I-D Action:draft-stevant-softwire-accounting-02.txt

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A New Internet-Draft is available from the on-line Internet-Drafts directories.

	Title           : Accounting on Softwires
	Author(s)       : B. Stevant, et al.
	Filename        : draft-stevant-softwire-accounting-02.txt
	Pages           : 10
	Date            : 2009-04-20

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.1.  Motivation

The Softwires WG is working on a solution to bring IPvX connectivity
over an IPvY network [RFC4925].  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 service.

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
[RFC2867].

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.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 ([RFC4925]).  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 customer.



/---------------------------\







 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 Architecture3.  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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