The Relationships among Cloud Computing, Fog Computing, and Dew Computing

Dew Computing and Fog Computing are two new computing paradigms appeared after the widely acceptance of Cloud Computing. Apparently, dew and fog are metaphors coming from cloud which is the initial metaphor. They had different goals and went through different paths. Here we try to clarify the differences between them and the relationships among all the three computing paradigms..

When we traced back to the origin of Fog Computing, we found that it was first proposed by Flavio Bonomi, Vice President of Cisco Systems, in a keynote presentation at the Eighth ACM International Workshop on Vehicular Inter-Networking (VANET) in Sept. 2011. Cisco defines Fog Computing as a paradigm that extends Cloud Computing and services to the edge of the network. Similar to Cloud, Fog provides data, compute, storage, and application services to end-users. The distinguishing Fog characteristics are its proximity to end-users, its dense geographical distribution, and its support for mobility [9]. It took a few years for this idea to grow [6-9]. A comprehensive definition was proposed in 2014 [8]:

Fog computing is a scenario where a huge number of heterogeneous (wireless and sometimes autonomous) ubiquitous and decentralised devices communicate and potentially cooperate among them and with the network to perform storage and processing tasks without the intervention of third-parties. These tasks can be for supporting basic network functions or new services and applications that run in a sandboxed environment. Users leasing part of their devices to host these services get incentives for doing so.

The research related to Dew Computing started in 2012 and were reflected in [1-3, 6] between 2013 to 2015. The foundation of Dew Computing is Cloud-dew Architecture; the application of Cloud-dew Architecture is Dew Computing.

Although Dew Computing was devised to make Websites available without an Internet connection, its usage is not limited there. Cloud-dew Architecture [2], as a fundamental computing architecture that concerns the distribution of workloads between central servers and local computers, has a great potential to be used in various areas.

The initial definition of Dew Computing described in [6] is:

Dew Computing is a personal computer software organization paradigm in the age of Cloud Computing. Its goal is to fully realize the potentials of personal computers and cloud services. In this paradigm, software on a personal computer is organized according to the Cloud-dew Architecture; a personal computer or cell phone with such organized software could be called a dew computer or a dew phone. A dew computer (phone) typically provides rich functionality independent of cloud services, but also collaborates with cloud services.

For the convenience of further discussion, we classify computing devices into two categories: The first category is computer, including desktop, laptop, hand-held, and all other kinds of computers. The second category is automation device, including sensors, controllers, chips, disks, network devices, and so on. Computers can be directly operated and programmed by human users. Automation devices usually have computing power, sometimes they have pretty strong computing power, but they are not operated directly by human users when they are in normal running mode.

Some simple cell phones are automation devices; some smartphones are computers. Servers can be both computers and automation devices. When a server is being programmed by a human user, it is a computer; when a server is running automatically without human intervention, it is an automation device.

With such classification, we found out that Fog Computing mainly involves automation devices while Dew Computing mainly involves computers.

The reason that Fog Computing mainly involves automation devices is because Fog Computing was proposed with Internet of Things (IoT) as its background.

Currently, at each end point of the Internet is a human user. The key idea of IoT is that the Internet should be extended so that many “things” are connected to IoT directly without human intervention. Because Cloud Computing cannot satisfy the needs of IoT, Fog Computing was proposed as a new paradigm to organize and use automation devices. Fog Computing will be widely used with the progress of IoT.

Dew Computing is mainly an Internet concept, instead of an IoT concept; it mainly involves computers, but not automation devices.

The major goal of Fog Computing is to make IoT more efficient. The major goal of Dew Computing is to realize the potentials of personal computers and cloud services.

The unique features of Fog Computing are its proximity to end-users, its dense geographical distribution, and its support for mobility.

The most unique feature of Dew Computing is that personal computers provide rich and cloud-friendly collaborative services to end-users according to Cloud-dew Architecture.

Although Dew Computing was not proposed to solve IoT problems, it does not mean Dew Computing cannot be used in IoT. Actually, Dew Computing provides a perfectly solution in organizing IoT control centers. This topic will be discussed separately.

Metaphorically, a drop of dew is much bigger than the particles in the fog. Thus Dew Computing deals with computers while Fog Computing deals with automation devices.

Metaphorically, a cloud is far away, fog is closer, and finally dew is on the ground. Thus Cloud Computing is distant and is dependant on Internet connections; Fog Computing is at the proximity of users; Dew Computing is right at the user end.

If we observe from future IoT computing devices viewpoint, Cloud Computing involves big servers and huge databases; Dew Computing involves middle-size computers and databases; Fog Computing involves huge amount of tiny automation devices. Dew Computing is in the middle to collaborate with cloud services and control fog devices.

If we observe from user viewpoint, we will find Dew Computing is right in the center because the ultimate goal of Cloud Computing and Fog Computing is to serve human users.

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