Q&A Hero

Communication

Q: A generic term for sharing the capacity of a data link is ________.
Q: A __________ is a device that allows a user to access the Internet and other online services through a cable TV network.
Q: With ________ multiplexing data from various sources are carried in repetitive frames.
Q: With ________ multiplexing a number of signals are carried simultaneously on the same medium by allocating to each signal a different frequency band.
Q: The two most common forms of multiplexing are frequency division multiplexing and ________.
Q: The schemes for providing high speed digital transmission of the subscriber line are collectively referred to as ________.A) DMT/QAMB) SDSLC) VDSLD) xDSL
Q: ________ was developed to provide the same type of service as HDSL but over a single twisted pair line. A) SDSL B) QAM C) VDSL D) AMI
Q: ________ was developed in the late 1980s by BellCore to provide a more cost effective means of delivering a T1 data rate. A) xDSL B) HDSL C) QAM D) DMT
Q: ADSL uses ________ multiplexing to exploit the capacity of twisted pair. A) synchronous time division B) statistical time division C) time division D) frequency division
Q: From customer to carrier is ________. A) symmetric B) upstream C) downstream D) asymmetric
Q: From the carrier's central office to the customer's site is ________. A) asymmetric B) upstream C) headend D) downstream
Q: To support data transfer to and from a cable modem, a cable TV provider dedicates ________ channels. A) one B) two C) four D) three
Q: The transmitted data in synchronous TDM are organized into ________. A) blocks B) frames C) channels D) frequencies
Q: Two problems that an FDM system must cope with are crosstalk and ________ noise. A) blanketed B) amplified C) intermodulation D) channeled
Q: In FDM, because multiple carriers are to be used, each is referred to as a ________. A) subcarrier B) channel C) WDM D) subscriber
Q: ________ multiplexing is commonly used for multiplexing digitized voice streams and data streams. A) Time division B) Frequency division C) Statistical time division D) Synchronous time division
Q: The ________ multiplexing is the most heavily used. A familiar example is broadcast and cable television. A) statistical time division B) time division C) frequency division D) synchronous time division
Q: The ________ accepts the multiplexed data stream, separates the data according to channel, and delivers data to the appropriate output lines. A) high capacity fiber B) coaxial link C) multiplexer D) demultiplexer
Q: Synchronous time division multiplexing can be used with ________ signals. A) analog B) digital signals or analog signals carrying digital data C) digital D) digital signals carrying digital data
Q: Frequency division multiplexing can be used with ________ signals. A) digital signals carrying digital data B) analog signals carrying digital data C) analog D) digital
Q: At a higher level of utilization a larger buffer is needed to hold the backlog.
Q: Flow control and error control can be provided on a per-channel basis by using a data link control protocol such as HDLC.
Q: The long distance carrier system provided in the US and throughout the world was designed to transmit voice signals over high capacity transmission links such as optical fiber, coaxial cable, and microwave.
Q: Synchronous TDM is called synchronous because synchronous transmission is used.
Q: Synchronous time division multiplexing is possible when the achievable data rate of the medium exceeds the data rate of digital signals to be transmitted.
Q: The true potential of optical fiber is fully exploited when multiple beams of light at different frequencies are transmitted on the same fiber.
Q: The higher the data rate, the least cost-effective the transmission facility.
Q: FDMA is a technique used to share the spectrum among multiple stations.
Q: Large numbers of voice and data transmissions can be carried simultaneously using multiplexing.
Q: The multiplexer combines data from the input lines and transmits over a lower capacity data link.
Q: Typically two communicating stations will not utilize the full capacity of a data link.
Q: An individual cable modem subscriber may experience access speeds from 500 kbps to 1.5 Mbps or more, depending on the network architecture and traffic load.
Q: In TDD, data are transmitted in both directions at the same time.
Q: With time division multiplexing, modulation equipment is needed to move each signal to the required frequency band and multiplexing equipment is needed to combine the modulated signals.
Q: Multiplexing allows several transmission sources to share a larger transmission capacity.
Q: An error detecting code calculated from the remaining bits of the frame, exclusive of flags, is the ________.
Q: High level data link control defines three types of frames, each with a different control field format. They are: information frames, unnumbered frames, and ________.
Q: Since there is no assurance that the flag field pattern will not appear somewhere inside the frame, a procedure known as ________ is used to prevent destroying synchronization.
Q: The most important data link control protocol is ________.
Q: With ________ ARQ the only frames retransmitted are those that receive a negative acknowledgment or those that time out.
Q: ________ control refers to mechanisms that detect and correct errors that occur in the transmission of frames.
Q: If two stations exchange data each needs to maintain two windows, one for transmit and one for receive, and each side needs to send the data and acknowledgments to the other. To provide efficient support for this requirement a feature known as ________ is typically provided.
Q: Most data link control protocols allow a station to cut off the flow of frames from the other side by sending a ________ message, which acknowledges former frames but forbids transfer of future frames.
Q: The form of flow control where A and B are connected via a full-duplex link and A maintains a list of sequence numbers that it is allowed to send without receiving any acknowledgment and B maintains a list of sequence numbers that it is prepared to receive is ________ flow control.
Q: The form of flow control where a source entity transmits a frame and must wait until it receives an acknowledgment back from the destination entity before sending the next frame is ________ flow control.
Q: A technique for assuring that a transmitting entity does not overwhelm a receiving entity with data is ________.
Q: A layer of logic is added above the physical layer to achieve necessary control. This logic is referred to as a ________ protocol.
Q: Containing virtually all of the features found in other data link control protocols, ________ is a widely used data link control protocol.
Q: ________ control is achieved by retransmission of damaged frames that have not been acknowledged or for which the other side requests a retransmission.
Q: The layer of control that provides error detection and error and flow control is known as a ________ protocol.
Q: _______ provide the ARQ mechanism in HDLC when piggybacking is not used. A) I-frames B) R-frames C) U-frames D) S-frames
Q: The flag field pattern is ________. A) 01111110 B) 01111010 C) 00111110 D) 01111101
Q: In the HDLC frame structure the FCS and flag fields following the data field are referred to as a ________. A) header B) trailer C) bit stuffing D) information frames
Q: In the high level data link control frame structure the flag, address, and control fields that precede the information field are known as a ________. A) header B) trailer C) FAC D) ARQ
Q: The form of error control based on sliding-window flow control that is most commonly used is: A) ACK-ARQ B) selective-reject ARQ C) go-back-N ARQ D) piggybacking
Q: RR and RNR are examples of an ________. A) error repair request B) acknowledgment frame C) open acknowledgment frame D) interior window
Q: Each ________ includes a field that holds the sequence number of that frame plus a field that holds the sequence number used for acknowledgment. A) SAF B) window C) data frame D) relay frame
Q: With ________ flow control the transmission link is treated as a pipeline that may be filled with frames in transit. A) linking B) sliding-window C) ARQ D) stop-and-wait
Q: The flow control in which the destination can stop the flow of data simply by withholding acknowledgment of the receipt of a frame is ________ flow control A) data B) stop-and-wait C) frame acknowledgment D) ARQ
Q: The time it takes for a station to emit all of the bits of a frame onto the medium is the ________ time. A) link B) relay C) propagation D) transmission
Q: Data are sent in blocks called ________. A) links B) units C) entities D) frames
Q: The transmission medium between systems is referred to as a ________ when a data link control protocol is used. A) data link B) flow link C) transmission link D) control link
Q: The ________ time is the time it takes for a bit to traverse the link between source and destination. A) relay B) flow C) transmission D) propagation
Q: In a data link control protocol, ________ control is achieved by retransmission of damaged frames. A) DLHC B) data C) error D) flow
Q: ________ enables a receiver to regulate the flow of data from a sender so that the receiver's buffers do not overflow. A) Flow control B) Link control C) Data control D) Error control
Q: HDLC uses asynchronous transmission.
Q: Selective reject is a useful choice for a satellite link because of the long propagation delay involved.
Q: The effect of ARQ is to turn an unreliable data link into a reliable one.
Q: Only one frame may be in the pipe at a time with sliding-window flow control.
Q: In situations where the bit length of the link is greater than the frame length, serious inefficiencies result.
Q: Transmission time is not proportional to the length of the frame.
Q: The initiation, maintenance, and termination of a sustained data exchange require management procedures for the exchange.
Q: It is usually desirable to have a physically separate communications path for control information.
Q: The sending station must not send frames at a rate faster than the receiving stations can absorb them.
Q: The beginning and end of each frame must be recognizable for effective communication between two directly connected transmitting-receiving stations.
Q: DLHC is a widely used data link control.
Q: Error control enables a receiver to regulate the flow of data so that the receiver's buffers do not overflow.
Q: It is necessary to impose a layer of control in each communicating device that provides functions such as flow control, error detection, and error control.
Q: The receiver must be able to distinguish control information from the data being transmitted.
Q: Synchronization and interfacing techniques are sufficient by themselves.
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