Network

                                                        NETWORK

Network:

      A network is a group of two or more computer systems linked together.

Uses of Network:

1.  To facilitate communication via email, video conferencing, instant messaging, etc.
2. To enable multiple users to share a single hardware device like a printer or scanner
3. To enable file sharing across the network
4. To allow for the sharing of software or operating programs on remote systems
5. To make information easier to access and maintain among network users

There are various types of Networks available it can be shown in below:

•    LAN (Local Area Networks)
•    WAN(Wide Area Networks)
•    CAN(Campus Area Networks)
•     MAN(Metropolitan Area Networks)
•     HAN(Home Area Networks)

1.LAN (Local Area Networks)

     A local area network (LAN) is a computer network that in used to interconnect computers in a single room, rooms within a building or buildings on one site are called Local Area Network (LAN). LAN transmits data with a speed of several megabits per second (106 bits per second). The transmission medium is normally coaxial cables .

Major Characteristics of LAN :

• Every computer has the potential to communicate with any other computers of the network
• High degree of interconnection between computers
• Easy physical connection of computers in a network
• Inexpensive medium of data transmission
• High data transmission rate

Advantages of LAN

• The reliability of network is high because the failure of one computer in the network does not effect the functioning for other computers.
• Addition of new computer to network is easy.
• High rate of data transmission is possible.
• Peripheral devices like magnetic disk and printer can be shared by other computers.

Disadvantages of LAN
If the communication line fails, the entire network system breaks down.

2. Campus Area Networks (CANs): 

   A campus area network (CAN) is a network of multiple interconnected local area networks (LAN) in a limited geographical area. A CAN is smaller than a wide area network (WAN) or metropolitan area network (MAN).A CAN is also known as a Corporate Area Network (CAN).

Advantages of CAN:

• Cost-effective
• Wireless, versus cable
• Multidepartmental network access
• Single shared Data Transfer Rate (DTR)

3.Home-Area Networks (HANs):
           A home-area network (HAN) connects in-home digital devices, such as PCs, mobile phones, entertainment technology, thermostats, home security systems and smart appliances, into a common network. 

Advantages of HAN

• The main advantage of a network is that multiple users can simultaneously interact with each other and share resources for example the internet connection.
• After the home network is created, as many wireless devices like laptops and mobile phones can connect to it *if it's a wireless router that is* and more PC's can also be connected with easy.
• It is easy to create if known how to - we will be explaining at a later stage just how simple it is showing a step to step guide.
• You can also add devices to the network like a printer. This will allow anyone with access rights to be able to print a file on any of the computers connected to the network.

Disadvantages of HAN

• Buying all the equipment required *dependant on how many computers will be on the network* can be expensive
• Complete set up of a network can be difficult and challenging for people who are computer illiterate
• Depending on the network topology type, a broken cable can halt the whole network.
• If the admin of the network doesn't know about securing the wireless on the router, anyone within range could be stealing the Internet connection and in result potentionally have access to personal data.
• "Wireless includes the potential for radio interference due to weather, other wireless devices, or obstructions like walls".

4.Metropolitan Area Networks (MANs)

 A metropolitan area network (MAN) is a large computer network that usually spans a city or a large campus. A MAN usually interconnects a number of local area networks (LANs) using a high-capacity backbone technology, such as fiber-optical links, and provides up-link services to wide area networks (or WAN) and the Internet.

Advantages of MAN

• Sharing of resources such as printers; hence cost effective. 
• It can send local emails.
• It connects all of your computers and servers together on the network , and is typically very fast.

5.Wide Area Networks (WANs)  

          A WAN consists of two or more local-area networks(LANs).Computers connected to a wide-area network are often connected through public networks, such as the telephone system. They can also be connected through leased lines or satellites. The largest WAN in existence is the Internet.

Advantages Of WAN

• Covers a large geographical area so long distance businesses can connect on the one network.
• Shares software and resources with connecting workstations.
•  Messages can be sent very quickly to anyone else on the network. These messages can have pictures, sounds, or data included with them (called attachments).
•  Expensive things (such as printers or phone lines to the internet) can be shared by all the computers on the network without having to buy a different peripheral for each computer.
• Everyone on the network can use the same data. This avoids problems where some users may have older information than others.
• Share information/files over a larger area.
• Large network cover.

Disadvantages Of WAN

•       Are expensive and generally slow.
•       Need a good firewall to restrict outsiders from entering and disrupting the network.
•       Setting up a network can be an expensive and complicated experience.
•      The bigger the network the  more expensive it is.
•      Protection against hackers and viruses adds more complexity and expense.
•      Information may not meet local needs or interests.
•      Vulnerable to hackers or other outside threats.

What is the difference between a LAN, a MAN, and a WAN?

            LAN: A LAN (local area network) is a group of computers and network devices connected together, usually within the same building. By definition, the connections must be high speed and relatively inexpensive.A LAN connection is a high-speed connection to a LAN. On the IUB campus, most connections are either Ethernet (10Mbps) or Fast Ethernet (100Mbps), and a few locations have Gigabit Ethernet (1000Mbps) connections.

         MAN: A MAN (metropolitan area network) is a larger network that usually spans several buildings in the same city or town. The IUB network is an example of a MAN.

        WAN: A WAN (wide area network), in comparison to a MAN, is not restricted to a geographical location, although it might be confined within the bounds of a state or country. A WAN connects several LANs, and may be limited to an enterprise (a corporation or an organization) or accessible to the public. The technology is high speed and relatively expensive. The Internet is an example of a worldwide public WAN.

Topology:
          Toplogy means  in communication networks, it is a usually schematic description of the arrangement of a network, including its nodes and connecting lines. There are two ways of defining network geometry: the physical topology and the logical (or signal) topology.


Physical Topology
        The physical topology of a network is the actual geometric layout of workstations.Graph Theory is used for studying network topology: nodes’ distance, interconnectivity, the rate of transmission and signal’s types of two networks might vary but their topologies could be identical.
The Physical Topologies are seven types.Namely,

1. Point-to-Point topology,
2. Bus (point-to-multipoint) topology,
3. Ring topology,
4. Star topology,
5. Hybrid topology,
6. Mesh topology and
7. Tree topology. 

1.Point-to-Point Network Topology

              It is the basic model of typical telephony. The simplest topology is a permanent connection between two points. The value of a demanding point-to-point network is proportionate to the number of subscribers’ potential pairs. It is possible to establish a permanent circuit within many switched telecommunication systems: the telephone present in a lobby would always connect to the same port, no matter what number is being dialed. A switch connection would save the cost between two points where the resources could be released when no longer required.

2.Bus Network Topology

LANs that make use of bus topology  connects each node to a single cable. Some connector connects each computer or server to the bus cable. For avoiding the bouncing of signal a terminator is used at each end of the bus cable. The source transmits a signal that travels in both directions and passes all machines unless it finds the system with IP address, the intended recipient. The data is ignored in case the address is unmatched. The installation of one cable makes bus topology an inexpensive solution as compared to other topologies; however the maintenance cost is high. If the cable is broken all systems would collapse.

Linear Bus: If all network nodes are connected to a combine transmission medium that has two endpoints the Bus is Linear. The data transmitted between these nodes is transmitted over the combine medium and received by all nodes simultaneously.

Distributed Bus: If all network nodes are connected to a combine transmission medium that has more than two endpoints created by branching the main section of the transmitting medium.

3.Star Network Topology

            The topology when each network host is connected to a central hub in LAN is called Star. Each node is connected to the hub with a point-to-point connection. All traffic passes through the hub that serves as a repeater or signal booster. The easiest Star topology to install is hailed for its simplicity to add more nodes but criticized for making hub the single point of failure. The network could be BMA (broadcast multi-access) or NBMA (non-broadcast multi-access) depending on whether the signal is automatically propagated at the hub to all spokes or individually spokes with those who are addressed.

Extended Star: A network that keeps one or more than one repeaters between the central node or hub and the peripheral or the spoke node, supported by the transmitter power of the hub and beyond that supported by the standard of the physical layer of the network.

Distributed Star: The topology is based on the linear connectivity that is Daisy Chained with no top or centre level connection points.

4.Ring Network Topology

            Ring topology is one of the old ways of building computer network design and it is pretty much obsolete. FDDI, SONET or Token Ring technologies are used to build ring technology. It is not widely popular in terms of usability but incase if you find it any where it will mostly be in schools or office buildings.
Such physical setting sets up nodes in a circular manner where the data could travel in one direction where each device on the right serves as a repeater to strengthen the signal as it moves ahead.

5.Mesh Network Topology

        The exponent of the number of subscribers is proportionate to the value of the fully meshed networks.

Fully Connected: For practical networks such topology is too complex and costly but highly recommended or small number of interconnected nodes.
Partially Connected: This set up involves the connection of some nodes to more than one nodes in the network via point-to-point link. In such connection it is possible to take advantage of the redundancy without any complexity or expense of establishing a connection between each node.

6.Tree Network Topology

The top level of the hierarchy, the central root node is connected to some nodes that are a level low in the  hierarchy by a point-to-point link where the second level nodes that are already connected to central root would be connected to the nodes in the third level by a point-to-point link. The central root would be the only node having no higher node in the hierarchy. The tree hierarchy is symmetrical. The BRANCHING FACTOR is the fixed number of nodes connected to the next level in the hierarchy. Such network must have at least three levels. Physical Linear Tree Topology would be of a network whose Branching Factor is one.

7.Hybrid Topology:

A hybrid is a combination of two or more basic network topologies, such as a star-bus, star-ring, or tieredtopology. In a hybrid topology, central and distributed topologies are combined to meet the needs

an organization.