Configuring Differentiated Services 1139
DiffServ for VoIP
One of the most valuable uses of DiffServ is to support Voice over IP (VoIP). 
VoIP traffic is inherently time-sensitive: for a network to provide acceptable 
service, a guaranteed transmission rate is vital. This example shows one way 
to provide the necessary quality of service: how to set up a class for UDP 
traffic, have that traffic marked on the inbound side, and then expedite the 
traffic on the outbound side. The configuration script is for Router 1 in the 
accompanying diagram: a similar script should be applied to Router 2.
Figure 40-18. DiffServ VoIP Example Network Diagram
Internet
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Layer 3 Switch 
Operating as 
Router 1
Layer 3 Switch 
Operating as 
Router 2
Port 1/0/2
Port 1/0/3