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and may discard some low priority packets in case of bandwidth shortage.
If devices of each hop in a network support differentiated service, an end-to-end
QoS solution can be created. QoS configuration is flexible, the complexity or simplicity
depends on the network topology and devices and analysis to incoming/outgoing traffic.
9.1.1.3 Basic QoS Model
The basic QoS consists of five parts: Classification, Policing, Remark, Queuing and
Scheduling, where classification, policing and remark are sequential ingress actions, and
Queuing and Scheduling are QoS egress actions.
Fig 9-3 Basic QoS Model
Classification: Classify traffic according to packet classification information and
generate internal DSCP value based on the classification information. For different
packet types and switch configurations, classification is performed differently; the
flowchart below explains this in detail.
Sort the packet traffic
according to the
classification info and ACLs
and convert classification
info to DSCP value
Decide whether the
traffic is in profile or out
of profile according to
the packet DSCP value
and plicing policy
Forward in profile
packets,
degrade/discard
outprofile packets
Place packets into priority
queues according to CoS
value and service
according the queue
Ingress
egress
Generate
DSCP
Queuing and
scheduling
Remark
Policing
Classification
