Encapsulation is the computer-networking process of concatenating layer-specific headers or

trailers Trailer may refer to: Transportation * Trailer (vehicle), an unpowered vehicle pulled by a powered vehicle ** Baggage trailer, a large flatbed baggage trolley ** Bicycle trailer, a wheeled frame for hitching to a bicycle to tow cargo or passen ...

with a service data unit (i.e. a payload) for transmitting

information Information is an Abstraction, abstract concept that refers to something which has the power Communication, to inform. At the most fundamental level, it pertains to the Interpretation (philosophy), interpretation (perhaps Interpretation (log ...

over computer networks. Deencapsulation (or de-encapsulation) is the reverse computer-networking process for receiving information; it removes from the

protocol data unit In telecommunications, a protocol data unit (PDU) is a single unit of information transmitted among peer entities of a computer network. It is composed of protocol-specific control information and user data. In the layered architectures of c ...

(PDU) a previously concatenated header or trailer that an underlying communications layer transmitted. Encapsulation and deencapsulation allow the design of modular

communication protocols A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any variation of a physical quantity. The protocol defines the rules, syntax, semantics, and synchronization of ...

so to logically separate the function of each communications layer, and abstract the structure of the communicated information over the other communications layers. These two processes are common features of the computer-networking models and protocol suites, like in the

OSI model The Open Systems Interconnection (OSI) model is a reference model developed by the International Organization for Standardization (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems inter ...

and

internet protocol suite The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are ...

. However, encapsulation/deencapsulation processes can also serve as malicious features like in the

tunneling protocol In computer networks, a tunneling protocol is a communication protocol which allows for the movement of data from one network to another. They can, for example, allow private network communications to be sent across a public network (such as the ...

s.Raman, D., Sutter, B. D., Coppens, B., Volckaert, S., Bosschere, K. D., Danhieux, P., & Buggenhout, E. V. (2012, November). DNS tunneling for network penetration. In International Conference on Information Security and Cryptology (pp. 65-77). Springer, Berlin, Heidelberg. The

physical layer In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer: the layer most closely associated with the physical connection between devices. The physical layer provides an electrical, mechani ...

is responsible for physical transmission of the data, link encapsulation allows

local area network A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, campus, or building, and has its network equipment and interconnects locally managed. LANs facilitate the distribution of da ...

ing, IP provides global addressing of individual computers, and TCP selects the process or application (i.e., the TCP or UDP port) that specifies the service such as a

Web Web most often refers to: * Spider web, a silken structure created by the animal * World Wide Web or the Web, an Internet-based hypertext system Web, WEB, or the Web may also refer to: Computing * WEB, a literate programming system created by ...

TFTP The Trivial File Transfer Protocol (TFTP) is a simple Lockstep (computing), lockstep communication protocol for transmitting or receiving files in a client-server application. A primary use of TFTP is in the early stages of nodes booting on a l ...

server. For example, in the IP suite, the contents of a web page are encapsulated with an

HTTP header HTTP header fields are a list of strings sent and received by both the client program and server on every HTTP request and response. These headers are usually invisible to the end-user and are only processed or logged by the server and client ...

, then by a TCP header, an IP header, and, finally, by a frame header and trailer. The frame is forwarded to the destination node as a

stream A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...

bit The bit is the most basic unit of information in computing and digital communication. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represented as ...

s, where it is decapsulated into the respective PDUs and interpreted at each layer by the receiving node. The result of encapsulation is that each lower-layer provides a service to the layer or layers above it, while at the same time each layer communicates with its corresponding layer on the receiving node. These are known as adjacent-layer interaction and same-layer interaction, respectively. In discussions of encapsulation, the more abstract layer is often called the upper-layer protocol while the more specific layer is called the lower-layer protocol. Sometimes, however, the terms upper-layer protocols and lower-layer protocols are used to describe the layers above and below IP.

References

External links

*{{IETF RFC, 1983: Internet Users' Glossary (contains an entry for encapsulation) Computer network technology Network protocols Data transmission Packets (information technology)

See also

References

External links