An internet work is a collection of individual networks, connected by intermediate networking devices, that functions as a single large network. The networking devices are the vital tools for communication. Whenever you have a set of computers or networking devices to be connected, you make the connections, depending on the physical layout and your requirements Depending on the physical layout or topology of the network, there are three types of networks.
LAN
LAN stands for Local Area Network. These networks evolved around the PC revolution. LANs enabled multiple users in a relatively small geographical area to exchange files and messages, as well as access shared resources such as file servers.
WAN
WAN stands for Wide Area Network. The interconnection of various LAN’s through telephone network, which unites geographically distributed users is achieved through WAN. In short when we log on to the internet, we become a part of a WAN.
MAN
MAN stands for Metropolitan Area Network. It is usually the interconnection between various LAN’s in a particular geographical area like a metropolitan city like Bombay. Hence the name.
Internetworking evolved as a solution to three key problems: isolated LANs, duplication of resources, and a lack of network management. Isolated LANS made electronic communication between different offices or departments impossible. Duplication of resources meant that the same hardware and software had to be supplied to each office or department, as did a separate support staff. This lack of network management meant that no centralized method of managing and troubleshooting networks existed.
Open Systems Interconnection Model
The OSI model is the basic model describing the data movement through a network. The Open Systems Interconnection (OSI) reference model describes how information from a software application in one computer moves through a network medium to a software application in another computer. The OSI reference model is a conceptual model composed of seven layers, each specifying particular network functions. The OSI model divides the tasks involved with moving information between networked computers into seven smaller, more manageable task groups. A task or group of tasks is then assigned to each of the seven OSI layers.
The following list details the seven layers of the Open System Interconnection (OSI) reference model:
• Layer 7—Application layer (A)
• Layer 6—Presentation layer (P)
• Layer 5—Session layer (S)
• Layer 4—Transport layer (T)
• Layer 3—Network layer (N)
• Layer 2—Data Link layer (D)
• Layer 1—Physical layer (P)
Tip To Remember
People Do Need To Send Packets Away.
The first letter of each word is related to the alphabet associated with the name of the OSI layer. P of People stands for Physical Layer of the OSI model and so on.
Protocol
The OSI model provides a conceptual framework for communication between computers, but the model itself is not a method of communication. Actual communication is made possible by using communication protocols. In the context of data networking, a protocol is a formal set of rules and conventions that governs how computers exchange information over a network medium. A protocol implements the functions of one or more of the OSI layers. A wide variety of communication protocols exist, but all tend to fall into one of the following groups: LAN protocols, WAN protocols, network protocols, and routing protocols. LAN protocols operate at the network and data link layers of the OSI model and define communication over the various LAN media. WAN protocols operate at the lowest three layers of the OSI model and define communication over the various wide-area media. Routing protocols are network-layer protocols that are responsible for path determination and traffic switching. Finally, network protocols are the various upper-layer protocols that exist in a given protocol suite.
This being the beginning session, I haven’t dwelled into the details. Lets start small and end big! So till then get these fundamentals ingrained in your mind.

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