Cisco Certified Network Associate Day One. Welcome back everybody. I am Imran Rafai, your trainer for this
entire series. Today we would be starting with network
fundamentals and when I say fundamentals we would
deal with the very very basic of the networking industry. So this video ideally is not only for the people who are going for
the CCNA certification but anybody who's interested to, OR looking
to start a career in networking feel free to watch this
because you are going to learn as lot. But CCNA as a
certification, is a very valuable certification and I urge
everybody to go ahead and take that certification because it is
gonna add a lot of value. Before I go any further I would ask everybody to concentrate on the first
three days of our video because we will be covering the very basic concepts which, if I can dare, I would say is going to be the base of your entire networking career, maybe even twenty years from now. So please concentrate and be clear with every concept we cover
here. And in case you still have doubts
please feel free to email me at imran.rafai@NWKING.ORG imran.rafai@NWKING.ORG imran.rafai@NWKING.ORG imran.rafai@NWKING.ORG Alright, without further
ado, let us get into the video. Let's start
with the very basic question, "What is a network" well when I asked this question
to my students more often than not I get answers like
Facebook Twitter Picasa whatever whatever
you see on the screen but well that is social network, that's not
the network we are here to learn and that definitely is not the network I
am going to talk about what I am intrested in is it this network the network between
computers well this network is also the foundation
or the base on which applications like Twitter Facebook
picassa is built on. So we learn about this network and maybe if we have time
over the course of this this series, we will talk a little bit
about those applications here and there. While
preparing for this video lecture I was preparing this a image that you
see on the screen and I was thinking okay let me see how to explain this
concept to students who are starting on at the networking industry so how do I explain this concept without
actually using a lot of technical terms Or saying - 'okay this thing communicates with that thing over this thing' - I mean it was
difficult and then I thought okay I need a better
way to explain this and I i remember the story that a teacher of mine told me
when she taught me networking. It is about the olden days of how Kings exchanged
messages with the ally, they would pass the message to a messenger who used to ride on horse backs and they used to go through all these paved paths along the road and then they used to go through the city gate and then this go to other King and
deliver the message. So if you compare that to computer
network the the messenger sending the message so the 'message' is like the data that
you send and the data could be anything it could be a doc file - a Word document or it could be
an excel file it could be an image could be a Video.... it could be anythng... the DATA. And the road on which the the messenger
travelled that basically is the network.
Of course computer network is much more
interesting than just paving roads, but if you see that is the very
reason why computer network is invented..... to communicate between
computers! If you see this image you would see.... let
me just take a highlighter..... you will see that we have
the Windows PC, we have Linux systems, an iMac and we have laptop, mobile phone, palm
top you have web servers, maybe it's running
on CentOS, you have database server file servers but in spite of them all running on different
operating systems, they all can communicate absolutely
perfectly with each other!!! This is the magic of computer networks the computer network runs on a global standard called the OSI Models and things like that which defines
clearly what when any manufacturer manufactures a
networking device what and how they should communicate
with each other! So they all know the language of networking and that enables them to communicate
with each other. Let's try to break this a little more
further and see how Internet works! So if you look at the picture on your
screens this is the very basic network! TWO computers connected with a wire... in
this case we will use a cat5 cable, a cat 5 cable looks
something like this! And they come in different colors,
you have blue colour ones, red color ones and
this is obviously another color. And this outer cover is just a
protective layer. Inside you have eight tiny cables these cables go into a connector
called RJ45 that looks something like this that you
see on the screen. And on the back of your computer and most the computer that you have
today you have a port a port like this that is your interface, your network
interface card. So your network interface card is where this RJ45 connects and using this you can communicate these two computers can communicate with each other. This is the very basic form of networking and this is called as ETHERNET! Let me just write it down. Its E sorry about my
handwriting. It's very difficult to write on screen especially with my mouse but lemme just......ETHERNET! Maybe for my next video I will buy a stylus so that I can just write it with a more legible handwriting. Alright but for now... Yeah.... this cable connects between
these two computers and you can have a very basic network. But what happens if you have more than
two computers so lets say you have five computers. You
obviously .... I mean there is one way obviously you can go on adding more network interface cards on your
computer then you can have but a better of connecting is by
making use of a networking device maybe a switch or hub - of course switch
and hub are two different devices they have totally different functions...we
will obviously learn about them in future video episodes but for now you know we have a
networking device.... in this case it is a switch and these computers can communicate with each other. So for instance this guy has got a word document that he wants to send across the network to this guy, all he has to do
is send it across to his IP address! 'What is an IP address?' you would ask. IP addresses is how computers recognize each other on the
network! We will learn about IP addresses in the
next video series but for now just know they are
identifiers for computers! Another critical reason why people use
networking is because of devices like this. Maybe,
let's assume, that this was a very expensive printer or scanner that the company
invested in. If networking was not available the
way this device would be connected is to this .... let me just change the colour to show that it is.... okay lets use BLACK. This is how it would have had to be connected
directly to the computer. Now let's assume that this user maybe
prints one page a day and maybe all the users in this company
has similar requirement that they have to print one or two pages every day! So the company will have to invest on more printer, so you will have one more print here. This guy will have one more printer so company will have to unnecessarily invest on a lot of printers when the usage on them... in all the printers are gonna be very
very minimal! Better way for companies to
invest money on IT infrastructures is to have one printer very expensive good quality printer. Plug it onto the network and everybody can print to it! That's a lot of money saved and that's
very efficient way of using IT Budget! So that is the very basic requirement and the reason why we have
computer network! So a computer network in a local office
you know maybe one home office, in a room...in a
single company.... that's called as a LAN or Local Area Network and 'local' signify
that is very local to a geographical area! If this same local LANs, now these are LANs and you have another LAN here and let's assume that your company has
two offices, one in New York and then you have another office in Boston! One way you could communicate or create a network between the the two offices of your company is....
ofcourse if you had the kind of money that is required to
cable from New York to Boston and of course if you can get the
permissions you could run your own private cable from your Boston office to
New York office.... no problem at all! But not too many companies have that
kind of money and not many companies would like to waste that kind of money. We have a better way of doing it! You could connect your office to a local
ISP ISP is nothing but Internet Service
Provider. and the similar thing happens on the other end...Boston connects their office to an ISP ...Internet Service
Provider and ISP's already have their backbone, very massive, high bandwidth connections between their offices! So your data that you sent from here
goes through the network to the ISP from ISP to the ISP in Boston and then
through that they go back to the Boston office and a
computer. So this computer can communicate with this
computer absolutely fine using the ISP. Now this forms the Wide Area Network where LANs are inter-connected with each other
to form a Wide Area Network and 'wide' here signifies a wide geographical area! It could be
across the country it could be in different cities in the
the same country or maybe in different countries.... basically
it's a WAN. So that is how it works...now how do
you connect from ISP to your Local Area Network... how do you connect? Well.... in normal situation... what happens
is you get a a jack on the wall you might have a small jack on the
wall and your LAN ....you just connect it to the jack! So
from the switch... or from the router of your company you connect it to the jack! On the backend this ISP, they would lay cable.... maybe they would lay it
under the ground .....they lay a cable to their office and from their office they go here from
From their office again maybe underground they lay a cable to the Boston office. Again there will be
a wall socket that is provided and you just plug a cable from the wall to your Router.... and that is how your WAN link works. Well this is
also INTERNET because we are using the ISP. Internet is nothing but a very
massive WAN which covers the entire world, where you have a lot of public resources!
So if you google this is the definition of
what an internet is! "A global computer network
providing a variety of information and
communication facilities consisting of interconnected networks
using standardized communication protocols!". WOW... that is big definition... Well that's exactly what it is ...you know....
Internet is nothing but you have a lot of WANs. So
you have a WAN here you have a WAN here you have a WAN here you have a WAN here and then just WANs
are connected with each other. So you have another WAN here and you
have another WAN here another one here another one here maybe
few more here....I know in India there are quite a lot... you have all these things and they are
connected .....let's say for instance you are connected from here its connected here, from here connected here
and this is connected..... this is connected this is connected....this is connected ....this
is connected...... so this is nothing but how an
internet works! So for instance if from India somebody has to communicate to New York this is how the data will
transfer.... they will go.. if this thing disconnects you will have the data going through a longer path! So
this is what internet is .....it is just nothing
but interconnections of a lot of WANs! Let's find out more about the applications we were talking about earlier. There are lot of usage of the Internet
or networking as a whole.... we have YouTube, CNN EBay, Skype.... this is just very, very very few examples that use the
Internet! But they're lots of sites and
applications which use the internet as you already know! Now how it works is YouTube for
instance is owned by Google ...So Google has put a public server somewhere on the Internet that is accessible to anybody on internet! So if I want to watch a video on youtube I go to my web browser and type 'www.youtube.com' The process that takes place in the
background is much more complicated ....I'm simplifying this whole process.... we will look into exactly how it works in future video.....but for now
when somebody times 'youtube.com' and hit enter my computer sends an HTTP request to YouTube's public server! When the server gets that information it says 'Ah fine that is an HTTP request ...so I will send an HTMLfile back' and it creates and sends that HTML file back to me. My web browser takes that and says..'Ah
that's an HTML file and I know how to process it'. So it processes that and your YouTube
website come to life and you see that it shows a lot of videos and you click
on one of those videos this process repeats... they send you back the Video and
that's how that works. Similarly it happens to eBay....
you go to CNN, Skype that's how it works! So this is how
internet works.... basically they have a public
server... they put all the files there your computer request that....they send the
file back to you and this is how internet helps you run this globalized world! When we talk about internet, very
critically we need to talk about the speed of Internet! Before we get to the speed of internet
lets get to 'What is the difference between bit and
byte?' Bit is the smallest information computer can understand.... it's
either 0 or 1 Whereas byte is nothing but.... its formed by 8 bits.... so 8 bits together form one byte! It could be some thing like 11011101.... whatever ....something! So that is a BYTE. So eight BITs form one
BYTE. Now a lot of people get confused - DATA
is always denoted by 'bytes'... so when I say I
have 1gb of RAM it is one gigaBYTE of RAM but when I tell I have a 10 Mbps
connection it is 10 mbps... connection 'bits' per
second mega'BITS' per second connection. If you confuse these two.... it's going to
be very very difficult at one mBps.... 'byte' per second connection is 8 mbps connection ....eight times the speed of what it is supposed to be!
So speed is always denoted by the small 'b'
data size is always in big 'B'. In computer world kilo is always '1024'
so.... one kilo bit is 1024 bits.... similarly one kilobyte is 1024 bytes! Right so for instance let me see I have
1 Mbps connection and I have a file of 128 KBytes. So lets say for instance you have WORD and in word you type the alphabet 'A'.... now with one .... to produce that one alphabet ....that takes about one BYTE.... capital 'B' of space.... so one BYTE is how much it needs to store this alphabet A..... one BYTE is is 8 BITs.... right?..... according the convertion.... so to type A... it
takes eight bits or one BYTE of data. Alright having known that
let's look at this example.... so you have 128 KB.... that is BYTE a file of 128 KB now it needs to go across a network with speeds of 1 Mbps.... one megabits per second! How much time will it take? It is a very simple question .... let's try to convert 128 kilobyte if we convert it to bits it is...... 128 into 8 bits... this
conversion if you know! bit to byte..... its 8 right? So 128 BYTE is..... if you convert it into bits .....it is 1024 kilobits of data right? so 1024 kilobits where is that .... its 1024 kilobits is
nothing but 1 megabit..... right? One Megabit! What is the speed .....it is 1 megabit per second is the speed of our connection..... so on a
connection of 1mbps a 1mb file will take exactly one second!!! So that's what speed is..... so understand
this...... the difference between speed and data....... the difference between bit and byte. So if you can understand different between
bit and byte..... the whole process of understanding further videos can be
very very easy!!! When we talk about speed we need to want to talk about three other critical factors that is..... Speed Delay and Availability....the three of them always go hand in hand! Like for instance now ....when you connect a cable from your router to your PC it tells you that it is connected at 100 Mbps that's because today with our LAN cards...the maximum they can do is a 100 Mbps! but then don't forget that speed that
they're telling is the speed between your computer and the router! Your internet connection
maybe is a 1mbps connection! so if you send 100MB/s data 100 MB per second data it will not go through your internet because your internet can only do
1 Mbps! Similarly you go..... lets say from your bangalore office
to New York office... you are sending a file. So from bangalore office it goes through our gateway.... from gateway we have a 1mbps slow connection. It then comes to our bangalore ISP. Bangalore ISP to Mumbai ISP they have a 100 Mbps line..... very fast and then from Mumbai to Dubai they
have a 10mbps line... a little slower connection.... from Dubai again to Cairo they have a 100 bps line and then Cairo to Madrid, let us say you have a 100 mbps line. So similarly
they have a slower and faster.... different speed connections. So basically when I say Internet
this what happens.... internet... if you pull off the cloud it is nothing but a lot of routers...
jumping here and there! Now even if I have a very high
speed connection your data-throughput between your
bangalore and New York office will depend on slower connections in between. So even if I
had a very high speed connection... a 100 Mbps
line in Bangalore... It can only travel at the slowest
link in between. So our slowest link is the 10 Mbps line
that we have here. So from New York office to Bangalore office, the maximum it can do is the 1 mbps
line that we have in New York. So this is how it works. This is not the exact data
flow from Bangalore to New York. I have just given you an example... it need
not obviously go via Dubai and Cairo... Maybe it goes through some other
location but basically it actually....the data packet
flows through one location to another location to another location. So like I said the speed always
depends on different factors..... of the link speed that
you have in between. Another critical factor is of dealey. Now when I send a data from New York to Banglore it has to....like we have already discussed... it has to pass through a lot of nodes in between. But let's assume that we have another office in Boston I love Boston, dont I? So lets say we have Boston office and we send data from New
York to Boston office.... it has to pass through less number of
nodes and hence it would reach much more quicker. So that's another factor. If the distance
between the two devices is long you will have delay in the communication. And that's why today, if you see, if you
go to Google... even 'Google.com' for instance... or you go to 'YouTube.com'... they redirect you to
a content delivery network closer to your place. So if you are in Singapore and you say 'google.com' or you go to 'youtube.com' YouTube would not connect you to the
Google Server or YouTube server in United States. It will connect your to a content delivery network close to
Singapore, may be in Singapore. So there is not much delay or there is in-significant delay in the
communication and the the whole process is much much more
fast. So that is the delay part of it. And availability, again for instance the link between Cairo and Dubai is
down. Communication between New York and
Banglore would not happen or it would happen but then
it has to take maybe a longer path. You might have another path which goes via russia and then it comes
via... ... it goes via China and comes
to India and it is a long long long process. So thats another thing about
availablility. Availability is if all the links in between are up
and running! Another thing we need to discuss in
today video is network topology. Network topology ...there are three fundamental network
topology....The STAR topology, the RING topology and the BUS topology. They are very very olden ways of how
computers were connected but even in today's world they are in use. I will show you how. Now for instance STAR. How does STAR work? STAR is where all the computers or devices are connected to a central switch or a connecting device. Now if this line goes down it doesn't
affect everybody else.... only this guy goes off the network. So in RING for instance every computer is connected to each other. So if
this guy goes down the communication between these 2 devices can still happen through this way. Right? So that's how this works. Now in bus topology .... let's say for instance.... this is
again like that....you have a device here... this is connected to this device... you have another device here that is connected to that. So every computer is connected to their own little device. Right... now if the link goes down here this part of the network can communicate
the each other but not with another device from the other segment of
the network. That's how a bus network works! Let's see how it is implemented in today's world. We go back to our old example that we saw earlier in this
video and if you see this switch and these systems or PCs
are connected in a star formation - everybody is
connected to this central switch! Here the server also similar thing
happens. Everybody is connected to the switch! These devices are connected to the
access point in STAR formation or.... so to say! And if you look at the switch, the switch
is connected in a bus formation. Now if the link goes down
here, this part of the network can communicate with each other but it cannot communicate with anybody else from this part of the
network. Sometimes you might even have
networks where this is connected like this and this is connected like this.... so even
if this goes down this switch can still access this network
around this path and they can get access
to these these windows.... I mean... these systems
here! So in real-world the network
topology that we use is called HYBRID - which
makes use of the STAR and RING.... maybe even the BUS. So it's a combination of all the three or
either of them! And that's how it is...So it is a hybrid
network that we use in today's world. I think that is about all the
information that I wanted to speak about in this first video. We will further get into a lot of other
topics in our second video. This is the review of
what we did today....Go through all the topics that is mentioned here and see if you understood. If you din't you can always go back
and try to learn little bit more. And even after that if you have conclusion if you want more clarity on any topic...please feel free to write into 'imran.rafai@nwking.org' and I will look into it and I will answer your queries. And of-course subscribe to our
YouTube channel and you can keep getting all our videos LIVE on YouTube. Thank you for watching and please visit our WEBSITE! BYE.
