Understanding Firewall Types

Firewalls primarily function using at least one of three methods: packet filtering, Network Address Translation (NAT), and proxy services. Crystal Enterprise works with each of these firewall types. Packet filtering rejects TCP/IP packets from unauthorized hosts and rejects connection attempts to unauthorized services. NAT translates the IP address of internal hosts to hide them from outside access—NAT is often referred to as “IP masquerading.” Proxy services make high-level application connections on behalf of internal hosts to completely break the network layer connection between internal and external hosts. Let's look at these different types in more detail.

Packet Filtering

Packet filtering inspects and selectively ...

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