Overview

The version of the Internet Protocol upon which today's Internet is based is version 4, IPv4. The next version of IP is IPv6 ^[1]. At a high level, the reasons for IPv6 are the changing requirements for the Internet and shortcomings in IPv4. These reasons are related in some ways; some IPv4 design choices that were appropriate at the time they were made are no longer the best choices for today and tomorrow's Internet. For example, the IPv4 header checksum is recomputed at each hop, because of the unreliability of some links in the past. This is a shortcoming for modern networks with more reliable links, where it is harder to justify the overhead involved in doing this error check at every hop. We will explore the reasons and motivations for IPv6 in more detail when we discuss the IPv6 design considerations in Section 9.1.

The basic protocols for IPv6 have been specified from as early as 1998. So one of the big questions in telecommunications is, when will IPv6 take off? Despite all of the changing requirements listed above, it is difficult to switch from a working system without a simple and compelling reason as a catalyst for change. In the case of IPv6, this reason is that the IPv4 address space is being depleted. Due to address depletion, IPv4 will no longer be viable in the near future. Estimates place the end of IPv4 somewhere in the range of 2008 to 2015 ^[2]. However, the...