Sams Teach Yourself TCP/IP in 24 Hours, Fourth Edition

Why a New IP?

The IP addressing system described in Hour 4, “The Internet Layer,” has served the Internet community for nearly a generation, and those who developed it are justifiably proud of how far TCP/IP has come. But the Internet community has one big problem: The world might run out of addresses. This looming address crisis might seem surprising, because the 32-bit address field of the current IP format can provide over three billion possible host IDs. But it is important to remember how many of these three billion addresses are actually unusable.

A network ID is typically assigned to an organization, and that organization controls the host IDs associated with its own network. Recall from Hour 4 that IP addresses were originally intended ...