All public IPv4 addresses that transverse the Internet must be registered with a Regional Internet Registry (RIR). Organizations can lease public addresses from an SP, but only the registered holder of a public Internet address can assign that address to a network device. However, with a theoretical maximum of 4.3 billion addresses, IPv4 address space is severely limited. When Bob Kahn and Vint Cerf first developed the suite of TCP/IP protocols including IPv4 in 1981, they never envisioned what the Internet would become. At the time, the personal computer was mostly a curiosity for hobbyists and the World Wide Web was still more than a decade away.