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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 transmitted in the spare time.

The shortage of PQ is: when there is network congestion, there are more packets in superior group for a long

time, the packets in inferior priority will wait longer.

(2)WRR

WRR queue scheduler divides a port into 4 or 8 outputting queues (QSW-2900 has 4 queues, that is, 3, 2, 1, 0)

and each scheduler is in turn to guarantee the service time for each queue. WRR can configure a weighted value (that

is, w3, w2, w1, w0 in turn) which means the percentage of obtaining the resources. For example: There is a port of

100M. Configure its WRR queue scheduler value to be 50, 30, 10, 10 (corresponding w3, w2, w1, w0 in turn) to

guarantee the inferior priority queue to gain at least 10Mbit/s bandwidth, to avoid the shartage of PQ queue scheduler

in which packets may not gain the service.

WRR possesses another advantage. The scheduler of many queues is in turn, but the time for service is not

fixed——if some queue is free, it will change to the next queue scheduler to make full use of bandwidth resources.

(3) WRR with maximum delay

Compared with WRR, WRR with maximum delay can guarantee the maximum time from packets entering

superior queue to leaving it will not beyond the configured maximum delay.

11. The cos-map relationship of hardware priority queue and priority of IEEE802.1p protocol

System will map between 802.1p protocol priority of packet and hardware queue priority. For each packet,

system will map it to specified hardware queue priority according to 802.1p protocol priority of packet.

12. Flow mirror

Flow mirror means coping specified data packet to monitor interface to detect network and exclude failure.

13. Statistics based on flow

Statistics based on flow can statistic and analyse the packets customer interested in.

14. Copy packet to CPU

User can copy specified packet to CPU according to the need of its QoS strategies.

System realizes QoS function according to accessing control list, which includes: flow monitor, interface

speed limit, packet redirection, priority mark, queue scheduler, flow mirror, flow statistics and coping packet to CPU.