OSI model

Layer 1 Physical layer

The Physical layer is the first layer of the OSI model, overseeing the transmission and reception of unstructured raw data across physical media. It encompasses the hardware specifications, including cables, switches, and signals, as well as the physical infrastructure aspects like voltages, pin configurations, and data rates.

Layer 2 Data link

The Data Link layer is the second layer of the OSI model, responsible for node-to-node data transfer and error detection and correction. It ensures reliable communication between directly connected devices and manages how data packets are framed and addressed. Ethernet, switch, bridge are key technologies at this layer.

Layer 3 Network

The Network layer is the third layer of the OSI model, responsible for routing data packets between devices across different networks. It manages logical addressing and determines the best path for data transmission, utilizing protocols like IP, ICMP, IPSec, and IGMP.

Layer 4 Transport layer

The Transport layer is the fourth layer of the OSI model, responsible for end-to-end communication and data flow control. It ensures complete data transfer, manages error recovery, and can offer services like segmentation and reassembly of data streams, utilizing protocols such as TCP and UDP.

Layer 5 Session layer

The Session layer is the fifth layer of the OSI model, responsible for establishing, maintaining, and terminating communication sessions between applications. It manages session control and synchronization, ensuring that data exchanges resonate correctly across applications. API’s, sockets, and WinSock are important components at this layer.

Layer 6 presentation layer

The Presentation layer is the sixth layer of the OSI model, responsible for translating, encrypting, and compressing data for the application layer. It ensures that data is presented in a readable format, adapting data structures between different systems. SSL, SSH, IMAP, FTP, MPEG, JPEG and other formats are associated with this layer.

Layer 7 application layer

The Application layer is the seventh layer of the OSI model, closest to the end user. It provides interfaces and protocols for applications to communicate, enabling services such as email, file transfers, and web browsing. HTTP, FTP, IRC, SSH, DNS and other protocols operate at this layer.