OSI architecture

Thebestindonesia.com – To accommodate the need for communication between different types of computers, an international standard governing the architecture of communication between computers is needed. The advantages of this international standard are:

• Vendors will feel compelled to implement these standards to hope their products will be more widely accepted in the market.
• Computer users hope that vendors implementing these international standards will offer a variety of products they need.

The communication architecture standard that can accommodate communication needs between various types of computers is the open system (OSI). OSI is based on the concept of cooperation between distributed applications. The design accommodated in OSI includes the computer itself, software, and peripheral devices installed on the computer, including the terminal.

OSI models

In OSI, the communication function is divided into several layers (layers) arranged hierarchically. Each layer performs several functions needed to communicate with other systems. Each layer operates by relying on the layer below it to perform more specific functions, and at other times the coating provides the services needed by the layer above it.

OSI layers

1. Physical Layer

This layer provides the physical interface between data transmission devices and transmission media and the rules required for data exchange. Some of the important characteristics of the physical layer include the following:

• Mechanics relating to terminal points or baffles. For example, a connector with a certain number of pins is connected to a signal-sending wire.
• Electrical related to the required voltage level and timing (time setting) to determine the bit conditions. This characteristic determines the data rate and distance that can be achieved in sending data.
• Functional: determines the function that needs to be carried out by each conductor of the conducting medium. For example, some conductors function to transmit data while others transmit control signals.
• Procedural: determines the sequence of events in sending data. This order is based on their functional characteristics. For example, a control signal sent from one terminal will be followed by a corresponding control signal from another terminal.

Examples of physical layer standards used in OSI include RS-232. C and EIA-232-D.

Read also : Computer and Network Security

2. Data Link Layer

Suppose the physical layer only manages the flow bit by bit. In that case, the Data Link Layer deals with reliability issues and provides the functions needed to enable, maintain and deactivate a data transmission link. The main working principle of the Data Link Layer is to present data to the required layer to manage the transmission link (link).

3. Network Layer

The network layer provides the services required to send information between computers over some short communication networks. The network layer provides the functions for establishing, maintaining, and terminating connections over several networks. At this layer, the computer system dialogues with the network to determine the destination address. It requires certain facilities, such as priority. . In such cases, the communication function can be entirely handled by the data link layer. One of the most popular OSI standards for the network layer is X.25.

Read also : Computer Networks and Distributed Systems

4. Transport layers

The transport layer provides a reliable mechanism for exchanging data between computers. This layer ensures that the data sent is entirely free of errors in sequential/chronic conditions and there is no loss or duplication of data.

The transport layer also takes care of optimizing the use of network services and providing the required quality of service. For example, the transport layer determines maximum delay, priority, and security.

Read also : Distributed Process Management

5. Session Layer

The Session Layer provides a dialog control mechanism between two systems. In some cases, only a few roles are needed for this session layer, and often, this layer is not needed at all. Some of the primary services provided by this layer are:

• Dialogic discipline: this can be simultaneous two-way (full duplex) or two-way back and forth (hall duplex).
• Grouping: data streams can be tagged to define data groups.
• Recovery: in this case, the session layer provides a mechanism in which if there is a failure in one of the data-sending processes, the session layer will send back all the data from beginning to end.

6. Presentation Layer

At this layer, the data format sent by each application is set. Thus, the presentation layer provides the services needed for the data transformation process. For example, this layer provides facilities for data compression and encryption.

7. Application Layer

The application layer provides facilities for application programs to communicate with the OSI environment. This layer provides the management functions and mechanisms generally required to support distributed applications such as file transfers, e-mail, and remote access to a computer terminal.