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Chapter 1
Introduction
- 1.1 Introduction
- 1.2 Developing Gateway Applications
- 1.3 Fusion Application Development
- 1.3.1 PSTN
- 1.3.2 Packet Network
- 1.3.3 Voice Data Conversion (PCM/Digital
- 1.3.4 H.323 Stack Software
- 1.3.5 Demonstration
- 1.3.6 Fusion
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1.1 Introduction
- Fusion consists of hardware and software for creating and running IP telephony gateway applications. IP telephony is the convergence of circuit-switched networks, such as PSTNs (public switched telephone networks) and PBXs, with packet-switched networks such as the Internet, and private local area networks (LANs). This chapter provides an overview of Fusion gateway applications and the Fusion development environment.
- Gateway applications carry voice data between packet networks and PSTNs. These applications convert voice data between PCM form (carried over PSTNs), and data packet form (carried over IP/LAN networks). Voice data can be sent over packet networks to compatible computer client terminals, or transferred to other Fusion gateways. This allows users to make and receive telephone calls from ordinary telephones or client workstations, and allows organizations to route these calls over IP data networks.
Figure 1. Fusion Gateway Applications
1.2 Developing Gateway Applications
- Fusion includes a set of software APIs that enable applications to link PSTN calls to IP sessions, and to control the flow of data between PSTN and packet networks. Fusion hardware and software components are based on NMS standard Alliance Generation (AG) and TX Series products.
- Figure 2 shows a typical Fusion gateway application using NMS hardware and software.
Figure 2. Typical Fusion Gateway System
1.3 Fusion Application Development
- This section provides an overview of the hardware and software that make up the Fusion development environment.
- The Fusion application development environment consists of the following components:
- Data conversion hardware and software
- IP/packet network interface hardware and software
- Demonstration programs
- The basic Fusion gateway application structure is shown in Figure 3.
Figure 3. Fusion Gateway Application Overview
1.3.1 PSTN Interface
- Fusion includes hardware and software for controlling the interface to public switched telephone networks. Fusion gateway applications need one or more of the following PSTN interface boards:
- AG-8/80 boards which provide 8 ports of voice processing along with
analog telephone connections for loop start or DID interfaces (systems that
use AG-8 line interface boards must also use an AG-8/80 to act as a
baseboard for the AG-RT daughterboard).
Note: The total number of ports a Fusion gateway application can support depends on the host system's hardware configuration, and the type(s) of data conversion the gateway performs.
- To control the PSTN environment, Fusion gateway applications use CT Access. CT Access is a modular runtime and development environment for voice and call processing applications. It provides a simple and consistent standard API for applications to execute telecommunication functions on telephony boards. The following APIs are standard software components of CT Access:
- Switching service
- Voice Message service
- Fusion software includes the optional Host-based Fusion (HBF) service, which is also a CT Access service.
1.3.2 Packet Network Interface
- The Fusion application development environment also includes hardware and software for controlling the interface to IP packet switched networks. TX2000 and TX3000 boards provide an MVIP compliant interface and on-board support for a variety of network interfaces such as Ethernet.
- Fusion includes a set of TX Series APIs for controlling the flow of data to and from packet networks. These APIs include the following:
- Common Management API
- TelePathx (TPX) API
- Virtual Port Data and Configuration API
- Real Time Protocol (RTP) and Real Time Control Protocol (RTCP) API
- For more information about controlling the packet network interface, refer to Chapter 5.
1.3.3 Voice Data Conversion (PCM/Digital Packets)
- Fusion applications use AG RealTime (AG-RT) daughterboards to convert PCM data from PSTNs into data packets that can be transferred over packet networks (and vice versa). AG-RT and AG-RT/2 daughterboards conserve host resources by performing low latency operations that require extensive processing or memory resources (such as full duplex speech encoding).
- AG Transcoding and Rate Adaptation Unit (TRAU) programs run on AG-RT daughterboards, and are used to convert data from one form to another. These programs convert PCM data into data packets and data packets to PCM. Each type of AG TRAU program encodes data according to a different algorithm (for example, GSM, G.723.1, or G.711). AG TRAU programs also perform other operations such as on-board echo cancellation, and mu-law or A-law encoding.
- Gateway applications use functions from the AG TRAU service (an extension of the ADI service) to control AG TRAU program operations. Refer to the Fusion AG TRAU Developer's Reference Manual for more information about the AG TRAU service.
1.3.4 H.323 Stack Software
- H.323 is the specification that defines packet standards for terminals, equipment, and services for multimedia communications over any packet network, including the Internet. Fusion includes an optional H.323 stack for performing the following operations at the TX packet network interface:
- Conference management
- The H.323 stack also includes functions for controlling calls between remote hosts at different points on packet networks (according to the H.245 protocol), and functions for controlling the flow of data through channels on remote hosts (according to the H.225 protocol).
Note: The Fusion H.323 stack is optional for Fusion gateways that use the MVIP bus. These gateway applications may also use proprietary call control standards for controlling calls at the packet network interface. However, Host-basedFfusion systems must use the Fusion H.323 stack.
1.3.5 Demonstration Programs
- Fusion includes the following demonstration programs:
- Three demonstration programs for testing end-to-end data transmission on
AG-8, AG-T1/E1, and ISDN systems.
- A test program (the TRAU Exerciser) for setting up and tearing down AG
TRAU data conversion channels on AG-RT daughterboards.
- For information about Fusion demonstration programs refer to Chapter 6. For more information about these demonstration programs, refer to the Host-based Fusion Developer's Manual.
1.3.6 Fusion Features
- Fusion provides the following features for gateway application developers:
- APIs for controlling the following aspects of the PSTN interface:
- Voice record and play operations
- Digit (DTMF) collection
- DTMF and tone generation and detection
- Call progress analysis
- MVIP switching
- On-board DSP operations that include:
- A-law and mu-law encoding
- G.711 TRAU programs for performing G.711 (PCM) speech encoding
and decoding (AG-RT/2 daughterboards only)
- GSM TRAU programs for performing ETSI GSM 6.10 speech encoding
and decoding
- G.723.1 TRAU programs for performing G.723.1 speech encoding and
decoding
- Program specific functions for controlling DSP operations such as gain
control and echo cancellation
- APIs for controlling the following elements of the packet network interface:
- Simultaneous session control
- Standard Internet protocols on a dedicated board for maximum
performance, including Transmission Control Protocol / Internet
Protocol (TCP/IP), and User Datagram Protocol (UDP)
- Optional support for the ITU H.323 specification (including the H.245 and
H.225 protocols), enabling interoperability with other H.323-compliant
clients and gateways
- Support for Gatekeeper functions for address translation, control access and
bandwidth management
- Configurable on-board jitter buffer to control voice data latency (controlled
by RTP in AG-RT/2 configurations)
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