Types of Firewalls
Before we delve into the dark waters of firewall technologies, let’s see what types of firewalls exist and which type is best suited for your needs in particular circumstances. In some cases, different types of firewalls may be combined on one system or one product; these are known as hybrid firewalls.
Network-Level (Packet) Firewalls
Network-level firewalls operate at Layers 3 and 4 of the OSI Reference Model and cover network and transport protocols.They can differentiate between applicationlevel protocols (using port numbers at the Transport (TCP/UDP) layer), but they do not work at the application protocol levels. In fact, these firewalls are nothing more than packet filters. Network-level firewalls are further categorized ...
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