When the TCP client receives the echo of a character, it waits a certain time before sending the ACK. Why does the TCP client delay? How long is this delay? How much does the delay vary?

What will be an ideal response?

In interactive applications, TCP sender does not wait until the application data fills a
complete TCP segment since interactive applications are generally delay sensitive. Usually TCP sends data, which is small in volume, as soon as it arrives from the application. This results in an inefficient use of bandwidth since small segments mainly consist of protocol headers. Delayed acknowledgements are used by the receiver of these small segments to see if theacknowledgement can be piggybacked along with data going back to the sender. This often
reduces the number of segments. Delayed acknowledgements require the receiver of data to wait for a certain amount of time before sending an ACK. Usually the delay is 200ms. If during this delay, the receiver has data for the sender; the ACK will be piggybacked to the data.