Variable Bit Rate - Cisco 10000 Series Configuration Manual

Chapter 3 Configuring QoS Policy Actions and Rules
Configuring UBRs
To configure a UBR, enter the following commands in ATM VC configuration mode:
Command
Step 1
Router(config)# interface type
slot/module/port.subinterface
Step 2
Router(config-if)# atm pxf queuing
or
Router(config-if)# no atm pxf queuing
Step 3
Router(config-subif)# pvc vci/vpi
Step 4
Router(config-atm-vc)# ubr output-pcr

Variable Bit Rate

Variable bit rate (VBR) connections are classified as one of the following:
•
•
OL-7433-09
Real time (VBR-rt)—Used for connections that transmit at a rate varying with time and that can be
described as bursty, often requiring large amounts of bandwidth when active. The VBR-rt class is
intended for applications that require tightly constrained delay and delay variation such as
compressed voice video conferencing—for example, video conferencing requires real-time data
transfer with bandwidth requirements that can vary in proportion to the dynamics of the video image
at any given time. The VBR-rt category is characterized in terms of peak cell rate (PCR), sustained
cell rate (SCR), and maximum burst size (MBS).
Nonreal time (VBR-nrt)—Used for connections that are bursty but are not constrained by delay and
delay variation boundaries. For those cells in compliance with the traffic contract, a low cell loss is
expected. Non-time critical data file transfers are an example of a VBR-nrt connection. A VBR-nrt
connection is characterized by PCR, SCR, and MBS.
Purpose
Specifies an interface or subinterface and enters interface
configuration mode.
Specifies one of two ATM PXF queuing modes for an
interface or ATM port.
Do not change this queuing mode while VCs are
Note
configured on the interface. If you need to change the
mode, delete the VCs first and then change the mode.
Changing the mode while VCs are configured can
produce undesired results, and the change does not
take effect until the router reloads.
Configures a PVC on the subinterface and enters ATM VC
configuration mode.
vci is the virtual channel identifier.
vpi is the virtual path identifier.
Creates a UBR.
output-pcr is the output peak cell rate. The router configures
a shaped UBR when you specify the output PCR. Otherwise,
the router configures unshaped UBR.
Cisco 10000 Series Router Quality of Service Configuration Guide
QoS Inheritance
3-15