Computer Networking


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Computer Network Slides Prepared by sir Khuram Rizvi....

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Computer Networking

  1. 1. Computer Network Section - IV Stage II -ICMAP
  2. 2. Outline <ul><li>Fundamentals </li></ul><ul><li>Types of Network </li></ul><ul><ul><li>(LAN, WAN,MAN,VAN,VPN,Intranet,Extranet) </li></ul></ul><ul><li>Protocols </li></ul><ul><li>Network Topologies </li></ul><ul><ul><li>(Star, Bus, Ring, Mesh, Hybrid) </li></ul></ul><ul><li>Network Devices </li></ul><ul><li>Network Media/Cables </li></ul><ul><li>Internet Security Risk </li></ul><ul><li>Security Measures </li></ul>Stage II -ICMAP
  3. 3. Computer Network <ul><li>The connection or two or more computer systems using a communication channel is called computer network. </li></ul><ul><li>Group of connected computer connected through a hub/switch/modem to share information through communication medium is called network. </li></ul>Stage II -ICMAP
  4. 4. Centralized Data Processing <ul><li>Places all hardware, software, and processing in one location </li></ul><ul><li>Very inconvenient and inefficient </li></ul><ul><ul><li>Input data had to be physically transported to computer </li></ul></ul><ul><ul><li>Processed material had to be delivered to users </li></ul></ul>Return Stage II -ICMAP
  5. 5. Distributed Data Processing <ul><li>Uses computers that are at a distance from central computer </li></ul><ul><li>Local computers had access to central computers </li></ul><ul><ul><li>Some processing done on local computers, some on central computers </li></ul></ul>Return Stage II -ICMAP
  6. 6. Digital and Analog Transmission <ul><li>Digital transmission </li></ul><ul><ul><ul><ul><li>Sends data as distinct pulses, either on or off </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Similar to how data travels through computer </li></ul></ul></ul></ul><ul><li>Analog transmission </li></ul><ul><ul><ul><li>Continuous electrical signal in the form of a wave </li></ul></ul></ul><ul><ul><ul><ul><li>Called carrier wave </li></ul></ul></ul></ul><ul><ul><ul><li>Many communications media already in place for analog (voice) transmission </li></ul></ul></ul><ul><ul><ul><ul><li>Phone lines are most common </li></ul></ul></ul></ul>Stage II -ICMAP
  7. 7. Components of Communication System <ul><li>1. Transmitter </li></ul><ul><li>2. Medium </li></ul><ul><li>3. Receiver </li></ul>Stage II -ICMAP
  8. 8. Asynchronous Transmission <ul><li>Also called start/stop transmission </li></ul><ul><ul><li>Start bit transmitted at the beginning of each group of bits </li></ul></ul><ul><ul><li>Stop bit sent at end of each group </li></ul></ul><ul><ul><li>Each group typically consists of one character </li></ul></ul><ul><li>Receiving device gets start signal and sets up mechanism to accept the group </li></ul><ul><li>Used for low-speed communications </li></ul>Return Stage II -ICMAP
  9. 9. Synchronous Transmission <ul><li>Large block of characters transmitted </li></ul><ul><li>Internal clocks of devices synchronized </li></ul><ul><li>Error-check bits make sure all characters received </li></ul><ul><li>Much faster, but equipment is more expensive </li></ul>Return Stage II -ICMAP
  10. 10. Transmission Mode <ul><li>1. Simplex </li></ul><ul><li>2. Half-Duplex </li></ul><ul><li>3. Full-Duplex </li></ul>Stage II -ICMAP
  11. 11. Simplex, Half-Duplex, and Full-Duplex Transmission <ul><li>Simplex transmission sends data in one direction only </li></ul><ul><ul><li>Example: television broadcasting </li></ul></ul><ul><li>Half-duplex transmission sends data in both directions, but only one way at a time </li></ul><ul><ul><li>Example: bank teller sends data about a deposit; after data received, a confirmation returns </li></ul></ul><ul><li>Full-duplex transmission allows transmission in both directions at same time </li></ul><ul><ul><li>Example: a conversation </li></ul></ul><ul><ul><li>Typically used for high-speed data communication </li></ul></ul>Stage II -ICMAP
  12. 12. Simplex Communication <ul><li>Simplex communication is a mode in which data only flows in one direction. Because most modern communications require a two-way interchange of data and information, this mode of transmission is not as popular as it once was. </li></ul><ul><li>However, one current usage of simplex communications in business involves certain point-of-sale terminals in which sales data is entered without a corresponding reply. </li></ul>Stage II -ICMAP
  13. 13. Half-Duplex Communication <ul><li>Half-duplex communication adds an ability for a two-way flow of data between computer terminals. In this directional mode, data travels in two directions, but not simultaneously. </li></ul><ul><li>Data can only move in one direction when data is not being received from the other direction. This mode is commonly used for linking computers together over telephone lines. </li></ul>Stage II -ICMAP
  14. 14. Full-Duplex Communication <ul><li>The fastest directional mode of communication is full-duplex communication. Here, data is transmitted in both directions simultaneously on the same channel. Thus, this type of communication can be thought of as similar to automobile traffic on a two-lane road. </li></ul><ul><li>Full-duplex communication is made possible by devices called multiplexers. Full-duplex communication is primarily limited to mainframe computers because of the expensive hardware required to support this directional mode. </li></ul>Stage II -ICMAP
  15. 15. Network Uses <ul><li>Electronic mail (e-mail) </li></ul><ul><li>Facsimile (fax) technology </li></ul><ul><li>Groupware </li></ul><ul><li>Teleconferencing </li></ul><ul><li>Electronic data interchange </li></ul><ul><li>Electronic fund transfers </li></ul><ul><li>Computer commuting </li></ul><ul><li>The Internet </li></ul>Stage II -ICMAP
  16. 16. The Internet <ul><li>A global network of hundreds of thousands of Computers </li></ul><ul><li>Widely considered to be the defining technology of the beginning of this century </li></ul>Return Stage II -ICMAP
  17. 17. The Internet Service Provider and the Browser <ul><li>An Internet service provider (ISP) provides the server computer and software to connect to the Internet </li></ul><ul><ul><li>Online service, such as America Online, includes Internet access, Internet service, and a browser </li></ul></ul><ul><li>When you connect to the Internet, the browser displays a home page </li></ul>Return Stage II -ICMAP
  18. 18. Uniform Resource Locator (URL) <ul><li>The complete, unique address of a Web page </li></ul><ul><ul><li>Web page URL begins with http </li></ul></ul><ul><ul><ul><li>HyperText Transfer Protocol – allows communication by using links to transfer data between sites </li></ul></ul></ul><ul><ul><li>Domain name – address of site’s host computer </li></ul></ul><ul><ul><ul><li>Last part of domain name is called a top-level domain </li></ul></ul></ul><ul><ul><ul><li>Identifies country or purpose of organization </li></ul></ul></ul>Return Stage II -ICMAP
  19. 19. Local Area Network (LAN) <ul><ul><li>Contains printers, servers and computers </li></ul></ul><ul><ul><li>Systems are close to each other </li></ul></ul><ul><ul><li>Contained in one office or building </li></ul></ul><ul><ul><li>Organizations often have several LANS </li></ul></ul><ul><ul><li>LAN is a number of computers connected to each other by cable in a single location, usually a single floor of building or all the computers in a small company </li></ul></ul>Stage II -ICMAP
  20. 20. Wide Area Network (WAN) <ul><li>Set of connecting links between LAN. These links are made over telephone lines leased from various telephone companies </li></ul><ul><li>Wide Area Networks (WAN) </li></ul><ul><ul><li>Two or more LANs connected </li></ul></ul><ul><ul><li>Over a large geographic area </li></ul></ul><ul><ul><li>Typically use public or leased lines </li></ul></ul><ul><ul><ul><li>Phone lines </li></ul></ul></ul><ul><ul><ul><li>Satellite </li></ul></ul></ul><ul><ul><li>The Internet is a WAN </li></ul></ul>Stage II -ICMAP
  21. 21. Difference between LAN & WAN Stage II -ICMAP LAN WAN <ul><li>Covers small geographical area </li></ul><ul><li>Computers are directly connected through physical cable for data transmission </li></ul><ul><li>LAN card is used for data transmission </li></ul><ul><li>Data transmission speed is very high </li></ul><ul><li>Installation and configuration cost is less than WAN </li></ul>Covers large or wide geographical area No physical cable or wire is used and data is sent and received through microwave system or satellite. Modem is used for data transmission slow Higher than LAN
  22. 22. Metropolitan Area Network (MAN) <ul><li>Metropolitan Area Network (MAN) </li></ul><ul><ul><li>Large network that connects different organizations </li></ul></ul><ul><ul><li>Shares regional resources </li></ul></ul><ul><ul><li>An example of a regional resource is a supercomputer. For example, Pittsburgh has the Pittsburgh Super Computing center ( The various colleges in Pittsburgh connect to the center through a MAN in Pittsburgh. </li></ul></ul>Stage II -ICMAP
  23. 23. Client/Server Network <ul><ul><li>Nodes and servers share data roles </li></ul></ul><ul><ul><li>Nodes are called clients </li></ul></ul><ul><ul><li>Servers are used to control access </li></ul></ul><ul><li>Client requests data from server </li></ul><ul><li>Server passes only the requested data </li></ul><ul><ul><li>Client may perform some processing, but most data processed on server </li></ul></ul>Stage II -ICMAP
  24. 24. Peer to Peer Networks (P2PN) <ul><ul><li>All nodes are equal </li></ul></ul><ul><ul><li>Nodes access resources on other nodes </li></ul></ul><ul><ul><li>Each node controls its own resources </li></ul></ul><ul><ul><li>Most modern OS allow P2PN </li></ul></ul><ul><ul><li>All computers have equal status </li></ul></ul><ul><ul><li>Users share each other’s files, printers, etc. as needed </li></ul></ul><ul><ul><li>Common in small offices </li></ul></ul><ul><ul><li>Networks tend to be slow </li></ul></ul><ul><ul><li>Kazaa </li></ul></ul>Stage II -ICMAP
  25. 25. Intranets <ul><li>A private Internet-like network </li></ul><ul><ul><li>Internal to a certain company </li></ul></ul><ul><ul><li>Easy to set up </li></ul></ul><ul><ul><li>Can be linked to the Internet </li></ul></ul><ul><li>Users can retrieve information such as benefits information and job openings </li></ul><ul><ul><li>Submit vacation requests, applications for open positions, employee handbooks, corporate policies, and other information in a central location </li></ul></ul>Stage II -ICMAP
  26. 26. Extranet <ul><li>Refer to applications and services that are Intranet based, and use extended, secure access to external users or enterprises. This access is usually accomplished through passwords, user IDs, and other application-level security </li></ul>Stage II -ICMAP
  27. 27. Virtual Private Network <ul><li>Technology that uses the Internet as a channel for private data communication </li></ul><ul><li>Uses tunneling technology </li></ul><ul><li>Offers many benefits over a private network </li></ul><ul><ul><li>Much cheaper than dedicated lines </li></ul></ul><ul><ul><li>Data is secure </li></ul></ul><ul><ul><li>Turns remote network administration over to ISP </li></ul></ul>Stage II -ICMAP
  28. 28. Tunneling <ul><li>Also called encapsulation </li></ul><ul><li>Transfers data between two similar networks over an intermediate network </li></ul><ul><ul><li>Data packets follow Point-to-Point Tunneling Protocol (PPTP) </li></ul></ul><ul><ul><li>Data embedded in TCP/IP packets carried by the Internet </li></ul></ul><ul><li>Data packets are encoded before encapsulation </li></ul><ul><ul><li>When received, they are separated and returned to their original format </li></ul></ul><ul><ul><li>Provides security for data packets </li></ul></ul>Return Stage II -ICMAP
  29. 29. Value-Added Network (VAN) <ul><li>A value-added network (VAN) is a private network provider (sometimes called a turnkey communications line) that is hired by a company to facilitate electronic data interchange ( EDI ) or provide other network services. </li></ul><ul><li>Before the arrival of the World Wide Web, some companies hired value-added networks to move data from their company to other companies. With the arrival of the World Wide Web, many companies found it more cost-efficient to move their data over the Internet instead of paying the minimum monthly fees and per-character charges found in typical VAN contracts. In response, contemporary value-added network providers now focus on offering EDI translation, encryption , secure e-mail, management reporting, and other extra services for their customers. </li></ul>Stage II -ICMAP
  30. 30. Virtual Area Network (VAN) <ul><li>A virtual area network (VAN) is a network on which users are enabled to share a more visual sense of community through high band-width connections. </li></ul><ul><li>It is something like a metropolitan area network (MAN) or extended local areanetwork ( LAN ) in which all users can meet over high-bandwidth connections, enabling &quot;face-to-face&quot; online &quot;coffeehouses,&quot; remote medical diagnosis and legal consultation, and online corporate or extracorporate workgroups, focus groups, and conferences. </li></ul><ul><li>A VAN requires multi-megabyte data flow and can be implemented through the use of Asymmetric Digital Subscriber Line but more likely through the installation of cable modem . Since the high-bandwidth connections imply a common infrastructure, the first VANs are likely to be local or regional. However, a VAN can also be national or international in geographic scope, assuming all users share similar capabilities. </li></ul>Stage II -ICMAP
  31. 31. Baseband & Broadband Signaling <ul><li>Baseband </li></ul><ul><li>1)Uses digital signalling </li></ul><ul><li>2)No frequency-division multiplexing </li></ul><ul><li>3)Bi-directional transmission </li></ul><ul><li>4)Signal travels over short distances </li></ul><ul><li>Broadband </li></ul><ul><li>1)Uses analog signalling </li></ul><ul><li>2)Unidirectional transmission </li></ul><ul><li>3)Frequency-division multiplexing is possible </li></ul><ul><ul><li>4) Any data connection faster than 56 Kbps </li></ul></ul><ul><li>4)Signal can travel over long distances before being attenuated </li></ul>Stage II -ICMAP
  32. 32. Integrated Systems Digital Network (ISDN) <ul><li>Special type of telephone circuit </li></ul><ul><ul><li>Can move data at 128,000 bps </li></ul></ul><ul><ul><li>Includes two phone lines, so you can talk on the phone while online </li></ul></ul><ul><ul><ul><li>Two data channels each support 64 Kbps </li></ul></ul></ul><ul><li>Drawbacks </li></ul><ul><ul><li>Expensive, especially at installation </li></ul></ul><ul><ul><li>Not available in all areas </li></ul></ul>Return Stage II -ICMAP
  33. 33. Digital Subscriber Line (DSL) <ul><ul><li>Offers speeds up to 30 Mbps </li></ul></ul><ul><ul><li>Simultaneous use of phone and data </li></ul></ul><ul><ul><li>Asynchronous DSL </li></ul></ul><ul><ul><ul><li>Different up and download speeds </li></ul></ul></ul><ul><li>Drawbacks </li></ul><ul><ul><li>You must be within three miles of telephone company’s switching office </li></ul></ul><ul><ul><li>Costly </li></ul></ul><ul><ul><li>Not available in all areas </li></ul></ul>Stage II -ICMAP
  34. 34. Network Protocols <ul><li>Protocol - a set of rules for the exchange of data between a terminal and a computer or two computers </li></ul><ul><ul><li>Agreement on how data is to be sent and receipt acknowledged </li></ul></ul><ul><ul><li>Needed to allow computers from different vendors to communicate </li></ul></ul><ul><li>Language of the network </li></ul><ul><ul><li>Rules of communication </li></ul></ul><ul><ul><li>Error resolution </li></ul></ul><ul><ul><li>Defines collision and collision recovery </li></ul></ul><ul><ul><li>Size of packet </li></ul></ul><ul><ul><li>Naming rules for computers </li></ul></ul>Stage II -ICMAP
  35. 35. Network Packet and Payload <ul><li>Packets </li></ul><ul><ul><li>Pieces of data transmitted over a network </li></ul></ul><ul><ul><li>Packet header </li></ul></ul><ul><ul><ul><li>Contains control information </li></ul></ul></ul><ul><ul><ul><li>Sending and receiving address </li></ul></ul></ul><ul><ul><li>Packet payload </li></ul></ul><ul><ul><ul><li>Contains actual data </li></ul></ul></ul>Stage II -ICMAP
  36. 36. Protocol Data Units (PDUs) Stage II -ICMAP
  37. 37. Network Protocols <ul><li>Transmission Control Protocol/Internet Protocol (TCP/IP) </li></ul><ul><ul><li>Most popular protocol </li></ul></ul><ul><ul><li>Required for Internet access </li></ul></ul><ul><ul><li>TCP creates and reassembles packets </li></ul></ul><ul><ul><li>IP handles addressing </li></ul></ul><ul><ul><ul><li>Ensures that packets are routed to their ultimate destination </li></ul></ul></ul><ul><ul><ul><li>Machines assigned a name of 4 numbers </li></ul></ul></ul><ul><ul><ul><ul><li>IP address </li></ul></ul></ul></ul><ul><ul><li>Dynamic Host Configuration Protocol </li></ul></ul><ul><ul><ul><li>Simplifies assignment of IP addresses </li></ul></ul></ul><ul><li>NetBEUI </li></ul><ul><ul><li>Network BIOS Extended User Interface </li></ul></ul><ul><ul><li>Used by Windows to name computers </li></ul></ul><ul><ul><li>It provides services related to the session layer of the OSI model allowing applications on separate computers to communicate over a local area network . </li></ul></ul>Stage II -ICMAP
  38. 38. Network Protocols <ul><li>IPX/SPX </li></ul><ul><ul><li>Internet Packet Exchange/Sequenced Packet Exchange </li></ul></ul><ul><ul><li>Associated with Novell Netware </li></ul></ul><ul><ul><li>Replaced by TCP/IP </li></ul></ul><ul><li>IPX is a network layer protocol while SPX is a transport layer protocol . The SPX provides connection-oriented services between two nodes on the network. </li></ul><ul><li>IPX and SPX both provide connection services similar to TCP/IP , with the IPX protocol having similarities to IP , and SPX having similarities to TCP . </li></ul><ul><li>IPX/SPX was primarily designed for local area networks (LANs), and is a very efficient protocol for this purpose (typically its performance exceeds that of TCP/IP on a LAN). TCP/IP has, however, become the de facto standard protocol. This is in part due to its superior performance over wide area networks and the Internet (which uses TCP/IP exclusively), and also because TCP/IP is a more mature protocol, designed specifically with this purpose in mind. </li></ul>Stage II -ICMAP
  39. 39. Ethernet - LAN Protocols <ul><li>Dominant network protocol </li></ul><ul><li>Uses either bus or star topology </li></ul><ul><li>Node “listens” to see when the network is available </li></ul><ul><ul><li>If two computers transmit at same time, collision occurs </li></ul></ul><ul><ul><li>Network detects the collision </li></ul></ul><ul><ul><li>Each computer waits random amount of time and retransmits </li></ul></ul>Return Stage II -ICMAP
  40. 40. Token Ring - LAN Protocols <ul><li>Uses ring topology </li></ul><ul><li>Token (electrical signal) controls which node can send messages </li></ul><ul><ul><li>Token circulates among nodes </li></ul></ul><ul><ul><li>A computer waits for an empty token, attaches message, and transmits </li></ul></ul><ul><li>Only one token, so only one device can access network at a time </li></ul>Return Stage II -ICMAP
  41. 41. File Transfer Protocol (FTP) <ul><li>A protocol for transferring files among computers </li></ul><ul><li>Requires FTP Client and FTP Server </li></ul><ul><li>FTP servers maintain collections of downloadable files </li></ul><ul><ul><li>Downloading can often be done anonymously, without logging in </li></ul></ul><ul><li>Many FTP servers can be accessed through Web browser </li></ul>Return Stage II -ICMAP
  42. 42. Telnet <ul><li>A protocol that allows remote users to log onto a host computer </li></ul><ul><ul><li>Users use their own PCs </li></ul></ul><ul><ul><li>Users log in over the Internet </li></ul></ul><ul><ul><li>Users’ experience is the same as if they were sitting at the host computer’s local terminal </li></ul></ul><ul><li>Remote user typically has to have a user ID and password </li></ul>Return Stage II -ICMAP
  43. 43. OSI Model <ul><li>Open System Interconnection (OSI) </li></ul><ul><li>Created by International Organization for Standardization (ISO) </li></ul><ul><li>primary model for network communications </li></ul>Stage II -ICMAP
  44. 44. Comparison of OSI and TCP/IP Stage II -ICMAP
  45. 45. Physical Layer Stage II -ICMAP
  46. 46. Data Link Layer Stage II -ICMAP
  47. 47. Network Layer Stage II -ICMAP
  48. 48. Transport Layer Stage II -ICMAP
  49. 49. Session Layer Stage II -ICMAP
  50. 50. Application Layer Stage II -ICMAP
  51. 51. Network Topology <ul><li>The physical layout of a network i.e. wires and equipment </li></ul><ul><ul><li>Choice affects </li></ul></ul><ul><ul><ul><li>Network performance </li></ul></ul></ul><ul><ul><ul><li>Network size </li></ul></ul></ul><ul><ul><ul><li>Network collision detection </li></ul></ul></ul><ul><ul><li>Star </li></ul></ul><ul><ul><li>Ring </li></ul></ul><ul><ul><li>Bus </li></ul></ul><ul><ul><li>Mesh </li></ul></ul><ul><ul><li>Hybrid </li></ul></ul>Stage II -ICMAP
  52. 52. Bus Topology <ul><li>Also called linear bus </li></ul><ul><ul><li>One wire connects all nodes </li></ul></ul><ul><ul><li>Terminator ends the wires </li></ul></ul><ul><ul><li>If messages collide with other messages, sending node resends message </li></ul></ul><ul><ul><li>Nodes can be added/removed from network without affecting network </li></ul></ul><ul><ul><li>Advantages </li></ul></ul><ul><ul><ul><li>Easy to setup </li></ul></ul></ul><ul><ul><ul><li>Small amount of wire </li></ul></ul></ul><ul><ul><li>Disadvantages </li></ul></ul><ul><ul><ul><li>Slow </li></ul></ul></ul><ul><ul><ul><li>Easy to crash </li></ul></ul></ul>Stage II -ICMAP
  53. 53. Bus Topology Stage II -ICMAP
  54. 54. Star Topology <ul><ul><li>All nodes connect to a hub </li></ul></ul><ul><ul><ul><li>Packets sent to hub </li></ul></ul></ul><ul><ul><ul><li>Hub sends packet to destination </li></ul></ul></ul><ul><ul><ul><li>Helps prevent collisions among messages </li></ul></ul></ul><ul><ul><li>Advantages </li></ul></ul><ul><ul><ul><li>Easy to setup </li></ul></ul></ul><ul><ul><ul><ul><li>One cable can not crash network </li></ul></ul></ul></ul><ul><ul><ul><ul><li>If a node fails, network does not fail </li></ul></ul></ul></ul><ul><ul><ul><li>Disadvantages </li></ul></ul></ul><ul><ul><ul><ul><li>One hub crashing downs entire network </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Uses lots of cable </li></ul></ul></ul></ul><ul><ul><li>Most common topology </li></ul></ul>Stage II -ICMAP
  55. 55. Star Topology Stage II -ICMAP
  56. 56. Ring Topology <ul><li>Nodes connected in a circle </li></ul><ul><ul><li>Tokens used to transmit data </li></ul></ul><ul><ul><ul><li>Nodes must wait for token to send </li></ul></ul></ul><ul><li>Data messages travel around ring in a single direction </li></ul><ul><ul><li>Each node checks message to see whether that node is addressee, If not, message passed to next node </li></ul></ul><ul><ul><li>Advantages </li></ul></ul><ul><ul><ul><li>Time to send data is known </li></ul></ul></ul><ul><ul><ul><li>No data collisions </li></ul></ul></ul><ul><ul><li>Disadvantages </li></ul></ul><ul><ul><ul><li>Complex software required for token management </li></ul></ul></ul><ul><ul><ul><li>Slow </li></ul></ul></ul><ul><ul><ul><li>Lots of cable </li></ul></ul></ul>Stage II -ICMAP
  57. 57. Ring Topology Stage II -ICMAP
  58. 58. Mesh Topology <ul><li>All computers connected together </li></ul><ul><ul><li>Internet is a mesh network </li></ul></ul><ul><ul><li>Advantage </li></ul></ul><ul><ul><ul><li>Data will always be delivered </li></ul></ul></ul><ul><ul><ul><li>Reliable </li></ul></ul></ul><ul><ul><ul><li>Fault Tolerant </li></ul></ul></ul><ul><ul><ul><li>Dedicated Path –Fast transmission </li></ul></ul></ul><ul><ul><ul><li>No Collision </li></ul></ul></ul><ul><ul><li>Disadvantages </li></ul></ul><ul><ul><ul><li>Lots of cable- Expensive </li></ul></ul></ul><ul><ul><ul><li>Hard to setup </li></ul></ul></ul>Stage II -ICMAP
  59. 59. Mesh Topology Stage II -ICMAP
  60. 60. Hybrid Topology Stage II -ICMAP
  61. 61. Network Hardware <ul><li>Modem </li></ul><ul><li>Network Interface Card (NIC) </li></ul><ul><li>Hub </li></ul><ul><li>Bridge </li></ul><ul><li>Switch </li></ul><ul><li>Router </li></ul><ul><li>Gateway </li></ul><ul><li>Amplifier </li></ul><ul><li>Repeater </li></ul>Stage II -ICMAP
  62. 62. Modem <ul><li>Converts digital signal to analog and vice versa </li></ul><ul><li>Conversion from digital to analog called modulation </li></ul><ul><li>Conversion from analog to digital called demodulation </li></ul><ul><li>Measured in bits per second (bps) </li></ul><ul><ul><li>Fastest current modems transmit at 56,000 bps </li></ul></ul>Return Stage II -ICMAP
  63. 63. Network Interface Cards (NIC) <ul><li>Ethernet Card /Network Adapters </li></ul><ul><ul><li>Network adapter </li></ul></ul><ul><li>Connects each computer to wiring in the network </li></ul><ul><ul><li>Handles sending, receiving, and error checking of transmitted data </li></ul></ul><ul><ul><li>Connects node to the media </li></ul></ul>Stage II -ICMAP
  64. 64. Hubs <ul><li>Center of a star network </li></ul><ul><ul><li>All nodes receive transmitted packets </li></ul></ul><ul><ul><li>Slow and insecure </li></ul></ul><ul><ul><li>Active Hub –Amplification </li></ul></ul><ul><ul><li>Passive Hub – no amplification </li></ul></ul>Stage II -ICMAP
  65. 65. Bridge <ul><li>Connects two or more LANs together </li></ul><ul><ul><li>Packets sent to remote LAN cross </li></ul></ul><ul><ul><ul><li>Other packets do not cross </li></ul></ul></ul><ul><ul><li>Segments the network on MAC addresses </li></ul></ul><ul><li>Bridge allows connection of similar networks (those using the same protocol) </li></ul>Stage II -ICMAP
  66. 66. Switches <ul><li>Replacement for hubs </li></ul><ul><ul><li>Only intended node receives transmission </li></ul></ul><ul><ul><li>Fast </li></ul></ul><ul><ul><li>Secure </li></ul></ul><ul><ul><li>Keep track of MAC Addresses </li></ul></ul><ul><ul><li>Intelligent Device </li></ul></ul>Stage II -ICMAP
  67. 67. Routers <ul><li>Router </li></ul><ul><ul><li>Connects two or more LANs, WANs together </li></ul></ul><ul><ul><li>Packets sent to remote LAN cross </li></ul></ul><ul><ul><li>Connect internal networks to the Internet </li></ul></ul><ul><ul><li>Selection of best available path and path forwarding </li></ul></ul><ul><ul><li>Need configured before installation </li></ul></ul>Stage II -ICMAP
  68. 68. Gateway <ul><li>Connects two dissimilar networks </li></ul><ul><ul><li>Primary function is converting protocol among networks i.e. protocol translation </li></ul></ul>Stage II -ICMAP
  69. 69. Amplifier <ul><li>An Amplifier is an electronic device that increases the voltage , current , or power of a signal . Amplifiers are used in wireless communications and broadcasting, and in audio equipment of all kinds. </li></ul>Stage II -ICMAP
  70. 70. Repeater <ul><li>In digital communication systems, a repeater is a device that receives a digital signal on an electromagnetic or optical transmission medium and regenerates the signal along the next leg of the medium. </li></ul>Stage II -ICMAP
  71. 71. Types of Communications Media <ul><li>Unshielded /Shielded Twisted pairs </li></ul><ul><li>Coaxial cables </li></ul><ul><li>Fiber optics </li></ul>Stage II -ICMAP
  72. 72. Twisted-Pair <ul><li>Two wires twisted around each other to reduce electrical interference </li></ul><ul><li>Inexpensive </li></ul><ul><li>Already in place (for telephone systems) </li></ul><ul><li>Susceptible to electrical interference and noise - anything causes signal distortion </li></ul><ul><li>Most common LAN cable + telephone systems </li></ul><ul><li>May be shielded from interference </li></ul><ul><li>Speeds range from 1 Mbps to 1,000 Mbps </li></ul>Return Stage II -ICMAP
  73. 73. Unshielded and Shielded TP <ul><li>Unshielded Twisted Pair (UTP) </li></ul><ul><ul><li>Ordinary telephone wire </li></ul></ul><ul><ul><li>Cheapest </li></ul></ul><ul><ul><li>Easiest to install </li></ul></ul><ul><ul><li>Suffers from external EM interference </li></ul></ul><ul><li>Shielded Twisted Pair (STP) </li></ul><ul><ul><li>Metal braid or sheathing that reduces interference </li></ul></ul><ul><ul><li>More expensive </li></ul></ul><ul><ul><li>Harder to handle (thick, heavy) </li></ul></ul>Stage II -ICMAP
  74. 74. Coaxial Cable <ul><li>A center conductor wire surrounded by layer of insulation and metallic sheath </li></ul><ul><li>Commonly used to connect to cable TV </li></ul><ul><li>Higher bandwidth and less susceptibility to noise than twisted pair </li></ul><ul><li>Shielded from interference </li></ul><ul><li>Speeds up to 10 Mbps </li></ul><ul><ul><li>Television distribution </li></ul></ul><ul><ul><li>Antenna to TV </li></ul></ul><ul><ul><li>Cable TV </li></ul></ul><ul><li>Long distance telephone transmission </li></ul><ul><ul><li>Can carry 10,000 voice calls simultaneousl y </li></ul></ul>Return Stage II -ICMAP
  75. 75. Fiber Optic <ul><li>Use light instead of electricity to send data </li></ul><ul><li>Much higher bandwidth than coaxial cable </li></ul><ul><li>Immune to electrical interference </li></ul><ul><li>Materials cheaper than coaxial, but installation costs high </li></ul><ul><li>Very secure </li></ul><ul><li>Hard to work with </li></ul><ul><li>Speeds up to 100 Gbps( billion bits per second ) </li></ul>Stage II -ICMAP
  76. 76. Computer Crime <ul><li>Hacker – someone who attempts to gain access to computer systems illegally </li></ul><ul><ul><li>Originally referred to as someone with a high degree of computer expertise </li></ul></ul><ul><ul><li>Social engineering – a tongue-in-cheek term for con artist actions </li></ul></ul><ul><ul><ul><li>Persuade people to give away password </li></ul></ul></ul><ul><ul><ul><li>information </li></ul></ul></ul>Stage II -ICMAP
  77. 77. Methods Computer Criminals Use <ul><li>Bomb </li></ul><ul><li>Data diddling </li></ul><ul><li>Denial of service attacks </li></ul><ul><li>Piggybacking </li></ul><ul><li>Salami technique </li></ul><ul><li>Scavenging </li></ul><ul><li>Trapdoor </li></ul><ul><li>Trojan horse </li></ul><ul><li>Zapping </li></ul><ul><li>Worm </li></ul><ul><li>Virus </li></ul><ul><li>Spamming </li></ul><ul><li>Cookies </li></ul>Stage II -ICMAP
  78. 78. Bomb <ul><li>Causes a program to trigger damage under certain conditions </li></ul><ul><ul><li>Usually set to go off at a later date </li></ul></ul><ul><li>Sometimes planted in commercial software </li></ul><ul><ul><li>Shareware is more prone to having a bomb planted in it </li></ul></ul>Return Stage II -ICMAP
  79. 79. Data Diddling <ul><li>Refers to changing data before or as it enters the system </li></ul><ul><li>Auditors must verify accuracy of the source data as well as the processing that occurs </li></ul>Return Stage II -ICMAP
  80. 80. Denial of Service(DOS) Attack <ul><li>Hackers bombard a site with more requests than it can possibly handle </li></ul><ul><ul><li>Prevents legitimate users from accessing the site </li></ul></ul><ul><ul><li>Hackers can cause attacks to come from many different sites simultaneously </li></ul></ul>Return Stage II -ICMAP
  81. 81. Piggybacking <ul><li>An illicit user “rides” into the system on the back of an authorized user </li></ul><ul><ul><li>If the user does not exit the system properly, the intruder can continue where the original user has left off </li></ul></ul><ul><li>Always log out of any system you log into </li></ul>Return Stage II -ICMAP
  82. 82. Scavenging <ul><li>Searching company trash cans and dumpsters for lists of information </li></ul><ul><ul><li>Thieves will search garbage and recycling bins of individuals looking for bank account numbers, credit card numbers, etc. </li></ul></ul>Return Stage II -ICMAP
  83. 83. Trapdoor <ul><li>An illicit program left within a completed legitimate program </li></ul><ul><ul><li>Allows subsequent unauthorized and unknown entry by the perpetrator to make changes to the program </li></ul></ul><ul><li>Salami Technique </li></ul><ul><ul><li>An embezzlement technique where small “slices” of money are funneled into accounts </li></ul></ul>Return Stage II -ICMAP
  84. 84. Trojan Horse <ul><li>Involves illegal instructions placed in the middle of a legitimate program </li></ul><ul><ul><li>Program does something useful, but the Trojan horse instructions do something destructive in the background </li></ul></ul>Return Stage II -ICMAP
  85. 85. Worm <ul><li>A program that transfers itself from computer to computer </li></ul><ul><li>self-replicating computer program . </li></ul><ul><ul><li>Plants itself as a separate file on the target computer’s disks </li></ul></ul>Return Stage II -ICMAP
  86. 86. Virus <ul><li>A set of illicit instructions that passes itself on to other files </li></ul><ul><ul><li>Transmitting a virus </li></ul></ul><ul><ul><li>Can cause tremendous damage to computer and data </li></ul></ul><ul><li>Antivirus software </li></ul><ul><ul><li>Detects virus signature </li></ul></ul><ul><ul><li>Scans hard disk every time you boot the computer </li></ul></ul><ul><li>Viruses tend to show up on free software or software downloaded from the Internet </li></ul><ul><li>Often distributed as e-mail attachments </li></ul><ul><ul><li>Do not open e-mail attachments without scanning them or if you do not know the person sending the e-mail </li></ul></ul>Return Stage II -ICMAP
  87. 87. Spamming <ul><li>Mass advertising via e-mail </li></ul><ul><ul><li>Can overflow your e-mail inbox </li></ul></ul><ul><ul><li>Bogs down your e-mail server, increasing the cost of e-mail service </li></ul></ul><ul><li>Zapping </li></ul><ul><ul><li>Refers to a variety of software designed to bypass all security systems </li></ul></ul>Return Stage II -ICMAP
  88. 88. Cookies <ul><li>A small text file stored on your hard drive </li></ul><ul><li>File is sent back to the server each time you visit that site </li></ul><ul><li>Web sites can easily collect information when a user just visits the site </li></ul><ul><ul><li>Web sites use cookies to store your preferences </li></ul></ul><ul><li>Stores preferences, allowing Web site to be customized </li></ul><ul><ul><li>Stores passwords, allowing you to visit multiple pages within the site without logging in to each one </li></ul></ul><ul><ul><li>Tracks surfing habits, targeting you for specific types of advertisements </li></ul></ul>Return Stage II -ICMAP
  89. 89. Computer Forensics <ul><li>Uncovering computer-stored information suitable for use as evidence in courts of law </li></ul><ul><li>Some experts are available for hire, but most are on the staffs of police departments and law firms </li></ul>Stage II -ICMAP
  90. 90. Security: Playing It Safe <ul><li>Security – a system of safeguards </li></ul><ul><ul><li>Protects system and data from deliberate or accidental damage </li></ul></ul><ul><ul><li>Protects system and data from unauthorized access </li></ul></ul><ul><ul><ul><li>Controlling Access </li></ul></ul></ul><ul><ul><ul><ul><li>Biometric Devices </li></ul></ul></ul></ul><ul><ul><ul><li>Encryption </li></ul></ul></ul><ul><ul><ul><li>Firewall </li></ul></ul></ul><ul><ul><ul><li>Digital Signature </li></ul></ul></ul>Stage II -ICMAP
  91. 91. Controlling Access <ul><li>Four means of controlling who has access to the computer </li></ul><ul><ul><li>What you have </li></ul></ul><ul><ul><li>What you know </li></ul></ul><ul><ul><li>What you do </li></ul></ul><ul><ul><li>What you are </li></ul></ul>Stage II -ICMAP
  92. 92. What You Have <ul><li>Requires you to have some device to gain access to the computer </li></ul><ul><ul><li>Badge, key, or card to give you physical access to the computer room or a locked terminal </li></ul></ul><ul><ul><li>Debit card with a magnetic strip gives you access to your bank account at an ATM </li></ul></ul><ul><ul><li>Active badge broadcasts your location by sending out radio signals </li></ul></ul>Return Stage II -ICMAP
  93. 93. What You Know & Do <ul><li>What You Know </li></ul><ul><ul><li>Requires you to know something to gain access </li></ul></ul><ul><ul><li>Password and login name give you access to computer system </li></ul></ul><ul><li>What You Do </li></ul><ul><ul><li>Software can verify scanned and online signatures </li></ul></ul>Return Stage II -ICMAP
  94. 94. What You Are <ul><li>Uses biometrics – the science of measuring body characteristics </li></ul><ul><ul><li>Uses fingerprinting, voice pattern, retinal scan, etc. to identify a person </li></ul></ul><ul><li>Can combine fingerprinting and reading a smart card to authenticate </li></ul>Return Stage II -ICMAP
  95. 95. Biometric Devices <ul><li>Biometrics refers to methods for uniquely recognizing humans based upon one or more intrinsic physical or behavioral traits. In information technology, in particular, biometrics is used as a form of identity access management and access control. It is also used to identify individuals in groups that are under surveillance. </li></ul><ul><li>Biometric Devices read personal characteristics and attributes (voice ,face, retina etc) to authenticate a </li></ul><ul><li>before allowing him to use the computer </li></ul>Stage II -ICMAP
  96. 96. Encryption <ul><li>Scrambling data so that it can only be read by a computer with the appropriate key </li></ul><ul><ul><li>Encryption key converts the message into an unreadable form </li></ul></ul><ul><ul><li>Message can be decrypted only by someone with the proper key </li></ul></ul><ul><li>Private key encryption – senders and receivers share the same key </li></ul><ul><li>Public key encryption – encryption software generates the key </li></ul>Return Stage II -ICMAP
  97. 97. Firewall <ul><li>A combination of hardware and software that sits between an organization’s network and the Internet </li></ul><ul><ul><li>All traffic between the two goes through the firewall </li></ul></ul><ul><ul><li>Protects the organization from unauthorized access </li></ul></ul><ul><ul><li>Can prevent internal users from accessing inappropriate Internet sites </li></ul></ul>Return Stage II -ICMAP
  98. 98. Digital Signature <ul><li>An electronic signature that can be used to authenticate the identity of the sender of a message or the signer of a document, and possibly to ensure that the original content of the message or document that has been sent is unchanged. </li></ul><ul><li>The ability to ensure that the original signed message arrived means that the sender cannot easily repudiate it later. </li></ul><ul><li>A Digital Certificat e contains the digital signature of the certificate-issuing authority so that anyone can verify that the certificate is real. </li></ul>Stage II -ICMAP
  99. 99. Bluetooth <ul><li>Uses radio waves to connect mobile devices. </li></ul><ul><li>A wireless protocol for exchanging data over short distances from fixed and mobile devices, creating personal area networks (PANs). It can connect several devices, overcoming problems of synchronization. </li></ul><ul><li>A short-range radio technology aimed at simplifying communications among Internet devices and between devices and the Internet. </li></ul>Stage II -ICMAP
  100. 100. WAP(W ireless A pplication P rotocol ) <ul><li>A secure specification that allows users to access information instantly via handheld wireless devices such as mobile phones, pagers, two-way radios, smart phones. </li></ul><ul><li>Supports most wireless networks i.e.CDMA, GSM,. </li></ul><ul><li>WAP is supported by all operating systems. </li></ul><ul><li>WAPs that use displays and access the Internet run what are called micro browsers--browsers with small file sizes that can accommodate the low memory constraints of handheld devices and the low-bandwidth constraints of a wireless-handheld network. </li></ul>Stage II -ICMAP