PANA Working Group P. Jayaraman
Internet-Draft Net.Com
Expires: January 14, 2005 R. Lopez
Univ. of Murcia
Y. Ohba (Ed.)
Toshiba
M. Parthasarathy
Nokia
A. Yegin
Samsung
July 16, 2004
PANA Framework
draft-ietf-pana-framework-01
Status of this Memo
By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed,
and any of which I become aware will be disclosed, in accordance with
RFC 3668.
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.
This Internet-Draft will expire on January 14, 2005.
Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
PANA design provides support for various types of deployments.
Access networks can differ based on the availability of lower-layer
Jayaraman, et al. Expires January 14, 2005 [Page 1]
Internet-Draft PANA Framework July 2004
security, placement of PANA entities, choice of client IP
configuration and authentication methods, etc. This I-D defines a
general framework for describing how these various deployment choices
are handled by PANA and the access network architectures.
Additionally, two possible deployments are described in detail: using
PANA over DSL networks and WLAN networks.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Specification of Requirements . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5
3. General PANA Framework . . . . . . . . . . . . . . . . . . . 6
4. Environments . . . . . . . . . . . . . . . . . . . . . . . . 11
5. IP Address Configuration . . . . . . . . . . . . . . . . . . 13
6. Data Traffic Protection . . . . . . . . . . . . . . . . . . 16
7. PAA-EP Protocol . . . . . . . . . . . . . . . . . . . . . . 17
7.1 PAA and EP Locations . . . . . . . . . . . . . . . . . . . 17
7.1.1 Single PAA, Single EP, Co-located . . . . . . . . . . 18
7.1.2 Separate PAA and EP . . . . . . . . . . . . . . . . . 18
7.2 Notification of PaC Presence . . . . . . . . . . . . . . . 20
7.3 Filter Rule Installation . . . . . . . . . . . . . . . . . 20
8. Network Selection . . . . . . . . . . . . . . . . . . . . . 21
9. Authentication Method Choice . . . . . . . . . . . . . . . . 23
10. Example Cases . . . . . . . . . . . . . . . . . . . . . . . 24
10.1 DSL Access Network . . . . . . . . . . . . . . . . . . . 24
10.1.1 Bridging Mode . . . . . . . . . . . . . . . . . . . 24
10.1.2 Router Mode . . . . . . . . . . . . . . . . . . . . 25
10.1.3 PANA and Dynamic Internet Service Provider
Selection . . . . . . . . . . . . . . . . . . . . . 25
10.2 Wireless LAN Example . . . . . . . . . . . . . . . . . . 26
10.2.1 PANA with Bootstrapping IPsec . . . . . . . . . . . 28
10.2.2 PANA with Bootstrapping WPA/IEEE 802.11i . . . . . . 32
10.2.3 Capability Discovery . . . . . . . . . . . . . . . . 34
11. Open Issue . . . . . . . . . . . . . . . . . . . . . . . . . 35
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 36
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 37
13.1 Normative References . . . . . . . . . . . . . . . . . . . 37
13.2 Informative References . . . . . . . . . . . . . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 40
A. Other Possible Cases for PANA with Bootstrapping IPsec in
Wireless LAN . . . . . . . . . . . . . . . . . . . . . . . . 41
A.1 IPv4 . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
A.2 IPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Intellectual Property and Copyright Statements . . . . . . . 46
Jayaraman, et al. Expires January 14, 2005 [Page 2]
Internet-Draft PANA Framework July 2004
1. Introduction
PANA is a link-layer agnostic network access authentication protocol
that runs between a node that wants to gain access to the network and
a server on the network side. PANA defines a new EAP [RFC3748] lower
layer that uses IP between the protocol end points.
The motivation to define such a protocol and the requirements are
described in [I-D.ietf-pana-requirements]. Protocol details are
documented in [I-D.ietf-pana-pana]. [I-D.ietf-pana-ipsec] describes
use of IPsec for access control following PANA-based authentication.
IPsec can be used for per-packet access control, but nevertheless it
is not the only way to achieve this functionality. Alternatives
include reliance on physical security and link-layer ciphering.
Separation of PANA server from the entity enforcing the access
control is envisaged as an optional deployment choice. SNMP
[I-D.ietf-pana-snmp] is chosen as the protocol to carry associated
information between the separate nodes.
PANA design provides support for various types of deployments.
Access networks can differ based on the availability of lower-layer
security, placement of PANA entities, choice of client IP
configuration and authentication methods, etc.
PANA can be used in any access network regardless of the underlying
security. For example, the network might be physically secured, or
secured by means of cryptographic mechanisms after the successful
client-network authentication.
The PANA client, PANA authentication agent, authentication server,
and enforcement point are the relevant functional entities in this
design. PANA authentication agent and enforcement point(s) can be
placed on various elements in the access network (e.g., access point,
access router, dedicated host).
IP address configuration mechanisms vary as well. Static
configuration, DHCP, stateless address autoconfiguration are possible
mechanisms to choose from. If the client configures an IPsec tunnel
for enabling per-packet security, configuring IP addresses inside the
tunnel becomes relevant, for which there are additional choices such
as IKE.
This I-D defines a general framework for describing how these various
deployment choices are handled by PANA and the access network
architectures. Additionally, two possible deployments are described
in detail: PANA over DSL networks and WLAN networks.
Jayaraman, et al. Expires January 14, 2005 [Page 3]
Internet-Draft PANA Framework July 2004
1.1 Specification of Requirements
In this document, several words are used to signify the requirements
of the specification. These words are often capitalized. 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].
Jayaraman, et al. Expires January 14, 2005 [Page 4]
Internet-Draft PANA Framework July 2004
2. Terminology
Pre-PANA address (PRPA)
This is an IP address configured on a PANA client before starting
the PANA protocol exchange.
Post-PANA address (POPA)
This is an IP address (optionally) configured on a PANA client
after a successful authentication.
IPsec Tunnel Inner Address (IPsec-TIA)
This is an IP address configured on a PANA client as the inner
address of an IPsec tunnel mode SA.
IPsec Tunnel Outer Address (IPsec-TOA)
This is the address configured on a PANA client as the outer
address of an IPsec tunnel mode SA.
Secure Association Protocol
A protocol that provides a cryptographic binding between the
initial entity authentication (and authorization) exchange to the
subsequent exchange of data packets. Examples of secure
association protocols include the 4-way handshake in IEEE 802.11i
[802.11i], and IKE [RFC2409] in IP-based access control.
Jayaraman, et al. Expires January 14, 2005 [Page 5]
Internet-Draft PANA Framework July 2004
3. General PANA Framework
PANA protocol is designed to facilitate authentication and
authorization of clients in access networks. PANA is an EAP
[RFC3748] lower-layer that carries EAP authentication methods
encapsulated inside EAP between a client host and an agent in the
access network. While PANA enables the authentication process
between the two entities, it is only a part of an overall AAA and
access control framework. A AAA and access control framework using
PANA is comprised of four functional entities.
PANA Client (PaC):
The PaC is the client implementation of the PANA protocol. This
entity resides on the end host that is requesting network access.
The end hosts are, for example, laptops, PDAs, cell phones,
desktop pcs that are connected to a network via a wired or
wireless interface. A PaC is responsible for requesting network
access and engaging in the authentication process using the PANA
protocol
PANA Authentication Agent (PAA):
The PAA is the server implementation of the PANA protocol. A PAA
is in charge of interfacing with the PaCs for authenticating and
authorizing them for the network access service.
The PAA consults an authentication server in order to verify the
credentials and rights of a PaC. If the authentication server
resides on the same host as the PAA, an API is sufficient for this
interaction. When they are separated (a much more common case in
public access networks), a protocol needs to run between the two.
LDAP [RFC3377] and AAA protocols like RADIUS [RFC2865] and
Diameter [RFC3588] are commonly used for this purpose.
The PAA is also responsible for updating the access control state
(i.e., filters) depending on the creation and deletion of the
authorization state. The PAA communicates the updated state to
the enforcement points in the network. If the PAA and EP are
residing on the same host, an API is sufficient for this
communication. Otherwise, a protocol is required to carry the
authorized client attributes from the PAA to the EP. While not
prohibiting other protocols, currently SNMP [I-D.ietf-pana-snmp]
is suggested for this task.
The PAA resides on a node that is typically called a NAS (network
access server) in the local area network. PAA can be hosted on
any IP-enabled node on the same IP subnet as the PaC. For example
on a BAS (broadband access server) in DSL networks, or PDSN in
3GPP2 networks.
Jayaraman, et al. Expires January 14, 2005 [Page 6]
Internet-Draft PANA Framework July 2004
Authentication Server (AS):
The server implementation that is in charge of verifying the
credentials of a PaC that is requesting the network access
service. The AS receives requests from the PAA on behalf of the
PaCs, and responds with the result of verification together with
the authorization parameters (e.g., allowed bandwidth, IP
configuration, etc). The AS might be hosted on the same host as
the PAA, on a dedicated host on the access network, or on a
central server somewhere on the Internet.
Enforcement Point (EP):
The access control implementation that is in charge of allowing
access to authorized clients while preventing access by others.
An EP learns the attributes of the authorized clients from the
PAA.
The EP uses non-cryptographic or cryptographic filters to
selectively allow and discard data packets. These filters may be
applied at the link-layer or the IP-layer. When cryptographic
access control is used, a secure association protocol needs to run
between the PaC and EP. Link or network layer protection (for
example TKIP, IPsec ESP) is used after the secure association
protocol established the necessary security association to enable
integrity protection, data origin authentication, replay
protection and optionally confidentiality protection.
An EP must be located strategically in a local area network to
minimize the access of unauthorized clients to the network. For
example, the EP can be hosted on the switch that is directly
connected to the clients in a wired network. That way the EP can
drop unauthorized packets before they reach any other client host
or beyond the local area network.
Figure 1 illustrates these functional entities and the interfaces
(protocols, APIs) among them.
Jayaraman, et al. Expires January 14, 2005 [Page 7]
Internet-Draft PANA Framework July 2004
RADIUS/
Diameter/
+-----+ PANA +-----+ LDAP/ API +-----+
| PaC |<----------------->| PAA |<---------------->| AS |
+-----+ +-----+ +-----+
^ ^
| |
| +-----+ |
IKE/ +-------->| EP |<--------+ SNMP/ API
4-way handshake +-----+
Figure 1: PANA Functional Model
Some of the entities may be co-located depending on the deployment
scenario. For example, the PAA and EP would be on the same node
(BAS) in DSL networks. In that case a simple API is sufficient
between the PAA and EP. In small enterprise deployments the PAA and
AS may be hosted on the same node (access router) that eliminates the
need for a protocol run between the two. The decision to co-locate
these entities or otherwise, and their precise location in the
network topology are deployment decisions.
Use of IKE or 4-way handshake protocols for secure association is
only required in the absence of any lower-layer security prior to
running PANA. Physically secured networks (e.g., DSL) or the
networks that are already cryptographically secured on the link-layer
prior to PANA run (e.g., cdma2000) do not require additional secure
association and per-packet ciphering. These networks can bind the
PANA authentication and authorization to the lower-layer secure
channel that is already available.
Figure 2 illustrates the signaling flow for authorizing a client for
network access.
Jayaraman, et al. Expires January 14, 2005 [Page 8]
Internet-Draft PANA Framework July 2004
PaC EP PAA AS
| | | |
IP address o | | |
config. | PANA | | AAA |
|<------------------------------>|<-------------->|
| | SNMP | |
(Optional) | |<-------------->| |
IP address o | | |
config. | Sec.Assoc. | | |
|<------------->| | |
| | | |
| Data traffic | | |
|<-----------------> | |
| | | |
Figure 2: PANA Signaling Flow
The EP on the access network allows general data traffic from any
authorized PaC, whereas it allows only limited type of traffic (e.g.,
PANA, DHCP, router discovery) for the unauthorized PaCs. This
ensures that the newly attached clients have the minimum access
service to engage in PANA and get authorized for the unlimited
service.
The PaC MUST configure an IP address prior to running PANA. After
the successful PANA authentication, depending on the deployment
scenario the PaC MAY need to re-configure its IP address or configure
additional IP address(es). The additional address configuration MAY
be executed as part of the secure association protocol run.
An initially unauthorized PaC starts the PANA authentication by
discovering the PAA on the access network, followed by the EAP
exchange over PANA. The PAA interacts with the AS during this
process. Upon receiving the authentication and authorization result
from the AS, the PAA informs the PaC about the result of its network
access request.
If the PaC is authorized to gain the access to the network, the PAA
also sends the PaC-specific attributes (e.g., IP address,
cryptographic keys, etc.) to the EP by using SNMP. The EP uses this
information to alter its filters for allowing data traffic from and
to the PaC to pass through.
In case cryptographic access control needs to be enabled after the
PANA authentication, a secure association protocol runs between the
PaC and the EP. The PaC should already have the input parameters to
this process as a result of the successful PANA exchange. Similarly,
the EP should have obtained them from the PAA via SNMP. Secure
Jayaraman, et al. Expires January 14, 2005 [Page 9]
Internet-Draft PANA Framework July 2004
association exchange produces the required security associations
between the PaC and the EP to enable cryptographic data traffic
protection. Per-packet cryptographic data traffic protection
introduces additional per-packet overhead but the overhead exists
only between the PaC and EP and will not affect communications beyond
the EP. In this sense it is important to place the EP as close to
the edge of the network as possible.
Finally data traffic can start flowing from and to the newly
authorized PaC.
Jayaraman, et al. Expires January 14, 2005 [Page 10]
Internet-Draft PANA Framework July 2004
4. Environments
The PANA protocol can be used on any network environment whether
there is a lower-layer secure channel prior to PANA, or one has to be
enabled upon successful PANA authentication.
With regard to network access authentication two types of networks
need to be considered:
a. Networks where a secure channel is already available prior to
running PANA
This type of network is characterized by the existence of
protection against spoofing and eavesdropping. Nevertheless, user
authentication and authorization is required for network
connectivity.
One example is a DSL network where the lower-layer security is
provided by physical means (a.1). Physical protection of the
network wiring ensures that practically there is only one client
that can send and receive IP packets on the link. Another example
is a cdma2000 network where the lower-layer security is provided
by means of cryptographic protection (a.2). By the time the
client requests access to the network-layer services, it is
already authenticated and authorized for accessing the radio
channel, and link-layer ciphering is enabled.
The presence of a secure channel before PANA exchange eliminates
the need for executing a secure association protocol after PANA.
The PANA session can be bound to the communication channel it was
carried over. Also, the choice of EAP authentication method
depends on the presence of this security during PANA run. Use of
some authentication methods outside a secure channel is not
recommended (e.g., EAP-MD5).
b. Networks where a secure channel is created after running PANA
These are the networks where there is no lower-layer protection
prior to running PANA. A successful PANA authentication enables
generation of cryptographic keys that are used with a secure
association protocol to enable per-packet cryptographic
protection.
PANA authentication is run on an insecure channel that is
vulnerable to eavesdropping and spoofing. The choice of EAP
method must be resilient to the possible attacks associated with
such an environment. Furthermore, the EAP method must be able to
create cryptographic keys that will later be used by the secure
association protocol.
Jayaraman, et al. Expires January 14, 2005 [Page 11]
Internet-Draft PANA Framework July 2004
Whether to use a link-layer per-frame security (b.1) or a network
layer security (b.2) is a deployment decision. This decision also
dictates the choice of the secure association protocol. If
link-layer protection is used, the protocol would be link-layer
specific. If IP-layer protection is used, the secure association
protocol would be IKE and the per-packet security would be
provided by IPsec AH/ESP regardless of the underlying link-layer
technology.
Jayaraman, et al. Expires January 14, 2005 [Page 12]
Internet-Draft PANA Framework July 2004
5. IP Address Configuration
The PaC configures an IP address before the PANA protocol exchange
begins. This address is called a pre-PANA address (PRPA). After a
successful authentication, the client may have to configure a
post-PANA address (POPA) for communication with other nodes, if PRPA
is a local-use (e.g., link-local or private address) or a temporarily
allocated IP address. An operator might choose allocating a POPA
only after successful PANA authorization either to prevent waste of
premium IP resources until the client is authorized, or to enable
client identity based address assignment.
In case the PaC is a IPv4/IPv6 dual-stacked host, it may configure
more than one PRPA. After a successful PANA authentication the PaC
may configure multiple POPAs.
There are different methods by which a PRPA can be configured.
1. In some deployments (e.g., DSL networks) the PaC may be
statically configured with an IP address. This address SHOULD be
used as PRPA.
2. In IPv4, most clients attempt to configure an address dynamically
using DHCP [RFC2131]. If they are unable to configure an address
using DHCP, they can configure a link-local address using
[I-D.ietf-zeroconf-ipv4-linklocal].
When the network access provider is able to run a DHCP server on
the access link, the client would configure the PRPA using DHCP.
This address may be from a private address pool [RFC1918]. Also,
the lease time on the address may vary. For example, a PRPA
configured solely for running PANA can have a short lease time.
PRPA may be used for local-use only (i.e., only for on-link
communication, such as for PANA and IPsec tunneling with EP), or
also for ultimate data communication.
In case there is no running DHCP server on the link, the client
would fall back to configuring a PRPA via zeroconfiguration
technique [I-D.ietf-zeroconf-ipv4-linklocal]. This yields a
long-term address that can only be used for on-link communication.
3. In IPv6, clients configure a link-local address [RFC2462] when
they initialize an interface. This address SHOULD be used as a
PRPA.
When a PRPA is configured, the client starts the PANA protocol
exchange. By that time, a dual-stacked client might have configured
both an IPv4 address, and one or more IPv6 addresses as PRPAs. When
Jayaraman, et al. Expires January 14, 2005 [Page 13]
Internet-Draft PANA Framework July 2004
the client successfully authenticates to the network, it may be
required to configure POPAs for its subsequent data communication
with the other nodes.
If the client is already configured with a non-temporary address that
can be used with data communication, it is not required to configure
a POPA. Otherwise, the PANA-Bind-Request message allows the PAA to
indicate the available configuration methods to the PaC. The PaC can
choose one of the methods and act accordingly.
1. If the network relies on physical or link-layer security, the PaC
can configure a POPA using DHCP [RFC2131][RFC3315] or using IPv6
stateless auto-configuration [RFC2461]. If IPv4 is being used, a
PRPA is likely to be a link-local or private address, or an
address with a short DHCP lease. An IPv4 PRPA SHOULD be
unconfigured when the POPA is configured to prevent IPv4 address
selection problem [I-D.ietf-zeroconf-ipv4-linklocal]. If IPv6 is
used, the link-local PRPA SHOULD NOT be unconfigured [RFC3484].
If the PaC is a dual-stacked host, it can configure both IPv4 and
IPv6 type POPAs.
The PaC with a PRPA and the PAA with IP address X can perform
on-link communication as required by PANA. In IPv4, the PRPA and
IP address X have the same on-link prefix. In IPv6, the two
addresses are link-local addresses. When the PaC replaces its
IPv4 PRPA with an IPv4 POPA, the PaC and PAA SHOULD create host
routes to each other, as they do not share the same on-link prefix
any more. This is needed for the PaC with the IPv4 POPA and the
PAA with IP address X to continue on-link communication. In this
case, the PaC SHOULD create a host route to IP address X, and the
PAA SHOULD create a host route to the IPv4 POPA. PANA defines a
mechanism for the PaC to report the POPA to the PAA.
2. If the network uses IPsec for protecting the traffic on the link
subsequent to PANA authentication [I-D.ietf-pana-ipsec], the PaC
would use the PRPA as the outer address of IPsec tunnel mode SA
(IPsec-TOA). The PaC also needs to configure an inner address
(IPsec-TIA). There are different ways to configure an IPsec-TIA
which are indicated in a PANA-Bind-Request message.
When an IPv4 PRPA is configured, the same address may be used as
both IPsec-TOA and IPsec-TIA. In this case, a POPA is not
configured. Alternatively, an IPsec-TIA can be obtained via the
configuration method available within [RFC3456] for IPv4, and
[I-D.ietf-ipsec-ikev2] for both IPv4 and IPv6. This newly
configured address constitutes a POPA. Please refer to
[I-D.ietf-pana-ipsec] for more details.
Jayaraman, et al. Expires January 14, 2005 [Page 14]
IKEv2 can enable configuration of one IPv4 IPsec-TIA and one IPv6
IPsec-TIA for the same IPsec tunnel mode SA. Therefore, IKEv2 is
recommended for handling dual-stacked PaCs where single execution
of PANA and IKE is desired.
Although there are potentially a number of different ways to
configure a PRPA, and POPA when necessary, it should be noted that
the ultimate decision to use one or more of these in a deployment
depends on the operator. The decision is dictated by the operator's
choice of per-packet protection capability (physical and link-layer
vs network-layer), PRPA type (local and temporary vs global and
long-term), and POPA configuration mechanisms available in the
network.
Jayaraman, et al. Expires January 14, 2005 [Page 15]
Internet-Draft PANA Framework July 2004
6. Data Traffic Protection
Protecting data traffic of authenticated and authorized client from
others is another component of providing a complete secure network
access solution. Authentication, integrity and replay protection of
data packets is needed to prevent spoofing when the underlying
network is not physically secured. Encryption is needed when
eavesdropping is a concern in the network.
When the network is physically secured, or the link-layer ciphering
is already enabled prior to PANA, data traffic protection is already
in place. In other cases, enabling link-layer ciphering or
network-layer ciphering might rely on PANA authentication. The user
and network have to make sure that an appropriate EAP method which
generates keying materials is used. Once the keying material is
available, it needs to be provided to the EP(s) for use with data
traffic protection.
Network-layer protection, i.e., IPsec, can be used when data traffic
protection is required but link-layer protection is not available.
Note that the keying material generated by an EAP method is not
readily usable by IPsec AH/ESP or most link layer mechanisms. A
fresh and unique session key derived from the EAP method is still
insufficient to produce an IPsec SA since both traffic selectors and
other IPsec SA parameters are missing. The shared secret can be used
in conjunction with a key management protocol like IKE [RFC2409] to
turn a session key into the required IPsec SA. The details of such a
mechanism is outside the scope of PANA protocol and is specified in
[I-D.ietf-pana-ipsec]. PANA provides bootstrapping functionality for
such a mechanism by carrying EAP methods that can generate initial
keying material.
Using network-layer ciphers should be regarded as a substitute for
link-layer ciphers when the latter is not available. Network-layer
ciphering can also be used in addition to link-layer ciphering if the
added benefits outweigh its cost to the user and the network. In
this case, PANA bootstraps only the network-layer ciphering and
link-layer is protected using any of the existing link-layer specific
methods.
Jayaraman, et al. Expires January 14, 2005 [Page 16]
Internet-Draft PANA Framework July 2004
7. PAA-EP Protocol
The PANA protocol provides client authentication and authorization
functionality for securing network access. The other component of a
complete solution is the access control which ensures that only
authenticated and authorized clients can gain access to the network.
PANA enables access control by distinguishing authenticated and
authorized clients from others and generating filtering information
for access control mechanisms.
Access control can be achieved by placing EPs (Enforcement Points) in
the network for policing the traffic flow. EPs should prevent data
traffic from and to any unauthorized client unless it's either PANA
or one of the other allowed traffic types (e.g., ARP, IPv6 neighbor
discovery, DHCP, etc.).
When a PaC is authenticated and authorized, the PAA should notify
EP(s) and ask for installing filtering rules to allow the PaC to sent
and receive data traffic. SNMP is used between PAA and EP(s) for
this purpose when these entities are not co-located
[I-D.ietf-pana-snmp].
This section describes the possible models on the location of PAA and
EP, as well as the basic authorization information that needs to be
exchanged between PAA and EP. When PAA and EP are not co-located in
a single device, there are other issues such as dead or rebooted peer
detection and consideration for specific authorization and accounting
models. However, these issues are closely related to the PAA-EP
protocol solution and thus not discussed in this document. See
[I-D.ietf-pana-snmp] for further discussion.
7.1 PAA and EP Locations
EPs' location in the network topology should be appropriate for
performing access control functionality. The closest IP-capable
access device to the client devices is the logical choice. PAA and
EPs on an access network should be aware of each other as this is
necessary for access control. Generally this can be achieved by
manual configuration. Dynamic discovery is another possibility, but
this is left to implementations and outside the scope of this
document.
Since PANA allows the separation of EP and PAA, there are several
models depending on the number of EPs and PAAs and their locations.
This section describes all possible models on the placement of PAA(s)
and EP(s).
Jayaraman, et al. Expires January 14, 2005 [Page 17]
Internet-Draft PANA Framework July 2004
7.1.1 Single PAA, Single EP, Co-located
This model corresponds to the legacy NAS model. Since the PAA and
the EP are co-located, the PAA-EP communication can be implemented
locally by using, e.g., IPC (Inter-Process Communication). The only
difference from the legacy NAS model is the case where there are
multiple co-located PAA/EP devices on the same IP link and the PAA/EP
devices are L2 switches or access points. In this case, for a PaC
that attaches to a given PAA/EP device, other PAA/EP devices should
not be discovered by the PaC even if those devices are on the same IP
link. Otherwise, the PaC may result in finding a PAA that is not the
closest one to it during the PANA discovery and initial handshake
phase and performing PANA with the PAA, which does not correspond to
the legacy NAS model. To prevent this, each PAA/EP device on an L2
switch or access point should not forward multicast PANA discovery
message sent by PaCs attached to it to other devices.
7.1.2 Separate PAA and EP
When PAA is separated from EP, two cases are possible with regard to
whether PAA and EP are located in parallel or serial when viewed from
PaC, for each of models described in this section.
In the first case, PAA is located behind EP. The EP should be
configured to always pass through PANA messages and address
configuration protocol messages used for configuring an IP address
used for initial PANA messaging. This case can typically happen when
the EP is an L2 switch or an access point (the EP also has an IP
stack to communicate with PAA via a PAA-EP protocol).
+---+ +---+ +---+
|PaC|--------|EP |--------|PAA|
+---+ +---+\ +---+
\
+---- Internet
Figure 3: PAA and EP in Serial
In the other case, PAA is located in parallel to EP. Since the EP is
not on the communication path between PaC and PAA, the EP does not
have to configure to pass through PANA messages or address
configuration protocol messages in this case. This case can
typically happen when the EP is a router and the PAA is an
authentication gateway without IP routing functionality.
Jayaraman, et al. Expires January 14, 2005 [Page 18]
Internet-Draft PANA Framework July 2004
+---+
+-----|PAA|
/ +---+
+---+/
|PaC|
+---+\
\ +---+
+-----|EP |---- Internet
+---+
Figure 4: PAA and EP in Parallel
In the remaining of this section, PaC is not shown in figures and the
figures cover both the serial and parallel models.
7.1.2.1 Single PAA, Single EP, Separated
The model benefits from separation of data traffic handling and AAA.
The EP does not need to have a AAA protocol implementation which
might be updated relatively more frequently than the per-packet
access enforcement implementation.
7.1.2.2 Single PAA, Multiple EPs
In this model, a single PAA controls multiple EPs. The PAA may be
separated from any EP or co-located with a particular EP. This model
might be useful where it is preferable to run a AAA protocol at a
single, manageable point. This model is particularly useful in an
access network that consists of a large number of access points on
which per-packet access enforcement is made. When a PaC is
authenticated to the PAA, the PAA should install access control
filters to each of the EPs under control of the PAA if the PAA cannot
tell which EP the PaC is attached to. Even if the PAA can tell which
EP the PaC is attached to, the PAA may install access control filters
to those EPs if the PaC is a mobile device that can roam among the
EPs. Such pre-installation of filters can reduce handoff latency.
If different access authorization policies are applied to different
EPs, different filter rules for a PaC may be installed on different
EPs.
Jayaraman, et al. Expires January 14, 2005 [Page 19]
Internet-Draft PANA Framework July 2004
+---+
|EP |--+
+---+ \
\
+---+ +---+
|EP |----|PAA|
+---+ +---+
/
+---+ /
|EP |--+
+---+
Figure 5: An example model for a single PAA and multiple EPs
7.1.2.3 Multiple PAAs
The PANA protocol allows multiple PAAs to exist on the same IP link
and to be visible to PaCs on the link. PAAs may or may not be
co-located with EPs as long as authorization results do not depend on
whichever PAAs are chosen by a PaC [I-D.ietf-pana-pana].
7.2 Notification of PaC Presence
When PAA and EP are separated and PAA is configured to be the
initiator of the discovery and initial handshake phase of PANA, EP
has the responsibility to detect presence of a new PaC and notifies
the PAA(s) of the presence [I-D.ietf-pana-requirements]. Such a
presence notification is carried in a PAA-EP protocol message
[I-D.ietf-pana-snmp].
7.3 Filter Rule Installation
Filtering rules to be installed on EP generally include a device
identifier of PaC, and also cryptographic keying material (e.g., IKE
pre-shared key [RFC2409]) when cryptographic data traffic protection
is needed (See Section 6). Each keying material is uniquely
identified with a keying material name (e.g., ID_KEY_ID in IKE
[RFC2409]) and has a lifetime for key management, accounting, access
control and security reasons in general. In addition to the device
identifier and keying material, other filter rules, such as the IP
filter rules specified in NAS-Filter-Rule AVPs carried in Diameter
EAP application [I-D.ietf-aaa-eap] may be installed on EP.
Jayaraman, et al. Expires January 14, 2005 [Page 20]
Internet-Draft PANA Framework July 2004
8. Network Selection
The network selection problem statement is made in
[I-D.ietf-eap-netsel-problem]. The PANA protocol
[I-D.ietf-pana-pana] provides a way for networks to advertise which
ISPs are available and for PaC to choose one ISP from the advertised
information. When a PaC chooses an ISP in the PANA protocol
exchange, the ultimate destination of the AAA exchange is determined
based on the identity of the chosen service provider. It is also
possible that the PaC does not choose a specific ISP in the PANA
protocol exchange. In this case, both the ISP choice and the AAA
destination are determined based on the PaC's identity, where the
identity may be an NAI [RFC2486] or the physical port number or L2
address of the subscriber.
As described in [I-D.ietf-eap-netsel-problem], network selection is
not only related to AAA routing but also related to payload routing.
Once an ISP is chosen and the PaC is successfully authenticated and
authorized, PaC is assigned an address by the ISP whose IP prefix may
be different from that of the AR. This affects the routing of the
subsequent data traffic between AR and PaC. A suggested solution is
to add host route from AR to PaC's POPA address and host route from
PaC to AR.
Consider a typical DSL network where the AR, EP, and PAA are
co-located on a BAS (Broadband Access Server) in the access network
operated by a NAP (Network Access Provider). Figure 6 shows a
typical model for ISP selection.
<---- NAP ----><--------- ISP --------->
+---ISP1
/
+---+ +---------+/
|PaC|----|AR/EP/PAA|
+---+ +---------+\
BAS \
+---ISP2
Figure 6: A Network Selection Model
When network selection is made at L3 with the use of the PANA
protocol instead of L2-specific authentication mechanisms, the IP
link between PaC and PAA needs to exist prior to doing PANA (and
prior to network selection). In this model, the PRPA is either given
by NAP or a link-local address is auto-configured. After the
successful authentication with the ISP, PaC may acquire an address
(POPA) from the ISP. It also learns the address of the AR, e.g.,
Jayaraman, et al. Expires January 14, 2005 [Page 21]
Internet-Draft PANA Framework July 2004
through DHCP, to be used as its default router. The address of the
AR may or may not be in the same IP subnet as that of the PaC's POPA.
If they don't share the same prefix, they SHOULD use host routes to
reach each other. Note that the physically secured DSL networks do
not require IPsec-based access control. Therefore the PaCs use one
IP address at a time where POPA replaces PRPA upon configuration.
Jayaraman, et al. Expires January 14, 2005 [Page 22]
Internet-Draft PANA Framework July 2004
9. Authentication Method Choice
Authentication methods' capabilities and therefore applicability to
various environments differ among them. Not all methods provide
support for mutual authentication, key derivation or distribution,
and DoS attack resiliency that are necessary for operating in
insecure networks. Such networks might be susceptible to
eavesdropping and spoofing, therefore a stronger authentication
method needs to be used to prevent attacks on the client and the
network.
The authentication method choice is a function of the underlying
security of the network (e.g., physically secured, shared link,
etc.). It is the responsibility of the user and the network operator
to pick the right method for authentication. PANA carries EAP
regardless of the EAP method used. It is outside the scope of PANA
to mandate, recommend, or limit use of any authentication methods.
PANA cannot increase the strength of a weak authentication method to
make it suitable for an insecure environment. There are some
EAP-based approaches to achieve this goal (see
[I-D.josefsson-pppext-eap-tls-eap],[I-D.ietf-pppext-eap-ttls]
,[I-D.tschofenig-eap-ikev2]). PANA can carry these EAP encapsulating
methods but it does not concern itself with how they achieve
protection for the weak methods (i.e., their EAP method payloads).
Jayaraman, et al. Expires January 14, 2005 [Page 23]
Internet-Draft PANA Framework July 2004
10. Example Cases
10.1 DSL Access Network
In a DSL access network, PANA is seen applicable in the following
scenarios.
A typical DSL access consists of a NAS device at the DSL-access
provider and a DSL-modem (CPE) at the customer premises. The CPE
devices support multiple modes of operation and PANA is applicable in
each of these modes.
Host--+ +-------- ISP1
| DSL link |
+----- CPE ---------------- NAS ----+-------- ISP2
| (Bridge/NAPT/Router) |
Host--+ +-------- ISP3
<------- customer --> <------- NAP -----> <---- ISP --->
premise
Figure 7: DSL Model
The devices at the customer premises have been shown as "hosts" in
the above network.
DSL networks are protected by physical means. Eavesdropping and
spoofing attacks are prevented by keeping the unintended users
physically away from the network media. Therefore, generally
cryptographic protection of data traffic is not necessary.
Nevertheless, if enhanced security is deemed necessary for any
reason, IPsec-based access control can be enabled on DSL networks as
well by using the method described in [I-D.ietf-pana-ipsec].
10.1.1 Bridging Mode
In the bridging mode, the CPE acts as a simple layer-2 bridge. The
hosts at the customer premises will function as clients to obtain
addresses from the NAS device by using DHCP or PPPoE.
If PPPoE is used, authentication is typically performed using CHAP or
MS-CHAP.
PANA will be applicable when the hosts use DHCP to obtain IP address.
DHCP does not support authentication of the devices on either side of
the DSL access line. In the simplest method of address assignment,
the NAS will allocate the IP address to a host with a lease time
reasonably sufficient to complete a full PANA based authentication
Jayaraman, et al. Expires January 14, 2005 [Page 24]
Internet-Draft PANA Framework July 2004
which will be triggered immediately after the address assignment.
The hosts will perform the PaC function and the NAS will perform the
PAA, EP and AR functions.
Host--+
(PaC) |
+----- CPE ---------------- NAS ------------- ISP
| (Bridge) (PAA,EP,AR)
Host--+
(PaC)
Figure 8: Bridge Mode
The DSL service provider's trunk network should not be accessible to
any host that has not successfully completed the PANA authentication
phase.
10.1.2 Router Mode
In this mode, the CPE acts as a router for the customer premises
network. The CPE itself may obtain the IP address using DHCP or be
configured with a static IP address. Once the CPE is authenticated
using PANA and is provided access to the service provider's network,
the NAS should begin exchanging routing updates with the CPE. All
devices at the customer premises will then have access to the service
provider's network.
Host--+
|
+----- CPE ---------------- NAS ------------- ISP
| (Router, PaC) (PAA,EP,AR)
Host--+
Figure 9: Router Mode
It is possible that both ends of the DSL link are configured with
static IP addresses. PANA-based mutual authentication of CPE and NAS
is desirable before data-traffic is exchanged between the customer
premises network and the service provider network. The CPE router
may also use NAPT (Network Address Port Tranlation).
10.1.3 PANA and Dynamic Internet Service Provider Selection
In some installations, a NAS device is shared by multiple service
providers. Each service provider configures the NAS with a certain
IP address space.
The devices at the customer premises network indicate their choice of
Jayaraman, et al. Expires January 14, 2005 [Page 25]
Internet-Draft PANA Framework July 2004
service provider and the NAS chooses the IP address from the
appropriate service provider's pool. In many cases, the address is
assigned not by the NAS but by the AAA server that is managed fully
by the service provider.
This simplifies the management of the DSL access network as it is not
always necessary to configure each DSL access line with the service
provider's identity. The service provider is chosen dynamically by
the CPE device. This is typically known as "dynamic Internet Service
Provider selection". The AAA function is usually overloaded to
perform dynamic ISP selection.
If the CPE device uses a PPP based protocol (PPP or PPPoE), the ISP
is chosen by mapping the username field of a CHAP response to a
provider.
If the CPE uses DHCP, the 'client-id' field of the DHCP-discover or
DHCP-request packet is mapped to the provider.
10.1.3.1 Selection as Part of the DHCP protocol or an Attribute of DSL
Access Line
The ISP selection, therefore the IP address pool, can be conveyed
based on the DHCP protocol exchange (as explained earlier), or by
associating the DSL access line to the service provider before the
PANA authentication begins. When any of these schemes is used, the
IP address used during PANA authentication (PRPA) is the ultimate IP
address and it does not have to be changed upon successful
authorization.
10.1.3.2 Selection as Part of the PANA Authentication
The ISP selection of the client can be explicitly conveyed during the
PANA authentication. In that case, the client can be assigned a
temporary IP address (PRPA) prior to PANA authentication. This IP
address might be obtained via DHCP with a lease reasonably long to
complete PANA authentication, or via the zeroconf technique
[I-D.ietf-zeroconf-ipv4-linklocal]. In either case, successful PANA
authentication signalling prompts the client to obtain a new (long
term) IP address via DHCP. This new IP address (POPA) replaces the
previously allocated temporary IP address.
10.2 Wireless LAN Example
This section describes how PANA can be used on WLAN networks. In
most common WLAN deployments the IP addresses are dynamically
configured. Therefore this section does not cover the scenarios
where the IP address is statically configured. There are two models
Jayaraman, et al. Expires January 14, 2005 [Page 26]
Internet-Draft PANA Framework July 2004
depending on which layer security is bootstrapped from PANA
authentication, L2 or L3. When PANA authentication is used for
bootstrapping L3 security, L2 security is not necessarily to exist
even after PANA authentication. Instead, IPsec-based data traffic
protection is bootstrapped from PANA. The PAA can indicate the PaC
as to whether L2 or L3 protection is needed, by including a
Protection-Capability AVP in PANA-Bind-Request message. In both
cases, the most common deployment would be illustrated in Figure 10,
where EP is typically co-located with AP (access point) when PANA is
used for bootstrapping L2 security or with AR when PANA is used for
bootstrapping L3 security.
Jayaraman, et al. Expires January 14, 2005 [Page 27]
Internet-Draft PANA Framework July 2004
+-----+
|AP/EP|----+
+-----+ |
|
+---+ +-----+ | +---------+
|PaC| |AP/EP|----+----|AR/PAA/EP|----- Internet
+---+ +-----+ | +---------+
|
+-----+ |
|AP/EP|----+
+-----+
Figure 10: PANA Wireless LAN Model
10.2.1 PANA with Bootstrapping IPsec
In this model, data traffic is protected by using IPsec tunnel mode
SA and an IP address is used as the device identifier of PaC (see
Section 5 for details). Some or all of AP, DHCPv4 Server (including
PRPA DHCPv4 Server and IPsec-TIA DHCPv4 Server), DHCPv6 Server, PAA
and EP may be co-located in a single device. EP is always co-located
with AR and may be co-located with PAA. When EP and PAA are not
co-located, PAA-EP protocol is used for communication between PAA and
EP.
Note that for all of the cases described in this section, PBR
(PANA-Bind-Request) and PBA (PANA-Bind-Answer) exchange in PANA
[I-D.ietf-pana-pana] should occur after installing the authorization
parameter to AR, so that IKE can be performed immediately after PANA
is successfully completed.
10.2.1.1 IPv4
Case A: IPsec-TIA obtained by using DHCPv4
In this case, the IPsec-TIA and IPsec-TOA are the same as the
PRPA, and all configuration information including the IP address
is obtained by using DHCPv4 [RFC2131]. No POPA is configured.
Case A is the simplest compared to other ones and might be used in
a network where IP address depletion attack on DHCP is not a
significant concern. The PRPA needs to be a routable address
unless NAT is performed on AR.
Jayaraman, et al. Expires January 14, 2005 [Page 28]
Internet-Draft PANA Framework July 2004
PaC AP DHCPv4 Server PAA EP(AR)
| Link-layer | | | |
| association| | | |
|<---------->| | | |
| | | | |
| DHCPv4 | | |
|<-----------+------------>| | |
| | | | |
|PANA(Discovery and Initial Handshake phase |
| & PAR-PAN exchange in Authentication phase) |
|<-----------+-------------------------->| |
| | | | |
| | | |Authorization|
| | | |[IKE-PSK, |
| | | | PaC-DI, |
| | | | Session-Id] |
| | | |------------>|
| | | | |
|PANA(PBR-PBA exchange in Authentication phase) |
|<-----------+-------------------------->| |
| | | | |
| | IKE | |
|<-----------+---------------------------------------->|
| | | | |
| | | | |
Figure 11: An example case for configuring IPsec-TIA by using
DHCPv4
Case B: IPsec-TIA obtained by using IKE
In this case, the PRPA is obtained by using DHCPv4 and used as
IPsec-TOA. The POPA is obtained by using IKE (via a Configuration
Payload exchange or equivalent) and used as IPsec-TIA.
Case C: IPsec-TIA obtained by using RFC3456
Like Case B, the PRPA is obtained by using DHCPv4. The difference
is that the POPA (eventually used as IPsec-TIA) and other
configuration parameter are configured by running DHCPv4 over a
special IPsec tunnel mode SA [RFC3456]. Note that the PRPA DHCPv4
Server and IPsec-TIA DHCPv4 Server may be co-located on the same
node.
Note: this case may be used only when IKEv1 is used as the IPsec
key management protocol (IKEv2 does not seem to support RFC3456
equivalent case).
Jayaraman, et al. Expires January 14, 2005 [Page 29]
Internet-Draft PANA Framework July 2004
PaC AP DHCPv4 Server PAA EP(AR)
| Link-layer | | | |
| association| | | |
|<---------->| | | |
| | | | |
| DHCPv4 | | |
|<-----------+------------>| | |
| | | | |
|PANA(Discovery and initial handshake phase |
| & PAR-PAN exchange in authentication phase) |
|<-----------+-------------------------->| |
| | | |
| | |Authorization|
| | |[IKE-PSK, |
| | | PaC-DI, |
| | | Session-Id] |
| | |------------>|
| | | |
|PANA(PBR-PBA exchange in authentication phase) |
|<-----------+-------------------------->| |
| | | |
| | IKE | |
| (with Configuration Payload exchange or equivalent) |
|<-----------+---------------------------------------->|
| | | |
| | | |
Figure 12: An example case for IPsec-TIA obtained by using IKE
Jayaraman, et al. Expires January 14, 2005 [Page 30]
Internet-Draft PANA Framework July 2004
PRPA
PaC AP DHCPv4 Server PAA
| Link-layer | | |
| association| | |
|<---------->| | |
| | | |
| DHCPv4 | |
|<-----------+-------->| |
| | |
|PANA(Discovery and initial handshake phase
| & PAR-PAN exchange in authentication phase)
|<-----------+-------------------------->|
| | |
| | EP(AR) |
| | |Authorization|
| | |[IKE-PSK, |
| | | PaC-DI, |
| | | Session-Id] |
| | |<------------|
| | | |
|PANA(PBR-PBA exchange in authentication phase)
|<-----------+-------------------------->|
| | |
| IKEv1 phase I & II |
| (to create DHCP SA) |
|<-----------+------------>|
| | |
| DHCP over DHCP SA |
|<-----------+------------>|
| | |
| IKEv1 phase II |
| (to create IPsec SA for data traffic)
|<-----------+------------>|
Figure 13: An example case for configuring IPsec-TIA by using
RFC3456
10.2.1.2 IPv6
In the case of IPv6, the IPsec-TOA (PRPA) is the IPv6 link-local
address. IPsec-TIA (POPA) is obtained by using Configuration Payload
exchange of IKE version 2 (Note that there is no standard method for
configuring IPsec-TIA in IKEv1). Other configuration information may
be obtained in the same Configuration Payload exchange or may be
obtained by running an additional DHCPv6.
Jayaraman, et al. Expires January 14, 2005 [Page 31]
Internet-Draft PANA Framework July 2004
PaC AP EP(AR) PAA
| Link-layer | | |
| association| | |
|<---------->| | |
| | | |
| | | |
|PANA(Discovery and Initial Handshake phase
| & PAR-PAN exchange in Authentication phase)
|<-----------+-------------------------->|
| | | |
| | | |
| | |Authorization|
| | |[IKE-PSK, |
| | | PaC-DI, |
| | | Session-Id] |
| | |<------------|
| | | |
|PANA(PBR-PBA exchange in authentication phase)
|<-----------+-------------------------->|
| | | |
| IKEv2 | |
|(w/Configuration Payload | |
| exchange to obtain IPsec-TIA) |
|<-----------+------------>| |
| | | |
Figure 14: An example sequence for configuring IPsec-TIA in IPv6
10.2.2 PANA with Bootstrapping WPA/IEEE 802.11i
In this model, PANA is used for authentication and authorization, and
L2 ciphering is used for access control, the latter is enabled by the
former. The L2 ciphering is based on using PSK (Pre-Shared Key) mode
of WPA (Wi-Fi Protected Access) [WPA] or IEEE 802.11i [802.11i],
which is derived from the EAP MSK as a result of successful PANA
authentication. In this document, the pre-shared key shared between
station and AP is referred to as PMK (Pair-wise Master Key). In this
model, MAC address is used as the device identifier in PANA.
This model allows the separation of PAA from APs (EPs). A typical
purpose of using this model is to reduce AP management cost by
allowing physical separation of RADIUS/Diameter client from access
points, where AP management can be a significant issue when deploying
a large number of access points.
By bootstrapping PSK mode of WPA and IEEE 802.11i from PANA it is
also possible to improve wireless LAN security by providing protected
Jayaraman, et al. Expires January 14, 2005 [Page 32]
Internet-Draft PANA Framework July 2004
disconnection procedure at L3.
This model does not require any change in the current WPA and IEEE
802.11i specifications. This also means that PANA doesn't provide
any L2 security features beyond those already provided for in WPA and
IEEE 802.11i.
The IEEE 802.11 specification [802.11] allows Class 1 data frames to
be received in any state. Also, the latest version of IEEE 802.11i
[802.11i] optionally allows higher-layer data traffic to be received
and processed on their IEEE 802.1X Uncontrolled Ports. This feature
allows processing IP-based traffic (such as ARP, IPv6 neighbor
discovery, DHCP, and PANA) on IEEE 802.1X Uncontrolled Port prior to
client authentication. (Note: WPA and its corresponding version of
IEEE 802.11i draft do not explicitly define this operation, so it may
be safer not to use this in WPA).
Until the PaC is successfully authenticated, only a selected type of
IP traffic is allowed over the IEEE 802.1X Uncontrolled Port. Any
other IP traffic is dropped on the AP without being forwarded to the
DS (Distribution System). Upon successful PANA authentication, the
traffic switches to the controlled port. Host configuration,
including obtaining an (potentially new) IP address, takes place on
this port. Usual DHCP-based, and also in the case of IPv6 stateless
autoconfiguration, mechanism is available to the PaC. After this
point, the rest of the IP traffic, including PANA exchanges, are
processed on the controlled port.
When a PaC does not have a PMK for the AP, the following procedure is
taken:
1. The PaC associates with the AP.
2. The PaC configures a PRPA by using DHCP (in the case of IPv4) or
configures a link-local address (in the case of IPv6), and then
runs PANA by using the address.
3. Upon successful authentication, the PaC obtains a PMK for each AP
controlled by the PAA.
4. The AP initiates IEEE 802.11i 4-way handshake to establish a PTK
(Pair-wise Transient Key) with the PaC, by using the PMK.
5. The PaC obtains a POPA by using any method that the client
normally uses.
Jayaraman, et al. Expires January 14, 2005 [Page 33]
Internet-Draft PANA Framework July 2004
10.2.3 Capability Discovery
When a PaC is a mobile, there may be multiple APs available in its
vicinity. Each AP are connected to one of the following types of
access networks.
a) Free access network
There is no IEEE 802.1X or PANA authentication in this access
network.
b) PANA-secured network
There is PANA authentication in this access network.
c) IEEE 802.1X-secured network
There is IEEE 802.1X authentication in this access network.
Type (c) is distinguished from others by checking the capability
information advertised in IEEE 802.11 Beacon frames (IEEE 802.11i
defines RSN Information Element for this purpose). Types (a) and (b)
are not distinguishable until the PaC associates with the AP, get an
IP address, and engage in PANA discovery. The default PaC behavior
would be to act as if this is a free network and attempt DHCP. This
would be detected by the access network and trigger unsolicited PANA
discovery. A type (b) network would send a PANA-Start-Request to the
client and block general purpose data traffic. This helps the client
discover whether the network is type (a) or type (b). Or if the PaC
is pre-provisioned with the information that this is a PANA enabled
network, it can attempt PAA discovery immediately. The PaC behavior
after connecting to an AP of type (b) network is described in Section
10.2, Section 10.2.1 and Section 10.2.2.
Jayaraman, et al. Expires January 14, 2005 [Page 34]
Internet-Draft PANA Framework July 2004
11. Open Issue
Certain combination of network environments and timing cases may
require further considerations.
If PaC changes access point right after a successful PANA
authorization but before POPA configuration, it might be confused
whether the new IP address configured via the new access point is the
POPA of the ongoing session or a PRPA of a new session. When the
PRPA and POPA types or configuration mechanisms are different this is
not a problem. One possible combination where such clues are not
available is when PaC moves from a Case A of Section 10.2.1.1
(IPsec-TIA obtained by using DHCPv4) network to a Case D of Appendix
A.1 (IPsec-TIA obtained by using RFC3118) network.
In another example, when PaC switches from one wired Ethernet hub to
another (without the use of bootstrapping IPsec) before configuring
the POPA. In this case, PaC may not able to know whether an obtained
address is the POPA in the same subnet or a PRPA in a new subnet.
For these cases, a mechanism to remove the ambiguity (PRPA vs. POPA)
may need to be defined.
Jayaraman, et al. Expires January 14, 2005 [Page 35]
Internet-Draft PANA Framework July 2004
12. Acknowledgments
We would like to thank Bernard Aboba, Yacine El Mghazli, Randy Turner
and Hannes Tschofenig for their valuable comments.
Jayaraman, et al. Expires January 14, 2005 [Page 36]
Internet-Draft PANA Framework July 2004
13. References
13.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J. and H.
Levkowetz, "Extensible Authentication Protocol (EAP)", RFC
3748, June 2004.
[I-D.ietf-zeroconf-ipv4-linklocal]
Aboba, B., "Dynamic Configuration of Link-Local IPv4
Addresses", draft-ietf-zeroconf-ipv4-linklocal-17 (work in
progress), July 2004.
[RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.
[RFC2461] Narten, T., Nordmark, E. and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461, December
1998.
[RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, February 2003.
[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, November 1998.
[I-D.ietf-ipsec-ikev2]
Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
draft-ietf-ipsec-ikev2-14 (work in progress), June 2004.
[I-D.ietf-pana-snmp]
Mghazli, Y., Ohba, Y. and J. Bournelle, "SNMP usage for
PAA-2-EP interface", draft-ietf-pana-snmp-00 (work in
progress), April 2004.
[I-D.ietf-pana-pana]
Forsberg, D., Ohba, Y., Patil, B., Tschofenig, H. and A.
Yegin, "Protocol for Carrying Authentication for Network
Access (PANA)", draft-ietf-pana-pana-04 (work in
progress), May 2004.
[I-D.ietf-pana-ipsec]
Parthasarathy, M., "PANA enabling IPsec based Access
Control", draft-ietf-pana-ipsec-03 (work in progress), May
2004.
Jayaraman, et al. Expires January 14, 2005 [Page 37]
Internet-Draft PANA Framework July 2004
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and
M. Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.
[RFC3456] Patel, B., Aboba, B., Kelly, S. and V. Gupta, "Dynamic
Host Configuration Protocol (DHCPv4) Configuration of
IPsec Tunnel Mode", RFC 3456, January 2003.
13.2 Informative References
[RFC3377] Hodges, J. and R. Morgan, "Lightweight Directory Access
Protocol (v3): Technical Specification", RFC 3377,
September 2002.
[RFC2865] Rigney, C., Willens, S., Rubens, A. and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)", RFC
2865, June 2000.
[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G. and J.
Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G. and
E. Lear, "Address Allocation for Private Internets", BCP
5, RFC 1918, February 1996.
[I-D.ietf-eap-netsel-problem]
Arkko, J. and B. Aboba, "Network Discovery and Selection
Problem", draft-ietf-eap-netsel-problem-00 (work in
progress), January 2004.
[RFC2486] Aboba, B. and M. Beadles, "The Network Access Identifier",
RFC 2486, January 1999.
[I-D.ietf-pana-requirements]
Yegin, A. and Y. Ohba, "Protocol for Carrying
Authentication for Network Access (PANA)Requirements",
draft-ietf-pana-requirements-08 (work in progress), June
2004.
[I-D.ietf-aaa-eap]
Eronen, P., Hiller, T. and G. Zorn, "Diameter Extensible
Authentication Protocol (EAP) Application",
draft-ietf-aaa-eap-08 (work in progress), June 2004.
[I-D.yegin-eap-boot-rfc3118]
Jayaraman, et al. Expires January 14, 2005 [Page 38]
Internet-Draft PANA Framework July 2004
Yegin, A., Tschofenig, H. and D. Forsberg, "Bootstrapping
RFC3118 Delayed DHCP Authentication Using EAP-based
Network Access Authentication",
draft-yegin-eap-boot-rfc3118-00 (work in progress),
February 2004.
[RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP
Messages", RFC 3118, June 2001.
[I-D.josefsson-pppext-eap-tls-eap]
Josefsson, S., Palekar, A., Simon, D. and G. Zorn,
"Protected EAP Protocol (PEAP)",
draft-josefsson-pppext-eap-tls-eap-07 (work in progress),
October 2003.
[I-D.ietf-pppext-eap-ttls]
Funk, P. and S. Blake-Wilson, "EAP Tunneled TLS
Authentication Protocol (EAP-TTLS)",
draft-ietf-pppext-eap-ttls-04 (work in progress), April
2004.
[I-D.tschofenig-eap-ikev2]
Tschofenig, H. and D. Kroeselberg, "EAP IKEv2 Method
(EAP-IKEv2)", draft-tschofenig-eap-ikev2-03 (work in
progress), February 2004.
[DSL] DSL Forum Architecture and Transport Working Group, "DSL
Forum TR-058 Multi-Service Architecture and Framework
Requirements", September 2003.
[802.11i] Institute of Electrical and Electronics Engineers, "Draft
supplement to standard for telecommunications and
information exchange between systems - lan/man specific
requirements - part 11: Wireless medium access control
(mac) and physical layer (phy) specifications:
Specification for enhanced security", IEEE 802.11i/D10.0,
2004.
[802.11] Institute of Electrical and Electronics Engineers,
"Information technology - telecommunications and
information exchange between systems - local and
metropolitan area networks - specific requirements part
11: Wireless lan medium access control (mac) and physical
layer (phy) specifications", IEEE Standard 802.11,
1999(R2003).
[WPA] The Wi-Fi Alliance, "WPA (Wi-Fi Protected Access)", Wi-Fi
WPA v2.0, 2003.
Jayaraman, et al. Expires January 14, 2005 [Page 39]
Internet-Draft PANA Framework July 2004
Authors' Addresses
Prakash Jayaraman
Network Equipment Technologies, Inc.
6900 Paseo Padre Parkway
Fremont, CA 94555
USA
Phone: +1 510 574 2305
EMail: prakash_jayaraman@net.com
Rafa Marin Lopez
University of Murcia
30071 Murcia
Spain
EMail: rafa@dif.um.es
Yoshihiro Ohba
Toshiba America Research, Inc.
1 Telcordia Drive
Piscateway, NJ 08854
USA
Phone: +1 732 699 5365
EMail: yohba@tari.toshiba.com
Mohan Parthasarathy
Nokia
313 Fairchild Drive
Mountain View, CA 94043
USA
Phone: +1 408 734 8820
EMail: mohanp@sbcglobal.net
Alper E. Yegin
Samsung Advanced Institute of Technology
75 West Plumeria Drive
San Jose, CA 95134
USA
Phone: +1 408 544 5656
EMail: alper.yegin@samsung.com
Jayaraman, et al. Expires January 14, 2005 [Page 40]
Internet-Draft PANA Framework July 2004
Appendix A. Other Possible Cases for PANA with Bootstrapping IPsec in
Wireless LAN
This section describes other possible cases for PANA with
Bootstrapping IPsec in wireless LAN environments.
Appendix A.1 IPv4
Case D: IPsec-TIA obtained by using RFC3118
In this case, the POPA is configured and used as both IPsec-TIA
and IPsec-TOA. The IPsec-TIA is assigned by using RFC3118
(authenticated DHCP) [RFC3118] before running IKE. The DHCP-PSK
needed for authenticated DHCP is distributed from the PAA to the
POPA DHCPv4 server by using the method specified in
[I-D.yegin-eap-boot-rfc3118]. The PRPA is assigned by using
DHCPv4 and may be assigned with a short lease period in order to
provide some level of robustness against IP address depletion
attack. The IPsec-TIA is bound to an IPsec SA by using specifying
the IPsec-TIA as the SA Identification in IKEv1 phase II or IKEv2
CREATE_CHILD_SA exchange as specified in [I-D.ietf-pana-ipsec].
Once the IPsec-TIA is obtained, the PANA re-authentication based
on PUR (PANA-Update-Rquest) and PUA (PANA-Update-Answer) exchange
is performed with using the obtained IPsec-TIA in order to inform
PAA of the update of PaC-DI. The IKE procedure should occur after
the PUR-PUA exchange procedure. The PaC unconfigures the PRPA
immediately after the IPsec-TIA is obtained.
Jayaraman, et al. Expires January 14, 2005 [Page 41]
Internet-Draft PANA Framework July 2004
PRPA
PaC AP DHCPv4 Server PAA EP(AR)
| Link-layer | | | |
| association| | | |
|<---------->| | | |
| | | | |
| DHCPv4 | | |
|<-----------+--------->| | |
| | | | |
|PANA(Discovery and Initial Handshake phase |
| & PAR-PAN exchange in Authentication phase) |
|<-----------+-------------------------->| |
| | | |
| | | |
| | POPA | |
| | DHCPv4 Server |Authorization|
| | |Authorization|[IKE-PSK, |
| | |[DHCP-PSK, | PaC-DI, |
| | | Session-Id] | Session-Id] |
| | |<------------|------------>|
| | | | |
|PANA(PBR-PBA exchange in Authentication phase) |
|<-----------+-------------------------->| |
| | | | |
| Authenticated DHCPv4 | | |
| (RFC3118) | | |
|<-----------+------------>| | |
| | | | |
| PANA(PUR-PUA exchange using POPA as PaC-DI) |
|<-----------+-------------------------->| |
| | | | |
| | IKE | |
|<-----------+---------------------------------------->|
| | | | |
| | | | |
Figure 15: An example case for IPsec-TIA obtained by using RFC3118
Appendix A.2 IPv6
Case A: IPsec-TIA obtained by using DHCPv6
This case is similar to Case A in IPv4, except that a link-local
address is used as the PRPA and IPsec-TOA, and that the DHCPv6
procedure can occur at any time after link-layer association and
before IKE.
Jayaraman, et al. Expires January 14, 2005 [Page 42]
Internet-Draft PANA Framework July 2004
This case is not recommended since there is an ambiguity on
whether IPv6 Neighbor Discovery for the POPA should run on the
physical interface or inside the IPsec tunnel or both.
PaC AP DHCPv6 Server PAA EP(AR)
| Link-layer | | | |
| association| | | |
|<---------->| | | |
| | | | |
| DHCPv6 | | |
|<-----------+------------>| | |
| | | | |
|PANA(Discovery and Initial Handshake phase |
| & PAR-PAN exchange in Authentication phase) |
|<-----------+-------------------------->| |
| | | | |
| | | |Authorization|
| | | |[IKE-PSK, |
| | | | PaC-DI, |
| | | | Session-Id] |
| | | |------------>|
| | | | |
|PANA(PBR-PBA exchange in Authentication phase) |
|<-----------+-------------------------->| |
| | | | |
| | IKE | |
|<-----------+---------------------------------------->|
| | | | |
| | | | |
Figure 16: An example case for IPsec-TIA obtained by using DHCPv6
Case B: IPsec-TIA obtained by using IPv6 stateless address
autoconfiguration
In this case, the IPsec-TOA (link-local address) and IPsec-TIA
(global address) are configured through IPv6 stateless address
autoconfiguration before running IKE. Other configuration
information can be obtained by using several methods including
authenticated DHCPv6, Configuration Payload exchange and DHCPv6
over IPsec SA.
This case is not recommended for the same reason as Case A of
IPv6.
Jayaraman, et al. Expires January 14, 2005 [Page 43]
Internet-Draft PANA Framework July 2004
PaC AP PAA EP(AR)
| Link-layer | | |
| association| | |
|<---------->| | |
| | | |
| | | |
|PANA(Discovery and Initial Handshake phase |
| & PAR-PAN exchange in Authentication phase) |
|<-----------+-------------------------->| |
| | | |
| | |Authorization|
| | |[IKE-PSK, |
| | | PaC-DI, |
| | | Session-Id] |
| | |------------>|
| | | |
|PANA(PBR-PBA exchange in Authentication phase) |
|<-----------+-------------------------->| |
| | | |
| IPv6 stateless address autoconfiguration |
| (can occur at any time before Association and IKEv2) |
|<-----------+---------------------------------------->|
| | | |
| | IKEv2 | |
|<-----------+---------------------------------------->|
| | | |
Figure 17: An example sequence for IPsec-TIA obtained by using
IPv6 stateless address autoconfiguration
Case C: IPsec-TIA obtained by using authenticated DHCPv6
This case is similar to Case C of IPv4, except that a link-local
address is used as the PRPA, and that there is no need for
additional PUR-PUA exchange to update the PaC-DI.
Jayaraman, et al. Expires January 14, 2005 [Page 44]
Internet-Draft PANA Framework July 2004
PaC AP DHCPv6 Server PAA EP(AR)
| Link-layer | | | |
| association| | | |
|<---------->| | | |
| | | | |
| | | | |
|PANA(Discovery and Initial Handshake phase |
| & PAR-PAN exchange in Authentication phase) |
|<-----------+-------------------------->| |
| | | | |
| | |Authorization|Authorization|
| | |[DHCP-PSK, |[IKE-PSK, |
| | | Session-Id] | PaC-DI, |
| | | | Session-Id] |
| | |<------------|------------>|
| | | | |
|PANA(PBR-PBA exchange in Authentication phase) |
|<-----------+-------------------------->| |
| | | | |
| Authenticated DHCPv6 | | |
|<-----------+------------>| | |
| | | |Authorization|
| | | | [IKE-PSK, |
| | | | PaC-DI, |
| | | | Session-Id]|
| | | |------------>|
| | IKE | |
|<-----------+---------------------------------------->|
| | | | |
| | | | |
Figure 18: An example case for configuring IPsec-TIA by using
authenticated DHCPv6
Jayaraman, et al. Expires January 14, 2005 [Page 45]
Internet-Draft PANA Framework July 2004
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights 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; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat 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 implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM 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.
Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Jayaraman, et al. Expires January 14, 2005 [Page 46]