Chapter 2

NMS ISDN Programming Model

This chapter: Provides an overview of Natural Access services. Summarizes typical NMS ISDN application initialization steps. Explains NMS ISDN event handling.

An NMS ISDN for Natural Call Control application is built primarily on the Natural Access platform. This section provides background information about Natural Access and summarizes the main elements of the Natural Access environment. You must have Natural Access installed on your system to build applications using NMS ISDN.
For more detailed information about Natural Access, see the Natural Access Developer's Reference Manual.

Natural Access telephony functions are subdivided into groups of logically related functions, called services. Each service has a standard API.
A context organizes services and accompanying resources around a single processing context. A context usually represents an application instance controlling a single telephone call. A service may only be opened once on a context.
An event queue is the communication path from a service to an application. A service generates events indicating certain conditions or state changes. An application retrieves the events from the event queue.

In this phase...	The application...
Initialize Natural Access	· Makes switch connections to route D channel data to the HDLC controller, and to route B channel information to DSP resources (if necessary). · Initializes Natural Access services, and creates one context for each B channel. The application also creates a dummy context for each D channel.
Initialize NMS ISDN Protocol Stack	· Invokes isdnStartProtocol to start up an ISDN protocol stack instance on each dummy context.
Initialize TCP	· Uses nccStartProtocol or adiStartProtocol to start a Trunk Control Program (TCP) on each B channel context, loading country specific parameters if necessary.
Establish Call	· Uses NCC or ADI service call control functions to place outgoing calls and/or receive incoming calls.
Perform Tasks	· Uses functions from Natural Access, Natural Media, or other APIs to play or record voice, generate or detect DTMF tones, send and receive faxes, and other tasks.
Disconnect Call	· Uses NCC or ADI service call control functions to disconnect and release the call. The application then establishes another call, or:
Stop Protocol Stack	· Invokes isdnStopProtocol to stop the ISDN protocol stack.

Before you can run an NMS ISDN application, you must initialize and load DSP files, Trunk Control Programs (TCPs) and protocol stack runfiles to your board(s). The items to load to the boards are specified in a configuration file.
To load the components to your boards, run oamsys, the board initialization and monitoring utility. (For versions prior to Natural Access 4.0, use agmon.) This utility reads the configuration file and sets up your boards as described in the configuration file. To learn how to create configuration files, see the NMS ISDN Installation Manual. To learn how to use oamsys, see the NMS OAM System User's Manual.

All events from...	Are prefixed with...
NMS ISDN	ISDNEVN_ (for example, ISDNEVN_SOMETHING_HAPPENED)
NCC service	NCCEVN_
ADI service	ADIEVN_
Natural Access	CTAEVN_

Service	Structure containing eventmask parameter	Documented in
NCC	NCC_START_PARMS	Natural Call Control Service Developer's Reference Manual
ADI	ADI_CALLCTL_PARMS	ADI Service Developer's Manual

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