Logical Layering

OpenRG is logically layered according to the threefold scheme displayed in figure 17.2. The Main Task (coordination logic) and functional tasks exist in the Client Application layer. POSIX-compliant APIs are used to interface between the Client Application layer and the kernel, providing operating system independence.

The operating system is responsible for the actual data flow, with packet handling carried out by the kernel. For example, the Firewall, routing and NAT/NAPT are managed exclusively by the kernel.

Device drivers create a hardware-independent abstraction between the Main Task and low-level components such as Flash memory, network interface hardware, buttons, LEDs, etc.

Figure 17.2: Logical Layering