HP Compaq Presario,Presario 1910, Руководство пользователя

Страница: 506 / 578

493
End-to-end QoS
Figure 471 End-to-end QoS model
As shown in Figure 471 , 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 restriction or punishment 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.
This section is focused on traffic classification, and the subsequent sections will introduce the other
technologies in details.
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.
WAN
Traffic classification
Traffic policing
Congestion management
Congestion avoidance
Traffic shaping
Traffic policing
Congestion management
Congestion avoidance
Traffic shaping
Traffic policing
Congestion management
Congestion avoidance
Traffic shaping
Traffic classification
Traffic policing
Congestion management
Congestion avoidance
Traffic shaping