• Chapter 3:

    Question 9: MSDU and PSDU are essentially the same thing (True/False).  And the answer is True.

    I thought it is really MPDU and PSDU?

    In the book it explains as, "both terms refer to layer 3 and up payloads encapsulated or unencapsulated".  So if that is the case then technically MSDU and PPDU are the same as well or MPDU and PSDU or MPDU and PPDU...

    Just looking for some clarity on this.

    Thank you

  • [Edit:] MSDU and PSDU are definitely not the same thing. That must be a (very unfortunate) typo in the book. Is it the Certitrek book?

    I wrote the explanation below for the MPDU/PSDU case.

    * * *

    Yes, it is true. It depends on where you look at it from. If you look from physical layer (PLCP) the same data structure is known as PSDU. The PLCP Service Data Unit is what the physical layer is going to transmit.. If you look at it from the data-link layer (MAC) it is known as MPDU or MAC Protocol Data Unit.

    In a sense what is a protocol data unit from the layer above becomes the service data unit to be transferred on the next layer. The opposite goes for receiving.

    The bits are the same on the layer boundary, just the point of view changes.

  • Thank you for the confirmation, yes it is a CertiTrek book. 

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