OSI Model Layers and Network Infrastructure Fundamentals

The Seven Layers of the OSI Reference Model

Physical Layer (Layer 1)

The Physical Layer of the OSI reference model is responsible for the physical connections of the computer to the network. It is responsible for transmitting bits of information through the medium used for transmission.

Data Link Layer (Layer 2)

The Data Link Layer is concerned with physical addressing, network topology, network access, error notification, ordered distribution of frames, and flow control.

Network Layer (Layer 3)

The aim of the Network Layer is to ensure data arrives from the origin to the destination, even though both are not connected directly. The devices that facilitate such a task are called routers.

Transport Layer (Layer 4)

The function of the Transport Layer is to carry data (found in the package) from the source machine to the destination, regardless of the type of physical network being used.

Session Layer (Layer 5)

This layer is responsible for maintaining and controlling the dialogue between the two computers that are transmitting data. It is responsible for maintaining the link between the two computers during data transmission.

Presentation Layer (Layer 6)

The Presentation Layer is responsible for managing the data structure and performing conversions of the abstract representation of data necessary for the correct interpretation of them.

Application Layer (Layer 7)

The Application Layer provides applications (or users) access to the services of other layers and defines the protocols used by applications to exchange data, such as email (POP and SMTP), database management, and file servers (FTP). The user typically does not interact directly with the implementation level; they usually interact with programs that, in turn, interact with the application level.

Essential Networking Concepts and Definitions

• Network (Red): Some computers and/or devices connected to each other so that they can share information, services, and resources.
• Protocol: A set of preset rules to reach a common agreement.
• Network Topology: Bus, Token Ring, and Star.
• Geographical Classifications: LAN, MAN, WAN, and CAN (Campus).
• Types of Networks: Peer-to-Peer (Point-to-Point) or Client-Server.
• Internet: A public network (Red Public).
• Intranet: A private network.
• Extranet: A private network with access granted to authorized third parties.
• Computer (Compu): CPU, primary memory (Memo Pcipal), secondary memory, input devices, output devices, and communications.
• Buses: Data, direction, and control.
• System Software (Soft System): Operating Systems such as Windows, Linux, and Unix.
• Application Software (Soft Applications): Programming languages (Cobol, Visual, Assembler) and Office suites.
• Database (BD): Designed to retrieve data fast, safely, and effectively.