Patent ID: 8583801

Claim:
A proxy DNS server system comprising: a local cache storing cached DNS answers from previous queries, each of the cached DNS answers having a TTL value, cached DNS answers having an expired TTL value are considered expired answers; an outage avoidance system configured to handle empty answers and errors from DNS server systems in a DNS server cluster that are not equipped with an outage avoidance system, and comprising: a query processing module that: is configured to receive a DNS query from a client; checks the local cache for a non-expired answer to the DNS query; and upon not finding one, is configured to pass the DNS query to a remote DNS server system via one of the DNS server systems; an outage avoidance processing module that is configured to, upon indication that the one of the DNS server systems received an empty answer, an error message, or no response from the remote DNS server system: check the local cache for an expired answer to the DNS query; and return the expired answer to the client, and wherein the proxy DNS server system is configured to route various DNS queries to the DNS server systems in the DNS server cluster.