Which OSI Layer Ensures Reliable Delivery Without Duplication?
Which of the following OSI model layers will ensure messages are transmitted to their destinations and no data is duplicated?
Community Votes
100% of anonymous learners picked answer D. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
Tests precise knowledge of OSI layer responsibilities, specifically how the Transport layer uses sequence numbers and ACKs to eliminate duplicates, contrasting with the Network layer's connectionless best-effort model.
The Transport layer guarantees reliable end-to-end delivery while preventing data duplication through sequence numbering and acknowledgments. Community consensus strongly confirms that TCP mechanisms at this layer are solely responsible for message integrity and order across networks.
Candidates frequently select the Session layer, mistakenly equating session synchronization and checkpointing with transport-level reliability and packet duplication prevention.
Community Discussion (6 comments)
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Expert Analysis
Why the Answer Is Correct
The Transport layer (Layer 4) is explicitly designed for end-to-end communication reliability. Protocols like TCP implement segmentation, sequence numbering, acknowledgments (ACKs), and retransmission timers to ensure data arrives intact, in order, and without duplication. Flow and congestion control mechanisms further stabilize transmission across varying network conditions.Why the Other Options Are Wrong
The Data Link layer handles frame delivery between directly connected nodes using MAC addresses and basic CRC error detection, but lacks end-to-end reliability. The Network layer manages logical addressing and routing but operates on a connectionless, best-effort basis with no built-in duplication prevention. The Session layer establishes, manages, and terminates connections between applications, focusing on dialogue control rather than packet integrity.Community Comment Notes
Users consistently validate the Transport layer answer, citing its role in error control, flow control, and duplication tracking [1]. Multiple commenters reinforce that sequence-based delivery and retransmission logic are hallmark Transport layer functions [2, 3]. The discussion aligns perfectly with official exam objectives emphasizing Layer 4 reliability mechanisms over lower-layer framing or upper-layer session management.Official Reference
Exam Strategy
When encountering questions about reliability, ordering, or duplication prevention, immediately map those keywords to the Transport layer. Memorize that Layer 3 routes packets but does not guarantee delivery, while Layer 4 ensures the application receives exactly what was sent without repeats or gaps.