Robust Domain Name Resolution

• US 20100274970A1
• Filed: 03/12/2010
• Published: 10/28/2010
• Est. Priority Date: 04/23/2009
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: OpenDNS Incorporated (Cisco Systems, Inc.)
• Inventors: Treuhaft, Noah, Damm, Michael, Ulevitch, David
• Granted Patent: US 8,676,989 B2
• Time in Patent Office: Days
• US Class Current: 711/118
• CPC Class Codes: H04L 61/3025 Domain name generation or assignment
• CPC Class Codes: H04L 61/35 involving non-standard use of addresses for implementing network functionalities, e.g. coding subscription information within the address or functional addressing, i.e. assigning an address to a function
• CPC Class Codes: H04L 61/4511 using domain name system [DNS]
• CPC Class Codes: H04L 61/58 Caching of addresses or names

Abstract

A recursive DNS nameserver system and related domain name resolution techniques are disclosed. The DNS nameservers utilize a local cache having previously retrieved domain name resolution to avoid recursive resolution processes and the attendant DNS requests. If a matching record is found with a valid (not expired) TTL field, the nameserver returns the cached domain name information to the client. If the TTL for the record in the cache has expired and the nameserver is unable to resolve the domain name information using DNS requests to authoritative servers, the recursive DNS nameserver returns to the cache and accesses the resource record having an expired TTL. The nameserver generates a DNS response to the client device that includes the domain name information from the cached resource record. In various embodiments, subscriber information is utilized to resolve the requested domain name information in accordance with user-defined preferences.

Claims

1. A computer-implemented method of processing domain name system (DNS) requests, comprising:

receiving at a recursive nameserver a request from a client for domain name information associated with a domain name;

determining whether a local cache contains a domain name record corresponding to the domain name;

if the local cache contains the domain name record corresponding to the domain name, determining whether the domain name record is expired;

in response to determining that the domain name record is expired, issuing one or more requests for the domain name information to one or more authoritative name servers; and

if the domain name information is not received from the one or more name nameservers, transmitting a DNS response to the client that includes information from the expired domain name record.

2. The method of claim 1, further comprising:

obtaining the domain name record from the local cache if the domain name information is not received from the one or more nameservers;

setting a time-to-live (TTL) value in the domain name record to zero; and

wherein transmitting the DNS response includes transmitting the domain name record to the client.

3. The method of claim 1, wherein:

the domain name record includes an internet protocol (IP) address associated with the domain name.

4. The method of claim 3, wherein the IP address indicates a physical address for the domain name.

5. The method of claim 1, wherein the client is a first client and the request is a first request, the method further comprising:

accessing subscriber information associated with the first client;

transmitting the DNS response to the first client with information from the expired domain name record in response to the subscriber information for the first client;

receiving at the recursive nameserver a second request from a second client for domain name information associated with the domain name;

accessing subscriber information associated with the second client; and

providing a response to the second client indicating that the domain name information cannot be resolved in response to the subscriber information for the second client.

6. The method of claim 5, wherein:

the subscriber information for the first client contains one or more resolution preferences; and

the subscriber information for the second client contains one more resolution preferences.

7. The method of claim 6, further comprising:

transmitting a notification to the first client that the domain name information is expired.

8. The method of claim 7, wherein the notification is part of the response.

9. The method of claim 7, further comprising:

generating the DNS response to include an IP address for a server providing a web page containing the notification and a link to an IP address for the domain name.

10. The method of claim 1, further comprising:

associating a flag with the domain name record in the local cache; and

generating the DNS response in accordance with the flag and one or more user preferences.

11. The method of claim 1, further comprising:

detecting one or more anomalies associated with the one or more authoritative nameservers; and

modifying at least one domain name record in the local cache in response to detecting the one or more anomalies.

12. The method of claim 11, wherein modifying the at least one domain name record includes setting a flag in the domain name record indicating the domain name record should not be deleted.

13. The method of claim 1, further comprising:

determining that the domain name information has not been received from the one or more authoritative nameservers in response to a server failure response from the one or more authoritative nameservers or in response to an expiration of an allotted time period for receiving the domain name information from the one or more authoritative nameservers.

14. A system for processing domain name system requests, comprising:

a communications interface configured to exchange data with a communications network;

a local cache configured to store domain name information for domain names;

one or more processors in communication with the communications interface and the local cache, the one or more processors configured to process a request for domain name information associated with a domain name by determining whether the local cache contains the requested domain name information in a domain name record, generating and transmitting a DNS response to the client with information from the domain name record in the local cache if a TTL field of the domain name record has not expired, generating and transmitting one or more DNS requests for the domain name information from one or more authoritative servers if the TTL field of the domain name record has expired, and if the one or more authoritative servers do not respond with the domain name information, generating and transmitting a DNS response to the client with information from the domain name record in the local cache having the expired TTL field.

15. A system according to claim 14, wherein:

the local cache is stored in a cluster of recursive nameservers.

16. A system according to claim 15, wherein:

the cluster of recursive nameservers includes a first nameserver and a second nameserver, the first recursive nameserver stores a first cluster cache segment and the second nameserver stores a second cluster cache segment.

17. One or more processor readable storage devices having processor readable code stored thereon, the processor readable code programs one or more processors to perform a method comprising:

receiving at a recursive nameserver a request from a client for domain name information associated with a domain name;

determining whether a local cache contains a domain name record corresponding to the domain name;

if the local cache contains the domain name record corresponding to the domain name, determining whether the domain name record includes an expired TTL value;

in response to an expired TTL value, issuing one or more requests for the domain name information to one or more authoritative name servers; and

if the domain name information is not received from the one or more name nameservers, transmitting a DNS response to the client that includes information from the domain name record having an expired TTL value.

18. One or more processor readable storage devices according to claim 17, wherein the client is a first client and the request is a first request, the method further comprising:

accessing subscriber information associated with the first client;

determining from the subscriber information for the first client that the first client wants to receive information from domain name records having an expired TTL value;

transmitting the DNS response to the first client with information from the domain name record having the expired TTL value in response to the subscriber information for the first client;

receiving at the recursive nameserver a second request from a second client for domain name information associated with the domain name;

determining that the local cache contains the domain name record corresponding to the domain name and that the domain name record includes an expired TTL value;

issuing one or more requests for the domain name information to the one or more authoritative servers in response to the second request and determining that the domain name record contains an expired TTL value;

accessing subscriber information associated with the second client;

determining from the subscriber information for the second client that the second client does not want to receive information from domain name records having an expired TTL value; and

providing a response to the second client indicating that the domain name information cannot be resolved.

19. One or more processor readable storage devices according to claim 18, further comprising:

transmitting a notification to the first client that the domain name information includes information from a domain name record having an expired TTL value.

20. A computer program product embodied on a computer readable medium containing instructions executable by one or more processors, the executable instructions comprising:

code for determining whether a local cache contains requested domain name information in a domain name record;

code for generating and transmitting a DNS response to the client with information from the domain name record in the local cache if the domain name record is not expired;

code for generating and transmitting one or more DNS requests for the domain name information to one or more authoritative servers if the domain name record is expired; and

code for generating and transmitting a DNS response to the client with information from the expired domain name record if the one or more authoritative servers do not respond with the domain name information.

21. One or more processor readable storage devices having processor readable code stored thereon, the processor readable code for programming one or more processors to perform a method comprising:

storing subscriber information for a first client and a second client;

receiving a request from the first client for domain name information of a first domain name;

determining that a domain name record for the first domain name is expired and that one or more authoritative nameservers for the first domain name are unavailable;

transmitting a first response with the domain name record to the first client in accordance with the subscriber information for the first client; and

transmitting a second response without the domain name record to the second client in accordance with the subscriber information for the second client.

22. One or more processor readable storage devices according to claim 21, wherein the second response is a failure response.

23. One or more processor readable storage devices according to claim 21, wherein the second response includes an IP address for a web page including a notification that the domain name information is currently unavailable and a link to retrieve the domain name record that is expired.

24. One or more processor readable storage devices according to claim 21, wherein determining that the domain name record for the first domain is expired includes determining that a TTL value for the domain name record is expired.

25. A method of processing domain name system requests, comprising:

monitoring one or more authoritative nameservers for one or more anomalies, the one or more authoritative nameservers containing domain name information for a first domain name;

storing at a recursive nameserver a domain name record including at least a portion of the domain name information for the first domain name, the domain name record including a TTL value; and

in response to the one or more anomalies at the one or more authoritative nameservers, modifying the domain name record for the first domain name at the recursive nameserver.

26. A method according to claim 25, wherein the monitoring one or more authoritative nameservers for one or more anomalies includes:

receiving input from a user identifying an anomaly for the one or more authoritative nameservers.

27. A method according to claim 25, wherein the monitoring one or more authoritative nameservers for one or more anomalies includes:

determining whether the one or more authoritative nameservers fail to respond to one or more DNS requests.

28. A method according to claim 25, wherein modifying the domain name record includes storing an indication that the domain name record is not to be overwritten.

29. A method according to claim 25, wherein:

storing the domain name record includes applying a first hashing algorithm to the at least a portion of the domain name information; and

modifying the domain name record includes applying a second hashing algorithm to the at least a portion of the domain name information.

30. A computer-implemented method of processing domain name system requests, comprising:

storing at a recursive nameserver domain name information for a domain name;

issuing a domain name system request to one or more authoritative nameservers for the domain name information after said storing; and

modifying the domain name information at the recursive nameserver in response to a failure to receive a response to the DNS request from the one or more authoritative nameservers for the domain name.

31. A computer-implemented method according to claim 30, wherein the domain name information is first domain name information and the domain name is a first domain name, the method further comprising:

storing at the recursive nameserver second domain name information for a second domain name; and

modifying the second domain name information at the recursive nameserver in response to the failure to receive a response from the one or more authoritative nameservers for the first domain information.

32. A computer-implemented method according to claim 30, where the modifying the domain name record for the first domain name at the recursive nameserver includes setting a flag indicating that the domain name record is not to be overwritten.

33. A computer-implemented method of processing domain name system requests, comprising:

storing at a recursive nameserver domain name information for a domain name using a first hashing parameter;

issuing a domain name system request to one or more authoritative nameservers for the domain name after said storing; and

storing the domain name information at the recursive nameserver using a second hashing parameter in response to a failure to receive a response from the one or more authoritative nameservers for the domain name information.

34. A computer-implemented method according to claim 33, wherein:

the first hashing parameter is a closed addressing based hashing algorithm; and

the second hashing parameter is an open addressing based hashing algorithm.