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Difficulty: MediumOSI Model Layers and Functions

During a network performance audit of a bulk file transfer, an engineer observes that the host systems are negotiating window sizes to manage transmission speed and assigning sequence numbers to reassemble out-of-order data segments. Which layer of the OSI model is responsible for performing these flow control, segmentation, and error-recovery functions?

  1. Transport LayerAnswer
  2. B
    Network Layer
  3. C
    Data Link Layer
  4. D
    Session Layer

Answer

The Transport Layer is responsible for flow control, segmentation, sequence numbering, and end-to-end error recovery.
The Transport Layer (Layer 4) provides transparent transfer of data between end systems. It breaks upper-layer data into manageable segments, assigns sequence numbers to reassemble segments in order, and implements windowing mechanisms to regulate flow control.

Step-by-Step Solution

1
Identify the operational features described in the scenario
The scenario highlights window size negotiation (flow control) and sequence number assignment for data segment reassembly.
These functions ensure reliable and controlled data delivery across end-to-end host connections.
2
Map these functions to the correct OSI layer model level
The Transport Layer (Layer 4) is specifically designated to perform end-to-end segmentation, sequence tracking, and flow control.
Lower layers handle logical routing and physical framing, while higher layers govern session synchronization and data syntax formatting.

Key Concept

OSI Transport Layer Functions (Segmentation, Flow Control, and Sequence Tracking)
Estimated Time:1m 0s
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Topics

OSI Model Layers and Functions

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