TCP/IP vs OSI model

TCP/IP being the first of the models, is the foundation model from which Internet is based on. Into days world it is extremely unlikely to find a network that is not running TCP/IP.

TCP/IP  consisting of the 4 layers, Network, Internet, Transport and Applications.

  •  Network interface (layer 1):  physical components of network connectivity between the network and the IP protocol.
  •  Internet (layer 2): Contains all functionality that manages the movement of data between two network devices over a routed network.
  •  Host-to-host (layer 3): Manages the flow of traffic between two hosts or devices, ensuring that data arrives at the application on the host for which it is targeted.
  •  Application (layer 4): Acts as final endpoints at either end of a communication session between two network host.

The OSI model was  developed some 10 years later to compete with the TCP/IP. OSI Networking model is still used todays as an excellent tool to describe and explain network communication.

The OSI model  is broken down into 7 layers that are used to describe a specific aspect of network communications.

  • Physical (layer 1): Provides access to the cable electrical signals ones and zeros.
  • Data Link (layer 2): Provides Physical addressing, ensures data is error free.
  • Network (Layer 3): Provides “logical” addressing, finds best path a destination .
  • Transport (layer 4): determines “how” the data is sent, defines well-know services(ports).
  • Session (layer 5) : Starts and ends sessions, logically keeps sessions separate.
  • Presentation (layer 6): Takes data and formats into a generic language understandable by applications.
  • Application (layer 7): Interfaces with applications -provides access to Apps.


TCP/IP in my opinion is the most widely know out of the two Network models , but  when working with and describing networks, especially when relating to fault finding I always refer to the OSI network model, as I believe breaking  everything down into individual layers helps describe and isolate specific faults.


Pyles, J. Carrell, J.L. Tittel, E. (2013). Guide to TCP/IP: IPv6 and IPv4 (Fifth Edition). Boston:CENGAGE Learning

Cioara, J.(2008). CCNA Mega Guide: CCNA (640-802).

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