RFC4058: Protocol for Carrying Authentication for Network Access (PANA) Requirements

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Network Working Group                                      A. Yegin, Ed.
Request for Comments: 4058                                   Samsung AIT
Category: Informational                                          Y. Ohba
                                                                R. Penno
                                                        Juniper Networks
                                                             G. Tsirtsis
                                                                 C. Wang
                                                                May 2005

     Protocol for Carrying Authentication for Network Access (PANA)

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).


   It is expected that future IP devices will have a variety of access
   technologies to gain network connectivity.  Currently there are
   access-specific mechanisms for providing client information to the
   network for authentication and authorization purposes.  In addition
   to being limited to specific access media (e.g., 802.1X for IEEE 802
   links), some of these protocols are limited to specific network
   topologies (e.g., PPP for point-to-point links).  The goal of this
   document is to identify the requirements for a link-layer agnostic
   protocol that allows a host and a network to authenticate each other
   for network access.  This protocol will run between a client's device
   and an agent in the network where the agent might be a client of the
   AAA infrastructure.

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Table of Contents

   1. Introduction ....................................................3
   2. Requirements Notation ...........................................3
   3. Terminology .....................................................4
   4. Requirements ....................................................4
      4.1. Authentication .............................................4
           4.1.1. Authentication of Client ............................4
           4.1.2. Authorization, Accounting, and Access Control .......6
           4.1.3. Authentication Backend ..............................7
           4.1.4. Identifiers .........................................7
      4.2. IP Address Assignment ......................................7
      4.3. EAP Lower Layer Requirements ...............................7
      4.4. PAA-to-EP Protocol .........................................8
      4.5. Network ....................................................8
           4.5.1. Multi-access ........................................8
           4.5.2. Disconnect Indication ...............................8
           4.5.3. Location of PAA .....................................9
           4.5.4. Secure Channel ......................................9
      4.6. Interaction with Other Protocols ..........................10
      4.7. Performance ...............................................10
      4.8. Congestion Control ........................................10
      4.9. IP Version Independence ...................................10
      4.10. Denial of Service Attacks ................................10
      4.11. Client Identity Privacy ..................................10
   5. Security Considerations ........................................11
   6. Acknowledgements ...............................................11
   A. Problem Statement ..............................................12
   B. Usage Scenarios ................................................13
   References ........................................................16
      Normative References ...........................................16
      Informative References .........................................16

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1.  Introduction

   Secure network access service requires access control based on the
   authentication and authorization of the clients and the access
   networks.  Initial and subsequent client-to-network authentication
   provides parameters that are needed to police the traffic flow
   through the enforcement points.  A protocol is needed to carry
   authentication parameters between the client and the access network.
   See Appendix A for the associated problem statement.

   The protocol design will be limited to defining a messaging protocol
   (i.e., a carrier) that will allow authentication payload to be
   carried between the host/client and an agent/server in the access
   network for authentication and authorization purposes regardless of
   the AAA infrastructure that may (or may not) reside on the network.
   As a network-layer protocol, it will be independent of the underlying
   access technologies and applicable to any network topology.

   The intent is not to invent new security protocols and mechanisms but
   to reuse existing mechanisms such as EAP [RFC3748].  In particular,
   the requirements do not mandate the need to define new authentication
   protocols (e.g., EAP-TLS [RFC2716]), key distribution or key
   agreement protocols, or key derivation methods.  The desired protocol
   can be viewed as the front-end of the AAA protocol or any other
   protocol/mechanisms the network is running at the background to
   authenticate its clients.  It will act as a carrier for an already
   defined security protocol or mechanism.

   An example of a protocol being extended for use in authenticating a
   host for network access is Mobile IPv4.  A Mobile IPv4 registration
   request message is used as a carrier for authentication extensions
   (MN-FA [RFC3344] or MN-AAA [RFC3012]) that allows a foreign agent to
   authenticate mobile nodes before providing forwarding service.  The
   goal of PANA is similar in that it aims to define a network-layer
   transport for authentication information.  However, PANA will be
   decoupled from mobility management and will rely on other
   specifications for the definition of authentication payloads.

   This document defines common terminology and identifies requirements
   of a protocol for PANA that will be used to define and limit the
   scope of the work to be done in this group.

2.  Requirements Notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

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3.  Terminology

   PANA Client (PaC)

      The client side of the protocol that resides in the host device
      which is responsible for providing the credentials to prove its
      identity for network access authorization.

   PANA Client Identifier (PaCI)

      The identifier that is presented by the PaC to the PAA for network
      access authentication.  A simple username and NAI [RFC2794] are
      examples of PANA client identifiers.

   Device Identifier (DI)

      The identifier used by the network as a handle to control and
      police the network access of a client.  Depending on the access
      technology, this identifier might contain an IP address, a link-
      layer address, or a switch port number, etc. of a connected

   PANA Authentication Agent (PAA)

      The access network side entity of the protocol whose
      responsibility is to verify the credentials provided by a PANA
      client and grant network access service to the device associated
      with the client and identified by a DI.

   Enforcement Point (EP)

      A node on the access network where per-packet enforcement policies
      (i.e., filters) are applied on the inbound and outbound traffic of
      client devices.  Information such as DI and (optionally)
      cryptographic keys are provided by PAA per client for constructing
      filters on the EP.

4.  Requirements

4.1.  Authentication

4.1.1.  Authentication of Client

   PANA MUST enable authentication of PaCs for network access.  A PaC's
   identity can be authenticated by verifying the credentials (e.g.,
   identifier, authenticator) supplied by one of the users of the device
   or the device itself.  PANA MUST only grant network access service to
   the device identified by the DI, rather than separate access to

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   multiple simultaneous users of the device.  Once network access is
   granted to the device, methods used by the device on arbitrating
   which user can access the network is outside the scope of PANA.

   PANA MUST NOT define new security protocols or mechanisms.  Instead,
   it MUST be defined as a "carrier" for such protocols.  PANA MUST
   identify which specific security protocol(s) or mechanism(s) it can
   carry (the "payload").  EAP is a candidate protocol that satisfies
   many requirements for authentication.  PANA would be a carrier
   protocol for EAP.  If the PANA Working Group decides that extensions
   to EAP are needed, it will define requirements for the EAP WG instead
   of designing such extensions.

   Providing authentication, integrity and replay protection for data
   traffic after a successful PANA exchange is outside the scope of this
   protocol.  In networks where physical layer security is not present,
   link-layer or network-layer ciphering (e.g., IPsec) can be used to
   provide such security.  These mechanisms require the presence of
   cryptographic keying material at PaC and EP.  Although PANA does not
   deal with key derivation or distribution, it enables this by carrying
   EAP and allowing appropriate EAP method selection.  Various EAP
   methods are capable of generating basic keying material that cannot
   be directly used with IPsec because it lacks the properties of an
   IPsec SA (security association) including secure cipher suite
   negotiation, mutual proof of possession of keying material, freshness
   of transient session keys, key naming, etc.  These basic (initial)
   EAP keys can be used with an IPsec key management protocol, like IKE,
   to generate the required security associations.  A separate protocol,
   called secure association protocol, is required to generate IPsec SAs
   based on the basic EAP keys.  This protocol MUST be capable of
   enabling IPsec-based access control on the EPs.  IPsec SAs MUST
   enable authentication, integrity and replay protection of data
   packets as they are sent between the EP and PaC.

   Providing a complete secure network access solution by securing
   router discovery  [RFC1256], neighbor discovery [RFC2461], and
   address resolution protocols [RFC826] is outside the scope as well.

   Some access networks might require or allow their clients to get
   authenticated and authorized by the network access provider (NAP) and
   ISP before the clients gain network access.  NAP is the owner of the
   access network who provides physical and link-layer connectivity to
   the clients.  PANA MUST be capable of enabling two independent
   authentication operations (i.e., execution of two separate EAP
   methods) for the same client.  Determining the authorization
   parameters as a result of two separate authentications is an
   operational issue and therefore outside the scope of PANA.

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   Both the PaC and the PAA MUST be able to perform mutual
   authentication for network access.  Providing only the capability of
   a PAA authenticating the PaC is not sufficient.  Mutual
   authentication capability is required in some environments but not in
   all of them.  For example, clients might not need to authenticate the
   access network when physical security is available (e.g., dial-up

   PANA MUST be capable of carrying out both periodic and on-demand re-
   authentication.  Both the PaC and the PAA MUST be able to initiate
   both the initial authentication and the re-authentication process.

   Certain types of service theft are possible when the DI is not
   protected during or after the PANA exchange [RFC4016].  PANA MUST
   have the capability to exchange DI securely between the PaC and PAA
   where the network is vulnerable to man-in-the-middle attacks.  While
   PANA MUST provide such a capability, its utility relies on the use of
   an authentication method that can generate keys for cryptographic
   computations on PaC and PAA.

4.1.2.  Authorization, Accounting, and Access Control

   After a device is authenticated by using PANA, it MUST be authorized
   for "network access." That is, the core requirement of PANA is to
   verify the authorization of a PaC so that PaC's device may send and
   receive any IP packets.  It may also be possible to provide finer
   granularity authorization, such as authorization for QoS or
   individual services (e.g., http vs. ssh).  However, while a backend
   authorization infrastructure (e.g., RADIUS or Diameter based AAA
   infra) might provide such indications to the PAA, explicit support
   for them is outside the scope of PANA.  For instance, PANA is not
   required to carry any indication of the services authorized for the
   authenticated device.

   Providing access control functionality in the network is outside the
   scope of PANA.  Client access authentication SHOULD be followed by
   access control to make sure only authenticated and authorized clients
   can send and receive IP packets via the access network.  Access
   control can involve setting access control lists on the EPs.  PANA
   protocol exchange identifies clients that are authorized to access
   the network.  If IPsec-based access control is deployed in an access
   network, PaC and EPs should have the required IPsec SA in place.
   Generating the IPsec SAs based on EAP keys is outside the scope of
   PANA protocol.  This transformation MUST be handled by a separate
   secure association protocol (see section 4.1.1).

   Carrying accounting data is outside the scope of PANA.

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4.1.3.  Authentication Backend

   PANA protocol MUST NOT make any assumptions on the backend
   authentication protocol or mechanisms.  A PAA MAY interact with
   backend AAA infrastructures such as RADIUS or Diameter, but it is not
   a requirement.  When the access network does not rely on an IETF-
   defined AAA protocol (e.g., RADIUS, Diameter), it can still use a
   proprietary backend system, or rely on the information locally stored
   on the authentication agents.

   The interaction between the PAA and the backend authentication
   entities is outside the scope of PANA.

4.1.4.  Identifiers

   PANA SHOULD allow various types of identifiers to be used as the PaCI
   (e.g., username, Network Access Identifier (NAI), Fully Qualified
   Domain Name (FQDN), etc.).  This requirement generally relies on the
   client identifiers supported by various EAP methods.

   PANA SHOULD allow various types of identifiers to be used as the DI
   (e.g., IP address, link-layer address, port number of a switch,

   A PAA MUST be able to create a binding between the PaCI and the
   associated DI upon successful PANA exchange.  This can be achieved by
   PANA communicating the PaCI and DI to the PAA during the protocol
   exchange.  The DI can be carried either explicitly as part of the
   PANA payload, or implicitly as the source of the PANA message, or
   both.  Multi-access networks also require use of a cryptographic
   protection along with DI filtering to prevent unauthorized access
   [RFC4016].  The keying material required by the cryptographic methods
   needs to be indexed by the DI.  As described in section 4.1.2, the
   binding between DI and PaCI is used for access control and accounting
   in the network.

4.2.  IP Address Assignment

   Assigning an IP address to the client is outside the scope of PANA.
   PaC MUST configure an IP address before running PANA.

4.3.  EAP Lower Layer Requirements

   The EAP protocol imposes various requirements on its transport
   protocols that are based on the nature of the EAP protocol, and need
   to be satisfied for correct operation.  Please see [RFC3748] for the
   generic transport requirements that MUST be satisfied by PANA.

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4.4.  PAA-to-EP Protocol

   PANA does not assume that the PAA is always co-located with the
   EP(s).  Network access enforcement can be provided by one or more
   nodes on the same IP subnet as the client (e.g., multiple routers),
   or on another subnet in the access domain (e.g., gateway to the
   Internet, depending on the network architecture).  When the PAA and
   the EP(s) are separated, another transport for client provisioning is
   necessary.  This transport is needed to create access control lists
   in order to allow authenticated and authorized clients' traffic
   through the EPs.  PANA Working Group will preferably identify an
   existing protocol solution that allows the PAA to deliver the
   authorization information to one or more EPs when the PAA is
   separated from EPs.  Possible candidates include, but are not limited
   to COPS, SNMP, Diameter, etc.

   The communication between PAA and EP(s) MUST be secure.  The
   objective of using a PAA-to-EP protocol is to provide filtering rules
   to EP(s) for allowing network access of a recently authenticated and
   authorized PaC.  The chosen protocol MUST be capable of carrying DI
   and cryptographic keys for a given PaC from PAA to EP.  Depending on
   the PANA protocol design, support for either of the pull model (i.e.,
   EP initiating the PAA-to-EP protocol exchange per PaC) or the push
   model (i.e., PAA initiating the PAA-to-EP protocol exchange per PaC),
   or both may be required.  For example, if the design is such that the
   EP allows the PANA traffic to pass through even for unauthenticated
   PaCs, the EP should also allow and expect the PAA to send the
   filtering information at the end of a successful PANA exchange
   without the EP ever sending a request.

4.5.  Network

4.5.1.  Multi-access

   PANA MUST support PaCs with multiple interfaces, and networks with
   multiple routers on multi-access links.  In other words, PANA MUST
   NOT assume that the PaC has only one network interface, that the
   access network has only one first hop router, or that the PaC is
   using a point-to-point link.

4.5.2.  Disconnect Indication

   PANA MUST NOT assume that the link is connection-oriented.  Links may
   or may not provide disconnect indication.  Such notification is
   desirable in order for the PAA to clean up resources when a client
   moves away from the network (e.g., inform the enforcement points that
   the client is no longer connected).  PANA SHOULD have a mechanism to

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   provide disconnect indication.  PANA MUST be capable of securing
   disconnect messages in order to prevent malicious nodes from
   leveraging this extension for DoS attacks.

   This mechanism MUST allow the PAA to be notified about the departure
   of a PaC from the network.  This mechanism MUST also allow a PaC to
   be notified about the discontinuation of the network access service.
   Access discontinuation can occur due to various reasons such as
   network systems going down or a change in the access policy.

   In case the clients cannot send explicit disconnect messages to the
   PAA, it can still detect their departure by relying on periodic
   authentication requests.

4.5.3.  Location of PAA

   The PAA and PaC MUST be exactly one IP hop away from each other.
   That is, there must be no IP routers between the two.  Note that this
   does not mean they are on the same physical link.  Bridging and
   tunneling (e.g., IP-in-IP, GRE, L2TP, etc.) techniques can place two
   nodes just exactly one IP hop away from each other although they
   might be connected to separate physical links.  A PAA can be on the
   network access server (NAS) or WLAN access point or first hop router.
   The use of PANA when the PAA is multiple IP hops away from the PaC is
   outside the scope of PANA.

   A PaC may or may not be pre-configured with the IP address of PAA.
   Therefore the PANA protocol MUST define a dynamic discovery method.
   Given that the PAA is one hop away from the PaC, there are a number
   of discovery techniques that could be used (e.g., multicast or
   anycast) by the PaC to find out the address of the PAA.

4.5.4.  Secure Channel

   PANA MUST NOT assume the presence of a secure channel between the PaC
   and the PAA.  PANA MUST be able to provide authentication especially
   in networks which are not protected against eavesdropping and
   spoofing.  PANA MUST enable protection against replay attacks on both
   PaCs and PAAs.

   This requirement partially relies on the EAP protocol and the EAP
   methods carried over PANA.  Use of EAP methods that provide mutual
   authentication and key derivation/distribution is essential for
   satisfying this requirement.  EAP does not make a secure channel
   assumption, and supports various authentication methods that can be
   used in such environments.  Additionally, PANA MUST ensure that its
   design does not contain vulnerabilities that can be exploited when it
   is used over insecure channels.  PANA MAY provide a secure channel by

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   deploying a two-phase authentication.  The first phase can be used
   for creation of the secure channel, and the second phase for client
   and network authentication.

4.6.  Interaction with Other Protocols

   Mobility management is outside the scope of PANA.  However, PANA MUST
   be able to co-exist and MUST NOT unintentionally interfere with
   various mobility management protocols, such as Mobile IPv4 [RFC3344],
   Mobile IPv6 [RFC3775], fast handover protocols [FMIPv6] [FMIPv4], and
   other standard protocols like IPv6 stateless address auto-
   configuration [RFC2461] (including privacy extensions [RFC3041]), and
   DHCP [RFC2131] [RFC3315].  PANA MUST NOT make any assumptions on the
   protocols or mechanisms used for IP address configuration of the PaC.

4.7.  Performance

   PANA design SHOULD efficiently handle the authentication process in
   order to gain network access with minimum latency.  For example, it
   may minimize the protocol signaling by creating local security

4.8.  Congestion Control

   PANA MUST provide congestion control for the protocol messaging.
   Under certain conditions PaCs might unintentionally get synchronized
   when sending their requests to the PAA (e.g., upon recovering from a
   power outage on the access network).  The network congestion
   generated from such events can be avoided by using techniques like
   delayed initialization and exponential back off.

4.9.  IP Version Independence

   PANA MUST work with both IPv4 and IPv6.

4.10.  Denial of Service Attacks

   PANA MUST be robust against a class of DoS attacks such as blind
   masquerade attacks through IP spoofing.  These attacks would swamp
   the PAA, causing it to spend resources and prevent network access by
   legitimate clients.

4.11.  Client Identity Privacy

   Some clients might prefer hiding their identity from visited access
   networks for privacy reasons.  Providing identity protection for
   clients is outside the scope of PANA.  Note that some authentication

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   methods may already have this capability.  Where necessary, identity
   protection can be achieved by letting PANA carry such authentication

5.  Security Considerations

   This document identifies requirements for the PANA protocol design.
   Due to the nature of this protocol, most of the requirements are
   security related.  The actual protocol design is not specified in
   this document.  A thorough discussion on PANA security threats can be
   found in PANA Threat Analysis and Security Requirements [RFC4016].
   Security threats identified in that document are already included in
   this general PANA requirements document.

6.  Acknowledgements

   Authors would like to thank Bernard Aboba, Derek Atkins, Steven
   Bellovin, Julien Bournelle, Subir Das, Francis Dupont, Dan Forsberg,
   Pete McCann, Lionel Morand, Thomas Narten, Mohan Parthasarathy,
   Basavaraj Patil, Hesham Soliman, and the PANA Working Group members
   for their valuable contributions to the discussions and preparation
   of this document.

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Appendix A.  Problem Statement

   Access networks in most cases require some form of authentication in
   order to prevent unauthorized usage.  In the absence of physical
   security (and sometimes in addition to it) a higher layer (L2+)
   access authentication mechanism is needed.  Depending on the
   deployment scenarios, a number of features are expected from the
   authentication mechanism.  For example, support for various
   authentication methods (e.g., MD5, TLS, SIM, etc.), network roaming,
   network service provider discovery and selection, separate
   authentication for access (L1+L2) service provider and ISP (L3), etc.
   In the absence of a link-layer authentication mechanism that can
   satisfy these needs, operators are forced to either use non-standard
   ad-hoc solutions at layers above the link, insert additional shim
   layers for authentication, or misuse some of the existing protocols
   in ways that were not intended by design.  PANA will be developed to
   fill this gap by defining a standard network-layer access
   authentication protocol.  As a network-layer access authentication
   protocol, PANA can be used over any link-layer that supports IP.

   DSL networks are a specific example where PANA has the potential for
   addressing some of the deployment scenarios.  Some DSL deployments do
   not use PPP [RFC1661] as the access link-layer (IP is carried over
   ATM and the subscriber device is either statically or DHCP-
   configured).  The operators of these networks are left either using
   an application-layer web-based login (captive portal) scheme for
   subscriber authentication, or providing a best-effort service only as
   they cannot perform subscriber authentication required for the
   differentiated services.  The captive portal scheme is a non-standard
   solution that has various limitations and security flaws.

   PPP-based authentication can provide some of the required
   functionality.  But using PPP only for authentication is not a good
   choice, as it incurs additional messaging during the connection setup
   and extra per-packet processing.  It also forces the network topology
   to a point-to-point model.  Aside from resistance to incorporating
   PPP into an architecture unless it is absolutely necessary, there is
   even interest in the community in removing PPP from some of the
   existing architectures and deployments (e.g., 3GPP2, DSL).

   Using Mobile IPv4 authentication with a foreign agent instead of
   proper network access authentication is an example of protocol
   misuse.  The Registration Required flag allows a foreign agent to
   force authentication even when the agent is not involved in any
   Mobile IPv4 signalling (co-located care-of address case).  This
   enables the use of a mobility-specific protocol for an unrelated

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   PANA will carry EAP above IP in order to enable any authentication
   method on any link-layer.  EAP can already be carried by [IEEE-
   802.1X] and PPP.  IEEE 802.1X can only be used on unbridged IEEE 802
   links, hence it only applies to limited link types.  Inserting PPP
   between IP and a link-layer can be perceived as a way to enable EAP
   over that particular link-layer, but using PPP for this reason has
   the aforementioned drawbacks and is not a good choice.  While IEEE
   802.1X and PPP can continue to be used in their own domains, they do
   not take away the need to have a protocol like PANA.

Appendix B.  Usage Scenarios

   PANA will be applicable to various types of networks.  Based on the
   presence of lower-layer security prior to running PANA, the following
   types cover all possibilities:

   a) Physically secured networks (e.g., DSL networks).  Although data
      traffic is always carried over a physically secured link, the
      client might need to be authenticated and authorized when
      accessing the IP services.

   b) Networks where L1-L2 is already cryptographically secured before
      enabling IP (e.g., cdma2000 networks).  Although the client is
      authenticated on the radio link before enabling ciphering, it
      additionally needs to get authenticated and authorized for
      accessing the IP services.

   c) No lower-layer security present before enabling IP.  PANA is run
      in an insecure network.  PANA-based access authentication is used
      to bootstrap cryptographic per-packet authentication and integrity

   PANA is applicable to not only large-scale operator deployments with
   full AAA infrastructure, but also to small disconnected deployments
   like home networks and personal area networks.

   Since PANA enables decoupling AAA from the link-layer procedures,
   network access authentication does not have to take place during the
   link establishment.  This allows deferring client authentication
   until the client attempts to access differentiated services (e.g.,
   high bandwidth, unlimited access, etc.) in some deployments.
   Additionally, multiple simultaneous network access sessions over the
   same link-layer connection can occur as well.

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   The following five scenarios capture the PANA usage model in
   different network architectures with reference to its placement of
   logical elements such as the PANA Client (PaC) and the PANA
   Authentication Agent (PAA) with respect to the Enforcement Point (EP)
   and the Access Router (AR).  Note that PAA may or may not use AAA
   infrastructure to verify the credentials of PaC in order to authorize
   network access.

   Scenario 1: PAA co-located with EP but separated from AR

   In this scenario (Figure 1), PAA is co-located with the enforcement
   point on which access control is performed.  This might be the case
   where PAA is co-located with the L2 access device (e.g., an IP-
   capable switch).

               PaC -----EP/PAA--+
                                +------ AR ----- (AAA)
               PaC -----EP/PAA--+

        Figure 1: PAA co-located with EP but separated from AR.

   Scenario 2: PAA co-located with AR but separated from EP

   In this scenario, PAA is not co-located with EPs but is placed on the
   AR.  Although we have shown only one AR here, there could be multiple
   ARs, one of which is co-located with the PAA.  Access control
   parameters have to be distributed to the respective enforcement
   points so that the corresponding device on which PaC is authenticated
   can access the network.  A separate protocol is needed between PAA
   and EP to carry access control parameters.

              PaC  ----- EP --+
                              +------ AR/PAA --- (AAA)
              PaC  ----- EP --+

        Figure 2: PAA co-located with AR but separated from EP

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   Scenario 3: PAA co-located with EP and AR

   In this scenario (Figure 3), PAA is co-located with the EP and AR on
   which access control and routing are performed.

              PaC ----- EP/PAA/AR--+
              PaC ----- EP/PAA/AR--+

        Figure 3: PAA co-located with EP and AR.

   Scenario 4: Separated PAA, EP, and AR

   In this scenario, PAA is neither co-located with EPs nor with ARs.
   It still resides on the same IP link as ARs.  After successful
   authentication, access control parameters will be distributed to
   respective enforcement points via a separate protocol and PANA does
   not play any explicit role in this.

                PaC ----- EP -----+--- AR ---+
                                  |          |
                PaC ----- EP --- -+          |
                                  |          |
                PaC ----- EP -----+--- AR -- + ----(AAA)
                                  +--- PAA

        Figure 4: PAA, EP and AR separated.

   Scenario 5: PAA separated from co-located EP and AR

   In this scenario, EP and AR are co-located with each other but
   separated from PAA.  PAA still resides on the same IP link as ARs.
   After successful authentication, access control parameters will be
   distributed to respective enforcement points via a separate protocol
   and PANA does not play any explicit role in this.

                PaC --------------+--- AR/EP ---+
                                  |             |
                PaC --------------+             |
                                  |             |
                PaC --------------+--- AR/EP -- + ----(AAA)
                                  +--- PAA

        Figure 5: PAA separated from EP and AR.

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RFC 4058                   PANA Requirements                    May 2005


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.

   [RFC4016]     Parthasarathy, M., "Protocol for Carrying
                 Authentication and Network Access (PANA) Threat
                 Analysis and Security Requirements", RFC 4016, March

Informative References

   [FMIPv4]  Malki, K., "Low Latency Handoffs in Mobile IPv4", Work in
                 Progress, June 2004.

   [IEEE-802.1X] Institute of Electrical and Electronics Engineers,
                 "Local and Metropolitan Area Networks: Port-Based
                 Network Access Control", IEEE Standard 802.1X,
                 September 2001.

   [RFC826]      Plummer, D., "Ethernet Address Resolution Protocol: Or
                 converting network protocol addresses to 48.bit
                 Ethernet address for transmission on Ethernet
                 hardware", STD 37, RFC 826, November 1982.

   [RFC1256]     Deering, S., "ICMP Router Discovery Messages", RFC
                 1256, September 1991.

   [RFC1661]     Simpson, W., "The Point-to-Point Protocol (PPP)", STD
                 51, RFC 1661, July 1994.

   [RFC2131]     Droms, R., "Dynamic Host Configuration Protocol", RFC
                 2131, March 1997.

Yegin, et al.                Informational                     [Page 16]
RFC 4058                   PANA Requirements                    May 2005

   [RFC2461]     Narten, T., Nordmark, E., and W. Simpson, "Neighbor
                 Discovery for IP Version 6 (IPv6)", RFC 2461, December

   [RFC2716]     Aboba, B. and D. Simon, "PPP EAP TLS Authentication
                 Protocol", RFC 2716, October 1999.

   [RFC2794]     Calhoun, P. and C. Perkins, "Mobile IP Network Access
                 Identifier Extension for IPv4", RFC 2794, March 2000.

   [RFC3012]     Perkins, C. and P. Calhoun, "Mobile IPv4 Challenge/
                 Response Extensions", RFC 3012, November 2000.

   [RFC3041]     Narten, T. and R. Draves, "Privacy Extensions for
                 Stateless Address Autoconfiguration in IPv6", RFC 3041,
                 January 2001.

   [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.

   [RFC3344]     Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
                 August 2002.

   [RFC3775]     Johnson, D., Perkins, C., and J. Arkko, "Mobility
                 Support in IPv6", RFC 3775, June 2004.

   [FMIPv6]      Koodli, R., Ed., "Fast Handovers for Mobile IPv6", Work
                 in Progress.

Authors' Addresses

   Alper E. Yegin (editor)
   Samsung Advanced Institute of Technology
   75 West Plumeria Drive
   San Jose, CA  95134

   Phone: +1 408 544 5656
   EMail: alper.yegin@samsung.com

Yegin, et al.                Informational                     [Page 17]
RFC 4058                   PANA Requirements                    May 2005

   Yoshihiro Ohba
   Toshiba America Research, Inc.
   1 Telcordia Drive
   Piscataway, NJ  08854

   Phone: +1 732 699 5305
   EMail: yohba@tari.toshiba.com

   Reinaldo Penno
   Juniper Networks
   10 Technology Park Drive
   Westford, MA 01886-3146

   EMail: rpenno@juniper.net

   George Tsirtsis
   Bedminster One
   135 Route 202/206 South
   Bedminster, NJ  07921

   Phone: +44 20 88260073
   EMail: G.Tsirtsis@Flarion.com

   Cliff Wang
   316 Riggsbee Farm
   Morrisville, NC  27560

   Phone: +1 919 548 4207
   EMail: cliffwangmail@yahoo.com

Yegin, et al.                Informational                     [Page 18]
RFC 4058                   PANA Requirements                    May 2005

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