IPv4 IPv6

decomposition of quad-dotted ipv4 address representation binary value

internet protocol version 4 (ipv4) first publicly used version of internet protocol. ipv4 developed research project defense advanced research projects agency (darpa), united states department of defense agency, before becoming foundation internet , world wide web. described ietf publication rfc 791 (september 1981), replaced earlier definition (rfc 760, january 1980). ipv4 included addressing system used numerical identifiers consisting of 32 bits. these addresses typically displayed in quad-dotted notation decimal values of 4 octets, each in range 0 255, or 8 bits per number. thus, ipv4 provides addressing capability of 2 or approximately 4.3 billion addresses. address exhaustion not concern in ipv4 version presumed test of darpa s networking concepts. during first decade of operation of internet, became apparent methods had developed conserve address space. in 1990s, after redesign of addressing system using classless network model, became clear not suffice prevent ipv4 address exhaustion, , further changes internet infrastructure needed.

the last unassigned top-level address blocks of 16 million ipv4 addresses allocated in february 2011 internet assigned numbers authority (iana) 5 regional internet registries (rirs). however, each rir still has available address pools , expected continue standard address allocation policies until 1 /8 classless inter-domain routing (cidr) block remains. after that, blocks of 1024 addresses (/22) provided rirs local internet registry (lir). of september 2015, of asia-pacific network information centre (apnic), réseaux ip européens network coordination centre (ripe_ncc), latin america , caribbean network information centre (lacnic), , american registry internet numbers (arin) have reached stage. leaves african network information center (afrinic) sole regional internet registry still using normal protocol distributing ipv4 addresses.