Domain name system specialist Nominum has added web redirection to its carrier software, a once-controversial capability that shows surfers advertising instead of web error messages.

Web redirection occurs when a user types a non-existent domain name into a browser. Instead of receiving a "Page Not Found" error message, the user is redirected to a web page, such as an ad-sponsored search page.

In 2003, VeriSign added a web redirect service to the .com and .net domains that it operates, and the reaction from the internet engineering and user communities was overwhelmingly negative.

Weeks later, VeriSign was forced to pull its Site Finder redirection service, which offered users the opportunity to buy unassigned web addresses that were typed into the browser. Criticism of Site Finder focused on the fact that VeriSign had implemented it in the .com and .net zones. Nominum is taking a different approach to web redirection with its new Vantio NXR software.

Nominum's software allows its carrier customers to redirect error traffic to the page of their choice. Nominum provides the underlying technology for web redirection, but not the web-redirection service.

Nominum asserts that redirection of web errors is useful to carriers if it is done correctly, by allowing them to provide branded search pages to their customers.

Nominum estimates that 15 percent to 30 percent of all DNS traffic is for non-existent domains.

These user errors are "a significant opportunity for the service provider," said Albert Gouyet, vice president of marketing for Nominum. "The end user gets more help from a carrier-branded search page, and carriers can use the service to monetise this traffic."

Nominum said it has four carrier customers for Vantio NXR - two in North America and two in Asia - that all have more than one million subscribers.

Gouyet said web-redirection services should redirect only web browser errors, not applications such as email. He said that such services shouldn't degrade DNS performance, because of all the applications that depend on DNS. He added that users should be provided the opportunity to opt out of web-redirection services.

He said Nominum's Vantio NXR enables carriers to provide a better web-redirection service by avoiding these problems.

"Nominum's underlying technology, called SureSurf, lets carriers determine what gets redirected and what doesn't," Gouyet says. "It has very fine-grained controls."

Gouyet says that Nominum's Vantio NXR is "night and day different" from VeriSign's Site Finder. "VeriSign did this at the top-level domain, in a non-discriminatory fashion, without an opt-out. Our solution is at the edge of the network, closer to the subscribers, and allows an opt-out. It does web redirection more intelligently. It's a completely different value proposition."

Carriers are starting to reconsider the years-long ban against web redirection. For example, EarthLink enabled a DNS redirect service last year.

"Carriers are rolling out this type of service," Gouyet says. "We think this is a much better way and a more responsible way to do it as long as it is closer to the subscribers."

It's unclear whether the internet user community will see the differences in Nominum's approach to web redirection.

"Nominum is much more of a software vendor rather than service organisation like VeriSign," said Elisabeth Rainge, program director for telecom software research at IDC. "Nominum is taking a hands-off approach to the kinds of things that raised alerts in VeriSign's service."

Rainge wouldn't hazard a guess about whether Nominum's new Vantio NXR will prove to be controversial.

"Things have changed culturally," she says. "People are more used to being redirected by choice. A search engine isn't really a search engine; it's an advertising machine. I don't think [Nominum's Vantio NXR] is very far afield from what people are already accepting."