Encapsulation

• A. Encrypting data for secure transmission.
• B. Removing a header or trailer from a lower OSI layer.
• C. Wrapping data with headers as it travels down the OSI layer
• D. Splitting data into multiple frames at the transport layer.

Answer: (C)

Encapsulation is the process of wrapping data with headers (and sometimes trailers) as it moves downward through the OSI layers. At each step, the layer below adds its own header (and sometimes trailer), turning the upper-layer data into a new protocol data unit that the next layer can use for delivery. For example, after the application or upper-layer data is passed down, the transport layer adds a header with port numbers and sequencing information, the network layer adds an IP header with addressing, and the data link layer adds a frame header/trailer with MAC addresses and error checking. This continual wrapping creates a properly formatted unit for transmission over the network.

That description best captures encapsulation. Encrypting data is a security technique and not the same as encapsulation. Removing headers is decapsulation, not encapsulation. Splitting data into multiple frames at the transport layer describes fragmentation/segmentation, not the wrapping process.