Purpose
Command or Action
Once you specify a specific PVC in the range,
you can continue to configure options that are
Step 5
specific to that PVC, such as the
class-vc
command.
Exits ATM PVC range configuration mode and returns to privileged
EXEC mode.
Router(config-if-atm-vc-range-pvc)#
end
Step 6
Configuring Traffic Parameters for PVCs
After creating a PVC, you can also configure it for the type of traffic quality of service (QoS) class to be used
over the circuit:
•
Constant Bit Rate (CBR)
—
Configures the CBR service class and specifies the average cell rate for the
PVC.
•
Unspecified Bit Rate (UBR)
—
Configures the UBR service class and specifies the output peak rate (PCR)
for the PVC. This is the default configuration.
•
Variable Bit Rate
–
Non-real Time (VBR-nrt)
—
Configures the VBR-nrt service class and specifies the
output PCR, output sustainable cell rate (SCR), and output maximum burst size (MBS) for the PVC.
•
Variable Bit Rate
–
Real Time (VBR-rt)
—
Configures the VBR-rt service class and the peak rate and
average rate burst for the PVC.
Each service class is assigned a different transmit priority, which the Cisco ASR 1000 Series Router uses to
determine which queued cell is chosen to be transmitted out of an interface during any particular cell time
slot. This ensures that real-time QoS classes have a higher likelihood of being transmitted during periods of
congestion. THe following table lists the ATM QoS classes and their default transmit priorities.
Transmit Priority
Service Category
0 (highest)
CBR
1
VBR-rt
2
VBR-nrt
3
UBR
You can configure a PVC for only one QoS service class. If you enter more than one type, only the most
recently configured QoS class takes effect on the circuit.
To configure the traffic parameters for a PVC, perform the following procedure beginning in global
configuration mode:
Cisco ASR 1000 Series Aggregation Services Routers SIP and SPA Software Configuration Guide, Cisco IOS XE
Everest 16.5
OL-14127-17
75
Configuring the ATM SPAs
Configuring Traffic Parameters for PVCs