ITU-T I.220 PDF

Introduction

This Recommendation provides the dynamic description of basic telecommunication services. The dynamic description for basic telecommunication services using the circuit-mode means of service establishment/disestablishment is provided in § 2. The packet-mode description is for further study.

The dynamic description shows the flow of events, and states within the service, in a time-sequenced format and identifies all possible actions relevant to the service as perceived by end-users.

Although the service is described from the end-user perspective it does not concern details of the human-tomachine interface itself. In addition, the service description considers the network as a single entity. For example, information flows between nodes within the network are not shown.

End-user perceptions of the service are shown in terms of "user/network" interactions. Internal network actions are included whenever they are or can be perceived by an end-user during the operation of the service, and as required by SDL drawing rules.

The terminology and the meaning of the "user/network" interactions are provided in Annex A. The means for developing dynamic descriptions, e.g. the SDL symbols and their usage, is further elaborated in Recommendation I.210.

Note - In the development of the circuit-mode dynamic description, the bearer services (speech, 3.1 kHz audio, unrestricted) and the teleservices (telephony, Teletex, Telefax 4, mixed-mode and Videotex) were considered. Others are for further study.