connections and reliability of data transfer to the application layer, which is concerned with providing a particular functionality using the network and with the interface to the user.2

Both technology (equipment and software) suppliers and service providers tend to specialize in one or two of these layers, each of which seeks to serve all applications and all media. As a consequence, creating a new application may require the participation and cooperation of a set of complementary layered capabilities. This structure results in a horizontal industry structure, quite distinct from the vertically integrated industry structure of the Bell System era.

All these changes suggest a new definition of telecommunications: Telecommunications is the suite of technologies, devices, equipment, facilities, networks, and applications that support communication at a distance.

The range of telecommunications applications is broad and includes telephony and video conferencing, facsimile, broadcast and interactive television, instant messaging, e-mail, distributed collaboration, a host of Web- and Internet-based communication, and data transmission.3 Of course many if not most software applications communicate across the network in some fashion, even if it is for almost incidental purposes such as connecting to a license server or downloading updates. Deciding what is and is not telecommunications is always a judgment call. Applications of information technology range from those involving almost no communication at all (word processing) to simple voice communications (telephony in its purest and simplest form), with many gradations in between.

As supported by the horizontally homogeneous layered infrastructure, applications of various sorts increasingly incorporate telecommunications as only one capability among many. For example telephony, as it evolves into the Internet world, is beginning to offer a host of new data-based features and integrates other elements of collaboration (e.g., visual material or tools for collaborative authoring). Another important trend is machine-to-machine communication at a distance, and so it cannot be assumed that telecommunications applications exclusively involve people.


Like telecommunications itself, the telecommunications industry is broader than it was in the past. It encompasses multiple service providers, including telephone companies, cable system operators, Internet service providers, wireless carriers, and satellite operators. The industry today includes software-based applications with a communications emphasis and intermediate layers of software incorporated into end-to-end communication services. It also includes suppliers of telecommunications equipment and software products sold directly to consumers and also to service providers, as well as the telecommunications service providers


The descriptions of layers were adapted from the Open Systems Interconnect Reference Model (ISO 7498-1), which provides a useful tool for conceptualizing network layers—see <>.


The term “telecommunications” takes on a particular significance with respect to the Telecommunications Act of 1996 and implementing regulations. The broad definition adopted here is intended solely to capture the scope of relevant research, not to make any statement about what technologies and services should or should not be considered telecommunications for regulatory purposes.

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