https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=14594
Guy Harris <g...@alum.mit.edu> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |NOTABUG
--- Comment #1 from Guy Harris <g...@alum.mit.edu> ---
Wireshark reports what it sees in the packet:
9.4.2.18 Supported Channels element
The Supported Channels element contains a list of channel subbands (from those
channels defined in 17.3.8.4.3) in which a STA is capable of operating. The
format of the Supported Channels element is shown in Figure 9-144.
One (first channel, number of
channels) tuple for each subband
+------------+----------+---------------+-----------+
| Element ID | Length | First Channel | Number of |
| | | Number | Channels |
+------------+----------+---------------+-----------+
Octets: 1 1 1 1
Figure 9-144—Supported Channels element format
The Element ID and Length fields are defined in 9.4.2.1.
The First Channel Number field is set to the first channel (as defined in
17.3.8.4.3) in a subband of supported channels.
The Number of Channels field is set to the number of channels in a subband of
supported channels.
By "contains a list" it presumably means that, after the Element ID (36) and
Length, there's a sequence of one or more pairs of First Channel Number and
Number of Channels. That's how Wireshark dissects it - it just iterates over
the First Channel Number/Number of Channels pairs.
So whatever sent the packet sent it as:
0x24 Element ID: 36
0x0a Length: 10
0x24 First Channel Number: 36
0x04 Number of Channels: 4
0x34 First Channel Number: 52
0x04 Number of Channels: 4
0x64 First Channel Number: 100
0x0c Number of Channels: 12
0x95 First Channel Number: 149
0x04 Number of Channels: 4
0xa5 First Channel Number: 165
0x01 Number of Channels: 1
This means that the channels that the machine that sent the packet supports
are:
36-39
52-55
100-111
149-153
165
so it has 5 ranges of channels in which it can operate, with channel 165 being
in the 5th of those ranges.
The ranges are based solely on a division of the channels into sequences of
contiguous channel numbers; think of it as a form of compression. The same
value *could* have been sent as 25 individual channel numbers.
The ranges, in this case, happen to be sorted by the lowest channel number, so
that happens to put the one-channel range containing channel 165 into the fifth
range. That does not, in any way, indicate anything about the regulatory
status of that channel in any locale, so changes to U-NII-3 are irrelevant to
the range in which a given channel appears.
--
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