[STDS-802-11-TGM] Resolution (rejection) for CID 8137

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All,

This is my proposed resolution text for CID 8137 (also copied here):

8137

133.54

5.1.5.1

Re CID 7817 --- shouldn't scoreboarding be after integrity validation? Otherwise your BA bitmap could be poisoned by forged MPDUs

Move "Block Ack Scoreboarding" to be above "MPDU Encryption (TX) / Decryption (RX) and Integrity (optional)" in Figure 5-1 and Figure 5-2 (2x)

Proposed resolution:

REJECTED. While checking MPDU integrity before doing scoreboarding would perhaps help with one particular type of DoS attack, it has sufficient problems to make this overly restrictive for implementations. For example, it is likely that Block Ack scoreboarding and normal ACK generation are done at the same point in the stack, especially for HT-immediate Block Ack. Since this implies that there is only a SIFS time duration to complete the frame reception, it puts significant burden on an implementation to check the MPDU Header and FCS, perform Address 1 checks and duplicate detection, and (with the proposed change) the MPDU Decryption and Integrity check, in time to send the ACK. Further, the text in 4.5.4.4 (Data confidentiality), last paragraph, makes it clear that frames which fail integrity check are still acknowledged, to prevent wasting WM bandwidth on retries of frames that are being discarded. Thus, the proposed change would trade one problem for a different problem.

Comments welcome!

Mark

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