Control plane architecture for automatically switched optical network

• US 20030235153A1
• Filed: 03/31/2003
• Published: 12/25/2003
• Est. Priority Date: 06/20/2002
• Status: Active Grant

• Current Assignee: Ciena Corporation, Ciena Luxembourg S.a.r.l. (Ciena Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Lee, Yang Sup, Oprea, Dan
• Granted Patent: US 7,339,889 B2
• Time in Patent Office: Days
• US Class Current: 370/229
• CPC Class Codes: H04Q 11/0062 Network aspects
• CPC Class Codes: H04Q 11/0071 Provisions for the electrical-optical layer interface
• CPC Class Codes: H04Q 2011/0079 Operation or maintenance aspects
• CPC Class Codes: H04Q 2011/0086 Network resource allocation, dimensioning or optimisation

Abstract

Methods and apparatus are provided for bandwidth management within Automatically Switched Optical Networks. An Optical Connection Controller (OCC) provides threshold based load balancing using an upper and a lower threshold for each port of a network element, and once port usage exceeds the upper threshold no more connections are allowed through the port until the port usage falls below the lower threshold. The OCC also minimizes fragmentation of a port so as to reduce the probability of call rejection as a result of fragmentation. The OCC also maintains a database of shortest paths between a network element and each destination, so that connections can be re-established quickly through alternate paths in the event of failure of a link or node. The OCC also provides the entire network with notification of a fault, thereby enhancing CR-LDP fault notification messaging.

Claims

1. A method of determining an acceptability of a port for a connection in an Automatically Switched Optical Network, the port having a current port load, the method comprising:

if the current port load is below a lower threshold, determining that the port is acceptable;

if the current port load is above an upper threshold, determining that the port is not acceptable; and

if the current port load is between the lower threshold and the upper threshold, determining whether the current port load was most recently above the upper threshold or below the lower threshold, and;

if the current port load was most recently above the upper threshold, determining that the port is not acceptable; and

if the current port load was most recently below the lower threshold, determining that the port is acceptable.

2. The method of claim 1 wherein determining whether the current port load was most recently above the upper threshold or below the lower threshold comprises:

maintaining a value of a flag by setting the value of the flag to a first value if the current port load falls below the lower threshold and setting the value of the flag to a second value if the current port load reaches the upper threshold;

if the value of the flag is equal to the first value, determining that the current port load was most recently below the lower threshold; and

if the value of the flag is equal to the second value, determining that the current port load was most recently above the upper threshold.

3. The method of claim 1 wherein the step of determining a current port load comprises signalling a network element on which the port is located.

4. The method of claim 1 further comprising maintaining a port load database for storing the current port load, and wherein determining a current port load comprises consulting the port load database using the port as an index.

5. The method of claim 4 further comprising updating the port load database to take into account newly established connections.

6. The method of claim 4 wherein maintaining a port load database comprises storing one current port load for each of a plurality of destinations, and wherein the step of consulting the port load database further uses a destination of a connection as an index.

7. The method of claim 6 further comprising:

maintaining a database of lower thresholds; and

selecting the lower threshold from the database of lower thresholds using the destination of the connection as an index.

8. The method claim 4 wherein maintaining the port load database comprising one current port load for each of a plurality of paths, and wherein the step of consulting the port load database further uses a path of a connection as an index.

9. The method of claim 8 further comprising:

maintaining a database of lower thresholds; and

selecting the lower threshold from the database of lower thresholds using the path of the connection as an index.

10. An Optical Connection Controller adapted to carry out the method of claim 1.

11. A processor comprising instructions for carrying out the method of claim 1.

12. A method of assigning a starting slot to a connection through a port in a network element of an Automatically Switched Optical Network, the port having a plurality of sequentially numbered slots, including a first slot, the method comprising;

beginning with the first slot, repeating for each slot in sequential order until an acceptable slot is found;

determining whether the slot is an acceptable slot for the connection; and

if the slot is an acceptable slot for the connection, assigning the slot as the starting slot of the connection.

13. The method of claim 12 wherein determining whether a slot is an acceptable slot comprises determining whether there are sufficient contiguous free slots including and following the slot to accommodate a requested bandwidth for the connection.

14. The method of claim 12 wherein determining whether a slot is an acceptable slot comprises:

determining whether there are sufficient contiguous free slots including and following the slot to accommodate a requested bandwidth for the connection, and whether a provisioned configuration indicates that the slot has a number which may be assigned to the connection.

15. The method of claim 12 wherein the first slot is the slot having a number lower than all other slots.

16. The method of claim 12 wherein the first slot is the slot having a number greater than all other slots.

17. An Optical Connection Controller adapted to carry out the method of claim 12.

18. A processor comprising instructions for carrying out the method of claim 12.

19. A method of relaying a notification of a fault in an Automatically Switched Optical Network including a first Optical Connection Controller (OCC) and at least one other OCC, comprising:

at the first OCC, receiving the notification of the fault; and

relaying the notification of the fault to all of the at least one other OCCs.

20. A method by which an Optical Connection Controller (OCC) relays a notification of a fault in an Automatically Switched Optical Network, comprising:

receiving the notification of the fault;

determining whether the notification has previously been relayed;

if the notification has not previously been relayed, relaying the notification to each OCC within a set of OCCs.

21. The method of claim 20 wherein the step of determining whether the notification has previously been relayed comprises:

determining a message identification of the notification;

comparing the message identification with a stored message identification;

if the message identification is equal to the stored message identification, determining that the notification has already been relayed; and

if the message identification is not equal to the stored message identification;

determining that the notification has not already been relayed; and

replacing the stored message identification with the message identification.

22. The method of claim 20 wherein the set of OCCs includes each neighbouring OCC to which the OCC is linked.

23. An Optical Connection Controller adapted to carry out the method of claim 20.

24. A processor comprising instructions for carrying out the method of claim 20.

25. A method of selecting a path between a network element and a destination in an Automatically Switched Optical Network having links interconnecting nodes, comprising the steps of:

maintaining a database of paths between the network element and the destination; and

selecting one of the paths from the database.

26. The method of claim 25 further comprising the step of generating the database of paths, comprising for each one of at least one path:

eliminating from a model of the Network none or more of the links;

performing a Dijkstra computation on the model of the Network, in which the none or more of the links have been eliminated, using bandwidth availability along each link as a cost function;

from the Dijkstra computation, selecting a shortest path to the destination; and

storing the shortest path in the database in association with the destination.

27. An Optical Connection Controller adapted to carry out the method of claim 25.

28. A processor comprising instructions for carrying out the method of claim 25.

29. An Optical Connection Controller adapted to carry out the method of claim 26.

30. A processor comprising instructions for carrying out the method of claim 26.

31. An Optical Connection Controller (OCC) for use in an Automatically Switched Optical Network, the OCC being responsible for a network element having at least one port, each port having a variable port load and a plurality of slots including a first slot, the OCC being adapted to:

determine that a port is acceptable for new connections until the port load of the port reaches an upper threshold, after which it is determined that the port is not acceptable for new connections until the port load falls below a lower threshold; and

assign a starting slot to a connection such that the starting slot is as close to the first slot as permitted by a bandwidth requirement of the connection.