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Now if we're going to talk about networking we should really define what a network is.

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So what is a network?

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No I'm not talking about a social media network.

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I'm not talking about your contacts. Let's say on Facebook or Linked In or Twitter or tick-tock or whatever

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your social media platform of choice is. 

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We're not talking about a social media network.

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In this case we're talking about a computer network.

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So what is a computer network?

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Here’s a challenge

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I'm going to ask the robots what a computer network is.

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See how much you understand by this definition.

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Alexa, what is a computer network? A computer network is a digital telecommunications network for sharing

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resources between nodes which are computing devices that use a common telecommunications technology.

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Data transmission between nodes is supported over data links consisting of physical cable media such

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as twisted pair of fiber optic cables or by wireless methods such as Wi-Fi microwave transmission or

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free-space optical communication. OK, so there's the course.

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We're finish now.

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We all understand what computer networking is.

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Yeah.

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If only.

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Now if you're a robot you may be able to understand everything about computer networking just by listening

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to those two paragraphs.

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But I think for us we need to spend quite a bit more time to really understand what a computer network

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is and understand how computer networks work.

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Let's start firstly with the why? Why do we have computer networks?

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What's the whole point of the Internet.

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What's the whole point of all this infrastructure that's been built around the world.

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And the big reason to have a network as per this definition is to share resources.

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We want to share information or share some kind of resource with someone else.

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Now what is a resource in the old days.

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A common example of a resource would be a printer.

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If you had an office with 100 people in the office you could buy a printer for every workstation or

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for every PC

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And that's what they had to do before the days of networking.

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They either had to have a printer for every computer or have no printers or what they had to do is do

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something like this where they copy a file onto a floppy disk and then go over to the printing station

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and then print it manually.

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It's not cost-effective to buy a printer for every workstation or for every person.

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It makes much more sense to have a centralized resource in this case a printing resource and share that

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resource amongst the people in the office.

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So rather than having let's say 100 printers for 100 people you only let's say have 10 printers.

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So you've reduced the cost by creating a shared resource a resource that can be shared by what are called

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clients.

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So we have client devices or PCs in this example that are sharing a resource in this case a printer.

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Another example is file sharing.

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This is very common.

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I want to share a file with you.

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So how do I do that?

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Now in the old days the way to do that was to get a floppy disk like this.

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The problem with these floppy disks is in the old days they're only supported one point for four megabytes.

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It's not a very big drive but there you go really old example.

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So they'd have to if they wanted to share a photograph or a file with someone else they'd have to copy

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it to this floppy disk then walk using what we would call sneakernet.  

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So they'd firstly have to copy the photo or the file onto this disk then walk using sneakernet across

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the office put it into the other computer and then access the file.

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So that's how they would share a resource.

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In this case a file or a photograph.

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Now today we still use this kind of technology by using USB thumb drives.

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So if I wanted to share a resource with you like a photograph or a file I could copy it onto this USB

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drive and then give it to you and then you'd copy it to your computer.

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So sneakernet the original type of networking if you like is where a human being would take a resource

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copy of file or a photograph into this USB drive.

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I'd walk to your computer and then give it to you and share the resource with you.

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But that's not very effective.

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It's not scalable doesn't work that well.

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You, let's be honest, most humans would be too lazy to have to walk around the office to share files.

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It's much easier just to share files using a digital transmission mechanism or medium and they're different

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types of digital transmission mechanisms.

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Why are we doing this?

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We are trying to share a resource between what in this definition is called a node and they define that

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as a computing device.

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So a node is a computing device.

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And there are many types of computing devices.

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We could have Windows laptops.

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We could have Mac books.

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We could have phones.

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We could have servers.

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Those are often the devices that most consumers will think about.

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And I've mentioned printers already has another one.

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But in networking, we have specialized devices such as hubs, switches, routers and firewalls to name a

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few.

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So stepping back a second.

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Why do we have a computer network?

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We want to share resources which could be a printer, could be a file, could be a video.

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So videos are very popular these days.

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You watching this video through a computer network I'm sharing this information with you using a data

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link in the Wikipedia definition.

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They talk about a data link being a physical cable such as twisted pair, fiber optic cables, Wi-Fi or

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some type of data link where I'm sharing information with you.

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So the big idea here is I'm sharing a resource with you and I need a way to get that to you.

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You need a device that can receive the resource, we need some kind of transmission media which could

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be physical cables or it could be wireless.

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So the idea is rather than having to physically transport a file on a USB drive or in the very

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very old days using a floppy disk we use a cable or some kind of mechanism to transmit data from one

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device to another or from one device to many devices.