context of an ims network ims application servers as 1 as n 312 314 and the cscf 316 utilize the services of the saucf 310 via the unique service authorization amp utilization diameter application sauda interface the s cscf 316 plays an important part in voice over ip calls because all calls for a given subscriber traverse the s cscf 316 when no as 312 314 is involved in a voip call the s cscf 316 may request service level policies for a subscriber from the saucf fig3 also shows legacy non ims application servers such as the mmsc 318 and a web proxy 308 legacy network elements also utilize the service authorization amp utilization diameter application interface to the saucf 310 to support service level policies finally the services provided by the saucf 310 may be utilized by network elements other than application servers for example fig3 shows a firewall 306 communicating with the saucf 310 that may provide restriction or privacy services to a subscriber note that interfaces 332 340 carry the service authorization and utilization diameter application fig3 also shows network elements and functions shown in fig2 that include the pcrf 326 and hss 324 the saucf also enforces.