Mobile phone calls cannot be made or continued when the caller is in one of these holes. There are also tier-2 service providers that lease network from the tier 1 providers and then provide the services to their clients. Tier 3 operators, on the other hand, would be the best option for them.323 was initially commenced to provide a method for transporting multimedia communication over local area network but later it evolved to address the growing requirements of VoIP networks. Computer works on limited resources and its functionality comes down when we are working on 2-3 or more applications at a time. Depending upon your needs you can opt for any of these services. When buying anything online that claims to have a grate deal of value for a phenomenal price, the first instinct is, too good to be true. Vonage subscriber growth has exploded over the past few years, but how many of those customers realize how vulnerable their calls are to eavesdropping by third parties? Vonage, like many other VOIP providers, uses SIP for call signaling and several RTP codecs for the audio portion.e. The Tier 3 service providers or operators, avails some portion of network from either Tier1 or Tier2 operators. The end users have to select the provider that delivers services in those areas. With the advent of VoIP a definite change has come over the telecom industry.VoIP termination service is slowly and steadily moving ahead in the race with its competitor PSTN service. Hence, communication has attained an elevated status in today's competitive world where a countries economy is dependent to a large extent on the revenue generated by the business houses. A multipoint control unit can be used in both ways, integrated with a terminal, gateway, and gatekeeper or detached; it enables conferencing between two or



