Method for switching between active and standby units using IP swapping in a telecommunication network

• US 6,487,591 B1
• Filed: 12/08/1998
• Issued: 11/26/2002
• Est. Priority Date: 12/08/1998
• Status: Expired due to Term

• Current Assignee: Cisco Systems, Inc.
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Sustek, Richard F., Budhraja, Virendra Kumar
• Primary Examiner(s): Maung, Zarni
• Assistant Examiner(s): CALDWELL, ANDREW T
• Application Number:
  US09/208,615
• Time in Patent Office: 1,449 Days
• Field of Search: 709/220, 709/221, 709/223, 709/228, 709/245, 370/216-220, 714/1-4, 714/10, 714/13, 379/9, 713/1, 713/100, 710/104
• US Class Current: 709/223
• CPC Class Codes: H04L 1/22 using redundant apparatus to increase reliability

Abstract

Replacing the functionality of an active digital loop carrier subsystem (DLCSS) or active module with a standby DLCSS or standby module in an IP addressable telecommunication switch is effected by providing only a single externally-known IP address for the module pair and then swapping the IP address of the active module for the IP address of the standby module so that externally-connected devices recognize only the IP address for the module in use. A central network management station in communication with a local nonvolatile memory element controls the IP address swapping.

Claims

1. A communications system comprising:

a signal redirection element comprising a first memory location and a second memory location;

a first subsystem comprising a first memory element, the first memory element storing an address stored in the first memory location, the first subsystem operable to receive communications addressed to the address stored in the first memory clement;

a second subsystem comprising a second memory element, the second memory element storing an address stored in the second memory location, the second subsystem operable to receive communications addressed to the address stored in the second memory element; and

the signal redirection element operable to store an active subsystem address in the first memory location and to store a standby subsystem address in the second memory location, such that the first subsystem acts in an active status and the second subsystem acts in a standby status, the signal redirection element further operable to sense a prompt to change active status of the first subsystem, and, responsive to sensing the prompt, to store the active subsystem address in the second memory location and to store the standby subsystem address in the first memory location, the change of addresses in the signal redirection element mirrored in the first memory element and the second memory element, thus swapping the active status and the standby status between the first subsystem and the second subsystem and causing the second subsystem to operate in the active status independent of the first subsystem.

2. The system of claim 1, further comprising a central controller coupled to the first subsystem and the second subsystem, the central controller communicating with a selected one of the first subsystem and the second subsystem using the active subsystem address.

3. The system of claim 1, wherein the signal redirection element is an electrically erasable programmable read-only memory (EEPROM).

4. The system of claim 1, wherein the signal redirection element is further operable to sense the prompt during a polling cycle and to store the active subsystem address in the second memory location during the polling cycle.

5. The system of claim 1, wherein:

the first subsystem comprises a first plurality of line interface cards and a first memory element, the first memory element storing the address stored in the first memory location; and

the second subsystem comprises a second plurality of line interface cards and a second memory element, the second memory element storing the address stored in the second memory location.

6. The system of claim 1, wherein the prompt is a fault in the first subsystem.

7. A method for providing switchover from an active subsystem to a standby subsystem comprising:

storing an active subsystem address in a first memory location of a signal redirection element;

storing a standby subsystem address in a second memory location of the signal redirection element;

duplicating content of the first memory location in a first memory element of a first subsystem, the first memory element storing an address for communications to the first subsystem;

duplicating content of the second memory location in a second memory element of a second subsystem, the second memory element storing an address for communications to the second subsystem;

sensing a prompt to change active status of the first subsystem; and

in response to the prompt;

storing the active subsystem address in the second memory location of the signal redirection element; and

storing the standby subsystem address in the first memory location of the signal redirection element, the change of addresses in the signal redirection element mirrored in the first memory element and the second memory element, thus causing the second subsystem to operate in an active status independent of the first subsystem.

8. The method of claim 7, wherein the signal redirection element is an electrically erasable programmable read-only memory (EEPROM) and the first memory element and the second memory element are volatile memory devices.

9. The method of claim 7, wherein the prompt is a fault in the first subsystem.

10. The method of claim 7, further comprising:

sensing the prompt within a polling cycle; and

in response to the prompt;

storing the active subsystem address in the second memory location of the signal redirection element during the polling cycle; and

storing the standby subsystem address in the first memory location of the signal redirection element during the polling cycle.

11. A communications apparatus comprising:

a back plane comprising a signal redirection element having a first memory location and a second memory location;

a first subsystem comprising a first plurality of line cards coupled to the back plane and a first main controller subsystem (MCS) coupled to the back plane, the first MCS having a first memory element, the first memory element mirroring an address stored in the first memory location;

a second subsystem comprising a second plurality of line cards coupled to the back plane and a second main controller subsystem (MCS) coupled to the back plane, the second MCS having a second memory element, the second memory element mirroring an address stored in the second memory location;

the signal redirection element operable to store an active system address in the first memory location and to store a standby subsystem address in the second memory location, the signal redirection element further operable to sense a prompt to change active status of the first subsystem, and, responsive to sensing the prompt, to store the active system address in the second memory location and the standby subsystem address in the first memory location, the change of addresses in the signal redirection element mirrored in the first memory element and the second memory element thus causing the second subsystem to operate in an active status and the first subsystem to operate in a standby status; and

the active subsystem operable to receive network traffic addressed to the active system address using the active line cards, and the active MCS operable to switch the network traffic between the active line cards, such that the apparatus services the network traffic without routing the network traffic through the inactive subsystem.