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Versions: (draft-nmcgill-l2tp-radius-ext-nas-port) 00 01 02

Please publish to l2tpext@ietf.org



Network Working Group                                          N. McGill
Internet-Draft                                             cisco Systems
Expires: June 3, 2008                                       T. Mistretta
                                                        Juniper Networks
                                                               I. Goyret
                                                          Alcatel-Lucent
                                                             M. Townsley
                                                                G. Weber
                                                           cisco Systems
                                                                Dec 2007


                  RADIUS & L2TP Extended NAS-Port AVPs
             draft-ietf-l2tpext-radius-ext-nas-port-02.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
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   This Internet-Draft will expire on June 3, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document defines additional Layer 2 Tunneling Protocol (L2TP)
   and Remote Authentication Dial In User Service (RADIUS) Attribute-



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   Value Pairs (AVPs) to communicate Network Access Server (NAS)
   informational UTF-8 text and port usage information between L2TP
   peers during call establishment to facilitate authorization,
   accounting and logging.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Specification of Requirements  . . . . . . . . . . . . . .  4
   2.  L2TP Extended NAS-Port AVPs  . . . . . . . . . . . . . . . . .  4
   3.  RADIUS Extended NAS-Port AVP . . . . . . . . . . . . . . . . .  7
     3.1.  Table of Attributes  . . . . . . . . . . . . . . . . . . . 10
     3.2.  Interactions with other RADIUS attributes  . . . . . . . . 10
     3.3.  Diameter Compatibility . . . . . . . . . . . . . . . . . . 10
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
   Intellectual Property and Copyright Statements . . . . . . . . . . 14




























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1.  Introduction

   It is often desirable to send adjunct and port usage information from
   the L2TP Access Concentrator (LAC) to the L2TP Network Server (LNS)
   during call setup.  Such information MAY be used for:


      Logging
         to describe system and port related information in a human-
         readable, vendor-specific form.
      Authorization
         to restrict users to particular given access types or
         interfaces.
      Accounting
         to determine port usage on a per-user basis, for example, via
         RADIUS accounting [RFC2866].
      Auditing
         to ensure that the LNS vendor is being allocated the proper
         contractual resources by the LAC vendor.

   L2TPv2 [RFC2661] and L2TPv3 [RFC3931] already have a Physical Channel
   ID AVP that may be used to provide port usage information.  However,
   its usefulness is limited in multi-vendor LAC/LNS environments where
   the vendor- specific bit encoding used for this AVP will often not be
   understood by L2TP peers from differing vendors.

   This makes the task of de-constructing the Physical Channel ID AVP
   contents at the LNS for (RADIUS) authorization/accounting server
   extremely difficult.

   Additionally, it is length limited to 4 octets of information which
   is inadequate in access servers supporting multiple access types and
   large numbers of ports.

   This document defines extensions whereby such port usage information
   may be transferred in a vendor-independent fashion between mixed-
   vendor LAC and LNSs, thus facilitating detailed and matching logging
   and accounting at each end of the tunnel.













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   The following diagram depicts a typical dialin scenario for L2TP with
   RADIUS accounting servers at the LNS:


                  Authen/Accounting
                    RADIUS server
                        |
                        |
                        |
                        |
      intranet - - - - LNS - - - - - internet - - - -LAC - - - -client
                        <----------------------------->
                                   L2TP tunnel


1.1.  Specification of Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].


2.  L2TP Extended NAS-Port AVPs

   The following collection of Extended NAS-Port AVPs, attribute types
   TBD, allow detailed logging and port usage information to be
   transmitted between L2TP peers.  This format is common to all
   Extended NAS-Port AVPs; only the Attribute Type is different for
   each:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |M|H| rsvd  |      Length       |        Vendor ID (IETF)       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         Attribute Type        |        Attribute Value...
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        [until Length is reached]...                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   NOTES:

   o  Each Extended NAS-Port AVP is encoded as the IETF Vendor ID 0

   o  Each AVP has defined behaviour associated with it, namely:






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      RELAYED AVP:  See [I-D.ietf-l2tpext-tunnel-switching], section 3.
         AVP Behavior, for definition.  In summary, if this AVP is
         received by a node participating in a multi-hop scenario, then
         the AVP MUST be copied as-is to the next hop.

      STACKED AVP:  See [I-D.ietf-l2tpext-tunnel-switching], section 3.
         AVP Behavior, for definition.  In summary, if this AVP is
         received by a node participating in a multi-hop scenario, then
         the AVP MUST be copied as-is to the next hop.  A locally
         generated AVP MUST be generated and appended in the outbound
         message to the next hop.  If no value is appropriate then an
         AVP of Length 6 (minimum AVP length) MUST be appended.  This
         null attibute value may be used for all AVPs where no value is
         appropriate.

   o  The value of all bits MUST be preserved in any AVPs copied.


   The following are valid values for the Attribute Type field in
   control channel related messages:

      L2TP-AVP-TBD-1 - Platform Information

         This AVP, value length 0-253, allows a UTF-8 [RFC3629] string
         to be sent with a human-readable description of the platform.

         Examples: "Model 457", or "TPX-1700".

         This information MUST NOT be parsed and as such termination
         action MUST NOT be based on the contents of this attribute.

         The M-bit MUST be set to 0.  The H-bit MAY be set based on the
         current L2TP node's policy.  This AVP is a stackable AVP.

      L2TP-AVP-TBD-2 - System Identification Information

         This AVP, value length 0-253, allows a UTF-8 [RFC3629] string
         to be sent with a human-readable description of the router's
         identification within the provider's network.

         Examples: "CommCo LAC", or "SuperProvider AS".

         This information MUST NOT be parsed and as such termination
         action MUST NOT be based on the contents of this attribute.

         The M-bit MUST be set to 0.  The H-bit MAY be set based on the
         current L2TP node's policy.  This AVP is a stackable AVP.




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      L2TP-AVP-TBD-4 - Software Information

         This AVP, value length 0-253, allows a UTF-8 [RFC3629] string
         to be sent with a human-readable description of the software
         running on the platform.

         Examples: "Version 4-0.12(c)-2", or "Rev 10.4.2-beta".

         This information MUST NOT be parsed and as such termination
         action MUST NOT be based on the contents of this attribute.

         The M-bit MUST be set to 0.  The H-bit MAY be set based on the
         current L2TP node's policy.  This AVP is a stackable AVP.

      For tunnels, these AVPs are valid either on SCCRQ or SCCCN.  If
      sent on both, the SCCCN AVP MUST override the SCCRP value.

   The following are valid values for the Attribute Type field in
   session related messages:

      L2TP-AVP-TBD-3 - Call Information

         This AVP, value length 0-253, allows a UTF-8 [RFC3629] string
         to be sent with a human-readable description of the call.

         Examples could include "Atlanta POP", or "Neptune-304x using
         frame2 module".

         This information MUST NOT be parsed and as such termination
         action MUST NOT be based on the contents of this attribute.

         The M-bit MUST be set to 0.  The H-bit MAY be set based on the
         current L2TP node's policy.  This AVP is a stackable AVP.

      L2TP-AVP-TBD-6 - Shelf
      L2TP-AVP-TBD-7 - Slot
      L2TP-AVP-TBD-8 - Module
      L2TP-AVP-TBD-9 - Adapter
      L2TP-AVP-TBD-10 - Interface
      L2TP-AVP-TBD-11 - Line
      L2TP-AVP-TBD-12 - Port
      L2TP-AVP-TBD-13 - Channel
      L2TP-AVP-TBD-14 - Physical Interface
      L2TP-AVP-TBD-15 - Physical Sub-interface
      L2TP-AVP-TBD-16 - Virtual Path
      L2TP-AVP-TBD-17 - Virtual Circuit





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      L2TP-AVP-TBD-18 - Virtual Lan
      L2TP-AVP-TBD-18 - Virtual Interface
      L2TP-AVP-TBD-20 - Virtual Sub-interface

         These AVPs, length 0 or 4, are unsigned octet integers value,
         representing a specific Extended NAS-Port AVP value at this
         L2TP node.

         The M-bit MUST be set to 0.  The H-bit MAY be set based on the
         current L2TP node's policy.  These AVPs are relayed AVPs.

      All Extended NAS-Port AVPs SHOULD be used in conjunction with the
      port type values defined in [RFC2865] and [RFC2866].

      For incoming calls, these AVPs are valid either on ICRQ or ICCN.
      If sent on both, the ICCN AVP MUST override the ICRQ value.  For
      outgoing calls, the AVPs are valid on OCRP and OCCN, with similar
      override behavior.


3.  RADIUS Extended NAS-Port AVP

   The RADIUS Extended NAS-Port AVP closely resembles its L2TP counter-
   part and allows detailed port-usage/accounting information to be
   provided in multi-vendor environments.

   The key distinction is that for RADIUS we have a single new attribute
   (due to lack of available RADIUS type attributes) with multiple
   Extensions, encoded as string attribute-value pairs of the form
   "<extension>=<value>".  These Extensions exist in a one-to- one
   mapping with the previously defined L2TP AVPs.

   The following format is common to all Extended NAS-Port AVPs; only
   the Extension string name is different for each:

     0                   1                   2
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
    |Extnd. NAS-Port|    Length     |  "extension=value"...
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

   Type

      RADIUS-AVP-TBD-1 for Extended NAS-Port

   Length





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      >= 3

   Value

      This attribute is of string format, with the following definition:

      "<extension>=<value>"

      Where "<extension>" is one of the following case-sensitive
      strings:

         "platform" - Platform Information

            This AVP extension, length 3-255, allows a UTF-8 [RFC3629]
            string to be sent with a human-readable description of the
            platform.

            Examples: "platform=Model 457", or "platform=TPX-1700".

            This information MUST NOT be parsed and as such termination
            action MUST NOT be based on the contents of this attribute.

         "system-id" - System Identification Information

            This AVP extension, length 3-255, allows a UTF-8 [RFC3629]
            string to be sent with a human-readable description of the
            routers identification within the provider's network.

            Examples: "system-id=CommCo LAC", or "system-
            id=SuperProvider AS".

            This information MUST NOT be parsed and as such termination
            action MUST NOT be based on the contents of this attribute.

         "call" - Call Information

            This AVP extension, length 3-255, allows a UTF-8 [RFC3629]
            string to be sent with a human-readable description of the
            call.

            Examples could include "call=Atlanta POP", or "call=Neptune-
            304x using frame2 module".

            This information MUST NOT be parsed and as such termination
            action MUST NOT be based on the contents of this attribute.






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         "software" - Software Information

            This AVP extension, length 3-255, allows a UTF-8 [RFC3629]
            string to be sent with a human-readable description of the
            software running on the platform.

            Examples: "software=Version 4-0.12(c)-2", or "software=Rev
            10.4.2-beta".

            This information MUST NOT be parsed and as such termination
            action MUST NOT be based on the contents of this attribute.

         "shelf" - Shelf
         "slot" - Slot
         "module" - Module
         "adapter" - Adapter
         "intf" - Interface
         "line" - Line
         "port" - Port
         "channel" - Channel
         "phys-intf" - Physical Interface
         "phys-subintf" - Physical Sub-interface
         "vpi" - Virtual Path
         "vci" - Virtual Circuit
         "vlan" - Virtual Lan
         "vintf" - Virtual Interface
         "vsubintf" - Virtual Sub-interface

            These AVPs, length 3-255, allow a UTF-8 [RFC3629] string to
            be sent with the integer value of the relevant Extended NAS-
            Port AVP.

            Examples: "vpi=3", "vci=0", "vlan=4094"

   For L2TP tunnels, these attributes MUST be used, if available, to log
   information obtained via the corresponding L2TP Extended NAS-Port
   AVPs.  See section 2.

   To cater for L2TP multi-hop environments, if an L2TP Extended NAS-
   Port AVP is available, but without a corresponding value, then the
   associated RADIUS AVP MUST be encoded as "<extension>"

   The sequence of RADIUS Extended NAS-Port AVPs MUST follow that of any
   L2TP Extended NAS-Port AVPs received.

   For scenarios without L2TP, these attributes MAY also be used in
   preference over the RADIUS NAS-Port attribute to provide finer
   granularity during accounting.



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   Where an attribute was not received from L2TP it is considered
   optional to send.

   For non L2TP environments, all Extensions are optional.

   All strings are NOT null terminated.

   Any numbers encoded as the value part of the Extension MUST be as
   strings with a minimum value of "0".  Only unsigned values MUST be
   sent.

   The use of the character '"' in this document is included purely as a
   visual aid in identifying the beginning and end of strings.  It MUST
   NOT be included as part of the end format, unless specifically
   encoded as data within the AVP Value section.

3.1.  Table of Attributes

   The following table provides a guide to which attributes may be found
   in which kinds of packets, and in what quantity.

   For Authentication:

         Request  Accept  Reject  Challenge   Attribute
         0+       0       0       0           Extended NAS-Port

   For Accounting:

         Request  Response                    Attribute
         0+       0                           Extended NAS-Port

3.2.  Interactions with other RADIUS attributes

   Extended NAS-Port overlaps in functionality with NAS-Port.  However,
   whereas the encoding of NAS-Port is limited to 32 bits and often
   vendor specific, Extended NAS-Port is not.  NAS-Port may still
   continue to be used but preference SHOULD be given to information
   received in Extended NAS-Port.

   If a RADIUS vendor detects conflicting values between NAS-Port and
   Extended NAS-Port, Extended NAS-Port SHOULD be taken as the more
   accurate value.

3.3.  Diameter Compatibility

   The RADIUS Extended NAS-Port attribute defined in this section may be
   translated for transmission via Diameter [RFC3588] by AAA Translation
   Agents as described by Section 9 of [RFC4005].



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   Such a translation might represent the extended NAS-Port information
   as a single Diameter attribute of type Grouped.  Each RADIUS
   <extension> valued defined in section 3 would map to a new Diameter
   attribute, all of which would be encapsulated in a single Grouped
   Extended-NAS-Port attribute.  The ABNF for such an attribute might
   look like:

        Extended-NAS-Port     ::= < AVP Header: DIAMETER-AVP-TBD-1 >
            [ NAS-Port-Platform ]
            [ NAS-Port-System-Id ]
            [ NAS-Port-Call ]
            [ NAS-Port-Software ]
            [ NAS-Port-Vendor ]
            [ NAS-Port-Shelf ]
            [ NAS-Port-Slot ]
            ...


4.  Security Considerations

   This document describes mechanisms where port termination-related
   information can be sent between L2TP peers.  Users of these AVPs
   should have the understanding that any information sent could be used
   for malicious purposes.  If this is a concern, any of the L2TP
   Extended NAS-Port List AVPs MAY be hidden.


5.  IANA Considerations

   All values referenced with AVP-TBP need to be assigned an IETF
   "Attribute Type" from the "Control Message Attribute Value Pairs"
   maintained by IANA for L2TP.


6.  Acknowledgements

   The authors wish to thank Carlos Pignato for comments received.


7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3588]  Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
              Arkko, "Diameter Base Protocol", RFC 3588, September 2003.



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   [RFC2661]  Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn,
              G., and B. Palter, "Layer Two Tunneling Protocol "L2TP"",
              RFC 2661, August 1999.

7.2.  Informative References

   [RFC2866]  Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, June 2000.

   [RFC3931]  Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
              Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [I-D.ietf-l2tpext-tunnel-switching]
              Jain, V., "PPP over L2TP Tunnel Switching",
              draft-ietf-l2tpext-tunnel-switching-08 (work in progress),
              March 2007.

   [RFC4005]  Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
              "Diameter Network Access Server Application", RFC 4005,
              August 2005.


Authors' Addresses

   Neil McGill
   cisco Systems
   3rd Floor
   96 Commercial Street
   Edinburgh, EH6 6LX
   UK

   Email: nmcgill@cisco.com


   Tom Mistretta
   Juniper Networks
   10 Technology Park Drive
   Westford, MA  01886
   US

   Email: thomas.mistretta@verizon.net




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   Ignacio Goyret
   Alcatel-Lucent
   1801 Harbor Bay Parkway
   Alameda, CA  94502

   Email: igoyret@alcatel-lucent.com


   W. Mark Townsley
   cisco Systems

   Email: mark@townsley.net


   Greg Weber
   cisco Systems
   10850 Murdock Road
   Knoxville, TN  37932
   US

   Email: gdweber@cisco.com






























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Full Copyright Statement

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