Basics Of A Computer Network

The world is a better place when we all are connected with each other through a connection that is available, reliable, and secure. In the technical world, more importantly in the computer world, devices need a communication path by which they can connect and communicate with each other. There are 8.4 billion devices all over the world and 20.4 billion will be set up in the next few years. Well, that’s a huge number and each device needs a constant connection to communicate and make service available to all mankind. This article provides a simple explanation of the basics of networking by which you can correlate devices and their connection using some cables, services, and several configurations needed to implant any software or hardware in the system.

The first question that arises in our mind while working or studying is what exactly is a computer network? So, to simply define that – It is a network of computers that are connected with each other using a physical medium, such as cables, and each computer has a physical as well as a logical address to communicate with each other and outside the network.

Figure 1. Structure of Computer Network

Two computers can be said to be interconnected when they interchange or exchange information via a cable, such as copper cable, fiber optic, or wireless communication. At a granular level, let’s understand network a bit more in an elaborate manner. A network is termed as a connection or interconnection of devices that can communicate with each other. In a network, three components are needed –

Device
A device could be any end system or host who is in demand for communication with other devices. For example – Laptops, Desktop, Cellular Phone, and workstation.
Transmission Media
A medium by which we can exchange the information with devices. It is the connection line that enables us to interchange the information. They are of two types – Wired medium and Wireless medium. For the sake of this article, we are very much grounded to a wired connection and we will see the wireless connection in our later articles.
Addressing
An address in the network is similar to our home address. Take an example of a letter handed over by a postman to our home. He can find our home with the help of an address noted on the letter. In the same way, devices have an addressing mechanism where each device has one physical address which is unique and permanent throughout your networking. he other is a logical address and it is static as well as dynamic in nature and can be modified with malicious intent.

Apart from that, we have something called as – “connecting device” that also sits in the networking system, that resembles the intermediate devices that help in regaining the network or assist in connecting the network, for example – Router, Switches, Repeater, and Hub.

The next thing we need to understand is how two computers are actually in communication. Suppose, we have two computers, PC1 and PC2, who want to trade off. For that, they need a transmission media – Cable. In the below figure, you can see that PC1 and PC2 are connected using a cable. In a deeper manner, the cable consists of electric current flowing through it (I hope you know that a PC is initially connected to an electric board, and then we feed one more cable to connect with other PCs). These electric currents have a wave-like structure and can be seen in an oscilloscope or in a graph by plotting two dimensions – time and amplitude (you can refer to your elementary school book for amplitude or time definition or you can visit this reference to know about it).

Let’s assume that we had provided 5 voltage (Refer Ohm’s Law) to the cable, so in the first period of time, +5V comes up and the signal is ON and in the next period of time, -5V comes up and the signal is OFF. So, a communication between two PC’s or many PC’s is an electric current which flickers in OFF and ON condition – will see this through explanation on Data Communication later in the article.

Figure 2. Communication between two PC

This electric current wave is elongated if PCs are kept at a distance. So, the wave is going to behave according to the computers' distance, . If the computers are very near to each other, i.e., shorter distance, it takes less time to exchange information. Otherwise, the larger the distance, the longer the time to exchange information. The next thing we need to understand are different types of “interconnecting devices” that help in the proliferation of networks.

Repeater

It is the device that helps in receiving the signal and again retransmits it. This is helpful when the computers are kept at a longer distance. Now, from the above diagram, you know that "the larger the distance, the longer the time to communicate". It happens because electric current is,

Where I = Electric Current, V = Voltage and R = Resistance. The electric current depends on Voltage but is inversely proportional to Resistance and therefore, the electric current is going to decrease with distance. So at a larger distance, we have to put repeaters in between, which can regain the current and retransmit it to further distance.

Figure 3. Working of Router

Router

In a computer network, information is in the form of data and if we specifically talk about the router, then the data is in the form of packets. In reality, these packets roam around here and there from one computer to another. It is a network device that forwards the packets from one PC to another using a routing algorithm. Generally, these algorithms take the shortest path so that a packet reaches its destination without any delay. To operate it, every router maintains a routing table which consists of logical address (IP address) useful in directing the packets to their correct destination. (We will talk about routing in the later articles). Keep in mind that Router connects the computer which is not in the local network, it is used to connect two different networks.

Figure 4. Role of Router in Computer Network

Hub

It is another network device that actually broadcasts the data coming to it to every computer or device it is connected to. It is a comparably dumber device than that of a Switch. It is particularly used in small and simple network segments, such as Home LAN.

Figure 5. Role of Hub in Computer Network

Switch

When you have a large network, a hub is insufficient in maintaining the connection. Therefore, there is a need for an alternative intelligent device, "Switch". A switch is used to find the computers based on their physical addresses (MAC Address), to receive, process and forward the data to its correct destination. It is similar to that of Hub. It broadcasts the data in order to find the PC to which the other PC wants to connect, and it maintains the switching table that has MAC addresses and next hop information. The response of broadcast is in the form of unicasts and there is no problem of flooding with this device.

From the above definition, I understand there is a need to explain “Flooding”. As I told you about the HUB, it is a dumb device because it forwards any data that it receives to each computer it connects to. Flooding is a term that says an incoming data/packet is sent through every other computer except the one who sends the incoming packet. Hub possibly doesn’t recognize the devices and broadcasts the data to every computer even though that computer doesn’t have any relation with that data and therefore, the Flooding in Hub leads to higher bandwidth consumption. In contrast to Hub, Switch is intelligent as it learns from its switching table who and who not to broadcast to.

In the next short article, we will understand the difference between broadcast, multicast, and unicast and in addition to that, we will understand certain other network terminology too. I hope you like it. Thank you for reading!!!