Internet Engineering Task Force Y. Shirasaki, Ed.
Internet-Draft S. Miyakawa
Expires: April 30, 2009 NTT Communications
A. Nakagawa
KDDI CORPORATION
J. Yamaguchi
IIJ
H. Ashida
iTSCOM
October 27, 2008
NAT444 with ISP Shared Address
draft-shirasaki-nat444-isp-shared-addr-00
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Copyright (C) The IETF Trust (2008).
Abstract
This document describes a network model with ISP Shared Address and
Carrier Grade NAT (CGN) called NAT444. NAT444 is the only scheme not
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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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definition of NAT444 Model . . . . . . . . . . . . . . . . . . 3
3. Pros and Cons of NAT444 Model . . . . . . . . . . . . . . . . 4
3.1. Pros of NAT444 Model . . . . . . . . . . . . . . . . . . . 4
3.2. Cons of NAT444 Model . . . . . . . . . . . . . . . . . . . 4
4. Address Block of ISP's Network . . . . . . . . . . . . . . . . 4
4.1. Global Address . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Private Address . . . . . . . . . . . . . . . . . . . . . 4
4.2.1. Hairpining Issue . . . . . . . . . . . . . . . . . . . 4
4.2.2. Address Block Duplication Issue . . . . . . . . . . . 5
4.3. Class-E Address (240/4) . . . . . . . . . . . . . . . . . 5
4.4. ISP Shared Address . . . . . . . . . . . . . . . . . . . . 5
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . . 6
Appendix A. Example IPv6 Transition Scenario . . . . . . . . . . 6
Appendix B. Example Architectures . . . . . . . . . . . . . . . . 9
B.1. Direct Routing inside CGN . . . . . . . . . . . . . . . . 9
B.2. CGN Bypassing . . . . . . . . . . . . . . . . . . . . . . 10
B.3. Global Address Customers inside CGN . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . . . 13
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1. Introduction
IPv4 address is said to be run out soon. Unless ISP takes any
action, it will not be able to provide the service to new customers.
This document explains a NAT444 model. This model is base on the
environment where customers have been using Private Address [RFC1918]
inside their CPE, and 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.
It triggers ISPs to take actions for keeping assigning IPv4 address
to their customers using non-Global IPv4 Address. NAT444 is one of
the solutions for this issue.
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 Carrier Grade NAT
(CGN) [I-D.nishitani-cgn]. CGN is supposed to be installed in the
ISP's network.
The first IPv4 address block is Private Address inside CPE. The
second one is a IPv4 Address block between CPEs and CGN. It could be
Global Address, Private Address (10/8), Class-E (240/4)
[I-D.wilson-class-e], or (newly defined) ISP Shared Address. The
third one is IPv4 Global Addresses that is outside CGN and directly
connected to the IPv4 Internet.
( The IPv4 Internet )
[ISP-A] [ISP-B]
| |
IPv4 Global Address | | IPv4 Global Address
+----+----+ +----+----+
| CGN | | CGN |
+----+----+ +----+----+
Any IPv4 Address | | Any IPv4 Address
+----+----+ +----+----+
| CPE NAT | | CPE NAT |
+----+----+ +----+----+
IPv4 Private Address | | IPv4 Private Address
+----+----+ +----+----+
|IPv4 Host| |IPv4 Host|
+---------+ +---------+
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3. Pros and Cons of NAT444 Model
3.1. 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 model doesn't require address family translation.
- This model doesn't require DNS rewriting.
3.2. Cons of NAT444 Model
This network model has some technical restrictions.
- Some application such as SIP and FTP 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 support inspecting and rewriting the packets.
- Because both IPv4 route and IPv6 route exist, it doubles the number
of IGP route inside the CGN.
- UPnP doesn't work with double NAPTs.
4. Address Block of ISP's Network
The address block mentioned in this section is the one between CPE
and CGN. The best address block is "ISP Shared Address" which is
defined in [I-D.shirasaki-isp-shared-addr] and briefly described in
this section.
4.1. Global Address
ISP cannot assign IPv4 Global Address any more after the exhaustion.
4.2. Private Address
It has two major problems.
4.2.1. Hairpining Issue
If both source and destination address of the packet are inside CGN,
it has to go through CGN. 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 CGN for
rewriting the source address from Private Address to Global Address.
Additionally, if Private Address and Global Address co-exist inside
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CGN, ISP has to use Policy Based Routing (PBR).
4.2.2. Address Block Duplication Issue
The Private Address in ISP's network could conflict with its
customer's network address. Most 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.
4.3. 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.
4.4. 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]
5. 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.
6. 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]
7. Security Considerations
Each customer inside a CGN 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.
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If a Global Address of the CGN is listed on the blacklist, other
customers who share the same address could be affected.
8. References
8.1. 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]
Miyakawa, S., Nakagawa, A., Yamaguchi, J., and H. Ashida,
"ISP Shared Address after IPv4 Address Exhaustion",
draft-shirasaki-isp-shared-addr-00 (work in progress),
June 2008.
[I-D.nishitani-cgn]
Nishitani, T. and S. Miyakawa, "Carrier Grade Network
Address Translator (NAT) Behavioral Requirements for
Unicast UDP, TCP and ICMP", draft-nishitani-cgn-00 (work
in progress), July 2008.
[I-D.wilson-class-e]
Wilson, P., Michaelson, G., and G. Huston, "Redesignation
of 240/4 from "Future Use" to "Private Use"",
draft-wilson-class-e-02 (work in progress),
September 2008.
8.2. 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
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ISP provides IPv6 connectivity to customers with softwire [RFC4925].
ISP installs CGN 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 | :
+----------+----------+ :
| CGN | :
+----------+----------+ :
IPv4 ISP Shared 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|
+---------------------------------+
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.
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(The IPv4 Internet) (The IPv6 Internet)
| | IPv6
| +----------+------------+
| | Softwire Concentrator |
| +----------+------------+
+---------+------------+ ^
IPv4 Global Address | :
+----------+------------+ :
| CGN | : IPv6 over IPv4 Softwire
+----------+------------+ : (e.g. IPv6 over IPv4 L2TP)
IPv4 ISP Shared 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.
(The IPv4 Internet) (The IPv6 Internet)
| |
+---------+ |
IPv4 Global Address | |
+--------+--------+ |
| CGN | | IPv6
+--------+--------+ |
IPv4 ISP Shared 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.
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(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 CGN
This architecture enables direct communication between customers
inside same CGN. It has the following advantages.
- The packets don't go through CGN. (No hairpining)
- The customers inside CGN can use bidirectional applications (e.g.
TV Conference, VPN).
- No need to use Policy Based Routing.
(The IPv4 Internet)
| Global Address
+----+----+
| CGN |
+----+----+
|
ISP Shared +-----------+----------+ ISP Shared
Address | .......... | Address
+----+----+ : : +----+----+
| CPE NAT | : : | CPE NAT |
+----+----+ : : +----+----+
Private | : : | Private
Address | v v | Address
+----+----+ +----+----+
|IPv4 Host| |IPv4 Host|
+---------+ +---------+
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B.2. CGN Bypassing
This architecture is bypassing the NAT function of CGN. 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 CGN external port.
-ISP's servers outside CGN can access CPE. (e.g. ICMP echo, SNMP,
remote access)
-ISP's servers outside CGN can distinguish which customer's
connection it receives. (e.g. DNS, Mail)
(The IPv4 Internet)
|
| +--------+ Network Monitor
| | Server | (ICMP echo, SNMP)
| +----+---+ DNS, Mail, Web, etc
Global | | ^
Address +----------------------+ :
| ....................
| . : |
+----+----+ : : +----+----+ bypass NAT:
| CGN | : bypass : | CGN | 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 CGN
This architecture enables co-existing Global Address and ISP Shared
Address inside CGN.
It enables direct communications from ISP Shared Address customer to
Global Address customer inside same CGN. 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 CGN. (No hairpining)
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- The customers inside CGN can use bidirectional applications (e.g.
TV Conference, VPN).
- No need to use Policy Based Routing.
(The IPv4 Internet)
|
| Global Address
+----+----+
| CGN | 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
Tokyo Opera City Tower 21F, 3-20-2 Nishi-Shinjuku, Shinjuku-ku
Tokyo 163-1421
Japan
Phone: +81 3 6800 3262
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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