Measurements and analysis of M/M/1 and M/M/c queuing delay models of the two IP-PBXs in various remote location

Voice over Internet Protocol (VoIP) is a general term for a family of transmission technologies to delivery of voice communications over IP networks such as the Internet or other packet-switched networks. VoIP systems employ session control protocols to control the set-up and tear-down of calls as well as audio codecs which encode speech allowing transmission over an IP network as digital audio via an audio stream. In this paper, Codec in bandwidth management was investigated. Codec is used between different implementations of VoIP variedly; some implementations rely on narrowband and compressed speech, while others support high fidelity stereo codecs. The Session Initiation Protocol(SIP) is becoming a popular signaling protocol for VoIP base applications. The IP-PBX is a software application which provides call routing services by parsing and forwarding all the incoming SIP packets in various remote IP telephony network. Then, the M/M/l and M/M/c performance model of the IP-PBX was simulated and some of the key performance benchmarks such as average response time to process the SIP calls and mean number of jobs in the system was reviewed.