Abstract
The object of research is an approach of functionality extension for simulation toolkits based on iFogSim. It is assumed by the native approach that enhancement of functionalities should be achieved by inheriting the fog device class and defining new features in its body. However, this approach makes it impossible to use inherited simulators together and significantly decreases flexibility even when utilizing a single simulator. Another problem related exclusively to iFogSim is a specific communication scheme between application modules, which results in data routing limitations in fog architectures and odd data streams taken into account. This paper introduces an alternative extension approach incorporating a peculiar inheritance scheme which tries to reconsider the standard approach from a behavioral design patterns point of view. The key feature of the suggested approach is an extraction of fog device features from the native class into separate behavioral classes. Meanwhile, the designed inheritance scheme allows to flexibly override and combine behaviors. According to the approach principles the developed simulator extends iFogSim with application modules addressing capabilities solving limitations, along with implementing users’ mobility and dynamic wireless connectivity as it is done in MobFogSim. With the aim to check its correctness, the designed toolkit was validated with the standard for iFogSim case study of «EEG Tractor Beam game» application. The validation included four scenarios. In the first two scenarios the features of users’ mobility and dynamic base station connectivity were validated. And in the next scenarios that utilized address routing the obtained delay and network usage values were compared with theoretically calculated ones. The validation results indicated the correct simulator behavior, and introduced functionalities extension approach, being more complex in comparison with the inative one, can significantly improve flexibility of the simulator
Highlights
The simulation process is not a necessary stage in information system design and implementation
This paper introduces an alternative extension approach incorporating a peculiar inheritance scheme which tries to reconsider the standard approach from a behavioral design patterns point of view
The key principles of the approach are: – all behavioral logic is implemented in Java-interfaces; – behavioral classes do not contain any logic and only specify and combine necessary behavioral interfaces; – stateful properties are located in entity interfaces while behavioral interfaces are stateless; – simulation events must be handled exclusively in behavioral interfaces; – extended behaviors can interact with base behaviors either by delegation of accepted event handling or by generating new events
Summary
The simulation process is not a necessary stage in information system design and implementation. G. ability to control internal and external system parameters, repeat experiment at any time, discover and handle system bottlenecks in advance, and save money reducing physical hardware utilization. These benefits are topical for designing both cloud and fog computing systems. Preparation of a real testing environment would require enlisting a huge amount of hardware resources while the achieved results could not have been accurately reproduced because of stochastic nature. This was the driving force of the development of cloud and fog computing simulation toolkits. In the context of the paper only three of them would be discussed:
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