Video Applications; Critical Database Applications; Web Browsing Applications; File Server Applications - Extreme Networks ExtremeWare XOS Guide Manual

Video Applications

Video applications are similar in 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. For example, in the playback of stored video streams,
some applications can transmit large amounts of data for multiple streams in one "spike," with the
expectation that the end-stations will buffer significant amounts of video-stream data. This can present a
problem to the network infrastructure, because it must be capable of buffering the transmitted spikes
where there are speed differences (for example, going from Gigabit Ethernet to Fast Ethernet). Key QoS
parameters for video applications include minimum bandwidth and priority.

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
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. In addition,
RED can be used to reduce session loss if the queue that floods Web traffic becomes over-subscribed.

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 11 summarizes QoS guidelines for the different types of network traffic.
Table 11: Traffic Type and QoS Guidelines
Traffic Type
Voice
Video
Database
ExtremeWare XOS 10.1 Concepts Guide
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-based applications. In addition, Web-based
Key QoS Parameters
Minimum bandwidth, priority
Minimum bandwidth, priority, buffering (varies)
Minimum bandwidth
Applications and Types of QoS
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