I'm new to Wireshark. I'd like to know what are fixed and tagged parameters and the difference between them. Web search didn't help. Kindly explain it to me in simple terms.
1 Answer
I don't believe that is a thing in wireshark. However, there are a pair of fields in wireshark's decode output for the 802.11 protocol with these names. In that context, fixed parameters are those which exist for all frames (at specified offsets), and tagged parameters are variable. They exist in the tagged parameters area, and include a tag (to show which parameter is being specified) and some paramater-specific data. There might be several of them. Other than the details of how they are encoded and whether they appear in all packets, the distinction is not very meaningful.
This technique is used in other protocols too (with different names). For instance, DHCP options are encoded in a similar fashion.
answered Jul 15, 2013 at 5:37
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Thanks. But, what do you mean by 'exist in all frames'? For eg., The
timestamp and beacon intervalfields exist only in Beacon frame. Thelisten intervalfield exists in Association Request, but not in Beacon frame. But, they are under fixed parameters.– GomuCommented Jul 15, 2013 at 6:55 -
All frames of the frame type, specifically. They are structurally defined, and not optional, where they are expected. It is not possible to semantically create a frame without them (and they are at a fixed location), which is not true of tagged options. Commented Jul 15, 2013 at 7:11
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But, as I mentioned previously, though they both are management frames, they still have some fields as optional.– GomuCommented Jul 15, 2013 at 7:24
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Yes. Not all fields are fixed. Also, yes, different frame types may have different fixed fields, but those fields are then fixed, and not individually tagged. That is all. Commented Jul 15, 2013 at 17:30