Which layer is responsible for end-to-end communication in the telecommunications service model?

The transport layer is indeed responsible for end-to-end communication in the telecommunications service model. This layer ensures that data is transferred reliably and efficiently from the source to the destination across the network.

The primary functions of the transport layer include establishing connections, maintaining the flow of data, implementing error checking and correction, and ensuring that data packets are delivered in sequence, which is crucial for maintaining the integrity of the communication session. Protocols such as TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) operate at this layer to facilitate these tasks.

In contrast, the application layer focuses on the interface and communication processes related to user applications, the network layer handles the routing and forwarding of data packets between devices across various networks, and the data link layer is responsible for node-to-node communication and frames the data for transmission over a physical medium. Each of these layers plays a specific role, but it is the transport layer that specifically manages the responsibility of ensuring that data reaches its destination intact and in the correct order.