Juan:'I know that it sounds stupid, but how is it possible that I can open the same word document on any of the workstations in the office. It doesn't matter which computer I'm on here, I can still open it.'
Peter:'That's because all the computers or workstations in the office are connected to each other in a network. For our office, this network is called a LAN which is an abbreviation of 'Local Area Network'.'
Juan:'So every computer I use in the office can access or open any file or document on my computer?'
Peter:'No, they can't. You can only open files and documents from any computer/workstation you use here, when the file or document is saved on a server and not on your computer. A server is basically a powerful computer on the network which is dedicated to doing one thing, like storing files, or connecting to the internet or running an application etc... All the computers or workstations that people use at their desks can connect to these servers. Any application or file which people want to be shared or used by multiple computers are stored or put on to a server. If you don't want to share a file with anybody, you can save or store it to the local drive of your computer or laptop. A local drive is the hard drive on your computer. But is does mean that you can't open the file from another computer and if the computer breaks, the file is lost. So it's better to save it to your own personal folders on a network drive. This is like a local personal drive for each user of a network, but all files are stored on a file server, a server dedicated to saving/storing files. It is backed up regularly. So even if the file server breaks down, there will always be a copy of all the files or documents stored on a different file server.'
Juan:'So how does my computer access and open the word document on the file server?'
Peter:'Well, your computer is connected to the LAN or office's computer network by an ethernet cable at the back of the computer. The ethernet cable is used to send and receive all the data from the computer to the server, other computers, the internet etc...'
Juan:'Like emails or web pages?'
Peter:'Yes, when you open a document on a server, the ethernet cable sends the request to the file server and the file server sends the data in the file to your computer through the ethernet cable to your computer. This data comes to your computer in what is called packets. For example, when a file server sends a word document that is on a network drive to your computer, the document is not sent all together, but is divided into small parts which are then sent one by one. When these small parts or packets reach your computer they are reassembled or joined back together and make the document. Data is sent on computer network in packets to make the network run quicker.'
Juan:'It sounds complicated. But how does the file server know where to send the document or any type of data?'
Peter:'Well, every computer, server, printer etc... has its own unique address. This is called an IP address. So, that's how a file server knows where to send a word document.'
Juan:'So, there's a direct ethernet cable from all the computers on the LAN network in the office to the file server?'
Peter:'No. In most offices, schools etc..., there are too many computers or servers to connect an ethernet cable directly between each one. In our office there are 213 workstations/computers and 13 servers. It would be impossible for each computer to have 225 different ethernet cable. Each computer or server only has one ethernet cable. Those cables connects directly to a device called a switch. A switch is electronic box that is used to direct the data traffic on the network to the correct IP address. All data is sent from a computer or server to it first. It's like a postman, when it receives the data (like an email, file, update) it reads the IP address of where it wants to go to (which is contained in the data) and sends it to the computer, server, printer on the network with that IP address.'
Juan:'Makes sense. But what happens if I want to send an email to somebody outside the company?'
Peter:'Well, the email is divided into packets and these packets are sent from your computer through the ethernet cable to the switch. When the switch reads the IP address in the packets of data and knows that it's not for a computer or server on the LAN network, it sends the packets to the router on the LAN network. A router is another piece of hardware or device on the network that is used to send or receive data traffic from a LAN network (like in our office) to or from computers or servers from outside the LAN network (like the internet, other companies or other offices).'
Juan:'So if I open a web page from the internet on my computer here, the data of the web page comes to my computer from the internet through the router, then the switch, then the ethernet cable and finally to my computer?'
Peter:'Basically, yes. The router is the first place on the LAN network that receives data from outside of the LAN network. The router often has a firewall on it to make sure that any data it receives doesn't contain a virus or words or material which have been banned or prohibited by the company. Some companies ban their staff from accessing some websites and it's this software or program on the router that stops the web page.'
Juan:'Thanks Peter for explaining it.'