Podcast
Questions and Answers
What is the primary function of the Data Link Layer in the OSI model?
What is the primary function of the Data Link Layer in the OSI model?
Which sublayer of the Data Link Layer is defined by IEEE 802.2?
Which sublayer of the Data Link Layer is defined by IEEE 802.2?
Which access method is used in legacy shared networks like hubs?
Which access method is used in legacy shared networks like hubs?
What type of addressing is unique to each NIC and used for local delivery?
What type of addressing is unique to each NIC and used for local delivery?
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Which of the following describes CSMA/CD?
Which of the following describes CSMA/CD?
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Which topology is characterized by one central router connected to multiple branches?
Which topology is characterized by one central router connected to multiple branches?
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Which is NOT a typical data link layer protocol?
Which is NOT a typical data link layer protocol?
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When a frame crosses a router to reach a new network, which addressing is updated?
When a frame crosses a router to reach a new network, which addressing is updated?
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Study Notes
Data Link Layer (Layer 2) Overview
- Layer 2 is responsible for communication between network interface cards (NICs) on the same physical network.
- Encapsulates Layer 3 packets (IP packets) into frames for transmission.
- Frame structure typically includes a header (source/destination Layer 2 addresses), data (Layer 3 packet), and a trailer (error detection, e.g., FCS/CRC).
Sublayers: LLC and MAC
- Logical Link Control (LLC): Defined by IEEE 802.2; communicates with upper-layer protocols (like IP); identifies the Layer 3 protocol within the frame.
- Media Access Control (MAC): Handles data link addressing (source and destination MAC addresses); manages frame delimiting, error detection (FCS), and media access (how devices share the medium).
Media Access Control Methods
- Half-Duplex: One device transmits at a time; used in legacy shared networks (hubs); contention-based access (CSMA/CD or CSMA/CA).
- Full-Duplex: Devices can transmit and receive simultaneously; common in modern switched Ethernet.
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Contention-Based Access (Shared Media):
- CSMA/CD (Ethernet hubs): detects collisions.
- CSMA/CA (Wireless LAN): avoids collisions; uses acknowledgments.
Network Topologies
- Physical Topology: Physical layout (e.g., star, extended star, point-to-point).
- Logical Topology: How data flows through the network (often star or bus logically).
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WAN Topologies:
- Point-to-point: Simplest, direct link.
- Hub-and-spoke: Central router to many branches.
- Mesh: Multiple interconnected routers.
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LAN Topologies:
- Star/Extended Star: Most common for Ethernet.
- Bus and Ring: Legacy.
Layer 2 Addressing (MAC Addresses)
- MAC addresses are unique physical addresses for each NIC or interface; used for local delivery on the same network.
- Frames only contain MAC addresses within the same network segment.
- Routers update MAC addresses when frames cross to new networks.
Data Link Layer Protocols
- Ethernet (IEEE 802.3)
- 802.11 Wireless LAN
- WAN protocols (PPP, HDLC, Frame Relay, etc.) - often replaced by Ethernet in modern WANs.
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Description
Dive into the intricacies of the Data Link Layer, focusing on its role in facilitating communication between network interface cards. This quiz covers encapsulation, frame structures, the LLC and MAC sublayers, and the various media access control methods. Test your understanding of these essential networking concepts.
