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Clarifying fog computing and networking: 10 questions and answers / Mung, Chiang; Sangtae, Ha; Chih Lin, I; Risso,
FULVIO GIOVANNI OTTAVIO; Tao, Zhang. - In: IEEE COMMUNICATIONS MAGAZINE. - ISSN 0163-6804. - STAMPA.
- 55:4(2017), pp. 18-20. [10.1109/MCOM.2017.7901470]
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Clarifying fog computing and networking: 10 questions and answers
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DOI:10.1109/MCOM.2017.7901470
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IEEE
Tutorial
Clarifying Fog Computing and Networking: 10
Questions and Answers
By Mung Chiang, Sangtae Ha, Chih -Lin I, Fulvio Risso, and Tao Zhang
1. What Is Fog Computing and How Is It Different from Edge Computing?
Fog computing is an end-to-end horizontal architecture that distributes computing, storage, control, and
networking functions closer to users along the cloud-to-thing continuum. The word “edge” may carry different
meanings. A common usage of the term refers to the edge network as opposed to the core network, with
equipment such as edge routers, base stations, and home gateways. In that sense, there are several differences
between fog and edge. First, fog is inclusive of cloud, core, metro, edge, clients, and things. The fog
architecture will further enable pooling, orchestrating, managing, and securing the resources and functions
distributed in the cloud, anywhere along the cloud-to-thing continuum, and on the things to support end-to-
end services and applications. Second, fog seeks to realize a seamless continuum of computing services from
the cloud to the things rather than treating the network edges as isolated computing platforms. Third, fog
envisions a horizontal platform that will support the common fog computing functions for multiple industries
and application domains, including but not limited to traditional telco services. Fourth, a dominant part of edge
is mobile edge, whereas the fog computing architecture will be flexible enough to work over wireline as well as
wireless networks.
2. Is Fog Just a Smaller Cloud?
First, the size of the fog is flexible — it can range from a single small fog node to large fog systems comparable
to existing clouds, depending on the application needs. While fog will bring many cloud-like services closer to
end users and can have smaller footprints than the cloud, it has a different vision from that of smaller or mini-
clouds. Mini-clouds tend to be designed as isolated computing platforms. Fog envisions a seamlessly integrated
cloud-fog-thing architecture to enable computing anywhere along the cloud-to-things continuum. Fog-to-cloud
and fog-to-fog interactions will therefore be a focus of an end-to-end fog computing architecture to distribute
computing functions, and then manage, pool, orchestrate, and secure the distributed resources and functions.
Fog may form a hierarchical architecture between the cloud and the things, with fog nodes at different
architectural levels collaborating with each other to support end-to-end applications. Fog also concerns the
control of cyber-physical systems and D2D communication, in addition to computation and storage in clouds,
big or small.
3. Is Fog Equivalent to IoT?
Fog is an architecture. The Internet of Things (IoT) often refers to a set of services and applications. An
architecture decides the allocation of functionalities. It formulates and answers questions such as “who does
what, and at what timescale and location?” An architecture supports many applications, some in existence
today and others more futuristic. For example, TCP/IP represents an Internet architecture. It includes several
key principles, such as addressing, and allocation of functionalities, such as congestion-independent, hop-by-
hop routing, and congestion-dependent, end-to-end session control. Applications that leverage TCP/IP have
come from a wide and increasing range: from the web to emails and from P2P to video streaming. The
relationship between fog and IoT is similar to that between the Internet architecture and the web applications.
Fog also supports other areas of applications, such as those in fifth generation (5G) cellular or embedded
artificial intelligence.
4. Is Fog for Computation, or Communication, or Control?
Fog is an umbrella term that includes an architecture for computation, an architecture for communication, an
architecture for storage, and an architecture for control (both control of the network itself and networked
control in cyber-physical systems). For example, fog computing explores new ways to decompose a
computational task so as to match an underlying computation substrate that is heterogeneous (in hardware
and software capabilities), volatile (in availability, mobility, and security), and constrained (by bandwidth or
battery). Fog communication explores how devices may talk to each other despite intermittent global
connectivity. Fog control explores how clients might crowd-sense network conditions and self-configure, and
how to leverage small and almost deterministic latency to enable feedback control loops.
5. What Are the Unique Advantages Offered by Fog?
Unique advantages that are potentially offered by fog can be summarized with an acronym: “SCALE.” These
advantages in turn enable new services and business models, and may help broaden revenues, reduce cost, or
accelerate product rollouts. Security: While fog faces unique security challenges, it also offers certain
advantages. In particular, by reducing the distance that information needs to traverse, there is less chance of
eavesdropping. By leveraging proximity-based authentication challenges, identity verification can be
strengthened. Cognition: Awareness of client-centric objectives. A fog architecture, aware of customer
requirements, can best determine where to carry out the computing, storage, and control functions along the
cloud-to-thing continuum. Fog applications, being close to the end users, can be built to be better aware of and
closely reflect customer requirements. Agility: Rapid innovation and affordable scaling. It is usually much faster
and cheaper to experiment with client and edge devices rather than waiting for vendors of large network and
cloud boxes to initiate or adopt an innovation. Fog will make it easier to create an open marketplace for
individuals and small teams to use open application programming interfaces (APIs), open software
development kits (SDKs), and the proliferation of mobile devices to innovate, develop, deploy, and operate
new services. Latency: Real-time processing and cyber-physical system control. Fog enables data analytics at
the network edge and can support time-sensitive control functions for local cyber-physical systems. This is
essential for not only commercial applications but also for the Tactile Internet vision to enable embedded AI
applications with millisecond reaction times. Efficiency: Pooling resources along the cloud-to-thing continuum.
Fog can distribute computing, storage, and control functions anywhere between the cloud and the endpoint to
take full advantage of the resources available along this continuum. It can also allow applications to leverage
otherwise idle computing, storage, and networking resources abundantly available on network edge and end-
user devices such as tablets, laptops, smart home appliances, connected vehicles and trains, and network edge
routers. Fog’s closer proximity to the endpoints will enable it to be more closely integrated with end-user
systems to enhance overall system efficiency and performance. This is especially important for performance-
critical cyber-physical systems.
6. Is Fog Good or Bad for Security and Privacy?
Fog systems and applications will often be distributed and operated remotely. Some fog systems can also be
resource-constrained. Compared to centralized clouds, such distributed, remote, and resource-constrained fog
systems pose additional security challenges often encountered in distributed systems. On the other hand, fog
can bring more processing resources closer to the endpoints to help better protect the vast population of
diverse endpoints that often do not have sufficient resources to adequately protect themselves. In other
words, fog systems can provide a wide range of local security services to make the IoT as a whole more secure.
For example, fog systems can perform local security monitoring, local threat detection, and local threat
protection functions on behalf of the endpoints. Fog nodes can also serve as proxies of the endpoints to help
manage and update the security credentials and software on the endpoints, eliminating the often impractical
needs for all the endpoints to directly communicate with the remote cloud for such functions.
7. Will the Need for Fog Diminish as Network Capacity and Delay Improve
over Time?
While it is true that a primary benefit of fog computing is its ability to reduce latency and delay, the drivers for
fog go far beyond pure latency issues to include a variety of operational, regulatory, business, and reliability
issues. For example, instead of the traditional way of adding new applications by adding dedicated new local
servers and networking gear, fog can provide a common end-to-end platform for all services provided to each
customer. This can provide a unified platform to support life cycle management, networking, and security for
all applications, which will reduce system complexity and costs and also allow applications from different
providers to better interact with each other rather than stay siloed on their dedicated hardware and software
platforms. Fog can enable critical services to be operated autonomously or managed from the cloud, the
perimeter, or a variety of points in the network. Fog is equally advantageous for areas where network
connectivity can be unreliable due to weather or other conditions. It can also significantly reduce network
bandwidth loads through its proximity to where the data is generated. With fog, local operational and business
policies can be applied to enable more efficient local data processing and analytics on premises.
As another example in cellular networks, cloud RAN, with centralized or distributed network architecture, has
the advantage of being physically close to the end users and the capability of utilizing the network resources at
the edge. Consequently, the cloud radio access network (C-RAN) will be an integral part of the solution to meet
stringent network delay requirements that the traditional RAN network may fail to meet. Consequently, the
Third Generation Partnership Project (3GPP) is now discussing a RAN architecture that contains both the
central units and the distributed units. Extending prior notions in C-RAN, fog network is unique in the sense
that the end user computing and storage resource is considered as an integral part of the whole network, by
forming ad hoc subnets among end nodes. Careful exploitation of such features will bring unique values for fog
networks.
8. What New Technologies and Standards, If Any, Do We Need to Develop for
Fog?
Fog systems will need to interact with each other, with the clouds, and with a diverse range of user end
devices. Therefore, the success and wide adoption of fog computing will rely on standards. While fog
computing can benefit from many existing standards, new standards may also be required, for example, in the
following areas:
Building unified fog-cloud platforms: Interfaces and protocols for the fog and the cloud to interact with
each other to enable unified cloud-fog service platform and applications, move computing functions
and applications between the cloud and the fog, pool resources distributed in the cloud and the fog,
and manage the life cycle of the fog systems and applications.
Support distributed and hierarchical fog systems over possibly heterogeneous, volatile, and
constrained physical resources: interfaces and protocols for different hierarchical levels in a fog system
to interact with each other, and for different fog systems at the same hierarchical level to collaborate
with each other to serve as each other’s backup.
Access to fog services: A fog system, bringing resources closer to end users, can enable a wide range of
new fog-based services. Standards will be required for users and their devices to interact with the fog
system to discover, request, and receive fog services. So will automatic and lightweight bidding
mechanisms for access to fog resources and services to reinforce the economic sustainability of the fog
computing model, and enabling economic transactions.
Data management: Local processing and management of data is one of the important drivers for fog
computing. Data, however, comes from an increasingly wide range of sources. Data management also
imposes widely diverse requirements from industry to industry. New standards may be required to
manage the diverse data, such as storing, accessing, and securing the data distributed in the fog and
cloud.
Security and privacy: A distributed and remotely operated fog system can pose new security challenges
not present in centralized systems. Addressing these new challenges may require new standards. For
example, fog computing will need to run a diverse set of local hardware platforms. Therefore, new
interfaces may be required for fog software to interact with the various hardware platforms, which
may be provided by different vendors, to ensure a trusted computing environment. New interfaces and
protocols may be required for automatic detection of security compromises in a distributed and
remote fog system, and also for remote and automatic responses to security compromises.
Furthermore, although standards may exist for some fog computing needs, additional requirements in fog
computing environments (e.g., low-latency, large number of resource-constrained devices) may necessitate
new standards that are more suitable for fog computing environments.
9. What New Research Challenges Do We Have to Address to Enable Fog?
Research challenges in fog span a wide range: from computation decomposition over heterogeneous and
constrained nodes to cloud-fog interface definition, from state consistency in dispersive computing to elastic
storage over volatile substrate, from pricing for economic incentives to scalable security measures.
Fundamental to these topics is the intrinsic trade-off between “local” and “global” and between “brick” and