15. qos_ lpt car and principle issue1.00

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LPT and CAR Principle

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� Upon completion of this course, you will be

able to:

�Know the function of LPT

�Know the function and principle of CAR

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ChapterChapter 1 1 LPTLPT technologytechnology

ChapterChapter 2 CAR 2 CAR technologytechnology

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LPT (Link State Pass Through)

� Principle: LPT can transfer end-to-end connectivity of port link

state( UP/DOWN). If link state is DOWN, both side equipments will switch

immediately to backup path.

MSTP

OptiX

OptiX

Microwave networkstandbystandby

RS-A

RS-B

LINKLINK--DOWN DOWN

NE1NE2

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LPT－Optical Line Failure

MSTP

OptiX

OptiX

Microwave networkstandbystandby

RS-A

RS-B

LINKLINK--DOWN DOWN

NE1NE2

Fiber broken, Fiber broken, protection failedprotection failed

LINKLINK--DOWN DOWN

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ChapterChapter 1 1 LPTLPT technologytechnology

ChapterChapter 2 CAR 2 CAR technologytechnology

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Traditional IP Network

� Packets are treated in the same way according to the FIFO.

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Packet Classification

� Packets arriving at the interface are first classified and then enter the tail of the corresponding queues according to their respective types.

The transmission of the packets is based on the priority.

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Flow Classification

� Classification of the data packets into several service types,

which can be conducted according to different criteria.

� The port flow means the classification of the data packets

according to the ports concerned.

� The port+VLAN flow means the classification of the data

packets according to the port+VLAN criterion

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CAR: Committed Access Rate

� The CAR mode adopts token bucket for traffic control.

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Principle of dual-bucket 3-color mode

� Each token bucket has its own capacity and token generation speed, which are respectively cir, cbs, pir, pbs. Cir indicates

the guaranteed rate, while pir the peak rate

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Shaping

� The typical function of traffic shaping is to restrict the traffic and burst flowing out of a certain link in a certain network, so that

packets of this type can be transmitted at an even rate. Traffic

shaping is usually implemented through buffer and token

bucket.

� When the packet transmission rate is too high, the packets are

first buffered and then transmitted at an even speed under the control of the token bucket.

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CoS: Class of Service

� Congestion management is used to classify these packets and group them into different queues. The queue scheduling processes the packets of different priority levels accordingly, that is, packets of higher priority level are processed first.

� VLAN pri CoS: When a certain flow is configured with this kind of CoS, the packets of the flow are scheduled to a certain specified queue according to the VLAN Pri value carried in the packets.

� IP TOS CoS: When a certain flow is configured with this kind of CoS, the packets of the flow are scheduled to a certain specified queue according to the IP TOS value of the IPv4 carried in the packets.

� DSCP CoS: When a certain flow is configured with this kind of CoS, the packets of the flow are scheduled to a certain specified queue according to the IP DSCP value of the IPv6 carried in the packets.

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QoS Comparison of Ethernet Boards

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QoS Comparison of Ethernet Boards (Cont.)

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� What’s the function of LPT?

� What are the function and principle of

CAR?

Summary

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