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I have the attached photos for a capture for Wifi Frames in Wireshark.

alt text

When I was analyzing the frame format for different packets, I found that when I move from the MCS Information field to the A-MPDU status field, three bytes are being escaped by Wireshark. So I checked the Radio Tap header format, and I found nothing is mentioned about these three bytes. So could you please clarify why three bytes are ignored by the parser.

Additionally according to the A-MPDU Status field definition in the following Site, the structure should be aligned by 4 bytes. So the subfields should be multiple of 4 bytes i.e. The A-MPDU Status should be 16 Bytes long, correct?


  1. The three Bytes have a value of zero.

  2. The original capture file can be found in the following link Capture File

asked 12 Jun '15, 11:37

Hany%20Assasa's gravatar image

Hany Assasa
accept rate: 0%

This is because the A-MPDU Status field requires a 4 bytes alignment, meaning that the structure must start at a multiple of 4 bytes. The 3 bytes set to 0 are padding between the end of the MCS field and the beginning of the A-MPDU Status field. You can read the "Alignment in Radiotap" paragraph on for more details.

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answered 12 Jun '15, 12:01

Pascal%20Quantin's gravatar image

Pascal Quantin
accept rate: 30%

edited 12 Jun '15, 12:07

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question asked: 12 Jun '15, 11:37

question was seen: 3,300 times

last updated: 12 Jun '15, 12:07

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