The bandwidth command is part of the parent policy. In this instance, the bandwidth command not
only sets the minimum bandwidth for the class but also resets the reference point for the bandwidth
percent statements in the child policy.
Note
For main interface service policies:
•
If bandwidth is configured in the parent class, parent minimum bandwidth is used as a reference for the
child bandwidth percentages.
•
If bandwidth is not configured in the parent class, the implicit minimum bandwidth, which is a portion
of the total unallocated bandwidth allocated to the class based on the explicit or implicit bandwidth
remaining, is used as a reference.
Implicit bandwidth remaining is an equal share of unallocated bandwidth among all queuing classes
without either bandwidth or bandwidth remaining actions.
For subinterface policies:
•
If bandwidth is configured in the parent class, parent minimum bandwidth is used as a reference for
child bandwidth percentages.
•
If bandwidth remaining is configured in the parent class, bandwidth-remaining-percent * interface-rate
is used as a reference.
•
If bandwidth is not configured in the parent class, shape rate is used as a reference.
In the following example, the hierarchical policy is attached to the main interface, and the parent classes are
a mix of bandwidth and shape only classes:
policy-map hqos
class c1
bandwidth percent 40
service-policy child
class c2
shape average 500000000
service-policy child
The reference for the child policy in class c2 is the implicit bandwidth of class c2 bounded by the shape rate
of class c2. Therefore, the reference = (60 percent * interface bandwidth) / 3 bounded by 500000000 kbps.
In the following example, the hierarchical policy is a class-default only parent shape configured on subinterfaces:
policy-map sub_int_hqos
class c1ass-default
shape average 40
service-policy child
The class-default parent shape rate is used as reference.
When the percent keyword is used with the bandwidth command, the bandwidth of the interface is defined
as being the Layer 2 capacity excluding the Gigabit Ethernet or POS encapsulation but including the High-Level
Data Link Control (HDLC) flags, frame check sequence (FCS), and so on. These have to be included because
they are applied per packet, and the system cannot predict how many packets of a particular packet size are
being sent out.
For example, the following policy is applied to an OC-192 interface:
policy-map oc-192
class c1
bandwidth percent 50
Cisco IOS XR Modular Quality of Service Command Reference for the Cisco CRS Router, Release 4.0
6 OL-23235-03
Quality of Service Commands on the Cisco IOS XR Software
bandwidth (QoS)
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