Canonical name (CNAME) handling for global server load balancing

• US 7,574,508 B1
• Filed: 08/07/2002
• Issued: 08/11/2009
• Est. Priority Date: 08/07/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Foundry Networks Incorporated (Broadcom, Inc.)
• Inventors: Kommula, Sunanda Lakshmi
• Primary Examiner(s): Winder; Patrice
• Assistant Examiner(s): Duong; Thomas
• Application Number:
  US10/214,921
• Time in Patent Office: 2,561 Days
• Field of Search: 709/226, 709238-244, 709/223, 709/203
• US Class Current: 709/226
• CPC Class Codes: H04L 61/4511 using domain name system [DNS]
• CPC Class Codes: H04L 67/1001 for accessing one among a plurality of replicated servers
• CPC Class Codes: H04L 67/1008 based on parameters of servers, e.g. available memory or workload monitoring of computer activity G06F11/30
• CPC Class Codes: H04L 67/101 based on network conditions
• CPC Class Codes: H04L 67/1012 based on compliance of requirements or conditions with available server resources
• CPC Class Codes: H04L 67/1021 based on client or server locations

Abstract

Canonical name (CNAME) handling is performed in a system configured for global server load balancing (GSLB), which orders IP addresses into a list based on a set of performance metrics. When the GSLB switch receives a reply from an authoritative DNS server, the GSLB switch scans the reply for CNAME records. If a CNAME record is detected and it points to a host name configured for GSLB, then a GSLB algorithm is applied to the reply. This involves identifying the host name (pointed to by the CNAME record) in the reply and applying the metrics to the list of returned IP addresses corresponding to that host name, to reorder the list to place the “best” IP address at the top. If the CNAME record in the reply points to a host name that is not configured for GSLB, then the GSLB sends the reply unaltered to the inquiring client.

Claims

1. A method of providing load balancing in a network, the method comprising:

receiving, by a load balance switch, a domain name system (DNS) reply to a DNS query to resolve a name into a network address;

checking, by said load balance switch, the received DNS reply for an alias associated with a canonical name (CNAME) record; and

if the alias associated with the CNAME record is detected in said received DNS reply by said checking and if a host name that is mapped to by the alias is configured for load balancing, applying by said load balance switch a load balancing algorithm to a list of network addresses provided by the received DNS reply.

2. The method of claim 1, further comprising:

if the alias associated with the CNAME record is detected by said checking, determining by said load balance switch if said host name that is mapped to by the alias is configured for load balancing,

wherein said applying the load balancing algorithm to the list of network addresses is performed if the host name, associated with the list of network addresses, is said determined by said load balance switch to be configured for load balancing.

3. The method of claim 1 wherein the list of network addresses provided in the DNS reply includes virtual IP addresses.

4. The method of claim 1, further comprising sending by said load balance switch the list of network addresses, having the load balancing algorithm applied thereto, to a client program.

5. The method of claim 1 wherein said applying the load balancing algorithm includes arranging, by said load balance switch, the network addresses in said list based on a set of performance metrics.

6. The method of claim 2, further comprising if the host name is determined by said load balance switch not to be configured for load balancing, sending by said load balance switch the list of network addresses as a response to said DNS query without applying the load balancing algorithm to the list.

7. The method of claim 1, further comprising if the alias associated with the CNAME record is not detected by said checking:

determining by said load balance switch if said host name, which corresponds to said list of network addresses provided by the DNS reply, is configured for load balancing;

if that host name is determined by said load balance switch to be configured for load balancing, applying by said load balance switch the load balancing algorithm to said corresponding list of network addresses; and

if that host name is determined by said load balance switch not to be configured for load balancing, sending by said load balance switch said corresponding list of network addresses, unaltered by the load balancing algorithm, as a response to said DNS query.

8. The method of claim 1, further comprising enabling said load balance switch to check said DNS reply for the alias associated with the CNAME record.

9. The method of claim 1 wherein the alias includes a common zone relative to the host name but a different host.

10. A method for providing load balancing in a network, the method comprising:

receiving, by a load balance switch, a domain name system (DNS) reply to a DNS query to resolve a name;

checking, by said load balance switch, the received DNS reply for an alias associated with a canonical name (CNAME) record;

if the alias associated with the CNAME record is detected in said received DNS reply by said checking, determining by said load balance switch if a host name that is mapped to by the alias is configured for load balancing; and

if the host name is said determined to be configured for load balancing, arranging by said load balance switch a list of network addresses provided by the received DNS reply based on a set of performance metrics;

wherein if the host name is said determined not to be configured for load balancing, said load balance switch does not apply at least one of the performance metrics to said list of network addresses.

11. The method of claim 10, further comprising if the alias associated with the CNAME record is not detected in said received DNS reply by said checking:

determining, by said load balance switch, whether said host name, which corresponds to said list of network addresses provided by the received DNS reply is configured for load balancing; and

if that host name is said determined to be configured for load balancing, applying by said load balance switch the load balancing algorithm to said list of network addresses;

wherein if that host name is said determined not to be configured for load balancing, said load balance switch does not alter said list of network addresses by the load balancing algorithm.

12. The method of claim 10 wherein the alias that maps to the host name includes a common zone relative to the host name but a different host.

13. The method of claim 10, further comprising at least one of enabling and disabling said load balance switch to check for the alias associated with the CNAME record.

14. The method of claim 10 wherein said determining if the host name that is mapped to by the alias is configured for load balancing includes:

identifying by the load balance switch the host name from within the received DNS reply; and

checking by the load balance switch at least one configuration setting to determine if the identified host name is configured for load balancing.

15. The method of claim 10 wherein said determining if the host name that is mapped to by the alias is configured for load balancing includes:

if the host name is not indicated in the received DNS reply, identifying by the load balance switch the host name from the CNAME record; and

checking by the load balance switch at least one configuration setting to determine if the identified host name is configured for load balancing.

16. The method of claim 10 wherein said checking the received DNS reply for the alias associated with the CNAME record includes identifying by said load balance switch the CNAME record in the received DNS reply as an address record that points to another address record.

17. An article of manufacture, comprising:

a storage medium having instructions stored thereon that are executable by a load balance switch to;

check, by said load balance switch, a domain name system (DNS) reply that is received by said load balance switch and that replies to a DNS query to resolve a names for an alias associated with a canonical name (CNAME) record; and

if the alias associated with the CNAME record is detected in said received DNS reply by said check and if a host name that is mapped to by the alias is configured for load balancing, apply by said load balance switch a load balancing algorithm to a list of network addresses provided by the received DNS reply.

18. The article of manufacture of claim 17 wherein the storage medium further includes instructions stored thereon that are executable by said load balance switch to:

determine by said load balance switch if said host name that is mapped to by the alias is configured for load balancing, if the alias associated with the CNAME record is detected by said check,

wherein said apply the load balancing algorithm to the list of network addresses is performed, if the host name, associated with the list of network addresses, is said determined by said load balance switch to be configured for load balancing.

19. The article of manufacture of claim 17 wherein the storage medium further includes instructions stored thereon that are executable by said load balance switch to:

send by said load balance switch the list of network addresses, having the load balancing algorithm applied thereto, to a client program.

20. The article of manufacture of claim 17 wherein the instructions to apply the load balancing algorithm to the list of network addresses include instructions executable by said load balance switch to:

arrange by said load balance switch the network addresses as an ordered list based on a set of performance metrics.

21. The article of manufacture of claim 18 wherein the storage medium further includes instructions stored thereon that are executable by said load balance switch to:

send the list of network addresses without applying the load balancing algorithm to the list, if the host name is said determined not to be configured for load balancing.

22. The article of manufacture of claim 17 wherein the storage medium further includes instructions stored thereon that are executable by said load balance switch to, if the alias associated with the CNAME record is not detected by said check:

determine by said load balance switch if said host name corresponding to said list of network addresses provided by the received DNS reply is configured for load balancing;

if that host name is said determined to be configured for load balancing, apply by said load balance switch the load balancing algorithm to said list of network addresses,

wherein if that host name is said determined not to be configured for load balancing, said load balance switch does not alter said list of network addresses with the load balancing algorithm.

29. The article of manufacture of claim 17 wherein the instructions to apply said load balancing algorithm to said list of network addresses includes instructions executable by said load balance switch to:

place, by said load balance switch, a preferred network address at a top of said list of network addresses, the storage medium further including instructions stored thereon that are executable by said load balance switch to;

provide, by said load balance switch, said list of network addresses, having said preferred network address placed at the top, to a client program.

23. An apparatus to provide load balancing in a network, the apparatus comprising:

a load balance switch including;

a proxy module to receive domain name system (DNS) reply to a DNS query to resolve a name;

a parser in cooperation with the proxy module to check the received DNS reply for an alias associated with a canonical name (CNAME) record; and

a controller coupled to the proxy module and to the parser, the controller being operative to, if the alias associated with the CNAME record is detected in said received DNS reply by the parser and if a host name that is mapped to by the alias is configured for load balancing, apply a load balancing algorithm to a list of network addresses provided by the received DNS reply.

24. The apparatus of claim 23 wherein the DNS reply to the DNS query is received by the proxy module from an authoritative domain name server.

25. The apparatus of claim 23 wherein the controller is further operative to determine if said host name that is mapped to by the alias is configured for load balancing.

26. The apparatus of claim 25 wherein the controller is further operative to send the list of network addresses, via the proxy module, without application of the load balancing algorithm to the list, if the host name is determined by the controller to not be configured for load balancing.

27. The apparatus of claim 23 wherein the load balancing algorithm includes an arrangement of the network addresses provided by the received DNS reply as an ordered list based on a set of performance metrics.

28. The apparatus of claim 23 wherein the controller is further operative to, if the alias associated with the CNAME record is not detected in said received DNS reply by said parser, determine if said host name, which corresponds to said list of network addresses provided by the received DNS reply, is configured for load balancing, wherein:

if that host name is said determined to be configured for load balancing by the controller, the controller is operative to apply the load balancing algorithm to said list of network addresses, and wherein;

if that host name is determined not to be configured for load balancing by the controller, the controller is operative to send said list of network addresses, unaltered by the load balancing algorithm, to a client program.