Which Diameter command does an Application Server use on Sh to read user data?

Interview
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Q. Which Diameter command does an Application Server use on Sh to read user data?

a) AAR
b) CCR
c) UDR
d) CER

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:arrow_right: Correct answer: Letter c.

In the IMS architecture, the Sh interface is used between the Application Server (AS) and the HSS to manage subscriber-related data, such as user profiles or service triggers.

When the Application Server needs to read user data stored in the HSS, it uses the UDR (User Data Request) Diameter command. The HSS responds with a UDA (User Data Answer) message.

Other commands like AAR or CCR serve completely different functions (e.g., resource authorization or charging).

Q. Which Diameter command does an Application Server use on Sh to read user data?

a) :x: AAR
→ Incorrect. AAR (AA-Request) is used for authorization/authentication in Rx or Gx, not reading subscriber data on Sh.

b) :x: CCR
→ Incorrect. CCR (Credit-Control Request) is used for online charging, not user data retrieval.

c) :white_check_mark: UDR
→ Correct. UDR (User Data Request) is the standard Diameter command for accessing subscriber data over the Sh interface.

d) :x: CER
→ Incorrect. CER (Capabilities-Exchange Request) is used in establishing a Diameter peer connection, not for user data queries.