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In-Profile: Traffic within the QoS policing policy range (bandwidth or burst value) is called "In-P rofile".
Out-of-P rofile: Traffic out the QoS policing policy range (bandwidth or burst value) is called "Out-of-Profile".
17.1.2 QoS Implementation
To implement the Chassis Switch software QoS, a general, mature reference model should be given. QoS can
not creat e new bandwidt h, but can maximize the adjustment and configuration for the current bandwidth
resource. Fully implemented QoS can achieve complet e management over the net work traffic. The following
is as accurate as possible a description of QoS.
The data transfer specifications of IP cover only addresses and s ervices of source and destination, and
ensure correct packet transmission using OSI layer 4 or above protocols such as TCP. However, rather than
provide a mechanism for providing and protecting packet transmission bandwidth, IP provide bandwidth
service by the best effort. This is acceptable for services like Mail and FTP, but for increasing multimedia
business data and e-business data transmission, this best effort method cannot satisfy the bandwidth and
low-lag requirement.
Based on differentiated service, QoS specifies a priority for each packet at the ingress. The classification
information is carried in Layer 3 IP packet header or Layer 2 802.1Q frame header. QoS provides same
service to packets of the same priority, while offers different operations for packets of different priority.
QoS-enabled switch or router can provide different bandwidth according to the packet classification
information, and can remark on the classification information according to the policing policies configured, and
may discard some low priority packets in case of bandwidth shortage.
If devices of each hop in a network support differentiated service, an end-to-end QoS solution can be created.
QoS configuration is flexible, the complexity or simplicity depends on the net work topology and devic es and
analysis to incoming/outgoing traffic.
17.1.3 Basic QoS Model
The basic QoS consists of five parts: Classification, Policing, Remark, Queuing and Scheduling, where
classification, policing and remark are sequential ingress actions, and Queuing and Scheduling are QoS
egress actions.
Classification
Sort
the
packet
according
to
classification info and ACLs
and convert classification
info to DSCP value
Ingress
Generate
DSCP
Policing
l
traffic
Decide
whether
the
traffic is in-profile or
out-of-profile according
to the packet DSCP
value and plicing policy
Figure 17-1-3 Basic QoS Model
Remark
Forward
in-profile
the
packets,
degrade/discard
out-of-profile
packets
17-2
egress
Queuing and
scheduling
Place packets into priority
queues according to CoS
value
and
service
according
the
queue
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