Communication, no doubt plays a key role in being productive in our daily activities. Banks, companies, organisations and individuals share information or data, communicating for various purposes to achieve a goal.

But have you ever wondered how group of computers communicates with one another and other computer hardware devices, why not let me have some of your time to take you through basics of how these communication processes are achieved regarding computer network communication.

<center><img src="https://cdn.steemitimages.com/DQmdhcwrTbmXQZMeke1PxTN7twtrwSdTziZTotGkAqb7Qbu/business-3370832_1280.jpg" /><br/><br/><sup><sup><a href="https://pixabay.com/en/business-computer-office-laptop-3370832/">Image Credit: Pixabay</a></sup></sup></center>

Without taking much time, just in a simple way, I'd describe data communication as the exchange of data between devices via some form of transmission medium. A group of computers and other devices (such as printer)  connected by communication links forms a network. A link thus, is a physical communication pathway that transfers data from one device to another.

Data flow occur in different forms, defining the directions of flow of signal between linked devices. Data flow can occur in;

<div class="pull-right"><center><img src="https://cdn.steemitimages.com/DQmfMCNo8r2jBoaz8LvMaKKmnLZsdt64J1tQq1exHmr3ZfU/Simplex-duplex.png"/><br/><br/><sup><sup><a href="https://commons.m.wikimedia.org/wiki/File:Simplex-duplex.png"> Wikimedia Creative Commons BY-SA 3.0 License: Transmission Mode</a></sup></sup></center></div>

I, Simplex: This is way in which communication is only unidirectional. One transmits while other can only receive, signal transmission does not occur simultaneously.

II, Half Duplex: Each device can both transmit and receive but not at the same time. One can only send while the other receive.

III, Full Duplex: Device on full duplex transmission mode can transmit and receive at the same time.


![u7rR1iU.png](https://cdn.steemitimages.com/DQmXPujsMDZRzqttqArZG9MuAdQN4597mXdbiTi6cxxbGP9/u7rR1iU.png)

Network of computers are available in different forms, a simple form can have it as a peer-to-peer network where every computer communicate with each other directly with no computer having higher authority than another, it can also exist in a  Client-server form of network which involve the use of a central server to facilitate communication and resource sharing between other computers on the network.
The Client-server form of network supports larger network, provides stronger security,  more flexible as compared to peer-to-peer but comes more expensive.

However, there are various ways in which network of computers are laid out, one which is referred to as Network Topology. Network Topology gives a representation of all links and linking devices to each other forming the network. It can be simply referred to as the physical or logical layout of links in a network.

<center><h2> TYPES OF TOPOLOGY</h2></center>
<div class="pull-left"><center><img src="https://cdn.steemitimages.com/DQmTjrpfP2iWHjLnxeRX1XLP7pafddy2YAGTNZs987RYjx1/800px-Bus_Network_Topology.png"/><br/><br/><sup><sup><a href="https://commons.m.wikimedia.org/wiki/File:Bus_Network_Topology.png"> Wikimedia Creative Commons BY-SA 3.0 License: Bus Topology</a></sup></sup></center></div>

• Bus Topology: this is a configuration that connects all nodes to a single communication line carrying message in all direction. It is cheap and easy to install and as seen in the picture beside, it comes with the disadvantage of loss in transmission if a break in bus cable occur.

<div class="pull-right"><center><img src="https://cdn.steemitimages.com/DQmdgqBRdsVbGiPFq5H2ewAJUusmyZ6ZxAhb7L84CSWmRbf/Intercpunetstar.png"/><br/><br/><sup><sup><a href="https://commons.m.wikimedia.org/wiki/File:Intercpunetstar.png"> Wikimedia Creative Commons BY-SA 3.0 License: Star Topology</a></sup></sup></center></div>

• ‎Star Topology: As the name suggests, star configuration is one in which that centers around one major device to which all others are connected and through which coordination of messages are done. Here, Fault is easy to identify and isolate, failure of one does not affect the other but are found mor expensive to install compared to that of Bus.

<div class="pull-left"><center><img src="https://cdn.steemitimages.com/DQmVEHZaGMiR6Qsj6aCuVWakVb4Xcv87bGmqbPEA1R5m5xn/NetworkTopology-Ring.png"/><br/><br/><sup><sup><a href="https://commons.m.wikimedia.org/wiki/File:NetworkTopology-Ring.png
"> Wikimedia Creative Commons BY-SA 3.0 License: Ring Topology</a></sup></sup></center></div>

• ‎Ring Topology: Here, we have the configuration in form of ring where all nodes are connected in a closed loop on which messages travel in one direction. This is very easy to install but a break in the ring can disable the entire network.
<div class="pull-right"><center><img src="https://cdn.steemitimages.com/DQmVfNU5Ed8AdxF6iXRL6mUN8uJ6LvrHCswRCWHDcH6vqrm/NetworkDecentral.svg.png"/><br/><br/><sup><sup><a href="https://commons.m.wikimedia.org/wiki/File:NetworkDecentral.svg
"> Wikimedia Creative Commons BY-SA 3.0 License: Mesh Topology</a></sup></sup></center></div>

• ‎Mesh Topology: This Topology is the best logical topology wen it comes to data flow but very complex in terms of physical design. Here, each device is connected to every other device, giving the most fault tolerant of all.

*The type of Topology to be chosen depend mainly on number of users, the purpose of the topology, and it's reliability.*

Network of computer thus come in different categories which is determined by size, distance covered or physical architecture

•  Local Area Network (LAN): Local area network is a type of network designed to allow resources to be shared between devices in an office, often limited to few kilometers which are mostly privately owned.

• ‎Metropolitan Area Network (MAN): It is a computer network larger than LAN, it covers area of few city buildings of surrounding areas.

• ‎Wide Area Network: This network connects two or more LAN over a large distance, it provides long distance transmission over a large area.


![DQmSJFCmiPGGtTrvw93vM77RZsA56t47xh9DbFpbqJxfgoA_1680x8400.png](https://cdn.steemitimages.com/DQmTTonVbYYMNewGRJVpJUhz9Ji9n43zYT9Ne6u8EdkEwTM/DQmSJFCmiPGGtTrvw93vM77RZsA56t47xh9DbFpbqJxfgoA_1680x8400.png)

**Let's now take a little dig into Networking proper**

Here, we would look at how internetwork is formed, the collection of individual networks functioning as a single large network. This concept of internetworking involves the technique of connecting different networks by using intermediary devices (the gateway devices). Internetworking helps in data communication among  different networks coupled with the use the internet Routing protocol.

<center><h2>THE GATEWAY DEVICE</h2></center>

Gateway Devices are data communication devices  such as routers that provides a remote network with connectivity to host a network. But before we talk about routers, let's have a look at hubs and switches.

<div class="pull-left"><center><img src="https://cdn.steemitimages.com/DQmSHpS1r7e7vcHXPeyXre4HzRGoQhPeEcvrbQayxNv3cXQ/800px-Knams-15-knsq-14.jpg"/><br/><br/><sup><sup><a href="https://commons.m.wikimedia.org/wiki/File:Knams-15-knsq-14.jpg
"> Wikimedia Creative Commons BY-SA 3.0 License: Hub</a></sup></sup></center></div>

• Hub: Hub is one of the devices used for connecting multiple computers together in a Local area network (LAN) for the purpose of resource sharing. Hub was one of the firstly introduced networking device by the Institution of Electrical and electronics engineering (IEEE), Hub works by receiving information  from a node and forwarding to other nodes. Hub was the first to be introduced, it works in such an old fashioned way. Hubs are unable to tell one device to the other, hub receives information from one port of the device and sends to all other ports neglecting the fact that maybe the information is meant for those connecting computers or not. For instance, if you intend sending information across a LAN to one major computer connected by a hub, the information will all be received by all other computers connected to the hub. However, Hub is characterized with the simplest and cheapest way to create a network but it has a way of wasting the rate at which data is sent, causes unnecessary traffic and it operates at half-duplex i.e. cannot at the same time, send and receive data.

![u7rR1iU.png](https://cdn.steemitimages.com/DQmXPujsMDZRzqttqArZG9MuAdQN4597mXdbiTi6cxxbGP9/u7rR1iU.png)

<div class="pull-right"><center><img src="https://cdn.steemitimages.com/DQmYRVRKSUuM5dtMgtyAkkQvAV3HrhUsepHVqvKFiwrhPdW/network-197300_1280.jpg"/><br/><br/><sup><sup><a href="https://pixabay.com/en/network-connection-pc-web-address-197300
"> Pixabay: Switch</a></sup></sup></center></div>

• Switch: This is neither the electrical nor mechanical switches this time, but computer networking switches. It was the second developed by IEEE, definitely expecting some level of development on the firstly introduced device right? Okay, let's keep following. Switches are able to connect multiple computers together in a Local area network i.e. provided with more ports to accommodate more computer devices, but not just that. Unlike hub, switches creates a switch table ( that's where the name comes in) to match ports to which information is intended to be delivered to. Switches are able to differentiate between computers and stores up the layout in its address book. Switches helps in managing bandwidth usage, minimizes traffic and optimized it's performance operating in full-duplex.

<div class="pull-left"><center><img src="https://cdn.steemitimages.com/DQmQMDwiwVnmjyLHw3EqQYqhufbTKZa2Vgup9a25QuxzT1L/router-157597_1280.png"/><br/><br/><sup><sup><a href="https://pixabay.com/en/router-wireless-network-connection-157597/
"> Pixabay: Router</a></sup></sup></center></div>

• ‎Router: Here comes the big boss, 'Router'. Routers are gateway devices used to send data or technically speaking, routes packet of data between different networks. Unlike Switches and hub, instead of facilitating communication just between local computers, router also works to routes data to other networks, thereby allowing internetwork communication including the internet.

>For data communication to be achieved within network of devices with the help of the gateway devices, a special set of rules are used in communication between the endpoints. Network protocol is it that defines conventions for communication between devices, it is a widely agreed upon format for data transmission between devices, specifying how data is sent and received as messages.

A reference model of networking protocol was developed by Open System Interconnection [(OSI)](https://en.m.wikipedia.org/wiki/OSI_model)  defining networking framework to implement protocols in seven layers. This layers having their distinct function in achieving data communication

<center><img src="https://cdn.steemitimages.com/DQmVsxD6LbJYXUjTYYbvPem8WksQwJwSDQRUBnVW3Z2EsnG/Osi-model.png"/><br/><br/><sup><sup><a href="https://commons.m.wikimedia.org/wiki/File:Osi-model.png">Wikimedia Creative Commons BY-SA 3.0 License: OSI Reference Model</a></sup></sup></center>

As shown in the figure above, the model comprises seven layers; 

Layer 7 - Application layer
Layer 6-  Presentation layer
Layer 5-  Session layer
Layer 4- Transport layer
Layer 3-  Network Layer
Layer 2-  Data link Layer
Layer 1-  Physical Layer

Here's a simple way you could code these layers:

All people seem to need data processing (taking from top-bottom)

The [OSI](https://en.m.wikipedia.org/wiki/OSI_model) reference model helps us understand better the networking concept and how hardware and software interacts. To get a full gist of how this works, do check this [post]( https://steemit.com/steemstem/@henrychidiebere/osi-model-demystifying-the-internet) by @henrychidiebere which focus on the OSI reference model.


<center><h2>NETWORK SECURITY </h2></center>

There are various levels of security installed or configured on system network to ensure the restriction of unauthorized access to the network. A weakly protected network leave hackers finding their way into the network, overriding the whole operation of a system.

<center><img src="https://cdn.steemitimages.com/DQmarMWk5nf8jVEitaoFunuNAa9r44HHbNQnw4Ua9eXxuZz/internet-1971623_1280.jpg" /><br/><br/><sup><sup><a href="https://pixabay.com/en/internet-security-network-privacy-1971623/">Image Credit: Pixabay</a></sup></sup></center>

Network security i'd  say is one of the most important aspect of computer networking. A network of system left unprotected is prone to attack, either to the software or hardware part of the system. Network security is such an essential part of computer networking designed to protect and manage access to network and data. Network Security ensures defense against external forces interfering with the network.

![DQmSJFCmiPGGtTrvw93vM77RZsA56t47xh9DbFpbqJxfgoA_1680x8400.png](https://cdn.steemitimages.com/DQmTTonVbYYMNewGRJVpJUhz9Ji9n43zYT9Ne6u8EdkEwTM/DQmSJFCmiPGGtTrvw93vM77RZsA56t47xh9DbFpbqJxfgoA_1680x8400.png)

Firewall is one of the security mechanism used in securing the network, it acts like a physical structure that stands between user information and external interference. Firewalls are set of programmes that keeps networks secured by restricting permission of unauthorized member. They are automatically built into gateway devices like switches and routers operating in conjunction with both software and hardware to carry out these set of rules.

Cryptography is another mechanism used in network security involving the process of encryption and decryption of messages in order to be safely transferred from sender to receiver.
‎
*The principles of network security ensure efficient network security such as:*

I, Message Integrity: Network security ensures message arrived at the receiver end exactly the way it has been sent, maintaining the integrity of the message. Message integrity is extremely important especially when it takes place over the internet.

II, Entity Authentication: This ensures the origin of the message is rightfully identified, helping in establishment of proof of identities.

III, Message Confidentiality: This ensures that only  the sender and the intended recipient should only
be able to access the content of the message, to all others, the message must be garbage.

IV, Message Non-repudiation: This ensures sender not being able to deny sending a message that he has sent ( i.e. a situation where a user denies a message she had sent). Non- repudiation helps by not allowing sender of a message to refute the claim of not sending the message.

V, The principle of network security also determines who should access the network and ensure available of resources to authorized parties at all times.


<center><h2>CONCLUSION </h2></center>

Data communication helps in resource sharing across different ends and has been very vital in getting information across to people, making day-to-day activities easily performed and achieved. Data communication within a network of computer are achieved in different ways depending on the purpose and number of users in the network.
Effective data communication is thereby required in achieving seamless communication between network of devices and it's characterized by its accuracy, timeless and ragged delay in delivery of data. Data shouldn't just be communicated but also prevented from attacks from external forces which makes network security an important aspect of computer networking. Providing security for Network ensures the reliability and integrity of the network, protecting network from being a victim of online hackers.

#### REFERENCES


+  [Network Security](https://en.m.wikipedia.org/wiki/Network_security)

+  ‎[Computer Networking communication](http://ecomputernotes.com/computernetworkingnotes/communication-networks/what-is-data-communication)

+  [Computer Studies](https://peda.net/kenya/ass/subjects2/computer-studies/form-4/itcn)

+  [Wikipedia](https://en.m.wikipedia.org/wiki/OSI_model)


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