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Qtech QSW-3200-28T [65/136] Brief introduction of qos

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Chapter 8 QOS CONFIGURATION

8.1 Brief introduction of QOS

In traditional packet network, all packets are equal to be handled. Each switch and router

handles packet by FIFO to make best effort to send packets to the destination and not to

guarantee the transmission delay and delay variation.

With the fast development of computer network, the requirement of network is higher. More

and more voice, image and important data which are sensitive about bandwidth, delay and

jittering transferred through network, which greatly enrich network service resources and the

requirement of quality of service is higher for the network congestion. Now, Ethernet becomes

the leading technology in every independent LAN, and many LAN in the form of Ethernet have

become a part of internet. With the development of Ethernet technology, Ethernet connecting

will become one of main connecting for internet users. To realize end-to-end QoS solution has

to consider the service guarantee of Ethernet QoS, which needs Ethernet device applies to

Ethernet technology to provide different levels of QoS guarantee for different types of service

flow, especially the service flow highly requiring delay and jitter.

1. Flow

Flow is traffic which means all packets through switch.

2. Traffic classification

Traffic classification means adopting certain regulation to recognize packet with some

features. Clasification rule means the filtration regulation configured by the administrator

according to managing need which can be simple, such as realizing flow with the feature of

different priority according to the ToS field of IP packet head and can be complicated, such as

information of integrated link layer (layer 2), network layer (layer 3), transmission layer (layer

4), such as MAC address, IP protocol, source address, destination address or application

program interface number to classify packet. General classification is limited in the head of

encapsulation packet. Use packet content to be classification standard is singular.

3. Access control list

To classify flow is to provide service distinctively which must be connected resource

distributing. To adopt which kind of flow control is related to the stage it is in and the current

load of the network. For example: monitor packet according to the promised average speed

rate when the packet is in the network and queue scheduling manage the packet before it is

out of the node.

4. Packet filtration

Packet filtration is to filtrate service flow, such as deny, that is, deny the service flow which is

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.

Qtech QSW-3200-28T [65/136] Brief introduction of qos

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