Field index

Every field defined here, grouped by layer. Each has its own page and its own permanent link — addressed by key rather than by position, so restructuring never breaks one.

314 fields · 314 unverified

Show fields that apply to

PHY

802.11a non-HT OFDM 802.11ac VHT 802.11ax HE ER SU 802.11ax HE MU 802.11ax HE SU 802.11ax HE TB 802.11b HR/DSSS long preamble 802.11b HR/DSSS short preamble 802.11be EHT MU 802.11g ERP-OFDM 802.11n HT mixed-format

all none

Class

control data management

all none

Mechanism

acknowledgement aggregation association block ack discovery measurement medium reservation multi user power save protection qos scheduling user data

all none

PHY 112

• Aggregation ? HT-SIG › HT-SIG2 HT mixed-format PPDU 1 PHY Set when the PSDU carries an A-MPDU.
• Bandwidth ? U-SIG EHT MU PPDU 1 PHY Channel width, up to 320 MHz.
• Bandwidth ? HE-SIG-A › HE-SIG-A1 HE SU PPDU 1 PHY Channel width used for this transmission.
• Beam Change ? HE-SIG-A › HE-SIG-A1 HE SU PPDU 1 PHY Whether the spatial mapping changes between the legacy and HE portions.
• Beamformed ? HE-SIG-A › HE-SIG-A2 HE SU PPDU 1 PHY Whether a beamforming steering matrix was applied.
• Beamformed ? VHT-SIG-A › VHT-SIG-A2 VHT PPDU 1 PHY Whether a steering matrix was applied.
• BSS Color ? U-SIG EHT MU PPDU 1 PHY A short identifier for the transmitting BSS.
• BSS Color ? HE-SIG-A › HE-SIG-A1 HE SU PPDU 1 PHY A short identifier for the transmitting BSS.
• BW ? VHT-SIG-A › VHT-SIG-A1 VHT PPDU 1 PHY Channel width — 20, 40, 80 or 160 MHz.
• CBW 20/40 ? HT-SIG › HT-SIG1 HT mixed-format PPDU 1 PHY Whether the transmission occupies 20 or 40 MHz.
• Coding ? HE-SIG-A › HE-SIG-A2 HE SU PPDU 1 PHY BCC or LDPC.
• CRC ? HR/DSSS PPDU (long preamble) HR/DSSS long preamble PPDU 2 PHYs A 16-bit check over the SIGNAL, SERVICE and LENGTH fields.
• CRC ? HE-SIG-A › HE-SIG-A2 HE SU PPDU 1 PHY A four-bit check over the HE-SIG-A contents.
• CRC ? HT-SIG › HT-SIG2 HT mixed-format PPDU 1 PHY Eight-bit check over both HT-SIG symbols.
• CRC ? VHT-SIG-A › VHT-SIG-A2 VHT PPDU 1 PHY Eight-bit check over both VHT-SIG-A symbols.
• Data field ? EHT MU PPDU EHT MU PPDU 1 PHY The PSDU, modulated at the rate named in the preamble.
• Data field ? HE ER SU PPDU HE ER SU PPDU 1 PHY The PSDU, at one of the three lowest modulation schemes.
• Data field ? HE MU PPDU HE MU PPDU 1 PHY The PSDU. Several stations' data, each on its own resource unit.
• Data field ? HE SU PPDU HE SU PPDU 1 PHY The HE data field, carrying the PSDU handed down by the MAC.
• Data field ? HE TB PPDU HE TB PPDU 1 PHY The PSDU, padded to exactly the duration the Trigger frame demanded.
• Data field ? HT mixed-format PPDU HT mixed-format PPDU 1 PHY The HT data field, carrying the PSDU.
• Data field ? VHT PPDU VHT PPDU 1 PHY The VHT data field, carrying the PSDU.
• DATA field ? ERP-OFDM PPDU ERP-OFDM PPDU 1 PHY SERVICE, the PSDU, tail and pad bits, modulated at the rate the SIGNAL field named.
• DATA field ? non-HT PPDU non-HT OFDM PPDU 1 PHY Everything after the SIGNAL field: a service field, the PSDU handed down by the MAC, and the tail and padding needed to fill whole OFDM symbols.
• DCM ? HE-SIG-A › HE-SIG-A1 HE SU PPDU 1 PHY Dual carrier modulation, trading throughput for robustness.
• Doppler ? HE-SIG-A › HE-SIG-A2 HE SU PPDU 1 PHY Indicates midamble use for high-mobility channels.
• EHT MU PPDU ? EHT MU PPDU 1 PHY An extremely high throughput transmission — legacy preamble, universal signal field, EHT preamble, data, and a packet extension.
• EHT-LTF ? EHT MU PPDU EHT MU PPDU 1 PHY Long training fields, one set per spatial stream, for channel estimation.
• EHT-SIG ? EHT MU PPDU EHT MU PPDU 1 PHY Per-user signalling: which stations are in this transmission, on which resource units, at which rates.
• EHT-STF ? EHT MU PPDU EHT MU PPDU 1 PHY Short training for the EHT portion, retuning the receiver's gain after the legacy fields.
• ERP-OFDM PPDU ? ERP-OFDM PPDU 1 PHY An extended rate PHY transmission — the OFDM preamble and data of Clause 17, followed by a signal extension.
• Format ? HE-SIG-A › HE-SIG-A1 HE SU PPDU 1 PHY Distinguishes an HE SU PPDU from an HE trigger-based one.
• GI+LTF Size ? HE-SIG-A › HE-SIG-A1 HE SU PPDU 1 PHY Guard interval and HE-LTF symbol duration.
• Group ID ? VHT-SIG-A › VHT-SIG-A1 VHT PPDU 1 PHY Identifies which set of stations a multi-user transmission is addressed to.
• HE ER SU PPDU ? HE ER SU PPDU 1 PHY A high-efficiency transmission built to survive a worse channel than the ordinary single-user format.
• HE MU PPDU ? HE MU PPDU 1 PHY A high-efficiency downlink transmission to several stations at once.
• HE SU PPDU ? HE SU PPDU 1 PHY A high-efficiency single-user transmission — legacy preamble, HE preamble, data, and a packet extension.
• HE TB PPDU ? HE TB PPDU 1 PHY A trigger-based uplink transmission — one of several sent simultaneously on different resource units.
• HE-LTF ? HE ER SU PPDU HE ER SU PPDU 1 PHY Long training fields for channel estimation.
• HE-LTF ? HE MU PPDU HE MU PPDU 1 PHY Long training fields, one set per spatial stream.
• HE-LTF ? HE SU PPDU HE SU PPDU 1 PHY Long training symbols, one or more per spatial stream, used to estimate the channel for the HE data that follows.
• HE-LTF ? HE TB PPDU HE TB PPDU 1 PHY Long training fields for channel estimation.
• HE-SIG-A ? HE ER SU PPDU HE ER SU PPDU 1 PHY The same fifty-two bits the single-user format carries, sent over four symbols instead of two.
• HE-SIG-A ? HE MU PPDU HE MU PPDU 1 PHY Two symbols of parameters common to the whole transmission, including how long the HE-SIG-B that follows is.
• HE-SIG-A ? HE SU PPDU HE SU PPDU 1 PHY Two OFDM symbols carrying the parameters needed to decode the rest of the transmission.
• HE-SIG-A ? HE TB PPDU HE TB PPDU 1 PHY Two symbols of common parameters. Its Format bit is zero, which is what marks this as trigger-based rather than single-user.
• HE-SIG-A1 ? HE-SIG-A HE SU PPDU 1 PHY The first HE-SIG-A symbol — mostly PHY parameters.
• HE-SIG-A2 ? HE-SIG-A HE SU PPDU 1 PHY The second HE-SIG-A symbol — mostly coding and duration.
• HE-SIG-B ? HE MU PPDU HE MU PPDU 1 PHY Which stations are in this transmission, on which resource units, at which rates.
• HE-STF ? HE ER SU PPDU HE ER SU PPDU 1 PHY Short training for the HE portion.
• HE-STF ? HE MU PPDU HE MU PPDU 1 PHY Short training for the HE portion.
• HE-STF ? HE SU PPDU HE SU PPDU 1 PHY A short training field for the HE portion, used to reset automatic gain control after the signalling fields.
• HE-STF ? HE TB PPDU HE TB PPDU 1 PHY Short training, at twice the length of the single-user field.
• HR/DSSS PPDU (long preamble) ? HR/DSSS long preamble PPDU 1 PHY A direct-sequence transmission — synchronisation, a start delimiter, a header, then the data.
• HR/DSSS PPDU (short preamble) ? HR/DSSS short preamble PPDU 1 PHY A direct-sequence transmission with the shortened synchronisation field and a header sent at twice the rate.
• HT Length ? HT-SIG › HT-SIG1 HT mixed-format PPDU 1 PHY PSDU length in octets, up to 65535.
• HT mixed-format PPDU ? HT mixed-format PPDU 1 PHY A high-throughput transmission that a legacy station can still recognise and defer to.
• HT-LTF ? HT mixed-format PPDU HT mixed-format PPDU 1 PHY Long training symbols, one per space-time stream, four microseconds each.
• HT-SIG ? HT mixed-format PPDU HT mixed-format PPDU 1 PHY Two OFDM symbols carrying everything needed to decode the HT portion.
• HT-SIG1 ? HT-SIG HT mixed-format PPDU 1 PHY The first HT-SIG symbol — rate, width and length.
• HT-SIG2 ? HT-SIG HT mixed-format PPDU 1 PHY The second HT-SIG symbol — coding, guard interval and a CRC.
• HT-STF ? HT mixed-format PPDU HT mixed-format PPDU 1 PHY Short training for the HT portion, resetting gain control after the signalling fields.
• Legacy Long Training Field ? non-HT PPDU non-HT OFDM PPDU 9 PHYs A guard interval followed by two identical long symbols, used for fine frequency correction and to estimate the channel on every subcarrier.
• Legacy Short Training Field ? non-HT PPDU non-HT OFDM PPDU 9 PHYs Ten repetitions of a short symbol. The receiver uses them to detect that a signal is present, set its gain, and make a coarse estimate of frequency offset and symbol timing.
• LENGTH ? HR/DSSS PPDU (long preamble) HR/DSSS long preamble PPDU 2 PHYs The time the PSDU will take, in microseconds — not its size in octets.
• LENGTH ? SIGNAL field non-HT OFDM PPDU 9 PHYs The number of octets in the PSDU, from 1 to 4095.
• MCS ? HE-SIG-A › HE-SIG-A1 HE SU PPDU 1 PHY Modulation and coding scheme for the data field.
• MCS ? HT-SIG › HT-SIG1 HT mixed-format PPDU 1 PHY Modulation and coding index, 0 to 76.
• non-HT PPDU ? non-HT OFDM PPDU 1 PHY A complete non-HT transmission: the preamble the receiver uses to find and synchronise to the signal, a SIGNAL field describing how to demodulate what follows, and the DATA field carrying the frame itself.
• NSTS / Partial AID ? VHT-SIG-A › VHT-SIG-A1 VHT PPDU 1 PHY Stream counts in a multi-user frame; a shortened association identifier in a single-user one.
• NSTS and Midamble Periodicity ? HE-SIG-A › HE-SIG-A1 HE SU PPDU 1 PHY Number of space-time streams, and midamble spacing where used.
• Packet Extension ? EHT MU PPDU EHT MU PPDU 1 PHY Airtime after the data that carries nothing, giving the receiver time to finish processing.
• Packet Extension ? HE ER SU PPDU HE ER SU PPDU 1 PHY Processing time after the data.
• Packet Extension ? HE MU PPDU HE MU PPDU 1 PHY Processing time after the data.
• Packet Extension ? HE SU PPDU HE SU PPDU 1 PHY Extra time at the end of the transmission, giving the receiver room to finish processing.
• Packet Extension ? HE TB PPDU HE TB PPDU 1 PHY Processing time after the data.
• Pad Bits ? DATA field non-HT OFDM PPDU 2 PHYs Enough zero bits to fill out the final OFDM symbol.
• PHY Version Identifier ? U-SIG EHT MU PPDU 1 PHY Which generation this transmission belongs to. Zero for 802.11be.
• PLCP Header ? HR/DSSS PPDU (short preamble) HR/DSSS short preamble PPDU 1 PHY The same forty-eight header bits as the long preamble, sent at 2 Mb/s rather than 1.
• PSDU ? HR/DSSS PPDU (short preamble) HR/DSSS short preamble PPDU 1 PHY The frame itself, at the rate named in the SIGNAL field.
• PSDU ? DATA field ERP-OFDM PPDU 1 PHY The frame itself.
• RATE ? SIGNAL field non-HT OFDM PPDU 9 PHYs Selects the modulation and coding rate used for the DATA field.
• Repeated L-SIG ? HE SU PPDU HE SU PPDU 5 PHYs An exact repeat of the L-SIG symbol.
• SERVICE ? HR/DSSS PPDU (long preamble) HR/DSSS long preamble PPDU 2 PHYs Modulation and clock-locking flags, plus a length extension bit.
• SERVICE field ? DATA field non-HT OFDM PPDU 2 PHYs Synchronises the receiver's descrambler and reserves the remaining bits.
• SFD ? HR/DSSS PPDU (long preamble) HR/DSSS long preamble PPDU 1 PHY Start frame delimiter — a fixed 16-bit pattern marking the end of synchronisation and the start of the header.
• SFD ? HR/DSSS PPDU (short preamble) HR/DSSS short preamble PPDU 1 PHY The start frame delimiter, sent in reverse bit order from the long preamble's.
• Short GI ? HT-SIG › HT-SIG2 HT mixed-format PPDU 1 PHY A 400 ns guard interval instead of 800 ns.
• Short GI ? VHT-SIG-A › VHT-SIG-A2 VHT PPDU 1 PHY A 400 ns guard interval instead of 800 ns.
• SIGNAL ? HR/DSSS PPDU (long preamble) HR/DSSS long preamble PPDU 2 PHYs The data rate for the PSDU, in units of 100 kb/s.
• Signal Extension ? ERP-OFDM PPDU ERP-OFDM PPDU 1 PHY Six microseconds of nothing after the data, so that receivers in the same band have time to finish.
• SIGNAL field ? non-HT PPDU non-HT OFDM PPDU 9 PHYs One OFDM symbol, always sent at 6 Mb/s with BPSK and rate-1/2 coding so that any receiver can read it. Tells the receiver the rate and length of what follows.
• Spatial Reuse ? HE-SIG-A › HE-SIG-A1 HE SU PPDU 1 PHY Whether and how neighbouring stations may transmit concurrently.
• STBC ? HE-SIG-A › HE-SIG-A2 HE SU PPDU 1 PHY Space-time block coding in use.
• STBC ? HT-SIG › HT-SIG2 HT mixed-format PPDU 1 PHY Difference between space-time streams and spatial streams.
• STBC ? VHT-SIG-A › VHT-SIG-A1 VHT PPDU 1 PHY Space-time block coding in use.
• SYNC ? HR/DSSS PPDU (long preamble) HR/DSSS long preamble PPDU 1 PHY 128 scrambled one bits, giving the receiver time to acquire the signal and settle its gain and timing.
• SYNC ? HR/DSSS PPDU (short preamble) HR/DSSS short preamble PPDU 1 PHY Fifty-six scrambled zero bits at 1 Mb/s, for the receiver to lock on to.
• Tail ? DATA field non-HT OFDM PPDU 2 PHYs Six bits returning the convolutional encoder to the zero state at the end of the frame.
• TXOP ? U-SIG EHT MU PPDU 1 PHY How long the transmit opportunity lasts, readable without decoding any MAC header.
• TXOP ? HE-SIG-A › HE-SIG-A2 HE SU PPDU 1 PHY Duration information for stations that can decode HE-SIG-A.
• U-SIG ? EHT MU PPDU EHT MU PPDU 1 PHY Two OFDM symbols carrying a version number and the parameters every generation needs, in a layout later amendments must preserve.
• UL/DL ? HE-SIG-A › HE-SIG-A1 HE SU PPDU 1 PHY Direction of the transmission.
• Version dependent fields ? U-SIG EHT MU PPDU 1 PHY The half of U-SIG that each amendment defines for itself — for 802.11be, the PPDU type, the EHT-SIG size and coding, and a CRC.
• VHT PPDU ? VHT PPDU 1 PHY A very-high-throughput transmission.
• VHT-LTF ? VHT PPDU VHT PPDU 1 PHY Long training symbols, four microseconds each, one per space-time stream across all users.
• VHT-MCS ? VHT-SIG-A › VHT-SIG-A2 VHT PPDU 1 PHY Modulation and coding index, 0 to 9.
• VHT-SIG-A ? VHT PPDU VHT PPDU 1 PHY Two OFDM symbols of common signalling, sent before the training.
• VHT-SIG-A1 ? VHT-SIG-A VHT PPDU 1 PHY Bandwidth, group and stream configuration.
• VHT-SIG-A2 ? VHT-SIG-A VHT PPDU 1 PHY Guard interval, coding, rate and a CRC.
• VHT-SIG-B ? VHT PPDU VHT PPDU 1 PHY Per-user signalling, sent after the training rather than before it.
• VHT-STF ? VHT PPDU VHT PPDU 1 PHY Short training for the VHT portion.

MAC 114

• +HTC/Order ? Frame Control QoS Data frame 11 PHYs Indicates an HT Control field is present. Its meaning has changed across amendments, which is why it carries two names.
• A-MPDU ? A-MPDU 7 PHYs An aggregate of MPDU subframes sharing one preamble.
• A-MPDU Parameters ? HT Capabilities HT Capabilities element 10 PHYs The largest aggregate this station can receive, and the spacing it needs between subframes.
• A-MPDU subframe ? A-MPDU A-MPDU 7 PHYs One delimiter, one MPDU, and padding to a four-octet boundary.
• A-MSDU Present ? QoS Control QoS Data frame 11 PHYs Set when the frame body holds several aggregated MSDUs rather than one.
• Ack Policy ? QoS Control QoS Data frame 11 PHYs How, or whether, this frame should be acknowledged.
• Address 1 — Receiver ? QoS Data MPDU QoS Data frame 11 PHYs The receiver address: the station this frame is being transmitted to over the air right now.
• Address 2 — Transmitter ? QoS Data MPDU QoS Data frame 11 PHYs The transmitter address — the station physically sending this frame.
• Address 3 ? QoS Data MPDU QoS Data frame 11 PHYs The address whose meaning depends entirely on To DS and From DS — the original source, the final destination, or the BSSID.
• Address 4 ? QoS Data MPDU QoS Data frame 11 PHYs The original sender, in a frame travelling between two access points.
• AID ? Frame Body Association Response frame 10 PHYs The identifier this station will be known by within the BSS.
• AID12 ? User Info Trigger frame 10 PHYs The low twelve bits of the association identifier this instruction is for.
• AKM Suite Count ? RSN RSN element 10 PHYs How many authentication and key management suites follow.
• AKM Suite List ? RSN RSN element 10 PHYs How a station proves it may join and how the keys get derived.
• ASEL Capabilities ? HT Capabilities HT Capabilities element 10 PHYs Antenna selection support.
• Association Request MPDU ? Association Request frame 10 PHYs A management frame requesting membership of a BSS.
• Association Response MPDU ? Association Response frame 10 PHYs A management frame accepting or refusing an association request.
• BA Ack Policy ? BA Control Compressed Block Ack 11 PHYs Whether this Block Ack itself needs acknowledging.
• BA Control ? Compressed Block Ack MPDU Compressed Block Ack 11 PHYs Which variant of Block Ack this is, and which traffic class it covers.
• Beacon Interval ? Frame Body Beacon frame 10 PHYs How often a beacon is sent, in time units of 1024 microseconds.
• Beacon MPDU ? Beacon frame 10 PHYs A management frame advertising a BSS and its parameters.
• Bitmap Control ? TIM TIM element 10 PHYs A traffic indicator for group-addressed frames, plus an offset into the bitmap that follows.
• Block Ack Bitmap ? Compressed Block Ack MPDU Compressed Block Ack 11 PHYs Sixty-four bits, one per frame, counting up from the starting sequence number. Set means received.
• Block Ack Starting Sequence Control ? Compressed Block Ack MPDU Compressed Block Ack 11 PHYs The sequence number the bitmap starts counting from.
• Capability Information ? Frame Body Beacon frame 10 PHYs Sixteen bits advertising what the BSS supports and requires.
• Channel constraint ? Country Country element 10 PHYs First channel number, how many channels follow it, and the maximum transmit power permitted across them.
• Common Info ? Trigger MPDU Trigger frame 10 PHYs Everything that applies to all of the triggered stations at once: what kind of response is wanted, how long it must be, and how it must be modulated.
• Compressed Bitmap ? BA Control Compressed Block Ack 11 PHYs Set for the compressed variant — one bit per MPDU rather than one per fragment.
• Context-dependent octet ? QoS Control QoS Data frame 11 PHYs TXOP Limit or AP PS Buffer State when sent by an AP; TXOP Duration Requested or Queue Size when sent by a client.
• Country ? Country element 10 PHYs The regulatory domain the AP is operating under.
• Country String ? Country Country element 10 PHYs Two characters of ISO country code, then one saying whether the limits that follow are for indoor use, outdoor use, or both.
• CRC ? A-MPDU subframe › MPDU Delimiter A-MPDU 7 PHYs An eight-bit check over the preceding two octets.
• Current Channel ? DS Parameter Set DS Parameter Set element 10 PHYs The channel number the BSS is operating on.
• Delimiter Signature ? A-MPDU subframe › MPDU Delimiter A-MPDU 7 PHYs A fixed byte, 0x4E, that a receiver scans for when hunting for the next subframe.
• DS Parameter Set ? DS Parameter Set element 10 PHYs The current operating channel.
• DTIM Count ? TIM TIM element 10 PHYs How many beacons remain until the next DTIM.
• DTIM Period ? TIM TIM element 10 PHYs How many beacon intervals lie between DTIMs.
• Duration/ID ? QoS Data MPDU QoS Data frame 11 PHYs Usually the time in microseconds that other stations should treat the medium as busy. In some control frames it carries an association identifier instead.
• Element ID ? SSID SSID element 10 PHYs Identifies which element this is. Zero here.
• EOF ? A-MPDU subframe › MPDU Delimiter A-MPDU 7 PHYs Marks a delimiter that carries no MPDU — padding to the end.
• EOSP ? QoS Control QoS Data frame 11 PHYs End of service period.
• ESS ? Frame Body › Capability Information Beacon frame 10 PHYs Set by an access point.
• Extended Supported Rates ? Extended Supported Rates element 10 PHYs Additional supported rates, continuing from the Supported Rates element.
• Fragment Number ? Sequence Control QoS Data frame 11 PHYs Which fragment of the current MSDU this is. Zero if unfragmented.
• Frame Body ? Association Request MPDU Association Request frame 10 PHYs Two fixed fields, then the element list.
• Frame Body ? Association Response MPDU Association Response frame 10 PHYs Three fixed fields, then the element list.
• Frame Body ? Beacon MPDU Beacon frame 10 PHYs Three fixed fields, then the element list.
• Frame Body ? Probe Request MPDU Probe Request frame 10 PHYs Elements only. There are no fixed fields in this frame.
• Frame Body ? Probe Response MPDU Probe Response frame 10 PHYs Three fixed fields, then the element list.
• Frame Check Sequence ? QoS Data MPDU QoS Data frame 11 PHYs A 32-bit cyclic redundancy check over the header and body.
• Frame Control ? QoS Data MPDU QoS Data frame 11 PHYs Identifies what kind of frame this is and carries the flags that change how the rest of the header is read.
• From DS ? Frame Control QoS Data frame 11 PHYs Set when the frame is coming from the distribution system.
• Further subframes ? A-MPDU A-MPDU 7 PHYs The remaining subframes, each structured exactly like the one above.
• Further User Info fields ? Trigger MPDU Trigger frame 10 PHYs One more per station being triggered, each structured exactly like the one above.
• Group Data Cipher Suite ? RSN RSN element 10 PHYs The cipher protecting broadcast and multicast traffic: three octets of organisation identifier, then one selecting the suite.
• HT Capabilities ? HT Capabilities element 10 PHYs What an 802.11n-capable station or AP supports.
• HT Capabilities Information ? HT Capabilities HT Capabilities element 10 PHYs Sixteen bits of radio capability.
• HT Extended Capabilities ? HT Capabilities HT Capabilities element 10 PHYs Support for transitioning between PCO channel widths, and for the MCS feedback the beamforming fields below rely on.
• IBSS ? Frame Body › Capability Information Beacon frame 10 PHYs Set by a station in an independent BSS. Mutually exclusive with ESS — both set is malformed.
• Length ? SSID SSID element 10 PHYs The length of everything after this octet, in octets.
• Listen Interval ? Frame Body Association Request frame 10 PHYs How many beacon intervals the station may sleep through before it wakes to check for buffered traffic.
• Maximum A-MSDU Length ? HT Capabilities Information HT Capabilities element 10 PHYs Clear for 3839 octets, set for 7935.
• MFPC ? RSN Capabilities RSN element 10 PHYs Management frame protection CAPABLE.
• MFPR ? RSN Capabilities RSN element 10 PHYs Management frame protection REQUIRED — a station that cannot do it is refused.
• More Data ? Frame Control QoS Data frame 11 PHYs Set by an AP to tell a dozing station that more frames are buffered for it.
• More Fragments ? Frame Control QoS Data frame 11 PHYs Set when further fragments of this MSDU follow.
• MPDU Delimiter ? A-MPDU subframe A-MPDU 7 PHYs Four octets marking the start of a subframe and giving its length.
• MPDU Length ? A-MPDU subframe › MPDU Delimiter A-MPDU 7 PHYs Length of the MPDU that follows, in octets.
• Multi-TID ? BA Control Compressed Block Ack 11 PHYs Set when one frame acknowledges several traffic classes at once.
• Padding ? A-MPDU subframe A-MPDU 7 PHYs Zero to three octets, rounding the subframe to a four-octet boundary.
• Padding ? Trigger MPDU Trigger frame 10 PHYs Optional padding, so a station has time to read its own instructions before it must start transmitting.
• Pairwise Cipher Suite Count ? RSN RSN element 10 PHYs How many pairwise cipher suites follow.
• Pairwise Cipher Suite List ? RSN RSN element 10 PHYs The ciphers offered for unicast traffic, four octets each.
• Partial Virtual Bitmap ? TIM TIM element 10 PHYs One bit per association identifier, set when that station has traffic buffered.
• Power Management ? Frame Control QoS Data frame 11 PHYs Indicates the sending station's power save state after this exchange completes.
• Privacy ? Frame Body › Capability Information Beacon frame 10 PHYs Set when data frames in this BSS are encrypted.
• Probe Request MPDU ? Probe Request frame 10 PHYs A management frame soliciting a response from access points.
• Probe Response MPDU ? Probe Response frame 10 PHYs A management frame answering a Probe Request.
• Protected Frame ? Frame Control QoS Data frame 11 PHYs Set when the frame body has been encrypted.
• Protocol Version ? Frame Control QoS Data frame 11 PHYs Always 0 for every version of the standard published so far.
• QoS ? Frame Body › Capability Information Beacon frame 10 PHYs Whether the BSS supports the QoS facility, and therefore whether QoS Data frames will appear.
• QoS Control ? QoS Data MPDU QoS Data frame 11 PHYs Present only in QoS subtypes. Carries the traffic class and how this frame should be acknowledged.
• QoS Data MPDU ? QoS Data frame 11 PHYs A complete MAC frame: header, body, and frame check sequence.
• Rates ? Extended Supported Rates Extended Supported Rates element 10 PHYs One octet per rate, in half-megabit units, with the top bit marking a rate as part of the basic set.
• Rates ? Supported Rates Supported Rates element 10 PHYs One octet per rate. Top bit set means basic; the low seven bits give the rate in units of 500 kb/s.
• Retry ? Frame Control QoS Data frame 11 PHYs Set when this frame is a retransmission.
• RSN ? RSN element 10 PHYs The robust security network element — the negotiated terms of protection for this BSS.
• RSN Capabilities ? RSN RSN element 10 PHYs What this station or AP supports about management frame protection.
• RU Allocation ? User Info Trigger frame 10 PHYs Which resource unit — which block of subcarriers — this station must transmit on.
• Sequence Control ? QoS Data MPDU QoS Data frame 11 PHYs Identifies this frame within a sequence, and its fragment position.
• Sequence Number ? Sequence Control QoS Data frame 11 PHYs Increments per MSDU, wrapping at 4095. All fragments of one MSDU share it.
• Short GI for 20 MHz ? HT Capabilities Information HT Capabilities element 10 PHYs A 400 ns guard interval instead of 800 ns.
• Short Preamble ? Frame Body › Capability Information Beacon frame 10 PHYs Whether the short DSSS preamble is allowed — 96 microseconds instead of 192.
• Short Slot Time ? Frame Body › Capability Information Beacon frame 10 PHYs A 9 µs slot instead of 20 µs.
• SSID ? SSID element 10 PHYs The service set identifier — what the network calls itself.
• SSID ? SSID SSID element 10 PHYs Zero to 32 octets of network name.
• Starting Sequence Number ? Block Ack Starting Sequence Control Compressed Block Ack 11 PHYs The sequence number corresponding to bit zero of the bitmap.
• Status Code ? Frame Body Association Response frame 10 PHYs Zero for success; anything else is the reason for refusal.
• Subtype ? Frame Control QoS Data frame 11 PHYs The specific frame within its type. Read together with Type — a subtype value means nothing on its own.
• Supported Channel Width Set ? HT Capabilities Information HT Capabilities element 10 PHYs Clear for 20 MHz only; set for 20 and 40 MHz.
• Supported MCS Set ? HT Capabilities HT Capabilities element 10 PHYs A bitmap of which of the 77 modulation and coding schemes this station can receive, plus its highest supported data rate.
• Supported Rates ? Supported Rates element 10 PHYs Up to eight rates, one octet each.
• TID ? QoS Control QoS Data frame 11 PHYs Traffic identifier — which access category this frame belongs to, and so how long the sender waited before transmitting it.
• TID_INFO ? BA Control Compressed Block Ack 11 PHYs Which traffic class this Block Ack covers. Block Ack agreements are per-TID, so voice and background traffic are acknowledged separately.
• TIM ? TIM element 10 PHYs The traffic indication map.
• Timestamp ? Frame Body Beacon frame 10 PHYs The AP's microsecond clock, used by every station to stay synchronised with it.
• To DS ? Frame Control QoS Data frame 11 PHYs Set when the frame is destined for the distribution system.
• Transmit Beamforming Capabilities ? HT Capabilities HT Capabilities element 10 PHYs Whether and how this station can participate in beamforming, as sounder or as responder.
• Trigger MPDU ? Trigger frame 10 PHYs A control frame soliciting a simultaneous uplink transmission from one or more stations.
• Trigger Type ? Common Info Trigger frame 10 PHYs What the triggered stations are being asked for.
• Type ? Frame Control QoS Data frame 11 PHYs The broad class of frame.
• UL Length ? Common Info Trigger frame 10 PHYs How long the solicited transmission must be, expressed as the LENGTH field the responding PPDU will carry.
• User Info ? Trigger MPDU Trigger frame 10 PHYs One station's instructions: who it is, which subcarriers it gets, and at what rate and power it must transmit.
• Version ? RSN RSN element 10 PHYs Always 1. No version 2 has ever been defined.

Encryption 28

• CCMP Header ? Protected Frame Body CCMP-128 protection 11 PHYs Carries the packet number used to build the nonce, and identifies which key was used.
• Descriptor Type ? EAPOL-Key EAPOL-Key descriptor 11 PHYs Which key descriptor this is. 2 for the RSN descriptor.
• EAPOL Key IV ? EAPOL-Key EAPOL-Key descriptor 11 PHYs An initialisation vector for the older RC4 key wrap.
• EAPOL PDU ? EAPOL header 11 PHYs An EAPOL frame — a four-octet header and the packet body it describes.
• EAPOL-Key ? EAPOL-Key descriptor 11 PHYs The key descriptor carried by every message of a four-way handshake.
• Encrypted Key Data ? Key Information EAPOL-Key descriptor 11 PHYs The Key Data field is wrapped rather than plaintext.
• ExtIV ? CCMP Header › Key ID octet CCMP-128 protection 11 PHYs Always 1 for CCMP, indicating the extended IV octets are present.
• Install ? Key Information EAPOL-Key descriptor 11 PHYs Tells the receiver to install the derived pairwise key for use.
• Key Ack ? Key Information EAPOL-Key descriptor 11 PHYs A response is expected to this message.
• Key Data ? EAPOL-Key EAPOL-Key descriptor 11 PHYs The RSN element in messages 2 and 3, plus the wrapped group key in message 3. Empty in messages 1 and 4.
• Key Data Length ? EAPOL-Key EAPOL-Key descriptor 11 PHYs Octets of key data following. Zero in message 4.
• Key Descriptor Version ? Key Information EAPOL-Key descriptor 11 PHYs Which algorithms compute the MIC and wrap the key data.
• Key ID octet ? CCMP Header CCMP-128 protection 11 PHYs Identifies the key and marks the extended IV as present.
• Key Information ? EAPOL-Key EAPOL-Key descriptor 11 PHYs The bits that say which message of the handshake this is and what the receiver should do with it.
• Key Length ? EAPOL-Key EAPOL-Key descriptor 11 PHYs Length of the pairwise key to be installed, in octets. 16 for CCMP-128.
• Key MIC ? Key Information EAPOL-Key descriptor 11 PHYs The MIC field further down is populated.
• Key MIC ? EAPOL-Key EAPOL-Key descriptor 11 PHYs Proof that the sender derived the same pairwise key, computed over this whole EAPOL frame with this field zeroed.
• Key Nonce ? EAPOL-Key EAPOL-Key descriptor 11 PHYs A number used once. The AP's in message 1, the station's in message 2.
• Key Replay Counter ? EAPOL-Key EAPOL-Key descriptor 11 PHYs Increments per exchange, and a reply must carry the counter of the message it answers.
• Key RSC ? EAPOL-Key EAPOL-Key descriptor 11 PHYs The starting packet number for the group key being installed.
• Key Type ? Key Information EAPOL-Key descriptor 11 PHYs Set for a pairwise key, clear for a group key.
• KeyID ? CCMP Header › Key ID octet CCMP-128 protection 11 PHYs Which of the four key slots was used. Non-zero values indicate a group key.
• MIC ? Protected Frame Body CCMP-128 protection 11 PHYs Message integrity code covering the payload and parts of the header.
• Packet Body Length ? EAPOL PDU EAPOL header 11 PHYs Octets of packet body following this field.
• Packet Type ? EAPOL PDU EAPOL header 11 PHYs What kind of EAPOL packet this is.
• Protected Frame Body ? CCMP-128 protection 11 PHYs An encrypted frame body — cipher header, ciphertext, and message integrity code.
• Protocol Version ? EAPOL PDU EAPOL header 11 PHYs Which revision of 802.1X the sender implements.
• Secure ? Key Information EAPOL-Key descriptor 11 PHYs Both sides now hold the keys; protection is established.

LLC 6

• Control ? LPDU LLC with SNAP header 11 PHYs Always 0x03, meaning unnumbered information — no sequencing, no acknowledgement at this layer.
• DSAP ? LPDU LLC with SNAP header 11 PHYs Destination service access point. Always 0xAA when SNAP follows.
• EtherType ? LPDU LLC with SNAP header 11 PHYs What protocol the payload is.
• LPDU ? LLC with SNAP header 11 PHYs The LLC protocol data unit — an LLC header, a SNAP extension, and the payload they describe.
• OUI ? LPDU LLC with SNAP header 11 PHYs Organizationally unique identifier. All zeroes means the next field is an EtherType.
• SSAP ? LPDU LLC with SNAP header 11 PHYs Source service access point. Always 0xAA when SNAP follows.

Network 39

• ARP Packet ? ARP packet 11 PHYs An address resolution request or reply, sized for Ethernet hardware addresses and IPv4 protocol addresses.
• Checksum ? ICMP Message ICMP echo message 11 PHYs Ones-complement checksum over the whole ICMP message, header and data.
• Code ? ICMP Message ICMP echo message 11 PHYs Narrows the type. Zero for echo; for Destination Unreachable it says whether the network, host, protocol or port was the problem.
• Destination Address ? IPv4 Datagram IPv4 datagram 11 PHYs Where it is going.
• Destination Address ? IPv6 Packet IPv6 packet 11 PHYs Where it is going.
• DSCP ? IPv4 Datagram IPv4 datagram 11 PHYs Differentiated services code point — the traffic class.
• ECN ? IPv4 Datagram IPv4 datagram 11 PHYs Explicit congestion notification.
• Flags ? IPv4 Datagram IPv4 datagram 11 PHYs Reserved, Don't Fragment, More Fragments.
• Flow Label ? IPv6 Packet IPv6 packet 11 PHYs Labels a sequence of packets the sender wants handled as one flow.
• Fragment Offset ? IPv4 Datagram IPv4 datagram 11 PHYs Where this fragment sits in the original datagram, in 8-octet units.
• Hardware Address Length ? ARP Packet ARP packet 11 PHYs Octets per hardware address. Six for Ethernet.
• Hardware Type ? ARP Packet ARP packet 11 PHYs What kind of hardware address is being resolved.
• Header Checksum ? IPv4 Datagram IPv4 datagram 11 PHYs Ones-complement checksum over the header only, not the payload.
• Hop Limit ? IPv6 Packet IPv6 packet 11 PHYs Decremented by each router; the packet dies at zero.
• ICMP Message ? ICMP echo message 11 PHYs An ICMP echo request or reply — the thing ping sends.
• Identification ? IPv4 Datagram IPv4 datagram 11 PHYs Groups the fragments of one original datagram.
• Identifier ? ICMP Message ICMP echo message 11 PHYs Matches replies to requests. Echo messages only.
• IHL ? IPv4 Datagram IPv4 datagram 11 PHYs Header length in 32-bit words. Five means a twenty-octet header with no options.
• IPv4 Datagram ? IPv4 datagram 11 PHYs An IPv4 packet — header plus payload.
• IPv6 Packet ? IPv6 packet 11 PHYs An IPv6 packet — a fixed header plus its payload.
• Next Header ? IPv6 Packet IPv6 packet 11 PHYs What follows this header — a transport protocol, or an extension header.
• Operation ? ARP Packet ARP packet 11 PHYs Whether this is the question or the answer.
• Payload Length ? IPv6 Packet IPv6 packet 11 PHYs Octets after this forty-octet header, extension headers included.
• Protocol ? IPv4 Datagram IPv4 datagram 11 PHYs What the payload is.
• Protocol Address Length ? ARP Packet ARP packet 11 PHYs Octets per protocol address. Four for IPv4.
• Protocol Type ? ARP Packet ARP packet 11 PHYs What kind of protocol address is being resolved.
• Sender Hardware Address ? ARP Packet ARP packet 11 PHYs The sender's MAC address.
• Sender Protocol Address ? ARP Packet ARP packet 11 PHYs The sender's IPv4 address.
• Sequence Number ? ICMP Message ICMP echo message 11 PHYs Increments per request. Echo messages only.
• Source Address ? IPv4 Datagram IPv4 datagram 11 PHYs Where the datagram came from.
• Source Address ? IPv6 Packet IPv6 packet 11 PHYs Where the packet came from.
• Target Hardware Address ? ARP Packet ARP packet 11 PHYs The address being asked for. All zeroes in a request, because not knowing it is the reason for sending.
• Target Protocol Address ? ARP Packet ARP packet 11 PHYs The IPv4 address whose hardware address is wanted.
• Total Length ? IPv4 Datagram IPv4 datagram 11 PHYs Header plus payload, in octets.
• Traffic Class ? IPv6 Packet IPv6 packet 11 PHYs Six bits of differentiated services code point and two of explicit congestion notification — the same split as IPv4's DSCP and ECN.
• TTL ? IPv4 Datagram IPv4 datagram 11 PHYs Hop limit. Decremented by each router; the packet dies at zero.
• Type ? ICMP Message ICMP echo message 11 PHYs What kind of message this is.
• Version ? IPv4 Datagram IPv4 datagram 11 PHYs Always 4 here.
• Version ? IPv6 Packet IPv6 packet 11 PHYs Always 6 here.

Transport 15

• Acknowledgment Number ? TCP Segment TCP segment 11 PHYs The next sequence number the sender of this segment expects.
• Checksum ? TCP Segment TCP segment 11 PHYs Covers the header, the data, and a pseudo-header built from the IP addresses above.
• Checksum ? UDP Datagram UDP datagram 11 PHYs Covers the header, the data, and a pseudo-header built from the addresses one lane up. Zero means not computed.
• Data Offset ? TCP Segment TCP segment 11 PHYs Header length in 32-bit words. Five means no options.
• Destination Port ? TCP Segment TCP segment 11 PHYs The receiving endpoint's port.
• Destination Port ? UDP Datagram UDP datagram 11 PHYs The receiving endpoint's port.
• Flags ? TCP Segment TCP segment 11 PHYs The eight control bits.
• Length ? UDP Datagram UDP datagram 11 PHYs Header plus data, in octets. Never below 8.
• Sequence Number ? TCP Segment TCP segment 11 PHYs Position of the first data octet in this segment within the stream.
• Source Port ? TCP Segment TCP segment 11 PHYs The sending endpoint's port.
• Source Port ? UDP Datagram UDP datagram 11 PHYs The sending endpoint's port. May be zero when no reply is expected.
• TCP Segment ? TCP segment 11 PHYs A TCP segment — header plus application data.
• UDP Datagram ? UDP datagram 11 PHYs A UDP datagram — an eight-octet header plus application data.
• Urgent Pointer ? TCP Segment TCP segment 11 PHYs Offset to urgent data, when URG is set.
• Window ? TCP Segment TCP segment 11 PHYs How many more octets the sender of this segment is willing to accept.