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Versions: (draft-mawatari-v6ops-464xlat) 00 01 02 03 04 05 06 07 08 09 10 RFC 6877

Internet Engineering Task Force                              M. Mawatari
Internet-Draft                          Japan Internet Exchange Co.,Ltd.
Intended status: BCP                                        M. Kawashima
Expires: November 9, 2012                       NEC AccessTechnica, Ltd.
                                                                C. Byrne
                                                            T-Mobile USA
                                                             May 8, 2012


       464XLAT: Combination of Stateful and Stateless Translation
                      draft-ietf-v6ops-464xlat-03

Abstract

   This document describes an architecture (464XLAT) for providing
   limited IPv4 connectivity across an IPv6-only network by combining
   existing and well-known stateful protocol translation RFC 6146 in the
   core and stateless protocol translation RFC 6145 at the edge. 464XLAT
   is a simple and scalable technique to quickly deploy limited IPv4
   access service to mobile and wireline IPv6-only edge networks without
   encapsulation.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 9, 2012.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Requirements Language  . . . . . . . . . . . . . . . . . . . .  3
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Motivation and Uniqueness of 464XLAT . . . . . . . . . . . . .  4
   5.  Network Architecture . . . . . . . . . . . . . . . . . . . . .  5
     5.1.  Wireline Network Architecture  . . . . . . . . . . . . . .  6
     5.2.  Wireless 3GPP Network Architecture . . . . . . . . . . . .  7
   6.  Applicability  . . . . . . . . . . . . . . . . . . . . . . . .  7
     6.1.  Wireline Network Applicability . . . . . . . . . . . . . .  7
     6.2.  Wireless 3GPP Network Applicability  . . . . . . . . . . .  8
   7.  Implementation Considerations  . . . . . . . . . . . . . . . .  9
     7.1.  IPv6 Address Format  . . . . . . . . . . . . . . . . . . .  9
     7.2.  IPv4/IPv6 Address Translation Chart  . . . . . . . . . . .  9
     7.3.  Traffic Treatment Scenarios  . . . . . . . . . . . . . . . 10
     7.4.  DNS Proxy Implementation . . . . . . . . . . . . . . . . . 11
     7.5.  IPv6 Prefix Handling . . . . . . . . . . . . . . . . . . . 11
     7.6.  Relationship between CLAT and NAT44  . . . . . . . . . . . 11
     7.7.  CLAT in a Gateway  . . . . . . . . . . . . . . . . . . . . 11
     7.8.  CLAT to CLAT communications  . . . . . . . . . . . . . . . 12
   8.  Deployment Considerations  . . . . . . . . . . . . . . . . . . 12
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 13
     12.2. Informative References . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14















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1.  Introduction

   The IANA unallocated IPv4 address pool was exhausted on February 3,
   2011.  Each RIR's unallocated IPv4 address pool will exhaust in the
   near future.  It will be difficult for many networks to assign IPv4
   addresses to end users, despite substantial IP connectivity growth
   required for mobile devices, smart-grid, and cloud nodes.

   This document describes an IPv4 over IPv6 solution as one of the
   techniques for IPv4 service extension and encouragement of IPv6
   deployment. 464XLAT is not a one for one replacement of full IPv4
   functionality.  The 464XLAT IPv4 service is limited to application
   that function in a client server model and is not fit for IPv4 peer-
   to-peer communication or inbound IPv4 connections.

   The 464XLAT architecture described in this document uses IPv4/IPv6
   translation standardized in [RFC6145] and [RFC6146].  It does not
   require DNS64 [RFC6147] since a host may simply send IPv4 packets,
   including packets to an IPv4 DNS server, which will be translated on
   the CLAT to IPv6 and back to IPv4 on the PLAT. 464XLAT networks may
   use DNS64 to enable single stateful translation [RFC6146] instead of
   464XLAT double translation where possible.  It is also possible to
   provide single IPv4/IPv6 translation service, which will be needed in
   the future case of IPv6-only servers and peers to be reached from
   legacy IPv4-only hosts.  The 464XLAT architecture encourages IPv6
   transition by making IPv4 services reachable across IPv6-only
   networks and providing IPv6 and IPv4 connectivity to single-stack
   IPv4 or IPv6 servers and peers.

   Running a single-stack IPv6-only network has several operational
   benefits in terms of increasing scalability and decreasing
   operational complexity.  Unfortunately, there are important cases
   where IPv6-only networks fail to meet subscriber expectations, as
   described in [RFC6586].  The 464XLAT overcomes the issues described
   in [RFC6586] to provide subscribers the full IPv6 and limited IPv4
   functionality while providing the network operator the benefits of a
   simple yet highly scalable single-stack IPv6 network.


2.  Requirements Language

   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].







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3.  Terminology

   PLAT:   PLAT is Provider side translator(XLAT) that complies with
           [RFC6146].  It translates N:1 global IPv6 packets to global
           IPv4 packets, and vice versa.

   CLAT:   CLAT is Customer side translator(XLAT) that complies with
           [RFC6145].  It algorithmically translates 1:1 private IPv4
           packets to global IPv6 packets, and vice versa.  The CLAT
           function is applicable to a router or an end-node such as a
           mobile phone.  CLAT SHOULD perform router function to
           facilitate packets forwarding through the stateless
           translation even if it is an end-node.  In addition to
           stateless translation, the CLAT as a common home router or 3G
           router is expected to perform gateway functions such as DHCP
           server and DNS proxy for local clients.

   UE:     The 3GPP term for user equipment.  The most common type of UE
           is a mobile phone.

   PDP:    A Packet Data Protocol (PDP) Context is the equivalent of a
           virtual connection between the host and a gateway.


4.  Motivation and Uniqueness of 464XLAT

   1.  Minimal IPv4 resource requirements, maximum IPv4 efficiency

       464XLAT has low barriers to entry since only a small amount of
       IPv4 addresses are needed to support the stateful translation
       [RFC6146] function in the PLAT.  With port-overloading, one IPv4
       address can support millions of simultaneous translations.

       Given that network operators are deploying IPv6-only access
       networks because IPv4 resources are scarce, solutions that
       require dual-stack (no IPv4 multiplexing) or stateless address
       sharing (bounded static address multiplexing) are simply not
       IPv4-efficient enough to solve the two-pronged challenge of
       increasing IPv4 address scarcity and continued exponential
       network edge growth for network operators.

   2.  No new protocols required, quick deployment

       464XLAT can be deployed today, it uses existing RFCs ([RFC6145]
       and [RFC6146]), and there exists implementations for both
       wireline networks (CLAT in the home router) and wireless 3GPP
       networks (CLAT in the UE).  The ability to quickly deploy 464XLAT
       is a critical feature given the urgency of IPv4 exhaustion and



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       brisk pace of internet growth.

   3.  Cost-effective transition to IPv6

       When combined with DNS64 [RFC6147], the 464XLAT architecture only
       requires double translation in the case of IPv4-referrals or
       IPv4-only socket calls.  Consequently, the network traffic in the
       ISP backbone network is predominately IPv6 end-to-end or single
       translation.  This is especially cost-effective in wireless 3GPP
       GSM and UMTS networks that would otherwise require two separate
       PDP connections to support IPv4 and IPv6.

       While translation on the CLAT is not always used, the CLAT
       function is crucial for enabling the IPv4-only applications.  All
       IPv6-native flows pass end-to-end without any translation.  This
       is a beneficial solution for end-users, content providers, and
       network operators that scale best with end-to-end IPv6
       communication.

   In summary, the 464XLAT architecture works today for service
   providers that require large-scale strategic IPv6 deployments to
   overcome the challenges of IPv4 address scarcity.  Since 464XLAT is
   stateful, there is no tight coupling or IPv4 address coordination
   between the PLAT and the CLAT.  Unlike other transition architectures
   associated with tunneling or
   [I-D.mdt-softwire-mapping-address-and-port], 464XLAT assumes that
   IPv4 is scarce and IPv6 must work with today's existing systems as
   much as possible.  In the case of tunneling, the tunneling solutions
   like Dual-Stack Lite [RFC6333] are known to break existing network
   based deep packet inspection solutions like 3GPP standardized Policy
   and Charging Control (PCC). 464XLAT does not require much IPv4
   address space to enable the stateful translation [RFC6146] function
   in the PLAT while providing global IPv4 and IPv6 reachability to
   IPv6-only wireline and wireless subscribers.


5.  Network Architecture

   464XLAT architecture is shown in the following figure.












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5.1.  Wireline Network Architecture


                                  ----
                                 | v6 |
                                  ----
                                    |
    ----      |                 .---+---.                    .------.
   | v6 |-----+                /         \                  /        \
    ----      |    ------     /   IPv6    \     ------     /   IPv4   \
              +---| CLAT |---+  Internet   +---| PLAT |---+  Internet  |
    -------   |    ------     \           /     ------     \           /
   |v4p/v6 |--+                `---------'                  `----+----'
    -------   |                                                  |
    -----     |                                                -----
   | v4p |----+                                               | v4g |
    -----     |                                                -----

          <- v4p -> XLAT <--------- v6 --------> XLAT <- v4g ->


     v6  : Global IPv6
     v4p : Private IPv4
     v4g : Global IPv4

                    Figure 1: Wireline Network Topology

























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5.2.  Wireless 3GPP Network Architecture


                                   ----
                                  | v6 |
                                   ----
                                     |
                                 .---+---.
                                /         \
                               /   IPv6    \
                              |   Internet  |
                               \           /
    UE / Mobile Phone           `---------'
   +----------------------+          |
   |  ----     |          |      .---+---.                   .------.
   | | v6 |----+          |     /         \                 /        \
   |  ----     |    ------|    / IPv6 PDP  \     ------    /   IPv4   \
   |           +---| CLAT |---+ Mobile Core +---| PLAT |--+  Internet  |
   |           |    ------|    \    GGSN   /     ------    \          /
   |           |          |     \         '                 `----+---'
   |  ------   |          |      `-------'                       |
   | | v4p |---+          |                                    -----
   |  ------   |          |                                   | v4g |
   +----------------------+                                    -----

           <- v4p -> XLAT <--------- v6 --------> XLAT <- v4g ->


     v6  : Global IPv6
     v4p : Private IPv4
     v4g : Global IPv4

                 Figure 2: Wireless 3GPP Network Topology


6.  Applicability

6.1.  Wireline Network Applicability

   When an ISP has IPv6 access network infrastructure and 464XLAT, the
   ISP can provide IPv4 service to end users across an IPv6 access
   network.  The result is that edge network growth is no longer tightly
   coupled to the availability of scarce IPv4 addresses.

   If the IXP or another provider operates the PLAT, the ISP is only
   required to deploy an IPv6 access network.  All ISPs do not need IPv4
   access networks.  They can migrate their access network to a simple
   and highly scalable IPv6-only environment.  Incidentally, Japan



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   Internet Exchange(JPIX) is providing 464XLAT trial service since July
   2010.  In addition to this, the effectiveness of 464XLAT was
   confirmed in the WIDE camp Spring 2012.  The result is described in
   [I-D.hazeyama-widecamp-ipv6-only-experience].

6.2.  Wireless 3GPP Network Applicability

   The vast majority of mobile wireless networks are compliant to Pre-
   Release 9 3GPP standards.  In Pre-Release 9 3GPP networks, GSM and
   UMTS networks must signal and support both IPv4 and IPv6 PDP
   attachments to access IPv4 and IPv6 network destinations.  Since
   there are 2 PDPs required to support 2 address families, this is
   double the number of PDPs required to support the status quo of 1
   address family, which is IPv4.  Doubling the PDP count to support
   IPv4 and IPv6 is generally not operationally viable since a large
   portion of the network cost is derived from the number of PDP
   attachments, both in terms of licenses from the network hardware
   vendors and in terms of actual hardware resources required to support
   and maintain the PDP signaling and mobility events.  Doubling the
   number of PDP attachments has been one of the major barriers to
   introducing IPv6 in mobile networks.  Dual-stack IPv4 and IPv6 simply
   costs more from the network provider perspective and does not result
   in any new revenues.  In 3GPP Release 9 and forward, 2 PDPs are no
   longer required but the scarcity of IPv4 addresses remain.

   Now that both global and private IPv4 addresses are scarce to the
   extent that it is a substantial business risk and limiting growth in
   many areas, the mobile network providers must support IPv6 to solve
   the IP address scarcity issue.  It is not feasible to simply turn on
   additional IPv6 PDP network attachments since that does not solve the
   near-term IPv4 scarcity issues and it increases cost in most cases.
   The most logical path forward is to replace IPv4 with IPv6 and
   replace the common NAT44 with stateful translation [RFC6146] and
   DNS64 [RFC6147].  Extensive live network testing with hundreds of
   friendly-users has shown that IPv6-only network attachments for
   mobile devices supports over 85% of the common applications on the
   Android mobile operating systems.  The remaining 15% of applications
   do not work because the application requires an IPv4 socket or the
   application does an IPv4-referral.  These findings are consistent
   with the mobile IPv6-only user experience in [RFC6586].

   464XLAT in combination with stateful translation [RFC6146] and DNS64
   [RFC6147] allows 85% of the Android applications to continue to work
   with single translation or native IPv6 access.  For the remaining 15%
   of applications that require IPv4 connectivity, the CLAT function on
   the UE provides a private IPv4 address and IPv4 default-route on the
   host for the applications to reference and bind to.  Connections
   sourced from the IPv4 interface are immediately routed to the CLAT



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   function and passed to the IPv6-only mobile network, destine to the
   PLAT.  In summary, the UE has the CLAT function that does a stateless
   translation [RFC6145], but only when required.  The mobile network
   has a PLAT that does stateful translation [RFC6146].


7.  Implementation Considerations

7.1.  IPv6 Address Format

   IPv6 address format in 464XLAT is defined in Section 2.2 of
   [RFC6052].

7.2.  IPv4/IPv6 Address Translation Chart

   IPv4/IPv6 address translation chart is shown in the following figure.


                                           Source IPv4 address
                                          +----------------------------+
                                          | Global IPv4 address        |
                                          | assigned to IPv4 pool@PLAT |
                               +--------+ +----------------------------+
                               |  IPv4  |  Destination IPv4 address
                               | server | +----------------------------+
                               +--------+ | Global IPv4 address        |
                                   ^      | assigned to IPv4 server    |
                                   |      +----------------------------+
                               +--------+
                               |  PLAT  | Stateful XLATE(IPv4:IPv6=1:n)
                               +--------+
                                   ^
                                   |
        Source IPv6 address   (IPv6 cloud)
        +--------------------------------------------------------------+
        | IPv4-Embedded IPv6 address                                   |
        | defined in Section 2.2 of RFC6052                            |
        +--------------------------------------------------------------+
         Destination IPv6 address
        +--------------------------------------------------------------+
        | IPv4-Embedded IPv6 address                                   |
        | defined in Section 2.2 of RFC6052                            |
        +--------------------------------------------------------------+
                              (IPv6 cloud)
                                   ^
                                   |
                                   |
                                   |



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                               +--------+
                               |        | Case 1: CLAT will have a
                               |        | dedicated IPv6 prefix
                               |        |   -> Stateless XLATE
                               |        |      (IPv4:IPv6=1:1)
                               |  CLAT  |
                               |        | Case 2: CLAT will not have a
                               |        | dedicated IPv6 prefix
                               |        |   -> NAT44 -> Stateless XLATE
                               |        |               (IPv4:IPv6=1:1)
                               +--------+
                                   ^       Source IPv4 address
                                   |      +----------------------------+
                               +--------+ | Private IPv4 address       |
                               |  IPv4  | | assigned to IPv4 client    |
                               | client | +----------------------------+
                               +--------+  Destination IPv4 address
                                          +----------------------------+
                                          | Global IPv4 address        |
                                          | assigned to IPv4 server    |
                                          +----------------------------+

                    IPv4/IPv6 Address Translation Chart

7.3.  Traffic Treatment Scenarios


        +--------+-------------+-----------------------+-------------+
        | Server | Application |   Traffic Treatment   | Location of |
        |        | and Host    |                       | Translation |
        +--------+-------------+-----------------------+-------------+
        |  IPv6  |    IPv6     |    End-to-end IPv6    |    None     |
        +--------+-------------+-----------------------+-------------+
        |  IPv4  |    IPv6     | Stateful Translation  |    PLAT     |
        +--------+-------------+-----------------------+-------------+
        |  IPv4  |    IPv4     |        464XLAT        |  PLAT/CLAT  |
        +--------+-------------+-----------------------+-------------+
        |  IPv6  |    IPv4     | Stateless Translation |    CLAT     |
        +--------+-------------+-----------------------+-------------+

                        Traffic Treatment Scenarios

   The above chart shows most common traffic types and traffic
   treatment.







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7.4.  DNS Proxy Implementation

   The CLAT SHOULD implement a DNS proxy as defined in [RFC5625].  The
   case of an IPv4-only node behind CLAT querying an IPv4 DNS server is
   undesirable since it requires both stateful and stateless translation
   for each DNS lookup.  The CLAT SHOULD set itself as the DNS server
   via DHCP or other means and proxy DNS queries for IPv4 and IPv6
   clients.  Using the CLAT enabled home router or UE as a DNS proxy is
   a normal consume gateway function and simplifies the traffic flow so
   that only IPv6 native queries are made across the access network.
   The CLAT SHOULD allow for a client to query any DNS server of its
   choice and bypass the proxy.

7.5.  IPv6 Prefix Handling

   From the delegated DHCPv6 [RFC3633] prefix, a /64 is dedicated to
   source and receive IPv6 packets associated with the stateless
   translation [RFC6145].

   In another cases where the access network does not allow for a
   dedicated translation prefix, the CLAT will do NAT44 such that all
   private IPv4 sourced LAN packets appears from one private IPv4
   address which is statelessly translated to one IPv6 address.

   The CLAT MAY discover the Pref64::/n of the PLAT via some method such
   as DHCPv6 option, TR-069, DNS APL RR [RFC3123] or
   [I-D.ietf-behave-nat64-discovery-heuristic].

7.6.  Relationship between CLAT and NAT44

   If the CLAT does not have dedicated IPv6 prefix for translation, the
   CLAT does NAT44 as an internal function which never appears on the
   wire.

   Incoming source IPv4 packets from the LAN of [RFC1918] addresses are
   NAT44 to the CLAT host address on the LAN of one [RFC1918] address.
   Then, the CLAT will do a stateless translation [RFC6145] so that the
   IPv4 packets from one [RFC1918] address are translated to the CLAT
   LAN IPv6 address as described in [RFC6052].

7.7.  CLAT in a Gateway

   The CLAT is a stateless translation feature which can be implemented
   in a common home router or mobile phone that has a mobile router
   feature.  The router with CLAT function SHOULD provide common router
   services such as DHCP of [RFC1918] addresses, DHCPv6, and DNS
   service.  The router SHOULD set itself as the DNS server advertised
   via DHCP or other means to the clients so that it may implement the



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   DNS proxy function to avoid double translation of DNS request.

7.8.  CLAT to CLAT communications

   While CLAT to CLAT IPv4 communication may work when the client IPv4
   subnets do not overlap, this traffic flow is out of scope. 464XLAT is
   a hub and spoke architecture focused on enabling IPv4-only services
   over IPv6-only access networks.


8.  Deployment Considerations

   Even if the Internet access provider for consumers is different from
   the PLAT provider (another Internet access provider or Internet
   exchange provider, etc.), it can implement traffic engineering
   independently from the PLAT provider.  Detailed reasons are below:

   1.  The Internet access provider for consumers can figure out IPv4
       source address and IPv4 destination address from translated IPv6
       packet header, so it can implement traffic engineering based on
       IPv4 source address and IPv4 destination address (e.g. traffic
       monitoring for each IPv4 destination address, packet filtering
       for each IPv4 destination address, etc.).  The tunneling methods
       do not have such a advantage, without any deep packet inspection
       for processing the inner IPv4 packet of the tunnel packet.

   2.  If the Internet access provider for consumers can assign IPv6
       prefix greater than /64 for each subscriber, this 464XLAT
       architecture can separate IPv6 prefix for native IPv6 packets and
       XLAT prefix for IPv4/IPv6 translation packets.  Accordingly, it
       can identify the type of packets ("native IPv6 packets" and
       "IPv4/IPv6 translation packets"), and implement traffic
       engineering based on IPv6 prefix.

   This 464XLAT architecture has two capabilities.  One is a IPv4 ->
   IPv6 -> IPv4 translation for sharing global IPv4 addresses, another
   is a IPv4 -> IPv6 translation for reaching IPv6-only servers from
   IPv4-only clients that can not support IPv6.  IPv4-only clients must
   be support through the long period of global transition to IPv6.


9.  Security Considerations

   To implement a PLAT, see security considerations presented in Section
   5 of [RFC6146].

   To implement a CLAT, see security considerations presented in Section
   7 of [RFC6145].  The CLAT MAY comply with [RFC6092].



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10.  IANA Considerations

   This document has no actions for IANA.


11.  Acknowledgements

   The authors would like to thank JPIX NOC members, JPIX 464XLAT trial
   service members, Seiichi Kawamura, Dan Drown, Brian Carpenter, Rajiv
   Asati, Washam Fan, Behcet Sarikaya, Jan Zorz, Remi Despres, Tatsuya
   Oishi, Lorenzo Colitti, Erik Kline, Ole Troan, Maoke Chen, and Gang
   Chen for their helpful comments.  We also would like to thank Fred
   Baker and Joel Jaeggli for their support.


12.  References

12.1.  Normative References

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

   [RFC6052]  Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
              Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
              October 2010.

   [RFC6144]  Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
              IPv4/IPv6 Translation", RFC 6144, April 2011.

   [RFC6145]  Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
              Algorithm", RFC 6145, April 2011.

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, April 2011.

12.2.  Informative References

   [I-D.hazeyama-widecamp-ipv6-only-experience]
              Hazeyama, H., Hiromi, R., Ishihara, T., and O. Nakamura,
              "Experiences from IPv6-Only Networks with Transition
              Technologies in the WIDE Camp Spring 2012",
              draft-hazeyama-widecamp-ipv6-only-experience-01 (work in
              progress), March 2012.

   [I-D.ietf-behave-nat64-discovery-heuristic]
              Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
              IPv6 Prefix Used for IPv6 Address Synthesis",



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              draft-ietf-behave-nat64-discovery-heuristic-07 (work in
              progress), March 2012.

   [I-D.mdt-softwire-mapping-address-and-port]
              Bao, C., Troan, O., Matsushima, S., Murakami, T., and X.
              Li, "Mapping of Address and Port (MAP)",
              draft-mdt-softwire-mapping-address-and-port-03 (work in
              progress), January 2012.

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, February 1996.

   [RFC3123]  Koch, P., "A DNS RR Type for Lists of Address Prefixes
              (APL RR)", RFC 3123, June 2001.

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              December 2003.

   [RFC5625]  Bellis, R., "DNS Proxy Implementation Guidelines",
              BCP 152, RFC 5625, August 2009.

   [RFC6092]  Woodyatt, J., "Recommended Simple Security Capabilities in
              Customer Premises Equipment (CPE) for Providing
              Residential IPv6 Internet Service", RFC 6092,
              January 2011.

   [RFC6147]  Bagnulo, M., Sullivan, A., Matthews, P., and I. van
              Beijnum, "DNS64: DNS Extensions for Network Address
              Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
              April 2011.

   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              Stack Lite Broadband Deployments Following IPv4
              Exhaustion", RFC 6333, August 2011.

   [RFC6459]  Korhonen, J., Soininen, J., Patil, B., Savolainen, T.,
              Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
              Partnership Project (3GPP) Evolved Packet System (EPS)",
              RFC 6459, January 2012.

   [RFC6586]  Arkko, J. and A. Keranen, "Experiences from an IPv6-Only
              Network", RFC 6586, April 2012.







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Authors' Addresses

   Masataka Mawatari
   Japan Internet Exchange Co.,Ltd.
   KDDI Otemachi Building 19F, 1-8-1 Otemachi,
   Chiyoda-ku, Tokyo  100-0004
   JAPAN

   Phone: +81 3 3243 9579
   Email: mawatari@jpix.ad.jp


   Masanobu Kawashima
   NEC AccessTechnica, Ltd.
   800, Shimomata
   Kakegawa-shi, Shizuoka  436-8501
   JAPAN

   Phone: +81 537 23 9655
   Email: kawashimam@vx.jp.nec.com


   Cameron Byrne
   T-Mobile USA
   Bellevue, Washington  98006
   USA

   Email: cameron.byrne@t-mobile.com























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