What Is the OSI Model?

What Is the OSI Model?

The OSI Model, also known as the Open Systems Interconnection Model, is one of the original models that computers used to communicate with each other across a network.

While the internet doesn’t use the OSI Model, it is used in many other applications and is important to understand.

Where Is the OSI Model Used?

The OSI Model isn’t as streamlined or straightforward as the TCP/IP Model, so techs use it in specific situations.

One of the most common reasons to use an OSI model is to ensure proper data security across levels. For example, an OSI Model may be more appropriate if a company has multiple transactions across vendors and the data needs to be secure.

What Are the Layers of the OSI Model?

There are seven layers to the OSI Model, each with an independent function.

Layer 1: Physical Layer

The first layer of the OSI Model contains any physical or electrical requirement for connection across networks, including wire composition and voltage requirements.

Data passes physically along a wire at this level in strings of 1s and 0s.

Layer 2: Data Link Layer

The second layer of the OSI Model is the level where data transfers across two physically connected nodes. This layer contains protocols for data communication across multiple nodes, and data generally passes across a chain of nodes so that the end-to-end connection occurs smoothly.

Layer 3: Network Layer

The Network Layer organizes data pathways for optimization of data transfer. This layer can sometimes fragment data to make the transfer more efficient.

This layer is where an IP Protocol or other routing protocols might occur.

Layer 4: Transport Layer

The Transport Layer, as the name suggests, takes the work of the lower levels and builds upon it to ensure end-to-end data transfer from the sender to the receiver. It reduces pressure on the upper levels by doing the bulk of the base work.

Layer 5: Session Layer

This layer provides instantaneous two-way communication between parties for an application. This layer is necessary for the application layer (layer seven) to function properly.

This layer is responsible for the recent ease of online shopping and the ability to instantly place items in a cart or bid on auctionable items.

Layer 6: Presentation Layer

The Presentation Layer is responsible for one-sided interaction with an application. If you only need a presentation view to interact with text or a video, this layer provides the necessary data to have the information presented to you.

This layer has an additional function. Encryption and decryption of data take place at the Presentation Layer.

Layer 7: Application Layer

The application layer holds all of the protocols for device communication across the network. This is the highest level of the model because it doesn’t give services to any other layer, but rather uses the supports laid out by the lower levels.

All Together

The OSI Model calls its parts ‘layers’ for a reason. Starting from the ground up, each piece supports the function of the next layer. Many call the model layers a ‘stack’ when working together because they build off each other.

How Is the TCP/IP Model Different Than the OSI Model?

The TCP/IP Model combines the Physical Layer and the Data Link Layer into a network interface. The Presentation, Session, and Application layers of the OSI Model are all condensed into an Application layer in the TCP/IP Model.

The internet uses the TCP/IP Model because of its simple and quick nature. The TCP/IP layer is older than the OSI layer, and more people have implemented it than the OSI Model.

The TCP/IP Model is simpler to set up, but it is generally harder to troubleshoot or resolve issues with this model.

What Are Some Advantages of the OSI Model?

The OSI Model has several advantages. Some of these include:

  • A good generic model to start with.
  • It is easier to isolate and locate issues.
  • It is easier to solve problems.
  • The seven layers are highly independent of each other, and problems tend to not flow across layers.
  • Great if you want to build a network yourself.
  • The flexibility of implementation of protocols.
  • Division of communication roles makes layers work less hard.
  • Most device manufacturers support the OSI Model.

What Are Some Disadvantages of the OSI Model?

While there are plenty of good things about the OSI Model, it also has its flaws. Some downsides to the OSI Model include:

  • The OSI Model is more complicated than the TCP/IP Model.
  • Moving across seven layers can make the OSI Model slower.
  • The interdependence of layers that helps isolate issues can also harm information flow if one of the layers isn’t functioning properly.
  • The OSI Model tends to cost more than other models.

In Conclusion

The OSI Model is an important method for connection and communication across networks. Although the TCP/IP Model occurs more frequently, there are many benefits to the segregated layers of the OSI Model.


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Mike K. Watson

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