A2 初級 4689 分類 收藏
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 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 CCMA 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
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 ha specs
and this go through all these number the peep
pot along the road and in the is to go through this did 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 detail that you send in the data could be anything
it could be a good
doc file a Word document or it could be an excel file it could be any major
could be you BDO it could be anything that detail
and abroad on which the the messenger traveled
that that basically is the network course
computer network has much more interesting than just paving
drawers up but
if you if you see backed is the very pleasing my computer netbook is
invented to communicate between computers
if you see this image you would see let me just take a
a highlighter you will see that we have the Windows PC
we have Linux systems an iMac
and we have laptop more bite for on palm top
you have bebe so is maybe it's running on saint always him database server
spite service but
in spite of the 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 ok
a global standard called or same orders sand and
and things like that which defines clearly what
when any manufacture manufactures its a networking device
what time how they should communicate with each other
so the only language of networking
and backed 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
to computers connected with the wire in this case we will use
a catfight cable a cap to keep a look something like this:
and this has becoming different colors you have
blue-collar ones red color ones from and this is this obviously another color
and this the out a Kabul is just a protective layer
inside you have eight tiny keepers
these keep it going to a connector called RG fortify keep it
that looks something like this that you see on the screen and back of your
and most the computer that you have today
you have a port adj a port like this
that is yard interferes your network interface card
so your network interface card is ready RG fortify 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 ET hedge
E arson net Ethernet let me just
right down its E sorry book my handwriting and
it's very difficult to right on screen
especially with my mouse bat lemme
chess eat net
maybe for my next video out by ice time is so that I can just
right tit more legible
handwriting alright but for now up
yes at this key believe connects between these two computers
and you can have a very basic network
but what happens if you have more than to computers so
let you have fight computers me you obviously kit I mean there's one we
obviously can't go on adding more
meet network interface cards on your computer then you can have
but a better bf connecting is by you making use of a networking device
maybe a switch or hub of course which and how but two different devices
they have totally different functions we will obviously learned about them in
future we do. pursuits
backed up for now you know we have a networking device in this case is a
and these computers can communicate with each other
so for instance this guy is caught over a document that he want to send across
the network to this guy all he has to do is centered across
to use IP address what is an IP address
you would ask IP addresses how
computers to recognize each other on the network
the BB learn about IP addresses in the next
I video series but for now just not be a identifiers
for computers another
critical reason why people use networking is
because of devices like this in a maybe let's assume that this was a very
printer or scanner that the company invested in
if networking was not available the wheat this device be connected is
to this let me just check the college's sure that it is
I okay lets you select to this is
it would have had to be connected directly to the computer
no let's assume that this user maybe print one
beat Adi and maybe all the
users in this computer in this company has similar requirement that they have
to pre wanna poop eaters
every day so the company will have been missed on more
printer still have one more print area this guy will have one more printer
so company will have unnecessarily
invest on a lot of printers been the uses of damn
in all the sprinters are gonna be very very minimal
better before computer companies to invest money on IT infrastructures to
how one compute one printer
very expensive good quality printer light 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 backed 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 and a rule mine are in a single company that's called as a lamb
local area network and local signify that is very local
to a geographer clearly a
if this seem local lantz not desert
Lance and you have not the land here
and let's assume that your company has two offices one in New York and then you
have another office in Boston
wanna be you could communicate create a network between the
the the two offices a few companies because we had to
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 we aced that kind of money
be a better way of doing it no
you could connect your office to local ISP
ISP is nothing but Internet Service Provider
and the similar thing happens on the IBM Boston connects
their office to an ISP Internet Service Provider
and ISP's already have the backbone very massive a high bandwidth connections
between the office
she got beat da that you sent from here course through the network to the ISP
from ISB to the ISBE in Boston and then through that
to go back to the Boston office and a computer to this computer
can commit come you keep with this computer absolutely fine
using the ISP not this
farms the wide ATM network bad
lands are into connected with each other to form a very
wide ATM network and wide here signifies
a wide geographical Adia it could be across the country
it could be in different cities and then the same country
maybe a different countries basically it's a web
so dot is how it works now how to how do you connect from highspeed to
York ER a locally and that's what would you can replace p
when non months situation what happens is you
you get a a jack on the wall
you might have a smaller jack on the wall and y'all your land can
lawn you just connected to the jack so from your from the sewage from that out
of your company
you connected to the check back and design a speedy would
the leaked cable maybe they would kill aid under under the
ground bill a cable to the office
and from the office they go here from Denmark of it again maybe underground
daily a cable
Judah Boston office again there will be a wall socket
that is provided and you just blow to keep from the wall to you
your rotor and that's how
you are when link works when this is also
intended to be using the ISP
intimate is nothing but a better team massive
when 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
about it. of information and communication facilities
consisting of interconnected networks using standardized communication
protocols well that is pig definition I
well that's exactly what it is you know internet
is nothing but you have a lot of and do you have a man here you have a band here
you have a plan here
you have a ban het and then just brands are connected with each other
so you have another ran here and you have another man here
another one here another one here maybe fuel
more here I know in India that up Whitelock
you have all these things and get connected let's when singer connector
from here
connected here from here connected here at these disconnected this is connected
this is going to this is connected this is connected
so this is nothing but how an internetwork so for instance if from
India somebody has to communicate
to New York this is a hold the data transfer there in court
if this thing disconnects you have somebody
the data going through along a pop so this is what
network internet is it is just nothing but interconnections of a lot of events
let's find out more about applications were talking about earlier
don't don't lot of use it off Internet are
networking as a whole we have YouTube CNN
EB Skype is just very ferried
very very few examples that a use the Internet
but they're Lord of sites and applications which use the internet as
you already know
know how it works is YouTube for instance is owned by Google to Google
has put a
public so a summit on the Internet that is accessible
to anybody on internet
so if I want to watch a video on youtube
ice I go to my web browser and type www youtube dot com
at the process that takes plays in the background
is much more complicated I'm simplifying this would process we will look into
exactly how it works
in for this video series but for now when sometimes
YouTube docked calm and hit enter
my computer sends a HTTP request
to YouTube's public sewer
when summer gets that information it is %uh find that some HTTP request so I
send damaged him if I backs it creates an html5 back
and it sends an estimate fight back to me
might that does it take seventies %uh 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 them
it shows a lot of videos and you click on one of those videos this process
they send you back to beat your and and that's how that works
to similarly it happens to eBay you know you go to CNN Skype
that's how it works so this is how internet
works basically they have a public servant they put all the files there
your computer request that this in the fight back to you and this
is how a internet helps you
run that this global global ice storm worked
when we talk about instant very critically we need to talk about to
speed up internet
before we get to the speed up internet lets get to
what is the difference between bit and bite
bit is the smallest
information computer can understand it's either 0 or 1
but as byte is nothing but for me it spawned by 8
bits so a bits together form one but
it could be some like 1101
one 101 whatever something
to that some bite so eight bits from one but
now a lot of people get confused detail is
always denoted by bites so when I say I have 1gb of
RAM it is one key got bite
RAM but when I tell I have a 10 Mbps connection
it is 10 am BBS connection bits per second make up bits per second
if you confuse these two it's going to be very very difficult
at one Mbps bite per second connection
is 8 Mbps connection eight games
the speed of what it is supposed to be so
speed is always denoted by the small be data size is always
imus big be
n in computer while kilo is always 1024 so
one kilo bit is 1024 bit similarly
one kilobyte is 1024 bite
right so for instance let me see I have 1 Mbps connection
and I have a fight of 128 KB bites
so letter for instance you have booked an inward you type
at the alphabet eighty now with one
252 to do that one alphabet thats
takes about one bite capital
be of myspace so one
bite is how much it need to store this
at for but 8 its one bite is
about it is 8 beats right
according the convertion so too baby it takes eight bits on one
by to beat up alright having known that let's look at this example to
you have 128 keep be that is bite
file if I love 120 128 KB
now it meets to go across Asus netbook puts be 21
Mbps one makeup bits per second
how much time will it take to a simple question let's try to convert
128 kilobyte if he could what to do
bits it is 128 into eat dip this conversion if you're not
bit bite it's more eight right
so one bite 128 byte
isn't too if you convert it into
bits it is 1024
kilobits of data
right so one 24 kilobits
where is that its 124 kilobits is nothing went 1
make a bit right on makeup it
but the speed it is 1 megabit per second is
the speed of our connection so on a connection to 1mbps
8 1mb fighting which take
exactly one second
so that's what speed is so I'm stumped this the difference between speed
and data the difference but in bed and bite
so if you can understand different but a bit and bite the whole process
of understanding for the videos can be very very easy
when we talk about speed we need to want to talk about three other critical
factors that speed
deleon available at three of them all these go hand in hand
like for instance now when you can to keep you from your router to York
PC it is you that is connected at 100 Mbps
that's because today on land con a the maximum they can do is a 100 Mbps
but they don't forget that speed that they're telling is the speed between
your computer
and the hotel your internet connection maybe you wanna bps connection
so if you send 100 bps data
100 MB per second data it will not go to use
internet because your intent can only do one Mbps
similarly you go that
fled to france does your banker office to New York office be sending a fight
so from bangor office it goes through a gate be from get where we have a wanna
be a slow connection
it comes to our bangor ice-t_ bangor ISP to Mumbai is
they have a 100 Mbps lay very fast
and then huh from Mumbai to Dubai they have but any BP is limitless
little slow connection from Dubai again to cairo
they have 100 bps line and then add credit to Madrid Letty
you have a 100 bps line to similarly they have
a smaller hi addition different speeds around the world
to basically when I send it to Internet this what happens intimate
if you if you pull off the cloud
it is nothing but a lot of rope is jumping could be here and that
now if I even if I have a very high speed connection
you're beat-up throughput between your bangor and New York office we depend on
slow connections in between so even if I had up
very high speed connection to 100 Mbps line Bangla
right eat ken only travel at the slowest link in between
so our stores link is the 10 Mbps land that we have here
so from New York office band office it will August
the magnet can do is the two the one MPs line that we have
in now New York so this is how it works
so I mean this is not the exact data flow from one bank go to New York
I've just just giving an example it need not of his quiet by in credo
the beat goes for some other other location but basically it
actually that did the packet data packet flows through one location to another
location to another location
was so like I said the speed always depends on
different factors of the link speed that you have one in between
again there's a critical factor factor is of dealey no
been a send the data from New York to Banglore
it has two like him already discussed has to pass through a lot of Nord in
but let's assume that we have a lot of is in Boston
I love Boston don't ahead so let's say we have
Boston office an we senator from New York to Boston
it has to pass through less number of nodes and Hans
it would reach much more quick up so
that's another factor if the distance between the two devices
is long you will
have delay in communication
and that's what to do if you see if you go to Google I mean even Google Doc
conferences are you go to
%uh YouTube dot com det redirect you to a content delivery network
closer to your place so PI in Singapore and you say
Google dot com are you HOT you go to YouTube dot com
YouTube would not connect you to the group with several YouTube server
in United States e2 will connect your to
up content delivery network close to Singapore may be in thinkable
so that diz does not much a delay on
days in significant delay in the communication and the
the whole process is much much more first so that's
that's the delay but if it and Republic again for instance the
the link between Cairo and the by is down
communication between New York and Banglore food
not happen or it would happen but then it has to take maybe along about the
might have another pot
which cause why russia and then it comes why are
and I know it goes why China and comes to India and annotate that's a long long
process sought thats another thing about available at every ability is
is if all the links in between are up and running
another thing we need to discuss in today s plea deal
is network topology the network topology
death three parliamentary network topology stock topology the ring
topology and the bus topology
the very very wooden ease of how computers work
connected but even today's world
they are in use I'm sure how
know when to stop how to start work start is wet all the computers or
devices are connected to a central
switch are a connecting device
know if this line goes down it doesn't affect everybody else only
this guy cause of the network
so in Greenpoint since every
computers connected to each other so if this guy goes down
the communication to in peace to devices can still happen through
this way right so that's how
this works none in bus
topology let's say for instance this is a game like that you have a different
device you're disconnected this devise you're not the device here that's gone
to every computer is connected to be a on little device
right now if d-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 net for
that's how a bus networks let's see how
it is implemented in today's but because back to our ordered
example that we saw earlier in in this video
and if you see this which
and these data systems are the species are connected
in a star formation everybody's connected to this entry switch
here to serve all too similar thing happened in everybody's connected to the
these devices are connected to the access point in stop on a mission
are I and but also to see
and if you look at the switch the switch is connected in
a bus formation 0 if Dept link goes down here
despite the network can communicate with each other but it cannot communicate
with anybody is from this part of the network
%uh sometimes you might even have networks where this is connected like
and this is coming to like this so even if this goes down
this which can still access this network at around
despite and they can you know get access to these
these windows the mean these systems here
so in good into real-world the network topology
that we use is called hybrid which the makes use of the start and
ring maybe I even but the bus
so it's a combination of all the key art either of them
and that's how it is so it is a hybrid that what the fuse in today's world
I think that is about all the information that I wanted
to speak about in this first video
we will for the get into a lot of other topics
in a second video this is the review of what we did
today I go to all the
I'll topics that have mentioned herein see if you understood any
if you think you can always call back and tried Dunleavy added more
a even of that if you have conclusion if you want more clarity on
any topic these feed feed to right into
in Ron doctor by at end up puking daughter large E
and I've look into it and I believe and you
we and of course subscribe to our YouTube channel
and you Kim getting all our viewers live
on you thank you for watching and
his visit our website by


CCNA 基本網路教學 (200-120 CCNA | Day 1: Network Fundamentals | Free Cisco Video Training 2014 | NetworKing)

4689 分類 收藏
阿勳 發佈於 2014 年 4 月 16 日
  1. 1. 單字查詢


  2. 2. 單句重複播放


  3. 3. 使用快速鍵


  4. 4. 關閉語言字幕


  5. 5. 內嵌播放器


  6. 6. 展開播放器


  1. 英文聽力測驗


  1. 點擊展開筆記本讓你看的更舒服

  1. UrbanDictionary 俚語字典整合查詢。一般字典查詢不到你滿意的解譯,不妨使用「俚語字典」,或許會讓你有滿意的答案喔