Introduction to Data-Link Layer
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Questions and Answers

What is the role of the data-link layer in the TCP/IP protocol suite?

  • It defines protocols for physical layer communication.
  • It provides node-to-node communication and services to the network layer. (correct)
  • It manages the connection between various networks.
  • It exclusively handles routing decisions for data packets.

How does a data unit travel across the Internet according to the data-link layer?

  • It utilizes only wireless networks for transmission.
  • It is processed by the application layer before any travel.
  • It travels directly from source to destination in one step.
  • It must pass through many nodes interconnected by links. (correct)

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

  • It is encapsulated into a frame before being sent. (correct)
  • It is forwarded directly to the final destination.
  • It is split into multiple packets for easier handling.
  • It is only decapsulated before transmission.

What must the data-link layer of each intermediate node do when a data packet is transiting?

<p>Both encapsulate and decapsulate the datagram. (B)</p> Signup and view all the answers

Which statement best describes the relationship between the data-link layer and the physical layer?

<p>The data-link layer receives services from the physical layer. (C)</p> Signup and view all the answers

What type of connections characterize communication at the data-link layer?

<p>Node-to-node connections. (D)</p> Signup and view all the answers

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

<p>To encapsulate the datagram in a frame before transmission. (D)</p> Signup and view all the answers

What is the primary function of links in the context of the data-link layer?

<p>To physically connect nodes in a network. (D)</p> Signup and view all the answers

Which scenario illustrates the need for flow control in data-link layers?

<p>The producer generates frames at a much faster rate than the consumer can process. (C)</p> Signup and view all the answers

What happens when the buffer at the receiving data-link layer becomes full?

<p>It sends a signal to the sender to slow down or stop transmission. (D)</p> Signup and view all the answers

Why might several standard protocols exist in the data-link layer?

<p>To address diverse types of networks and communication needs. (D)</p> Signup and view all the answers

How is error control typically managed in the data-link layer?

<p>By detecting errors and either correcting or retransmitting frames. (C)</p> Signup and view all the answers

What is the significance of transforming frames into bits at the sending node?

<p>It is necessary for the frame to be transmitted over the electromagnetic signals. (A)</p> Signup and view all the answers

What happens if the destination IP address in a datagram is changed?

<p>The packet never reaches its destination. (B)</p> Signup and view all the answers

What is another term used synonymously with link-layer address?

<p>MAC address (B)</p> Signup and view all the answers

What strategy is NOT typically used for flow control in data-link layers?

<p>Using an unlimited buffer for all incoming frames. (B)</p> Signup and view all the answers

Which of the following is true regarding framing in data-link layers?

<p>Frames may contain both a header and a trailer. (C)</p> Signup and view all the answers

How do link-layer addresses change as a frame moves from one link to another?

<p>They are changed every time the frame transitions between links. (C)</p> Signup and view all the answers

Why is error detection and correction significant in the data-link layer?

<p>It helps ensure the integrity of frames during transmission. (D)</p> Signup and view all the answers

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

<p>Unicast address (B)</p> Signup and view all the answers

Which type of address allows for communication to all entities in a link?

<p>Broadcast address (B)</p> Signup and view all the answers

What protocol helps a node obtain the link-layer address associated with an IP address?

<p>Address Resolution Protocol (ARP) (C)</p> Signup and view all the answers

What type of address facilitates one-to-many communication within a local link?

<p>Multicast address (A)</p> Signup and view all the answers

What is the role of the last router in the forwarding path of a datagram?

<p>It knows the IP address of the destination host. (C)</p> Signup and view all the answers

What is typically considered an issue in the network layer or the transport layer instead of the data-link layer?

<p>Congestion control (B)</p> Signup and view all the answers

In a point-to-point link, how is the medium utilized?

<p>It is dedicated to two devices. (A)</p> Signup and view all the answers

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

<p>Media access control (MAC) (B)</p> Signup and view all the answers

What types of links can data-link layers control?

<p>Both point-to-point and broadcast links (B)</p> Signup and view all the answers

Why can a datagram in the Internet not reach its destination using only IP addresses?

<p>Each datagram may take a different path. (A)</p> Signup and view all the answers

What is a characteristic of a broadcast link?

<p>It allows multiple pairs of devices to communicate simultaneously. (C)</p> Signup and view all the answers

What does the data link control (DLC) sublayer manage?

<p>All issues common to both point-to-point and broadcast links (D)</p> Signup and view all the answers

In the context of frames and link-layer protocols, what is a common outcome of congestion?

<p>Frame loss (A)</p> Signup and view all the answers

What is the primary purpose of the Address Resolution Protocol (ARP)?

<p>To map an IP address to a link-layer address (D)</p> Signup and view all the answers

What occurs when a host sends an ARP request packet?

<p>The query is broadcasted over the link using a broadcast address (D)</p> Signup and view all the answers

Which layer of the network model does the Address Resolution Protocol belong to?

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

When Alice needs to send data to Bob, what information must she already have?

<p>Bob's network-layer (IP) address (D)</p> Signup and view all the answers

What type of address does ARP return when it resolves an IP address?

<p>Link-layer address (D)</p> Signup and view all the answers

Which of the following best describes a node in the context of the Internet?

<p>A device that connects to a network, such as a host or router (C)</p> Signup and view all the answers

What type of addresses does ARP use in its request packet?

<p>Both link-layer and IP addresses of sender, and IP address of receiver (C)</p> Signup and view all the answers

What happens to packets in the Internet as they traverse its architecture?

<p>They travel through a set of nodes and links (B)</p> Signup and view all the answers

Why is it important not to change an end-to-end address from the source to the destination?

<p>It ensures data integrity throughout the transmission. (B)</p> Signup and view all the answers

How many IP addresses and link-layer addresses should a router possess when connected to five links?

<p>Five IP addresses and five link-layer addresses. (D)</p> Signup and view all the answers

In a private small internet configured in a mesh topology, are routers necessary?

<p>No, because all hosts connect directly. (B)</p> Signup and view all the answers

Why may a router be needed in a specific communication scenario?

<p>To enable communication between different network segments. (C)</p> Signup and view all the answers

What type of switching does the current Internet use at the data-link layer?

<p>Packet-switching exclusively. (D)</p> Signup and view all the answers

What happens if system B does not run the ARP program?

<p>System A will fail to deliver packets to system B. (C)</p> Signup and view all the answers

What should system A do before broadcasting an ARP request to map from N2 to L2?

<p>Always check its cache for existing mappings. (D)</p> Signup and view all the answers

What is the difference between a forwarding table and ARP in terms of mapping?

<p>A forwarding table maps IP addresses to link-layer addresses, while ARP maps link-layer addresses to IP addresses. (A)</p> Signup and view all the answers

Flashcards

Framing in Data-Link Layer

The process of adding a header and sometimes a trailer to a data packet to create a frame, preparing it for transmission across a physical link.

Flow Control in Data-Link Layer

A mechanism to prevent the receiving data-link layer from being overwhelmed by an excessive rate of frames from the sending data-link layer.

Error Control in Data-Link Layer

The process of detecting and correcting errors that might occur during transmission of frames across a physical link.

Router

A device that connects different networks, forwarding data packets between them.

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LAN (Local Area Network)

A network that connects devices within a limited geographical area, typically a building or campus.

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WAN (Wide Area Network)

A network that covers a larger geographical area, often connecting different cities or countries.

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Encapsulation

The process of adding a header to a network layer datagram, creating a data-link layer frame.

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Decapsulation

The process of removing the data-link layer header (frame) from a datagram, revealing the original network layer packet.

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Data-Link Layer

The layer responsible for transmitting data packets between nodes in a network.

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Frame

The data unit used at the data-link layer, encapsulating the network layer datagram.

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Datagram

The data unit used at the network layer, containing a payload of data and network headers.

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Point-to-Point Link

A communication link dedicated exclusively to two devices, ensuring direct communication without sharing bandwidth.

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Broadcast Link

A communication link shared by multiple pairs of devices, where data transmission occurs in a broadcast manner.

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Data Link Control (DLC)

A sublayer of the data-link layer responsible for managing data transmission over both point-to-point and broadcast links.

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Media Access Control (MAC)

A sublayer of the data-link layer that handles communication specifically on broadcast links.

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Link-Layer Address

A unique identifier assigned to each device at the data-link layer, allowing for communication within a network segment.

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IP Address

A network layer address that identifies a specific device on the internet, used for routing data across the network.

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Congestion Control

The process of preventing a network from becoming overwhelmed by excessive data transmission, often implemented at the network or transport layer.

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Unicast

A one-to-one communication method where data is sent from a single source to a single destination.

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Multicast

A one-to-many communication method where data is sent from a single source to multiple destinations simultaneously.

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Broadcast

A one-to-all communication method where data is sent from a single source to every device on the network.

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ARP (Address Resolution Protocol)

A protocol used by devices on a network to find the corresponding link-layer address (MAC address) for a known IP address.

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Decapsulation in Data-Link Layer

The process of removing the data-link layer header (frame) from a datagram, revealing the original network layer packet.

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Address Resolution Protocol (ARP)

A protocol within the network layer that translates a network layer (IP) address to a link-layer address, enabling devices to communicate at the data-link layer.

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Link-layer address (MAC address)

A unique address assigned to each network interface card (NIC) that identifies a device on a local network, allowing for communication between devices.

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Nodes

Devices or hosts connected to a network. These can be computers, routers, switches, or other network devices.

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Links

A physical connection between two or more nodes in a network, allowing data to be transmitted between them.

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Flow Control

A mechanism that regulates the flow of data between nodes to prevent the receiver from being overwhelmed.

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Why does a router have multiple interfaces?

A router typically has multiple interfaces to connect to different networks. This allows it to forward data packets between these networks efficiently.

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Why shouldn't an end-to-end address be changed?

Changing an end-to-end address during data transmission can cause confusion and disrupt the delivery process. Each packet needs to know its final destination throughout its journey.

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How many addresses does a router need for five links?

A router connected to five links should have five link-layer addresses (one for each link) and at least two IP addresses (one for each network it connects).

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Do we need routers in a mesh topology?

A mesh topology means each host is directly connected to every other host. In this case, routers aren't strictly necessary, as hosts can communicate directly. However, routers can still improve efficiency and scalability.

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Why do we not need a router in a mesh topology?

In a mesh topology, direct communication between hosts is possible, eliminating the need for routers. Routers are typically used to connect different networks, not directly connected hosts.

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Circuit-switching or packet-switching in the Internet?

The Internet uses packet-switching at the data-link layer. Data is divided into packets, which are individually routed and then reassembled at the destination. This makes it more efficient than circuit-switching, where a dedicated connection is established before data transmission.

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What are the end-to-end addresses?

End-to-end addresses in this scenario are Los Angeles Airport and Chicago Airport. These represent the source and destination points for the journey.

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What are the link-layer addresses?

Link-layer addresses in this scenario would be the unique identifiers for each device Alice uses to travel, such as her boarding pass for the flight.

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Study Notes

  • TCP/IP does not define protocols in the data-link or physical layer. These layers support the upper three TCP/IP layers.
  • The data-link layer is covered over several chapters. This chapter provides a general overview of the concept of links and nodes, the services provided, and point-to-point and broadcast links.
  • Data-link layer addressing is explained, covering the rationale, three types of link layer addresses, and Address Resolution Protocol (ARP), connecting network layer addresses to data-link layer addresses for packet delivery through the Internet.

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Related Documents

Chapter 9: Introduction to Data-Link Layer PDF

Description

This quiz covers the essential concepts of the data-link layer in the TCP/IP model. It explores link addressing, types of link layer addresses, and the role of Address Resolution Protocol (ARP) in mapping network layer addresses to data-link layer addresses. Understand the fundamental principles that support the upper layers of TCP/IP architecture.

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