24-Port Managed Gigabit Switch
3.12 Quality of Sevice (QoS)
3.12.1 QoS Introduction
QoS stands for Quality of Service. QoS is a generic name for a set
of algorithms which attempt to provide different levels of quality to
ensure high-quality performance for critical applications as VoIP
packets. So the goal of QoS is to provide preferential delivery
service for the applications that need it by ensuring sufficient
bandwidth, controlling latency and forwarding sequence, and
reducing data loss.
Traditionally, the concept of quality in networks meant that all
network traffic was treated equally. The result was that all network
traffic received the network’s best effort, with no guarantees for
reliability, delay, variation in delay, or other performance
characteristics. With best-effort delivery service, however, a single
bandwidth-intensive application can result in poor or unacceptable
performance for all applications. The QoS concept of quality is one
in which the requirements of some applications and users are more
critical than others, which means that some traffic needs
preferential treatment.
3.12.2 Well-known Priority
1. 802.1Q VLAN Frame
The figure below shows the 802.1Q VLAN frame structure. There
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