Wireshark-bugs: [Wireshark-bugs] [Bug 9754] New: Improper rate display 11ac
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From: bugzilla-daemon@xxxxxxxxxxxxx
Date: Thu, 13 Feb 2014 02:21:17 +0000
Bug ID 9754
Summary Improper rate display 11ac
Classification Unclassified
Product Wireshark
Version 1.10.5
Hardware x86
OS Mac OS X 10.9
Status UNCONFIRMED
Severity Major
Priority Low
Component Wireshark
Assignee bugzilla-admin@wireshark.org
Reporter ericsr@gmail.com 

Build Information:
Paste the COMPLETE build information from "Help->About Wireshark", "wireshark
-v", or "tshark -v".
--
This improper rate display ONLY happens when I am connected to an 80MHz
channel.

OK, that's not coming from the radiotap Rate field, it's looked up in a table
using the MCS rate index, bandwidth, and guard interval length, from the
radiotap MCS field, as indices. The table comes from information in section
20.6 "Parameters for HT MCSs" in the 802.11 spec.

I think the VHT field in the radiotap header is for 11ac.

If the driver for the adapter in the version you're using of the OS you're
using (Mountain Lion or Mavericks, probably, in your case, but similar stuff
would need to be done for Linux and *BSD, for example) supplies the VHT field,
then there is code in Wireshark 1.10.x to handle that field. If it's not
calculating the correct data rate, either the driver isn't supplying the right
VHT field values or isn't supplying them at all, in which case you'd have to
ask Apple whether there's a fix in the works, or the rate isn't being
calculated correctly from that field value, in which case Wireshark would need
to be changed.

If the driver is not supplying the VHT field, but is supplying the MCS field,
then Wireshark is doing the best that it can, and you'd have to ask Apple
whether there's a fix in the works.

You should file a bug on the Wireshark Bugzilla on this, and attach a raw
capture file (not a screenshot of Wireshark's display of the capture file)
containing a packet showing the problem. (If it was captured on a protected
network - WEP or WPA/WPA2-encrypted - you do NOT need to supply the password
for the network; we don't need any information other than the radiotap header
information.)

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