What does encapsulation at the Transport Layer involve?

What does encapsulation at the Transport Layer involve?

• A. Removing headers
• B. Adding a header including source and destination port numbers
• C. Encrypting payload
• D. Discarding duplicate packets

Answer: (B)

The transport layer encapsulation is about wrapping the application data with a transport header that carries addressing and control information, most importantly the source and destination port numbers. Those port numbers identify the specific processes on both ends, allowing multiple parallel conversations to share one IP address without confusion. The transport header (TCP or UDP) sits on top of the data from the session/application layers and is passed down to the network layer as a single unit—the segment or datagram. This port-based addressing enables multiplexing and correct delivery to the target application. Removing headers would be decapsulation, not encapsulation. Encrypting the payload is a security operation that can occur inside or above the transport layer (e.g., TLS), not the transport-layer encapsulation itself. Discarding duplicate packets relates to reliability mechanisms, not the act of adding the transport header during encapsulation.

The transport layer encapsulation is about wrapping the application data with a transport header that carries addressing and control information, most importantly the source and destination port numbers. Those port numbers identify the specific processes on both ends, allowing multiple parallel conversations to share one IP address without confusion. The transport header (TCP or UDP) sits on top of the data from the session/application layers and is passed down to the network layer as a single unit—the segment or datagram. This port-based addressing enables multiplexing and correct delivery to the target application.

Removing headers would be decapsulation, not encapsulation. Encrypting the payload is a security operation that can occur inside or above the transport layer (e.g., TLS), not the transport-layer encapsulation itself. Discarding duplicate packets relates to reliability mechanisms, not the act of adding the transport header during encapsulation.