Computer Networks Lecture 8: Reliable Data Transfer
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Questions and Answers

What is the main goal of reliability in data transfer?

  • Maximizing data throughput
  • Ensuring no data loss or bit errors (correct)
  • Reducing sender and receiver states
  • Minimizing delay in data transfer

    • What is the function called for ensuring reliable data transfer?

  • Flow Control Protocol (FCP)
  • Reliable Data Transfer (rdt) (correct)
  • Finite State Machine (FSM)
  • Congestion Avoidance Algorithm (CAA)

    • How are sender and receiver sides of reliable data transfer protocol developed?

  • Using Finite State Machines (FSMs) (correct)
  • By minimizing the number of states
  • Through congestion control mechanisms
  • By increasing the data transfer speed

    • What is the role of finite state machines (FSM) in reliable data transfer?

    <p>To specify sender and receiver states</p> Signup and view all the answers

    In reliable data transfer, what determines the next state of the sender and receiver?

    <p>Next event or action taken on state transition</p> Signup and view all the answers

    What does reliable data transfer aim to achieve with regards to data loss and bit errors?

    <p>Minimizing both data loss and bit errors</p> Signup and view all the answers

    What does rdt2.0 use to detect bit errors in the channel?

    <p>Checksum</p> Signup and view all the answers

    What does the receiver explicitly tell the sender if the packet is received OK?

    <p>ACK</p> Signup and view all the answers

    What does the receiver explicitly tell the sender if the packet had errors?

    <p>NAK</p> Signup and view all the answers

    What does the sender do on receipt of a NAK?

    <p>Retransmits the packet</p> Signup and view all the answers

    What feedback messages are used in rdt2.0 for error detection?

    <p>ACK and NAK</p> Signup and view all the answers

    What happens if ACK/NAK is not received in rdt2.0?

    <p>Possible duplicate handling</p> Signup and view all the answers

    What mechanism does rdt2.0 use to handle duplicates?

    <p>Sender adds sequence number</p> Signup and view all the answers

    What does the receiver do if a duplicate packet is received in rdt2.0?

    <p>(Doesn't deliver up) Discards the duplicate packet</p> Signup and view all the answers

    What does the sender do after sending one packet in rdt2.0?

    <p>(Doesn't deliver up) Waits for retransmission</p> Signup and view all the answers

    What is used by rdt2.0 to detect if a packet was received without errors?

    <p>Checksum.</p> Signup and view all the answers

    If ACK/NAK is not received at sender end in rdt2.0, what will happen?

    <p>Automatic retransmission.</p> Signup and view all the answers

    How does rdt2.0 handle a scenario where ACK/NAK is not received at sender's end?

    <p>Retransmits current pkt.</p> Signup and view all the answers

    What is the main objective of reliable data transfer?

    <p>Avoiding data loss and bit errors</p> Signup and view all the answers

    In reliable data transfer, what determines the next state of the sender and receiver?

    <p>Finite state machines (FSM)</p> Signup and view all the answers

    What is the function called for ensuring reliable data transfer?

    <p>Reliable data transfer (rdt)</p> Signup and view all the answers

    What does the receiver explicitly tell the sender if the packet is received without errors?

    <p>ACK</p> Signup and view all the answers

    What feedback messages are used in reliable data transfer for error detection?

    <p>ACK/NAK</p> Signup and view all the answers

    What does rdt2.0 use to detect bit errors in the channel?

    <p>Checksums</p> Signup and view all the answers

    What does rdt2.0 use to recover from errors in the channel?

    <p>Both ACKs and NAKs</p> Signup and view all the answers

    What is the fatal flaw in rdt2.0 if ACK/NAK is not received?

    <p>The sender retransmits current packet</p> Signup and view all the answers

    What is used in rdt2.0 to detect bit errors in the channel?

    <p>Checksum</p> Signup and view all the answers

    What is the role of acknowledgements (ACKs) in rdt2.0?

    <p>To explicitly tell the sender that the packet was received OK</p> Signup and view all the answers

    What feedback messages are used in rdt2.0 for error detection?

    <p>Control messages (ACK,NAK)</p> Signup and view all the answers

    What additional mechanism does rdt2.0 have beyond rdt1.0 for error detection during conversation?

    <p>Error detection feedback</p> Signup and view all the answers

    What does the receiver do if a duplicate packet is received in rdt2.0?

    <p>Discard and not deliver up the duplicate packet</p> Signup and view all the answers

    What happens if the ACK/NAK is not received at the sender's end in rdt2.0?

    <p>The sender retransmits current packet</p> Signup and view all the answers

    What is the function called for ensuring reliable data transfer?

    <p>rdt_send(data)</p> Signup and view all the answers

    What is the main goal of reliability in data transfer?

    <p>To ensure no bit errors or loss of packets in the channel</p> Signup and view all the answers

    What determines the next state of the sender and receiver in reliable data transfer?

    <p>Control messages (ACK,NAK)</p> Signup and view all the answers

    What does the sender do after sending one packet in rdt2.0?

    <p>Waits indefinitely for a response from the receiver</p> Signup and view all the answers

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