S6t (application id: 16777345)

The S6t interface is a key element in the 3GPP architecture for managing Machine-Type Communication (MTC) devices, particularly in the context of the Internet of Things (IoT). S6t interface enables communication between the Service Capability Exposure Function (SCEF) and the Home Subscriber Server (HSS). The primary purpose of the S6t interface is to facilitate the configuration, monitoring, and management of MTC devices by allowing the SCEF to interact with the HSS.
The S6t interface plays a crucial role in scenarios where devices need to be managed remotely without human intervention. It supports various functions such as the configuration of monitoring events, management of communication patterns, and the retrieval of subscription data.

S6t architecture ensures that the SCEF can interact with the HSS to perform several key functions:

• Configuration and Deletion of Monitoring Events: The SCEF uses the S6t interface to configure specific monitoring events for individual UEs or groups of UEs. These events could include changes in device status, such as connectivity or location.
• Configuration and Query of Communication Patterns: The SCEF can manage how and when devices communicate with the network by configuring communication patterns through the S6t interface.
• Translation of Identifiers: The S6t interface supports the translation of external group identifiers into IMSI Group IDs, facilitating the management of device groups based on their identifiers.
• Authorization and Notification for Non-IP Data Delivery (NIDD): The interface allows the SCEF to authorize UEs for NIDD services, ensuring that devices can send and receive data without needing a direct IP connection.

S6t interface workflow:
The workflow of the S6t interface typically involves the following steps:

1. Configuration of Monitoring Events:
   • The SCEF sends a request to the HSS to set up monitoring events for specific UEs or groups of UEs. These events could trigger actions when certain conditions are met, such as a device moving into a new location or a change in connectivity status.
   • The HSS processes the request and stores the necessary monitoring configurations.
2. Reporting of Monitoring Events:
   • Once a configured event occurs, the HSS generates a report and sends it back to the SCEF via the S6t interface. This enables real-time monitoring and management of MTC devices.
3. Management of Communication Patterns:
   • The SCEF configures or queries communication patterns through the S6t interface, determining how devices communicate with the network (e.g., setting specific time windows for data transmission).
4. Translation of Identifiers:
   • The SCEF may need to translate an external group identifier into an IMSI Group ID for management purposes. The S6t interface facilitates this translation, allowing the SCEF to effectively manage groups of devices.
5. Authorization for NIDD:
   • For devices using NIDD, the SCEF authorizes their communication through the S6t interface. The HSS confirms the authorization and updates its records accordingly.

For complete technical specification of S6t interface in Diameter protocol please refer to: [3GPP TS 29.336]