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Network Working Group                                         B. Stevant
Internet-Draft                                                L. Toutain
Intended status: Informational                         GET/ENST Bretagne
Expires: April 14, 2007                                        F. Dupont
                                                                D. Binet
                                                                  FT R&D
                                                        October 11, 2006

                        Accounting on Softwires

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Copyright Notice

   Copyright (C) The Internet Society (2006).

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Internet-Draft           Accounting on Softwires            October 2006


   For access network operators, accounting information are crucial:
   they provide information for billing and give an overview of the
   traffic usage.  This document defines the requirements for accounting
   information needed on Softwires.

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1.  Motivation

   The Softwires WG is working on a solution to bring IPvX connectivity
   over an IPvY network [ID.problemstatement].  This solution may be
   deployed and managed by access network operators to provide for
   example IPvX continuity of service.  Operators should then consider
   the Softwires solution as an extension of their access network

   For operators, AAA [RFC2865] is the key feature for access network
   deployment: Authentication verifies user credentials, Authorization
   ensures access network integrity and Accounting provides information
   for billing and network management.  Information from accounting
   usually includes measurements of in and out octets and packets

   As an alternative access network, the Softwires solution should
   provide similar AAA features.  For instance accounting on the
   softwire should gives to the operator measurements of the traffic
   generated by the user using this access network.  In a dual stack
   (IPvX and IPvY) network, the operator may want to manage information
   about the comparative usage of both protocols, for example for
   billing purpose.  When the softwire is used to access IPvX over IPvY,
   accounting information will be specific to IPvX.  Operators should be
   able to differentiate for which version of IP such information are
   relevant.  This differentiation may become important if such
   operators offer a softwire solution for both IPvX over IPvY and IPvY
   over IPvX access networks.

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2.  Study case

   In this section is given an example of IPv6 access over IPv4 network
   which is similar to the Hub-and-Spokes problem stated in the
   Softwires WG ([ID.problemstatement]).  The Point6box architecture
   uses L2TP [RFC2661] and PPP for IPv6 tunneling over IPv4 (see
   Figure 1).  Radius manages AAA parameters for the access network
   created by the tunnel.  On the server side, PPP sends to RADIUS
   accounting information measuring the traffic generated by the

   /---------------------------\                         CPEv6
   |          +--------------+ |    DHCPv6              +-----+
   |    /....>| DHCPv6 relay |<........................>| P   |
   |    .     +--------------+ |                 CPEv4  | o   |  |
   |    .     | L2TP IPv6    | |    L2TP        +-----+ | i   |  |-- X
   |    .     |  server      |=======================b=== n B |  |
   |    v     +--------------+ |   @@  @@       |    r| | t o |  |
   | +--------+  ^             |  @  @@  @      | N  i|-| 6 x |  |-- Y
   | | DHCPv6 |  |             |--@ IPv4 @------| A  d| +-----+  |
   | | server |  |             |  @  @@  @      | T  g|          |
   | +--------+  |             |   @@  @@ PEv4  |    e|----------|
   \-------------|-------------/                +-----+   RA->   |-- Z
                 |      PEv6                                     |
     +--------+  |                                             clients
     | RADIUS |  | RADIUS
     | server |<-/
     +--------+            IPv4/v6 ISP               Customer

                 Figure 1: Point6Box Service Architecture

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3.  Problem statement

   The accounting information defined for tunnels [RFC2867] includes
   attributes Acct-{Input,Output}-Octets and Acct-{Input,Output}-Packets
   for traffic measurements.  These attributes do not depend of the
   version of IP used by the monitored traffic.  Operators may not be
   able to differenciate IPv4 from IPv6 traffic in their accounting
   statistics.  This non-differentiation even leads to mis-usages: In
   the current PPP implementation from BSD, the values of these
   attributes are only based on IPv4 statistics collected from IPCP
   protocol.  No statistics are collected for IPv6 from IPV6CP.

   This proposal should decide which attributes may be candidate for IP-
   version differentiation.  In operating system MIBs, values for in/out
   octets on a network interface are independent of the IP version.
   Having such values for each version may be usefull for monitoring and
   billing purpose.  However the differentiation is done for in/out IPv4
   and IPv6 packets on a network interface.  Operators can extract from
   these values some hints about the usage of each version of the IP
   protocol but can not give quantitative report of bandwidth usage.

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4.  Proposed solutions

4.1.  Summing accounting informations

   In the Point6Box solution, the PPP negociation only initiates the
   IPV6CP protocol on the tunnel.  The PPP statistics handling requires
   some modifications to get IPv6-specific accounting information in
   Radius attributes.  A minor modification of the code may consist in
   filling the RADIUS attributes with the sum of both IPCP and IPV6CP
   values.  But still no differentiation is made on the version of IP
   used.  Such solution do not match the requirements stated before.

4.2.  Differentiation based on context

   A RADIUS accounting entry, as defined in [RFC2867], also includes the
   NASIPAddress attribute, which gives the IP address of the NAS used as
   the softwire endpoint.  Based on this information, an operator can
   decide if this softwire is based on IPv4 or IPv6.  In the case of
   provider only deploying IPv6 over IPv4 and IPv4 over IPv6 softwires,
   the nature of the traffic reported in the accounting information
   depends of the address family of NASIPAddress (if NASIPAddress is
   IPv4, accounted traffic is IPv6, if NASIPAddress is IPv6, accounted
   traffic is IPv4).  However, this solution requires extra checking
   when building accounting report and obviously does not work in case
   of IPvX over IPvX softwires.

4.3.  Differentiation based on Attributes

   Another solution is to have separate accounting attributes for IPv4
   and IPv6.  The accounting information should then be provided
   depending on the softwire access:

   o  IPv4-only access: Only IPv4 accounting values are provided.  IPv6
      accounting values should be filled as null,

   o  IPv6-only access: Only IPv6 accounting values are provided.  IPv4
      accounting values should be filled as null,

   o  Dual stack IPv4 and IPv6 access: Values for both protocols should
      be provided.

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5.  Security Considerations

   The Point6Box approach and the proposed extension of RADIUS only use
   already existing protocols and add supplementary attributes.  No new
   security should be introduced.

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6.  References

6.1.  Normative References

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

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

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

   [RFC2867]  Zorn, G., Aboba, B., and D. Mitton, "RADIUS Accounting
              Modifications for Tunnel Protocol Support", RFC 2866,
              June 2000.

6.2.  Informative References

              Li, X., Durand, A., Miyakawa, S., Palet, J., Parent, F.,
              and D. Ward, "Softwire Problem Statement",
              draft-ietf-softwire-problem-statement-00.txt (work in
              progress), December 2005.

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Appendix A.  Revision History

   Changes between -00 and -01:

   o  Add new solution in Section 4.2.

   o  Moved paragraph about system MIBs in Section 3.

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Authors' Addresses

   Bruno Stevant
   GET/ENST Bretagne
   2 rue de la Chataigneraie
   CS 17607
   35576 Cesson-Sevigne Cedex

   Fax:   +33 2 99 12 70 30
   Email: Bruno.Stevant@enst-bretagne.fr

   Laurent Toutain
   GET/ENST Bretagne
   2 rue de la Chataigneraie
   CS 17607
   35576 Cesson-Sevigne Cedex

   Fax:   +33 2 99 12 70 30
   Email: Laurent.Toutain@enst-bretagne.fr

   Francis Dupont

   Email: Francis.Dupont@fdupont.fr

   David Binet
   FT R&D

   Email: David.Binet@francetelecom.com

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