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EES4710BD 10 Slots L2/L3/L4 Chassis Switch
Chapter 16 QoS Configuration
16.1 Introduction to QoSQoS (Quality of Service) is a set of capabilities that allow you to create differentiated services for
network traffic, thereby providing better service for selected network traffic. QoS is a guarantee for
service quality of consistent and predictable data transfer service to fulfill program requirements.
QoS cannot generate extra bandwidth but provides more effective bandwidth management
according to the application requirements and network management policies.
16.1.1 QoS Terms
CoS: Class of Service, the classification information carried by Layer 2 IEEE 802.1Q frames. It
takes 3 bits of the Tag field in the frame header for user priority level in the range of 0 to 7.
Fig 16-1 CoS priority
ToS: Type of Service, a one byte field carried in Layer 3 IPv4 packet headers to symbolize the
service type of IP packets. The ToS field can be IP Precedence value or DSCP value.
Fig 16-2 ToS priority
IP Precedence: IP priority, classification information carried in Layer 3 IP packet header, occupying
3 bits, in the range of 0 to 7.
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.
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 policy and manages the classified packets.
Remark: Ingress action of QoS, performs allowing, degrading or discarding operations to packets
according to the policies.
Queuing: Egress QoS action, put the packets to appropriate egress queues according to the packet
CoS value.
Scheduling: QoS egress action, configure the weight for eight egress queue WRR (Weighted Round