Questions and Answers
What is the primary responsibility of the link layer?
Which technique is NOT commonly used for error detection in the link layer?
In the context of local area networks (LANs), what does a MAC address represent?
What is the main difference between half-duplex and full-duplex communication?
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What does link virtualization in networking primarily involve?
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Which of the following best describes datagram transfer in the link layer?
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Which of the following protocols is commonly associated with local area networks (LANs)?
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What is the primary purpose of the Address Resolution Protocol (ARP)?
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Which of the following best describes the function of error checking in data transmission?
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Which type of MAC addressing is used for local addressing within a LAN?
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What error detection method uses bits added to the data to verify accuracy?
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What does CSMA/CD stand for in the context of Ethernet networking?
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Which of the following is NOT a characteristic of Ethernet?
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What is the significance of the 48-bit MAC address?
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What type of network topology did Ethernet evolve from?
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Study Notes
Link Layer and LANs: Goals
- Key principles include error detection/correction, sharing broadcast channels, link layer addressing, and local area networks (LANs) such as Ethernet and VLANs.
- Focus on instantiation and implementation of various link layer technologies.
Link Layer: Roadmap
- Introduces concepts of error detection and correction, multiple access protocols, and LANs.
- Covers addressing methods like ARP, Ethernet mechanisms, switches, and VLANs.
- Discusses link virtualization through MPLS and data center networking.
- Explains the lifecycle of a web request.
Link Layer: Introduction
- Terminology includes nodes (hosts and routers) and links connecting adjacent nodes.
- Responsibilities include transferring datagrams over a link; includes wired, wireless, and LAN examples.
- Encapsulation leads to the formation of layer-2 packets, called frames.
Link Layer: Context
- Datagram transfer varies by link protocols (e.g., WiFi and Ethernet) which provide differing services like reliable data transfer.
- Uses a transportation analogy, comparing a datagram to a tourist navigating through various transport modes.
Link Layer: Services
- Framing includes creating frames for link access, with distinct reliability from end-to-end delivery.
- Ensures reliable delivery by encapsulating data, adding headers/trailers, and employing MAC addresses for identification.
- Flow control manages pacing between nodes to ensure smooth communication.
- Error detection/correction employs techniques such as parity checking and CRC to maintain data integrity.
- Distinguishes between half-duplex and full-duplex communication modes.
Where is the Link Layer Implemented?
- Implemented in each host via a Network Interface Card (NIC), combining hardware, software, and firmware elements.
Interfaces Communicating
- On the sending side, the datagram is encapsulated into a frame.
- The receiving side performs error checking, ensures reliable transfer, and manages flow control.
Error Detection
- Methods include Error Detection and Correction (EDC) bits, parity checking (single-bit and two-dimensional), Internet checksum, and cyclic redundancy check (CRC) which provides reliable error checking through specific calculations.
Multiple Access Links and Protocols
- Types of links include point-to-point and broadcast (shared medium).
- Includes protocols for channel partitioning, random access, and rotational access.
MAC Addresses
- MAC addresses serve local addressing in LANs (48-bit), while IP addresses function at the network layer (32-bit).
- Mac addresses are administered by IEEE, similar to social security numbers and postal addresses.
ARP: Address Resolution Protocol
- ARP maps IP addresses to MAC addresses, involving an ARP request and response for addressing resolution.
Routing to Another Subnet: Addressing
- Involves creating and sending IP datagrams, followed by frame encapsulation and transmission, managed at routers and ultimately reaching the destination.
Ethernet
- Ethernet is the predominant wired LAN technology, transitioning from bus to switched topology.
- Frame structure includes a preamble, addresses, type, data, and CRC.
- Characteristics depict Ethernet as unreliable and connectionless, utilizing CSMA/CD with binary backoff for MAC protocol.
- Features various speed standards and physical media options like copper and fiber.
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Description
Test your understanding of the principles and technologies of the link layer, including error detection, network addressing, and local area networks like Ethernet and VLANs. This quiz will cover essential topics and concepts related to sharing a broadcast channel and implementing various link layer technologies.
