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tcp/ip model

What is The TCP/IP Model?

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What is The TCP/IP Model?
What is The TCP/IP Model?

Till now, you must have learned about the Open Systems Interconnection (OSI) model. However, it is essential to know that the OSI model is now dominated by the TCP/IP model. In this blog, we will learn about the TCP/IP model.

Once you learn about the TCP/IP model, you can quickly validate your networking knowledge. In the end, we will also learn about the differences between the TCP/IP and the OSI model. So make sure that you stick to the end of the blog.

Note: If you haven’t read the previous blog of our CCNA 200-301 series, I highly recommend you do so. 

Let’s begin learning the TCP/IP model.

What is TCP/IP Model?

The term TCP in the TCP/IP model stands for Transmission Control Protocol. Whereas, IP is a full form of Internet Protocol. It was created and proposed by ARPA. The very purpose of this model was to connect the military.

You must know that the TCP/IP model is also called the Internet Layering Model or the Internet Reference Model.

TCP/IP model

Note: We can only communicate with the Internet through both TCP and IP.

Where is the TCP/IP Model Used?

When a source computer is communicating with a destination computer, it always follows the TCP/IP model. The goal of this model is to maintain the continuation of the conversation between the source and destination even if the transmission stops working.

The TCP protocol works in the Transport Layer, whereas the IP protocol works in the Network Layer. The TCP layer validates the proper sequence and transport of data packets. The IP protocol takes charge of the following:

  • It chooses the route for the data packet delivery.
  • It finds out the IP address of the sender and the destination address.

Therefore, the TCP/IP model uses two main protocols and it cannot function with just one protocol.

What are the Four Layers of The TCP/IP Model?

I request you to check out our OSI model blog before you start to learn about the different layers of the TCP/IP model.

You can find either 4 or 5 layers of the TCP/IP model. Yet, we will learn the 4 different layers of the TCP/IP model in this blog. The following are the layers of the TCP/IP model:

  • Process/Application Layer
  • Host-to-Host/Transport Layer
  • Internet Layer
  • Network Access/Link Layer

Note: You must remember that there is no major difference in the working of the TCP/IP model and the OSI model. There is a difference in the number of layers between the two models.

difference in the number of layers between the two models.

Let’s start learning about the different layers of the TCP/IP model.

1. Network Access Layer:

  • The network access layer is the bottommost layer of the TCP/IP model.
  • This layer can be considered similar to the Data Link and the Physical Layer of the OSI model.
  • The protocols present in this layer help in the transmission of the data.
  • This layer uses the following protocols:
    • Ethernet
    • FDDI
    • X.25
    • Token ring
    • Frame relay
  • This layer mainly works on the physical level.

2. Internet Layer:

  • It is present above the Network Access Layer. Therefore, it is the second layer of the TCP/IP model.
  • The other name for the Internet layer is the Network Layer corresponding to the Network Layer of the OSI model.
  • Its functions are quite similar to that of the Network Layer of the OSI model.
  • The function of this layer is to send packets from any kind of network. It does not matter what route is taken, the packet is delivered irrespectively.
  • The protocols used in this layer are as follows:
    • IP: It is the Internet Protocol (IP). It delivers the packet from the source to the destination by identifying the IP addresses. These include IPv4 and IPv6.
    • ARP: The function of the Address Resolution Protocol (ARP) is to identify the hardware address of a host from an already existing IP address.
    • ICMP: It is called the Internet Control Message Protocol (ICMP). It informs the host about any network issue.

3. Host-to-Host Layer:

  • The Host-to-Host Layer is very similar to the Transport Layer of the OSI model.
  • This layer performs the following tasks:
    • End-to-end communication
    • Flow control
    • Reliability
    • Correction of any errors in the data
  • The two main protocols that are used in this layer are:
    • User Datagram Protocol: It provides end-to-end delivery of the data. It makes us aware of the error but does not tell us about the error.
    • Transmission Control Protocol: It performs segmentation and sequencing of the data. It also takes on the important task of flow control.

4. Application Layer:

  • The Application Layer performs the functions of three layers of the OSI model namely, the Application, Presentation, and Session Layer. 
  • All the high-level protocols are managed by the Application layer.
  • The main protocols that are used in the Application Layer are the following:
    • HTTP: The Hypertext Transfer Protocol (HTTP) helps in accessing the data over the World Wide Web. It is mainly used in hypertext regions.
    • SSH: The Secure Shell (SSH) maintains an encrypted connection. It is considered over the Telnet.
    • FTP: The File Transfer Protocol (FTP). Files are transferred from one computer to another by the FTP protocol.

This marks the end of the layers of the TCP/IP model layers.

How Does The TCP/IP Model Differ From the OSI Model?

TCP/IP Model 

OSI Model

It is called the Transmission Control Protocol/Internet Protocol Model.

The OSI model is also known as the Open Systems Interconnection Model.

It is created by the International Standard Organization (ISO)/.

It is created by the Advanced Research Project Agency Network (ARPANET).

It has 4-5 layers.

It has 7 layers in total.

It has a horizontal approach.

It has a vertical approach.

Protocols were developed before the model.

The model was developed before the protocols.

The Data Link Layer and the Physical Layer are combined as a Host-to-Host layer.

The Data Link Layer and the Physical Layer are not combined. They are different.

The protocols cannot be replaced with ease.

The protocols can be replaced.

This model does not have rigid and strict boundaries.

This model has very strict borders.

It’s a Wrap!

The TCP/IP model is a protocol-based model that forms the basis of the transmission of data from source to destination. It is a better model to understand the transmission of data than the OSI Model.

It is very important to understand the OSI model before you start learning about the TCP/IP model in the CCNA course. 

Stay tuned for the upcoming blog of our CCNA 200-301 series. 

Happy studying!

What is OSI Model in CCNA? Understand Its 7 Layers

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OSI Model in CCNA
OSI Model in CCNA

OSI model in CCNA is a reference or conceptual model used to describe computer network communication. It stands for Open System Interconnection (OSI). The foundation of this model was kept forward by International Organization for Standardization (ISO) in 1984.

Even if you’re entirely new to networking, it is very important to understand the OSI model in detail. It is one of the most important concepts in networking is the OSI model. You must note that even in the interviews for Cisco Certified Network Associate (CCNA), it is the most-asked topic.

Note: If you haven’t read the previous blog of our CCNA 200-301 series, I highly recommend you do so.

In this blog, you will learn about the seven layers of the OSI model in CCNA. This is the third blog of our CCNA 200-301 blog series.  

OSI Model in CCNA

Why Should You Learn the OSI Model?

OSI model in CCNA is just a reference model and it was invented later after the Internet. It means that you need to know it so that you can understand networking and its rules very well. 

For example, if you’re searching for anything on Google via your laptop, the information you type reaches the Google servers following a certain set of rules.

These days, we follow the TCP/IP model that is based on the OSI model in CCNA Course. The OSI model has seven layers whereas, the TCP/IP model has four layers in total. Now that you know why you need to learn about the OSI model in CCNA Course, let’s begin learning its layers.

The Seven Layers of the OSI Model in CCNA

The seven layers of the OSI model in CCNA from top to bottom are as follows:

  • Application Layer
  • Presentation Layer
  • Session Layer
  • Transport Layer
  • Network Layer
  • Data Link Layer
  • Physical Layer
OSI Model in CCNA

Note: the mnemonic to learn the OSI model is All People Seem To Need Data Processing. 

We can only understand these layers from top to bottom. The topmost layer interacts the most with the end user followed by the other layers. Similarly, the bottom-most layer interacts the least with the end user. 

Let’s begin with the layers one by one.

1. Application Layer

Let’s say you go on your laptop or your PC and search for YouTube.com, voila, this is where the application layer of your laptop/PC has done its work. 

In other words, the Application Layer helps an individual interact with another individual via software applications. These applications include Yahoo, Facebook, Google, etc.

The function of the layer:

Therefore, the application layer which is the top-most layer of the OSI model serves as a platform for the application services to access the network. It also shows the received information to the user.

Note: We can also call the Application Layer a Desktop Layer.

OSI Model in CCNA

2. Presentation Layer

The presentation layer tells us about the format of the data. You must be thinking, what does that mean?

For example, if you surf on Google for sunset images. You would find millions of images with various file formats such as jpeg., png., etc. Similarly, if you search for a video on YouTube, it could be an MP4 or an Avi file.

Functions of the layer:

  • The presentation layer is also called the translation layer as it translates the data in the required format to transmit it over the network.
  • The other function of this layer is to encrypt/decrypt data. Encryption refers to changing the form or code of data and decryption refers to bringing that data back into its original form.

It also performs compression/decompression. If we reduce the size of an image, this is called compression, and vice-versa.

3. Session Layer:

The session layer creates and manages sessions via port numbers. 

For example, if you open a Google tap and search for ‘Network Kings’, this is a single session with a unique port number. Then, you open another Google tab and search ‘Cisco’, this is a different session with a different port number.

Therefore, these different port numbers do not disturb the various services. There are different port numbers for different internet services such as sending an email, opening a website, etc.

The function of the layer:

The session layer assigns port numbers to different sessions on the Internet.

OSI Model in CCNA

4. Transport Layer

The transport layer is considered the biggest layer of the OSI model. It helps in the end-to-end delivery of the data from source to destination.

For example, if you’re searching for the ‘best CCNA course’ on Google, the data is delivered by the transport layer from the source (user) to the destination (Google server).

The functions of the layer:

  • The TCP/UDP protocols also work in this layer.
  • The TCP performs flow control, meaning it avoids data congestion by controlling the flow of the data.
  • It also performs data segmentation, meaning it breaks the data into small packets. It occurs at the sender’s end.

It also performs sequencing and error correction.

OSI Model in CCNA

Note: The Protocol Data Unit (PDU) of the Application, Presentation, and Session layer is Data. When the data reaches the Transport layer, it is segmented. Therefore, the PDU of the Transport layer is Segment.

5. Network Layer:

The Network Layer tags the source IP Address to the incoming data from the Transport Layer. It shows the address of your PC as well.

The functions of the layer:

  • Routers (networking devices) work in the network layer. 
  • They tag the IP addresses. This is called logical addressing.
  • They also choose the best path from source to destination. This is called routing.

The protocols that work in the Network Layer are Ip and Ipx. You must also know that the segments in the network layer are called packets. This means that the PDU of the network layer is Packets (the IP address is tagged).

6. Data Link Layer:

OSI Model

Now, the packet reaches the Data Link layer from the Network Layer. This packet now has two addresses: an IP Address and a unique MAC Address. It has both the Source MAC (SMAC) and the Destination MAC (DMAC). These addresses change as they travel further.

The functions of the layer:

  • It allows the sending of a set of bits to the receiver. This is called framing.
  • This layer adds physical addresses i.e., MAC addresses of the sender.
  • It also performs flow control and error control.

Switches work in this layer.

7. Physical Layer:

All the physical components such as cables, and connectors work in this layer. This layer also includes analog, digital, electrical, etc. Hubs also work in this layer as they do not learn the MAC address, unlike switches.

The functions of the layer:

  • It helps in synchronizing the bits.
  • It also controls the number of bits sent per second, i.e., the transmission rate.

It also decides how different nodes are structured in a network (star, bus topology).

It’s a Wrap!

That’s it! You’ve now learned about all the layers of the OSI model in CCNA Course. If you like video content, you can learn the OSI model in Hindi.

In this blog, we have studied different layers of the OSI Model in CCNA. Stay tuned for more blogs for the CCNA 200-301 series!

Watch the video here:
https://www.youtube.com/watch?v=_b5dBF-Kyk4

Happy learning!