Packet filter also known as the "Packet Filter", it is the most traditional firewall, the most basic filtering technology. Firewall is also produced from this technology. packet filtering technology is in the process of communications data filtering, prior to the required safety rules packet through due to those which do not comply with the safety rules of packet discarded.This security rules is the fundamental of the firewall. It is through the application of a variety of network, communication and port types to provide the use. The firewall packet filtering, the first is based on the header of the packet contained in part of the source ip addresses,destination ip addresses, protocol type (TCP packet, UDP packet, ICMP packet), the source port,the destination port and the transmission of packet direction and other information, the judgement is in accord with the safety rules, to determine whether allow the packet through.
This article introduces the concept of firewall, as well as its produce, definition and classification. On the current common network firewall, network firewall of working principle. The network firewall for modular analysis, which, with the focus on the issues related to achieve network packet capture module, the network protocol analysis module and memory modules of the design and implementation.
