System information

44
AS/400 IBM Network Station: Techniques for Deployment in a WAN
block size equal to the MTU or frame size. Users must be aware that some
routers, switches and gateways do not support this fragmentation
capability. Twinax MTU or frame size are fixed. Therefore, fragmentation
does not apply to twinax attached Network Stations.
The number of TFTP jobs on the AS/400 server is also a performance
factor. The optimal number, for a system with a single LAN IOP, is about
six (the default). The TFTP jobs are a pool of AS/400 jobs that download
the kernel to Network Stations. They are on a f
irst come, first serve basis.
If there are more Network Station requests than jobs, the excess is
ignored (not queued). If a request is not satisfied, the Network Station
repeats its request, every five seconds. In general, there should be six
TFTP jobs for each LAN IOP that has attached Network Stations.
The following tables and figures show how the TFTP block size affects the
kernel and configuration initialization time, for a few AS/400 system sizes.
The tables also show what happens when 1, 10, 50, and 100 Network
Stations simultaneously (such as, after a power outage) request TFTP
initialization. The times represent the number of seconds when the last
Network Station completes its TFTP and RFS download. The data in the
following tables was obtained in a dedicated environment. That is, only
BOOTP, TFTP and RFS were running on the AS/400 server and there was
no other load on the LAN. In each test case, the base pool was cleared
before beginning the test.
Each of the following runs had the following configured:
• 8K Maximum Transmission Unit (MTU)
• 8K Frame Size
• 6 TFTP jobs
Results listed here do not represent any particular customer environment.
Actual performance may vary significantly from what is provided here.
Important