Verizon Communications Inc. has filed a [tag]patent infringement[/tag] [tag]lawsuit[/tag] against Vonage Holdings Corp. The suit is based upon information in technical documents and diagrams, which was filed with the SEC in their pursuit to go public.

In the suit, Verizon alleges that Vonage is using technology that was developed by Verizon and its predecessor companies. Seven patents related to voice over Internet protocol (VOIP), the technology that facilitates Internet calls, have been identified in the suit. Specifically, Verizon alleges that its patents cover techonology that routes call from the Internet to landline phones. Other Verizon patents include calling features such as voicemail and Internet call waiting.

Vonage counters that the technology the company uses has been developed internally or is licensed through third parties. The company has 1.6 million subscribers, which is a small fraction of the telephone market in the U.S.

This suit is a headache for Vonage, which had a far-from-stellar IPO. The offering was so horendous, that shareholder lawsuits have already started. The launch price of the Vonage stock was $17, but since the offering last month, the share price has dropped fifty percent.