Frame Check Sequence FCS

A 32-bit cyclic redundancy check over the header and body.

Reading a capture

Covers the MAC frame only — not the PHY preamble, which has no CRC at all. A frame that fails this check is discarded silently, so a capture showing gaps in sequence numbers may be showing you frames that arrived corrupt rather than frames that were never sent.

Where it sits

QoS Data MPDU > Frame Check Sequence

• Open in the explorer — Ack
• Open in the explorer — TCP over IPv4, in a protected QoS Data frame, aggregated
• Open in the explorer — Association Request
• Open in the explorer — Association Response
• Open in the explorer — Beacon
• Open in the explorer — Compressed Block Ack
• Open in the explorer — CTS
• Open in the explorer — Four-way handshake message 1
• Open in the explorer — Four-way handshake message 2
• Open in the explorer — Four-way handshake message 3
• Open in the explorer — Four-way handshake message 4
• Open in the explorer — Probe Request
• Open in the explorer — Probe Response
• Open in the explorer — ARP request in a QoS Data frame
• Open in the explorer — ICMP echo over IPv4, in a QoS Data frame
• Open in the explorer — UDP over IPv6, in a QoS Data frame
• Open in the explorer — TCP over IPv4, in a protected QoS Data frame
• Open in the explorer — TCP over IPv4, in an open QoS Data frame
• Open in the explorer — UDP over IPv4, in a QoS Data frame
• Open in the explorer — RTS
• Open in the explorer — Trigger frame

Accuracy

Clause

802.11-2024 §9.2.4.8

Byte order

little-endian — least significant octet first

Verified

Not verified against the standard. Treat this as a claim, not a fact.