2011 Fall Conference of Korea Information and Communications Society

The Recent Trends and Analysis on IPv4/IPv6 Transition Mechanism

Lee Jae Yong*, Bong Jin Sook*, Jee Hyun Wang, Yongtae Shin*

*Soongsil Univ., Yongsan International School of Seoul.

(*jylee, *jsbong)@cherry.ssu.ac.kr, , *)

Summary

A transition to IPv6, the next generation of internet address System, from IPv4 is in the desperate need because IANA (Internet Assigned Numbers Authority) has claimed to stop the global IPv4 address allocation on February of 2011. There are many ongoing researches in IETF (Internet Engineering Task Force) on the transition of IPv4 to IPv6, as IPv6 will be applied in the near future. This paper briefly discusses the transition mechanisms of IPv4 to IPv6, which is recently being researched, andits concept and significant characteristics.

1. Introduction

An increase in network devices such as smart phones or IPTV, and in network services such as cloud service or integrated wire and wireless services, has resulted in growing demands of IP. This brought the depletion of preexisted IPv4 addresses and the need of IPv6 to replace IPv4. There are many ongoing researches in IETF (Internet Engineering Task Force) on the transition of IPv4 to IPv6, as IPv6 will be applied in the near future [4].

This paper explains the transition mechanisms for IPv4 to IPv6 that are recently being researched and analyzes their significant characteristics. Chapter 3 glances over the new transition mechanisms; chapter 4 compares and analyzes the characteristics of these transition mechanisms; chapter 5 presents the conclusion.

2. Related Research

The classification of IPv4/IPv6 transition mechanisms is as written in Table 1.

<table1> Classification of IPv4/IPv6 Transition Mechanisms

Dual-Stack / N/A
Tunneling / *Configured Tunneling
*Automatic Tunneling
- 6to4, DSTM , ISATAP, Tunnel Broker, Teredo
(Address) Translation / * Network layer translation
- NAT-PT/SIIT, BIS
*Transport layer translation
- TRT, SOCKS Gateway
* Application layer translation
- BIA

The transition mechanisms aredivided into Dual-Stack, Tunneling, and (Address)Translation mechanisms.

Dual-Stack handles all IPv4 and IPv6 protocols in one system. Thus the one physical system supporting Dual-Stack supports both IPv4 and IPv6.

A tunneling mechanism creates a tunnel at IPv4 network in order to communicate for traffic moving from an IPv6 network to a nearby IPv4 network and ultimately to transit to a desired IPv6 network.

Translation mechanisms interwork IPv4 and IPv6 network using an address converter. Because it is not possible for one mechanism to be applied to all situations, eachmechanism should be appropriately utilized according to the given situation.

3. Recent IPv4/ IPv6 Transition Mechanisms

3.1 6rd (IPv6 rapid deployment)

6rd is a developed mechanism tomodify and improve upon the problems of 6to4 for the service provider to provide IPv6 service faster and easier in IPv4 site. 6rd communicates by using IPv6 prefix (ISPv6 prefix), which is allocated by each ISP in replace of 6to4’s 2002::/16, and by using anycast address, which is selected by ISP (Internet Service Provider).6rd can solve problems arose from 6to4’s open relay, since ISP supervisesBR, which acts as relay. Moreover, packets come from 6rd assure the validity to be head towards an ISP site because 6rd uses prefix given to each ISP.


6rd’s configuration is as follows:

(figure 1) configuration of 6rd

6rd uses only CE router when communicating within the inner IPv4 network and forms a tunnel between CE and BR when communicating with IPv6 network outside of BR.

3.2 CGN (Carrier-Grade NAT)

CGN is a combined transition mechanism that minimizes the network’s structural change that occurs in IPv4 to IPv6 transition. CGN uses both Dual-Stack home gateway and Dual-Stack CGN, which can both be reused during different transition periods. Thus, in this transition period, CGN can be operated through the whole transition solely with upgrades or reboots, without the need to change the device. The early stage of transition uses CGN, which is later replaced by DS-Lite CGN.

CGN, having all the NAT’s functions and the automatic tunneling characteristics that can be found in 6rd,aids for the recently facing shortage of IPv4 addresses and faster applications of IPv6[1].

CGN’s configuration is as follows:


(figure 2) Configuration of CGN

CGN, a device that performs NAT functions, is used as the terminal of a tunnel for the communication to IPv6

3.3 DS-Lite (Dual Stack Lite)

DS-Lite is a CGN basis solution that enables IPv4 communication to the end when the service provider provides IPv6 network and can be usedas a DS-Lite mode by upgrading or resetting CGN devices.

DS-Lite has an advantage that can be applied in networks sharing IPv4 addresses by providing IPv4-in-IPv6 and NAT functions [2].


DS-Lite’s configuration is as follows:

(figure 3) Configuration of DS-Lite

3.4 NAT64 (Network Address Translation64)

NAT64 is a translation mechanism that converts the information of IP header and ICMP to an IPv4 or to an IPv6 version for the communication between IPv6 and IPv4 networks and can be viewed as an expanded mechanism of NAT-PT.

NAT64 is composed of a NAT64 router that converts an IPv6 header to an IPv4 header by basing on IPv6 prefixes and IPv4 address domains and by using DNS64 server and IP/ICMP conversion algorithm that provides IPv6 address[3].

NAT64’s configuration is as follows:


(figure 4) Configuration of NAT 64

4. Comparison and Analysis of the Characteristics of Transition Mechanisms

Comparison and analysis of transitionmechanisms are shown in <table 2>.

<table2> Feature of Transition Mechanisms

6rd / CGN / DS-Lite / NAT64
Mechanism
Classification / Tunneling / Tunneling / Tunneling / Translation
Section / CE – BR / HG – CGN / CPE – AFTR / -
Scalability / Very High / High / High / Middle
Use of NAT / - / O / O / O
Notes / Prefix Configuration by each ISP / NAT+Tunneling(6rd) / Troubleshooting of Double-NAT / Enhancement of NAT-PT

Transition mechanismsare classified according to the roles, namely Tunneling and Translation. Atunnel sectionexplains where the Tunneling is used if using a Tunneling mechanism. Analysis for Scalability is based on its applicability to diverse networks. CGN and DS-Lite should be considered of the point of changing the equipments, and NAT64 has the limitation only on to the beginning of the communication of IPv6 networks. Use of NAT notifies how well each mechanism can be applied to NAT applied environment. Notes summarize the merits of each mechanism.

5. Conclusion

In order for introducing IPv6 and transition into IPv6, the variousprojects, such as establishing the foundation of the IPv6 Service Supporting System and of the IPv6 Supply and Promotion, and activating the researches and the test on IPv6 Network Base Service are ongoing in Korea,by Korea Communication Committee and by Korea Internet Security Agency.

This paper is compared and analyzed the compositions and the characteristics of newly researched on transition mechanisms such as 6rd, CGN, DS-Lite, and NAT 64. Further researches are needed to analyze the possible securityproblems and to develop the plan to enhance the security to minimize the problems when applyingon IPv4/ IPv6 transition mechanisms.

References

[1] S. Jiang, D. GUO, B. Carpenter, An Incremental Carrier-Grade NAT (CGN) for IPv6 Transition, RFC 6264, 2011. 06.

[2] A. Durand, R. Droms, J. Woodyatt, T. Lee, Dual-Stack Lite Broadband Deployments Following IPv4 Exhaustion, RFC 6333, 2011. 08.

[3] M. Bagnulo, P. Matthews, I. van Beijnum, Stateful NAT64: Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers Draft-ietf-behave-v6v4-xlate-stateful-12, RFC 6146, 2011. 01.

[4] J. Arkko, F. Baker, IPv6 Transition Guidelines, RFC 6180, 2011. 05.

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