Introduction to Computer Networks

Welcome to the ICT world

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Computers crashed into our lives a few decades ago and each they keep changing the way we work, interact, and even live. We all have to thank the computer for something they do for us, and the same goes for the Internet. However, we generally see what directly impacts us. If you want to understand what computer networks are and what they can do for you from a business perspective, you are in the right place.

Computer networks are everywhere

How networks work

Stop for a moment and think about what you do on a daily basis with your computer, smartphone, or tablet. If you are like me, almost anything you do requires an Internet connection. Download some music from iTunes? Internet required. Chatting with your friends on Facebook? Internet required. Sending an email or surfing Google? Internet required. And the reason all of these things require the Internet is the fact that they are on the Internet. With that, I mean that whether you are surfing on your favorite website or you are watching the last season of Breaking Bad on Netflix, both the website and the Breaking Bad episode do not reside on your computer. Instead, they reside somewhere on the Internet. When you use them, your PC will fetch the required content temporarily, and keep them only for the time needed.

Services from the internet
Some services offered by the Internet (e-mails, website navigation, file sharing, video hosting and search engines/information).

The most popular way to represent the Internet is through a cloud. That’s because it does not have an exact form, it is always evolving and you don’t know exactly what is inside of it. However, in the end, even the Internet is made of tangible components. In order to craft a definition for “the Internet”, we must have to understand what a computer network is first. And this is extremely simple, as you might have guessed: a computer network is a set of devices connected together.

Think about your house for a moment, you are likely to have some kind of Internet connection working with a router, generally provided by your Internet Provider. Well, all your computers, smartphones, tablets, smart TV and such connects to that router and they can talk to each other. This is a very basic example of a computer network: your home devices talking to one another via the router. Now you are ready for defining the Internet.

The Internet

The Internet is a collection of computer networks interconnected with one another.

Therefore you, with your home network, are part of the Internet! But how do computer networks connect to one another? They do that via some border devices, which are often the same as the devices you will find inside your network. So, how can you define where a network ends and where the contiguous network starts? It is simpler than you might think, a single “private” network is owned by the same entity (the same person or organization), so that entity will have access and full control on its own devices. Your private network, in other words, is limited to the devices you control. But services available to you do not come from your private network most of the time, they are provided instead by someone else.

This is what the Internet is about: all the networks part of the Internet are either using or offering services from or to the other networks. By granting Internet access to your home or business you will be able to use tons of different services – basically anything that a computer can offer, multiplied by all computers connected to the Internet actually offering services. You have endless possibilities, but the trending ones are listed below.

  • E-mails and Instant Messaging, they allow you to share information and communicate instantly with someone even thousands of miles away, some provider of these services are Gmail and Facebook, just to name two of them
  • Free information and resources, millions of websites are out there, each rich of things you might want to know, from news to technical articles
  • File sharing, these services allow you to store your files on the Internet and then access them from any other device, from any point in the world – they even allow you to keep your files in sync among all your devices. The top file sharing providers include Dropbox, Google Drive, and OneDrive
  • Video streaming (even real-time), these services allow you to view any uploaded video any time you want, on-demand. We can agree that the most popular provider for this service is YouTube, but other opportunities exists on the web

And these were just the tip of the iceberg, as you get more and more technically confident you will learn about more and more services accessible to you from the Internet. All in all, Internet access is a must-have.

Private Networks

Now that we clearly understand the benefits of having Internet access, the question is: what are the benefits of a private network? First, let’s clarify that: a private network is a network managed by yourself (it is private to you), but this does not necessarily mean that you are the one accessing it. For example, Google allows users to access its private network to do searches (of course there is some level of control of “who can do what”). So, why do you need to have a private network, if you can get almost anything from the Internet? This is what this section is about.

Even if you have just a PC and a router to connect to the Internet, this is a private network. Even to that, you can start adding features. You could get similar features from the Internet, so what’s the difference? Instead of relying on some external providers, you have everything inside your network. This way, we can assume that you will have your services always available. However, the major benefit is that you are in control of everything, and keep classified information inside your network.

You can have services that you completely control and that you do not have to pay monthly: you pay just once for the setup. This grants you more privacy and also some technical benefits, such as speed. You know that if you want fast Internet access you have to pay for that, whereas with your home router you can have access to devices (and services) within your local network even ten times faster.

Small private networks

A clear example of that would be a NAS appliance. NAS stands for Network Attached Storage and it is basically your own, private, file sharing. A basic one can host two hard disks in a redundant flavor: it keeps an exact copy of your data on both disks so that even if one of the two goes broken you will have your data untouched. With around 100$ you can get a great NAS appliance like the Intel SS4000-E Entry Storage System and then you can start adding two disks (or even one if you don’t mind losing your data) such as the Seagate ST4000DM000 and you will have an amazing 4TB storage. You connect the NAS to your router and you are set to go. With 300$ once, you will get a 4TB fault-tolerant storage system, accessible from all your devices. The same services are not even provided from Dropbox, which requires you to have a business account. Then, you can have all the space you need for about 10$ per user per month. Again, these are alternatives to consider and the best choice may vary according to specific needs.

Local Services
With your router as a central point, you can grant Internet access to all your devices and then add a NAS to create a file storage system accessible from all your devices.

With the NAS example, we have learned that anyone may actually benefit from a private network designed for specific needs. However, the more your needs increase, the more you are likely to need a private network. In fact, companies and organizations are the ones taking the most advantage from private networks. As we presented earlier, they have a higher entrance cost (you have to buy anything), but then you can start to save money and have complete control over the services you need.

In our next example, imagine a midsized company. It has one main site and two branch offices. An option would be to have all three sites connected to the Internet, having a file-sharing system hosted on Dropbox, some e-mail system provided by Gmail for Business, and such. However, this way, computers are managed individually or on a per-site basis. This means that the person in charge of IT has to move between sites frequently. This is due to the fact that any change or new installation requires him to be there. It would probably turn into a situation where a single account can access all computers and anyone has access to it, just for ease of use. Pointless to say, but this would be a major security vulnerability.

A bigger private network

Now, take a look at this centralized setup and think about its major advantages. Then, read on.

Interconnecting sites
In this centralized setup, the two remote sites connect to the HQ (center), which is in charge to provide them services, including Internet access.

The first thing you should notice is that not all buildings are interconnected with each other. Instead, the two remote branches (left and right buildings) connect to the HQ site (central building) only. They do not even connect to the Internet themselves: instead, it is the HQ to provide Internet connectivity to them. This way, we can have full control of what is happening in our IT infrastructure. First, we have a safe channel to exchange data between the locations and therefore to control our devices: our person in charge of IT could easily implement a centralized account system allowing himself to create and configure accounts and privileges. Moreover, other services could be added: you could create a centralized (private) file-sharing system and you could also enable IP telephony to call between your sites at no cost. Possibilities are virtually endless.

Now let’s give you just a brief technical overview of what is involved in infrastructure like the one presented above. In order to deploy this kind of setup you will need two types of devices:

  • Intermediary devices, these devices allow other devices to talk with each other. Their role is to deliver data to other devices and they do not generate traffic all by themselves.
  • Hosts, these devices actually offer or use some kind of content or information. They send information between each other, and this traffic will be delivered through intermediary devices.

For now, do not worry about these definitions. They are not so specific and we will cover these topics in later articles.

However, everything comes at a price. This price is justified most of the time, but let’s see what this price is in the next section.

Managing the IT Infrastructure

In a home network, there is almost nothing to configure: you just turn on your router and connect your devices (either with a wire or via wireless). You might have to change the Wi-Fi network name (technically known as SSID) and password, but no more than that. However, as the network to manage gets bigger, the administrative burden increases. With that, the cost to manage the network itself increases too. If you are a small company, as soon as your network (and hopefully the company itself) gets big enough you are going to hire the “IT guy“.

This person is someone who knows a little about everything and can cope with simple tasks on different ICT fields such as configuring computers, installing a network, replacing broken hardware, fix your e-mail account, and such. This role is formally known as IT Manager, or “Local IT Manager” if that person is local to a single site (in a multi-site company). By the time your company gets even bigger – or by the time you start having some very specific technical needs, you will end up with at least the following roles.

Roles of IT
In order for an IT infrastructure to work as users expect, be up-to-date and secure, you will need at least these technical roles.

These key roles are explained below. If all these people work for you and you need no external help to maintain your network, you can say that you opted for In-house IT (self-maintained IT infrastructure).

  • Local IT Manager, as said above is the one who generally knows a little about everything. He is often in charge of giving direct support to the user and checking the problem as its desk if it is needed. In multi-site companies, he may cover single or multiple sites if not geographically distant. He is the on-site focal point other technicians can rely on to perform on-site tasks. Note: in the picture, he is scratching his head because often times he has no clue of the big picture.
  • Helpdesk Agent, she is in charge of providing basic user support remotely (chat or phone call). Her role is to react to faults and incidents on the infrastructure and perform small changes. For example, she will rename users, change permission, or do the first analysis on issues.
  • Network Specialist, this person is an implementer who is in charge of putting the network in place for the first time. He makes the initial configuration and let the network run. Responsibilities include analyzing other configurations seeking improvements.
  • Project Manager, this person manages specialists during a new set-up or deployment. He decides who does what and set deadlines – this role is obviously related to new installations only.
  • System Administrator, he maintains and manages daily server and services. He is generally specialized in a specific service, such as the e-mail server or the file-sharing.
  • UC Specialist – UC stands for Unified Communication. She is in charge of the telephony and video-conferencing infrastructure at a technical level. This role is conceptually similar to the Network Specialist, as both are implementation roles. However, the technologies involved here are different.

And the list goes on: Security Specialist, Data Center Specialist, Technical Team Leader, Service Manager… roles requiring technical skills you have to pay for. If you own a huge corporate this wouldn’t be a problem because your IT infrastructure is big enough to give them a good workload to keep them actively working 9-to-5. However, what do you do if you are in that position when just an IT Manager is not enough, and having an entire IT army is too expensive? The solution is in the next section!

Outsourcing IT maintenance

As you might have guessed, nowadays the most popular solution to anything is outsourcing. And IT makes no exception: it is even the sector where outsourcing started to happen. Here’s a definition of outsourcing.

With outsourcing, you delegate some tasks and/or roles to a third-party. Most of the time, you pay the third-party for a service. Therefore, you don’t even know how many people are working for you, or how long each. You just pay for a service to be granted.

This solution is cheaper if compared to in-house IT for midsized companies. Depending on the case, it can still remain cheaper even for large corporates. However, it is not just about money.

Outsourcing IT
When you outsource IT, the most common option is to have a local IT-manager. Have other services and roles provided by another company.

As in the picture, you will hire the local IT manager and have another company providing all the other services. You can hire specific roles temporarily as you need them or just pay for a service where they care about your infrastructure. In some solution, the whole IT infrastructure is not even yours: you rent it from the outsourcing company. There, you can rent the physical hardware or the service that the network provides to you. What is the benefit of the second choice? That you do not have to care about the complexity behind. You just use the service.


We could compare IT outsourcing to Netflix. With Netflix, you pay monthly to be able to watch movies and TV series. You do not pay for the movie itself, nor do you care about how they are able to deliver it to your computer. You pay and they give you the movies, taking care of everything else. No DVDs, no fixed schedules to watch movies: just movies. Outsourcing is just the same.

An example of IT outsourcing could be photocopiers machines. In a traditional model, your company buys photocopiers and then changes exhausted toner and buy new paper. On the other hand, with outsourcing, you can have another company taking care of everything. You do not pay an annual fee or the installation costs, but instead you pay a cost per copy. All the outsourcing company needs to know is how many copies are you going to print each year. Based on your range (such as 800k to 1 million copies) you will get a quote for the price of each copy (which is extremely tiny). Then, they will define how many photocopiers you need and they will get automatically notified if paper or ink are empty.

Without the IT Infrastructure

From time to time, I got questions like “Why would we need all that? After all, the way we are doing is just fine without a consolidated IT infrastructure“. The shortest answer is: ease of use. Since the beginning, technology had the end goal of making the life easier. The IT infrastructure makes no difference, and we will present the previous case of a company with three sites. We will do that two times, the first without a private network and the second without Internet at all.

Without a private network

Monthly, an accountant is in charge of compiling reports of the sales of each site, so he asks monthly an Excel report from the other two sites. These reports are duplicated in the network because they are stored in the remote branches and in the accountant’s computer. A secretary notices that she missed something out of that report and edit it, but the accountant is not aware of that and has its own copy. This creates discrepancies: “What was the right version of this file?”. The new marketing specialist wants to create a video advertisement and wants to share that with the other sites to get feedback before publishing it.

However, that video is a big file and cannot be attached to an e-mail, so he decides to use its own personal Google Drive account to share that. After a month, he notices he is running out of space on its Google Drive account. Because of that, he removes the video thinking it is now useless. Instead, a sales rep in a remote site was actually showing the video to customers, without even downloading. The video stream crash during the presentation and the representative are unable to make it work. This embarrassing situation cost you a client.

Without private network and Internet access

For the same situations, the accountant has to get the Excel report printed (and just that comes at a cost) and mailed to the HQ. Then, it has to read it through and re-write in the new report the information he needs. This approach is prone to a typo, as you may make them the first time you type, but also when you re-type. Let’s say that the accountant is not sure about a value. He has to call the remote site and wait for someone to find the value.

In other words, you are wasting the time of two people. The time you pay for. What about the marketing video? It has to be put on an external drive (CD, DVD, USB Flash drive…) and then snail-mailed to the other sites. Then, the marketing representative has to get feedback on the phone. If something is wrong in the video, he has to edit it and then snail mail it again. Therefore, that video is published in twice the time, or even more.

Okay, we understand the dark side. For the benefits related to a good IT infrastructure read on, the next section is for you.

Benefits of having an up-to-date IT Infrastructure

Let’s face it: any business needs some kind of IT infrastructure. We already understand the benefits of having an IT infrastructure, but let’s summarize them briefly:

  • Centralized management
  • Enhanced communication possibilities between sites
  • File and data sharing, allowing faster business processes
  • Business continuity using backups to avoid data loss

Then, you might say “Okay, but you put in place that infrastructure just once, what are the benefits of having it always up-to-date?” – and, trust me, it is a great question. To answer this question, we should picture the IT infrastructure, not as a passive element. Instead, it is like something that needs some kind of maintenance. For example, when something goes broken (a server, a Hard Disk…) someone has to know that and replace it. Moreover, when a new user joins the company someone has to create his account. So, you will be spending a certain amount of money on your IT systems anyway.

Given that, if you have someone (or an outsourcing company) taking care of your network proactively (before-it-happens) you will have an up-to-date IT infrastructure. With capacity planning, you don’t have to worry if the network can the new computer you prepared. Most importantly, you will not run out of space on your file storage. You will get security issues fixed before someone tries to breach in your private network. In a single sentence, you get ahead of your competitors.

The Conclusion

All in all, in this article we gave a look at what IT is, who uses it, and why. We have focused on the benefits of the IT infrastructure and explained IT roles and outsourcing possibilities. This article can give you a lot of useful information alone. However, if you are interested in computer networks at a technical level check out our CCNA Course. If so, before moving to the next article, ensure that you have a clear understanding of what we treated here.

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Alessandro Maggio

Project manager, critical-thinker, passionate about networking & coding. I believe that time is the most precious resource we have, and that technology can help us not to waste it. I founded with the same principle: I share what I learn so that you get value from it faster than I did.
Picture of Alessandro Maggio

Alessandro Maggio

Project manager, critical-thinker, passionate about networking & coding. I believe that time is the most precious resource we have, and that technology can help us not to waste it. I founded with the same principle: I share what I learn so that you get value from it faster than I did.

4 Responses

  1. wow !!!!!! This website is really awesome !! Thankyou so much man !! i do respect for what you have done !! Awaiting for 40 to 52 series !!!!!!!!!!!!!!!!

    1. Many thanks for such a positive feedback, I really appreciated it! Articles up to 52 are coming, one per week! I’ve already written them, and they only need a final review. On top of that, I am committed to write a complete CCNA course, and it will be about 70 articles in total!

      Enjoy your reading! 🙂

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