Data Networking is a way of electronically moving data from one location to another location. From a high-level view, it includes several protocols interconnected to move the information from one device to another one and it also includes hardware.
The Open Systems Interconnection (OSI) Model is a reference model that provides standardization to Data Networking. In a communication network, there are several types of systems using different hardware that wants to communicate or transfer data over a network. The OSI is of utmost importance in Data Networking because enable interoperability among different type of communication systems.
Layers of the OSI Model
Find in the table below the layers defined in the OSI Model as well as a description. The layers description appear from higher to lower layers.
| Layer | Purpose |
| Application Layer | Provides the sole means for the application process to access the OSIE. Hence the Application Layer has no boundary with a higher layer. |
| Presentation Layer | Provides for the representation of information. It provides for a common representation of the data transferred. |
| Session Layer | Provide the means necessary for cooperating presentation entities to organize and synchronize their dialogue and manage their data exchange. |
| Transport Layer | Provides transparent transfer of data between session-entities and relieves them from any concern with the detailed way in which reliable and cost-effective transfer of data is achieved. |
| Network Layer | Provides the functional and procedural means for connectionless-mode or connection- mode transmission among transport-entities and, therefore, provides to the transport-entities independence of routing and relay considerations. |
| Data Link Layer | Provides functional and procedural means for connectionless-mode among network-entities, and for connection-mode for the establishment, maintenance, and release data-link-connections among network-entities and for the transfer of data-link-service-data-units. A data-link-connection is built upon one or several physical connections. |
| Physical layer | Provides the mechanical, electrical, functional, and procedural means to activate, maintain, and de-activate physical connections for bit transmission between data-link-entities. A physical connection may involve intermediate open systems, each relaying bit transmission within the Physical Layer. Physical Layer entities are interconnected by utilizing a physical medium. |
An example of how it works
Imagine Alice is sending a message to Bob by making a phone. Let’s see some of the steps involved and how it relates to the OSI Model.
Alice marks Bob’s phone number. Once the connection is established Alice talks. When Alice’s message reaches the phone, it is captured by a microphone. The words are translated into an electrical signal to be transmitted to Bob’s phone. The signal is transmitted through wires. When the electrical signal reaches Bob’s phone, the signal is translated to what the receiver hears.
This is, of course, an oversimplified explanation of what really happens. If you were to be studying programming, you can call this description a level of abstraction.
Some elements that you can see in my oversimplified explanation are:
- Telephone, microphone, wires.
- The connection between two phones.
- Procedures to capture and send the message from one telephone to the other one.
The point to remember here is that the process of moving data from one place to another is complex. It involves many subprocesses, hardware, protocols, etc.
Because of this complexity and the variety of hardware that one can find nowadays, the OSI Model gives us a practical way to specify where every part of the communication will happen and what protocols must be used to guarantee interoperability among all the devices involved in data networking.
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