Extreme Networks ExtremeWare 7.2e, Installation And User Manual

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Applications and Types of QoS
ExtremeWare 7.2e Installation and User Guide 111
where there are speed differences (for example, going from Gigabit Ethernet to Fast Ethernet). Key QoS
parameters for video applications include minimum bandwidth, priority, and possibly buffering
(depending upon the behavior of the application).
Critical Database Applications
Database applications, such as those associated with ERP, typically do not demand significant
bandwidth and are tolerant of delay. You can establish a minimum bandwidth using a priority less than
that of delay-sensitive applications.
Web Browsing Applications
QoS needs for Web browsing applications cannot be generalized into a single category. For example,
ERP applications that use a browser front-end may be more important than retrieving daily news
information. Traffic groupings can typically be distinguished from each other by their server source and
destinations. Most browser-based applications are distinguished by the dataflow being asymmetric
(small dataflows from the browser client, large dataflows from the server to the browser client).
An exception to this may be created by some Java
™
-based applications. In addition, Web-based
applications are generally tolerant of latency, jitter, and some packet loss, however small packet-loss
may have a large impact on perceived performance due to the nature of TCP. The relevant parameter
for protecting browser applications is minimum bandwidth. The relevant parameter for preventing
non-critical browser applications from overwhelming the network is maximum bandwidth.
File Server Applications
With some dependencies on the network operating system, file serving typically poses the greatest
demand on bandwidth, although file server applications are very tolerant of latency, jitter, and some
packet loss, depending on the network operating system and the use of TCP or UDP.
NOTE
Full-duplex links should be used when deploying policy-based QoS. Half-duplex operation on links can
make delivery of guaranteed minimum bandwidth impossible.
Table 21 summarizes QoS guidelines for the different types of network traffic.
Table 21: Traffic Type and QoS Guidelines
Traffic Type Key QoS Parameters
Voice Minimum bandwidth, priority
Video Minimum bandwidth, priority, buffering (varies)
Database Minimum bandwidth
Web browsing Minimum bandwidth for critical applications, maximum bandwidth for non-critical
applications
File server Minimum bandwidth