ECE144 Data-Link Layer Chapter 3
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Questions and Answers

What type of communication does the data-link layer primarily handle?

  • Network-to-network communication
  • End-to-end communication
  • Node-to-node communication (correct)
  • Application-to-application communication

    • Which sublayer of the data-link layer specifically deals with issues related to broadcast links?

  • Frame control layer
  • Media access control (MAC) (correct)
  • Protocol control sublayer
  • Data-link control (DLC)

    • How does framing enhance data transmission at the data-link layer?

  • By separating messages into distinguishable units (correct)
  • By compressing data to save space
  • By adding encryption to packets
  • By converting messages into a binary format

    • What type of link dedicates the entire transmission medium to two devices?

    <p>Point-to-point link</p> Signup and view all the answers

    Which of the following is NOT a component addressed by the data-link control (DLC) sublayer?

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

    What is a common application of a broadcast link?

    <p>Cellular communication</p> Signup and view all the answers

    What is a key benefit of dividing messages into smaller frames?

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

    Which addresses are added to frames at the data-link layer to facilitate communication?

    <p>Source and destination addresses</p> Signup and view all the answers

    What is the primary function of Normal response mode (NRM)?

    <p>The primary station sends commands while the secondary responds.</p> Signup and view all the answers

    In Asynchronous balanced mode (ABM), how do the stations function?

    <p>Each station can act as both primary and secondary.</p> Signup and view all the answers

    What type of information do Information Frames (I-frames) transport?

    <p>User data and control information relating to that data.</p> Signup and view all the answers

    What identifies both the beginning and the end of an HDLC frame?

    <p>Flag containing the pattern 01111110.</p> Signup and view all the answers

    What is the primary purpose of the Control field in HDLC frames?

    <p>To indicate the type of frame and its functionality.</p> Signup and view all the answers

    The Frame Check Sequence (FCS) in HDLC is used for what purpose?

    <p>To enable error detection.</p> Signup and view all the answers

    Which statement correctly describes Supervisory frames (S-frames)?

    <p>They are only used when piggybacking is unavailable.</p> Signup and view all the answers

    How many possible U-frames can be created based on the segmentation defined in the HDLC format?

    <p>32 possible U-frames.</p> Signup and view all the answers

    What is the primary goal of error detection?

    <p>Determine if an error has occurred</p> Signup and view all the answers

    Which of the following is a method of error correction?

    <p>Forward error correction</p> Signup and view all the answers

    Which statement describes the complexity of error correction compared to error detection?

    <p>Error correction is more complex than error detection.</p> Signup and view all the answers

    What type of information is needed for error correction?

    <p>Number and location of corrupted bits</p> Signup and view all the answers

    Which of the following best describes High-Level Data-Link Control (HDLC)?

    <p>A bit-oriented protocol for point-to-point and multipoint links</p> Signup and view all the answers

    In what scenario is forward error correction particularly useful?

    <p>For systems with continuous data streams without retransmission</p> Signup and view all the answers

    What is a major limitation of error correction techniques?

    <p>Their effectiveness significantly decreases with the number of errors.</p> Signup and view all the answers

    Which of the following options represents a factor affecting error impact in detection?

    <p>Single-bit errors are treated the same as burst errors</p> Signup and view all the answers

    What occurs during the Establish State of the PPP protocol?

    <p>Options are negotiated between nodes.</p> Signup and view all the answers

    Which protocol under Authentication Protocols (AP) provides greater security by keeping the password secret?

    <p>Challenge Handshake Authentication Protocol (CHAP)</p> Signup and view all the answers

    What is the function of Network Control Protocols (NCPs) in PPP?

    <p>They configure the link for network-layer data.</p> Signup and view all the answers

    Which state follows the Authenticate State if authentication is not agreed upon?

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

    What is a key characteristic of Multilink PPP?

    <p>Allows a single logical PPP frame to be divided into multiple PPP frames.</p> Signup and view all the answers

    What happens during the Terminate State of the PPP protocol?

    <p>The connection ends and waits for the carrier signal to drop.</p> Signup and view all the answers

    Which option best describes the Link Control Protocol (LCP)?

    <p>It establishes, maintains, configures, and terminates links.</p> Signup and view all the answers

    Which of the following is NOT a state in the PPP phase transition?

    <p>Inactive State</p> Signup and view all the answers

    What does variable framing primarily focus on in data communication?

    <p>Sequence of bits</p> Signup and view all the answers

    In bit-oriented framing, what is the purpose of using a delimiter?

    <p>To indicate the start and end of a frame</p> Signup and view all the answers

    What problem can the flag pattern 01111110 create in bit-oriented protocols?

    <p>False flags in data frames</p> Signup and view all the answers

    What defines a single-bit error in data transmission?

    <p>A single bit being corrupted</p> Signup and view all the answers

    Which of the following is NOT a common technique for error detection?

    <p>Retransmission techniques</p> Signup and view all the answers

    What does error control primarily facilitate in data-link communication?

    <p>Recovering lost or damaged frames</p> Signup and view all the answers

    What is the role of bit stuffing in data framing?

    <p>To prevent flag patterns from appearing in data</p> Signup and view all the answers

    Which type of error refers to multiple bits being altered in a single transmission?

    <p>Burst error</p> Signup and view all the answers

    Study Notes

    • Node-to-node communication occurs at the data-link layer, contrasting with end-to-end communication in higher layers.
    • Data units must traverse multiple networks (LANs and WANs) and are facilitated by routers.
    • Nodes consist of end hosts and routers, while links connect these nodes.
    • Data-link layer manages the utilization of transmission mediums (cable, air).
    • Point-to-point links dedicate resources to two devices; broadcast links share resources among multiple devices.
    • Traditional home phones exemplify point-to-point links, while cellular networks illustrate broadcast links.
    • Divided into two sublayers:
      • Data-Link Control (DLC): Addresses issues for both point-to-point and broadcast links.
      • Media Access Control (MAC): Specifically manages issues for broadcast links.

    Framing

    • Bits are packed into frames for distinction; analogous to postal systems.
    • Each frame includes sender and destination addresses for effective communication.
    • Messages are broken into smaller frames which improves flow and error control.
    • Frames can be fixed or variable in size, and may utilize different framing protocols:
      • Character-oriented Framing: Traditional approach, but limited by character encoding issues.
      • Bit-oriented Framing: Uses bits for data representation and requires delimiters to separate frames.

    Bit Stuffing

    • Employed to prevent flag patterns (0 1 1 1 1 1 1 0) from appearing in data.
    • If five consecutive 1 bits are detected, an extra 0 is inserted, which is later removed by the receiver.

    Error Control

    • Incorporates error detection and correction strategies while addressing data loss and integrity during transmission.
    • Two error types:
      • Single-bit Error: Occurs in a single bit.
      • Burst Error: Involves multiple bits.
    • Error Detection Techniques include:
      • Exact-code coding, parity checking, and redundancy methods (Checksum, VRC, LRC, CRC).

    Error Correction

    • More complex than detection; focuses on identifying and correcting erroneous data.
    • Two primary methods:
      • Retransmission: Involves sending data again after detection of errors.
      • Forward Error Correction: Uses techniques like Hamming codes to correct errors without retransmission.
    • A bit-oriented protocol used for communication on point-to-point and multipoint links.
    • Defined transfer modes:
      • Normal Response Mode (NRM): Unbalanced configuration, primary node initiates communication.
      • Asynchronous Balanced Mode (ABM): Balanced configuration, each node can act as primary or secondary.

    HDLC Frame Types

    • Information Frames (I-frames): Carry user data and control info.
    • Supervisory Frames (S-frames): Convey control info without user data.
    • Unnumbered Frames (U-frames): Manage session and control information.

    HDLC Frame Structure

    • Flag: Synchronization pattern that indicates frame boundaries.
    • Address: Identifies secondary station's address.
    • Control: Bytes for flow and error control; varies based on frame type.
    • Information: Contains user data; length can vary.
    • Frame Check Sequence (FCS): Error detection field using CRC.

    Point-to-Point Protocol (PPP)

    • Extends HDLC for point-to-point communication; facilitates link establishment and data transfer with various protocol layers.
    • State Phases of PPP include:
      • Dead State
      • Establish State
      • Authenticate State
      • Open State
      • Terminate State

    PPP Protocols

    • Link Control Protocol (LCP): Configures and maintains the connection; negotiates options.
    • Authentication Protocols (APs): Verify user identity through methods like PAP and CHAP.
    • Network Control Protocols (NCPs): Configure links for multiple network-layer protocols.
    • Allows logical frames to be distributed across multiple physical channels, enhancing link efficiency.
    • Sequence numbering in PPP frames indicates the position of fragments within logical frames.

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    Description

    Explore the fundamentals of the Data-Link Layer in this quiz. Dive into key concepts such as framing, error control, and protocols that facilitate node-to-node communication. Perfect for students of Data Communications in course ECE144.

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