What are the differences and similarities between OSI and TCP IP models describe and explain?

The OSI model mainly emphasises the services, interfaces and protocols. Conversely, the TCP model is not able to distinctly describe these concepts.

Note: The TCP/IP enables only connectionless communication mode in the network layer. But both modes (Connectionless and connection-oriented) are in the transport layer.

However OSI model supports connectionless and connection-oriented communication over the network layer. But in the transport layer, connection-oriented communication is merely allowed. Refer to the article difference between connectionless and connection-oriented services, for a better understanding.

We will discuss some more differences in the content ahead.

Content: TCP/IP Model Vs OSI Model

1. Comparison Chart
2. What is TCP/IP Model?
   • Layers of TCP/IP Model
   • Advantages and Disadvantages
3. What is OSI Model?
   • Layers of OSI Model
   • Advantages and Disadvantages
4. Key Differences
5. Diagrammatic Comparison
6. Conclusion

Comparison Chart

What is TCP/IP MODEL?

TCP (Transmission Control Protocol)/IP (Internet Protocol) was developed by the Department of Defense (DoD) project agency. Unlike OSI Model, it consists of four layers each having its own protocols. Internet Protocols are the set of rules defined for communication over the network.

We consider TCP/IP as the standard protocol model for networking. TCP handles data transmission and IP handles addresses. The TCP/IP protocol suite has a set of protocols that includes

• TCP
• UDP
• ARP
• DNS
• HTTP
• ICMP, etc.

It is a robust and flexible model. The TCP/IP model is mostly used for interconnecting computers over the internet.

Layers of TCP/IP Model

Network Interface Layer

The layer act as an interface between the host and the network hardware. It specifies what operation must links (such as serial links) and classic ethernet perform? So that they can satisfy the requirements of a connectionless internet layer.

Internet Layer

The layer enables the host to transmit the packet over the network independently. The packets may arrive to their destination in a different order. It is the responsibility of the higher layer to rearrange them in proper order. The layer defines a packet format and the protocol such as:

• IP (Internet Protocol)
• A companion protocol such as ICMP (Internet Control Message Protocol).

Transport Layer

It enables a fault-free end-to-end delivery of the data between the source and destination. The data is in the form of datagrams. The protocols defined by this layer are:

• TCP (Transmission Control Protocol)
• UDP (User Datagram Protocol).

Application Layer

The layer permits users to access the services of global or private internet. The various protocols described in this layer are:

• Virtual terminal (TELNET)
• Electronic mail (SMTP)
• File transfer (FTP)

It also describes some additional protocols like:

• DNS (Domain Name System)
• HTTP (Hypertext Transfer Protocol)
• RTP (Real-time Transport Protocol)

The working of the application layer is a combination of the application, presentation and session layer of the OSI.

Advantages of Disadvantages of TCP/IP Model

Advantages

• With TCP/IP, we can establish connections between two computers in different kinds of networks.
• TCP/IP is a scalable client-server architecture.
• The model has flow control, error control, and congestion control mechanism.
• TCP/IP supports several routing protocols at each of its layers.

Disadvantages

• Difficult to set up and maintain when compared to IPX/SPX.
• It is quite slower than IPX/SPX.
• The model does not provide a clear separation between its services, interfaces and protocols.

What is of OSI Model?

OSI (Open System Interconnection) model was introduced by ISO (International Standard Organization). The model relies on the concept of layering and has a vertical set of layers, each having different functions. It follows a bottom-up approach to transferring the data. It is robust and flexible, but not tangible.

The main intent of the OSI reference model is to conduct the design and development of digital communication hardware. It also defines the designing of software in a way that it can efficiently interoperate.

Layers of OSI Model

OSI model consists of seven layers as described below:

Application Layer

The layer enables users to access the network by using interfaces and services. Such as electronic mail, shared database management, file access/transfer and other services.

Presentation Layer

The layer focuses on the syntax and semantics of the transmitting information. It performs tasks such as translation, encryption and compression. The layer encodes the actual information into bit streams. It is then converted into another form and compressed.

Session Layer

The layer establishes the session between different machines. It is also responsible to synchronize and maintain the interaction between them. The services provided by the layer are dialog control, token management and synchronization.

Transport Layer

The layer accepts the data from its preceding layer in the form of independent packets. Then it transmits that data to the succeeding layer. The other function carried out by this layer are:

• Service point addressing
• Connection control
• Segmentation and reassembly
• Flow control and error control

Network Layer

Logical addressing and routing are the major operations performed by the network layer. It translates the network logical address into a physical MAC address. So that, the two systems residing in the different networks could also communicate efficiently. A packet also requires a path that it can follow to reach the destination avoiding congestion and failed components. Thus, it also facilitates the automatic updation of the routes.

Data Link Layer

It is responsible for transforming the raw transmission service (Physical layer) into a reliable link. It makes the physical layer free from error by masking them so that the network layer does not notice them. The layer splits input data into frames. The tasks carried out in the data link layer are:

• Framing
• Access control
• Physical addressing
• Error and flow control

Physical Layer

It transmits the individual bits over the transmission channel. The physical layer deals with the description of:
The characteristics of the interface between the devices.

• Transmission media
• Representation of bits
• Synchronization of the bits
• Data rate
• Physical topology
• Line configuration
• Transmission mode

Advantages and Disadvantages of OSI Model

Advantages

• The OSI model is a generic model and it provides full guidance to develop any network model.
• Being a layered model it provides a clear separation between the layers, services and protocol.
• Supports both connection-oriented and connectionless services.

Disadvantages

• It is a theoretical model.
• The model is quite complex and hard to manage.
• It has addressed similar functions in different layers that make it even more complicated.

1. TCP/IP is a client-server model, i.e. when the client requests for service it is provided by the server. On the other hand, OSI is a conceptual model.
2. TCP/IP is a standard protocol used for every network including the Internet. However, OSI is not a protocol but a reference model used for understanding and designing the system architecture.
3. TCP/IP is a four-layered model. Although OSI has seven layers.
4. TCP/IP follows a horizontal approach. On the other hand, the OSI Model supports the Vertical approach.
5. TCP/IP is tangible, whereas, OSI is not.
6. TCP/IP follows top to bottom approach, However, OSI Model follows a bottom-up approach.

Diagrammatic Comparison

The TCP/IP Model was developed before OSI Model, and hence, the layers differ. Concerning the diagram, we can clearly see that TCP/IP Model has four layers namely, Network Interface, Internet, Transport and Application Layer.

On the other hand, the OSI model has seven layers. The model has merged data link and physical layers to make the network interface layer of the TCP/IP model. The Application layer of TCP/IP is a combination of the Session, Presentation and Application Layer of the OSI Model.

Conclusion

Concerning the above article, we can conclude that the TCP/IP Model is more reliable than OSI Model.

We use TCP/IP for end-to-end connection so as to transmit the data over the internet. Subsequently, TCP/IP is robust, flexible, and tangible and also suggests how data should be sent over the web. The transport layer of the TCP/IP Model checks whether the data has arrived in order, it has an error or not, whether lost packets are resent or not, acknowledgement is received or not, etc.

In contrast, the OSI model is just a conceptual framework to interpret how applications communicate over a network.