Chapter 39. Introduction to the IPv6 Protocol

SOME OF THE MAIN TOPICS IN THIS CHAPTER ARE

What's the Difference Between IPv4 and IPv6?

The IPv6 Headers

Other IPv6 Considerations

The Future of IPv6

The first Request for Comments (RFC) to define the next generation of the Internet Protocol (IP) was RFC 1883, "Internet Protocol, Version 6 (IPv6) Specification," published as a "standards track" RFC in 1995. When you consider that the Internet was expanding at a very rapid rate at that time (as it continues to do), it seemed a natural thing to develop a new version of IP to accommodate a larger address space, and to patch some holes in the current version of IP. Many other RFCs have been created since this original one. Specifically, RFC 2460 has updated RFC 1883. Other RFCs apply to very specific aspects of IPv6, such as changes to the Internet Control Message Protocol (ICMP) and other standard TCP/IP protocols and utilities. These RFCs are too numerous to be discussed in this chapter. You can, however, do a quick search at www.rfc-editor.org to get a list of all the RFCs related to IPv6.

During the years since, other technologies such as Network Address Translation (NAT) and Classless Interdomain Routing (CIDR) have enabled the current IPv4 address space to remain viable for the current Internet. Yet IPv6 encompasses many other capabilities. Currently, IPv6 is used only in very large enterprise networks, and in many routers at the Internet's core . The hardware to route and use IPv6 exists today. Indeed, in Windows XP and Windows Server 2003, you'll find that you can use IPv6.

Both NAT and CIDR are covered in greater detail in Chapter 25, "Overview of the TCP/IP Protocol Suite."

However, besides the increased address space, IPv6 offers many other features that will make it the ideal replacement for IPv4 (down to the desktop) in a few years.

This chapter is not meant to be as comprehensive as Chapters 25 through 29, which cover the current TCP/IP protocols, applications, and utilities. However, this chapter provides a good overview of what IPv6 has to offer. Some of the capabilities of IPv6 (such as security) have already been implemented in IPv4 technologies ( especially in Virtual Private Networks, or VPNs). The fact that some IPv6 features are already being backward implemented for IPv4 applications should give you an idea of the revolution that this newer IP version will bring.