REAL LIFE example!! (TCP/IP and OSI layers) // FREE CCNA // EP 4
Summary
TLDRIn this fourth episode of the free CCNA course, sponsored by Bozon Software, the tutorial delves into the TCP/IP and OSI networking models. It follows a packet's journey through a network, illustrating how it interacts with each layer. The video uses a simulation of Johnny ordering coffee from NetworkChuck.Coffee, detailing the process from the application layer to the physical layer. Key concepts like encapsulation, ports, IP and MAC addresses, and the roles of switches and routers are explained. The episode concludes with challenging quiz questions to test viewers' understanding of the OSI model and TCP.
Takeaways
- 🎓 This is the fourth episode of a free CCNA course sponsored by Bozon Software, which provides CCNA and CCNP labs and practice exams.
- 🌐 The video explains the TCP/IP and OSI networking models, which are essential for understanding how computers connect in a network.
- 📦 The tutorial follows a packet's journey through a network, demonstrating how it interacts with each layer of the OSI model.
- 🖥️ The scenario involves Johnny accessing 'networkchuck.coffee' over the internet to order coffee, using this as a practical example to explain networking concepts.
- 🔍 The video uses Packet Tracer software to simulate network traffic and analyze the packet's progression through the layers.
- 🔑 Layer 7, the Application Layer, is where Johnny's web browser initiates an HTTPS request to access the website, highlighting the use of HTTP and HTTPS protocols.
- 🛠️ Encapsulation is a key process explained, where data is wrapped with headers as it moves down from the Application Layer to the Physical Layer.
- 🔄 The video covers the Transport Layer (Layer 4), explaining the difference between TCP and UDP, and the importance of port numbers like 443 for HTTPS.
- 🌐 The Network Layer (Layer 3) is where IP addresses are used to direct packets to their destination, with routers playing a crucial role in this process.
- 🔗 The Data Link Layer (Layer 2) involves MAC addresses and the use of switches to direct frames to the next network device.
- 🔍 The Physical Layer (Layer 1) is the actual transmission of electrical signals over Ethernet cables, representing the physical medium of the network.
- 📝 The video concludes with a quiz to test understanding, focusing on the functions of the Application Layer and the protocols involved in reliable data transfer.
Q & A
What is the main focus of episode four of the CCNA course?
-The main focus of episode four is to understand how packets travel through a network, following the packet's journey as it interacts with each layer of the OSI model.
Why is Bozon Software mentioned in the video?
-Bozon Software is mentioned as the official sponsor of the CCNA course, making it possible for the course to be offered for free.
What are the two main networking models discussed in the video?
-The two main networking models discussed are the TCP/IP model and the OSI model, with the video using the OSI model for reference to explain the packet's journey.
What does Johnny want to do in the scenario presented in the video?
-Johnny wants to order some coffee from the website networkchuck.coffee by going over the internet.
What is the significance of the traffic being filtered to HTTP and HTTPS in the video?
-Filtering the traffic to HTTP and HTTPS allows the viewer to focus on web-related traffic, omitting other protocols such as ARP requests and DNS queries that were covered in previous videos.
What is the role of the application layer (Layer 7) in the OSI model as described in the video?
-The application layer is responsible for managing communications between applications, directing data to the correct program, and using protocols like HTTP and HTTPS for web browser interactions.
Why is the transport layer (Layer 4) important in the video's explanation?
-The transport layer is important because it determines how data is transported, using either TCP for reliable delivery or UDP for faster, less reliable transport, and includes port numbers to direct the data to the correct application.
What is encapsulation as explained in the video?
-Encapsulation in the video is the process of adding headers to the data as it moves down through the OSI model layers, with each layer adding its own information, such as ports for Layer 4 and IP addresses for Layer 3.
How does the video illustrate the difference between a packet and a frame?
-The video illustrates that a packet includes all layers above Layer 2, encapsulated with a Layer 3 header, while a frame includes all layers encapsulated down to Layer 2, with MAC addresses, and is what is sent over the physical medium.
What happens when a packet reaches a router as described in the video?
-When a packet reaches a router, the router de-encapsulates the packet to examine the Layer 3 header to determine the destination IP address and then uses its routing table to forward the packet to the next hop.
What is the purpose of the three-way handshake mentioned in the video?
-The three-way handshake is a process used by TCP to establish a connection-oriented, reliable data transfer between networked computers before actual data transmission begins.
Outlines
🌐 Introduction to Networking Models
The script introduces Episode Four of a free CCNA course, sponsored by Bozon Software. It emphasizes the importance of networking models like TCP/IP and OSI for computer connectivity. The video aims to illustrate how a packet traverses a network, interacting with different layers. The presenter uses the OSI model for reference, adding extra layers like session and presentation for clarity. The scenario involves Johnny ordering coffee from NetworkChuck.Coffee, and the video uses Packet Tracer to simulate this process. The focus is on HTTP and HTTPS traffic, and viewers are encouraged to download the Packet Tracer file for a hands-on experience.
📨 Application and Transport Layer Analysis
This section delves into the application and transport layers of the OSI model, detailing how Johnny's HTTP request to NetworkChuck.Coffee is processed. The application layer, layer 7, uses HTTP over SSL (HTTPS) to ensure secure communication. The script explains the concept of encapsulation, where data is wrapped in headers as it moves down the OSI stack. At the transport layer, layer 4, TCP is chosen for reliable data transfer on port 443. The process of adding headers and the significance of ports in directing traffic are discussed. The segment, which includes the data and layer 4 header, is highlighted as a key component in data transmission.
🔗 Network Layer and Encapsulation Process
The script continues with the network layer, layer 3, focusing on IP addresses and the role of routers. It describes how a packet is encapsulated with a layer 3 header containing source and destination IP addresses, turning the segment into a packet. The importance of the encapsulation process is reiterated, with a practical example of how data is passed down to the data link layer. The packet's journey from Johnny's laptop to the router is visualized, and the concept of frames, which include layer 2 headers, is introduced. The script explains how switches use MAC addresses to direct frames and how routers de-encapsulate packets to read layer 3 information.
🌐 Deep Dive into TCP/IP Suite and Quiz
The final paragraph summarizes the entire process of Johnny's request being handled by the TCP/IP suite, from encapsulation into a frame to its transmission across the network. It touches on the de-encapsulation process at NetworkChuck.Coffee's server, which reads the request and initiates a response. The script then transitions into a quiz format, challenging viewers with questions about the OSI model's application layer and the transport layer's role in ensuring reliable data transfer. The quiz is designed to test comprehension and application of the concepts discussed in the video.
Mindmap
Keywords
💡CCNA
💡Bozon Software
💡TCP/IP Model
💡OSI Model
💡Encapsulation
💡HTTP and HTTPS
💡Port 443
💡IP Addresses
💡MAC Addresses
💡Packet Tracer
💡Routers and Switches
Highlights
Introduction to episode four of a free CCNA course sponsored by Bozon Software.
Emphasis on the importance of TCP and OSI networking models for computer connectivity.
Overview of following a packet's journey through a network, interacting with each OSI layer.
Scenario setup where Johnny orders coffee from NetworkChuck.Coffee over the internet.
Explanation of using the OSI model for educational purposes despite the practical use of the TCP/IP model.
Use of Packet Tracer to simulate and visualize the network traversal process.
Description of traffic filtering to focus on HTTP and HTTPS protocols for web traffic.
Detail on the process of Johnny initiating a web request by typing a URL into his browser.
Explanation of the application layer (Layer 7) and the use of HTTP and HTTPS protocols.
Discussion on the transport layer (Layer 4), focusing on TCP for reliability and UDP for speed.
Clarification of port 443 being reserved for HTTPS traffic and port 80 for HTTP.
Introduction to the concept of encapsulation as data moves down the OSI model layers.
Explanation of the network layer (Layer 3) focusing on IP addresses and routing.
Discussion on the data link layer (Layer 2), involving MAC addresses and switches.
Illustration of how a switch directs frames based on MAC addresses using its CAM table.
Description of the process of de-encapsulation as data is received and processed by network devices.
Final steps in the data transmission process from the server back to Johnny's laptop.
Quiz time with challenging questions related to the OSI model functions and TCP.
Conclusion of the episode with a call to action for feedback and further engagement.
Transcripts
this is episode four of my free
ccna course and a huge shout out to
bozon software the official sponsor of
this ccna course
they are the reason this can be made
available for free so i highly encourage
you to go check them out
they have the absolute best ccna ccnp
labs and practice exams tcp and osi
networking models that define how we
connect our computers
without these we wouldn't have
networking so in this video we're going
to watch it happen we're going to follow
a packet as it goes
through a network and how it interacts
with each layer
let's do it
[Music]
okay same scenario as the last video
johnny wants some delicious
network chuck coffee so he needs to go
over the internet to access
networkchuck.coffee to
order some coffee let's watch his
packets go across the network
and we'll analyze the layers as it goes
across the network let's check it out
now i'll say it again in reality we're
using the tcp ip model which is this
but for reference i'm going to use the
osi model so i'll add in those extra
layers the session layer and the
presentation layer just going to add
those in there
stack them up and if you want to follow
along which i highly encourage you to do
that it's really helpful to watch this
actually happen
use your own computer so i got a link
below download this package tracer file
that i'm about to walk through
go ahead and do it right now i'll wait
for you if you pause otherwise here we
go
so using simulation mode we'll watch
johnny go all the way across the network
to access networkshop.com which is this
server right here
and order some delicious coffee so let's
click on simulation and watch this in
bullet time because it's
it's amazing now as we go through this i
want you to notice one thing
i have our traffic filtered meaning that
i'm
only looking at http in https traffic
web traffic things you might use to
access a website i'm telling you this
because you won't see things that we saw
in the last video like
arp requests to discover a device's mac
address you won't see a dns query
so johnny can discover the ip address in
narc shock.coffee if you want to see
those things you can
just go edit the filters right here you
can unlock all those goodies so we're
going to open up johnny's laptop here
we're going to navigate over to his
desktop and click on web browser
we're going to type in https colon whack
network chuck dot coffee
and go now nothing happened because
we're filtering traffic
let me step forward in time and watch
things happen there we go
so we see here we have our blue message
our blue packet that johnny is
getting ready to send out in our
simulation panel here you can actually
see we have two separate messages
why well one is what he's getting ready
the other is what he's sending out to
the switch
let's open up that first one and take a
look i'll just select that first message
right here
you can see we have our wonderful seven
layers of the osi even though we're
actually using tcpip
again i'm telling you the networking
world always uses the seven layers
always so let's analyze this first
johnny starts out by using layer 7.
what's layer 7 it's our application
layer
what application is he using well we get
a message right here
because we have that layer selected the
http client sends an http request to the
server what that basically means is that
johnny's web browser
is attempting to access a website so
simply this is the application layer the
protocol we're using here is the http
protocol
and actually we're using the https
because it's secure and encrypted
but this is an example of an application
layer protocol that is used by
things like hey your web browser you're
using that right now so johnny types in
networkchuck.com into his web browser
he hits enter and his computer gets to
work and so again the application
protocol we're using is https
and the computer takes this data and
gets it ready to send out now at this
point
the computer's goal is to get the data
all the way down through the layers down
to the physical layer so it can go
across our ethernet cable
through the internet to the other server
to the networkchuck.cof server but
what's happening in all this mess what's
going
on let's talk about it now we're gonna
skip these two layers for now we will go
into more detail later but again
typically they're
meshed into the application layer anyhow
so it's okay looking back at packet
tracer we're on to layer four now
layer four is our transport layer for
now the way i want you to think about it
is
how can we transport the data how can we
get it there and we really have two main
options we can use tcp
or udp now i'm not going to cover this
super in depth right now but just know
that when we use tcp
it's more reliable it's when we want to
make sure our message actually gets
there
we have mechanisms in place to make sure
that if it doesn't get there we can send
it again
whereas udp is not as reliable as tcp
and it's typically seen as a
faster transport method so when it comes
to the transport layer these are the two
main options we have and then we have
our ports now the destination port here
is destination 443
you might recognize this port 443 is
reserved for https traffic
you might also be familiar with port 80
which is http traffic
again we'll cover more in detail later
but just know that that's what's
happening right now
so i'll move on down through our layers
real quick put our data down here
and the transport information we're
going to use will slap on as a layer 4
header we'll attach that to our data
and inside this header are things like
hey we're going to be using tcp
and we'll be using port 443 now what
just happened here
is important the process of taking our
application data
and then scooting it on down here and
slapping on that layer 4 header
that's called encapsulation this
encapsulation process actually happened
up here as well
the web browser encapsulated whatever
johnny wanted to send to the network
coffee server which is him saying get me
some coffee it's a message saying get me
some coffee he encapsulated that into a
http header which is our data the way i
like to see this is let's say
for example the data is like a message a
letter we encapsulate that message into
a
http header which is our data when we
moved on down to the transport layer
we took that data envelope and we put it
inside another envelope we encapsulated
it and this new envelope has our data
inside and this is our layer 4 header
and that's the way i like to visualize
encapsulation we'll keep taking our
letters and just putting them inside
other
envelopes other letters until we get to
the bottom which is our data link and
i'll show you oh by the way this
message right here when we have our data
encapsulated with a layer 4 header
attached we call this message a segment
and now we're getting into familiar
territory we're at layer 3.
layer 3 again is our network layer and
if you watched our previous video you
know that layer 3 we're dealing with
iop addresses we're dealing with routers
love that stuff
so in this layer 3 header we see that we
have our source ip address
and we have our destination ip address
this ip address being johnny's ip
address and this ip address being the ip
address of the networkchuck.coffee
server
so we'll drag our segment down on to
layer 3
and we'll encapsulate that segment by
adding a layer 3
header and again our layer 3 header is
going to contain the ip address
information and we're basically telling
our router
where to send this we're giving our
router directions we're saying hey mr
router here's my source ip this is who
the
message is from which is 10.1.1.3 and
then the destination ip address which
was 23.227.38.65
now let's test your memory you would
have learned this from the last video
what is this new message we have what is
it called
what do we call that if you said packet
you're absolutely right a packet has
all the layers above it the transport
session presentation application
all those layers encapsulated with a
layer three header telling the router
hey here's where you send this info and
now we're at layer two
almost there layer two is our data link
layer with data link our layer two we're
dealing with mac addresses we're giving
our switch directions to the next stop
that our information is taking in this
case it'll be our router here we have
the
mac address of johnny's laptop and here
we have the mac address of the router
so now i'll move down our packet into
layer two
and we'll slap on our layer two header
and layer two also have a trailer as
well and this will encapsulate it into a
message that we call
well what do we call it what do we call
messages that deal with layer two
that deal with mac addresses and
switches if you set frames you gotta
this message is indeed a frame
a frame has all these layers
encapsulated down and inside these layer
two headers we have the directions for
the switch
telling the switch where to send his
message so in this case we have the
source mac address
which is johnny's mac address and then
we have the next stop the destination
which is our router and that's
pretty much it we've encapsulated all
the layers down to a frame and now we
can send that frame
over the physical layer the ethernet
cable so he hits the wire and boom
and actually he's up here so he goes
from johnny to the switch
let's watch it happen in packet tracer
if we step forward in time we see that
frame go to the switch if we open up
that frame
we're only seeing layer one and layer
two because the switch can't see
anything else
all these layers right here have been
encapsulated down
into this frame and when the switch
receives his frame he's got this bulky
envelope
but he only opens the first envelope and
he opens it up and goes oh
well it's going to this mac address
which if i look in my
cam table my mac address table i can see
that mac address belongs to this port
i'm going to send it out this port
that's where the router is see right
here he looked it up and
fast ethernet 06 is the port that the
router belongs to let's step forward in
time and watch it happen
boom it goes out to the router and boom
it also does it here
if we open up that message the router
did indeed receive a frame
and he made sure that it was for him it
came to his mac address
he will then do the opposite of
encapsulation he'll de-encapsulate it
which basically means he opens the next
envelope to see what the next layer says
so he takes a peek at layer 3. at this
point we're dealing with the packet with
the layer 3 header the layer 4 header
and the data
the router looks at the layer 3 header
sees where it needs to go what
is the destination ip address looks in
his routing table he's like yeah i know
where that goes
i've got my map i'm a layer 3 guy and he
then proceeds to send it out to the
switch
now something important happens here
remember the switch can only deal
with layer 2. if you recall from our
previous videos the router has to
somehow tell the switch
how to get to networkcheck.coffee he has
to tell him his mac address
otherwise the switch will have no idea
where to send it because he can't see ip
addresses so after the router learns the
mac address of
networkchuck.coffee using arp he
encapsulates his layer 3 header which is
the ip address information
inside a new layer 2 header and he
changed the source and destination mac
address
and he had to change it because before
the message he received the
source mac address was johnny and the
destination was himself
now he has to change it to being the
source is himself and the destination is
networkchuck.coffee so he encapsulates
that it's now a layer two frame
and he sends it off to the switch we'll
step forward in time and pack a tracer
here the message arrives at the switch
if we open that up
here we are again switch eyes we can
only see layer two and layer one the
switch looks in his cam table as mac
address table
sees that hey network check dot coffee
does indeed live on fast ethernet zero
one
that's where i'm gonna send that sucker
that's where i'm firing the electrical
signals and he does that let's watch we
step forward in time once more
boom the frame goes to
networkchuck.coffee
if we open the message up we now have
all the layers once more and here's what
just happened
the switch sent this frame to
networkcheck.coffee now because the
server
that runs networkcheck.coffee was built
obeying the guidelines of the tcpip
model when it receives a frame it knows
exactly what to do it'll first do
exactly what the router did
look at the layer 2 header make sure
that hey this is actually for me it's my
mac address
hey cool he'll take a look at the layer
2 header he'll open up that message and
go oh
yeah this is my mac address it's to me
awesome he'll then de-encapsulate
or open up the next message and look at
the layer 3 header and go
huh look it's for me too this is my ip
address
awesome he'll then de-encapsulate it
once more opening up the layer 4 message
and going oh hey
we're using tcp oh and awesome i love
443
reasoning port 443 and then he sends it
up to the next layer
and then finally the last layer the
application layer opens up that last
message and goes oh
it's for me https it's browser
information
it's website stuff awesome so real quick
a thousand foot view what johnny had to
do is he had to
use the entire tcp ip suite
encapsulating all this stuff down into a
frame
and then he sends this frame across the
physical network across
ethernet cables and such touching each
device a switch a router another switch
and then finally arriving at
networkchalk.coffee networkchuck.coffee
took that frame
and then de-encapsulated the entire
thing to look inside and see
what was meant for the web browser the
application information of course in
this case
the data was a request for his
web server johnny's wanting to buy some
coffee and johnny's like hey
i'm trying to get to the homepage of
networkcheck.com can you give me the
home page so i can shop
so the web server reads that request
which is inside the data and the whole
process starts over again
the networkcheck.cof server encapsulates
all the information
into a frame sends that to the switch
the switch sends it to the router
the router to the switch the switch to
johnny and this is what johnny receives
all right quiz time i hope you have your
copy ready because these questions i
chose are kind of difficult
one is from the old ccna and one is from
the
old ccnp route exam so let's see what
you got
let's go question number one which of
the following functions are performed
by the application layer of the osi
model select
three choices now if you just started
studying networking
this could be a difficult question for
you but when i encounter a difficult
test question i start with the process
of elimination
so let's take out things that we know
have nothing to do with the application
layer which again is layer seven
looking at this i think d is probably
not it at all
managing logical and physical addressing
when i hear that i think mac addresses
layer 2 definitely not layer 7.
another one that you might pick up on is
that b is probably not the answer either
ensuring error-free data delivery
between devices this makes me think
transport layer and specifically tcp tcp
gives us reliable delivery of our
packets
of our data so now we're down to four
choices and i'm gonna go ahead and
select the right answers
and i'll explain why a c
and e let's see if i'm right boom
now here's the tricky part though this
is correct for the osi model so these
three
options are absolutely applicable to
layer seven the one we didn't select
down here the one we didn't eliminate
this is part of the presentation layer
which is layer six
but as part of the tcp model layer six
layer seven and even layer five
are all clumped together in the
application layer and if we had talked
about the presentation
layer in detail you would have known
that this is not it but we didn't so
it's okay if you didn't get this
now c and e we probably could have just
guessed that without having even known
anything about layer seven managing
communications between applications
directing data to the correct program
programs another word for applications
a would have been a bit more fuzzy but
just from the process of elimination
we would have got that one question
number two which of the following relies
on a three-way handshake in order to
provide connection-oriented reliable
reliable data transfer between networked
computers
select the best answer now again this is
a question that has terms you have not
learned yet or possibly one of those
being the three-way handshake
we haven't talked about that yet but
through the process of elimination
we can look at these answers and go huh
that's probably not that so for example
arp
when we talked about routers and
switches we learned what arp does
it's how a host on a network can find
out what mac address belongs to a
certain ip address
so that's not it we can mark off a dns
we saw what that was in our
router video dns helps us map a friendly
name like netflix.com or
networkchuck.coffee to an ip address so
that's not it
and then down here even though it looks
kind of weird rarp
it stands for reverse arp and it's arp
and reverse
you got the mac address but you want to
find the ip address so that's not it
now we have two options and we just
learned about these didn't we
tcp and udp are two of the main
protocols we can select when we are
using the transport layer
now out of those two options which of
them do you think provide connection
oriented
reliable data transfer
well udp no it's fast but it's not
reliable
tcp yeah it is if we select this answer
and see
if we're right we are right now if you
got that right
that's impressive that's a ccnp level
question from the old ccmp route and the
route exam
i failed that three times three no two
times
it was a tough exam well guys that's
about it if you like this video hit that
like button if you have any questions or
comments or need help with the ccna
comment below or jump into my discord
server i got a link below for that as
well if you want to see more stuff
like this more courses check out this is
it.i o it's a collaboration between
myself and david bomble
it's pretty cool go check it out link
below and that was episode four the osi
model the tcp ip model
we saw what happened we saw it happen in
real time in the coming videos we're
going to explore them a bit more
jumping into the upper layers the
application the presentation the session
the transport we're going to dive deeper
into those layers
and yeah that's it i'll catch you guys
later
[Music]
foreign
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