IBM 8271 Nways F12 User Manual page 90

4-30 C 4: W
HAPTER ORKING
W W I
ITH THE EB NTERFACE
The Advanced Stack Setup page contains the following elements:
Forwarding Mode Fast Forward / Fragment Free / Store and Forward /
Intelligent
Allows you to set the Forwarding Mode for the stack:
Fast Forward — Packets are forwarded as soon as the destination
address is received and verified. The forwarding delay, or latency, for
all packets in this mode is 40µs but without checking time, error
packets are propagated onto the network.
Fragment Free — A minimum of 512 bits of the received packet is
buffered before to the packet is forwarded. This ensures that
collision fragments are not propagated through the network. The
forwarding delay, or latency, for all packets in this mode is 64µs.
Store and Forward — Received packets are buffered entirely before
they are forwarded. This ensures that only good packets are
forwarded to their destination. The forwarding delay for packets in
this mode varies between 64µs and 1.2ms, depending on the length
of the packet. In this mode the latency is 7µs (measured as the time
between receiving the last bit of the frame and transmitting the first
bit).
Intelligent — The stack monitors the amount of error traffic on the
network and changes the Forwarding Mode accordingly. If the stack
detects less than 20 errors a second, the Forwarding Mode is set to
Fast Forward. If the stack detects 20 or more errors a second, the
Forwarding Mode is set to Store and Forward until the number of
errors a second returns to zero.
The Model F12/F24 only supports the Store-and-Forward Forwarding
Mode. If the stack is set to another Forwarding Mode, the Model
F12/F24 uses the Store-and-Forward Forwarding Mode.
Spanning Tree Enabled / Disabled
Allows you to specify whether the stack uses the Spanning Tree
Protocol (STP). STP allows your network to be be more fault tolerant;
for more information, see "Spanning Tree Protocol" on page 6-1.
Broadcast Storm Control Enabled / Disabled
Allows you to specify whether the stack uses Broadcast Storm Control.
If Broadcast Storm Control is enabled, the stack automatically creates
an alarm for each port to monitor the level of broadcast traffic on that
port. If over 20% of the total traffic on a port is broadcast traffic, the