> Chapter 9 - Firewall > Firewall concepts
Firewall concepts
There are a number of concepts that are consistent throughout the firewall industry. Having a solid grasp of these ideas and terms can give you a better idea of what your FortiGate firewall is capable of and how it will fit within your network's architecture.
This chapter describes the following firewall concepts:
- What is a Firewall?
- IPv6
- NAT
- How packets are handled by FortiOS
- FortiGate modes
- Quality of Service
- Interfaces and zones