DNS outage avoidance method for recursive DNS servers

摘要

This disclosure describes systems, methods, and apparatus to protect users of the Internet from DNS outages. In particular, an outage avoidance system is provided that includes query processing, outage avoidance processing, and a local cache, all configured to extend the TTL of expired answers to DNS queries or to ignore the expiration of an answer's TTL value, and thereby provide the expired answer in response to a client request when a DNS server is unable to obtain an answer from a remote DNS server.

主权项

1. A domain name system (DNS) server system comprising:
a local cache storing cached DNS answers from previous DNS queries, each of the cached DNS answers having a time-to-live (TTL) value, cached DNS answers having an expired TTL value are expired DNS answers; an outage avoidance system comprising:
a query processing module that:
is configured to receive a DNS query from a client;checks the local cache for a non-expired DNS answer to the DNS query; and upon not finding one,is configured to pass the DNS query to a remote DNS server system;is configured to receive an empty answer, an error message, or no response from the remote DNS server system; andan outage avoidance processing module that is configured to, upon indication that the query processing module received an empty answer, an error message, or no response:
check the local cache for an expired answer to the DNS query; andreturn the expired answer to the client.