding A.10.
8) Miscellaneous editorial clarifications.
Changes from WG 00 to 01:
1) heldResponse renamed to locationResponse.
2) Changed namespace references for the PIDF-LO geoShape in the
schema to match the agreed GML PIDF-LO Geometry Shape Application
Schema.
3) Removed "options" element - leaving optionality/extensibility to
XML mechanisms.
4) Changed error codes to be enumerations and not redefinitions of
HTTP response codes.
5) Updated schema/examples for the above and removed some remnants of
the context element.
6) Clarified the definition of "Location Information (LI)" to include
a reference to the location (to match the XML schema and provide
consistency of usage throughout the document). Added an additional
statement in section 7.2 (locationType) to clarify that LCS MAY also
return a Location URI.
7) Modifed the definition of "Location Configuration Server (LCS)" to
be consistent with the current definiton in the requirements
document.
8) Updated Location Response (section 6.3) to remove reference to
context and discuss the used of a local identifier or unlinked
pseudonym in providing privacy/security.
9) Clarified that the source IP address in the request is used as the
identifier for the target/device for the HELD protocol as defined in
this document.
10) Miscellaneous editorial clarifications.
15. References
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15.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006.
[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.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
[I-D.ietf-geopriv-pdif-lo-profile]
Winterbottom, J., Thomson, M., and H. Tschofenig, "GEOPRIV
PIDF-LO Usage Clarification, Considerations and
Recommendations", draft-ietf-geopriv-pdif-lo-profile-14
(work in progress), November 2008.
[W3C.REC-xmlschema-1-20041028]
Thompson, H., Mendelsohn, N., Beech, D., and M. Maloney,
"XML Schema Part 1: Structures Second Edition", World Wide
Web Consortium Recommendation REC-xmlschema-1-20041028,
October 2004,
<http://www.w3.org/TR/2004/REC-xmlschema-1-20041028>.
[W3C.REC-xmlschema-2-20041028]
Biron, P. and A. Malhotra, "XML Schema Part 2: Datatypes
Second Edition", World Wide Web Consortium
Recommendation REC-xmlschema-2-20041028, October 2004,
<http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>.
[I-D.ietf-geopriv-lis-discovery]
Thomson, M. and J. Winterbottom, "Discovering the Local
Location Information Server (LIS)",
draft-ietf-geopriv-lis-discovery-04 (work in progress),
October 2008.
15.2. Informative References
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media
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Types", RFC 3023, January 2001.
[RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and
J. Polk, "Geopriv Requirements", RFC 3693, February 2004.
[RFC3825] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host
Configuration Protocol Option for Coordinate-based
Location Configuration Information", RFC 3825, July 2004.
[LLDP-MED]
TIA, "ANSI/TIA-1057 Link Layer Discovery Protocol - Media
Endpoint Discovery".
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
Registration Procedures for New URI Schemes", BCP 115,
RFC 4395, February 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[I-D.ietf-geopriv-l7-lcp-ps]
Tschofenig, H. and H. Schulzrinne, "GEOPRIV Layer 7
Location Configuration Protocol; Problem Statement and
Requirements", draft-ietf-geopriv-l7-lcp-ps-08 (work in
progress), June 2008.
[I-D.ietf-geopriv-lbyr-requirements]
Marshall, R., "Requirements for a Location-by-Reference
Mechanism", draft-ietf-geopriv-lbyr-requirements-05 (work
in progress), November 2008.
[I-D.ietf-sip-location-conveyance]
Polk, J. and B. Rosen, "Location Conveyance for the
Session Initiation Protocol",
draft-ietf-sip-location-conveyance-12 (work in progress),
November 2008.
[I-D.winterbottom-geopriv-deref-protocol]
Winterbottom, J., Tschofenig, H., Schulzrinne, H.,
Thomson, M., and M. Dawson, "An HTTPS Location
Dereferencing Protocol Using HELD",
draft-winterbottom-geopriv-deref-protocol-02 (work in
progress), July 2008.
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Appendix A. HELD Compliance to IETF LCP requirements
This appendix describes HELD's compliance to the requirements
specified in the [I-D.ietf-geopriv-l7-lcp-ps].
A.1. L7-1: Identifier Choice
"The L7 LCP MUST be able to carry different identifiers or MUST
define an identifier that is mandatory to implement. Regarding the
latter aspect, such an identifier is only appropriate if it is from
the same realm as the one for which the location information service
maintains identifier to location mapping."
COMPLY
HELD uses the IP address of the location request message as the
primary source of identity for the requesting device or target. This
identity can be used with other contextual network information to
provide a physical location for the Target for many network
deployments. There may be network deployments where an IP address
alone is insufficient to identify a Target in a network. However,
any necessary identity extensions for these networks is beyond the
scope of this document.
A.2. L7-2: Mobility Support
"The GEOPRIV Layer 7 Location Configuration Protocol MUST support a
broad range of mobility from devices that can only move between
reboots, to devices that can change attachment points with the impact
that their IP address is changed, to devices that do not change their
IP address while roaming, to devices that continuously move by being
attached to the same network attachment point."
COMPLY
Mobility support is inherently a characteristic of the access network
technology and HELD is designed to be access network agnostic.
Consequently HELD complies with this requirement. In addition HELD
provides specific support for mobile environments by providing an
optional responseTime attribute in location request messages.
Wireless networks often have several different mechanisms at their
disposal for position determination (e.g. Assisted GPS versus
location based on serving base station identity), each providing
different degrees of accuracy and taking different amounts of time to
yield a result. The responseTime parameter provides the LIS with a
criterion which it can use to select a location determination
technique.
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A.3. L7-3: ASP and Access Network Provider Relationship
"The design of the L7 LCP MUST NOT assume a business or trust
relationship between the Application Service Provider (ASP) and the
Access Network Provider. Requirements for resolving a reference to
location information are not discussed in this document."
COMPLY
HELD describes a location acquisition protocol between a Device and a
LIS. In the context of HELD, the LIS is within the Access Network.
Thus, HELD is independent of the business or trust relationship
between the Application Service Provider (ASP) and the Access Network
Provider. Location acquisition using HELD is subject to the
restrictions described in Section 9.
A.4. L7-4: Layer 2 and Layer 3 Provider Relationship
"The design of the GEOPRIV Layer 7 Location Configuration Protocol
MUST assume that there is a trust and business relationship between
the L2 and the L3 provider. The L3 provider operates the LIS and
needs to obtain location information from the L2 provider since this
one is closest to the end host. If the L2 and L3 provider for the
same host are different entities, they cooperate for the purposes
needed to determine end system locations."
COMPLY
HELD was specifically designed with this model in mind and readily
allows itself to chaining requests between operators without a change
in protocol being required. HELD is a webservices protocol which can
be bound to transports other than HTTP, such as BEEP. Using a
protocol such as BEEP offers the option of high request throughput
over a dedicated connection between an L3 provider and an L2 provider
without incurring the serial restriction imposed by HTTP. This is
less easy to do with protocols that do not decouple themselves from
the transport.
A.5. L7-5: Legacy Device Considerations
"The design of the GEOPRIV Layer 7 Location Configuration Protocol
MUST consider legacy residential NAT devices and NTEs in an DSL
environment that cannot be upgraded to support additional protocols,
for example to pass additional information through DHCP."
COMPLY
HELD is an application protocol and operates on top of IP. A HELD
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request from a host behind a residential NAT will traverse the NAT
acquiring the external address of the home router. The location
provided to the host therefore will be the address of the home router
in this circumstance. No changes are required to the home router in
order to support this function, HELD was designed specifically to
address this deployment scenario.
A.6. L7-6: VPN Awareness
"The design of the GEOPRIV Layer 7 Location Configuration Protocol
MUST assume that at least one end of a VPN is aware of the VPN
functionality. In an enterprise scenario, the enterprise side will
provide the LIS used by the client and can thereby detect whether the
LIS request was initiated through a VPN tunnel."
COMPLY
HELD does not preclude a LIS on the far end of a VPN tunnel being
aware that the client request is occurring over that tunnel. It also
does not preclude a client device from accessing a LIS serving the
local physical network and subsequently using the location
information with an application that is accessed over a VPN tunnel.
A.7. L7-7: Network Access Authentication
"The design of the GEOPRIV Layer 7 Location Configuration Protocol
MUST NOT assume prior network access authentication."
COMPLY
HELD makes no assumptions about prior network access authentication.
HELD strongly recommends the use of TLS with server-side certificates
for communication between the end-point and the LIS. There is no
requirement for the end-point to authenticate with the LIS.
A.8. L7-8: Network Topology Unawareness
"The design of the GEOPRIV Layer 7 Location Configuration Protocol
MUST NOT assume end systems being aware of the access network
topology. End systems are, however, able to determine their public
IP address(es) via mechanisms such as STUN or NSIS NATFW NSLP."
COMPLY
HELD makes no assumption about the network topology. HELD doesn't
require that the device know its external IP address, except where
that is required for discovery of the LIS.
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A.9. L7-9: Discovery Mechanism
"The L7 LCP MUST define a single mandatory to implement discovery
mechanism."
COMPLY
HELD uses the discovery mechanism in
[I-D.ietf-geopriv-lis-discovery].
A.10. L7-10: PIDF-LO Creation
"When a LIS creates a PIDF-LO per RFC 4119 then it MUST put the
<geopriv> element into the <device> element of the presence document
(see RFC 4479). This ensures that the resulting PIDF-LO document,
which is subsequently distributed to other entities, conforms to the
rules outlined in ". [I-D.ietf-geopriv-pdif-lo-profile]
COMPLY
HELD protocol overview (Section 4 ) describes the requirements on the
LIS in creating the PIDF-LO and prescribes that the PIDF-LO generated
by the LIS MUST conform to [I-D.ietf-geopriv-pdif-lo-profile].
Authors' Addresses
Mary Barnes (editor)
Nortel
2201 Lakeside Blvd
Richardson, TX
Email: mary.barnes@nortel.com
James Winterbottom
Andrew
PO Box U40
Wollongong University Campus, NSW 2500
AU
Phone: +61 2 4221 2938
Email: james.winterbottom@andrew.com
URI: http://www.andrew.com/
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Martin Thomson
Andrew
PO Box U40
Wollongong University Campus, NSW 2500
AU
Phone: +61 2 4221 2915
Email: martin.thomson@andrew.com
URI: http://www.andrew.com/
Barbara Stark
BellSouth
Room 7A43
725 W Peachtree St.
Atlanta, GA 30308
US
Email: barbara.stark@att.com
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Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
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This document and the information contained herein are provided on an
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