Just a few key concepts to show how networking fits into the bigger picture of technology.
OSI Model
The OSI(Open Systems Interconnection) Model is a conceptual framework that standardises the functions of a telecommunication or computing system into seven abstract layers.
Layer 1 (Physical Layer)
It is the first layer in the OSI model and is the bottom most layer(it helps to imagine a pyramid and this layer being at the bottom of it). It is responsible for transmitting raw bitstreams over a physical medium. It deals with the physical connection between devices and uses hardware such as Ethernet Cables, hubs and repeaters.
Layer 2 (Data Link Layer)
This layer provides node-to-node data transfer, a direct link between two physically connected nodes. It ensures that the data frames are sent with proper synchronization, error detection and correction. Switches and bridges operate at this layer and use MAC addresses to identify network devices.
Layer 3 (Network Layer)
This layer concerns with package forwarding and figuring out the best route for packages to travel by using routers to reach the destination network. It's responsible for logical addressing and path determination to ensure that the data reaches the correct destination. Routers work at this layer and use IP addresses to identify devices and determine the most effective path for data transmission.
Layer 4 (Transportation Layer)
Provides end-to-end communication services for applications. It handles the responsibility of the reliable/unreliable delivery of data, segmentation, reassembly of messages, flow control and error checking. Protocols such as TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) function at this layer. TCP offers reliable, connection-oriented transmission with error recovery, while UDP provides faster, connectionless communication without guaranteed delivery.
Layer 5 (Session Layer)
This layer concerns itself with handling the sessions between applications. It establishes, maintains, and terminates connections, allowing devices to hold ongoing communications known as sessions. This layer is important for session checkpointing (inserting synchronization points into network data streams to allow recovery from failures without restarting the session) and recovery, ensuring that data transfer can resume seamlessly after interruptions. Protocols and APIs (Application Programming Interfaces) operate at this layer and coordinate communication between systems and applications.
Layer 6 (Presentation Layer)
This layer acts as the translator between the network format and the application layer (Layer 7). It handles data representation to ensure that the data sent by the application layer of one system is readable by the other's application layer. It does this through things such as data encryption and decryption, converting data formats and data compression. Encryption protocols and data compression techniques operate at this layer to secure and optimize data transmission.
Layer 7 (Application Layer)
This is the topmost layer and provides network services directly to end-user applications. It concerns itself with resource sharing, remote file access, and other network services. Common protocols operating at this layer include HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), and DNS (Domain Name System) for resolving domain names to IP addresses. This layer serves as the interface between the network and the application software.
TCP/IP Model
The Transmission Control Protocol/Internet Protocol (TCP/IP) model is a abridged version of the OSI model. It is tailored for pratical implementation on the internet and other networks.
Link Layer
This is the bottommost and is ressponsible for handling the physical aspects of network hardware and media. It includes technologies such as Ethernet for wired connections and Wi-Fi for wireless connections. This layer corresponds to the Physical and Data Link Layers of the OSI model.
Internet Layer
This layer manages the logical adressing of devices and routing of packets across networks. Protocols such as IP (Internet Protocol) and ICMP (Internet Control Message Protocol) work at this layer. This layer corresponds to the Network Layer in the OSI model.
Transport Layer
At the Transport Layer, the TCP/IP model provides end-to-end communication services that are essential for the functioning of the internet. This includes the use of TCP (Transmission Control Protocol) for reliable communication and UDP (User Datagram Protocol) for faster, connectionless services. This layer ensures that data packets are delivered in a sequential and error-free manner, corresponding to the Transport Layer of the OSI model.
Application Layer
This layer contains protocols that offer specific data communication services to applications. Protocols such as HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), and SMTP (Simple Mail Transfer Protocol) are used at this layer and enable functionalities such as web browsing, file transfers, and email services. This layer corresponds to the top three layers of the OSI model: Session, Presentation, Application, providing interfaces and protocols necessary for data exchange between systems.
Protocols
Protocols are standardized rules that determine the formatting and processing of data to facilitate communication between devices in a network
HTTP (Hypertext Transfer Protocol) : Used for transferring web pages, allows browsers and servers to communicate in the delivery of web content. (Application Layer)
FTP (File Transfer Protocol) : Facilitates the transfer of files between systems. It provides a way for users to upload or download files to and from servers. (Application Layer)
SMTP (Simple Mail Transfer Protocol) : Handles the transmission of email and is responsible for sending messages from one server to another, ensuring they reach their intended recipients. (Application Layer)
TCP (Transmission Control Protocol) : Ensures reliable data transmission through error checking and recovery. It also establishes a connection between sender and receiver to guarantee the delivery of data in the correct order. (Transport Layer)
UDP (User Datagram Protocol) : Allows for fast, connectionless communication, which operates without error recovery and therefore makes it ideal for applications that require speed over reliability, such as streaming services. (Transport Layer)
IP (Internet Protocol) : Used for routing packets across network boundaries and handles the addressing and routing of packets to ensure they travel from the source to the destination across diverse networks. (Internet Layer)
