Defining Schedulers

An individual device interface has multiple queues assigned to store packets temporarily before transmission. To determine the order in which to service the queues, the device uses a round-robin scheduling method based on priority and the queue's weighted round-robin (WRR) credits. JUNOS schedulers allow you to define the priority, bandwidth, delay buffer size, rate control status, and RED drop profiles to be applied to a particular queue for packet transmission. For more information on schedulers, see the JUNOS Software Interfaces and Routing Configuration Guide.

Table 127: Schedulers Configuration Options

Field	Function	Action
Configure Schedulers Summary
Scheduler name	Displays the names of defined schedulers.	None
Scheduler priority	Displays the transmission priority of the scheduler, which determines the order in which an output interface transmits traffic from the queues.	None
Details of Scheduler
Name	Displays the scheduler name.	None
Value	Displays the CoS value.	None
Add	Opens a page that allows you to add a scheduler.	To add a scheduler, click Add.
Edit	Opens a page that allows you to edit a selected scheduler.	To edit a scheduler, select an existing scheduler in the summary page and click Edit.
Delete	Removes selected schedulers.	To remove an existing scheduler, select the scheduler and click Delete.
Add Scheduler/Edit Scheduler
Scheduler name	Specifies the name for a scheduler.	To name a scheduler, type the name—for example, be-scheduler.
Scheduler priority	Sets the transmission priority of the scheduler, which determines the order in which an output interface transmits traffic from the queues. You can set scheduling priority at different levels in an order of increasing priority from low to high. A high-priority queue with a high transmission rate might lock out lower-priority traffic.	To specify a priority, select one: high—Packets in this queue have high priority. low—Packets in this queue are transmitted last. medium—low—Packets in this queue have medium-low priority. medium—high—Packets in this queue have medium-high priority. strict—high—Packets in this queue are transmitted first.
Buffer size	Defines the size of the delay buffer. By default, queues 0 through 7 have the following percentage of the total available buffer space: Queue 0—95 percent Queue 1—0 percent Queue 2—0 percent Queue 3—0 percent Queue 4—0 percent Queue 5—0 percent Queue 6—0 percent Queue 7—5 percent Note: A large buffer size value correlates with a greater possibility of packet delays. This might not be practical for sensitive traffic such as voice or video.	To define a delay buffer size for a scheduler, select the appropriate option: To enforce exact buffer size, select Exact. To specify a buffer size as a temporal value (microseconds), select Temporal. To specify buffer size as a percentage of the total buffer, select Percent and type an integer from 1 through 100. To specify buffer size as the remaining available buffer, select Remainder.
Shaping rate	Defines the minimum bandwidth allocated to a queue. The default shaping rate is 100 percent, which is the same as no shaping at all.	To define a shaping rate, select the appropriate option: To specify shaping rate as an absolute number of bits per second, select rate and type an integer from 3200 to 160,000,000,000 bits per second. To specify shaping rate as a percentage, select percent and type an integer from 0 through 100.
Transmit rate	Defines the transmission rate of a scheduler. The transmit rate determines the traffic bandwidth from each forwarding class you configure. By default, queues 0 through 7 have the following percentage of transmission capacity: Queue 0—95 percent Queue 1—0 percent Queue 2—0 percent Queue 3—5 percent Queue 4—0 percent Queue 6—0 percent Queue 7—5 percent	To define a transmit rate, select the appropriate option: To specify a transmit rate, select rate and type an integer from 3200 to 160,000,000,000 bits per second. To enforce an exact transmit rate, select rate. To specify the remaining transmission capacity, select remainder. To specify a percentage of transmission capacity, select percent and type an integer from 1 through 100.