4. Port Level Egress Rate-Limiting

This section provides information to configure port level egress-rate using the command line interface.

4.1. Overview

Egress port rate limiting allows the device to limit the traffic that egresses through a port to a value less than the available link bandwidth.

This feature is useful when connecting the 7210 SAS to an Ethernet-over-SDH (EoSDH) (or microwave) network, where the network allocates predetermined bandwidth to the nodes connecting into it, based on the transport bandwidth requirement. When connecting to such a network it is important that the traffic sent into the SDH node does not exceed the configured values, since the SDH network does not have QoS capabilities and buffers required to prioritize the ingress traffic.

Egress rate attributes include:

  1. Allows for per port configuration of the maximum egress port rate, using the egress-rate CLI command.
  2. Ethernet ports configured as access and access uplink support this feature.
  3. The port scheduler distributes the available maximum egress bandwidth based on the CIR/PIR configuration parameters provisioned for the queues.
  4. The 7210 SAS-D and 7210 SAS-Dxp provide support for a burst parameter to control the amount of burst the egress port can generate.
  5. When ports are members of a LAG, all the ports use the same value for the egress-rate and the max-burst parameters.
  6. If frame overhead accounting (also known as Frame-based accounting) is enabled, then queue scheduler accounts for the Ethernet frame overhead.
  7. When an egress-rate sub-rate value is given, the access-uplink port egress queue rates that are specified using percentages will use the egress-rate value instead of the port bandwidth if egress rate is lesser than port bandwidth to configure the appropriate queue rates. Configuration of egress port rate to different values will result in a corresponding dynamic adjustment of rates for the egress queues configured on access-uplink ports.
  8. When the egress-rate sub-rate value is set, CBS/MBS of the associated network queues is not modified automatically.

4.2. Basic Configurations

To apply port level rate-limiting, perform the following:

  1. The egress-rate command is present in the *A:Dut-1>config>port>ethernet context.
  2. The egress-rate configures the maximum rate (in kbps).
  3. For 7210 SAS-D devices, the max-burst command configures a maximum-burst (in kilo-bits) associated with the egress-rate. This is an optional parameter and, if not defined, is set to 32kb for a 1G port by default. The user cannot configure max-burst without configuring egress-rate. The value should be between 32 and 16384 or default.
  4. For 7210 SAS-Dxp devices, the max-burst command configures a maximum-burst (in kilo-bits) associated with the egress-rate. This is an optional parameter and, if not defined, is set to 65kb for a 1G port and 98kb for a 10G port by default. The user cannot configure max-burst without configuring egress-rate. The value should be between 32 and 16384 or default.
  5. By default there is no explicit egress-rate command set on port and the port operates at the maximum line-rate speed it is operating at.

The following is a sample egress-rate configuration output for a port.

*A:Dut-1>config>port# info 
----------------------------------------------
        ethernet
            egress-rate 120000 max-burst 234
        exit
        no shutdown
----------------------------------------------
*A:Dut-1>config>port#
 

4.2.1. Modifying Port Level Egress-Rate Command

To modify egress-rate parameters you can simply apply a egress-rate command with new egress-rate and max-burst value.

The following is a sample egress-rate configuration output for a port.

*A:Dut-1>config>port# ethernet egress-rate 10000 max-burst default 
*A:Dut-1>config>port# info 
----------------------------------------------
        ethernet
            egress-rate 10000
        exit
        no shutdown
----------------------------------------------
*A:Dut-1>config>port#

4.2.2. Removing Port Level Egress-Rate Command

To remove egress-rate command from a port, use the no option with the egress-rate command. The rate for the egress-rate option and max-burst should not be used in this case.

CLI Syntax:
config>port>ethernet# no egress-rate

The following displays the removal of egress-rate configuration from a port.

*A:Dut-1>config>port# no ethernet egress-rate
*A:Dut-1>config>port# info 
----------------------------------------------
        ethernet
        exit
        no shutdown
----------------------------------------------
*A:Dut-1>config>port#

4.2.2.1. Default Egress-Rate Values

By default no egress-rate is configured for a port. For more information on the CLI and description, see Port Level Egress-Rate Command Reference.