RCA THOMSON SpeedTouchTM (Wireless) Business DSL Router - Manual (Page 14)

Chapter 2
Introduction
E-NIT-CTC-20041213-0013 v0.5
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2.1 What is Quality of Service?
Definition Quality of Service is the ability for an application to obtain the network service it
requires for successful operation.
Nowadays the total amount of data traffic increases, while new types of data
emerge, like: voice data, video data, audio data. These new types of data pose new
requirements for data transport, e.g. low latency, low data loss… To meet these
requirements, the entire network must ensure them via a connection service
guarantee. Such a connection service guarantee can both be applied to connection-
oriented networks (connection based) and to packet-oriented networks (data-stream
or data type based).
Quality of Service allows specifying a connection service guarantee via a set of
connection parameters. Throughout the network, this set of connection parameters
will be used to handle the connection data in a way to achieve the connection
service guarantee. This handling includes reserving bandwidth, priority based
queuing, scheduling, modifying data characteristics, …
Examples of connection parameters include the maximum amount of bandwidth that
may be used, the guaranteed amount of bandwidth that will always be available, the
maximum delay the data can experience throughout the network, a priority
indication,…
Misunderstandings A common misunderstanding about QoS is that QoS is about gaining a superior level
of network service for particular individuals.
The example below illustrates this.
The best illustration of why it is pointless to give enhanced network service to
particular individuals is shown by video-conferencing. Imagine John: he sees a
horrible quality image of the other video conference participant; but the other
participant sees John’s face perfectly. This is obviously not the desired result.
For John to also see a high-quality image, all participants in the video conference
need appropriate network service, not only John.
IP QoS provides such service. With IP QoS voice and/or video traffic can get a higher
priority then data traffic. This way good voice and video quality is guaranteed.
!
Note that QoS is no solution for overloaded networks, it only helps to shape
bursty peaks on the network. (See
Bandwidth versus QoS )