Which of the following layers of the TCP/IP model serves as the backbone for data...

In the TCP/IP model, theTransport layeris responsible forend-to-end communication between peer entitieson the source and destination systems. “Peer entities” here refers to the corresponding transport components (and the applications that use them) on two different hosts communicating across a network. This layer forms the practical “backbone” of host-to-host data flow because it provides the mechanisms that allow data to be deliveredfrom one endpoint process to another endpoint processreliably or efficiently, depending on the protocol used.

The Transport layer includes protocols such asTCPandUDP. TCP supports connection-oriented communication with sequencing, acknowledgments, retransmissions, and flow control—features that are fundamental when reconstructing sessions during network forensic investigations (e.g., rebuilding a file transfer or a web session). UDP provides connectionless delivery used by many services where speed is preferred over guaranteed delivery, which is also significant in investigations of DNS, streaming, or certain malware communications.

By contrast, theInternet layerfocuses on logical addressing and routing (IP), theNetwork access layerhandles local delivery on the physical/link network, and theApplication layerprovides user-facing protocols. Therefore, the layer enabling peer communication between endpoints is theTransport layer (C).