Sams Teach Yourself TCP/IP in 24 Hours, Fourth Edition

Address Resolution Protocol (ARP)

As you learned earlier in this hour, the computers on a local network use an Internet layer protocol called Address Resolution Protocol (ARP) to map IP addresses to physical addresses. A host must know the physical address of the destination network adapter to send any data to it. For this reason, ARP is an important protocol. However, TCP/IP is implemented in such a way that ARP and all the details of physical address translation are almost totally invisible to the user. As far as the user is concerned, a network adapter is identified by its IP address. Behind the scenes, though, the IP address must be mapped to a physical address for a message to reach its destination. (See Hour 3.)

Each host on a network ...