<P> An IP address serves two principal functions . It identifies the host, or more specifically its network interface, and it provides the location of the host in the network, and thus the capability of establishing a path to that host . Its role has been characterized as follows: "A name indicates what we seek . An address indicates where it is . A route indicates how to get there ." The header of each IP packet contains the IP address of the sending host, and that of the destination host . </P> <P> Two versions of the Internet Protocol are in common use in the Internet today . The original version of the Internet Protocol for use in the Internet is Internet Protocol version 4 (IPv4), first installed in 1983 . </P> <P> The rapid exhaustion of IPv4 address space available for assignment to Internet service providers and end user organizations by the early 1990s, prompted the Internet Engineering Task Force (IETF) to explore new technologies to expand the addressing capability in the Internet . The result was a redesign of the Internet Protocol which became eventually known as Internet Protocol Version 6 (IPv6) in 1995 . IPv6 technology was in various testing stages until the mid-2000s, when commercial production deployment commenced . </P> <P> IANA's primary IPv4 address pool was exhausted on 3 February 2011, when the last five blocks were allocated to the five RIRs . APNIC was the first RIR to exhaust its regional pool on 15 April 2011, except for a small amount of address space reserved for the transition to IPv6, intended to be allocated in a restricted process . Individual ISPs still had unassigned pools of IP addresses, and could recycle addresses no longer needed by their subscribers . </P>

When is an ip address assigned to a computer