Ethernet II frame
11 Jun 2019
Ethernet II packet and frame structure
- Preamble - the preamble of an Ethernet packet consists of a 56-bit (seven-byte) pattern of alternating 1 and 0 bits, allowing devices on the network to easily synchronize their receiver clocks
- SFD - a 1 byte value that marks the end of the preamble, which is the first field of an Ethernet packet, and indicates the beginning of the Ethernet frame
- DST MAC - a receiver of a frame presented as MAC address
- SRC MAC - a sender of a frame presented as MAC address
- Payload - The minimum payload is 42 octets when an 802.1Q tag is present and 46 octets when absent. The maximum payload is 1500 octets. Non-standard jumbo frames allow for larger maximum payload size.
- FCS - allows detection of corrupted data within the entire frame as received on the receiver side. The FCS value is computed as a function of all fields except the FCS
- Interpacket gap - Interpacket gap is idle time between packets. After a packet has been sent, transmitters are required to transmit a minimum of 96 bits (12 octets) of idle line state before transmitting the next packet.