Chapter 2 Traffic Classification, Policing, And Shaping; Traffic Classification; Traffic Policing And Traffic Shaping - 3Com 3C13636 Configuration Manual

3Com Router 3000 Ethernet Family
Configuration Guide
Chapter 2 Traffic Classification, Policing, and

2.1 Traffic Classification

Traffic classification is the prerequisite and foundation for differentiated service, which
uses certain rules to identify the packets with certain features.
To discriminate flows, you can set traffic classification rules using the priority bits of ToS
(type of service) field in the IP packet header, or using cell loss priority (CLP), the last bit
in the fourth byte of the ATM cell header. Alternatively, the network administrator may
define a traffic classification policy, for instance, integrating information such as source
IP address, destination IP address, MAC address, IP, or port number of the applications
to classify the traffic. In general, it can be a narrow range defined by a quintuple (source
IP address, source port number, destination IP address, destination port number and
the Transport Protocol), or can be all packets to a network segment.
In general, while packets being classified on the network border, the precedence bits in
the ToS byte of IP header are set so that IP precedence can be used as a direct packet
classification standard within the network. The queuing technologies, such as WFQ,
can use IP precedence to handle the packets. Downstream network can receive the
packets classification results from upstream network selectively, or re-classify the
packets with its own standard.
Traffic classification is used to provide differentiated service, so it must be associated
with certain kinds of traffic policing or resource-assignment mechanisms. To adopt what
kind of traffic policing action will depend on the current stage and load status of the
network. For example, to police the packets according to the committed rate when they
enter the network, to make traffic shaping before they flow out the nodes, to do queuing
in the event of congestion and to employ congestion avoidance when congestion
becomes worse.

2.2 Traffic Policing and Traffic Shaping

If no restrictions are imposed on the traffics from the users, bursting data sent by mass
users continuously will make the network become more congested. Thus for more
efficient network function and better network service for more users, the traffics from
the users must be restricted, for example, to restrict a traffic can only acquire the
specific assigned resources in certain time interval so as to prevent the network
congestion caused by excess burst.

Chapter 2 Traffic Classification, Policing, and Shaping

Shaping
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