This FortiOS Handbook chapter contains the following sections:
Parallel Path Processing introduces the concept of Parallel Path Processing.
Packet flow ingress and egress: FortiGates without network processor offloading describes the overall packet flow through a FortiGate with no network offloading (NP) hardware.
Packet flow: FortiGates with NP6 processors first packet of a new session similar to the previous section, the first packet in a new session that can be offloaded is processed in much the same way as on a FortiGate with no network processors.
Packet flow: FortiGates with NP6 processors - packets in an offloaded session describes the much simpler packet flow for a packet from an offloaded session.
UTM/NGFW packet flow: flow-based inspection describes how single pass UTM/NGFW processing occurs in a flow-based FortiGate or VDOM.
UTM/NGFW packet flow: proxy-based inspection describes how UTM/NGFW processing occurs in a proxy-based FortiGate or VDOM.
Comparison of inspection types shows how different security functions map to different inspection types.