Sh (application id: 16777292)

The Sh interface is a crucial component of the IP Multimedia Subsystem (IMS) architecture. It facilitates communication between the Home Subscriber Server (HSS) and various Application Servers (AS), enabling the exchange of user-related data necessary for service provision. The Sh interface is built on the Diameter protocol, ensuring reliable and secure transmission of subscriber information.

The primary purpose of the Sh interface is to manage and synchronize subscriber-related information between the HSS and AS. This includes the retrieval, updating, and notification of user profile data, which is essential for delivering personalized services in an IMS network. The Sh interface supports a wide range of services by allowing AS to access user-specific data stored in the HSS, such as service entitlements, preferences, and presence information.
Functional Components
Home Subscriber Server (HSS): The HSS is the central database that stores user profiles, service data, and subscription information. It is responsible for handling requests from AS for user data and sending notifications when this data changes.
Application Server (AS): The AS provides various IMS services to users, such as multimedia applications, messaging, and presence services. The AS communicates with the HSS via the Sh interface to retrieve or update user data and subscribe to notifications about changes in user profiles.

Sh interface workflow: 
Data Handling Procedures:

• Data Retrieval: 
  • The AS initiates a request to the HSS to retrieve user-specific data using the Sh-Query command. This data may include user identities, service profiles, and other relevant subscription information.
  • The HSS processes the request and sends the requested data back to the AS in the response message.
• Data Update:
  • The AS may update user data stored in the HSS by sending an Sh-Update command. This could include changes to service preferences or user identity data.
  • Upon successful update, the HSS confirms the change by sending an Sh-Update response.

Subscription and Notification Procedures:

• Subscription to Notifications:
  • The AS can subscribe to receive notifications about changes in user data by sending an Sh-Subs-Notif request to the HSS. This subscription ensures that the AS is kept informed of any updates in the user’s profile.
  • The HSS acknowledges the subscription and begins monitoring the relevant data.
• Notification of Data Changes:
  • When there is a change in the user data to which the AS has subscribed, the HSS sends an Sh-Notif command to the AS, indicating the nature of the update.
  • The AS processes the notification and sends back an Sh-Notif Resp message to confirm receipt.

Service Registration:

• User Registration:
  • When a user registers for a service, the AS may need to interact with the HSS to obtain or update user data relevant to the service.
  • The AS sends a Register command to the HSS, which may include data such as user identity or service preferences.
  • The HSS processes the registration and confirms with a 200 OK response.

For complete technical specification of Sh interface in Diameter protocol please refer to: [3GPP TS 29.328]