Fundamentals of Networking , devices, communication modes, protection methods

Introduction to network, network devices, protection methods, types of network

1. 1 Fundamentals Of Network Operating Systems

2. 2 Computer Network - It is a collection of computers and terminal devices connected together by a communication system. -computer networking provides the communication tools to allow computers to share information and abilities

3. Network Goals Resource sharing The aim is to make all the programs, data and peripherals available to any one on the network irrespective of the physical location of the resources and the user. Reliability: A file can have copies on two or three different machines, so if one of them is unavailable, the other copies could be used. 3

4. Communication medium: The changes at one end can be immediately noticed at another and hence it speeds up co operation among them Email Message broadcast Cost Factor: Personal computers have better price / performance ratio than micro computers. So it is better to have PC’s, one per user with data stored on one shared file server machine . 4

5. Need of Networking: File sharing provides sharing and grouping of data files over the network. Print sharing of computer resources such as hard disk and printers etc. email tools for communication with the e-mail address. Remote access able to access data and information, around the globe. Sharing database to multiple users at the same time by ensuring the intergrity. 5

6. ARPANET The advanced Research Projects Agency Network(ARPANET) was one of the World’s first operational packet switching networks, the first network to implement TCP/IP, which was to become the global Internet. The network was initially funded by the Advanced Research Projects Agency (ARPA, later DARPA) within the U.S. Department of Defense for use by its projects at universities and research laboratories in the US. 6

7. OSI Reference Model. (Open System Interconnection) A ll P eople S eem T o N eed D ata P rocessing PDU ( Protocol Data Units) 7 7. Application 6. Presentation 5. Session 4. Transport 3. Network 2. Data Link 1. Physical

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9. Physical Layer : The physical layer is concerned with transmitting raw bits over a communication channel. It also deals with mechanical , electrical and timing interfaces. Data Link Layer: The main function of the data link layer is to transform a raw transmission facility into a line that appears free of undetected transmission errors to the network layer. Network Layer :The Network layer controls the operation of the subnet. The main function is to determine how packets are routed from source to destination. 9

10. Transport layer : The basic function of transport layer is to accept data from above layer and split it up into smaller units if needed, and pass these to the network layer and ensure that the pieces all arrive correctly at the other end. Session Layer : The session layer allows users on different machines to establish sessions between them. 10

11. Presentation Layer : The presentation layer concerned with the syntax and semantics of the information transmitted concerned with moving bits around the layer . Application Layer: The application layer contains a variety of protocols that are commonly needed by the user. For example HTTP 11

12. TCP/IP Model 12 Transmission Control Protocol/Internet Protocol) TCP/IP is a layered set of protocols . This protocol assumes that there is a way to communicate reliably between the two computers. TCP is responsible for making sure that the commands get through to the other end. It keeps track of what is sent, and retransmits anything that did not get through.

13. TCP/IP is the base communication protocol of the internet. The part of TCP/IP uses numeric IP addresses to join network segments and TCP part of TCP/IP provides reliable delivery messages between networked computers. 13

14. The user need to know the "Internet address", in order to access another system. This is an address that looks like 128.64.194.1. It is actually a 32 bit number. However it is normally written as 4 decimal numbers, each representing 8 bits of the address. 14

15. Information is transferred as a sequence of “data grams ”. Each of these datagrams is sent through the network individually. A data gram is a unit of data, which is what the protocols deal with. A packet is a physical thing, appearing on an Ethernet or some wire. 15

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17. 17 INTERNET The Internet is a worldwide network of computer networks that evolved from the first network ARPAnet . It is an interconnection of large and small networks around the globe.

18. 18 INTERSPACE Interspace is a client/server software program that allows multiple users to communicate online with real-time audio, video and text chat . It is the most advanced form of communication.

19. Elementary Terminology of Networks Hardware components of network: Nodes (Workstations) It refers to the computer that are attached to a network and are seeking to share the resources of the network. If there were no nodes, there would be no network at all. 19

20. 2) Server : Servers can be of two types: (A) non-dedicated servers (B) dedicated servers 20

21. Non-dedicated Servers: On small networks, a workstation that can serve as a server is known as non-dedicated server . shared environment server is a functional unit to cater to various companies one computer works as a work station and as well as server, it is slower and requires more memory. 21

22. Dedicated Servers On bigger network installations, there is a computer reserved for server’s job and its only job is to help workstations access data, software and hardware resources. Help the client’s computer/workstations to just have properly authorized access request associating to software, hardware as well as data manipulation The networks using such server are known as MASTER SLAVE networks. 22

23. On a network, there may be several servers that allow the workstations to share specific resources. Eg : file server, printer server ,modem server. 23

24. 24 Types Of Computer Networks Local Area Network (LAN) Wide Area Network (WAN) Metropolitan Area Network (MAN)

25. 25 Local Area Network (LAN) Covers small area like class room, school, or a building. Inexpensive to install and also provide higher speed. The purpose of a LAN is to serve its users in resource sharing. The hardware as well as software resource are shared through LANs. On most LANs cables are used to connect the network interface cards in each computer.

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27. 27 Metropolitan Area Network (MAN) Spans the distance of a typical metropolitan city. Cost of installation and operation is higher. MANs use high-speed connections like fiber optics. Cable TV connections.

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29. Wide Area Network 29

30. 30 Wide Area Network A Wide Area Networks (WANs) is a group of computers that are separated by large distances and tied together. Wide Area Network (WAN) connect larger geographic areas, such as Bangalore India or the world. Satellite uplinks may be used to connect this type of network. It uses multiplexers to connect local and metropolitan networks to global communications networks like the internet. Multiplexers is a device that merges several low speed transmissions in to one high speed transmission.

31. 31 Difference between a LAN and a WAN

32. 32 Network elements 1. At least two individuals who have something to share. 2. A method or pathway for contacting. 3. Rules so that two or more individuals can communicate. ( protocols ). Protocol : A protocol is a set of rules that governs the communications between computers on a network .

33. 33 TOPOLOGIES Actual appearance or layout of networking Linear Bus Star Ring Tree Mesh

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35. The Bus or Linear Topology 35 All devices are connected to a single cable Terminator at end taps to add new nodes (computer). Each node sends packets by adding the destination address on the packet. Checks that bus is not busy and then transfers packets. The transmission from any station travels the length of the bus, in both direction, and can be received by all other stations.  The bus has terminators at either end which absorb the signal, removing it from the bus

36. 36 Advantages of the linear topology Inexpensive to install. Easy to add new nodes. Requires minimum length cable Works well for small networks. .

37. Disadvantages of the linear topology If cable breaks, whole network is down. Limited number of nodes can be attached Fault diagnosis is difficult. Fault isolation is difficult. Repeater configuration: When bus type network has its backbone extended using repeaters, configurations may be necessary. 37

38. 38 Star Topology Each node is connected to a central node called HUB  or Switch. All messages are routed through the central node. It is the topology used in most existing information network involving data processing or voice communication.

39. Advantages of the Star topology Ease of service: The star topology has a number of points which are joined. These provide easy access for service or reconfiguration of the network. One device per connection:In the star topology, failure of a single connection typically involves disconnecting the node. Disadvantage: If the central node fails no communication take place. 39

40. 40 The Ring or Circular topology Node are connected in ring pattern Each node on the ring acts as repeater on the network Allows data to be sent in both directions. The signal may be amplified before being repeated on the outward channel. Node to node around the ring.

41. Advantage and disadvantages of the Ring topology Advantage: It requires short cable length Disadvantage: If anyone node fails no communication in ring. Difficult to diagnose faults. Network reconfiguration is difficult. 41

42. 42 The Tree Topology A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star configured work stations connected to a linear bus cable. Allow for the expansion of an existing network. Transmission in this topology takes place in the same way as in the bus topology. In both cases, there is no  need to remove packets from the medium because when a signal reaches the end of the medium, it is absorbed by the terminators. Tree topology is best suited for the applications which have hierarchical flow of data and control.

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44. 44 Mesh Topology A pure mesh network has point to point connections between every node in the network. Amount of cable for large network is tremendous

45. Advantage: Expansion and modifications in topology can be done without disrupting other nodes Disadvantage: Overall cost of this network is high compared to other network 45

46. Graph Topology Nodes are connected together in an arbitrary fashion. A link may or may not connect two or more nodes . It is not necessary that all the nodes are connected. But if a path can be established in two nodes via one or more links is called a connected graph. 46

47. 47 TRANSMISSION MEDIUM Transmission medium means connecting cables or connecting media. telephone , microwave relay, satellite link, or physical cable.

48. TWISTED PAIR CABLE A pair of wires forms a circuit that can transmit data. Pair of cables is twisted to avoid noise interference generated by adjacent pairs. 48

49. Types of Twisted Pair Cables Unshielded Twisted Pair (UTP): is an unprotected cable,may be susceptible to electrical interference. Shielded Twisted Pair (STP): Two independent wires coated in a foil shielding that prevents electromagnetic interference and speed up the data transmission Properties: UTP –Least expensive, length- up to 100m, less protection from interference STP –Moderately expensive, length- up to 100m, offers greater protection from interference 49

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51. 51 Coaxial Cables Coaxial cabling has a single copper conductor at its center. A plastic layer provides insulation Between the center conductor and A braided metal shield The metal shield helps to block any Out side interference from fluorescent lights, motors and other Computers. A: outer plastic sheath B: woven copper shield C: inner dielectric insulator D: copper core

52. 52 Optical Fibers: Fiber optic cabling consists of center glass core surrounded by layers of protective materials Transmits light rather than electronic signal, thus eliminating problem of electrical interference Has high transmission capacity

53. Radio Wave It transmit the radio frequencies. Two parts: 1. The transmitter 2. The receiver The transmitter takes message (voice, pictures ), encodes it onto wave and transmits it. The receiver receives the radio waves and decodes the message. Both the transmitter and receiver use antennas to radiate and capture the radio signal. 53

54. Satellite (Satellite Microwave) Has time saving, fast implementation and broad coverage characteristics Number of communication satellite s owned by both government and private organization have been placed in stationary orbits about 22300 miles above earth’s surface T hese satellites act as relay stations for communication signals The satellites accept data / signals transmitted from an earth station , amplify them and retransmit them to the other side of the earth in only one step. 54

55. Apart from microwaves, radio waves and satellites, two other media are infrared and laser waves. Infrared : This type of transmission uses infrared light to send the data . The infrared light transmits data through the air and can propagate throughout a room ,but will not penetrate walls . It is used in handheld devices. 55

56. 2. Laser : The Laser transmission requires direct line-of-sight. It is unidirectional like microwave, but has much higher speed than microwaves. It requires laser transmitter and a photo-sensitive receiver at each end. The laser transmission is point-to-point transmission, 56

57. 57 Transmission/Switching Techniques Circuit Switching Circuit switching is a connection technique that directly connect the sender and receiver in an unbroken path. Ex: Telephone switching equipment First the complete physical connection between two computers is established and then data are transmitted from the source computer to the destination computer i.e , end to end path must exist before communication can take place. Message Switching With message switching there is no need to establish a dedicated path between two stations. When a station sends a message, it appends a destination address to the message. The message is then transmitted through the network, from node to node.

58. 58 Transmission/Switching Techniques Packet Switching: Packet switching can be seen as an option that tries to combine the advantages of messages and circuit switching and to minimize the disadvantages of both. In this method, a message is broken into small parts, called packets. Each packet is tagged with appropriate source and destination addresses. This fact allows packets to take a variety of possible paths through the network. A sequencing number is added to each packet. At the receiving end it is reordered by sequence number,and the original message is reconstructed.

59. 59 Communication modes Simplex : On a simplex channel, only one interface is a transmitter and every other interface is a receiver. The channels full bandwidth is always available for signals traveling from the transmitter to the receiver (s). The transmitting interface can not receive information and the receiving interface (s) can not transmit. Ex: Commercial broad cast radio and television

60. 60 Communication modes Half-Duplex : On a half-duplex channel, each interface serves as both transmitter and receiver, but only one interface can transmit at a time. Ex : walkie - Talkies

61. 61 Communication modes F ull Duplex : A full-duplex channel has two ends, each serving as both transmitter and receiver. Each interface can both transmit and receive at the same time. Ex: Modern telephone systems provide full-duplex channels.

62. NETWORK DEVICES Modem (Modulator and Demodulator): Used to connect computer system to internet. In transmitting end modem changes the digital data into analog data, so that can be carried by telephone lines . In receiving end modem changes the analog signal back into digital data Modems are of two types : 1.Internal modems: The modems that are fixed within the computer. 2.External modems: The modems that are connected externally to a computer as other peripherals are connected. 62

63. Ethernet Card If computers are part of Ethernet , have to install a special card called Ethernet Card . It contains connections for either Coaxial or Twisted pair cables (or both). 63

64. Hub A hub is a hardware device used to connect several computers together . 1.Active Hubs: Electrically amplify the signal as it moves from one connected device to another. 2. Passive Hubs: Allow the signals to pass from one computer to another without any change. 64

65. 65 Networking hardware Switches: Helps to manage flow of data across the network by segmenting network into different sub-networks

66. 66 Networking hardware Repeaters: A repeater is a device that amplifies a signal being transmitted on the network. It is used in long network lines, which exceed the maximum rated distance for a single run. There are 2 types: amplifier and signal repeater. Amplifier amplifies all incoming signals over the network. Signal repeater , collects the inbound packet and then retransmits the packet as if it were starting from the source station.

67. Bridges: A bridge is a device that lets us link two networks together. As a packet arrives at the bridge, the bridge examines the physical destination address of the packet. The bridge then decides whether or not to let the packet cross. 67

68. 68 Networking hardware Routers A device that works like a bridge but can handle different protocols. If the destination is unknown to a router it sends the traffic to another router (using logical addresses) which knows the destination . Router selects the best path to route a message based on the destination address and origin.

69. Gateway: A Gateway is a device that connects dissimilar networks. It is a node on a network that serves as an entrance to another network . In home, gateway is ISP that connects user to internet. In enterprises, the gateway node often acts as a proxy server and a firewall Proxy server: is a machine that is not actually a server but appears as a server. Firewall: a system designed to prevent unauthorized access to or from a private network. 69

70. Wireless Vs Mobile Computing Wireless communication is simply data communication without use of physical connectivity Mobile computing Mobile simply describing a computing device that is not restricted to a desktop. A mobile device may be a PDA, a small cell phone or web phone, a laptop computer or any other of numerous other devices that allow the user to complete the computing task without being connected to a network. 70

71. GSM GSM is short for Global System for Mobile communications , which is one of the digital cellular systems. It uses Subscriber Identification Module (SIM) cards, that store all the connection data and identification numbers we need to access a particular wireless service provider . GSM uses narrow band TDMA(Time Division Multiple Access) which allows 8 simultaneous calls on the same radio frequency TDMA  dividing radio frequency into time slots and then allocating slots to multiple calls 71

72. SIM card SIM – Subscriber Identity Module – is a chip card A SIM is a tiny computer chip that gives a cellular device its unique phone number. It has memory, a processor and the ability to interact with the user 72

73. CDMA CDMA is Code Division Multiple Access, a digital cellular technology that uses spread spectrum techniques. 73

74. WLL (Wireless in local loop) Wireless in local loop (WLL or WILL), is meant to server subscribers at homes or offices. It is analogous with local telephone service, but much more capable. 74

75. GPRS GPRS is the abbreviation for General Packet Radio Service . GPRS is used for wireless communication using a mobile device. 75

76. 1G, 2G, 3G, 4G and 5G Networks “G” in wireless networks refers to the “generation” 76

77. Applications in networking: SMS :Short message service Chat: Real time communication between 2 users Video Conferencing: live visual connection b/n 2 or more people residing in separate location Wi-Fi : refers to Wireless Fidelity Wi-Fi Hotspots : A hotspot is a venue that offers Wi-Fi access. WiMax : WiMax is a wireless digital communications system. WiMax can provide Broadband Wireless Access (BWA) up to 30 miles (50 km) for fixed stations and 3-10 miles (5-15 km) for mobile stations. 77

78. Network Security The problems encountered under network security are as follows Physical security holes: Hackers do it by guessing passwords of various users and then gaining access to systems. Software security holes: When badly written programs or software are compromised into doing things that they should not be doing. Inconsistent usage holes : When a system administrator assembles a combination of hardware and software, because of improper combination security problem may exist. 78

79. PROTECTION METHODS Authorization: Authorization is performed by asking the user a legal login ID. If the user is able to provide a legal login ID, he/she is considered an authorized user. Authentication: It is termed as password protection as the authorized user is asked to provide a valid password and if he or she is able to do this, he or she considered to be an authentic user. Encrypted Smart Cards: An encrypted smart card is a hand held smart card that can generate a token that a computer system can recognize. Every time a new and different token is generated, which even though cracked or hacked, cannot be used later. 79

80. 4. Bio Metric Systems: The Biometric systems involve some unique aspects of a person’s body such as finger prints, retinal patterns, etc to establish his/her identity. 5. Firewall: A system designed to prevent unauthorized access to or from a private network is called firewall. 80

81. There are several types of firewall techniques. Packet Filter: Looks as each packet entering or leaving the network and accepts or rejects it based on user defined rules. Application gateway: It applies security mechanisms to specific applications, such as FTP and Telnet Servers. This is very effective, but can impose performance degradation. Circuit Level Gateway: It applies security mechanisms when a connection is established. Proxy Server: It intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses. 81

82. 82 Cookies Cookies are messages that a web server transmits to a web browser so that a web server can keep track of the user’s activity on a specific web site. Hackers and Crackers : The Crackers malicious programmers who break into secure systems where as Hackers are more interested in gaining knowledge about computer systems and possibly using this knowledge for play full pranks.

83. Cyber Law: Cyber Law is a generic term, which refers to all the legal and regulatory aspects of internet and the WWW. India’s IT Act : In India the cyber laws are contained in the information technology act, 2000 which was notified on 17 October 2000. It is based on the United Nations Commission for International Trade Related Laws (UNCITRAL) model law. 83

84. Viruses Computer Virus is a malicious program that requires a host and is designed to make a system problem. It can spread from computer to computer and they can replicate themselves. 84

85. Types of viruses are: File Infectors : These types of viruses either infect executable files or attach themselves to a program file and create duplicate files. Boot Sector Viruses: Install themselves on the beginning tracks of a hard drive or the Master Boot Record or simply they change the pointer to an active boot sector. Macro Viruses : Infect data files like electronic spreadsheets or databases of several software packages. Network Viruses : These virus use protocols and commands of computer network to spread themselves on the network. Generally they use email or any data transfer files to spread themselves on the network. 85

86. The following are characteristics of a computer virus. It is able to replicate It requires a host program as a carrier It is activated by external action Its replication ability is limited to the system. 86

87. Virus Prevention 1.Never use a “Foreign” disk or CD without scanning it for viruses. 2.Always scan files downloaded from the internet or other sources. 3.Never boot your PC from a floppy unless you are certain that it is virus free. 4.Write protect your disks. 5.Use licensed software. 6.Password protect your PC to prevent unattended modification. 7.Install and use antivirus software. 8.Keep antivirus software up to date. Some of the antivirus are Kaspersky , Quick heal, K7, Norton 360, Micro trend titanium, AVG, Panda, ESET Nod32, Avast.McAFee etc., 87

88. Network Protocols HTTP(Hyper Text Transfer Protocol) The HTTP provides a standard for web browser and server to communicate HTTP is the foundation of data communication for the World Wide Web. HTTP defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. For example, when you enter a URL in your browser, this actually sends an HTTP command to the Web server directing it to fetch and transmit the requested Web page. 88

89. continued FTP(File Transfer Protocol) The File Transfer Protocol ( FTP ) is a standard network protocol used to transfer computer files from one host to another host. The protocol for exchanging files over the Internet. SLIP/PPP(Serial Line Internet Protocol) SLIP was the first protocol for relaying the IP packets over dial-up lines. Replaced by PPP 89

90. continued PPP(Point to Point Protocols) Used to transmit IP packets between 2 directly connected computers Has components like, Encapsulation : Encapsulates datagram Link Control Protocol : Establishes, terminates, manages the link Authentication protocols 90

91. 1 G I G networks are conceived and designed purely for voice calls with almost no consideration of data services. NMT,TAMS,AMPS, CNET are considered to be the first analog cellular systems which started early 1980s 91

92. 2 G GSM, CDMAOne , D-AMPS are digital cellular systems launched early 1990s Improved sound quality, better security 2.5 G: GPRS, CDMA2000 Data rates up to 144kbps GPRS offered data service 92

93. 3G CDMA 2000 1x EVDO, CDMA2000 3x 1, EDGE 3 G are cellular networks that have data rates of 384kbps and more UMTS(Universal Mobile Telecommunication System) is a broadband packet based transmission of text, digitized voice, video and multimedia at data rates higher than 2 mbps 93

94. 4 G Support for multiple applications and services Supports unicast, multicast, broadcast services and applications that relay on them Quality of service Network detection and network selection 94

95. 5 G Real wireless world with no more limitation to access and zone issues Wearable devices with AI technology IPV6 User can simultaneously connected to several wireless access technology and seamlessly move between them. Supports VPN-Virtual Private Network Uploading and downloading speed is very high 95

96. EDGE- Enhanced Data rate for Global Evolution EDGE is a data system used on top of GSM networks It provides nearly 3 times faster speed than outdated GPRS system EDGE meets the requirement for 3 G network 96