Question: In an IP Multimedia Subsystem (IMS), what is a characteristic of the Telephony Application Server (TAS) in relation to the network support for multimedia telephony service?
Option 1: It is a Diameter-based server providing authentication services.
Option 2: It is a SIP AS (Application Server) enabling multimedia messaging services.
Option 3: It is an HTTP server primarily used for file transfers in IMS.
Option 4: It is a SIP AS providing network support for the multimedia telephony service.
Explanation: This answer is correct because, according to IMS specifications, the Telephony Application Server (TAS) acts as a SIP (Session Initiation Protocol) Application Server, providing network support for delivering multimedia telephony services within the IMS framework, managing and controlling SIP sessions for voice and video calls.