Rewriting Frame Relay Headers

For J Series device interfaces with Frame Relay encapsulation, you can rewrite the discard eligibility (DE) bit based on the loss priority of Frame Relay traffic. For each outgoing frame with the loss priority set to low, medium-low, medium-high, or high, you can set the DE bit CoS value to 0 or 1.

You can combine a Frame Relay rewrite rule with other rewrite rules on the same interface. For example, you can rewrite both the DE bit and MPLS EXP bit.

This section is organized as follows:

Assigning the Default Frame Relay Rewrite Rule to an Interface

The default Frame Relay rewrite rule contains the following settings:

loss-priority low code-point 0;loss-priority medium-low code-point 0;loss-priority medium-high code-point 1;loss-priority high code-point 1;

This default rule sets the DE CoS value to 0 for each outgoing frame with the loss priority set to low or medium-low. This default rule sets the DE CoS value to 1 for each outgoing frame with the loss priority set to medium-high or high.

To assign the default rule to an interface, include the frame-relay-de default statement at the [edit class-of-service interfaces interface interface-name unit logical-unit-number rewrite-rules] hierarchy level:

[edit class-of-service interfaces interface-name unit logical-unit-number rewrite-rules]frame-relay-de default;

Defining a Custom Frame Relay Rewrite Rule

To define a custom Frame Relay rewrite rule, include the following statements at the [edit class-of-service] hierarchy level:

[edit class-of-service]rewrite-rules {frame-relay-de rewrite-name { import (rewrite-name | default);forwarding-class class-name {loss-priority level code-point (0 | 1);}}}

A custom rewrite rule sets the DE bit to the 0 or 1 CoS value based on the assigned loss priority of low, medium-low, medium-high, or high for each outgoing frame.

Applying the Rule to a Logical Interface

The rule does not take effect until you apply it to a logical interface. To apply a rule to a logical interface, include the frame-relay-de map-name statement at the [edit class-of-service interfaces interface-name unit logical-unit-number rewrite-rules] hierarchy level:

[edit class-of-service interfaces interface-name unit logical-unit-number rewrite-rules]frame-relay-de map-name;