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CoS Port Shaping

SUMMARY Port shaping enables you to control the amount of traffic passing through an interface. Port shaping enables you to shape the aggregate traffic through an interface to a rate that is less than the line rate for that interface. This can be useful to reduce downstream congestion.

This topic describes port shaping and how to configure port shaping.

Understanding Port Shaping

By default, shaping is not configured on an interface and traffic can be up to the line rate for that interface. When you configure port shaping on an interface, you specify a value that indicates the maximum amount of traffic that can pass through the interface.

Port shaping enables you to shape the aggregate traffic through a port or channel to a rate that is less than the line rate. You specify the port shaping rate as the peak rate at which traffic can pass through the interface. You specify the rate as a value in bits per second (bps) either as a decimal number or as a decimal number followed by the abbreviation k (1000), m (1,000,000), or g (1,000,000,000) and the value can range from 1000 through 160,000,000,000 bps. This value must be less than the maximum bandwidth for that interface.

You can configure port shaping on network interfaces, aggregated Ethernet interfaces (also known as link aggregation groups (LAGs)), and loopback interfaces.

Note:

On EX4650, QFX5110, QFX5120, QFX5200, QFX5210 Series switches, when you configure a shaping rate on an aggregated Ethernet (ae) interface, all members of the ae interface are shaped at the configured shaping rate. For example, consider an interface ae0 that consists of three interfaces: xe-0/0/0, xe-0/0/1, and xe-0/0/2. If you configure a shaping rate of X Mpbs on ae0, traffic up to the rate of X Mpbs flows through each of the three interfaces. Therefore, the total traffic flowing through ae0 can be at the rate of 3X Mbps.

Configuring Port Shaping

You can configure port shaping on network interfaces, aggregated Ethernet interfaces (also known as link aggregation groups (LAGs)), and loopback interfaces.

To configure port shaping on an interface:

  1. Ensure that the interface on which you want to configure port shaping is up and running.
  2. Assign a shaping-rate for the interface:

    For example:

    The value indicates the maximum amount of traffic (in bps) that can pass through the interface. This value must be less than the maximum bandwidth for that interface.

  3. Commit your changes.
  4. Verify your configuration.

    For example:

  5. Run show class-of-service interface interface-name to verify the shaping rate for the interface.

    For example:

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