Chapter 3
True/False CRC calculations are complicated, and therefore almost always implemented in software rather than hardware
False
True/False In practice, every kind of physical link (copper,fiber,wireless,etc.) requires robust error correcting codes in the data link layer
False
True/False Inserting a special byte count header at the beginning of a frame is a sufficient method for forming a bit stream into frames
False
True/False It is ok for the data link layer to pass all or part of the frame header up to the network layer
False
True/False sliding window protocols are appropriate for channels with long transit time, high bandwidth and short frame length
False
True/False A 1 bit sequence number is sufficient for a simple stop and wait protocol operating over a noisy channel.
True
True/False Error-correcting and error detecting codes typically rely on higher mathematics, and therefore certain industry standard codes have often been adopted
True
True/False Ethernet 802.1p (COS) is used to provide traffic priority
True
True/False For the flow control protocols in this chapter, it is assumed the the physical layer will occasionally lose entire frames during transmission
True
True/False Often protocols piggyback ACK information onto outgoing data frames
True
True/False The bit stream received by the data link layer is not guaranteed to be error free
True
True/False The data link layer converts the raw bit stream offered by the physical layer into a stream of frames
True
True/False The flow control protocols in this chapter rely on the physical layer to perform the checksums or other work that detect frame errors
True
True/False There is a standard polynomial used for CRC computations in both IEEE 802 and Ethernet
True
True/False With both bit and byte stuffing the length of a frame depends on the contents of the data it carries
True
Which of the following is not a function of the data link layer dealing with transmission errors providing a well defined service interface to the network layer providing end to end delivery of packets regulating the flow of data
Providing end to end delivery of packets
Which of the following causes the sender to re send a frame in a stop and wait protocol an acknowledgement frame arrives undamaged an acknowledgement frame arrives damaged the timer expires either b or c
either b or c
Error detecting and error correcting codes both rely on bit stuffing byte stuffing escape bytes extra bits added to the frame
extra bits added to the frame
True/False Unacknowledged connectionless service is never appropriate for real time data transfer
false
Which type of flow control scheme is most commonly seen in the data link and higher layers bit stuffing byte stuffing feedback based rate based
feedback based
Which problem is best addressed by the use of timers frames that are completely lost in transmission frames that arrive with only a few bits in error frames that arrive with only a few bits in error the need for acknowledgement messages
frames that are completely lost in transmission
Why is the Utopian simplex protocol unrealistic? it does not handle error correction it does not handle flow control it does not handle error correction or flow control it uses an unrealistically fast physical layer
it does not handle error correction or flow control
Which of the following is the simplest error detecting code checksums cyclic redundancy checks hamming codes parity bits
parity bits
Protocols in which the sender sends one frame and then waits for an acknowledgement before proceeding are called go back in sliding window stop and wait utopian
stop and wait
Which of the following is not an assumption made about all the flow control protocols in this chapter? neither sender nor receiver ever crashes the channel is assumed to be noise-free the physical layer, data link layer, and the network layer are independent processes the sender always has data to send
the channel is assumed to be noise-free
