This topic provides information about adjusting parameters for greater network performance.
Advanced Program-to-Program Communication (APPC) and Systems Network Architecture (SNA) host controller descriptions allow the specification of a group of LANxxxxxx parameters to provide performance-tuning capabilities for both local area network (LAN) and frame-relay connections. Because frame-relay networks operate at slower speeds than LANs, it might be necessary to adjust some of these parameters when you use the controller description for frame-relay connections.
If you specify the default value, *CALC, for the
LANxxxxxx parameters, then the IBM® 
iSeries™ system
automatically uses the values recommended for frame-relay connections. The
system adjusts these values to allow for network delays. For example, the
system might reduce them when using a high-speed network running at J1, T1,
or E1 speeds. Reducing these values allows quicker error detection, but it
also reduces the time allowed for error recovery.
You can display the values that the system chooses by using the Display Controller Description (DSPCTLD) command when the controller is active. Table 1 shows the values used for frame-relay connections when you specify *CALC for the LANxxxxxx parameters.
| Parameter | Function | *CALC value |
|---|---|---|
| LANCNNTMR | Sets wait time for polling remote station. | 20 seconds |
| LANCNNRTY | Sets number of poll retries sent to remote station. | 10 |
| LANRSPTMR | Sets wait time for frame retransmission. | 20 seconds |
| LANFRMRTY | Sets number of frame retransmission attempts. | 10 |
| LANACKTMR | Sets wait time for acknowledgment to remote station. | 1 second |
| LANACKFRQ | Sets number of frames received before sending acknowledgment. | 1 |
| LANINACTMR | Sets wait time for requesting response from remote station. | 25 seconds |
| LANMAXOUT | Sets number of outstanding frames allowed before requesting acknowledgment from remote station. | 2 |
| LANWDWSTP | Provides an alternative value equivalent to the LANMAXOUT parameter for use during periods of network congestion. The system provides an algorithm for returning the effective maximum outstanding frames value to that specified by the LANMAXOUT parameter as congestion subsides. | *NONE |
It should be noted that you might receive better performance with a larger frame size. In a mixed LAN and wide area network (WAN) environment, it might help to put CP Session support on the faster LAN controllers rather than the WAN controllers. The more data link connection identifiers (DLCIs) you have per network interface (NWI), the poorer the performance you have per DLCI.