VPG-based VPN service

Two main tasks are involved in the development of a network architecture: the development ofa software system and the design and analysis of algorithms. The first task focuses on softwareengineering aspects to satisfy the system requirements. The second concentrates on developingcontrol functions that meet performance objectives. A thorough evaluation of the performancecharacteristics of a network control system has to take into account both of these aspects. Ourapproach to evaluating a target architecture is to build a software prototype, designed according to this architecture, which runs the intended algorithms [CHA96b].The emulation platform consists of four building blocks: parallel simulation kernel, emulationsupport, real-time visualization and interactive control, and emulated system (Figure 9).Figure 8 Management console for a VPG-based VPN service. The upper layer represents theVP network, the lower layer the VPG network. The vertical bars on the VP network indicatethe utilization, the vertical bars on the VPG network the allocation of VPG bandwidth to VPs. The module for real-time visualization and interactive control contains an interface which provides 3-D visual abstractions of the system state. The emulation support module coordinatesthe exchange of control and monitoring messages between the graphical interface and the emulated system. It reads the states of the emulated system, and performs filtering and abstractionoperations before making the information available for visualization. Control information fromthe user is mapped onto a set of control parameters that are interpreted by the emulated system.