Chapter 3 Services
QoS
provides network service functions with different service qual-
ities to meet various demands.
QoS has the following features:
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Traffic classification
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Traffic policing
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Port rate limit
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Queue scheduling
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Traffic mirroring
Traffic
Classification
Traffic classification refers to classify packets and transmit them to
different system devices for processing. Traffic identification with
different priority features is based on the
field in
packet
head.
For example, classify packets based on information on the data
link layer, network layer, and transmission layer. This information
includes
address, IP protocol type, source (host, network seg-
ment) address, destination (host, network segment) address, and
port number of the application program.
Traffic Policing
Traffic policing is used to monitor service flow according to classi-
fication rule at the packets receiving port. It enables the service
flow to adapt to the allocated network resource, such as band-
width. Traffic policing is used for rate restriction on packets re-
ceiving port, monitoring traffic flowing to one network. If packet
rate is too fast, traffic policing can discard the packet or reset the
packet priority.
Port Rate Limit
Port rate limit is used to monitor and restrict the bandwidth oc-
cupied by the service traffic at the port that sends packets. This
enables the service traffic to adapt to the network resource. Port
rate limit sets a rate threshold at the port that sends packets. If
the traffic exceeds this rate, the packets are discarded. In this
way, sending rate is limited.
Queue Scheduling
Queue scheduling solves the problem that multiple packets com-
pete for the network resource when packets are forwarded. Queue
scheduling modes include the following:
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SP+WRR
These algorithms solve packet forwarding problems in each output
queue of device port according to their own principles. FSAP 9800
supports these three queue scheduling modes.
Traffic Mirroring
Traffic mirroring is used to monitor service flows according to the
traffic classification rule. This function copies data packets ac-
cording to the traffic classification rule to monitor port, facilitate
network detection, and locate the faults.
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