User Manual - Configuration Guide (Volume 3)
Versatile Routing Platform Chapter 1
QoS overview
1-2
overloaded. When the network is congested, it can also guarantee the lo w delay
high pass of some types of packets.

III. Differentiated Service

Differentiated service is to classify services with the same requirem ent, and to provide
different service quality according to the different classification. It does not need t he
support of special signaling, but implements the packets classification, traffic shaping,
traffic policing and queuing through some features of the IP packet. It can also adopt
different working modes to assort with the edge network or the core network.
Differentiated Service adopts the following technology as an important application to
provide point-to-point QoS guarantee:
z CAR: to police the traffic of one flow, several or all the flows.
z GTS: to shape the traffic of one flow, several or all the flows.
z Queuing technology: such queuing debugging technologies as First-In Firs t-Out
Queuing, Priority Queuing, Custom Queuing, Weighted fair queuing, Class Based
Weighted Fair Queuing operate congestion management on interfaces.
Differentiated Service implements VRP QoS, its specific performanc es are as follows:
z Packets classification
At the edge of the network, classify operations with different service quality into
different types. In the core network, execute the operation of corresponding service
quality level according to the classification.
z Congestion Management
When there is congestion on the interface, provide diversified queu ing mec hanism to
cache and allocate the congested packets.
z Congestion Avoidance
Avoid congestion through predicting the congestion state of the network. Congestion
Avoidance can decrease the packet loss rate and improve the efficiency of using
network.
z Traffic Policing
Control the traffic of single flow, several flows and all the packets, and m ake the service
quality customized.
z Traffic Shaping
Shape the traffic that does not accord with the predefined traffic f eatures so as to
facilitate the bandwidth matching. It also can shape every flow or all the packets on the
interface.
z Interface Speed Restriction
Tailor the bandwidth of the physical interface to enrich the managing methods of
network bandwidth.
1.3 Functions of QoS
The features of QoS enable the network to provide controllable and predicable ser vices
for different network applications and network traffic types. With QoS applied to the
network, the followings can be implemented:
z Network resource control. Users can control the network resources being used.
For example, the user can restrict the bandwidth resource to be cons umed for FTP
transmission in a specific connection, or provide higher priority for a more
important data access.
z Providing trimmed network service. If the user is an ISP, QoS can be used to
provide trimmed network service with different priorities for diff erent customers.