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C H A P T E R 10 Quality of Service (QoS)
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Applications and Types of QoS
Applications vary significantly in QoS requirements. These
applications are ones that you will most commonly encounter and
need to prioritize:
• Voice applications
• Video applications
• Critical database applications
• Web browsing applications
• File server applications
General guidelines for each traffic type are given below and
summarized in Table 10.1 on page 139. These are general
guidelines and not strict recommendations.
After the QoS parameters are set, you can monitor the performance
of the application to determine if the actual behavior of the
applications matches your expectations. It is important to
understand the needs and behavior of the particular applications you
want to protect or limit. Behavioral aspects to consider include:
• Bandwidth needs
• Sensitivity to latency and jitter
• Sensitivity and impact of packet loss
Voice Applications
Voice applications typically demand small amounts of bandwidth.
However, the bandwidth must be constant and predictable because
these applications are typically sensitive to latency (inter-packet
delay) and jitter (variation in inter-packet delay).
The most important QoS parameter to establish for voice
applications is minimum bandwidth, followed by priority.
Video Applications
Video applications are similar in QoS needs to voice applications,
with the exception that bandwidth requirements are somewhat
larger, depending on the encoding. It is important to understand the
behavior of the video application being used.