Preventing Unnecessary Retransmissions and Large Initial TCP Window Sizes

A.

The TCP (Transmission Control Protocol) is a transport layer protocol used by applications to establish reliable communication over an IP network. In a wide-area network (WAN) environment, TCP performance can be impacted by latency, packet loss, and congestion. To improve TCP performance in a WAN environment, SD-WAN solutions provide several TCP optimization features.

Among the given options, the TCP optimization feature used by WAN Edge to prevent unnecessary retransmissions and large initial TCP window sizes to maximize throughput and achieve better quality is SACK (Selective Acknowledgement).

SACK is a TCP option that enables a receiver to inform the sender about which packets have been successfully received, and which packets need to be retransmitted. This enables the sender to retransmit only the missing packets, instead of retransmitting all packets, which can lead to unnecessary retransmissions and reduced throughput.

In addition, WAN Edge can also optimize TCP performance by adjusting the TCP window size based on the available bandwidth and network conditions. The TCP window size is the amount of data that a sender can transmit before receiving an acknowledgment from the receiver. By adjusting the TCP window size, WAN Edge can prevent large initial TCP window sizes, which can cause congestion and reduce performance.

To summarize, the TCP optimization feature used by WAN Edge to prevent unnecessary retransmissions and large initial TCP window sizes to maximize throughput and achieve better quality is SACK (Selective Acknowledgement).