Asterisk allows to make call via PSTN and VOIP. It supports platforms like, Linux, BSD, MacOSX etc. It has an adding plugin for Voicemail, queuing, IVR. This tool is used by both the small and large level organization for inter communication between the employees. Asterisk is also known as the high-standard PBX replacement. It is used to connect the employees working from home through PBX over broadband connections. This tool can also be used for connecting offices in multistate over VoIP, providing all employees voicemail, integrated with web and mails.