This addressing scheme is co-ordinated by the Internet Service Providers who deal with a central agency, the Internet Assigned Number Authority . For private networks, the address is co-ordinated by the network manager. The protocol software must then map the IP address to the physical hardware. The protocol address of the next hop must be translated into an equivalent hardware address before a packet can be sent. Address Resolution Translation from a computer's protocol address to an equivalent hardware address is known as address resolution.
Address resolution is local to a network.
A host or a router uses address resolution when it needs to send to another computer on the same physical network. Bindings are stored as an array in a table in memory, which the software searches when it needs to resolve an address. The protocol address assigned to a computer is chosen carefully so the computer's hardware address can be computed from the protocol address using basic Boolean and arithmetic operations. One computer sends a message that requests an address binding, and another computer sends a reply that contains the requested information. A request contains an IP address and requests the corresponding hardware address.