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Internet Engineering Task Force                        Y. Shirasaki, Ed.
Internet-Draft                                               S. Miyakawa
Intended status: Informational                        NTT Communications
Expires: March 11, 2010                                      A. Nakagawa
                                                        KDDI CORPORATION
                                                            J. Yamaguchi
                                                                     IIJ
                                                               H. Ashida
                                                                  iTSCOM
                                                       September 7, 2009


                     NAT444 with ISP Shared Address
               draft-shirasaki-nat444-isp-shared-addr-02

Status of this Memo

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

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   This Internet-Draft will expire on March 11, 2010.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   Please review these documents carefully, as they describe your rights
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Abstract

   This document describes one of the network models that are designed
   for smooth transition to IPv6.  It is called NAT444 model.  NAT444
   model is composed of IPv6, and IPv4 with Large Scale NAT (LSN).

   NAT444 is the only scheme not to require replacing Customer Premises
   Equipment (CPE) even if IPv4 address exhausted.  But it must be noted
   that NAT444 has serious restrictions i.e. it limits the number of
   sessions per CPE so that rich applications such as AJAX and RSS feed
   cannot work well.

   Therefore, IPv6 which is free from such a difficulty has to be
   introduced into the network at the same time.  In other words, NAT444
   is just a tool to make IPv6 transition easy to be swallowed.  It is
   designed for the days IPv4 and IPv6 co-existence.



































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Definition of NAT444 Model . . . . . . . . . . . . . . . . . .  4
   3.  Behavior of NAT444 Model . . . . . . . . . . . . . . . . . . .  5
   4.  Pros and Cons of NAT444 Model  . . . . . . . . . . . . . . . .  7
     4.1.  Pros of NAT444 Model . . . . . . . . . . . . . . . . . . .  7
     4.2.  Cons of NAT444 Model . . . . . . . . . . . . . . . . . . .  7
   5.  Address Block of ISP's Network . . . . . . . . . . . . . . . .  8
     5.1.  Global Address . . . . . . . . . . . . . . . . . . . . . .  8
     5.2.  Private Address  . . . . . . . . . . . . . . . . . . . . .  8
       5.2.1.  Policy Based Routing Issue . . . . . . . . . . . . . .  8
       5.2.2.  Address Block Duplication Issue  . . . . . . . . . . .  8
     5.3.  Class-E Address (240/4)  . . . . . . . . . . . . . . . . .  8
     5.4.  ISP Shared Address . . . . . . . . . . . . . . . . . . . .  9
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     9.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Appendix A.  Example IPv6 Transition Scenario  . . . . . . . . . . 10
   Appendix B.  Example Architectures . . . . . . . . . . . . . . . . 12
     B.1.  Direct Routing inside LSN  . . . . . . . . . . . . . . . . 12
     B.2.  LSN Bypassing  . . . . . . . . . . . . . . . . . . . . . . 13
     B.3.  Global Address Customers inside LSN  . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
























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1.  Introduction

   The only permanent solution of the IPv4 address exhaustion is to
   deploy IPv6.  Now, just before the exhaustion, it's time to make a
   transition to IPv6.

   After the exhaustion, unless ISP takes any action, end users will not
   be able to get IPv4 address.

   The servers that have only IPv4 address will continue to exist on the
   Internet after the IPv4 address exhaustion.  In this situation, IPv6
   only hosts cannot reach IPv4 only hosts.

   This document explains NAT444 model that bridges the gap between the
   coming IPv6 Internet and the present IPv4 Internet.


2.  Definition of NAT444 Model

   NAT444 Model is a network model that uses two Network Address and
   Port Translators (NAPTs) with three types of IPv4 address blocks.

   The first NAPT is in CPE, and the second NAPT is in Large Scale NAT
   (LSN) [I-D.nishitani-cgn].  LSN is supposed to be installed in the
   ISP's network.

   The first IPv4 address block is Private Address [RFC1918] inside CPE.
   The second one is an IPv4 Address block between CPEs and LSN.  It
   could be Global Address, Private Address (10/8), Class-E (240/4), or
   (newly defined) ISP Shared Address.  The third one is IPv4 Global
   Addresses that is outside LSN.  The ISPs using NAT444 provide IPv6
   connectivity by dual stack model.



















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       (The IPv4 Internet)    (The IPv6 Internet)
                |                       |
                +---------+             |
   IPv4 Global Address    |             |
                 +--------+--------+    |
                 |       LSN       |    |
                 +--------+--------+    |
                     IPv4 |             | IPv6
                          +-------------+
               Dual Stack |
          +---------------+----------------+
          |  IPv4 NAT/IPv6 Dual Stack CPE  |
          +---------------+----------------+
   IPv4 Private Address / |
   IPv6 Dual Stack        |
              +-----------+-------------+
              |IPv4/IPv6 Dual Stack host|
              +-------------------------+


3.  Behavior of NAT444 Model

   The IPv6 packets from the host reach the IPv6 Internet without using
   NAT functionality.

   The following figure shows the behavior of the IPv4 packet from the
   host to the IPv4 server via two NATs.  The first NAT in CPE
   overwrites the Source IP Address and Source Port from 10.0.0.2:tt to
   w.w.w.w:uu.  Then the second NAT in LSN overwrites them from
   w.w.w.w:uu to y.y.y.y:vv.  Destination IP Address and Port are not
   overwritten.




















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                +-------------+
   (Port=80)    | IPv4 Server |  ^
      x.x.x.x-> +------+------+  :
                       |         :
   IPv4 Global Address |         :
                       |         :
              (The IPv4 Internet):(Dst=x.x.x.x:80/Src=y.y.y.y:vv)
                       |         :
   IPv4 Global Address |         :
                       |         :
       y.y.y.y->  +----+----+    :
        (Port=vv) |   LSN   |    ^
       z.z.z.z->  +----+----+    :
                       |         :
          IPv4 Address |         :(Dst=x.x.x.x:80/Src=w.w.w.w:uu)
                       |         :
     w.w.w.w-> +-------+-------+ :
     (Port=uu) | IPv4 NAT CPE  | ^
    10.0.0.1-> +-------+-------+ :
                       |         :
   IPv4 Private Address|         :
                       |         :
      10.0.0.2->  +----+----+    :(Dst=x.x.x.x:80/Src=10.0.0.2:tt)
        (Port=tt) |IPv4 Host|
                  +---------+

   The following figure explains the behavior of returning IPv4 packet
   via two NATs.  The first NAT in LSN overwrites the Destination IP
   Address and Port Number from y.y.y.y:vv to w.w.w.w:uu.  Then the
   second NAT in CPE overwrites them from w.w.w.w:u to 10.0.0.2:tt.





















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                 +-------------+
       (Port=80) | IPv4 Server |  :
       x.x.x.x-> +------+------+  :
                        |         :
    IPv4 Global Address |         :
                        |         :
               (The IPv4 Internet):(Dst=y.y.y.y:vv/Src=x.x.x.x:80)
                        |         :
   IPv4 Global Address  |         :
                        |         :
         y.y.y.y-> +----+----+    :
         (Port=vv) |   LSN   |    v
         z.z.z.z-> +----+----+    :
                        |         :
          IPv4 Address  |         :(Dst=w.w.w.w:uu/Src=x.x.x.x:80)
                        |         :
      w.w.w.w-> +-------+-------+ :
      (Port=uu) | IPv4 NAT CPE  | v
     10.0.0.1-> +-------+-------+ :
                        |         :
   IPv4 Private Address |         :(Dst=10.0.0.2:tt/Src=x.x.x.x:80)
                        |         :
        10.0.0.2-> +----+----+    :
         (Port=tt) |IPv4 Host|    v
                   +---------+


4.  Pros and Cons of NAT444 Model

4.1.  Pros of NAT444 Model

   This network model has following advantages.

   - This is the only network model that doesn't require replacing CPEs
   those are owned by customers.
   - This network model is composed of the present technology.
   - This network model doesn't require address family translation.
   - This network model doesn't require DNS rewriting.
   - This network model doesn't require additional fragment for the
   packets because it doesn't use tunneling technology.

4.2.  Cons of NAT444 Model

   This network model has some technical restrictions.

   - Some application such as SIP requires special treatment, because IP
   address is written in the payload of the packet.  Special treatment
   means application itself aware double NAPT or both of two NAPTs



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   support inspecting and rewriting the packets.
   - Because both IPv4 route and IPv6 route exist, it doubles the number
   of IGP route inside the LSN.
   - UPnP doesn't work with double NAPTs.


5.  Address Block of ISP's Network

   The address block mentioned in this section is the one between CPE
   and LSN.  The best address block is "ISP Shared Address" which is
   defined in [I-D.shirasaki-isp-shared-addr] and briefly described in
   this section.

5.1.  Global Address

   ISP cannot assign IPv4 Global Address any more after the exhaustion.

5.2.  Private Address

   It has two major problems.

5.2.1.  Policy Based Routing Issue

   If both source and destination address of the packet are inside LSN,
   it has to go through LSN.  The reason is that some servers reject
   receiving packets when the source address of receiving packet is
   Private Address.  Therefore packets have to go through the LSN for
   rewriting the source address from Private Address to Global Address.
   Additionally, if Private Address and Global Address co-exist inside
   LSN, the ISP has to use Policy Based Routing (PBR).

5.2.2.  Address Block Duplication Issue

   The Private Address in ISP's network could conflict with its
   customer's network address.  Many CPEs between customer's network and
   ISP's network cannot route the packet under this situation.  To avoid
   this, ISP has to negotiate with its all customers not to use the
   reserved Private Address block.

5.3.  Class-E Address (240/4)

   It is known that some equipment such as routers and servers reject
   packets from or to this address block.  So, to use this address block
   in ISP's network, ISP has to request its customers to replace their
   equipment.  In addition to that, ISP might have to replace their
   equipment when it doesn't handle Class-E address packets properly.





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5.4.  ISP Shared Address

   ISP Shared Address is the newly defined IPv4 address block that is to
   be allocated from IANA free pool.  It doesn't have any problem.
   Spending some blocks from the exhausting IANA free pool could be
   regarded as a problem, but from long view, this problem is much
   smaller than its great merit.  ISP Shared Address is defined in
   [I-D.shirasaki-isp-shared-addr]


6.  Acknowledgements

   Thanks for the input and review by Shirou Niinobe, Takeshi Tomochika,
   Tomohiro Fujisaki, Dai Nishino, JP address community members, AP
   address community members and JPNIC members.


7.  IANA Considerations

   IANA is to allocate a certain size of address block from IANA free
   pool.  The size of it is described in [I-D.shirasaki-isp-shared-addr]


8.  Security Considerations

   Each customer inside a LSN looks using the same Global Address. from
   outside an ISP.  In case of incidents, the ISP must have the function
   to trace back the record of each customer's access without using only
   IP address.

   If a Global Address of the LSN is listed on the blacklist, other
   customers who share the same address could be affected.


9.  References

9.1.  Normative References

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

   [RFC4925]  Li, X., Dawkins, S., Ward, D., and A. Durand, "Softwire
              Problem Statement", RFC 4925, July 2007.

   [I-D.shirasaki-isp-shared-addr]
              Shirasaki, Y., Miyakawa, S., Nakagawa, A., Yamaguchi, J.,
              and H. Ashida, "ISP Shared Address",



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              draft-shirasaki-isp-shared-addr-02 (work in progress),
              March 2009.

   [I-D.nishitani-cgn]
              Nishitani, T., Miyakawa, S., Nakagawa, A., and H. Ashida,
              "Common Functions of Large Scale NAT (LSN)",
              draft-nishitani-cgn-02 (work in progress), June 2009.

9.2.  Informative References

   [PROP58]   Niinobe, S., Tomochika, T., Yamaguchi, J., Nishino, D.,
              Ashida, H., Nakagawa, A., and T. Hosaka, "Proposal to
              create IPv4 shared use address space among LIRs", 2008,
              <http://www.apnic.net/policy/proposals/
              prop-058-v001.html>.


Appendix A.  Example IPv6 Transition Scenario

   The steps of IPv6 transition are as follows.

   Step 1: Enabling softwire client in host

   ISP provides IPv6 connectivity to customers with softwire [RFC4925].
   ISP installs LSN and softwire concentrator in its network.  A
   softwire client in host connects to the IPv6 internet via ISP's
   concentrator.  ISP can use existing IPv4 equipments.  Customers can
   just use existing CPE.

     (The IPv4 Internet)  (The IPv6 Internet)
              |                    | IPv6
              |        +-----------+-----------+
              |        | Softwire Concentrator |
              |        +-----------+-----------+
              +---------+----------+  ^
    IPv4 Global Address |             :
             +----------+----------+  :
             |         LSN         |  :
             +----------+----------+  :
       Any IPv4 Address |             : IPv6 over IPv4 Softwire
          (ISP Network) |             : (e.g. IPv6 over IPv4 L2TP)
             +----------+----------+  :
             |  IPv4 NAT only CPE  |  :
             +----------+----------+  :
   IPv4 Private Address |             v
        +---------------+-----------------+
        |IPv4/IPv6 Softwire Client in host|
        +---------------------------------+



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   Step 2: Enabling softwire client in CPE

   A customer enables softwire client in CPE.  A softwire client in CPE
   connects to the IPv6 internet via ISP's concentrator.  A Customer's
   network is now dual stack.

       (The IPv4 Internet)    (The IPv6 Internet)
                |                      | IPv6
                |           +----------+------------+
                |           | Softwire Concentrator |
                |           +----------+------------+
                +---------+------------+  ^
   IPv4 Global Address    |               :
               +----------+------------+  :
               |         LSN           |  : IPv6 over IPv4 Softwire
               +----------+------------+  : (e.g. IPv6 over IPv4 L2TP)
         Any IPv4 Address |               :
           (ISP Network)  |               v
          +---------------+--------------------+
          |IPv4 NAT/IPv6 Softwire client in CPE|
          +---------------+--------------------+
   IPv4 Private Address / |
   IPv6 Dual Stack        |
              +-----------+-------------+
              |IPv4/IPv6 Dual Stack host|
              +-------------------------+

   Step 3: Moving on to dual stack

   ISP provides dual stack access to CPE.  A CPE uplink is now dual
   stack.




















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       (The IPv4 Internet)    (The IPv6 Internet)
                |                       |
                +---------+             |
   IPv4 Global Address    |             |
                 +--------+--------+    |
                 |       LSN       |    | IPv6
                 +--------+--------+    |
       Any IPv4 Address / |             |
        IPv6 Dual Stack   +-------------+
           (ISP Network)  |
          +---------------+----------------+
          |  IPv4 NAT/IPv6 Dual Stack CPE  |
          +---------------+----------------+
   IPv4 Private Address / |
   IPv6 Dual Stack        |
              +-----------+-------------+
              |IPv4/IPv6 Dual Stack host|
              +-------------------------+

   Step 4: Moving on to pure IPv6

   IPv6 transition completes.

   (The IPv6 Internet)
            |
       IPv6 |
   +--------+----------+
   |     IPv6 CPE      |
   +--------+----------+
       IPv6 |
   +--------+----------+
   |     IPv6 host     |
   +-------------------+


Appendix B.  Example Architectures

   This section explains example architectures how to design NAT444 with
   ISP Shared Address.

B.1.  Direct Routing inside LSN

   This architecture enables direct communication between customers
   inside same LSN.  It has the following advantages.

   - The packets don't go through LSN.  (No hairpining)
   - The customers inside LSN can use bidirectional applications (e.g.
   TV Conference, VPN).



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   - No need to use Policy Based Routing.

                 (The IPv4 Internet)
                          | Global Address
                     +----+----+
                     |   LSN   |
                     +----+----+
                          |
   ISP Shared +-----------+----------+ ISP Shared
      Address |      ..........      | Address
         +----+----+ :        : +----+----+
         | CPE NAT | :        : | CPE NAT |
         +----+----+ :        : +----+----+
      Private |      :        :      | Private
      Address |      v        v      | Address
         +----+----+            +----+----+
         |IPv4 Host|            |IPv4 Host|
         +---------+            +---------+

B.2.  LSN Bypassing

   This architecture is bypassing the NAT function of LSN.  It has the
   following advantage.

   - The customers inside an ISP can use bidirectional applications
   (e.g.  TV Conference, VPN).
   -Any communication in single ISP doesn't consume LSN external port.
   -ISP's servers outside LSN can access CPE. (e.g.  ICMP echo, SNMP,
   remote access)
   -ISP's servers outside LSN can distinguish which customer's
   connection it receives. (e.g.  DNS, Mail)




















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    (The IPv4 Internet)
              |
              |                 +--------+ Network Monitor
              |                 | Server | (ICMP echo, SNMP)
              |                 +----+---+ DNS, Mail, Web, etc
       Global |                      |  ^
      Address +----------------------+  :
              |      ....................
              |      .        :      |
         +----+----+ :        : +----+----+ bypass NAT:
         |   LSN   | : bypass : |   LSN   | Dst=ISP's Global Address
         +----+----+ :  NAT   : +----+----+  or ISP Shared Address
   ISP Shared |      :        :      |
      Address |      :        :      | ISP Shared Address
         +----+----+ :        : +----+----+
         | CPE NAT | :        : | CPE NAT |
         +----+----+ :        : +----+----+
      Private |      :        :      | Private
      Address |      v        v      | Address
         +----+----+            +----+----+
         |IPv4 Host|            |IPv4 Host|
         +---------+            +---------+

B.3.  Global Address Customers inside LSN

   This architecture enables co-existing Global Address and ISP Shared
   Address inside LSN.

   It enables direct communications from ISP Shared Address customer to
   Global Address customer inside same LSN.  It has the following
   advantage.

   - The ISP can put ISP Shared Address customer and Global Address
   customer in the same concentrator.
   - The packets don't go through LSN.  (No hairpining)
   - The customers inside LSN can use bidirectional applications (e.g.
   TV Conference, VPN).
   - No need to use Policy Based Routing.













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   (The IPv4 Internet)
            |
            | Global Address
       +----+----+
       |   LSN   | bypass NAT: Src/Dst=Global Address
       +----+----+
            | Global Address and ISP Shared Address co-existing
            +----------------------+
            |      .........       |
       +----+----+ :        : +----+----+
       | Firewall| :        : | CPE NAT |
       +----+----+ :        : +----+----+
     Global |      :        :      | Private
    Address |      v        :      | Address
      +-----+-----+           +----+----+
      |IPv4 Server|           |IPv4 Host|
      +-----------+           +---------+


Authors' Addresses

   Yasuhiro Shirasaki (editor)
   NTT Communications Corporation
   NTT Hibiya Bldg. 7F, 1-1-6 Uchisaiwai-cho, Chiyoda-ku
   Tokyo  100-8019
   Japan

   Phone: +81 3 6700 8530
   Email: yasuhiro@nttv6.jp


   Shin Miyakawa
   NTT Communications Corporation
   Granpark Tower 17F, 3-4-1 Shibaura, Minato-ku
   Tokyo  108-8118
   Japan

   Phone: +81 3 6733 8671
   Email: miyakawa@nttv6.jp












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   Akira Nakagawa
   KDDI CORPORATION
   GARDEN AIR TOWER, 3-10-10, Iidabashi, Chiyoda-ku
   Tokyo  102-8460
   Japan

   Email: ai-nakagawa@kddi.com


   Jiro Yamaguchi
   Internet Initiative Japan Inc.
   Jinbocho Mitsui Bldg., 1-105 Kanda Jinbo-cho, Chiyoda-ku
   Tokyo  101-0051
   Japan

   Phone: +81 3 5205 6500
   Email: jiro-y@iij.ad.jp


   Hiroyuki Ashida
   its communications Inc.
   3-5-7 Hisamoto Takatsu-ku Kawasaki-shi
   Kanagawa  213-0011
   Japan

   Email: ashida@itscom.ad.jp

























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