Changes between Version 3 and Version 4 of 802.11/PacketFlow


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Timestamp:
Jul 30, 2013, 12:26:06 AM (11 years ago)
Author:
murphpo
Comment:

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  • 802.11/PacketFlow

    v3 v4  
    2929The final section of each packet buffer is the packet payload (a.k.a. the MPDU, for data frames, MMPDU for management frames). The Rx PHY does not interpret these bytes in any way. The MAC code must ensure this section of the packet buffer contains a valid MAC header and corresponding payload.
    3030
    31 === Frame Check Sequences (FCS) ===
     31=== Checksums ===
    3232
    33 The 802.11 standard specifies a standard CRC-32 checksum for all packet payloads. The 32-bit checksum is always transmitted as the last 4 bytes of the packet payload.
     33The 802.11 standard requires Frame Check Sequence (FCS) be attached to all transmitted frames. The checksum is calculated using the standard CRC32 scheme and covers all bytes of the MAC payload. The 32-bit checksum is always transmitted as the last 4 bytes of the packet payload.
    3434
    3535The Tx PHY automatically calculates and inserts the 32-bit checksum in the transmitted packet. The MAC code must include the FCS bytes in the length value in the SIGNAL field, but the MAC code does not need to calculate the actual checksum. The FCS values calculated by the Tx PHY are not written to the Tx packet buffer.