Disassociation and deauthentication (disassociation and deauthentication) IBSS data pending indication notification information (ATIM) frame Quipment offer you the best. FrameMac Light High Speed Steel Frame Structure Housing Production E. Database of IS steel shapes is provided in numerous options.Precision Steel Roll-forming Technology Howick Ltd. It is used to analyzing steel structures, Graphical modeling is possible through text input also.Data link layerThe data link layer is divided into LLC(Logical Link Control, logical link control) sublayer and MAC(Media Access Control, media access control) sub-layer. This chapter mainly introduces how the data link layer and physical layer assemble and transmit data packets. It is gradually transmitted from the upper layer of the OSI model to the physical layer, and finally the data is transferred from the physical layer to other devices, and each layer will add the header information of this layer to the data. Supplement 802.11 and Ethernet frame conversionFirst of all, we need to know that the data is transmitted in the computer.
Frame Structural Program Mac Light HighIn the initial specified specifications, 802.11 frames can transmit up to 2034 bytes of data. Responsible for transmitting upper layer data (payload) between workstations. 802.11 MAC frame includes Layer 2 header, frame body and frame tail。The MAC frame header will be described in detail later in this chapter.Framebody is the data transmitted from the network layer, namely MSDU, also known as data bit. Music editing software for mac os xThe frames used by 802.11 are not large. 802.11 usually does not fill the frame to the minimum length. The upper layer protocol is marked with an additional header type bit, and at the same time it is used as the beginning of the data carried by 802.11.2. There is no upper layer protocol mark in the 802.11 frame. Preventing fragmentation must be handled at the protocol layer.The difference between 802.11 and other link layer protocols:1. And do not respond.At this time, the data frame is ready for downward transmission. If FCS is wrong, discard it immediately. The underlying algorithms of CRC and FCS are the same.The FCS calculation range covers all bits in the MAC header and the frame body. The composition and related meaning of the frame header will be introduced below.The frame header, which is the MAC header, has a maximum of 30 bytes (the IEEE 802.11n frame MAC header has a maximum of 36 bytes). 802.11 frame format Frame structureAs we mentioned earlier, 802.11 frames are composed of three parts: frame header, frame body and frame tail. After the PPDU is created, the PMD sublayer modulates the PPDU into data bits and then starts transmission. The preamble part is used to synchronize 802.11 wireless transmission and reception RF interface cards. The PLCP sublayer turns the data frame from the data link layer into a PLCP Protocol Data Unit (PLCP Protocol Data Unit, PPDU), then the PMD sublayer will perform data modulation processing and transmit in bit mode.After PLCP receives PSDU (MAC layer MPDU), it prepares to transmit PSDU(PLCP Service Data Unit, PLCP Service Data Unit), and create PPDU, Add the preamble and PHY header to the PSDU. The upper layer is PLCP(Physical Layer Convergence Procedure, physical layer convergence protocol) sublayer, the lower layer is PMD(Physical Medium Dependent, physical medium related) sublayer. (9) SortThrough this field, when sending to an energy-saving station (maybe in a dormant state), the AP can change the sending order of broadcast and multicast MSDUs relative to unicast MSDUs. This field can only be set to "1" in data frames and "authentication" management frames. (8) Protected frameWhen the value of this field is set to "1", it indicates that the frame body has been encrypted. (7) More dataThis field is meaningful only when the station is in PS mode, and it indicates that more data is cached for the station on the AP.When the AP sends broadcast/multicast frames to a station, if the AP has additional broadcast/multicast frames to be sent to the station within the same beacon interval, the The field is set to "1", and the site has been notified not to go to sleep. It allows workstations that have not received the Beacon beacon frame to announce the contention-free period so that the NAV can be updated to an appropriate value to avoid interference with contention-free transmission.3. Therefore the duration/ID bit is 32768, and this value is interpreted as NAV. Frames transmitted during contention-free period: 14bit is 0, 15bit is 1. The value represents the estimated number of microseconds of the medium used for the current transmission.2. To ensure that no frames are lost, the workstation that wakes up from the sleep state must send a PS-poll frame to obtain the previously temporarily stored frame from the base station. Sleeping workstations must wake up regularly. The mobile station can turn off the antenna to save power. Corresponding is the original address, transmission address, receiving address and destination address. AddressIEEE 802.11 network nodes can be divided into four categories according to their functions and locations: source, transmitter, receiver and destination. The AID value is between 1-2007. Sequence control fieldThe sequence control field occupies 16 bits, of which the sequence number subfield occupies 12 bits, and the fragment subfield occupies 4 bits. ScenesNote: The BSSID in address 3 is used to filter non-secondary BSS frames. The content of each address field depends on the values of the two fields "To DS" and "From DS". Generally, the 801.11 frame only uses the first three address fields, and the address 4 field is only used for the wireless distribution system (WNS).
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