Encapsulation (networking)
In computer networking, encapsulation is to include data from an upper layer protocol into a lower layer protocol. This is a method of abstraction for networking by allowing different layers to add features/functionality. For example (see image), the internet is based upon the Internet Protocol (IP — specifically IPv4) and most applications use either the User Datagram Protocol (UDP) or Transmission Control Protocol (TCP). Thus, a chunk of user data is encapsulated in a UDP datagram which is then encapsulated in an IP packet which is then sent over a data link layer protocol (e.g., Ethernet). The data link layer is responsible for physical transmission of the data; IP adds addressing of individual computers; UDP adds "application addressing" (i.e., the port specifies the service like a web or TFTP server).
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