Avaya IP Telephony Guía de configuración descargar pdf (Pagina 198)

198 Quality of Service

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Implementing QoS in IP networks

The information under the headings in this section explain how to implement QoS in IP networks:

• “Traffic mix” on page 198

• “Business Communications Manager router QoS support” on page 199

Corporate intranets are developed to support data services. Accordingly, normal intranets are

designed to support a set of QoS objectives dictated by these data services.

When an intranet takes on a real-time service, users of that service set additional QoS objectives in

the intranet. Some of the targets can be less controlled, compared with the targets set by current

services, while other targets are more controlled. For intranets not exposed to real-time services in

the past, but which now need to deliver IP telephony traffic, QoS objectives for delay can set an

additional design restriction on the intranet.

One method of determining requirements is to subject all intranet traffic to additional QoS

restrictions, and design the network to the strictest QoS objectives. An exact plan for the design

improves the quality of data services, although most applications cannot identify a reduction of,

say, 50 ms in delay. Improvement of the network results in a network that is correctly planned for

voice, but over planned for data services.

Another plan is to consider using QoS in the intranet. This provides a more cost-effective solution

to engineering the intranet for non-homogenous traffic types.

Traffic mix

This section describes QoS works with the IP telephony, and what new intranet-wide results can

occur.

Before putting into operation QoS in the network, determine the traffic mix of the network.

QoS depends on the process and ability to determine traffic (by class) so as to provide different

services.

With an intranet designed only to deliver IP telephony traffic, where all traffic flows are equal

priority, there is no need to consider QoS. This network can have one class of traffic.

In most corporate environments, the intranet supports data and other services. When planning to

provide voice services over the intranet the installer must determine the following:

• Is there existing QoS? What kind? IP telephony traffic must take advantage of established

mechanisms if possible.

• What is the traffic mix? If the IP telephony traffic is light compared to data traffic on the

intranet, then IP QoS can work. If IP telephony traffic is heavy, data services can be affected if

QoS is biased toward IP telephony traffic.

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Avaya IP Telephony Guía de configuración Pagina 198