HP V1910, Руководство пользователя

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End-to-end QoS
a.
End-to-end QoS model
As shown in a , traffic classification, traffic policing, traffic shaping, congestion management, and
congestion avoidance are the foundations for a network to provide differentiated services. Mainly they
implement the following functions:

Traffic classification uses certain match criteria to organize packets with different characteristics into
different classes. Traffic classification is usually applied in the inbound direction of a port.

Traffic policing polices particular flows entering or leaving a device according to configured
specifications and can be applied in both inbound and outbound directions of a port. When a flow
exceeds the specification, some restrictive measures can be taken to prevent overconsumption of
network resources.

Traffic shaping proactively adjusts the output rate of traffic to adapt traffic to the network resources of
the downstream device and avoid unnecessary packet drop and congestion. Traffic shaping is usually
applied in the outbound direction of a port.

Congestion management provides a resource scheduling policy to arrange the forwarding sequence
of packets when congestion occurs. Congestion management is usually applied in the outbound
direction of a port.
 Congestion avoidance monitors the usage status of network resources and is usually applied in the
outbound direction of a port. As congestion becomes worse, it actively reduces the amount of traffic by
dropping packets.
Among these QoS technologies, traffic classification is the basis for providing differentiated services. Traffic
policing, traffic shaping, congestion management, and congestion avoidance manage network traffic and
resources in different ways to realize differentiated services.
Traffic classification
When defining match criteria for classifying traffic, you can use IP precedence bits in the type of service
(ToS) field of the IP packet header, or other header information such as IP addresses, MAC addresses, IP
protocol field and port numbers. You can define a class for packets with the same quintuple (source address,
source port number, protocol number, destination address and destination port number for example), or for
all packets to a certain network segment.
When packets are classified on the network boundary, the precedence bits in the ToS field of the IP packet
header are generally re-set. In this way, IP precedence can be directly adopted to classify the packets in the
network. IP precedence can also be used in queuing to prioritize traffic. The downstream network can either