Outbound Traffic - HP ProCurve 6400cl Series Management And Configuration Manual

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Guaranteed Minimum Bandwidth (GMB) on the Series 5300xl Switches
For a given port, when the demand on one or more outbound queues exceeds
the minimum bandwidth configured for those queues, the switch apportions
unallocated bandwidth to these queues on a priority basis. As a result, speci­
fying a minimum bandwidth for a high-priority queue but not specifying a
minimum for lower-priority queues can starve the lower-priority queues dur­
ing periods of high demand on the high priority queue. For example, if a port
configured to allocate a minimum bandwidth of 80% for outbound high-
priority traffic experiences a demand above this minimum, then this burst
starves lower-priority queues that do not have a minimum configured.
Normally, this will not altogether halt lower priority traffic on the network,
but will likely cause delays in the delivery of the lower-priority traffic.
The sum of the GMB settings for all four outbound queues on a given port
cannot exceed 100%.
Configuring Guaranteed Minimum Bandwidth for Outbound
Traffic
For any port or group of ports you can configure either the default minimum
bandwidth settings for each outbound priority queue or a customized band-
width allocation. For most applications, HP recommends configuring GMB
with the same values on all ports on the switch so that the outbound traffic
profile is consistent for all outbound traffic. However, there may be instances
where it may be advantageous to configure special profiles on connections to
servers or to the network infrastructure (such as links to routers, other
switches, or to the network core).
Syntax: [ no ] int < port-list > bandwidth-min output
Configures the minimum bandwidth allocation for the
outbound priority queue for each port in < port-list >. The
default values are:
• Queue 1 (low priority): 8%
• Queue 2 (normal or unmarked priority): 16%
• Queue 3 (medium priority): 30%
• Queue 4 (high priority): 45%
The no form of the command disables GMB for all ports in
< port-list >. In this state, which is the equivalent of setting
all outbound queues on a port to 0 (zero), a high level of
higher-priority traffic can starve lower-priority queues,
which can slow or halt lower-priority traffic in the
network. You can configure bandwidth minimums from
either the global configuration level (as shown above) or
from the port context level. For information on outbound
port queues, refer to table 13-1, "Per-Port Outbound
Priority Queues" on page 13-10.
Port Traffic Controls
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