What advantage does selective acknowledgment provide in NETTCP?

• A. It reduces the packet size needed for acknowledgments
• B. It improves recovery times for lost packets
• C. It eliminates the need for cumulative acknowledgments
• D. It simplifies the acknowledgment process

Answer: (B)

Selective acknowledgment is advantageous because it significantly improves recovery times for lost packets during data transmission. In a network protocol context, particularly in TCP (Transmission Control Protocol), selective acknowledgment allows the receiver to inform the sender about all the segments that have been received successfully, rather than just the last contiguous segment. This means that if a packet is lost, the sender can retransmit only the specific lost packets instead of having to resend a larger amount of data that may not need to be retransmitted.

By providing information about exactly which packets are missing, the sender can promptly address any gaps in the data stream, thus minimizing the time it takes to ensure all data is correctly received. This targeted approach leads to more efficient use of bandwidth and lowers latency in communication, as there is no need for unnecessary retransmissions of data that the receiver has already successfully received.

In contrast, cumulative acknowledgments would only inform the sender about the last correctly received packet, potentially causing delays as previously acknowledged packets are resent even if they were received. Therefore, the incorporation of selective acknowledgment is a significant improvement in optimizing data recovery in network communications.