Criteria for Evaluating AAA Protocols for Network Access

Network Working Group                                 B. Aboba, Microsoft
Request for Comments: 2989   P. Calhoun, S. Glass, Sun Microsystems, Inc.
Category: Informational T. Hiller, P. McCann, H. Shiino, P. Walsh, Lucent
                                 G. Zorn, G. Dommety, Cisco Systems, Inc.
                           C. Perkins, B. Patil, Nokia Telecommunications
                                   D. Mitton, S. Manning, Nortel Networks
                                              M. Beadles, SmartPipes Inc.
                                                         X. Chen, Alcatel
                         S. Sivalingham, Ericsson Wireless Communications
                                                       A. Hameed, Fujitsu
                                                  M. Munson, GTE Wireless
                                              S. Jacobs, GTE Laboratories
                            B. Lim, LG Information & Communications, Ltd.
                                                   B. Hirschman, Motorola
                                                   R. Hsu, Qualcomm, Inc.
                         H. Koo, Samsung Telecommunications America, Inc.
                                                   M. Lipford, Sprint PCS
                                            E. Campbell, 3Com Corporation
                                                Y. Xu, Watercove Networks
                                  S. Baba, Toshiba America Research, Inc.
                                            E. Jaques, Vodaphone Airtouch
                                                            November 2000


        Criteria for Evaluating AAA Protocols for Network Access

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 (2000).  All Rights Reserved.

Abstract

   This document represents a summary of Authentication, Authorization,
   Accounting (AAA) protocol requirements for network access.  In
   creating this document, inputs were taken from documents produced by
   the Network Access Server Requirements Next Generation (NASREQ),
   Roaming Operations (ROAMOPS), and MOBILEIP working groups, as well as
   from TIA 45.6.

   This document summarizes the requirements collected from those
   sources, separating requirements for authentication, authorization
   and accounting.  Details on the requirements are available in the
   original documents.

1.  Introduction

   This document represents a summary of AAA protocol requirements for
   network access.  In creating this documents, inputs were taken from
   documents produced by the NASREQ [3], ROAMOPS [2], and MOBILEIP [5]
   working groups, as well as from TIA 45.6 [4].  This document
   summarizes the requirements collected from those sources, separating
   requirements for authentication, authorization and accounting.
   Details on the requirements are available in the original documents.

1.1.  Requirements language

   In this document, the key words "MAY", "MUST, "MUST NOT", "optional",
   "recommended", "SHOULD", and "SHOULD NOT", are to be interpreted as
   described in [1].

   Please note that the requirements specified in this document are to
   be used in evaluating AAA protocol submissions.  As such, the
   requirements language refers to capabilities of these protocols; the
   protocol documents will specify whether these features are required,
   recommended, or optional.  For example, requiring that a protocol
   support confidentiality is NOT the same thing as requiring that all
   protocol traffic be encrypted.

   A protocol submission is not compliant if it fails to satisfy one or
   more of the MUST or MUST NOT requirements for the capabilities that
   it implements.  A protocol submission that satisfies all the MUST,
   MUST NOT, SHOULD and SHOULD NOT requirements for its capabilities is
   said to be "unconditionally compliant"; one that satisfies all the
   MUST and MUST NOT requirements but not all the SHOULD or SHOULD NOT
   requirements for its protocols is said to be "conditionally
   compliant."

1.2.  Terminology

   Accounting
             The act of collecting information on resource usage for the
             purpose of trend analysis, auditing, billing, or cost
             allocation.

   Administrative Domain
             An internet, or a collection of networks, computers, and
             databases under a common administration.  Computer entities
             operating in a common administration may be assumed to
             share administratively created security associations.

   Attendant A node designed to provide the service interface between a
             client and the local domain.

   Authentication
             The act of verifying a claimed identity, in the form of a
             pre-existing label from a mutually known name space, as the
             originator of a message (message authentication) or as the
             end-point of a channel (entity authentication).

   Authorization
             The act of determining if a particular right, such as
             access to some resource, can be granted to the presenter of
             a particular credential.

   Billing   The act of preparing an invoice.

   Broker    A Broker is an entity that is in a different administrative
             domain from both the home AAA server and the local ISP, and
             which provides services, such as facilitating payments
             between the local ISP and home administrative entities.
             There are two different types of brokers; proxy and
             routing.

   Client    A node wishing to obtain service from an attendant within
             an administrative domain.

   End-to-End
             End-to-End is the security model that requires that
             security information be able to traverse, and be validated
             even when an AAA message is processed by intermediate nodes
             such as proxies, brokers, etc.

   Foreign Domain
             An administrative domain, visited by a Mobile IP client,
             and containing the AAA infrastructure needed to carry out
             the necessary operations enabling Mobile IP registrations.
             From the point of view of the foreign agent, the foreign
             domain is the local domain.

   Home Domain
             An administrative domain, containing the network whose
             prefix matches that of a mobile node's home address, and
             containing the AAA infrastructure needed to carry out the
             necessary operations enabling Mobile IP registrations.
             From the point of view of the home agent, the home domain
             is the local domain.

   Hop-by-hop
             Hop-by-hop is the security model that requires that each
             direct set of peers in a proxy network share a security
             association, and the security information does not traverse
             a AAA entity.

   Inter-domain Accounting
             Inter-domain accounting is the collection of information on
             resource usage of an entity within an administrative
             domain, for use within another administrative domain.  In
             inter-domain accounting, accounting packets and session
             records will typically cross administrative boundaries.

   Intra-domain Accounting
             Intra-domain accounting is the collection of information on
             resource within an administrative domain, for use within
             that domain.  In intra-domain accounting, accounting
             packets and session records typically do not cross
             administrative boundaries.

   Local Domain
             An administrative domain containing the AAA infrastructure
             of immediate interest to a Mobile IP client when it is away
             from home.

   Proxy     A AAA proxy is an entity that acts as both a client and a
             server.  When a request is received from a client, the
             proxy acts as a AAA server.  When the same request needs to
             be forwarded to another AAA entity, the proxy acts as a AAA
             client.

   Local Proxy
             A Local Proxy is a AAA server that satisfies the definition
             of a Proxy, and exists within the same administrative
             domain as the network device (e.g., NAS) that issued the
             AAA request.  Typically, a local proxy will enforce local
             policies prior to forwarding responses to the network
             devices, and are generally used to multiplex AAA messages
             from a large number of network devices.

   Network Access Identifier
             The Network Access Identifier (NAI) is the userID submitted
             by the client during network access authentication.  In
             roaming, the purpose of the NAI is to identify the user as
             well as to assist in the routing of the authentication
             request.  The NAI may not necessarily be the same as the
             user's e-mail address or the user-ID submitted in an
             application layer authentication.

   Routing Broker
             A Routing Broker is a AAA entity that satisfies the
             definition of a Broker, but is NOT in the transmission path
             of AAA messages between the local ISP and the home domain's
             AAA servers.  When a request is received by a Routing
             Broker, information is returned to the AAA requester that
             includes the information necessary for it to be able to
             contact the Home AAA server directly.  Certain
             organizations providing Routing Broker services MAY also
             act as a Certificate Authority, allowing the Routing Broker
             to return the certificates necessary for the local ISP and
             the home AAA servers to communicate securely.

   Non-Proxy Broker
             A Routing Broker is occasionally referred to as a Non-Proxy
             Broker.

   Proxy Broker
             A Proxy Broker is a AAA entity that satisfies the
             definition of a Broker, and acts as a Transparent Proxy by
             acting as the forwarding agent for all AAA messages between
             the local ISP and the home domain's AAA servers.

   Real-time Accounting
             Real-time accounting involves the processing of information
             on resource usage within a defined time window.  Time
             constraints are typically imposed in order to limit
             financial risk.

   Roaming Capability
             Roaming capability can be loosely defined as the ability to
             use any one of multiple Internet service providers (ISPs),
             while maintaining a formal, customer-vendor relationship
             with only one.  Examples of cases where roaming capability
             might be required include ISP "confederations" and ISP-
             provided corporate network access support.

   Session record
             A session record represents a summary of the resource
             consumption of a user over the entire session.  Accounting
             gateways creating the session record may do so by
             processing interim accounting events.

   Transparent Proxy
             A Transparent Proxy is a AAA server that satisfies the
             definition of a Proxy, but does not enforce any local
             policies (meaning that it does not add, delete or modify
             attributes or modify information within messages it
             forwards).

2.  Requirements Summary

   The AAA protocol evaluation criteria for network access are
   summarized below.  For details on the requirements, please consult
   the documents referenced in the footnotes.

2.1.  General requirements

   These requirements apply to all aspects of AAA and thus are
   considered general requirements.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  General                  | NASREQ  | ROAMOPS | MOBILE  |
   |  Reqts.                   |         |         |   IP    |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Scalability             |    M    |   M     |    M    |
   |      a                    |   12    |   3     |  30 39  |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Fail-over               |    M    |         |    M    |
   |      b                    |   12    |         |   31    |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Mutual auth             |    M    |         |    M    |
   |   AAA client/server       |   16    |         |   30    |
   |      c                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Transmission level      |         |   M     |    S    |
   |   security                |         |   6     |  31 39  |
   |      d                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Data object              |    M    |   M     |    M    |
   |  Confidentiality          |   26    |   6     |   40    |
   |      e                    |         |         |         |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Data object              |    M    |   M     |    M    |
   |  Integrity                |   16    |   6     |  31 39  |
   |      f                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Certificate transport    |    M    |         |  S/M    |
   |      g                    |   42    |         |31,33/46 |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Reliable AAA transport   |    M    |         |    M    |
   |  mechanism                |   22    |         |  31 32  |
   |      h                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Run Over IPv4           |    M    |   M     |    M    |
   |                           |   11    |   1     |   33    |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Run Over IPv6           |    M    |         |    S    |
   |                           |   11    |   1     |   47    |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Support Proxy and        |    M    |         |    M    |
   |  Routing Brokers          |   12    |         |  31 39  |
   |      i                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Auditability             |    S    |         |         |
   |      j                    |   25    |         |         |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Dual App and Transport  |         |   O     |     M   |
   |    Security not required  |         |   6     |    40   |
   |      k                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Ability to carry         |    M    |         |    S    |
   |  service-specific attr.   |   43    |         |  31 33  |
   |      l                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Key
   M = MUST
   S = SHOULD
   O = MAY
   N = MUST NOT
   B = SHOULD NOT
   Clarifications

   [a]  The AAA protocol must be capable of supporting millions of users
        and tens of thousands of simultaneous requests.  The AAA
        architecture and protocol MUST be capable of supporting tens of
        thousands of devices, AAA servers, proxies and brokers.

   [b]  In the event of failure to communicate with a given server, the
        protocol must provide a mechanism to change service to another
        backup or secondary server.

   [c]  This requirement refers to the ability to support mutual
        authentication between the AAA client and server.

   [d]  The AAA protocol requires authentication, integrity protection
        and confidentiality at the transmission layer.  This security
        model is also referred to as hop-by-hop security, whereas the
        security is established between two communicating peers.  All of
        the security is removed when the AAA message is processed by a
        receiving AAA entity.

   [e]  The AAA protocol requires confidentiality at the object level,
        where an object consists of one or more attributes.  Object
        level confidentiality implies that only the target AAA entity
        for whom the data is ultimately destined may decrypt the data,
        regardless of the fact that the message may traverse one or more
        intermediate AAA entities (e.g., proxies, brokers).

   [f]  The AAA protocol requires authentication and integrity
        protection at the object level, which consists of one or more
        attributes.  Object level authentication must be persistent
        across one or more intermediate AAA entity (e.g., proxy, broker,
        etc), meaning that any AAA entity in a proxy chain may verify
        the authentication.  This implies that data that is covered by
        object level security CANNOT be modified by intermediate
        servers.

   [g]  The AAA protocol MUST be capable of transporting certificates.
        This requirement is intended as an optimization, in lieu of
        requiring that an out-of-band protocol be used to fetch
        certificates.

   [h]  This requirement refers to resilience against packet loss,
        including:

        1. Hop-by-hop retransmission and fail-over so that reliability
           does not solely depend on single hop transport
           retransmission.

        2. Control of the retransmission mechanism by the AAA
           application.
        3. Acknowledgment by the transport that a message was delivered
           successfully, separate from message semantics or syntax
           evaluation.
        5. Piggy-backing of acknowledgments in AAA messages.
        6. Timely delivery of AAA responses.

   [i]  In the Mobile IP AAA architecture, brokers can be in the
        forwarding path, in which case they act as transparent proxies
        (proxy brokers).  Alternatively, it is also possible to conceive
        of brokers operating as certifying authorities outside of the
        forwarding path (routing brokers).

   [j]  An auditable process is one in which it is possible to
        definitively determine what actions have been performed on AAA
        packets as they travel from the home AAA server to the network
        device and back.

   [k]  The AAA protocol MUST allow communication to be secured.
        However, the AAA protocol MUST also allow an underlying security
        service (e.g., IP Security) to be used.  When the latter is
        used, the former MUST NOT be required.

   [l]  The AAA protocol MUST be extensible by third parties (e.g.,
        other IETF Working Groups), in order to define attributes that
        are specific to the service being defined.  This requirement
        simply means that the AAA protocol MUST allow groups other than
        the AAA WG to define standard attributes.

2.2.  Authentication Requirements

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   | Authentication            | NASREQ  | ROAMOPS | MOBILE  |
   | Reqts.                    |         |         |   IP    |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   NAI Support             |    M    |   M     |   S/M   |
   |      a                    |    9    |   2     |32,34,39/|
   |                           |         |         |   40    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   CHAP Support            |    M    |   M     |         |
   |      b                    |   10    |   3     |         |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   EAP Support             |    M    |   S     |         |
   |      c                    |   10    |   3     |         |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   PAP/Clear-Text Support  |    M    |   B     |         |
   |      d                    |   26    |   3     |         |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Re-authentication       |    M    |         |    S    |
   |   on demand               |   17    |         |   33    |
   |      e                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Authorization Only      |    M    |         |         |
   |   without Authentication  |    9    |         |         |
   |      f                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Key
   M = MUST
   S = SHOULD
   O = MAY
   N = MUST NOT
   B = SHOULD NOT
   Clarifications

   [a]  The AAA protocol MUST allow the use of Network Access
        Identifiers (NAI) [8] to identify users and/or devices.

   [b]  The AAA protocol MUST allow CHAP [20] authentication information
        to be transported.  This is commonly used by Network Access
        Servers that request authentication of a PPP user.

   [c]  The AAA protocol MUST allow for Extensible Authentication
        Protocol (EAP) [14] payload to be transported.  Since some EAP
        authentication mechanisms require more than one round trip, the
        AAA protocol must allow for such authentication mechanisms to be
        used.  The actual EAP authentication mechanism negotiated MUST
        be transparent to the AAA protocol.  When EAP is used,
        authentication typically occurs between the user being
        authenticated and his/her home AAA server.

   [d]  While PAP is deprecated, it is still in widespread use for its
        original intended purpose, which is support of clear-text
        passwords.  As a result, a AAA protocol will need to be able to
        securely transport clear-text passwords.  This includes
        providing for confidentiality of clear-text passwords traveling
        over the wire, as well as protecting against disclosure of
        clear-text passwords to proxies in the forwarding path.

   [e]  The AAA protocol MUST allow for a user to be re-authenticated
        on-demand.  The protocol MUST allow for this event to be
        triggered by either the user, access device (AAA client), or the
        home or visited AAA server.

   [f]  The AAA protocol MUST NOT require that credentials of the user
        be provided during authorization.  The AAA protocol supports
        authorization by identification or assertion only.

2.3.  Authorization Requirements

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   | Authorization             | NASREQ  | ROAMOPS | MOBILE  |
   | Reqts.                    |         |         |   IP    |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Static and Dynamic      |         |         |         |
   |   IPv4/6 Address Assign.  |    M    |   M     |   M     |
   |      a                    |   11    |   5     | 32 36   |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   RADIUS gateway          |    M    |   M     |    M    |
   |   capability              |   44    |   3     |    45   |
   |      b                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Reject                  |    M    |   M     |   M     |
   |   capability              |   12    |   4     |  39     |
   |      c                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Precludes layer 2       |    N    |   N     |         |
   |   tunneling               |   11    |   5     |         |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Re-Authorization on      |    M    |         |   S     |
   |   demand                  |   18    |         | 30 33   |
   |      d                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Support for Access Rules,|    M    |         |         |
   |  Restrictions, Filters    | 11, 19  |         |         |
   |      e                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  State Reconciliation     |    M    |         |         |
   |      f                    |   20    |         |         |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Unsolicited Disconnect   |    M    |         |         |
   |      g                    |   18    |         |         |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Key
   M = MUST
   S = SHOULD
   O = MAY
   N = MUST NOT
   B = SHOULD NOT

   Clarifications

   [a]  The AAA protocol MUST allow a server to provide a static or
        dynamic address during the authorization phase of a user and/or
        device.  The address assigned MUST be either of type IPv4 or
        IPv6.  If both the client AND the server are aware of a pre-
        configured address, then it is considered static.  Anything else
        is dynamic.

   [b]  This requirement refers to the ability of a new AAA protocol be
        sufficiently compatible with the large installed base of
        attributes for existing approaches (RADIUS), such that a server
        implementation could speak both protocols, or translate between
        them.

   [c]  This requirement refers to the ability of a proxy broker to deny
        access without forwarding the access request to the AAA server,
        or to deny access after receiving an access accept from the AAA
        server.

   [d]  This requirement refers to the ability of the AAA client or
        server to trigger re-authorization, or to the ability of the
        server to send updated authorization information to the device,
        such as "stop service."  Authorization can allow for a time
        period, then additional authorization can be sought to continue.
        A server can initially authorize a user to connect and receive
        services, but later decide the user is no longer allowed use of
        the service, for example after N minutes.  Authorizations can
        have a time limit.  Re-authorization does not necessarily imply
        re-authentication.

   [e]  This requirement refers to the ability to of the protocol to
        describe access operational limitations and authorization
        restrictions to usage to the NAS which includes (but is not
        limited to):

        1. Session expirations and Idle Timeouts
        2. Packet filters
        3. Static routes
        4. QoS parameters

   [f]  This requirement refers to the ability of the NAS to use the AAA
        server to manage resource allocation state.  This capability can
        assist with, but it is not synonymous with, simultaneous user
        login control, port usage limitations, or IP address pooling.

        The design must provide for recovery from data loss due to a
        variety of faults, including NAS and AAA server reboots, and
        NAS/AAA server communication outages, and MUST be independent of
        the accounting stream.  The granularity of the recovery of state
        information after an outage may be on the order of a fraction of
        a minute.  In order to provide for state recovery, explicit
        session/resource status and update and disconnect messages will
        be required.

        Because of potential multi-domain issues, only systems that
        allocate or use a resource should track its state.

   [g]  This requirement refers to the ability of the AAA server to
        request the NAS to disconnect an active session for
        authorization policy reasons.

2.4.  Accounting Requirements

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   | Accounting                | NASREQ  | ROAMOPS | MOBILE  |
   | Reqts.                    |         |         |   IP    |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Real-time accounting    |    M    |    M    |   M     |
   |      a                    |   14    |    7    |  31     |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Mandatory Compact       |         |    M    |         |
   |    Encoding               |         |    7    |         |
   |      b                    |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Accounting Record       |         |    M    |   M     |
   |    Extensibility          |         |    7    |  33     |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Batch Accounting        |    S    |         |         |
   |      c                    |   21    |         |         |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Guaranteed Delivery     |    M    |         |    M    |
   |      d                    |   22    |         |   31    |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |   Accounting Time Stamps  |    M    |         |    M    |
   |      e                    |   23    |         |   40    |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Dynamic Accounting       |    M    |         |         |
   |      f                    |   48    |         |         |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Key
   M = MUST
   S = SHOULD
   O = MAY
   N = MUST NOT
   B = SHOULD NOT

   Clarifications

   [a]  This requirement may be loosely defined as reporting
        synchronously with events.  Typically the time window is on the
        order of seconds, not milliseconds.

   [b]  The AAA protocol's Accounting data format MUST NOT be bloated,
        imposing a large overhead for one or more accounting data
        elements.

   [c]  This requirement refers to the ability to buffer or store
        multiple accounting records, and send them together at some
        later time.

   [d]  This is an application layer acknowledgment.  This is sent when
        the receiving server is willing to take responsibility for the
        message data.

   [e]  This requirement refers to the ability to reflect the time of
        occurrence of events such as log-on, logoff, authentication,
        authorization and interim accounting.  It also implies the
        ability to provide for unambiguous time-stamps.

   [f]  This requirement refers to the ability to account for dynamic
        authentication and authorization.  To support this, there can be
        multiple accounting records for a single session.

2.5.  Unique Mobile IP requirements

   In addition to the above requirements, Mobile IP also has the
   following additional requirements:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Encoding of Mobile IP    |         |         |   M     |
   |  registration messages    |         |         |   33    |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Firewall friendly        |         |         |   M     |
   |      a                    |         |         |   35    |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           |         |         |         |
   |  Allocation of local Home |         |         |   S/M   |
   |  agent                    |         |         |  37/41  |
   |                           |         |         |         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Key
   M = MUST
   S = SHOULD
   O = MAY
   N = MUST NOT
   B = SHOULD NOT

   Clarifications

   [a]  A firewall friendly protocol is one which is designed to
        accommodate a firewall acting as a proxy.  For example, this
        would permit a Home Agent AAA server situated behind a firewall
        to be reachable from the Internet for the purposes of providing
        AAA services to a Mobile IP Foreign Agent.

        Notes

        [1] Section 4.2.1 of [2]
        [2] Section 4.2.2 of [2]. Also see [8].
        [3] Section 4.2.3 of [2]. Also see [14].
        [4] Section 4.2.4 of [2].
        [5] Section 4.2.5 of [2].
        [6] Section 4.2.6 of [2].
        [7] Section 4.3 of [2].
        [8] Section 6 of [3].  Also see [6].
        [9] Section 8.2.2.2 of [3].  Also see [14].
        [10] Section 8.2.2.1 of [3].  Also see [14].
        [11] Section 8.3.2.2 of [3].  Also see [7].
        [12] Section 8.1.1 of [3].
        [13] Section 8.1.4.4 of [3].
        [14] Section 8.4.1.2 of [3].

        [15] Section 8.4.2 of [3].
        [16] Section 8.1.3 of [3].
        [17] Section 8.2.1.2 of [3].
        [18] Section 8.3.1.1 of [3].
        [19] Section 8.3.2.1 of [3].  Also see [7].
        [20] Section 8.3.2.3 of [3].  Also see [6], [7].
        [21] Section 8.4.1.3 of [3].
        [22] Section 8.4.1.1 of [3].
        [23] Section 8.4.1.4 of [3].
        [24] Section 8.4.3.1 of [3].
        [25] Section 8.4.3.2 of [3].
        [26] Section 8.2.3.1 of [3].
        [27] Section 8.3.3.1 of [3].
        [28] Section 8.1.4.1 of [3].
        [29] Refer [15]
        [30] Section 3 of [5]
        [31] Section 3.1 of [5]
        [32] Section 4 of [5]
        [33] Section 5 of [5]
        [34] Section 5.1 of [5]
        [35] Section 5.2 of [5]
        [36] Section 5.3 of [5]
        [37] Section 5.4 of [5]
        [38] Section 5.5 of [5]
        [39] Section 6 of [5]
        [40] Section 5.1 of [4]
        [41] Section 5.2.2 of [4]
        [42] Section 8.2.2.2 of [3]
        [43] Section 8.1.2.3 of [3]
        [44] Section 8.1.2.2 of [3]
        [45] Section 5.4 of [4]
        [46] Section 7 of [4]
        [47] Section 8 of [5]
        [48] Section 8.4.1.5 of [3]

3.  References

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [2]  Aboba, B. and G. Zorn, "Criteria for Evaluating Roaming
        Protocols", RFC 2477, January 1999.

   [3]  Beadles, M. and D. Mitton, "Criteria for Evaluating Network
        Access Server Protocols", Work in Progress.

   [4]  Hiller, T., et al., "Cdma2000 Wireless Data Requirements for
        AAA", Work in Progress.

   [5]  Glass, S., Hiller, T., Jacobs, S. and C. Perkins, "Mobile IP
        Authentication, Authorization, and Accounting Requirements", RFC
        2977, October 2000.

   [6]  Mitton, D., Beadles, M., "Network Access Server Requirements
        Next Generation (NASREQNG) NAS Model", RFC 2881, July 2000.

   [7]  Mitton, D., "Network Access Server Requirements: Extended RADIUS
        Practices", RFC 2882, July 2000.

   [8]  Aboba,  B. and M. Beadles, "The Network Access Identifier", RFC
        2486, January 1999.

   [9]  Rigney, C., Willens, S., Rubens, A. and W. Simpson, "Remote
        Authentication Dial In User Service (RADIUS)", RFC 2865, June
        2000.

   [10] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.

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

   [12] Sklower, K., Lloyd, B., McGregor, G., Carr, D. and T. Coradetti,
        "The PPP Multilink Protocol (MP)", RFC 1990, August 1996.

   [13] Simpson, W., Editor, "PPP LCP Extensions", RFC 1570, January
        1994.

   [14] Blunk, L. and J. Vollbrecht, "PPP Extensible Authentication
        Protocol (EAP)", RFC 2284, March 1998.

   [15] Solomon, J. and S. Glass, "Mobile-IPv4 Configuration Option for
        PPP IPCP", RFC 2290, Feb 1998

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

   [17] Perkins, C., "IP Mobility Support", RFC 2002, Oct 1996.

   [18] Johnson, D. and C. Perkins, "Mobility Support in IPv6", Work in
        Progress.

   [19] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy
        Implementation in Roaming", RFC 2607, June 1999.

   [20] Simpson, W., "PPP Challenge Handshake Authentication Protocol
        (CHAP)", RFC 1994, August 1996.

4.  Security Considerations

   This document, being a requirements document, does not have any
   security concerns.  The security requirements on protocols to be
   evaluated using this document are described in the referenced
   documents.

5.  IANA Considerations

   This memo does not create any new number spaces for IANA
   administration.

6.  Acknowledgments

   Thanks to the members of the Mobile IP, AAA, and NASREQ working
   groups who have discussed and commented on these requirements. We
   would also like to thank the members of the AAA evaluation team, Mike
   St. Johns, Barney Wolf, Mark Stevens, David Nelson, Dave Mitton,
   Basavaraj Patil and Stuart Barkley for their thorough review of this
   document.

7.  Authors' Addresses

   Bernard Aboba
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA 98052

   Phone: +1 425-936-6605
   Fax:   +1 425-936-7329
   EMail: bernarda@microsoft.com


   Pat R. Calhoun
   Network and Security Research Center, Sun Labs
   Sun Microsystems, Inc.
   15 Network Circle
   Menlo Park, CA 94025

   Phone: +1 650-786-7733
   EMail: pcalhoun@eng.sun.com
   Steven M. Glass
   Sun Microsystems
   1 Network Drive
   Burlington, MA 01845

   Phone: +1 781-442-0504
   Fax:   +1 781-442-1677
   EMail: steven.glass@sun.com


   Tom Hiller
   Wireless Data Standards & Architectures
   Lucent Technologies
   263 Shuman Drive
   Room 1HP2F-218
   Naperville, IL 60563

   Phone: +1 630-976-7673
   EMail: tom.hiller@lucent.com


   Peter J. McCann
   Lucent Technologies
   Rm 2Z-305
   263 Shuman Blvd
   Naperville, IL  60566

   Phone: +1 630-713 9359
   EMail: mccap@lucent.com


   Hajime Shiino
   Lucent Technologies Japan Ltd.
   25 Mori Bldg. 1-4-30 Roppongi,
   Minato-ku Tokyo
   Japan

   Phone: +81-3-5561-3695
   EMail: hshiino@lucent.com

   Glen Zorn
   Cisco Systems, Inc.
   500 108th Avenue N.E., Suite 500
   Bellevue, WA 98004

   Phone: +1 425-468-0955
   EMail: gwz@cisco.com
   Gopal Dommety
   IOS Network Protocols
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134-1706

   Phone: +1 408-525-1404
   Fax:   +1 408-526-4952
   EMail: gdommety@cisco.com


   Charles E. Perkins
   Communications Systems Lab
   Nokia Research Center
   313 Fairchild Drive
   Mountain View, CA

   Phone: +1 650-625-2986
   Fax:   +1-650-625-2502
   EMail: charliep@iprg.nokia.com


   Basavaraj Patil
   Nokia Networks
   6000 Connection Dr.
   Irving, TX 75039

   Phone: +1 972-894-6709
   Fax:   +1 972-894-5349
   EMail: Basavaraj.Patil@nokia.com


   David Mitton
   Nortel Networks
   880 Technology Park Drive
   Billerica, MA 01821

   Phone: +1 978-288-4570
   EMail: dmitton@nortelnetworks.com


   Serge Manning
   Nortel Networks
   2201 Lakeside Blvd
   Richardson, TX  75082-4399

   Phone: +1 972-684-7277
   EMail: smanning@nortelnetworks.com
   Mark Anthony Beadles
   SmartPipes, Inc.
   565 Metro Place South
   Suite 300
   Dublin, OH 43017

   Phone: +1 614-923-5657
   EMail: mbeadles@smartpipes.com


   Pat Walsh
   Lucent Technologies
   263 Shuman Blvd.
   1F-545
   Naperville, IL

   Phone: +1 630-713-5063
   EMail: walshp@lucent.com


   Xing Chen
   Alcatel USA
   1000 Coit Road
   Plano, TX 75075

   Phone: +1 972-519-4142
   Fax:   +1 972-519-3300
   EMail: xing.chen@usa.alcatel.com


   Sanjeevan Sivalingham
   Ericsson Wireless Communications Inc.,
   Rm Q-356C
   6455 Lusk Blvd
   San Diego, CA 92126

   Phone: +1 858-332-5670
   EMail: s.sivalingham@ericsson.com


   Alan Hameed
   Fujitsu
   2801 Telecom Parkway
   Richardson, TX 75082

   Phone: +1 972-479-2089
   Mark Munson
   GTE Wireless
   One GTE Place
   Alpharetta, GA  30004

   Phone: +1 678-339-4439
   EMail: mmunson@mobilnet.gte.com


   Stuart Jacobs
   Secure Systems Department
   GTE Laboratories
   40 Sylvan Road,
   Waltham, MA 02451-1128

   Phone: +1 781-466-3076
   Fax:   +1 781-466-2838
   EMail: sjacobs@gte.com


   Byung-Keun Lim
   LG Electronics, Ltd.
   533, Hogye-dong, Dongan-ku, Anyang-shi,
   Kyungki-do,431-080
   Korea

   Phone: +82-31-450-7199
   Fax:   +82-31-450-7050
   EMail: bklim@lgic.co.kr


   Brent Hirschman
   1501 Shure Dr.
   Arlington Hieghts, IL 60006

   Phone: +1 847-632-1563
   EMail: qa4053@email.mot.com


   Raymond T. Hsu
   Qualcomm Inc.
   6455 Lusk Blvd.
   San Diego, CA 92121

   Phone: +1 619-651-3623
   EMail: rhsu@qualcomm.com
   Haeng S. Koo
   Samsung Telecommunications America, Inc.
   1130 E. Arapaho Road
   Richardson, TX 75081

   Phone: +1 972-761-7755
   EMail: hskoo@sta.samsung.com


   Mark A. Lipford
   Sprint PCS
   8001 College Blvd.; Suite 210
   Overland Park, KS  66210

   Phone: +1 913-664-8335
   EMail: mlipfo01@sprintspectrum.com


   Ed Campbell
   3Com Corporation
   1800 W. Central Rd.
   Mount Prospect, IL 60056

   Phone: +1 847-342-6769
   EMail: ed_campbell@3com.com


   Name: Yingchun Xu
   WaterCove Networks
   One Century Centre, Suite 550
   1750 E. Golf Road
   Schaumburg, IL

   Phone: +1 847-477-9280
   EMail: yxu@watercove.com


   Shinichi Baba
   Toshiba America Research, Inc.
   PO Box 136,
   Convent Station, NJ 07961-0136

   Phone: +1 973-829-4795
   EMail: sbaba@tari.toshiba.com
   Eric Jaques
   Vodafone AirTouch
   2999 Oak Road, MS-750
   Walnut Creek, CA 94596

   Phone: +1 925-279-6142
   EMail: ejaques@akamail.com

8.  Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.

9.  Full Copyright Statement

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.