Brocade FastIron Ethernet Switch Traffic Management Guide - Manual (Page 97)

and store-and-forward mode. The store-and forward command changes the switching methodology to
store-and-forward.
A store-and-forward switch makes a forwarding decision on a data packet after it has received the
whole frame and checked its integrity, a cut-through switch engages in the forwarding process soon
after it has made the forwarding decision of an incoming frame. With cut-through switching, a packet
may start to forward before the entire packet has been received. Therefore, it drastically reduces
forwarding latency, especially for longer packets. However, there are many factors to consider when
selecting which switching mode is best for your environment. In some cases it is desirable to change
from the default mode and set your device to store-and-forward.
The table below describes some of the differences in the way packets are handled depending on the
switching mythology that you set on your device.
Cut-through Store-and-forward
Forwarding Data Forwarding starts before entire packet is
received Wait for entire packet received before processing
Latency Low Latency, less more 1 micro second Higher Latency / Latency depends on frame size
FCS Errors FCS Errors may be propagated from one
switch to another FCS errors are checked and error packets are
discarded in the MAC receive.
MTU size MTU size is validated by MAC receive.
Oversize packets are marked as error packets,
but not dropped in the MAC received. MTU size is validated by MAC receive. Oversize
packet will be drop at the MAC layer.
Examples To globally enable store-and-forward mode and change the default mode from cut-through, enter the
following command:
Brocade(config)# store-and-forward
Brocade(config)# write memory
Brocade(config)# end
Brocade# reload
History
Release version Command history
08.0.10b The store-and-forward command was introduced.
symmetrical-flow-control enable
Enables symmetrical flow control (SFC) globally for priorities 0-4 by default and optionally for all
priorities (0-7).
Syntax symmetrical-flow-control enable [ all ]
no symmetrical-flow-control enable
Command Default SFC is globally disabled.
Parameters all
Specifies SFC on all priorities. If you do not specify the all keyword, SFC is enabled only on
priorities 0-4. This parameter is optional.
symmetrical-flow-control enable
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