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Configure Quality of Service
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GS752TP, GS728TP, and GS728TPP Gigabit Smart Switches
Class of Service
The Class of Service (CoS) queueing feature lets you directly configure certain aspects of
switch queueing. This configuration provides the desired QoS behavior for different types of
network traffic when the complexities of DiffServ are not required. The priority of a packet
arriving at an interface can be used to steer the packet to the appropriate outbound CoS
queue through a mapping table. CoS queue characteristics that affect queue mapping, such
as minimum guaranteed bandwidth, or transmission rate shaping are user configurable at the
queue (or port) level.
Four queues per port are supported.
From the Class of Service menu under the QoS tab, you can access the following sections:
• Basic CoS Configuration
• CoS Interface Configuration
• Queue Configuration
• 802.1p to Queue Mapping
• DSCP to Queue Mapping
Basic CoS Configuration
Use the CoS Configuration screen to set the Class of Service global trust mode. Each port in
the switch can be configured to trust one of the packet fields (802.1p or IP DSCP, which is set
globally), or to not trust a packet’s priority designation (untrusted mode). If the port is set to a
trusted mode, it uses the global trust mode configuration. This mapping table indicates the
CoS queue to which the packet must be forwarded on the appropriate egress ports. The
trusted field must exist in the packet for the mapping table to be of any use, so default actions
are performed when this is not the case. These actions involve directing the packet to a
specific CoS level configured for the ingress port as a whole, based on the existing port
default priority as mapped to a traffic class by the current 802.1p mapping table.
Alternatively, when a port is configured as untrusted, it does not trust any incoming packet
priority designation and uses the port default priority value instead. All packets arriving at the
ingress of an untrusted port are directed to a specific CoS queue on the appropriate egress
ports, in accordance with the configured default priority of the ingress port. This process is
also used for cases where a trusted port mapping is unable to be honored, such as when a
non-IP packet arrives at a port configured to trust the IP DSCP value.
To configure global CoS settings:
1. Select QoS CoS Basic CoS Configuration.
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