Ethernet Protocol

Data link layer and frame handling

Overview

Ethernet is the foundation of local area network (LAN) communication. It defines framing, addressing, and media access.

Ethernet Frame Structure

Field	Length	Purpose
Destination MAC	6 bytes	Target hardware address
Source MAC	6 bytes	Sender hardware address
EtherType	2 bytes	Protocol type (IPv4, IPv6, ARP)
Payload	46-1500 bytes	Data (IP packet or other)
CRC	4 bytes	Error checking

MAC Addressing

48-bit MAC addresses identify devices on local network:

• Unicast - Single recipient (bit 0 = 0)
• Broadcast - All recipients (FF:FF:FF:FF:FF:FF)
• Multicast - Group recipients (bit 0 = 1)

Key Takeaways