Chapter 1 vii content.docx

Basic components of a network Computers are connected to a network using some special hardware devices called network devices or components of a computer network. Below are the different components of a computer network Server A server is a computer that manages the network resources, software an...

Basic components of a network Computers are connected to a network using some special hardware devices called network devices or components of a computer network. Below are the different components of a computer network Server A server is a computer that manages the network resources, software and files. It is normally dedicated to an allocated task and it performs no other task. For example, a file server is a computer that manages storage and retrieval of files. A print server is a computer that manages one or more. printers required on a network. Workstation A workstation is a computer intended for individual use in a networking environment. It is like a personal computer except that it is also connected to other computers and to the main computer, that is, the server. Network Interface card A network interface card (NIC) is a piece of hardware placed inside the system unit. It is part of the motherboard, the platform which connects all the different parts of a computer. It is designed to allow computers to communicate over a computer. It provides physical access to a networking medium. Hub A hub is a device that connects multiple devices and makes them work as a single network segment. A hub has multiple ports. A specific cable connects the hub to the NIC. The NIC transfers the data on a computer to a hub, which then transfers it to the other connected computers. Transmission channels Each computer on a network is interconnected through transmission channels. These channels can be wired or wireless. Data is exchanged between two computers on a network using these channels The wired channels can be cables such as twisted pair, axial and fibre-optics. The wireless channels can work through satellites using microwaves or radio waves. You will learn more about the types of transmission channels later in this chapter. Different FACT FILE A switch is a smarter replacement of a hubs A hub transfers the data received from an NIC to all the computers, a switch transfers it to the specific computer. Types of network A network can be categorised by geographical area Personal Area Network (PAN) This is a network for communication among personal devices. The devices can include mobile phones, computers, cameras, laptops and tablets. These devices are connected through a wired or wireless 'Personal Area Network'. A PAN covers a short radius of only a few meters. It is used to share or transfer files, songs, etc. A USB cable is used to connect a wired PAN. Bluetooth and Wi-Fi are part of a wireless PAN. Local Area Network (LAN) When computers are interconnected within a limited geographical area, they form a \"Local Area Network. For example, a u network within a building. Such a network covers a radius of a few kilometers. an office or a school.In addition to operating in a limited space, LANs are also typically owned, controlled and managed by a single person or organization. A LAN which is created with the help of Wi Fi, without using cables, is called a WLAN. Wide Area Network (WAN) When a network is spread across cities, countries or even continents, covering a large geographical area, it becomes a \"Wide Area Network\". The internet is the largest WAN, covering the world. Metropolitan Area Network (MAN) When computers are interconnected within the same geographical area, for example in different branches of an organization in one city, it becomes a \'Metropolitan Area Network. Local libraries or different divisions of the same school in a city are examples Client-Server architecture Client-Server architecture is defined as a specific type of network which consists of a single powerful computer acting as a server, usually connected to multiple computers called clients. Generally one server supports many clients. The server has powerful central processors, added memory, and larger disk drives in comparison to the clients. A server device typically stores files and databases including more complex applications like websites. The client contains the software programs based on the requirements of its users. Network clients make requests to a server by sending messages, and servers respond to their clients by acting on each request and returning results. A client-server network can be used by desktop computers and laptops, as well as other mobile devices that are properly equipped. Client-Server architecture An example of a client-server is when you try to access your bank account from a computer. A client program on your computer forwards the request to a server program at the bank. The server accesses the data of that specific account and sends the request back with the account details to the client computer. Advantage: The centralised handling of data provides increased security For example, password protection which ensures that the data is only available to qualified individuals. Disadvantage: It runs the risk of system overload. If too many different clients attempt to reach a shared network at the same time, there may be a failure or slowing down of the connection. Peer-to-peer architecture Peer-to-peer architecture is a type of network in which each workstation has equivalent capabilities and responsibilities. The workstations are connected to each other but do not have a server. Files can be shared among workstations, and a printer connected to one workstation can be also accessed by other workstations. Peer-to-peer networks can be set up among only a few computers within an office or single room. Such a network is much simpler to set up in comparison to client-server networks. Peer-to-peer architecture Advantage: It supports distributed processing, so the increased load does not affect the system overall. Disadvantage: It does not support centrally managed security, nor does it provide data backup. Network topology The physical arrangement of cables, computers and other peripheral devices to form a network is known as a topology A few examples of network topologies are described below. Bus topology A bus topology is made up of a main single cable with terminators at both ends. It is a shared communication medium that makes the backbone of the system. Computers and other devices including the server are connected to this linear cable for communication. Advantages It is easy to install. It does not require much cabling, so it is very cost effective. Disadvantages. If the backbone cable fails, the entire network stops working. In the case of an entire network shut-down, it becomes very difficult to locate the problem area. Star topology Star topology is the most commonly used topology. In such a setup all the workstations are connected to a central connection point called a hub. Any data that is sent first goes to the central hub and is redirected from there to the destination computer. Advantages: It is easy to add and remove workstations by upgrading the hub It is easy to install. Disadvantages: It requires more cable length. Failure in the central hub will break down the entire network. Ring topology In a ring topology, every workstation has two neighbours for communication purposes. All messages travel through a ring in the same direction either clockwise or anticlockwise. Advantages It is easier to detect faults in the network. Fewer cable wires are required. Disadvantages. A failure in any cable or device breaks the loop, leading to breakdown of the entire network. Adding or removing a device/workstation requires rewiring and re-routing all the existing cables. **Types of transmission channels** The medium used for transmission of data between the nodes in a network is called a transmission channel. This channel can be wired or wireless. **Wired transmission channels** Wired transmission channels help in the transmission of data over a wire-based network. A few examples of wired channels are explained here. Coaxial cable: This is one of the cheapest and the most commonly used wire-based networking mediums. This type of cable is suitable for transmitting low-powered signals over a small distance. It is widely used in small networks, cable TV, etc. Twisted pair cable. This consists of two independently insulated wires, twisted around one another. The twisting stops the disruption of signals due to adjacent pairs or other sources Fibre-optic cable: This is made up of optical fibres that use the concept of light for transmission of data. High speed data can be made to travel over a long distance with less damage. It is steadily replacing copper wire as an appropriate means of communication through signal transmission. Wireless transmission channels Wireless communication is the transfer of information over a distance without use of wires. It is the fastest growing segment of the communication industry today. The distances involved may be short, that is, a few metres as in the case of a television remote control. They may also be long, as in the case of thousands or millions of kilometres for radio communications. There are many types of wireless networks that make data communication possible, both over long range and short range. All of these networks operate at different frequencies. Some examples of wireless communication are: Remote controls for electronic devices Bluetooth Mobile phones Wireless networking Wireless computer devices like mouses and keyboards Satellite televisions Radio waves There can be various channels for wireles transmission. A few are explained here Radio waves: Radio waves are generally used for long-distance wireless communication. Signals can pass through thick objects such as non-metallic can thick plication (AM/FM), communication satellites, radars, computer networks, etc. Infrared: Infrared is one of the oldest forms of wireless communication. It is an electromagnetic radiation. It is suitable for short-distance communication. For example a television and a remote control connect to each other using infrared rays. The signals travel in a straight line and cannot go through walls. Microwave: Microwave is the most commonly used wireless transmission medium, which is spread widely across the world. Most of the wireless access points and wireless devices work on microwave communication. This communication medium is not only cost effective, it is also extensively used in cellular communication. Bluetooth: Bluetooth is another wireless communication medium operating over short distances. It has a normal range of approximately 3-300 feet depending on the connected devices. These devices can be mobile phones, personal computers, laptops, digital cameras, MP3 players, etc. Bluetooth enabled devices form a small network. In Bluetooth technology, eight devices can be connected to each other at the same time, Bluetooth can also be found in headsets, hands-free kits, wireless keyboards and mouses. Bluetooth uses radio wave technology which is not very expensive and has low power consumption **Mobile operating systems** Initially, when mobile phones were introduced in the late 90s, they were just designed to support making and receiving calls and sending simple text messages. Usage of mobile phones has increased drastically over the last few years, which has brought a huge revolution in the features of mobile handsets. Modern mobile phones are just like a compact computer loaded with basic applications. These mobile applications can be designed and uploaded easily. Wireless establishment of connections can be achieved through Bluetooth and infrared technologies. Mobile phones like this are called smartphones. To manage all these important features in phones, we need a special type of operating system called a Mobile Operating System (or mobile OS). This operating system is used in smartphones, tablets and other mobile devices. Differences between mobile OS and desktop OS Desktop operating systems are designed with computers in mind. They provide an environment that helps different application software to function better, with a wide range of connected hardware. Desktop OS also supports multiple users sharing a network. Mobile phones are compact computers with limited power, processing speed and memory. Keeping these limitations in mind, separate operating systems, specially designed for mobiles, were introduced. The development of both computer and mobile OS is different for different users. The following factors determine the OS requirements for smartphones: A mobile phone is a compact machine with a small battery size, so the OS should be designed in a simple way to work with limited power for a longer period of time. Limited memory is available in mobile phones, therefore the OS should be less complex to occupy less storage capacity. Mobile phones are equipped with an in-built keyboard, so a different Graphical User Interface (GUI) is required. Types of mobile OS The technological advances mentioned above resulted in development of various solutions suitable for the functioning of mobile phones. Some of the popular mobile OS are Android by Google, iOS by Apple, BlackBerry OS by RIM and webOS by Hewlett Packard. A detailed description of these OS is given below. Android OS This is one of the most popular operating systems, designed by Android Inc in Silicon Valley, before Google bought it in 2005. Its first commercial version was officially launched in 2008. It is an open source and freely available Linux-based operating system mainly designed for smartphones and tablets with touchscreens. It has the basic operating system features, with calls and messaging services that can be used to establish connections using different communication networks on different devices. Different versions of the Android OS are named after desserts. For example, Android 1.5 is known as \'Cupcake\', 1.6 as \'Donut\', 2.0/2.1 as \'Eclair\', 2.2 as Froyo\" and 2.3 as \'Gingerbread\". Android 9.0 was the last version given a dessen codename. Since it is an open source system, it can be easily used and modified by anyone, making it more prone to malwares and data stealing 108 This is a mobile operating system designed by Apple Incorporation mainly for iPhos iPods and iPads. It was made available commercially in 2007 as an operating system for iPhones. It is the second most popular mobile operating system after Android. 10s is a closed source system owned by Apple and no other company or person can use it or modify it, therefore providing strong security features against data theft or malware iOS 14 is the latest version of iOS in iPhones and iPads BlackBerry OS This mobile operating system has been developed by Blackberry Limited for its own devices just as iOS has been designed only for iPhones. The BlackBerry platform is best known for strong wireless activation and synchronisation of emails, calendar, notes, contacts and tasks. Blackberry 10 is the latest version of this OS. Nowadays, this mobile OS seems to be losing popularity because of increasing market demand for Android and iOS-based phones. webOS This operating system was developed by Palm Incorporation. It is a Linux-based open source operating system which was taken over by HP and later sold to LG for smart phones and smart TVs. webOS strongly supports multitasking and is better than iOS when running multiple applications at one time. Its various versions are Pre, Pixi and Veer for smartphones. Since 2014, LG has been using webOS for its smart projectors, refrigerators and smart TVs. Mobile applications development Mobile application development is a set of instructions written to develop applications for smartphones and mobile devices. Mobile apps are small software units with limited functionalities. The first mobile apps were device specific, but recently app developers have developed applications that can work efficiently on multiple platforms, including Android and iOS Due to a rapid increase in the use of smartphones, there are now more mobile users in comparison to desktop users. With mobile apps, the user can access general information about any product, prices, booking forms, search features, user accounts, messengers, news feeds and much more. GLOSSARY --------------- ---------------------------------------------------------------------------------------------------------------------------- Android OS An open source and freely available Linux based mobile OS. BlackBerry OS The mobile OS developed by Blackberry Limited for its own devices Client A computer connected to the server on a network. File server A computer connected to the server on a network. Hub The central connection point on a network. IOS The mobile OS designed by Apple Incorporation, mainly for iPhones, iPods and iPads. Mobile OS A special type of operating system for managing important features in smartphones, tablets and other mobile devices. Print server A computer that manages the printers required on a network. Server A computer that manages the network resources. Topology The physical arrangement of computers on a network. webOS A Linux-based open source operating system which was taken over by HP and later sold to LG for smart phones and smart TVs. Workstation A computer intended for individual use on a network.