Configuring Tail Drop - Cisco ASR 9000 Series Service Configuration Manual

How to Configure Modular QoS Congestion Avoidance on Cisco ASR 9000 Series Routers
Command or Action
Step 9
interface type inteface-path-id
Example:
RP/0/RSP0/CPU0:router(config)# interface
gigabitethernet 0/2/0/0
Step 10
service-policy {input | output} policy-map
Example:
RP/0/RSP0/CPU0:router(config-if)#
service-policy output policy1
Step 11
end
or
commit
Example:
RP/0/RSP0/CPU0:router(config-cmap)# end
or
RP/0/RSP0/CPU0:router(config-cmap)# commit

Configuring Tail Drop

Packets satisfying the match criteria for a class accumulate in the queue reserved for the class until they
are serviced. The queue-limit command is used to define the maximum threshold for a class. When the
maximum threshold is reached, enqueued packets to the class queue result in tail drop (packet drop).
The queue-limit value uses the guaranteed service rate (GSR) of the queue as the reference value for the
queue_bandwidth. If the class has bandwidth percent associated with it, the queue-limit is set to a
proportion of the bandwidth reserved for that class.
If the GSR for a queue is zero, use the following to compute the default queue-limit:
•
•
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide
QC-82
1 percent of the interface bandwidth for queues in a nonhierarchical policy.
1 percent of minimum parent shape and interface rate for queues within a hierarchical policy.
Configuring Modular QoS Congestion Avoidance on Cisco ASR 9000 Series Routers
Purpose
Enters configuration mode and configures an interface.
Attaches a policy map to an input or output interface to be
used as the service policy for that interface.
In this example, the traffic policy evaluates all traffic
•
leaving that interface.
•
Saves configuration changes.
When you issue the end command, the system prompts
•
you to commit changes:
Uncommitted changes found, commit them before
exiting(yes/no/cancel)?
[cancel]:
– Entering yes saves configuration changes to the
running configuration file, exits the configuration
session, and returns the router to EXEC mode.
Entering no exits the configuration session and
–
returns the router to EXEC mode without
committing the configuration changes.
Entering cancel leaves the router in the current
–
configuration session without exiting or
committing the configuration changes.
Use the commit command to save the configuration
•
changes to the running configuration file and remain
within the configuration session.
OL-23108-02