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  • Hi,
    Consider the following configurations,

    MPDU size : 1000 bytes
    RTS threshold :512 bytes
    protection type : CTS to self.
    protection rate : 2 Mbps

    In the above configuration will it send RTS frame?
    If it sends RTS frame what will be the rate for RTS frame?

  • By (Deleted User)

    Consider the following configurations:
    MPDU size : 1000 bytes
    RTS threshold :512 bytes
    protection type : CTS to self.
    protection rate : 2 Mbps

    In the above configuration will it send RTS frame?
    If it sends RTS frame what will be the rate for RTS frame?


    In this case the 802.11g client card is using CTS-to-Self instead of an RTS/CTS exchange. Therefore there is no RTS frame, only a CTS frame. The CTS frame will be sent using DSSS technology at a configured Basic rate (required rate) which looks like it is 2 Mbps is this configuration.

    Most vendor's client cards implement CTS-to-Self by default as a protection mechanism, however some vendor's such as Intel let the user choose between RTS/CTS or CTS-to-Self

  • so if legacy protection is enabled with CTS to self, even though the MPDU size exceeds the RTS threshold, it may or may not (Vendor specific) transmit RTS frame.
    Is that correct?

  • By (Deleted User)

    so if legacy protection is enabled with CTS to self, even though the MPDU size exceeds the RTS threshold, it may or may not (Vendor specific) transmit RTS frame.
    Is that correct?


    Two separate issues, If CTS-to-Self is being used, there is no RTS frame period. The setting is simply a threshold as to when the protection mechanism is used. For example, if the MPDU theshold is 1000 bytes, then the protection mechanism is used with any ERP-OFDM frames larger than 1000 bytes. If the MPDU theshold is 750 bytes, then the protection mechanism is used with any ERP-OFDM frames larger than 750 bytes.

  • By (Deleted User)

    Download and read this white paper. Required reading if you want to learn about the protection mechanism:

    http://cwnp.com/learning_center/search_details.php?doc_id=l7w2

  • I'm not sure whether there hasn't been a little misunderstanding, I'll rephrase the original question as I see it if I may-

    When there's a 1000B MPDU about to be sent, with RTS threshold at 512B and CTS-to-self protection enabled at ERP-STA, given Use_Protection=1, will the ERP-STA transmit CTS-to-self followed by RTC/CTS exchange, or will it suffice with RTC/CTS due to threshold settings?

  • By (Deleted User)

    When there's a 1000B MPDU about to be sent, with RTS threshold at 512B and CTS-to-self protection enabled at ERP-STA, given Use_Protection=1, will the ERP-STA transmit CTS-to-self followed by RTC/CTS exchange, or will it suffice with RTC/CTS due to threshold settings?


    Now I understand the question. The only way to check would be to test it and look at it an a sniffer. My guess is that the RTS/CTS mechanism would override the CTS to self, I seriously doubt that a card would use both CTS-to-Self and RTS/CTS. I think the bigger question is, why in the world do you have you have your RTS Theshold set at 512 Bytes in the first place?

  • As of 512B threshold, I guess it was just an example for the purpose of the question..

    Anyways, thanks for clarification, and I've got another q if I may..

    Mister Multipath, the material you suggested for reading states that a management frame from nonERP-STA may force AP into endorsing the protection mechanism.. If I understand correctly, an auth request is a management frame, however the material puts weight on avoiding the assoc frame, even if it's gonna be unsuccesful, rather than the auth request.
    Is it correct that auth request from nonERP-STA will not trigger ERP-AP to set Use_Protection=1 ?

  • By (Deleted User)

    the material you suggested for reading states that a management frame from nonERP-STA may force AP into endorsing the protection mechanism.. If I understand correctly, an auth request is a management frame, however the material puts weight on avoiding the assoc frame, even if it's gonna be unsuccesful, rather than the auth request. Is it correct that auth request from nonERP-STA will not trigger ERP-AP to set Use_Protection=1 ?


    That is correct, It is the associate request from the non-ERP station (802.11b) that triggers the ERP-AP to set Use_Protection=1

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