QTech QSW-2800 series Configuration Manual - 19.1.2 Qos Implementation
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DSCP: Differentiated Services Code Point, classification information carried in Layer 3 IP
packet header, occupying 6 bits, in the range of 0 to 63, and is downward compatible with IP
Precedence.
MPLS TC(EXP):
A field of the MPLS packets means the service class, there are 3 bits, the ranging from 0 to 7.
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 0-2 in three color algorithm, the ranging is 0-1 in dual color
algorithm.
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. Configure the weight for eight egress queues WRR
(Weighted Round Robin).
In-Profile: Traffic within the QoS policing policy range (bandwidth or burst value) is called In-
Profile.
Out-of-Profile: Traffic out the QoS policing policy range (bandwidth or burst value) is called
Out-of-Profile.
19.1.2 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