Configuring Adaptive Shaping for Frame Relay

For J Series devices and SRX210, SRX240, and SRX650 devices, you can configure adaptive shapers, which allow you to shape Frame Relay logical interfaces to a maximum rate, based on congestion. Adaptive shaping is triggered by the backward explicit congestion notification (BECN) bit in Frame Relay packet headers. Thus, adaptive shaping allows you to use the information provided in Frame Relay packet headers to detect possible congestion and to adjust your bandwidth limitation accordingly.

Adaptive shaping is triggered when the last ingress packet on the logical interface has its BECN bit set to 1. When adaptive shaping is triggered, the output queues on the logical interface are shaped according to the adaptive shaper configuration.

Adaptive shaping is an alternative to regular logical interface shaping. If the last ingress packet has its BECN bit set to 0, the logical interface queues are shaped according to the shaping-rate statement at the [edit class-of-service interfaces interface-name unit logical-unit-number] hierarchy level, which should be configured at a higher rate than the rate you configure for the adaptive shaper. If you do not include the shaping-rate statement in the configuration, the default logical interface bandwidth is the average of unused bandwidth for the number of logical interfaces that require default bandwidth treatment. For more information about shaping rates and bandwidth sharing, see Configuring Excess Bandwidth Sharing.

To configure an adaptive shaper, you can include the following statements at the [edit class-of-service] hierarchy level of the configuration:

[edit class-of-service]adaptive-shapers {adaptive-shaper-name {trigger type shaping-rate (percent percentage | rate);}}interfaces {interface-name {unit logical-unit-number {adaptive-shaper adaptive-shaper-name;}}}

Note: For more information on configuring and applying an adaptive shaper using the configuration editor, see Configuring and Applying an Adaptive Shaper.

Configuring an Adaptive Shaper

To configure an adaptive shaper, include the adaptive-shapers statement at the [edit class-of-service] hierarchy level:

[edit class-of-service]adaptive-shapers {adaptive-shaper-name {trigger type shaping-rate (percent percentage | rate);}}

The trigger type can be becn only. If the last ingress packet on the logical interface has its BECN bit set to 1, the output queues on the logical interface are shaped according to the associated shaping rate.

The associated shaping rate can be a percentage of the available interface bandwidth from 0 through 100 percent. Alternatively, you can configure the shaping rate to be an absolute peak rate, in bits per second (bps) from 3200 through 32,000,000,000 bps. You can specify the value 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).

Applying an Adaptive Shaper to a Logical Interface

To apply an adaptive shaper to a logical interface, include the adaptive-shaper 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]adaptive-shaper adaptive-shaper-name;