The Federal Communications Commission (FCC) order requiring full VOIP E911 service takes affect at midnight Monday, and most experts say it's likely that some providers of residential VOIP have fallen short. But on what scale? (See E911 Deadline: A Stretch for Most.)

To comply with the order, PSTN-connected VOIP providers must be able to connect the 911 calls from their customers to a local emergency operator. (See FCC Requires VOIP E911.) This entails an interconnection arrangement with a given market's local exchange carrier in order to connect with the PSAPs, or public safety access points. (See Vonage to Buy E911 Service From RBOCs.)

The VOIP provider must also be able to provide emergency operators with a subscriber's call-back number and location information, in case that caller becomes unable to talk. (See FCC Extends 911 Deadline.)

Collecting accurate information of this kind is difficult when many residential VOIP customers are "nomadic." That is, they can unplug their VOIP service and plug it back in somewhere else, leaving their provider with outdated location information.

According to the order, VOIP providers must discontinue service to such customers. (See VOIP Carriers Track 911 Solutions.)

Observers say VOIP providers whose customers are stationary, such as enterprise or cable modem customers, have likely achieved 100 percent compliance with the FCC's order.

Providers like Nuvio Corp. and SunRocket Inc., which service large numbers of residential customers, may be forced to limit service to subscribers in certain parts of the country.

By the end of Monday, VOIP providers must file to the FCC a detailed account of their service, E911 infrastructure and compliance efforts. The commission, observers say, will pay special attention to VOIP providers who do not answer by the deadline.

In terms of enforcement, the FCC's E911 order prescribes fines of up to $11,000 per day per non-compliant subscriber line, according to Nuvio CEO Jason Talley. Talley says his company is taking the FCC order, and the threat of penalties, very seriously. He declined to say how many Nuvio customers would be affected by today's deadline.

— Mark Sullivan, Reporter, Light Reading