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Applying Scheduler Maps and Shaping Rate to DLCIs and VLANs

By default, output scheduling is not enabled on logical interfaces. Logical interfaces without shaping configured share a default scheduler. This scheduler has a committed information rate (CIR) that equals 0. (The CIR is the guaranteed rate.) The default scheduler has a peak information rate (PIR) that equals the physical interface shaping rate.

Note: If you apply a shaping rate, you must keep in mind that the transit statistics for physical interfaces are obtained from the packet forwarding engine, but the traffic statistics are supplied by the PIC. Therefore, if shaping is applied to the PIC, the count of packets in the transit statistics fields do not always agree with the counts in the traffic statistics. For example, the IPv6 transit statistics will not necessarily match the traffic statistics on the interface. However, at the logical interface (DLCI) level, both transit and traffic statistics are obtained from the Packet Forwarding Engine and will not show any difference.

Logical interface scheduling (also called per-unit scheduling) allows you to enable multiple output queues on a logical interface and associate an output scheduler and shaping rate with the queues. You can configure logical interface scheduling on the following PICs:

• Adaptive Services PIC, on link services IQ (lsq-) interfaces
• Channelized E1 IQ PIC
• Channelized OC3 IQ PIC
• Channelized OC12 IQ PIC (Per-unit scheduling is not supported on T1 interfaces configured on this PIC.)
• Channelized STM1 IQ PIC
• Channelized T3 IQ PIC
• E3 IQ PIC
• Gigabit Ethernet IQ PIC
• Gigabit Ethernet IQ2 PIC
• IQE PICs
• Link services PIM (ls- interfaces) on J Series routers

For Juniper Networks J Series Services Routers only, you can configure per-unit scheduling for virtual channels. For more information, see the J Series router documentation.

For Channelized and Gigabit Ethernet IQ PICs only, you can configure a shaping rate for a VLAN or DLCI and oversubscribe the physical interface by including the shaping-rate statement at the [edit class-of-service traffic-control-profiles] hierarchy level. With this configuration approach, you can independently control the delay-buffer rate, as described in Oversubscribing Interface Bandwidth.

Physical interfaces (for example, t3-0/0/0, t3-0/0/0:0, and ge-0/0/0) support scheduling with any encapsulation type pertinent to that physical interface. For a single port, you cannot apply scheduling to the physical interface if you apply scheduling to one or more of the associated logical interfaces.

For Gigabit Ethernet IQ2 PIC PICs only, you can configure hierarchical traffic shaping, meaning the shaping is performed on both the physical interface and the logical interface. You can also configure input traffic scheduling and shared scheduling. For more information, see CoS on Enhanced IQ2 PICs Overview.

Logical interfaces (for example. t3-0/0/0.0, ge-0/0/0.0, and t1-0/0/0:0.1) support scheduling on DLCIs or VLANs only. Furthermore, logical interface scheduling is not supported on PICs that do not have IQ.

Note: In the Junos OS implementation, the term logical interfaces generally refers to interfaces you configure by including the unit statement at the [edit interfaces interface-name] hierarchy level. As such, logical interfaces have the logical descriptor at the end of the interface name, as in ge-0/0/0.1 or t1-0/0/0:0.1, where the logical unit number is 1. Although channelized interfaces are generally thought of as logical or virtual, the Junos OS sees T3, T1, and NxDS0 interfaces within a channelized IQ PIC as physical interfaces. For example, both t3-0/0/0 and t3-0/0/0:1 are treated as physical interfaces by the Junos OS. In contrast, t3-0/0/0.2 and t3-0/0/0:1.2 are considered logical interfaces because they have the .2 at the end of the interface names. Within the [edit class-of-service] hierarchy level, you cannot use the .logical descriptor when you assign properties to logical interfaces. Instead, you must include the unit statement in the configuration. For example: [edit class-of-service]user@host# set interfaces t3-0/0/0 unit 0 scheduler-map map1

Table 1 shows the interfaces that support transmission scheduling.

To configure transmission scheduling on logical interfaces, perform the following steps:

1. Enable scheduling on the interface by including the per-unit-scheduler statement at the [edit interfaces interface-name] hierarchy level:
   [edit interfaces interface-name]per-unit-scheduler;

   When you include this statement, the maximum number of VLANs supported is 768 on a single-port Gigabit Ethernet IQ PIC. On a dual-port Gigabit Ethernet IQ PIC, the maximum number is 384.

2. Associate a scheduler with the interface by including the scheduler-map statement at the [edit class-of-service interfaces interface-name unit logical-unit-number] hierarchy level:
   [edit class-of-service interfaces interface-name unit logical-unit-number]scheduler-map map-name;
3. Configure shaping on the interface by including the shaping-rate statement at the [edit class-of-service interfaces interface-name unit logical-unit-number] hierarchy level:
   [edit class-of-service interfaces interface-name unit logical-unit-number]shaping-rate rate;

   By default, the logical interface bandwidth is the average of unused bandwidth for the number of logical interfaces that require default bandwidth treatment. You can specify a peak bandwidth rate in bps, either as a complete decimal number or as a decimal number followed by the abbreviation k (1000), m (1,000,000), or g (1,000,000,000). The range is from 1000 through 32,000,000,000 bps. For the IQ2 Gigabit Ethernet PIC, the minimum is 80,000 bps, and for the IQ2 10 Gigabit Ethernet PIC, the minimum is 160,000 bps.

   For FRF.16 bundles on link services interfaces, only shaping rates based on percentage are supported.

   Note: If you apply a shaping rate, you must keep in mind that the transit statistics for physical interfaces are obtained from the packet forwarding engine, but the traffic statistics are supplied by the PIC. Therefore, if shaping is applied to the PIC, the count of packets in the transit statistics fields do not always agree with the counts in the traffic statistics. For example, the IPv6 transit statistics will not necessarily match the traffic statistics on the interface. However, at the logical interface (DLCI) level, both transit and traffic statistics are obtained from the Packet Forwarding Engine and will not show any difference.

Example: Applying Scheduler Maps and Shaping Rate to DLCIs and VLANs

Associate the scheduler sched-map-logical-0 with logical interface unit 0 on physical interface t3-1/0/0, and allocate 10 Mbps of transmission bandwidth to the logical interface.

Associate the scheduler sched-map-logical-1 with logical interface unit 1 on physical interface t3-1/0/0, and allocate 20 Mbps of transmission bandwidth to the logical interface.

The allocated bandwidth is shared among the individual forwarding classes in the scheduler map. Although these schedulers are configured on a single physical interface, they are independent from each other. Traffic on one logical interface unit does not affect the transmission priority, bandwidth allocation, or drop behavior on the other logical interface unit.

For another example, see the Junos OS Feature Guides.