Which layer of the TCP/IP Protocol Stack Is responsible for port numbers?

The Network layer is responsible for logical addressing via IP addresses and routing decisions, not port numbers.

The Transport layer is responsible for port numbers, which are used by protocols such as TCP and UDP to direct data to the correct application process on a host. Port numbers enable multiplexing - allowing multiple applications to share a single IP address by distinguishing their individual traffic streams.

The Internet layer in the TCP/IP model handles IP addressing and packet forwarding, not port-based multiplexing.

The Application layer defines protocols such as HTTP and DNS that use port numbers, but it does not define or manage the port numbering mechanism itself.