Peer-to-Peer Protocols and Local Area Networks Coursera Quiz Answers

All Weeks Peer-to-Peer Protocols and Local Area Networks Coursera Quiz Answers

Peer-to-Peer Protocols and Local Area Networks Week 01 Quiz Answers

Practice Assessment – Peer-to-Peer Protocols

Q1. In networks where errors are infrequent, which approach is favored for efficiency?

• Hop-by-hop approach
• End-to-end approach
• Either one of the above
• Neither one of the above

Q2. Which of the following statements is true about the stop-and-wait ARQ protocol?

• Stop-and-wait is only efficient if the link delay-bandwidth product is large
• Stop-and-wait is only efficient if the link bandwidth is high
• Stop-and-wait is only efficient if the link bandwidth is low
• Stop-and-wait is only efficient if the link delay-bandwidth product is small

Q3. Consider a situation where an interactive application produces a packet to send each keystroke from the client and the server echoes each keystroke that it receives from the client. Which of following strategies for sending ACK frames in a Go-Back-N is appropriate for the situation?

• send an ACK frame immediately after each frame is received
• send an ACK frame after every other frame is received
• send an ACK frame when the next piggyback opportunity arises
• Any one of the above

Q4. Consider a bulk data transfer application where a server sends a large file that is segmented in a number of full-size packets that are to be transferred to the client. Assume the channel has a low probability of error. Which of following strategies for sending ACK frames in a Go-Back-N is appropriate for the situation?

• send an ACK frame when the next piggyback opportunity arises
• Any one of the above
• send an ACK frame after every other frame is received
• send an ACK frame immediately after each frame is received

Q5. Consider Selective Repeat ARQ flow control protocol. In the following scenario, what should be the value of frame number x at receiver B?

• 3
• 2
• 4
• None of the above

Q6. ARQ protocols combine error detection, retransmission and sequence numbering to provide reliability

• True
• False

Q7. A service model specifies a level of performance that can be expected in the transfer of information.

• True
• False

Q8. A service offered at a given layer can include which of the following feature(s)

• Sequencing
• Reliability
• Timing
• All of the above

Q9. Digital communication technologies may introduce errors in communication, which of the following can be used to provide reliable communication

• UDP
• TCP
• DNS
• HDLC

Q10. Ensuring that information is not altered during transfer is associated with

• Confidentiality
• Availability
• Integrity
• Authentication

Graded Assessment – Peer-to-Peer Protocols

Q1. Given 3 bits for sequence numbers, what is the maximum sliding window size at the receiver in Go Back 3 ARQ?

• 3
• 7
• 8
• None of the above

Q2. Given 3 bits for sequence numbers in Selective Repeat ARQ. If the sender already set the sliding window size to be 4, what is the maximum sliding window size at the receiver?

• 3
• 8
• 7
• None of the above

Q3. Consider Selective Repeat ARQ flow control protocol. In the following scenario, what should be the value of frame number x at receiver B?

• 3
• 2
• 4
• None of the above

Q4. In the scenario above, what should be the value of frame number y at receiver B?

• 3
• 8
• 7
• None of the above

Q5. If the probability of error is very low in a communication link, which of the following statements is true about performance of ARQ protocol?

• Stop-and-wait and Go-back-N ARQ protocols have similar performance
• Stop-and-wait and Selective Repeat ARQ protocols have similar performance
• Go-back-N ARQ and Selective Repeat ARQ protocols have similar performance
• None of the above

Q6. In peer-to-peer protocol, the purpose of Automatic Repeat Request is

• to ensure a sequence of information packet is delivered with an ACK request
• to ensure a sequence of information packet is delivered without errors or duplication despite transmission errors and losses
• to ensure a sequence of information packet is delivered in order
• to ensure a sequence of information packet is delivered out-of-order

Q7. Which of the basic elements of ARQ is associated with negative acknowledgement

• Timeout mechanism
• NAKs
• ACKs
• Error detecting code

Q8. In Go-Back-N ARQ, a procedure where transmission of a new frame is begun before the completion of time of the previous frame transmission is called

• Transitioning
• Pipelining
• Channeling
• None of the above

Q9. In Stop-and-Wait protocol, sequence number are not required

• True
• False

Q10. The disadvantage of Stop-and-Wait protocol

• Error free communication channel does not exist
• Acknowledgement may get lost
• Deadlock situation may occur
• All of the above

Peer-to-Peer Protocols and Local Area Networks Week 02 Quiz Answers

Practice Assessment – Reliable Services and Data Link Controls

Q1. Which of the following statements are true for the best-effort service of IP?

• Packets can arrive with errors or be lost
• Packets can arrive out-of-order
• Packets can arrive after very long delays
• All of the above

Q2. Which of following services belong to the data link layer?

• Insert framing information into the transmitted stream to indicate the boundaries that define frames
• Provide error control to ensure reliable transmission
• Provide flow control to prevent the transmitter from overrunning the receiver buffer
• All of the above

Q3. Which ARQ flow control protocol is used by TCP?

• Stop-and-Wait
• Selective Repeat
• Go-back-N
• None of the above

Q4. By framing, frame boundaries can be determined using

• Character Counts
• Control Characters
• Flags
• All of the above

Q5. Which of following statements are true about framing protocols?

• PPP uses character-based framing which requires byte stuffing
• HDLC uses Flag-based framing which required bit stuffing
• All of the above
• None of the above

Q6. In IP network, which of the following statement is incorrect

• Packets can arrive out-of-order
• Packets can arrive with errors or be lost
• Packets can arrive after long delays
• Packets always arrive on time

Q7. Framing involves identifying the beginning and end of a block of information within a digital stream

• True
• False

Q8. Which of the following statements are true for PPP byte stuffing

• Malicious users may inflate bandwidth
• Size of frame varies unpredictably due to byte insertion
• All of the above
• None of the above

Q9. In PPP authentication, which of the following is true for Password Authentication Protocol

• After several attempts, LCP closes link
• Transmitted unencrypted, susceptible to eavesdropping
• Initiator must send ID and password
• Initiator and authenticator share a secret key

Q10. In HDLC frame format, flag is used to identify secondary station (1 or more octets)

• True
• False

Graded Assessment – Reliable Services and Data Link Controls

Q1. Perform the bit stuffing procedure for the following binary sequence: 1101111111011111110101. What is the outcome?

• 110111110110111110110101
• 110111111101111111010100
• 0010000000100000001010
• None of the above

Q2. Perform bit de-stuffing for the following sequence: 11101111101111100111110.

• 11101111111111011111
• 00010000010000011000001
• 11100111111110011111
• None of the above

Q3. PPP is a data link protocol for point-to-point lines in Internet. Its framing is based on which of the following?

• Byte stuffing
• Bit stuffing
• Word stuffing
• None of the above

Q4. HDLC is another data link control protocol widely in use. Its framing is based on which of the following?

• Byte stuffing
• Bit stuffing
• Word stuffing
• None of the above

Q5. Which of following statements are true for HDLC?

• supports various data transfer modes
• supports multi-point links and point to point links
• implements error control and flow control mechanisms
• All of the above

Q6. In PPP authentication, which of the following is true for Challenge-Handshake Authentication Protocol (CHAP)

• After several attempts, LCP closes link
• Authenticator can reissue challenge during session
• Initiator and authenticator share a secret key
• Initiator must send ID and password

Q7. In error detection and loss recovery, which of the following statement is correct

• Frames may undergo errors in transmission
• CRCs detect errors and such frames treated as lost
• Frames lost due to loss-of-synchronization or receiver buffer overflow
• All of the above

Q8. In multiplexing, Last IN First Out (LIFO) is used to determine the order of packet transmission

• True
• False

Q9. Generic Framing Procedure (GFP) allows the implementation of multiple transport modes that may coexist within the same transport channel

• True
• False

Q10. In Generic Framing Procedure (GFP), which of the following sentences are correct

• GFP uses a variation of HEC-based self delineation technique
• GFP uses an explicit payload length indicator provided in its frame header to accommodate variable length PDUs
• GFP provides flexible encapsulation framework that supports either a fixed or variable length frame structure
• GFP rely on byte-stuffing mechanism to delineate protocol data units (PDUs)

Peer-to-Peer Protocols and Local Area Networks Week 03 Quiz Answers

Practice Assessment – Medium Access Controls

Q1. What is the primary function of medium access control?

• It is to deal with the flow control of a shared communication link.
• It is to minimize or eliminate the incidence of collisions of a shared communication link.
• It is to deal with the congestion control of a shared communication link.
• None of the above

Q2. What is the primary benefit provided by the Slotted ALOHA compared to ALOHA?

• Higher maximum throughput
• Lower access delay
• Both of the above
• None of the above

Q3. What is the vulnerable period of collisions in ALOHA?

• Round-trip propagation delay
• One frame transmission time
• Two frame transmission time
• None of the above

Q4. What is the vulnerable period of collisions in Slotted ALOHA?

• Round-trip propagation delay
• One frame transmission time
• Two frame transmission time
• None of the above

Q5. What is the vulnerable period of collisions in Carrier Sense Multiple Access (CSMA)?

• Round-trip propagation delay
• None of the above
• One frame transmission time
• One propagation delay

Q6. The primary function of Media Access Control is to minimize or eliminate the instance of the collisions to achieve a reasonable utilization of the medium

• True
• False

Q7. In media sharing techniques, which of the following are channelization approaches

• Code Division Multiple Access
• Data Division Multiple Access
• Frequency Division Multiple Access
• Time Division Multiple Access

Q8. Corresponding box of Carrier Sense Multiple Access/Collision Detection can be replaced by one of the

• P-persistent process
• I-persistent process
• Persistent process
• Non-persistent process

Q9. Random access is also called the

• Controlled access
• Channelization
• Authentication
• Contention methods

Q10. In Carrier Sense Multiple Access (CSMA), possibility of collision still exist because of

• Propagation delay
• Collision delay
• Transmit delay
• None of the above

Graded Assessment – Medium Access Controls

Q1. Polling is a scheduling approach for dynamic medium access control. Which of following statements are correct?

• Polling can provide bounds on access delay to the shared medium
• Polling performance can deteriorate with large delay-bandwidth product
• Polling can provide fairness through regulated access opportunities
• All of the above

Q2. In a collision-free reservation system that has a large number of light-traffic stations, and the delay-bandwidth product is larger than 1. Which of following MAC protocol is a good fit for stations to reserve mini-slots?

• 1-persistent CSMA
• Slotted ALOHA
• CSMA/CD
• None of the above

Q3. In Carrier Sense Multiple Access with collision detection (CSMA-CD), how long will it take a collision to be detected and resolved?

• Round-trip propagation delay
• One propagation delay
• One frame transmission time
• None of the above

Q4. Suppose that the ALOHA protocol is used to share a 56 kbps satellite channel. Suppose that frames are 1000 bits long. What is the maximum throughput of the system in number of frames per second.

• 1 frame per second
• 10 frames per second
• 100 frames per second
• None of the above

Q5. Consider building a CSMA/CD network running at 1Gbps over a 1-km cable. The signal speed in the cable is 200,000 km/sec. What is the minimum frame size?

• 64 Bytes
• 640 Bytes
• 1250 Bytes
• None of the above

Q6. In media access control, which of the following statements are true for Channelization

• Widely used in internet traffic
• Inflexible in allocating bandwidth to users with different requirements
• Inefficient for bursty traffic
• Does not scale well to large numbers of users

Q7. Time-out period is equal to maximum possible propagation delay of

• Round-trip
• Triangle-trip
• Square-trip
• Rectangle-trip

Q8. In Carrier Sense Multiple Access (CSMA), if station senses medium before trying to use it then chance of collision can be

• Increased
• Reduced
• Doubled
• Highlighted

Q9. Carrier Sense Multiple Access (CSMA) is based on medium called

• Listen before sending
• Sense before Collision
• Listen before talk
• Sense before transmit

Q10. Which of the following is not true for MAC scheduling

• Can provide fairness to stations
• More efficient channel utilization
• Reduced computational or procedural complexity
• Less variability in delays

Peer-to-Peer Protocols and Local Area Networks Week 04 Quiz Answers

Practice Assessment – Local Area Networks

Q1. Which of following features are typically true for local area networks?2

• All of the above
• Low error rate
• Low round-trip delay
• High speed

Q2. Use HDLC and Ethernet to identify similarities between medium access control and data link control protocols. Which of following statements are true?

• Both contains framing information that delineates the beginning and end of each frame.
• Both check the CRC in the received frames for errors
• Both implement error control and flow control for reliable transmission.
• None of the above

Q3. Use IEEE 802.3 and IEEE 802.11 to discuss differences between wired and wireless LANs. Which of following statements are true about the differences?

• Error rate
• All of the above
• Station mobility
• Collision detection

Q4. Which of following is not a primary responsibility of the MAC sublayer in LANs?

• Protocol data unit addressing
• Reliable connection-oriented service
• Fragmentation and reassembly of MAC service data unit
• Channel access

Q5. In Ethernet, slot time that is at least the round-trip propagation delay, is the critical system parameter for

• All of the above
• upper bound on time to detect collision
• upper bound on time to acquire channel
• quantum for re-transmission scheduling

Q6. Which one of the following event is not possible in wireless LAN.

• Acknowledgement of data frames
• Collision avoidance
• Multi-mode data transfer
• Collision detection

Q7. In 802.11 protocol, MAC can alternate between Contention Periods (CPs) and Contention-Free Periods (CFPs)

• True
• False

Q8. CSMA/CD is not used in DCF because

• a station is unable to listen to the channel for collisions while transmitting
• physical carrier sense detects the presence of other WLAN users
• in idle state, a station is unable to listen to the channel for collisions
• None of the above

Q9. In infrastructure network supporting voice and data traffic, data traffic is transported through the CP and voice traffic through the CFP

• True
• False

Q10. In 802.11 protocol, which of the following statements are true for Basic Service Set (BSS)

• Location in a Basic Service Area (BSA)
• Stations in BSS can communicate with each other
• Distinct collocated BSS’s cannot coexist
• Multiple BSSs interconnected by Central System (CS)

Graded Assessment – Local Area Networks

Q1. Consider a Gigabit Ethernet hub with stations at a 100-meter distance and average frame size of 512 bytes. Assume the propagation speed is at 2/3 of light speed. What is the value of normalized delay-bandwidth product?

• 0.0122
• 0.122
• 1.22
• None of the above

Q2. Wireless data communication is compelling, because of

• Its easy and low-cost deployment
• Its support to personal and mobile devices
• Its high reliability to noise and interference
• All of the above

Q3. Why not use CSMA/CD in a wireless LAN? The primary reason is

• The round-trip delay in a wireless LAN is too large
• The frame is usually very small in a wireless LAN
• The hidden station problem
• All of the above

Q4. In IEEE 802.11 MAC for wireless LANs, which of following inter-frame space (IFS) is used to transmit high-priority frames such as ACKs?

• PIFS
• None of the above
• SIFS
• DIFS

Q5. Which of following statements identifies the similarity between HDLC (data link control) and Ethernet (medium access control)

• Both implement error control and flow control functions to provide reliable transmission
• Both provide connection-oriented packet transfer services to the network layer
• Both contain framing information that delineates the beginning and end of each frame
• All of the above

Q6. Which multiple access technique is used by IEEE 802.11 standard for wireless LAN?

• CSMA/CA
• CSMA/CD
• CDMA
• ALOHA

Q7. Which of the following are management services offered by the MAC sublayer in wireless LAN

• Network management
• Roaming within ESS
• Power management
• Storage management

Q8. In CSMA/CA, An amount of time divided into slots called

• Contention procedure
• Contention energy
• Contention signals
• Contention window

Q9. In medium access control sublayer, medium usage is mediated by the access control during contention period

• True
• False

Q10. In Carrier Sense Multiple Access/Collision Detection (CSMA/CD), to continue transmission process we use a

• Signal
• Loop
• Access point
• Station

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