The Option 3x and 4G-Only Device feature complies with the following standards:

• 3GPP TS 23.003 [2]

• 3GPP TS 24.301 [23]

• 3GPP TS 29.272 [70]

• 3GPP TS 29.274

• 3GPP TS 29.212

This feature has the following limitations:

• Ultra low latency QCIs are not supported.

• PRA:

  • PRA is supported only towards PCF and not CHF.

  • PRA is applied only based on RAT type of the connecting device and not based on the device type. It is applied to both 4G and 5G devices when connected from LTE.

  • A maximum of four PRA-IDs are processed in a single PCF update message. If a PCF update has more than four PRA-IDs, then the other PRA-IDs are ignored.

  • Only the PRA-ID will be sent in the "Presence Reporting Area Action" IE on S5 interface. User location information will not be sent.

  • Only the PRA-ID will be sent in the "repPraInfos" IE on N7 interface. User location information will not be sent.

  • PRA Set is not supported due to which "Additional PRA Information" is not supported on S5 and N7 interfaces.

• Secondary RAT Data Usage Report:

  • Supports only Option 3 and Option 3x (NR Secondary RAT) UEs on S5 interface.

  • Does not support E-UTRAN Secondary RAT on N2 interface.

This section describes how to configure the default NSSAI in SMF, which it includes in sliceInfo IE in the Policy Create Request message. The SMF sends this message towards the PCF during the session creation from 4G-only UEs.

Use the following sample configuration to configure the default NSSAI in the SMF:

config 
   profile dnn profile_name 
      nssai { sd sd_value | sst sst_value } 
      exit 

NOTES:

• profile dnn profile_name : Specify the DNN profile name. profile_name must be an alphanumeric string.

• nssai { sd sd_value | sst sst_value } : Configure the default NSSAI.

  • sd sd_value : Specify the slice descriptor (sd). sd_value must be a 6-digit hex string ([0-9a-fA-F]{6} - 000000 – ffffff). For example, 1A2B3c.

  • sst sst_value : Specify the slice type (sst) value. sd_value must be an integer in the range of 0–255.

To enable SMF to support the DCNR capability for the sessions handled using the DNN profile, use the following sample configuration:

config 
   profile dnn profile_name    
      dcnr { false | true } 
      exit 

NOTES:

• profile dnn profile_name : Specify the DNN profile name. profile_name must be an alphanumeric string.

• dcnr { false | true } :

  • false : Configure the DNN profile to have DCNR flag set to false. The DCNR configuration is disabled by default.

  • true : Configure the DNN profile to have DCNR flag set to true.

    This configuration enables the SMF to support DCNR capability. When the DCNR capability is enabled, the UE sends the DCNR flag to indicate that it supports dual connectivity.

This section describes how to enable the DCNR flag and configure the appropriate precedence for DCNR.

Defining the UPF Group

Use the following sample configuration to configure the UPF group and define DCNR in the UPF Group profile.

config 
   profile upf-group profile_name 
      dcnr { false | true } 
      exit 

NOTES:

• profile upf-group profile_name : Specify the UPF group name that must be associated to the specified UPF network configuration. profile_name must be an alphanumeric string.

• dcnr { false | true } : Configure the DCNR capability.

  • false : Disable support for DCNR. This is the default setting.

  • true : Enable support for DCNR.

Associating UPF Selection Query Parameters

Use the following sample configuration to associate the defined UPF group with the UPF network element in the DNN profile.

config 
   profile dnn profile_name 
      upf-selection-policy  upfpolicy_name 
      exit 

NOTES:

• policy dnn profile_name : Enter the DNN Profile configuration mode. profile_name must be an alphanumeric string.

• upf-selection-policy upfpolicy_name : Specify the name of the UPF selection policy that must be associated to the DNN profile. upfpolicy_name must be an alphanumeric string.

Configuring Precedence for DCNR

Use the following sample configuration to configure the appropriate precedence for DCNR in the UPF Selection Policy profile.

config 
   policy upf-selection upf_name 
      precedence precedence_num 
         dcnr 
         exit 
      exit 

NOTES:

• policy upf-selection upf_name : Specify the UPF policy name that must be associated with the DNN profile. profile_name must be an alphanumeric string.

• precedence precedence_num : Assign the precedence value to the UPF policy. precedence_num must be an integer in the range of 1–4.

• dcnr : Configure the DCNR capability.

Use the following sample configuration to configure secondary RAT usage reports before being sent to CHF.

config 
   profile charging profile_name 
      max-secondary-rat-reports report_range 
      exit 

NOTES:

• profile charging profile_name : Enter the Charging Profile configuration mode.

• max-secondary-rat-reports report_range : Configure the maximum number of secondary RAT usage reports to trigger GTPP (Gz) or CHF update. report_range must be an integer in the range of 0–50. Default value: 0.

Use the following sample configuration to configure presence reporting.

config 
   profile dnn dnnprofile_name 
      presence-reporting { false | true } 
      exit 

NOTES:

• profile dnn dnnprofile_name : Enter the DNN Profile Configuration mode.

• presence-reporting { false | true } : Configure presence reporting for the DNN.

  • false : Disable presence reporting. This is the default setting.

  • true : Enable presence reporting.

show subscriber supi supi_id nf-service smf  

In the output of the preceding show command, check the value associated with the field "dncr". This field displays one of the following values:

• Enabled

• None

• UE Requested and Enabled

If the feature is configured, then the "dcnr" field displays "Enabled".

The following configuration is an example output of the show subscriber supi nf-service smf command:

unknown] smf# show subscriber supi imsi-123456789012345 nf-service smf
subscriber-details 
{
"subResponses": [
{
"status": true,
"genericInfo": {
……
},
"sScMode": 1,
"chargEnabled": true,
"uetimeZone": "+00:15+1",
"allocatedIp": "209.165.201.12",
"eUtranLocation": {
"ecgi": {
"mcc": "123",
"mnc": "456",
"eutraCellId": "1234567"
},
"tai": {
"mcc": "123",
"mnc": "456",
"tac": "1820"
}
},
"alwaysOn": "None",
"dcnr": "Enabled",   
……
"policySubData": {
 "TotalDynamicRules": 3,
…………
Presence Information: "Enabled",   
 "praIdList": [  -> list of all enabled PRA IDs
          "8388608",  Status = IN
          "8388618" Status = OUT
        ]
 },

The SMF uses the "dcnr" label in the session gauge "smf_session_counter" and "smf_service_stats" for collecting the DCNR session count. When the SMF session is DCNR supported, the "dcnr" label value is enabled. The label does not support non-DCNR sessions.

The following is a sample query to count the active DCNR SMF sessions:

nts{action_type="rejected",app_name="smf",cluster="smf",data_center="unknown",
failure_type="hdr_decode_failure",hdr_decode_fail_reason="",instance_id="0",interface_type="
",message_type="",reject_cause="",service_name="gtpc-ep"} 2

smf_session_counter: sum (smf_session_counters{dcnr_on="enable"}) by (dcnr)

smf_service_stats: sum (smf_session_stats{dcnr_on="enable"}) by (dcnr, status, reason)

smf_session_counters{ presence-reporting ="enable"}) by (presence-reporting)

DCNR Session Count

For DCNR, Session Count supports the "dcnr" label in the existing session gauge "smf_session_counter". If the SMF session is a DCNR session, then the "dcnr" label value is "enable", otherwise it is "disable" for DCNR session.

The following is a sample query to count the DCNR active SMF sessions:

sum (smf_session_counters{dcnr_on="enable"}) by (dcnr)

For DCNR statistics, the existing "smf_service_stats" counter supports the "dcnr" label. For DCNR sessions, this counter pegs the following labels and values:

• Attempt Statistics – dcnr= "enable" and status= "attempted"

• Success Statistics – dcnr= "enable" and status= "success"

• Failure Statistics – dcnr= "enable" and status= "failures"

The following is a sample query for DCNR statistics:

sum (smf_session_stats{dcnr_on="enable"}) by (dcnr, status, reason)

Secondary RAT Data Usage Reports

The Secondary-Rat-Data-Usage-Reports support the "smf_secondary_rat_usage_report_stats" counter. Labels for these statistics include ebi, qfi, rat_type, reason, service_name, and status. This counter pegs with the following labels and values:

• ebi=ebi-val

• qfi=qfi-val

• rat_type=NR

• reason=success/failure

• service_name=smf-service

• status=ReceivedFromSgw/SentToChf

The following is a sample query for DCNR statistics:

sum (smf_secondary_rat_usage_report_stats”) by (qfi, status, reason)

Presence Reporting

For Presence Reporting, Session Count supports the "pra" label in the existing session gauge "smf_session_counter". If the SMF session has presence reporting enabled, then the "presence-reporting" label value is "enable" else it is "none" if presence reporting is not enabled.

The following is a sample query to count the DCNR active SMF sessions:

sum (smf_session_counters{ pra ="enable"}) by (pra)

For Presence Reporting, statistics support the "presence-reporting" label in the existing counter "smf_service_stats". For presence-reporting session, this counter pegs the following labels and values:

• Attempt Statistics – pra = "enable" and status= "attempted"

• Success Statistics – pra = "enable" and status= "success"

• Failure Statistics – pra = "enable" and status= "failures"

The following is a sample query for DCNR statistics:

sum (smf_session_stats{ pra ="enable"}) by (pra, status, reason)

The Option 3x and 4G-Only Device feature supports the following bulk statistics in SMF schema:

The show subscriber nf-service smf supi supi_id full CLI command displays the DCNR active session with presence reporting enabled for the Option-3x feature.

Note	In 2021.02 and later releases, the namespace keyword is deprecated and replaced with the nf-service keyword.

[unknown] smf# show subscriber nf-service smf supi imsi-310260789012345 full

subscriber-details 
{
  “subResponses”: [
    {
      “status”: true,
      “genericInfo”: {
        “supi”: “imsi-310260789012345”,
        “pei”: “imei-123456786666660”,
        “pduSessionId”: 5,
        “pduSesstype”: “Ipv4PduSession”,
        “accessType”: “3GPP_ACCESS”,
        “dnn”: “fast.t-mobile.com”,
        “plmnId”: {
          “mcc”: “123”,
          “mnc”: “456”
        },
…
        “alwaysOn”: “None”,
        “dcnr”: “Enabled”,
        “wps”: “Non-Wps Session”,
        “ratType”: “EUTRA”,
        “ueType”: “NR Capable UE”,
        “iwkEpsInd”: true,
        “sessTimeStamp”: “2021-01-12 12:40:39.931012285 +0000 UTC”,
        “callDuration”: “4m25.36784895s”,
        “ipPool”: “poolv4”,
        “commonId”: 16777223,
        “linkedEbi”: 5,
        “smfIwkEpsInd”: true,
        “snssai”: {
          “sd”: “Abf123”,
          “sst”: 1
        },
        “authStatus”: “Unauthenticated”,
        “roamingStatus”: “Roamer”,
        “uePlmnId”: {
          “mcc”: “310”,
          “mnc”: “260”
        }
      },
      “policySubData”: {
        “TotalDynamicRules”: 2,
        “TotalFlowCount”: 2,
        “TotalNonGBRFlows”: 1,
        “TotalGBRFlows”: 1,
        …
        “presenceReporting”: “Enabled”,
        “praList”: [
          {
            “praId”: “0x80000b”,
            “presenceState”: “Inactive”
          },
          {
            “praId”: “0x800000”,
            “presenceState”: “InArea”
          },
          {
            “praId”: “0x80000a”,
            “presenceState”: “OutOfArea”
          }
        ]
      },
      …
      }
    }
  ]
}

This section describes the alerts supported for DCNR enabled UEs with presence-reporting enabled. You can enhance these alerts as per 4G procedure or as per the intent of the end user.

Examples of DCNR statistics or gauges are pdn_sess_create, pdn_inter_sgw_handover, pdn_mbr, pcf_req_ded_brr_mod, pcf_req_ded_brr_create, pcf_req_ded_brr_delete, delete_session_request, smf_initiated_pdn_detach, ue_req_pdn_sess_rel, and so on.

Use the following SMF service bulk statistics to monitor the failures or issues associated with DCNR UEs.

This section provides the basic error conditions and logs that are captured to debug the failures for the Option-3x feature.

DCNR Disabled UE or 4G capable UE only

The following example displays the error log for DCNR disabled UE or 4G capable UE only.

2021/01/24 10:11:22.648 smf-service [ERROR] [GenericGtpMsg.go:1811] [smf-service.smf-app.sgw] secRatUsageRpt recvd wrongly for DNCR disbled UE, ignoring report

2020/12/19 13:17:17.834 smf-service [ERROR] [GenericGtpMsg.go:1834] [smf-service.smf-app.sgw] secRatUsageRpt recvd wrongly for 4gOnly UE, ignoring report

Secondary RAT Usage with invalid EBI

The following example displays the error log for secondary RAT usage with invalid EBI.

2021/01/24 11:38:18.917 smf-service [DEBUG] [GenericGtpMsg.go:1824] [smf-service.smf-app.sgw] Secondary Rat Data Usage Report Recvd
2021/01/24 11:38:18.917 smf-service [WARN] [IntMethods.go:137] [smf-service.Policy.gen] Qos Flow not found with EBI [8]
2021/01/24 11:38:18.917 smf-service [ERROR] [GenericGtpMsg.go:1853] [smf-service.smf-app.sgw]  Qfi invalid in secRatUsageRpt

Secondary RAT Usage invalid RAT Type

The following example displays the error log for secondary RAT usage with invalid RAT type.

2021/01/24 11:42:21.474 smf-service [DEBUG] [GenericGtpMsg.go:1824] [smf-service.smf-app.sgw] Secondary Rat Data Usage Report Recvd
2021/01/24 11:42:21.474 smf-service [ERROR] [GenericGtpMsg.go:1861] [smf-service.smf-app.sgw]  Rat type invalid in secRatUsageRpt

Secondary RAT Usage with intended PGW set to zero

The following example displays the error log for secondary RAT usage with intended P-GW set to zero (IRPGW:0).

2021/01/24 11:33:10.390 smf-service [DEBUG] [GenericGtpMsg.go:1824] [smf-service.smf-app.sgw] Secondary Rat Data Usage Report Recvd
2021/01/24 11:33:10.390 smf-service [ERROR] [GenericGtpMsg.go:1865] [smf-service.smf-app.sgw]  secRatUsageRpt.IRPGW is false

PRA ID received greater than four

The following example displays the error log when PRA ID received is greater than four.

2021/01/24 14:48:26.085 smf-service [DEBUG] [policy_types.go:659] [smf-service.Policy.gen] praConfig:true for dnn:fast.t-mobile.com
2021/01/24 14:48:26.085 smf-service [DEBUG] [policy_pcf.go:1939] [smf-service.Policy.gen] Added PRA ID: 9388618
2021/01/24 14:48:26.085 smf-service [DEBUG] [policy_pcf.go:1939] [smf-service.Policy.gen] Added PRA ID: 9388608
2021/01/24 14:48:26.085 smf-service [DEBUG] [policy_pcf.go:1939] [smf-service.Policy.gen] Added PRA ID: 8388618
2021/01/24 14:48:26.085 smf-service [DEBUG] [policy_pcf.go:1939] [smf-service.Policy.gen] Added PRA ID: 9388619
2021/01/24 14:48:26.085 smf-service [WARN] [policy_pcf.go:1934] [smf-service.Policy.gen] Max 4 PRAs allowed, ignoring the PRA-ID (8388608) from PCF
2021/01/24 14:48:26.085 smf-service [WARN] [policy_pcf.go:1934] [smf-service.Policy.gen] Max 4 PRAs allowed, ignoring the PRA-ID (8388619) from PCF