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1 QoS Configuration
When configuring QoS, go to these sections for information you are interested in:
z Overview
z QoS Features Supported by the Switch 4200G series
z Introduction to QoS Features
z QoS Configuration
z QoS Configuration Examples
Overview
Introduction to QoS
Quality of Service (QoS) is a concept concerning service demand and supply. It reflects the ability to
meet customer needs. Generally, QoS focuses on improving services under certain conditions rather
than grading services precisely.
In an internet, QoS evaluates the ability of the network to forward packets of different services. The
evaluation can be based on different criteria because the network may provide various services.
Generally, QoS refers to the ability to provide improved service by solving the core issues such as delay,
jitter, and packet loss ratio in the packet forwarding process.
Traditional Packet Forwarding Services
On traditional IP networks, devices treat all packets equally and handle them using the first in first out
(FIFO) policy. All packets share the resources of the network and devices. How many resources the
packets can obtain completely depends on the time they arrive. This service is called best-effort. It
delivers packets to their destinations as possibly as it can, without any guarantee for delay, jitter, packet
loss ratio, reliability and so on.
This service policy is only suitable for applications insensitive to bandwidth and delay, such as WWW,
e-mail, and FTP.
New Requirements from Emerging Applications
The Internet has been growing along with the fast development of networking technologies. More and
more people use the Internet to transmit data, share video and do a lot of other things.
Besides traditional applications such as WWW, e-mail and FTP, network users are experiencing new
services, such as tele-education, telemedicine, video telephone, videoconference and
Video-on-Demand (VoD). Enterprise users expect to connect their regional branches together with VPN
technologies to carry out operational applications, for instance, to access the database of the company
or to monitor remote devices through Telnet.
These new applications have one thing in common, that is, they all have special requirements for
bandwidth, delay, and jitter. For example, videoconference and VoD require high bandwidth, low delay
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