TCP/IP and OSI layers

Published on: November 10, 2023 by Eric

Both the OSI and TCP/IP models provide a framework for understanding networking, there are some key differences, between them. The OSI Model has seven distinct layers, and is more theoretical and structured while the TCP/IP framework is more practical and streamlined, with four layers and is used in actual networking as opposed to being a refernece model

The OSI model

  1. The Physical layer deals with the physical transmission of data over the network medium, for example encapsulating data into Ethernet frames for transmission
  2. The data link layer is responsible for establishing, maintaining, and terminating connections between devices, including error detection and correction
  3. The network layer enables devices to communicate across different networks, including routing, addressing, and logical addressing (IP addresses)
  4. The transport layer ensures reliable data transmission between hosts. It segments and reassembles data packets, provides flow control, and manages error detection and recovery.
  5. The session layer establishes, maintains, and synchronizes communication sessions between devices, including session initiation, maintenance, and termination.
  6. The presentation layer handles data translation, encryption, and decryption
  7. The application layer provides network services directly to end-users or applications, this includes protocols such as HTTP, SMTP, FTP, and DNS

The TCP/IP Model

The TCP/IP model, also known as the Internet protocol suite, is a more practical and widely used networking model. It consists of four layers that map roughly to the OSI model but have a few differences in functionality

  1. The Link Layer / Network Interface Layer combines the functionality of the OSI model’s physical and data link layers. It handles the physical transmission of data and provides addressing and error detection at the link level
  2. The Internet Layer / Network Layer Equivalent to the OSI model’s network layer, the Internet layer is responsible for routing packets across multiple networks. It utilizes IP addressing and routing protocols like IP, ICMP, and ARP
  3. The Transport Layer is similar to the OSI model’s transport layer, the TCP/IP transport layer provides end-to-end communication services, including protocols like TCP and UDP
  4. The Application Layer corresponds to the OSI model’s application, presentation, and session layers combined. It includes protocols and services that enable user applications to interact with the network, such as HTTP, FTP, SMTP, and DNS