Network WG James Polk
Internet-Draft Cisco Systems
Intended status: Proposed Standard Feb 25, 2013
Expires: Aug 25, 2013
Dynamic Host Configuration Protocol (DHCP) IPv4 and IPv6
Option for a Location Uniform Resource Identifier (URI)
draft-ietf-geopriv-dhcp-lbyr-uri-option-19
Abstract
This document creates a Dynamic Host Configuration Protocol (DHCP)
Option for transmitting a client's geolocation Uniform Resource
Identifier (URI). This Location URI can then be dereferenced in a
separate transaction by the client or sent to another entity and
dereferenced to learn physically where the client is located, but
only while valid.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 25, 2013.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. DHCP LocationURI Option Format and Rules .. . . . . . . . . . 4
2.1. Overall Format of LocationURI Option in IPv4 . . . . . 4
2.2. Overall Format of LocationURI Option in IPv6 . . . . . 5
2.3. Rules for both LocationURI and Valid-For Options . . . 6
3. DHCP Option Operation . . . . . . . . . . . . . . . . . . . . 7
4. Architectural Assumptions . . . . . . . . . . . . . . . . . . 8
4.1 Harmful URIs and URLs . . . . . . . . . . . . . . . . . . 8
4.2 Valid Location URI Schemes or Types . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . 13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
This document creates a Dynamic Host Configuration Protocol (DHCP)
Option for transmitting a client's geolocation Uniform Resource
Identifier (URI) [RFC3986]. In this scenario, the DHCP client is a
Geopriv Target (i.e., the entity whose geolocation is associated
with the location URI). The DHCP implementation of the client can
then make this location information available to other applications
for their usage. This location URI points to a Location Server
[RFC5808] which has the geolocation of the client (e.g., previously
uploaded into a wiremap database then the client attaches to a known
wall-jack, or by means of 802.11 geolocation mechanisms).
Applications within the Target can then choose to dereference this
location URI and/or transmit the URI to another entity as a means of
conveying where the Target is located. Both Conveying and
Dereferencing a location URI is described in [RFC6442]. Session
Initiation Protocol (SIP) [RFC3261] is not the only protocol that
can dereference a location URI; there is also HTTP-Enabled Location
Delivery (HELD) [RFC6753] and HTTP [RFC2616].
A Location Server (LS) stores the Target's location as a presence
document, called a Presence Information Data Format - Location
Object (PIDF-LO), defined in RFC 4119 [RFC4119]. The Location Server
is the entity contacted during the act of dereferencing a Target's
location. If the dereferencing entity has permission, defined in
[RFC6772], the location of the target will be received. The LS
will grant permission to location inquiries based on the rules
established by a Rule Holder [RFC3693]. The LS has the ability to
challenge any request for a target's location, thereby providing
additive security properties before location revelation.
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Possessing a location URI has advantages over having a PIDF-LO,
especially when a target's location changes. With a location URI,
when a target moves, the location URI does not change (at least
within the same domain). The location URI can still be given out as
the reference to the Target's current location. The opposite is true
if the location is conveyed by value in a message. Once the Target
moves, the previously given location is no longer valid, and if the
Target wants to inform another entity about its location, it has to
send the PIDF-LO to the location recipient (again).
A problem exists within existing RFCs that provide location to the
UA ([RFC6225] and [RFC4776]). Those DHCP Options for geolocation
values require an update of the entire location information (LI)
every time a client moves. Not all clients will move frequently,
but some will. Refreshing location values every time a client moves
does not scale in certain networks/environments, such as IP-based
cellular networks, enterprise networks or service provider networks
with mobile endpoints. An 802.11 based access network is one
example of this. Constantly updating Location Configuration
Information (LCI) to endpoints might not scale in mobile
(residential or enterprise or municipal) networks in which the
client is moving through more than one network attachment point,
perhaps as a person walks or drives with their client down a
neighborhood street or apartment complex or a shopping center or
through a municipality (that has IP connectivity as a service).
If the client was provided a location URI reference to retain and
hand out when it wants or needs to convey its location (in a
protocol other than DHCP), a location URI that would not change as
the client's location changes (within a domain). Scaling issues
would be significantly reduced to needing an update of the location
URI only when a client changes administrative domains - which is
much less often. This delivery of an indirect location has the
added benefit of not using up valuable or limited bandwidth to the
client with the constant updates. It also relieves the client from
having to determine when it has moved far enough to consider asking
for a refresh of its location.
In enterprise networks, if a known location is assigned to each
individual Ethernet port in the network, a device that attaches to
the network, such as a wall-jack (directly associated with a
specific Ethernet Switch port) will be associated with a known
location via a unique circuit-ID that's used by the Relay Agent
Information Option (RAIO) defined in RFC 3046 [RFC3046]. This
assumes wall-jacks have an updated wiremap database. RFC 6225
[RFC6225] and RFC 4776 [RFC4776] would return an LCI value of
location for either IPv4 or IPv6. This document specifies how a
location URI is returned using DHCP. The location URI points to a
PIDF-LO contained on an LS. Performing a dereferencing transaction,
that Target's PIDF-LO will be returned. If local configuration has
the requirement of only assigning unique location URIs to each
client at the same attachment point to the network (i.e., same RJ-45
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jack or same 802.11 Access Point - except when triangulation is
used), then unique location URIs will be given out. They will all
have the same location at the record, relieving the backend Sighter
or LS from individually maintaining each location independently.
The location URI Option can be useful in IEEE 802.16e connected
endpoints or IP cellular endpoints. The location URI Option can be
configured on a router, such as a residential home gateway, such
that the router receives this Location URI Option as a client with
the ability to communicate to downstream endpoints as a server.
How an LS responds to a dereference request can vary, and a policy
established by a Ruleholder [RFC3693] for a Location Target as to
what type of challenge(s) is to be used, how strong a challenge is
used or how precise the location information is given to a
Location Recipient (LR). This document does not provide mechanisms
for the LS to tell the client about policies or for the client to
specify a policy for the LS. While an LS should apply an appropriate
access-control policy, clients must assume that the LS will provide
location in response to any request (following the possession model
[RFC5808]). For further discussion of privacy, see the Security
Considerations.
This document IANA-registers the new IPv4 and IPv6 DHCP Options for
a location URI and Valid-For.
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].
2. Format of the DHCP LocationURI Option
2.1 Overall Format of LocationURI Option in IPv4
The LocationURI Option format for IPv4 is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code XXX | Length=XX | Valid-For .....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
..... Valid-For (Cont'd) | LocationURI... .....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
..... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1. IPv4 Fields for this LocationURI Option
Code XXX: The code for this DHCPv4 option (IANA assigned).
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Length=XX: The length of this option, counted in bytes - not
counting the Code and Length bytes. This is a variable
length Option, therefore the length value will change
based on the length of the URI within the Option.
Valid-For: The time, in seconds, the LocationURI is to be
considered valid for dereferencing. The Valid-For is
always represented as a four-byte unsigned integer.
LocationURI: Location URI - This field, in bytes, is the URI
pointing at the location record where the PIDF-LO for
the Location Target resides. The LocationURI is always
represented in ASCII.
2.2 Overall Format of LocationURI Option in IPv6
The LocationURI Option format for IPv6 is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Valid-For |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LocationURI... .....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
..... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2. IPv6 fields of this LocationURI Option
option-code: The code for this DHCPv6 option (IANA assigned).
option-len: The length of this option, counted in bytes - not
counting the option-code and option-len bytes. This is
a variable length Option, therefore the length value
will change based on the length of the URI within the
Option.
Valid-For: see Section 2.1
LocationURI: see Section 2.1
2.3 Rules for the LocationURI Option
The LocationURI Option has the following rules:
o Implementation of the Location URI Option is REQUIRED on the DHCP
server and client.
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o Clients SHOULD be expected to have to request the Location URI
Option from servers. Although local policy can have servers
perform an unsolicited push of a Location URI Option to a client.
Applications on a client can use the Location URI (value) until the
Valid-For value reaches zero. If there is no Valid-For Option value,
then the counter did not ever start (a null value), and applications
on a client continue to use the Location URI value until given a new
Location URI Option (with or without a Valid-For value) which
overwrites any previous Location URI and Valid-For Option values.
o A Location URI Option with a non-zero Valid-For field MUST NOT
transmit the Location URI once the Valid-For field counts down to
zero.
o A received Location URI Option containing all zeros in the
Valid-For field means that Location URI has no lifetime, and not
"no lifetime left". All zeros in the Valid-For field equates to a
null value.
o Receipt of the Location URI Option containing all zeros in the
Valid-For field MUST NOT cause any error in handling the Location
URI.
o When the Valid-For timer reaches zero, the client MUST purge any
location URI received via DHCP from its memory.
The choice of the Valid-For value is a policy decision for the
operator of the DHCP server. Like location URIs themselves, it can
be statically configured on the DHCP server or provisioned
dynamically (via an out-of-band exchange with a Location Information
Server) as requests for location URIs are received.
o Clients receiving a Location URI Option start the Valid-For timer
upon receipt of the DHCP message containing the Option.
o Clients MUST NOT trigger an automatic DHCP refresh on expiry of
the Valid-For timer; rather, they MUST follow normal DHCP
mechanics.
If the Valid-For timer is set to expire before the lease refresh,
the client will not have the ability to hand out its location until
the lease refresh, inadvertently allowing a gap of coverage. If the
Valid-For timer is set to expire after the lease refresh, some
wayward application on the client can divulge that location URI
after it is no longer valid, meaning the location could be stale or
just plain wrong.
o Servers SHOULD set the Valid-For timer to that of the lease
refresh, or bad things can happen.
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3. DHCP Option Operation
The [RFC3046] RAIO can be utilized to provide the appropriate
indication to the DHCP Server where this DISCOVER or REQUEST message
came from, in order to supply the correct response.
Caution SHOULD always be used involving the creation of large
Options, meaning that this Option may need to be in its own INFORM,
OPTION or ACK message. DHCP messages are limited in size, and long
URIs will require the use of multiple messages and concatenation
[RFC3396]. It is, therefore, best to limit the total length of a
URI, including any parameters, to 220 bytes.
Location URIs MUST NOT reveal identity information of the user of
the device, since DHCP is a cleartext delivery protocol. For
example, creating a location URI such as
sips:34LKJH534663J54@example.com
is better than a location URI such as
sips:aliceisat123mainstatlantageorgiaus@example.com
The username portion of the first example URI provides no direct
identity information (in which 34LKJH534663J54 is considered to be a
random number in this example).
In the <presence> element of a PIDF-LO document, there is an
'entity' attribute that identifies what entity *this* presence
document (including the associated location) refers to. It is up to
the PIDF-LO generator, either Location Server or an application in
the endpoint, to insert the identity in the 'entity' attribute.
This can be seen in [RFC4119]. The considerations for populating
the entity attribute value in a PIDF-LO document are independent
from the considerations for avoiding exposing identification
information in the username part of a location URI.
This Option is used only for communications between a DHCP client
and a DHCP server. It can be solicited (requested) by the client,
or it can be pushed by the server without a request for it. DHCP
Options not understood MUST be ignored [RFC2131]. A DHCP server
supporting this Option might or might not have the location of a
client. If a server does not have a client's location, but needs to
provide this Location URI Option to a client (for whatever reason),
an LS is contacted. This server-to-LS transaction is not DHCP,
therefore it is out of scope of this document. Note that this
server-to-LS transaction could delay the DHCP messaging to the
client. If the server fails to have location before it transmits its
message to the client, location will not be part of that DHCP
message. Any timers involved here are a matter of local
configuration.
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The dereference of a target's location URI would not involve DHCP,
but an application layer protocol, such as SIP or HTTP, therefore
dereferencing is out of scope of this document.
In the case of residential gateways being DHCP servers, they usually
perform as DHCP clients in a hierarchical fashion up into a service
provider's network DHCP server(s), or learn what information to
provide via DHCP to residential clients through a protocol, such as
PPP. In these cases, the location URI would likely indicate the
residence's civic address to all wired or wireless clients within
that residence.
4. Architectural Assumptions
The following assumptions are made once the client has obtained a
location URI, and not about DHCP operation specifics (in no
particular order):
o Any user control (what [RFC3693] calls a 'Ruleholder') for access
to the dereferencing step is assumed to be out of scope of this
document. An example authorization policy is in [RFC6772].
o The authorization security model vs. possession security model
discussion can be found in [RFC5606], describing what is expected
in each model of operation. It should be assumed that a location
URI attained using DHCP will operate under a possession model by
default. An authorization model can be instituted as a matter of
local policy. An authorization model means possessing the
location URI does not give that entity the right to view the
PIDF-LO of the target whose location is indicated in a presence
document. The dereference transaction will be challenged by the
Location Server only in an authorization model. The nature of
this challenge is out of scope of this document.
o This document does not prevent some environments from operating
in an authorization model, for example - in less tightly
controlled networks. The costs associated with authorization vs.
possession models are discussed in Section 3.3.2 of [RFC5606].
4.1 Harmful URIs and URLs
There are, in fact, some types of URIs that are not good to receive,
due to security concerns. For example, any URLs that can have
scripts, such as "data:" URLs, and some "HTTP:" URLs that go to web
pages that have scripts. Therefore,
o URIs received via this Option SHOULD NOT be automatically sent to
a general-browser to connect to a web page, because they could
have harmful scripts, unless
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o the browser has been set up to defend against harmful scripts,
or
o the browser does not run scripts automatically.
o This Option MUST NOT contain "data:" URLs [RFC2397], because they
could contain harmful scripts.
4.2 Valid Location URI Schemes or Types
URIs carried by this DHCP Option MUST have one of the following URI
schemes:
1. sip:
2. sips:
3. pres:
4. http:
5. https:
URIs using the "pres" scheme are dereferenced using the presence
event package for SIP [RFC3856], so they will reference a PIDF-LO
document when location is available. Responses to requests for URIs
with other schemes ("sip", "sips", "http", and "https") MUST have
media type 'application/pidf+xml'[RFC4119]. Alternatively, HTTP and
HTTPS URIs MAY refer to information with media type
'application/held+xml', in order to support HELD dereferencing
[RFC6753]. Clients can indicate which media types they support
using the "Accept" header field in SIP [RFC3261] or HTTP [RFC2616].
See RFC 3922 [RFC3922] for using the "pres:" URI with XMPP.
It is RECOMMENDED that implementers follow Section 4.6 of RFC 6442
[RFC6442] as guidance regarding which Location URI schemes to
provide in DHCP. That document discusses what a receiving entity
does when receiving a URI scheme that is not understood. Awareness
to the two URI types there is important for conveying location, if
SIP is used to convey a Location URI provided by DHCP.
5. IANA Considerations
5.1 The IPv4 Option number for the Location URI Option
This document IANA registers the DHCP Location URI Option Number in
the BOOTP Vendor Extensions and DHCP Options subregistry of the
Dynamic Host Configuration Protocol (DHCP) and Bootstrap Protocol
(BOOTP) Parameters registry located.
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Data
Tag Name Length Meaning Reference
---- ---- ------ ------- ---------
XXX LocationURI N GeoLocation URI [this document]
The authors have no preference at this time on what number IANA
chooses.
5.2 The IPv6 Option-Code for the Location URI Option
This document IANA registers the DHCPv6 Option Code in the DHCP
Option Codes subregistry of the Dynamic Host Configuration Protocol
for IPv6 (DHCPv6) registry.
Value Description Reference
---- ------------------ ----------
XX OPTION_GEOLOCATION_URI [this document]
The authors have no preference at this time on what number IANA
chooses.
5.3 Valid Location URI Schemes
This document creates a new IANA registry (Valid Location URI
Schemes) of acceptable location URI schemes (or types) for this DHCP
Location URI Option of the Dynamic Host Configuration Protocol
(DHCP) and Bootstrap Protocol (BOOTP) Parameters registry.
Initial values are given below; new assignments are to be made
following the "IETF Review" policies [RFC5226].
"Valid Location URI Schemes"
Location
URI Scheme Reference
---------- ---------
sip: [this document]
sips: [this document]
pres: [this document]
http: [this document]
https: [this document]
6. Security Considerations
Where critical decisions might be based on the value of this
location URI option, DHCP authentication as defined in
"Authentication for DHCP Messages" [RFC3118] and "Dynamic Host
Configuration Protocol for IPv6 (DHCPv6)" [RFC3315] SHOULD be used
to protect the integrity of the DHCP options.
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A real concern with RFC 3118 or RFC 3315 is that neither is widely
deployed because each requires pre-shared keys to successfully work
(i.e., in the client and in the server). Most implementations do
not accommodate this.
DHCP, initially, is a broadcast request (a client looking for a
server), and a unicast response (answer from a server) type of
protocol. There is no privacy protection for DHCP messages, an
eavesdropper who can monitor the link between the DHCP server and
requesting client can discover the Location URI.
Once a client has a Location URI, it needs information on how the
location server will control access to dereference requests. A
client might treat a tightly access-controlled URI differently from
one that can be dereferenced by anyone on the Internet (i.e., one
following the "possession model"). Since the client does not know
what policy will be applied during this validity interval, clients
MUST handle location URIs as if they could be dereferenced by
anybody until they expire. For example, such open location URIs
should only be transmitted in encrypted channels. Nonetheless,
location servers SHOULD apply appropriate access control policies,
for example by limiting the number of queries that any given client
can make, or limiting access to users within an enterprise.
Extensions to this option, such as [ID-POLICY-URI] can provide
mechanisms for accessing and provisioning policy. Giving users
access to policy information will allow them to make more informed
decisions about how to use their location URIs. Allowing users to
provide policy information to the LS will enable them to tailor
access control policies to their needs (within the bounds of policy
that the LS will accept).
As to the concerns about the location URI itself, as stated in the
document (see Section 3), it MUST NOT have any user identifying
information in the URI user-part/string itself. The location URI
also needs to be hard to guess that it belongs to a specific user.
In some cases a DHCP server may be implemented across an
uncontrolled network. In those cases, it would be appropriate for a
network administrator to perform a threat analysis (see RFC 3552)
and take precautions as needed.
Link-layer confidentiality and integrity protection may also be
employed to reduce the risk of location disclosure and tampering.
7. Acknowledgements
Thanks to James Winterbottom, Marc Linsner, Roger Marshall and
Robert Sparks for their useful comments. And to Lisa Dusseault for
her concerns about the types of URIs that can cause harm. To
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Richard Barnes for inspiring a more robust Security Considerations
section, and for offering the text to incorporate HTTP URIs. To
Hannes Tschofenig and Ted Hardie for riding me to comply with their
concerns, including a good scrubbing of the nearly final doc.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option", RFC
3046, January 2001.
[RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP
Messages", RFC 3118, June 2001.
[RFC3315] R. Droms, Ed., J. Bound, B. Volz, T. Lemon, C. Perkins, M.
Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003
[RFC3261] J. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J.
Peterson, R. Sparks, M. Handley, and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, May 2002.
[RFC3396] T. Lemon, S. Cheshire, "Encoding Long Options in the Dynamic
Host Configuration Protocol (DHCPv4)", RFC 3396, November
2002
[RFC3856] J. Rosenberg, "A Presence Event Package for the Session
Initiation Protocol (SIP)", RFC 3856, August 2004
[RFC3922] P. Saint-Andre, " Mapping the Extensible Messaging and
Presence Protocol (XMPP) to Common Presence and Instant
Messaging (CPIM)", RFC 3922, October 2004
[RFC3986] T. Berners-Lee, R. Fielding, L. Masinter, "Uniform Resource
Identifier (URI): Generic Syntax", RFC 3986, January 2005
[RFC4119] J. Peterson, "A Presence-based GEOPRIV Location Object
Format", RFC 4119, December 2005
[RFC5226] T. Narten, H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", RFC 5226, May 2008
[RFC6442] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance
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for the Session Initiation Protocol", RFC 6442, December
2011.
[RFC6753] J. Winterbottom, H. Tschofenig, H. Schulzrinne, M. Thomson,
M. Dawson, "A Location Dereferencing Protocol Using HELD",
October 2012
8.2. Informative References
[RFC2397] L. Masinter, "The "data" URL scheme", RFC 2397, August 1998
[RFC2616] R. Fielding, J. Gettys, J., Mogul, H. Frystyk, L.,
Masinter, P. Leach, T. Berners-Lee, "Hypertext Transfer
Protocol - HTTP/1.1", RFC 2616, June 1999
[RFC3693] J. Cuellar, J. Morris, D. Mulligan, J. Peterson. J. Polk,
"Geopriv Requirements", RFC 3693, February 2004
[RFC6225] Polk, J., Linsner, M., Thomson, M., and B. Aboba,
"Dynamic Host Configuration Protocol Options for
Coordinate-Based Location Configuration Information",
RFC 6225, July 2011.
[RFC4776] H. Schulzrinne, "Dynamic Host Configuration Protocol
(DHCPv4 and DHCPv6) Option for Civic Addresses Configuration
Information ", RFC 4776, November 2006
[RFC5606] J. Peterson, T. Hardie, J. Morris, "Implications of
'retransmission-allowed' for SIP Location Conveyance",
August 2009
[RFC5808] R. Marshall, "Requirements for a Location-by-Reference
Mechanism", RFC 5808, May 2010
[RFC6772] H. Schulzrinne, H. Tschofenig, J. Morris, J. Cuellar, J.
Polk, "Geolocation Policy: A Document Format for Expressing
Privacy Preferences for Location Information", January 2013
[ID-POLICY-URI] R. Barnes, M. Thomson, J. Winterbottom, "Location
Configuration Extensions for Policy Management", "work in
progress", November 2011
Authors' Address
James Polk
3913 Treemont Circle
Colleyville, Texas 76034
USA
Email: jmpolk@cisco.com
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