ARP

ARP stands for Address Resolution Protocol.

IP packets are sent between IP addresses, but the Ethernet frames in which they are packaged are sent between MAC (hardware) addresses. Therefore the MAC address of the destination IP address must be known before an IP packet can be sent onto an Ethernet network.

The Address Resolution Protocol (ARP) is used to obtain MAC address information. FreeRTOS+TCP (like most if not all IP stacks) stores IP address to MAC address mappings in an ARP table (sometimes called the ARP cache). ARP is handled automatically by the TCP/IP stack.

Useful links:

• TCP/IP Networking Basics
• FreeRTOS+TCP networking tutorial

Other networking basics pages:

• Ethernet Networking and Addressing
• MTU - Maximum Transmission Unit
• IP Networking
• IP Network Addressing
• ARP - Address Resolution Protocol
• Subnets / Netmasks
• Gateways and Routers
• UDP Networking
• TCP Networking
• MSS - Maximum Segment Size
• Port Numbers
• Sockets
• Binding
• Clients and Servers
• Static IP Addresses
• DHCP - Dynamic Host Control Protocol
• Name Resolution
• DNS - Domain Name Service
• LLMNR - Link-local Multicast Name Resolution
• NBNS - NetBIOS Name Service
• Bytes Order and Endian