System information

Planning Considerations

Releases 1 though 2.5. All methods are suitable in Release 3. For

Releases 1 though 2.5, NVRAM uses TFTP to load the

kernel/configuration files and, after login, uses RFS. For Release 3,

NVRAM uses TFTP to load the kernel and RFS for all subsequent files.

BOOTP and DHCP use TFTP to load the kernel and then use RFS to load

all subsequent files.

For Releases 1 though 2.5, the Network Station tries 10 times, with a five

second timeout, to locate and read the kernel using TFTP. After 10 attempts,

an error message is sent. For Release 3, the Network Station can be

configured to try indefinitely to locate and read the kernel.

For Releases 1 though 2.5, if NVRAM is selected, the Network Station reads

the configuration files using TFTP. The Network Station tries 10 times, with a

three second timeout, to read each file. If unsuccessful, it skips that file and

then tries to read the next file, which eventually results in an unsuccessful

initialization. RFS has an infinite retry and does not skip files. From a

reliability perspective, this makes NVRAM, for Releases 1 though 2.5, the

least preferred booting mechanism.

With Network Station Manager Release 3, subnet broadcast is available over

Ethernet, token-ring, and twinax. When this option is selected, TFTP data (for

example, the kernel is about 2MB), is broadcast from the AS/400 server to

any requesting Network Station.That is, the kernel is sent one time so that

each Network Station receives it. When subnet broadcast is off, the kernel is

sent individually to each Network Station, which means a lot more data on the

LAN or twinax. The broadcast is only to a subnet (such as any Network

Station on a single ring, such as 9.5.112.x).

When Network Stations from different subnets request the kernel, the AS/400

server provides a broadcast to each subnet. The data below shows that

subnet broadcast uses less AS/400 CPU. Subnet broadcast is the preferred

boot option (twinax has some special considerations discussed later). There

is a caution, some routers do not support broadcast and broadcast can cause

other problems, if not configured properly.

Subnet broadcast is supported on twinax. Unlike Ethernet and token-ring

protocols, the twinax protocol does not support broadcast. What this means

for twinax, is that, when subnet broadcast is selected, each frame is sent

individually to each device. When all devices are expecting the broadcast,

this option works well (less AS/400 CPU). When all devices are not expecting

the broadcast, this option results in more data on the twinax cable. The

following information shows this.

In general, customers should not use subnet

broadcast for twinax.