This paper analyzes performance of MEGACO (Media Gateway Control Protocol) based on Diameter which is an Authentication, Authorization,andAccounting (AAA) protocol developed within the Internet Engineering Task Force(IETF).Diameter is loosely based on Remote Authentication Dial In User Service (RADIUS), which has previously been used to provide AAA services for dial-up and terminal server access environments. An analytical model is provided for the performance of a MEGACO network while there is a Diameter server to guarantee Authentication in call flow. Ultimately, the M/M/c and M/D/c traffic models are provided to evaluate QoS (Quality of Service) in the call flow and some of the key performance benchmarks response time to process the MEGACO calls and mean number of jobs in the system when there is security mechanism is studied. Keywords MEGACO, Diameter, Media Gateway Controller, Queuing Analysis, Performance Analysis