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Networking ‘n’ its types:
Networking and Its Types
Networking-
* Interconnwction of Two or More Computers and Peripherals.
* Allow users to share information and resources.
Types Of Computer Networks-
There are basically three types of computer Networks-
* LAN(Local Area Network)
* MAN(Metropolitian Area Network)
* WAN(Wide Area Network)
LAN-
* Connects Computers and Workstations covering a local area like Office or Home.
MAN-
* Connects network within a City.
WAN-
* Covers a wide Geographic Area which includes multiple Computers or LANs eg.INTERNET.
computer network
A computer network
can be divided into a small segments called Local Area Network (LAN), networking between computers in a building of a office, medium sized networks (MAN), communication between two offices in a city and wide area networks (WAN) networking between the computers, one is locally placed and the other can be thousands of miles away in another city or another country in the world.
WAN connectivity is achieved by a device known as “Router”. The internet is the world’s largest WAN, where millions of computers from all over the globe and connected with each other.
Networking is the practice of linking two or more computers or devices with each other. The connectivity can be wired or wireless. A computer network can be categorized in different ways, depends on the geographical area as mentioned above.
There are two main types of the computer networking client-server and peer to peer. In the client server computing, a computer plays a major role known as server, where the files, data in the form of web pages, docs or spread sheet files, video, database & resources are placed.
All the other computers in the client/server networks are called clients and they get the data from the server. In the peer to peer networks all the computers play the same role and no computer act as a centralized server. In the major businesses around the world client-server networks model is in major use.
A network topology defines the structure, design or layout of a network. There are different topologies like bus, ring, star, mesh, hybrid etc. The star topology is most commonly used topology. In the star topology, all the computers in the network are connected with a centralized device such as hub or switch. Thus forms a star like structure. If the hubs/switch fails to work for any reason then all the connectivity and communication between the computers will be halted.
A common communication language is used by the computers and the communication devices is known as protocols. The most commonly used and popular protocol on the internet and in the home and other networks is called TCP/IP. TCP/IP is not a single protocol but it is a suite of several protocols.A computer network can be a wired or wireless and TCP/IP protocol can work both in types of a network.Data flow or communication can be divided into seven logical layers called OSI layers model that was developed by Intel and Xerox Corporation and was standardized by ISO.
1. Application layer
2. Presentation layer
3. Session layer
4. Transport layer
5. Network layer
6. Data Link layer
a. Media access control sub-layer
b. Logical link control sub-layer
7. Physical layer
A network can be divided into different scales and ranges and it depends on the requirement of the organization and the geographical location. Computer Network can be divided into Local Area Network, Personal Area Network, Campus Area Network, Wireless Local Area Network, Metropolitan Area Network and Wide Area Network.
There are several communication connection methods like HomePNA, Power line communication, Ethernet and Wifi connection method. A network can also be categorized into several different types based on the services it provides like Server farms, Storage area networks, Value control networks, Value-Added networks, SOHO networks, Wireless and Jungle networks.
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Data Exchange in OSI model………
Information flow: The flow of information is from the top layer (usually application layer) to the physical layer at information source node; and from the physical layer up to the application later at the destination node as illustrated below.
The information exchange process occurs between peer OSI layers. Each layer in the source system adds control information to data and each layer in the destination system analyzes and removes the control information from that data.
If System A has data from a software application to send to System B, the data is passed to the application layer. The application layer in System a then communicates any control information required by the application layer in System B by prepending a header to the data. The resulting information unit (a header and the data) is passed to the presentation layer, which pretends its own header containing control information intended for the presentation layer in System B. The information unit grows in size as each layer prepends its own header (and in some cases a trailer) that contains control information to be used by its peer layer in System B. At the physical layer, the entire information unit is placed onto the network medium.
The physical layer in System B receives the information unit and passes it to the data-link layer. The data link layer in System B then reads the control information contained in the header prepended by the data link layer in System A. The header is then removed, and the remainder of the information unit is passed to the network layer. Each layer performs the same actions: The layer reads the header from its peer layer, strips it off, and passes the remaining information unit to the next highest layer. After the application layer performs these actions, the data is passed to the recipient software application in System B, in exactly the form in which it was transmitted by the application in System A.
OSI Model and TCP/IP Model
The OSI model by IBM is the biggest boon that systems developer can have had for their karma in the past life.
What exactly is the OSI model?
As I had mentioned it is actually a layered stack, with 7 layers. Each of these 7 layers are implemented by different protocols for each layer. But keep in mind, its not necessary that all these layers have to be used, when trying to device a system. A system can also make away with any of the 7 layers like say the Session Layer or the Application Layer.
Consider a Router for example. A Router is a device, which works in the Network Layer of the OSI Model. Its main function is to route packets that arrive at its ports. Router takes a routing decision for each of the packet that arrives at its port, on the basis of Routing Tables.
Routing Tables are somewhat similar to the Time Table we follow while attending our courses in college. Depending on the subject scheduled in the timetable for a particular day, we decide whether to attend the lecture or not. In a similar way the Router looks at the destination address (which is the IP address) of the packet that is to be routed.
Now remember that an IP address is made up of a Host ID and a Network ID (I will cover IP addresses in depth in the future articles). The Router looks at the Network ID and compares it with the other Network ID’s present in its Routing Tables. If the particular Network ID is found to be present in the Router’s Table, the packet is routed to the appropriate destination successfully. If the Network ID of the packet is not present in the Router’s Routing Table, then the router forwards the packet to the next nearest router and this process continues till the packet reaches its intended destination.
This is very similar to what you do when you are asked where someone stays, while walking on the road. You are shown the address by the person, who wants to reach a place (Consider this Address as the Destination IP address). Now what you do is directly look at the name of the street. This is because the name of the building is not something you will be immediately familiar with, as a building with the same name will surely exist in thousand different streets.
If you are very well aware of the geography of the place, then by looking at the Street (Network ID) you tell the person where the street is. ( similar to a Router finding that the Network ID field of the IP address of the packet is present in its Routing Table). If you don’t know the street or the address, you tell the person to ask some one else ( that is you forward him to the next nearest Router).
OSI model doesn’t say you do things this way. It just tells you “ Hey keep in mind that these things should be covered while designing a feasible network solution “.
TCP/IP Model
The TCP/ IP model superseded the OSI model. This is the model that is currently most widely used. The various layers in the TCP/IP model are :
5) Application
4) Transport
3) Internet work
2) Data Link
1) Physical
Note that the Sessions and Application Layer present in the OSI Model are absent in the TCP/IP Model.
In the 1990’s, TCP/IP has become firmly established as the dominant commercial architecture and as the protocol suite upon which the bulk of new protocol development is to be done.
There are a number of reasons for the success of the TCP/IP model over the OSI model:
1. Internet is built on the foundation of the TCP/IP suite. The tentacles of the Internet and the World Wide Web have spread throughout the world and that is the main reason for the success of TCP/IP model over the OSI model.
2. TCP/IP protocols were initially researched under a project in the Department of Defense (DOD). DOD was committed to international standards and most of its operational requirements couldn’t be met by the OSI model. So it started to develop the TCP/IP. Since the DOD is the largest consumer of software products in the world, the vendors were encouraged to develop TCP/IP based products.
In the next article I will cover more about the various layers in the OSI Model and the TCP/IP Model.
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