Computer Network Models (Fully Explained)
Networking engineering is a complex endeavor that encompasses software, firmware, chip-level engineering, hardware, and electrical signals. To simplify network engineering, the entire networking concept is segmented into various layers. Each layer is responsible for a specific task and operates independently of the others. However, collectively, nearly all networking functions rely on these layers. The layers exchange data among themselves and depend on one another solely for input and output processing.
Layered Tasks
In the layered architecture of the Network Model, an entire network process is broken down into smaller tasks. Each of these tasks is assigned to a specific layer that focuses solely on processing that task. Every layer performs only designated functions.
In a layered communication system, one layer of a host manages the tasks performed by or to be performed by its corresponding layer at the same level on a remote host. The task can be initiated by either the lowest or the highest layer. If the task originates from the topmost layer, it is forwarded to the layer beneath it for additional processing. The lower layer follows suit, processing the task and passing it down to the next lower layer. Conversely, if the task is initiated by the lowest layer, the process follows the reverse path.
Each layer consolidates all the procedures, protocols, and methods necessary to carry out its specific task. All layers recognize their counterparts through encapsulation headers and trailers.
OSI Model
The Open System Interconnect (OSI) is an open standard applicable to all communication systems. The OSI model, established by the International Standard Organization (ISO), consists of seven layers:
- Application Layer: This layer is tasked with providing an interface for the application user. It includes protocols that interact directly with the user.
- Presentation Layer: This layer specifies how data in the native format of a remote host should be displayed in the native format of the local host.
- Session Layer: This layer is responsible for managing sessions between remote hosts. For instance, after user/password authentication is completed, the remote host keeps this session active for a certain period, avoiding repeated authentication requests during that time.
- Transport Layer: This layer ensures end-to-end delivery of data between hosts.
- Network Layer: This layer handles address assignment and provides unique addressing for hosts within a network.
- Data Link Layer: This layer is tasked with reading and writing data to and from the communication line. It also detects link errors at this level.
- Physical Layer: This layer specifies the hardware components, cabling, wiring, power output, pulse rate, and more.
Internet Model
The Internet operates using the TCP/IP protocol suite, commonly referred to as the Internet suite. This suite outlines the Internet Model, which consists of a four-layer architecture. While the OSI Model serves as a general communication framework, the Internet Model is specifically designed for all communications on the internet. The internet functions independently of its underlying network architecture, as does its model. The layers of this model include:
- Application Layer: This layer outlines the protocols that allow users to interact with the network. Examples include FTP and HTTP.
- Transport Layer: This layer specifies how data should be transmitted between hosts. The primary protocol at this layer is the Transmission Control Protocol (TCP), which ensures that data is delivered in the correct order and manages end-to-end delivery.
- Internet Layer: The Internet Protocol (IP) operates at this layer, facilitating host addressing and recognition, as well as defining routing processes.
- Link Layer: This layer provides the means for sending and receiving actual data. Unlike its counterpart in the OSI Model, this layer operates independently of the underlying network architecture and hardware.
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