Cisco CRS Command Reference Manual page 79

Quality of Service Commands on the Cisco IOS XR Software
When the queue limit is configured in time units, the guaranteed service rate of the class is used to calculate
the queue limit in bytes. For example: time_unit in ms * guaranteed_service_rate in kbps / 8 is equivalent to
queue-limit in bytes.
The following restrictions apply to queue limits:
• Queue limit should be at least the maximum MTU size, which is 9 * 1024 bytes = 9kb.
• Queue limit cannot exceed 1 GB, which is the maximum packet buffer size in ingress and egress queuing
• Only time-based units are allowed on bundle targets.
Guaranteed Service Rate
The guaranteed service rate is defined as the service rate of the queue when all queues are backlogged and
derived as:
minimum_bandwidth + (bandwidth_remaining_percent * unallocated_bandwidth)
The following example shows the guaranteed service rate calculation:
policy-map sample_policy
class c1
class c2
class class-default
guaranteed service rate of c1 = 30 percent LR + (40 percent * 50 percent * LR)
guaranteed service rate of c2 = 20 percent LR + (30 percent * 50 percent * LR)
guaranteed service rate of class-default = 30 percent * 50 percent * LR
• Where LR is line rate of the target on which service policy "sample_policy" is attached.
• 50 percent is unallocated bandwidth.
Task ID
Task ID
qos
Examples
The following example shows how to set the queue limit for a class to 1000000 packets for policy map policy1:
RP/0/RP0/CPU0:router(config)# policy-map policy1
RP/0/RP0/CPU0:router(config-pmap)# class class1
RP/0/RP0/CPU0:router(config-pmap-c)# queue-limit 1000000
Related Commands
Command
class (policy-map), on page 10
OL-23235-03
ASICs.
bandwidth percent 30
bandwidth remaining percent 40
bandwidth percent 20
Cisco IOS XR Modular Quality of Service Command Reference for the Cisco CRS Router, Release 4.0
Operations
read, write
Description
Specifies the name of the class whose policy you want to create
or change.
queue-limit
73