How do I improve TCP/IP throughput?

The best possible throughput for a TCP connection is calculated using the formula R = B / T, where:

• R is the throughput rate in bytes per second.

• B is the smaller of the TCP Send Buffer on the sending system and the TCP Receive Buffer on the receiving system, in bytes.

• T is the average Round-Trip-Time between the systems, in seconds.

Expressed another way, in order to achieve a desired throughput rate the buffer sizes on both systems must be at least B = R * T.

For z/OS systems, the default sizes used for connections are configured on the TCPCONFIG statement in the TCPIP PROFILE as the TCPRCVBUFRSIZE and TCPSENDBFRSIZE values. Individual applications can override this specification (both higher and lower), reference their documentation to see if this is performed and if the size is configurable. You can use the NETSTAT ALL report (filtered on the application name) while a connection is active to see what settings are in use (and the Smoothed Round-Trip-Time calculated).