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Chapter 7: Elements of Network Connectivity

Lesson 1: Connectivity Devices

Exercise 7.1: Troubleshooting Problem

What can you do to start the troubleshooting process?

The first step is to carry out a simple test on your hardware. Much complex equipment is microprocessor-driven hardware with built-in software. Simply by following the shut-down and restart procedure for these devices (sometimes this is a simple on-off switch) you can restart the equipment and restore it to proper functioning again.

If shutting down and restarting the entire system does not get the system running, call the service provider and ask it to test the T1 line and verify that it is correctly configured.

If neither of those two options solve the problem, you will need to contact your vendor and ask for help in troubleshooting the WAN equipment you have. Very few experienced systems engineers have the expertise needed to successfully troubleshoot this kind of scenario.

Lesson 2: Connection Services

Exercise 7.2: Case Study Problem

  1. Identify at least two network items in each branch-office network site that need upgrading.
  2. Each site could upgrade to include the following:

    New cabling: from 10 Mbps Ethernet to 100Mbp Category 5.
    New cards: from 10 Mbps Ethernet to 100Base.
    New architecture: from linear bus to star bus (100BaseT) with hubs.

  3. The separate branch offices need to maintain voice and data communications with each other. Which type of WAN connection (link) might you use to connect the three sites to each other?
  4. Use a T1 link, because it can carry voice and data simultaneously. (T1 is available through a carrier such as AT&T, MCI, Sprint, and others.) Note that E1 is a rough equivalent of T1 and is used outside the U.S.

  5. Which type of device could be used to collect the multiple signals from voice and data and put them on the same WAN link?
  6. A multiplexer mixes both types of signals and places them on the same WAN link.

  7. Which type of connectivity device should be used to connect the LAN to the multiple paths in the WAN illustrated in the diagram above?
  8. A router is the ideal device to connect the LAN to the multiple WAN paths. Routers can use multiple paths and can use best-path algorithms to determine the best path for each transmission.

Chapter Review

  1. An external modem is a small box that is connected to the computer by a ______________ cable running from the computer's port to the modem's computer-cable connection.
  2. serial

  3. The modem at the _______________ end converts digital signals into analog signals.
  4. sending

  5. Baud rate refers to the speed of oscillation of the _____________ _____________ on which a bit of data is carried.
  6. sound wave

  7. The bps can be greater than the __________ rate.
  8. baud

  9. Asynchronous transmission occurs over __________________ __________.
  10. telephone lines

  11. The Microcom Network Protocol (MNP) is a standard for asynchronous __________ - _____________ control.
  12. data-error

  13. In asynchronous communication, it is possible to double throughput by using ____________________ without having to pay for a faster channel speed.
  14. compression

  15. Synchronous communication relies on a _____________ scheme coordinated between two devices.
  16. timing

  17. More advanced, complex repeaters can act as multiport _________ to connect different types of media.
  18. hubs

  19. Repeaters do not have a __________________ function and so will pass along all data from one segment to the next.
  20. filtering

  21. A repeater takes a weak signal and ______________________ it.
  22. regenerates

  23. A repeater functions at the ________________ layer of the OSI reference model.
  24. physical

  25. If the volume of traffic from one or two computers or a single department is flooding the network with data and slowing down the entire operation, a ________________ could isolate those computers or that department.
  26. bridge

  27. The bridge builds a routing table based on the ________________ addresses of computers that have sent traffic through the bridge.
  28. source

  29. Bridges work at the OSI __________ - _________ layer and, specifically, the _____________ ______________ ________________ sublayer.
  30. data-link, Media Access Control

  31. Bridges are often used in large networks that have widely dispersed segments joined by __________________ ___________.
  32. telephone lines

  33. Under spanning tree algorithm (STA), software can sense the existence of more than one _____________, determine which would be the most efficient, and then configure the bridge to use that one.
  34. route

  35. Bridges connect two segments and regenerate the signal at the ______________ level.
  36. packet

  37. Routers work at the _________________ layer of the OSI reference model.
  38. network

  39. Because they must perform complex functions on each packet, routers are _________________ than most bridges.
  40. slower

  41. Routers do not look at the destination node address; they look only at the _________________ address.
  42. network

  43. Unlike bridges, routers can accommodate multiple active ____________ between LAN segments and choose among them.
  44. paths

  45. The two major types of routers are ____________ and __________________.
  46. static, dynamic

  47. A brouter will ______________ nonroutable protocols.
  48. bridge

  49. Most often, gateways are dedicated ________________ on a network.
  50. servers

  51. The gateway takes the data from one environment, strips it, and repackages it in the __________________ ___________ from the destination system.
  52. protocol stack

  53. Gateways are ___________ specific, which means that they are dedicated to a particular type of transfer.
  54. task

  55. With the exception of ADSL, public telephone lines require users to _______________ make a connection for each communication session.
  56. manually

  57. The three factors an administrator must take into account when considering how best to implement communication between two modems are __________________, _______________, and __________.
  58. throughput, distance, cost

  59. Leased lines provide ___________________ connections that do not use a series of switches to complete the connection.
  60. dedicated

  61. A good remote-access option that offers stable lines for companies that are constantly communicating between networks is to use ______________ lines.
  62. leased (dedicated)

  63. The ____________ - _____ - _____________ _____________________ _ __________________ allows a remote client to establish a secure connection to the corporate LAN over the Internet and RAS.
  64. Point-to-Point Tunneling Protocol

  65. Because the PSTN was designed primarily for voice, _________ - _____ lines do not have the consistent quality required for secure data communications.
  66. dial-up

  67. A dedicated line is _______________ and more _______________ than a dial-up connection.
  68. faster, reliable

  69. One advantage that dedicated lines offer over dial-up lines is that the service company implements ____________ _______________________ to improve communication, thereby ensuring line quality.
  70. line conditioning

  71. Digital lines provide ______________ - ___ - _____________ synchronous communication.
  72. point-to-point

  73. Because DDS uses ________________ communication, it does not require modems.
  74. digital

  75. T1 uses a technology called ____________________ in which several signals from different sources are collected into a component and fed into one cable for transmission.
  76. multiplexing

  77. T1 can accommodate 24 ____________________ data transmissions over each two-wire pair.
  78. simultaneous

  79. Subscribers who do not need or cannot afford the bandwidth of an entire T1 line can subscribe to one or more T1 _________________.
  80. channels

  81. With packet switching, the data is broken down into packets, and each packet is tagged with a _____________________ _________________ and other information.
  82. destination address

  83. At the destination, the packets are _____________________ into the original message.
  84. reassembled

  85. Two packets from the original data package can arrive out of sequence because they followed different ____________ to reach the same destination.
  86. paths

  87. Virtual circuits are composed of a series of ________________ connections between the sending computer and the receiving computer.
  88. logical

  89. Because of its extensive ____________ _______________, X.25 can appear to be slow.
  90. error checking

  91. X.25 was originally developed for the __________________ environment.
  92. mainframe

  93. Frame-relay data travels from a network over a ________________ _________________ line to a data switch and into the frame-relay network.
  94. digital leased

  95. Frame-relay networks can also provide subscribers with __________________ as needed, which lets the customer make nearly any type of transmission.
  96. bandwidth

  97. Frame-relay networks are faster at performing basic ________________ - __________________ operations than are X.25 networks.
  98. packet-switching

  99. ATM is an advanced implementation of ______________ ______________ that provides high-speed data transmission rates.
  100. packet switching

  101. ATM transmits data in 53-byte _________ rather than variable-length frames.
  102. cells

  103. ATM switches are multiport devices that can act as either ____________ to forward data from one computer to another within a network or _________________ to forward data at high speeds to remote networks.
  104. hubs, routers

  105. ATM uses switches as ___________________________ to permit several computers to put data on a network simultaneously.
  106. multiplexers

  107. ATM can be used with existing _____________ designed for other communications systems.
  108. media

  109. Basic Rate ISDN divides its available ________________ into three data channels.
  110. bandwidth

  111. FDDI is a specification that describes a high-speed (100 Mbps) token-ring LAN that uses ___________ - __________ media.
  112. fiber-optic

  113. FDDI can be used for __________________ networks to which other, low-capacity LANs can connect.
  114. backbone

  115. A computer on an FDDI network can transmit as many frames as it can produce within a predetermined time before letting the ____________ go.
  116. token

  117. Traffic in an FDDI network consists of two similar streams flowing in opposite directions around two counter-rotating ______________.
  118. rings

  119. An advantage of the dual-ring topology is ______________________.
  120. redundancy

  121. To isolate serious failures in the ring, FDDI uses a system called _________________ in which a computer that detects a fault sends a signal onto the network.
  122. beaconing