Configure Congestion Management

In a complex network, congestion is common because the current bandwidth cannot satisfy the normal forwarding. Congestion may cause a series of negative problems as follows: the system breaks down because of abundant network resources, the network resource utility is low because of decreased network throughput, and packet transmission delay and jitter increase. Scheduling policy for the port queue is a method for managing the congestion.

Configuration Condition

None

Configure Scheduling Policy of Port Queue

The queue-based scheduling policy sends out the classified traffic by a certain priority-level algorithm. Each queue algorithm solves a certain network traffic problem and has great influence on bandwidth resource allocation, delay, and jitter. Queue scheduling processes the packets of different priorities in levels. A packet with high priority will be sent preferentially.

The common scheduling includes SP (Strict Priority), RR (Round Robin), WRR (Weighted Round Robin), and WDRR (Weighted Deficit Round Robin).

SP (Strict Priority): There are eight queues on the port, queue 0-7. Queue 7 has the highest priority and queue 0 has the lowest priority.

RR (Round Robin): After one queue schedules one packet, turn to the next queue.

WRR (Weighted Round Robin): It is the weighted scheduling based on packet. You can configure the number of the packets scheduled by each queue before turning to the next queue.

WDRR (Weighted Deficit Round Robin): It is the improvement for the WRR algorithm. The algorithm is based on two variables, that is, quantum and credit counter. The quantum means the weight in the unit of byte and it is a configurable parameter. The credit counter means the accumulation and consumption of the quantum, which is a status parameter and cannot be configured. In the initial state, the credit counter of each queue is equal to the quantum. Every time the queue sends a packet, subtract the byte number of the packet from the credit counter. When the credit counter is lower than 0, stop the scheduling of the queue. When all queues stop scheduling, supplement quantum for all queues.

Table 1-13 Configure the scheduling policy for the port queue