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Versions: 00 01 02 draft-ietf-radext-nai

Network Working Group                                  DeKok, Alan (Ed.)
INTERNET-DRAFT                                                FreeRADIUS
Obsoletes: 4282
Category: Standards Track
9 September 2009

                     The Network Access Identifier

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   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
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   In order to provide roaming services, it is necessary to have a
   standardized method for identifying users.  This document defines the
   syntax for the Network Access Identifier (NAI), the user identity
   submitted by the client during network authentication.  "Roaming" 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.  This document is a revised version
   of RFC 4282, which addresses issues with international character
   sets, as well as a number of other corrections to the previous RFC.

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Table of Contents

Appendix A - Changes from RFC4282 ............................    3
1.  Introduction .............................................    4
   1.1.  Terminology .........................................    4
   1.2.  Requirements Language ...............................    5
   1.3.  Purpose .............................................    6
   1.4.  Motivation ..........................................    6
2.  NAI Definition ...........................................    7
   2.1.  UTF-8 Syntax and Normalization ......................    7
   2.2.  Formal Syntax .......................................    7
   2.3.  NAI Length Considerations ...........................    8
   2.4.  Support for Username Privacy ........................    9
   2.5.  International Character Sets ........................    9
   2.6.  The Normalization Process ...........................   10
   2.7.  Routing inside of AAA Systems .......................   10
   2.8.  Compatibility with E-Mail Usernames .................   11
   2.9.  Compatibility with DNS ..............................   11
   2.10.  Realm Construction .................................   12
      2.10.1.  Historical Practices ..........................   12
   2.11.  Examples ...........................................   13
3.  Security Considerations ..................................   14
4.  IANA Considerations ......................................   14
5.  References ...............................................   15
   5.1.  Normative references ................................   15
   5.2.  Informative references ..............................   16
Appendix A - Changes from RFC4282 ............................   18

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1.  Introduction

   Considerable interest exists for a set of features that fit within
   the general category of "roaming capability" for network access,
   including dialup Internet users, Virtual Private Network (VPN) usage,
   wireless LAN authentication, and other applications.  Interested
   parties have included the following:

   o  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.

   o  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.

   o  Wireless LAN hotspots providing service to one or more ISPs.

   o  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 VPN, enabled by tunneling protocols such as the
      Point-to-Point Tunneling Protocol (PPTP) [RFC2637], the Layer 2
      Forwarding (L2F) protocol [RFC2341], the Layer 2 Tunneling
      Protocol (L2TP) [RFC2661], and the IPsec tunnel mode [RFC4301].

   In order to enhance the interoperability of roaming services, it is
   necessary to have a standardized method for identifying users.  This
   document defines syntax for the Network Access Identifier (NAI).
   Examples of implementations that use the NAI, and descriptions of its
   semantics, can be found in [RFC2194].

   This document is a revised version of [RFC4282], which originally
   defined internationalized NAIs.  Differences and enhancements
   compared to RFC 4282 are listed in Appendix A.

1.1.  Terminology

   This document frequently uses the following terms:

   Network Access Identifier

      The Network Access Identifier (NAI) is the user identity 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.  Please note
      that the NAI may not necessarily be the same as the user's e-mail

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      address or the user identity submitted in an application layer

   Network Access Server

      The Network Access Server (NAS) is the device that clients connect
      to 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).  In IEEE 802.11, it is referred to as an
      Access Point.

   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.

   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).

1.2.  Requirements Language

   In this document, several words are used to signify the requirements
   of the specification.  The key words "MUST", "MUST NOT", "REQUIRED",
   and "OPTIONAL" in this document are to be interpreted as described in

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1.3.  Purpose

   As described in [RFC2194], there are a number of providers offering
   network access services, 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 network 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.

1.4.  Motivation

   The changes from [RFC4282] are listed in detail in Appendix A.
   However, some additional discussion is appropriate to motivate those

   The motivation to revise [RFC4282] began with internationalization
   concerns raised in the context of [EDUROAM].  Section 2.1 of
   [RFC4282] defines ABNF for realms which limits the realm grammer to
   English letters, digits, and the hyphen "-" character.  The intent
   appears to have been to encode, compare, and transport realms with
   the ToASCII operation defined in [RFC3490].  There are a number of
   problems with this approach:

   o Section 2.1 did not contain ABNF for the UTF-8 form of the
      realm.  This makes it impossible to create an inter-operable
      internationalized version of the realm.

   o  Section 2.5 required mappings that are language-specific,
      and which are nearly impossible to perform correctly without
      information about that language.

   o  Section 2.5 requires normalization of user names, which
      may conflict with local system or administrative requirements.

   o  The recommendations in Section 2.5 for treatment of
      bidirectional characters have proven to be unworkable.

   o  The prohibition against use of unassigned code points in
      Section 2.5 effectively prohibits support for new scripts.

   o  The document's requirement that realms are ASCII conflicts
      with the Extensible Authentication Protocol (EAP) and RADIUS,
      which are both 8-bit clean, and which both recommend the use of

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      UTF-8 for identities.

   o  No Authentication, Authorization, and Accounting (AAA)
      client, proxy, or server has implemented any of the requirements
      in [RFC4282] Section 2.5, among other sections.

   With international roaming growing in popularity, it is important for
   these issues to be corrected in order to provide robust and inter-
   operable network services.

2.  NAI Definition

2.1.  UTF-8 Syntax and Normalization

   UTF-8 characters can be defined in terms of octets using the
   following ABNF [RFC5234], taken from [RFC3629]:

   UTF8-xtra-char  =   UTF8-2 / UTF8-3 / UTF8-4

   UTF8-2          =   %xC2-DF UTF8-tail

   UTF8-3          =   %xE0 %xA0-BF UTF8-tail /
                       %xE1-EC 2(UTF8-tail) /
                       %xED %x80-9F UTF8-tail /
                       %xEE-EF 2(UTF8-tail)

   UTF8-4          =   %xF0 %x90-BF 2( UTF8-tail ) /
                       %xF1-F3 3( UTF8-tail ) /
                       %xF4 %x80-8F 2( UTF8-tail )

   UTF8-tail       =   %x80-BF

   These are normatively defined in [RFC3629], but are repeated in this
   document for reasons of convenience.

   See [RFC5198] for a discussion of normalization; the use of
   normalization form NFC for NAIs is REQUIRED.

2.2.  Formal Syntax

   The grammar for the NAI is given below, described in Augmented
   Backus-Naur Form (ABNF) as documented in [RFC5234].  The grammar for
   the user and realm portion is based on a combination of the "nai"
   defined in [RFC4282] Section 2.1, and the "utf8-addr-spec" defined in
   [RFC5335] Section 4.4.

   nai            =   utf8-username

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   nai            =/  "@" utf8-realm
   nai            =/  utf8-username "@" utf8-realm

   utf8-username  =  dot-string
   dot-string     =  string
   dot-string     =/ dot-string "." string
   string         =  utf8-atext
   string         =/ string utf8-atext

   utf8-atext     =  ALPHA / DIGIT /
                     "!" / "#" /
                     "$" / "%" /
                     "&" / "'" /
                     "*" / "+" /
                     "-" / "/" /
                     "=" / "?" /
                     "^" / "_" /
                     "`" / "{" /
                     "|" / "}" /
                     "~" /

   utf8-realm     =  1*( label "." ) label

   label          =  utf8-rtext *(ldh-str)
   ldh-str        =  *( utf8-rtext / "-" ) utf8-rtext
   utf8-rtext     =  ALPHA / DIGIT / UTF8-xtra-char

2.3.  NAI Length Considerations

   Devices handling NAIs MUST support an NAI length of at least 72
   octets.  Support for an NAI length of 253 octets is RECOMMENDED.
   However, the following implementation issues should be considered:

   o  NAIs are often transported in the User-Name attribute of the
      Remote Authentication Dial-In User Service (RADIUS) protocol.
      Unfortunately, RFC 2865 [RFC2865], Section 5.1, states that "the
      ability to handle at least 63 octets is recommended."  As a
      result, it may not be possible to transfer NAIs beyond 63 octets
      through all devices.  In addition, since only a single User-Name
      attribute may be included in a RADIUS message and the maximum
      attribute length is 253 octets; RADIUS is unable to support NAI
      lengths beyond 253 octets.

   o  NAIs can also be transported in the User-Name attribute of
      Diameter [RFC3588], which supports content lengths up to 2^24 - 9
      octets.  As a result, NAIs processed only by Diameter nodes can be

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      very long.  Unfortunately, an NAI transported over Diameter may
      eventually be translated to RADIUS, in which case the above
      limitations apply.

2.4.  Support for Username Privacy

   Interpretation of the username part of the NAI depends on the realm
   in question.  Therefore, the username portion SHOULD be treated as
   opaque data when processed by nodes that are not a part of the
   authoritative domain (in the sense of Section 4) for that realm.

   In some situations, NAIs are used together with a separate
   authentication method that can transfer the username part in a more
   secure manner to increase privacy.  In this case, NAIs MAY be
   provided in an abbreviated form by omitting the username part.
   Omitting the username part is RECOMMENDED over using a fixed username
   part, such as "anonymous", since it provides an unambiguous way to
   determine whether the username is intended to uniquely identify a
   single user.

   For roaming purposes, it is typically necessary to locate the
   appropriate backend authentication server for the given NAI before
   the authentication conversation can proceed.  As a result, the realm
   portion is typically required in order for the authentication
   exchange to be routed to the appropriate server.

2.5.  International Character Sets

   This specification allows both international usernames and realms.
   International usernames are based on the use of Unicode characters,
   encoded as UTF-8.  Internationalization of the realm portion of the
   NAI is based on "Internationalized Email Headers" [RFC5335].

   In order to ensure a canonical representation, characters of the
   username portion in an NAI MUST fulfill the ABNF in this
   specification as well as the requirements specified in [IDNAbis].  In
   practice, these requirements consist of the following item:

   o  Realms MUST be of the form that can be registered as a
      Fully Qualified Domain Name (FQDN) within the DNS name system.

   This list is significantly shorter, and simpler, than the list in
   Section 2.5 of [RFC4282].  Specifying the realm requirements in this
   way means that realm requirements depend on specifications that are
   referenced here, rather than copied here.

   In general, the restriction above means following the requirements as
   specified in [IDNAbis].  However, that document is in flux at the

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   time of this writing, and the issues with [RFC4282] mandate a timely
   update to it.

2.6.  The Normalization Process

   All normalization MUST be performed by end systems that take "local"
   text as input.  That is, text that is in an encoding other than
   UTF-8, or that has locale-specific variations.  In a network access
   setting, such systems are typically the client (e.g. EAP supplicant)
   and the Authentication, Authorization, and Accounting (AAA) server.

   All other AAA systems (proxies, etc.)  MUST NOT perform
   normalization.  These other systems do not have access to locale and
   character set information that is available to end systems.

   That is, all processing of NAIs from "local" character sets and
   locales to UTF-8 is performed by edge systems, prior to the NAIs
   entering the AAA system.  Inside of an AAA system, NAIs are sent over
   the wire in their canonical form, and this canonical form is used for
   all NAI and/or realm comparisons.

   In contrast to the comments in [RFC4282] Section 2.4, we expect AAA
   systems to perform NAI comparisons, matching, and AAA routing based
   on the NAI as it is received.  This requirement provides a canonical
   representation, ensures that intermediate systems such as AAA proxies
   do not need to perform translations, and can be expected to work
   through systems that are unaware of international character sets.

   For example, much of the common realm routing can be done on the
   "utf8-realm" portion of NAI, through simple checks for equality.
   This routing can be done even if the AAA proxy is unaware of
   internalized domain names.  All that is required is for the AAA proxy
   to be able to enter, store, and compare 8-bit data.

   EAP supplicants MUST normalize user names that get placed in the EAP-
   Response/Identity field.  They MUST NOT copy localized text into that
   field.  This normalization SHOULD be performed once, and then cached
   for subsequent use.

2.7.  Routing inside of AAA Systems

   Many systems require that the "utf8-realm" portion of the NAI be used
   to route requests within a AAA proxy network.  The semantics of this
   operation involves a logical AAA routing table, where the
   "utf8-realm" portion acts as a key, the contents of the table are one
   or more "next hop" AAA servers.

   Intermediate nodes MUST use the "utf8-realm" portion of the NAI

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   without modification to perform this lookup.  Comparisons between the
   NAI as given in a AAA packet, and as provisioned in a logical AAA
   routing table SHOULD be done as a byte-for-byte equality test.  The
   "utf8-realm" provisioned in the logical AAA routing table SHOULD be
   provisioned prior to the proxy receiving any AAA traffic, and SHOULD
   be supplied by the "next hop" system that also supplies the other
   information about the next hop.

   This "next hop" information may be IP address, port, RADIUS shared
   secret, TLS certificates, or a DNS host name.

2.8.  Compatibility with E-Mail Usernames

   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
   is based on the BNF described in [RFC5198], it has been modified for
   the purposes of Section 2.2, and does not permit quoted text along
   with "folding" or "non-folding" whitespace that is commonly used in
   email addresses.  As such, it is not necessarily equivalent to
   usernames used in e-mail.

   However, it is a common practice to use email addresses as user
   identifiers in AAA systems.  The ABNF in Section 2.2 is defined to be
   close to the "utf8-addr-spec" portion of [RFC5335], while still being
   compatible with [RFC4282].

   In contrast to the comments in [RFC4282] Section 2.5, we state that
   the internationalization requirements for NAIs and e-mail addresses
   are substantially similar.  Both of the NAI and email identifiers may
   be the same, and need to be entered by the user himself and his own
   operator.  There is therefore good reason for the
   internationalization requirements to be similar.

2.9.  Compatibility with DNS

   The "realm" portion of the NAI is intended to be compatible with
   domain names used in DNS systems.  However, the "realm" portion
   within an AAA system is treated as a UTF-8 string, not as an ASCII
   string for use within the DNS protocol.  AAA systems MUST NOT use the
   ToAscii function to encode the "utf8-realm" portion of the NAI within
   an AAA protocol.

   When the realm portion of the NAI is used as the basis for name
   lookups within the DNS system, the ToASCII operation define in
   [RFC3490] MAY be used to convert internationalized realm names to
   ASCII.  This function is normally handled by a DNS resolver library
   on the local system.  When this function is not handled by a DNS
   resolver library, the AAA system MAY perform the ToAscii conversion

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   itself, before passing the modified realm name to the DNS resolver

   There are, however, a number of problems with this approach.  A AAA
   proxy may not have sufficient information in order to perform the
   ToAscii conversion properly.  We therefore RECOMMEND that only the
   owner of the realm perform the ToAscii conversion.  We RECOMMEND that
   the owner of the realm pre-provision to all proxies the "utf8-realm"
   portion of the NAI, along with the canonical form returned by the
   ToAscii function.  This canonical form can then be used in the
   logical AAA routing table discussed above, in order to perform DNS

   This last suggestion does not negate the benefits of using DNS to
   automatically discover the location of a "next hop" AAA server.  Many
   AAA proxies require a business or legal relationship prior to routing
   any traffic.  This relationship can be leveraged to bootstrap the DNS
   information located in the logical AAA routing table.

2.10.  Realm Construction

   The home realm usually appears in the realm portion of the NAI, but
   in some cases a different realm can be used.  This may be useful, for
   instance, when the home realm is reachable only via intermediate

   Such usage may prevent interoperability unless the parties involved
   have a mutual agreement that the usage is allowed.  In particular,
   NAIs MUST NOT use a different realm than the home realm unless the
   sender has explicit knowledge that (a) the specified other realm is
   available and (b) the other realm supports such usage.  The sender
   may determine the fulfillment of these conditions through a database,
   dynamic discovery, or other means not specified here.  Note that the
   first condition is affected by roaming, as the availability of the
   other realm may depend on the user's location or the desired

   The use of the home realm MUST be the default unless otherwise

2.10.1.  Historical Practices

   Some systems have historically used NAI modifications with multiple
   "prefix" and "suffix" decorations to perform explicit routing through
   multiple proxies inside of a AAA network.  This practice is NOT
   RECOMMENDED for the following reasons:

   o  Using explicit routing paths is fragile, and is unresponsive to

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      changes in the network due to servers going up or down, or to
      changing business relationships.

   o  There is no RADIUS routing protocol, meaning that routing paths
      have to be communicated "out of band" to all intermediate AAA
      nodes, and also to all end-user systems (supplicants) expecting to
      obtain network access.

   o  Using explicit routing paths requires thousands, if not
      millions of end-user systems to be updated with new path
      information when a AAA routing path changes.  This adds huge
      expense for updates that would be better done at only a few AAA
      systems in the network.

   o  Manual updates to RADIUS paths are expensive, time-consuming,
      and prone to error.

   o  Re-writing of the User-Name in AAA servers means that it may not
      match the EAP-Response/Identity fields.  This mismatch may cause
       the home AAA server to reject the request as being malformed.

   o  Creating compatible formats for the NAI is difficult
      when locally-defined "prefixes" and "suffixes" conflict with
      similar practices elsewhere in the network.  These conflices mean
      that connecting two networks may be impossible in some cases, as
      there is no way for packets to be routed properly in a way that
      meets all requirements at all intermediate proxies.

   o  Leveraging the DNS name system for realm names establishes
      a globally unique name space for realms.

   In summary, network practices and capabilities have changed
   significantly since NAIs were first overloaded to define AAA routes
   through a network.  While explicit path routing was once useful, the
   time has come for better methods to be used.

2.11.  Examples

   Examples of valid Network Access Identifiers include the following:


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   Examples of invalid Network Access Identifiers include the following:

   One example given in [RFC4282] is still permitted by the ABNF, but it
   is NOT RECOMMMENDED because of the use of the ToAscii function to
   create an ASCII encoding from what is now a valid UTF-8 string.


3.  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 that transmit the username in
   clear-text across the Internet, such as in RADIUS, described in
   [RFC2865] and [RFC2866].  In order to prevent snooping of the
   username, protocols may use confidentiality services provided by
   protocols transporting them, such as RADIUS protected by IPsec
   [RFC3579] or Diameter protected by TLS [RFC3588].

   This specification adds the possibility of hiding the username part
   in the NAI, by omitting it.  As discussed in Section 2.4, this is
   possible only when NAIs are used together with a separate
   authentication method that can transfer the username in a secure
   manner.  In some cases, application-specific privacy mechanism have
   also been used with NAIs.  For instance, some EAP methods apply
   method-specific pseudonyms in the username part of the NAI [RFC3748].
   While neither of these approaches can protect the realm part, their
   advantage over transport protection is that privacy of the username
   is protected, even through intermediate nodes such as NASes.

4.  IANA Considerations

   In order to avoid creating any new administrative procedures,
   administration of the NAI realm namespace piggybacks on the

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   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 require use
   of the DNS for location of the authentication server.  While Diameter
   [RFC3588] supports the use of DNS for location of authentication
   servers, existing RADIUS implementations typically use proxy
   configuration files in order to locate authentication servers within
   a domain and perform authentication routing.  The implementations
   described in [RFC2194] did not use DNS for location of the
   authentication server within a domain.  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.

5.  References

5.1.  Normative references

     Bradner, S., "Key words for use in RFCs to Indicate Requirement
     Levels", RFC 2119, March, 1997.

     Faltstrom, P., Hoffman, P., and A. Costello, "Internationalizing
     Domain Names in Applications (IDNA)", RFC 3490, March 2003.

     Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63,
     RFC 3629, November 2003.

     Klensin J., and Padlipsky M., "Unicode Format for Network
     Interchange", RFC 5198, March 2008

     Crocker, D. and P. Overell, "Augmented BNF for Syntax
     Specifications: ABNF", RFC 5234, January 2008.

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INTERNET-DRAFT        The Network Access Identifier     9 September 2009

5.2.  Informative references

     Aboba, B., Lu, J., Alsop, J., Ding, J., and W. Wang, "Review of
     Roaming Implementations", RFC 2194, September 1997.

     Valencia, A., Littlewood, M., and T. Kolar, "Cisco Layer Two
     Forwarding (Protocol) "L2F"", RFC 2341, May 1998.

     Hamzeh, K., Pall, G., Verthein, W., Taarud, J., Little, W., and G.
     Zorn, "Point-to-Point Tunneling Protocol", RFC 2637, July 1999.

     Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn, G., and B.
     Palter, "Layer Two Tunneling Protocol "L2TP"", RFC 2661, August

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

     Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.

     Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication Dial In
     User Service) Support For Extensible Authentication Protocol
     (EAP)", RFC 3579, September 2003.

     Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. Arkko,
     "Diameter Base Protocol", RFC 3588, September 2003.

     Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
     Levkowetz, "Extensible Authentication Protocol (EAP)", RFC 3748,
     June 2004.

     Aboba, B. et al., "The Network Access Identifier", RFC 4282,
     December 2005.

     Kent, S. and S. Keo, "Security Architecture for the Internet
     Protocol", RFC 4301, December 2005.

DeKok, Alan                  Standards Track                   [Page 16]

INTERNET-DRAFT        The Network Access Identifier     9 September 2009

     Y. Abel, Ed., "Internationalized Email Headers", RFC 5335,
     September 2008.

     http://eduroam.org, "eduroam (EDUcational ROAMing)"

     Klensin, J., "Internationalized Domain Names in Applications
     (IDNA): Protocol", draft-ietf-idnabis-protocol-15.txt, (work in


   The initial text for this document was [RFC4282], which was then
   heavily edited.  The original authors of [RFC4282] were Bernard
   Aboba, Mark A. Beadles, Jari Arkko, and Pasi Eronen.

   The ABNF validator at http://www.apps.ietf.org/abnf.html was used to
   verify the syntactic correctness of the ABNF in Section 2.

DeKok, Alan                  Standards Track                   [Page 17]

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Appendix A - Changes from RFC4282

   This document contains the following updates with respect to the
   previous NAI definition in RFC 4282 [RFC4282]:

   o  The formal syntax in Section 2.1 has been updated to forbid
      non-UTF8 characters.  e.g. characters with the "high bit" set.

   o  The formal syntax in Section 2.1 has been updated to allow
      UTF-8 in the "realm" portion of the NAI.

   o  The formal syntax in [RFC4282] Section 2.1 applied to the
      NAI after it was "internationalized" via the ToAscii function.
      The contents of the NAI before it was "internationalized" were
      left indeterminate.  This document updates the formal syntax to
      define an internationalized form of the NAI, and forbids the use
      of the ToAscii function for NAI "internationalization".

   o  All use of the ToAscii function has been moved to normal
      requirements on DNS implementations when realms are used as the
      basis for DNS lookups.  This involves no changes to the existing
      DNS infrastructure.

   o  The discussions on internationalized character sets in Section 2.4
      have been updated.  The suggestion to use the ToAscii function for
      realm comparisons has been removed.  No AAA system implemented the
      suggestion, so this change should have no operational impact.

   o The section "Routing inside of AAA Systems" section is new in this
      document.  The concept of a "local AAA routing table" is also new,
      although it accurately describes the functionality of wide-spread

   o  The "Compatibility with E-Mail Usernames" and "Compatibility
      with DNS" sections have been revised and updated.  We now note
      that the ToAscii function is required to be used only when a realm
      name is used for DNS lookups, and even then the function is only
      used by a DNS resolving library on the local system, and even then
      we recommend that only the home network perform this conversion.

   o  The "Realm Construction" section has been updated to note
      that editing of the NAI is NOT RECOMMENDED.

   o The "Examples" section has been updated to remove the instance
      of the IDN being converted to ASCII.  This behavior is now

Authors' Addresses

DeKok, Alan                  Standards Track                   [Page 18]

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   Alan DeKok
   The FreeRADIUS Server Project

   Email: aland@freeradius.org

DeKok, Alan                  Standards Track                   [Page 19]

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