3617008
| Question | Answer |
| Two sublayers of Data-Link Layer | Upper - Logical Link Control (LLC) Bottom - Media Access Control (MAC) |
| MSDU | MAC Service Data Unit From Layer 3 to become MSDU |
| MSDU contains what? | Data payload containing IP packet and LLC data. |
| When was A-MSDU introduced? | 802.11n |
| What is an MPDU | An encapsulated MSDU to be sent to MAC sublayer |
| Basic components of an MPDU | MAC header Frame body FCS |
| Sublayers of Physical Layer | Upper - Physical Layer Convergence Procedure (PLCP) Lower - Physical Medium Dependent (PMD) |
| What is a PLCP | View of the MPDU from the physical layer |
| What is the PPDU? | PLCP Protocol Data Unit. Created from PSDU. Adds preamble and PHY header to PSDU. |
| Four address fields in 802.11 frames | Source Address - original sender Destination Address - final destination Transmitter Address - MAC of radio Receiver Address - Receiving radio BSSID - Identifies MAC of AP radio |
| Three major frame types | Management Control Data |
| MMPDU | Management MAC Protocol Data Unit Management frame. |
| 14 management frame types | Association request/response Reassociation request/response Probe request/response Beacon Announcement traffic indication message (ATM) Disassocciation Authentication Deauthentication Action Action No ACK Timing advertisement |
| What is a control frame | Assists delivery of data frames on a basic rate |
| Nine control frame subtypes | Power Save Poll (PS-Poll) Request to Send (RTS) Clear to Send (CTS) Acknowledgement (ACK) Content Free-End (CF-End) [PCF only] CF-End + CF-ACK [PCF only] Block ACK Request (BlockAckReq) [HCF only] Block ACK (BlockACK) [HCF only] Control wrapper |
| 15 Data frame subtypes | Data Null function Data + CF-ACK [PCF only] Data + CF-Poll [PCF only] Data + CF-ACK + CF-Poll [PCF only] CF-ACK (no data) [PCF only] CF-Poll (no data) [PCF only] CF-ACK + CF-Poll (no data) [PCF only] QoS Data [HCF] QoS Null [HCF] QoS Data + CF-ACK [HCF] QoS Data + CF-Poll [HCF] QoS Data + CF-ACK + CF-Poll [HCF] QoS CF-Poll [HCF] QoS CF-ACK + CF-Poll [HCF] |
| What's in a beacon? | Time stamp Spread spectrum Channel info Data rates Service set capabilities TIM QoS RSN Vendor info |
| Passive scanning | STA listens for beacons |
| Active scanning | STA transmits probe request |
| State Machine | Unauthenticated, unassociated Authenticated, unassociated Authenticated, associated |
| Reassociation steps | 1. STA sends reassociation request to new AP 2. New AP ACKs STA 3. New AP communicates w/ original AP to notifify roaming. 4. Original AP forwards buffered data to new AP. 5. AP sends reassociation response frame to STA 6. Client sends ACK to new AP. |
| Disassociation and Deauthentication | Is a notification, not a request. |
| RTS/CTS | Protection mechanism for 802.11g/b and legacy 802.11 stations to coexist within same BSS. |
| CTS-to-Self | Protection mechanism for mixed-mode environments |
| Active Mode | Continuous aware mode. 0 value in power management field indicates Active Mode. |
| Power Save Mode | STA shuts down some transceivers to conserve power. Power Management bit set to 1. AP buffers frames for STA. |
| TIM | Traffic Indication Map. Association Identifier (AID) keeps track of STA. AID indicates when STA has buffered data. Stored in beacon frame. |
| Two States in Power Save Mode | Awake Doze |
| DTIM | Delivery Traffic Indication Message Used with multicast/broadcast traffic. |
| ATIM | Announcement Traffic Indication Message. Notifies STA if buffered data needs to be delivered. Used in ad hoc mode. |
| WMM Power Save / U-APSD | Unscheduled Automatic Power Save Delivery |
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