One of the major challenges for the future of the Internet is its ability to scale to connect billions of people and devices. A key part of scalability is the Internet Protocol (IP). The Internet Protocol specifies how communications take place between one device and another through an addressing system. Each device must have an IP address in order to communicate. However, the currently used version of the Internet Protocol, IPv4, is expected to run out of previously unallocated addresses in 2012. IPv4 addresses are nearing full allocation, with just 8% of addresses remaining in March 2010.