Communication system and method providing optimal restoration of failed paths
First Claim
1. In a telecommunications network having a plurality of nodes interconnected by a plurality of spans each having working and spare links, a method of restoring traffic disrupted by at least one failed link, comprising the steps of:
- (a) designating one of a pair of nodes bracketing said one failed link a sender node and an other of said pair of nodes a chooser node, and nodes interconnecting said sender and chooser nodes via said plurality of spans tandem nodes;
(b) transmitting restoration signals from said sender node to said chooser node along said interconnected tandem nodes, each of said restoration signals including data identifying said sender and chooser nodes, index data and probability data indicative of the likelihood that the path traversed by said each restoration signal is to be used for restoring the disrupted traffic;
(c) adding to said each restoration signal contention data as said each restoration data traverses along each one of said tandem nodes;
(d) after receiving said restoration signals for a predetermined time period, said chooser node transmitting reverse restoration signals to backtrack the restoration paths traversed by said received restoration signals, said reverse restoration signals each including particular contention and probability of use data derived from the data carried by a corresponding restoration signal received by said chooser node; and
(e) upon receipt of an expected number of said reverse restoration signals, said sender node reviewing the respective contention and probability of use data attached to each of said received reverse restoration signals to select an optimal restoration path for restoring the disrupted traffic.
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Accused Products
Abstract
To restore partial outages within a communication network having numerous switching nodes and links interconnecting the nodes, a three-stage distributed restoration protocol is activated to use spare links to bypass failed links and restore normal network connectivity. The three-stage protocol detects and resolves contention for spare resources among separate restoration processes and is therefore particularly advantageous in the event of multiple simultaneous network failures. A conservative flooding approach is used during the first forward signalling stage. Data elements added to the forward signals convey the likelihood that the path will be needed for restoration. The second reverse signalling stage uses reverse signals with attached contention data to detect contention among separate processes for spare resources and to alert the respective processes. The final path implementation stage involves reviewing the reverse signals and using the attached contention data to make informed choices of restoration paths that result in the highest degree of overall network restoration. The present invention, including node logic and specific signal structures and multiple-pass signalling, allows for shared awareness among diverse restoration processes so that they may work collectively to best utilize available spare resources.
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Citations
27 Claims
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1. In a telecommunications network having a plurality of nodes interconnected by a plurality of spans each having working and spare links, a method of restoring traffic disrupted by at least one failed link, comprising the steps of:
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(a) designating one of a pair of nodes bracketing said one failed link a sender node and an other of said pair of nodes a chooser node, and nodes interconnecting said sender and chooser nodes via said plurality of spans tandem nodes; (b) transmitting restoration signals from said sender node to said chooser node along said interconnected tandem nodes, each of said restoration signals including data identifying said sender and chooser nodes, index data and probability data indicative of the likelihood that the path traversed by said each restoration signal is to be used for restoring the disrupted traffic; (c) adding to said each restoration signal contention data as said each restoration data traverses along each one of said tandem nodes; (d) after receiving said restoration signals for a predetermined time period, said chooser node transmitting reverse restoration signals to backtrack the restoration paths traversed by said received restoration signals, said reverse restoration signals each including particular contention and probability of use data derived from the data carried by a corresponding restoration signal received by said chooser node; and (e) upon receipt of an expected number of said reverse restoration signals, said sender node reviewing the respective contention and probability of use data attached to each of said received reverse restoration signals to select an optimal restoration path for restoring the disrupted traffic. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of restoring communications in a telecommunications network having a plurality of nodes interconnected by a plurality of spans each having working and spare links, at least one of said links having failed, comprising the steps of:
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(a) designating one of a pair of nodes bracketing said one failed link a sender node and an other of said pair of nodes a chooser node, and nodes interconnecting said sender and chooser nodes via said plurality of spans tandem nodes; (b) said sender node i) assessing the number of failed links; ii) identifying a span and spare ports within said span for flooding restoration signals; iii) limiting the number of restoration signals to be transmitted along spare links in said span to the number of failed links assessed; iv) selecting an output port for each restoration signal to be sent; v) repeating steps ii to iv for each span connected to said sender node; vi) transmitting at least one restoration signal to said chooser node through each output port of said each span, each of said restoration signals including data identifying said sender and chooser nodes, and probability data indicative of the likelihood that the path traversed by said one restoration signal is to be used for restoring the communications carried by said one failed link; (c) each of said tandem nodes, upon receipt of a restoration signal at a port of a span connected thereto, updating a contention metric associated with said port to indicate the probability that said port is to be used for restoration of the disrupted traffic; maintaining a record of restoration signals dispatched along each span connected to said each tandem node for said pair of sender and chooser nodes; selecting the port with the lowest contention metric as an output port for forwarding received restoration signals to nodes downstream from said each tandem node; (d) said chooser node, after receiving restoration signals for a predetermined period of time, choosing from among the received restoration signals one having a corresponding restoration path; calculating a probability of use metric for said chosen restoration path; transmitting a reverse restoration signal including a probability of use metric to said chosen restoration path, said reverse restoration signal including particular contention and probability of use data derived from data carried by said chosen restoration signal; (e) said sender node, upon receipt of an expected number of said reverse restoration signal, reviewing the respective contention and probability of use data attached to each of said received reverse restoration signals to select an optimal restoration path for restoring the communications carried by said failed link. - View Dependent Claims (16, 17, 18, 19)
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20. In a telecommunications network having a plurality of nodes interconnected by a plurality of spans each having working and spare links, a system for restoring traffic disrupted by at least one failed link, one of a pair of nodes bracketing said one failed link being designated a sender node and an other of said pair of nodes being designated a chooser node, and nodes interconnecting said sender and chooser nodes via said plurality of spans being designated tandem nodes, said system comprising:
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processor switch means in said sender node for flooding restoration signals to said chooser node along said interconnected tandem nodes, each of said restoration signals including data identifying said sender and chooser nodes, index data and probability data indicative of the likelihood that the path traversed by said each restoration signal is to be used for restoring the disrupted traffic; processor switch means in each of said tandem nodes for adding to said each restoration signal contention data as said each restoration data traverses along said each tandem node; and processor switch means in said chooser node for receiving said restoration signals, after receiving said restoration signals for a predetermined time period, said chooser node processor switch means transmitting reverse restoration signals to backtrack the restoration paths traversed by said received restoration signals, said reverse restoration signals each including particular contention and probability of use data derived from the data carried by a corresponding restoration signal received by said chooser node; upon receipt of an expected number of said reverse restoration signals, said sender node processor switch means reviewing the respective contention and probability of use data attached to each of said received reverse restoration signals to select an optimal restoration path for restoring the disrupted traffic. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
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Specification