Question

Which among the following may result in the failure of link-layer checksum?

(a) Negative acknowledgment

(b) Error burst

(c) Route failure

(d) Packet loss

I got this question during a job interview.

I want to ask this question from Next Generation Wireless Network in chapter Next Generation Wireless Network of Cognitive Radio

Answer 1

The correct answer is:

(b) Error burst

Explanation:

A link-layer checksum is used to detect errors in transmitted data over a network. The checksum is calculated at the sender's side, and the receiver computes its own checksum to verify data integrity. If there is a mismatch, the receiver knows that an error has occurred.

Here's a breakdown of the options:

• (a) Negative acknowledgment: A negative acknowledgment (NACK) is a message sent by the receiver to inform the sender that an error occurred in the received data. This does not directly relate to the failure of the checksum itself; it simply indicates that there was an error, and the sender may retransmit the data.

• (b) Error burst: Correct. An error burst refers to a situation where multiple bits in a sequence are corrupted, typically due to noise or interference over a communication channel. If an error burst affects the transmitted data, it can cause the checksum to fail because the corrupted data would no longer match the checksum calculated by the sender.

• (c) Route failure: Route failures refer to issues in the routing path of data, which would likely affect higher layers of the network (such as the network layer or transport layer), not the checksum at the link layer.

• (d) Packet loss: Packet loss refers to the loss of packets during transmission, which typically occurs due to congestion, routing issues, or errors. While packet loss can lead to retransmissions, it doesn't directly cause the failure of the checksum since the data would still be transmitted and checked correctly if received.

Therefore, the correct answer is (b) Error burst, as bursts of errors can corrupt multiple bits in a packet, causing the checksum validation to fail.