OSI and TCP IP Models - Best Explanation
Summary
TLDRThis script delves into the OSI model, emphasizing its role as a communication guideline. It explains the encapsulation and decapsulation processes, the significance of protocol data units (PDUs), and the function of transport layer protocols like TCP and UDP. The lecture also contrasts the OSI model with the TCP/IP model, highlighting the importance of standards in physical and data link layers for device interoperability, and discusses the abstraction of network communication into binary data.
Takeaways
- đ The OSI model serves as a reference and guideline to understand and delegate responsibilities within the communication process.
- đ Communication involves both encapsulation (going down the stack) and decapsulation (going up the stack).
- đĄïž Encapsulation is critical for ensuring messages are successfully transmitted from the sender to the receiver.
- đ Layers 7, 6, and 5 are grouped together, primarily responsible for producing a Protocol Data Unit (PDU) in binary format for the transport layer.
- đŒïž The PDU is essential for the transport layer, which handles the identification of applications and services through port addresses.
- đą The transport layer uses source and destination port addresses to identify services or applications, distinguishing them from network layer addresses.
- đŠ The transport layer segments data for security, performance, and to allow for multiplexing.
- đ The network layer is responsible for creating packets, using protocols like IP to define source and destination network addresses.
- đ The data link layer adds a header and trailer to create frames, which are crucial for physical transmission over networks.
- đ The physical layer deals with the actual transmission of data, converting the abstract bits into physical signals.
- đ The TCP/IP model is a simplified version of the OSI model, focusing on the application and internet layers for internet communication.
- đ§ Standards such as 802.11 for Wi-Fi ensure compatibility and performance across network devices.
Q & A
What is the OSI model and its purpose?
-The OSI model is a reference or guideline that helps in delegating responsibilities and understanding the communication process in a network. It outlines the seven layers of network communication, from the physical layer to the application layer, and the processes that occur at each layer.
What is the difference between encapsulation and decapsulation in the OSI model?
-Encapsulation is the process of adding header information to data as it moves down the OSI model stack, preparing it for transmission. Decapsulation is the reverse process that occurs as data moves up the stack, where the header information is removed to retrieve the original data.
What does the term 'PDU' stand for and why is it significant?
-PDU stands for Protocol Data Unit. It is significant because it represents the unit of data handled at different layers of the OSI model. Each layer adds its own header to the PDU, which is then passed to the next layer down the stack.
Why is the encapsulation process critical to communication?
-The encapsulation process is critical because it ensures that the message is properly formatted and includes all necessary information for successful transmission from the sender to the receiver, including addressing and error-checking.
What are the functions of the transport layer in the OSI model?
-The transport layer is responsible for identifying the applications that make requests and those that receive them. It segments the data into manageable pieces, assigns source and destination port addresses, and ensures the reliable delivery of data.
What is the difference between port addresses and IP addresses?
-Port addresses are used by the transport layer to identify specific services or applications on a host, while IP addresses, used by the network layer, identify the host or network interface on the network. Port addresses are logical, whereas IP addresses are used for routing packets to the correct destination.
Why is segmentation important in the transport layer?
-Segmentation is important for security, performance, and to allow multiple communications to occur simultaneously through a process called multiplexing. It breaks up data into segments that can be independently managed and transmitted.
What is the role of the TCP protocol in the OSI model?
-TCP (Transmission Control Protocol) is a transport layer protocol that ensures reliable data transmission. It adds features like error-checking and flow control to the data segments, sacrificing speed for reliability.
What is the purpose of the network layer in the OSI model?
-The network layer is responsible for packetizing the data segments received from the transport layer, adding a header with source and destination IP addresses, and routing the packets to the correct destination across different networks.
What is the TCP/IP model, and how does it differ from the OSI model?
-The TCP/IP model is a simplified version of the OSI model, focusing on the two main protocols, TCP and IP. It groups the first three layers of the OSI model under the application layer and combines the data link and physical layers into the network access layer, emphasizing practicality over theoretical comprehensiveness.
What is the significance of the data link layer in the OSI model?
-The data link layer is responsible for creating frames from packets, adding a header and trailer for error-checking and synchronization. It connects the logical processes of the OSI model with the physical transmission of data.
Why are standards important in the physical layer?
-Standards are important in the physical layer to ensure compatibility and interoperability between different devices on a network. They define the physical and electrical specifications for devices, such as Ethernet standards (e.g., 802.11 for Wi-Fi).
Outlines
đ OSI Model and Encapsulation Process
This paragraph discusses the OSI model as a reference guideline for understanding communication processes and delegating responsibilities. It emphasizes the importance of the encapsulation process in sending messages from the sender to the receiver, highlighting the role of layers six and seven and the production of a Protocol Data Unit (PDU) in binary format. The paragraph also touches on the convergence of networks and the identification of data types through file extensions and port addresses, explaining the transport layer's role in identifying services and applications through source and destination ports. It concludes with the segmentation of data for security, performance, and multiplexing, mentioning TCP as a protocol that prioritizes reliability over time.
đ Network Layer and IP Protocol
The second paragraph delves into the network layer's role in transforming segments into packets, with IP being the key protocol that instructs how to achieve this. It explains the concept of source and destination addresses at the network layer and distinguishes them from port addresses used by the transport layer to identify services or applications. The paragraph also introduces the data link layer, which adds a header and trailer to create a frame, and emphasizes the importance of standards like Ethernet for physical connectivity and compatibility among network devices. It concludes with the significance of matching interface cards, such as 802.11 AC, with wireless routers to maximize network potential.
đ TCP/IP Model and Network Communication
This paragraph contrasts the OSI model with the TCP/IP model, which is less elaborate and focuses on the development of the Internet, emphasizing the importance of TCP for reliability and IP for routing. It explains how the TCP/IP model groups certain layers differently, placing more emphasis on the application layer and considering the first three layers as software-based. The paragraph also discusses the division of responsibilities in network communication, the importance of identifying the subject of communication, and the analogy of a translator for the role of a software driver in hardware-software interaction. It concludes with the idea that different models can organize and delegate responsibilities in network communication processes.
đ ïž Hardware-Software Interaction and Model Comparison
The final paragraph extends the discussion to hardware, using the example of game consoles and graphics processing units (GPUs) to illustrate the importance of both hardware capabilities and software drivers. It emphasizes the need for good translation between hardware and software, likening a poor driver to an ineffective translator. The paragraph draws a parallel between the organization of network communication processes and the division of labor in hardware-software development, suggesting that effective communication and delegation are key to optimizing performance, whether in networks or in the interaction between hardware and software.
Mindmap
Keywords
đĄOSI Model
đĄEncapsulation
đĄDecapsulation
đĄProtocol Data Unit (PDU)
đĄApplication Layer
đĄTransport Layer
đĄSegment
đĄTCP/IP Model
đĄIP Address
đĄData Link Layer
đĄPhysical Layer
đĄMultiplexing
Highlights
The OSI model serves as a reference and guideline for understanding and delegating responsibilities in communication processes.
Communication process includes both directions: encapsulation (down the stack) and decapsulation (up the stack).
Encapsulation is critical for getting the message from the sender to the receiver in network communication.
Layers 7, 6, and 5 are grouped together, responsible for producing a Protocol Data Unit (PDU) for the transport layer.
PDU should be in binary format by the time it reaches the transport layer, representing data with encryptions and compressions.
The convergence of digital networks allows for phone, internet, and TV services over the same line due to the binary nature of data.
Identification of data types on the application layer is typically done through file extensions like .exe or .jpg.
Transport layer uses port addresses to identify services or applications, distinguishing them from the network layer's IP addresses.
The transport layer's PDU is called a segment, which is created by breaking up the data into pieces for security, performance, and multiplexing.
TCP is a protocol that prioritizes reliability over time, adding features to ensure data integrity.
UDP is a protocol designed for speed, sacrificing some reliability for faster communication.
The network layer's PDU is called a packet, created by taking the transport layer's segment and adding IP addresses for routing.
IP addresses are used to identify devices on a network, distinguishing them from port addresses used by the transport layer.
The data link layer produces a frame, adding a header and trailer to the packet for physical transmission.
Physical and data link layers work together to convert logical data into physical signals that can be transmitted.
Standards like 802.11 for Wi-Fi ensure compatibility between network devices and interface cards.
The TCP/IP model is a simplified version of the OSI model, focusing on the two key protocols TCP and IP for internet communication.
The TCP/IP model groups the first three layers of the OSI model under the application layer, emphasizing software aspects.
The network access layer in the TCP/IP model combines the data link and physical layers, focusing on physical connectivity.
Different models like OSI and TCP/IP organize and delegate responsibilities differently, reflecting various business approaches.
Transcripts
so
like I was telling you guys the OSI
model is more of a reference a guideline
to help us delegate responsibilities to
help us understand what the
communication process entails and so I
had you guys just list them out from top
to bottom but remember the communication
process entails both directions
going down the stack is what we call
encapsulating and going up the stack we
call decapsulation
and today I hope to explain why the
encapsulation process is very critical
to the communication
that is to get the message from the
sender to the receiver
layer six sorry layer seven layer six
and layer 5 can be grouped in in fact
the sole responsibly for the three of
these is to produce what for the
transport layer
yeah so by the time we get down to the
transport layer
the pdu
to look something like this it should be
in a binary format so these three layers
produce a pdu
that we will call data
pdu is short for what protocol data unit
depending on the application all the
encryptions in the compressions
these zeros and ones are going to be
something that's really trivial I mean
that's what network people see all the
time or just zeros and ones they don't
know if it's an email or it's a voice
communication or whether it's a video
stream in fact that's what we call the
converging Network right the digital
converging Network this is why Time
Warner and all the other companies can
offer you phone internet TV all in the
same line it's all zeros and ones once
you get into zeros and ones you need to
identify that typically on the
application layer we identify zeros and
ones
by a file extension
a DOT EXE
represents zeros and ones used to
execute instructions a DOT jpeg jpg
represents those zeros and once to
display a picture
likewise we have identifications used in
networking sometimes we call these
addresses
to identify the application of the
service
that's the first thing that the
transport layer is going to do
the transport layer is going to identify
what applications make in the request
and what app sorry what service is going
to receive this
applications make requests
Services receive them
all right
so the way we identify them is to report
addresses
it's going to be a source
and there's going to be a destination
we stamp each and every one
of the pdu for the transport layer with
the source and destination what is the
pdu call of the transport layer
segment
and why is it called a segment because
what is the second thing or I should say
technically this would be the first
thing
yeah it takes the date and breaks up
into pieces hence we call those pieces
segments right so the pdu for the
transport layer
it's called a segment
why do we segment our data
security performance
and we can also allow multiple
Communications to occur relatively at
the same time which we call multiplexing
right
what was the one of the protocols
that defined
the segment because remember protocol
data unit right so if we're producing a
pdu there's got to be a protocol that
told me how to produce that pdu correct
so what was one of the protocols
TCP was one of them absolutely
and TCP we said time's irrelevant I'm
going to sacrifice time over reliability
okay this is why those big fat Cadillacs
I've launched a bunch of luxury items in
there that add weight to the car but a
sports car which is going to cost more
than a Cadillac I mean if you're getting
like a high-end sports car probably
going to trim all that fat because they
want speed correct
so what was the other protocol designed
UDP
TCP is the most popular one
all right we passed that segment down to
the network layer
and what is that Network layer going to
produce what are we going to take that
segment and make it into
packet
and what is one of the most popular
protocols on this layer that tells the
operating system how to take a segment
and make it into a packet
IP
and with IP
we have a source
and a destination address
much much bigger than Port addresses but
nevertheless same principle
but what's the difference between these
addresses what does the transport layer
use addresses for
they're both logical but which one does
the Tran what does the transport layer
use addresses for to identify what
they're called Port addresses but what
do they use to identify
services or applications
because look above the transport layer
the transport layer is looking up and
says okay who's getting this data who's
getting that data the way they know that
is through Port addresses okay so what
are the addresses used at the network
layer what do they use to identify
the key is Network what is the
definition of a network
to where more devices connected together
so they got to identify the devices on
the network
so the sender
and the receiver's IP address goes here
into the packet
all right so the packet gets passed down
and that becomes what
so we're in a data link layer
and we're going to produce what we call
a frame
remember the frame is the only time we
add a header and a trailer
and that frame
uses well we could use all kinds of
different protocols
I always like to talk to data link layer
with the physical layer because its idea
is to connect all that logical stuff
now the way I explained in my last class
and I got a kick out of it but I think
it clicked can you guys tell me what
Internet Explorer smells like
I know you guys are gonna say it smells
like because it's a piece of
but what about Firefox what about Chrome
what do they smell like what do they
feel like when you guys touch Internet
Explorer what does it feel like
felt a little heavy squishy
it doesn't have
smell
it doesn't have texture because it's all
virtual
it's abstract right
if I tell you what a nine if I ask you
what a nine volt battery feels like you
guys can tell me right
that's down here the physical stuff is
what we touch what we work with so this
layer is to take that abstract stuff and
make it into something real
and we need standards
we need standards that tell me okay I
can work with all that logical stuff
give me all those zeros and ones and I'm
going to convert into something that
people can touch taste hear feel it's
see
all depends on your interface card
now I say here because if you could hear
like my dog or Beyond
you can hear the Wi-Fi network sending
messages
and they operate a 2.4 gigahertz
Spectrum that's well beyond our hearing
and you guys are going to be glad for
that
I mean the way we listen to FM radios
which are in the megahertz is you need a
tuner to tune into that frequency and
then to
tone it down to a range that you can
hear correct
networks we call them modems
but nevertheless those signals are all
over us they're in this classroom all
time I'm sending one from this
microphone to my phone
drive me nuts if you guys heard or saw
all those things
but they do exist
the question is
how do I know that the interface card
that I bought
is going to work
with my other devices on my network
there's got to be standards like when
you go shopping for a hard drive it says
USB or a flash drive it says USB you
know you have a USB port and you expect
it to work
so when you guys go shopping for
interface cards or network devices what
are you looking for when you guys go
shopping for wireless cards or wireless
routers what do you look for
says Wi-Fi maybe but more importantly it
says 802.11
followed by a letter
so where the latest one is 802.11 AC
in order to use all that bandwidth to
use that wireless router to its full
potential what kind of interface card
are you going to need
an 802.11 AC interface card
so don't stop halfway and buy just a
wireless router
go the extra mile and buy the interface
card that uses the full potential out of
that wireless router
clear about that if I was setting up a
wired Network like we've been doing in
Packet Tracer you click on the computer
it says what for the interface card
fast
ether and that is a protocol or a
standard
that happens
right here the data link
ethernet has source
and destination addresses
but they're physical
that means the company that made that
interface card
burned an address into that card that
you cannot change
we'll get more into the difference
between physical and logical
right physical just takes those bits
and produces a signal
they carry them
that's it
now I tell my students
there are other models that explain the
same process
some are less elaborate as this
one of the most popular models
that we used as a substitute
to the OSI model is called the TCP slash
IP model and if you want to take a guess
why it's called TCP slash IP
because the persons that develop the
internet
focused on two protocols and only two
protocols TCP slash IP
they need to make sure data is reliable
because went back when it was called
arpanet
everything was very sensitive
with all this research
there wasn't any like voice or video or
any of that kind of crap
in fact the reason why the Internet was
developed was because a cold war
situation that we've connected are
missile silos so when Washington DC was
attacked we could still give the launch
codes over in Alaska
or turkey or wherever so we had
developed a very reliable Network so if
pathway gets disconnected we have
another way to get there another route
and that's what IP
says
so they said you know what
we developed this thing
let's create a model
that shows a grand overview of how this
behaves
and they said in order to use our
network if you want to send a web page
you need a web browser
and so they said
the first three layers are going to be
accomplished
under the application layer
so I just grouped the first three in
fact we've looked at layer 7 6 and 5
didn't I say that's all software stuff
OSI models a little bit more thorough
and said you know what I don't want a
cartographer writing the user interface
for my web browser
and thank God for that because if the
cryptographer did do that they would
hide the OK button it's a secret
likewise I wouldn't want a programmer
Who develops user interfaces
to write the cryptography program
because they would say oh it's real easy
passwords password
because their job is to make the
application user friendly
the cryptographer's job is to make it
very unfriendly
so that when you see it it doesn't make
any sense
very thorough and so what I like to see
is does that happen over here absolutely
because so there's like a division and
probably in that division there are
these departments because they need to
be accomplished
we do need session stuff we do need
presentation stuff but TCP was like yeah
that's all in the software
and that's we're going to do and it too
will produce data
and it too is interconnected and it's
going to connect to
the transport layer
and it two would produce segments
because I don't care
how you communicate but eventually in
your communication process you're going
to need to identify
what you're talking about the subject
right
have you ever talk to somebody then out
of the blue they bring something up and
you're like we were just talking about
uh Hell on Wheels why are you talking
about the weather next week what did it
have anything to do with the topic right
so in there you're gonna need some way
to identify what application or what
service you're talking with
so transport layer transport layer all
the same
remember these are the people that
developed the Internet
so their layer isn't going to be called
the network layer or rather they're
going to call it the inner Network layer
and what does inner mean anyway enter
it's just abbreviated from
interconnected
so just a bunch of networks connected
together
networks are networks whether they're
dropped together or not they all need to
behave the same way and it too is going
to produce
a packet
all right this is a very simple model so
it's going to take the last two
and group them together
and they're going to call this the
network access layer and oh hell does
that cause problems so far I have a 99
failure rate on my exam
when I give a multiple choice question
and I say
uh which
layer on the OSI model
is the same as the network access layer
and I will only give you one it'll be
like Network layer Network transport and
session something like that and students
want to say this one
network network it's got to be the same
thing
and it's not
the key here is access
going on to the network we're talking
about the physical stuff
so it takes both the data link and the
physical stuff in here
and it too
cause it's pdu a frame now let me give
you an example away from networks into
Hardware because I'm a hardware guy I
love reading Hardware magazines I love
staying on latest edge with CPUs gpus
and all that stuff especially the stuff
with the phones like iPhone just
released a new processor they're called
their motion processor and I'm just like
oh wow just another processor great what
does it do and so I'm looking at this
and I remember back in the 90s you know
we get into little geek fights and say
oh Nvidia is better than ATI or some
crap like that and then somebody would
say well no ATI has gotten great
processors and their gpus are excellent
they have more transistors and they have
more shaders and everything and I'm like
oh yeah whippy do and just like you guys
might be getting a pissing contest with
about Xbox 360 versus the PlayStation 3.
oh yeah PlayStation 3 has a lot of
muscle
compared to the Xbox
but what drives us to
these game consoles
content
likewise
I was so discouraged with ATI because
they had shitty Developers
the people at the valve drivers
didn't know what they were doing because
ATI needed to save money so they said
you know what you're an engineer you're
also going to develop the driver
what is a software driver it acts as a
translator between the hardware and the
operating system right
if you're a translator isn't doing a
good job translating you could find
yourself in prison right
likewise if your driver isn't using the
hardware to its full potential
you wasted all your money on all that
muscle and what you have is a dumb jock
I can't read and so you've paid a
millions of dollars to play football
well you guys understand a game plan and
so now he's running to the opposite
field goal or running to the opposite
end zone and you're like well you're big
and strong well you're pretty stupid
so I'm gonna get rid of you don't bring
out any teams I kept it Loose likewise
so what happened is over here Nvidia
decided to follow a model like this and
said we'll pay for engineers
and we'll also pay for software
developers that do nothing but developed
drivers
you need them
but they just have more levels
which might cost them more but hopefully
they produce a better product
over here the same process has to be
done the communication process has to
happen
however
how we group them and organize or
delegate responsibility is our business
model
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