About SCEF Testing
SCEF (Service Capability Exposure Function) interacts with 3GPP entities by various interfaces. It also has different API’s for Application servers.
The S6t reference point is located between the Services Capability Exposure Function (SCEF) and the Home Subscriber Server (HSS). S6t reference point is used for:
1. Connect the SCEF to HSS containing subscription and UE related information;
2. Monitoring event configuration/deletion by the SCEF at the HSS; and
3. Monitoring event reporting by the HSS to the SCEF.
4. Configuration/deletion of communication pattern parameters by the SCEF to HSS
In our simulation, when SCEF has established socket with HSS it sends the CIR request to HSS.
The T6a reference point is located between SCEF and MME. The T6b reference point is between SCEF and SGSN. T6a/b reference point is used for:
1. Monitoring event configuration by the SCEF at the serving MME/SGSN
2. Monitoring event reporting by the serving MME/SGSN to the SCEF
3. To manage connection between MME and the SCEF on T6a
4. To send MT data on T6a
5. To receive MO data on T6a
As per the 3GPP TS, the Diameter session on S6t is established at the request of the SCEF by initiating Configuration-Information-request command.
S6t messages are carried within the Diameter Application (s) with application Id 16777345. Below are all the messages over S6t interface that will be supported:
Command Code values for S6t (3GPP TS 29.336 v13.4.0)
Message |
Abbreviation |
Direction |
Command Code |
Configuration-Information-Request |
CIR |
SCEF->HSS |
8388718 |
Configuration-Information -Answer |
CIA |
HSS->SCEF |
8388718 |
Reporting-Information-Request |
RIR |
HSS->SCEF |
8388719 |
Reporting-Information-Answer |
RIA |
SCEF->HSS |
8388719 |
NIDD-Information-Request |
NIR |
SCEF->HSS |
8388726 |
NIDD-Information-Answer |
NIA |
HSS->SCEF |
8388726 |
As per the 3GPP TS, the Diameter session on T6a/b is established at the request of the SCEF by initiating Configuration-Information-request command.
T6a/b messages are carried within the Diameter Application (s) with application Id 16777346. Below are all the messages over T6a/b interface that will be supported:
Message |
Abbreviation |
Direction |
Command Code |
Configuration-Information-Request |
CIR |
SCEF->MME/SGSN |
8388718 |
Configuration-Information -Answer |
CIA |
MME/SGSN->SCEF |
8388718 |
Reporting-Information-Request |
RIR |
MME/SGSN ->SCEF |
8388719 |
Reporting-Information-Answer |
RIA |
SCEF-> MME/SGSN |
8388719 |
Connection-Management-Request |
CMR |
MME -> SCEF |
8388732 |
Connection-Management-Answer |
CMA |
SCEF>MME
|
8388732 |
MO-Data-Request Command |
ODR |
MME->SCEF |
8388733 |
MO-Data-Answer |
ODA |
SCEF->MME |
8388733 |
MT-Data-Request |
TDR |
SCEF->MME |
8388734 |
MT-Data-Answer |
TDA |
MME->SCEF |
8388734 |
Support Non-IP Data Delivery through T6a reference point on Landslide’s MME node.
Enable T6a Interface on MME Node Test Case to support Non-IP Data Delivery (NIDD) through T6a reference point between Mobility Management Entity (MME) and Service Capability Exposure Function (SCEF) (as depicted in Figure 1) for reporting UE Loss of Connectivity, UE reachability, location of the UE and change in location of the UE, and Communication Failure.
Figure 1.
This capability provides the ability to send data over the control plane (MME/SGSN) in a NAS message, thus reducing the total number of control plane messages required for small data delivery.
NIDD is part of the CIoT EPS optimization accomplished by delivery using SCEF. The non IP PDN must be established by the UE to send Non-IP Data via SCEF. The UE embeds the data it wants to send in the transparent container without using IP stack. The MME forwards such data to SCEF by PDN connectivity. PDN connectivity request is a procedure used by the UE to request the setup of a default EPS bearer to a PDN using NAS signalling. If this request is accepted by the network, then it initiates the establishment of a default EPS bearer context activation procedure. MME will trigger a SCEF connection through Connection Management procedure.
This section describes the procedures for Non-IP Data Delivery via SCEF (as depicted in Figure 2 below).
1. UE performs EPS attach procedure (PDN Connectivity through NAS EPS) with PDN type of “Non-IP” and the subscription information corresponding to the APN.
2. MME verifies that the APN provided by the UE is allowed by subscription (i.e. APN name configured must match APN name from ESM message container and must support Control Plane CIoT EPS Optimization).
3. MME initiates a T6a connection towards SCEF through Connection-Management Request (CMR) corresponding to the SCEF-ID indicator for that APN and allocate EPS Bearer Identity (EBI) once PDN connection is established.
4. UE sends the Mobile Originated Non-IP data to MME.
5. MME forwards the Mobile Originated Non-IP data to SCEF by MO-Data-Request (ODR).
6. MME forwards the Mobile Terminated Non-IP Data to UE when MT-Data-Request is received from SCEF.
7. Connection Management stops upon detaching.
Figure 2:
