User's Manual

Table Of Contents
372
Users Manual of CS-6306R
2. Differentiated service
As to the differentiated service, if a special service is to be transmitted in a network, each packet should be
specified with a corresponding QoS tag. The switch uses this QoS rule to conduct classification and complete
the intelligent queuing. The QoS of the switch provides Strict Priority (SP), Weighted Round Robin (WRR),
Deficit Round Robin (DRR) and First-Come-First-Served (FCFS).
40.1.1.3 Queue Algorithm of QoS
Each queue algorithm is the important basis to realize QoS. The QoS of the switch provides the following
algorithms: Strict Priority (SP), Weighted Round Robin (WRR), Deficit Round Robin (DRR) and
First-Come-First-Served (FCFS).
1. Strict priority
This algorithm means to first provide service to the flow with the highest priority and after the highest-priority
flow comes the service for the next-to-highest flow. This algorithm provides a comparatively good service to
those flows with relatively high priority, but its shortage is also explicit that the flows with low priority cannot
get service and wait to die.
2. Weighted round robin
Weighted Round Robin (WRR) is an effective solution to the defect of Strict Priority (SP), in which the
low-priority queues always die out. WRR is an algorithm that brings each priority queue a certain bandwidth
and provides service to each priority queue according to the order from high priority to low priority. After the
queue with highest priority has used up all its bandwidth, the system automatically provides service to those
queues with next highest priority.
3. Weighted Fair Queuing
Weighted Round Robin (WRR) is an effective solution to the defect of Strict Priority (SP), in which the
low-priority queues always die out. WRR is an algorithm that brings each priority queue a certain bandwidth
and provides service to each priority queue according to the order from high priority to low priority. After the
queue with highest priority has used up all its bandwidth, the system automatically provides service to those
queues with next highest priority.
4. First come first served
The First-Come-First-Served queue algorithm, which is shortened as FCFS, provides service to those
packets according to their sequence of arriving at a switch, and the packet that first arrives at the switch will
be served first.