Friday, April 25, 2008

802.11 MAC frame

Frame format=Mac header + framebody(variable length)+FCS(32bit CRC)
Mac header=Frame Control(2)+Duration/ID(2)+Addr1(6)+Addr2(6)+Addr3(6)+Seq control(2)+Addr4(6)+Qos Control(2)
FrameControl=Protocol version +Type+SubType+ToDS+FromDS+MoreFrag+Retry+PwrMgt+MoreData+ProtectedFrame+Order
Based on type and SubType value of Frame Control, all 802.11 frames can be classified as
1. Management frame (Type=00)
(Re)Association request (Re)Association Response
Probe Request Probe Response Action
Beacon, ATIM, Diassociation, (De)authentication
mac header=frame control+duration + addr1+SA+BSSID+squence control
framebody=0-2312 bytes
fcs=4 bytes
* Beacon frame format

2. Control Frame (Type=01)
RTS,CTS,ACK,PS-Poll
Block Ack REquest, Block Ack
CF-End, CF-End+CF-ACk
RTS Mac header: Frame Control+Duration +RA+TA+FCS
CTS Mac header: Frame Control+Duration+RA+FCS

3. Data Frame(Type=10)
Data, Data+CF-Ack, Data+CF-Poll
Qos Data, Qos Data+CF-Ack
Mac header=full mac header
framebody=0-23424 data bytes
FCS
.....

1 comment:

笑楚 said...

Hi!
How can I know the detail Info of the Frame body area?