End-To-End Qos; Traffic Classification - HP FlexNetwork NJ5000 User Manual

End-to-end QoS

Figure 437 End-to-end QoS model

Traffic classification

Traffic policing
Congestion management
Congestion avoidance
Traffic shaping
As shown in
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.
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 used to classify the
packets in the network. IP precedence can also be used in queuing to prioritize traffic. The
Traffic policing
Congestion management
Congestion avoidance
Traffic shaping
Figure 437, traffic classification, traffic policing, traffic shaping, congestion management,
Traffic policing
WAN
Congestion management
Congestion management
Congestion avoidance Congestion avoidance
Traffic shaping
Traffic shaping
400
Traffic classification
Traffic policing