/mcpQuality of Service for Voice over IP
VoIP QoS over ATM
41
QoSVoIP.mif
The following configuration example shows how to configure VoIP over ATM using PVC bundles to
separate voice and data PVCs:
VoIP QoS over ATM Solution Using Shared Data and Voice ATM PVCs
If you decide to use separate PVCs for voice and data, you must adjust the bandwidth allocation
accordingly as voice traffic grows beyond the bandwidth configured on the voice PVC. This manual
reprovisioning is not necessary when voice and data share the same PVC, provided that voice always
gets the priority it needs. You can configure VoIP traffic to have absolute priority over data traffic by
configuring LLQ on the ATM PVC.
Configuration Example 17: QoS for VoIP over ATM with Separate Voice and Data PVCs
Commands
Description
ip cef
!
Enables IP Cisco Express Forwarding (CEF)
switching. You must enable IP CEF switching for this
solution to work.
interface ATM 2/0/0
no ip address
!
interface ATM 2/0/0.1 point-to-point
ip address 10.1.1.2 255.255.255.252
bundle qosmap
Creates a PVC bundle group called qosmap.
protocol ip 10.1.1.1 broadcast
pvc-bundle control 1/100
precedence 6-7
Maps IP Precedence 6 and 7 traffic to a virtual path
identifier (VPI) or virtual channel identifier (VCI) of
1/100.
pvc-bundle voice 1/101
vbr-rt 6000 5000 1000
precedence 5
Maps IP Precedence 5 traffic (VoIP) to a VPI or VCI
of 1/101 with an SCR of 5 Mbps and some bursting
capabilities.
pvc-bundle web 1/102
cbr 5000
precedence 4
Maps IP Precedence 4 traffic to 1/102 with an SCR of
5 Mbps.
pvc-bundle data 1/103
precedence 0-3
Maps other precedence traffic to a PVC with a VPI or
VCI of 1/103.
In this example, four traffic classes based on IP Precedence are mapped to four separate ATM PVCs
in a bundle. The voice PVC has a guaranteed bandwidth of 5 Mbps with some bursting capabilities,
and the web traffic PVC is also guaranteed 5 Mbps but with no bursting (CBR). Control traffic and
all other traffic flows are not given any ATM rate guarantees.