DNS outage avoidance method for recursive DNS servers
First Claim
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1. 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, andwherein the proxy DNS server system is configured to route various DNS queries to the DNS server systems in the DNS server cluster.
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Abstract
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.
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Citations
15 Claims
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1. A proxy DNS server system comprising:
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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. - View Dependent Claims (2, 3, 4, 5)
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6. A method of handling a DNS query from a client comprising:
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receiving a DNS query from a client via a proxy DNS server system that distributes DNS queries to a DNS server system and other DNS server systems in a DNS server cluster, wherein the DNS server system does not have an outage avoidance system; checking a first local cache of the DNS server system handling the DNS query for a non-expired answer to the DNS query; forwarding the DNS query to a remote DNS server system; receiving an empty answer, an error, or no answer from the remote DNS server system; checking a second local cache of a proxy DNS server system for an expired answer to the DNS query; and returning the expired answer to the client in response to the DNS query. - View Dependent Claims (7, 8)
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9. A method of operating a DNS proxy server system comprising:
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routing various DNS queries to a plurality of DNS server systems in a DNS server cluster wherein at least one of the DNS server systems is not equipped with an outage avoidance system; receiving a DNS query from a client; checking a local cache of the DNS proxy server system for a non-expired answer to the DNS query; upon not finding a non-expired answer, passing the DNS query to one of the DNS server systems in the DNS server cluster; receiving an empty answer, an error, or no answer from the at least one of the DNS server systems not equipped with an outage avoidance system; check the local cache of the DNS proxy server system for an expired answer to the DNS query; and return the expired answer to the client. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification