04. Physical Layer

1. A network administrator is troubleshooting connectivity issues on a server. Using a tester, the administrator notices that the signals generated by the server NIC are distorted and not usable. In which layer of the OSI model is the error categorized? Topic 4.2.0 — The NIC has responsibilities in both Layer 1 and Layer 2. The NIC encodes the frame as a series of signals that are transmitted onto the local media. This is the responsibility of the physical layer of the OSI model. The signal could be in the form of electrical, optical, or radio waves.
network layer
presentation layer
data link layer
physical layer

2. What type of cable is used to connect a workstation serial port to a Cisco router console port? Topic 4.4.0 — UTP cable wire pairs can be terminated in different configurations for use in different applications. To use a UTP cable for consoling into a Cisco router from a PC serial port, it must be terminated as a rollover or console cable.

3. Why are two strands of fiber used for a single fiber optic connection? Topic 4.5.0 — Light can only travel in one direction down a single strand of fiber. In order to allow for full-duplex communication two strands of fiber must be connected between each device.
The two strands allow the data to travel for longer distances without degrading.
They allow for full-duplex connectivity.
They increase the speed at which the data can travel.
They prevent crosstalk from causing interference on the connection.

4. Which procedure is used to reduce the effect of crosstalk in copper cables? Topic 4.4.0 — In copper cables, crosstalk is a disturbance caused by the electric or magnetic fields of a signal on one wire interfering with the signal in an adjacent wire. Twisting opposing circuit wire pairs together can effectively cancel the crosstalk. The other options are effective measures to counter the negative effects of EMI and RFI, but not crosstalk.
designing a cable infrastructure to avoid crosstalk interference
wrapping the bundle of wires with metallic shielding
avoiding sharp bends during installation
twisting opposing circuit wire pairs together
requiring proper grounding connections

5. What is one advantage of using fiber optic cabling rather than copper cabling? Topic 4.5.0 — Copper cabling is usually cheaper and easier to install than fiber optic cabling. However, fiber cables generally have a much greater signaling range than copper.
It is usually cheaper than copper cabling.
It is able to be installed around sharp bends.
It is easier to terminate and install than copper cabling.
It is able to carry signals much farther than copper cabling.

6. A network administrator is designing a new network infrastructure that includes both wired and wireless connectivity. Under which situation would a wireless connection be recommended? Topic 4.6.0 — When the end-user devices need mobility to connect to the network, wireless is recommended. If an end-user device only has an Ethernet NIC, the user will only be able to use Ethernet cabling. If RFI is an issue, wireless is not recommended. An end-user device that requires a dedicated connection for performance would perform better with a dedicated Ethernet cable.
The end-user device needs mobility when connecting to the network.
The end-user device only has an Ethernet NIC.
The end-user device requires a dedicated connection because of performance requirements.
The end-user device area has a high concentration of RFI.

7. Which type of UTP cable is used to connect a PC to a switch port? Topic 4.4.0 — A rollover cable is a Cisco proprietary cable used to connect to a router or switch console port. A straight-through (also called patch) cable is usually used to interconnect a host to a switch and a switch to a router. A crossover cable is used to interconnect similar devices together, for example, between two switches, two routers, and two hosts.

8. What is the definition of bandwidth? Topic 4.2.0 — Bandwidth is the measure of the capacity of a network medium to carry data. It is the amount of data that can move between two points on the network over a specific period of time, typically one second.
the amount of data that can flow from one place to another in a given amount of time
the measure of usable data transferred over a given period of time
the speed at which bits travel on the network
the speed of bits across the media over a given period of time

9. Which statement correctly describes frame encoding? Topic 4.2.0 — Frame encoding converts a stream of data bits into a predefined code that is recognized by both the sender and receiver. These codes are used for a variety of purposes, such as distinguishing data bits from control bits, and identifying the beginning and end of a frame.
It generates the electrical, optical, or wireless signals that represent the binary numbers of the frame.
It uses the characteristic of one wave to modify another wave.
It transmits data signals along with a clock signal which occurs at evenly spaced time durations.
It converts bits into a predefined code in order to provide a predictable pattern to help distinguish data bits from control bits.

10. What is a characteristic of UTP cabling? Topic 4.4.0 — Cladding and immunization from electrical hazards are characteristics for fiber-optic cabling. A woven copper braid or metallic foil is used as a shield for the inner coaxial cable conductor. Cancellation is a property of UTP cabling where two wires are located adjacent to one another so each magnetic field cancels out the adjacent magnetic field.
immunity to electrical hazards
woven copper braid or metallic foil

11. A wireless LAN is being deployed inside the new one room office that is occupied by the park ranger. The office is located at the highest part of the national park. After network testing is complete, the technicians report that the wireless LAN signal is occasionally affected by some type of interference. What is a possible cause of the signal distortion? Topic 4.6.0 — Wireless LAN connectivity is not affected by trees or the elevation of the equipment. Because this is a one room office in an isolated area, there will not be a large number of wireless devices or source of interference operating in the immediate vicinity. The use of a microwave oven could result in signal interference.
the microwave oven
the large number of trees that surround the office
the elevated location where the wireless LAN was installed
the number of wireless devices that are used in the wireless LAN

12. What is the purpose of the OSI physical layer? Topic 4.1.0 — The physical layer is responsible for transmitting the actual signals across the physical media as bits. Exchanging frames, controlling media access, and performing error detection are all functions of the data link layer.
controlling access to media
transmitting bits across the local media
exchanging frames between nodes over physical network media
performing error detection on received frames

13. Which characteristic describes crosstalk? Topic 4.4.0 — EMI and RFI can distort network signals because of interference from fluorescent lights or electric motors. Attenuation results in deterioration of the network signal as it travels along copper cabling. Wireless devices can experience loss of signals because of excessive distances from a access point, but this is not crosstalk. Crosstalk is the disturbance caused by the electric or magnetic fields of the signal carried on an adjacent wire within the same cable.
the weakening of the network signal over long cable lengths
the loss of wireless signal over excessive distance from the access point
the distortion of the network signal from fluorescent lighting
the distortion of the transmitted messages from signals carried in adjacent wires

14. What is indicated by the term throughput? Topic 4.2.0 — Throughput is the measure of the transfer of bits across the media over a given period of time. Throughput is affected by a number of factors such as, EMI and latency, so it rarely matches the specified bandwidth for a network medium. The throughput measurement includes user data bits and other data bits, such as overhead, acknowledging, and encapsulation. The measure of the usable data transferred across the media is called goodput.
the guaranteed data transfer rate offered by an ISP
the time it takes for a message to get from sender to receiver
the measure of the usable data transferred across the media
the capacity of a particular medium to carry data
the measure of the bits transferred across the media over a given period of time

15. Which standards organization oversees development of wireless LAN standards? Topic 4.2.0 — IANA oversees the management of IP address allocation and domain names. ISO is the largest developer of international networking standards and is famous for the Open Systems Interconnection (OSI) model. TIA focuses on communication standards. The IEEE 802 standards are many, but the ones that affect an entry-level network professional are Ethernet (802.3), wireless LANs (802.11), and wireless PANs (802.15).

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