Web Caching and Replication

3.6. Retransmission

A major goal of TCP is to transmit data reliably. However, reliable transmission of data over an unreliable network layer like IP requires the retransmission of lost data. A general approach is that the sender would retransmit the TCP segments that have not been acknowledged by the receiver within a certain time after the initial transmission. This poses an interesting problem: how long should the sender wait before retransmitting such data? If data is retransmitted too soon, the data might actually not have been lost, and the retransmission might be redundant. If the data is retransmitted too late, the advertised window will not advance as discussed in Section 3.4, causing the sending host to limit its transmission rate unnecessarily. ...