Classification - Cisco Catalyst 2950 Software Manual

Understanding QoS
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Actions at the egress interface include queueing and scheduling:
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Figure 13-2 Basic QoS Model

Classification

Classify the packet
based on the ACL.
Classification
Note This feature is available only if your switch is running the enhanced software image.
Classification is the process of distinguishing one kind of traffic from another by examining the fields
in the packet.
Classification occurs only on a physical interface basis. No support exists for classifying packets at the
VLAN or the switched virtual interface level.
You specify which fields in the frame or packet that you want to use to classify incoming traffic.
Catalyst 2950 Desktop Switch Software Configuration Guide
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Classifying distinguishes one kind of traffic from another. For more information, see the
"Classification" section on page
Policing determines whether a packet is in or out of profile according to the configured policer, and
the policier limits the bandwidth consumed by a flow of traffic. The result of this determination is
passed to the marker. For more information, see the
Marking evaluates the policer and configuration information for the action to be taken when a packet
is out of profile and decides what to do with the packet (pass through a packet without modification,
mark down the DSCP value in the packet, or drop the packet). For more information, see the
"Policing and Marking" section on page
Queueing evaluates the CoS value and determines which of the four egress queues in which to place
the packet.
Scheduling services the four egress queues based on their configured weighted round robin (WRR)
weights.
Actions at ingress
In profile or
out of profile
Policing
Determine if the
packet is in profile or
out of profile based
on the policier
associated with the
filter.
13-4.
"Policing and Marking" section on page
13-6.
Mark
Based on whether
the packet is in or
out of profile and the
configured
parameters,
determine whether
to pass through,
mark down, or drop
the packet. The
DSCP and CoS are
marked or changed
accordingly.
Chapter 13 Configuring QoS
Actions at egress
Queueing and
scheduling
Based on the CoS,
determine into which
of the egress
queues to place the
packet. Then service
the queues
according to the
configured weights.
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13-6.