Oracle will buy Acme Packet Inc., a Bedford company that makes equipment for telecommunications companies, for about $2.1 billion. Acme’s gear is used by more than 1,900 service providers and enterprises around the world. Its technology will complement Oracle’s offerings for telecom providers. Oracle, a database software maker, will pay $29.25 per share for Acme. Acme’s board approved the acquisition, but it is still subject to shareholder and regulatory approval.