TCP/IP and OSI models explained and compared

Dmitrii Korolkov

Let’s talk about fundamentals of network TCP/IP and OSI models. Let’s keep in mind that each layer has it’s own protocol which will be listed below. The first difference at glance is that TCP model consists of 5 layers versus 7 in OSI which are:

Application , Transport, Network , Data-link, Physical  vs Application, Presentation, Session, Transport, Network , Data-link, Physical

Application layer – provides interface communication between software and applications that need to communicate.

Presentation – defines and negotiates data formats. Also includes encryption.

Session layer – defines how to start, control and end the sessions, also includes messages management.

Protocols: Telnet, FTP, DNS, TFTP , etc.

Transport – provides data delivery error recovery and flow control.

Protocols: TCP, UDP.

Network – defines addressing, forwarding and path determination.

Protocols: IP, ARP, RARP.

Data-link layer – defines the rules when the device can send data to the particular medium.

Physical – sets the standards of physical characteristics  of data transmission.

Protocols: Ethernet, TokenRing, etc.

Benefits of OSI:

  1. Less complex – broken down on the more layers is easier to understand.
  2. Standard interfaces – additional layers allows different companies to integrate different solutions and architecture which is beneficial for the market and competition.  
  3. Easier to catch up – more detailed and broken down structure allow to learn the process of application communication faster.
  4. Easier to develop using OSI because of lack of complications, updating the architecture will be less complex.
  5. Multi-vendor availability – by using the same standards , it allows different computers and networking gear interact with each other in the same network.
  6. Modular engineering – different vendors – comanies can write software for various layers, for example company A writes software for Application layer, where Company B goes lower and works with Network layers.

Benefits of TCP/IP:

  1. Independent form operation system
  2. Good choice for salable infrastructure.
  3. Helps to establish connection between 2 types of computers.
  4. Provides and establishes connection between organizations.
  5. Supports a big range of protocols.
  6. And more!

Difference betwen TCP/IP and OSI:

I can point the most simple and fundamental differences between them:

  1. Different headers size: 5 bytes on OSI vs 20 bytes on TCP/IP
  2. OSI is good for setting and standardtize motherboard, routers, switches (hardware) vs TCP/IP helps to establish communication between 2 computers.

If you are interested in networking architecture and it’s concepts, I would recommend the CISCO certification, there are a lot of thing to learn and explore, the whole science. Giving the brief information on TCP/IP and OSI models, it should give you a little understanding which model to use and when!

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