Avaya 882 Manuel D’Utilisation

25-2

User Guide for the Avaya P580 and P882 Multiservice Switches, v6.1

Chapter 25

In a network that has time-sensitive traffic (VoIP) or bandwidth-intensive 
traffic (real-time or near-real-time streaming-video), QoS makes it possible 
for you to prioritize the time-sensitive traffic and assign larger amounts of 
bandwidth to those applications that require it.

VoIP traffic has relatively low bandwidth requirements, but cannot tolerate 
latency or frame loss. Therefore, this traffic needs a high priority to ensure 
its timely delivery. On the other hand, streaming video is bandwidth-
intensive but has large “jitter buffers” so can tolerate some latency. Thus, 
you can assign streaming video traffic a lower priority than voice, but must 
assign streaming video more bandwidth than voice. 

To successfully implement QoS, you must have a thorough knowledge of 
the traffic patterns in the network. You need this information to: 

■

Classify traffic and assign it the required priority and bandwidth.

■

Identify the areas of the network where bottlenecks might occur and 
that therefore need bandwidth limiting. 

■

Identify the areas of the network where time-sensitive traffic is 
being delayed and needs to be prioritized better.

An example of managing QoS across the network is to define traffic classes 
and manage these on a network-wide basis. The four classes and their 
priorities might look like those outlined in 

.

* Note:  For information about DSCP (DiffServ Code Point), see 

” later in this chapter.

Highest Priority

7

56

Network Management 
Traffic, OSPF, Spanning 
Tree, etc.

Time Sensitive 
Traffic

5

40

Real-time voice, video 
conferences.

High Priority 
Data

1

8

SAP, Web, etc. Dependent 
upon your business.

Best Effort

0

0

Everything else.