An Introduction to TCP/IP

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Internet, a name we are all familiar with and a necessity for today’s world is nothing but a connection of many small networks that join together. From social networking to e-commerce, internet is changing the world in every possible way. But what provides this internet the framework is the question that many of us wonder and the answer is TCP/IP.

What is TCP/IP?

TCP stands for Transmission Control Protocol whereas IP stands for Internet Protocol. The TCP/IP model provides the backbone to the today’s internet. As compared to the OSI (Open System Interconnection) model that was proposed initially, the TCP/IP model has less number of layers and incorporates the Session and Presentation layer into the Application layer itself.

                              OSI vs TCP/IP

The Layers of the OSI model are as follows:

  1. Physical Layer : It deals with design issues related with mechanical, electrical and procedural interfaces as well the physical medium. It merely accepts and transmits data stream without any regards to meaning and structure.
  2. Data Link Layer (DLL) : Deals with design issues to transfer data that is free from errors to network layer. It handles data in frames and is responsible for creating and recognizing frame boundaries. It transmits the frames sequentially at every node (router).
  3. Network Layer : Helps in controlling the operations of subnet (set of routers). It is concerned with how to route the packets of data and also deals with the congestion control of the network.
  4. Transport Layer : It is the first end to end layer thus the information sent is accessible to the source and destination only. It is based on reliable data exchange, independent of network and applications being used at the top layers.
  5. Session Layer : It is end to end layer and deals with the synchronization between data streams from source to destination. It makes uses of Token scheme to manage different sessions.
  6. Presentation Layer : It is also end to end layer and deals with the data representation like encoding/decoding, encryption/decryption, etc.
  7. Application Layer : Manages different applications like FTP (File Transfer Protocol), e-mail, etc. and is also an end to end layer.

Working of TCP/IP:

The Application Layer is the layer where we as a user work on our gadgets using protocols like HTTP (Hyper Text Transfer Protocol), FTP, etc. This layer integrates the Application, Presentation and Session layer of the OSI model into one layer and helps in using the resources, encrypt / decrypt the message, synchronization, etc. It then passes the data to the Transport layer where it is sent on the Internet from source (user) to destination using protocols like TCP and UDP (User Datagram Protocol) depending on the criteria of connection-oriented (reliable) or connection less (unreliable) transfer which is similar to the OSI model. The lower layers that is the Internet, Network Access and the Physical layer helps in sending the data through the different networks to the intended destination.

Each layer thus provides a specific function that are well defined and the layers are created where different level of abstraction is needed to reduce inter-dependency among different layers. This fits the Object-Oriented Programming concept where layers act as an object with a set of operations that processes outside the object can invoke.

The advantage for TCP/IP model was that the model was devised after the protocols were defined that helped the model to adapt quickly whereas the OSI model was built first with no clear description on its architecture because of which it failed to deliver and was never used on a large scale.

The disadvantage of TCP/IP model is that the level of abstraction in OSI model is better as compared to TCP/IP and OSI model gives a clear distinction between interface, services and protocols amongst different layer.

To overcome the disadvantages of TCP/IP model, a Hybrid model is used in the present day technology that incorporates the feature of both the models and provides better services to the consumers.

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  1. Pingback: Mind Map of Protocols used in Different OSI Layers

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