Introduction to Data-Link Layer
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Questions and Answers

What addresses would be used for end-to-end communication between Los Angeles Airport and Chicago Airport?

  • IP addresses of the airports (correct)
  • End-to-end IP addresses of the passengers
  • Link-layer MAC addresses of the aircraft
  • Postal addresses of the respective airports

    • If Alice cannot find a direct flight from Los Angeles to Chicago and changes flights in Denver, what type of addresses are used for the communication between the airports?

  • None, as the flight connects are handled automatically
  • Only the link-layer addresses of each airport
  • Both link-layer and end-to-end addresses are required (correct)
  • Only the end-to-end addresses of the passenger

    • When sending a letter via postal services, how does the post office utilize addresses?

  • It uses only end-to-end addresses for delivery
  • It ignores postal addresses for efficient sorting
  • It addresses mail only to the destination without using any address format
  • It relies on both end-to-end and local addressing for routing (correct)

    • If Link 2 is broken in a network, how might communication still occur between Alice and Bob?

    <p>Alice can route her message through alternative links</p> Signup and view all the answers

    In a network that does not support broadcasting, how should the ARP request be sent?

    <p>Through sending unicast requests to individual hosts</p> Signup and view all the answers

    What type of address is used for one-to-one communication in networking?

    <p>Unicast Address</p> Signup and view all the answers

    Which character in a multicast address must be an even number?

    <p>The second digit</p> Signup and view all the answers

    What is the main purpose of a broadcast address in a network?

    <p>To send data to all entities in the link</p> Signup and view all the answers

    What is the size of a unicast or multicast link-layer address in Ethernet?

    <p>48 bits</p> Signup and view all the answers

    Which term describes the action of sending a frame to multiple specific nodes within a local link?

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

    What address format represents a broadcast address in Ethernet?

    <p>FF:FF:FF:FF:FF:FF</p> Signup and view all the answers

    What does the Address Resolution Protocol (ARP) primarily do?

    <p>Resolve IP addresses to MAC addresses</p> Signup and view all the answers

    In which scenario would a broadcast address be used?

    <p>Updating all nodes with routing information</p> Signup and view all the answers

    What is the primary service provided by the data-link layer?

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

    How many data-link layers does the router actually have based on the description?

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

    What happens to a datagram at the data-link layer of a router?

    <p>It is decapsulated from one frame and encapsulated in another</p> Signup and view all the answers

    Which of the following correctly describes a frame in the data-link layer context?

    <p>A datagram encapsulated in a specific format for transmission</p> Signup and view all the answers

    What is the purpose of a frame trailer in data-link layer communication?

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

    What transport occurs between the source host and the router?

    <p>The datagram is encapsulated in a frame for transport</p> Signup and view all the answers

    Which of the following statements is false regarding the data-link layer?

    <p>Data-link layers handle routing decisions</p> Signup and view all the answers

    What is often the first step performed by a data-link layer before sending data?

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

    What is the primary responsibility of the data-link layer at a sending node?

    <p>Encapsulating the datagram in a frame</p> Signup and view all the answers

    Why is encapsulation and decapsulation necessary at each intermediate node?

    <p>Each link may use a different protocol with a different frame format</p> Signup and view all the answers

    What analogical component represents the data-link layer of a source node?

    <p>The taxi that takes the traveller to the train station</p> Signup and view all the answers

    What must the data-link layer of the destination node do with the datagram?

    <p>Decapsulate the datagram from the frame</p> Signup and view all the answers

    What does the process at the intermediate nodes require?

    <p>Both encapsulation and decapsulation</p> Signup and view all the answers

    What is a potential consequence of varying link-layer addresses across links?

    <p>It requires encapsulation and decapsulation at each node</p> Signup and view all the answers

    Which analogy best describes the encapsulation process in network communication?

    <p>Changing mode of transportation during a trip</p> Signup and view all the answers

    Which of the following statements is true regarding the data-link layer functionality?

    <p>The data-link layer plays a crucial role in transporting packets between different link protocols</p> Signup and view all the answers

    What is the primary advantage of using ARP over traditional broadcast frames for sending datagrams?

    <p>It reduces the number of broadcast frames processed by other systems.</p> Signup and view all the answers

    How many broadcast frames does system A need to send without using ARP if it has 10 datagrams to send?

    <p>180 broadcast frames</p> Signup and view all the answers

    What happens after system B responds to system A's ARP request?

    <p>System A stores system B's link-layer address in its cache memory.</p> Signup and view all the answers

    What is the function of the hardware type field in an ARP packet?

    <p>To define the type of the link-layer protocol</p> Signup and view all the answers

    What is the function of the Address Resolution Protocol (ARP)?

    <p>To map an IP address to its corresponding link-layer address</p> Signup and view all the answers

    Which layer of the Internet is primarily responsible for the creation and delivery of a frame?

    <p>Data-link layer</p> Signup and view all the answers

    If system A does not use ARP, how many broadcast frames must each of the 18 systems process?

    <p>180 broadcast frames</p> Signup and view all the answers

    Which of the following accurately describes the encapsulation process of an ARP packet?

    <p>ARP packets are encapsulated directly into a data-link frame.</p> Signup and view all the answers

    What type of address is stored in the source hardware address field of an ARP packet?

    <p>The link-layer address of the sender</p> Signup and view all the answers

    What is the role of the forwarding table in packet delivery?

    <p>To locate the next node's IP address for forwarding packets</p> Signup and view all the answers

    Why is processing broadcast frames considered expensive or time-consuming?

    <p>It involves discarding frames that are not intended for them.</p> Signup and view all the answers

    What distinguishes a point-to-point link from a broadcast link?

    <p>Point-to-point links connect exactly two nodes, while broadcast links allow communication to all nodes in the network.</p> Signup and view all the answers

    Can two hosts in different networks possess identical link-layer addresses?

    <p>Yes, as link-layer addresses are unique only within their local networks</p> Signup and view all the answers

    What are nodes in the context of the Internet?

    <p>Any devices connected to the Internet, including routers and hosts</p> Signup and view all the answers

    Is the size of the ARP packet fixed?

    <p>No, it varies based on the network type and addressing scheme used</p> Signup and view all the answers

    How does the data-link layer ensure accurate packet delivery?

    <p>By applying error control and flow control mechanisms</p> Signup and view all the answers

    Study Notes

    • The TCP/IP protocol suite does not define protocols in the data-link or physical layers.
    • These layers are network territories that make up the internet.
    • Wired or wireless networks provide services to the upper three layers of the TCP/IP suite.
    • The data-link layer has standard protocols in the market.
    • This chapter introduces the general concepts and issues of the data-link layer in networks.
    • Data-link layer involves establishing links and nodes.
    • Data-link layer provides various services.
    • Two types of data-link layer links include point-to-point and broadcast links.
    • Data-link layer addressing is necessary.
    • It describes three link-layer address types (found in some protocols).
    • Address Resolution Protocol (ARP) maps network layer addresses to data-link layer addresses.
    • This aids in finding the next node's address to deliver a packet.
    • The data-link layer is positioned between the physical and network layers.
    • It provides services to the network layer and receives services from the physical layer.
    • It’s a node-to-node service.
    • It encapsulates data-grams into frames.
    • It delivers datagrams to the next node in the path by encapsulating and decapsulating.
    • A data-link layer can use the full or fractional capacity of a link.
    • A point-to-point link dedicates the link to two devices.
    • A broadcast link shares the link between many devices.

    Two Sublayers

    • The data-link layer is divided into two sublayers: data link control (DLC) and media access control (MAC).
    • DLC addresses issues common in point-to-point and broadcast links.
    • MAC deals specifically with broadcast links.
    • The data-link layer uses addresses at the link level.
    • IP addresses identify locations on the internet, but link layer addresses are needed to pass messages between nodes.
    • Link-layer addresses change at each routing hop.
    • Addresses include types like unicast, multicast, and broadcast.

    Address Resolution Protocol (ARP)

    • ARP translates IP addresses to corresponding link addresses.
    • ARP runs at the network layer.
    • ARP sends a request via broadcast.
    • Devices receiving the request, check IP addresses and respond with their link layer address if the request matches.
    • Data-link layer functions like encapsulating and decapsulating datagrams in frames.
    • The addresses of the source and destination nodes are essential for data-link layer communication.
    • Data-link layer addresses are necessary for transmitting data to the next node along the path.
    • Each device in the network uses its data-link layer to deliver the packet.
    • The framing service involves encapsulating datagrams into frames.
    • Frames contain a header and sometimes a trailer.
    • Different data-link layer protocols use different frame formats.
    • Flow control manages the rate of frames to prevent buffer overflow.
    • The sending data-link layer is the producer, and the receiving is consumer.
    • Frame buffer is necessary for receiving frames, because the receiving rate may be slower than transmission rate.
    • A Data-link layer is subject to transmission errors.
    • Error detection and correction are required to handle these errors.
    • In that case, error detection takes precedence.
    • The receiving device checks for errors and requests re-transmission if necessary.
    • Congestion in the data-link layer is addressed by protocols at the network and transport layers.
    • End-to-end nature of congestion control is important.

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    Related Documents

    Data Communications and Networks, 5e (PDF) - Chapter 9 - Introduction to Data-Link Layer

    Description

    This quiz covers the fundamental concepts of the data-link layer within the TCP/IP protocol suite. It explores link establishment, addressing methods, and the various services provided at this layer. Understanding these principles is crucial for networking professionals.

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