Low-overhead fault-tolerance techniques for optical and other cross-connect systems

• US 6,850,704 B1
• Filed: 07/12/2000
• Issued: 02/01/2005
• Est. Priority Date: 09/14/1999
• Status: Expired due to Term

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Dave, Bharat P.
• Primary Examiner(s): Sedighian, M. R.
• Assistant Examiner(s): Kim, David S
• Application Number:
  US09/614,436
• Time in Patent Office: 1,665 Days
• Field of Search: 359/110, 359/117, 359/128, 359/139, 359/135, 370/220, 370/217, 370/360, 370/389, 370/411, 714/821, 714/797, 714/766, 714/820, 714/822, 714/823, 714/824, 714/819
• US Class Current: 398/2
• CPC Class Codes: H04L 1/22 using redundant apparatus to increase reliability
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 2011/0043 Fault tolerance
• CPC Class Codes: H04Q 2011/0077 Labelling aspects, e.g. multiprotocol label switching [MPLS], G-MPLS, MPAS

Abstract

Fault tolerance is provided in a cross-connect system having only duplicated switch fabrics, instead of the triplicated switch fabrics of the prior art. In addition to the two information switch fabrics, the cross-connect system has a relatively small code switch fabric which switches check-code signals generated at each input interface for each input signal sent to an information switch fabric. Fault-detection and error-recovery components in each output interface (1) generate local check-code signals for each outgoing signals received from an information switch fabric and (2) compare those local check-code signals to the corresponding check-code signal received from the code switch fabric to detect a failure and to select a healthy signal as the output signal for that output interface. In one embodiment, input and output interfaces are clustered, and the corresponding input and output check-code signals are multiplexed, for even greater savings in overhead (e.g., fewer check-code cables to and from the code switch fabric).

Claims

1. A cross-connect system, comprising:

(a) two information switch fabrics;

(b) a plurality of input interfaces, each of which is coupled to transmit an input information signal to each of the two information switch fabrics;

(c) a plurality of output interfaces, each of which is coupled to receive an output information signal from each of the two information switch fabrics; and

(d) a code switch fabric, coupled to receive an input check-code signal from each input interface corresponding to the corresponding input information signal and to transmit an output check-code signal to the corresponding output interface, wherein;

total number of all input check-code signal bits based on each portion of the corresponding input information signal is smaller than the total number of bits in said each portion;

the code switch fabric has a smaller data size than each of the two information switch fabrics; and

each output interface generates a local check-code signal for an output information signal and compares the local check-code signal to the output check-code signal to select one of the two output information signals as an output signal for the output interface.

2. The invention of claim 1, wherein each output interface generates a local check-code signal for each of the two output information signals and compares the two local check-code signals to the output check-code signal to select one of the two output information signals as the output signal for the output interface.

3. The invention of claim 1, wherein:

the two information switch fabrics are optical switch fabrics; and

the code switch fabric is an electrical switch fabric.

4. The invention of claim 1, wherein:

one or more sets of two or more input interfaces are clustered together to form one or more input interface clusters, wherein the input check-code signals from the two or more input interfaces of each input interface cluster are multiplexed together for transmission from the input interface cluster to the code switch fabric over a single input cable; and

one or more sets of two or more output interfaces are clustered together to form one or more output interface clusters, wherein the output check-code signals for the two or more output interfaces of each output interface cluster are multiplexed together for transmission from the code switch fabric to the output interface cluster over a single output cable.

5. The invention of claim 1, wherein two or more input check-code signals are shuffled together prior to routing through the code switch fabric.

6. The invention of claim 1, wherein each output interface comprises:

(1) two buffers, each coupled to receive an output information signal from a different information switch fabric;

(2) two code generation modules, each configured to generate a local check-code signals for a different output information signal;

(3) a compare module configured to compare the two local check-code signals with the output check-code signal received from the code switch fabric; and

(4) a selector configured to select one of the two output information signals as the output signal for the output interface based on the comparison by the compare module.

7. The invention of claim 1, wherein signals from different input interfaces are differently delayed to account for differences in distance between the input interfaces and the switch fabrics and between the switch fabrics and the output interfaces.

8. The invention of claim 1, wherein:

the two information switch fabrics are optical switch fabrics;

the code switch fabric is an electrical switch fabric;

one or more sets of two or more input interfaces are clustered together to form one or more input interface clusters, wherein the input check-code signals from the two or more input interfaces of each input interface cluster are multiplexed together for transmission from the input interface cluster to the code switch fabric over a single input cable;

one or more sets of two or more output interfaces are clustered together to form one or more output interface clusters, wherein the output check-code signals for the two or more output interfaces of each output interface cluster are multiplexed together for transmission from the code switch fabric to the output interface cluster over a single output cable;

two or more input-check-code signals are shuffled together prior to routing through the code switch fabric;

each output interface comprises;

(1) two buffers, each coupled to receive an output information signal from a different information switch fabric;

(2) two code generation modules, each configured to generate a local check-code signals for a different output information signal;

(3) a compare module configured to compare the two local check-code signals with the output check-code signal received from the code switch fabric; and

(4) a selector configured to select one of the two output information signals as the output signal for the output interface based on the comparison by the compare module; and

signals from different input interfaces are differently delayed to account for differences in distance between the input interfaces and the switch fabrics and between the switch fabrics and the output interfaces.

9. A method for switching signals in a cross-connect system, comprising the steps of:

(a) generating an input check-code signal for each input information signal, the total number of all input check-code signal bits based on each portion of the corresponding input information signal is smaller than the total number of bits in said each portion;

(b) routing each input information signal through two information switch fabrics to generate two output information signals for the input information signal;

(c) routing the input check-code signal through a code switch fabric to generate an output check-code signal, wherein the code switch fabric has a smaller data size than each of the two information switch fabrics;

(d) generating a local check-code signal for an output information signal; and

(e) comparing the output check-code signal to the local check-code signal to select one of the two output information signals as an output signal corresponding to the input information signal.

10. The invention of claim 9, wherein:

step (d) comprises the step of generating a local check-code signal for each of the two output 3 information signals; and

step (e) comprises the step of comparing the output check-code signal to the two local check-code signals to select one of the two output information signals as the output signal corresponding to the input information signal.

11. The invention of claim 9, wherein:

the two information switch fabrics are optical switch fabrics; and

the code switch fabric is an electrical switch fabric.

12. The invention of claim 9, wherein:

the input check-code signals for two or more different input information signals are multiplexed together for transmission to the code switch fabric over a single input cable; and

the output check-code signals for two or more different information signals are multiplexed together for transmission from the code switch fabric over a single output cable.

13. The invention of claim 9, wherein two or more input check-code signals are shuffled together prior to routing through the code switch fabric.

14. The invention of claim 9, wherein different signals are differently delayed to account for differences in distance to and from the switch fabrics.

15. The invention of claim 9, wherein:

step (d) comprises the step of generating a local check-code signal for each of the two output information signals;

step (e) comprises the step of comparing the output check-code signal to the two local check-code signals to select one of the two output information signals as the output signal corresponding to the input information signal;

the two information switch fabrics are optical switch fabrics;

the code switch fabric is an electrical switch fabric;

the input check-code signals for two or more different input information signals are multiplexed together for transmission to the code switch fabric over a single input cable;

the output check-code signals for two or more different information signals are multiplexed together for transmission from the code switch fabric over a single output cable;

two or more input check-code signals are shuffled together prior to routing through the code switch fabric; and

different signals are differently delayed to account for differences in distance to and from the switch fabrics.