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