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Configuring a Large Delay Buffer on a Channelized T1 interface

On J-series Services Routers you can configure large delay buffers on channelized T1/E1 interfaces only. To configure large-delay buffer sizes, you must first enable the large buffer feature on the channelized T1/E1 PIM and then configure a buffer size for each queue in the CoS scheduler.

Each channelized T1/E1 interface can be configured as a single clear channel, or for channelized (NxDS0) operation, where N denotes channels 1 to 32 for an E1 interface and channels 1 to 24 for a T1 interface.

In this configuration, you enable the large delay buffer option on a channelized T1 PIM with an interface speed of 1.5 Mbps and a maximum delay buffer time of 500,000 microseconds. Based on the interface speed and the maximum delay buffer time, you can calculate the available delay buffer size for the interface. For more information, see Maximum Delay Buffer Sizes Available to Interfaces.

Next, you specify a queue buffer of 30 percent in a scheduler be-scheduler and associate the scheduler to a defined forwarding class be-class using a scheduler map large-buf-sched-map. Finally, you apply the scheduler map to the channelized T1 interface t1-3/0/0. As a result, a buffer of 9600 bytes is assigned to the queue associated with forwarding class be-class (see Table 144). You can specify a delay buffer size for other queues following the instructions in this example.

To configure large delay buffers for channelized T1/E1 interfaces:

  1. Navigate to the top of the configuration hierarchy in either the J-Web or CLI configuration editor.
  2. Perform the configuration tasks described in Table 145.
  3. If you are finished configuring the router, commit the configuration.
  4. Go on to one of the following tasks:

Table 145: Configuring a Large Delay Buffer

Task

J-Web Configuration Editor

CLI Configuration Editor

Navigate to the Chassis level in the configuration hierarchy.

  1. In the J-Web interface, select Configuration>Edit Configuration>View and Edit.
  2. Next to Chassis, click Configure or Edit.

From the [edit] hierarchy level, enter

edit chassis

Enable the large buffer size feature on the channelized T1/E1 PIM in slot 3.

  1. Next to Fpc, click Add new entry.
  2. In the Slot box, type the slot number 3.
  3. Next to Pic, click Add new entry.
  4. In the Slot box, type 0.
  5. Next to Q pic large buffer, select the check box.
  6. Click OK.

Enter

set fpc 3 pic 0 q-pic-large-buffer

Navigate to the Class-of-service level in the configuration hierarchy.

On the main Configuration page next to Class of service, click Configure or Edit.

From the [edit] hierarchy level, enter

edit class-of-service

Create be-scheduler and specify a buffer size of 30 percent for it.

  1. Next to Schedulers, click Add new entry.
  2. In the Scheduler name box, type the name of the scheduler—be-scheduler.
  3. Next to Buffer size, click Configure.
  4. From the Buffer size choice list, select percent.
  5. In the Percent box, type 30.
  6. Click OK.

Enter

set schedulers be-scheduler buffer-size percent 30

Configure the scheduler map large-buf-scheduler-map to associate schedulers with defined forwarding classes.

For information about configuring forwarding classes, see Assigning Forwarding Classes to Output Queues.
  1. On the Class of service page, next to Scheduler maps, click Add new entry.
  2. In the Map name box, type the name of the scheduler map—large-buf-sched-map.
  3. Next to Forwarding class, click Add new entry.
  4. In the Class name box, type the name of the forwarding class to be associated with the scheduler—be-class.
  5. In the Scheduler box, type the name of the scheduler to be associated with the forwarding class—be-scheduler.
  6. Click OK.

From the [edit class-of-service] hierarchy level, enter

set scheduler-maps large-buf-sched-map forwarding-class be-class scheduler be-scheduler

Apply the scheduler map to the channelized T1 interface.

Note:

For information about configuring channelized T1/E1 interfaces, see the J-series Services Router Basic LAN and WAN Access Configuration Guide.
  1. On the Class of service page, next to Interfaces, click Add new entry.
  2. In the Interface name box, type the name of the interface to which the scheduler map is to be applied—t1-3/0/0.
  3. Next to Unit, click Add new entry.
  4. In the Unit number box, type 0.
  5. In the Scheduler map box, type the name of the scheduler map—large-buf-sched-map.
  6. Click OK.

From the [edit class-of-service] hierarchy level, type

set interfaces t1-3/0/0 unit 0 scheduler-map large-buf-sched-map

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