DNS Outage Avoidance Method for Recursive DNS Servers

• US 20130198269A1
• Filed: 02/01/2013
• Published: 08/01/2013
• Est. Priority Date: 02/01/2012
• Status: Active Grant

• Current Assignee: Akamai Technologies, Inc.
• Original Assignee: Xerocole Incorporated (Akamai Technologies, Inc.)
• Inventors: Fleischman, Robert M., Waters, William Thomas, Wyatt, Robert Alton
• Granted Patent: US 8,583,801 B2
• Time in Patent Office: Days
• US Class Current: 709/203
• CPC Class Codes: H04L 61/4511 using domain name system [DNS]
• CPC Class Codes: H04L 61/50 Address allocation
• CPC Class Codes: H04L 61/58 Caching of addresses or names
• CPC Class Codes: H04L 67/568 Storing data temporarily at an intermediate stage, e.g. caching
• CPC Class Codes: H04L 69/40 for recovering from a failure of a protocol instance or entity, e.g. service redundancy protocols, protocol state redundancy or protocol service redirection management of faults, events, alarms or notifications in data switching networks H04L41/06

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.

Claims

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; and

an 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; and

return the expired answer to the client.

2. The DNS server system of claim 1, wherein the outage avoidance processing module modifies a TTL value of the expired answer as part of returning the expired answer to the client.

3. The DNS server system of claim 1, wherein the outage avoidance processing module ignores the TTL value of the expired answer as part of returning the expired answer to the client.

4. The DNS server system of claim 1, wherein a proxy DNS server system is configured to mediate communications between the client and the DNS server system.

5. The DNS server system of claim 4, wherein the DNS server system is part of a cluster of DNS server systems.

6. The DNS server system of claim 5, wherein the proxy DNS server system comprises:

a local cache; and

an outage avoidance system having;

a query processing module; and

an outage avoidance processing module.

7. The DNS server system of claim 1, wherein the DNS server system is a recursive DNS server system.

8. The DNS server system of claim 1, wherein the remote DNS server system comprises one or more authoritative DNS servers.

9. 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 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 a DNS server system;

an outage avoidance processing module that is configured to, upon indication that the DNS server system 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.

10. The proxy DNS server system of claim 9, wherein the proxy DNS server system is configured to route various DNS queries to different DNS server systems, including the DNS server system.

11. The proxy DNS server system of claim 10, wherein the different DNS server systems are part of a DNS server cluster.

12. The proxy DNS server system of claim 11, wherein the outage avoidance system is configured to handle empty answers and errors from DNS server systems in the DNS server cluster that are not equipped with an outage avoidance system.

13. The proxy DNS server system of claim 10, wherein the proxy DNS server system is configured to select which DNS server system to route a DNS query to based on load balancing considerations.

14. The proxy DNS server system of claim 10, wherein the proxy DNS server system selects which DNS server system to route a DNS query to based on attempts to match DNS queries with one of the DNS server systems most likely to have an answer to the DNS query.

15. The proxy DNS server system of claim 9, wherein the proxy DNS server system is configured to have firewall functionality.

16. The proxy DNS server system of claim 9, wherein the proxy DNS server system is configured to filter queries based on security considerations.

17. A method of handling a DNS query from a client when an answer is not available on a local cache of a DNS server handling the DNS query and a remote server further handling the DNS query provides an empty answer, an error, or no answer, the method comprising:

receiving a DNS query from a client;

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 first local cache of a DNS server system for a first expired answer to the DNS query, or checking a second local cache of a proxy DNS server system for a second expired answer to the DNS query if the DNS server system does not have an outage avoidance system; and

returning the first or second expired answer to the client in response to the DNS query.

18. The method of claim 17, wherein the proxy DNS server system checks the second local cache for a non-expired answer to the DNS query before forwarding the DNS query to the DNS server system.

19. The method of claim 18, wherein the DNS server system checks the first local cache for a non-expired answer to the DNS query before forwarding the DNS query to the remote DNS server system.

20. An outage avoidance processing module of a server system, the outage avoidance processing module configured to:

receive an error message from a query processing module of the server system;

check a local cache of the server system for an expired answer to a DNS query that lead to return of the error message; and

return the expired answer to a client that generated the DNS query.

21. The outage avoidance processing module of claim 20, wherein the server system is a DNS server system.

22. The outage avoidance processing module of claim 20, wherein the server system is a proxy DNS server system.