Address Resolution Protocol

Address Resolution Protocol (ARP) is a telecommunications protocol used for resolution of network layer addresses into link layer addresses during internetwork transmissions. This function is critical in multiple-access networks for determining link layer addresses when relaying network layer transmissions. ARP was defined by RFC 826 in 1982.[1] It is Internet Standard STD 37.
ARP has been implemented in many combinations of network and overlaying internetwork technologies, such as IPv4, Chaosnet, DECnet and Xerox PUP over the IEEE 802 group, FDDI, X.25, Frame Relay and ATM, IPv4 over IEEE 802.3 and IEEE 802.11 being the two most common cases.
NDP is the ICMPv6-based equivalent to ARP in IPv6 internetworks.