by Matthew G. Naugle
Wiley Computer Publishing, John Wiley & Sons, Inc.
ISBN: 0471196568 Pub Date: 11/01/98
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Illustrated TCP/IP
by Matthew G. Naugle Wiley Computer Publishing, John Wiley & Sons, Inc. ISBN: 0471196568 Pub Date: 11/01/98 |
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The ARP packet format is shown. It contains just a few fields, but notice one thing: It does not reside on top of IP. It has its own Ethernet Type field (0806), which identifies the protocol ownership of the packet and allows it to uniquely identify itself. It never leaves its local segment, so why use IP?
There are five main fields: the operation (ARP request or ARP reply), the source and destination IP addresses, and the source and destination hardware addresses (more commonly known as MAC addresses).
The type of hardware identifies the LAN (10-Mbps Ethernet, for example), the type of protocol identifies the protocol being used. This makes ARP versatile. It can be used with other types of protocols as well. The most famous one is AppleTalk through the AppleTalk ARP protocol.
The ARP process is shown next.
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