On February 3, it finally happened: the stash of IPv4 Internet protocol addresses that are used to identify and locate computers connected to the Internet was exhausted.

Fortunately, engineers realized the limitations of IPv4 a long time ago and lined up a successor, called IPv6, in 1998. IPv6 uses 128 bits rather than 32, producing a pool of numbers that is staggeringly huge — some 3.4 x 10 to the 38, or 48 octillion addresses for every person on Earth. The trouble is that although most servers and all major operating systems have adopted support for IPv6, Internet service providers have been agonizingly slow to follow suit.