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osi and tcp/ip model layers and their functions

Difference Between OSI and TCP/IP Models

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Difference Between OSI and TCP/IP Models
Difference Between OSI and TCP/IP Models

Are you looking for the difference between the OSI and TCP/IP models? Look no further! This blog will provide in-detailed information regarding the OSI and TCP/IP models in networking. 

Therefore keep reading the blog till the end to familiarize yourself with the concepts.

What is OSI?

The OSI (Open Systems Interconnection) model is a conceptual framework describing layers used by computer systems to communicate over a network. 

The OSI model illustrates computing functions into a versatile set of rules and provisions to support compatibility between different derivatives and software.

What are the layers of the OSI model?

There are seven layers of the TCP/IP model, namely-

  • Application Layer
  • Presentation Layer
  • Session Layer
  • Transport Layer
  • Network Layer
  • Data Link Layer
  • Physical Layer

What is TCP/IP?

The TCP/IP (Transmission Control Protocol/Internet Protocol) model deals with the connection-orientated protocols determining that a device must establish a link before transmitting, acquiring or swapping the data or information. 

Also, one must ensure the closure of the connection after exchanging the data and information in the TCP/IP model.

What are the layers of the TCP/IP model?

There are four layers of the TCP/IP model, namely-

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

Difference between OSI and TCP/IP.

The difference between OSI and TCP/IP models is as follows-

 

 

OSI

TCP/IP

Full Form

Open System Interconnection

Transmission Control Protocol

Developer

ISO (International Standard Organization) has developed the OSI model.

ARPANET (Advanced Research Project Agency Network) has developed TCP/IP model.

Definition

An autonomous measure and generic protocol used as a transmission gateway between the network and the end user refers to the OSI model.

A standard protocol leading to the development of the internet and acting as a transmission protocol establishing the connection among the hosts refers to TCP/IP model.

Transport Layer

The transport layer assures the delivery of the packets in the OSI model.

The transport layer does not ensure the delivery of packets in the TCP/IP model.

Approach

The OSI model works on a vertical approach.

The TCP/IP model works on a horizontal approach.

Session/Presentation Layer

The session and presentation layers are separate in the OSI model.

The session and presentation layers are not distinguishable in the TCP/IP model.

Model

OSI is a reference model via which various networks get built.

The TCP/IP is an executed model of OSI.

Service

The network layer provides connection-oriented and connectionless services in the OSI model.

The network layer delivers solely connectionless service in the TCP/IP model.

Protocols

The protocols are hidden and can get easily replaced in the OSI model.

The protocols can not get easily replaced in the TCP/IP model.

Layering

A total of seven layers are there in the OSI model.

A total of four layers are there in the TCP/IP model.

Dependency

It does not depend on protocols.

It depends on protocols.

Usage

The usage of the OSI model is low.

The usage of the TCP/IP model is high.

Standardization

The OSI model standardizes routers, motherboards, switches, and other hardware.

The TCP/IP model provides no standardization but a connection between computers.

Distinction

OSI model distinctions between the services, protocols, and interface.

The TCP/IP model does not distinguish between the services, protocols, and interfaces.

Reliability

OSI model is reliable.

TCP/IP model is reliable.

 

Explain the similarities between OSI and TCP/IP models.

The similarities between the OSI and TCP/IP models are as follows-

  • Both models are layered and build upon one another to provide end-to-end communication.
  • Both models have physical layering for transmitting raw data over a physical medium.
  • Both models have a network layer for routing data between networks.
  • Both models have a transport layer to provide reliable or unreliable end-to-end delivery of data.
  • Both models have an application layer to provide services to end users.
  • Both models have a session layer to manage the maintenance and termination of sessions between applications.
  • Both models have a presentation layer to handle the translation and encryption of data.
  • Both models use protocols to define the rules and formats for communication between different layers and devices.
  • Both models are open standards that get widely used in networking.
  • Both models have limitations and weaknesses; network engineers often use their combination to design and troubleshoot complex networks.

Use of OSI and TCP/IP models

The OSI and TCP/IP models get used in the following ways-

  • Web Browsing

While browsing the internet, your web browser sends a request to a server via multiple OSI layers. The request gets broken down into packets using TCP/IP, which then transmit across the internet to the server to create the requested webpage.

  • Email

While sending an email, a client uses the Simple Mail Transfer Protocol (SMTP) to send the message, which uses the OSI model to process and route the message to its intended recipient.

  • Video Conferencing

While in a video conference, the audio and video data gets broken down into packets using TCP/IP and sent across the network, forming the audio and video stream.

  • Online Gaming

Online games use TCP/IP to transmit game data between players.

Wrapping Up!

The OSI and TCP/IP models are crucial networking components that help to transmit data and information between users and devices. They share the same architecture, have pre-defined standards, require a simplified troubleshooting procedure, and have identical ‘transport‘ and ‘network‘ layers functionality.

For more details, refer to our blogs on the OSI and TCP/IP model to learn the concepts better. Also, for any queries and questions, feel free to write in the box below. 

Happy Learning!

FAQs:

01. Mention the different layers of the OSI model.

There are seven layers of the TCP/IP model, namely- Application Layer, Presentation Layer, Session Layer, Transport Layer, Network Layer, Data Link Layer, Physical Layer,

02. Mention the different layers of the TCP/IP model.

There are four layers of the TCP/IP model, namely- Process/Application Layer, Host-to-Host/Transport Layer, Internet Layer, Network Access/Link Layer,

03. Is the OSI model reliable?

The transport layer ensures the delivery of packets in the OSI model, making it reliable.

04. Is the TCP/IP model reliable?

The transport layer does not ensure the delivery of packets in the TCP/IP model, but it is still reliable.

05. What is the advantage of OSI over TCP?

The advantage of using OSI over TCP is that the protocols are hidden and easily replaceable in the OSI model than the TCP/IP model.

06. How are TCP and OSI similar?

TCP and OSI are similar since both models use protocols to define the rules and formats for communication between different layers and devices and are layered and built upon one another to provide end-to-end communication.

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!