User Manual - Configuration Guide (Volume 3)

Chapter 3

Versatile Routing Platform

Congestion Management

I. FIFO

 

queue

Packets leaving the interface

 

Packets sent from this interface

Dequeuing dispatch

 

Figure QC-3-2Schematic diagram of FIFO queuing

As shown in the figure above, packets enter FIFO queue in sequence. The dequeuing sequence is the same as the incoming queue sequence, that is, the packet that arrives earlier will be sent earlier, while the packet arrives later will be sent later. FIFO does not make any judgement on the packets, and allocation of network bandwidth and resource are determined according to the arriving sequence of the packets. Therefore, vicious application may occupy all network resources, seriously affecting data transmission of key services.

II. PQ

Classification Packets sent

from this interface

Queue

high

medium

normal

low

Packets leaving the interface

Dequeuing dispatch

Figure QC-3-3Schematic diagram of priority queuing

As shown in the figure above, PQ is used to provide strict priority for important network data. It ensures that the most important data in the network unit using PQ can be processed as fast as possible. PQ can flexibly specify the priority sequence according to network protocol (for example, IP and IPX), data inflow interface, length of the packet and source address/destination address.

When the queues are dispatched, PQ first sends the packets in the queue with higher priority in strict compliance with high-to-low sequence. If the queue with higher priority is empty, the packets in the queue with lower priority can be sent. The packets in the queue with lower priority might be congested due to the existence of packets in the queue with higher priority. Therefore, the packets of key service (for example, ERP) are put in the queue with higher priority, and the packets of ordinary service (for example, E-mail) are put in the queue with lower priority. In this way, it can be ensured that packets of key services are transmitted with priority, and the packets of ordinary services are transmitted in the idle intervals during the processing of the key service data.

3-5

Page 86
Image 86
Huawei v200r001 user manual Fifo