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QoS Configuration
z
The term switch used throughout this chapter refers to a switching device in a generic sense or the
switching engine of the WX3000 series.
z
The sample output information in this manual was created on the WX3024. The output information
on your device may vary.
Overview
Introduction to QoS
Quality of service (QoS) is a concept generally existing in occasions with service supply and demand. It
evaluates the ability to meet the need of the customers in service. Generally, the evaluation is not to
grade precisely. Its purpose is to analyze the conditions where the service is the best and the conditions
where the service still needs improvement and then to make improvements in the specified aspects.
In an internet, QoS evaluates the ability of the network to deliver packets. The evaluation on QoS can
be based on different aspects because the network provides various services. Generally speaking, QoS
is the evaluation on the service ability to support the core requirements such as delay, jitter, and packet
loss ratio in the packet delivery.
Traditional Packet Forwarding Service
In traditional IP networks, packets are treated equally. That is, the FIFO (first in first out) policy is
adopted for packet processing. Network resources required for packet forwarding is determined by the
order in which packets arrive. All the packets share the resources of the network. Network resources
available to the packets completely depend on the time they arrive. This service policy is known as
Best-effort, which delivers the packets to their destination with the best effort, with no assurance and
guarantee for delivery delay, jitter, packet loss ratio, reliability, and so on.
The traditional Best-Effort service policy is only suitable for applications insensitive to bandwidth and
delay, such as WWW, file transfer and E-mail.
New Applications and New Requirements
With the expansion of computer network, more and more networks become part of the Internet. The
Internet gains rapid development in terms of scale, coverage and user quantities. More and more users
use the Internet as a platform for their services and for data transmission.
Besides the traditional applications such as WWW, E-mail, and FTP, new services are developed on the
Internet, such as tele-education, telemedicine, video telephone, videoconference and
