The OSI (Open Systems Interconnection) model is a conceptual framework that defines how network protocols and systems interact and communicate with each other. Which is interesting to know and essential for understanding the nuts and bolts of the "internet". It consists of seven layers, each with its own specific functions and responsibilities. Here's a short overview of the OSI model from top to bottom:
7. Application Layer: This is end user layer. It represents end-user or application-specific functionality. Simply a network process to applications that allows to access network services and interact with the network.
- Protocols: HTTP, FTP, DNS, SSH, P2P, SMTP etc.
- Attack: exploit
6. Presentation Layer:
- This layer deals with the syntax and semantics of the data exchanged between applications. It performs data translation, compression, encryption, and formatting to ensure compatibility between different systems.
- Protocols: HTML, DOC, JPEG, SSL/TLS etc.
- Attack: Phishing
5. Session Layer:
- This Layer establishes, manages, and terminates connections between applications. It provides mechanisms for session establishment, maintenance, and synchronization between communicating entities. Starter of interhost communication.
- Protocols: API, Sockets, WinSock etc.
- Attack: Hijacking.
4. Transport Layer:
- The Transport Layer ensures reliable and efficient data delivery between end systems. It segments data from the upper layers into smaller units (segments/packets) and provides error recovery and flow control.
- Protocols: TCP, UDP.
- Attack: Reconnaissance/ DOS.
3. Network Layer:
- The Network Layer enables end-to-end communication between hosts across different networks. It defines logical addressing, routing, and packet forwarding. Routers operate at this layer.
- Protocols: IP, IPsec, IGMP, ICMP, OSPF etc.
- Attack: MITM, Sniffing.
2. Data Link Layer:
- The Data Link Layer provides reliable point-to-point or point-to-multipoint data transfer between network nodes. Data chunk from uper level devided into smaller unites knows as frame. It handles error detection and correction, framing, and flow control. Ethernet switches operate at this layer.
- Protocols: Aloha, CSMA, PCF, DCF etc.
- Attack: Spoofing, Sniffing.
1. Physical Layer:
- The Physical Layer deals with the physical transmission of data bits over the network medium. It defines the electrical, mechanical, and physical characteristics of the physical medium, such as cables, connectors, and signaling. Direct binary transmission between devices.
- Includes: Cables, hub, repeaters, SDH, DSL, DSLAM etc.
- Attack: Sniffing.
The OSI model provides a standardized framework for understanding network communication processes, allowing different network protocols and technologies to interoperate effectively. Each layer has specific functions and interacts with adjacent layers using defined protocols and interfaces. Well that is a topic for another blog. There are certain layer overlapes in technologies/protocols like routers consist layer 3 to 1. Switch consists layer 2 and 1. Bluetooth technology requires all seven layers and many more. This is a basic overview of the model. How altogether works? This is another topic of blog. Stay tuned..
One more thing, to memorize the layers, a phrase can be used such “Please Do Not Throw Sausage Pizza Away”.
