When Load/Overload support is enabled, UP selection is implemented as given below, with a UP group:

• If none of the UP is in overload condition, Load Control Information (LCI) is used for UP selection. In this case, the least loaded UP will be selected.

• If all UPs are in the overload state, UP selection is based on the Overload Control Information (OCI). In this case the least overloaded UP is selected.

  • After a particular UP is selected, the reduction metric is still applied to this UP for throttling.

  • If throttling needs to be dropped, UP selection request is rejected for that PDN connection.

• In some scenarios where some of the UPs are in Overload condition and some of the UPs are not in Overload condition, the selection is done based on the OCI value.

• If the LCI or the OCI value are the same for a peer node, the session count information is used for UP selection.

The CP informs the UP about the Load/Overload support enabled. Based on this information UP decides to send the Load/Overload information towards CP peer or not.

Load/Overload support at CP is configured as part of the Sx-Service node configuration. This information is sent to the UP during Sx Association Response or Sx Association Update request, if the information has changed through dynamix configuration.

Note	If CP does not support Load/Overload feature through supported CLI, it ignores the reported Load/Overloadby UP. In that case, UP selection continues with the session count information.

Once the UP is in Overload situation, CP starts throttling the Sx Establishment Request message towards UP. This avoids new calls (Low priority/non-emergency) towards the overloaded UP.

Throttling happens based on reported OCI values – Overload Reduction metric value. The value is calculated in percentage. It randomly drops the required percentage of Sx Establishment Request towards that UP Peer. This results in call drop at CP with "sx-no-resource" disconnect reason. Also, respective statistics are incremented for the same.

Note	The eMPS (high priority) subscribers' Session/ Emergency Subscribers' session is not throttled.

Once the UP is in Self-Protection state, it starts rejecting all the new sessions (non-eMPS session only), Sx Establishment Request, and Sx Modification Request for the existing sessions (non-eMPS session only).

Being in Self-Protection mode, if there are no improvement in the Load condition at UP, it starts triggering Session Termination Request towards CP in a staggered manner through Sx Report Request message indicating that UP is in Self-Protection. Based on this, CP starts initiating Sx Termination Request for those sessions.

Self Protection Termination Request (SPTER): This bit is set from UP towards CP for initiating Self-Protection based termination. The CP releases the call with disconnect reason as "graceful-term-up-self-protectn".

Note	When Actual Load value is greater than the Session-Termination-Start-Threshold value, Session termination is triggered towards CP.

This feature has the following known limitations:

• The maximum number of Load/Overload profiles supported on UP is 8.

• If the Load/Overload profiles are not configured in all UPs in the UP group, it can lead to uneven distribution of sessions. It is recommended that all UPs must be configured with the Load/Overload support in a single UP group.

• After session recovery, SessMgr instance gets to relearn Load/Overload values from SxDemux. The SxDemux communicates these values only when there is a change in Load/Overload values.

• Toggling the Load Control configurations on the fly (enable to disable or disable to enable) is not supported.

• All UPs in a UP group should either be enabled or disabled. Having one of the UP enabled and another as disabled in a UP group is not supported as it can result in improper Load/Overload values on CP.

• It's recommended to disable Load Control for all IMS UPs.

Use the following commands to configure load control profile.

configure 
   userplane-load-control-profile profile_name 
   end 

Configuring User Plane Load Control Profile Parameters

Use the following configuration to configure UP Load profile parameters:

configure 
   userplane-load-control-profile profile_name 
      system-weightage system-cpu-utilization utilization_value system-memory-utilization utilization_value license-session-utilization utilization_value 
      sessmgr-weightage sessmgr-cpu-utilization utilization_value system-memory-utilization utilization_value 
      inclusion-frequency advertisement-interval interval_value change-factor changefactor_value 
      end 

NOTES:

• inclusion-frequency : Configures parameters to decide inclusion frequency of load control information IE.

• advertisement-interval : Advertisement interval is the periodic interval after which the load value is advertised. Configures the advertisement interval for load control. The default value is 300. Set the value as 0 (zero) to include LCI IE in every applicable message.

• change-factor : Change-factor is the delta increase or decrease in the load value based on which the load advertisement occurs. Configures the change factor for load control. The default value is 5.

• sessmgr-weightage : Configures sessmgr weightage for various load control parameters. Total weightage of all the parameters should be 100. The default ratio is 65% weightage to sessmgr-cpu-utilization and 35% weightage to sessmgr-memory-utilization.

• sessmgr-cpu-utilization : Configures session manager CPU utilization weightage in percentage. Default weightage in load factor is 35%.

• sessmgr-memory-utilization : Configures session manager memory utilization weightage in percentage. Default weightage in load factor is 65%.

• system-weightage : Configures system weightage for various load control parameters. Total weightage of all the parameters should be 100. The default values are 40% weightage to system-cpu-utilization, 30% weightage to system-memory-utilization and 30% weightage to license-session-utilization.

• system-cpu-utilization : Configures system CPU utilization weightage in percentage. Default weightage in load factor is 40%.

  Note	The value displayed in the show cpu table CLI command is based on the average value of 5 minutes, 10 minutes, and 15 minutes. Use the result of the average value for system CPU utilization to verify the utilization manually.

• system-memory-utilization : Configures system memory utilization weightage in percentage. Default weightage in load factor is 30%.

  Note	The value displayed in the show cpu table CLI command is based on the average value of 5 minutes, 10 minutes, and 15 minutes. Use the result of the average value for system memory utilization to verify the utilization manually.

• license-session-utilization : Configures license session utilization weightage for User Plane service in percentage. Default weightage in load factor is 30%. The license utilization percentage is equal to the utilization percentage of the current UP sessions out of the maximum UP sessions.

Use the following commands to configure overload control profile.

configure 
   userplane-overload-control-profile profile_name 
   end 

Configuring User Plane overload Control Profile Parameters

Use the following configuration to configure UP overload profile parameters:

configure 
   userplane-overload-control-profile profile_name 
      overload-threshold system lower-limit limit_value upper-limit limit_value sessmgr lower-limit limit_value upper-limit limit_value vpp-cpu lower-limit limit_value upper-limit limit_value 
      system-weightage system-cpu-utilization utilization_value system-memory-utilization utilization_value license-session-utilization utilization_value 
      sessmgr-weightage sessmgr-cpu-utilization utilization_value system-memory-utilization utilization_value 
      inclusion-frequency advertisement-interval interval_value change-factor changefactor_value 
      tolerance tolerance_value 
      validity-period validity_period 
      end 

NOTES:

• inclusion-frequency : Configures parameters to decide inclusion frequency of overload control information IE.

• advertisement-interval : Advertisement interval is the periodic interval after which the overload value is advertised. Configures the advertisement interval for overload control. The default value is 300. Set the value as 0 (zero) to include LCI IE in every applicable message.

• change-factor : Change-factor is the delta increase or decrease in the overload value based on which the overload advertisement occurs. Configures the change factor for overload control. The default value is 5.

• tolerance : Configures the Overload tolerance limits.

• validity-period : Configures validity of overload control information. Default value is 600.

• overload-threshold : Configures Overload thresholds limits for system, sessmgr and vpp-cpu.

• system : Configures overload system threshold after which node moves to self-protection mode.

• vpp-cpu : Configures the overload vpp-cpu threshold after which node moves to self-protection mode.

• sessmgr : Configures the overload threshold for session manager after which node moves to self-protection mode.

• upper-limit limit_value : Configures the various upper limit values. Following are the various upper limit values:

  • System Threshold Upper Limit : Configures overload system threshold after which node moves to self-protection mode. Default limit value is 80%.

  • Sessmgr Threshold Upper Limit : Configures overload SessMgr threshold after which node moves to self-protection mode. Default limit value is 60%.

  • vpp-cpu Threshold Upper Limit : Configures overload vpp-cpu threshold L2 after which node moves to self-protection mode. Default limit value is 60%.

• lower-limit limit_value : Configures the various lower limit values. Following are the various lower limit values:

  • System Threshold Lower Limit: Configures overload system threshold after which node moves to self-protection mode. Default limit value is 60%.

  • Sessmgr Threshold Lower Limit: Configures overload SessMgr threshold after which node moves to self-protection mode. Default limit value is 50%.

  • vpp-cpu Threshold Lower Limit : Configures overload vpp-cpu threshold L1 after which node moves to self-protection mode. Default limit value is 50%.

• sessmgr-weightage : Configures sessmgr weightage for various overload control parameters. Total weightage of all the parameters should be 100. The default ratio is 65% weightage to sessmgr-cpu-utilization and 35% weightage to sessmgr-memory-utilization.

• sessmgr-cpu-utilization : Configures session manager CPU utilization weightage in percentage. Default weightage in overload factor is 35%.

• sessmgr-memory-utilization : Configures session manager memory utilization weightage in percentage. Default weightage in overload factor is 65%.

• system-weightage : Configures system weightage for various overload control parameters. Total weightage of all the parameters should be 100. The default values are 40% weightage to system-cpu-utilization, 30% weightage to system-memory-utilization and 30% weightage to license-session-utilization.

• system-cpu-utilization : Configures system CPU utilization weightage in percentage. Default weightage in overload factor is 40%.

  Note	The value displayed in the show cpu table CLI command is based on the average value of 5 minutes, 10 minutes, and 15 minutes. Use the result of the average value for system CPU utilization to verify the utilization manually.

• system-memory-utilization : Configures system memory utilization weightage in percentage. Default weightage in overload factor is 30%.

  Note	The value displayed in the show cpu table CLI command is based on the average value of 5 minutes, 10 minutes, and 15 minutes. Use the result of the average value for system memory utilization to verify the utilization manually.

• license-session-utilization : Configures license session utilization weightage for User Plane service in percentage. Default weightage in overload factor is 30%. The license utilization percentage is equal to the utilization percentage of the current UP sessions out of the maximum UP sessions.

Use the following commands to associate the Overload Control profile to a use plane service.

configure 
   context context_name 
      user-plane-service service_name 
      [ no ] associate userplane-load-control-profile profile_name 

NOTES:

• associate : This command associates the user plane overload control profile with a user plane service.

The CP Function Features IE indicates the features supported by CP. Only features having an impact on the (system-wide) UP function behaviour are signalled in this IE.

The following features are supported by CP:

• LOAD (Load Control)

• OVRL (Overload Control)

Use the following configuration to configure the supported features on CP through the Sx Protocol:

configure 
   context context_name 
      sx-service service_name 
         sx-protocol supported-features { load-control | overload-control } 
         no sx-protocol supported-features [ load-control | overload-control ] 
         end 

NOTES:

• supported-features : Configures supported features for Sx interface by CP. Default value is Disabled.

• load-control : Enables or disables Load control feature support on CP function.

• overload-control : Enables or disables the Overload control feature on CP function.

This section provides information regarding show commands and their outputs in support of the feature.

Following bulkstats are available in support of Load and Overload Support on Sx feature.

The following SNMP Traps are added in support of this feature:

• UPlaneSelfOverload: When system enters into Self-Protection mode.

• UPlaneSelfOverloadClear: When system is out of Self-Protection mode.