A Model of IPv6/IPv4 Dual Stack Internet Access Service
RFC 4241

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 04

Network Working Group                                       Y. Shirasaki
Request for Comments: 4241                                   S. Miyakawa
Category: Informational                                      T. Yamasaki
                                                      NTT Communications
                                                           A. Takenouchi
                                                                     NTT
                                                           December 2005

          A Model of IPv6/IPv4 Dual Stack Internet Access Service

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

IESG Note

   This RFC is not a candidate for any level of Internet Standard.  The
   IETF disclaims any knowledge of the fitness of this RFC for any
   purpose and notes that the decision to publish is not based on IETF
   review apart from IESG review for conflict with IETF work.  The RFC
   Editor has chosen to publish this document at its discretion.  See
   RFC 3932 for more information.

Abstract

   This memo is a digest of the user network interface specification of
   NTT Communications' dual stack ADSL access service, which provide a
   IPv6/IPv4 dual stack services to home users.  In order to simplify
   user setup, these services have a mechanism to configure IPv6
   specific parameters automatically.  The memo focuses on two basic
   parameters:  the prefix assigned to the user and the addresses of
   IPv6 DNS servers, and it specifies a way to deliver these parameters
   to Customer Premises Equipment (CPE) automatically.

Shirasaki, et al.            Informational                      [Page 1]
RFC 4241               Dual Stack Access Service           December 2005

1. Introduction

   This memo is a digest of the user network interface specification of
   NTT Communications' dual stack ADSL access service, which provide
   IPv6/IPv4 dual stack services to home users.  In order to simplify
   user setup, these services have a mechanism to configure IPv6
   specific parameters automatically.  The memo focuses on two basic
   parameters:  the prefix assigned to the user and the addresses of
   IPv6 DNS servers, and it specifies a way to deliver these parameters
   to Customer Premises Equipment (CPE) automatically.

   This memo covers two topics: an architecture for IPv6/IPv4 dual stack
   access service and an automatic configuration function for IPv6-
   specific parameters.

   The architecture is mainly targeted at a leased-line ADSL service for
   home users.  It assumes that there is a Point-to-Point Protocol (PPP)
   logical link between Customer Premises Equipment (CPE) and Provider
   Edge (PE) equipment.  In order to exclude factors that are specific
   to access lines, this architecture only specifies PPP and its upper
   layers.  To satisfy [RFC3177], the prefix length that is delegated to
   the CPE is /48, but /64 is also a possible option.

   In this architecture, IPv6/IPv4 dual stack service is specified as
   follows.

     o IPv6 and IPv4 connectivities are provided over a single PPP
       logical link.

     o IPv6 connectivity is independent of IPv4 connectivity.  IPV6CP
       and IPCP work independently over a single PPP logical link.

   Figure 1 shows an outline of the service architecture.  NTT
   Communications has been providing a commercial service based on this
   architecture since the Summer 2002.

          |                                             _____________
   [HOST]-+ +-----------+               +----------+   /             \
          | | Customer  |   ADSL line   | Provider |  | ISP core and  |
          +-+ Premises  +---------------+   Edge   |--| The internet  |
          | | Equipment | to subscriber +-----+----+   \_____________/
   [HOST]-+ +-----------+                     |         |   |
          |                             +-----+------+  | +-+----------+
                                        | AAA server |  | | DNS server |
                                        +------------+  | +------------+
                                                      +-+--------------+
                                                      | NTP server etc.|
    Figure 1: Dual Stack Access Service Architecture  +----------------+

Shirasaki, et al.            Informational                      [Page 2]
RFC 4241               Dual Stack Access Service           December 2005

   The automatic configuration function aims at simplification of user
   setup.  Usually, users have to configure at least two IPv6-specific
   parameters: prefix(es) assigned to them [RFC3769] and IPv6 DNS
   servers' addresses.  The function is composed of two sub-functions:

     o Delegation of prefix(es) to be used in the user site.

     o Notification of IPv6 DNS server addresses and/or other server