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Which of the following statements is TRUE about CSMA/CD:

  1. IEEE $802.11$ wireless LAN runs CSMA/CD protocol
  2. Ethernet is not based on CSMA/CD protocol
  3. CSMA/CD is not suitable for a high propagation delay network like satellite network
  4. There is no contention in a CSMA/CD network
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5 Answers

Best answer
32 votes
32 votes

Answer is C.

CSMA/CD was used in early days, $802.3$ not in $802.11$

There will be contention in this protocol.

Ethernet is based on csma/cd early in $1980$s.

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30 votes
30 votes

some info about "contention slot"

Contention Protocols resolve a collision after it occurs.These Protocols execute a collision resolution protocol after each collision

eg. Pure/Slotted Aloha, CSMA/CA(wireless), CSMA/CD(ethernet)

CSMA/CD  : -To detect a collision, in the worst case, it takes twice the maximum propagation delay of the medium

Ethernet requires a minimum packet size and restricts the maximum length of the medium

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20 votes
20 votes
The reason is in csma/Cd transmission time >=2*propagation delay so high prop. Time implies high transmission time so it's not efficient transmit a frame for a long time... So option c
13 votes
13 votes
Efficiency of CSMA/CD= 1/(1+6.44a)=1/(1+6.44(Tp/Tt))

Tp=propagation time

Tp=transmission time

so if propagation time increases efficiency will decrease

So C is the Answer
Answer:

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