Cross-connect multirate/multicast SDH/SONET rearrangement procedure and cross-connect using same
First Claim
1. A method for finding a path for a composite signal through a switching matrix the switching matrix having only switching elements any of which are potentially available for use as part of a connection for the signal, the method for use even when all possible paths through the switching matrix are blocked, the signal requiring a certain bandwidth and so a certain fraction of the throughput capacity of the switching matrix, each of the possible paths constituting a set of connections from an input switch, through the switching matrix, to an output switch, the switching matrix carrying existing signals on existing paths created by having made existing connections, the method comprising the steps of:
- 1) searching for the path only among possible paths that do not require rearranging any existing connections, and, if the path is found, using the path for the new signal;
2) if the path is not found in step 1, picking as a target path a partially blocked possible path through the switching matrix, the partially blocked possible path blocked by some existing connections carrying some existing signals requiring less bandwidth than the new signal; and
3) finding a different path for each existing signal carried by existing connections of the target path by recursively applying steps 1-2, with each existing signal carried by existing connections of the target path treated, in turn, as the new signal in steps 1-2;
wherein the searching for the path considers only paths providing a bandwidth adequate for the signal without fragmenting the signal into components.
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Accused Products
Abstract
A connection procedure for finding by rearrangement a path for multirate, multicast traffic through an SDH cross-connect with subnetwork connection protection. If no free path for a new payload through the SDH switching hardware is available, the switching procedure looks for a path that is adequate and blocked by the least existing payload capacity. If the hunt is successful, the procedure rearranges the existing connections to make possible a path for the new payload. The procedure does not interrupt the existing connections; thus it is a "hitless" procedure. Connections for existing payloads that must be moved to make way for the new payload are queued and the connection procedure is applied recursively, to each in turn, until the queue is empty.
54 Citations
13 Claims
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1. A method for finding a path for a composite signal through a switching matrix the switching matrix having only switching elements any of which are potentially available for use as part of a connection for the signal, the method for use even when all possible paths through the switching matrix are blocked, the signal requiring a certain bandwidth and so a certain fraction of the throughput capacity of the switching matrix, each of the possible paths constituting a set of connections from an input switch, through the switching matrix, to an output switch, the switching matrix carrying existing signals on existing paths created by having made existing connections, the method comprising the steps of:
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1) searching for the path only among possible paths that do not require rearranging any existing connections, and, if the path is found, using the path for the new signal; 2) if the path is not found in step 1, picking as a target path a partially blocked possible path through the switching matrix, the partially blocked possible path blocked by some existing connections carrying some existing signals requiring less bandwidth than the new signal; and 3) finding a different path for each existing signal carried by existing connections of the target path by recursively applying steps 1-2, with each existing signal carried by existing connections of the target path treated, in turn, as the new signal in steps 1-2; wherein the searching for the path considers only paths providing a bandwidth adequate for the signal without fragmenting the signal into components. - View Dependent Claims (2, 3)
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4. A method for finding a path for a new composite signal through a switching matrix the switching matrix having only switching elements any of which are potentially available for use as part of a connection for the signal, even when all possible paths through the switching matrix are blocked, the signal consisting of consecutive frames, each frame consisting of consecutive slots, the switching matrix having an input stage array consisting of a plurality of input switches (IN, where N=0, 1, . . . , r1), a middle stage array consisting of a plurality of middle switches (M1, M2, . . . , Mm), and an output stage array consisting of a plurality of output switches (ON, where N=0, 1, . . . , r2), and having existing connections for carrying existing signals, the new signal requiring a certain bandwidth, and arriving at input switch Ix and destined for output switch Oy, the path for the new signal consisting of connections of selected slots across a selected middle switch from an input switch to an output switch, the method using one of the existing signals or the new signal as a desired signal for which connections are to be rearranged or made in finding the path for the new signal, and taking initially the new signal as the desired signal, the method comprising the steps of:
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1) searching for a free path for the desired signal, and, if said free path is found, using said free path for the desired signal, but if said free path is not found, generating a list of possible paths from the paths already searched, sorted by how blocked each possible path is; 2) for each path in the list of possible paths, selecting as a target path (Ix, Mz C, Oy) the next least blocked path, the target path comprising a middle switch Mz selected from the plurality of middle switches (M1, M2, . . . , Mm) and a connecting channel C made up of slots some of which must be freed, said slots that make up the connecting channel C also making up channels hierarchically under the connecting channel, the channels hierarchically under the connecting channel being free or not free depending on whether the slots making them up are all free or not all free respectively; 3) queuing the channels that are hierarchically under the connecting channel C and that are not free; and 4) recursively applying steps 1-3 for each queued channel, so as to find another path for that queued channel wherein in searching for a free path and in generating a list of possible paths, only paths consisting of consecutive slots are considered. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12)
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13. A switching matrix for providing a connection for a composite signal, the switching matrix having only switching elements any of which are potentially available for use as part of a connection for the signal, the switching matrix comprising
a stage of input switches, a stage of output switches, one or more stages of middle switches, and means for finding a path for a signal from one of the input switches to one of the output switches even when all possible paths through the switching matrix are blocked, the signal requiring a certain bandwidth and therefore a certain fraction of the throughput capacity of the switching matrix, a path constituting a set of connections from an input switch, through the switching matrix, to an output switch, the switching matrix carrying existing signals on existing paths created by having made existing connections, said finding means having: -
1) means for searching for the path for the new signal, wherein the path does not require rearranging any existing connections, and, if the path is found, using the path for the new signal; 2) means for picking as a target path a partially blocked possible path through the switching matrix, the partially blocked possible path blocked by some existing connections carrying some existing signals requiring less bandwidth than the new signal; and 3) means for finding a different path for each existing signal carried by existing connections of the target path, by recursively using the means for searching for the path for the new signal and the means for picking as a target path a possible path through the switching matrix, with each existing signal carried by existing connections of the target path treated, in turn, as the new signal wherein the paths used are always paths providing a bandwidth adequate for the signal, for which a path is to be found, without fragmenting the signal into components.
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Specification