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Example: Configuring a Large Delay Buffer on a Channelized T1 Interface
This example shows how to configure a large delay buffer on a channelized T1 interface to help slower interfaces avoid congestion and packet dropping when they receive large bursts of traffic.
Requirements
Before you begin, enable the large buffer feature on the channelized T1/E1 PIM and then configure a buffer size for each queue in the CoS scheduler. See Scheduler Buffer Size Overview.
Overview
On devices, you can configure large delay buffers on channelized T1/E1 interfaces. Each channelized T1/E1 interface can be configured as a single clear channel, or for channelized (NxDS0) operation, where N denotes channels 1 to 24 for a T1 interface and channels 1 to 32 for an E1 interface.
In this example, you specify a queue buffer of 30 percent
in scheduler be-scheduler and associate the scheduler to
a defined forwarding class be-class using scheduler map large-buf-sched-map. Finally, you apply the scheduler map to
channelized T1 interface t1-3/0/0.
Configuration
Procedure
CLI Quick Configuration
To quickly configure this example, copy the
following commands, paste them into a text file, remove any line breaks,
change any details necessary to match your network configuration,
copy and paste the commands into the CLI at the [edit] hierarchy
level, and then enter commit from the configuration mode.
set chassis fpc 3 pic 0 q-pic-large-buffer set class-of-service schedulers be-scheduler buffer-size percent 30 set class-of-service scheduler-maps large-buf-sched-map forwarding-class be-class scheduler be-scheduler set class-of-service interfaces t1-3/0/0 unit 0 scheduler-map large-buf-sched-map
Step-by-Step Procedure
The following example requires you to navigate various levels in the configuration hierarchy. For instructions on how to do that, see Using the CLI Editor in Configuration Mode in the Junos OS CLI User Guide.
To configure a large delay buffer on a channelized T1 interface:
Enable the large buffer size feature on the channelized T1 interface.
[edit] user@host# edit chassis user@host# set fpc 3 pic 0 q-pic-large-buffer
Create best-effort traffic and specify a buffer size.
[edit] user@host# edit class-of-service user@host# set schedulers be-scheduler buffer-size percent 30
Configure the scheduler map to associate schedulers with defined forwarding classes.
[edit class-of-service] user@host# set scheduler-maps large-buf-sched-map forwarding-class be-class scheduler be-scheduler
Apply the scheduler map to the channelized T1 interface.
[edit class-of-service] user@host# set interfaces t1-3/0/0 unit 0 scheduler-map large-buf-sched-map
Results
From configuration mode, confirm your configuration
by entering the show class-of-service and show chassis commands. If the output does not display the intended configuration,
repeat the configuration instructions in this example to correct it.
[edit]
user@host# show class-of-service
interfaces {
t1-3/0/0 {
unit 0 {
scheduler-map large-buf-sched-map;
}
}
}
scheduler-maps {
large-buf-sched-map {
forwarding-class be-class scheduler be-scheduler;
}
}
schedulers {
be-scheduler {
buffer-size percent 30;
}
}
[edit]
user@host# show chassis
fpc 3 {
pic 0 {
q-pic-large-buffer;
}
}
If you are done configuring the device, enter commit from configuration mode.