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The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Network Interface / Internet "Layer Connection" Protocols            9  Address Resolution and the TCP/IP Address Resolution Protocol (ARP)

Dynamic Address Resolution Caching and Efficiency Issues 1 ARP Overview, Standards and History

The most widely used network layer protocol in the world—by far—is the TCP/IP Internet Protocol. It's no surprise then, that the most important address resolution protocol is the TCP/IP protocol bearing the same name as the technique itself: the Address Resolution Protocol (ARP). ARP is a full-featured dynamic resolution protocol used to match IP addresses to underlying data link layer addresses. Originally developed for Ethernet, it has now been generalized to allow IP to operate over a wide variety of layer two technologies.

In this section I describe the operation and features of ARP. I begin with an overview of the protocol, and a discussion of its defining standards and history. I briefly outline how addresses are specified in ARP and its general operation, as well as describing the message format used for ARP messages. I then turn to the important matter of caching in ARP and how that is used to improve performance. I conclude with a discussion of proxying in ARP, which is needed to support special network connectivity situations.

Dynamic Address Resolution Caching and Efficiency Issues 1 ARP Overview, Standards and History