Firewall

The security and the privacy of the Internet are very important for a computer user. I memorize a protector of computer, which is called firewall. But how does it protect the Internet of computer? Firewall is generally divided into three major parts, which are application-level gateways, filtering firewall and proxy servers.

Application Level Gateway is to build the network application layer protocol filtering and forwarding capabilities. It is aimed at a specific network application service protocol which can use the specified logic of data filtering and forms the necessary analysis of the data packets, registration, statistics, and makes reports while filtering. The practical application of the gateway is usually installed on a dedicated workstation system.

Packet filtering technology is the optional network layer packets which is known as the Access Control List and are based on the logic within the system and then set up filters. It is confirmed whether to allow the packet to go through by examining the data stream in each packet's source address, destination address, used port number, and protocol or to determine their combination. Packet filtering firewall is easy to install and use, moreover, the performance of network and transparency is good, and it is usually installed in the router.

Agent Service is also known as link-level gateway or TCP channel. It is also attributable to a class of application-level gateway. It is used for data packet filtering and the introduction of firewall technology is done to overcome the shortcomings of application gateway which is characterized by all the network communication.

The role of the firewall in the network system is that it can effectively prevent the external invasion, and it can control the network information that is access to flow. It is used to deal the flow of blogs and audit, and it hides internal IP addresses and the network details of the structure.

A firewall is not only a separator or a limiter, but also a parser which can effectively monitor the internal network and ensure that the internal network is security and private.