Transport Layer Services and Protocols
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Questions and Answers

What is the primary purpose of port scanning?

  • To find vulnerabilities and identify running network applications (correct)
  • To improve network speed
  • To establish TCP connections
  • To monitor network traffic

    • UDP provides reliable transmission through connection establishment.

    False

    Which port number is primarily used for HTTP traffic on web servers?

    80

    The most used port scanner that is free and open source is called _____?

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

    Match the following transport protocols with their characteristics:

    <p>TCP = Connection-oriented with handshaking UDP = Connectionless without handshaking HTTP = Application layer protocol that runs over TCP DNS = Application layer protocol that typically uses UDP</p> Signup and view all the answers

    What does TCP do each time it retransmits a segment?

    <p>Sets the next timeout interval to twice the previous value</p> Signup and view all the answers

    A duplicate ACK indicates that a segment has been lost.

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

    What mechanism does TCP use to retransmit a segment upon receiving three duplicate ACKs?

    <p>Fast retransmit</p> Signup and view all the answers

    To avoid overflowing the connection's receive buffer, TCP provides a __________ service.

    <p>flow-control</p> Signup and view all the answers

    Which of the following protocols does TCP's error recovery mechanism resemble?

    <p>A hybrid of Go-Back-N and Selective Repeat</p> Signup and view all the answers

    TCP stores out-of-order segments in the receive buffer until they can be processed.

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

    Match the following terms with their definitions:

    <p>Duplicate ACK = Reacknowledges a segment already acknowledged Fast retransmit = Resends a missing segment before the timer expires Flow control = Prevents sender from overwhelming the receiver Cumulative acknowledgments = Acknowledgments that indicate receipt of all previous segments</p> Signup and view all the answers

    What happens when TCP receives bytes that are correct and in sequence?

    <p>They are placed in the receive buffer.</p> Signup and view all the answers

    What happens when a sender receives ACK3 in a Go-Back-N protocol?

    <p>Packets from 0 to 3 are acknowledged.</p> Signup and view all the answers

    In Selective Repeat, the sender retransmits all packets starting from the last acknowledged packet.

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

    What type of service does TCP provide?

    <p>Full-duplex service</p> Signup and view all the answers

    In the TCP connection establishment process, the client sends a special segment first, known as the ______.

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

    What distinguishes Selective Repeat from Go-Back-N protocol?

    <p>It retransmits only the suspected erroneous packets.</p> Signup and view all the answers

    TCP connections are considered point-to-point, allowing multicast connections.

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

    What happens during the timeout in a Selective Repeat protocol?

    <p>Only the missing packet is resent</p> Signup and view all the answers

    In a Go-Back-N protocol, acknowledgements are ______.

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

    What is required for two application processes to start sending data via TCP?

    <p>A handshake process.</p> Signup and view all the answers

    What is the main problem with stop-and-wait protocols in networking?

    <p>They require acknowledgment for every packet sent.</p> Signup and view all the answers

    What does flow control primarily prevent?

    <p>Overflow at the receiver</p> Signup and view all the answers

    Flow control and congestion control achieve the same goal.

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

    Pipelining allows the sender to send multiple packets without waiting for acknowledgments.

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

    Name the two basic approaches toward pipelined error recovery.

    <p>Go-Back-N and Selective Repeat</p> Signup and view all the answers

    What variable does TCP use to enable flow control?

    <p>receive window</p> Signup and view all the answers

    The default RcvBuffer size in many systems is typically set to _____ bytes.

    <p>4096</p> Signup and view all the answers

    In Go-Back-N, the sender is allowed to send up to ______ packets before receiving an acknowledgment.

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

    Match the following concepts with their definitions:

    <p>Go-Back-N = Sender can send multiple packets but must wait for the first unacknowledged packet. Selective Repeat = Receiver acknowledges individually and can reorder packets. Stop-and-Wait = Sender sends a packet and waits for acknowledgment before sending the next. Pipelining = Technique that allows multiple packets to be in transit at the same time.</p> Signup and view all the answers

    Match the following elements of TCP flow control:

    <p>RcvBuffer = Size of receive buffer set via socket options rwnd = Receiver's advertised free buffer space LastByteRead = Last byte read by the application LastByteRcvd = Last byte arrived from the network</p> Signup and view all the answers

    What happens when a packet is lost in the Go-Back-N protocol?

    <p>The receiver discards all packets with sequence numbers greater than the lost packet.</p> Signup and view all the answers

    How does sender A manage the amount of unacknowledged data?

    <p>By limiting it to the receiver’s rwnd value</p> Signup and view all the answers

    Host B uses the LastByteRcvd and LastByteRead to manage flow control.

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

    In pipelining, the range of sequence numbers must decrease.

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

    What is a consequence of using pipelining in networking?

    <p>Increased sequence number range and buffering of multiple packets.</p> Signup and view all the answers

    What must Host B do to advertise free buffer space?

    <p>Include rwnd value in TCP header</p> Signup and view all the answers

    The Go-Back-N protocol allows for the sender's window size to be ______.

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

    Flow control is achieved only by the _____ end points.

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

    What is the role of many operating systems in relation to the RcvBuffer?

    <p>They autoadjust RcvBuffer sizes</p> Signup and view all the answers

    What is one key aspect of the Selective Repeat protocol?

    <p>It allows the receiver to buffer packets and acknowledge them individually.</p> Signup and view all the answers

    Study Notes

    Transport Layer Services

    • A transport-layer protocol enables logical communication between application processes on different hosts.
    • Applications use this for message exchange, unaffected by underlying infrastructure details.
    • Transport protocols reside in end systems, not routers.

    Transport Layer Segments

    • Transport layer takes application messages, breaks them into smaller segments, and adds headers.
    • These segments are then passed to the network layer.

    Relationship Between Transport and Network Layers

    • Transport layer provides logical communication between processes.
    • Network layer provides logical communication between hosts.

    Transport Layer Protocols in the Internet

    • UDP (User Datagram Protocol) is unreliable and connectionless.
    • TCP (Transmission Control Protocol) is reliable and connection-oriented.

    Multiplexing and Demultiplexing

    • Multiplexing gathers data from different sockets and encapsulates them into segments.
    • Demultiplexing delivers data segments to the appropriate sockets on the destination host.
    • Sockets have unique identifiers, and segments have source and destination port fields for delivery.
    • Well-known port numbers are reserved for specific applications (e.g., HTTP).

    Reliable Data Transfer

    • Reliable data transfer ensures data transmission without corruption or loss, and in the correct order.
    • Protocols can include mechanisms like acknowledgments and retransmissions.
    • ARQ (Automatic Repeat reQuest) protocols are used for reliable transfer.

    UDP Segment Structure

    • UDP segments have four fields: source port, destination port, length, and checksum.

    UDP Checksum

    • Used for error detection during transmission.

    TCP Connection-Oriented Transport

    • TCP connection establishment uses a three-way handshake.
    • TCP sockets, identified by four-tuples (source IP, source port, destination IP, destination port).
    • TCP provides flow control to prevent buffer overflow.

    TCP Segment Structure

    • TCP segments use sequence numbers and acknowledgment numbers for reliable data transfer.
    • Include source port, destination port, sequence number, acknowledgment number, and header length fields as well as options (variable length).

    TCP Retransmission Scenarios

    • Lost ACKs, premature timeouts, etc., can lead to retransmissions.

    TCP Connection Management

    • TCP uses a three-way handshake for connection initiation.
    • The process includes SYN, SYN-ACK, and ACK segments.
    • TCP connection closing uses a four-way handshake.

    TCP Congestion Control

    • Mechanism to manage network congestion by controlling the sender's transmission rate.
    • Includes slow start, congestion avoidance, and fast recovery strategies.
    • The congestion window size (cwnd) controls the rate of transmission.

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    Related Documents

    Transport Layer, PDF

    Description

    This quiz covers the fundamental concepts of transport layer services, including segmentation, multiplexing, and the relationship between transport and network layers. It also explores key transport protocols like TCP and UDP, focusing on their characteristics and functionalities in the Internet. Test your understanding of how these protocols enable communication between applications.

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