NAT uses a system of local and external addresses to hide an intranet user from other networks.

NAT helps protect the intranet from exposure to unwanted traffic by providing one single external address to remote users. Certainly, most ADSL Routers have a built-in Firewall and NAT functionality that can be setup to work with H.323 and SIP video conferencing systems. The NAT or Proxy Server works on the concept that there is an outside world (Internet) and an inside world (intranet) and it separates and protects the intranet from the Internet.įirewalls now usually include a NAT capability. Proxy Servers are now equipping themselves with security features such as Network Address Translation (NAT). The firewall is generally installed at a specific location in much a manner that no incoming requests can by-pass it and gain access to the internal network.Ī Proxy Server acts as an intermediary server that makes network requests on behalf of internal users, so that organisations can ensure security, control and caching services. The firewall can also control what Internet resources the organisations users may access. Firewalls usually work by blocking access of certain network protocols to specific ports. An organisation with its own internal network (intranet) whose users also requires access to the Internet, usually installs a firewall to prevent unauthorised Internet users from accessing its internal network. A firewall is a set of security mechanisms that an organisation implements to prevent unsecured access from the outside world to its internal network.

Sip port numbers