hello welcome to the first lesson in the first module of my new course on networking fundamentals in this module we'll be exploring how data flows through the internet crucial to that is understanding the various devices which are involved to make that possible in this lesson we'll be exploring these various devices and the related concepts we'll be doing this in two parts in this video we'll unpack hosts ip addresses and networks and in the next video we'll explore these devices and let's just jump right into it by defining our first term host hosts are any device which sends or receive traffic for example your computer is a host your laptop your phone your printer your servers those are all considered hosts but we're also in the cloud days which means there's many cloud resources that can also be considered as host cloud servers for example moreover we're also in the internet of things days which means anything you have at your house that sends or receive traffic is also considered a host that smart tv you stream to those speakers that are all synchronized with each other smart watches your thermometer that you can control remotely that refrigerator that remind you when you're out of milk all those devices are sending and receiving traffic and therefore can be considered as hosts why this is important is because all these devices follow the same rules for how they communicate to the internet later in this module we'll be looking at everything a host does when sending or receiving data from the internet in doing so we'll actually be explaining how all these devices communicate with the internet hosts typically fall in one of two categories clients or servers clients are the hosts that are initiating the request and servers are the hosts that are responding to requests for example let's just say this is the web server for the website www. site. com well when this computer over here is making a request to ask for the website site.
com it's initiating a request and therefore it is considered the client when the web server site. com is providing the content for site. com it's responding to the request therefore it is considered the server keep in mind however the terms client and server are relative to a specific communication meaning at some point this web server is going to have to update its files from a file server or a database server well for that the web server has to make a request to the file server to ask for new files in that communication the web server is the client and the file server is the server we can take it a step further this file server at some point might need to run some sort of software update well when it's making the request to the update server to download the new software it's acting as the client and when the update server is providing the updates back to the file server it's acting as the server so the terms client server are specific to the communication that is occurring now we've been calling this a web server but i want to clearly define what that is a server is nothing more than a computer with software installed which knows how to respond to specific requests this guy right here is really just a computer that has software installed that knows how to serve web pages you can turn any device into a web server by simply installing the proper web server software it's the same way with the file server and the update server we discussed a second ago in the end they are merely computers with software that knows how to provide files or provide updates each server you encounter is simply a computer responding to requests so that wraps up our discussion on hosts next we want to define ip addresses ip addresses are the identity of each host and every single host must have an ip address if it means to communicate on the internet just like you need a phone number in order to send or receive phone calls or you need a mailing address in order to send and receive mail you need an ip address in order to send or receive packets on a network this is what the ip address is it is the identity of every single host now these ip addresses are actually going to be stamped on everything that each host sends for example when this client over here makes a web request to site.
com on this packet which includes what web page it is asking for the client is going to stamp the source and destination ip addresses the source ip address is going to be the client's ip address and the destination ip address is going to be the server's ip address in the same way when the server responds by providing the web page it's also going to stamp the source and destination ip addresses for that communication here the source ip address will be the server and then the destination ip address will be the client everything sent on the internet is going to have this source and destination ip address now an ip address itself is really just 32 bits a bit is a one or a zero which means every single ip address is really just a different combination of 32 ones and zeros what we do is we take those 32 bits and break them up into four chunks which we call octets and we convert each of those octets into a decimal number this is how we get to what we know of as an ip address the smallest binary number you can get with eight bits is zero and the largest binary number you can get with eight bits is 255. that's why every ip address you come across is going to be four instances of the numbers 0 through now in this module we are not going to be exploring binary we've already created some videos that discuss binary if you're interested in learning about binary and how this conversion happens please check out those videos there'll be a link in the description either way that is what an ip address is now these ip addresses are typically assigned in some sort of hierarchy so let me explain that imagine this is the acme corporation and the acme corporation owns every ip address that starts with 10 dot anything well maybe the acme corporation has three different offices one in new york one in london and one in tokyo and each of those offices is going to have a subset of the acme corporation ip space new york might have everything that starts with 10. 20 london might have everything that starts with 10 not 30 and tokyo might have everything that starts with 10.
40 moreover the new york office might have a few different teams for instance they might have a sales team an engineering team and a marketing team and each of those teams would have their own dedicated ip address space sales team could have everything that starts with 10 20. 55 the engineering team would have everything starts with 10 20. 66 and marketing would have 10 20.
77 the london and tokyo offices probably have those same teams as well but each of their ip address space is going to start with the prefix for that particular location this allows the ip address to sort of pinpoint where a particular host exists for example if we had the ip address 10. 30.
