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Update to latest 2.1.1 rev of the capture frame format.

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pizza 15 years ago
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82b621373d
  1. 54
      doc/capturefrm.txt

54
doc/capturefrm.txt

@ -1,5 +1,5 @@
AVS Capture Frame Format
Version 2.1
Version 2.1.1
1. Introduction
The original header format for "monitor mode" or capturing frames was
@ -39,7 +39,7 @@ The following fields make up the AVS capture header:
8 mactime uint64
16 hosttime uint64
24 phytype uint32
28 channel uint32
28 frequency uint32
32 datarate uint32
36 antenna uint32
40 priority uint32
@ -50,7 +50,7 @@ The following fields make up the AVS capture header:
60 encoding uint32
64 sequence uint32
68 drops uint32
72 sniffer_addr uint8[6]
72 receiver_addr uint8[6]
78 padding uint8[2]
------------------------------
80
@ -72,11 +72,17 @@ in bytes.
Many WLAN devices supply a relatively high resolution frame reception
time value. This field contains the value supplied by the device. If
the device does not supply a receive time value, this field shall be
set to zero. The units for this field are microseconds.
set to zero. The units for this field are microseconds.
If possible, this time value should be absolute, representing the number
of microseconds elapsed since the UNIX epoch.
4.4 hosttime
The hosttime field is set to the current value of the host maintained
clock variable when the frame is received.
clock variable when the frame is received by the host.
If possible, this time value should be absolute, representing the number
of microseconds elapsed since the UNIX epoch.
4.5 phytype
The phytype field identifies what type of PHY is employed by the WLAN
@ -94,11 +100,13 @@ device used to capture this frame. The valid values are:
phytype_ofdm_dot11_a 8
phytype_dss_ofdm_dot11_g 9
4.6 channel
For all PHY types except FH, this field is just an unsigned integer
and will be set to the current receiver channel number at the time
the frame was received. For frequency hopping radios, this field
is broken in to the following subfields:
4.6 frequency
This represents the frequency or channel number of the receiver at the
time the frame was received. It is interpreted as follows:
For frequency hopping radios, this field is broken in to the
following subfields:
Byte Subfield
------------------------
@ -107,6 +115,15 @@ is broken in to the following subfields:
Byte2 Hop Index
Byte3 reserved
For non-hopping radios, the frequency is interpreted as follows:
Value Meaning
-----------------------------------------
< 256 Channel number (using externally-defined
channelization)
< 10000 Center frequency, in MHz
>= 10000 Center frequency, in KHz
4.7 datarate
The data rate field contains the rate at which the frame was received
in units of 100kbps.
@ -190,11 +207,10 @@ This is a counter of the number of known frame drops that occured. This
is particularly useful when the system or hardware cannot keep up with
the sniffer load.
4.16 sniffer_addr
This specifies the mac address of the sniffer, six octets in length.
This field is followed by two octets of padding to keep the structure 32-bit
word aligned.
4.16 receiver_addr
This specifies the MAC address of the receiver of this frame.
It is six octets in length. This field is followed by two octets of
padding to keep the structure 32-bit word aligned.
================================
@ -207,3 +223,11 @@ Changes: v2->v2.1
* Mactime is specified in microseconds, not nanoseconds
* Added 64QAM, 16QAM, BPSK, QPSK encodings
================================
Changes: v2.1->v2.1.1
* Renamed 'channel' to 'frequency'
* Clarified the interpretation of the frequency/channel field.
* Renamed 'sniffer address' to 'receiver address'
* Clarified timestamp fields.

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