24.4233GPPExtensible Markup Language (XML) Configuration Access Protocol (XCAP) over the Ut interface for Manipulating NGN PSTN/ISDN Simulation ServicesPSTN/ISDN simulation servicesRelease 8TISPANTS
The protocol described in the present document allows to manipulate settings and variables related that influence the execution of one or more PSTN/ISDN simulation services. Manipulation of supplementary services take place over the
Ut interface (UE to AS), as shown in figure 1.
Figure 1: Ut interface
Manipulation of services does not usually take place during real‑time operation. Typically users manipulate their services configuration data prior to the invocation and execution of the service.
Authentication of the user with HTTP may take place directly at the AS, such as in figure 1, or with the support of an Authentication Proxy, such as in figure 2. The architecture for authentication is provided in TS 187 003  with the remark that the Network Application Function (NAF) is effectively an AS providing an NGN PSTN/ISDN simulation service in an NGN.
Figure 2: Authentication proxy in the Ut interface path