Business Information Management PDF

Business Information Management Dr. Michael P. O’Brien Module: MI4007 Week 4 (Lecture 2 of 2) 1 What is a Network? A network is simply two or more computers that are linked together. The most common types of networks are: Local Are...

Business Information Management Dr. Michael P. O’Brien Module: MI4007 Week 4 (Lecture 2 of 2) 1 What is a Network? A network is simply two or more computers that are linked together. The most common types of networks are: Local Area Networks (LANS) and Wide Area Networks (WANS). The primary difference between the two is that a LAN is generally confined to a limited geographical area, whereas a WAN covers a large geographical area. Most WANs are made up of several connected LANs. 2  Types of Network Local Area Network (LAN) – a network that spans a small area such as a building or an office. – Software applications and other resources are stored on a file server. – Print servers enable multiple users to share the same printer. Wide Area Network (WAN) – a network that spans a wide geographical area; there are several types of WANS – Metropolitan area network (MAN) – Public access network (PAN) – Value added network (VAN) – Virtual private network (VPN) 3 Types of Network Intranet – An intranet is a private LAN designed for use by everyone within an organization. An intranet might consist of an internal e-mail system, a message board and one or more Web site portals that contain company news, forms, and personnel information. Access to an intranet’s web site is restricted by a firewall. Extranet – a network that connects people within your company with people who are outside your company--all within a secure, password-protected network that can be accessed from anywhere. 4  Benefits of a Network Information sharing: Authorised users can use other computers on the network to access and share information and data. This could include special group projects, databases, etc. Hardware sharing: One device connected to a network, such as a printer or scanner, can be shared by many users. Software sharing: Instead of purchasing and installing a software program on each computer, it can be installed on the server. All of the users can then access the program from a single location. Collaborative environment: Users can work together on group projects by combining the power and capabilities of diverse equipment. 5 Risks of Network Computing The security of a computer network is challenged everyday by: – Equipment malfunctions. – System failures. Note: equipment malfunctions and system failures may be caused by natural disasters such as floods, storms, or fires, and electrical disturbances. – Virus attacks. – Hackers/crackers. 6  Communications Media Communications Channel – To transfer data from one computer to another requires some type of link through which the data can be transmitted. This link is known as the communications channel. – To send data through the channel requires some type of transmission media, which may be either physical or wireless. – Data transfer rates are measured in bps (bits per second) 7 Physical Media Twisted-pair cable – consists of two independently insulated wires twisted around each other (least expensive type of cable - the kind that is used in many telephone systems) Coaxial cable – consists of an insulated center wire grounded by a shield of braided wire (the primary type of cabling used by the cable television industry; it is more expensive than twisted pair) Fiber-optic cable – contains hundreds of clear fiberglass or plastic fibers (threads) (made from thin, flexible glass tubing; bandwidth is greater, so it can carry more data; it is lighter than metal wires and is less susceptible to interference; it is fragile and expensive) ISDN line – a special digital telephone line that transmits and receives information at very high speeds 8  Wireless Media Microwave system – transmits data via high-frequency radio signals through the atmosphere. Satellite system – receive transmitted signals, amplify them, and then transmit the signals to the appropriate locations. Cellular technology – uses antennae resembling telephone towers to pick up radio signals within a specific area (cell). Infrared technology – transmits data as infrared light waves from one device to another Bluetooth – a wireless technology standard used for exchanging data between fixed and mobile devices over short distances 9 How are Networks Categorised? Networks are usually classified using three properties: Topology Protocol Architecture 10  Network Topologies Network Topology (or layout) – refers to the way computers and peripherals are configured to form networks. – Bus topology – all computers are linked by a single line of cable. – Star topology – multiple computers and peripheral devices are linked to a central computer, called a host. – Ring topology – each computer or workstation is connected to two other computers, with the entire network forming a circle. – Mesh topology – each computer and network device is interconnected with one another. 11 Network Topologies Network Topology (or layout) – Star Topology refers to the way computers and peripherals are configured to form networks. – Bus topology – all computers are linked by a single line of cable. – Star topology – multiple computers and peripheral Ring Topology devices are linked to a central computer, called a hub. Mesh Topology – Ring topology – each computer or workstation is connected to two other computers, with the entire network forming a circle. – Mesh topology – each computer and network device is interconnected with one another. 12  Network Topologies Topology Advantages Disadvantages Cheap. Simple to install. Difficult to reconfigure. Bus Less cable used compared to If main cable is damaged – network will fail. other topologies. As more nodes added, performance becomes slower. Node failure doesn’t affect the More expensive than bus. Star whole network Coordinator failure causes whole network to More computers can be added fail without disruption Efficient. Easy to install. Reconfiguration difficult. More cable wires Ring required. Great speed. One faulty device affects entire network. Very expensive. Highly fault tolerant. Reconfiguration extremely difficult. Mesh Extremely expensive. Very complex 13 Network/Communication Protocols A protocol is simply an agreed-on set of rules and procedures for transmitting data between two or more devices. Features determined by the protocol are: – How the sending device indicates it has finished sending the message. – How the receiving device indicates it has received the message. – The type of error checking to be used. 14  Network/Communication Protocols Most networks use the Ethernet protocol. On the Internet, the major protocol is TCP/IP (an acronym for Transmission Control Protocol/Internet Protocol). – Transmission Control Protocol divides a message or file into packets that are transmitted over the Internet and then reassembled when they reach their destination. – Internet Protocol is responsible for the address of each packet so it is sent to the correct destination. – Web browsers, for example, use TCP/IP to communicate with Web servers. The TCP/IP address for a website or web server is typically not easy to remember. To remedy this issue, a domain name is used instead. For example, 216.58.216.164 is one of the IP addresses for Google and google.com is the domain name. 15 Example of an Ethernet Bus Ethernet LANs use a bus topology. All stations are connected to a single long cable. Any station can send a signal along the cable, which all other stations will receive. Unlike ring topologies, the cable doesn't close a loop. 16  Internet Protocol Suite TCP/IP – The Internet protocol hierarchy – Governs the operation of the Internet – Four layers: Network Internet Transport Application 17 Transmission Control Protocol/Internet Protocol Watch this brief video on YouTube https://youtu.be/KEWe-5Bk3Q0 18  Other Communication Protocols ; File transfer protocol (FTP)– used to transmit files. ; Simple mail transfer protocol (SMTP) – used to transmit e-mail messages. ; Post office protocol (POP) – allows the recipient to retrieve messages. ; Wireless application protocol – enables wireless devices to access and use the Internet using a client/server network. ; 802.11 – protocol for wireless LAN technology 19 Network Architecture Network architecture – refers to the way a network is designed and built. The two major types are: – Peer-to-peer architecture – Computers connect with each other in a workgroup to share files, printers, and Internet access. This is used to connect a small number of computers. – Client/server architecture – sends information from a client computer to a server, which then relays the information back to the client computer, or to other computers on the network. 20  Networking Hardware & Software Hub – electronic device (with a number of ports) used in a LAN to link groups of computers. Repeaters (also called amplifiers) – electronic devices that receive signals and amplify and send them along the network. Routers - electronic devices used to ensure messages are sent to their intended destinations. Gateway – consists of hardware and/or software that allows communications between dissimilar networks. Bridge – consists of hardware and/or software that allows communication between two similar networks. 21 Firewalls A firewall is a network security system that monitors and controls the incoming and outgoing network traffic based on predetermined security rules. A firewall typically establishes a barrier between a trusted, secure internal network and another outside network, such as the Internet, that is assumed not to be secure or trusted. 22 23