1-Physical Layer
- The physical layer deals with the transmission of raw data bits over a physical medium, such as copper wires, optical fibers, or wireless channels.
- It defines specifications such as voltage levels, data rates, modulation techniques, and physical connectors.
- Tasks at this layer include signal encoding, modulation, line coding, and physical topology management.
- Example devices and protocols: Ethernet cables, fiber optic transceivers, USB, HDMI, IEEE 802.11 (Wi-Fi), IEEE 802.3 (Ethernet).
2-Data Link Layer
- The data link layer is divided into two sublayers: Logical Link Control (LLC) and Media Access Control (MAC).
- LLC provides error detection and correction, flow control, and frame synchronization.
- MAC is responsible for addressing and accessing the shared physical medium, controlling media access through techniques like CSMA/CD (Ethernet) or CSMA/CA (Wi-Fi).
- Tasks include framing, error detection, error correction, and media access control.
- Example devices and protocols: Ethernet switches, Ethernet frames, Point-to-Point Protocol (PPP), IEEE 802.3 (Ethernet), IEEE 802.11 (Wi-Fi)
3-Network Layer
- The network layer is responsible for routing packets from the source to the destination across multiple networks.
- It uses logical addressing (such as IP addresses) to identify devices and determines the best path for data transmission.
- Key functions include addressing, routing, packet forwarding, and fragmentation/reassembly.
- Example devices and protocols: Routers, IP packets, Internet Protocol (IPv4, IPv6), Open Shortest Path First (OSPF), Border Gateway Protocol (BGP).
4-Transport Layer
- The transport layer provides end-to-end communication between hosts and ensures data reliability and integrity.
- It segments and reassembles data into manageable units and provides error detection, flow control, and congestion control mechanisms.
- Key protocols include Transmission Control Protocol (TCP) for reliable connection-oriented communication and User Datagram Protocol (UDP) for connectionless communication.
- Tasks include segmentation, multiplexing, error detection, error recovery, and flow control.
- Example protocols: TCP, UDP, SCTP (Stream Control Transmission Protocol).
5-Session Layer
- The session layer establishes, maintains, and synchronizes communication sessions between applications.
- It manages session setup, maintenance, and termination, including authentication and authorization.
- This layer also handles session checkpointing and recovery in case of failures.
- Example functions include session establishment, data exchange synchronization, and session termination.
6-Presentation Layer
- The presentation layer ensures that data exchanged between applications is readable and usable.
- It handles data translation, encryption, compression, and data formatting for compatibility between different systems.
- Tasks include data encryption/decryption, data compression/decompression, and data format conversion.
- Example functions include data encryption, data compression, and data conversion.
7-Application Layer
- The application layer provides network services directly to end-users and applications.
- It enables user access to network resources and supports various application protocols.
- Tasks include providing user interfaces, managing communication sessions, and supporting network applications.
- Example protocols and applications: HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), DNS (Domain Name System).