True/False
Indicate whether the statement is
true or false.
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1.
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In a star topology, a single connection failure
will halt all traffic between all sites.
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2.
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Dial-up ISDN does not convert a computer’s
digital signals to analog before transmitting them over the PSTN.
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3.
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ATM is a WAN technology that functions in the Data
Link layer.
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4.
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SONET specifies framing and multiplexing techniques
at the Physical layer.
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5.
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After SONET, BPL has the best maximum throughput available.
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Multiple Choice
Identify the choice that best
completes the statement or answers the question.
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1.
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WANs typically send data over ____ available
communications networks.
a. | privately | c. | individually | b. | publicly | d. | serially |
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2.
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The individual geographic locations connected by a
WAN are known as ____.
a. | WAN sites | c. | network service providers | b. | WAN links | d. | central offices |
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3.
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Because WAN connections require routers or other
Layer 3 devices to connect locations, their links are not capable of carrying ____
protocols.
a. | open | c. | routable | b. | standard | d. | nonroutable |
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4.
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On most modern WANs, a ring topology relies on ____
rings to carry data.
a. | flexible | c. | serial | b. | open | d. | redundant |
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5.
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____ WANs are the most fault-tolerant type of WAN
because they provide multiple routes for data to follow between any two points.
a. | Bus | c. | Mesh | b. | Star | d. | Tiered |
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6.
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The ____ encompasses the entire telephone system,
from the wires that enter homes and businesses to the network centers that connect different regions
of a country.
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7.
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A(n) ____ is the place where a telephone company
terminates lines and switches calls between different locations.
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8.
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A ____ connection is one in which a user connects
her computer, via a modem, to a distant network and stays connected for a finite period of
time.
a. | remote | c. | dial-up | b. | direct | d. | virtual |
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9.
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The portion of the PSTN that connects any residence
or business to the nearest CO is known as the ____.
a. | demarcation point | c. | local
loop | b. | NIU (Network Interface Unit) | d. | central
office |
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10.
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____ means that a telephone company connects
residential users to its network with fiber-optic cable.
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11.
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____ is an updated, digital version of X.25 that
also relies on packet switching.
a. | DSL | c. | Frame
relay | b. | ISDN | d. | ATM |
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12.
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In a process called ____, two 64-Kbps ISDN B
channels can be combined to achieve an effective throughput of 128 Kbps.
a. | slicing | c. | merging | b. | linking | d. | bonding |
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13.
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A ____ converts digital signals into analog signals
for use with ISDN phones and other analog devices.
a. | terminal adapter | c. | smart
jack | b. | DSLAM | d. | terminator |
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14.
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ISDN PRI uses ____ B channels and one 64-Kbps D
channel.
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15.
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The speed of a T-carrier depends on its ____
level.
a. | signal | c. | channel | b. | hierarchy | d. | traffic |
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16.
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At the customer’s demarcation point, either
inside or outside the building, RJ-48 connectors terminate in a ____.
a. | terminal adapter | c. | CSU/DSU | b. | smart
jack | d. | switch |
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17.
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A ____ aggregates multiple DSL subscriber lines and
connects them to the carrier’s CO.
a. | terminal adapter | c. | smart
jack | b. | DSLAM | d. | terminator |
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18.
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Broadband cable requires many subscribers to share
the same local line, thus raising concerns about ____ and actual (versus theoretical)
throughput.
a. | access | c. | noise | b. | costs | d. | security |
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19.
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What sets ATM apart from Ethernet is its ____ size.
a. | channel | c. | variable packet | b. | frame | d. | fixed packet |
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20.
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SONET’s extraordinary ____ results from its
use of a double-ring topology over fiber-optic cable.
a. | throughput | c. | fault
tolerance | b. | low cost | d. | latency |
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21.
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The data rate of a particular SONET ring is
indicated by its ____, a rating that is internationally recognized by networking professionals and
standards organizations.
a. | OC (Optical Carrier) level | c. | BRI (Basic Rate Interface) | b. | CIR (committed information rate) | d. | DS0 (digital
signal, level 0) |
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Completion
Complete each
statement.
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1.
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____________________ are connections between
network nodes that, although based on potentially disparate physical links, logically appear to be
direct, dedicated links between those nodes.
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2.
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A(n) ____________________ uses TDM (time division
multiplexing) over two wire to divide a single channel into multiple channels.
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3.
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____________________ encapsulates incoming Ethernet
or token ring frames, then converts them into ATM cells for transmission over an ATM
network.
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4.
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A(n) ____________________ node in synchronous
communications recognizes that it should be receiving data by looking at the time on the
clock.
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5.
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A(n) ____________________ combines individual SONET
signals on the transmitting end, and another multiplexer separates combined signals on the receiving
end.
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Matching
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Match each item with a statement below: a. | bus
topology WAN | f. | upstream | b. | star topology WAN | g. | asymmetrical
communications | c. | mesh topology
WAN | h. | symmetrical technology | d. | tiered topology
WAN | i. | signal level | e. | downstream |
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1.
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Contain sites that are connected in star or ring
formations are interconnected at different levels, with the interconnection points being organized
into layers to form hierarchical groupings.
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2.
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Occurs when data travels from the carrier’s
switching facility to the customer.
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3.
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Contains a single site acting as the central
connection point for several other points.
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4.
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Occurs when downstream throughput is higher than
upstream throughput.
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5.
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Refers to the T-carrier’s Physical layer
electrical signaling characteristics as defined by ANSI standards in the early 1980s.
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6.
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Occurs when data travels from the customer to the
carrier’s switching facility.
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7.
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Occurs when each site is directly connected to no
more than two other sites in a serial fashion.
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8.
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Provides equal capacity for data traveling both
upstream and downstream.
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9.
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Incorporates many directly interconnected
sites.
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Short Answer
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1.
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Describe the fundamental properties WANs and LANs
have in common.
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2.
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Define and describe a PSTN.
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3.
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Describe an important difference between frame
relay and X.25.
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4.
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Define a fractional T1 and explain why an
organization might implement it.
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5.
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Define the term xDSL and name the better known DSL
varieties.
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6.
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Explain how a cable modem is utilized in broadband
cable connections.
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7.
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Explain how ATM relies on virtual
circuits.
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8.
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List and describe the key strengths of
SONET.
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9.
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Describe the most important advantage of
SONET.
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10.
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Why is SONET technology typically not implemented
by small or medium-size businesses?
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