HP manual 481

End-to-end QoS

Figure 454 End-to-end QoS model

Traffic classification			Traffic classification
Traffic policing
			Traffic policing
	Traffic policing	Traffic policing

WAN

		Congestion management
Congestion management	Congestion management		Congestion management
Congestion avoidance	Congestion avoidance	Congestion avoidance	Congestion avoidance
Traffic shaping	Traffic shaping	Traffic shaping	Traffic shaping

As shown in Figure 454, 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.

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