H3C Technologies H3C S7500E Series Switches - Manual (Page 29)

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QoS Overview
The S7500E Series Ethernet Switches are distributed devices supporting Intelligent Resilient
Framework (IRF). Two S7500E series can be connected together to form a distributed IRF device. If
an S7500E series is not in any IRF, it operates as a distributed device; if the S7500E series is in an
IRF, it operates as a distributed IRF device. For introduction of IRF, see IRF Configuration Guide.
This chapter covers the following topics:
z Introduction to QoS
z Introduction to QoS Service Models
z QoS Techniques Overview
Introduction to QoS
In data communications, Quality of Service (QoS) is the ability of a network to provide differentiated
service guarantees for diversified traffic regarding bandwidth, delay, jitter, and drop rate.
The network resources are always scarce. Wherever there is contention for resources, there is the
demand for QoS to prioritize important traffic flows over trivial traffic flows. When making a QoS
scheme, a network administrator must plan network resources carefully considering the characteristics
of various applications to balance the interests of diversified users and fully utilize network resources.
The following part introduces the QoS service models, and some mature QoS techniques in wide use.
Appropriately using these techniques in specific environments, you can improve QoS effectively.
Introduction to QoS Service Models
This section covers three typical QoS service models:
z Best-effort service
z Integrated service (IntServ)
z Differentiated service (DiffServ)
Best-Effort Service Model
Best effort is a single service model and also the simplest service model. In the best effort service
model, the network delivers the packets at its best effort but does not guarantee delay or reliability.
The best-effort service model is the default model in the Internet and is applicable to most network
applications. It is implemented through FIFO queuing.