Figure 26.3: MPLS TC
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 pack-
ets 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.
26.1.2 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 des-
tination, 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.
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