Domain Name System (DNS) has been getting a lot of attention lately. Case in point, Google just announced the release of Public DNS, their network of DNS resolving servers that use a concept called prefetching. Google claims that their technology will reduce latency throughout the whole DNS structure.
"Neustar, Inc. and OpenDNS today (December 10, 2009) announced the implementation of a Neustar-sponsored initiative that will provide near-real time updating of the Domain Name System (DNS) across the Internet, utilizing Neustar databases to form the DNS Real-time Directory. This provides a centralized cloud-based system that allows Neustar customers and participating providers to publish DNS modifications in real time to participating ISPs and recursive service providers, creating a better experience for Internet users around the world."Some history
Neustar's idea has to do with "Time-to-Live" (TTL), an attribute that all DNS records have. TTL is a timer that dictates how long a DNS record is held by DNS resolving name servers. You may ask, why not store it indefinitely?
It's because of the components of a DNS zone file. Using TTL forces the resolving name server to query an authoritative source for that particular DNS record when the local record expires. That, in a roundabout way, makes sure the local copy is reasonably accurate.The problem
In a perfect world, it would make sense to have a short TTL. That provides the best chance for having the correct DNS record. Unfortunately, short TTLs would create excessive loading on the authoritative name servers — almost to a point of simulating a DDoS attack.
A typical DNS record TTL is 86,400 seconds. Therein lies the problem that Neustar wants to fix. A resolving name server could be using an inaccurate DNS record for up to 24 hours after the authoritative name server made changes.
I just went through this with a client. The client wanted to use a different public IP address for their e-mail server. I suggested making the change during the weekend to limit the negative effects. I also worked with the ISP to change the TTL to something much less than 24 hours. Despite all the preparation, the propagation was not total until sometime Sunday.Another example
Another example of when TTL gets in the way happened to the Swedish domain .SE this past October. The Internet Infrastructure Foundation sent out an incorrect DNS zone file to authoritative name servers. The bad DNS record then proceeded to trickle down to all resolving name servers.
The foundation found the mistake within an hour and rectified it. Still, resolving name servers worldwide were returning invalid DNS records for the .SE domain. That was, until the record's TTL expired or the record was manually flushed from the server.One possible fix
The solution being offered by Neustar marries their UltraDNS platform with DNS Real-time Directory. In theory, the directory becomes the clearinghouse for all changes made to DNS zone files. When changes are made to a zone file, a message is sent (using UltraDNS) to all participating resolving name servers, telling them to clear the invalid record.
The next time a query is made for the flushed DNS record, the resolving name server must itself send a query to an authoritative name server. An accurate record is returned and forwarded to the computer trying to resolve the domain name. This approach would have eliminated the appearance of .SE Web sites being down due to the Swedish DNS mistake.OpenDNS buys in
What makes Neustar's technology immediately effective is OpenDNS's involvement. OpenDNS adds credence to Neustar and provides a significant user base. David Ulevitch, founder and chief technical officer of OpenDNS, offered the following comment (quoted in Neustar's press release):
"We were pleased to work with Neustar on this initiative. Collaborating with Neustar means OpenDNS is now not only one of the largest recursive DNS services on the planet, but also the most up-to-date. Neustar provides a world-class authoritative DNS service. OpenDNS provides a world-class recursive DNS service. We look forward to other service providers adopting the DNS Real-time Directory as the standard for real-time updates."Final thoughts
OpenDNS is a strong player in the world of DNS, especially when it comes to user security and privacy. This collaboration will make it more so.
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