transmitting bits across the local media
Why are two strands of fiber used for a single fiber optic connection?
They allow for full-duplex connectivity.
Full-duplex data transmission means that data can be transmitted in both
Which characteristic describes crosstalk?
the distortion of the transmitted messages from signals carried in adjacent wires
Which procedure is used to reduce the effect of crosstalk in copper cables?
twisting opposing circuit wire pairs together
Match the situation with the appropriate use of network media.
Copper Cables
horizontal cabling structure
desktop PCs in offices in an enterprise
Match the situation with the appropriate use of network media.
Fiber Optic
backbone cabling in an enterprise
long-haul networks
Match the situation with the appropriate use of network media.
Wireless
guest access in a coffee shop
waiting rooms in a hospital
A network administrator is measuring the transfer of bits across the company backbone for a mission critical financial application. The administrator notices that the network throughput appears lower than the bandwidth expected. Which three factors could influence the differences in throughput? (Choose three.)
Explanation: Throughput usually does not match the specified bandwidth of physical links due to multiple factors. These factors include, the amount of traffic, type of traffic, and latency created by the network devices the data has to cross.
What are two characteristics of fiber-optic cable? (Choose two.)
* It is not affected by EMI or RFI.
* Each pair of cables is wrapped in metallic foil.
* It combines the technique of cancellation, shielding, and twisting to protect data.
* It typically contains 4 pairs of fiber-optic wires.
* It is more expensive than UTP cabling is.
Explanation: Fiber-optic cabling supports higher bandwidth than UTP for longer distances. Fiber is immune to EMI and RFI, but costs more, requires more skill to install, and requires more safety precautions.
What is a primary role of the Physical layer in transmitting data on the network?
* create the signals that represent the bits in each frame on to the media
* provide physical addressing to the devices
* determine the path packets take through the network
* control data access to the media
create the signals that represent the bits in each frame on to the media
Explanation: The OSI physical layer provides the means to transport the bits that make up a frame across the network media. This layer accepts a complete frame from the data link layer and encodes it as a series of signals that are transmitted to the local media.
With the use of unshielded twisted-pair copper wire in a network, what causes crosstalk within the cable pairs?
Explanation: Crosstalk is a type of noise, or interference that occurs when signal transmission on one wire interferes with another wire. When current flows through a wire a magnetic field is produced. The produced magnetic field will interface the signal carried in the adjacent wire.
____ cable consists of four pairs of color-coded wires that have been twisted together and then encased in a flexible plastic sheath.
Unshielded Twisted Pair
____ cable uses four pairs of wires, each wrapped in a foil shield, which are then wrapped in an overall metallic braid or foil.
Shielded Twisted Pair
____ cable uses a copper conductor and a layer of flexible plastic insulation surrounds the copper conductor.
Coaxial
____ cable is a flexible, extremely thin, transparent strand of glass surrounded by plastic insulation.
Fiber
In addition to the cable length, what two factors could interfere with the communication carried over UTP cables? (Choose two.)
Explanation: Copper media is widely used in network communications. However, copper media is limited by distance and signal interference. Data is transmitted on copper cables as electrical pulses. The electrical pulses are susceptible to interference from two sources:
Electromagnetic interference (EMI) or radio frequency interference (RFI) – EMI and RFI signals can distort and corrupt the data signals being carried by copper media.
Crosstalk – 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.
Which two devices commonly affect wireless networks? (Choose two.)
Explanation: Radio Frequency Interference (RFI) is the interference that is caused by radio transmitters and other devices that are transmitting in the same frequency.
Which two statements describe the services provided by the data link layer? (Choose two.)
Explanation: The data link layer is divided into two sub layers, namely Logical Link Control (LLC) and Media Access Control (MAC). LLC forms a frame from the network layer PDU into a format that conforms to the requirements of the network interface and media. A network layer PDU might be for IPv4 or IPv6. The MAC sub layer defines the media access processes performed by the hardware. It manages the frame access to the network media according to the physical signaling requirements (copper cable, fiber optic, wireless, etc.)
What is the function of the CRC value that is found in the FCS field of a frame?
Explanation: The Cyclic Redundancy Check (CRC) value in the Frame Check Sequence (FCS) field of the received frame is compared to the computed CRC value of that frame, in order to verify the integrity of the frame. If the two values do not match, then the frame is discarded.
What is contained in the trailer of a data-link frame?
Explanation: The trailer in a data-link frame contains error detection information that is pertinent to the frame included in the FCS field. The header contains control information, such as the addressing, while the area that is indicated by the word “data” includes the data, transport layer PDU, and the IP header.
Which statement describes a characteristic of the frame header fields of the data link layer?
Explanation: All data link layer protocols encapsulate the Layer 3 PDU within the data field of the frame. However, the structure of the frame and the fields that are contained in the header vary according to the protocol. Different data link layer protocols may use different fields, like priority/quality of service, logical connection control, physical link control, flow control, and congestion control.
A network team is comparing physical WAN topologies for connecting remote sites to a headquarters building. Which topology provides high availability and connects some, but not all, remote sites?
partial mesh
Explanation: Partial mesh topologies provide high availability by interconnecting multiple remote sites, but do not require a connection between all remote sites. A mesh topology requires point-to-point links with every system being connected to every other system. A point-to-point topology is where each device is connected to one other device. A hub and spoke uses a central device in a star topology that connects to other point-to-point devices.
Which two fields or features does Ethernet examine to determine if a received frame is passed to the data link layer or discarded by the NIC? (Choose two.)
Explanation: An Ethernet frame is not processed and is discarded if it is smaller than the minimum (64 bytes) or if the calculated frame check sequence (FCS) value does not match the received FCS value. Auto-MDIX (automatic medium-dependent interface crossover) is Layer 1 technology that detects cable straight-through or crossover types. The source MAC address is not used to determine how the frame is received. CEF (Cisco Express Forwarding) is a technology used to expedite Layer 3 switching.
Which media communication type does not require media arbitration in the data link layer?
deterministic
half-duplex
full-duplex
controlled access
full-duplex
Explanation: Half-duplex communication occurs when both devices can both transmit and receive on the medium but cannot do so simultaneously. Full-duplex communication occurs when both devices can transmit and receive on the medium at the same time and therefore does not require media arbitration. Half-duplex communication is typically contention-based, whereas controlled (deterministic) access is applied in technologies where devices take turns to access the medium.