Lecture 13 & 14

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It for Managers


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Computer Communication Networks & Distributed Database:

Computer Communication Networks & Distributed Database By Arun Mishra

The Concept of Network:

The Concept of Network The term Network means an interconnected or interrelated chain, group, or system. The typical hardware in a network of computers consists of the following components: computers, peripherals such as printers, scanners, plotters and modems, cables, network interface cards, hubs and switches, repeaters, bridges, routers, gateways.

Networks and Corporate Infrastructure :

Networks and Corporate Infrastructure A network consists of two or more connected computers. Each computer on the network contains a network interface device called a network interface card (NIC) . The connection medium for linking network components can be a telephone wire, coaxial cable, or radio signal in the case of cell phone and wireless local area networks.

Networks and Corporate Infrastructure (Continued):

Networks and Corporate Infrastructure (Continued) The network operating system (NOS) routes and manages communications on the network and coordinates network resources. Networks also contain a switch or a hub acting as a connection point between the computers. Hubs are very simple devices that connect network components, sending a packet of data to all other connected devices.

Networks and Corporate Infrastructure (Continued):

Networks and Corporate Infrastructure (Continued) A switch has more intelligence than a hub and can filter and forward data to a specified destination. Switches are used within individual networks. A router is a special communications processor used to route packets of data through different networks, ensuring that the message sent gets to the correct address.

Components of a Simple Network :

Components of a Simple Network

Classification of Networks:

Classification of Networks Local Area Network (LAN) Metropolitan Area Network (MAN) Wide Area Network (WAN) Virtual Private Networks (VPNs) Wireless Networks

Local Area Network (LAN):

Local Area Network (LAN) LAN is a network of computers contained within a limited area say a building. The network provides an intelligent switching capability between the devices for purpose of sharing. For instance an expensive laser printer in network can be shared by many microcomputers in a network.

Local Area Network (LAN):

Local Area Network (LAN) Connects computers within a limited physical area, such as an office, classroom, or building

Metropolitan Area Network (MAN):

Metropolitan Area Network (MAN) A metropolitan area network (MAN) is a network that spans a metropolitan area, usually a city and its major suburbs. Its geographic scope falls between a WAN and a LAN. MANs sometimes provide Internet connectivity for local area networks in a metropolitan region.

Wide Area Network (WAN):

Wide Area Network (WAN) Wide area networks (WANs) span broad geographical distances—entire regions, states, continents, or the entire globe. The most universal and powerful WAN is the Internet. Computers connect to a WAN through public networks such as the telephone system, private cable systems, or through leased lines or satellites.

Wide Area Network (WAN):

Wide Area Network (WAN) Covers a large geographic area

Virtual Private Networks (VPNs):

Virtual Private Networks (VPNs) A virtual private network (VPN) is a private network that has been configured within a public network to take advantage of the economies of scale and management facilities of large networks, including the Internet. The VPN provides the organization with the same capabilities at a much lower cost than owned or leased lines that can be used only by one organization. Although some VPNs run over proprietary networks open only to subscribers, many companies are turning to VPNs based on the Internet Protocol (IP) that run over the public Internet.

Virtual Private Networks (VPNs):

Virtual Private Networks (VPNs)

Network topologies:

Network topologies The three basic network topologies are the bus, star, and ring.

Star Topology:

Star Topology In a star topology, all devices on the network connect to a single hub. a simple star network in which all network components connect to a single hub. All network traffic flows through the hub. In an extended star, multiple layers or hubs are organized into a hierarchy.

Bus Topology:

Bus Topology In a bus topology, one station transmits signals, which travel in both directions along single transmission segment. All of the signals are broadcast in both directions to the entire network. All machines on the network receive the same signals, and software installed on the clients enables each client to listen for messages addressed specifically it. Bus networks are the most common Ethernet topology.

Ring Topology:

Ring Topology A ring topology connects network components in a closed loop. Messages pass from computer to computer in only one direction around the loop, and only one station at a time may transmit. Ring networks are used primarily in older LANs using Token Ring networking software.

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Peer-to-Peer Networks Client/Server Computing Packet Switching TCP/IP and Connectivity Key Digital Networking Technologies

Peer-to-Peer Networks:

Peer-to-Peer Networks In a peer-to-peer network, all nodes have an equal relation to one another. Each node usually has access to some resources on other nodes, so users can share files, programs, or devices on other users' systems. Some peer-to-peer networks use a server, but some do not.

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Peer-to-Peer Network

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Client/server computing is a distributed computing model in which much of the processing power is located within small, inexpensive client computers. The powerful clients are linked to one another through a network that is controlled by a network server computer. The server sets the rules of communication for the network and provides every client with an address so others can find it on the network. Client/Server Computing:

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In packet-switched networks, messages are first broken down into small bundles of data called packets. These packets are sent along different communication paths and then the packets are reassembled once they reach their destinations. Packet switching makes more efficient use of the communications capacity of a network. The packets include information for directing the packet to the right address and for checking transmission errors along with the data. Packet Switching:

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Packed-Switched Networks and Packet Communications

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TCP/IP is the communications protocol used by the Internet and all Internet devices. TCP/IP provides for breaking up digital messages into packets, routing them to the proper addresses, and then reassembling them into coherent messages . TCP/IP uses a suite of protocols: TCP and IP . TCP/IP and Connectivity:

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Handles the movement of data between computers Establishes a connection between the computers, sequences the transfer of packets, and acknowledges the packets sent Transmission Control Protocol (TCP):

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Responsible for the delivery of packets Includes the disassembling and reassembling of packets during transmission Internet Protocol (IP):

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The TCP/IP Reference Model

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The different kinds of physical transmission media used by the networks are: Twisted Wire Coaxial Cable Fiber Optics and Optical Networks Wireless Transmission Physical Transmission Media

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Functions of the Modem

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The Wireless Revolution Mobile phones have become mobile platforms for delivering digital data, used for recording and downloading photos, video and music, Internet access, and transmitting payments. An array of technologies provides high-speed wireless access to the Internet for PCs and other wireless handheld devices and cell phones. Businesses increasingly use wireless to cut costs, increase flexibility, and create new products and services.

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Wireless communication helps businesses easily stay in touch with customers, suppliers, and employees. Wireless networking increases worker productivity and output, as workers take less time to establish contact with people and to access information. Companies can save on wiring offices, moving, and making network changes by using wireless networks. Wireless technology has also been the source of new products, services, and sales channels in a variety of industries. Business Value of Wireless Networking

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All wireless media rely on various parts of the electromagnetic spectrum. Microwave systems transmit high-frequency radio signals through the atmosphere. Communication satellites are used for geographically dispersed organizations. Wireless Transmission Media and Devices

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Devices for Wireless Transmission: Paging systems Cellular telephones Personal Digital Assistants (PDAs) Smart phones

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Standards: Global System for Mobile Communication (GSM) Code Division Multiple Access (CDMA) Cellular Generations: 1G: Analog cellular networks for voice communication 2G: Digital wireless networks, primarily for voice communication; limited data transmission capability 3G: High-speed; mobile; supports video and other rich media; always-on transmission for e-mail, Web browsing, instant messaging Cellular Network Standards and Generations

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Mobile Wireless Standards for Web Access Wireless Application Protocol (WAP): Uses Wireless Markup Language (WML) and micro-browsers I-mode: Uses compact HTML and allows for continuous connection Wireless Application Protocol (WAP) versus I-mode

Slide 37:

Global Wireless Network Standards: The Institute of Electrical and Electronics Engineers (IEEE) established a hierarchy of complementary standards for wireless computer networks. IEEE 802.15 (Bluetooth) for the Personal Area Network (PAN) IEEE 802.11 (Wi-Fi) for the Local Area Network (LAN ) IEEE 802.16 ( WiMax ) for the Metropolitan Area Network (MAN) IEEE 802.20 (proposed) standard for the Wide Area Network (WAN)

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Bluetooth Can link up to 8 devices in 10-m area Low power requirements A Bluetooth Network (PAN)

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Wi-Fi Three standards: 802.11a, 802.11b, 802.11g Infrastructure mode: Devices use access point to communicate with wired network Ad-hoc mode (peer-to-peer): Wireless devices communicate directly with each other

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An 802.11 Wireless LAN

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A distributed database system consists of a collection of sites, connected together via some kind of communication network, in which: Each site is a full database system site in its own right. The sites have agreed to work together so that a user at any site can access data anywhere in the network exactly as if the data were all stored at the user’s own site. Definition of Distributed Database:

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Databases can be decentralized either by partitioning or by replicating Partitioned database: Database is divided into segments or regions. For example, a customer database can be divided into Eastern customers and Western customers, and two separate databases maintained in the two regions . Distributed database:

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Duplicated database: The database is completely duplicated at two or more locations. The separate databases are synchronized in off hours on a batch basis. Regardless of which method is chosen, data administrators and business managers need to understand how the data in different databases will be coordinated and how business processes might be effected by the decentralization. Distributed database:

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Distributed Databases

Banking Example :

Banking Example Using distributed database technology, a bank may implement their database system on a number of separate computer systems rather than a single, centralized mainframe. The computer systems may be located at each local branch office: for example, Amritsar, Patiala, and Delhi. A network linking the computer will enable the branches to communicate with each other, and DDBMS will enable them to access data stored at another branch office. Thus, a client living in Amritsar can also check his/her account during the stay in Patiala or Delhi.

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