Adjust WAN protocols for optimum iSeries server performance

Wide area network (WAN) protocols affect the communications performance on the iSeries™ server. Let us use X.25 for our example. For each X.25 communications controller, the iSeries server has some processing limitations for the line, the line speed, and the total number of virtual circuits that can be used. Performance degradation can be reduced by observing these limitations.

To optimize the iSeries system performance for wide area networks, perform these tasks:

• Reduce the total number of frames by using larger frames.
• To take advantage of these large frame sizes, change the MAXFRAME parameter on the line description (LIND) to reflect the maximum value. For X.25, increase the DFTPKTSIZE and MAXFRAME parameters to their maximum value.
• Configure a WAN line as full-duplex to provide you with a higher throughput for applications that can take advantage of this mode. This can also provide higher throughput for multiple users.
• Increase frame relay to capacity.

The data rate for a given protocol might increase as frame size increases. Under these circumstances, the central processing unit (CPU) and the input/output processor (IOP) do not do as much processing. Fewer and larger frames also make more efficient use of the communications line (higher effective data rate) because of fewer overhead bytes and line turn-arounds.

Frame relay has equivalent performance over RS449, X.21, and V.35 assuming equal line speeds and conditions. Frame relay performance (CPU time) is similar to or slightly better than Synchronous Data Link Control. For properly tuned large transfer applications, the CPU and IOP have no problem using the line speed to capacity.

For information about configuring iSeries system communications, see the Communications Configuration book.