Layer 2 Ethernet frame (packet) sizes

The Layer 2 Ethernet frame (packet) as described here includes Ethernet headers, i.e. the CRC, but not the Inter Frame Gap, Preamble, or Start of Frame Delimiter (SFD).

The maximum frame size depends on the interface MTU (Maximum Transmission Unit); the default value is 1500 bytes.

The minimum frame size for IPv4 is 64 bytes, where the Ethernet header takes up 18 bytes, the IPv4 header 20 bytes, and the UDP header 8 bytes. The remaining 18 bytes are payload, where Netrounds places a sequence number, a timestamp, a checksum, and a stream ID.

  • Minimum IPv4 packet size = 18 (Ethernet) + 20 (IPv4) + 8 (UDP) + 18 (payload) = 64 bytes

For IPv6 the minimum frame size is 84 bytes, since the IPv6 header is 40 bytes long.

  • Minimum IPv6 packet size = 18 (Ethernet) + 40 (IPv6) + 8 (UDP) + 18 (payload) = 84 bytes

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