IBM SAN32M1, Installation And Service Manual

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SAN32M1 Fabric Switch Installation and Service Manual 122
• Back Pressure. Click this check box to display a checkmark and
enable this option. If enabled, a back pressure entry will be
made to the Event Log and an SNMP trap will be generated if
trap recipients are configured through the Configure SNMP
dialog box.
A back pressure event occurs when the percentage of time the
ISL has a low BB credit condition exceeds the low BB credit
threshold. A separate event also occurs when the backpressure
condition ends.
5. Set the Low BB Credit Threshold.
NOTE: Earlier versions of this dialog box may display Credit Starvation
Threshold instead of Low BB Credit Threshold. They are the same threshold
value.
NOTE: Using default settings for low BB credit threshold should work
well in most cases. This step is not required.
This is the percentage of time that the transmitting link cannot
transmit because BB_Credit is unavailable. In other words, it is
the percent of time that the link can be “starved” and is treated as
“back-pressured” by the rerouting algorithm. This value is also
used when determining routes for a transmit link. A
back-pressured ISL cannot be the recipient of traffic rerouted from
other ISLs, and traffic on a back-pressured ISL may be rerouted
even if the ISL is not congested.
• Click Default Threshold and a default value (1 to 99%) will
appear in the threshold field. If the default is enabled, you
cannot enter values into the field.
• Click in the threshold field and enter a value from 1 to 99.
6. Click Activate to enable these values on the switch and close the
dialog box.
Pop-Up menu
Right click on columns in the Configuration Threshold table to display
menu options that globally change values in the column cells.
Use algorithmic threshold
Right click in the column to display these options: