Data Link Layer Quiz

Overview of the Data-Link Layer

• Second layer in the OSI model, ensures reliable communication on the same network.
• Organizes data into frames, manages MAC addressing, checks for errors, and controls data flow.
• Sits between the Physical Layer (raw bit transmission) and the Network Layer (data routing).

Functions of the Data-Link Layer

• Framing: Structures raw bits into frames with added headers and trailers for network transmission.
• Addressing: Uses unique MAC addresses for identifying source and destination devices, with each NIC having a manufacturer-assigned MAC address.
• Error Detection and Correction: Employs techniques like cyclic redundancy checks (CRC) to detect errors; frames can be corrected or retransmitted upon error detection.
• Flow Control: Regulates data transmission rate to prevent sender from overwhelming the receiver, helping avoid data loss.
• Media Access Control: Manages shared access to the transmission medium using protocols like CSMA/CD for wired and CSMA/CA for wireless networks.
• Physical Addressing: Assigns physical addresses to devices for correct frame delivery within the same network segment.
• Error Reporting: Reports unacknowledged frame errors to higher layers for corrective measures.

Sublayers of the Data-Link Layer

• Logical Link Control (LLC):

  • Provides interface between the Network Layer and MAC sublayer.
  • Manages error control, flow control, frame synchronization, and sequence numbers for data order.

• Media Access Control (MAC):

  • Controls device access to physical transmission medium.
  • Handles MAC addressing and manages collision detection/avoidance.

MAC Addressing and Network Topologies

• MAC Addresses: 48-bit identifiers in hexadecimal format (e.g., 00:1A:2B:3C:4D:5E) for local network identification.
• Network Topologies:
  • Bus Topology: All devices share a common line; devices listen before transmitting to prevent collisions.
  • Star Topology: Devices connect to a central hub/switch that manages data transmission.
  • Ring Topology: Devices connected in a circle; data passes from one device to the next until reaching its destination.