Networks

Networks

1. Define Computer Networks

   • Networks are systems that are formed by links. For example, roads that connect groups of people together create a physical network.
     • People use the following networks every day:
       • Mail delivery system
         • Telephone system
           • Public transportation system
             • Corporate computer network
               • The Internet
   • Networks share information and use various methods to direct the manner in which information flows. The information on the network goes from one place to another, sometimes via different paths, to arrive at the appropriate destination. For example, the public transportation system is a network similar to a computer network.
   • A host is any device that sends and receives information on the network. Some devices can serve either as hosts or peripherals. For example, a printer connected to your laptop that is on a network is acting as a peripheral.
     • Many different types of devices can connect to a network:
       • Desktop computers
         • Laptop computers
           • Tablet computers
             • Smartphones
               • Printers
                 • File and print services
                   • Game consoles
                     • home appliances
   • Computer networks are used globally in businesses, homes, schools, and government agencies. Many of the networks are connected to each other through the Internet.
     • A network can share many different types of resources and data:
       • Services, such as printing or scanning
         • Storage space on removable devices, such as hard drives or optical drives
           • Applications, such as databases
             • Information, stored on other computers
               • Documents
                 • Calendars, synchronizing between a computer and a smartphone
   • Network devices link together using a variety of connections:
     • Copper cabling - Uses electrical signals to transmit data between devices
       • Fiber-optic cabling - Uses glass or plastic fiber to carry information as light pulses
         • Wireless connection - Uses radio signals, infrared technology, or satellite transmissions

2. Features and benefits

   • The benefits of networking computers and other devices include lowered costs and increased productivity. In a network, resources can be shared to reduce data duplication and data corruption
     • Require Fewer Peripherals
       • Each computer on the network does not need to have its own printer or backup device. Multiple printers can be set up in a central location and shared among the network users
         • Increase Communication Capabilities
           • Networks provide several different collaboration tools that can be used to communicate between network users. Online collaboration tools include email, forums and chats, voice and video, and instant messaging.
             • Avoid File Duplication and Corruption
               • A server manages network resources. Servers store data and share it with users on a network. Confidential or sensitive data can be protected and shared with the users who have permission to access that data.
                 • Lower Cost Licensing
                   • Application licensing can be expensive for individual computers. Many software vendors offer site licenses for networks, which can dramatically reduce the cost of software.
                     • Centralize Administration
                       • Centralized administration reduces the number of people needed to manage the devices and data on the network, reducing time and cost to the company. Individual network users do not need to manage their own data and devices.
                         • Conserve Resources
                           • Data processing can be distributed across many computers to prevent one computer from becoming overloaded with processing tasks.

3. Types of Networks

   • LANs
     • This type of network is called a Local Area Network (LAN). A LAN can be as small as a single local network installed in a home or small office. Over time, the definition of a LAN has evolved to include interconnected local networks consisting of many hundreds of devices that are installed in multiple buildings and locations.
   • WLANs
     • A Wireless LAN (WLAN) is a LAN that uses radio waves to transmit data between wireless devices. In a traditional LAN, devices are connected together using copper cabling.
   • PANs
     • A personal area network (PAN) is a network that connects devices, such as mice, keyboards, printers, smartphone, and tablets within the range of an individual person. All of these devices are dedicated to a single host and are most often connected with Bluetooth technology.
   • MANs
     • A metropolitan area network (MAN) is a network that spans across a large campus or a city. The network consists of various buildings interconnected through wireless or fiber optic backbones.
   • WANs
     • A wide area network (WAN) connects multiple smaller networks such as LANs that are in geographically separated locations. The most common example of a WAN is the Internet. The Internet is a large WAN that is composed of millions of interconnected LANs.
   • Peer-To-Peer
     • In a client/server network, the client requests information or services from the server. The server provides the requested information or service to the client. Servers on a client/server network commonly perform some of the processing work for client machines, for example, sorting through a database before delivering only the records requested by the client.
   • Client/Server
     • In a peer-to-peer network, there is no hierarchy among the computers, nor are there any dedicated servers. Each device, also called a client, has equivalent capabilities and responsibilities. Individual users are responsible for their own resources and can decide which data and devices to share or install.

4. Network devices

   • Modems
     • A modem is an electronic device that connects to the Internet via an ISP. The modem converts digital data to analog signals for transmission over a phone line. Because the analog signals change gradually and continuously, they can be drawn as waves. In this system.
   • Hubs, Bridges and Switches
     • Hubs extend the range of a network by receiving data on one port and then regenerating the data and sending it out to all other ports. A hub can also function as a repeater. A repeater extends the reach of a network because it rebuilds the signal, which overcomes the effects of data degradation over distance.
     • Bridges keep a record of all the devices on each segment to which the bridge is connected. When the bridge receives a frame, the bridge examines the destination address to determine if the frame is to be sent to a different segment or dropped. The bridge also helps to improve the flow of data by keeping frames confined to only the segment to which the frame belongs.
     • Switches are sometimes called multiport bridges. A typical bridge has two ports, linking two segments of the same network. A switch has several ports, depending on how many network segments are to be linked. A switch is a more sophisticated device than a bridge.
   • Routers and wireless access point
     • Routers connect networks to each other. Switches use MAC addresses to forward a frame within a single network. Routers use IP addresses to forward packets to other networks. A router can be a computer with special network software installed or a device built by network equipment manufacturers.