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TCP/IP vs. OSI: What’s the Difference?

Author Moore

Date 03/25/2023

The OSI and TCP/IP models are two fundamental conceptual models used to describe the network communication process. This article will elucidate the distinctions between these two models.

Ethernet Switches play a crucial role in data transfer between devices in computer networking, operating at different layers of the Open Source Interconnect (OSI) model which refers to the layer of a generic protocol. The generic protocol model specifies common rules for sending and receiving packets between different network layers. Layer 2 switches forward packets using MAC addresses within the same network, while Layer 3 switches use IP addresses to transfer data between different networks. Apart from the OSI model, the Transmission Control Protocol (TCP) and Internet Protocol (IP) model is another conceptual model used to describe network communication, consisting of four layers. The OSI has seven and TCP/IP has four layers. Understanding these models is vital for efficient and secure network design and implementation.


OSI Reference Model Layers


The OSI model consists of seven layers as a conceptual framework that standardizes the division of labor and interaction among various software and hardware components involved in network communication.



Layer 7: Application Layer


The OSI model's application layer is responsible for providing communication functions to software applications as needed, making it the layer closest to end users. Its primary functions include confirming the availability of communication resources and partners to facilitate data transfer. Additionally, this layer defines protocols for end applications, such as DNS, FTP, HTTP, IMAP, POP, SMTP, SNMP, and Telnet (which emulates a terminal).


Layer 6: Presentation Layer


The compatibility of data with communication resources is checked by the presentation layer, which can convert it into a format that is acceptable to both the application layer and lower layers. It ensures that data is transmitted accurately by formatting it in a way that the receiving application can understand. This layer is responsible for data compression, encryption, and decryption, and it also handles the conversion of data between different character encoding schemes. The presentation layer's main objective is to ensure that the data received by the application layer is presented in a format that the application can understand, regardless of the underlying network protocols used for transmission. The presentation layer is responsible for safeguarding the integrity of data transmission and ensuring accuracy and security during data transfer.


Layer 5: Session Layer


The session layer manages the communication links between computers. Its primary functions are to create, manage, sustain, and terminal the connections between the local and remote applications. Additionally, Layer 5 software handles authentication and authorization processes and ensures the successful delivery of data.


Layer 4: Transport Layer


The transport layer is responsible for transmitting data sequences from the source host to the destination host. It ensures that the data being transferred is of high quality and integrity via error correction and similar functions. One of the main functions of the transport layer is to provide explicit flow control, which helps to manage the rate at which data is sent and received to prevent network congestion. Although the TCP and User Datagram Protocols (UDP) do not strictly conform to the OSI model, they are considered essential protocols in layer 4 due to their ability to handle data transmission in different scenarios. The transport layer can make sure the data transmission is more efficient and reliable.

Layer 3: Network Layer


The network layer manages packet routing using logical addressing and switching functions. A network connects multiple nodes, and each node has an address. When a new message is transmitted from one node to another, it provides the message content and the destination node's address, and the network delivers the message to the destination node, The network might split a lengthy message into multiple segments and transmit them individually, possibly redirecting them through other nodes. reassembling the fragments at another node.


Layer 2: Data Link Layer


The data link layer serves as a means of transferring data from node to node, handling the packaging and unpacking of information into frames. Additionally, it defines protocols for establishing and terminating connections between physically connected devices, such as Point-to-Point Protocol (PPP). The data link layer is typically comprised of two sublayers, one called the media access control (MAC) layer, and the other one is the logical link control (LLC) layer. The MAC layer is responsible for managing how devices in a network gain access to media and obtain permission to transmit data, while the logical link control layer can identify and encapsulate network layer protocols, as well as oversee error checking and frame synchronization.


Layer 1: Physical Layer


The physical layer defines the medium on which data is transmitted and defines all the electrical and physical specifications of all data transmission links. such as the voltage levels, current, and signaling rate of the transmission medium, and the characteristics of the transmission medium, such as fiber type, bandwidth, and operating wavelength. Additionally, it ensures the accurate transmission and reception of data by encoding, modulating, and detecting errors in the signals. Ultimately, the physical layer is responsible for converting digital data into signals that can be transmitted over the communication medium.


TCP/IP Model Layers


The TCP/IP model, which is also referred to as the Internet protocol suite, is a layered reference model consisting of four layers. Although TCP and IP are the foundational protocols and give the model its name, there are not only TCP/IP protocols but also other protocols utilized within this framework.


Application Layer


In the TCP/IP model, the application layer enables applications to access services from other layers and establishes the protocols utilized by applications to exchange data. Some well-known protocols in the application layer are HTTP, FTP, SMTP, Telnet, DNS, SNMP, and the Routing Information Protocol (RIP).


Transport Layer


The host-to-host transport layer, also referred to as the transport layer, works for furnishing the application layer with session and datagram communication services. The primary protocols employed by this layer include TCP and UDP. TCP delivers a dependable communication service that is connection-oriented and one-to-one. It assumes responsibility for ordering and acknowledging transmitted packets, as well as retrieving any lost packets during transmission. On the other hand, UDP offers a connectionless, one-to-one, or one-to-many, unreliable communication service. It is commonly utilized when transferring small amounts of data that can fit into a single packet.


Internet Layer


The Internet layer bears the responsibility of executing host addressing, packaging, and routing tasks. Its main protocols include IP, ARP, ICMP, and IGMP. IP, a routable protocol, handles IP addressing, routing, packet fragmentation, and reassembly. ARP, on the other hand, discovers the network access layer address, which may refer to a hardware address associated with a specific Internet layer access. ICMP provides diagnostic functionalities and error reporting in case IP packet delivery fails. IGMP manages IP multicast groups. The IP header, which contains the IP address, is added to the packets in this layer. Presently, both 32-bit IPv4 and 128-bit IPv6 addresses are in use.