GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools

Problem, Formatting or Query -  Send Feedback

Was this page helpful?-10+1


rfc:rfc2486

Network Working Group B. Aboba Request for Comments: 2486 Microsoft Category: Standards Track M. Beadles

                                          WorldCom Advanced Networks
                                                        January 1999
                   The Network Access Identifier

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1999).  All Rights Reserved.

1. Abstract

 In order to enhance the interoperability of roaming and tunneling
 services, it is desirable to have a standardized method for
 identifying users.  This document proposes syntax for the Network
 Access Identifier (NAI), the userID submitted by the client during
 PPP authentication. It is expected that this will be of interest for
 support of roaming as well as tunneling.  "Roaming capability" may 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 where roaming capabilities
 might be required include ISP "confederations" and ISP-provided
 corporate network access support.

2. 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.

Aboba & Beadles Standards Track [Page 1] RFC 2486 The Network Access Identifier January 1999

      National ISPs wishing to combine their operations with those of
      one or more ISPs in another nation to offer more comprehensive
      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 tunneling protocols such as PPTP, L2F, L2TP, and IPSEC tunnel
      mode.
 In order to enhance the interoperability of roaming and tunneling
 services, it is desirable to have a standardized method for
 identifying users.  This document proposes syntax for the Network
 Access Identifier (NAI).  Examples of implementations that use the
 NAI, and descriptions of its semantics, can be found in [1].

2.1. Terminology

 This document frequently uses the following terms:
 Network Access Identifier
           The Network Access Identifier (NAI) is the userID submitted
           by the client during PPP 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.
           Please note that the NAI may not necessarily be the same as
           the user's e-mail address or the userID submitted in an
           application layer authentication.
 Network Access Server
           The Network Access Server (NAS) is the device that clients
           dial in order to get access to the network. In PPTP
           terminology this is referred to as the PPTP Access
           Concentrator (PAC), and in L2TP terminology, it is referred
           to as the L2TP Access Concentrator (LAC).
 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.

Aboba & Beadles Standards Track [Page 2] RFC 2486 The Network Access Identifier January 1999

 Tunneling Service
           A tunneling service is any network service enabled by
           tunneling protocols such as PPTP, L2F, L2TP, and IPSEC
           tunnel mode.  One example of a tunneling service is secure
           access to corporate intranets via a Virtual Private Network
           (VPN).

2.2. 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 [9].

2.3. Purpose

 As described in [1], there are now a number of services implementing
 dialup roaming, and the number of Internet Service Providers involved
 in roaming consortia is increasing rapidly.
 In order to be able to offer roaming capability, one of the
 requirements is to be able to identify the user's home authentication
 server.  For use in roaming, this function is accomplished via the
 Network Access Identifier (NAI) submitted by the user to the NAS in
 the initial PPP authentication.  It is also expected that NASes will
 use the NAI as part of the process of opening a new tunnel, in order
 to determine the tunnel endpoint.

2.4. Notes for Implementors

 As proposed in this document, the Network Access Identifier is of the
 form user@realm.  Please note that while the user portion of the NAI
 conforms to the BNF described in [5], the BNF of the realm portion
 allows the realm to begin with a digit, which is not permitted by the
 BNF described in [4]. This change was made to reflect current
 practice; although not permitted by the BNF described in [4], FQDNs
 such as 3com.com are commonly used, and accepted by current software.
 Please note that NAS vendors may need to modify their devices so as
 to support the NAI as described in this document. Devices handling
 NAIs MUST support an NAI length of at least 72 octets.

3. Formal definition of the NAI

 The grammar for the NAI is given below, described in ABNF as
 documented in [7].  The grammar for the username is taken from [5],
 and the grammar for the realm is an updated version of [4].
 nai         = username / ( username "@" realm )

Aboba & Beadles Standards Track [Page 3] RFC 2486 The Network Access Identifier January 1999

 username    = dot-string
 realm       = realm "." label
 label       = let-dig * (ldh-str)
 ldh-str     = *( Alpha / Digit / "-" ) let-dig
 dot-string  = string / ( dot-string "." string )
 string      = char / ( string char )
 char        = c / ( "\" x )
 let-dig     = Alpha / Digit
 Alpha       = %x41-5A / %x61-7A   ; A-Z / a-z
 Digit       = %x30-39  ;0-9
 c           = < any one of the 128 ASCII characters, but
                not any special or SP >
 x           = %x00-7F
               ; all 127 ASCII characters, no exception
 SP          = %x20 ; Space character
 special     = "<" / ">" / "(" / ")" / "[" / "]" / "\" / "."
                / "," / ";" / ":" / "@" / %x22  / Ctl
 Ctl         = %x00-1F / %x7F
               ; the control characters (ASCII codes 0 through 31
               ; inclusive and 127)
 Examples of valid Network Access Identifiers include:
      fred@3com.com
      fred@foo-9.com
      fred_smith@big-co.com
      fred=?#$&*+-/^smith@bigco.com
      fred@bigco.com
      nancy@eng.bigu.edu
      eng!nancy@bigu.edu
      eng%nancy@bigu.edu

Aboba & Beadles Standards Track [Page 4] RFC 2486 The Network Access Identifier January 1999

 Examples of invalid Network Access Identifiers include:
      fred@foo
      fred@foo_9.com
      @howard.edu
      fred@bigco.com@smallco.com
      eng:nancy@bigu.edu
      eng;nancy@bigu.edu
      <nancy>@bigu.edu

4. References

 [1]  Aboba, B., Lu J., Alsop J., Ding J. and W. Wang, "Review of
      Roaming Implementations", RFC 2194, September 1997.
 [2]  Rigney C., Rubens A., Simpson W. and S. Willens, "Remote
      Authentication Dial In User Service (RADIUS)", RFC 2138, April
      1997.
 [3]  Rigney C., "RADIUS Accounting", RFC 2139, April 1997.
 [4]  Mockapetris, P., "Domain Names  -  Implementation  and
      Specification", STD 13, RFC 1035, November 1987.
 [5]  Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821,
      August 1982.
 [6]  Gulbrandsen A. and P. Vixie, "A DNS RR for specifying the
      location of services (DNS SRV)", RFC 2052, October 1996.
 [7]  Crocker, D. and P. Overrell, "Augmented BNF for Syntax
      Specifications: ABNF", RFC 2234, November 1997.
 [8]  Kent, S. and R. Atkinson, "Security Architecture for the
      Internet Protocol", RFC 2401, November 1998.
 [9]  Bradner,  S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.

5. Security Considerations

 Since an NAI reveals the home affiliation of a user, it may assist an
 attacker in further probing the username space. Typically this
 problem is of most concern in protocols which transmit the user name
 in clear-text across the Internet, such as in RADIUS, described in
 [2] and [3].  In order to prevent snooping of the user name,
 protocols may use confidentiality services provided by IPSEC,
 described in [8].

Aboba & Beadles Standards Track [Page 5] RFC 2486 The Network Access Identifier January 1999

6. IANA Considerations

 This document defines a new namespace that will need to be
 administered, namely the NAI realm namespace. In order to to avoid
 creating any new administrative procedures, administration of the NAI
 realm namespace will piggyback on the administration of the DNS
 namespace.
 NAI realm names are required to be unique and the rights to use a
 given NAI realm for roaming purposes are obtained coincident with
 acquiring the rights to use a particular fully qualified domain name
 (FQDN).  Those wishing to use an NAI realm name should first acquire
 the rights to use the corresponding FQDN. Using an NAI realm without
 ownership of the corresponding FQDN creates the possibility of
 conflict and therefore is to be discouraged.
 Note that the use of an FQDN as the realm name does not imply use of
 the DNS for location of the authentication server or for
 authentication routing.  Since to date roaming has been implemented
 on a relatively small scale, existing implementations typically
 handle location of authentication servers within a domain and perform
 authentication routing based on local knowledge expressed in proxy
 configuration files. The implementations described in [1] have not
 found a need for use of DNS for location of the authentication server
 within a domain, although this can be accomplished via use of the DNS
 SRV record, described in [6].  Similarly, existing implementations
 have not found a need for dynamic routing protocols, or propagation
 of global routing information.  Note also that there is no
 requirement that the NAI represent a valid email address.

7. Acknowledgements

 Thanks to Glen Zorn of Microsoft for many useful discussions  of
 this problem space.

Aboba & Beadles Standards Track [Page 6] RFC 2486 The Network Access Identifier January 1999

8. Authors' Addresses

 Bernard Aboba
 Microsoft Corporation
 One Microsoft Way
 Redmond, WA 98052
 Phone: 425-936-6605
 EMail: bernarda@microsoft.com
 Mark A. Beadles
 WorldCom Advanced Networks
 5000 Britton Rd.
 Hilliard, OH 43026
 Phone: 614-723-1941
 EMail: mbeadles@wcom.net

Aboba & Beadles Standards Track [Page 7] RFC 2486 The Network Access Identifier January 1999

9. Full Copyright Statement

 Copyright (C) The Internet Society (1999).  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.

Aboba & Beadles Standards Track [Page 8]

/data/webs/external/dokuwiki/data/pages/rfc/rfc2486.txt · Last modified: 1999/01/20 23:04 (external edit)