Use of logical addresses to implement module redundancy

• US 6,473,396 B1
• Filed: 01/04/1999
• Issued: 10/29/2002
• Est. Priority Date: 01/04/1999
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Kumar, Sampath H.
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): HOANG, THAI D
• Application Number:
  US09/226,527
• Time in Patent Office: 1,394 Days
• Field of Search: 370/216, 370/220, 370/221, 370/228, 370/392, 370/397, 370/399, 370/395.54, 709/245, 709/253, 714/4, 714/11, 714/13
• US Class Current: 370/220
• CPC Class Codes: H04L 61/00 Network arrangements, protocols or services for addressing or naming
• CPC Class Codes: H04L 61/10 of different types
• CPC Class Codes: H04L 67/1001 for accessing one among a plurality of replicated servers
• CPC Class Codes: H04L 67/1034 Reaction to server failures by a load balancer

Abstract

An apparatus is described to implement a module redundant system using logical addresses. The apparatus may comprise a bus on which a plurality of server modules may be coupled to. One of the server modules may be configured to be active and remaining server modules may be configured to be on standby. A plurality of client modules may be coupled to the bus and configured to be in communication with the active server module using logical addresses.

Claims

1. An apparatus, comprising:

a bus;

a plurality of server modules coupled to said bus, one of said server modules configured to be active and each remaining server module configured to be on standby; and

a plurality of client modules coupled to said bus that direct information to said active server module by including with said information a logical address that is based upon a function performed by said active server module.

2. The apparatus of claim 1, wherein at least one of said client modules further comprises a lookup table that correlates a VP/VC address to said logical address.

3. The apparatus of claim 1 wherein, after a said remaining server module is converted from standby to active because said active server has ceased to function properly, said converted server accepts further information from said client modules based upon said logical address.

4. The apparatus of claim 1 wherein said information is sent in the form of a packet having a header, said header further comprising:

1) an address; and

2) an indication whether said address is a logical address or a physical address.

5. The apparatus of claim 4, wherein said indication is represented with a single bit within said header.

6. The apparatus of claim 1, wherein said active server module directs a communication to at least one of said remaining server modules configured to be on standby by including with said communication a physical address that is based upon a physical location of said standby server module that is to receive said communication.

7. The apparatus of claim 1, wherein said active server module directs a communication to at least one of said remaining server modules configured to be on standby over a separate line that is not a part of said bus.

8. The apparatus of claim 1, wherein said active server module is configured to detect a physical address and a logical address, and said remaining server modules configured to be on standby configured to detect said physical address.

9. An apparatus, comprising

a plurality of client modules that are coupled to an active server module through a bus so that said client modules can send information to said active server module, said active server configured to perform a function upon said information, said information having a destination address is a logical address, said logical address based upon said function performed by said active server, said apparatus further comprising at least one standby server module that becomes a new active server module so as to perform said function in place of said active server if said active server module fails.

10. The apparatus of claim 9 wherein, so long as said standby server module does not become said new active server, said standby server does not perform said function on said information because said information has said logical address.

11. The apparatus of claim 10 wherein, as part of standby server module transitioning to said new active server module, said new active server module begins to perform said function on said information because said information has said logical address.

12. The apparatus of claim 9 wherein said active server module directs at least one communication to said standby server module by including in said communication a second destination address that causes said communication to be received by said standby server module because said second destination address is a physical address based upon a physical location of said standby server module.

13. The apparatus of claim 12 wherein said communication helps said standby server module recognize whether or not said active server module has failed.

14. The apparatus of claim 9 wherein said active standby module directs at least one communication to said active server module by including in said communication a second destination address that causes said communication to be received by said active server module because said second destination address is a physical address that is based upon a physical location of said active server module.

15. The apparatus of claim 14 wherein a response to said communication by said active server module, or lack thereof, helps said standby server module recognize whether or not said active server module has failed.

16. The apparatus of claim 9 wherein said active server module sends additional information to a first of said client modules, said additional information having a destination address, said destination address being a physical address that is based upon a physical location of said first client module.

17. An apparatus, comprising:

a) means for sending information from a client server module to an active server module, said information having a destination address that is based upon a function that is performed by said active server module on said information;

b) means for communicating between said active server module and one or more standby server modules that can replace said active server module so as to perform said function if said active server module fails, said communicating for recognizing whether or not said active server module has failed, said communicating including a second destination address, said second destination address being a physical address that is based upon a physical location of a server module that is at the receiving end of said communicating.

18. The apparatus of claim 17 wherein said means for sending information further comprises a bus.

19. The apparatus of claim 18 wherein said means for communicating further comprises said bus.

20. The apparatus of claim 18 wherein said means for communicating further comprised a separate signal line that is not a part of said bus.

21. A method, comprising:

a) sending information from a client module to an active server module, said active server module configured to perform a function on said information, said information having a destination address, said destination address being a logical address that is based upon said function;

b) performing said function on said information;

c) recognizing that said active server has failed; and

d) sending more information from said client module to a new active server module that performs said function, said new active server having transitioned from a standby server in response to said recognizing that said active server has failed, said more information having said destination address.

22. The method of claim 21 further comprising communicating between said active server module and standby server module, prior to said recognizing that said active server module server has failed, said communicating including a second destination address, said second destination address being a physical address that is based upon a physical location of a server module that is at the receiving end of said communicating.

23. The method of claim 22 wherein said communicating further comprises said active server sending separate communications to said standby server module at fixed time intervals.

24. The method of claim 22 wherein said communicating further comprises said standby server module sending separate communications to said active server module at fixed time intervals.

25. The method of claim 21 wherein said standby server, prior to said recognizing that said active server has failed, stores said information in a buffer on a first-in first-out basis until said buffer overflows such that the earliest of said information is purged.

26. The method of claim 21 further comprising sending, prior to said recognizing that said active server has failed, additional information from said active server module to said client module, said sending including a second destination address, said second destination address being a physical address that is based upon a physical location of a client module.