PANA Working Group P. Jayaraman
Internet-Draft Net.Com
Expires: January 12, 2006 R. Lopez
Univ. of Murcia
Y. Ohba (Ed.)
Toshiba
M. Parthasarathy
Nokia
A. Yegin
Samsung
July 11, 2005
PANA Framework
draft-ietf-pana-framework-05
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Copyright (C) The Internet Society (2005).
Abstract
PANA (Protocol for carrying Authentication for Network Access) design
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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. This document 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 wireless LANs.
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 ISP Selection . . . . . . . . . . . 26
10.2 Wireless LAN Example . . . . . . . . . . . . . . . . . . 27
10.2.1 PANA with Bootstrapping IPsec . . . . . . . . . . . 27
10.2.2 PANA with Bootstrapping WPA/IEEE 802.11i . . . . . . 32
10.2.3 Capability Discovery . . . . . . . . . . . . . . . . 34
11. Security Considerations . . . . . . . . . . . . . . . . . . 35
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . 36
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 37
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 38
14.1 Normative References . . . . . . . . . . . . . . . . . . 38
14.2 Informative References . . . . . . . . . . . . . . . . . 39
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 40
A. Other Possible Cases for PANA with Bootstrapping IPsec in
Wireless LAN . . . . . . . . . . . . . . . . . . . . . . . . 42
A.1 IPv4 . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
A.2 IPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Intellectual Property and Copyright Statements . . . . . . . 48
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1. Introduction
PANA (Protocol for carrying Authentication for Network Access) 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 [RFC4058]. 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 document 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 (Digital Subscriber Line) networks and WLANs
(Wireless LANs).
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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].
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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.
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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 node 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
(Authentication Authorization and Accounting) 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 node that is requesting network access.
PaCs can be end hosts, such as laptops, PDAs, cell phones, desktop
PCs, or routers 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 node 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.
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 node, 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.
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The PAA resides on a node that is typically called a NAS (network
access server) in the access network. For example on a BAS
(Broadband Access Server) in DSL networks, or PDSN (Packet Data
Serving Node) in 3GPP2 networks. The PAA may be one or more IP
hops away from the PaCs.
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 node as
the PAA, on a dedicated node on the access network, or on a
central server somewhere in 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 node
or beyond the local area network.
Figure 1 illustrates these functional entities and the interfaces
(protocols, APIs) among them.
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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 IEEE 802.11i 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.
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PaC EP PAA AS
| | | |
IP address ->| | | |
config. | PANA | | AAA |
|<------------------------------>|<-------------->|
| | SNMP | |
(Optional) | |<-------------->| |
IP address ->| | | |
reconfig. | 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, etc.) 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 (e.g., via
IKE).
An initially unauthorized PaC starts the PANA authentication by
discovering the PAA, 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. The secure
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association protocol 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.
Finally data traffic can start flowing from and to the newly
authorized PaC.
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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
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association protocol.
Whether to use a link-layer per-packet 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.
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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 the PRPA
is a local-use (e.g., a 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 (e.g., globally routable) 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 node, 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 a
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.
The 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 end-to-end 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 automatically configure a link-local address
[RFC2462] when they initialize an interface. Additionally, they
may also configure global address(es) when DHCP or router
advertisements with global prefixes are made available to the
them.
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In case PAA is not on the same IP subnet as the PaCs are, the
deployment must ensure that a non-link-local PRPA is configurable by
the clients.
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.
Regardless of whether the PaC has both IPv4 and IPv6 PRPAs or only
one of those, only one PANA run is required. A dual-stack device
that implements PaC or PAA MUST be able to run PANA over both IPv4
and IPv6. When a dual-stack PaC or PAA initiates PANA
authentication, it chooses either IPv4 or IPv6 where the choice is
made depending on the deployment. A dual-stack PaC or PAA that is
initiated PANA authentication by its peer MUST use the same IP
version that the peer is using.
When 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 node, it can configure both IPv4 and
IPv6 type POPAs. The available POPA configuration methods are
indicated within the PANA protocol.
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.
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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.
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. In this case, the same IP version
that has been used for PANA is used for IKE, and the IKE entity on
the dual-stack PaC will request one or both of IPv4 and IPv6
IPsec-TIAs from the IKE entity on the EP and obtain the one(s)
that is(are) available on the EP.
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.
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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
insufficient to be used alone by IPsec AH/ESP or most link layer
mechanisms. In addition to the fresh and unique session key derived
from the EAP method, IPsec also needs 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; link-
layer ciphering is enabled using any of the existing link-layer
specific methods.
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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 send
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. When the access control is
performed at link-layer, an IP-capable access device on the same link
as the client devices is the logical choice. When IPsec-based or
non-cryptographic access control mechanisms are used, the EPs'
location can range from the first-hop router to other routers within
the access network. The first-hop router may be preferred in order
to limit the access of unauthorized IP traffic.
PAA and EPs 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
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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).
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 link-layer 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 link-layer 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 link-layer 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
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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.
+---+
+-----|PAA|
/ +---+
+---+/
|PaC|
+---+\
\ +---+
+-----|EP |---- Internet
+---+
Figure 4: PAA and EP in Parallel
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 on 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.
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+---+
|EP |--+
+---+ \
\
+---+ +---+ +---+
|PaC| |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 [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 [RFC4058]. 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. When
IPsec is used the filter rules are applied to IP packets carried
inside the IPsec tunnel, otherwise, the filter rules are applied to
IP packets that are not protected with IPsec.
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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 a PaC
to choose one ISP from the advertised information. When the 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 identifier may be an NAI
[RFC2486] or the physical port number or link-layer 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, the PaC is assigned an address by the ISP.
Consider a typical DSL network where the AR (access router), 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 network-layer with the use of the
PANA protocol instead of link-layer specific authentication
mechanisms, the IP link between the PaC and PAA needs to exist prior
to doing PANA (and prior to network selection). In this model, the
PRPA is either given by the NAP or a link-local address is auto-
configured. After the successful authentication with the ISP, the
PaC may acquire an address (POPA) from the ISP. It also learns the
address of the access router (AR), e.g., 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. Note that the physically
secured DSL networks do not require IPsec-based access control.
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Therefore the PaC uses one IP address at a time where the POPA
replaces the PRPA upon configuration.
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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. 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).
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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.
In the current DSL deployment, a DSLAM (DSL Access Multiplexor) which
is placed between the CPE and NAS is a transparent device from PANA
perspective. In a future DSL model, the PAA may reside in the DSLAM
which may directly connect ISP routers through VLANs.
Host--+ +-------- ISP1
| DSL link |
+----- CPE ----- DSLAM ----- NAS ----+-------- ISP2
| (Bridge/ |
Host--+ NAPT/Router) +-------- ISP3jG
<------- 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 link-layer 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.
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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
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 ----- DSLAM ----- 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 ----- DSLAM ----- 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).
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10.1.3 PANA and Dynamic ISP 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
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.
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10.2 Wireless LAN Example
This section describes how PANA can be used on WLANs. 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 depending on
which layer security is bootstrapped from PANA authentication, link-
layer or IP-layer. When PANA authentication is used for
bootstrapping IP-layer security, link-layer 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 link-layer or IP-layer 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 link-layer
security or with AR when PANA is used for bootstrapping IP-layer
security.
+-----+
|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 the 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, a PBR
(PANA-Bind-Request) and PBA (PANA-Bind-Answer) exchange in PANA
[I-D.ietf-pana-pana] should occur after installing the authorization
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parameter to the AR, so that IKE can be performed immediately after
the PANA authentication is successfully completed. The PAA can
obtain the required device identifer (i.e., the IPsec-TOA in this
case) to be installed on the AR from the IP header of a PANA message
sent by the PaC before sending the PBR. However, when the PBR/PBA
exchange fails, the authorization parameters already installed on the
AR must be immediately revoked to avoid unauthorized access.
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.
PaC AP DHCPv4 Server PAA EP(AR)
| Link-layer | | | |
| association| | | |
|<---------->| | | |
| | | | |
| DHCPv4 | | |
|<-----------+------------>| | |
| | | |
|PANA(Discovery and handshake phase | |
| & PAR/PAN exchange in authentication |
| and authorization phase) | |
|<-----------+-------------------------->| |
| | | |
| | |Authorization|
| | |[IKE-PSK, |
| | | PaC-DI, |
| | | Session-Id] |
| | |------------>|
| | | |
|PANA(PBR/PBA exchange in | |
| authentication and authorization phase) |
|<-----------+-------------------------->| |
| | | |
| | IKE | |
|<-----------+---------------------------------------->|
| | | |
Figure 11: An example case for configuring IPsec-TIA by using
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DHCPv4
Case B: IPsec-TIA obtained by using IKE
In this case, the PRPA is obtained by using DHCPv4 and used as the
IPsec-TOA. The POPA is obtained by using IKE (via a Configuration
Payload exchange or equivalent) and used as the IPsec-TIA. An
example sequence for Case B is shown in Figure 12.
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).
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PaC AP DHCPv4 Server PAA EP(AR)
| Link-layer | | | |
| association| | | |
|<---------->| | | |
| | | | |
| DHCPv4 | | |
|<-----------+------------>| | |
| | | | |
|PANA(Discovery and handshake phase | |
| & PAR/PAN exchange in | |
| authentication and authorization phase) |
|<-----------+-------------------------->| |
| | | |
| | |Authorization|
| | |[IKE-PSK, |
| | | PaC-DI, |
| | | Session-Id] |
| | |------------>|
| | | |
|PANA(PBR/PBA exchange in | |
| authentication and authorization phase) |
|<-----------+-------------------------->| |
| | |
| | IKE |
| (with Configuration Payload exchange) |
|<-----------+---------------------------------------->|
| | | |
| | | |
Figure 12: An example case for IPsec-TIA obtained by using IKE
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PaC AP DHCPv4 Server PAA
| Link-layer | | |
| association| | |
|<---------->| | |
| | | |
| DHCPv4 | |
|<-----------+-------->| |
| | |
|PANA(Discovery and handshake phase |
| & PAR/PAN exchange in |
| authentication and authorization phase)
|<-----------+-------------------------->|
| | |
| | | EP(AR)
| | | |Authorization
| | | |[IKE-PSK,
| | | | PaC-DI,
| | | | Session-Id]
| | |----------->|
| | | |
|PANA(PBR/PBA exchange in authentication | |
| and authorization 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
IPsec-TIA (POPA) is obtained by using IKE (via a Configuration
Payload exchange or equivalent). Other configuration information may
be obtained in the same Configuration Payload exchange or may be
obtained by running an additional DHCPv6.
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PaC AP PAA EP(AR)
| Link-layer | | |
| association| | |
|<---------->| | |
| | | |
| | | |
|PANA(Discovery and handshake phase |
| & PAR/PAN exchange in |
| authentication and authorization phase)
|<-----------+------------>| |
| | | |
| | | |
| | |Authorization|
| | |[IKE-PSK, |
| | | PaC-DI, |
| | | Session-Id] |
| | |------------>|
| | | |
|PANA(PBR/PBA exchange in | |
| authentication and authorization phase)
|<-----------+------------>| |
| | |
| IKEv2 |
| (with Configuration Payload exchange) |
|<-----------+-------------------------->|
| | | |
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
link-layer ciphering is used for access control. Successful PANA
authentication enables link-layer ciphering which is based on PSK
(Pre-Shared Key) mode of WPA (Wi-Fi Protected Access) [WPA] or IEEE
802.11i [802.11i]. In this document, the key shared between a
station and an AP is referred to as the PMK (Pair-wise Master Key).
The PMK is derived from the EAP AAA-Key as a result of successful
PANA authentication. In this model, MAC addresses are used as the
device identifiers in PANA.
This model allows the separation of PAA from EPs(APs). 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. Additionally, this centralized AAA
framework enhances mobility-related performance (inter-AP but intra-
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PAA mobility does not require additional PANA executions).
By bootstrapping PSK mode of WPA and IEEE 802.11i from PANA it is
also possible to improve wireless LAN security by providing protected
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 link-layer 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, IEEE 802.11i [802.11i] optionally
allows higher-layer data traffic to be received and processed on the
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.
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 at 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.
3. Upon successful authentication, the PaC obtains a separate 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.
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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, gets 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.
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11. Security Considerations
Security is discussed throughout this document. For protocol-
specific security considerations, refer to [I-D.ietf-pana-pana].
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12. IANA Considerations
This document has no actions for IANA.
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13. Acknowledgments
We would like to thank Bernard Aboba, Yacine El Mghazli, Randy
Turner, Hannes Tschofenig and Lionel Morand for their valuable
comments.
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14. References
14.1 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-ikev2-17 (work in progress),
October 2004.
[I-D.ietf-pana-snmp]
Mghazli, Y., "SNMP usage for PAA-EP interface",
draft-ietf-pana-snmp-04 (work in progress), July 2005.
[I-D.ietf-pana-pana]
Forsberg, D., "Protocol for Carrying Authentication for
Network Access (PANA)", draft-ietf-pana-pana-08 (work in
progress), May 2005.
[I-D.ietf-pana-ipsec]
Parthasarathy, M., "PANA Enabling IPsec based Access
Control", draft-ietf-pana-ipsec-06 (work in progress),
May 2005.
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[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.
14.2 Informative References
[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-02 (work in
progress), October 2004.
[RFC2486] Aboba, B. and M. Beadles, "The Network Access Identifier",
RFC 2486, January 1999.
[RFC4058] Yegin, A., Ohba, Y., Penno, R., Tsirtsis, G., and C. Wang,
"Protocol for Carrying Authentication for Network Access
(PANA) Requirements", RFC 4058, May 2005.
[I-D.ietf-aaa-eap]
Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible
Authentication Protocol (EAP) Application",
draft-ietf-aaa-eap-10 (work in progress), November 2004.
[I-D.yegin-eap-boot-rfc3118]
Yegin, A., Tschofenig, H., and D. Forsberg, "Bootstrapping
RFC3118 Delayed DHCP Authentication Using EAP-based
Network Access Authentication",
draft-yegin-eap-boot-rfc3118-01 (work in progress),
January 2005.
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[RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP
Messages", RFC 3118, June 2001.
[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 v3.1, 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
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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
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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 PaC
unconfigures the PRPA immediately after the IPsec-TIA is obtained.
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 PUR (PANA-Update-Request) and
PUA (PANA-Update-Answer) exchange is performed with using the
obtained IPsec-TIA in order to inform the PAA of the update of the
IP address of the PaC. The IKE procedure should occur after the
PANA-Update exchange.
Note that different DHCP servers may be used for obtaining the
PRPA and the POPA, when the PRPA address space and POPA address
space are under different administrative domains.
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PaC AP DHCPv4 Server PAA EP(AR)
| Link-layer | | | |
| association| | | |
|<---------->| | | |
| | | | |
| DHCPv4 | | |
|<-----------+--------->| | |
| | | | |
|PANA(Discovery and handshake phase | |
| & PAR/PAN exchange in | |
| authentication and authorization phase) |
|<-----------+-------------------------->| |
| | | | |
| | | | |
| | |Authorization | |
| | |[DHCP-PSK, | |
| | | Session-Id] | |
| | |<---------------| |
| | | | |
|PANA(PBR/PBA exchange in | |
| authentication and authorization phase) |
|<-----------+-------------------------->| |
| | | | |
|Authenticated DHCPv4 | | |
| (RFC3118) | | |
|<-----------+--------->| | |
| | | |
| PANA(PUR/PUA exchange in access phase based on POPA) |
|<-----------+-------------------------->| |
| | | |
| | |Authorization|
| | |[IKE-PSK, |
| | | PaC-DI, |
| | | Session-Id] |
| | |------------>|
| | IKE | |
|<-----------+---------------------------------------->|
| | | |
| | | |
Figure 15: An example case for IPsec-TIA obtained by using RFC3118
Appendix A.2 IPv6
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Case A: IPsec-TIA obtained by using DHCPv6
This case is similar to Case A in IPv4, except that the DHCPv6
procedure can occur at any time after link-layer association and
before IKE.
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 handshake phase | |
| & PAR/PAN exchange in | |
| authentication and authorization phase) |
|<-----------+-------------------------->| |
| | | |
| | |Authorization|
| | |[IKE-PSK, |
| | | PaC-DI, |
| | | Session-Id] |
| | |------------>|
| | | |
|PANA(PBR/PBA exchange in | |
| authentication and authorization 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 and IPsec-TIA 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.
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This case is not recommended for the same reason as Case A of
IPv6.
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PaC AP PAA EP(AR)
| Link-layer | | |
| association| | |
|<---------->| | |
| | | |
| | | |
|PANA(Discovery and handshake phase | |
| & PAR/PAN exchange in | |
| authentication and authorization phase) |
|<-----------+-------------------------->| |
| | | |
| | |Authorization|
| | |[IKE-PSK, |
| | | PaC-DI, |
| | | Session-Id] |
| | |------------>|
| | | |
|PANA(PBR/PBA exchange in | |
| authentication and authorization phase) |
|<-----------+-------------------------->| |
| | | |
| IPv6 stateless address autoconfiguration |
| (can occur at any time after association and before IKE)
|<-----------+---------------------------------------->|
| | | |
| | IKE | |
|<-----------+---------------------------------------->|
| | | |
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 there is no
need for additional PANA-Update exchange to update the the IP
address of the PaC.
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PaC AP DHCPv6 Server PAA EP(AR)
| Link-layer | | | |
| association| | | |
|<---------->| | | |
| | | | |
| | | | |
|PANA(Discovery and handshake phase | |
| & PAR/PAN exchange in | |
| authentication and authorization phase) |
|<-----------+-------------------------->| |
| | | | |
| | |Authorization|Authorization|
| | |[DHCP-PSK, |[IKE-PSK, |
| | | Session-Id] | PaC-DI, |
| | | | Session-Id] |
| | |<------------|------------>|
| | | | |
|PANA(PBR/PBA exchange in | | |
| authentication and authorization phase) |
|<-----------+-------------------------->| |
| | | | |
| Authenticated DHCPv6 | | |
|<-----------+------------>| | |
| | | |Authorization|
| | | | [IKE-PSK, |
| | | | PaC-DI, |
| | | | Session-Id]|
| | | |------------>|
| | IKE | |
|<-----------+---------------------------------------->|
| | | | |
| | | | |
Figure 18: An example case for configuring IPsec-TIA by using
authenticated DHCPv6
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