What is SmartCache?
SmartCache - Here's how it works: When an authoritative DNS provider suffers an outage, all of the Websites it provides service for are taken offline. They are inaccessible for everyone on the Internet. But no longer for OpenDNS users. Our servers will now immediately look for the last known good address for the site in our caches, and use that to load the site. So effectively OpenDNS users will be able to access Websites that appear down for everyone else. For our millions of users at businesses, schools and libraries around the world, saving them Internet access interruptions and the time they waste is invaluable.
The OpenDNS Global Network receives over 40 billion DNS queries daily from 50 million active Internet users and their devices (aka. stub client). When each subsequent DNS query is received, OpenDNS name servers already know the answer (much more often than your regional ISP name servers). Hence, users do not wait on the authoritative name servers to return this same answer. The OpenDNS Global Network knows nearly every publicly addressable host’s IP address Internet-wide at any given time.
However, this is not what makes the caching technology unique. Many authoritative DNS outages, attacks or failures have impacted business-critical content servers such as salesforce.com, amazon.com and petco.com. Or even millions of domains, for example, when the entire top-level domain used by Germany (.de) became unreachable. When such incidents occur – which is not uncommon – the OpenDNS Global Network still returns the last-known correct address using exclusive caching logic. Whereas the rest of the Internet’s users will not be able to reach the domain
Authoritative DNS outages happen frequently and can be a big problem. In March of 2009, it was reported that major authoritative DNS provider UltraDNS suffered an outage that took Salesforce.com, Amazon.com and Petco.com offline for several hours. In such a case, SmartCache fixes the inaccessibility problem and allows people to visit those sites despite the authoritative server outage.
This is just one in a long series of DNS innovations we've developed and passed on to you. Most recently it was blocking the Conficker worm from phoning home. By blocking the domain names the worm used, we were and continue to be able to protect people around the globe. We want our customers to know that we are committed to continually innovate and give you easy-to-use services that make your Internet experience better.
SmartCache is turned on by default for all users and only applies to queries where the authoritative server hands back a SERVFAIL response code or the query simply goes unanswered.