Which of the following is NOT a function of the transport layer?

The transport layer is responsible for providing end-to-end communication services for applications. Its primary functions include ensuring data delivery, which involves error recovery and acknowledgment of received packets; flow control, which manages the rate of data transmission to prevent overwhelming the network; and segmentation of data, which breaks down larger messages into smaller packets suitable for transmission.

Routing data between networks, however, is a function of the network layer rather than the transport layer. The network layer is tasked with determining the optimal path for data to travel through the network and is concerned with logical addressing and forwarding packets to their appropriate destination across multiple interconnected networks. Therefore, identifying routing data as a function of the transport layer is incorrect, making it the right answer to the question.