What happens to data as it moves through the OSI model layers?

• A. It is decrypted at each layer
• B. It is encapsulated with headers and processed at each layer
• C. It is transmitted without changes
• D. Each layer only forwards data without modification

Answer: (B)

As data moves through the OSI layers, each layer wraps the data with its own header (and sometimes a trailer) and performs its designated processing. This encapsulation adds control information needed for functions like routing, error detection, sequencing, and port addressing as the data descends from the application toward the physical layer. When the data reaches the destination, the process is reversed: each layer decapsulates by removing its header and passes the remaining data up to the next layer, until the original data is delivered to the application. This behavior—encapsulation at each layer with headers and layered processing—best describes what happens.