PSTN-Internet Interworking Product Types

We have deliberately avoided reviewing specific vendor products. Instead, we outline generic families of existing products, describing their features, major parameters, and—whenever applicable—criteria for interworking with other products. Because new products emerge constantly and existing products are updated frequently, you should expect the product capabilities listed here to change.

You should obtain the latest descriptions from the product vendors for details like prices and performance characteristics. The product families we focus on correspond to the three categories of PSTN-Internet interworking:

1. Carrying voice across both the IP networks and the PSTN. Products include IP telephony gateways [usually called voice-over-IP (VoIP) gateways in the trade], gatekeepers, multipoint conferencing units, and private branch exchanges (PBXs).
2. Combining PSTN transport and the Internet access to PSTN services. Products include intelligent network service nodes and intelligent peripherals. The messaging platforms that support unified messaging also fit here, because a central feature is that they rely on IN control. Note: You could argue that multimedia support by these products justifies including them in the previous item, while access support warrants placing them in the next list item.
3. Carrying data over PSTN lines on the way to IP networks. Products that support remote access and VPN applications include access servers, Signalling System No. 7 gateways, and class 5 (that is, local) switches with multiservice capabilities.