One document matched: draft-ietf-pana-usage-scenarios-04.txt
Differences from draft-ietf-pana-usage-scenarios-03.txt
Internet-Draft Yoshihiro Ohba (Editor)
Expires: August, 2003 Subir Das
Basavaraj Patil
Hesham Soliman
Alper Yegin
February 20, 2003
Problem Statement and Usage Scenarios for PANA
<draft-ietf-pana-usage-scenarios-04.txt>
Status of This Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
This document addresses a set of problems which a network layer
protocol called PANA (Protocol for carrying Authentication for
Network Access) is trying to solve in the area of network access
authentication and describes several usage scenarios where PANA is
applicable. It also helps to facilitate the discussion for PANA
requirements and security threat analysis that are used as basis of
actual PANA protocol design.
Expires August, 2003 [Page 1]
Internet-Draft PANA Usage Scenarios February 20, 2003
Table of Contents
1 Introduction ............................................ 2
2. Problem Statement ....................................... 2
3. Usage Scenarios ......................................... 4
3.1. PANA with Physical Layer Security ....................... 4
3.2. PANA with Link-Layer Security ........................... 5
3.3. PANA in the Absence of Any Lower-Layer Security ......... 6
3.4. Mobile IP ............................................... 6
3.5. Personal Area Networks .................................. 7
3.6. Limited Free Access ..................................... 8
4. Acronyms ................................................ 8
5. Security Considerations ................................. 9
6. Acknowledgments ......................................... 9
7. References .............................................. 9
7.1. Normative References .................................... 9
7.2. Informative References ................................. 10
8. Authors' Information ................................... 10
9. Intellectual Property Notices .......................... 11
10. Copyright Notice ....................................... 11
1 Introduction
Networks in most cases require some form of authentication in order
to prevent unauthorized access. Only authenticated and authorized
clients should be able to attach to an access network for sending and
receiving IP packets.
There are various mechanisms to provide this required functionality.
In its simplest form, unintended clients can be physically kept away
from the access networks. But there exist some scenarios where a
solution based on physical security might not be practical. Public
access networks and wireless networks are such examples. In the
absence of physical security (and sometimes in addition to it) a
higher layer access authentication mechanism is needed. Link-layer
based authentication mechanisms are used whenever they can serve the
needs of a particular deployment. Ability to support multiple
authentication methods or to perform both network access provider and
Internet service provider authentication are not available to all
link-layers. An even higher layer authentication mechanisms are
needed whenever such additional requirements are not met by the
underlying link-layers. Generally a network or higher layer
mechanism can be used instead of or in addition to available link-
layer and physical security. Currently there is not a standard
protocol to perform network access authentication above link-layer.
Instead, a number of ad-hoc and inadequate solutions are being used.
PANA will be developed to fill this gap by defining a network-layer
access authentication protocol.
This I-D discusses the need for a standard network access
authentication protocol and covers various usage scenarios where such
a protocol is applicable.
2. Problem Statement
Expires August, 2003 [Page 2]
Internet-Draft PANA Usage Scenarios February 20, 2003
Access networks usually require clients to go through an
authentication and authorization process unless physical security is
used as a substitute. Network access authentication of clients
necessitates a protocol between the client and the network to execute
one or more authentication methods (e.g., CHAP, TLS, SIM, etc.). In
the light of proliferation of various access technologies (e.g.,
GPRS, IEEE 802.11, DSL, etc.), it is important that the
authentication methods are not tied to the underlying link-layer.
Authentication protocol must be able to carry various authentication
methods regardless of the underlying access technologies.
An important aspect of network access is the ability to enable
dynamic service provider selection. Regardless of their network
access provider (NAP), clients should be able to select an Internet
access provider (ISP) of their choice. This is usually achieved by
clients presenting an identifier which carries domain information
during the authentication process unless some other link-layer
specific selectors are used during link establishment. An example of
such client identifier would be the NAI[RFC2486] (e.g.,
john@anyisp.com.) The authentication agent in the access network
would consult the backend authentication servers in the given domain,
and the respective ISP service will be used once the client access is
authorized. This is also essential in providing roaming service to
clients. A single authentication between the client and the ISP is
generally sufficient for both NAP and ISP access by relying on the
pre-established trust relation between the NAP and the ISP.
Nevertheless, there are some scenarios where NAPs and ISPs require
their independent authentication with the client. If the NAP
authentication is performed using a link-layer mechanism, ISP
authentication can be left to a network-layer mechanism. An example
of a multi-layer authentication can be seen in cdma2000 networks as
described in section 3.2.
A network-layer authentication mechanism that will support various
authentication methods can be developed by using a protocol that
carries EAP [RFC2284bis]. EAP acts as an encapsulation of arbitrary
authentication methods, but it still requires a transport between the
client and the access network. Among all the link-layers, only IEEE
802 defines how to carry EAP on the link-layer [802.1X]. Any other
link-layer has to resort to using PPP/PPPoE [RFC1661,RFC2516] as a
link-layer agnostic way of carrying EAP. Inserting this additional
layer(s) between the link-layer and network-layer to achieve this
goal is an inadequate method. Using PPP just for client
authentication incurs extra round-trips, generates overhead of PPP
processing for data packets, and forces the network topology into a
point-to-point model.
In general terms, PANA will be defined as a network-layer transport
for EAP. It is believed that EAP is a key protocol in supporting
various authentication methods for network access, and its
applicability should not be limited to access networks that are using
IEEE 802 and PPP links. PANA can be used over any link-layer that
does not support EAP encapsulation. PPP might be perceived as a
link-layer agnostic transport for EAP, but using PPP solely for
authentication purpose incurs unnecessary cost and imposes additional
limitations.
Expires August, 2003 [Page 3]
Internet-Draft PANA Usage Scenarios February 20, 2003
The primary purpose of PANA is to authenticate a client to a server
for the network access purpose. Initial client authentication needs
to be bound to subsequent traffic to prevent spoofing and hijacking
of data packets. Therefore, this authentication might be required to
generate cryptographic keying material unless presence of a secure
physical or link-layer channel is assured prior to it. The task of
generating and distributing such keying material can be accomplished
by various authentication methods carried by EAP. PANA is only
responsible for carrying EAP and it should not have to deal with the
keying material. Once the keying material is present, it can be used
with link-layer ciphers, or IPsec for providing subsequent per-packet
authentication. It should be noted that the keying material produced
by the authentication methods is generally not readily usable by
IPsec. A key exchange protocol like IKE [RFC2409] might be used to
create the required IPsec security associations. The mechanisms that
are used to turn keying material produced by the initial
authentication method into link-layer or network-layer ciphers are
outside the scope of PANA.
Until a standard solution like PANA is developed, architectures that
use neither IEEE 802 nor PPP as link-layers are forced to design
their own ad-hoc mechanisms to the problem. One such mechanism is
the application-layer authentication method implemented by http
redirects and web-based login. In addition to being a non-standard
solution, this provides an incomplete network access authentication
with well-known vulnerabilities, and therefore regarded as a stop-gap
mechanism.
Another method designed to provide network access authentication is
based on overloading an existing network-layer protocol. Mobile IPv4
[RFC3344] protocol has a built-in authentication mechanism.
Regardless of whether mobile nodes need to use a foreign agent in an
access network, registration via a foreign agent can be required by
using an appropriate flag in the agent advertisements. This forces
the nodes to register with a foreign agent, and therefore utilizes
Mobile IPv4 protocol for network access authentication. Such a
solution has very limited applicability as a link-layer agnostic
method since it relies on the deployment of Mobile IPv4 protocol.
3. Usage Scenarios
The first three subsections describe PANA usage scenarios categorized
in terms of lower-layer security. Other subsections describe
scenarios that are not categorized in terms of lower-layer security.
3.1. PANA with Physical Layer Security
In the networks where a certain degree of security is provided at
physical layer, authenticating the client is still essential since
physical layer does not provide information on the client, but per-
packet authentication and encryption may not necessarily be provided
at higher layers. DSL networks that are implemented on top of point-
to-point phone lines are such an example. In this type of networks,
PANA can be used for client authentication and a hook to an
appropriate access control.
Expires August, 2003 [Page 4]
Internet-Draft PANA Usage Scenarios February 20, 2003
In DSL networks, there are a number of deployment scenarios with
regard to client configuration and client authentication. In DSL
networks where PPP or PPPoE is used for both configuration and
authentication (and IP encapsulation), the providers may not require
to migrate to use PANA. On the other hand, there are some DSL
networks that use some configuration method other than PPP or PPPoE,
i.e., DHCP or static configuration. Those networks use either an ad-
hoc network access authentication method such as http-redirect with
web-based login or no authentication method at all. A standard,
link-layer agnostic network access authentication is needed for this
type of DSL networks and PANA can be used to fill the demand. In
addition, the variation in DSL deployment scenarios, particularly the
variation in physical topology between DSL modem and ISP edge router,
makes it difficult to define a single authentication scheme which
operates at lower-layer and works with any physical topology. It is
highly possible that an link-layer agnostic, single network access
authentication solution will be demanded for future DSL deployments
as long as the variation is supposed to exist.
3.2. PANA with Link-Layer Security
Certain link-layers in radio networks such as GSM and cdma2000
provide their own authentication mechanisms as well as ciphering of
data sent over the physical air interface. This air-
interface/technology specific authentication enables authorization
for accessing the link by the NAP, and provides per-packet
authentication, integrity and replay protection on the link-layer.
But it does not necessarily provide authorization at the network-
layer which can be done by authenticating the client to an ISP. So
this still necessitates another layer of authentication. It should
be noted that this second authentication takes place over a secure
channel.
cdma2000 is a good example of such an architecture where multi-
layered authentication for network access takes place. cdma2000
networks require the user/device to authenticate with the MSC/VLR
before providing access to the packet data network. The technology
specific access authentication which uses the CAVE (cellular
authentication and voice encryption) algorithms also provides cipher
keys to the mobile and the base station for securing the link layer
for all subsequent voice and data carried on the air interface. In
the Simple IP mode of cdma2000 services, the ISP authentication is
provided by using PPP in the stack. Currently there are proposals to
remove PPP from the architecture and adopt a simple framing scheme
such as HDLC or variants. One of the functionalities of PPP that
needs to be taken over by another protocol or mechanism is the
authentication capability. In such a scenario, network access
authentication may be done using PANA protocol.
Where a multi-layer authentication for network access is needed, and
access technology specific authentication is already provided by
another protocol, PANA can be used as the network-layer
authentication protocol. In this case PANA will be running over a
cryptographically secured channel.
Expires August, 2003 [Page 5]
Internet-Draft PANA Usage Scenarios February 20, 2003
3.3. PANA in the Absence of Any Lower-Layer Security
There are scenarios where neither physical nor link-layer access
control is available on the network. One possible cause of this
scenario is the lack of adequate authentication capabilities on the
link-layer technology being used. Link-layer technologies generally
provide sufficient cipher suite support but inadequate authentication
method support. It is desirable to support arbitrary authentication
methods without being limited to the ones that are specific to the
underlying technology. Another cause of missing lower-layer
authentication is due to the difficulty of deployment. Assuring
physical security or enabling link-layer security might not be
practical for various reasons. In the absence of such lower-layer
security and authentication mechanism not only providers are unable
to control the unauthorized use of their networks but also users feel
insecure while exchanging sensitive information. In order to support
authentication functionality in such systems, many providers today
use a higher-layer authentication scheme, such as http-redirect
commonly known as web-based login. In this method, once the link is
established, users' traffic are re-directed to a web server which in
turn generates a web-based login forcing users to provide the
authentication information. While this method solves the problem
partially by allowing only authorized users to access the network, it
however does not enable the lower-layer security such as, per-packet
authentication and encryption, etc. Moreover, it is a non-standard
ad hoc solution that provides only limited authentication method
support.
In such scenarios, a standard mechanism is necessary which can
provide network access authentication irrespective of whether the
underlying layers are secured or not. A solution like PANA at the
network layer may be adequate if it can specify appropriate
authentication methods that can derive and distribute keys for
authentication, integrity and confidentiality of data traffic either
at the link or at the network layer. For example, if link-layer does
not support the desired authentication method but supports ciphering,
PANA can be used to bootstrap the latter. On the other hand, if
link-layer neither supports the desired authentication method nor
ciphering, PANA can be used to bootstrap higher layer security
protocols, such as, IKE and IPsec. Thus successful PANA
authentication can result to a secured network environment although
the underlying layers were not secured at the beginning. Also
assuming PANA will provide support to various authentication schemes,
providers will have advantage using a single framework across
multiple environments.
3.4. Mobile IP
Mobile IPv4 defines its own authentication extensions to authenticate
and authorize mobile nodes at the foreign agents and home agents.
One of the possible modes of Mobile IPv4 is when the mobile node uses
a co-located care-of address and doesn't rely on any mobility
management functionality of the foreign agent on the access network.
In this case, mobile node can send its registration request directly
to the home agent. Even in the co-located care-of address case, the
protocol has a way to require mobile nodes to register with a foreign
Expires August, 2003 [Page 6]
Internet-Draft PANA Usage Scenarios February 20, 2003
agent by setting Registration-Required bit in the agent
advertisements. This forces mobile nodes to send their registration
requests via foreign agent, even though they do not have to interact
with that agent otherwise.
This type of Mobile IP registrations are used for performing network
access authentication. This method can only be used in IPv4 networks
where every client implements mobile node functionality. Even for
IPv4 clients, a better approach would be to replace this protocol-
specific authentication method by a common authentication protocol
such as PANA. PANA can be used with any client regardless of Mobile
IPv4 support and it can support various authentication methods. PANA
can also be used with IPv6 clients, or dual-stack clients. Mobile
IPv6 [MIPv6] protocol doesn't define a foreign agent in the access
networks and provide any protocol support for access authentication.
Network access authentication can be handled by PANA regardless of IP
version of the clients and independent of whether they support or use
Mobile IP.
3.5. Personal Area Networks
A personal area network (PAN) is the interconnection of devices
within the range of an individual person. For example connecting a
cellular phone, PDA, and laptop together via short range wireless or
wireless links would form a PAN.
Devices in a PAN can directly communicate with each other, and access
the Internet if any one of them is specifically designated as a
mobile router for providing gateway functionality. Just like any
access network, a PAN also requires authentication and authorization
prior to granting access to its clients. A mobile router can
terminate the link-layer from different PAN nodes, and therefore it
acts as the first-hop router for them. Additionally, it can also
perform access control as an authentication agent. Different nodes
might be using different link-layer technologies to connect to a
mobile router. Therefore, it is desirable to use authentication
methods independent of the underlying link and rely on a link-layer
agnostic authentication protocol like PANA to carry authentication
information.
Another characteristic of PANs is its small scale. Only a handful of
nodes are expected to be part of a given PAN; therefore the
authentication process does not necessarily require a managed backend
AAA infrastructure for credential verification. Locally stored
information can be used in this kind of PANA deployment without
relying on a AAA backend.
The 3GPP architecture allows separation of MT (mobile termination,
such as cellular phone) and TE (terminal equipment, such as laptop)
[RFC3314]. TE can be connected to the Internet via MT by
establishing a PPP connection. One or more TEs can be connected to a
MT to form a PAN. The current architecture does not allow direct
communication between the TEs (if more than one are connected to the
MT) without having to go through the cellular interface of the MT.
This architecture will benefit from using shared links (e.g.,
Expires August, 2003 [Page 7]
Internet-Draft PANA Usage Scenarios February 20, 2003
Ethernet) between the TE and MT. Shared links would allow TEs to
communicate directly to each other without having to send data
through the power-limited MT or over the expensive air interface.
PANA can be used for authenticating PAN nodes when shared links are
used between the TEs and MT.
3.6. Limited Free Access
Certain networks might allow clients to access a limited topology
without any explicit authentication and authorization. However, the
policy may be such that an access beyond this topology requires
authentication and authorization. For example, in an airport
network, information such as, flight arrival and departure gate
numbers, airport shops and restaurants, etc., are offered as free
services by the airlines or airport authorities for their passengers.
In order to access such information, users' can simply plug in their
devices into the network without performing any authentication. In
fact, the network will only offer link-layer connectivity and limited
network layer access to users. On the other hand, access to further
services or sites using such local networks requires authentication
and authorization. If users want such services, the access network
can detect that attempt and initiate authentication. This also
allows the network to initiate the authentication whenever
appropriate. Once users perform the authentication it will be
allowed to go beyond the free access zone. PANA can be an enabler to
such limited free access scenarios and can offer a flexible access
control framework for public hot-spot networks.
4. Acronyms
AAA: Authentication, Authorization and Accounting
DSL: Digital Subscriber Line
EAP: Extensible Authentication Protocol
GPRS: General Packet Radio Service
HDLC: High-level Data Link Control
IKE: Internet Key Exchange
ISP: Internet Service Provider
MSC: Mobile Switching Center
MN: Mobile Node
MT: Mobile Termination
NAI: Network Access Identifier
NAP: Network Access Provider
PPP: Point-to-Point Protocol
Expires August, 2003 [Page 8]
Internet-Draft PANA Usage Scenarios February 20, 2003
PPPoE: PPP over Ethernet
TE: Terminal Equipment
UE: User Equipment
VLR: Visiting Location Register
5. Security Considerations
This Internet-Draft identifies the need for a standard network-layer
authentication protocol and illustrates a number of possible usage
scenarios. The actual protocol design is not specified in this
draft, neither are the security considerations around it. The
scenarios described in this document are used as input to a separate
security threats analysis document [SECTHREAT]. Eventually, the
requirements are derived from both the scenarios described in this
document and also the threats analyzed in the latter document. These
requirements are being collected in the [PANAREQ] Internet-Draft.
The readers are urged to read these two documents for security
considerations around designing PANA.
6. Acknowledgments
The authors would like to thank Bernard Aboba, James Carlson, Jacques
Caron, Francis Dupont, Paal Engelstad, Henry Haverinen, Prakash
Jayaraman, James Kempf, Thomas Narten, Erik Nordmark, Reinaldo Penno,
Phil Roberts, David Spence, Barani Subbiah, Hannes Tschofenig, George
Tsirtsis, John Vollbrecht, Cliff Wang and the rest of the PANA
Working Group for the ideas and support they have given to this
document.
7. References
7.1. Normative References
[MIPv6] D. Johnson, et al., "Mobility Support in IPv6", (draft-ietf-
mobileip-ipv6-20.txt).
[PANAREQ] R. Penno, et al., "Protocol for Carrying Authentication for
Network Access (PANA) Requirements and Terminology" (draft-ietf-
pana-requirements-04.txt).
[RFC1661] W. Simpson, "The Point-to-Point Protocol (PPP)", RFC 1661
(STD 51), July 1994.
[RFC2284bis] L. Blunk, et al., "Extensible Authentication Protocol
(EAP)" (draft-ietf-eap-rfc2284bis-01.txt).
[RFC2409] D. Harkins and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, November 1998.
[RFC2486] B. Aboba, et al., "The Network Access Identifier", RFC
2486, January 1999.
Expires August, 2003 [Page 9]
Internet-Draft PANA Usage Scenarios February 20, 2003
[RFC2516] L. Mamakos, et al., "A Method for Transmitting PPP Over
Ethernet (PPPoE)", RFC 2516, February 1999.
[RFC3314] M. Wasserman et al., "Recommendations for IPv6 in Third
Generation Partnership Project (3GPP) Standards", RFC 3314,
September 2002.
[RFC3344] C. Perkins, "IP Mobility Support for IPv4", RFC 3344,
August 2002.
[SECTHREAT] M. Parthasarathy, "PANA Threat Analysis and security
requirements" (draft-ietf-pana-threats-01.txt).
7.2. Informative References
[802.1X] IEEE Standard for Local and Metropolitan Area Networks,
"Port-Based Network Access Control", IEEE Std 802.1X-2001.
8. Authors' Information
Yoshihiro Ohba
Toshiba America Research, Inc.
P.O. Box 136
Convent Station, NJ 07961-0136
USA
Phone: +1 973 829 5174
Fax: +1 973 829 5601
Email: yohba@tari.toshiba.com
Subir Das
MCC 1D210R, Telcordia Technologies
445 South Street, Morristown, NJ 07960
Phone: +1 973 829 4959
email: subir@research.telcordia.com
Basavaraj Patil
Nokia
6000 Connection Dr.
Irving, TX. 75039
USA
Phone: +1 972-894-6709
Email: Basavaraj.Patil@nokia.com
Hesham Soliman
Ericsson Radio Systems AB
Torshamnsgatan 29,
Kista, Stockholm 16480
Sweden
Phone: +46 8 4046619
Fax: +46 8 4047020
Email: Hesham.Soliman@era.ericsson.se
Alper E. Yegin
DoCoMo USA Labs
181 Metro Drive, Suite 300
San Jose, CA, 95110
Expires August, 2003 [Page 10]
Internet-Draft PANA Usage Scenarios February 20, 2003
USA
Phone: +1 408 451 4743
Email: alper@docomolabs-usa.com
9. Intellectual Property Notices
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
10. Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Expires August, 2003 [Page 11]
| PAFTECH AB 2003-2026 | 2026-04-23 06:11:11 |