difference between osi and tcp-ip model

Difference Between OSI and TCP-IP Model

In this blog, we will compare the OSI model with TCP/IP model and understand the difference between OSI and TCP-IP Model. Still, before moving to the differences, we need to understand both these models and their layers. 

So, let’s start with the OSI model of computer networking. 

OSI Model of Computer Networking

OSI stands for Open System Interconnection. The OSI Model was developed by (ISO) International Standard organization to help standardize communication between computers.  

The original objective behind the OSI model of computer networking was to make communication possible between two different vendors. Because, when the internet was growing at the beginning of the time, different vendors could not communicate with each other and, OSI Model came as the standard model for discussing, teaching, and learning the networking procedures in the field of Information technology.  

So, the OSI model was developed, but it was never implemented and remained as just a reference model for study purposes only. 

There are 7 layers in OSI Model. Let’s understand the OSI Model layers. 

The OSI Model Layers

layers of OSI Model

The 7 OSI model layers are as follows: 

Layer Name PDU (Protocol Data Unit)
Application Layer Data 
Presentation Layer Data 
Session Layer Data 
Transport Layer Segmentation 
Network Layer Packet 
Data Link Layer Frame 
Physical Layer Signals, Bits 

Let’s get into more details about each and every layer.  

  1. Application Layer  

This layer offers network services to end-user applications and provides interfacing of data. 

In this layer, the user interacts with application software like google chrome and Mozilla Firefox & Edge. 

As for web browsing, we use HTTP & HTTPs. For file sharing, we use FTP. 

  1. Presentation Layer 

The name itself represents that this layer presents the data from the application layer and marks it with a formatting code. 

Like it marks the text file as .txt, audio file as .mp3 and many more extensions, so the machine can identify what is the file actually we are sending or receiving. 

  1. Session Layer  

This layer actually deals with the connection. 

The major functions of this layer are: 

  • Establish Connection 
  • Manage the Connection 
  • Session Restore – restores the connection 
  1. Transport Layer –  

This layer is an intermediate layer between the upper layers and lower layers. 

It delivers and receives the data across the network from source to destination. 

Major functions of the transport layer are – 

  • Segmentation
  • Connection Management

Segmentation – The process of breaking the large data files into smaller files that the network can accommodate. (According to the bandwidth of the user) 

The Transport layer uses the two protocols for connection management. 

TCP UDP 
Connection oriented Connection less 
TCP is reliable UDP is not reliable 
3-way handshake process No handshake 
Also guarantees ordering of messages. Do not guarantee ordering of messages. 
Heavy-weight protocol Light-weight protocol 
Flow control No flow control 
Slow protocol because of responsibilities. Fast protocol because of no responsibilities. 
HTTP, TELNET, FTP, ETC DHCP, DNS, SNMP, ETC 
  1. Network Layer – 

The Network layer is responsible for providing IP addresses.  

Router and Multi-layer switches work on this layer. 

The Main functions of the network layer are Addressing, Routing & forwarding. 

Data is known as packet in the network layer. 

  1. Data-Link Layer – 

This layer encodes and decodes data packets into bits using its transmission protocol.  

Framing is also done on this layer. 

Framing means when the packet comes from the network layer into data link, it converts the packet into frames and sends it to the physical layer. 

Data-link layer is divided into two sublayers- MAC (Media Access Control) & LLC (Logical Link Control) 

  1. Physical Layer – 

This layer is responsible for connecting the device to physical connections like HUB and Repeaters. 

Electric voltage, radio frequency or pulses are the medium through which the data is transmitted. 

Cables and connectors are being used here in this layer. 

Summary of OSI Model

Layers Encapsulation Process & PDU 
Application Layer DATA 
Presentation Layer DATA 
Session Layer DATA 
Transport Layer Segments (Identification of TCP/UDP + Upper Data) 
Network Layer Packet (SRC/DST IP + TCP/UDP + Upper Data) 
Data-Link Layer Frame (SRC/DST IP + SRC/DST MAC+ TCP/UDP + Upper Data) 
Physical Layer The whole process is decapsulated 

These are seven of the OSI Model Layers.  Let’s move to the TCP/IP Model. 

TCP/IP Model in Computer Network

The TCP/IP Model in Computer Network was designed by the Department of Defense (DOD), and it is based on standard protocols. 

The TCP/IP model is also known as IP Stack, and this model is practically being implemented. This model is a widely adopted model due to its simplicity, and it is also known as the concise version of OSI model. 

TCP Layers:

As compared to OSI Model, there are 4 TCP layers which are: 

TCP/IP Model

Functions of TCP Layers – 

  • Application, Presentation & Session – SMTP, TELNET, FTP, TFTP, DNS, SNMP, ETC 
  • Transport Layer – TCP/UDP 
  • Internet Layer –  ARP, IP, IGMP, ICMP 
  • Network Access Layer – Bits & Signals 

So, there are 7 layers in the OSI Model whereas in TCP/IP, we only have 4 layers, and the working is same as discussed in OSI model. 

Difference between OSI and TCP-IP Model

OSI Model TCP/IP Model 
It was developed by ISO It was developed by DOD 
We have 7 layers in OSI  We have 4 layers in TCP/IP  
It’s the reference model used for study purposes, never implemented This is the concise version of OSI, and it is logical model which is being implemented 
It is a protocol-independent standard, and it acts as a communication gateway between network and end-user. It is based on standard protocols. This is a protocol for communication that allows hosts to connect to networks. 
It follows a vertical approach. It follows a horizontal approach. 
The transport layer in OSI Model is connection-oriented. Th transport layer of TCP/IP Model is both connectionless and connection-oriented. 
The network layer of the OSI Model is both connectionless and connection-oriented. The network layer of TCP/IP model is connectionless. 
In OSI Model, the protocols are hidden and can be replaced easily. In TCP/IP Model, replacement of the protocols is not an easy process. 
Provides quality services Doesn’t provide quality services 
Devices like routers, switches, protocols get standardization. Doesn’t provide standardization to any devices. 

These are the main difference between OSI and TCP-IP model. You can best learn about OSI and TCP/IP networking model in CIsco CCNA 200-301 training by PyNet Labs.

Also, you can watch this video and learn more,

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