Transitioning to IPv6 271
Figure 7-8 IPv4 and IPv6
In addition to its technical and business potential, IPv6 offers a virtually unlimited supply
of IP addresses. Because of its generous 128-bit address space, IPv6 generates a virtually
unlimited stock of addresses??”enough to allocate more than 4.3 billion addresses (the entire
IPv4 Internet address space) to every person on the planet.
The Internet will be transformed after IPv6 fully replaces IPv4. Many people within the
Internet community have analyzed the issue of IPv4 address exhaustion and published their
reports. However, the estimates of when IPv4 address exhaustion will occur vary greatly
among the reports. Some predict IPv4 address exhaustion by 2008 or 2009, and others say
it will not happen until 2013 or beyond. Nevertheless, IPv4 will not disappear overnight.
Rather, it will coexist with and then gradually be replaced by IPv6.
The change from IPv4 to IPv6 has already begun, particularly in Europe, Japan, and the
Asia-Paci?¬?c region. These areas are exhausting their allotted IPv4 addresses, which makes
IPv6 all the more attractive and necessary. Some countries, such as Japan, are aggressively
adopting IPv6.
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