In Carrier Sense Multiple Access (CSMA), the possibility of collision still exist because of
a. Transmit delay
b. Propagation delay
c. sender-receiver delay
d. Sense delay
The correct answer and explanation is:
The correct answer is d. Sense delay.
Carrier Sense Multiple Access (CSMA) is a protocol used in networks to manage how devices access a shared communication medium. The core idea is that before a device begins transmitting data, it first “listens” to the channel to check if it’s in use. If the channel is clear, the device proceeds with the transmission. However, if the channel is already in use, the device waits and retries after some time.
Despite this “carrier sense” mechanism, collisions can still happen due to sense delay. This refers to the time it takes for a device to sense the state of the medium before transmitting. When a device senses that the channel is clear, it may not immediately realize that another device is just about to transmit, due to the propagation delay of the signals.
When multiple devices simultaneously or nearly simultaneously sense the channel as idle and begin transmitting, their signals may collide. These collisions occur because the devices fail to detect each other’s transmission in time. In CSMA/CD (Carrier Sense Multiple Access with Collision Detection), which is an extension of CSMA, devices can detect a collision after it occurs and then retransmit the data. However, collisions still happen frequently in environments with high traffic because of sense delay.
In simple terms, sense delay is the primary reason collisions are still possible, even though devices are trying to avoid transmitting while others are using the medium. This delay in detecting the status of the communication channel can lead to overlapping transmissions and, ultimately, collisions.