Chapter 5 - Network Cabling
How does a time domain reflectometer (TDR) work?
A TDR issues a signal on a cable and then measures the way the signal bounces back (or reflects) to the TDR. Bad connectors, crimps, bends, short circuits, cable mismatches, bad wiring, or other defects modify the signal's amplitude before it returns to the TDR, thus changing the way it reflects. The TDR then accepts and analyzes the return signal, and based on its condition and the amount of time the signal took to return, determines cable imperfections
What is the difference between bandwidth and throughput?
Bandwidth is the amount of data that could theoretically be transmitted during a given period of time. In an analogy, the bandwidth of a three-lane freeway is the number of vehicles that can pass a checkpoint in one minute when traffic is bumper-to-bumper and traveling at the maximum speed limit. In practice, that bandwidth never happens. Still, we could increase potential bandwidth by adding more lanes to the freeway. At the same time, consider that adding too many lanes for the amount of anticipated traffic, so that some lanes are never used, would be a waste of resources. Throughput is the measure of how much data is actually transmitted during a given period of time. In our analogy, throughput measures the actual traffic on the three-lane freeway that passes in one minute. Using all the available bandwidth results in more accidents and traffic jams than if bandwidth exceeds actual throughput by a little. However, this beneficial effect is limited-providing a lot more potential bandwidth than actual throughput does not achieve additional improvement in performance unless you need to account for regular spikes in traffic.
A serial cable with an RJ-45 connector is capable of being used through an RJ-45 Ethernet port. a. True b. False
False
A short circuit is one where needed connections are missing, such as when a wire breaks. a. True b. False
False
What is a fiber distribution panel, and how is it used?
It is usually a case on a rack where fiber cables converge, connect with each other, and connect with fiber optic terminal equipment from the ISP. Splices at the FDP (or elsewhere on the network) might be accomplished by joining two fiber cables in a permanent bond, or various connectors might be used to create temporary splices. The transition between single mode fiber and multimode fiber cabling might also occur at an FDP.
How does modal bandwidth affect the performance of a multimode fiber segment?
Modal bandwidth is a measure of the highest frequency of signal a multimode fiber can support over a specific distance and is measured in MHz-km. It is related to the distortion that occurs when multiple pulses of light, although issued at the same time, arrive at the end of a fiber at slightly different times. The higher the modal bandwidth, the longer a multimode fiber can carry a signal reliably.
What are the different transceiver types that have made the GBIC obsolete?
Newer transceivers that have made the GBIC obsolete include: * SFP (small form-factor pluggable)-Provides the same function as GBICs and is more compact, allowing more ports per linear inch. Also known as mini GBICs or SFP GBICs. Typically used for 1 Gbps connections, but theoretically capable of 5 Gbps. * XFP (10 Gigabit small form-factor pluggable)-Supports up to 10 Gbps and is slightly larger than SFP with lower power consumption than SFP+. * SFP+-Developed later than XFP and is the same module size as SFP; theoretical maximum transmission speed is 16 Gbps. * QSFP (quad small form-factor pluggable)-Complies with the 802.3ba standard, squeezing four channels in a single transceiver and supporting data rates up to 40 Gbps (4 x 10 Gbps). * QSFP+-Generally the same technology as QSFP while supporting data rates over 40 Gbps. Highest speed format currently is QSFP28 with a total theoretical maximum data rate of 112 Gbps (4 x 28 Gbps). * CFP (centum form-factor pluggable)-Intended for 100-Gbps network connections, with each succeeding generation (CFP, CFP2, CFP4) becoming smaller and more energy-efficient. Centum is Latin for 100.
In order to achieve 1000Base-T over CAT5e cable, 2 pairs of copper are needed. a. True b. False
False
RG-59 is more expensive than RG-6, but has better resistance to attenuation. a. True b. False
False
The ST and SC fiber connectors are the most commonly found connectors due to their smaller sizes. a. True b. False
False
When tracing a wire, how do you utilize a toner and probe kit?
Place the tone generator at one end of a wire using the appropriate connector. Swipe the tone locator over each of the terminations you suspect to be the other end of that wire. You can verify the location of the wire's termination when you hear the tone. Work by trial and error, guessing which termination corresponds to the wire over which you've generated a signal until the tone locator indicates the correct choice.
What is the difference between single mode fiber and multimode fiber, and how do they compare?
SMF (single mode fiber) consists of a narrow core of 8 to 10 microns in diameter. Laser-generated light travels a single path over the core, reflecting very little. Because it reflects little, the light does not disperse as the signal travels along the fiber. This continuity allows SMF to accommodate the highest bandwidths and longest distances (without requiring repeaters) of all network transmission media. MMF (multimode fiber) contains a core with a larger diameter than SMF, usually 50 or 62.5 microns, over which many pulses of light generated by a laser or LED light source travel at various angles. Signals traveling over multimode fiber experience greater attenuation than those traversing single mode fiber. Therefore, MMF is not suited to distances longer than a few kilometers. On the other hand, MMF is less expensive to install and, therefore, typically used to connect routers, switches, and servers on the backbone of a network or to connect a desktop workstation to the network.
Describe the two different shapes and polishes currently used on SMF ferrules to reduce back reflection.
Shapes and polishes currently used on SMF ferrules to reduce back reflection include: * UPC (Ultra Polished Connector)-Extensive polishing of the tips creates a rounded surface on a UPC (Ultra Polished Connector), which allows the two internal fibers to meet and increases efficiency over older types of connections. * APC (Angle Polished Connector)-The latest advancement in ferrule technology uses the principles of reflection to its advantage. The APC (Angle Polished Connector) still uses a polished curved surface, but the end faces are placed at an angle to each other. The industry standard for this angle is 8 degrees.
What is the biggest limiting factor on fiber-optic cable length?
The maximum length limitation is due primarily to optical loss, or the degradation of the light signal after it travels a certain distance away from its source (just as the light of a flashlight dims after a certain number of feet). Optical loss accrues over long distances and grows with every connection point in the fiber network. Dust or oil in a connection (for example, from people handling the fiber while splicing it) can further exacerbate optical loss
A continuity tester should not be used on a live network segment. a. True b. False
True
A time domain reflectometer sends a signal and analyzes the return signal's change in amplitude to determine where cable imperfections may exist. a. True b. False
True
A wavelength mismatch occurs when transmissions are optimized for one type of cable but sent over a different type of cable. a. True b. False
True
Latency on data networks is based on a calculation of a packet's round trip time (RTT). a. True b. False
True
Multimode fiber contains a core that is larger than a single mode fiber core. a. True b. False
True
Noise can degrade or distort a signal on a network; what are some of its causes?
Two common sources of noise are: * EMI (electromagnetic interference)-Caused by motors, power lines, televisions, copiers, fluorescent lights, microwave ovens, manufacturing machinery, and other sources of electrical activity (including a severe thunderstorm). One type of EMI is RFI (radio frequency interference), or electromagnetic interference caused by radio waves. (Often, you'll see EMI referred to as EMI/RFI.) Strong broadcast signals from radio or TV antennas can generate RFI. * crosstalk-Occurs when a signal traveling on one wire or cable infringes on the signal traveling over an adjacent wire or cable. The resulting noise, or crosstalk, is equal to a portion of the second line's signal. If you've ever been on a traditional, landline phone and heard the conversation on a second line in the background, you have heard the effects of crosstalk.
What kind of tool can you use to measure voltage on a cable length? a. continuity tester b. multimeter c. time domain reflectometer d. light meter
b. multimeter
What is the industry standard angle for an Angle Polished Connector (APC)? a. 8 degrees b. 12 degrees c. 14 degrees d. 16 degrees
a. 8 degrees
. PoE+ devices are defined by what IEEE standard? a. 802.3at b. 802.3af c. 802.3fc d. 802.3c
a. 802.3at
What statement describes a transmission flaw that is occurring due to attenuation? a. A customer modem is continuously losing signal due to large distance from the transmitting device. b. A network switch interface is dropping due to a powerful radio transmitter in the adjacent room. c. A customer's video conferencing application is experiencing delay in audio and video that comes and goes. d. Two network interfaces are experiencing problems at the same time due to the cables having adjacent runs.
a. A customer modem is continuously losing signal due to large distance from the transmitting device.
Why should you terminate coaxial cable with connectors that are rated for the exact cable type? a. A mismatched connector will have different impedance ratings, causing data errors. b. A mismatched connector will not fit the coaxial cable for termination. c. A mismatched connector will work fine, but breaks cabling standards. d. A mismatched connector will destroy the equipment it is connected to.
a. A mismatched connector will have different impedance ratings, causing data errors.
What statement correctly describes "jitter"? a. Jitter is what happens when packets experience varying amounts of delay and arrive out of order. b. Jitter is the loss of 50% or more packets in a given data stream, causing a connection to falter. c. Jitter is the fluctuation of a signal's strength as it travels away from its source. d. Jitter is the transmission of signal onto unintended pairs in a copper cable.
a. Jitter is what happens when packets experience varying amounts of delay and arrive out of order.
Which statement accurately describes what near end crosstalk (NEXT) is? a. NEXT is crosstalk that occurs between wire pairs near the source of a signal. b. NEXT is crosstalk that occurs near the opposite end of a signal source. c. NEXT is crosstalk that occurs when an EMI source is near the data signal source. d. NEXT is crosstalk that occurs only when a cable segment exceeds the bend radius.
a. NEXT is crosstalk that occurs between wire pairs near the source of a signal.
You have been awarded a contract for wiring a new federal building. What twisted-pair wiring standard must you use? a. TIA/EIA 568A b. TIA/EIA 568B c. TIA/EIA 568F d. TIA/EIA rollover
a. TIA/EIA 568A
Telephone connections follow what registered jack standard? a. registered jack 11 (RJ-11) b. registered jack 12 (RJ-12) c. registered jack 45 (RJ-45) d. registered jack 100 (RJ-100)
a. registered jack 11 (RJ-11)
Bidirectional transceivers utilize what technology to separate the data in each direction? a. wavelength division multiplexing b. time division multiplexing c. frequency division multiplexing d. statistical time division multiplexing
a. wavelength division multiplexing
When terminating an Ethernet cable, about how far should the cable sheath extend into the plug? a. 1/2 inch b. 3/8 inch c. 4/5 inch d. 1/5 inch
b. 3/8 inch
Which of the following statements about fiber-optic cabling is accurate? a. Fiber-optic cabling has a low resistance to signal noise. b. Light experiences virtually no resistance when traveling through glass. c. Fiber-optic cable is cheaper than shielded twisted pair cabling. d. The maximum length for a fiber segment is 20km.
b. Light experiences virtually no resistance when traveling through glass.
What statement regarding the Power Over Ethernet standards is inaccurate? a. The amount of power provided is 15.4 watts for standard PoE devices. b. Power over Ethernet requires CAT6 or better copper cable. c. Electric current may run over a pair of wires used for data transmission. d. A device that supplies power for PoE is known as power sourcing equipment.
b. Power over Ethernet requires CAT6 or better copper cable.
Broadband cable Internet service and cable TV are most commonly delivered over long distances via what type of cable? a. RG-59 b. RG-6 c. RG-20 d. LRG-50
b. RG-6
Utilizing time slots that are adjusted according to priority and need is an example of what type of multiplexing on copper lines? a. time division multiplexing b. statistical time division multiplexing c. frequency division multiplexing d. wavelength division multiplexing
b. statistical time division multiplexing
A Fast Ethernet connection utilizes what pins on an RJ-45 plug? a. 1, 2, 4, 5 b. 1, 2, 3, 5 c. 1, 2, 3, 6 d. 1, 2, 7, 8
c. 1, 2, 3, 6
What is the maximum supported throughput of a CAT6 cable? a. 100 Mbps b. 1 Gbps c. 10 Gbps d. 100 Gbps
c. 10 Gbps
What is the fastest Ethernet standard that can possibly be used on twisted-pair cabling? a. 100Base-T b. 1000Base-T c. 10GBase-T d. 10TBase-T
c. 10GBase-T
The 1000Base-LX utilizes light with what wavelength? a. 850 nanometers b. 1200 nanometers c. 1300 nanometers d. 1550 nanometers
c. 1300 nanometers
What is the minimum category of UTP cable required in order to support Gigabit speeds? a. Cat 3 b. Cat 5 c. Cat 5e d. Cat 6
c. Cat 5e
Which of the following statements correctly describes the SFP+ transceiver? a. SFP+ provides the same function as GBICs and is more compact. It is theoretically capable of 5 Gbps. b. SFP+ supports up to 10 Gbps and is slightly larger than SFP, with lower power consumption than XFP. c. SFP+ is the same size as SFP, and supports a theoretical maximum transmission speed of 16 Gbps. d. SFP+ complies with the 802.3ba standard, allowing four channels in a single transceiver and supporting up to 40 Gbps data rates.
c. SFP+ is the same size as SFP, and supports a theoretical maximum transmission speed of 16 Gbps.
What multiplexing technology lowers cost by spacing frequency bands wider apart to allow for cheaper transceiver equipment? a. statistical time division multiplexing b. dense wavelength division multiplexing c. coarse wavelength division multiplexing d. spaced wavelength division multiplexing
c. coarse wavelength division multiplexing
Noise that can degrade or distort a signal on a network is measured with what unit? a. joules b. volts c. decibels d. farads
c. decibels
A typical fiber termination kit should include what tool for cutting a clean slice through fiber strands? a. fiber stripper b. fiber snipper c. fiber cleaver d. fiber saw
c. fiber cleaver
When viewing the pinout for T568B, what is the correct order of wire colors, starting at pin 1? a. white/green, green, white/orange, blue, white/blue, orange, white/brown, brown b. blue, white/blue, green, white/green, orange, white/orange, brown, white/brown c. white/orange, orange, white/green, blue, white/blue, green, white/brown, brown d. white/brown, brown, white/green, blue, white/blue, green, orange, white/orange
c. white/orange, orange, white/green, blue, white/blue, green, white/brown, brown
Both 10GBase-ER and 10GBase-EW have what maximum distance limitation on a segment of single mode fiber? a. 550m b. 300m c. 10km d. 40km
d. 40km
A junior administrator is having issues connecting to a router's console port using a TIA/EIA 568B standard cable and a USB serial to RJ-45 adapter, despite verifying terminal settings. What is the issue? a. Router console ports are only used when connected to other routers. b. The router console port is providing an Ethernet connection, instead of a serial connection. c. The USB standard is incompatible with the serial connection used by the console port. d. The cable must be a rollover cable.
d. The cable must be a rollover cable.
In a coaxial cabling, what does the RG rating measure? a. The number of twists in the copper core. b. The overall thickness of the cable. c. The maximum distance the cable is rated for, in kilometers. d. The materials used for shielding and conducting cores.
d. The materials used for shielding and conducting cores.
You've been handed a fiber with a 1.25-mm ferrule that requires a connector. What is the most commonly used connector for this ferrule size? a. subscriber connector (SC) b. straight tip (ST) c. Mechanical Transfer-Registered Jack (MTRJ) d. local connector (LC)
d. local connector (LC)
Signals that can travel in only one direction on a medium are referred to as what type of signal? a. full-duplex b. duplex c. half-duplex d. simplex
d. simplex
