By extension the value of the network services are determined by the users' applications, so it is in the provider's interest to find and promote applications for a network service. We're using the concept of layers to delineate various aspects of networks. Telecommunication Modes and Media Academics and techies have very different ways of talking about how we communicate. Once again we're going to simplify. Telephony is real time, interactive audio.
Television is real time one-way audio and video.
E-mail is asynchronous, interactive text. A network service is defined by the mode of communication it supports, and the mode of communication in turn determines how the service might be applied. Digital media handles information that has been reduced to a stream of bits. It can be processed and stored using a computer, analog media cannot. Computers can work with and respond to digital text because it consists of machine-readable symbols .