How many types of control frames are only used in PCF mode?
A.
0
B.
1
C.
2
D.
3
E.
4
F.
5
How many types of control frames are only used in PCF mode?
How many types of control frames are only used in PCF mode?
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How many types of control frames are only used in PCF mode?
How many types of control frames are only used in PCF mode?
A.
0
B.
1
C.
2
D.
3
E.
4
F.
5
5
http://www.ciscopress.com/articles/article.asp?p=1271797&seqNum=2
I guess the magic word here is “only”.
Ack for example is not only used in PCF. So, which are left?
The control frames that are used in PCF mode are as follows:
Contention Free End (CF+End)
Contention Free End Ack (CF +end_ack_)
CF-Ack
CF Ack+CF Poll
CF-Poll
Wireless LANs come in three frame types:
Management frames: Used for joining and leaving a wireless cell. Management frame types include association request, association response, and reassociation request.
Control frames: Used to acknowledge when data frames are received.
Data frames: Frames that contain data.
Point coordination function (PCF) is a Media Access Control (MAC) technique used in IEEE 802.11 based WLANs. It resides in a point coordinator also known as Access Point (AP), to coordinate the communication within the network. The AP waits for PIFS duration rather than DIFS duration to grasp the channel. PIFS is less than DIFS duration and hence the point coordinator always has the priority to access the channel.
i thought the answer is C.2
2. Control Frames
802.11 Control frames assit with the delivery of the data frames.
Control frames must be heard by all the stations, therefore they must be transmitted at one of the basic rates
Control frames are also used to clear the channel,acquire the channel and provide the unicast frame acknowledgements
They contain only header information
Following are the list of control frame subtypes as defined by 802.11 standard
Power Save(PS) Poll
Request to Send (RTS)
Clear to send (CTS)
Acknowledgement(ACK)
Contention-Free(CF)-End (PCF only)
CF-End+CF-ACK (PCF only)
Black-ACK(HCF)
Black Ack Request(HCF)
can anyone please clarify this?
I think correct answer is 3. Explanation
Question : Think what is control frames
Answer :Control frames: Used to acknowledge when data frames are received. Now
Question : Think what is Contention Point
Answer : Access Point
So, Access Point acknowledged Three time when it received data as given below
(1) Probe Response Acknowledgment Data+CF-ACK
(2) Authentication Response CF-ACK
(3) Association Response Contention Free End (CF-End) Data+CF-Ack
Please correct me if i am wrong.