Internet Engineering Task Force Y. Shirasaki, Ed. Internet-Draft S. Miyakawa Intended status: Informational NTT Communications Expires: September 10, 2009 A. Nakagawa KDDI CORPORATION J. Yamaguchi IIJ H. Ashida iTSCOM March 9, 2009 NAT444 with ISP Shared Address draft-shirasaki-nat444-isp-shared-addr-01 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on September 10, 2009. Copyright Notice Copyright (c) 2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Shirasaki, et al. Expires September 10, 2009 [Page 1] Internet-Draft NAT444 with ISP Shared Address March 2009 Abstract This document describes one of the network models that is 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. Shirasaki, et al. Expires September 10, 2009 [Page 2] Internet-Draft NAT444 with ISP Shared Address March 2009 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 Shirasaki, et al. Expires September 10, 2009 [Page 3] Internet-Draft NAT444 with ISP Shared Address March 2009 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) [I-D.wilson-class-e], 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. Shirasaki, et al. Expires September 10, 2009 [Page 4] Internet-Draft NAT444 with ISP Shared Address March 2009 (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. Shirasaki, et al. Expires September 10, 2009 [Page 5] Internet-Draft NAT444 with ISP Shared Address March 2009 +-------------+ (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. Shirasaki, et al. Expires September 10, 2009 [Page 6] Internet-Draft NAT444 with ISP Shared Address March 2009 +-------------+ (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 Shirasaki, et al. Expires September 10, 2009 [Page 7] Internet-Draft NAT444 with ISP Shared Address March 2009 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. Shirasaki, et al. Expires September 10, 2009 [Page 8] Internet-Draft NAT444 with ISP Shared Address March 2009 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", Shirasaki, et al. Expires September 10, 2009 [Page 9] Internet-Draft NAT444 with ISP Shared Address March 2009 draft-shirasaki-isp-shared-addr-01 (work in progress), October 2008. [I-D.nishitani-cgn] Nishitani, T., Miyakawa, S., Nakagawa, A., and H. Ashida, "Common Functions of Large Scale NAT (LSN)", draft-nishitani-cgn-01 (work in progress), November 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. 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, . 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. Shirasaki, et al. Expires September 10, 2009 [Page 10] Internet-Draft NAT444 with ISP Shared Address March 2009 (The IPv4 Internet) (The IPv6 Internet) | | IPv6 | +-----------+-----------+ | | Softwire Concentrator | | +-----------+-----------+ +---------+----------+ ^ IPv4 Global Address | : +----------+----------+ : | LSN | : +----------+----------+ : 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. (The IPv4 Internet) (The IPv6 Internet) | | IPv6 | +----------+------------+ | | Softwire Concentrator | | +----------+------------+ +---------+------------+ ^ IPv4 Global Address | : +----------+------------+ : | LSN | : 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 Shirasaki, et al. Expires September 10, 2009 [Page 11] Internet-Draft NAT444 with ISP Shared Address March 2009 ISP provides dual stack access to CPE. A CPE uplink is now dual stack. (The IPv4 Internet) (The IPv6 Internet) | | +---------+ | IPv4 Global Address | | +--------+--------+ | | LSN | | 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. (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. Shirasaki, et al. Expires September 10, 2009 [Page 12] Internet-Draft NAT444 with ISP Shared Address March 2009 - 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. (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) Shirasaki, et al. Expires September 10, 2009 [Page 13] Internet-Draft NAT444 with ISP Shared Address March 2009 (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. Shirasaki, et al. Expires September 10, 2009 [Page 14] Internet-Draft NAT444 with ISP Shared Address March 2009 (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 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 Shirasaki, et al. Expires September 10, 2009 [Page 15] Internet-Draft NAT444 with ISP Shared Address March 2009 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 Shirasaki, et al. Expires September 10, 2009 [Page 16]