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Configuring the Transmission Rate

The transmission rate control determines the actual traffic bandwidth from each forwarding class you configure. The rate is specified in bits per second (bps). Each queue is allocated some portion of the bandwidth of the outgoing interface.

This bandwidth amount can be a fixed value, such as 1 megabit per second (Mbps), a percentage of the total available bandwidth, or the rest of the available bandwidth. You can limit the transmission bandwidth to the exact value you configure, or allow it to exceed the configured rate if additional bandwidth is available from other queues. This property allows you to ensure that each queue receives the amount of bandwidth appropriate to its level of service.

Note: For 8-port, 12-port, and 48-port Fast Ethernet PICs, transmission scheduling is not supported.

On J-series Services Routers, you can use the transmit-rate statement to assign the WRR weights within a given priority level and not between priorities. For more information, see Configuring Priority Scheduling.

To configure transmission scheduling, include the transmit-rate statement at the [edit class-of-service schedulers scheduler-name] hierarchy level:



[edit class-of-service schedulers scheduler-name]

transmit-rate (rate | percent percentage | remainder) <exact
| rate-limit>;

You can specify the transmit rate as follows:

rate—Transmission rate, in bits per second. The rate can be from 3200 through 160,000,000,000 bps.
percent percentage—Percentage of transmission capacity.
remainder—Use remaining rate available. In the configuration, you cannot combine the remainder and exact options.
exact—(Optional) Enforce the exact transmission rate or percentage you configure with the transmit-rate rate or transmit-rate percent statement. Under sustained congestion, a rate-controlled queue that goes into negative credit fills up and eventually drops packets. You specify the exact option as follows:[edit class-of-service schedulers scheduler-name] transmit-rate rate exact; [edit class-of-service schedulers scheduler-name] transmit-rate percent percentage exact;

Note: Use of the exact option (transmit-rate rate exact) is not supported on the Enhanced Queuing Dense Port Concentrators (DPCs) on MX-series routers.

In the configuration, you cannot combine the remainder and exact options.

rate-limit—(Optional) Limit the transmission rate to the specified amount. You can configure this option for all 8 queues of a logical interface (unit) and apply it to shaped or unshaped logical interfaces. If you configure a zero rate-limited transmit rate, all packets belonging to that queue are dropped.

Note: You can apply a transmit rate limit to logical interfaces on MultiServices 100, 400, or 500 PICs. Typically, rate limits are used to prevent a strict-high queue (such as voice) from starving lower priority queues. You can only rate-limit one queue per logical interface. To apply a rate-limit to a MulticServices PIC interface, configure the rate limit in a scheduler and apply the scheduler map to the MultiServices (lsq-) interface at the [edit class-of-service interfaces] hierarchy level. For more information about configuring schedulers and scheduler maps, see Configuring a Scheduler.

For more information, see the following sections:

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