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DNS could slow broadband service

Poor-performing DNS servers could bog down broadband service, even on superfast connections, Nominum says.

A broadband provider's claim of superfast speeds may only be as good as its weakest link, which could be its domain name server software.

A report issued Thursday by Nominum, a company that sells domain name system (DNS) server software, indicated that some broadband service providers need to bulk up their DNS servers to ensure that broadband users actually get all the benefits of their high-speed connections.

"We hear stories about carriers spending billions of dollars to build new fiber-to-the-home networks or 3G (third-generation) wireless networks," said Paul Mockapetris, inventor of the DNS architecture and chairman and chief scientist at Nominum. "But broadband providers should also spend some money adding more DNS capability. Pure bandwidth doesn't solve the problem if the DNS servers can't respond quickly."

DNS functions as the "phonebook" of the Internet, mapping text-based domain names such as www.cnet.com to the numerical Internet Protocol addresses used by computers. Internet users typically use the DNS service run by their service provider.

When DNS servers are running slow or when they drop queries, people experience Web pages loading slower, delays in sending and receiving e-mails, and poor response times when they're trying to play interactive video games.

More than 48 million American households have broadband access today, according to the Leichtman Research Group. To entice consumers to use their service, phone companies and cable operators have focused a lot of attention and marketing dollars on convincing potential customers that their service is the fastest. Verizon Communications is spending $20 billion over the next few years to build a fiber-to-the-home network called Fios, which it claims provides the fastest Internet access network in the United States.

In the survey commissioned by Nominum and conducted by VeriTest in April, Verizon's Fios network and its DSL (digital subscriber line) service actually had the worst response times of any broadband provider measured. According to VeriTest data, the Verizon Fios service had an average DNS response time of about 180 milliseconds. By contrast Comcast, which is a Nominum customer, had the fastest response time of roughly 40 milliseconds.

Bobbi Henson, a Verizon spokeswoman, said the company has been upgrading and tweaking its DNS servers over the past several months. She also said the company has conducted its own tests with VeriTest, which show very different results.

"We would dispute that we have the slowest DNS look-ups in the industry," she said. "We conduct our own studies monthly. We are always looking at the overall performance of our DNS servers and tweaking them to improve performance."

At the end of the day, all the broadband providers in the report had response times in either tens or hundreds of milliseconds, hardly enough time for the average user to even notice, said Joe Laszlo, an analyst at Jupiter Research. He acknowledged that upgrading networks to increase raw bandwidth takes the bottleneck out of one part of the network, and inevitably exposes flaws in other parts of the network. But he said he doesn't believe DNS is the biggest culprit in noticeably slowing Internet service.

"So much of the perceived performance of a service depends on how fast your browser in your computer can process Web pages or how quickly your graphics card can render images," he said. "Slow DNS response times could impact the speed of the service, but I don't think it's the No. 1, No. 2 or even No. 3 issue that creates noticeable delays for users."