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 supported on the 7210 SAS-Series platforms.

4.1.1. Applications

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, access uplink and network 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. Provides 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 is enabled, then queue scheduler accounts for the Ethernet frame overhead.

4.1.2. Effect of Port Level Rate-Limiting on Network Queue Functionality

  1. When an egress-rate sub-rate value is given, the network queue (on network ports or access uplink ports) 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 queues configured on network ports, or access uplink ports.
  2. When the egress-rate sub-rate value is set, CBS/MBS of the associated network queues will not change.

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) for the port. The value should be between 1 and 1000000 kbps and between 1 and 10000000 kbps for 10G port.
  3. The max-burst command configures a maximum-burst (in kilo-bits) associated with the egress-rate. This is optional parameter and if not defined then, by default, it is set to 64kb for a 1G port and 64kb for a 10G port. User cannot configure max-burst without configuring egress-rate. The value should be between 64 and 16384 or default.
  4. By default there is no egress-rate command set on port. By default egress-rate for a port is maximum (equal to line-rate).
  5. On 10G port, if Egress port Rate Limiter (ERL) configured is more than 8Gig it is recommended to configure burst value higher than 80kbits to avoid packet drops.

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 is a sample removal of egress-rate configuration output 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.