telecommunication Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...

, a ''n''-entity is an active element in the ''n''-th layer of the Open Systems Interconnection--Reference Model (OSI-RM) that (a) interacts directly with elements, ''i.e.'', entities, of the layer immediately above or below the ''n''-th layer, (b) is defined by a unique set of rules, ''i.e.'',

syntax In linguistics, syntax () is the study of how words and morphemes combine to form larger units such as phrases and sentences. Central concerns of syntax include word order, grammatical relations, hierarchical sentence structure ( constituency) ...

, and

information Information is an abstract concept that refers to that which has the power to inform. At the most fundamental level information pertains to the interpretation of that which may be sensed. Any natural process that is not completely random ...

formats, including

data In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted ...

and control formats, and (c) performs a defined set of functions. The ''n'' refers to any one of the 7 layers of the OSI-RM. In an existing layered open system, the ''n'' may refer to any given layer in the system. Layers are conventionally numbered from the lowest, ''i.e.'', 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. This layer may be implemented by a PHY chip. The ...

, to the highest, so that the -th layer is above the ''n''-th layer and the -th layer is below.

References

{{FS1037C Network architecture OSI protocols Reference models