Comparing IP Voice Solutions
IP voice solutions are a set of comprehensive systems—normally including IP PBX, voice gateway, media server, unified messages, IVR, CTI, messaging integration, contact center and media terminals, and so forth. Also, IP voice solutions can work on mixed TDM systems and IP systems.
Open Architecture and Standards
Figure 1 is a typical IP voice solution architecture; it should have two core fundamental architectural layers. One is the network layer that integrates TDM and IP's key products and the other one is the application layer that runs any application such as IVR, CTI, CRM, ACD, and Contact Center over the network layer. Any applications under open architecture can seamlessly integrate with both the TDM and IP network.
To ensure the best usability and robustness for the IP voice solutions, the design of IP voice solutions should address the following service-level requirements:
- Open and standards-based architecture: Enable the IP voice solutions with the flexibility of a comprehensive solution portfolio that interoperates with existing TDM technologies and systems, while protecting existing investment.
- Extensibility: The IP voice solutions should have the ability to have additional functionality added or to modify existing functionality without impacting the existing functionality.
- Scalability: The IP voice solutions will provide the ability to quickly and easily extend the network infrastructure and application to handle increased contact loads or much more agents or new components and applications.
- Reusability: Addresses the ease with any functional components or concepts within the IP voice solutions can be reused by other applications.
- Maintainability: The IP voice solutions should have the ability to deal with technical issues in existing functionality without impacting other subsystem or components of the IP voice environment.
- Performance: The IP voice solutions should have good performance across all solutions. For example, good Quality of Service (QoS) mechanisms ensure high voice quality through tight control of delay, loss, and jitter.
- Manageability: The IP voice solutions must be easy to be used and managed by most the administrator and technical staff. Also, choose good network management products to provide network administration, operations, troubleshooting, configuring, fault monitoring, and element management.
IP PBX and Media Server
The IP PBX and media server is the core component of the IP voice solution. IP PBX and media server perform call processing capabilities and PBX features over the IP network infrastructure as well as extend and manage enterprise telephony features and capabilities to IP telephony network devices, media terminals, and applications such as media processing devices, messaging devices, IP phones, VoIP gateway, IVR, CTI applications, and so forth. The IP PBX and media server could be worked on single-site models and multi-site WAN models:
- Single-site call processing model: In the single-site model, each site or campus has its own IP PBX or media server to perform call processing functions; also, there are no voice calls communication over the WAN network. If you want to implement external calls or call remote sites, you can use PSTN.
- Multi-site WAN model with centralized call processing: In the multi-site WAN model, the IP PBX can either resides at a central campus or each site, and communication with remote branch offices or between sites normally takes place over the IP WAN or PSTN.
In the marketplace, the Cisco CallManager, Avaya 8xxx series Media Server, and Nortel Succession are the leading IP PBX and media server.
Voice Gateway and TDM/IP PBX integration
Voice Gateways provide a connection or a bridge between an IP telephony network and PSTN. Also, one can say that it is a connector between the TDM system and the IP network. Voice gateways play a core role in the integration between TDM PBX and IP PBX.
Voice Gateways can range from analog gateways to digital trunk gateways. Normally, the analog gateway consists of an analog station gateway and analog trunk gateways. The analog station gateways can connect IP PBX to analog telephones, IVR systems, fax machines, and voice mail systems with FXS ports. The analog trunk gateways can connect IP PBX to PSTN central office (CO) or PBX trunks with FXO ports. The digital trunk gateways connect IP PBX to the PSTN or to a PBX via digital trunks such as Primary Rate Interface (PRI), Basic Rate Interface (BRI), or T1 Channel Associated Signaling (CAS). Digital T1 PRI trunks may also be used to connect to certain legacy voice mail systems.
The Cisco, Avaya, and Nortel systems have shipped to the market much many voice gateways. For details see their Web sites.