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Chapter 23 QoS Configuration
23.1 Introduction to QoS
QoS (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 requirement and network management
policy.
23.1.1 QoS Terms
QoS: Quality of Service, provides a guarantee for service quality of consistent and predictable
data transfer service to fulfill program requirements. QoS cannot generate new bandwidth but
provides more effective bandwidth management according to the application requirement and
network management.
QoS Domain: QoS Domain supports QoS devices to form a net-topology that provides Quality
of Service, so this topology is defined as QoS Domain.
CoS: Class of Service, the classification information carried by Layer 2 802.1Q frames, taking
3 bits of the Tag field in frame header, is called user priority level in the range of 0 to 7.
Figure 23-1: CoS priority
ToS: Type of Service, a one-byte field carried in Layer 3 IPv4 packet header to symbolize the
service type of IP packets. Among ToS field can be IP Precedence value or DSCP value.
Figure 23-2: ToS priority
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