• सुखार्थी त्यजते विद्यं विध्यार्थी त्यजते सुखम्सु sखर्थीन: कुतॊ विद्या कुतॊ विध्यार्थीन: सुखम् ||
  • “Luxury people leave knowledge, but a student leaves Luxury No knowledge for one who seeks Luxury, No luxury for student”
  • न चोर हार्यं न च राज हार्यं न भात्रू भाज्यं न च भारकारि |व्ययं कृते वर्धत एव नित्यं विद्याधनं सर्वधनप्रधानम ||
  • Cannot be snatched away by thief, cannot be snatched away by king, Cannot be divided among brothers, Not heavy either If spent daily, it always keeps growing. The wealth of knowledge is the precious of wealth of all”

Reference Models

Layered Approach

Network is a combination of hardware and software. The hardware consists of the physical equipment that carries signals. Software consists of instruction sets that make possible the services that we expect from a network.

To reduce complexity, most networks are organized as a stack of layers which can perform independent functions. Each layer is built in a hierarchical fashion. The number of layers, the name of each layer, the contents of each layer, and the function of each layer differ from network to network.


Each layer offers certain services to the higher layers, hiding those layers from the details of how the offered services are actually implemented.

OSI Model

International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards was established in 1947. An ISO standard that covers all aspects of network communications is the Open Systems Interconnection model. It was first accepted in 1979 and published in February 1980.

Why all networking standards come under IEEE802._____ (Institute of Electrical and Electronics Engineers I-80 is for year of induction and 2 is for month February)

An OSI model is a set of protocols that allows any two different systems to communicate regardless of their underlying architecture. OSI model facilitates communication between different systems without requiring changes to the logic of the underlying hardware and software.


The OSI model is not a protocol; it is a model for understanding the network architecture and helps us in designing a flexible, robust and inter-operable network that allows communication between all types of computer systems.

 It consists of seven separate but related layers, each of which defines a part of the process of moving information across a network.

Layers of OSI model

Some mnemonic phrases to help you remember the layers of the OSI model:


All People Seems To Need Double Power  


Please  Do       Not    Take   SPA  


Aaj Phir Se Test  Nahin  Dena  Padega  

Devices used at different layers:

Protocols dealt at different layers: