3Com WX3000 QoS Supported by Devices, Major Traffic Control Techniques, Traffic Classification

Video-on-Demand (VoD). Enterprise users expect to connect their regional branches together using VPN techniques for coping with daily business, for instance, accessing databases or manage remote equipments through Telnet.

All these new applications have one thing in common, that is, they have special requirements for bandwidth, delay, and jitter. For instance, bandwidth, delay, and jitter are critical for videoconference and VoD. As for other applications, such as transaction processing and Telnet, although bandwidth is not as critical, a too long delay may cause unexpected results. That is, they need to get serviced in time even if congestion occurs.

Newly emerging applications demand higher service performance from IP networks. In addition to simply delivering packets to their destinations, better network services are demanded, such as allocating dedicated bandwidth, reducing packet loss ratio, avoiding congestion, regulating network traffic, and setting priority of the packets. To meet those requirements, the network should be provided with better service capability.

Major Traffic Control Techniques

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.

zTraffic classification identifies specific packets based on certain matching rules. It is a prerequisite for differentiated service.

zTraffic policing confines traffics to a specific specification. You can configure restriction or punishment measures against the traffics exceeding the specification to protect the benefits of carriers and to prevent network resources from being abused.

zTraffic shaping actively adjusts the output rate of traffics. It can enable the traffics to match the capacity of the downstream network devices, so as to prevent packets from being dropped and network congestion.

zCongestion management handles resource competition during network congestion. Generally, it adds packets to queues first, and then forwards the packets by using a scheduling algorithm.

zCongestion avoidance monitors the use of network resources and drops packets actively when congestion reaches certain degree. It relieves network load by adjusting traffics.

Traffic classification is the basis of all the above-mentioned traffic management technologies. It identifies packets using certain rules and makes differentiated services possible. Traffic policing, traffic shaping, congestion management, and congestion avoidance are methods for implementing network traffic control and network resource management. They are occurrences of differentiated services.

QoS Supported by Devices

Traffic Classification

Traffic here refers to service traffic; that is, all the packets passing the device.

Traffic classification means identifying packets that conform to certain characteristics according to certain rules. It is the foundation for providing differentiated services.

In traffic classification, the priority bit in the type of service (ToS) field in IP packet header can be used to identify packets of different priorities. The network administrator can also define traffic classification policies to identify packets by the combination of source address, destination address, MAC address, IP protocol or the port number of an application. Normally, traffic classification is done by checking the

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