Accton Technology ES4710BD - Manual (Page 333)

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E ES4710BD 10 Slots L2/L3/L4 Chassis Switch
Robin).
In Profile: Traffic within the QoS policy range (bandwidth or burst value) is called “In Profile".
Out of Profile: Traffic out the QoS policy range (bandwidth or burst value) is called “Out of
Profile".
16.1.2 QoS Implementation
To implement Layer 3 switch software QoS, a general, mature reference model should be given.
QoS can not create new bandwidth, but can maximize the adjustment and configuration for current
bandwidth resources. Fully implemented QoS can achieve complete management over the network
traffic. The following is as accurate as possible a description of QoS.
The data transfer specifications of IP cover only addresses and services of source and destination,
and ensure correct packet transmission using OSI layer 4 or higher protocols such as TCP. However,
rather providing and protecting packet transmission bandwidth, IP provides bandwidth service by
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-latency requirement.
Based on differentiated service, QoS specifies a priority for each packet at the ingress. The
classification information is carried in the Layer 3 IP packet header or Layer 2 IEEE 802.1Q frame
header. QoS provides same service to packets of the same priority, while offering different
operations for packets of different priority. A QoS-enabled switch or router can provide different
bandwidths 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 network
topology, devices and analysis to incoming/outgoing traffic.
16.1.3 Basic QoS Model
The basic QoS consists of five parts: Classification, Policing, Remarking, Queuing and Scheduling,
Classification, policing and remarking are sequential ingress actions. Queuing and Scheduling are
QoS egress actions.