Network Working Group H. Tschofenig
Request for Comments: 5687 Nokia Siemens Networks
Category: Informational H. Schulzrinne
Columbia University
January 2010
GEOPRIV Layer 7 Location Configuration Protocol:
Problem Statement and Requirements
Abstract
This document provides a problem statement, lists requirements, and
captures design aspects for a GEOPRIV Layer 7 (L7) Location
Configuration Protocol (LCP). This protocol aims to allow an end
host to obtain location information, by value or by reference, from a
Location Information Server (LIS) that is located in the access
network. The obtained location information can then be used for a
variety of different protocols and purposes. For example, it can be
used as input to the Location-to-Service Translation (LoST) Protocol
or to convey location within SIP to other entities.
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Fixed-Wired Environment . . . . . . . . . . . . . . . . . 3
3.2. Moving Network . . . . . . . . . . . . . . . . . . . . . . 6
3.3. Wireless Access . . . . . . . . . . . . . . . . . . . . . 7
4. Discovery of the Location Information Server . . . . . . . . . 8
5. Identifier for Location Determination . . . . . . . . . . . . 10
6. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 13
7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 15
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . . 17
10.2. Informative References . . . . . . . . . . . . . . . . . . 17
1. Introduction
This document provides a problem statement, lists requirements, and
captures design aspects for a GEOPRIV Layer 7 (L7) Location
Configuration Protocol (LCP). The protocol has two purposes:
o It is used by a Device to obtain its own location (referred as
"Location by Value" or LbyV) from a dedicated node, called the
Location Information Server (LIS).
o It enables the Device to obtain a reference to location
information (referred as "Location by Reference" or LbyR). This
reference can take the form of a subscription URI, such as a SIP
presence-based Uniform Resource Identifier (URI), an HTTP/HTTPS
URI, or another URI. The requirements related to the task of
obtaining an LbyR are described in a separate document, see
[LBYR-REQS].
The need for these two functions can be derived from the scenarios
presented in Section 3.
For this document, we assume that the GEOPRIV Layer 7 LCP runs
between the Device and the LIS.
This document is structured as follows. Section 4 discusses the
challenge of discovering the LIS in the access network. Section 5
compares different types of identifiers that can be used to retrieve
location information. A list of requirements for the L7 LCP can be
found in Section 6.
This document does not describe how the access network provider
determines the location of the Device since this is largely a matter
of the capabilities of specific link-layer technologies or certain
deployment environments.
2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in RFC 2119
[RFC2119], with the qualification that unless otherwise stated these
words apply to the design of the GEOPRIV Layer 7 Location
Configuration Protocol.
The term Location Information Server (LIS) refers to an entity
capable of determining the location of a Device and of providing that
location information, a reference to it, or both via the Location
Configuration Protocol (LCP) to the Target.
This document also uses terminology from [RFC3693] (such as Target)
and [RFC5012] (such as Internet
Access Provider (IAP), Internet Service Provider (ISP), and
Application Service Provider (ASP)).
With the term "Access Network Provider" we refer to the IAP and the
ISP) without further distinguishing these two entities, as it is not
relevant for the purpose of this document. An additional
requirements document on LIS-to-LIS [LIS2LIS] shows a scenario where
the separation between IAP and ISP is important.
3. Scenarios
This section describes a few network scenarios where the L7 LCP may
be used. Note that this section does not aim to exhaustively list
all possible deployment environments. Instead, we focus on the
following environments:
o DSL/Cable networks, WiMAX-like (Worldwide Interoperability for
Microwave Access) fixed access
o Airport, City, Campus Wireless Networks, such as 802.11a/b/g,
802.16e/WiMAX
o 3G networks
o Enterprise networks
Note that we use the term 'host' instead of Device for better
readability.
3.1. Fixed-Wired Environment
Figure 1 shows a Digital Subscriber Line (DSL) network scenario with
the Access Network Provider and the customer premises. The Access
Network Provider operates link- and network-layer devices
(represented as a Node) and the LIS.
+---------------------------+
| |
| Access Network Provider |
| |
| +--------+ |
| | Node | |
| +--------+ +----------+ |
| | | | LIS | |
| | +---| | |
| | +----------+ |
| | |
+-------+-------------------+
| Wired Network
<----------------> Access Network Provider demarc
|
+-------+-------------------+
| | |
| +-------------+ |
| | NTE | |
| +-------------+ |
| | |
| | |
| +--------------+ |
| | Device with | Home |
| | NAPT and | Router |
| | DHCP server | |
| +--------------+ |
| | |
| | |
| +------+ |
| | Host | |
| +------+ |
| |
|Customer Premises Network |
| |
+---------------------------+
Figure 1: Fixed-Wired Scenario
The customer premises consists of a router with a Network Address
Translator with Port Address Translation (NAPT) and a DHCP server as
used in most Customer Premises Networks (CPNs) and the Network
Termination Equipment (NTE) where Layer 1 and sometimes Layer 2
protocols are terminated. The router in the home network (e.g.,
broadband router, cable or DSL router) typically runs a NAPT and a
DHCP server. The NTE is a legacy device and in many cases cannot be
modified for the purpose of delivering location information to the
host. The same is true of the device with the NAPT and DHCP server.
It is possible for the NTE and the home router to physically be in
the same box, or for there to be no home router, or for the NTE and
host to be in the same physical box (with no home router). An
example of this last case is where Ethernet service is delivered to
customers' homes, and the Ethernet network interface card (NIC) in
their PC serves as the NTE.
Current CPN deployments generally fall into one of the following
classifications:
1. Single PC
1. with Ethernet network interface card (NIC), with Point-to-
Point Protocol Over Ethernet (PPPoE), or Dynamic Host
Configuration Protocol (DHCP) on PC; there may be a bridged
DSL or cable modem as the NTE, or the Ethernet NIC might be
the NTE.
2. with USB-based DSL access or a cable modem access using
Point-to-Point Protocol over ATM (PPPoA), PPPoE, or DHCP on
PC.
Note that the device with NAPT and DHCP of Figure 1 is not
present in such a scenario.
2. One or more hosts with at least one router (DHCP Client or PPPoE,
DHCP server in router; Voice over IP (VoIP) can be a soft client
on a PC, a stand-alone VoIP device, or an Analog Terminal Adaptor
(ATA) function embedded in a router):
1. combined router and NTE.
2. separate router with NTE in bridged mode.
3. separate router with NTE (NTE/router does PPPoE or DHCP to
WAN, router provides DHCP server for hosts in LAN; double
NAT).
The majority of fixed-access broadband customers use a router. The
placement of the VoIP client is mentioned to describe what sorts of
hosts may need to be able to request location information. Soft
clients on PCs are frequently not launched until long after
bootstrapping is complete, and are not able to control any options
that may be specified during bootstrapping. They also cannot control
whether a VPN client is running on the end host.
3.2. Moving Network
One example of a moving network is a WiMAX-fixed wireless scenario.
This also applies to "pre-WiMAX" and "WiMAX-like" fixed wireless
networks. In implementations intended to provide broadband service
to a home or other stationary location, the customer-side antenna/NTE
tends to be rather small and portable. The LAN-side output of this
device is an Ethernet jack, which can be used to feed a PC or a
router. The PC or router then uses DHCP or PPPoE to connect to the
access network, the same as for wired access networks. Access
providers who deploy this technology may use the same core network
(including network elements that terminate PPPoE and provide IP
addresses) for DSL, fiber to the premises (FTTP), and fixed wireless
customers.
Given that the customer antenna is portable and can be battery-
powered, it is possible for a user to connect a laptop to it and move
within the coverage area of a single base antenna. This coverage
area can be many square kilometers in size. In this case, the laptop
(and any SIP client running on it) would be completely unaware of
their mobility. Only the user and the network are aware of the
laptop's mobility.
Further examples of moving networks (where end devices may not be
aware that they are moving) can be found in busses, trains, and
airplanes.
Figure 2 shows an example topology for a moving network.
+--------------------------+
| Wireless |
| Access Network Provider |
| |
| +----------+|
| +-------+ LIS ||
| | | ||
| +---+----+ +----------+|
| | Node | |
| | | |
| +---+----+ |
| | |
+------+-------------------+
| Wireless Interface
|
+------+-------------------+
| | Moving Network |
| +---+----+ |
| | NTE | +--------+ |
| | +---+ Host | |
| +-+-----++ | B | |
| | \ +--------+ |
| | \ |
|+---+----+ \ +---+----+ |
|| Host | \ | Host | |
|| A | \+ B | |
|+--------+ +--------+ |
+--------------------------+
Figure 2: Moving Network
3.3. Wireless Access
Figure 3 shows a wireless access network where a moving host obtains
location information or references to location information from the
LIS. The access equipment uses, in many cases, link-layer devices.
Figure 3 represents a hotspot network found, for example, in hotels,
airports, and coffee shops. For editorial reasons we only describe a
single access point and do not depict how the LIS obtains location
information since this is very deployment specific.
+--------------------------+
| Access Network Provider |
| |
| +----------+|
| +-------| LIS ||
| | | ||
| +--------+ +----------+|
| | Access | |
| | Point | |
| +--------+ |
| | |
+------+-------------------+
|
+------+
| Host |
+------+
Figure 3: Wireless Access Scenario
4. Discovery of the Location Information Server
Note that this section lists mechanisms that were discussed in the
GEOPRIV Layer 7 Location Configuration Protocol design team. They
are included to show challenges in the problem space and are
listed for completeness reasons. They do not in any way mean that
there is consensus about any of the mechanisms or that the IETF
recommends any of the procedures described in this section.
When a Device wants to retrieve location information from the LIS, it
first needs to discover it. Based on the problem statement of
determining the location of the Device, which is known best by
entities close to the Device itself, we assume that the LIS is
located in the local subnet or in the access network. Several
procedures have been investigated that aim to discover the LIS in
such an access network.
DHCP-based Discovery:
In some environments, the Dynamic Host Configuration Protocol
(DHCP) might be a good choice for discovering the fully-qualified
domain name (FQDN) or the IP address of the LIS. In environments
where DHCP can be used, it is also possible to use the already
defined location extensions. In environments with legacy devices,
such as the one shown in Section 3.1, a DHCP-based discovery
solution may not be possible.
DNS-based Discovery:
Before a Domain Name System (DNS) lookup can be started, it is
necessary to learn the domain name of the access network that runs
an LIS. Several ways to learn the domain name exist. For
example, the end host obtains its own public IP address, for
example, address via Simple
Traversal of the UDP Protocol through NAT (STUN) [RFC5389], and
performs a reverse DNS lookup (assuming the data is provisioned
into the DNS). Then, the DNS Service (SRV) record or the DNS
Naming Authority Pointer (NAPTR) record for that domain is
retrieved. A more detailed description of this approach can be
found in [LIS-DISC].
Redirect Rule:
A redirect rule at an entity in the access network could be used
to redirect the L7 LCP signaling messages (destined to a specific
port) to the LIS. The Device could then discover the LIS by
sending a packet with a specific (registered) port number to
almost any address (as long as the destination IP address does not
target an entity in the local network). The packet would be
redirected to the respective LIS being configured. The same
procedure is used by captive portals whereby any HTTP traffic is
intercepted and redirected.
To some extent, this approach is similar to packets that are
marked with a Router Alert option [RFC2113] and intercepted by
entities that understand the specific marking. In the above-
mentioned case, however, the marking is provided via a registered
port number instead of relying on a Router Alert option.
This solution approach would require a deep packet inspection
capability at an entity in the access provider's networks that
scans for the occurrence of particular destination port numbers.
Multicast Query:
A Device could also discover an LIS by sending a DNS query to a
well-known address. An example of such a mechanism is multicast
DNS (see [RFC4795] and [mDNS]). Unfortunately, these mechanisms
only work on the local link.
Anycast:
With this solution, an anycast address is defined (for IPv4 and
IPv6) in the style of [RFC3068] that allows the Device to route
discovery packets to the nearest LIS. Note that this procedure
would be used purely for discovery and is therefore similar to the
local Teredo server discovery approach outlined in Section 4.2 of
[TEREDO-SEL].
The LIS discovery procedure raises deployment and security issues.
The access network needs to be designed to prevent man-in-the-middle
adversaries from presenting themselves as an LIS to Devices. When a
Device discovers an LIS, it needs to ensure (and be able to ensure)
that the discovered entity is indeed an authorized LIS.
5. Identifier for Location Determination
Note that this section lists mechanisms that were discussed in the
GEOPRIV Layer 7 Location Configuration Protocol design team. They
are included to show challenges in the problem space and are
listed for completeness reasons. They do not in any way mean that
there is consensus about any of the mechanisms or that the IETF
recommends any of the procedures described in this section.
The LIS returns location information to the Device when it receives a
request. Some form of identifier is therefore needed to allow the
LIS to retrieve the Device's current location (or a good
approximation of it) from a database.
The chosen identifier needs to have the following properties:
Ability for Device to learn or know the identifier:
The Device MUST know or MUST be able to learn of the identifier
(explicitly or implicitly) in order to send it to the LIS.
Implicitly refers to the situation where a device along the path
between the Device and the LIS modifies the identifier, as it is
done by a NAT when an IP address based identifier is used.
Ability to use the identifier for location determination:
The LIS MUST be able to use the identifier (directly or
indirectly) for location determination. Indirectly refers to the
case where the LIS uses other identifiers internally for location
determination, in addition to the one provided by the Device.
Security properties of the identifier:
Misuse needs to be minimized whereby an off-path adversary MUST
NOT be able to obtain location information of other Devices. An
on-path adversary in the same subnet SHOULD NOT be able to spoof
the identifier of another Device in the same subnet.
The following list discusses frequently mentioned identifiers and
their properties:
Media Access Control (MAC) Address:
The MAC address is known to the Device itself, but not carried
over an IP hop and therefore not accessible to the LIS in most
deployment environments (unless carried in the L7 LCP itself).
Asynchronous Transfer Mode (ATM) Virtual Path Identifier / Virtual
Circuit Identifier (VPI/VCI):
The VCI/VPI is generally only seen by the DSL modem. Almost all
routers in the United States use 1 of 2 VPI/VCI value pairs: 0/35
and 8/35. This VC is terminated at the digital subscriber line
access multiplexer (DSLAM), which uses a different VPI/VCI (per
end customer) to connect to the ATM switch. Only the network
provider is able to map VPI/VCI values through its network. With
the arrival of Very high rate Digital Subscriber Line (VDSL), ATM
will slowly be phased out in favor of the Ethernet.
Ethernet Switch (Bridge)/Port Number:
This identifier is available only in certain networks, such as
enterprise networks, typically available via the IEEE 802.1AB
protocol [802.1AB] or proprietary protocols like the Cisco
Discovery Protocol (CDP) [CDP].
Cell ID:
This identifier is available in cellular data networks and the
cell ID may not be visible to the Device.
Host Identifier:
The Host Identifier introduced by the Host Identity Protocol (HIP)
[RFC5201] allows identification of a particular host.
Unfortunately, the network can only use this identifier for
location determination if the operator already stores a mapping of
host identities to location information. Furthermore, there is a
deployment problem since the host identities are not used in
today's networks.
Cryptographically Generated Address (CGA):
The concept of a Cryptographically Generated Address (CGA) was
introduced by [RFC3972]. The basic idea is to put the truncated
hash of a public key into the interface identifier part of an IPv6
address. In addition to the properties of an IP address, it
allows a proof of ownership. Hence, a return routability check
can be omitted. It is only available for IPv6 addresses.
Network Access Identifiers:
A Network Access Identifier [RFC4282] is used during the network
access authentication procedure, for example, in RADIUS [RFC2865]
and Diameter [RFC3588]. In DSL networks, the user credentials
are, in many cases, only known by the home router and not
configured at the Device itself. To the network, the
authenticated user identity is only available if a network access
authentication procedure is executed. In case of roaming, the
user's identity might not be available to the access network since
security protocols might offer user identity confidentiality and
thereby hide the real identity of the user allowing the access
network to only see a pseudonym or a randomized string.
Unique Client Identifier
The Broadband Forum has defined that all devices that expect to be
managed by the TR-069 interface, see [TR069], have to be able to
generate an identifier that uniquely identifies the device. It
also has a requirement that routers that use DHCP to the WAN use
RFC 4361 [RFC4361] to provide the DHCP server with a unique client
identifier. This identifier is, however, not visible to the
Device when legacy NTE devices are used.
IP Address:
The Device's IP address may be used for location determination.
This IP address is not visible to the LIS if the Device is behind
one or multiple NATs. This may not be a problem since the
location of a Device that is located behind a NAT cannot be
determined by the access network. The LIS would in this case only
see the public IP address of the NAT binding allocated by the NAT,
which is the expected behavior. The property of the IP address
for a return routability check is attractive to return location
information only to the address that submitted the request. If an
adversary wants to learn the location of a Device (as identified
by a particular IP address), then it does not see the response
message (unless he is on the subnetwork or at a router along the
path towards the LIS).
On a shared medium, an adversary could ask for location
information of another Device. The adversary would be able to see
the response message since it is sniffing on the shared medium
unless security mechanisms, such as link-layer encryption, are in
place. With a network deployment as shown in Section 3.1 with
multiple Devices in the Customer Premises being behind a NAT, the
LIS is unable to differentiate the individual Devices. For WLAN
deployments as found in hotels, as shown in Section 3.3, it is
possible for an adversary to eavesdrop data traffic and
subsequently to spoof the IP address in a query to the LIS to
learn more detailed location information (e.g., specific room
numbers). Such an attack might, for example, compromise the
privacy of hotel guests.
6. Requirements
The following requirements and assumptions have been identified:
Requirement L7-1: Identifier Choice
The L7 LCP MUST be able to carry different identifiers or MUST
define an identifier that is mandatory to implement. Regarding
the latter aspect, such an identifier is only appropriate if it is
from the same realm as the one for which the location information
service maintains identifier-to-location mapping.
Requirement L7-2: Mobility Support
The L7 LCP MUST support a broad range of mobility from devices
that can only move between reboots, to devices that can change
attachment points with the impact that their IP address is
changed, to devices that do not change their IP address while
roaming, to devices that continuously move by being attached to
the same network attachment point.
Requirement L7-3: ASP and Access Network Provider Relationship
The design of the L7 LCP MUST NOT assume a business or trust
relationship between the Application Service Provider (ASP) and
the Access Network Provider. Requirements for resolving a
reference to location information are not discussed in this
document.
Requirement L7-4: Layer 2 and Layer 3 Provider Relationship
The design of the L7 LCP MUST assume that there is a trust and
business relationship between the L2 and the L3 provider. The L3
provider operates the LIS that the Device queries. It, in turn,
needs to obtain location information from the L2 provider since
this one is closest to the Device. If the L2 and L3 provider for
the same Device are different entities, they cooperate for the
purposes needed to determine locations.
Requirement L7-5: Legacy Device Considerations
The design of the L7 LCP MUST consider legacy devices, such as
residential NAT devices and NTEs in a DSL environment, that cannot
be upgraded to support additional protocols, for example, to pass
additional information towards the Device.
Requirement L7-6: Virtual Private Network (VPN) Awareness
The design of the L7 LCP MUST assume that at least one end of a
VPN is aware of the VPN functionality. In an enterprise scenario,
the enterprise side will provide the LIS used by the Device and
can thereby detect whether the LIS request was initiated through a
VPN tunnel.
Requirement L7-7: Network Access Authentication
The design of the L7 LCP MUST NOT assume prior network access
authentication.
Requirement L7-8: Network Topology Unawareness
The design of the L7 LCP MUST NOT assume Devices being aware of
the access network topology. Devices are, however, able to
determine their public IP address(es) via mechanisms, such as
Simple Traversal of User Datagram Protocol (UDP) Through Network
Address Translators (NATs) (STUN) [RFC5389] or Next Steps in
Signaling (NSIS) NAT/Firewall NSIS Signaling Layer Protocol (NSLP)
[NSLP] .
Requirement L7-9: Discovery Mechanism
The L7 LCP MUST define a mandatory-to-implement LIS discovery
mechanism.
Requirement L7-10: PIDF-LO Creation
When an LIS creates a Presence Information Data Format (PIDF)
Location Object (LO) [RFC4119], then it MUST put the <geopriv>
element into the <device> element of the presence document (see
[RFC4479]). This ensures that the resulting PIDF-LO document,
which is subsequently distributed to other entities, conforms to
the rules outlined in [RFC5491].
7. Security Considerations
By using a Geolocation L7 Location Configuration Protocol, the Device
(and consequently the Target that will in many cases be the a human user of such a Device) device, if applicable) exposes themselves
to a privacy risk whereby an unauthorized entity receives location
information. Providing confidentiality protected location to the
requestor depends on the success of four steps:
1. The client MUST have a means to discover a LIS.
2. The client MUST authenticate the discovered LIS.
3. The LIS MUST be able to determine location and return it to the
authorized entity.
4. The LIS MUST securely exchange messages without intermediaries
eavesdropping or tampering with them.
This document contains various security-related requirements
throughout the document addressing the above-mentioned steps. For a
broader security discussion of the overall geolocation privacy
architecture, the reader is referred to [GEOPRIV-ARCH].
8. Contributors
This contribution is a joint effort of the GEOPRIV Layer 7 Location
Configuration Requirements Design Team of the IETF GEOPRIV Working
Group. The contributors include Henning Schulzrinne, Barbara Stark,
Marc Linsner, Andrew Newton, James Winterbottom, Martin Thomson,
Rohan Mahy, Brian Rosen, Jon Peterson, and Hannes Tschofenig.
We would like to thank the GEOPRIV Working Group Chairs, Andy Newton,
Randy Gellens, and Allison Mankin, for creating the design team.
Furthermore, we would like thank Andy Newton for his support during
the design team mailing list, for setting up Jabber chat conferences,
and for participating in the phone conference discussions.
The design team members can be reached at:
Marc Linsner: mlinsner@cisco.com
Rohan Mahy: rohan@ekabal.com
Andrew Newton: andy@hxr.us
Jon Peterson: jon.peterson@neustar.biz
Brian Rosen: br@brianrosen.net
Henning Schulzrinne: hgs@cs.columbia.edu
Barbara Stark: Barbara.Stark@bellsouth.com
Martin Thomson: Martin.Thomson@andrew.com
Hannes Tschofenig: Hannes.Tschofenig@nsn.com
James Winterbottom: James.Winterbottom@andrew.com
9. Acknowledgements
We would also like to thank Murugaraj Shanmugam, Ted Hardie, Martin
Dawson, Richard Barnes, James Winterbottom, Tom Taylor, Otmar Lendl,
Marc Linsner, Brian Rosen, Roger Marshall, Guy Caron, Doug Stuard,
Eric Arolick, Dan Romascanu, Jerome Grenier, Martin Thomson, Barbara
Stark, Michael Haberler, and Mary Barnes for their WGLC review
comments.
The authors would like to thank NENA for their work on [NENA] as it
helped to provide some of the initial thinking.
The authors would also like to thank Cullen Jennings for his feedback
as part of the IESG processing. Additionally, we would like to thank
Alexey Melnikov, Dan Romascanu, and Robert Sparks.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J.,
and J. Polk, "Geopriv Requirements", RFC 3693,
February 2004.
[RFC5012] Schulzrinne, H. and R. Marshall, "Requirements for
Emergency Context Resolution with Internet
Technologies", RFC 5012, January 2008.
10.2. Informative References
[802.1AB] "IEEE 802.1AB-2005 IEEE Standard for Local and
Metropolitan Area Networks Station and Media Access
Control Connectivity Discovery", May 2005, <http://
standards.ieee.org/getieee802/download/
802.1AB-2005.pdf>.
[CDP] Wikipedia, "Cisco Discovery Protocol (CDP)", <http://
en.wikipedia.org/wiki/Cisco_Discovery_Protocol>.
[GEOPRIV-ARCH] Barnes, R., Lepinski, M., Cooper, A., Morris, J.,
Tschofenig, H., and H. Schulzrinne, "An Architecture
for Location and Location Privacy in Internet
Applications", Work in Progress, July 2009.
[LBYR-REQS] Marshall, R., "Requirements for a Location-by-
Reference Mechanism", Work in Progress,
September 2009.
[LIS-DISC] Thomson, M. and J. Winterbottom, "Discovering the
Local Location Information Server (LIS)", Work
in Progress, September 2007.
[LIS2LIS] Winterbottom, J. and S. Norreys, "LIS to LIS Protocol
Requirements", Work in Progress, November 2007.
[NENA] "NENA 08-505, Issue 1, 2006 (December 21, 2006), NENA
Recommended Method(s) for Location Determination to
Support IP-Based Emergency Services - Technical
Information Document (TID)", December 2006, <http://
www.nena.org/sites/default/files/
08-505_20061221.pdf>.
[NSLP] Stiemerling, M., Tschofenig, H., Aoun, C., and E.
Davies, "NAT/Firewall NSIS Signaling Layer Protocol
(NSLP)", Work in Progress, November 2008.
[RFC2113] Katz, D., "IP Router Alert Option", RFC 2113,
February 1997.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service
(RADIUS)", RFC 2865, June 2000.
[RFC3068] Huitema, C., "An Anycast Prefix for 6to4 Relay
Routers", RFC 3068, June 2001.
[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and
J. Arkko, "Diameter Base Protocol", RFC 3588,
September 2003.
[RFC3972] Aura, T., "Cryptographically Generated Addresses
(CGA)", RFC 3972, March 2005.
[RFC4119] Peterson, J., "A Presence-based GEOPRIV Location
Object Format", RFC 4119, December 2005.
[RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen,
"The Network Access Identifier", RFC 4282,
December 2005.
[RFC4361] Lemon, T. and B. Sommerfeld, "Node-specific Client
Identifiers for Dynamic Host Configuration Protocol
Version Four (DHCPv4)", RFC 4361, February 2006.
[RFC4479] Rosenberg, J., "A Data Model for Presence", RFC 4479,
July 2006.
[RFC4795] Aboba, B., Thaler, D., and L. Esibov, "Link-local
Multicast Name Resolution (LLMNR)", RFC 4795,
January 2007.
[RFC5201] Moskowitz, R., Nikander, P., Jokela, P., and T.
Henderson, "Host Identity Protocol", RFC 5201,
April 2008.
[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)",
RFC 5389, October 2008.
[RFC5491] Winterbottom, J., Thomson, M., and H. Tschofenig,
"GEOPRIV Presence Information Data Format Location
Object (PIDF-LO) Usage Clarification, Considerations,
and Recommendations", RFC 5491, March 2009.
[TEREDO-SEL] Ward, N., "Teredo Server Selection", Work
in Progress, July 2007.
[TR069] "TR-069, CPE WAN Management Protocol v1.1, Version:
Issue 1 Amendment 2", December 2007, <http://
www.broadband-forum.org/technical/download/
TR-069_Amendment-2.pdf>.
[mDNS] Cheshire, S. and M. Krochmal, "Multicast DNS", Work
in Progress, September 2009.
Authors' Addresses
Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo 02600
Finland
Phone: +358 (50) 4871445
EMail: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at
Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Phone: +1 212 939 7004
EMail: hgs+ecrit@cs.columbia.edu
URI: http://www.cs.columbia.edu