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Chapter 1

Introduction

1.1 Introduction
1.2 About ISDN
1.2.1 About ISDN Protocols and Protocol Layering
1.2.2 About ISDN Carriers
1.3 About the AG ISDN Software
1.3.1 AG ISDN Product Configurations
1.3.2 About the AG ISDN NCC Configuration
1.4 About AG ISDN Software Components
1.4.1 About the readme File
1.4.2 About the AG ISDN Function Libraries
1.4.3 About the Header Files
1.4.4 About ISDN Protocol Stack Downloadable Object Modules
1.4.5 About the AG Configuration File
1.4.6 About the Demonstration Programs
1.4.7 About the Trunk Control Program (TCP)
1.4.8 About Parameter Files
1.5 Other Components
1.5.1 About AG Quad Boards
1.5.2 About AG-T1 and AG-E1 Boards
1.5.3 About CT Access
1.5.4 agmon and the AG Configuration File
1.5.5 About DSP files
1.6 Developing an AG ISDN Application

1.1 Introduction

The AG ISDN product allows you to create powerful applications that interact with ISDN services in a variety of ways, using the NMS CT Access application programming interfaces (APIs) and one or more AG boards.

This chapter:

1.2 About ISDN

Integrated Services Digital Network (ISDN) is a continually evolving international standard for networking a wide range of services, including voice and non-voice services. The network is completely digital, from one end to the other: voice information is digitized and sent in digital form. Signaling information is sent separately from voice information, using a method called common channel signaling (CCS).

1.2.1 About ISDN Protocols and Protocol Layering

ISDN communications can be described at many levels, from the way bits are transferred from machine to machine to the sets of messages computers pass to one another. A scheme for communication at a certain level is called a protocol.

In the late 1970's, the International Standards Organization (ISO) established the Open Systems Interconnect (OSI) model for communication. ISDN is based on this model. In OSI, seven separate levels, or layers, of communication are defined. The first three layers, called the chained layers, are the lowest levels. The chained layers are:

Layers higher than these are end-to-end layers. They describe how information is exchanged and delivered end-to-end. They also define process-to-process communication, and describe application-independent user services, user interfaces and applications, etc.

Figure 1. OSI Protocol Layering Model



The functionality provided by a layer includes the services and functions of all of the layers below it. A Service Access Point (SAP) is the point at which a layer provides services to the layer directly above it. With each SAP is associated a unique Service Access Point Identifier (SAPI).






1.2.2	 About ISDN Carriers





ISDN is transmitted over standard T1 and E1 carriers. These are typically four-wire digital transmission links. T1 is used mainly in the United States, Canada, Hong Kong, and Japan. E1 is used throughout most of the rest of the world.



Data on a T1 or E1 trunk is transmitted in channels. Each channel carries information digitized at 64000 bits per second (bps). For primary rate ISDN, T1 carries 24 channels. E1 carries 32 channels.



With primary-rate ISDN, the channels are usually used as follows:




In setups with multiple T1 ISDN trunks, a Non-Facility Associated Signaling (NFAS) configuration is often used.  In this configuration, the D channel on one of the ISDN trunks carries signaling for all channels one several other trunks.  This leaves channel 24 free on each of the other trunks to be used as another B channel.  (See Figure 3.)


 



Figure 3.	 Sample NFAS Configuration




NFAS configurations are not supported on E1 trunks.






1.3	 About the AG ISDN Software





Alliance Generation (AG) ISDN protocol software allows you to write CT Access applications that communicate with T1 or E1 trunks to perform voice processing functions and call control using ISDN Common Channel Signaling protocols.



AG ISDN software is designed to use one or more AG Quad, AG-T1, or AG-E1 boards as the physical interface to trunk lines. In addition to line interfaces, these boards also feature powerful on-board digital signal processing (DSP) resources that can handle much of the call control and voice processing overhead. For more information, see Section 1.5.1, About AG Quad Boards and Section 1.5.2, About AG-T1 and AG-E1 Boards.






1.3.1	 AG ISDN Product Configurations





Using AG ISDN software, you can access ISDN services in three ways:




You specify the configuration to use when initializing the ISDN protocol stack, as described in Chapter 3.






1.3.2	 About the AG ISDN NCC Configuration





AG ISDN allows you to access ISDN call control services using the standard CT Access Natural Call Control API. The AG ISDN product provides access via standard API function calls - the same function calls used with any other trunk protocol (such as CAS or loop start). The AG ISDN Natural Call Control interface is described in this manual.



In this configuration (see Figure 4) the following components run on the board:




In NCC configuration, ISDN protocol stack instances are started and stopped using two functions from the AG ISDN library.  No other functions from this library are used in this configuration.  A daemon program included with the AG ISDN software can start the stack before ISDN applications are launched, and stop the stack after they are shutdown. Chapter 6 documents this daemon program.



B channel information is routed to the DSP resources through the AG board's MVIP switch. The switch has certain default behavior, described in Section 3.3. Alternatively, the switch can be controlled using the CT Access Switching service.


 



Figure 4.	 AG ISDN Application Architecture (Using Natural Call Control)






1.4	 About AG ISDN Software Components





ISDN is implemented differently around the world. For this reason, NMS provides several versions of its AG ISDN software for different regions. The package for a region contains the software modules you need to allow an AG board to communicate on a T1 or E1 trunk in one or more countries in that region.



The ISDN software package for a given region contains the following:




The sections that follow briefly describe each of these components.






1.4.1	 About the readme File





This ASCII text file contains release information that does not appear in other documentation. The file is named readme.isd. Consult this file to learn where the AG ISDN software components are located after installation.






1.4.2	 About the AG ISDN Function Libraries





This component runs on the host PC. It is used by the application program to interact with the ISDN protocol stacks running on the AG board.



The library is supplied as an extension to the ADI library.  It is a dynamic-link library (DLL) under Windows NT, and it is a shared object under UNIX. The library has different names under different operating systems: 





 Operating System



 CT Access Lib Name




 Windows NT



 adiisdn.lib and adiisdn.dll




 UNIX



 libadiisdn.so



















1.4.3	 About the Header Files





Two header files are supplied with AG ISDN software: 





 Filename



 Description




 isdnval.h



 Contains defines for Q.931 messages created by the stack.




 adiisd.h



 Contains TCP parameter structures.



















1.4.4	 About ISDN Protocol Stack Downloadable Object Modules





A downloadable object module file contains the basic low-level software which an AG board requires to support ISDN. The module is transferred from the host into on-board memory using the agmon utility when the AG board boots.



Different module files are supplied for different configurations. The file you use depends upon what AG board type you are using. For more information about the downloadable object modules, see the AG ISDN Installation Manual.






1.4.5	 About the AG Configuration File





The AG configuration file contains information which agmon reads to determine how to set up your boards for use. This file also contains country-specific information, and defines what trunks are assigned to which D-channels.



Several example files are included, describing ISDN configurations for different boards or regions. You can use these files to create a file describing your hardware and software setup. For details, see the AG ISDN Installation Manual and AG Runtime Configuration and Developer's Manual.






1.4.6	 About the Demonstration Programs





Several demonstration programs are included, with their source code files and makefiles. For details, see Chapter 6.






1.4.7	 About the Trunk Control Program (TCP)





One trunk control program (TCP) is included, named isd0.tcp. This TCP is for use with the AG ISDN software in NCC configuration.



The TCP is transferred to on-board memory by agmon. An instance of the TCP is associated with each CTA context. A TCP mediates transactions between CT Access, DSP resources, and the ISDN protocol stack.






1.4.8	 About Parameter Files





Parameter files are supplied with AG ISDN software. They contain parameters and values that configure the AG ISDN TCP. Some of these parameters are country-specific; that is, different values are supplied for them depending upon the target country. 



The following parameter files are supplied for each software package: 





 File Type/Name



 Description




 A binary parameter file. 


 This file is named isdcty.pf, where cty is the three character code of the target country.  For example, the code for Australia is aus. Thus the version of this file for Australia is isdaus.pf.



 The complete set of parameters and default values, including country-specific parameters which should not be changed.




 An ASCII parameter file. 


 This file is named adiisd.par. 



 A subset of the parameters which the user can change without affecting the regulatory approvals in the target country. 
















These files are useful only if you are configuring the AG ISDN software for NCC configuration (as documented in this manual). For more information, see Section 3.6.2, Starting a TCP on a CTA Context. 







WARNING:







Changing the values of most of the parameters in the binary country-specific parameter file may affect the regulatory approvals in the target country.






















1.5	 Other Components





In addition to the AG ISDN software, you will need the following components to build an ISDN protocol application:






1.5.1	 About AG Quad Boards





Boards in the family of AG Quad products have up to four T1 or E1 trunk interfaces, and up to eight on-board DSPs which provide up to 120 ports of call processing and up to 60 ports of programmable voice processing. Each AG Quad board occupies a PCI slot in the host computer.



AG Quad boards connect to other boards via the H.100 bus. The H.100 bus allows the AG boards to share data, signaling, and switching information with other boards on the H.100 bus and the MVIP bus. For example, you can connect two or more AG Quad boards for applications that perform trunk-to-trunk switching. You can add additional DSP resources, analog station interfaces, or loop start line interfaces on other AG boards. You can also use compatible products from other manufacturers with AG Quad boards.



For detailed information on AG Quad boards, see the AG Quad Installation and Developer's Manual.






1.5.2	 About AG-T1 and AG-E1 Boards





AG-T1 and AG-E1 boards interface one T1 or E1 trunk with the host computer. The boards also have six on-board DSPs. Each board occupies a standard ISA slot in the host computer.



The AG-T1 and AG-E1 can connect to other boards via the MVIP bus. The MVIP bus is an interoperable subset of the H.100 bus.



For detailed information on the AG-T1 and AG-E1 boards, see the AG-T1 and AG-E1 Installation and Developer's Manual.


Note:  ISDN is only supported on AG-T1 and AG-E1 boards revision D-1 and later. If your AG-T1 or AG-E1 board was purchased prior to June 1996, you may need a hardware upgrade. For more information, contact NMS Developer Support. 







WARNING:







Natural MicroSystems obtains board-level approvals certificates for supported countries. Some countries require that you obtain system-level approvals before connecting a system to the public network. To learn what approvals you require, contact the appropriate regulatory authority in the target country.





















1.5.3	 About CT Access





CT Access is a complete development environment for telephony applications. It provides a standard set of telephony functions grouped into logical services, each of which has a standard API. CT Access provides functions for telephony-related tasks such as call control, tone and DTMF tone generation and detection, and voice playing and recording.



CT Access includes a service which controls switching on MVIP-compliant devices. You can use this service to make or break connections, send patterns, sample data, etc. This service supports both MVIP-95 and MVIP-90 specifications. Alternatively, you can use the swish standalone utility to control switching interactively or in a batch mode.



For general information about installing and using CT Access, see the CT Access documentation.






1.5.4	 agmon and the AG Configuration File





When you set up your system, you specify configuration information for all AG boards in the system in an AG configuration file. This information includes: whether a board performs MVIP switching, which board is the MVIP clock master, which software modules to transfer to the AG board's memory on startup (including which TCPs to load), and other settings. To learn how to modify your AG configuration file to set up your AG ISDN software, see the AG ISDN Installation Manual and the AG Runtime Configuration and Developer's Manual.



To configure your boards based on the information in the AG configuration file, run the agmon utility. agmon transfers to each board all software modules specified in the file, and performs any other configuration activities needed. Leave it running so that it can monitor the AG boards for errors and other events.



Whenever you make a change to your AG configuration file, restart agmon to make your changes effective.



agmon is installed with CT Access. For more information, see the AG Runtime Configuration and Developer's Manual.






1.5.5	 About DSP files





DSP files enable the AG board's on-board digital signal processors to perform certain tasks, such as voice recording, playback or DTMF detection. DSP files are transferred from the host into on-board memory when agmon runs.



DSP files have the extension .dsp. Several DSP files are installed with your CT Access software. You specify the files to use for your configuration in the AG configuration file. To learn how, see the AG ISDN Installation Manual.



Several DSP files are installed with CT Access. Refer to the ADI Service Function Reference Manual for more general information about DSP files.






1.6	 Developing an AG ISDN Application





To create an AG ISDN application: 





 Step



 Where Step is Documented




1.	 Install AG Quad T, AG Quad E, AG Dual T,
AG Dual E, AG-T1, or AG-E1 boards in a system, and any other boards you will need in your application. 



 The installation manuals for your AG boards




2.	 Install CT Access. If using CT Access 2.0, also install AG Access 1.4 and CT Access 2.0 Service Pack 2.



 CT Access Installation Manual




3.	 Install the AG ISDN software for each target country or region that your application will be used in.



 AG ISDN Installation Manual




4.	 Edit your AG configuration file so it describes all AG boards in your system.



 The AG ISDN Installation Manual,  the installation manuals for your AG boards, and the AG Runtime Configuration and Developer's Manual




5.	 Test your hardware installation.



 The installation manuals for your AG boards




6.	 Write your application.



 This manual, the AG ISDN Messaging API Developer's Reference Manual, and the CT Access documentation set





















 
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