CS578 WiFiMAC network with complete updated questions & answers

CS578 WiFiMAC network with complete
updated questions & answers
How does wireless internet work? - answer Shares the medium:
- The air
- Access ctrl is important
- Channel assignment is importanrt


CSMA/ CA (Carrier Sense Multiple Access) - answer Procedure to
transmit information:
- Listen on desired channel
- If the channel is idle, it will send a packet.
- If the channel is active, the node waits until the channel is idle +
additional contention period.
- Afterwards, if the channel is idle, then the node transmits its packet. If
not, process is repeated until so.


CSMA/CA Backoff in 802.11 - answer DCF -> Distributed Coordinated
Function
D -> DCF Inter Frame Space (DIFS)
S -> Short Inter Frame Space (SIFS)
CW -> Contention Window
MPDU -> MAC Protocol Data Unit

, A -> ACK


If wired, how is a pkt transmitted? - answer All NICs receive the frame,
and exam the pkt's length and checksum.


The NIC that recognizes the frame destination address will forward the
contents of the frame to the network layer. All the other NICs will
discard the unwanted frame.


Additional CSMA/CD Notes: - answer Concept -> Tx -> Collision ->
Backoff -> Retry


When a corruption is detected by two or more NICs, each responds by
transmitting a jam sequence.


After a propagation delay NIC B is aware of the collision and sends a jam
sequence.


After another propagation delay both NICSs are aware of the collision.
NIC B stops sending the jam sequence while NIC A transmits a jam
sequence.


Afterwards the cable becomes idle again.