About Service Policy Definition; About Service Policy Enforcement; About The Dwrr Traffic Scheduler Queue - Cisco AP775A - Nexus Converged Network Switch 5010 Configuration Manual

QoS
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About Service Policy Definition

Service policies are specified using policy maps. Policy maps provide an ordered mapping of class maps
to service levels. You can specify multiple class maps within a policy map, and map a class map to a
high, medium, or low service level. The default priority is low. The policy map name is restricted to 63
alphanumeric characters.
As an alternative, you can map a class map to a differentiated services code point (DSCP).The DSCP is
an indicator of the service level for a specified frame. The DSCP value ranges from 0 to 63, and the
default is 0. A DSCP value of 46 is disallowed.
The order of the class maps within a policy map is important to determine the order in which the frame
is compared to class maps. The first matching class map has the corresponding priority marked in the
frame.
Note Refer to
http://www.cisco.com/en/US/tech/tk543/tk757/technologies_tech_note09186a00800949f2.shtml
further information on implementing QoS DSCP values.
Class maps are processed in the order in which they are configured in each policy map.
Note

About Service Policy Enforcement

When you have configured a QoS data traffic policy, you must enforce the data traffic configuration by
applying that policy to the required VSAN(s). If you do not apply the policy to a VSAN, the data traffic
configuration is not enforced. You can only apply one policy map to a VSAN.
You can apply the same policy to a range of VSANs.
Note

About the DWRR Traffic Scheduler Queue

The Cisco NX-OS software supports four scheduling queues:
•
•
The DWRR scheduler services the queues in the ratio of the configured weights. Higher weights translate
to proportionally higher bandwidth and lower latency. The default weights are 50 for the high queue, 30
for the medium queue, and 20 for the low queue. Decreasing order of queue weights is mandated to
ensure the higher priority queues have a higher service level, though the ratio of the configured weights
can vary (for example, one can configure 70:30:5 or 60:50:10 but not 50:70:10).
Table 64-2
modules.
Cisco MDS 9000 Family Fabric Manager Configuration Guide
64-8
Strict priority queues are queues that are serviced in preference to other queues—it is always
serviced if there is a frame queued in it regardless of the state of the other queues.
QoS assigns all other traffic to the DWRR scheduling high, medium, and low priority traffic queues.
describes the QoS behavior for Generation 1, Generation 2, and Generation 3 switching
Chapter 64 Configuring Fabric Congestion Control and QoS
OL-17256-03, Cisco MDS NX-OS Release 4.x
for