CompTIA Network+ (N10-009)Networking ConceptsMedium
A network engineer is troubleshooting an application that uses TCP to guarantee reliable, ordered delivery of data between a client and server. At which layer of the OSI model does TCP operate to provide this reliability?
- ALayer 4 - Transport
- BLayer 3 - Network
- CLayer 2 - Data Link
- DLayer 7 - Application
Show answer & explanationAnswer & explanation
Correct answer: A. Layer 4 - Transport
TCP operates at Layer 4, the Transport layer, where it provides reliable, ordered, and error-checked delivery through mechanisms like sequencing, acknowledgments, and retransmission. UDP also operates here but does not guarantee delivery.
Why the other options are wrong
- B. Layer 3 handles logical addressing and routing using IP addresses.
- C. Layer 2 handles frame addressing and switching using MAC addresses.
- D. Layer 7 Application handles user-facing protocols like HTTP and FTP.
OSI Layer 4 - Transport
The Transport layer manages end-to-end communication, segmentation, flow control, and reliability using protocols like TCP and UDP.
- TCP provides reliable, connection-oriented delivery
- UDP provides connectionless, best-effort delivery
- Port numbers operate at this layer to identify applications
Memory trick: 'TCP takes care of packets' — Transport ensures reliable delivery.