4. Port level egress rate-limiting

This section provides information to configure port level egress-rate command 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 a 10G port.
  3. 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 then, by default, it is set to 64 kb for a 1G port and 64 kb for a 10G port. Users cannot configure max-burst without configuring egress-rate. The max-burst value should be between 32 and 16384 or the default.
  4. By default there is no egress-rate command set on port. The default egress-rate for a port is the maximum (equal to line-rate).
  5. On 10G port, if Egress port Rate Limiter (ERL) configured is more than 8Gig, Nokia recommends configuring the burst value higher than 80kbits to avoid packet drops.

The following is a sample configuration output that shows the egress-rate configuration 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 an egress-rate command with new egress-rate and max-burst value.

The following is a sample configuration that shows a modified egress-rate configuration 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. Do not include the rate for the egress-rate and max-burst options. Use the following syntax to remove the egress-rate command from a port.

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

The following is a sample configuration output that shows 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.