Ingress Port Configuration
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Class of Service Queuing
The Class of Service (CoS) feature lets you give preferential treatment to certain types of
traffic over others. To set up this preferential treatment, you can configure the ingress ports,
the egress ports, and individual queues on the egress ports to provide customization that suits
your environment.
The level of service is determined by the egress port queue to which the traffic is assigned.
When traffic is queued for transmission, the rate at which it is serviced depends on how the
queue is configured and possibly the amount of traffic present in other queues for that port.
Some traffic is classified for service (i.e., packet marking) before it arrives at the switch. If you
decide to use these classifications, you can map this traffic to egress queues by setting up a
CoS Mapping table.
Ingress Port Configuration
Each ingress port on the switch has a default priority value (set by configuring VLAN Port
Priority in the Switching sub-menu) that determines the egress queue its traffic gets forwarded
to. Packets that arrive without a priority designation, or packets from ports you have identified
as “untrusted,” get forwarded according to this default.
Trusted and Untrusted Ports/CoS Mapping Table
The first task for ingress port configuration is to specify whether traffic arriving on a given
port is “trusted” or “untrusted.”
A trusted port means that the system will accept at face value a priority designation within
arriving packets. You can configure the system to trust priority designations based on one of
the following fields in the packet header:
•
802.1 Priority - values 0-7
•
IP DSCP - values 0-63
•
IP Precedence - values 0-7
You can also configure an ingress port as untrusted, where the system ignores priority
designations of incoming packets and sends the packet to a queue based on the ingress port’s
default priority.
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