VPN class in C++

In our implementation, a generic controller is realized as a container class in C++, whichincludes as base classes the subcontrollers, trigger, allocator, coordinator, etc. Interfacesoffered by these subcontrollers are implemented as virtual functions that are overloaded for aspecific realization of the controllers.The design of the generic controller shown in Figure 6 has brought us the following benefits.First, it was possible for us to design and implement all three classes of controllers --VPadmission controller, VPG controllers, and VPN controller-- as a refinement of the genericcontroller class. For example, the VP admission controller in Figure 5 has two "non-trivial"controller objects --the VC resource allocator and the coordinator-- and five "trivial" controllerobjects. (Trivial controller objects can be thought of as objects which perform no action exceptthat of forwarding data to another object. They are not shown in Figure 5). The VPG controller