Which layer is primarily associated with reliable data transfer and may involve retransmission of lost segments?

Which layer is primarily associated with reliable data transfer and may involve retransmission of lost segments?

• A. Network Layer
• B. Transport Layer
• C. Data Link Layer
• D. Physical Layer

Answer: (B)

Reliability and retransmission over an end-to-end path come from the Transport Layer. This layer is responsible for delivering data between processes on different hosts with mechanisms to ensure it arrives correctly, in order, and without gaps. In TCP, data is divided into segments, each segment is acknowledged by the receiver, and if an acknowledgment isn’t received or a segment is lost, the sender retransmits it. This end-to-end reliability is what the Transport Layer is designed to provide, across potentially many networks and hops. The Network Layer handles moving packets from source to destination and routing, but it doesn’t guarantee end-to-end reliability. The Data Link Layer can detect errors and may retry within a single link, but its scope is limited to that local link and it doesn’t manage reliability across an entire path. The Physical Layer is just about sending raw bits with no reliability guarantees.

Reliability and retransmission over an end-to-end path come from the Transport Layer. This layer is responsible for delivering data between processes on different hosts with mechanisms to ensure it arrives correctly, in order, and without gaps. In TCP, data is divided into segments, each segment is acknowledged by the receiver, and if an acknowledgment isn’t received or a segment is lost, the sender retransmits it. This end-to-end reliability is what the Transport Layer is designed to provide, across potentially many networks and hops.

The Network Layer handles moving packets from source to destination and routing, but it doesn’t guarantee end-to-end reliability. The Data Link Layer can detect errors and may retry within a single link, but its scope is limited to that local link and it doesn’t manage reliability across an entire path. The Physical Layer is just about sending raw bits with no reliability guarantees.