QoS Shaping Mode for Ethernet Interfaces Overview

The SAR scheduler is not available for Ethernet interfaces. However, you can still configure the operational shaping mode to shape ATM traffic based on either frames or cells by issuing the qos-shaping-mode command.

Frame shaping mode is the default for Ethernet interfaces on all E Series Broadband Services Routers. You can configure cell shaping mode for the following interfaces:

When you use cell shaping mode to configure the shaping or policing rate, the resulting traffic stream conforms exactly to the policing rates configured in downstream ATM switches. Using cell shaping also reduces the number of packet drops in the Ethernet network.

The setting for port 0 provides the default shaping mode for all ports on the same I/O module or IOA. Individual ports can have a specific shaping mode setting that overrides the setting for port 0.

If you do not configure the QoS shaping mode for a port, the shaping mode is calculated using the value for port 0 on the same I/O module or IOA. If the port's shaping mode is configured, the system uses the port's shaping mode.

Table 19 lists the possible combinations of the qos-shaping-mode command and the resultant operational shaping mode.

Table 19: Operational Shaping Modes

qos-shaping-mode
for Port 0

qos-shaping-mode for Other Ports

Operational Shaping Mode

Cell

Cell

Cell

Frame

Frame

Frame

Cell

Frame

Frame

Frame

Cell

Cell

Frame

No shaping mode

Frame

Cell

No shaping mode

Cell

No shaping mode

No shaping mode

Frame

To account for different layer 2 encapsulations, you can configure the byte adjustment application using QoS parameters. The byte adjustment is calculated differently for frame shaping mode than cell shaping mode.

Note: You can also use the QoS cell mode application with QoS parameters to configure the shaping mode for a port.

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