Switch User Manual

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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.
z Traffic classification identifies specific packets based on certain matching rules. It is a prerequisite
for differentiated service.
z Traffic 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.
z Traffic 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.
z Congestion management handles resource competition during network congestion. Generally, it
adds packets to queues first, and then forwards the packets by using a scheduling algorithm.
z Congestion 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