Voice over IP is one of the emerging trends in telecommunications that allows telephone calls to be made over computer networks like the Internet by converting analog voice signals into digital data packets. This two-way transmission of conversations using Internet Protocol (IP) combined with many new technologies- VOIP also bring in both security risks and opportunities. VOIP has a very diverse architecture than traditional circuit-based telephony, and this differentiation result in major security issues. Lower cost and greater flexibility that endow with a substantial cost savings over traditional long distance telephone calls, but VOIP should not be installed without vigilant consideration of the security problems introduced.

Firewalls are important tools for security in today’s IP networks; it’s generally the first line of defense against the attackers. Firewalls work by blocking traffic, which are supposed to be invasive, intrusive, or just simple malicious traffic flowing through them. Also Network Address Translation (NAT) is a dominant tool which can be used to hide Internal network addresses and facilitate a number of endpoints within a LAN to use the same (external) IP address. There are also several issues associated with the transmission of voice data across the NAT, including an incompatibility with IPsec that should be addressed properly while you are going to integrate any such tools for security reason.