Non-IP Data Over SCEF
Feature Summary and Revision History
Packet Data Network Disconnect or Detach Procedure
How it Works
- Connection Release
- Initiating Packet Data Network Disconnect or Detach Procedure
Monitoring and Troubleshooting
- show mme-service statistics

Non-IP Data Over SCEF

Feature Summary and Revision History

Summary Data


Applicable Product(s) or Functional Area	MME
Applicable Platform(s)	ASR 5500 VPC-DI VPC-SI
Feature Default	Disabled - Configuration Required
Related Changes in This Release	Not applicable
Related Documentation	Command Line Interface Reference Ultra IoT C-SGN Administration Guide

Revision History


Revision Details	Release
This release supports: Connection Management by SCEF Procedure to release a T6a connection between MME and SCEF. This release supports PDN disconnect and detach procedure towards the UE when it receives a MO Data Answer message with Permanent Failure from SCEF.	21.19
The feature is tested and qualified on the ASR 5500 platform. This release supports temporary buffering of single MT Data Request received from SCEF while UE is in idle mode.	21.3
First introduced.	N5.1 (21.1.V0)

Packet Data Network Disconnect or Detach Procedure

Before the implementation of Packet Data Network (PDN) Disconnect or Detach procedure in a network, MME followed the below process after receiving the permanent failure code:

The User Equipment (UE) connects to the network with Non-IP Data Delivery (NIDD) option and establishes T6a connection.
UE tries Mobile Originated (MO) NIDD whenever a Session DB on the SCEF gets cleared.
UE sends Non-Access Stratum (NAS) “MO REQUEST” with the data and receives NAS_SERVICE_ACCEPT.
The MME sends Diameter “MO-Data-Request” over T6A and receives “DIAMETER_ERROR_INVALID_EPS_BEARER (5651)” or “DIAMETER_ERROR_USER_UNKNOWN”.

However, there was data loss. This data loss was because of the lack of PDN Disconnect or Detach procedure initiation from MME towards the UE. UE may assume that it is T6a connected and retry MO NIDD indefinitely.

In StarOS 21.19 and later releases, the MME supports PDN Disconnect or Detach procedure towards the UE when it receives a MO Data Answer message with Permanent Failure Result-Code/Experimental-Result from SCEF. If the permanent failure is different from DIAMETER_ERROR_ INVALID_EPS_BEARER and from DIAMETER_ERROR_USER_UNKNOWN, then MME also initiates the "Connection Management by MME/SGSN" procedure to release the T6a connection between the MME and the SCEF.

How it Works

This section covers SCEF Initiated T6a Connection Release and Packet Data Network (PDN) Disconnect and Detach procedures.

Connection Release

MME allows Service Capability Exposure Function (SCEF) to initiate T6a connections release procedure in compliance with the 3GPP specifications 23.682 Release 15, Section 5.13.5.3 and 29.128 Release 15, Section 5.8.

Using one of the following procedures, the MME releases the T6a connection towards the SCEF(s) corresponding to the SCEF ID indicator for an APN:

User Equipment (UE)-initiated Detach procedure for E-UTRAN
MME-initiated Detach procedure
HSS-initiated Detach procedure
UE or MME requested PDN disconnection procedure.

In one of the following scenarios, the SCEF releases the T6a connection towards the MME corresponding to PDN connections:

When an NIDD Authorization Update request from the HSS indicates that the user is no longer authorized for NIDD.
Failure of SCEF or failure of SCS/AS connection
Based on a request from the SCS/AS
Based on removal of the APN associated with the T6a connection from the SCEF

SCEF Initiated T6a Connection Release Procedure

SCEF invokes Connection Management by SCEF procedure to release a T6a connection between MME and SCEF. This procedure is mapped to the commands Connection-Management-Request/Answer (CMR/CMA) in the Diameter application along with IEs.

The following table describes Connection Request management IE from SCEF.

Table 1. Connection Management SCEF Request
Information Element Name	Mapping to Diameter AVP	Category	Description
User Identity	User-Identifier	M	This information element contains the identity of the UE. This is a grouped AVP which contains the IMSI.
EPS Bearer Identity	Bearer-Identifier	M	This information element contains the identity of the EPS bearer, identifying the T6a connection to the applicable request.
T6a/b Connection Action	Connection Action	M	This information element contains T6a connection management action indicating a T6a connection establishment, a T6a connection release, or a T6a connection update.
Extended PCO	Extended- PCO	C	This information element contains Extended- Protocol Configuration Options (PCO), indicating that the SCEF needs to send updated extended PCO information (for example, APN Rate Control information) to the UE.
Supported Features	Supported-Features	O	Lists the features supported by the origin host.

SCEF sets the Connection-Action to CONNECTION_RELEASE (1) for a T6a Connection Release.

The following table describes SCEF Answer management from MME.

Table 2. Connection Management SCEF Answer
Information Element Name	Mapping to Diameter AVP	Category	Description
Result	Result-Code/Experimental-Result	M	This information element provides the result of the request. Result-Code AVP is used for errors defined in the Diameter Base Protocol. Experimental-Result AVP is used for T6a/b errors. This is a grouped AVP, which contains the 3GPP Vendor ID in the Vendor-Id AVP, and the error code in the Experimental-Result-Code AVP.
Supported Features	Supported-Features	O	This information element contains the list of features supported by the origin host.

After MME receives the Connection Management Request with Connection-Action set to 1 in t6a interface, MME does the following.

Table 3. T6a Connection Release Procedure by SCEF
Step	Description
1	Checks if the User Identity exists in the MME. If the User Identity does not exist, sets the Experimental-Result to DIAMETER_ERROR_USER_UNKNOWN in the Connection Management SCEF Answer.
2	Checks whether the T6a connection action indicates a T6a connection update or T6a connection release. If the T6a connection acttion is not update or release, then sets the Experimental-Result to DIAMETER_ERROR_OPERATION_NOT_ALLOWED in the Connection Management SCEF Answer.
3	Checks whether a T6a connection context exists for a user and the received EPS Bearer Identity. If T6a conection context does not exist, then sets the Experimental-Result to DIAMETER_ERROR_ INVALID_EPS_BEARER in the Connection Management SCEF Answer.
4	If the T6a connection action indicates T6a connection release, delete the T6a connection context at the MME. If successful, sets the Result code to DIAMETER_SUCCESS in the Connection Management SCEF Answer.
5	The MME performs the MME initiated Detach procedure.

Initiating Packet Data Network Disconnect or Detach Procedure

MME triggers the PDN Disconnect or Detach procedure based on the following conditions:

MME checks whether to trigger PDN Disconnect procedure or Detach procedure based on the PDN Count.
If the last PDN and Attach without PDN connectivity is supported by UE, then MME triggers the PDN Disconnect procedure.
If UE has more than one PDN, and UE sends MO Data Request procedure towards SCEF-specific PDN, and if MME receives MO Data answer with any permanent failure cause, MME triggers PDN disconnect procedure towards UE. MME initiates Connection release procedure towards SCEF except when the error is other than “DIAMETER_ERROR_USER_UNKNOW” and “DIAMETER_ERROR_INVALID_EPS_BEARER” .
If UE has only one PDN and Attach without PDN is not supported, then MME triggers Detach procedure. If permanent failure is different than Diameter_Error_User_Unknown and Invalid EPS Bearer ID, MME initiates a Connection Management procedure to release the T6a connection.
If UE has one PDN or more than one PDN and UE sends MO Data Request procedure towards SCEF-specific PDN, and if MME receives MO Data answer with failure cause as User-Unknown, MME triggers Detach procedure.

The following table describes error scenarios when MME initiates Detach/PDN disconnect towards UE and release of T6a connection towards SCEF .

Table 4. Detach/PDN disconnect Errors
DIAMETER_ERROR/No of PDNs	1 PDN & Attach without PDN Support by UE	>1 PDN	1 PDN & Attach without PDN not Support by UE
USER_UNKNOWN	Detach towards UE and no T6a Connection release towards SCEF	Detach towards UE and no T6a Connection release towards SCEF	Detach towards UE and no T6a Connection release towards SCEF
INVALID_EPS_BEARER	PDN Disconnect towards UE and no T6a Connection release towards SCEF	PDN Disconnect towards UE and no T6a Connection release towards SCEF	Detach towards UE and no T6a Connection release towards SCEF
OPERATION_NOT_ALLOWED	PDN Disconnect towards UE and T6a Connection release towards SCEF	PDN Disconnect towards UE and T6a Connection release towards SCEF	Detach towards UE and T6a Connection release towards SCEF
NIDD_CONFIGURATION_NOT_AVAILABLE	PDN Disconnect towards UE and T6a Connection release towards SCEF	PDN Disconnect towards UE and T6a Connection release towards SCEF	Detach towards UE and T6a Connection release towards SCEF
SCEF_REFERENCE_ID_UNKNOWN	PDN Disconnect towards UE and T6a Connection release towards SCEF	PDN Disconnect towards UE and T6a Connection release towards SCEF	Detach towards UE and T6a Connection release towards SCEF

Monitoring and Troubleshooting

This section provides information regarding show commands of data over T6A (SCEF) statistics for this feature.

show mme-service statistics

The ESM procedure statistics counters are added for the following:

Non-IP PDN Connections over SCEF (T6a)
Non-IP PDN Disconnects over SCEF (T6a)

The statistics added are as follows:

ESM Statistics: 
. 
. 
PDN Connections With PDN Type Override to ipv6: 
   Attempted:          0   Success:         0 
   Failures:           0 
NON-IP PDN Connections With SCEF: 
   Attempted:          0   Success:         0 
   Failures:           0 
NON-IP PDN Connections With SGI: 
   Attempted:          0   Success:         0 
   Failures:           0 
PDN Disconnections With SCEF: 
   Attempted:          0   Success:         0 
   Failures:           0

For PDN statistics, the following is displayed:

 
. 
. 
PDN Statistics: 
  All PDNs:            0   Connected PDNs:      0 
  Idle PDNs:           0 
NON-IP PDN Statistics: 
... 
... 
Data Over T6A (SCEF) Statistics: 
   Rx Packets:         0   Rx Bytes:            0 
   Tx Packets:         4   Tx Bytes:            84 
   Rx Drop Packets:    0   Rx Drop Bytes:       0 
   Tx Drop Packets:    0   Tx Drop Bytes:       0

show mme-service statistics monte

Following statistics are displayed for Monitoring events in MME:

Session Statistics:
Monitoring Events Statistics:
     Current number of UEs being monitored:             0

     Current number of reports configured:
     Loss of connectivity                                        :            0
     UE Reachability                                             :            0
     Location Reporting                                          :            0
     Communication Failure                                       :            0
     Availability after DDN Failure                              :            0
     UE Reachability and idle status indication                  :            0
     Availability after DDN Failure and idle status indication   :            0
     PDN connectivity status                                     :            0
Monitoring Events Statistics:

Monitoring Report Config Rx Count:
  Loss of connectivity                                        :            0
  UE Reachability                                             :            0
  Location Reporting                                          :            0
  Communication Failure                                       :            0
  Availability after DDN Failure                              :            0
   UE Reachability and idle status indication                  :            0
  Availability after DDN Failure and idle status indication   :            0
  PDN connectivity status                                     :            0

Monitoring Reports Tx Count:
  Loss of connectivity                                        :            0
  UE Reachability                                             :            0
  Location Reporting                                          :            0
  Communication Failure                                       :            0
  Availability after DDN Failure                              :            0
    UE Reachability and idle status indication                  :            0
  Availability after DDN Failure and idle status indication   :            0

show bulkstats variables mme | grep moni

On running the above command, the following session statistics is displayed:

%monitored-subscribers%                                     Int32     0   Gauge
         %monitored-loss-of-connectivity%                             Int32     0   Gauge
         %monitored-ue-reachability%                                  Int32     0   Gauge
         %monitored-location-reporting%                               Int32     0   Gauge
         %monitored-communication-failure%                            Int32     0   Gauge
         monitored-availability-after-ddn-failure%                    Int32     0   Gauge
         monitored-number-of-ue-geoarea%                              Int32     0   Gauge
         %monitored-uereachability-idleind%                            Int32     0   Gauge
         %monitored-availability-after-ddn-failure-idleind%            Int32     0   Gauge
         %monitored-pdn-connecitivty-status%                           Int32     0   Gauge

show bulkstats variables mme | grep monte

On running the above command , the following overall statistics is displayed:

%mme-monte-rx-loss-of-cnnectivity%                            Int32     0   Counter
%mme-monte-rx-ue-reachability%                                Int32     0   Counter
 %mme-monte-rx-location-reporting%                             Int32     0   Counter
 %mme-monte-rx-communication-failure%                          Int32     0   Counter
%mme-monte-rx-availability-after-ddnfailure%                  Int32     0   Counter
%mme-monte-rx-number-of-ue-geoarea%                           Int32     0   Counter
%mme-monte-rx-uereachability-idleind%                         Int32     0   Counter
%mme-monte-rx-availability-ddnfailure-idleind%                Int32     0   Counter
%mme-monte-rx-pdn-connectivity-status%                        Int32     0   Counter
 %mme-monte-tx-loss-of-connectivity%                           Int32     0   Counter
%mme-monte-tx-ue-reachability%                                Int32     0   Counter
%mme-monte-tx-location-reporting%                             Int32     0   Counter
%mme-monte-tx-communication-failure%                          Int32     0   Counter
 %mme-monte-tx-availability-ddn-failure%                       Int32     0   Counter
%mme-monte-tx-number-of-ue-geoarea%                           Int32     0   Counter
 %mme-monte-tx-uereachability-idleind%                         Int32     0   Counter
%mme-monte-tx-availability-ddnfailure-idleind%                Int32     0   Counter
%mme-monte-tx-pdn-connectivity-status%                        Int32     0   Counter
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Release Change Reference, StarOS Release 21.19/Ultra Services Platform Release 6.13

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Release Change Reference, StarOS Release 21.19/Ultra Services Platform Release 6.13

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