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Difficulty: Very hardOSI Model Layers and Functions

A telemetry system monitoring remote power sub-stations transmits Continuous High-Frequency (CHF) data streams over an unstable satellite connection back to a central control node. To prevent corrupted or incomplete transmissions caused by intermittent connectivity drops, the communication protocol inserts periodic synchronization markers (checkpoints) into the active data stream. When the connection breaks, the protocol uses these markers to resume data exchange from the last acknowledged checkpoint rather than re-initiating the entire transaction or re-authenticating the user channel. Which layer of the OSI reference model is directly responsible for providing this dialogue control and session checkpoint restoration capability?

  1. Session Layer (Layer 5)Answer
  2. B
    Transport Layer (Layer 4)
  3. C
    Presentation Layer (Layer 6)
  4. D
    Data Link Layer (Layer 2)

Answer

Session Layer (Layer 5) is responsible for dialogue control and checkpointing.
The correct answer identifies the Session Layer (Layer 5). The primary responsibilities of Layer 5 include establishing, maintaining, and terminating communication sessions between applications, as well as providing dialogue control (managing whose turn it is to transmit) and checkpointing/synchronization markers to enable resumption of data streams following network interruptions.

Step-by-Step Solution

1
Analyze the functional requirements in the scenario.
The scenario highlights dialogue control, insertion of synchronization markers (checkpoints), and session state resumption across connection drops.
Identifying the specific network function isolating the protocol mechanism is required to map it to the correct OSI layer.
2
Map the identified functions to OSI model layer definitions.
Dialogue control (duplex management) and synchronization/checkpointing are explicit, standard responsibilities defined for Layer 5 (Session Layer).
Layer 4 manages TCP/UDP transport segments, Layer 6 manages formatting/encryption, while Layer 5 specifically governs session dialogue boundaries.

Key Concept

OSI Session Layer (Layer 5) Functions & Dialogue Control
Estimated Time:2m 0s
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Topics

OSI Model Layers and Functions

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