Manual

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Москва, Новозаводская ул., 18, стр. 1
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Internal Priority: The internal priority setting of the switch chip, it’s valid range relates with the
chip, it’s shortening is Int-Prio or IntP.
Drop Precedence: When processing the packets, firstly drop the packets with the bigger drop
precedence, the ranging is 0-1. It’s shortening is Drop-Prec or DP.
Classification: The entry action of QoS, classifying packet traffic according to the
classification information carried in the packet and ACLs.
Policing: Ingress action of QoS that lays down the policing policy and manages the classified
packets.
Remark: Ingress action of QoS, perform allowing, degrading or discarding operations to
packets according to the policing policies.
Scheduling: QoS egress action. Add the packets to the corresponding egress queue
according to the internal priority. And then decide sending and dropping according to Drop
Precedence, sending algorithm and queue weight of egress queue.
12.1.2 QoS Implementation
To implement the 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 the
current bandwidth resource. 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 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
network topology and devices and analysis to incoming/outgoing traffic.
12.1.3 Basic QoS Model
The basic QoS consists of four parts: Classification, Policing, Remark and Scheduling, where
classification, policing and remark are sequential ingress actions, and Queuing and Scheduling