Fault localization using tandem connection monitors in optical transport network

1. An Optical Transport Network (OTN) fault localization method, comprising:

localizing a fault in a multi-domain OTN network to either an inter-domain link (IrDL) or an administrative domain in the multi-domain OTN network based on monitoring endpoint tandem connection monitors;

responsive to the fault being in the administrative domain, localizing the fault within the administrative domain through a first iterative process with a first fault localization tandem connection monitor within the administrative domain; and

responsive to the fault being in the inter-domain link (IrDL), localizing the fault to a network element or a link within the inter-domain link (IrDL) utilizing a second iterative process with a second fault localization tandem connection monitor within the inter-domain link,

wherein tandem connection monitors are moved in the first iterative process and the second iterative process to isolate the fault to a specific location comprising one of a switching fabric, a transport function, and a link, and wherein the tandem connection monitors are moved between specific locations subsequent to passing a test which shows that the fault is not present at a given specific location.

2. The OTN fault localization method of claim 1 , wherein the first iterative process and the second iterative process each comprise:

determining a next monitoring point;

configuring a fault localization tandem connection monitor at the determined next monitoring point;

executing a test between the fault localization tandem connection monitor and an associated endpoint tandem connection monitor;

if the test fails, determining a location of the fault based on a position of the fault localization tandem connection monitor; and

if the test succeeds and the fault localization tandem connection monitor is not at a last test point, repeating the determining, configuring, and executing steps.

3. The OTN fault localization method of claim 2 , wherein the OTN fault localization method is implemented automatically by a control plane operating in the multi-domain OTN network or partially implemented by the control plane operating in the multi-domain OTN network along with portions controlled by user input.

4. The OTN fault localization method of claim 2 , wherein the associated endpoint tandem connection monitor is set to an operational source mode and an operational sink mode, and wherein the fault localization tandem connection monitor is set to an operational source mode and a monitor sink mode.

5. The OTN fault localization method of claim 4 , wherein the monitor source mode comprises a non-intrusive monitor in a downstream direction that generates Backward Defect Indication (BDI)/Backward Error Indication (BEI) that is forwarded to an associated source function for insertion in an upstream direction.

6. The OTN fault localization method of claim 2 , wherein tandem connection monitors comprising the endpoint tandem connection monitors and the fault localization tandem connection monitor are assigned according to a roles-based scheme in the multi-domain OTN network.

7. The OTN fault localization method of claim 6 , wherein the tandem connection monitors are automatically assigned according to the roles-based scheme by a control plane in the multi-domain OTN network upon creation of an associated service.

8. The OTN fault localization method of claim 1 , wherein the first iterative process comprises:

configuring a first fault localization tandem connection monitor at an opposing side of a first switching fabric from an endpoint tandem connection monitor associated with the administrative domain;

executing a first test between the first fault localization tandem connection monitor and the endpoint tandem connection monitor;

if the first test fails, determining the first switching fabric is a location of the fault, else removing the first fault localization tandem connection monitor and configuring a second fault localization tandem connection monitor at an opposing side of a link from the first switching fabric;

executing a second test between the second fault localization tandem connection monitor and the endpoint tandem connection monitor; and

if the second test fails, determining the link is a location of the fault, else removing the second fault localization tandem connection monitor continue placing additional fault localization tandem connection monitors downstream until the location of the fault is found responsive to a failed test.

9. The OTN fault localization method of claim 1 , wherein the second iterative process comprises:

configuring a first fault localization tandem connection monitor at an opposing side of a first link from an endpoint tandem connection monitor associated with the inter-domain link (IrDL);

executing a first test between the first fault localization tandem connection monitor and the endpoint tandem connection monitor;

if the first test fails, determining the first link is a location of the fault, else removing the first fault localization tandem connection monitor and configuring a second fault localization tandem connection monitor at an opposing side of transport function from the first link;

executing a second test between the second fault localization tandem connection monitor and the endpoint tandem connection monitor; and

if the second test fails, determining the transport function is a location of the fault, else removing the second fault localization tandem connection monitor continue placing additional fault localization tandem connection monitors downstream until the location of the fault is found responsive to a failed test.

10. An Optical Transport Network (OTN), comprising:

at least two administrative domains each comprising a plurality of OTN network elements interconnected therebetween via intra-domain (IaDL) links within the at least two administrative domains;

an inter-domain link (IrDL) interconnecting the at least two administrative domains;

a first set of endpoint tandem connection monitors within each of the at least two administrative domains;

a second set of endpoint tandem connection monitors on the inter-domain link (IrDL); and

a controller communicatively coupled to each of the plurality of OTN network elements, wherein the controller is configured to:

detect a fault;

localize the fault to either one of the at least two administrative domains or the inter-domain link (IrDL) based on monitoring the first set of endpoint tandem connection monitors and the second set of endpoint tandem connection monitors;

responsive to the fault being in one of the at least two administrative domains, localize the fault within the one of the at least two administrative domains through a first iterative process with a first fault localization tandem connection monitor within the one of the at least two administrative domains; and

responsive to the fault being in the inter-domain link (IrDL), localize the fault to a network element or a link within the inter-domain link (IrDL) utilizing a second iterative process with a second fault localization tandem connection monitor within the inter-domain link,

wherein tandem connection monitors are moved in the first iterative process and the second iterative process to isolate the fault to a specific location comprising one of a switching fabric, a transport function, and a link, and wherein the tandem connection monitors are moved between specific locations subsequent to passing a test which shows that the fault is not present at a given specific location.

11. The OTN network of claim 10 , wherein, for the first iterative process and the second iterative process, the controller is configured to:

determine a next monitoring point;

configure a fault localization tandem connection monitor at the determined next monitoring point;

execute a test between the fault localization tandem connection monitor and an associated endpoint tandem connection monitor;

if the test fails, determine a location of the fault based on a position of the fault localization tandem connection monitor; and

if the test succeeds and the fault localization tandem connection monitor is not at a last test point, repeat the determine, configure, and execute steps.

12. The OTN network of claim 11 , wherein tandem connection monitors comprising the endpoint tandem connection monitors and the fault localization tandem connection monitor are assigned according to a roles-based scheme in the multi-domain OTN network.

13. The OTN network of claim 10 , wherein the controller is configured to implement a control plane, wherein the control plane is configured to isolate the fault.

14. The OTN network of claim 11 , wherein the associated endpoint tandem connection monitor is set to an operational source mode and an operational sink mode, and wherein the fault localization tandem connection monitor is set to an operational source mode and a monitor sink mode.

15. The OTN network of claim 14 , wherein the monitor source mode comprises a non-intrusive monitor in a downstream direction that generates Backward Defect Indication (BDI)/Backward Error Indication (BEI) that is forwarded to an associated source function for insertion in an upstream direction.