QoS Control QoS

Present only in QoS subtypes. Carries the traffic class and how this frame should be acknowledged.

Reading a capture

The upper octet is the awkward one: its meaning depends on who sent the frame and in what context, so the same bits mean different things from an AP and from a client.

Subfields

• TID — Traffic identifier — which access category this frame belongs to, and so how long the sender waited before transmitting it.
• EOSP — End of service period.
• Ack Policy — How, or whether, this frame should be acknowledged.
• A-MSDU Present — Set when the frame body holds several aggregated MSDUs rather than one.
• Context-dependent octet — TXOP Limit or AP PS Buffer State when sent by an AP; TXOP Duration Requested or Queue Size when sent by a client.

Where it sits

QoS Data MPDU > QoS Control

• Open in the explorer — TCP over IPv4, in a protected QoS Data frame, aggregated
• 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 — 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

Accuracy

Clause

802.11-2024 §9.2.4.5

Byte order

little-endian — least significant octet first

Verified

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