Recommendation I.220 - Common dynamic description of basic

telecommunication services

1.	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/dis-establishment is provided in section 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-to-machine 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(s) 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.

2.	Circuit-mode dynamic description of basic bearer and teleservices

(BASIC CALL PROCESS)

(BASIC CALL PROCESS

Macro definition outgoing call)

Note 1 - This is an event which may occur at the S/T reference interface and can be reflected at the user interface.

(BASIC CALL PROCESS

MACRO DEFINITION INCOMING CALL)

Note 2 - This is an event which may occur at the S/T reference interface but is not reflected at the user interface.

ANNEX A

(to Recommendation I.220)

Terminology for "user/network" interactions

SETUP	Interaction across the "user/network" interface regarding a service request.

REPORT	Interaction across the "user/network" interface regarding alerting of the users terminal function, interworking with a non-ISDN network, or routing progress.

CONNECT	Interaction across the "user/network" interface regarding completion of circuit cut-through.

DISCONNECT Interaction across the "user/network" interface

regarding a user who has disconnected or user A cannot be connected (e.g. Busy) to user B.

RELEASE	Interaction across the "user/network" interface regarding freeing of resources associated with the call/connection, such as call references and channels.

NDUB	Network determined user busy.

UDUB	User determined user busy.