Geopriv H. Tschofenig
Internet-Draft Siemens
Expires: January 17, 2006 F. Adrangi
Intel
M. Jones
A. Lior
Bridgewater
July 16, 2005
Carrying Location Objects in RADIUS
draft-ietf-geopriv-radius-lo-04.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document describes RADIUS attributes for conveying access
network ownership and location information based on a civic and
geospatial location format.
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The distribution of location information is a privacy sensitive task.
Dealing with mechanisms to preserve the user's privacy is important
and addressed in this document.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Delivery Methods for Location Information . . . . . . . . . . 7
3.1 Authentication/Authorization Phase Delivery . . . . . . . 7
3.2 Mid-session Authorization . . . . . . . . . . . . . . . . 8
4. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1 Scenario 1 - Use of Location Information in AAA . . . . . 10
4.2 Scenario 2 - Use of Location Information for Other
Services . . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.1 Operator-Namespace Attribute . . . . . . . . . . . . . . . 12
5.2 Operator-Name Attribute . . . . . . . . . . . . . . . . . 12
5.3 Location-Information Attribute . . . . . . . . . . . . . . 13
5.3.1 Civic Location Information . . . . . . . . . . . . . . 13
5.3.2 Geospatial Location Information . . . . . . . . . . . 15
6. Basic- and Extended-Policy-Rule Attributes . . . . . . . . . . 16
7. Location-Type Attribute . . . . . . . . . . . . . . . . . . . 17
8. Capability Attribute . . . . . . . . . . . . . . . . . . . . . 18
9. Diameter RADIUS Interoperability . . . . . . . . . . . . . . . 20
10. Attributes . . . . . . . . . . . . . . . . . . . . . . . . . 21
10.1 Operator-Namespace Attribute . . . . . . . . . . . . . . . 21
10.2 Operator-Name Attribute . . . . . . . . . . . . . . . . . 21
10.3 Location-Information Attribute . . . . . . . . . . . . . . 22
10.4 Basic Policy Rules Attribute . . . . . . . . . . . . . . . 26
10.5 Extended Policy Rules Attribute . . . . . . . . . . . . . 27
10.6 Location-Type Attribute . . . . . . . . . . . . . . . . . 28
10.7 Capability Attribute . . . . . . . . . . . . . . . . . . . 28
11. Table of Attributes . . . . . . . . . . . . . . . . . . . . 31
12. Matching with Geopriv Requirements . . . . . . . . . . . . . 32
12.1 Distribution of Location Information at the User's
Home Network . . . . . . . . . . . . . . . . . . . . . . . 32
12.2 Distribution of Location Information at the Visited
Network . . . . . . . . . . . . . . . . . . . . . . . . . 33
12.3 Requirements matching . . . . . . . . . . . . . . . . . . 34
13. Example . . . . . . . . . . . . . . . . . . . . . . . . . . 40
14. Privacy Considerations . . . . . . . . . . . . . . . . . . . 42
14.1 Entity in the visited network . . . . . . . . . . . . . . 42
14.2 Entity in the home network . . . . . . . . . . . . . . . . 43
15. Security Considerations . . . . . . . . . . . . . . . . . . 46
16. IANA Considerations . . . . . . . . . . . . . . . . . . . . 49
16.1 New Registry: Operator Type . . . . . . . . . . . . . . . 49
16.2 New Registry: Capabilities . . . . . . . . . . . . . . . . 49
17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 51
18. References . . . . . . . . . . . . . . . . . . . . . . . . . 52
18.1 Normative References . . . . . . . . . . . . . . . . . . . 52
18.2 Informative References . . . . . . . . . . . . . . . . . . 52
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 55
Intellectual Property and Copyright Statements . . . . . . . . 56
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1. Introduction
Wireless LAN (WLAN) access networks are being deployed in public
places such as airports, hotels, shopping malls, and coffee shops by
a diverse set of operators such as cellular network operators (GSM
and CDMA), Wireless Internet Service Providers (WISPs), and fixed
broadband operators.
When a user executes the network access authentication procedure to
such a network, information about the location and ownership of this
network needs to be conveyed to the user's home network to which the
user has a contractual relationship. The main intent of this
document is to enable location aware billing (e.g., determine the
appropriate tariff and taxation in dependence of the location of the
access network/user), location aware subscriber authentication and
authorization for roaming environments and to enable other location
aware services.
This document describes AAA attributes that are used by a AAA client
or a local AAA server in an access network for conveying location-
related information to the user's home AAA server. This document
defines attributes for RADIUS [1].
Although the proposed attributes in this draft are intended for
wireless LAN deployments, they can also be used in other types of
wireless and wired networks whenever location information is
required.
Location information needs to be protected against unauthorized
access and distribution to preserve the user's privacy with regard to
location information. [11] defines requirements for a protocol-
independent model for the access to geographic location information.
The model includes a Location Generator (LG) that creates location
information, a Location Server (LS) that authorizes access to
location information, a Location Recipient (LR) that requests and
receives information, and a Rule Maker (RM) that provides
authorization policies to the LS which enforces access control
policies on requests to location information.
Althougth this document focuses on the use cases of location based
authorization, charging, billing and taxation for network access
RADIUS might also be used for location-based authorization for
application layer services as well. The extensions defined in this
document are therefore not only applicable to a network access
scenario. A further description of these scenarios is outside the
scope of this document.
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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 [2].
RADIUS specific terminology is borrowed from [1] and [3].
Terminology related to privacy issues, location information and
authorization policy rules is taken from [11].
Based on today's protocols we assume that the location information is
provided by the access network where the end host is attached. As
part of the network attachment, which includes the execution of an
authentication and authorization protocol exchange, authentication is
accomplished. The authenticated identity can refer to a user, a
device or something else. Although there might often be a user
associated with the authentication process (either directly or
indirectly; indirectly when a binding between a device and a user
exists) there is no assurance that a particular real-world entity
(such as a person) triggered this process. Since location based
authorization is executed based on the network access authentication
of a particular "user" it might be reasonable to talk about user's
privacy within this document even though scenarios exist where this
might not apply (and device or network privacy might be the correct
term). Furthermore, the authors believe that there is a relationship
between the location of the network and the location of the entity
that triggered the network access authentication. Knowing the
location of a network (where the user or end host is attached to)
might in many networks also reveal the location of the user or end
host. In some networks it is even possible to provide a accurate
location of the user or end host. A similar assumption is also made
with regard to the location information obtained via DHCP (see for
example [4]). This information might be used by applications in
other protocols (such as SIP [12] with extensions [13]) to indicate
the location of a particular user even though the location "only"
refers to the location of the network or equipment within the
network. The assumption here is also that the location of the
network has some relationship to the location of the end host (and
subsequently to a user). This assumption might not hold in all
scenarios. Nevertheless, it seems to be reasonable.
Please note that the authors use the terms end host and user
interchangably with respect to the used identities as part of the
network access authentication. The term 'user' is used whenever the
privacy of the user could potentially be compromised.
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3. Delivery Methods for Location Information
Location Objects, which consist of location information and privacy
rules, are transported over the RADIUS protocol from visited access
network to the home AAA server. To embed a Location Object into
RADIUS a number of AVPs are used, such as Location-Information AVP,
Basic-Policy-Rules AVP, Extended-Policy-Rules AVP, Location-Type AVP,
Operator-Namespace AVP and Operator-Name AVP. These AVPs can be
delivered to the RADIUS server during the authentication/
authorization phase described in Section 3.1, or in the mid-session
using the dynamic authorization protocol framework described in
Section 3.2. This section describes messages flow for both delivery
methods.
3.1 Authentication/Authorization Phase Delivery
Figure 1 shows an example message flow for delivering location
information during the network access authentication/authorization
procedure. Upon a network authentication request from an access
network client, the NAS submits a RADIUS Access-Request message which
contains location information attributes among other required
attributes. The attributes (including location information) are
added based on some criteria, such as local policy and business
relationship with subscriber's home network provider. If no location
information is attached although required by the aaa server an error
message is returned.
The authentication and/or authorization procedure is completed based
on a number of criteria, including the newly defined Location-
Information, Operator-Namespace, Operator-Name, Location-Type,
Policy-Information attributes. A RADIUS Accounting Request message
may also carry location specific attributes.
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+---------+ +---------+ +---------+
| Network | | Network | | AAA |
| Access | | Access | | Server |
| Client | | Server | | |
+---------+ +---------+ +---------+
| | |
| Authentication phase | |
| begin | |
|---------------------->| |
| | |
| | |
| | RADIUS |
| | Access-Request |
| | + Location-Information |
| | attributes |
| |----------------------------->|
| | |
: : :
: Multiple Protocol Exchanges to perform :
: Authentication, Key Exchange and Authorization :
: ...continued... :
: : :
| | RADIUS |
| | Access-Accept |
| | + Rule set Information |
| |<-----------------------------|
| Authentication | |
| Accept | |
|<----------------------| |
| | |
| | RADIUS |
| | Accounting Request |
| | + Location-Information |
| | attributes |
| |----------------------------->|
| | |
Figure 1: Message Flow: Authentication/Authorization Phase Delivery
3.2 Mid-session Authorization
The mid-session delivery method uses the Change of Authorization
(COA) message as defined in [5]. At anytime during the session the
AAA server MAY send a COA message containing session identification
attributes to the access network. The COA message may instruct the
access network to generate an Authorize-Only Access-Request (Access-
Request with Service-Type set to "Authorize-Only") in which case the
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NAS MUST include the location infromation in this Access-Request.
Figure 2 shows the approach graphically.
+---------+ +---------+
| AAA | | AAA |
| Client | | Server |
| (NAS) | | |
+---------+ +---------+
| |
| COA + Service-Type "Authorize Only" |
|<----------------------------------------------|
| |
| COA NAK + Service-Type "Authorize Only" |
| + Error-Cause "Request Initiated" |
|---------------------------------------------->|
| |
| Access-Request + Service-Type "Authorize Only"|
| + Location Information attributes |
| + Location Information policy |
|---------------------------------------------->|
| |
| Access-Accept |
|<----------------------------------------------|
| |
Figure 2: Message Flow: Mid-session Authorization
Upon receiving the Authorize-Only message from the access network,
the AAA server MUST respond with either an Access-Accept message or
an Access-Reject message.
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4. Scenarios
In the following subsections we describe two scenarios for use of
location information. The location information may refer to the
(visited) network or to the user. How the network obtains the user's
location information is out of the scope of this document. There are
two consumers of location information: the AAA server and location-
based services. The privacy implications of these scenarios are
described in Section 14.
4.1 Scenario 1 - Use of Location Information in AAA
The home network operator requires location information for
authorization and billing purposes. The operator may deny service if
location information is not available, or it may offer limited
service. The NAS delivers location information to the home AAA
server.
The user's location is transferred from the NAS to the RADIUS server.
The NAS and intermediaries (if any) are not allowed to use that
information other than to forward it to the home network.
The RADIUS server authenticates and authorizes the user requesting
access to the network. If the user's location policies are available
to the RADIUS server, the RADIUS server must deliver those policies
in an Access Accept to the RADIUS client. This information may be
needed if intermediaries or other elements want to act as Location
Servers (see Section 4.2). If intermediaries do not receive these
policies then they MUST NOT make any use of the location information
other than forwarding it to the home network.
Location Information may also be reported in accounting messages.
Accounting messages are generated when the session starts, stops and
periodically. Accounting messages may also be generated when the
user roams during handoff. This information may be needed by the
billing system to calculate the user's bill. For example, there may
be different rates applied based on the location and there may be
different tax rates applied based on the location. Unless otherwise
specified by authorization rules, location information in the
accounting stream MUST NOT be transmitted to third parties.
The location information in the accounting stream MUST only be sent
in the proxy chain to the home network (unless specified otherwise).
4.2 Scenario 2 - Use of Location Information for Other Services
Location Servers are entities that receive the user's location
information and transmit it to other entities. In this second
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scenario, Location Servers comprise also the NAS and the RADIUS
server. The RADIUS servers are in the home network, in the visited
network, or in broker networks.
Unless explicitly authorized by the user's location policy, location
information MUST NOT be transmitted to other parties outside the
proxy chain between the NAS and the Home RADIUS server.
Upon authentication and authorization, the home RADIUS server must
transmit the ruleset (if available) in an Access-Accept. The RADIUS
client, intermediate proxies are allowed to share location
information if they received ruleset indicates that it is allowed.
Note that the NAS is the source of all location information that is
disseminated by RADIUS. The NAS tags the location information with
the policy rules or a reference to the policy rules received in an
Access-Accept. All location information in the accounting stream
will also be tagged.
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5. Overview
Location information and ownership of the access network is conveyed
in the following RADIUS attributes: Operator-Namespace, Operator-
Name, Location-Information and Location-Type. Furthermore, the
Basic-Policy-Rules and the Extended-Policy-Rules attributes are
attached to the Location-Information attribute turning location
information into a Location Object as defined in [11].
5.1 Operator-Namespace Attribute
This attribute contains the description of an operator namespace
which combined with the Operator-Name attribute serves to uniquely
identify the owner of an access network. The attribute value is a
non-NULL terminated string whose Length MUST NOT exceed 253 bytes.
This document defines three values for this attribute: GSM, CDMA, and
REALM. Additional namespaces require IANA registration and MUST be
associated with an organization responsible for assigning and
managing the operator namespace.
The GSM operator namespace can be used to indicate operator names
based on GSMA TADIG codes. The TADIG Working Group within the GSM
Association is the authority responsible for issuing unique Operator-
Name values for operators of this type.
The CDMA operator namespace can be used to indicate operator names
based on the Home Network Identifier (HNI). The HNI is the
concatenation of the 3-digit Mobile Country Code (MCC) and 3-digit
Mobile Network Code (MNC). The IMSI Oversight Council (IOC) is the
authority responsible for issuing unique Operator-Name values for
operators of this type.
The REALM operator namespace can be used to indicate operator names
based on any registered domain name. Such names are required to be
unique and the rights to use a given realm name are obtained
coincident with acquiring the rights to use a particular Fully
Qualified Domain Name (FQDN).
5.2 Operator-Name Attribute
This attribute contains an operator name which combined with the
Operator-Namespace attribute serves to uniquely identifies the owner
of an access network. The attribute value is a non-NULL terminated
string whose Length MUST NOT exceed 253 bytes. The attribute value
uniquely identifies the operator name within the scope of the
operator type.
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5.3 Location-Information Attribute
This document describes two formats for conveying location
information: civic and geospatial location information.
Section 5.3.1 defines the civic location information format.
Section 5.3.2 defines the geospatial location information format.
Additionally, the following fields provide more details about the
transmitted location information.
Entity: With the help of the 'Entity' field it is possible to
differentiate whether the described Location Object refers to
either the user's client device (as estimated by the network) or
to the location of the AAA client (such as NAS).
Method: The 'Method' field describes the method for obtaining
location information. GPS or manual configuration are possible
methods for obtaining location information. The inclusion of this
field should help the user's home network to deduce further
information about the accuracy and to provide an easier
translation into a Location Object for transmission to third party
entities (e.g., using SIP). Note that the values for this field
are taken from [14].
5.3.1 Civic Location Information
Civic location is a popular way to describe the location of an
entity. Using an unstructured (as a text string) or a custom format
for civic location format would limit automatic processing
capabilities are limited.
For this document, we take the civic location format defined in [4].
The civic location format includes a number of fields, including the
country (expressed as a two-letter ISO 3166 code) and the
administrative units A1 through A6 of [4] . This designation offers
street-level precision.
For completeness we include more detailed information from [4] with
regard to the defined civic location elements:
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+----------------------+----------------------+---------------------+
| Label | Description | Example |
+----------------------+----------------------+---------------------+
| country | The country is | US |
| | identified by the | |
| | two-letter ISO 3166 | |
| | code. | |
| | | |
| A1 | national | New York |
| | subdivisions (state, | |
| | region, province, | |
| | prefecture) | |
| | | |
| A2 | county, parish, gun | King's County |
| | (JP), district (IN) | |
| | | |
| A3 | city, township, shi | New York |
| | (JP) | |
| | | |
| A4 | city division, | Manhattan |
| | borough, city | |
| | district, ward, cho | |
| | (JP) | |
| | | |
| A5 | neighborhood, block, | Morningside Heights |
| | chome (JP) | |
| | | |
| A6 | street, banchi and | Broadway |
| | gou (JP) | |
| | | |
| AC | Additional code, JIS | 13203000003 |
| | address code (JP) | |
| | | |
| PRD | Leading street | N, W |
| | direction | |
| | | |
| POD | Trailing street | SW |
| | suffix | |
| | | |
| STS | Street suffix | Avenue, Street |
| | | |
| HNO | House number, | 123 |
| | numeric part only. | |
| | | |
| HNS | House number suffix | A, 1/2 |
| | | |
| LMK | Landmark or vanity | Low Library |
| | address | |
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| LOC | Additional location | Room 543 |
| | information | |
| | | |
| FLR | Floor | 5 |
| | | |
| NAM | Name (residence, | Joe's Barbershop |
| | business or office | |
| | occupant) | |
| | | |
| PC | Postal code | 10027-0401 |
+----------------------+----------------------+---------------------+
Table 1
More description of these civic location elements can be found in
Section 3.4 of [4]. These elements can be used to express further
information about the location, language specific settings via the
'language' item and encoding information via the 'script' item.
Section 13 shows usage examples of this attribute.
All attributes are optional and can appear in any order. The values
are encoded using UTF-8 [6].
5.3.2 Geospatial Location Information
This document reuses geospatial location information from [7] which
defines latitude, longitude, and altitude, with resolution indicators
for each. The value in the Altitude field either indicates meters or
floors (via the Altitude Type field). As a coordinate reference
system Section 2.1 of [7] defines (via extensible mechanism using
IANA registration) three values in the 'Datum' field: WGS 84, NAD 83
(with the associated vertical datum for the North American Vertical
Datum of 1988), NAD 83 (with the associated vertical datum for the
Mean Lower Low Water (MLLW). WGS 84 is used by the GPS system.
During a protocol run it is possible to return Location-Information
attributes which provide both types of location information elements.
If only one location information element is provided then civic
location SHOULD be included in the request.
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6. Basic- and Extended-Policy-Rule Attributes
In some environments it is possible for the user to attach
information about its privacy preferences. These preferences allow
the visited network, intermediate RADIUS proxies and the home network
to authorize the distribution of the user's location information.
Without the user providing authorization information two approaches
are possible:
o The user hides its location information from the access network
and from intermediate networks using the appropriate network
access authentication mechanism. Section 14 discusses these
issues in more details.
o The access network attaches default authorization policies which
indicates that intermediate networks and the home network should
not distribute the location information to other entities.
Additionally, the home network might have authorization policies
which control distribution of location information. Users can
dynamically change their policies using the authroization
framework defined in [15] and [16].
With regard to authorization policies this document reuses work done
in [14] and encodes it in an non-XML format. Two fields ('sighting
time' and 'time-to-live') are additionally included in the Location-
Information attribute to conform to the Geopriv Requirements [11],
Section 2.7. Two RADIUS attributes are used for this purpose: Basic-
Policy-Rule and Extended-Policy-Rule attribute. The Basic-Policy-
Rule attribute contains a fixed set of privacy relevant fields
whereas the Extended-Policy-Rule attribute contains a reference to a
more extensive authorization rule set.
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7. Location-Type Attribute
This document uses the values defined in the location type registry
[8].
By using these location types it is possible to define more accurate
location information. Note that multiple values can be specified in
this attribute.
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8. Capability Attribute
The capability attribute allows the RADIUS client to indicate whether
civic and/or geospatial location information can be provided to the
RADIUS server. This is useful to avoid sending location information
with every request if no further out-of-band arrangements are made
with regard to the transport of location information. The AAA server
uses the capability attribute to indicate that the AAA client has to
provide civic and/or geospatial location information as part of this
particular protocol exchange. If the AAA server does not send a
capability attribute then the AAA client MUST NOT return location
information. The user's authorization policies MUST be consulted by
the AAA server before requesting location information delivery from
the AAA client. If the AAA server encounters that the AAA client
does not support the desired location information it might respond
with an Access-Reject with the corresponding error cause attribute
(with the Location-Info-Required error code).
Figure 3 shows a simple protocol exchange where the AAA client
indicates that it is able to provide civic and geospatial location
information and the AAA server indicates that that civic location
information is desired for this particular exchange.
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+---------+ +---------+
| AAA | | AAA |
| Client | | Server |
| | | |
+---------+ +---------+
| |
| |
| RADIUS |
| Access-Request |
| + Capability |
| ('CIVIC_LOCATION', |
| 'GEO_LOCATION') |
|----------------------------->|
| |
| RADIUS |
| Access-Challenge |
| + Capability |
| ('CIVIC_LOCATION') |
|<-----------------------------|
| |
| RADIUS |
| Access-Request |
| + Location-Information |
| (civic-location) |
|----------------------------->|
| |
| .... |
Figure 3: Capability Exchange Example
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9. Diameter RADIUS Interoperability
In deployments where RADIUS clients communicate with DIAMETER servers
or DIAMETER clients communicate with RADIUS servers then a
translation agent will be deployed and operate. The NASREQ
specification [17] provides translation services. Furthermore, the
RADIUS attributes specified in this document are also applicable for
deployments where DIAMETER clients talk with DIAMETER servers.
DIAMETER AVP Code numbers for corresponding RADIUS attributes are
allocated as specified in DIAMETER Base Protocol specification
Section 4.1 [9].
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10. Attributes
This section defines the Operator-Namespace AVP, Operator-Name AVP,
Location-Information AVP, Basic Policy Rules AVP, Extended Policy
Rules AVP, Location-Type AVP and the Capability AVP.
10.1 Operator-Namespace Attribute
Operator-Namespace Attribute SHOULD be sent in Access-Request, and
Accounting-Request records where the Acc-Status-Type is set to Start,
Interim, or Stop.
A summary of the Operator-Namespace Attribute is shown below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Operator-Namespace ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type:
To Be Assigned by IANA - Operator-Namespace
Length:
>= 3 Bytes
Operator-Namespace:
The text field contains an Access Network Operator Type.
Example: REALM
10.2 Operator-Name Attribute
Operator-Name Attribute SHOULD be sent in Access-Request, and
Accounting-Request records where the Acc-Status-Type is set to Start,
Interim, or Stop.
A summary of the Operator-Name Attribute is shown below.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Operator-Name ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type:
To Be Assigned by IANA - Operator-Name
Length:
>= 3 Bytes
Operator-Name:
The text field contains an Access Network Operator Name.
Example: anyisp.com
10.3 Location-Information Attribute
Location-Information attribute SHOULD be sent in Access-Request, and
Accounting-Request records where the Acc-Status-Type is set to Start,
Interim or Stop if available.
The Location-Information Attribute has two variations depending on
civic or geospatial location information. The format is shown below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Code | Entity |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sighting Time ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sighting Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time-to-Live ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time-to-Live |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Method | Location-Info ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Type (8 bits):
To Be Assigned by IANA - Location-Information
Length (8 bits):
>= 3 Bytes
Code (8 bits):
Describes the location format that is carried in this attribute:
(0) describes civic location information
(1) describes geospatial location information
Entity (8 bits):
Describes which location this attribute refers to:
(0) describes the location of the user's client device
(1) describes the location of the AAA client
Sighting Time (64 bits):
NTP timestamp for the 'sighting time' field.
Time-to-Live (64 bits):
NTP timestamp for the 'time-to-live' field.
Method (8 bits):
Describes the way that the location information was
derived or discovered. The following values are defined:
(0) Global Positioning System (GPS)
(1) GPS with assistance (A-GPS)
(2) Manual configured information
(3) Provided by DHCP
(4) Triangulation: triangulated from time-of-arrival,
signal strength or similar measurements
(5) Cell: location of the cellular radio antenna
(6) IEEE 802.11 WLAN access point
Location-Info (variable):
Contains either civic or
geospatial location information attributes.
The following two fields need some explanation:
sighting time: This field indicates when the Location Information was
accurate. The data type of this field is a string and the format
is a 64 bit NTP timestamp [18].
time-to-live: This field gives a hint until when location information
should be considered current. Note that the time-to-live field is
different than retention-expires, which indicates the time the
recipient is no longer permitted to possess the location
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information and its encapsulating Location Object. The data type
of this field is a string and the format is a 64 bit NTP timestamp
[18].
For civic location information the Location-Info field in the above
structure is defined as followed:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Countrycode | Civic address elements ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Countrycode (16 bits):
Two-letter ISO 3166 country code in capital ASCII letters.
Civic address elements (variable):
The text field contains location information element.
The format of the civic address elements is described in Section 3.3
of [4] with a TLV pair (whereby the Type and Length fields are one
octet long). An example is given in Section 13.
For geospatial location information the Location-Info field is
defined as follows:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LaRes | Latitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Latitude | LoRes | Longitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Longitude | AT | AltRes | Altitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Altitude | Datum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
LaRes (6 bits):
Latitude resolution
Latitude (34 bits)
LoRes (6 bits):
Longitude resolution.
Longitude (34 bits)
Altitude (30 bits)
AltRes (6 bits):
Altitude resolution
AT (4 bits):
Altitude Type for altitude. The following codes are defined:
(1) Meters
(2) Floors
Datum (8 bits):
Coordinate reference system
The following codes for the this field are defined:
(1) WGS 84
(2) NAD 83 (with the associated vertical datum for
the North American Vertical Datum of 1988)
(3) NAD 83 (with the associated vertical datum for
the Mean Lower Low Water (MLLW))
The length of the Location-Information Attribute MUST NOT exceed 253
octets. The length of the geospatial location information format is
fixed with 16 bytes plus a four byte header.
The 'Datum' field contains an identifier for the coordinate system
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used to interpret the values of Latitude, Longitude and Altitude.
The field with value (2) and the value (3) both represent the NAD 83
coordinate reference system but they differ from each other with
regard to their vertical datum representation as briefly noted in
Section 5.3.2 and described in more detail in [7].
10.4 Basic Policy Rules Attribute
The Basic-Policy-Rules attribute MUST be sent in Access-Accept,
Access-Challenge, Access-Request, Access-Reject and Accounting-
Request messages if location information is transmitted with this
exchange. If authorization policy rules are available to the RADIUS
client then the Access-Request MUST carry the Basic-Policy-Rules
attribute to to the RADIUS server.
A summary of the Basic-Policy-Rules attribute is shown below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |R| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retention Expires ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retention Expires |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Note Well ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type :
To Be Assigned by IANA - Basic-Policy-Rules
Length:
> 3 Bytes
Flag (16 bits):
Only the first bit (R) is defined an corresponds to the
retransmission-allowed field. All other bits are reserved.
Retention Expires (64 bits):
NTP timestamp for the 'retention-expires' field.
Note Well (variable):
This field contains a URI which points to
human readable privacy instructions.
This document reuses fields of the 'usage-rules' element, described
in [14]. These fields have the following meaning:
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retransmission-allowed: When the value of this element is '0', then
the recipient of this Location Object is not permitted to share
the enclosed location information, or the object as a whole, with
other parties. The value of '1' allows to share the location
information with other parties by considering the extended policy
rules.
retention-expires: This field specifies an absolute date at which
time the Recipient is no longer permitted to possess the location
information. The data type of this field is a string and the
format is a 64 bit NTP timestamp [18].
note-well: This field contains a URI which points to human readable
privacy instructions. This field is useful when location
information is distributed to third party entities, which can
include humans in a location based service. RADIUS entities are
not supposed to process this field.
Whenever a Location Object leaves the AAA system the URI in the
note-well attribute MUST be expanded to the human readable text.
For example, when the Location Object is transferred to a SIP
based environment then the human readable text is placed in the
text is put into the 'note-well' attribute inside the 'usage-
rules' element inside the PIDF-LO document (see [14]).
10.5 Extended Policy Rules Attribute
The Extended-Policy-Rules attribute SHOULD be sent in Access-Accept,
Access-Challenge, Access-and Access-Reject messages if location
information is transmitted with this exchange. If authorization
policy rules are available to the RADIUS client then the Access-
Request MUST carry the Basic-Policy-Rules attribute to to the RADIUS
server.
Ruleset reference field of this attribute is of variable length. It
contains a URI that indicates where a richer ruleset is available.
The full ruleset SHOULD be fetched using Transport Layer Security
(TLS). As a deviation from [14] this field only contains a reference
and does not carry an attached rule set. This modification is
motivated by the size limitations imposed by RADIUS.
A summary of the Extended-Policy-Rules attribute is shown below.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Ruleset reference ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type :
To Be Assigned by IANA - Extended-Policy-Rules
Length:
> 3 Bytes
Ruleset reference:
The text field contains a URI which points to policy rules.
10.6 Location-Type Attribute
Location-Type Attribute SHOULD be sent in Access-Request, and
Accounting-Request records where the Acc-Status-Type is set to Start,
Interim, or Stop if available.
A summary of the Location-Type Attribute is shown below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Loc-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type (8 bits):
To Be Assigned by IANA - Location-Name
Length (8 bits):
4 Bytes
Loc-Type (16 bits):
The content of this field corresponds to the integer codes for
access network location type.
These integer codes for the location type can be found in Section 7.
10.7 Capability Attribute
The Capability attribute SHOULD be sent in the Access-Request and the
Access-Challenge messages.
A summary of the Capability attribute is shown below.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Capabilities ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type:
To Be Assigned by IANA - Operator-Name
Length:
>= 3 Bytes
Capabilities (128 bits):
This text field contains a numerical value that encodes the
corresponding capabilities.
Each value represents a bit position.
Currently the following capabilities are specified:
Capability Name:
CIVIC_LOCATION
Description:
In the direction from the AAA client to the AAA server this
capability refers to the ability to sent civic location
information. In the direction from the AAA server to the AAA
client this capability refers to the desire of the AAA server to
receive civic location.
Numerical Value:
A numerical value of this attribute is '0'.
Capability Name:
GEO_LOCATION
Description:
In the direction from the AAA client to the AAA server this
capability refers to the ability to sent geospatial location
information. In the direction from the AAA server to the AAA
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client this capability refers to the desire of the AAA server to
receive geospatial location.
Numerical Value:
A numerical value of this attribute is '2'.
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11. Table of Attributes
The following table provides a guide which attributes may be found in
which RADIUS messages, and in what quantity.
Request Accept Reject Challenge Accounting # Attribute
Request
0-1 0 0 0 0-1 TBD Operator-Name
0-1 0 0 0 0-1 TBD Operator-Namespace
0+ 0 0 0 0+ TBD Location-Information
0-1 0-1 0-1 0-1 0-1 TBD Basic-Policy-Rules
0-1 0-1 0-1 0-1 0-1 TBD Extended-Policy-Rules
0-1 0 0 0 0-1 TBD Location-Type
0-1 0 0 0-1 0 TBD Capability
The Location-Information attribute may appear more than once. This
is useful if the size of one Location-Information attribute exceeds
the maximum size of an AVP. This might happen in case of civic
location information that has a variable number of fields. The
individual fields used for representing civic location information
inside the Location-Information AVP (see Section 5.3.1 MUST NOT
appear more than once. For example, it is not allowed to have a
CAtype of 3 (indicating the name of the city) to appear more than
once.
The next table shows the occurrence of the error-cause attribute.
Request Accept Reject Challenge Accounting # Attribute
Request
0 0 0-1 0-1 0-1 TBD Location-Info-Required
0 0 0-1 0 0 101 Error-Cause
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12. Matching with Geopriv Requirements
This section compares the Geopriv requirements described in [11] and
the approach of distributing Location Objects with RADIUS.
The main usage scenario aimed for Location Object transport in RADIUS
assumes that the Location Server and the Location Recipient are co-
located at a single entity with regard to location based network
access authorization, taxation and billing. In Section 12.1 and
Section 12.2 we discuss privacy implications when RADIUS is not used
according to these usage scenario.
In Section 12.3 Geopriv requirements are matched against these two
scenarios.
12.1 Distribution of Location Information at the User's Home Network
This section focuses on location information transport from the local
AAA server (acting as the Location Generator) to the home AAA server
(acting as the Location Server). To use a more generic scenario we
assume that the visited AAA and the home AAA server belong to
different administrative domains. The Location Recipient obtains
location information about a particular Target via protocols
specified outside the scope this document (e.g., SIP, HTTP or an
API).
Please note that the main usage scenario defined in this document
assumes that the Location Server and the Location Recipient are co-
located into a single entity with regard to location based network
access authorization, taxation and billing.
The subsequent figure shows the interacting entities graphically.
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visited network | home network
|
| +----------+
| | Rule |
| | Holder |
| | |
| +----+-----+
| |
| rule|interface
| V
+----------+ | +----------+ +----------+
|Location | publication | Location | notification |Location |
|Generator |<------------->| Server |<------------->|Recipient |
| | interface | | interface | |
+----------+ | +----------+ +----------+
|
Local AAA RADIUS Home AAA SIP/HTTP/API/etc.
Server | Server
|
Figure 16: Location Server at the Home Network
The term 'Rule Holder' in Figure 16 denotes the entity which creates
the authorization ruleset.
12.2 Distribution of Location Information at the Visited Network
This section describes a scenario where Location Information is
distributed by the visited network.
In order for this scenario to be applicable the following two
assumptions must hold:
o The visited network deploys a Location Server and wants to
distribute Location Objects of a user
o The visited network is able to learn the user's identity
The visited network provides location information to a Location
Recipient (e.g., via SIP or HTTP). During the network access
authentication procedure the visited network is able to retrieve the
user's authorization policies from the home AAA server. This should
ensure that the visited network acts according to the user's
policies.
The subsequent figure shows the interacting entities graphically.
The transport of the Location Object is not shown in this figure
since this aspect is already covered in the previous paragraph.
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visited network | home network
|
+----------+ |
|Location | |
|Recipient | |
| | |
+----------+ |
^ | +----------+
| | | Rule |
| | | Holder |
notification | | |
interface | +----+-----+
| | |
| | rule|interface
v | V
+----------+ | +----------+
|Location | Rule Transport| Home AAA |
|Generator |<------------->| Server |
|& Server | RADIUS | |
+----------+ | +----------+
|
Figure 17: Location Server at the Visited Network
12.3 Requirements matching
Section 7.1 of [11] details the requirements of a "Location Object".
There are:
Req. 1. (Location Object generalities):
* Regarding requirement 1.1, the Location Object has to be
understood by the RADIUS server (and possibly a Diameter server
in case of interworking between the two) as defined in this
document. Due to the encoding of the Location Object it is
possible to convert it to the format used in GMLv3 [19]. The
same civic location information format is used in PIDF-LO [14]
and this document.
* Regarding requirement 1.2, some fields of the Location Object
defined in this document are optional. See Section 5.3.1 as an
example.
* Regarding requirement 1.3, the inclusion of the Location-Type
attribute which gives a further classification of the location.
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This attribute can be seen as an extension.
* Regarding requirement 1.4, the Location Object is extensible in
the same fashion as RADIUS is extensible.
* Regarding requirement 1.5, the Location Object is useful for
both receiving and sending location information as described in
this document.
* Regarding requirement 1.6, the Location Object contains both
location information and privacy rules. Location information
is described in Section 5.3 and the corresponding privacy rules
are detailed in Section 10.4 and in Section 10.5.
* Regarding requirement 1.7, the Location Object is usable in a
variety of protocols. The format of the object is reused from
other documents as detailed in the respective sections (see
Section 5.3, Section 10.4 and in Section 10.5).
* Regarding requirement 1.8, the encoding of the Location Object
has an emphasis on a lightweight encoding format. As such it
is useable on constrained devices.
Req. 2. (Location Object fields):
* Regarding requirement 2.1, the Target Identifier is carried
within the network access authentication protocol (e.g., within
the EAP-Identity Response when EAP is used and/or within the
EAP method itself). As described in Section 14 it has a number
of advantages if this identifier is not carried in clear text.
This is possible with certain EAP methods whereby the identity
in the EAP-Identity Response only contains information relevant
for routing the response to the user's home network. The user
identity is protected by the authentication and key exchange
protocol.
* Regarding requirement 2.2, the Location Recipient is in the
main scenario the home AAA server. For a scenario where the
Location Recipient is obtaining Location Information from the
Location Server via HTTP or SIP the respective mechanisms
defined in these protocols are used to identify the recipient.
The Location Generator cannot, a priori, know the recipients if
they are not defined in this protocol.
* Regarding requirement 2.3, the credentials of the Location
Recipient are known to the RADIUS entities based on the
security mechanisms defined in the RADIUS protocol itself.
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Section 15 describes these security mechanisms offered by the
RADIUS protocol. The same is true for requirement 2.4.
* Regarding requirement 2.5, Section 5.3 describes the content of
the Location Field. Motion and direction vectors as listed in
requirement 2.6 are not provided as attributes. It is,
however, possible to deduce the motion and direction of an
entity via the Mid-session Delivery mechanism as shown in
Figure 2.
* Regarding requirement 2.6, this document only describes one
Location Data Type for civic and for geospatial location
information, respectively. No negotiation needs to take place.
* Regarding requirement 2.7, timing information is provided with
'sighting time' and 'time-to-live' field defined in
Section 10.4.
* Regarding requirement 2.8, a reference to an external (more
detailed ruleset) is provided with the Section 10.5 attribute.
* Regarding requirement 2.9, security headers and trailers are
provided as part of the RADIUS protocol or even as part of
IPsec.
* Regarding requirement 2.10, a version number in RADIUS is
provided with the IANA registration of the attributes. New
attributes are assigned a new IANA number.
Req. 3. (Location Data Types):
* Regarding requirement 3.1, this document defines two Location
Data Types as described in Section 5.3.
* With the support of civic and geospatial location information
support requirement 3.2 is fulfilled.
* Regarding requirement 3.3, the geospatial location information
as defined in this document only refers to absolute
coordinates. However, the granularity of the location
information can be reduced with the help of the AltRes, LoRes,
LaRes fields described in the Location-Information attribute
(see Section 10.3).
* Regarding requirement 3.4, further Location Data Types can be
added via new coordinate reference systems (CRSs) (see Datum
field in the Location-Information attribute of Section 5.3),
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extensions to existing fields (e.g., new location types as
shown in Section 7) or via additional attributes.
Section 7.2 of [11] details the requirements of a "Using Protocol".
These requirements are listed below:
Req. 4.: The using protocol has to obey the privacy and security
instructions coded in the Location Object and in the corresponding
Rules regarding the transmission and storage of the LO. This
document requires, that RADIUS entities sending or receiving
location MUST obey such instructions.
Req. 5.: The using protocol will typically facilitate that the keys
associated with the credentials are transported to the respective
parties, that is, key establishment is the responsibility of the
using protocol. Section 15 specifies how security mechanisms are
used in RADIUS and how they can be reused to provide security
protection for the Location Object. Additionally, the privacy
considerations (see Section 14) are also relevant for this
requirement.
Req. 6. (Single Message Transfer): In particular, for tracking of
small target devices, the design should allow a single message/
packet transmission of location as a complete transaction. The
encoding of the Location Object is specifically tailored towards
the inclusion into a single message that even respects the (Path)
MTU size. The concept of a transaction is not immediately
applicable to RADIUS.
Section 7.3 of [11] details the requirements of a "Rule based
Location Data Transfer". These requirements are listed below:
Req. 7. (LS Rules): With the scenario shown in Figure 16 the
decision of a Location Server to provide a Location Recipient
access to location information is based on Rule Maker-defined
Privacy Rules which are stored at the home network or are
accessible for the home network. With regard to the scenario
shown in Figure 17 the Rule Maker-defined Privacy Rules are sent
from the home network to the visited network as part of the
Policy-Information attribute (see Section 10.4, Section 10.5 and
Section 14 for more details).
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Req. 8. (LG Rules): For mid-session delivery it is possible to
enforce the user's privacy rules for the transfer of the Location
Object. For the initial transmission of a Location Object the
user would have to use network access authentication methods which
provide user identity confidentiality which would render the
Location Object completely useless for the visited network. For
the scenario shown in Figure 16 the visited network is already in
possession of the users location information prior to the
authentication and authorization of the user. A correlation
between the location and the user identity might, however, still
not be possible for the visited network (as explained in
Section 14). The visited network MUST evaluate ruleset provided
by the home AAA server as soon as possible.
Req. 9. (Viewer Rules): The Rule Maker might define (via mechanisms
outside the scope of this document) which policy rules are
disclosed to other entities.
Req. 10. (Full Rule language): Geopriv has defined a rule language
capable of expressing a wide range of privacy rules which is
applicable in the area of the distribution of Location Objects. A
basic ruleset is provided with the Basic-Policy-Rules attribute
Section 10.4. A reference to the extended ruleset is carried in
Section 10.5. The format of these rules are described in [15] and
[16].
Req. 11. (Limited Rule language): A limited (or basic) ruleset is
provided by the Policy-Information attribute Section 10.4 (and as
introduced with PIDF-LO [14]).
Section 7.4 of [11] details the requirements of a "Location Object
Privacy and Security". These requirements are listed below:
Req. 12 (Identity Protection): Support for unlinkable pseudonyms is
provided by the usage of a corresponding authentication and key
exchange protocol. Such protocols are available, for example,
with the support of EAP as network access authentication methods.
Some EAP methods support passive user identity confidentiality
whereas others even support active user identity confidentiality.
This issue is further discussed in Section 15. The importance for
user identity confidentiality and identity protection has already
been recognized (see for example a document on 'EAP Method
Requirements for Wireless LANs' [20]).
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Req. 13. (Credential Requirements): As described in Section 15
RADIUS signaling messages can be protected with IPsec. This
allows a number of authentication and key exchange protocols to be
used as part of IKE, IKEv2 or KINK.
Req. 14. (Security Features): Geopriv defines a few security
requirements for the protection of Location Objects such as mutual
end-point authentication, data object integrity, data object
confidentiality and replay protection. As described in Section 15
these requirements are fulfilled with the usage of IPsec if the
mutual authentication refers to the RADIUS entities (acting as
various Geopriv entities) which directly communicate with each
other.
Req. 15. (Minimal Crypto): A minimum of security mechanisms are
mandated by the usage of RADIUS. Communication security for
Location Objects between AAA infrastructure elements is provided
by the RADIUS protocol (including IPsec and its dynamic key
management framework) rather than on relying on object security
via S/SIME (which is not available with RADIUS).
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13. Example
This section provides an example for a civic location information
format within the Location-Information attribute. The size of the
geo-spatial location information object is fixed and well-described
examples can be found in the Appendix of [7].
Due to the size limitations of the RADIUS attributes we give a more
detailed example borrowed from Section 4 of [4].
+-------------+-----------+-------------------+
| Type | Length | Value |
+-------------+-----------+-------------------+
| Type | 8 bits | TBD |
| Length | 8 bits | --total length-- |
| Code | 16 bits | 1 |
| Precision | 8 bits | 2 |
| Countrycode | 16 bits | DE |
| CAtype | 8 bits | 1 |
| CAlength | 8 bits | 7 |
| CAvalue | 7 bytes | Bavaria |
| CAtype | 8 bits | 3 |
| CAlength | 8 bits | 6 |
| CAvalue | 6 byte | Munich |
| CAtype | 8 bits | 6 |
| CAlength | 8 bits | 11 |
| CAvalue | 11 bytes | Marienplatz |
| CAtype | 8 bits | 19 |
| CAlength | 8 bits | 1 |
| CAvalue | 1 byte | 8 |
| CAtype | 8 bits | 24 |
| CAlength | 8 bits | 5 |
| CAvalue | 5 bytes | 80331 |
+-------------+-----------+-------------------+
The Length element provides the length of the entire payload minus
the length of the initial 'Type', the 'Length' and the 'Code'
attribute. The 'Entity' field has a value of '2' which refers to the
location of the user's client. The 'CountryCode' field is set to
'DE'. Note that the subsequent attributes are in Type-Length-Value
format. Type '1' indicates the region of 'Bavaria', '3' refers to
the city 'Munich', '6' to the street 'Marienplatz', the house number
'8' is indicated by the type '19' and the zip code of '80331' is of
type '24'.
The length of the elements need to consider the fact that all CAvalue
elements are UTF-8 encoded.
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The following example illustrates a civic address in Japan.
+-------------+-----------+-------------------+
| Type | Length | Value |
+-------------+-----------+-------------------+
| Type | 8 bits | TBD |
| Length | 8 bits | --total length-- |
| Code | 16 bits | 1 |
| Precision | 8 bits | 2 |
| Countrycode | 16 bits | JP |
| CAtype | 8 bits | 1 |
| CAlength | 8 bits | 5 |
| CAvalue | 7 bytes | Tokyo |
| CAtype | 8 bits | 3 |
| CAlength | 8 bits | 13 |
| CAvalue | 6 byte | Musashino-shi |
| CAtype | 8 bits | 5 |
| CAlength | 8 bits | 7 |
| CAvalue | 11 bytes | 3-chome |
| CAtype | 8 bits | 30 |
| CAlength | 8 bits | 8 |
| CAvalue | 1 byte | 180-8585 |
| CAtype | 8 bits | 32 |
| CAlength | 8 bits | 11 |
| CAvalue | 5 bytes | 13203000003 |
+-------------+-----------+-------------------+
Please note that the CAtype 32 ("additional code" item) provides an
additional, country-specific code identifying the location, such as
the Japan Industry Standard (JIS) address code.
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14. Privacy Considerations
This section discusses privacy implications for the distribution of
location information within RADIUS.
In many cases the location information of the network also reveals
the current location of the user with a certain degree of precision
depending on the mechanism used, the positioning system, update
frequency, where the location was generated, size of the network and
other mechanisms (such as movement traces or interpolation).
Two entities might act as Location Servers as shown in Section 4, in
Figure 16 and in Figure 17:
14.1 Entity in the visited network
In this scenario it is difficult to obtain authorization policies
from the end host (or user) immediately when the user attaches to the
network. In this case we have to assume that the visited network
does not allow unrestricted distribution of location information to
other than the intended recipients (e.g., to third party entities).
The visited network MUST behave according to the following
guidelines:
o Per default only the home network is allowed to receive location
information. The visited network MUST NOT distribute location
information to third parties without seeing the user's privacy
rule se.
o If the home network provides the Basic-Policy-Rules attribute
either as part of the Access-Accept, the Access-Reject or the
Access-Challenge message then the visited network MUST follow the
guidance given with these rules.
o If the home network provides the Extended-Policy-Rules attributes
either as part of the Access-Accept, the Access-Reject or the
Access-Challenge message then the visited network MUST fetch the
full ruleset at the indicated URL and MUST follow the guidance
given with these rules.
o If the RADIUS client in the visited network learns the basic rule
set or a reference to the extended rule set by means outside the
RADIUS protocol (e.g., provided by the end host) then it MUST
include the Basic-Policy-Rules and the Extended-Policy-Rules
attribute in the Access-Request message towards the home AAA
server. Furthermore, the visited network MUST evaluate these
rules prior to the transmission of location information either to
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the home network or a third party. The visited network MUST
follow the guidance given with these rules.
o If the RADIUS client in the visited network receives the Basic-
Policy-Rules attribute with Access-Accept or the Access-Challenge
message then the Basic-Policy-Rules MUST be attach in subsequent
RADIUS messages which contain the Location-Information attribute
(such as interim accounting messages).
o If the RADIUS client in the visited network receives the Extended-
Policy-Rules attribute with Access-Accept or the Access-Challenge
message then the Basic-Policy-Rules attribute MUST be attach in
subsequent RADIUS messages which contain the Location-Information
attribute (such as interim accounting messages).
14.2 Entity in the home network
The AAA server in the home network might be an ideal place for
storing authorization policies. The user typically has a contractual
relationship with his home network and hence the trust relationship
between them is stronger. Once the infrastructure is deployed and
useful applications are available there might be a strong desire to
use location information for other purposes as well (such as location
aware applications). Authorization policy rules described in [16]
and in [15] are tailored for this environment. These policies might
be useful for limiting further distribution of the user's location to
other location based services. The home AAA server (or a similar
entity) thereby acts as a location server for access to location
services.
The home network MUST behave according to the following guidelines:
o As a default policy the home network MUST NOT distribute the
user's location information to third party entities.
o If a user provides basic authorization policies then these rules
MUST be returned to the visited network in the Access-Accept, the
Access-Reject or the Access-Challenge message.
o If a user provides basic authorization policies then these rules
MUST be returned to the visited network in the Access-Accept, the
Access-Reject or the Access-Challenge message.
o If a user provides extended authorization policies then they MUST
be accessible for the visited networking using a reference to
these rule set. The Extended-Policy-Rules attribute MUST include
the reference and they MUST be sent to the visited network in the
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Access-Accept, the Access-Reject or the Access-Challenge message.
o The home network MUST follow the user provided rule set for both
local storage and for further distribution. With regard to the
usage of these rules the home network MUST ensure that the users
preferences are taken care of within the given boundaries (such as
legal regulations or operational considerations). For example, a
user might not want the home network to store information about
its location information beyond a indicated time frame. However,
a user might on the other hand want to ensure that disputes
concerning the billed amount can be resolved. location information
might help to resolve the dispute. The user might, for example,
be able to show that he has never been at the indicated place.
o If the policy rules provided by the user indicate that location
information must not be distributed at all then the home network
MUST provide the Basic-Policy-Rules to the RADIUS entity in the
visited network via an Access-Accept, the Access-Reject and the
Access-Challenge message. The RADIUS server in the user's home
network would set the 'Retention-Expires' and the 'Retransmission-
allowed' field to the user indicated value.
For the envisioned usage scenarios, the identity of the user and his
device is tightly coupled to the transfer of location information.
If the identity can be determined by the visited network or AAA
brokers, then it is possible to correlate location information with a
particular user. As such, it allows the visited network and brokers
to learn movement patterns of users.
The identity of the user can "leak" to the visited network or AAA
brokers in a number of ways:
o The user's device may employ a fixed MAC address, or base its IP
address on such an address. This enables the correlation of the
particular device to its different locations. Techniques exist to
avoid the use of an IP address that is based on MAC address [21].
Some link layers make it possible to avoid MAC addresses or change
them dynamically.
o Network access authentication procedures such as PPP CHAP [22] or
EAP [23] may reveal the user's identity as a part of the
authentication procedure. Techniques exist to avoid this problem
in EAP, for instance by employing private Network Access
Identifiers (NAIs) in the EAP Identity Response message [24] and
by method-specific private identity exchange in the EAP method
(e.g., [25], [26], [27]). Support for identity privacy within
CHAP is not available.
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o AAA protocols may return information from the home network to the
visited in a manner that makes it possible to either identify the
user or at least correlate his session with other sessions, such
as the use of static data in a Class attribute [1] or in some
accounting attribute usage scenarios [28].
o Mobility mechanisms may reveal some permanent identifier (such as
a home address) in cleartext in the packets relating to mobility
signaling.
o Application protocols may reveal other permanent identifiers.
Note that to prevent the correlation of identities with location
information it is necessary to prevent leakage of identity
information from all sources, not just one.
Unfortunately, most users are not educated about the importance of
identity confidentiality and there is a lack of support for it in
many protocols. This problem is made worse by the fact that the
users may be unable to choose particular protocols, as the choice is
often dictated by the type of network they wish to access, the kind
of equipment they have, or the type of authentication method they are
using.
A scenario where the user is attached to the home network is, from a
privacy point of view, simpler than a scenario where a user roams
into a visited network since the NAS and the home AAA are in the same
administrative domain. No direct relationship between the visited
and the home network operator may be available and some AAA brokers
need to be consulted. With subscription-based network access as used
today the user has a contractual relationship with the home network
provider which could allow higher privacy considerations to be
applied (including policy rules stored at the home network itself for
the purpose of restricting further distribution).
In many cases it is necessary to secure the transport of location
information along the RADIUS infrastructure. Mechanisms to achieve
this functionality are discussed in Section 15.
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15. Security Considerations
Requirements for the protection of a Location Object are defined in
[11]: Mutual end-point authentication, data object integrity, data
object confidentiality and replay protection. The distribution of
location information can be restricted with the help of authorization
policies. Basic authorization policies are attached to the location
information itself, in the same fashion as described in [14]. It is
possible that the user was already able to transfer some
authorization policies to the access network to restrict the
distribution of location information. This is, however, rather
unlikely in case of roaming users. Hence, it will be primarily the
NAS creating the Location Object which also sets the authorization
policies. If no authorization information is provided by the user
then the visited network MUST set the authorization policies to only
allow the home AAA server to use the provided location information.
Other entities, such as the visited network and possibly AAA brokers
MUST NOT use the location information for a purpose other than
described in this document. More extensible authorization policies
can be stored at the user's home network. These policies are useful
when location information is distributed to other entities in a
location-based service. This scenario is, however, outside the scope
of this document.
It is necessary to use authorization policies to limit the
unauthorized distribution of location information. The security
requirements which are created based on [11] are inline with threats
which appear in the relationship with disclosure of location
information as described in [29]. PIDF-LO [14] proposes S/MIME to
protect the Location Object against modifications. S/SIME relies on
public key cryptography which raises performance, deployment and size
considerations. Encryption would require that the local AAA server
or the NAS knows the recipient's public key (e.g., the public key of
the home AAA server). Knowing the final recipient of the location
information is in many cases difficult for RADIUS entities. Some
sort of public key infrastructure would be required to obtain the
public key and to verify the digital signature (at the home network).
Providing per-object cryptographic protection is, both at the home
and at the visited network, computationally expensive.
If no authentication, integrity and replay protection between the
participating RADIUS entities is provided then an adversaries can
spoof and modify transmitted AVPs. Two security mechanisms are
proposed for RADIUS:
o [1] proposes the usage of a static key which might raise some
concerns about the lack dynamic key management.
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o RADIUS over IPsec [30] allows to run standard key management
mechanisms, such as KINK [31], IKE and IKEv2 [32], to establish
IPsec security associations. Confidentiality protection MUST be
used to prevent eavesdropper gaining access to location
information. Confidentiality protection is not only a property
required by this document, it is also required for the transport
of keying material in the context of EAP authentication and
authorization. Hence, this requirement is, in many environments,
already fulfilled. Mutual authentication must be provided between
the local AAA server and the home AAA server to prevent man-in-
the-middle attacks from being successful. This is another
requirement raised in the area of key transport with RADIUS and
does not represent a deployment obstacle. The performance
advantages superior compared to the usage of S/MIME and object
security since the expensive authentication and key exchange
protocol run needs to be provided only once (for a long time).
Symmetric channel security with IPsec is highly efficient. Since
IPsec protection is suggested as a mechanism to protect RAIDUS
already no additional considerations need to be addressed beyond
those described in [30]. Where an untrusted AAA intermediary is
present, the Location Object MUST NOT be provided to the
intermediary.
In case that IPsec protection is not available for some reason and
RADIUS specific security mechanisms have to be used then the
following considerations apply. The Access-Request message is not
integrity protected. This would allow an adversary to change the
contents of the Location Object or to insert and modify attributes
and fields or to delete attributes. To address these problems the
Message-Authenticator (80) can be used to integrity protect the
entire Access-Request packet. The Message-Authenticator (80) is also
required when EAP is used and hence is supported by many modern
RADIUS servers.
Access-Request packets including Location attribute(s) without a
Message-Authenticator(80) attribute SHOULD be silently discarded by
the RADIUS server. A RADIUS server supporting the Location
attributes MUST calculate the correct value of the Message-
Authenticator(80) and MUST silently discard the packet if it does not
match the value sent.
Access-Accept, including Location attribute(s) without a Message-
Authenticator(80) attribute SHOULD be silently discarded by the NAS.
A NAS supporting the Location attribute MUST calculate the correct
value of a received Message-Authenticator(80) and MUST silently
discard the packet if it does not match the value sent.
RADIUS and DIAMETER make some assumptions about the trust between
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traversed AAA entities in sense that object level security is not
provided by neither RADIUS nor DIAMETER. Hence, some trust has to be
placed on the AAA entities to behave according to the defined rules.
Furthermore, the AAA protocols do not involve the user in their
protocol interaction except for tunneling authentication information
(such as EAP messages) through their infrastructure. RADIUS and
DIAMETER have even become a de-facto protocol for key distribution.
Hence, in the past there were some concerns about the trust placed
into the infrastructure particularly from the security area when it
comes to keying. The EAP keying infrastructure is described in [33].
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16. IANA Considerations
The authors request that the Attribute Types, and Attribute Values
defined in this document be registered by the Internet Assigned
Numbers Authority (IANA) from the RADIUS name spaces as described in
the "IANA Considerations" section of RFC 2865 [1], in accordance with
BCP 26 [10]. Additionally, the Attribute Type should be registered
in the Diameter name space.
This document defines the following AVPs:
Operator-Name
Operator-Namespace
Location-Information
Basic-Policy-Rules
Extended-Policy-Rules
Location-Name
Capability
Please refer to Section 11 for the registered list of numbers.
This document also instructs IANA to assign a new value for the
Error-Cause attribute [5], of "Location-Info-Required" TBA.
Additionally, IANA is requested to create the following new
registries:
16.1 New Registry: Operator Type
This document also defines a registry for the Operator-Namespace
attribute. Initially, IANA is requested to register the following
values and associated registry owners for the operator namespace:
+--------------------+----------------------------+
| Operator-Namespace | Registry Owner |
+--------------------+----------------------------+
| GSM | GSM Association: TADIG WG |
| CDMA | IMSI Oversight Council |
| REALM | IANA or delegate |
+--------------------+----------------------------+
Following the policies outline in [10] new Operator-Namespaces will
be assigned after Expert Review by the Geopriv working group or its
designated successor.
16.2 New Registry: Capabilities
This document creates a new IANA registry for capabilities.
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Currently two capabilities are defined as shown in Section 10.7
Following the policies outline in RFC 2434 [10], these tokens are
assigned on a 'First Come First Served' policy. Each registration
must include the name of the capability, a brief description and a
numerical value respresenting a bit in the capability bit-string:
Capability Name:
Identifier of the capability
Description:
Brief description indicating the meaning of the capability.
Numerical Value:
A numerical value that is placed into the Capability attribute.
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17. Acknowledgments
The authors would like to thank the following people for their help
with a previous version of this draft and for their input:
Chuck Black
Paul Congdon
Jouni Korhonen
Sami Ala-luukko
Farooq Bari
Ed Van Horne
Mark Grayson
Jukka Tuomi
Jorge Cuellar
Christian Guenther
Henning Schulzrinne provided the civic location information content
found in this draft. The geospatial location information format is
based on work done by J. Polk, J. Schnizlein and M. Linsner. The
authorization policy format is based on the work done by Jon
Peterson.
The authors would like to thank Victor Lortz, Jose Puthenkulam,
Bernrad Aboba, Jari Arkko, Parviz Yegani, Serge Manning, Kuntal
Chowdury, Pasi Eronen, Blair Bullock and Eugene Chang for their
feedback to an initial version of this draft. We would like to thank
Jari Arkko for his text contributions. Lionel Morand provided
detailed feedback on numerous issues. His comments helped to improve
the quality of this document. Jouni Korhonen and John Loughney
helped us with the Diameter RADIUS interoperability. Finally,
Andreas Pashalidis reviewed the final document and provided a number
of comments.
This document is based on the discussions within the IETF GEOPRIV
working group. Therefore, the authors thank Henning Schulzrinne,
James Polk, John Morris, Allison Mankin, Randall Gellens, Andrew
Newton, Ted Hardie, Jon Peterson for their time to discuss a number
of issues with us. We thank Stephen Hayes for aligning this work
with 3GPP activities.
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18. References
18.1 Normative References
[1] Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote
Authentication Dial In User Service (RADIUS)", RFC 2865,
June 2000.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", March 1997.
[3] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.
[4] Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCPv4
and DHCPv6) Option for Civic Addresses Configuration
Information", draft-ietf-geopriv-dhcp-civil-06 (work in
progress), May 2005.
[5] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B. Aboba,
"Dynamic Authorization Extensions to Remote Authentication Dial
In User Service (RADIUS)", RFC 3576, July 2003.
[6] Yergeau, F., "UTF-8, a transformation format of ISO 10646",
STD 63, RFC 3629, November 2003.
[7] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host
Configuration Protocol Option for Coordinate-based Location
Configuration Information", RFC 3825, July 2004.
[8] Schulzrinne, H. and H. Tschofenig, "Location Types Registry",
draft-ietf-geopriv-location-types-registry-01 (work in
progress), July 2005.
[9] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. Arkko,
"Diameter Base Protocol", RFC 3588, September 2003.
[10] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
18.2 Informative References
[11] Cuellar, J., Morris, J., Mulligan, D., Peterson, D., and D.
Polk, "Geopriv Requirements", RFC 3693, February 2004.
[12] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
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[13] Polk, J. and B. Rosen, "Session Initiation Protocol Location
Conveyance", draft-ietf-sip-location-conveyance-00 (work in
progress), June 2005.
[14] Peterson, J., "A Presence-based GEOPRIV Location Object
Format", draft-ietf-geopriv-pidf-lo-03 (work in progress),
September 2004.
[15] Schulzrinne, H., "A Document Format for Expressing Privacy
Preferences", draft-ietf-geopriv-common-policy-04 (work in
progress), February 2005.
[16] Schulzrinne, H., "A Document Format for Expressing Privacy
Preferences for Location Information",
draft-ietf-geopriv-policy-05 (work in progress), November 2004.
[17] Calhoun, P., Zorn, G., Spence, D., and D. Mitton, "Diameter
Network Access Server Application",
draft-ietf-aaa-diameter-nasreq-17 (work in progress),
July 2004.
[18] Mills, D., "Network Time Protocol (Version 3) Specification,
Implementation", RFC 1305, March 1992.
[19] "Open Geography Markup Language (GML) Implementation
Specification", OGC 02-023r4,
http://www.opengis.org/techno/implementation.htm", ,
January 2003.
[20] Stanley, D., Walker, J., and B. Aboba, "Extensible
Authentication Protocol (EAP) Method Requirements for Wireless
LANs", RFC 4017, March 2005.
[21] Narten, T. and R. Draves, "Privacy Extensions for Stateless
Address Autoconfiguration in IPv6", RFC 3041, January 2001.
[22] Simpson, W., "PPP Challenge Handshake Authentication Protocol
(CHAP)", RFC 1994, August 1996.
[23] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, "Extensible Authentication Protocol (EAP)",
RFC 3748, June 2004.
[24] Aboba, B., "The Network Access Identifier",
draft-ietf-radext-rfc2486bis-05 (work in progress),
February 2005.
[25] Arkko, J. and H. Haverinen, "Extensible Authentication Protocol
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Method for 3rd Generation Authentication and Key Agreement
(EAP-AKA)", draft-arkko-pppext-eap-aka-15 (work in progress),
December 2004.
[26] Josefsson, S., Palekar, A., Simon, D., and G. Zorn, "Protected
EAP Protocol (PEAP) Version 2",
draft-josefsson-pppext-eap-tls-eap-10 (work in progress),
October 2004.
[27] Tschofenig, H., "EAP IKEv2 Method (EAP-IKEv2)",
draft-tschofenig-eap-ikev2-06 (work in progress), May 2005.
[28] Adrangi, F., "Chargeable User Identity",
draft-ietf-radext-chargeable-user-id-05 (work in progress),
May 2005.
[29] Danley, M., "Threat Analysis of the Geopriv Protocol",
RFC 3694, September 2003.
[30] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication Dial
In User Service) Support For Extensible Authentication Protocol
(EAP)", RFC 3579, September 2003.
[31] Sakane, S., "Kerberized Internet Negotiation of Keys (KINK)",
draft-ietf-kink-kink-08 (work in progress), July 2005.
[32] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
draft-ietf-ipsec-ikev2-17 (work in progress), October 2004.
[33] Aboba, B., "Extensible Authentication Protocol (EAP) Key
Management Framework", draft-ietf-eap-keying-06 (work in
progress), April 2005.
[34] Schulzrinne, H., "RPID: Rich Presence Extensions to the
Presence Information Data Format (PIDF)",
draft-ietf-simple-rpid-07 (work in progress), June 2005.
[35] Adrangi, F., "Access Network Bandwidth Capability",
draft-adrangi-radius-bandwidth-capability-01 (work in
progress), July 2004.
[36] Aboba, B., "The Network Access Identifier",
draft-arkko-roamops-rfc2486bis-02 (work in progress),
July 2004.
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Authors' Addresses
Hannes Tschofenig
Siemens
Otto-Hahn-Ring 6
Munich, Bavaria 81739
Germany
Email: Hannes.Tschofenig@siemens.com
F. Adrangi
Intel Corporatation
2111 N.E. 25th Avenue
Hillsboro OR
USA
Email: farid.adrangi@intel.com
Mark Jones
Bridgewater Systems Corporation
303 Terry Fox Drive
Ottawa, Ontario K2K 3J1
CANADA
Email: mark.jones@bridgewatersystems.com
Avi Lior
Bridgewater Systems Corporation
303 Terry Fox Drive
Ottawa, Ontario K2K 3J1
CANADA
Email: avi@bridgewatersystems.com
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Tschofenig, et al. Expires January 17, 2006 [Page 56]
