The example voice over Internet protocol (VoIP) gateway network system highlights the features in Altera’s advanced FPGA devices and IP cores that can provide implementation-level benefits to VoIP developers. The VoIP gateway network system consists of a shelf, which contains three bus lines and two types of cards. Figure 1 shows an overview of the example VoIP gateway network system.
Figure 1. VoIP Network System Overview
The digital access card (DAC) is the first type of card in the VoIP network. It interfaces with the Internet infrastructure. The second type of card manages the interface between the telephone hardware and the routing network. Because much of its functionality is based on standard telephony requirements, it is known as a plain old telephone service (POTS) card. Additional DAC and POTS cards can be added to the system to meet the availability and performance needs of the service.
Telephones are connected externally to the POTS cards with a standard telephone wire. Each POTS card can handle up to 128 phone lines and the system can be scaled to meet specific needs by adding POTS cards to the board .
The DACs interface with the Internet via a T1 line. Each DAC can carry up to four T1 lines. In this example, the T1 lines connect the gateway to the Internet via a frame relay network. However, other types of networks can also be connected to a similar shelf .
Three separate buses allow control and data information to be passed between all the cards in the system. The TDM bus carries un-packetized voice data between all the cards in the system. The packet bus carries voice traffic in Ethernet packets between the DACs and the control bus manages communication between the DACs and POTS cards .
