Which layer within the TCP/IP model delivers packets to their destination across multiple networks?

The Internetwork Layer is responsible for delivering packets across multiple networks in the TCP/IP model. This layer manages the routing of data packets from the source network through various intermediate networks to reach the destination, ensuring that the packets are correctly directed through routers.

In this layer, protocols such as Internet Protocol (IP) are utilized, which provides the necessary addressing and routing functionalities. The layer also handles fragmentation and reassembly of packets to accommodate different transmission sizes across varying network technologies. This capability is essential for enabling communication between devices located in different subnetworks or across wide area networks (WANs).

While other layers have their specific roles—such as the Transport Layer managing end-to-end communication and ensuring data integrity, the Application Layer focusing on user interfaces and application services, and the Network Interface Layer dealing with hardware addressing and the actual transmission of frames over a physical medium—none of them are involved in the inter-network packet delivery across multiple networks like the Internetwork Layer.