Which TCP/IP layer is responsible for path determination and end-to-end forwarding of datagrams?

The Internet protocol layer is responsible for path determination and end-to-end forwarding of datagrams in the TCP/IP model. This layer encompasses the Internet Protocol (IP), which primarily facilitates the routing of packets across various networks to ensure that they reach their intended destination. It handles addressing and provides mechanisms for routing data packets through potentially complex inter-network paths. By making decisions about which paths data should take and directing packets accordingly, the Internet protocol layer plays a critical role in facilitating communication across diverse networks.

The application services layer, while crucial for enabling user applications to communicate over the network, does not deal with the specifics of how data is delivered between hosts. The transport layer ensures end-to-end communication and proper data flow and error handling but does not handle routing between networks. The network interface layer focuses on the physical transmission of data over a specific medium, rather than on the logical routing and forwarding of datagrams. Thus, the Internet protocol layer stands out as the core layer dedicated to path determination and end-to-end packet forwarding.