This article shall give you the abstract of WHY and HOW Sh-interface works.
Sh is a DIAMETER interface; having application ID 16777217, between Application Server (AS) and HSS. Application Server is place where actually the services are executed e.g. Call-Forwarding services related processing take place at Application server. Sh interface is used by AS to communicate with HSS; Application Server uses HSS as repository, AS can put some of its Transparent or Non-Transparent data, Transparent data is the information that HSS doesn't understand. Also fetches subscriber information (such as Subscriber status, Location information etc )from HSS .
This interface contains 4 messages.
1)User-Data-Request/Answer (AS--> HSS) [DATA Read]:
In this AS asks for subscriber related information from HSS; Subscriber related data at HSS either provisioned by operator and/or received from network and/or earlier stored by AS itself with the help of Profile-Update-Request/Answer.
2)Profile-Update-Request/Answer (AS-->HSS) [DATA Update]:
In this message AS stores/update its data at HSS for a particular subscriber and/or application.
[Subscriber for Notification]:
In this message AS takes a subscription that when ever there is change in particular data field, more particularly for a given subscriber then I(AS) must be informed. Even some time AS can ask for current data for a given subscriber in same Answer message
Here HSS downloads the Updated value of field at Application server, whose subsciption is earlier take by AS; when-ever subscriber field changed either by Operator or Network.
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