When three ISPs in South Australia were looking to add voice services to their portfolio and reduce running costs, they embarked on a VoIP infrastructure project using open source software.
Independent ISPs RBE Internet, netYP, and Webshield formed the Interconnect group to offer VoIP services, and contracted Adelaide-based OEG Australia to do the technology integration work.
The group evaluated a number of commercial products, but the initial cost was too high and each ISP would have had to pay an ongoing fee to access the technology.
OEG proposed the idea to build a carrier-grade VoIP platform with commodity servers and open source software.
OEG managing director Mike O'Connor said an entry cost of $100,000 for a commercial telephony system is high and "you are stuck with whatever they gave you, and they are not really designed for the local market".
"We looked at Asterisk and an early version of Yate, but Asterisk was never really designed to be carrier grade in that sense, it was meant to be a PABX," O'Connor said. "We wanted something designed for the purpose so we used OpenSER, a carrier-grade SIP routing platform which is extremely configurable and used by a lot of organizations."
The open source components used to build the system include RADIUS, MySQL, and CDRTool, with the Web-based administration tools developed in PHP.
"Those components gave us the basis of the system and some six weeks later we had an operational system with call routing, authentication, and IVR," O'Connor said, adding the system also has its in own Web-based billing system in PHP.
The features that OpenSER doesn't offer, like voicemail, were done with Asterisk, which is running on a separate machine, but is in the same environment.
The system came into production this time last year, but an AAPT "pipe kerfuffle" meant the group lost its main VoIP provider.
After getting back the services it lost, the group re-released its VoIP service and now has some 1800 user accounts, of which about two-thirds are active.
The system is fully redundant and load balanced using tools from the Linux Virtual Server project, so the system has a "Linux jail-like architecture without all the problems of virtual servers".
O'Connor is confident the system can scale horizontally to meet growing demand.
"We would need to expand 1000-fold before we hit any issues," he said. "Since it was installed it hasn't cost us a cent whereas any other design would require us to pay maintenance fees on a yearly basis or more often. So the only time we spend any money on it is when we improve it."