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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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