What is topology And its types

Topology

"The physical layout or the way in which network connections are made is known as topology."

Following are network topologies.

1) Bus topology

2) Star topology

3) Ring topology

4) Mesh topology

5) Hybrid topology

1. BUS TOPOLOGY :

STRUCTURE of Bus Topology

A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub, switch, or concentrator.
Data on a star network passes through the hub, switch, or concentrator before continuing to its destination. The hub, switch, or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow. This configuration is common with twisted pair cable; however, it can also be used with coaxial cable or fiber optic cable.

WORKING OF Bus Topology

The computers that send data also attach address of the destination computer with the data. All computers connected to the bus receive the data but only that computer accept it whose address matches the address attached with data.

In this topology only one computer at a time can send a data therefore the speed of network reduces as the number of computers attached to the bus increases.

ADVANTAGES of Bus Topology

• Easy to install and configure
• Inexpensive
• Easily extended 
  

Disadvantages of Bus Topology 

• Performance decreases
• Weak signals
• Difficult troubleshooting

2. STAR TOPOLOGY :

"In star topology all the cables run from the computers to a central location, where they all are connected to a device called HUB."

WORKING OF Star Topology

Each computer in a star network communicates with the central hub that resents the messages either to all computers (in a broad cast network) are only to destination computer (in a switch network).

Star network maybe designed to operate in a polled mode where each user is asked in turn .if it has any information to transmit and in case, if it has, the communication controller will either give full attention to that device until it has no more information to send or it will allow the device to send part of its information ,give another device a chance and then return back to original device.

ADVANTAGES of Star Topology

•  As compared to Bus topology it gives far much better performance, signals don’t necessarily get transmitted to all the workstations. A sent signal reaches the intended destination after passing through no more than 3-4 devices and 2-3 links. Performance of the network is dependent on the capacity of central hub.
•  Easy to connect new nodes or devices. In star topology new nodes can be added easily without affecting rest of the network. Similarly components can also be removed easily.
• Centralized management. It helps in monitoring the network.
• Failure of one node or link doesn’t affect the rest of network. At the same time its easy to detect the failure and troubleshoot it.

DISADVANTAGES of Star Topology

• Too much dependency on central device has its own drawbacks.
•  If it fails whole network goes down.
• The use of hub, a router or a switch as central device increases the overall cost of the network.
•  Performance and as well number of nodes which can be added in such topology is depended on capacity of central device.

3. RING TOPOLOGY :

"Ring topology looks like the bus topology with connected ends.
But In functionality it is different."

WORKING OF Ring Topology

•  Each computer is connected to the next computer in the form of ring.
• Each retransmit what it receives from the previous computer.
• The message flow in one direction.
• Ring topology connects computers on a single circle of cable.
• There is no terminated ends
• Signals travel around the loop in one direction and pass through each computer.
• Unlike bus topology, each computer acts like a repeater to boost the signal and send it to the next computer.
• It is called endless topology.
• In ring topology, data flows in ring and in clock-wise direction.
• Ring topology is based on “Token Ring Mechanism”.

Token Passing

• A token is passed around the network.
• The computer that has token can transmit data.
• Token is passed from computer to computer until it reaches to its destination.
• The destination device returns an acknowledgement to the sender.
• The destination device returns an acknowledgement to the sender.
• The token is then given to another device, giving it ability to transmit.
• The token is then given to another device, giving it ability to transmit
• The sending computer modified the token, puts address with the data and sends it around the ring.
• Data passed by each computer until it finds the computer with an address that matches.
• Token is used as a carrier.
• It is called token grab.

ADVANTAGES of Ring Topology

• when the load on the network increases, its performance is better than that of Bus topology.
• There is no need for network server to control the connectivity between workstations.
• Additional components do not affect the performance of network.
• Each computer has equal access to resource.
• Token ring technology reduces the need of server or central hub to manage the workstations.

DISADVANTAGES of Ring Topology

• If one node is disrupted then the whole network goes down.
• Only one machine can transmit on the network at a time.
• The failure of one machine will cause the entire network to fail.

4. MESH TOPOLOGY :

"The topology of a network whose components are all connected directly to every other component."

WORKING OF Ring Topology

For sending messages, check the cable connected into two devices. A message is send directly from sender to receiver because each one has individual and separate connection.

ADVANTAGES of Mesh Topology

• Eliminates traffic problems in links sharing.
• If one link becomes unusable, it does not incapacitate the entire system. Thus, act as robust.
• It has privacy and security.
• Point-to-point link make fault identification and fault isolation easy.

DISADVANTAGES of Mesh Topology

• Difficult to install and maintain.
• Expenisve.

5. HYBRID TOPOLOGY :

"A combination of two or more different topologies makes for a hybrid topology. When different topologies are connected to one another, they do not display characteristics of any one specific topology. "

WORKING OF Hybrid Topology

The Hybrid topology scheme combines multiple topologies into one large topology.The hybrid network is common in large wide area networks. Because each topology has its own strengths and weaknesses, several different types can be combined for maximum effectiveness.

ADVANTAGES of Hybrid Topology

• Any topology can be combined with another without making any changes to existing topology.  The speed of the topology is compatible because it combines the strengths of each of the topologies, eliminating weaknesses.  It is also more efficient.

DISADVANTAGES of Hybrid Topology 

• Installation and configuration of topology is difficult.  Because there are different topologies that need to connect.  At the same time, make sure none of them fail, which makes installation and configuration very difficult.

difference between primary and secondary storage

Difference Between Primary and Secondary Memory

PRIMARY MEMORY

1. Primary memory is also known as Main memory or Internal memory
2. In primary memory, data is directly accessed by the processing unit.
3. Semi conductor chips are used to store information in primary memory.
4. Information stored is temporary and it can be lost when there is a sudden power cut.
5. Data operated and stored in uniform manner.
6. Primary memory devices are more expensive than secondary storage devices.
7. Nature of Parts of Primary memory varies. RAM- volatile in nature. ROM- Non-volatile
8. It is very fast in interacting with micro processor.
9. Primary memory has limited storage capacity.
10. Examples: RAM, ROM, Cache memory, PROM, EPROM, Registers etc

SECONDARY MEMORY

1. Secondary memory is also known as External memory or Auxiliary memory
2. In secondary memory, data is first transferred to main memory and then routed to processing unit.
3. Magnetic disk, optical disks are used to store information in secondary memory.
4. Information stored is permanent unless one deletes it intentionally.
5. Data stored is not uniform in secondary memory.
6. Secondary memory devices are less expensive when compare to primary memory devices.
7. It’s always Non-volatile in nature.
8. It is little slow in interacting with micro processor.
9. Whereas secondary memory can store bulk amounts of data in a single unit.
10. Examples: Magnetic Tapes, Optical Disc, Floppy Disks, Flash memory [USB drives], Paper Tape, Punched cards etc
11. Comparison Chart

BASIS FOR COMPARISON	PRIMARY MEMORY	SECONDARY MEMORY
Basic	Primary memory is directly accessible by Processor/CPU.	Secondary memory is not directly accessible by CPU.
Altered Name	Main memory.	Auxiliary memory.
Data	Instructions or data to be currently executed are copied to main memory.	Data to be permanently stored is kept in secondary memory.
Volatility	Primary memory is usually volatile.	Secondary memory is non-volatile.
Formation	Primary memories are made of semiconductors.	Secondary memories are made of magnetic and optical material.
Access Speed	Accessing data from primary memory is faster.	Accessing data from secondary memory is slower.
Access	Primary memory is accessed by the data bus.	Secondary memory is accessed by input-output channels.
Size	The computer has a small primary memory.	The computer has a larger secondary memory.
Expense	Primary memory is costlier than secondary memory.	Secondary memory is cheaper than primary memory
Memory	Primary memory is an internal memory.	Secondary memory is an external memory.

difference between cloud computing and fog computing

Fog Computing vs. Cloud Computing for IoT Projects

By 2020, there will be 30 billion IoT devices worldwide, and in 2025, the number will exceed 75 billion connected things, according to Statista. All these devices will produce huge amounts of data that will have to be processed quickly and in a sustainable way. To meet the growing demand for IoT solutions, fog computing comes into action on par with cloud computing. Fog is even better at some things.

Number of connected devices worldwide from 2015 to 2025 (in billions)

Source: Statista

The purpose of this article is to compare fog vs. cloud and tell you more about fog vs cloud computing possibilities, as well as their pros and cons.

Cloud Computing

We’ve already got used to the technical term cloud, which is a network of multiple devices, computers and servers connected to each other over the Internet.

Such computing system can be figuratively divided into two parts:

• The frontend — consists of the client devices (computers, tablets, mobile phones).
• The backend — consists of data storage and processing systems (servers) that can be located far away from the client devices and make up the cloud itself.

These two layers communicate with each other directly by means of wireless connections.

Cloud computing technology provides various types of services that are categorized into three groups:

• IaaS (Infrastructure as a Service) — a remote data center with resources such as data storage capacity, processing power and networking.

• PaaS (Platform as a Service) — a development platform with tools and components for creating, testing and launching applications.

• SaaS (Software as a Service) — ready-made software tailored to a variety of business needs.

Read also: IaaS vs. PaaS vs. SaaS: What’s the Difference?

Connecting your company to the cloud, you get access to the above-mentioned services from any location and via different devices. Hence, availability is the greatest advantage. Moreover, there is no need to maintain local servers and worry about downtimes — the vendor supports everything for you, saving you money.

The integration of the Internet of Things with the cloud is a cost-effective way to do business. Off-premise services provide the necessary scalability and flexibility to manage and analyze data gathered by connected devices, while specialized platforms (e.g. Azure IoT Suite, IBM Watson, AWS, Google Cloud IoT) give developers the power to create IoT apps without big investments into hardware and software.

Pros of Cloud for IoT

Since connected devices have limited storage capacity and processing power, the integration with cloud computing comes to assistance:

• Improved performance (the communication between IoT sensors and data processing systems is faster)

• Storage capacities (highly scalable and unlimited storage space are able to integrate, aggregate and share the enormous amount of data)

• Processing capabilities (remote data centers provide unlimited virtual processing capabilities on-demand)

• Reduced costs (license fees are lower than the cost of the on-premise equipment and its continuous maintenance)

Cons of Cloud for IoT

Unfortunately, there is nothing immaculate, and cloud technology has some downsides, especially for the Internet of Things services.

• High latency (more and more IoT apps require very low latency, but cloud can’t guarantee it because of the distance between client devices and data processing centers)

• Downtime (technical issues and interruptions in networksmay occur for any reason in any Internet-based system and make customers suffer from an outage; many companies use multiple connection channels with automated failover to avoid problems)

• Security and privacy (your private data is transferred through globally connected channels alongside thousands of gigabytes of other users’ information; no surprise that the system is vulnerable to cyberattacks or data loss; the problem can be partially solved with the help of hybrid or private clouds)   

Read also: Private vs. Public Cloud Computing

Fog Computing

The term fog computing (or fogging) was coined by Cisco in 2014, so it is new for the general public. Fog and cloud computing are interconnected. In nature, fog is closer to the earth than clouds; in the technological world, it is just the same, fog is closer to end-users, bringing cloud capabilities down to the ground.

The definition may sound like this: fog is the extension of cloud computing that consists of multiple edge nodes directly connected to physical devices.

Such nodes are physically much closer to devices if compared to centralized data centers, which is why they are able to provide instant connections. The considerable processing power of edge nodes allows them to perform computation of a great amount of data on their own, without sending it to distant servers.

Fog can also include cloudlets — small-scale and rather powerful data centers located at the edge of the network. Their purpose is to support resource-intensive IoT apps that require low latency.

The main difference between fog computing and cloud computing is that cloud is a centralized system, while fog is a distributed decentralized infrastructure.

Fog computing is a mediator between hardware and remote servers. It regulates which information should be sent to the server and which can be processed locally. In this way, fog is an intelligent gateway that offloads clouds enabling more efficient data storage, processing and analysis.

One should note that fog networking is not a separate architecture and it doesn’t replace cloud computing but rather complements it, getting as close to the source of information as possible.

The new technology is likely to have the greatest impact on the development of IoT, embedded AI and 5G solutions, as they, like never before, demand agility and seamless connections.

Pros of Fog Computing

The fogging approach has many benefits for the Internet of Things, Big Data and real-time analytics. Here are the main advantages of fog computing over cloud computing:

• Low latency (fog is geographically closer to users and is able to provide instant responses)

• No problems with bandwidth (pieces of information are aggregated at different points instead of sending them together to one center via one channel)

• Loss of connection is impossible (due to multiple interconnected channels)

• High security (because data is processed by a huge number of nodes in a complex distributed system)

• Improved user experience (instant responses and no downtimes satisfy users)

• Power-efficiency (edge nodes run power-efficient protocols such as Bluetooth, Zigbee or Z-Wave)

Read also: IoT Protocols and Connectivity Options

Cons of Fog Computing

The technology doesn’t have any apparent disadvantages, but some shortcomings can be named:

• A more complicated system (fog is an additional layer in the data processing and storage system)

• Additional expenses (companies should buy edge devices: routers, hubs, gateways)

• Limited scalability (fog is not as scalable as cloud)

Fog Computing vs. Cloud Computing: Key Differences

Cloud vs. fog concepts are very similar to each other. But still, there is the difference between cloud and fog computing on some parameters. Here is a point-by-point comparison of fog computing and cloud computing:

1. Cloud architecture is centralized and consists of large data centers that can be located around the globe, thousand miles away from client devices. Fog architecture is distributed and consists of millions of small nodes located as close to client devices as possible.
2. Fog acts like a mediator between data centers and hardware, and hence  it is closer to end-users. If there is no fog layer, the cloud communicates with devices directly, which is time-consuming.
3. In cloud computing, data processing takes place in remote data centers. Fog processing and storage are done on the edge of the network close to the source of information, which is crucial for real-time control.
4. Cloud is more powerful than fog regarding computing capabilities and storage capacity.
5. The cloud consists of a few large server nodes. Fog includes millions of small nodes.
6. Fog performs short-term edge analysis due to instant responsiveness, while the cloud aims for long-term deep analysis due to slower responsiveness.
7. Fog provides low latency; cloud — high latency.
8. A cloud system collapses without an Internet connection. Fog computing uses various protocols and standards, so the risk of a failure is much lower.
9. Fog is a more secure system than the cloud due to its distributed architecture.

The table below helps better understand the difference between fog and cloud, summarizing their most important features.

Cloud and Fog Computing: a Comparison Chart

	Cloud	Fog
Architecture	Centralized	Distributed
Communication with devices	From a distance	Directly from the edge
Data processing	Far from the source of information	Close to the source of information
Computing capabilities	Higher	Lower
Number of nodes	Few	Very large
Analysis	Long-term	Short-term
Latency	High	Low
Connectivity	Internet	Various protocols and standards
Security	Lower	Higher

Final Thoughts

New requirements of the emerging technologies are the driving force behind IT development. The Internet of Things is a constantly growing industry that requires more efficient ways to manage data transmission and processing.

One of the approaches that can satisfy the demands of an ever-increasing number of connected devices is fog computing. It utilizes the local rather than remote computer resources, making performance more efficient and powerful and reducing bandwidth issues.

Companies should compare cloud vs. fog computing to make the most of the emerging opportunities and harness the true potential of the technologies.

SaM Solutions has 25 years of experience in IT consulting and custom software engineering. We have a wide range of cloud and IoT use cases, as well as vast expertise in using other technologies.