Data computer networks from rajeev institute of technology

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1. COMPUTER NETWORKS (BCS502) Dr. Prathibha G Assoc. Professor,ISE Rajeev Institute of Technology

2. Textbook Behrouz A. Forouzan , Data Communications and Networking, 5th Edition , Tata McGraw-Hill,2013 Reference Books: 1. Larry L. Peterson and Bruce S. Davie : Computer Networks – A Systems Approach, 4th Edition , Elsevier, 2019. 2. Nader F. Mir: Computer and Communication Networks, 2nd Edition , Pearson Education, 2015. 3. William Stallings, Data and Computer Communication 10th Edition , Pearson Education, Inc., 2014

3. Module 1

4. Data Communications Data communications are the exchange of data between two devices via some f orm of transmission medium such as a wire cable F our fundamental characteristics of Data Communication are: 1. Delivery: The system must deliver data to the correct destination. Data must be received by the intended device or user and only by that device or user. 2. Accuracy: The system must deliver the data accurately. Data that have been altered in transmission and left uncorrected are unusable. 3. Timeliness: The system must deliver data in a timely manner. Data delivered late are useless. In the case of video and audio, timely delivery means delivering data as they are produced, in the same order that they are produced, and without significant delay. This kind of delivery is called real-time transmission. 4. Jitter: Jitter refers to the variation in the packet arrival time. It is the uneven delay in the delivery of audio or video packets. For example, let us assume that video packets are sent every 30 ms. If some of the packets arrive with 30-ms delay and others with 40-ms delay, an uneven quality in the video is the result.

5. Data Communications- Components

6. Data Communications- Components(Contd...) Messag e: The message is the information (data) to be communicated. Popula r forms of information include text, numbers, audio, and video. Sender: The sender is the device that sends the data message. It can be a computer, workstatio n etc Receiver: The receiver is the device that receives the message. It can be a computer, workstation etc . Transmission medium: The transmission medium is the physical path by whic h a message travels from sender to receiver. Some examples of transmission media include twisted-pair wire, coaxial cable, fiber-optic cable, and radio waves . Protocol: A protocol is a set of rules that govern data communications. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating

7. Data Communications- Data Representation Text: Text is represented as a bit pattern , a sequence of bits (0s or 1s) Different sets of bit patterns have been designed to represent text symbols. Each set is called a code, and the process of representing symbols is called coding. Numbers: Numbers are also represented by bit patterns and the number is directly converted to a binary number . Images: Images are also represented by bit patterns In its simplest form, an image is composed of a matrix of pixels (picture elements), where each pixel is a small dot. The size of the pixel depends on the resolution After an image is divided into pixels, each pixel is assigned a bit pattern. If the image made only on black and-white dots (0 or 1) In the case of Gray scale black pixel - 00 dark gray- 01 light gray - 10 white pixel -11

8. Data Communications- Data Representation RGB : Each color is made of a combination of three primary colors: red, green, and blue YCM : color is made of a combination of three other primary colors: yellow, cyan, and magenta 4. Video: Video refers to the recording or broadcasting of a picture or movie It may be a continuous entity or combination of images, each a discrete entity, arranged to convey the idea of motion 5 . Audio : Audio refers to the recording or broadcasting of sound or music. It is continuous, not discrete

9. Data Communications- Data Flow S implex : H alf-duplex

10. Data Communications-Data Flow Full duplex

11. NETWORKS A network is the interconnection of a set of devices capable of communication D evice can be a host : large computer, desktop, laptop, workstation, cellular phone, or security system etc Connecting device : router- which connects the network to other networks switch- which connects devices together modem (modulator-demodulator)- which changes the form of data D evices in a network are connected using wired or wireless transmission media such a s cable or air

12. NETWORKS - Network Criteria A N etwork must be able to meet a certain number of criteria Performance It measures based on transit time and response time Performance is often evaluated by two networking metrics: throughput and delay If we try to send more data to the network, we may increase throughput but we increase the delay because of traffic congestion in the network Reliability T he frequency of failure, the time it takes a link to recover from a failure Security S ecurity issues include protecting data from unauthorized access, protecting d ata from damage and development

13. NETWORKS -Network attributes (Physical Structures ) 1. Type of Connection: Point-to-Point Dedicated link between two devices Multipoint or multidrop

14. NETWORKS -Network attributes (Physical Structures ) Physical Topology : The actual or the physical layout of a network Four basic topologies: Mesh Topology Find the number of physical links in a fully connected mesh network with n no de is n (n – 1) If the network

15. A dvantages : Dedicated links Robust Privacy or security Fault identification Disadvantages : Amount of cabling and the number of I/O ports Installation and reconnection Hardware required to connect each link is expensive

16. NETWORKS -Network attributes (Physical Structures ) Star Topology

17. Advantages: less expensive than a mesh topology, easy to install and reconfigure and less cabling needed If one link fails, only that link is affected Disadvantage The dependency of the whole topology on one single point, the hub. If the hub goes down, the whole system is dead.

18. Bus Topology Traditional Ethernet LANs

19. Advantages: Ease of installation , bus uses less cabling than mesh or star topologies Redundancy is eliminated Disadvantage Reconnection and fault isolation Fault or break in the bus cable stops all transmission The damaged area reflects signals back in the direction of origin, creating noise in both directions.

20. Ring Topology

21. Advantages: Ease of installation , bus uses less cabling than mesh or star topologies Redundancy is eliminated Disadvantage Unidirectional traffic A break in the ring (such as a disabled station) can disable the entire network This weakness can be solved by using a dual ring or a switch capable of closing off the break

22. Network Types - LAN ( Local Area Network) In the past, all hosts in a network were connected through a common cable, which meant that a packet sent from one host to another was received by all hosts The intended recipient kept the packet; the others dropped the packet M ost LANs use a smart connecting switch, which is able to recognize the destination address of the packet and guide the packet to its destination without sending it to all other hosts

23. Network Types - WAN ( Local Area Network) WAN has a wide geographical span, spanning a town, a state, a country, or even the world WAN interconnects connecting devices such as switches, routers, or modems. WANs today: point-to-point WANs switched WANs point-to-point WAN Switched WAN

24. Network Types - Internetwork T wo or more networks are connected, they make an internetwork, or internet

25. PROTOCOL LAYERING When communication is simple, we may need only one simple protocol; when the communication is complex, we may need to divide the task between different layers, in which case we need a protocol at each layer Scenarios : First Scenario:

26. PROTOCOL LAYERING Second Scenario :

27. Principles of Protocol Layering First Principle : Example: the third layer task is to listen (in one direction) and talk (in the other direction). The second layer needs to be able to encrypt and decrypt. The first layer needs to send and receive mail Second Principle : Example : Under layer 3 at both sites should be a plaintext letter. The object under layer 2 at both sites should be a ciphertext letter. The object under layer 1 at both sites should be a piece of mail

28. Logical Connections

29. TCP/IP PROTOCOL SUITE (Transmission Control Protocol/Internet Protocol ) It is a hierarchical protocol made up of interactive modules, each of which provides a specific functionality Layered Architecture :

30. Description of Each Layer Application Layer : Communication at the application layer is between two processes (two programs running at this layer). To communicate, a process sends a request to the other process and receives a response. Process-to-process communication is the duty of the application layer Protocols: Hypertext Transfer Protocol (HTTP) - Accessing the World Wide Web (WWW) Simple Mail Transfer Protocol (SMTP) - Electronic mail (e-mail) service File Transfer Protocol (FTP) - Used for transferring files from one host to another Terminal Network (TELNET) and Secure Shell (SSH) - Accessing a site remotely Simple Network Man_x0002_agement Protocol (SNMP) - used by an administrator to manage the Internet at global and local levels Domain Name System (DNS) : Used by other protocols to find the network-layer address of a computer Internet Group Management Protocol (IGMP) : Used to collect membership in a group

31. Description of Each Layer Transport Layer: The transport layer at the source host gets the message from the application layer, encapsulates it in a transport layer packet (called a segment or a user datagram in different protocols) and send Protocol: Transmission Control Protocol (TCP) - connection-oriented protocol that first establishes a logical connection between transport layers at two hosts before transferring data TCP provides : Flow control Error Control congestion control

32. Description of Each Layer Protocol: User Datagram Protocol (UDP) : connectionless protocol that transmits user datagrams without first creating a logical connection UDP does not provide flow, error, or congestion control Stream Control Transmission Protocol (SCTP) Designed to respond to new applications that are emerging in the multimedia

33. Description of Each Layer Network Layer : Creating a connection between the source computer and the destination computer Communication at the network layer is host-to-host several routers from the source to the destination, the routers in the path are responsible for choosing the best route for each packet Protocols : Internet Protocol (IP) : Defines the format of the packet IP is also responsible for routing a packet from its source to its destination IP is a connectionless protocol that provides no flow control, no error control, and no congestion control services Internet Control Message Protocol (ICMP) : Helps IP to report some problems when routing a packet Internet Group Management Protocol (IGMP) : Helps IP in multitasking

34. D escription of Each Layer Protocols : Dynamic Host Configuration Protocol (DHCP) : Helps IP to get the network-layer address for a host Address Resolution Protocol (ARP): Helps IP to find the link-layer address of a host or a router when its network-layer address is given Data-link Layer: Data-link layer is responsible for taking the datagram and moving it across the link. The link can be a wired LAN with a link-layer switch, a wireless LAN, a wired WAN, or a wireless WAN The data-link layer takes a datagram and encapsulates it in a packet called a frame TCP/IP does not define any specific protocol for the data-link layer.

35. D escription of Each Layer Physical Layer: Physical layer is responsible for carrying individual bits in a frame across the link Bits received in a frame from the data-link layer are trans_x0002_formed and sent through the transmission media

36. D escription of Each Layer

37. D escription of Each Layer

38. D escription of Each Layer

39. Encapsulation and Decapsulation

40. Encapsulation and Decapsulation Video1- https://www.youtube.com/watch?v=0y6FtKsg6J4 Video2 https://www.youtube.com/watch?v=aaJ1KcCDz-c

41. Encapsulation and Decapsulation Encapsulation at the Source Host: At the application layer , the data to be exchanged is referred to as a message. A message normally does not contain any header or trailer, but if it does, we refer to the whole as the message. The message is passed to the transport layer The transport layer takes the message as the payload, the load that the transportlayer should take care of. It adds the transport layer header to the payload , which contains the identifiers of the source and destination application programs that want to communicate plus some more information that is needed for the end-to-end delivery of the message, such as information needed for flow, error control, or congestion control . The result is the transport-layer packet, which is called the segment (in TCP) and the user datagram (in UDP) . The transport layer then passes the packet to the network layer.

42. Encapsulation and Decapsulation Encapsulation at the Source Host: The network layer takes the transport-layer packet as data or payload and adds its own header to the payload. The header contains the addresses of the source and destination hosts and some more information used for error checking of the header, fragmentation information, and so on . The result is the network-layer packet, called a datagram. The network layer then passes the packet to the data-link layer. The data-link layer takes the network-layer packet as data or payload and adds its own header, which contains the link-layer addresses of the host or the next hop (the router). The result is the link-layer packet, which is called a frame . The frame is passed to the physical layer for transmission.

43. Encapsulation and Decapsulation Decapsulation and Encapsulation at the Router After the set of bits are delivered to the data-link layer, this layer decapsulates the datagram from the frame and passes it to the network layer The network layer only inspects the source and destination addresses in the datagram header and consults its forwarding table to find the next hop to which the datagram is to be delivered. The contents of the datagram should not be changed by the network layer in the router unless there is a need to fragment the datagram if it is too big to be passed through the next link. The datagram is then passed to the data-link layer of the next link The data-link layer of the next link encapsulates the datagram in a frame and passes it to the physical layer for transmission.

44. Encapsulation and Decapsulation Decapsulation at the Destination Host : Each layer only decapsulates the packet received, removes the payload, and delivers the payload to the next-higher layer protocol until the message reaches the application layer

45. Addressing

46. Multiplexing and Demultiplexing

47. THE OSI MODEL (Open Systems Interconnection)

48. THE OSI MODEL (Open Systems Interconnection)

49. Switching: Packet Switching and its types Packet Switching : If the message is going to pass through a packet-switched network, it needs to be divided into packets of fixed or variable size In packet switching, there is no resource allocation for a packet. This means that there is no reserved bandwidth on the links, and there is no scheduled processing time for each packet. Resources are allocated on demand The allocation is done on a first come, first-served basis Two types of Packet Switchings are Datagram Networks Virtual-Circuit Networks

50. Packet Switching -Datagram Networks /connectionless network

51. Routing Table A switch in a datagram network uses a routing table that is based on the destination address Destination Address : The destination address in the header of a packet in a datagram network remains the same during the entire journey of the packet Efficiency

52. Delay

53. TRANSMISSION MEDIA A transmission medium can be broadly defined as anything that can carry info r mation from a source to a destination.

54. TRANSMISSION MEDIA

55. TRANSMISSION MEDIA- GUIDED MEDIA Types of Guided Media: T wisted-pair cable C oaxial cable F iber-optic cable Twisted-Pair Cable : A twisted pair consists of two conductors (normally copper), each with its own plastic insulation, twisted together

56. Unshielded Versus Shielded Twisted-Pair Cable

57. Unshielded Versus Shielded Twisted-Pair Cable

58. Unshielded Twisted-Pair Cable - Categories

59. Unshielded Twisted-Pair Cable - Connectors RJ - Registered Jack

60. Unshielded Twisted-Pair Cable - Connectors

61. Twisted-Pair Cable - Performance

62. Twisted-Pair Cable -Applications Twisted-pair cables are used in telephone lines to provide voice and data channels

63. Guided Media - Coaxial Cable

64. Guided Media - Coaxial Cable

65. Guided Media - Coaxial Cable - Standards

66. Guided Media - Coaxial Cable - Connectors To connect coaxial cable to devices, we need coaxial connectors M ost common type of connector is Bayonet Neill-Concelman (BNC)

67. Guided Media - Coaxial Cable - Connectors BNC T BNC Connector

68. Guided Media - Coaxial Cable - Performance C oaxial cable has a much higher bandwidth the signal weakens rapidly and requires the frequent use of repeaters

69. Guided Media - Coaxial Cable - Applications Coaxial cable was widely used in analog telephone networks where a single coaxial network could carry 10,000 voice signals D igital telephone networks where a single coaxial cable could carry digital data up to 600 Mbps Cable TV networks also use coaxial cables. T raditional Ethernet LANs C oaxial cable in telephone networks has largely been replaced today with fiberoptic cable .

70. Guided Media - Fiber- Optic Cable F iber-optic cable is made of glass or plastic and transmits signals in the form of light Light travels in a straight line as long as it is moving through a single uniform substance If a ray of light traveling through one substance suddenly enters another substance(of a different density), the ray changes direction

71. Guided Media - Fiber- Optic Cable I - A ngle of incidence

72. Fiber- Optic Cable - Propagation Modes

73. Fiber- Optic Cable - Fiber Size

74. Fiber-Optic Cable Connectors S ubscriber channel (SC) connector - Used for cable TV uses a push/pull locking system S traight-tip (ST) connector used for connecting cable to networking devices uses a bayonet locking system and is more reliable than SC MT-RJ is a connector that is the same size as RJ45

75. Fiber-Optic Cable - Performance

76. Fiber-Optic Cable - Applications Fiber-optic cable is often found in backbone networks because its wide bandwidth is cost-effective cable TV companies use a combination of optical fiber and coaxial cable Local-area networks such as 100Base-FX network (Fast Ethernet) and 1000Base-X also use fiber-optic cable

77. Fiber-Optic Cable - Advantages Higher bandwidth : Fiber-optic cable can support higher bandwidths (and hence data rates) than either twisted-pair or coaxial cable. Currently, data rates and bandwidth utilization over fiber-optic cable are limited not by the medium but by the signal generation and reception technology available Less signal attenuation : Fiber-optic transmission distance is significantly greater than that of other guided media. A signal can run for 50 km without requiring regeneration. We need repeaters every 5 km for coaxial or twisted-pair cable Immunity to electromagnetic interference : Electromagnetic noise cannot affect fiber-optic cables. Resistance to corrosive materials : Glass is more resistant to corrosive materials t han copper. Light weight. Fiber-optic cables are much lighter than copper cables. Greater immunity to tapping : Fiber-optic cables are more immune to tapping than copper cables. Copper cables create antenna effects that can easily be tapped.

78. Fiber-Optic Cable - Disadvantages Installation and maintenance : Fiber-optic cable is a relatively new technology. Its installation and maintenance require expertise that is not yet available everywhere Unidirectional light propagation : Propagation of light is unidirectional. If we need bidirectional communication, two fibers are needed. Cost : The cable and the interfaces are relatively more expensive than those of other guided media. If the demand for bandwidth is not high, often the use of optical fiber cannot be justified.

79. UNGUIDED MEDIA: WIRELESS Unguided medium transport electromagnetic waves without using a physical conductor Types are: Radio Waves Microwaves Infrared Electromagnetic spectrum for wireless communication

80. UNGUIDED MEDIA: WIRELESS Electromagnetic spectrum for wireless communication

81. UNGUIDED MEDIA: WIRELESS Unguided signals can travel from the source to the destination in several ways G round propagation : radio waves travel through the lowest portion of the atmosphere S ky propagation : higher-frequency radio waves radiate upward into the ionosphere where they are reflected back to earth line-of-sight propagation: very high-frequency signals are transmitted in straight lines directly from antenna to antenna Very high-frequency signals are transmitted in straight lines directly from antenna to antenna Antennas must be directional, facing each other, and either tall enough or close enough together not to be affected by the curvature of the earth

82. UNGUIDED MEDIA: Bands

83. UNGUIDED MEDIA: Radio Waves W aves ranging in frequencies between 3 kHz and 1 GHz Radio waves, particularly those of low and medium frequencies, can penetrate wall Omnidirectional Antenna :

84. UNGUIDED MEDIA: Radio Waves A ntenna transmits radio waves, they are propagated in all directions S ending and receiving antennas do not have to be aligned S ending antenna sends waves that can be received by any receiving antenna

85. UNGUIDED MEDIA: Radio Waves A ntenna transmits radio waves, they are propagated in all directions S ending and receiving antennas do not have to be aligned S ending antenna sends waves that can be received by any receiving antenna Applications: Radio waves are used for multicast communications, such as radio and television, and paging systems

86. UNGUIDED MEDIA: Microwaves F requencies between 1 and 300 GHz Microwaves are unidirectional S ending and receiving antennas need to be aligned Very high-frequency microwaves cannot penetrate walls. This characteristic can be a disadvantage if receivers are inside buildings High data rate is possible

87. UNGUIDED MEDIA: Microwaves Unidirectional Antenna: Applications: Microwaves are used for unicast communication such as cellular telephones, satellite networks, and wireless LANs

88. UNGUIDED MEDIA: Infrared Frequencies from 300 GHz to 400 THz can be used for short-range communication Having high frequencies, cannot penetrate walls Advantages: A short-range communication system in one room cannot be affected by another system in the next room We use our infrared remote control, we do not interfere with the use of the remote by our neighbors.

89. UNGUIDED MEDIA: Infrared Disadvantages: We cannot use infrared waves outside a building because the sun’s rays contain infrared waves that can interfere with the communication. Applications : Infrared signals can be used for short-range communication in a closed area using line-of-sight propagation