As per 3GPP standard:

• CP informs load and overload feature to the user-plane.

• User-plane decides to send load or overload information towards the CP peer or not.

Configure load and overload feature at CP as a part of PFCP Sxa endpoint node feature. This configuration in turn communicates to UP during Sx Association Response message or Sx Association Update Request message when change in configuration occurs.

The CP Function Feature IE indicates the supported CP function features. This IE contains features which have (system-wide) UP function behavior impact.

Note	If CP does not support load or overload feature through CLI then it ignores the user-plane reported load or overload information for the UP selection process.

When user-plane is in overload situation, cnSGW-C establishes throttling the Sx Establishment request message toward user-plane. This throttling avoids new calls (Low priority or non-emergency) towards the overloaded user-plane.

Throttling takes place as per the reported OCI values in percentage. Following actions takes place when throttling happens:

• Random drop of percentage in reported Sx Establishment Request messages towards that user-plane.

• Call drop occurs at cnSGW-C with sx_no_resource_available disconnect reason.

• Respective statistics get incremented.

User-plane triggers the session termination request towards cnSGW-C in pacing manner through Sx Report Request message. User-plane triggers session termination request when it is in self-protection mode and there is no improvement in load. This trigger happens with setting of SPTER (Self Protection Termination Request) bit.

cnSGW-C initiates Sx Termination Request for those PDNs and releases the PDN session with disconnect reason as userplane_requested_termination.

When the user-pane is in self-protection mode and rejects the new sessions with the cause PFCP_ENTITY_IN_CONGESTION (74), cnSGW-C selects different user-plane as per the failure template profile configuration.

Failure-handling profile is associated with UPF-Group.

Reselection of UPF follows the UPF selection process and considers the retries count to different UPF from profile configuration.

Note	Currently, only PFCP_ENTITY_IN_CONGESTION(74) is supported as cause code for retry and reselection of user-plane as part of this feature.

This section describes how to configure Sx Load/Overload.

Use the following commands to configure Sx Load/Overload configuration.

config
 instance instance-id instance_id 
   endpoint endpoint_name 
    interface interface_name 
     supported-features [ load-control | overload-control ] 
    exit 
   exit 

NOTES:

• endpoint endpoint_name - Specify the endpoint name.

• interface interface_name - Specify the interface name.

• supported-features [ load-control | overload-control ] - Enable load/overload control.

Sample Configuration

Following is a sample configuration.

configure
 instance instance-id 1
  endpoint pfcp
   interface sxa
    supported-features load-control overload-control
   exit

Verifying Sx Load/Overload Configuration

Use the following show command to view the Sx load/overload configuration.

show running-config instance instance-id 1 endpoint
instance instance-id 1
endpoint pfcp
interface sxa
supported-features load-control overload-control
exit
exit

This section describes how to configure failure handling profile.

Use the following commands to configure failure handling profile.

config
 profile failure-handling failure-handling_profile_name 
   interface interface_name 
     message message_type 
       cause-code cause_code 
         action action_type 
           max-retry max_retry_count 
       exit 
     exit 
   exit 
 profile upf-group upf-group_profile_name 
  failure-profile profile_name 
 exit 

NOTES:

• profile failure-handling failure-handling_profile_name - Specify the failure-handling profile name.

• interface interface_name - Specify the interface name.

• message message_type - Specify the message type.

• cause-code cause_code - Specify the cause ID (range of 2-255) or range of cause IDs (range of 2-255) separated by either '-' or ',' or both.

  -Or-

  Must be one of the following:

  • no-resource-available

  • no-response-received

  • pfcp-entity-in-congestion

  • reject

  • service-not-supported

  • system-failure

• action action_type - Specify the action type for the cause. Must be one of the following:

  • retry-terminate

  • terminate

• max-retry max_retry_count - Specify the maximum retry count for the retry-terminate action. Must be an integer in the range of 0-5. Default value is 1.

• profile upf-group upf-group_profile_name - Specify the UPF group profile name.

• failure-profile profile_name - Specify the UPF failure profile name.

Sample Configuration

Following is the sample configuration:

profile failure-handling fh1
 interface sxa
  message SessionEstablishmentReq
   cause-code pfcp-entity-in-congestion action terminate
  exit
 exit
exit
profile failure-handling fh2
 interface sxa
  message SessionEstablishmentReq
   cause-code 74 action retry-terminate max-retry 3
  exit
 exit
exit
profile upf-group g1
 failure-profile fh1
exit
profile upf-group g2
 failure-profile fh2
exit

UE Disconnect Statistics

sgw_ue_disconnect_stats{app_name="smf",cluster="cn",data_center="cn",instance_id=
"0",reason="sx_no_resource_available",service_name="sgw-service"} 1

sgw_ue_disconnect_stats{app_name="smf",cluster="cn",data_center="cn",instance_id=
"0",reason="userplane_requested_termination",service_name="sgw-service"} 1

PDN Disconnect Statistics

sgw_pdn_disconnect_stats{app_name="smf",cluster="cn",data_center="cn",instance_id=
"0",pdn_type="ipv4",rat_type="EUTRAN",reason="sx_no_resource_available",service_name="sgw-service"} 1

sgw_pdn_disconnect_stats{app_name="smf",cluster="cn",data_center="cn",instance_id=
"0",pdn_type="ipv4v6",rat_type="EUTRAN",reason="userplane_requested_termination",service_name="sgw-service"} 1

SGW Service Statistics

 sgw_service_stats{app_name="smf",cluster="cn",data_center="cn",fail_reason="sx_oci_throttling_reject",
instance_id="0",interface="interface_sgw_ingress",reject_cause="no_resources_available",service_name=
"sgw-service",sgw_procedure_type="initial_attach",status="rejected",sub_fail_reason=""} 1

sgw_service_stats{app_name="smf",cluster="cn",data_center="cn",fail_reason="",instance_id="0",
interface="interface_sgw_egress",reject_cause="",service_name="sgwservice",sgw_procedure_type=
"upf_initiated_deletion",status="attempted",sub_fail_reason=""} 1

sgw_service_stats{fail_reason="sx_cause_fail",interface="interface_sgw_ingress",reject_cause=
"service_denied",sub_fail_reason="pfcp_entity_in_congestion",sgw_procedure_type="initial_attach",
status="rejected"}

Session Report Request Throttling Statistics

A new status string validation_failurePFCP_Entity_In_Congestion is added in the existing statistics sgw_sx_session_report_stats. cnSGWc populates the session report statistics with this status value in case DLDR session report request is rejected in self-protection mode.

sgw_sx_session_report_stats{app_name="smf",cluster="Local",data_center="DC",gr_instance_id="1",
instance_id="0",reason="",service_name="sgw-service",status="validation_failurePFCP_Entity_In_Congestion",
sx_session_report_type="DLDR_NO_ARP"} 1