CPSC441

1. CPSC441

2. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

3. Signal Transmission Electronic energy to send signals that communicate from one node to another Two methods of transmitting data Digital signaling Analog signaling

4. Comparison of Digital and Analog

5. Bandwidth-Limited Signals

6. Bandwidth-Limited Signals

7. Digital Signaling Digital signal represents discrete state (on or off) Practically instantaneous change

8. Digital SignalingCurrent State Encoding Data is encoding by the presence or absence of a signal A positive voltage might represent a binary zero or binary one or visa versa The current state indicates the value of the data

9. Digital Signaling Current State

10. Digital Signaling State Transition

11. Analog Signaling Signals represented by an electromagnetic wave Signal is continuos and represents values in a range Uses one or more of the characteristics of an analog wave to represent ones and zeros

12. Characteristics of an Analog Signal

13. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

16. Wire Propagation Effects Propagation Effects Signal changes as it travels Receiver may not be able to recognise it

17. Propagation Effects: Attenuation Attenuation: signal gets weaker as it propagates Attenuation becomes greater with distance May become too weak to recognise

18. Propagation Effects: Distortion Distortion: signal changes shape as it propagates Adjacent bits may overlap May make recognition impossible for receiver

19. Propagation Effects: Noise Noise: thermal energy in wire adds to signal Noise floor is average noise energy Random signal, so spikes sometimes occur

20. Propagation Effects: SNR Want a high Signal-to-Noise Ratio (SNR) Signal strength divided by average noise strength As SNR falls, errors increase

21. Propagation Effects: Interference Interference: energy from outside the wire Adds to signal, like noise Often intermittent, so hard to diagnose

22. Propagation Effects: Termination Interference can occur at cable terminator (connector, plug) Often, multiple wires in a bundle Each radiates some of its signal Causes interference in nearby wires Especially bad at termination, where wires are unwound and parallel

23. Bandwidth Capacity of a media to carry information Total capacity may be divided into channels A channel is a portion of the total bandwidth used for a specific purpose

24. Bandwidth Baseband The total capacity of the media is used for one channel Most LANs use baseband Broadband Divides the total bandwidth into many channels Each channel can carry a different signal Broadband carries many simultaneous transmissions

25. Analog versus Digital Digital Is less error prone Distortion of the signal between the source and destination is eliminated Analog Little control over the signal distortion Old technology

26. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

27. Benefits of Digital Transmission Reliability Can regenerate slightly damaged signals There are only two states. Change to closest E.g., if two states are voltages +10v (1) and -10v (0) and the signal is +8v, the signal is a 1

28. Benefits of Digital Transmission Error detection and correction Can correct errors in transmission Add a few bytes of error-checking information Can ask for retransmission if an error is detected

29. Benefits of Digital Transmission Encryption Encrypt (scramble) messages so that someone intercepting them cannot read them

30. Benefits of Digital Transmission Compression Compress message before transmission Decompress at other end Compressed message places lighter load on transmission line, so less expensive to send Not always used

31. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

32. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

33. Analog Signaling Amplitude Modulation (ASK)

34. Analog Signaling Frequency Modulation (FSK)

35. Analog Signaling Phase Shift Keying (FSK)

36. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

37. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

38. Modems Modulation demodulation Used to connect a digital computer to an analog phone system Can be installed internally a card inserted into the motherboard Can be connected to the serial port (external modem)

39. Modems Transfer speeds Bit rate BPS Baud Bandwidth Compression appears to increases speed by decreasing the number of bits sent (usually some data does not compress well) sending and receiving modem must use same compression standard

40. Modems Error detection and correction asynchronous modems use parity check checksum counting the number of data words sent

41. Digital Modem Miss named Used to connect to a digital telephone ISDN (integrated Services Digital Network) is an example Again do not connect digital modems to an analog phone Higher quality lower errors

42. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

43. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

44. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

45. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

46. Network Media Types Types of Media Cable (conducted media) Coaxial Twisted pair (UTP) Shielded twisted pair (STP) Fiber optic Radiated Infrared Microwave Radio Satellite

47. Media Selection Criteria Cost For actual media and connecting devices such as NICs hubs etc Installation Difficulty to work with media Special tools, training

48. Media Selection Criteria Capacity The amount of information that can be transmitted in a giving period of time Measured as Bits per second bps (preferred) Baud (discrete signals per second) Bandwidth (range of frequencies)

49. Media Selection Criteria Node Capacity Number of network devices that can be connected to the media Attenuation Weakening of the signal over distance

50. Media Selection Criteria Electromagnetic Interference (EMI) Distortion of signal caused by outside electromagnetic fields Caused by large motors, proximity to power sources Other noise sources White (Gaussian) noise Impulse noise Crosstalk Echo

51. Cable Media Unshielded Twisted Pair UTP Shielded Twisted Pair STP Coaxial Fiber optic

52. Unshielded Twisted Pair (UTP) One or more pairs of twisted copper wires insulated and contained in a plastic sheath Twisted to reduce crosstalk

53. Unshielded Twisted Pair (UTP) Categories categories 1 and 2 voice grade low data rates up to 4 Mbps category 3 suitable for most LANs up to 16 Mbps category 4 up to 20 Mbps

54. Unshielded Twisted Pair (UTP) Categories category 5 supports fast ethernet more twists per foot more stringent standards on connectors Data grade UTP cable usually consists of either 4 or 8 wires, two or four pair Uses RJ-45 telephone connector

55. Unshielded Twisted Pair (UTP)

56. Shielded Twisted Pair (STP) Same as UTP but with a aluminum/polyester shield Connectors are more awkward to work with Usually comes in pre made lengths Different standards for IBM and Apple

57. Shielded Twisted Pair (STP)

58. Coaxial Cable Coax Two conductors sharing the same axis A solid center wire surrounded insulation and a second conductor

59. Coaxial Cable

60. Coaxial Cable Coax Size of Coax RG-8, RG-11 50 ohm Thick Ethernet RG-58 50 ohm Thin Ethernet RG-59 75 ohm Cable T.V. RG-62 93 OHM ARCnet

61. Fiber Optic Cable Thin strand(s) of glass or plastic protected by a plastic sheath and strength wires or gel Transmits laser (single mode) or LED (multi mode) Single mode more expensive but can handle longer distances

62. Fiber Optics Three examples of a light ray from inside a silica fiber impinging on the air/silica boundary at different angles. Light trapped by total internal reflection.

63. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

64. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

65. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

66. Fiber Optic Networks A fiber optic ring with active repeaters.

67. Fiber Optic NetworksStar connection

68. Fiber Cables A comparison of semiconductor diodes and LEDs as light sources.

69. Characteristics of Cable Media

70. Wireless Media Uses the earth’s atmosphere as a conducting media Main types radio wave microwave (including satellite) infrared

71. The Electromagnetic Spectrum The electromagnetic spectrum and its uses for communication.

72. Radio Transmission (a) In the VLF, LF, and MF bands, radio waves follow the curvature of the earth. (b) In the HF band, they bounce off the ionosphere.

73. Radio Wave Most radio frequencies are regulated Must obtain a license from a regulatory board (CRTC, FCC) A range of radio frequencies are unregulated

74. Radio Wave Low power single frequency uses one frequency limited range 20 to 30 meters usually limited to short open environments

75. Radio Wave High power single frequency long distance may use repeaters to increase distance line of sight or bounced of the earth?s atmosphere uses a single frequency

76. Radio Wave Spread Spectrum Maintains security of the radio transmission by: Spreading the carrier signal frequency Modulating the carrier frequency by a Pseudo Random signal

79. Radio Wave

80. Microwave Terrestrial line of sight use relay towers uses license frequencies

81. Communication Satellites

82. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

83. Communication Satellites The principal satellite bands.

84. Communication Satellites VSATs using a hub.

85. Globalstar

86. Infrared Uses same technology as remotes for T.V. signals can not penetrate objects Can be point to point or broadcast Point to point requires precise alignment of devices Point less immune to eavesdropping

87. Multiplexing several lines (one for each device) enter a multiplexer (mux) at the host side the host side mux combines all incoming signals combined signals are transmitted to a mux on the receiving side

88. Types of Multiplexers Frequency Division Multiplexing (FDM) Time Division Multiplexing (TDM) Statistical Time Division Multiplexing (STDM)

89. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

90. Frequency division multiplexed circuit

91. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

92. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

93. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

94. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

95. Time Division Multiplexing

96. Statistical Time Division Multiplexing (STDM) allows connection of more nodes to the circuit than the capacity of the circuit works on the premise that not all nodes will transmit at full capacity at all times must transmit a terminal identification may require storage

97. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

98. WAN Transmission Media Public Switched Telephone Network High speed, High bandwidth dedicated leased circuits High speed fiber optic cable Microwave transmission links Satellite links

99. Services provided by PSTN Voice – Plain Old Telephone Service (POTS) Based on the Voice Channel (3600 Hz) Data transmission services consist of services such as : switched 56 X.25 T1, T3 circuits Frame relay ISDN ATM

100. Switching Switching send data across different routes Three types of switching Circuit switching Message switching Packet switching

101. Switching Circuit Switching: A connection (electrical, optical, radio) is established from the caller phone to the callee phone. This happens BEFORE any data is sent. Message Switching: The connection is determined only when there is actual data (a message) ready to be sent. The whole message is re-collected at each switch and then forwarded on to the next switch. This method is called store-and-forward. This method may tie up routers for long periods of time - not good for interactive traffic. Packet Switching: Divides the message up into blocks (packets). Therefore packets use the transmission lines for only a short time period - allows for interactive traffic.

102. Circuit Switching Connects the sender and receiver by a single physical path for the duration of the session PSTN uses circuit switching Before transmission a dedicated circuit must be established

103. Circuit Switching Advantages guaranteed data rate once connected no channel access delay Disadvantages inefficient use of the transmission media (idle time) long connection delays (first time)

104. Message Switching Each message is treated as an independent unit has its own source and destination address Each is transmitted from device to device Each intermediate device stores the message until the next device is ready store and forward

105. Message Switching Route messages along varying paths for more efficiency Switching devices are often PCs with special software

106. Message Switching Advantages efficient traffic management reduces network congestion efficient use of network media messages can be sent when receiver down Disadvantages delay of storing and forwarding costly intermediate storage

107. Packet Switching Packet switching breaks messages into packets Packets travel different routes (independent routing) Each packet has its own header information Packets small enough to be stored in RAM thus quicker than message switching

108. Packet Switching Advantages improves the use of bandwidth over circuit switching can adjust routes to reflect network conditions shorter transmission delays than message switching (stored in RAM) less disk space smaller packets to retransmit

109. Packet Switching Disadvantages More RAM More complex protocols more processing power for switching device Greater number of packets greater chance for packet loss or damage

110. Packet Switching Two methods of packet switching Datagram packet switching Virtual circuit packet switching

111. Datagram Packet Switching Message divided into a stream of packets Each packet has it’s own control instructions Switching devices route each packet independently

112. Datagram Packet Switching Switching devices can route packets around busy network links Require sequence numbers to reassemble Small packet size facilitates retransmission due to errors

113. Virtual Circuit Packet Switching Similar to circuit switching Before transmission of the sending and receiving device agree on: maximum message size network path establish a logical connection (virtual circuit) All packets travel on the same virtual path

114. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

115. (a) circuit switching(b) message switching(c) packet switching

116. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

117. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

118. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

119. B-ISDN (Broadband Integrated Services Digital Network) Broadband transmission ? A type of data transmission in which a single medium (wire) can carry several channels at once (ex. Cable TV). Baseband transmission ? one signal at a time (most communication between computers). B-ISDN ? will offer video on demand, live television from many sources, full motion multimedia email, CD-quality music, LAN interconnection, high-speed data transport for science and industry and many more, ALL over the telephone line. A digital virtual circuit capable of 155 Mbps Underlying technology that makes B-ISDN possible ? ATM (Asynchronous Transfer Mode)

120. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.

121. Why all the interest in ATM? These days it is more common for companies to want to interconnect networks. There is one international standard for ATM networks and so interconnection is easier. ATM can be used to provide both LAN and WAN networks. ATM can be made to behave like other standard networks and so you do not have to throw away all your old equipment. ATM provides a high speed network.

122. ATM Technology ATM is based on Cell Relay technology. This uses virtual circuits to carry small packets (just 53 bytes long) over a predetermined path through the network. Section of the path can be shared by other virtual circuits, thus ensuring that the network is used more efficiently than in the case of circuit switching. Little error checking is performed by the network (this keeps overheads down). Instead, the transmitting and receiving hosts are responsible for error checking.

123. Establishing a Connection When information needs to be communicated, the sender NEGOTIATES a "requested path" with the network for a connection to the destination. When setting up this connection, the sender specifies the type, speed and other attributes of the call, which determine the end-to-end quality of service. The network then determines a path through the network, and sets up a virtual circuit along this path. An analogy for this is sending mail. One can choose to send 1st class, overnight, 2 day delivery, etc. and can ask for certified mail.

124. ATM Cells

125. ATM Cell Transmission

126. ATM Speed ATM can deliver data at rates of either 155.52 Mbps or 622.08 Mbps and higher data rates are likely to follow. ATM can operate at these high speed because specialised switching mechanisms have been developed that can switch the short 53 byte cells very quickly through the network. ATM can work over a variety of media. Coaxial cable and optical fibre are the most commonly used. ATM technology is currently being used to develop the next generation of high-bandwidth telephone systems.

127. In order to implement this algorithm we had to address these six issues. In order to implement this algorithm we had to address these six issues.