Comcast is making a move to IPv6, making IPv6 transit services available to its wholesale customers. This a significant development because in less than two years, the IPv4 (define) address space will be exhausted, but it doesn't mean there won't be any more Internet addresses. IPv4 has a 32-bit address size, allowing for only 4.3 billion addresses. In contrast, IPv6 is a 128-bit address space allowing for a staggering 340,282,366,920,938,463,463,374,607,431,768,211,456 possible addresses.
More info: InternetNews