Which device forwards data and operates at layer three of the Transmission Control Protocol/Internet Protocol (TCP/IP) model?

The device that forwards data and operates at layer three of the Transmission Control Protocol/Internet Protocol (TCP/IP) model is a router.

Explanation:

1. Layer Three of the TCP/IP Model: In the TCP/IP model, layer three corresponds to the Internet layer, which is responsible for routing packets of data from the source to the destination across network boundaries.

2. Function of a Router: A router operates at this layer by examining the destination IP address of incoming packets and determining the best path for these packets based on its routing table. It plays a crucial role in data forwarding between different networks, ensuring that data can traverse disparate network segments effectively.

3. Routing Protocols: Routers utilize various protocols (like RIP, OSPF, and BGP) to share information about network statuses and help figure out the optimal route for data transmission.

4. Conclusion: By making intelligent forwarding decisions and providing connectivity between multiple networks, routers facilitate efficient communication in complex network topologies.