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SIPPING Working Group                                      John Loughney
Internet-Draft                                                     Nokia
                                                       Gonzalo Camarillo

                                                           June 30, 2002

                          SIP-AAA Requirements
                   < draft-loughney-sip-aaa-req-01.txt >

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
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   Distribution of this memo is unlimited.

   Copyright (C) The Internet Society 2002.  All Rights Reserved.


   As SIP services are deployed on the Internet, there is a need for
   authentication, authorization and accounting of SIP sessions.  This
   document sets out the basic requirements for this work.

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Table of Contents

      1     Introduction
      1.1   Scope of This Document
      1.2   Terminology
      1.3   Requirements Language

      2     Requirements
      2.1   Common Requirements
      2.2   Authentication Requirements
      2.3   Authorization Requirements
      2.4   Accounting Requirements

      3     Scenarios
      3.1   WLAN Roaming Using Third Party Service Providers
      3.2   Simple 3GPP Example

      4     Security Considerations

      5     Acknowledgements

      6     References
      6.1   Normative
      6.2   Non-Normative

      7     Authors' Addresses

      8     Full Copyright Statement

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1  Introduction

   The AAA working group is chartered to work on authentication,
   authorization and accounting solutions for the Internet, which
   consists of a base protocol, applications, end-to-end security
   application and a general architecture for providing these services

   The applicability of AAA-based solutions for a number of protocols
   have been specified, for example the AAA requirements for Mobile IP

   SIP provides a signaling protocol for creating, modifying and
   terminating different types sessions such as Internet phone calls,
   multimedia distribution and multimedia conferences [SIP, SIP-BIS].

1.1 Scope of This Document

   SIP sessions have needs for session authentication, authorization and
   accounting.  This document outlines some of the requirements that SIP
   has for AAA.  This document is intended as a generic document for SIP
   AAA requirements.

   This document does not intend to develop a charging and/or billing
   mechanism for SIP.

   One possible use of this document would be to create a basic AAA
   application for SIP needs.  This could be a Diameter application,
   possibly where with Diameter running in Radius-compatibility mode.
   There may also be needs for a mechanism for tying this into a Web-
   services model.

1.2 Terminology

   AAA                     Authentication, Authorization and Accounting

   Accounting              In this draft, accounting is meant in a broad
                           sense, not simply charging or billing.

   Home AAA Server         Server where user with which the user maintains
                           an account relationship.

   Online Accounting       Downloading some kind of credit into the
                           access device, and deducting from that credit
                           as usage accumulates.

   Offline Accounting      Transferring records to a home accounting
                           server, for later billing and settlement,

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                           without doing any accounting-related control
                           or feedback for the services rendered.
   SIP                     Session Initiation Protocol

   UAC                     User Agent Client

   UAS                     User Agent Server

   Proxies                 Proxies are nodes which forward requests
                           and responses as well as make policy decisions.

1.3 Requirements Language

   In this document, the key words "MAY", "MUST", "MUST NOT",
   interpreted as described in [KEYWORDS].

2  Requirements

   In this section, we list the requirements.  It is assumed that
   different situations, deployment scenarios will affect which
   requirements are needed.  It is not intended that all requirements
   are needed to be supported.

2.1 Common Requirements

2.1.1 Ability to Integrate Different Networks, Services and Users

   The basic AAA architecture allows for the support of different access
   methods and technologies.  Service providers MUST be able to provide
   AAA services for SIP irrespective of access method or technology.

2.1.2 Updating SIP Server Entries

   The home AAA server MUST be able to update the entry of the assigned
   SIP server for the user when required.

2.1.3 Indication of Assigned Server

   The home AAA server MUST be able to provide the assigned server of
   the user to the SIP entities requesting it.

2.1.4 Call Setup Times

   AAA should not unduly burden call setup times where appropriate.

   It may be reasonable to support some delay during registration, but
   delay during sessions (especially real-time) are problematic.

2.1.5 SIP Server Allocation

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   The AAA infrastructure or the UAS MUST be able to allocate a SIP
   server for a subscriber when required, based on policies, load
   distribution etc.

2.1.6 Ability to Provide Session Information to the Parties Involved

   Ability for SIP Servers to provide the duration of a session, the
   parties involved, and other relevant information to the visited and
   home AAA servers as accounting information.

2.1.7 Security

   AAA data MUST be able to be securely transported. The endpoints MUST
   be authenticated before data is sent. The endpoints MAY be authorized
   to access certain types of AAA data.

   2.1.5 User De-authorization

   The home AAA server MUST be able to inform a SIP server when a
   particular user is no longer authorized to perform a particular task,
   even if it is an ongoing task.

2.2 Authentication Requirements

2.2.1 Authentication Based on SIP Requests

   The home AAA server MUST be able to authenticate a user based on any
   SIP request, except CANCEL.

2.2.2 Flexible Authentication of SIP requests

   The scheme supported for the authentication between the SIP servers
   and the AAA infrastructure MUST be flexible enough to accommodate a
   variety of authentication mechanisms.

2.3 Authorization Requirements

2.3.1 Ability to Authorize SIP Registration

   It MUST be possible for the Home AAA server to authorize any SIP
   request, except CANCEL.

2.3.2 Information transfer

   It MUST be possible to transfer a wide range or set of information
   needed to make an authorization decision.

2.3.3 Distribution of Profiles

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   A SIP entity performing authentication, authorization or accounting
   MUST be able to access the information needed to perform its task
   (e.g., user profile) in the AAA server.

2.3.4 Authorization Based on Policy

   The home AAA server MAY authorize a session (the end result of a
   successful SIP INVITE method); implementing whatever policy it
   wishes, such as based upon time of day, distance, etc.

2.4 Accounting Requirements

   Accounting is more than simple charging.  Accounting may be a simple
   list of services accessed, servers accessed, duration of session,
   etc.  Charging for SIP sessions can be extremely complex and requires
   some additional study.  It is not the intent of this section to focus
   on charging.

2.4.1 Separation of Accounting Information

   AAA accounting messages MUST be able separate "session duration"
   information from other information generated via additional services
   (e.g. 3-way calling, etc.)

2.4.2 Accounting Information Related to Session Progression

   There MUST be support for accounting transfers where the information
   contained in the accounting data has a direct bearing on the
   establishment, progression and termination of a session.

2.4.3 Accounting Information Not Related to Session Progression

   There MUST be support for accounting transfers where the information
   contained in the accounting data does NOT have a direct bearing on
   the establishment, progression and termination of a session.

2.4.4 Support for One-Time and Session-based Accounting Records

   SIP servers MUST be able to provide relevant accounting information
   for billing and inter-network settlement purpose to home and visited
   AAA servers. Both one-time event accounting records and session based
   (START, INTERIM, STOP records) accounting MUST be supported.

2.4.5 SIP Session Changes

   Accounting messages MUST be able to reflect changes in the SIP
   session that affects the charging of SIP session.

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2.4.6 Support for Accounting on Different Media Components

   The AAA accounting protocol MUST support accounting per media
   component (e.g. voice, video).  The AAA accounting Protocol MUST
   enable different parties to be charged per media component.

2.4.7 Support for Stateful and Stateless Accounting

   Stateful and stateless accounting MUST be possible.

2.4.8 Configuration of Accounting Generation Parameters

   Parameters for accounting generation must be either configurable in
   the SIP servers or communicated by the AAA servers.

2.4.9 Support for Arbitrary Correlation IDs

   Some networks need to be able to relate the accounting to some aspect
   of the session.  Therefore, there is a need to support arbitrary
   correlation IDs.

2.4.10 Support for Accounting Autoconfiguration

   The ability support for autoconfiguration (automatic discovery
   process of accounting servers, for example) to the SIP node MUST be

2.4.11 Support of Credit-based Charging

   Support for credit-based charging is needed.  The accounting
   application must be able to check the end user's account for coverage
   for the requested service event charge prior to execution of that
   service event. All the chargeable events related to a specific
   account must be prevented from the end user when the credit of that
   account is exhausted or expired.


   The scheme supported for the accounting between the SIP servers and
   the AAA infrastructure MUST be flexible enough to accommodate a
   variety of accounting mechanisms.

3  Scenarios

   This section outlines some possible scenarios for SIP and AAA
   interaction.  These are purely illustrative examples, and do not
   impose any requirements.

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3.1 WLAN Roaming Using Third Party Service Providers

   To be added.

3.2 Simple 3GPP Example

   To be added.

4  Security Considerations

   This document is informational in nature, so it does not directly
   affect the security of the Internet.  However, security is a basic
   requirement of this work.

5  Acknowledgements

   The authors would like to thank the participants of the SIP interim
   meeting, May 2002 for their comments. The authors would also thank
   Mary Barns, Pete McCann for their comments.

   The authors would like to thank the authors of the "AAA Requirements
   for IP Telephony/Multimedia" draft, which some of the information in
   this document is based on.

6  References

6.1  Normative

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

   [SIP]       M. Handley, H. Schulzrinne, E. Schooler, J. Rosenberg,
               "SIP: Session Initiation Protocol". RFC 2543, March 1999.

   [SIP-BIS]   J. Rosenberg, et. al, "SIP: Session Initiation Protocol".
               Work in Progress.

6.2  Non-Normative

   [AAA-PROB]  P. Calhoun, et. al, "AAA Problem Statements".  Work in Pro-

   [MIP-AAA]   S. Glass, S. Jacobs, C. Perkins, "Mobile IP Authentication,

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            Authorization, and Accounting Requirements". RFC 2977,
            October 2000.

7  Authors' Addresses

   Questions about this memo can be directed to:

    John Loughney
    Nokia Research Center
    It„merenkatu 11-13
    00180 Helsinki

    Phone:  +358 50 483 6242
    E-mail: john.Loughney@nokia.com

    Gonzalo Camarillo
    Advanced Signalling Research Lab.
    FIN-02420 Jorvas

    Phone: +358 9 299 3371
    Fax:   +358 9 299 3052
    Email: Gonzalo.Camarillo@ericsson.com

8  Full Copyright Statement

   Copyright (C) The Internet Society (2002).  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 docu-
   ment 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 develop-
   ing 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 lim-
   ited 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

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