Vonage is reportedly going to test the nerves of investors by filing for an initial public offering according to the Wall Street Journal, which said Vonage is looking to raise as much as $600 million.

Many analysts see Vonage as a pioneer in the IP telephony market, but not necessarily a long-term player. As it nears its millionth subscriber, Vonage could be at crossroads which either catapults it into a big-time competitor, which a successful IPO would help, or forces it to leave the market it started to established giants such as AT&T. Vonage and other VoIP providers may be forced to shut off some subscribers as soon as next week if those subscribers have not acknowledged being notified by the service providers of certain E911 limitations.

Vonage was launched in 2002 and has become the largest Internet phone company in the U.S. The news of their possible IPO comes a day after Internet companies Google and Skype traded announcements on their voice messaging services. Microsoft and Yahoo also are making plays for the voice-messaging market.

The IPO was not confirmed by Vonage executives, who declined to comment, said the Journal, but was reported last night on the online edition of the Daily Deal. So far, Vonage has raised over $400 million in venture capital