Transport Layer Services Overview
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Questions and Answers

What is the recommended value for β in the DevRTT calculation?

  • 0.10
  • 0.75
  • 0.50
  • 0.25 (correct)

    • The TimeoutInterval is calculated by the formula: TimeoutInterval = EstimatedRTT - 4 * DevRTT.

    False

    What does TCP use to create a reliable data transfer service?

    IP's unreliable best-effort service

    The TimeoutInterval value is doubled when a ______ occurs.

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

    Match the following TCP processes with their descriptions:

    <p>Encapsulation = Involves wrapping application data in a segment Timeout Handling = Retransmitting the segment that caused a timeout ACK Comparison = Checking received ACK against the sendBase Retransmission Timer = Associated with the oldest unacknowledged segment</p> Signup and view all the answers

    What is the primary function of a transport-layer protocol?

    <p>Converts application messages into transport-layer segments</p> Signup and view all the answers

    The transport layer protocols are implemented in network routers.

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

    Name the two distinct transport-layer protocols available in TCP/IP networks.

    <p>TCP and UDP</p> Signup and view all the answers

    The transport-layer packets are known as transport-layer __________.

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

    Match the transport-layer protocols with their characteristics:

    <p>UDP = Unreliable, connectionless service TCP = Reliable, connection-oriented service</p> Signup and view all the answers

    Which layer provides logical communication between hosts?

    <p>Network layer</p> Signup and view all the answers

    Transport-layer protocols operate only on the receiving side.

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

    What does the IP service model guarantee?

    <p>None of the above</p> Signup and view all the answers

    TCP provides unreliable data transfer.

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

    What is the purpose of UDP in the transport layer?

    <p>To provide process-to-process delivery and error checking services.</p> Signup and view all the answers

    Each port number is a ___-bit number ranging from 0 to 65535.

    <p>16</p> Signup and view all the answers

    Match the following protocols with their characteristics:

    <p>TCP = Reliable data transfer UDP = Unreliable service IP = Best-effort delivery Congestion Control = Traffic management</p> Signup and view all the answers

    What is the main function of demultiplexing?

    <p>To deliver data to the correct socket</p> Signup and view all the answers

    Transport-layer multiplexing is the process of gathering data chunks and sending them to the network layer.

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

    What is the role of sequence numbers in TCP?

    <p>To ensure the correct order of data segments.</p> Signup and view all the answers

    TCP uses ___ to prevent any connection from overwhelming the network with traffic.

    <p>congestion control</p> Signup and view all the answers

    Which of the following port numbers is considered a well-known port number?

    <p>21</p> Signup and view all the answers

    A UDP socket can be uniquely identified by a four-tuple.

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

    What type of multiplexing does a TCP socket use?

    <p>Connection-oriented multiplexing</p> Signup and view all the answers

    A TCP server application listens for connection establishment requests on port number _____.

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

    Match the following terms with their descriptions:

    <p>UDP = Connectionless protocol TCP = Connection-oriented protocol Well-known ports = Port numbers from 0 to 1023 Socket = Endpoint for sending or receiving data</p> Signup and view all the answers

    What information is part of the return address in a UDP socket?

    <p>Source port number</p> Signup and view all the answers

    If two TCP segments arrive with the same destination IP address and port, they will always be directed to the same socket.

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

    What enables TCP to support multiple simultaneous connections?

    <p>Four-tuple identification</p> Signup and view all the answers

    A new socket created by the server upon receiving a connection request is identified by the _____.

    <p>four-tuple</p> Signup and view all the answers

    What is the purpose of the connection-establishment bit in a TCP segment?

    <p>To establish a connection</p> Signup and view all the answers

    What happens when an ACK packet is received by the sender in the rdt2.0 protocol?

    <p>The sender returns to waiting for data from the upper layer.</p> Signup and view all the answers

    In the rdt2.0 protocol, the sender can send a new packet while waiting for an ACK or NAK.

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

    What is the primary purpose of adding checksum bits to ACK and NAK packets?

    <p>To detect errors in the packets.</p> Signup and view all the answers

    The rdt2.0 is known as a __________ protocol because it does not send a new packet until the previous one has been acknowledged.

    <p>stop-and-wait</p> Signup and view all the answers

    What action does the sender take if a NAK packet is received?

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

    The sender in rdt2.0 can differentiate between a corrupted ACK and a successful packet reception.

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

    Why is it important for the rdt2.0 protocol to include a sequence number in the data packets?

    <p>To identify packets and handle potential retransmissions correctly.</p> Signup and view all the answers

    The main event that triggers packet creation in the rdt2.0 protocol is __________.

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

    What is the role of udt_send(sndpkt) in the rdt2.0 protocol?

    <p>To send the constructed packet to the receiver.</p> Signup and view all the answers

    Study Notes

    Transport Layer Services

    • A transport-layer protocol facilitates logical communication between application processes on different hosts.
    • Applications use this layer, unaffected by the underlying physical infrastructure.
    • Transport layer protocols reside on end systems, not network routers.
    • Transport layer segments application messages into smaller chunks, adds a header, and passes the segment into a network-layer packet (datagram).
    • The network layer extracts the transport-layer segment from the datagram, transmitting it up to the transport layer where it is processed, and made available to the receiving application.

    Relationship Between Transport and Network Layers

    • Network-layer protocols provide communication between hosts.
    • Transport-layer protocols provide communication between processes on different hosts.

    Overview of the Transport Layer in the Internet

    • TCP/IP networks offer two transport-layer protocols to the application layer:
      • UDP (User Datagram Protocol): an unreliable, connectionless service.
      • TCP (Transmission Control Protocol): a reliable, connection-oriented service.
    • IP (Internet Protocol) is the network-layer protocol that provides logical communication between hosts in the network.
    • IP is a best-effort delivery service, without guarantees for segment delivery, guaranteed order, or data integrity.
    • UDP provides process-to-process delivery and error-checking.
    • TCP provides reliable data transfer via flow control, sequence numbers, acknowledgements, and timers. It also does congestion control.

    Multiplexing and Demultiplexing

    • Multiplexing gathers data from multiple sockets and encapsulates it into segments, preparing them for transmission.
    • Demultiplexing delivers segments to the correct socket.
    • UDP's multiplexing/demultiplexing relies on the destination IP address and destination port number.
    • TCP's multiplexing/demultiplexing relies on a four-tuple (source IP address, source port number, destination IP address, destination port number)

    Reliable Data Transfer

    • The responsibility of implementing reliable data transfer is on the data transfer protocol.
    • Data transfer protocols must guarantee no data loss or corruption and must transmit in the correct order.
    • Unidirectional data transfer from sender to receiver is considered.

    UDP Segment Structure

    • A UDP segment has a source port, destination port, length, and checksum fields
    • The length field specifies the number of bytes in the segment (including the header).

    UDP Checksum

    • UDP's checksum provides error detection.

    Principles of Reliable Data Transfer

    • The data transfer protocol is responsible for reliable data transfer: accurate and ordered delivery of each bit of data.
    • The sending side is invoked by a call to rdtsend().
    • The receiving side is called by rdt_rcv() when a packet arrives and deliver_data when the data is ready.

    Pipelined Reliable Data Transfer Protocols

    • Reliable data transfer protocols use positive and negative acknowledgements.

    TCP Connection-Oriented Transport

    • Before communication, processes on both sides of a TCP connection engage in a handshake.
    • A TCP connection is between one sender and receiver.
    • TCP is a full-duplex service allowing bidirectional data flow at the same time.

    TCP Segment Structure

    • TCP segments consist of a source port number, destination port number, sequence number, acknowledgement number, header length, flags, data, and checksum.

    Sequence Numbers and Acknowledgment Numbers

    • TCP views data as a stream of bytes, and sequence numbers reflect this view.
    • Sequence numbers are calculated over the stream of bytes and not the segments.

    Round-Trip Time Estimation and Timeout

    • TCP uses a timeout/retransmit strategy to recover from lost segments.
    • Timeout intervals are calculated based on the amount of time to transmit the segment and receive an acknowledgment.

    TCP Fast Retransmit

    • TCP fast retransmit detects packet loss by observing three duplicate ACKs in the receiver- to-sender direction.
    • If three duplicate ACKs are received, the sender assumes the missing segment was lost and retransmits it before the timeout.

    TCP Congestion Control

    • TCP's congestion control regulates the sender's rate, managing network traffic flow.
    • The rate is adjusted based on perceived network congestion, either through timeouts or with duplicate ACKS.
    • TCP adapts to network changes, growing or shrinking transmission rates according to feedback from the network.

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    Related Documents

    Transport Layer Summary PDF

    Description

    This quiz explores the key concepts of transport layer services, focusing on how they facilitate communication between application processes across different hosts. It also examines the relationship between transport and network layers, detailing the role of protocols like TCP and UDP in the TCP/IP architecture. Test your understanding of these essential networking concepts!

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