Which OSI layer adds the source port number to a PDU during encapsulation?

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Multiple Choice

Which OSI layer adds the source port number to a PDU during encapsulation?

Explanation:
Port numbers are added at the Transport layer to identify the sending and receiving processes on each host. As data from the application layer is encapsulated downward, the Transport layer wraps it with a header that includes the source port and destination port. This creates the transport PDU (a segment when using TCP, a datagram when using UDP). The port numbers let multiple conversations share the same network connection by multiplexing different applications, while the actual routing and addressing of the packets is handled by higher layers (IP) and lower layers (MAC addresses, etc.).

Port numbers are added at the Transport layer to identify the sending and receiving processes on each host. As data from the application layer is encapsulated downward, the Transport layer wraps it with a header that includes the source port and destination port. This creates the transport PDU (a segment when using TCP, a datagram when using UDP). The port numbers let multiple conversations share the same network connection by multiplexing different applications, while the actual routing and addressing of the packets is handled by higher layers (IP) and lower layers (MAC addresses, etc.).

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