The Next Hop Resolution Protocol (NHRP) is an extension of the ATM ARP routing mechanism that is sometimes used to improve the efficiency of routing computer network traffic over a non-broadcast, multiple access (NBMA) network. It is defined in IETF RFC 2332, and further described in RFC 2333. It can be used by a sender to determine a route with the fewest hops to a receiver. The protocol differs from ARP-type protocols in that it allows routing optimization across multiple IP subnets. NHRP is implemented by means of next-hop servers across IP subnets.