202 is the switch where the surveillance subject line resides the ssp is coupled to the signaling and media gateway sg mg component 204 via pri physically t1 e1 in addition the sg mg component 204 is coupled to the media gateway controller mgc call agent 206 via ip signaling protocol standard or proprietary the mgc call agent 206 is coupled to the calea device 209 over ip network 208 using sigtran pri protocol the physical connections of signaling and media gateway sg mg 204 media gateway controller mgc call agent 206 and calea device 209 to the ip network 208 are well known within the art of telecommunications engineering in fig3 there is shown a virtual primary rate interface pri device encapsulated by sigtran for facilitating ain calea 300 the present invention is advantageous because it allows calea applications to interact easily with a packet network yet while maintaining the time division multiplex tdm infrastructure of the resident network by encapsulating the pri in a device which has sigtranpri capablity the invention provides a virtual interface by which calea application can be implemented in the ip network by encapsulating pri protocol layer 2 amp layer 3 in the packet world the physical connection becomes virtual pri is an important protocol for large isdn users in comparison with the basic rate interface bri the other isdn protocol which is intended for personal or small enterprises pri is intended for use with high speed connections in general both bri and pri include a number of b channels and a d channel each b channel carries data voice and other services the d channel carries control and signaling information and data however with pris 23 b channels.