set dcb cn priority defense

Use this command to configure a default port congestion notification domain defense mode for all ports on the device for each priority.

Syntax

Parameters

Defaults

The default mode for domain defense depends upon the creation mode when the CNPV is created using set dcb cn priority. For creation enable, the default domain defense is edge. For creation disable, the default domain defense is disabled.

Mode

All command modes.

Usage

Note

CN is supported on the S-Series S140 and S180 modules. On non-supported S-Series modules, the Congestion Notification Domain Defense can be configured for either edge or disabled only. When edge configured, flows ingressing non-supported S-Series modules are remapped on ingress. Flows ingressing a supported S-Series module and egressing a non-supported S-Series module on the same chassis generate CNMs because congestion notification logic is performed on the ingress module.

Congestion notification domain defense provides a means of defending a congestion notification domain against incoming frames from outside of the domain. Domain defense assumes:

• That every bridge along a path between two congestion aware end-stations, using a particular CNPV, is properly configured for congestion notification and therefore belongs to the congestion notification domain
• That every bridge ensures that frames not in a CNPV use different queues than the CNPV queues for those end stations

Congestion notification defense protects the boundaries of a domain by preventing frames not in a congestion controlled flow from entering congestion point controlled queues. Domain defense takes advantage of the ability to change the priority value in the port-priority generation table based upon whether or not the port‘s neighbor is also configured with the same CNPV. If a frame with the same priority as the CNPV is not in the congestion controlled flow, the frame priority is changed to the configured alternate priority for that CNPV.

A default domain defense mode is configured at each congestion point port. There are four possible domain defense modes depending upon whether the CNPV is configured for the congestion point or where the congestion point port is located in the congestion notification domain:

• Disabled – A port for which congestion notification is disabled. This priority is not a CNPV. The priority regeneration table controls the remapping of ingress frames on this port for this priority. CN-TAGs are neither added by an end station nor removed by a bridge. This defense mode is the default defense mode when priority choice is set to admin. The disabled defense mode can only be set when the priority choice is set to admin. Priority choice can be set:
  • By default when creating the CNPV using the creation disable option
  • Using set dcb cn priority choice at the switch level
  • Using set dcb cn port-priority choice at the port level
• Edge – A congestion point port that resides at the edge of the congestion notification domain. On this port and for this CNPV, the ingress frame priority parameters are remapped to an alternate (non-CNPV) value, regardless of the priority regeneration table settings. CN-TAGs are not added by an end station, and are removed from frames by a bridge before egress. This mode is optional for an end station. The edge defense mode is the default defense mode when the priority choice is set to auto.
• Interior – A congestion point port that resides within the congestion notification domain between the flow‘s source reaction point and the destination end-station. This port does not yet know whether its neighbor is able to receive a CN-TAG in frames sent to it. On this port and for this CNPV, the ingress frame priority parameters are not remapped, regardless of the priority regeneration table settings. CN-TAGs are not added by an end station, and are removed from frames by a bridge before egress.
• InteriorReady – An interior congestion port that knows its neighbor is able to receive a CN-TAG in frames sent to it. On this port and for this CNPV, the ingress frame priority parameters are not remapped, regardless of the priority regeneration table settings. CN-TAGs can be added by an end station, and are not removed from frames by a bridge.

Defaults for domain defense can be configured by priority or by port. This command configures a global defense mode per congestion notification priority value for all ports on the device. A default domain defense can be set on a port basis for all congestion notification priority values on that port using set dcb cn port-priority defense.

Domain defense can be administratively configured, dynamically configured using LLDP, or based upon default values on a per port basis. The method used is referred to as “choice”. The priority choice method on a global basis is configured using set dcb cn priority choice. The port-priority choice method on a port basis is configured using set dcb cn port-priority choice.

The domain defense default configured using this command is only used if the port-priority choice set using set dcb cn port-priority choice is default and the global choice set dcb cn priority choice is admin.