What is Maximum Segment Size (MSS)?
The MSS is the largest segment of TCP data that the Winsock is prepared to receive on a particular connection. When the TCP connection is initially established, both sides agree to use the minimum of each other's advertised MSS value.If the MSS is too low, the data/header ratio will be low. And if the MSS is too high, this will lead to large IP datagrams and the packets will tend to fragment in transit where other networks may have small MTU's. Hence, performance can increase at times by reducing the MSS value.Since packet headers are normally 40 bytes in length, your MSS value should always be at least 40 less than the value of the MTU. As a rule of thumb, first try setting the MSS value to be the greatest power of 2 that is at least 40 less than the MTU value.
