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matching the traffic classification and permit other flows to pass. System adopts complicated

flow classification to filtrate all kinds of information of service layer 2 packets to deny useless,

unreliable, and doubtable service flow to strengthen network security.

Two key points of realizing packet filtration:

Step 1: Classify ingress flows according to some regulation;

Step 2: Filtrate distinct flow by denying. Deny is default accessing control.

5. Flow monitor

In order to serve customers better with the limited network resources, QoS can monitor service

flow of specified user in ingress interface, which can adapt to the distributed network resources.

6. Interface speed limitation

Interface speed limitation is the speed limit based on interface which limits the total speed rate

of interface outputting packet.

7. Redirection

User can re-specify the packet transmission interface based on the need of its own QoS

strategies.

8. Priority mark

Ethernet switch can provide priority mark service for specified packet, which includes: TOS,

DSCP, 802.1p. These priority marks can adapt different QoS model and can be defined in

these different models.

9. Choose interface outputting queue for packet

Ethernet switch can choose corresponding outputting queue for specified packets.

10. Queue scheduler

It adopts queue scheduler to solve the problem of resource contention of many packets when

network congestion. There are three queue scheduler matchings: Strict-Priority Queue (PQ),

Weighted Round Robin (WRR) and WRR with maximum delay.

(1) PQ

PQ(Priority Queueing)is designed for key service application. Key service possesses an

important feature, that is, require the precesent service to reduce the response delay when

network congestion. Priority queue divides all packets into 4 levels, that is, superior priority,

middle priority, normal priority and inferior priority (3, 2, 1, 0), and their priority levels reduce in

turn.

When queue schedulerimg, PQ precedently transmits the packets in superior priority according

to the priority level. Transmit packet in inferior priority when the superior one is empty. Put the

key service in the superior one, and non-key service (such as email)in inferior one to

guarantee the packets in superior group can be first transmitted and non-key service can be