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QoS Configuration
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bandwidth and low-lag requirement.
Based on differentiated service, QoS specifies a priority for each packet at the
ingress. The classification information is carried in Layer 3 IP packet header or Layer 2
802.1Q frame header. QoS provides same service to packets of the same priority, while
offers different operations for packets of different priority. QoS-enabled switch or router
can provide different bandwidth according to the packet classification information, and can
remark on the classification information according to the policing policies configured, 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.
20.1.3
Basic QoS Model
The basic QoS consists of four parts: Classification, Policing, Remark and Scheduling,
where classification, policing and remark are sequential ingress actions, and Queuing and
Scheduling are QoS egress actions.
Fig 20-3 Basic QoS Model
Classification: Classify traffic according to packet classification information and generate
internal priority based the classification information. For different packet types,
classification is performed differently; the flowchart below explains this in detail.