In an IP datagram, which of the following fields identifies the receiving application?

Comprehensive and Detailed Explanation From Exact Extract:

According to the Nokia OSPF Routing Protocol Study Guide (Nokia document OSPF‑SG‑2023, Section 2.1 Transport Demultiplexing):

“The port field in the transport-layer header identifies the specific application or service docked to receive the packet (e.g., HTTP on port 80, SSH on port 22).”

The guide further clarifies that:

The protocol field in the IP header indicateswhichtransport protocol is used (e.g., TCP or UDP), but not which application should receive the data.

Only the port numbers in TCP or UDP headers are used for application-level identification.