Rate and give feedback:  Feedback Received. Thank You!

Rate and give feedback: 

X

This document helped resolve my issue

Yes No

Additional Comments

800 characters remaining

May we contact you if necessary?

Name:  

E-mail: 

Enter a valid Email ID

Need product assistance? Contact Juniper Support

Submit

This site is protected by hCaptcha and its Privacy Policy and Terms of Service apply.

English  

English

Applying Scheduler Maps to Packet Forwarding Component Queues

On Intelligent Queuing (IQ) and Intelligent Queuing 2 (IQ2) interfaces, the traffic that is fed from the packet forwarding components into the PIC uses low packet loss priority (PLP) by default and is distributed evenly across the four chassis queues (not PIC queues), regardless of the scheduling configuration for each logical interface. This default behavior can cause traffic congestion.

The default chassis scheduler allocates resources for queue 0 through queue 3, with 25 percent of the bandwidth allocated to each queue. When you configure the chassis to use more than four queues, you must configure and apply a custom chassis scheduler to override the default. To apply a custom chassis scheduler, include the scheduler-map-chassis statement at the [edit class-of-service interfaces at-fpc/pic/*] hierarchy level.

To control the aggregated traffic transmitted from the chassis queues into the PIC, you can configure the chassis queues to derive their scheduling configuration from the associated logical interface’s. Include the scheduler-map-chassis derived statement at the [edit class-of-service interfaces type-fpc/pic/*] hierarchy level:

Caution: If you include the scheduler-map-chassis derived statement in the configuration, packet loss might occur when you subsequently add or remove logical interfaces at the [edit interfaces interface-name] hierarchy level. When fragmentation occurs on the egress interface, the first set of packet counters displayed in the output of the show interfaces queue command show the post-fragmentation values. The second set of packet counters (under the Packet Forwarding Engine Chassis Queues field) show the pre-fragmentation values. For more information about the show interfaces queue command, see the Junos OS Operational Mode Commands.

You can include both the scheduler-map and the scheduler-map-chassis derived statements in the same interface configuration. The scheduler-map statement controls the scheduler inside the PIC, while the scheduler-map-chassis derived statement controls the aggregated traffic transmitted into the entire PIC. For the Gigabit Ethernet IQ PIC, include both statements.

For more information about the scheduler-map statement, see Applying Scheduler Maps to Physical Interfaces. For information about logical interface scheduling configuration, see Applying Scheduler Maps and Shaping Rate to DLCIs and VLANs.

Generally, when you include the scheduler-map-chassis statement in the configuration, you must use an interface wildcard for the interface name, as in type-fpc/pic/*. The wildcard must use this format—for example. so-1/2/*, which means all interfaces on FPC slot 1, PIC slot 2. There is one exception—you can apply the chassis scheduler map to a specific interface on the Gigabit Ethernet IQ PIC only.

According to Junos OS wildcard rules, specific interface configurations override wildcard configurations. For chassis scheduler map configuration, this rule does not apply; instead, specific interface CoS configurations are added to the chassis scheduler map configuration. For more information about how wildcards work with chassis scheduler maps, see Examples: Scheduling Packet Forwarding Component Queues. For general information about wildcards, see the Junos OS Administration Library for Routing Devices.

Note: The interface applies wildcard configuration only if you do not add any specific configuration. If you add the specific interface configuration, then the interface deletes the applied wildcard configuration and applies the specified configuration.

Applying Custom Schedulers to Packet Forwarding Component Queues

Optionally, you can apply a custom scheduler to the chassis queues instead of configuring the chassis queues to automatically derive their scheduling configuration from the logical interfaces on the PIC.

To assign a custom scheduler to the packet forwarding component queues, include the scheduler-map-chassis statement at the [edit class-of-service interfaces type-fpc/ pic] hierarchy level:

When you apply a custom scheduler map to packet forwarding component queues, or when you modify the configuration of a custom scheduler map that is already applied to packet forwarding component queues, packets already in the chassis queues might be dropped. The amount of packet loss is not deterministic and depends on the offered traffic load at the time you apply or modify the custom scheduler map.

For information about defining the scheduler map referenced by map-name, see Configuring Scheduler Maps.

Examples: Scheduling Packet Forwarding Component Queues

Note: This same wildcard behavior applies to classifiers and rewrites as well as schedulers.