1. The Internet is the largest computer network in the world, connecting millions of computers. A network is a group of two or more computer systems linked together.

2. In 1969, the US Department of Defense started a project to allow researchers and military personnel to communicate with each other in an emergency. The project was called DARPAnet (Defence Advanced Research Projects Agency) and it is the foundation of the Internet. Later its also called ARPAnet (Advanced Research Projects Agency) 3. Throughout the 1970's, what would later become the Internet was developed. While mostly military personnel and scientists used it in its early days, the advent of the World Wide Web in the early 1990's changed all that. Current amount over 1.9 billion users around the world 4. The overall responsibility for managing Internet Protocol address or domain names at upper levels is vested in the Internet Assigned Numbers Authority (IANA), which delegates the actual administration of most functions to other bodies. At global regional levels, the principal bodies providing allocation and registration services that support the operation of the Internet globally are: RIPE NCC (Rseaux IP Europens Network Coordination Centre) ARIN (American Registry for Internet Numbers) APNIC (Asia Pacific Network Information Centre) LACNIC (Latin American and Caribbean IP address Regional Registry) AfriNIC (African Regional Registry for Internet Number Resources) 5. Dial-up-connections : speed 56kbps ISDN : speed 128 Kbps Broadband ADSL(Asymmetrical Digital Subscriber Line) Speed 2mbps Cable : speed 42 Mbps Lease lines : up to 12mbps FTTH- Fiber to the Home Wireless Wi-Fi Wi-max Satellite 6. As you now know, the Internet is the physical computer network (computer, monitor, modem, cables, phone lines, etc). 7. Tim Berners-Lee, a software engineer, invented the World Wide Web in 1991. The Web is a system of Internet servers that support specially-formatted documents. These specially formatted documents are text documents created in HTML, a formatting language. In conjunction with the World Wide Web, your web browser interprets these text documents so they become web pages. Web pages contain formatted text, graphics, sound, animation, and video, allowing point and click navigation. 8. An address that points to a particular document or other resource on the Internet, used most frequently on the World Wide Web (WWW). A computer user can visit an Internet document by typing its URL into a Web browser or similar application used to access the Internet. Eg: http://www.infortec-international.com/index.html 9. http://www.infortec-international.com/index.html protocolhost name/domain (network location)path/filename 10. http://www.infortec-international.com/home/about.html Protocol: http:// Host computer name: www Domain name: infortec-international Domain type: .com Path: /home File name: about.html 11. Domain names An internet web site address. Domain names are used in URLs to identify particular Web pages. The first-level set of domain names are the toplevel domains (TLDs), including the generic top-level domains (gTLDs), such as the prominent domains com, net and org, and the country code top-level domains (ccTLDs). 12. root Country DomainsGeneric Domains .com(commercial).lk(Sri lanka).net(network).uk(United Kingdom).org(organization).au(Australia).biz(business).us(United States).edu(education).ca(Canada).mil(military).in(India).gov(government).sg(Singapore) 13. "Interconnection, collection of computers for the purpose of sharing resources & Communication that we can take as a Network. Resources we can divide in to three categories, Information such as files & folders, Hardware such as printers and software such as MS office. 14. Is a method for communication File/Data sharing Sharing of printers and other resources Can centralize administration and support Can reduce the cost involved in communication & information gathering 15. Different types of computer network designs is by their scope or scale. LAN (Local Area Network) WAN (Wide Area Network) MAN (Metropolitan Area Network) WLAN (Wireless Local Area Network) PAN(Personal Area Network) CAN(Campus Area Network) 16. LAN (Local Area Network): A computer network that connect two or more electrical or electronic devices or equipments in a single network Eg: SLT 17. WAN (Wide Area Network): Connect two networks together Eg: Internetormoredifferent 18. MAN (Metropolitan Area Network): A data network designed for a town or city. In terms of geographic breath, MANs are larger than local-area networks (LANs), but smaller than wide-area networks (WANs). MANs are usually characterized by very high-speed connections using fiber optical cable or other digital media. 19. Wireless Local Area Network A LAN based on (Wi-Fi) wireless network technology 20. Peer-to-peer Architecture: (Workgroup) Client/Server Architectures: (Domain) 21. A type of network in which each workstation has equivalent capabilities and responsibilities. This differs from client/server architectures, in which some computers are dedicated to serving the others. Peer-to-peer networks are generally simpler, but they usually do not offer the same performance under heavy loads. 22. A network architecture in which each computer or process on the network is either a client or a server. Servers are powerful computers or processes dedicated to managing disk drives (file servers), printers (print servers), or network traffic (network servers).Clients are PCs or workstations on which users run applications. Clients rely on servers for resources, such as files, devices, and even processing power. 23. Intranet: A network based on TCP/IP protocols (an internet) belonging to an organization, usually a corporation, accessible only by the organization's members, employees, or others with authorization. An intranet's Web sites look and act just like any other Web sites, but the firewall surrounding an intranet fends off unauthorized access. 24. Extranet: A buzzword that refers to an intranet that is partially accessible to authorized outsiders. Whereas an intranet resides behind a firewall and is accessible only to people who are members of the same company or organization, an extranet provides various levels of accessibility to outsiders. You can access an extranet only if you have a valid username and password, and your identity determines which parts of the extranet you can view. 25. Data Communication Data Communication is the process of moving data & information from one place to another through a transmission system. 26. The communication media is the matter or substance that carries voice or data. Different types of transmission media are currently in use. All these types can be group two categories as Guided and Unguided media. The Guided media are follows through physical media and unguided media are those in which is the data is broadcast through air. 27. Transmission media Guided Media(wired) Twisted pair Coaxial cable Fiber opticsUnguided Media(wireless) Radio waves Microwaves Satellite Infrared Bluetooth 28. Guided Media: Cable is the medium through which information usually moves from one network device to another. There are several types of cable which are commonly used with LANs. In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types. 29. Twisted Pair Cable Unshielded Twisted Pair (UTP) Cable Shielded Twisted Pair (STP) Cable 30. Twisted pair Is the common medium Is mainly used in star topology networks Cheap and easy to work with There are several categories available in Twisted pairs CAT1, CAT2, CAT5, CAT5E 31. Categories of Unshielded Twisted Pair TypeUseCategory 1Voice Only (Telephone Wire)Category 2Data to 4 Mbps (Local Talk)Category 3 Category 4 Category 5Data to 10 Mbps (Ethernet) Data to 20 Mbps (16 Mbps Token Ring) Data to 100 Mbps (Fast Ethernet) 32. Unshielded Twisted Pair Connector RJ-45(Registered Jack) 33. Coaxial Cable 34. Coaxial cable Is mainly used in BUT topology networks Television Ariel to TV Cable TV Coaxial cable are in two categories : Thin Coaxial Thick Coaxial Difficult to handle 35. Fiber Optic Cable 36. Fiber optics Signals are sent as light beams and transmitted over a glass fiber. Fiber optic technology offers high bandwidth Optical fibers come in two types Single mode Multi mode 37. glass claddingWorking with light or rays 38. Ethernet Cable Summary SpecificationCable TypeMaximum length10BaseTTwisted Pair(STP/UTP)100 meters10Base2Thin Coaxial185 meters10Base5Thick Coaxial500 meters10BaseFFiber Optic2000 meters 39. Specificati on nameCable TypeMax. lengthNodes/seg10BaseTTwisted Pair100 m102410Base2Thin Coaxial185 m3010Base5Thick Coaxial500 m10010BaseFFiber Optic2000 m1024AdvantageCheapest system No hub needed Original cable, now obsolete Best between buildings 40. Unguided Media Radio Waves Omni directional Suffers from interferences Use to TV, Radio, Cell phone 41. Microwave Microwaves travel nearly in a straight line Tall building is a barrier 100 meter high towers, repeaters for every 80km Is widely used for mobile phone, television etc. 42. Satellite Used for long distance telephone Television Private business network Mostly used with Microwave Using in long distance communications Used for weather forecasting, television broadcast, amateur radio communications, Internet communications, and the Global Positioning System, 43. Infrared Is limited for a small area (eg: for a room) Walls/barriers will block the signals Mainly used for TV remote control, IRD port. 44. Bluetooth(802.15) Founding members are Ericsson, IBM, Intel, Nokia and Toshiba. Short range wireless communication technology. Used to data synchronization between 2 devices Is limited for a small area Mainly used in Mobile phones, digital cameras, headsets, scanners, keyboards, mouse and other devices to connect to a computer. 45. Network Topologies Topology refers to the shape of a network, or the network's layout. How different nodes in a network are connected to each other and how they communicate is determined by the network's topology. Topologies are either physical or logical. BUS, RING, STAR, MESH etc. 46. BUS Topology 47. RING Topology 48. STAR Topology 49. TREE Topology 50. MESH Topology 51. Considerations When Choosing a Topology: Money. Length of cable needed Future growth. Cable type. 52. A Protocol is a set of rules(standards) that governs the communications between computers on a network. Most common network protocol is TCP/IP Eg: http, ftp, smtp, telnet, ssh, https, etc. 53. Properties of Protocol Detection of the underlying physical connection (wired or wireless), Handshaking How to start and end a message How to format a message What to do with corrupted or improperly formatted messages (error correction) How to detect unexpected loss of the connection, and what to do next Termination of the session and or connection. 54. Internetworking Models When networks fist come in to being, computers could typically communicate with computers from the same manufacturer. In the late 1970s, the Open System Interconnection(OSI) reference model was created by the International Organization for Standardization(ISO) to break this barrier. It is describes how data and network information are communicated. 55. A reference model is a conceptual blue print of how communications should takes place. These processes divide into logical groups called layers. 56. 7. Application 6. Presentation 5. Session 4. Transport 3. Network 2. Data Link 1. PhysicalProvides the user interface to communicate to the computer. Eg HTTP ----------------------------------------------------Presents data to the 7th layer and data translation like encryption, conversion ----------------------------------------------------Manage presentation layers entities. (keep different application data separately) ----------------------------------------------------Performs error correction before retransmit.[Segments] ----------------------------------------------------Manages the device addressing.(IP addressing) , Routes data. [Packets] ----------------------------------------------------Combines packets in to bytes and error detection. [Frames] ----------------------------------------------------Moves bits between devices(physical connection/cabling, electronic singnals) [Bits] 57. Networking Hardware Servers Workstations Network Interface Cards Switches Repeaters Bridges Routers 58. Servers 59. A network server A network server is a computer designed to process requests and deliver data to other (client) computers over a local network or the Internet. Network servers typically are configured with additional processing, memory and storage capacity to handle the load of servicing clients. Common types of network servers include: Web servers proxy servers FTP servers online game servers Mail servers 60. Workstations 61. Network Interface Cards 62. Switch 63. Modem Short for modulator-demodulator. A modem is a device or program that enables a computer to transmit data over, for example, telephone or cable lines. Computer information is stored digitally, whereas information transmitted over telephone lines is transmitted in the form of analog waves. A modem converts between these two forms. 64. Repeater 65. Bridge 66. Router 67. Firewall 68. Firewall 69. Encryption 70. Wi-fi 71. Wi-max 72. MAC Address A MAC address, or Media Access Control address, is a 48- or 64-bit address associated with a network adapter. While IP addresses are associated with software, MAC addresses are linked to the hardware of network adapters. For this reason, the MAC address is sometimes called the hardware address, the burned-in address (BIA), or the physical address. MAC addresses are expressed in hexadecimal notation in the following format: 01-23-45-67-89-AB, in the case of a 48-bit address. 73. An identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example 192.160.10.240 could be an IP address. 74. What is an IP address A way to identify machines on a network A unique identifier 75. IP usage Used to connect to another computer Allows transfers of files and e-mail 76. IP structure IP addresses consist of four sections Each section is 8 bits long Each section can range from 0 to 255 Written, for example, 128.35.0.72 77. IP structure These four sections represent the machine itself and the network it is onThe network portion is assigned. The host section is determined by the network administrator 78. IP structure 5 Classes of IP address A B C D and E Class A reserved for governments Class B reserved for medium companies Class C reserved for small companies 79. IP structure Class D are reserved for multicasting Class E are reserved for future use 80. IP structure Class A begins 1 to 126 Class B begins 128 to 191 Class C begins 192 to 223 81. Reserved addresses Addresses beginning 127 are reserved for loopback and internal testingxxx.0.0.0 reserved for network address xxx.255.255.255 reserved for broadcast 82. IP Addresses IP addresses are: Unique Global and Standardised Essential 83. Class A :1.0.0.1 126.255.255.254 Class B :128.1.0.1 191.254.255.254 Class C :192.0.1.1 223.255.254.254 Class D : 224.x.x.x (multicasting & research purposes) Class E :240.x.x.x (for future use) 84. Current Private IP addresses as follows Class A 10.0.0.0 through 10.255.255.255 Class B 172.16.0.0 through 172.31.255.255 Class C 192.168.0.0 through 192.168.255.255 85. IPv4 addresses have 32 bits in them and so allow a maximum of four billion addresses 86. IPv6 stands for Internet Protocol version 6. It is the second version of the Internet Protocol to be used generally across the virtual world. IPv6 addresses have 128 bits. IPv6 is the future of Internet addressing, mainly because industry experts believe that they are close to running out of available addresses altogether. 87. 128 bits - written as eight 16-bit hex numbers. 5f1b:df00:ce3e:e200:0020:0800:2078:e3e3 88. How to Determine your IP Address? Go to the start menu and select Run.... Then type cmd in the box and click OK. At the C:> prompt type ipconfig. Then press Enter. Your IP address, subnet mask and default gateway will be printed on the window. If you want more detailed information about your network connection, type ipconfig /all at the prompt. Here you can get additional information about your IP configuration. 89. For Domain Name System (or Service or Server), an Internet service that translates domain names into IP addresses. Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address.Domain www.example.comIP Address > 198.105.232.4 90. DNS has a table of Domain names and IP addresses. Its map the domain name with the IP address and its route to the particular server.Domain www.yahoo.com mail.yahoo.comIP Address 104.102.1.103 104.102.2.107 91. CountryISPRegionalRoot0210.net041101030905 1208 yahoo.com www.yahoo.com06 104.10 2.1.1007313 yahoo server.orgDomain www.yahoo.com mail.yahoo.comIP Address 104.102.1.103 104.102.2.107 92. Short for Dynamic Host Configuration Protocol, a protocol for assigning dynamic IP addresses to devices on a network. With dynamic addressing, a device can have a different IP address every time it connects to the network. 93. How DHCP works?