The Address Resolution Protocol (ARP) is a critical protocol used in computer networking to map an IP address to a physical machine address (MAC address) within a local network. This mapping is essential for enabling communication between devices on the same network. Below is a detailed explanation based on the foundational RFCs and their extensions.
RFC 826: The Original ARP Specification
RFC 826, published in 1982, defines the Ethernet Address Resolution Protocol. It describes how ARP dynamically resolves IP addresses to 48-bit Ethernet MAC addresses. The protocol operates by broadcasting ARP requests on the network and receiving ARP replies from the target device.
Key Features:
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Packet Structure: ARP packets include fields for hardware type, protocol type, hardware address length, protocol address length, operation code (request or reply), sender/target hardware addresses, and sender/target protocol addresses.
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Dynamic Resolution: ARP dynamically builds a table of IP-to-MAC mappings, which is used for efficient communication.
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Broadcast Mechanism: ARP requests are broadcast to all devices on the local network, while replies are sent directly to the requester.
Workflow:
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A device sends an ARP request to determine the MAC address corresponding to a specific IP address.
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The target device responds with an ARP reply containing its MAC address.
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The requester updates its ARP table with the new mapping.
This protocol is widely used in IPv4 networks and forms the basis for many networking operations