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MPDU size

1 posts by 1 authors in: Forums > CWDP & CWAP - Enterprise Wi-Fi Design & Analysis
Last Post: October 2, 2006:
  • By Criss_Hyde
    Reply

    Hi Asoa:

    All the text you copy appears to me to be correct.

    The maximum size MAC service data unit (MSDU) allowed by the standard to be passed between the LLC sublayer and the MAC sublayer is 2304 octets. This is independent of encryption and fragmentation and is a number all candidates for The CWNP Program certification must commit to memory.

    TKIP's 8 octet message integrity code (MIC) is calculated once per MSDU, appended to the MSDU, and for the rest of MAC and PHY processing (such as fragmentation and further encryption) the MIC is treated as though it were part of the MSDU.

    Since the MIC is stripped off by the receiver before the MSDU is passed to the LLC sublayer, its 8 octets are never considered when applying the 2304 maxMSDU rule.

    See IEEE 802.11i section 8.3.2.2.

    If you still have questions, please ask on, and please be specific.

    I hope this helps. Thanks. /criss

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