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Defining Schedulers

Figure 42 shows the initial Quick Configuration page for defining schedulers, scheduler maps, and random early detection (RED) drop profiles. Using schedulers, you can assign attributes to queues and thereby provide congestion control to a particular class of traffic. These attributes include the amount of interface bandwidth, memory buffer size, transmit rate, RED drop profiles and priority.

To configure schedulers using the Quick Configuration pages:

  1. Create a drop profile by specifying the fill levels and drop probabilities. The drop profile map on the Scheduler page uses this drop profile. For a description of RED drop profile-related fields, see Table 127.
  2. Create a scheduler and specify attributes to it. For a description of scheduler-related fields, see Table 128.
  3. Associate the scheduler to a forwarding class. Because the forwarding class is assigned to a queue number, the queue inherits this scheduler's attributes. For a description of scheduler map-related fields, see Table 129.

Figure 42: Schedulers Quick Configuration Page

Schedulers Quick Configuration
Page

Table 127: RED Drop Profiles Quick Configuration Page Summary

Field

Function

Your Action

RED Drop Profiles Summary

RED Drop Profile Name

Displays the configured random early detection (RED) drop profile names.

RED attempts to avoid congestion by dropping packets from the head of a queue.

Allows you edit a specific drop profile.

To edit a RED drop profile, click its name.

Graph RED Profile

Opens a new window and displays a graph for a specific RED drop profile.

To view the graph for a specific RED drop profile, click Graph.

RED Drop Profile Information (Fill Level, Drop Probability)

Displays information about the data point type, the queue buffer fill level, and the drop probability for specific RED drop profiles.

None.

Add

Opens a page that allows you to add a RED drop profile.

To add a RED drop profile, click Add.

Delete

Removes a RED drop profile.

To remove a RED drop profile, select it and click Delete.

Add a RED Drop Profile/Edit RED Drop Profile

Graphed RED Profile

Displays a graph of RED drop profiles. Each data point in this graph is defined by a pair of x and y coordinates and represents the relationship between them.

The x axis represents the queue buffer fill level, which is a percentage value of how full the queue is.

The y axis represents the drop probability, which is a percentage value of the chances of a packet being dropped.

None.

Drop Profile Name

Specifies a name for a drop profile.

A drop profile consists of pairs of values between 0 and 100, one for queue buffer fill level and one for drop probability, that determine the relationship between a buffer's fullness and the likelihood it will drop packets. The values you assign to each pair must increase relative to the previous pair of values. With a few value pairs the system automatically constructs a drop profile.

To name a drop profile, type the name—for example, be-normal.

RED Drop Profile Type

Specifies whether a RED drop profile type is interpolated or segmented.

For more information about segmented and interpolated drop profiles, see the JUNOS Class of Service Configuration Guide.

To specify a RED drop profile type, select one of the following:

  • Interpolated—The value pairs are interpolated to produce a smooth profile.
  • Segmented—The value pairs are represented by line fragments, which connect each data point on the graph to produce a segmented profile.

Data Points

Specifies the points for generating the RED drop profile graph. Each data point is defined by a pair of x and y coordinates and represents the relationship between them.

The x axis represents the queue buffer fill level, which is a percentage value of how full the queue is. A value of 100 means the queue is full.

The y axis represents the drop probability, which is a percentage value of the chances of a packet being dropped. A value of 0 means that a packet is never dropped, and a value of 100 means that all packets are dropped.

To specify x and y coordinates for data points, type a number between 0 and 100 in the following boxes:

  • Fill level—Type the percentage value of queue buffer fullness for the x coordinate—for example, 95.
  • Drop profile—Type the percentage value of drop probability for the y coordinate—for example, 85.

Add

Adds the specified queue buffer fill level and drop probability as a data point for the graph.

To add the specified fill level and drop probability, click Add.

Delete

Removes a data point.

To remove a data point, select it and click Delete.

Table 128: Schedulers Quick Configuration Page Summary

Field

Function

Your Action

Scheduler Summary

Scheduler Name

Displays the names of defined schedulers.

Allows you to edit a specific scheduler.

To edit a scheduler, click its name.

Scheduler Information

Displays a summary of defined settings for a scheduler, such as bandwidth, delay buffer size, transmit and shaping rates, and RED drop profiles.

None.

Add

Opens a page that allows you to adds a scheduler.

To add a scheduler, click Add.

Delete

Removes a scheduler.

To remove a scheduler, select it and click Delete.

Add a Scheduler/Edit Scheduler

Scheduler Name

Specifies the name for a scheduler.

To name a scheduler, type the name—for example, be-scheduler.

Buffer Size

Defines the size of the delay buffer.

The delay buffer bandwidth provides packet buffer space to absorb burst traffic up to the specified duration of delay.

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—5 percent
  • Queue 4—0 percent
  • Queue 6—0 percent
  • Queue 7—0 percent

Note: A large buffer size value means a greater possibility for delaying packets in the network. 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 specify no buffer size, select Unconfigured.
  • 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.
  • To specify buffer size in microseconds, select Temporal, and type an integer within the range of the buffer size available to you on your platform—for example, 8192.

Drop Profile Map

Sets the drop profile for a specific packet loss priority (PLP) and protocol type.

By default, the drop profile is assigned to packets with low PLP, regardless of protocol type.

To configure a scheduler drop profile:

  1. Select a loss priority from the following:
    • low—Drop profile applies to packets with a low loss priority.
    • medium–low—Drop profile applies to packets with a medium-low loss priority.
    • high—Drop profile applies to packets with a high loss priority.
    • medium–high—Drop profile applies to packets with a medium-high loss priority.
    • any—Drop profile applies to all packets irrespective of the loss priority.
  2. From the Protocol list, select a protocol.
  3. From the Drop Profile list, select a profile.
  4. Click Add.

To remove a drop profile entry, select it and click Delete.

Scheduling 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 of the following:

  • high—Packets in this queue are transmitted first.
  • low—Packets in this queue are transmitted last.
  • medium–high—Packets in this queue are transmitted after high-priority packets.
  • medium–low—Packets in this queue are transmitted before low-priority packets.

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 no shaping rate, select Unconfigured.
  • To specify shaping rate as an absolute number of bits per second, select Absolute Rate and type an integer from 3200 through 32000000000.
  • 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—0 percent

To define a transmit rate, select the appropriate option:

  • To not specify transmit rate, select Unconfigured.
  • To specify the remaining transmission capacity, select Remainder Available.
  • To specify a percentage of transmission capacity, select Percent and type an integer from 1 through 100.

To enforce the exact transmission rate or percentage you configured, select the Exact Transmit Rate check box.

Table 129: Scheduler Maps Quick Configuration Page Summary

Field

Function

Your Action

Scheduler Maps Summary

Scheduler Map Name

Displays the names of defined scheduler maps. Scheduler maps link schedulers to forwarding classes.

Allows you to edit a scheduler map.

To edit a scheduler map, click its name.

Scheduler Map Information

For each map, displays the schedulers and the forwarding classes that they are assigned to.

None.

Add

Opens a page that allows you to add a scheduler map.

To add a scheduler map, click Add.

Delete

Removes a scheduler map.

To remove a scheduler map, select it and click Delete.

Add a Scheduler Map/Edit Scheduler Map

Scheduler Map Name

Specifies the name for a scheduler map.

To name a map, type the name—for example, be-scheduler-map.

Scheduler Mapping

Allows you to associate a preconfigured scheduler with a forwarding class.

Once applied to an interface, the scheduler maps affect the hardware queues, packet schedulers, and RED drop profiles.

To associate a scheduler with a forwarding class, locate the forwarding class and select the scheduler in the box next to it.


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