Reverse notification tree for data networks

1. A method for routing a message in a network between a first data switch and a second data switch, comprising:

establishing a downstream working path for data traffic, the downstream working path including the first and second data switches;

establishing an upstream reverse notification path associated with the downstream working path for signal traffic from a destination switch in the downstream working path to a protection switch in the downstream working path,

the first and second data switches being either between or the same as either the destination or protection switches in the downstream working path;

routing the message from the second data switch to the first data switch via the upstream reverse notification path, the message providing a fault status indication for the downstream working path; and

representing the upstream reverse notification path within a reverse notification tree, the upstream reverse notification path spanning different transmission media and at least a subset of switches included in the downstream working path.

2. The method of claim 1 , wherein the upstream reverse notification path is established co-incident with the downstream working path through the network.

3. The method of claim 1 , wherein the upstream reverse notification path is established through one or more data switches that are not part of the downstream working path.

4. The method of claim 1 wherein the upstream reverse notification path is established with a topology represented by a directed acyclical graph.

5. The method of claim 1 , further comprising:

identifying an indication at the second data switch that a fault has occurred in the downstream working path downstream of the second data switch;

inhibiting the routing of the message at the second data switch on the upstream reverse notification path in response to the indication; and

causing the data traffic to be re-routed, according to the reverse notification tree, to a protection path following receipt of the fault status indication.

6. The method of claim 5 , further comprising:

initiating re-routing of the data traffic away from the downstream working path in response to inhibiting the routing of the message.

7. The method of claim 5 , wherein the indication is identified in response to not receiving a status message from a data switch downstream of the second data switch on the upstream reverse notification path.

8. The method of claim 1 , further comprising:

identifying an indication at the second data switch that a fault has occurred in the downstream working path downstream of the second data switch;

generating an error message at the second data switch in response to the indication.

9. The method of claim 8 , further comprising:

forwarding the error message to the first data switch on the upstream reverse notification path.

10. The method of claim 8 , further comprising:

forwarding the message to the protection switch on the upstream reverse notification path, the protection switch operable to re-route the data traffic away from the downstream working path.

11. A reverse notification network in a network, comprising:

a downstream switching system operable to receive downstream data along a working path;

an upstream switching system operable to provide the downstream data to the downstream switching system over the working path; and

an upstream data link operable to couple the downstream switching system to the upstream switching system, the upstream data link being part of an upstream reverse notification path established by and from a destination switching system to at least a protection switching system in the working path, the upstream data link operable to send an upstream reverse notification message from the downstream switching system to the upstream switching system, the upstream reverse notification message providing a fault status for the working path,

the upstream switching system being operable to represent the upstream reverse notification path within a reverse notification tree, the upstream reverse notification path spanning different transmission media and at least a subset of switches included in the working path.

12. The reverse notification network of claim 11 , wherein the upstream reverse notification path is coincident with the working path.

13. The reverse notification network of claim 11 , wherein the downstream switching system maintains a table identifying other upstream switching systems including the upstream switching system.

14. The reverse notification network of claim 11 , wherein the downstream switching system is operable to identify an indication that a fault has occurred in the working path, the downstream switching system operable to inhibit the sending of the upstream reverse notification message to the upstream switching system in response to the indication.

15. The reverse notification network of claim 14 ,

the upstream switching system being further operable to initiate re-routing of the data traffic away from the working path in response to inhibiting of the sending of the upstream reverse notification message; and

the upstream switching system being still further operable to cause the data traffic to be redirected, according to the reverse notification tree, to a protection path following receipt of the fault status indication.

16. The network of claim 11 , wherein the network is a Multi-Protocol Label Switching network.

17. A system for routing a message in a network between a first data switch and a second data switch, comprising:

means for establishing a downstream working path for data traffic, the downstream working path including the first and second data switches;

means for establishing an upstream reverse notification path associated with the downstream working path for signal traffic from a destination switch in the downstream working path to a protection switch in the downstream working path, the first and second data switches being either between or the same as either the destination or protection switches in the downstream working path;

means for routing the message from the second data switch to the first data switch via the upstream reverse notification path, the message providing a fault status indication for the downstream working path; and

means for representing the upstream reverse notification path within a reverse notification tree, the reverse notification path spanning different transmission media and at least a subset of switches included in the downstream working path.

18. The system of claim 17 , further comprising:

means for identifying an indication at the second data switch that a fault has occurred in the downstream working path downstream of the second data switch;

means for inhibiting the routing of the message at the second data switch on the upstream reverse notification path in response to the indication.

19. The system of claim 18 , wherein the indication is identified in response to not receiving a status message from a data switch downstream of the second data switch on the upstream reverse notification path.

20. The system of claim 18 , further comprising:

means for initiating re-routing of the data traffic away from the downstream working path in response to inhibiting the routing of the message; and

means for causing the data traffic to be re-routed, according to the reverse notification tree, to a protection path following receipt of the fault status indication.

21. The system of claim 17 , further comprising:

means for identifying an indication at the second data switch that a fault has occurred in the downstream working path downstream of the second data switch;

means for generating an error message at the second data switch in response to the indication.