MXPA98001043A - Search for route in communication networks - Google Patents

Abstract

The present invention relates to a method for determining a restoration path (or an additional path) in a partially or fully-attached node communications network, comprising sending, from a fault node, a help message common over each extension corresponding to a fault route, the common help message comprises a respective route identification field (and a respective associated route path field) for each fault route, and an identification account field route. A node, which after receiving such a common help message, initially determines by itself that it is the master end node for a plurality of existing routes will generate and advance a common flood forward path finding message for those fault routes. A slave node will respond to receive an advance route finding signature to generate a respective return signature for the route for which it is a slave, and send it along the restoration route traversed by the received route finding signature. Any serial node in the restoration path, which has a capacity lower than those requested by the route being restored, will make connections for the available quantity, will make the signature return with the capacity field overwritten with the available quantity, and send a firm of path to the slave end for that route to dismantle the connections previously made in previous serial nodes and to inform the slave node of the amount of capacity deficit. The slave node responds by switching, to act as a master node and send a reverse route finding signature for the amount of deficit, and the master responds to the receipt of the signature back (whose amount of capacity is less than the of the known node, is requested for the route) is switched to act as a slave for that route and waits for a reverse route finding signature. The use of the common signature for a plurality of route identifications reduces the total time to achieve restoration.

Description

B SQUEDA AND ROUTE IN COMMUNICATION NETWORKS BACKGROUND OF THE INVENTION i. Field of the invention This invention relates to a method for searching, or determining, a route in a communication network; to a node arranged to carry out the method; and to a network comprising such nodes. A route may be necessary to replace an existing route, which has failed, and this route is referred to as a restoration route, or a route may be required to supplement an existing route, which is congested. As used herein, the term "additional route" encompasses both restoration routes and supplementary routes. 2. Description of the Related Art It is known, for example, from the article "The Self -Healing Network: A Fast Distributed Restoration Technique for Networks Using Digital Cross -Connect Machines",. D. Grover, IEEE Globecom 87 and United States Patent 4, 956, 835 (Wayne D. Grover) responds on the two nodes (known as failure nodes) connected to a fault extension to receive a failure alarm extension to start a real-time restoration procedure. The fault nodes determine based on their unique network identities (IDs), the node acts as a sender and the node acts as a reader (also known as master and slave, respectively). For each of the links of the fault extension, the sender repeatedly transmits (floods) respective route search signatures to its surrounding nodes (known as serial nodes), which advance the flood of signatures to the surrounding nodes. In one embodiment in the aforementioned US patent, a node knows only its own identity (ID) and learns the identity of the node to which connectivity has been lost by reading the last pale contents of a reception signature record in the port or affected ports that correspond to the link or failure links, and in an alternative mode, a node stores and maintains a surrounding node identification table. The node that decides to act as a selector now enters a waiting state and remains that way until it receives a route finding signature. Thereafter, it responds by transmitting a respective complementary reverse link signature (also known as a confirmation or return signature) to the serial node from which the route finding signature was received. The confirmation signature travels through the serial nodes establishing the required switching connections between the input and output ports of the node, and finally arrives at the sending node, which then stops transmitting the respective route finding signatures, and proceeds to transmit on that newly established restoration route for the traffic to which it has been transmitted on the corresponding link of the fault extension. The aforementioned US patent also discloses that the restoration mechanism can be used to automatically provide new circuit routes in a network by placing two nodes, among which the provision of additional (ie supplementary) circuit paths is desired, directly to the sender states and is read with respect to an artificial fault between the selected nodes. The nodes could be supplied with artificial fault information including the number of circuit routes that are being searched.

BRIEF DESCRIPTION OF THE INVENTION According to a first aspect of the present invention, there is provided a method for determining an additional path in a fully or partially entangled communications network of nodes, the method comprises the steps of: determining, in response to a first predetermined circumstance and according to a master / slave relationship, respectively predetermined, in each of a pair of nodes between which there is an existing route, a node of said pair, which is to act as a master end node with respect to the existing route and the other node acting as a slave end node; send from a node to its surrounding node, a forward route finding signature to stop the existing route and include a first field that contains identification data for the existing route; receive in a node, an advance route finding signature, determining from the contents of the first field whether the receiving node is the slave end node for the existing route and, in the event that it is not, advancing the sign of finding of forward path received towards its surrounding nodes; determine at the other node in response to a second predetermined circumstance, a potential additional route and send from the other node on the potential additional route, a route confirmation signature identified the potential additional route; and storing details of the potential restoration path in the node after receiving the route confirmation signature; and the method is characterized by the steps of: detecting at a node that a common circumstance has occurred with respect to a plurality of existing routes associated with the detection node; and generating in the detection node, a common signature corresponding to the common circumstance, the common signature comprising respectively first fields containing respective identification data for the plurality of existing routes, and a second field containing the number of the first fields.

The present invention is advantageous in situations where a node may otherwise generate individual signatures for each of the plurality of similar circumstances, for example, when an excavator cuts a pipeline carrying one or more extensions and a failure node does not allow the derivation restoration to the other node or failure nodes for a plurality of fault paths. The use of a common signature reduces the total amount of signature processing time that nodes take upon receipt. Instead of having to do with the protocol headers and developers for each of the succession of individual signatures, a node needs to perform the processing only once for a corresponding common signature. This reduction in processing time is very important for a restoration situation in a large network, where an extension failure can result in a large number of fault routes, and where otherwise a large corresponding number of signatures of help and route finding could be generated. Preferably, the detection node is a serial node for each of the plurality of existing routes, and the common circumstance is the inability of respective derivation routes for the plurality of routes existing between the detection node and a surrounding node or nodes associated, so that the common signature is a help signature to break the connections in the respective nodes of the plurality of existing routes and to initiate a restoration procedure in the respective end nodes of the plurality of existing routes, and where the The common signature is sent from the detection node to each of the surrounding nodes, which are associated with one or more of the plurality of existing routes and with those with operational links to the detection node. Preferably, the node is constituted to detect, and use and when it is a serial node for each of a plurality of existing routes, the incapacity of respective derivation routes for the plurality of existing routes between themselves and a node or nodes surrounding, the incapacity constitutes the common circumstance; generating a common signature as an auxiliary signature to break the connection at the respective nodes of the plurality of existing routes and to initiate a restoration process at respective extreme nodes of the plurality of existing routes; and sending the common signature to each of the surrounding nodes which is associated with one or more of the plurality of existing routes and with which the node has an operational link. Preferably the node is constituted by a node, the common circumstance is that a node is, in addition to acting as a master end node for the existing route, also acting as a master end node with respect to one or more of the other existing routes, by the that the common signature is a route finding signature. Preferably, the common signature is sent to all surrounding nodes of the node. According to a second aspect of the present invention, a node is provided to be used in a communications network totally or partially linked to nodes, the node being arranged to: respond, during use, to a first predetermined circumstance with respect to a route existing for which it is an extreme route, to determine if it will act as a master end node or slave end node; send, during use, to its surrounding nodes, in response to a determination that will act as the master end node, a forward path finding signature; receive, during use, a route finding signature and end if it is an end node or not for the existing route identified by the route finding signature, and, in response to a determination that is not such an extreme node, advancing the received route finding signature to the surrounding nodes, or, in response to a determination of what is such an extreme node and subsequently to a determination that the node is the slave end node for the existing route, determine, in response to a second predefined circumstance, a potential additional route, and send in the potential additional route, a route confirmation identifying the existing route; and storing, during use, the details of a potential additional route after receiving from it a route confirmation signature for an existing route, for which it is acting as a master end node; and characterized in that it is arranged to: detect, during use, the occurrence of a common circumstance with respect to a plurality of existing routes associated therewith; and generating a common signature corresponding to the common circumstance, the common signature comprising first respective fields containing respective identification data for the plurality of existing routes, and a second field containing the number of the first fields. Preferably, the node is arranged to detect, during use and when it is a serial node for each plurality of existing routes, the incapacity of the respective derivation routes for the plurality of routes existing between them and an associated node or surrounding nodes , the incapacity constituting the common circumstance; generating the common signature as a help signature to break the connections at the respective nodes of the plurality of existing routes and to initiate a restoration procedure at the respective end nodes of the plurality of existing routes; and sending the common signature to each surrounding node, which is associated with one or more of the plurality of existing routes and with whom the node has operational links. Preferably, the node is arranged so that, after a determination, in addition to acting as a master end node for the existing route, it also acts as a master end node with respect to one or more existing routes, generates the common signature as a signature of route finding, the determination constituting the common circumstance. Preferably, the node is arranged to send, during use, the common signature to all its surrounding nodes. According to a third aspect of the present invention, there is provided a fully or partially joined node communications network, wherein the nodes are substantially identical and in accordance with the second aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS A specific embodiment of the present invention will now be described by way of example with reference to the drawing in which: The Figure is a diagram of a network of interconnected nodes.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE MODALITIES The specific embodiment of the present invention relates to a real-time restoration procedure for establishing a restoration path in a communication network and the following description will be limited to this, although it will be appreciated that the procedure need not be solely the procedure of restoration in a network, but can be combined with a pre-planned restoration procedure. In Figure 1, a network 10 is shown consisting of a number of nodes each having a unique network identity, but for purposes of this description, only nodes A through J will be referred to. To avoid possible confusion, no the reference letter "I" is used. Of the many routes in the network 10 between the respective pairs of end nodes, this description will consider only three routes having unique "X", "Y", and "Z" route identifications. Route X is between the end nodes A and E, passing through the intermediate nodes (also known as series nodes) B, C and D, and comprising a sequence of bidirectional links within the extensions AB, BC, CD and DE; the route Y is between the end nodes A and G, passing through the intermediate nodes B, C and F and comprising a sequence of bidirectional links within the extensions AB, BC, CF, and FG; and the route Z is between the end nodes D and J, passing through the intermediate nodes C and H, and comprising a sequence of bidirectional links within the extensions DC, CH, and HJ. It will be appreciated that an extension is called from the two nodes it connects, and that, for example, the extension CD can also be named as in the DC extension, and that the name of the extension used in any case will be consistent with the extension. corresponding sequence of the reference letters from the end node to the end node for a route. During the practice, the node identifications and the route identifications will be numerical, but in this description they are alphabetical for convenience. The extensions between the nodes include working links and available links, and each work link is part of a respective unique route. The path capacity is expressed in terms of circuit numbers, but the capacity is aggregated, or subtracted, in link units. Consider that an excavator has cut a pipeline near node C and contains at that point both the CD extension and the CF extension. In this case the nodes C and D, that is, the fault nodes for the X route, after detecting the failure of the CD extension, decide that a restoration path has to be found between the nodes A and E, and similarly nodes C and F decide that a restoration path has to be found between nodes A and G, and nodes D and C decide that a restoration path must be found between nodes D and J. To facilitate the explanation, it will be assumed that no other route has failed, although it will be understood that, during practice, the fault nodes will correspondingly act to find a respective restoration path for each of the other routes, which have experienced a failure link. The order in which these restoration routes are established can be predetermined by placing the routes in order of priority, but such placement is not part of the present invention and will not be described. Each failure node will now generate, as a result of the aforementioned decision, a common help signature (hereinafter referred to as a help message) for its associated failure paths, and send the common help message to the respective end nodes of the routes. In this way, node C will send its common help message for routes X, Y and Z to nodes B and H, since these are the surrounding nodes for these routes, node F will send its common help message for route Y towards node G, and node D will send its common help message for route X to node E. It will be appreciated that although node D is a failure node for route Z, it is also an end node for that route. Each of the various signatures used in the restoration procedure has a header and a tracker, the header including a four-bit signature type field. The various types, as will be described in more detail below, are normal common route findings (also referred to as a common advance route finding), reverse common route finding (also referred to as common lag route finding), a route tracker, alarm, common help, backspace, and return (also known as confirmation). The information section of a common route finding signature comprises a four-bit flood count field, a four-bit path count field, a four-bit path identification account field, one or more fields of 16-bit path identification, and a corresponding number of fields of the 8-bit circuit number.

The information section of a common help signature comprises a four-bit path identification account field, one or more 16-bit path identification fields, and a corresponding number of 8-bit circuit number fields, per what in the case of the signature sent from node C to nodes B and H, its identification account field contains the number three, the three identification fields contain, respectively X, Y and Z, and the three fields of Associated circuit number contain the respective capabilities of these routes. Since the common help messages pass through their respective intermediate nodes, they break the connections in the corresponding fault path. Each node will advance a common help message received over the link or links, which correspond to the identification. or identifications of routes contained in the common help message. Each node knows its own network identification and contains a table storing the route identifications for which this end node is located, and the network identifications of the other end nodes.

When node B receives the common help message, it will inspect its stored table to find if it is an end node for any of the routes identified, and where, as the case may be, it is not an end node for route X or for the route Y, will transmit the common help message in the outgoing links associated with those routes (links of the BA extension), and will break the connections for those routes by removing the route and the link data from its connection table. Node H similarly advances the common help message to node J. When node A receives the common help message, it will determine that it is an end node for routes X and Y, and will continue to determine if it is a higher determination or lower determination with respect to the stored identifications of the other end nodes, ie E for the route X and G for the route Y, based on the unique network identifications (ordinal numbers) of the nodes. If the first one, then it will act as a master node (also known as a sending node), and if it is the last one then it will act as a slave node (also known as a node reader). In this example, node A has a higher determination network identification than node E and node G, and in this way when receiving the common help message it will assume, to establish a restoration path for routes X and Y , the role of the mae st ro. Similarly, when node E receives the respective common help message, it will determine that it is an end node for route X, and will proceed to determine whether it is of higher determination or lower determination in relation to the stored identification of the other end node. (A) for the route X. In this example, the node E has a determination network identification lower than the node A, and in this way when receiving the common help message it will assume, to establish a restoration route for the route X, the role of slave. Node A now broadcasts a common forward path finding signature for fault paths X and Y that is, sends the signature-in expansion links to its surrounding nodes. In turn, they advance the received signature, which is flooded in this way through the network. This signature contains the identifications of the X and Y routes, the respective requested capabilities for the routes, the number 2 in your route identification account field, and has your flood count field set to one. As the signature - floods through the network, the advance or delay nodes (that is, those nodes that are not extreme nodes for any route identification in the signature), increase the trajectory account field. . Retrieval nodes advance the common signature over all extensions and no verification is made to see if the extension capacity in one extension is sufficient for the total capacity of a fault route, and the nodes do not mark that capacity as reserved. The delay nodes verify the trajectory account of a received signature and do not pay attention if the account is greater than a predetermined maximum. This sets a limit to the geographical degree of flooding. In variants, the flood control additionally or alternatively comprises verifying a field time of origin in the signature and not taking any action if the signature is older than a predetermined limit. The master node A, when it has broadcast the common route finding signature, will enter a state at rest to wait for the receipt of respective return signatures. After node E determines that it is to act as a slave for fault path X, it starts (activates) a. time to wait for the receipt of a corresponding route finding signature that contains the route identification X and in this way indicating a potential restoration path of unknown capacity. At the first reception of the forward path finding signature within time, the slave node E generates a return signature (also referred to as a route confirmation signature) and sends it back through the node from which The advance route finding signature was received. This return signature is similar to the route finding signature, but differs in that the content of the signature type field is changed to identify the signature as a return signature that travels to the master node A, the account field of route identification is omitted, an individual route identification field containing the route identification X is used and an individual field is used for the requested capacity. The slave node ignores E ignores any route finding signature subsequently received for route X. Since the signature back passes through the nodes of the potential restoration path, each of these nodes verifies what capacity is available, makes appropriate connections between the corresponding switching ports, and creates an eight-bit node identification field, in which your node identification is written. The node compares the requested capacity with the available capacity, and if the requested capacity is less than the available capacity, it will make connections for the requested capacity and send the signature back to the next node of the potential restoration path. However, if the requested capacity is greater than the available capacity, the node will make connections for the available capacity and advance the signature with the number in the requested capacity field replaced by the available capacity, and also send the slave end node E a return signature containing the identification of the X route and the value of the difference between the requested capacity and the available capacity to remove connections that have already been made for the capacity and that can not be established in that restoration route in part i cular. Upon receiving the signature back, the master node A recognizes that there is now a restoration path, as identified by the intermediate node or signature delay identifications, and the capacity of that particular restoration path, and now sends a signature of route tracker to node E, through the restoration route, to inform you of the intermediate nodes of the restoration route. When the invention is used to find a supplementary route, the route tracker signature may be sent on the existing route. This use of a route tracking signature is known in the art and is not part of the present invention. Node A will recognize, from the contents of the circuit number field in the received return signature, that the capacity of the restoration path is less than the requested value, and will be switched to act as a slave node for route X for the deficiency and wait for the receipt of a reverse route finding signature for route X. Upon receiving the signature back, the slave node E changes to act as a master node for the X route, generates a route finding signature with its flood count field set in two and with the capacity requested in this signature set in the value in the signature of return (ie, insufficient circuits), and sends it to its surrounding nodes. This signature is also referred to as - a reverse route finding signature. It will be appreciated that signatures with odd flood counts can be identified as successive attempts made by the original master to find a restoration path, and that signatures with even flood counts can be correspondingly identified as successive attempts made by the original slave. Node A, now acting as a slave node, responds to a first reception of a reverse route finding signature by immediately sending a "return" signature on the link over which the reverse route finding signature was received. the appropriate code for a return signature in its signature type field, has its flood count field set to two, and also has its circuit number field set to the value in the reverse route finding signature received The node E, acting as a master and having sent inverse route finding signatures, is now in a wait state.The method described above for finding a restoration path in a network can be used to find a supplementary route by sending instructions from a network control center - to two extreme nodes of a congested route, so that they treat the congested route as fail and initiate the method of the invention to find for an additional route (also known as an alternative route) between the two extreme nodes. An advantage of the modality described above is that the number of separate signatures that a serial node has to handle is reduced as compared to the provisions that use individual signatures for each affected route, so that there is not only a reduction in the number of signatures. number of signatures that are received and left waiting for the node processor that is free and that deals with the larger wait signature, but also the total number of processing required for a restoration situation is reduced because they are less header and crawlers. The route of "identification Y in the above-described common help message of node C will pass through node B in series at substantially the same time as route identification X, instead of being contained in its own respective signature and processed separately , possibly being delayed with respect to the signature of route identification X. The finding of a restoration or supplementary route through this method in this way is faster than with previous methods using individual respective signatures.

Claims (11)

1. A method for determining an additional path in a fully or partially joined node communications network, the method comprising the steps of: determining, in response to a first predetermined circumstance and in accordance with a respective predetermined master / slave relationship in each one of the pairs of nodes between which exists an existing route, the first node of the pair that is to act as a master end node with respect to the existing route and the other node that acts as a slave end node; send from the first node to its surrounding nodes a forward path finding signature for the existing route and include a first field containing identification data for the existing route; receive in a node of the forward path finding signature, determining from the contents of the first field whether the receiving node is a slave end node for the existing route, and, in the event that this is not the case, advancing the sign of advance route finding received to surrounding nodes; determine at the other node in response to a second predetermined circumstance, a potential additional route and send from the other node in a potential additional route with a route confirmation signature identifying the additional potential route; and storing the potential restoration path details in the node after receiving the route confirmation signature thereon; and the method characterized by the steps of: detecting at a node that a common circumstance has occurred with respect to a plurality of existing routes associated with the detection node; and generating in the detection node, a common signature corresponding to the common circumstance, the common signature comprising first respective fields containing respective identification data for the plurality of existing routes, and a second field containing the number of first fields.

2. A method according to claim 1, wherein the detection node is a serial node for each of the plurality of existing routes, and the common circumstance is the - inability of respective derivation routes for the plurality of existing routes between the detection node and an associated surrounding node or nodes, whereby the common signature is a common help signature to break the connections at the respective nodes of the plurality of existing routes and to initiate a restoration procedure at the respective end nodes of the plurality of existing routes, and wherein the common signature is sent from the detection node to each surrounding node, which is associated with one or more of the plurality of existing routes and with which the detection node has operational links.

3. A method according to claim 1, wherein the detection node is constituted by a node, the common circumstance being that the first node is, in addition to acting as a master end node for the existing route, it also acts as an end node master with respect to one or more existing routes, so the common signature is a route finding signature.

4. A method according to claim 3, wherein the common signature is sent to all surrounding nodes of the node.

5. A node to be used in a communications network totally or partially joined by nodes, the node being arranged to: respond, during use, to a first predetermined circumstance with respect to an existing route for which it is an extreme route to determine if it will act as master end node or slave end node; send, during use, to its surrounding nodes, in response to a determination that it will act as a master end node, a forward path finding signature; receive, during use, a route finding signature and to determine if it is an end node or not for the existing route identified by the route finding signature, and, in response to a determination that it is not such an extreme node, advancing the received route finding signature to the surrounding nodes, or, in response to a determination that if it is an extreme node and subsequently a preceding determination that the node is the slave end node for the existing route, determine, in response to a second predetermined circumstance, a potential additional route, and send in the potential additional route a route confirmation identifying the existing route; and storing, during use, the details of a potential additional route after receiving therefrom a route confirmation signature for an existing route for which it is acting as a master end node; and characterized in that it is arranged to: detect, during use, the occurrence of a common circumstance with respect to a plurality of existing routes associated therewith; and generating a common source corresponding to the common circumstance, the common signature comprises first respective fields containing respective identification data for the plurality of existing routes, and a second field containing the number of the first fields.

6. A node according to claim 5, and arranged to detect, during use and when it is a serial node for each of the plurality? E existing routes, the incapacity of the respective derivation routes for the plurality of existing routes between the itself and an associated node or surrounding nodes, the incapacity constituting the common circumstance; generating the common signature as a help signature to break the connections at the respective nodes of the plurality of existing routes and to initiate a restoration procedure at respective extreme nodes of the plurality of existing routes; and sending the common signature to each surrounding node, which is associated with one or more of the plurality of existing routes and with whom the node has operational links.

7. A node according to claim 5, and arranged so that, after determining that, in addition to acting as a master end node for the existing route, it also acts with a master end node with respect to one or more existing routes, generates the common signature as a route finding firm, the determination constituting the common circumstance.

8. A node according to claim 7, and arranged to send, during use, the common signature to all surrounding nodes.

9. A node for use in a fully or partially joined network of communications of nodes, the node being substantially as described herein with reference to the drawings.

10. A total or partially joined network of communications of nodes comprising the nodes according to any of claims 5 to 9, wherein the nodes are substantially identical.

11. A method for determining an additional path in a partially or fully-attached communications network of nodes, the method being substantially as described herein with reference to the drawings. SUMMARY OF THE INVENTION A method for determining a restoration path (or an additional path) in a partially or fully joined node communications network is described, which comprises sending, from a fault node, a common help message about each extension that corresponds to a fault route, the common help message comprises a respective route identification field (and a respective associated route capability field) for each fault route, and a route identification account field. A node, which after receiving such a common help message, initially determines by itself that it is the master end node for a plurality of existing routes will generate and advance a flood common path finding message for those routes of failures A slave node will respond to receive a forward path finding signature to generate a respective return signature for the route for which it is a slave, and send it along the restoration route traversed by the received route finding signature . Any serial node in the restoration path, which has a capacity less than that requested by the route being restored, will make connections for the available quantity, advance the signature back with the capacity field overwritten with the available quantity, and send a path signature to the slave endpoint for that route to dismantle the v connections previously made in preceding serial nodes and to inform the slave node of the amount of capacity deficit. The slave node responds by switching, to act as a master node and send a reverse route finding signature for the amount of deficit, and the master responds to the receipt of the signature back (whose amount of capacity is less than the the known node, is requested for the route) is switched to act as a slave for that route and waits for a reverse route finding signature. The use of the common signature for a plurality of route identifications reduces the total time to achieve restoration.