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11 QUALITY OF SERVICE
This chapter includes the following sections for configuring Quality of
Service (QoS):
◆ “QoS Introduction” on page 79
◆ “Port-Based Priority” on page 80
◆ “DSCP-Based Priority” on page 81
◆ “Priority-to-Queue Mapping” on page 82
◆ “Packet Scheduling” on page 84
QOS INTRODUCTION
All switches or routers that access the Internet rely on class information to
provide the same forwarding treatment to packets in the same class. Class
information can be assigned by end hosts, or switches or routers along the
path. Priority can then be assigned based on a general policy, or a detailed
examination of the packet. However, note that detailed examination of
packets should take place close to the network edge so that core switches
and routers are not overloaded.
Switches and routers along the path can use class information to prioritize
the resources allocated to different traffic classes. The manner in which an
individual device handles traffic is called per-hop behavior. All devices
along a path should be configured in a consistent manner to construct a
consistent end-to-end Quality of Service (QoS) solution.
This section describes how to specify which data packets have greater
precedence when traffic is buffered in the switch due to congestion. This
switch provides eight priority queues for each port. Data packets in a port's
high-priority queue will be transmitted before those in the lower-priority
queues. You can set the default priority for each interface, the queuing
mode, and queue weights.
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