ROAMOPS Working Group                                    Bernard Aboba
     INTERNET-DRAFT                                   Microsoft Corporation
                         The Network Access Identifier
     1.  Status of this Memo
     This document is an Internet-Draft.  Internet-Drafts are working docu-
     ments of the Internet Engineering Task Force (IETF),  its  areas,  and
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     The  distribution  of  this memo is unlimited.  It is filed as <draft-
     ietf-roamops-nai-02.txt> and  expires September 15, 1997.  Please send
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     2.  Abstract
     This document describes issues relating to user identification in pro-
     vision of "roaming capability" for dialup  Internet  users.   "Roaming
     capability"  may  be  loosely defined as the ability to use any one of
     multiple Internet service providers (ISPs), while maintaining  a  for-
     mal,  customer-vendor  relationship  with only one.  Examples of cases
     where roaming capability might be  required  include  ISP  "confedera-
     tions" and ISP-provided corporate network access support.
     3.  Introduction
     Considerable  interest  has  arisen recently in a set of features that
     fit within the general category of  "roaming  capability"  for  dialup
     Internet users.  Interested parties have included:
          Regional  Internet  Service  Providers  (ISPs) operating within a
          particular state or province, looking to  combine  their  efforts
          with  those  of  other regional providers to offer dialup service
          over a wider area.
          National ISPs wishing to combine their operations with  those  of
          one  or  more  ISPs in another nation to offer more comprehensive
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     INTERNET-DRAFT                                            6 March 1997
          dialup service in a group of countries or on a continent.
          Businesses desiring to  offer  their  employees  a  comprehensive
          package of dialup services on a global basis.  Those services may
          include Internet access as well as  secure  access  to  corporate
          intranets via a Virtual Private Network (VPN), enabled by tunnel-
          ing protocols such as PPTP, L2F and L2TP.
     This document focuses on issues of  user  identification  for  use  in
     roaming  services.   However,  since roaming and tunneling are closely
     related, it is believed that the considerations  described  here  will
     also be of interest to those working on tunneling.
     3.1.  Terminology
     This document frequently uses the following terms:
     Network Access Identifier
               The  Network Access Identifier (NAI) is the userID submitted
               by the client during the PPP negotiation.  In  roaming,  the
               purpose  of  the  NAI  is to identify the user as well as to
               assist in the routing  of  the  authentication  request.  As
               such,  the  NAI  may  be  presented either in the form of an
               authentication route, or a pointer to such a  route.  Please
               note  that  the  NAI  may not necessarily be the same as the
               user's e-mail address or the userID submitted in an applica-
               tion  layer  authentication  (i.e.  HTTP authentication). In
               order to avoid confusion on  this  point,  a  new  term  was
     Network Access Server
               The  Network  Access Server (NAS) is the device that clients
               dial in order to get access to the network. In  PPTP  termi-
               nology  this  is referred to as the PPTP Access Concentrator
               (PAC), and in L2TP terminology, it is  referred  to  as  the
               L2TP Access Concentrator (LAC).
     RADIUS server
               This  is  a  server which provides for authentication/autho-
               rization via the protocol described in [3], and for account-
               ing as described in [4].
     RADIUS proxy
               In order to provide for the routing of RADIUS authentication
               and accounting requests, a RADIUS proxy may employed. To the
               NAS,  the  RADIUS  proxy acts as a RADIUS server, and to the
               RADIUS server, the proxy acts as a RADIUS client.
     3.2.  Purpose
     As described in[1], there are now at least four services  implementing
     dialup  roaming, and the number of Internet Service Providers involved
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     INTERNET-DRAFT                                            6 March 1997
     in roaming consortia is increasing rapidly.
     In order to be able to offer roaming capability, one of  the  require-
     ments is to be able to identify the user's home authentication server.
     For use in roaming, this function is accomplished via the NAI  submit-
     ted by the user to the NAS in the initial PPP authentication.
     This  document  proposes  syntax  and  semantics  for  the  NAI. It is
     expected that this will be of interest for support of roaming as  well
     as tunneling.  For example, references [5] and [6] refer to use of the
     NAI in determining the tunnel endpoint. However, these  references  do
     not  provide  guidelines  for  how  RADIUS  or tunnel routing is to be
     accomplished. In order to avoid the  possibility  of  conflicting  and
     non-interoperable implementations, references [7] and [8] describe how
     RADIUS and tunneling protocols may be integrated. This  document  pro-
     vides  guidance  in  the  use  of the NAI that is relevant to both the
     roaming and tunneling communities.
     4.  Formal Definition of the NAI
     As proposed in this specification, the Network Access Identifer is  of
     the  form  user@domain,  where  the domain is a fully qualified domain
     name (FQDN). The syntax for the NAI is independent of the method  used
     to route the authentication.
     In  order  to  support the determination of the existence of a roaming
     relationship path between the local ISP and the home  domain,  one  of
     two  methods  may  be  used.  If the number of domains to be served is
     small, then it is possible to provide roaming relationship information
     via  the  authentication  proxy  configuration  file. If the number of
     domains to be served is large, then a more scalable mechanism is  rec-
     ommended,  such  as use of the DNS Roaming Relationship (REL) resource
     record, as described in [10]. However, even  if  use  of  the  DNS  is
     enabled, an authentication proxy will typically consult its configura-
     tion file for information on roaming relationships, prior to  retriev-
     ing information via DNS.
     4.1.  BNF for the NAI
     The  grammar for the NAI is given below, using the augmented BNF nota-
     tion described in reference [9].
     FQDN =    token "."  token *[ "." token ]
     USERNAME = token
     Examples of valid Network Access Identifiers include:

     Examples of invalid Network Access Identifiers include:
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     INTERNET-DRAFT                                            6 March 1997

     5.  Acknowledgements
     Thanks to Glen Zorn of Microsoft for many useful discussions  of  this
     problem space.
     6.  References
     [1]  B. Aboba, J. Lu, J. Alsop, J. Ding.  "Review of Roaming Implemen-
     tations." draft-ietf-roamops-imprev-01.txt, Microsoft, Aimnet,  i-Pass
     Alliance, Asiainfo, January, 1997.
     [2]   B.  Aboba,  G. Zorn.  "Dialup Roaming Requirements." draft-ietf-
     roamops-roamreq-03.txt, Microsoft, March, 1997.
     [3]  C. Rigney, A. Rubens, W. Simpson, S. Willens.  "Remote  Authenti-
     cation  Dial  In  User Service (RADIUS)." RFC 2058, Livingston, Merit,
     Daydreamer, January, 1997.
     [4]  C. Rigney.  "RADIUS Accounting." RFC 2059,  Livingston,  January,
     [5]  K.  Hamzeh, T. Kolar, M. Littlewood, G. S. Pall, J. Taarud, A. J.
     Valencia, W. Verthein.  "Layer Two Tunneling Protocol -- L2TP." draft-
     ietf-pppext-l2tp-01.txt, Ascend Communications, December, 1996.
     [6]  K.  Hamzeh,  G.  S.  Pall,  J. Taarud, W. Verthein, W. A. Little.
     "Point-to-Point  Tunneling  Protocol  --   PPTP."   draft-ietf-pppext-
     pptp-00.txt, Ascend Communications, June, 1996.
     [7]  G. Zorn.  "RADIUS Attributes for Tunnel Protocol Support." draft-
     ietf-radius-tunnel-auth-00.txt, Microsoft Corporation, November, 1996.
     [8]  B.  Aboba.   "Implementation  of Mandatory Tunneling via RADIUS."
     draft-ietf-radius-tunnel-imp-00.txt, Microsoft Corporation,  February,
     [9]   R.  Fielding,  et al.  "Hypertext Transfer Protocol - HTTP/1.1."
     draft-ietf-http-v11-spec-07, UC Irvine, August, 1996.
     [10] B. Aboba.  "The Roaming Relationship (REL) Resource Record in the
     DNS."  draft-ietf-roamops-dnsrr-02.txt,  Microsoft Corporation, March,
     7.  Authors' Addresses
     Bernard Aboba
     Microsoft Corporation
     Aboba                                                         [Page 4]

     INTERNET-DRAFT                                            6 March 1997
     One Microsoft Way
     Redmond, WA 98052
     Phone: 206-936-6605
     Aboba                                                         [Page 5]