The purchase is intended to put it in a better position to compete with Cisco Systems in moving data securely over internet networks.
The deal is Oracle’s biggest since it bought Sun Microsystems in 2010 for about $7bn.
The company bought nearly a dozen companies in 2012, including Eloqua for $810m in December.
Telecom carriers have been dumping wireline and other legacy services as people increasingly use a newer breed of devices to access internet and businesses shift to IP (internet protocol) networks, an area where Acme Packet specialises.
“Users are increasingly connected and expect to communicate anytime and anywhere using their application, device, and network of choice,” Oracle said in a statement.
Oracle chief executive Larry Ellison, who has used acquisitions to boost the company’s revenue dramatically over the past decade, had said in October he would not rule out a big deal “down the road.”
The offer represents a 22 per cent premium to Acme Packet’s Friday close on the Nasdaq.