"We've received reports from clients of VoIP (Voice over Internet Protocol) dropouts, and have been investigating them for the past week," iiNet senior systems engineer Paul Raj Khangure told ZDNet Australia today.
The service, dubbed 'iiNetphone', debuted in late August 2005 and already has over 20,000 users, likely making it the most popular mass-market VoIP offering by a local company.
Khangure said tracking down the source of the problem had been difficult.
"Unfortunately we're having a lot of trouble in replicating the fault, which makes it almost impossible to get debug logs of the drops," he said.
But the problem is most likely related to some of the Juniper equipment iiNet is using.
"From correlating the information we've received from a number of clients, the reported problem appears to be with the Juniper Session Border Controllers (SBCs) when placed under load," said Khangure.
"This is particularly noticeable for people using the Perth and Sydney SBCs. Due to the difficulties in replicating the problem, we've not been able to conclusively confirm this though," Khangure noted.
iiNet will test another vendor's hardware to see if the Juniper kit was at fault.
"We'll be swapping out the Juniper SBCs in Perth with another vendor's later this week," said Khangure. "If this results in a reduction in the number of reports, we will have confirmation that the SBC may be the source of the reported dropouts."
"To test whether it's hardware or software related, we'll also be swapping out the Juniper SBCs in Sydney with a higher grade Juniper model, running the same software," he added.
Although a number of iiNet customers complaining about the problem in online forums had suspected their Belkin ADSL modems had been at fault, Khangure said it was unlikely this was the case.
"We don't believe it to be a problem with the Belkin units," he said.
"Given the majority of our clients use the iiNet-supplied Belkin hardware, it's not surprising that the majority of the drops have been reported from Belkin users. There have however been similar reports from clients using other vendors' hardware," he said.
The iiNetphone service also had difficulties shortly after its launch, with some users unable to make or receive calls to and from the more traditional networks of some other carriers.
Such services reflect an ongoing move by telcos and ISPs to provide so-called "triple-play" (data, voice and video) services over just one high-speed broadband connection.