IP Multimedia Subsystem (IMS) is now being a solution for packet switched networks. The future generation network is amalgamating the infrastructure of Wireless / wire-line for providing the standard interface for Internet services. Nevertheless, the network infrastructures like multimedia and non-multimedia do not have any native mechanism to interpret the key schema of client media tools to establish the communication such as voice and data. To establish, as such services, a signaling protocol of Session Initiation Protocol (SIP) is being put to use to control the communication on Internet for establishing, Maintaining and terminating the communication session. Many papers have been proposed for authentication and authorization for securing the communication media. However, so far, no paper has been proposed for interpreting the built-in schema of multimedia tools. Thus we propose the Interoperation Key Schema to successfully exchange the mismatched schema between media client and server. Also we analyze the proposed mechanism with Internet security systems of Internet Protocol Security (IPSec) and Transport Layer Security (TLS). We deploy a real time platform of multimedia to examine the interoperation success rate and call setup time between the media clients.  Index Terms—IP multimedia subsystem, session initiation protocol, internet protocol security and transport layer security