The Internet backbone is made up of technologies designed over 20 years ago to support telephone traffic.

True / False Questions
 

36. (p. 382) The Internet backbone is made up of technologies designed over 20 years ago to support telephone traffic.
TRUE

37. (p. 388) You can bring a T1 line into your organization and connect it to two CSU/DSU units.
FALSE

38. (p. 390) Many newer routers have a CSU/DSU built into them.
TRUE

39. (p. 390) E1 and T1 lines can be interconnected for international use.
TRUE

40. (p. 391) The number at the end of STS, such as STS-1, indicates the length of the cable.
FALSE

41. (p. 385) It is possible to use repeaters for analog signals.
FALSE

42. (p. 389) A dedicated line has an unlisted phone number.
FALSE

43. (p. 399) A modem running at 56 Kbps is actually running at 56 kilobaud.
FALSE

44. (p. 401) DSL provides a fully analog dedicated connection.
FALSE

45. (p. 411) A dedicated connection between two private networks requires a VPN.
FALSE

46. (p. 388) You can connect two CSU/DSU boxes together directly by using a T1 crossover cable.
TRUE

47. (p. 390) E1 and SONET use a derivative of the High-Level Data Link Control (HDLC) protocol as the control channel.
TRUE

48. (p. 392) Machines that forward and store packets using any type of packet switching protocol are called packet switches.
TRUE

49. (p. 402) There is no loss of quality or speed as distance increases away from a DSL switch.
FALSE

50. (p. 390) E1 (E-carrier level 1) is the European version of the T1 carrier.
TRUE

Fill in the Blank Questions
 

51. (p. 383) A(n) _______________ is a grouping of individual circuits served by a single multiplexer.
local exchange

52. (p. 383) A(n) _______________ is a building housing a local exchange.
central office

53. (p. 384) _______________ is physically connecting two phones on a single circuit.
circuit switching

54. (p. 385) In order to accommodate long distances, _______________ voice calls had to be converted to _______________.
analog; digital

55. (p. 387) A(n) _______________ converts an analog signal to digital.
modulator

56. (p. 387) A(n) _______________ converts a digital signal to analog.
demodulator

57. (p. 387) The shielded, two-pair cabling that connects two ends of a T1 connection is called a(n) _______________.
T1 line

58. (p. 389) Because T1 service is expensive, many providers offer a portion (one or more channels) of the T1 bundle to a customer, called _______________.
fractional T1 access

59. (p. 390) A(n) _______________ provides protection to a T1 or T3 line from lightning strikes and other types of electrical interference.
CSU

60. (p. 390) An E3 line is just a little slower than an American _______________ line.
T3

61. (p. 391) The primary standard for long-distance, high-speed, fiber-optic transmission in the United States is _______________.
SONET

62. (p. 391) The OC-768 Optical Carrier standard for fiber-optic networks has a speed of _______________.
39.8 Gbps

63. (p. 393) ATM transfer speeds range from _______________ to _______________ Mbps and greater.
155.52; 622.08

64. (p. 393-394) An MPLS-enabled router _______________ certain data to use a desired connection.
labels

65. (p. 396) A physical WAN connection includes a(n) _______________, which is the point to which the phone company runs the T1 or better line to your building.
demarc

66. (p. 396) The telephone company's responsibility for a WAN connection ends at the _______________.
demarc

67. (p. 397) Dedicated lines are always _______________, meaning that they never hang up on each other.
off the hook

68. (p. 397) Dial-up lines have _______________, and you must dial up to make a connection and hang up when done.
phone numbers

69. (p. 397) The overwhelming majority of dial-up connections use either PSTN or _______________.
ISDN

70. (p. 398) PSTN works with _______________ data.
voice

71. (p. 398) A telephone microphone converts analog sound into electrical waveforms that cycle 2400 times a second. Each cycle is a(n) _______________.
baud

72. (p. 388) Each 64-kbps channel in a DS1 signal is a(n) _______________.
DS0

73. (p. 400) _______________, consisting of a Bearer (B) and a Delta (D) channel, is a digital connection across the last mile.
ISDN

74. (p. 400) An ISDN B channel is actually a(n) _______________ channel.
DS0

75. (p. 381) _______________ is a version of DSL service that has the same upload and download speed, which is, theoretically, up to 15 Mbps.
SDSL

76. (p. 401) _______________ is a version of DSL service that has the same upload and download speed, which is, theoretically, up to 100 Mbps.
VDSL

77. (p. 401-402) Most homes that have DSL service have _______________.
ADSL

78. (p. 410) To set up a private dial-up connection to a LAN, you must have a system on the LAN that acts as a(n) _______________.
remote access server (RAS)

79. (p. 414) The Microsoft protocol for remote terminal connections is _______________.
Remote Desktop Protocol (RDP)

80. (p. 415) _______________ and _______________ are both VoIP standards that support multicasting, allowing users to show a video to multiple people or hold conference calls.
Session Initiation Protocol (SIP), H.323

81. (p. 406) The 802.16 standard is also known as __________.
WiMAX

82. (p. 401) VDSL stands for __________.
Very High Bitrate DSL

83. (p. 402) __________ stands for a group of DSL technologies that may be a rebranded T1 or partial T1 line.
xDSL

84. (p. 416) _______________ runs on top of RTP and uses TCP port 554.
Real Time Streaming Protocol (RTSP)

85. (p. 398) A company that provides local telephone service to individual customers is called a(n) __________.
Local Exchange Carrier (LEC)

Essay Questions
 

86. (p. 383) Explain what a central office does with an incoming analog voice call. 

When an analog voice call comes into a central office, it converts the call to digital, transports the digital signal across trunk lines, and when the digital signal arrives at another central office, it converts the signal from digital to analog to deliver to the destination.

87. (p. 385) Define the last mile in telephony terms. 

The last mile is the analog connection between the central office and individual customers.

88. (p. 387) Define DS0. 

DS0 is a 64-Kbps data stream created by converting analog sound into 8-bit chunks 8,000 times a second.

89. (p. 397-398) Describe POTS. 

Plain Old Telephone Service (POTS) is the old-school analog-wired telephone system in which the telephone wire runs up to your house and your telephone is connected to a wall-mounted phone jack.

90. (p. 387) Define T1. 

T1 is a copper-based digital telephone service, one of several T-carriers, which uses two wires for sending data and two wires for receiving data. Each end requires special equipment called a Channel Service Unit/Digital Service Unit (CSU/DSU). The signaling method is DS1, and the speed is 1.544 Mbps.

91. (p. 389) Who are the primary users of T3 service? 

T3 lines are used mainly by regional telephone companies and ISPs connecting to the Internet.

92. (p. 393-394) Compare QoS with MPLS. 

The QoS standards are concerned with the amount of bandwidth to use, not which port to use, while the MPLS router features are concerned with the type of data, labeling certain types of data to force use of a specific connection.

93. (p. 395) Give two reasons for using a telephony WAN connection, such as SONET or ATM. 

Two reasons to use a telephony WAN connection are to connect your LAN to the Internet, and to make a private, high-speed connection between two or more private LANs.

94. (p. 396) Traditionally, what were the first two steps to getting a WAN Internet connection? What has changed about this process? 

First, have the telephone company physically install a line, and then have an ISP provide Internet access via the line. This process is now simplified by the fact that almost every telephone company is also an ISP, so you just contact an ISP in your area.

95. (p. 399) A very common misconception is that baud and bits per second are the same. Explain why this problem exists. 

The misconception that baud and bits per second are the same is due to the unfortunate coincidence that the baud rate and bits per second are the same for modems until the data transfer rate surpasses 2400 bits per second.

96. (p. 378) How do modern modems get beyond the 2400-baud limit of the analog signals of PSTN lines? 

Modern modems modulate the 2400-baud signal multiple times in each cycle, and therefore achieve greater speeds, expressed in bits per second, in multiples of 2400.

97. (p. 401) In general terms, compare ISDN and DSL. 

Both ISDN and DSL are digital last-mile solutions, using the existing phone cabling, with special equipment. ISDN requires a terminal adapter that plugs into a special wall socket that looks like a standard RF-45 network jack. A DSL connection also has a special device, but it connects to a conventional RJ-11 wall jack. ISDN is actually still a dial-up connection, requiring the number for the far end of the ISDN connection, and a special identifier number for the near end, while DSL is an always-on connection. Finally, ISDN service has a top speed of 128 Kbps, and DSL service comes in a variety of speeds that begin at the low end with ISDN's top speed, but far outstrip ISDN in speeds of many megabits per second.

98. (p. 398) Briefly describe the limits of using a modem for dial-up. 

While many modem standards have overcome some of the limits of PSTN lines, the combination of the analog lines themselves, and the conversion from analog to digital, limits most PSTN lines to 33 Kbps, no matter what the modems can do.

99. (p. 399) What was the response to the problem of proprietary modem protocols that limited the ability of modems from different manufacturers to talk to each other? 

The response to the problem caused by proprietary modem protocols as a group of standards developed by the European standards body, the CCITT. These standards, known collectively as the V standards, were eventually adopted by modem manufacturers, enabling modems to more readily communicate with each other.

100. (p. 398) Explain the term network interface unit (NIU) in reference to your home telephone service. 

A network interface unit (NIU), also known as a demarc, is the small box on the side of a house that accepts incoming lines from the telephone company and splits them to the different wall outlets. NIU is more often used to describe this unit in a home installation, while demarc is used to describe this connection for a larger installation, as for a business.

101. (p. 401) Describe ADSL service. 

Asymmetric DSL (ADSL) service offers different download and upload speeds. The download speed is the faster of the two, with a maximum theoretical speed of up to 15 Mbps, and a maximum theoretical upload speed of up to 1 Mbps. In reality, ADSL providers offer a variety of speeds. The download speeds vary between 384 Kbps to 15 Mbps, and upload speeds may be in the range from 128 Kbps to 768 Kbps.

102. (p. 404) Explain why PPPoE is used with many DSL connections. Is it technically necessary for a DSL connection? 

PPPoE is used with many DSL connections not because it is technically necessary, but to give the DSL providers more control. With PPPoE you must log on with an account and password in order to access the DSL connection. For most people using a SOHO router with PPPoE support, you can configure this logon information into the router during the initial configuration.

103. (p. 406) Define broadband. 

Broadband is any last-mile data connection that is faster than PSTN.

104. (p. 398) What two devices are combined in a conventional internal modem? 

The two devices combined in a conventional internal modem are a UART and a modem.

105. (p. 401 and 411) Define a dedicated line, giving examples. 

A dedicated line is always on, and it is sometimes described as "off the hook." There is no phone number required for a dedicated line. T-carriers and DSL are examples of dedicated lines.

106. (p. 402) Why does ADSL make sense for most small office and home office (SOHO) users? 

Asymmetric DSL (ADSL) offers a faster download speed versus upload speed. This makes sense for most SOHO users because most of their use of the Internet involves download, such as for Web pages, and they need much fewer uploads.

107. (p. 402) Why are you unlikely to have VDSL to your home in the near future? 

I am unlikely to have VDSL to my home in the near future because of two issues: distance and fiber optics. The distance requirement for VDSL is 300 meters from the DSLAM, which will limit many home users, while the fiber-optic limit has to do with the fact that most VDSL suppliers in the United States (this may vary elsewhere) use fiber-optic cabling to increase distances. Fiber-optic service is not widely available to home users.

108. (p. 403) Explain the term DSL modem. 

Although the device we use to connect to DSL service is called a DSL modem, it is not actually a modem, but more like an ISDN terminal adapter. In spite of this distinction, the term caught on and is now in common usage.

109. (p. 406) Explain why someone would use satellite Internet access, comparing it to DSL and cable options. 

In spite of offering speeds much slower than either cable or most DSL services, satellite may be the only option for a home or business located in a remote location where PSTN service is either not available or too remote to offer DSL, and cable is simply not offered.

110. (p. 406-407) In general terms, describe the two types of wireless you may use for Internet connections. 

The two types of wireless service that I may use for Internet connections are mobile data services provided by cell phone companies, and Wi-Fi (802.11). The cell phone service is a WAN technology, while Wi-Fi is a LAN technology, but it is used in some areas when no other service is available.

111. (p. 407) Describe the current state of fiber for WAN connections. 

The telephone providers, faced with heavy competition of their DSL services by much faster cable services, are offering fast fiber services (where available) to compete with cable for ISP, television, and phone services.

112. (p. 408-409) List the six most common forms of remote access. 

The six most common forms of remote access are:
Dial-up to the Internet using a dial-up connection to connect to an ISP
Private dial-up using a dial-up connection to connect to your private network
Virtual private network using an Internet connection to connect to a private network
Dedicated connection using a non-dial-up connection to another private network or the Internet
Remote terminal using a terminal emulation program to connect to another computer
Voice over IP (VoIP)

113. (p. 409) Assuming you have all other requirements in place, how do you create a dial-up connection in your operating system? 

To create a dial-up connection in your operating system, use whatever software comes with your operating system that allows you to enter all the appropriate connection information. In Windows Vista and 7, the Set up a dial-up connection option in the Network and Sharing Center is the tool to use.

114. (p. 411-412) Describe a dedicated connection between two private LANs. 

A dedicated connection is a remote connection that is never disconnected. A dedicated connection between two private LANs would usually involve a high-speed service, such as T1, and would not go through the Internet. A CSU/DSU would be at each end of the T1 line, and it would connect to a router.

115. (p. 413-414) Describe a remote terminal connection. 

A remote terminal connection is one in which a client program on a remote computer is able to connect to a special server program on another computer, allowing you to control that computer (running programs and accessing data and local resources) as if you were actually sitting at the computer running the server program.

116. (p. 413) Describe the issues involved with splitting cable connections. 

Many home/small office connections are through cable television connections (using cable modems). Splitters enable multiple connections into the home or office. The issue is that splitting causes signal degradation - by half every time it is split. The quality of signal is measured in decibels (dB), where 0 dB is a solid signal, a negative number is signal loss, and a positive number is signal gain. Because dB is a logarithmic number, even a small change in number is a HUGE number in percentage. For example, splitting cable with a - 3dB signal gives you two - 6dB connections.

117. (p. 407-408) Describe BPL (Broadband over Power Line). 

BPL is a newer, experimental technology that proposes to provide networking over existing power line infrastructure. This process is called power line communications (PLC), and offers the possibility of both voice and high-speed data. BPL tries to provide high-speed Internet access using the electrical power grid that supplies power to homes and businesses. Although there has been some limited success from Ambient and Motorola corporations, serious challenges have caused many early failures due to electrical noise and interference.

118. (p. 407) Define LTE (Long-Term Evolution). 

LTE (Long-Term Evolution) is the only serious competitor to WiMAX technologies. It uses High-Speed Packet Access (HPSA), and GSM or 3G technology. LTE is widely supported by AT&T, Verizon, and Sprint, and it is very popular for portable Internet access from devices such as cellular phones.

119. (p. 398) What is the difference between a Local Exchange Carrier (LEC), and an Interexchange carrier (IXC)? 

A company that provides local telephone service to individual customers is called a Local Exchange Carrier (LEC). A company that provides long-distance service is called an Interexchange carrier (IXC). Classically, LECs owned the central offices and IXCs own the lines and equipment that interconnect them. Over time the line between LEC and IXC has become very blurred.

120. (p. 392) Describe X.25. 

The first generation of packet-switching technology was called X.25. It enabled remote devices to communicate with each other across high-speed digital links without the expense of individual leased lines. CompTIA also refers to X.25 as the CCITT Packet Switching Protocol.