MXPA97009594A - System and method for resolving substantially simultaneous bi-directional requests rese decapacity - Google Patents

Abstract

The present invention relates to a method for the arbitration of which of the two adjacent nodes of a telecommunications network has the right to use a reserve link to restore suspended traffic due to a failure in the network, if both adjacent nodes are disputing the reserve link, comprising the steps of: determining the total time it takes for a signal to travel along the reserve link from one of the adjacent nodes to the other adjacent node; It takes for a signal to travel along the reservation link from one of the nodes to the other, the decision that the reservation link is dedicated for the use of one of the nodes if it is decided that the signal sent by that one of the node has reached the other node before the signal sent by the other node is received by that one node, and the decision that the reserve link is going to be dedicated for the use of the other node if the signal is determined sent by that other node arrives at a node before the signal sent by the one node is received by that other node

Description

SYSTEM AND METHOD FOR RESOLVING SUBSTANTIALLY SIMULTANEOUS BI-DIRECTIONAL REQUESTS FOR RESERVATION CAPACITY RELATED REQUESTS This invention relates to an application for Russ et al entitled Method and System to resolve the competition for the Reserve Capacity Circuits of a Telecommunications Network (Registry No. RIC -95-005), assigned to the same assignee of the present invention and filed on June 6, 1995 with Serial No. 08 468, 302. The disclosure of the related '005 application is incorporated by reference herein and can be reviewed for an understanding of the concepts of distributed restoration algorithm schemes. This invention is also related to a request from Russ et al. entitled Automated Restoration of an Unrestored Link and Nodal Failures (Record No RIC 95-059), assigned to the same assignee as the present invention and presented together with same with Serial No. 08 / 483,579. This invention is also related to a request from Russ et al. entitled Automated Trajectory Verification for the Restoration of Base SHN (Registration No. RIC -95-010) assigned to the same assignee as the present invention, and which was filed together with the same having a serial No. 08 / 483,525. This invention is P1617 / 97MX further related to a request by J.Shat entitled Method and System for the Identification of Fault Places in a Communications Network (Registry No. RIC-95-022), assigned to the same assignee as the present invention and presented together with it having a Serial No. 08 / 481,984. This invention is further related to a request by Chow et al. entitled System and Method for the Restoration of a Telecommunications Network based on a Two-Way Access, filed on March 9, 1994, assigned to the same assignee as the present invention, having a Serial No. No. 08 / 207,638. The description of the application '638 is incorporated by reference herein.

FIELD OF THE INVENTION This invention relates to a distributed restoration scheme for restoring traffic interrupted by a failure in a telecommunications network and, more particularly to an improvement with which the competition for the same reservation link is resolved by bi requests. -directionals from adjacent cascade nodes.

BACKGROUND OF THE INVENTION A Distributed Restoration Algorithm (DRA) of P1Ó17 / 97MX self-healing network (SHN) as mentioned in .D. Grover in the U.S. Patent. 4,956,835 which diffuses multiplely a received flood signal (signature or message) in a reservation link on each logical space (except the one from which the flood signature is received), which contains reserve links available through the cascaded nodes connected to restore traffic due to a failed link. This results in a unidirectional ulti-diffusion of input flood signatures for each of the cascaded nodes in the network. To achieve a more complete understanding of the SHN scheme and the terms used herein, the reader should examine the description of the '835 patent. incorporated by reference herein. In the typical digital cross-connect switches (DCSs) bi-directional circuits are used. Even when the flooding of the SHN is regulated on a unidirectional basis, several abnormalities may occur. One of these abnormalities found by the inventor of the present invention is similar to the problem of "blocking" in telephony. This blocking problem occurs because the selection node in a SHN selection scheme will simply invert the link for a specific index and wait indefinitely for the P1617 / 97MX route traffic to alternate arrives. In accordance with this, any problem that results from the non-arrival of the traffic is not detected in the selection node. One such problem occurs when two unidirectional flood signatures use, each one, an address of a bi-directional booking link. If both of these signatures eventually reach their selector (s), the selector can reverse the link and effectively reserve an alternate route (route-alt), for each of the signatures that share a common reserve link. And because the traffic to be restored is bi-directional, the division of the reserve link will not properly restore the service to any of the flood trajectories. In a SHN environment, the disconnection of the sender results, without some of the failure links being reset. In other words, a blocking condition exists when two adjacent cascaded nodes are trying to reserve the same reserve link or reserve capacity, causing the reservation capacity dispute. Therefore, a solution is needed to automatically resolve the dispute over reserve capacity for two adjacent cascaded nodes.

P1617 / 97MX BRIEF DESCRIPTION OF THE PRESENT INVENTION The present invention, which relates to an improvement to the SHN, adds a cascade node flood rule and an associated arbitration method that serves as a mechanism to prevent simultaneous unidirectional flooding, in both directions, of a bi-directional reservation link. The rule prohibits any cascaded node from being broadcast multiple times in a reservation link, which is already receiving a flood signature from any sender / selector / index. This rule prevents one or more of the selectors from receiving signatures or flood messages and, consequently, the reverse link to alternate routes that share a common link with another sender / index / index. In the case where a cascaded node and its adjacent node each transmit a flood signature substantially at the same time outside, towards the same reservation link, an arbitration method is created where the adjacent nodes yield the reserve link to the node which transmits its flood symbol first. This creates a fair competition or competition scheme that optimizes the performance of the SHN's trajectory-seeking aspect. The arbitration method of the present invention requires a pre-event knowledge by the nodes, P1617 / 97MX either through a manual or automatic configuration, of the transmission delay between the adjacent nodes. Therefore, when a node detects a recent arrival flood signature from a reserve link on which it has just started to send its own flood signature, it can make a determination on whether it or the remote adjacent node was the one Really transmitted the first flood signature. Once such determination has been made, the node will respond, either by continuing the transmission of its flood signature, if it is determined that it began to flood first, or interrupts the transmission of its flood signature, if it determines that its transmission started only after the remote node had started its transmission of the flood signature. Each of the two adjacent nodes performs the arbitration method of the present invention independently of the other. An object of the present invention is, therefore, to provide a fair contest or competition between adjacent cascade nodes, each of which is attempting almost simultaneously to reserve the use of a reservation link connecting the two adjacent nodes. Another object of the present invention is to provide a rule for improving the operation of a P 1 < J 1 7/97 MX schema of a SHN that prohibits any node in cascade from being broadcast in multiple ways in a reservation link that has already multiplied a flood signature to it.

BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned objects and advantages of the present invention will be evident and the invention by itself will be better understood with reference to the following description of an embodiment of the invention together with the accompanying drawings, wherein: Figure 1 is a drawing of a plurality of connected nodes for the illustration of the blocking problem, in which two independent unidirectional flood signatures are flooded in the same port or reservation interface of a node; Figure 2 is an illustration of two alternate routes for a sending / selecting pair that does not realize that the two routes share a common link. Figure 3 is a simplified block diagram illustrating the connection between two adjacent nodes of the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION An anomalous blockage is illustrated in Fig. 1. As P161 / 97MX is displayed in a telecommunications network where the nodes 12, mainly from node 1 to node 12 are connected. Each of the nodes have reserve links, designated with S, and work links designated with. As is well known, work links are circuits where traffic is traveling and reserve links are reserve circuits for restoration purposes. As illustrated, a cable failure occurs, which may be due to a fiber cut that occurs between nodes 2 and 3. Even though node 2 is also connected to node 4, via a fast path, in reality there are respective failure spaces between nodes 2 and 3 and nodes 2 and 4. When faults occur, based on the SHN scheme and particularly its conventional arbitration method of selecting the sending / selecting pair based on the designated number of nodes, node 2 because it has a number smaller than any of nodes 3 and 4, becomes the sender for both sender / selector pairs. Therefore, as shown, node 2 is the sender (sender A), while node 4 is the sender for the first sender / sender pair, while sender 2 is sender (sender B), while node 3 is the selector P-617/97 X for the second pair of the sender / selector. To return suspended traffic to the route, given the fact that node 2 has two senders and two reserve links, each of the senders can use one of the reserve links S to send their flood signatures. However, for the present invention, in order not to complicate things, we will refer only to sender B, that is, to the sender / selector pair between nodes 2 and 3. Thus, for example, in the embodiment of this invention, it is assumed that sender B will use both reserve links S, to search for an alternate route for the selector of node 3. Because node 3 connects to nodes 1 and 6, as shown, the sender B can send out his flood signatures to node 6 via reserve link S2 and node 1 via reservation link Sl. As shown, the flood signature from node 2, which is routed to node 1, via reserve link Sl is also sent from node 1 to node 5, via reservation link S3. Therefore, the sender B of the flood signature is sent from node 5 to node 6, via reservation link S4. Therefore, as shown, node 6 is receiving the flood signatures from node 2 and node 5.

P1617 / 97MX If these respective flood signatures arrive at node 6 at almost the same time, the blocking problem exists. In other words, similar to the blocking condition that can exist in telephony, if two users take their respective phones at the same time and each one tries to call the other, then each one receives a busy signal. The same situation applies equally to the example illustrated in Figure 1. Figure 2 also illustrates the riddle of lethal admission. As shown, there are two potential alternate routes that connect to the sender B of node 2 to the selector of node 3. Specifically, the first alternate route goes from node 2 to node 6 to node 5, node 9, node 10, node 11, to node 7 and finally to node 3. It uses reserve links S2, S7, S8, S9, SIO, Sil, and S12. The second alternate route goes from the node 2, node 1 to node 5 to node 6 to node 7 and then to node 3. It uses the reserve links Sl, S3, S4, S5, and S6. More closely, it can be seen that traffic for the first alternate route sends traffic from node 6 to node 5, via reservation link S7, while the second alternate route sends traffic from node 5 to node 6 to along the reservation link S4. The respective traffic for alternate routes then goes in opposite directions. Actually, booking links Plbl7 / 97MX S7 and S4 are one and the same, since the same reservation link connects node 5 to node 6 and both are transported through the same ports to nodes 5 and 6. In other words, the same interface or the same reservation port, in node 6, is receiving the multicast of the flood signatures from both nodes 2 and 5, from both directions unidirectionally. As illustrated, in one direction, the affected reservation port is a precursor port that is receiving a flood signature from its adjacent node 5, while in the other direction, the port in node 6 is receiving a multi-cast flood signature from another direction, mainly from node 2. Thus, figure 2 shows an example of two alternate routes reserving the same link between nodes 5 and 6, mainly reservation link S47 (a designation that identifies both reserve links S4 and S7 as the same link). However, the same reservation link can not restore both alternate routes of traffic bi-directionally. In short, sender B will not know which path, if any, can be used to find an alternate route for selecting node 3. To prevent the situation illustrated in Figure 2, the present invention adds an internal rule to the schema of the SHN, which prohibits multicasting of P - "- 17 / 97MX any flood signature at any reserve port or reserve link that is commonly receiving a flood signature, this will in most cases prevent the situation presented in Figure 2. Even when Float signatures compete for reserve links, there are cases where a node can multiemit to a reserve port or even a reserve link at almost the same time that the same reservation or reserve link port is being multiemitted by a Flood signature from an adjacent node This is similar to the problem of deadly admission into telephony The inventor acknowledges that there are several methods of arbitration that can be used to remedy this problem of deadly admission, as long as there is a rule to prohibit mutiemission of any flood subject at any reserve port that is commonly receiving a flood signature. These methods can include a priority method where a certain node will always have priority over other nodes, such as a number based on the priority method. Another method can be based on the priority scheme of the Ethernet type, which basically detects the collision between two input signals, backs up both links and then retransmits the signal randomly.

P1617 / 97MX in the links, waiting for the next transmission to not cause any collision. With reference to Figure 3. the scheme of the particular dispute and the system of the present invention will be analyzed. As shown the intermediate nodes 5 and 6, each represented by a conventional digital cross-connect switch (DCS), such as an Alcatel 1633-SX switch, are connected to each other via a backup link S47. For ease, no other work links or reserve links or their respective interfaces are shown in Figure 3. In particular, each of the DCSs includes a processor P that has a stored memory M and a counter T connected to it. the DCS of node 6, the processor is designated 30, its storage memory 32 and its counter 34. Similarly, for the DCS of node 5, the processor is designated 36, its storage memory 38 and its stopwatch 40.- In addition, there is an interface unit in each of the DCSs designated 42, in node 6 DCS and 44 in node 5 DCS. Each of these interfaces is an integrated circuit card that acts as the port of entries to transport signals, messages or signatures, inside and outside of each DCS. Integrated to each of interfaces 42 and 44 P161 / 97MX is a detector to look for a loss of the signal of the link connected to it. In other words, if there is a signal failure, it is detected by the interfaces 42 and 44. The respective switches 46 and 48 are also connected to each of the interfaces 42 and 44 to prohibit the broadcast or multi-broadcast of any signal in a reservation link, for example on booking link S47. As further shown in Figure 3, the reserve link S47 is connected to the DCSs of nodes 5 and 6. Several reserve components or equipment, such as line termination equipment (LTE), are placed along the reserve link S47. ) 50 and 52, to transmit the light signals from the respective DCS. Sometimes the equipment or additional components, such as for example the component 54, is also placed and / or mounted along the links, such as the reserve link S47. Consequently, the time in which a signal or message passes through a link is dependent not only on the length of the link, but also on any delay caused by the equipment placed on the link, through which the signal or message You need to travel. These are precisely the characteristics of the link that the inventor has used in the formulation of the solution to the problem of mortal admission. Specifically, the supposed LTE 50 has a P1 61 7 / 7MX delay time of 6 μs, component 54 has a delay time of 3 ms and LTE 52 causes a delay time of 4 μs for a flood signature passing through it. It also assumes that there is a delay time of 5 ms, for a signal traveling from interface 42 of node 6 to interface 44 of node 5, through the length of reserve link S47, given the fact that light travels at 4.95 μs per kilometer. Therefore, even though it is not significant, there nevertheless exists a delay time, a period of time, for a signal or signature or message to pass from the interface 42 to the interface 44. For the modality shown in the Figure 3, it can be assumed that the delay time for a signal traveling from the interface port 42 to the interface port 44 is the same when the same type of signal travels from the interface port 44 to the interface port 42. However , it is not necessarily the case since the delay may be different for each of the addresses. Therefore, the delay time caused by the same components along a link can, in fact, be different depending on which direction a signal travels, for example between nodes 5 and 6. Be that as it may, the present invention uses this delay time as follows. A stopwatch, such as 34 on node 6 and 40 on node 5, which can be called a Plbl7 / 97MX cascade node link arbitration timer, which provides a predefined period of time for a signal to travel from one of the nodes, through a link, to the adjacent node. For the example of the embodiment of Figure 3, timer 34 of node 6 provides a predetermined or predefined time period of, for example, 50 ms, for a signal, such as a flood message, to travel from the port of the interface 42 of the node 6 to the port of the interface 44 of the node 5. Furthermore, it is assumed that the arbitration timer of the link of the cascaded node 40 of the node 5 has also provided a delay time of 50 ms for a signal, as a flood symbol, travel from the port of the interface 44 to the port of the interface 42. Of course, it must be considered that the timer 40 may, in fact, need to provide a different period of time for a signal to travel from the node 5 to node 6, as mentioned before. The provisioning of the predefined time period can be achieved by the node 6 that sends a sample signal through the reserve link periodically, before any failure, to obtain a delay time measurement. The same happens for the supply of the predefined period of time from a signal traveling from node 5 to node 6. The measurements P l? 517 / 97MX of the total delay time between the adjacent nodes can be done by first measuring the respective delay time of the different components, along the reserve link, and then adding these delay times with the delay originated only by the length of the link. The actual measurement of the various delay times can be carried out by the respective processors of the working nodes in conjunction with their respective detectors at the interfaces. Likewise, the delay data provided by the manufacturers of the components can be stored in the memory of the nodes, as a reference. Having provided a period of time, the present invention is also based on the premise that if, for example, node 6 has sent out a flood signature from interface port 42 to node 5 at time 0, then a 50 ms elapsed from time 0, node 6 knows that node 5 sent out its signal before node 6 did it. So, if the detector at interface 42 were to detect a signal that is sent from node 5 before the end of the 50 ms time period, everything else being equal, assuming that a signal similarly takes 50 ms to travel from node 5 to node 6, then node 6 knows that node 5 has sent P1617 / 97MX its signal prior to the node 6. This determination of who is first, is done by the processor 30 in the node 6, using both the predefined time period of the timer 34 and any of the additional indexes and required data retrieved from the memory 32. For example, the predefined time period of the node 5 may very well be stored in the memory 32 so that the processor 30 can make a comparison of when a signal is sent by the node 6, and when a signal is received by the node 6. In the example where the processor 30 has made a determination that the signal sent from the node 6 has reached the node 5 and still no signal from the node 5 has been detected by the interface 42, then node 6 knows that reserve link S47 will be reserved for use. Then, the alternate route shown in Figure 2 and indicated by the links S2, S47, S8, S9, SlO, Sil and S12, is the route that will be used to restore traffic between node 2 and the node 3. Meanwhile, knowing that the alternate route is to be reserved for node 6, node 5 can activate a switch, namely switch 48, to prohibit any signal from being broadcast on reservation link S47 by the node 5. In other words, the aforementioned rule of prohibiting other nodes from making the broadcast on a reservation link for which a P1 17 / 97MX flood message or signature has already been received. At the same time, from the perspective of node 5, the inverse happens, so that node 5 cedes its right to reserve link S47 for its use. The manner in which node 5 arrives at this decision is as follows. Assume that the node 5 has also ultidifundido a symbol of flood or restoration of the signal in a reserve link S47 almost at the same time that a flood signature was sent by the node 6, in the same link. Because node 5 performs its own arbitration regardless of what is being done by node 6, suppose that the flood signature sent by node 5 had reached node 6 at the end of the time period predefined by timer 40. Still before the end of such predefined time period, node 5 receives, via interface 44, a flood signature from node 6. Given the above and by the fact that the predefined time period for its flood signature does not has elapsed, node 5 realizes that node 6 has indeed sent a message before node 5 has sent one. In accordance with this, node 5 declines any attempt to reserve reserve link S47 for its own use. In essence, the present invention uses a P1617 / 97MX Priority arbitration of the type first to arrive first to attend, in which the two adjacent cascaded nodes determine, each independently, whether a common reservation link should be reserved or assigned, regardless of whether a signal is detected from the another node cascaded within a given period of time, from the moment it sent its own signal to such a cascaded node. If no signal from the adjacent cascade node is detected within the predetermined time period, then the node may reserve the reserve link for its own use. If a message is received from the adjacent cascaded node before the predetermined time has elapsed, then the node hands over the reserve link to the other cascaded node. Therefore, since the present invention is subject to many variations, modifications and changes in detail, it will be understood that all material described through this description and shown in the accompanying drawings, is interpreted as illustrative only and not as a limitation. In accordance with this, it will be understood that the invention is limited only by the spirit and scope of the appended claims.

Pl fa l 7 7MX

Claims (26)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. A method for the arbitration of which of the two adjacent nodes of a network of Telecommunications has the right to use a reserve link to restore traffic suspended due to a network failure, if both adjacent nodes are contesting the reservation link, which comprises the steps of: determining the total time it takes for a signal travels along the reservation link from one of the nodes adjacent to the other adjacent node; the determination of the total time taken for a signal to travel along the reserve link from one node to the other; the decision that the reserve link is dedicated for the use of one of the nodes if it is decided that the signal sent by that one node has reached the other node before the signal sent by the other node is received by that one node; and the decision that the reservation link is going to be dedicated for the use of the other node if it is determined that the signal sent by that other node arrives at a node before it P1617 / 97MX the signal sent by the one node is received by that other node. The method according to claim 1, wherein each of the determination steps further comprises the steps of: measuring the delay time caused by each routing signal component, placed along the reserve link, in a signal that passes through it; the measurement of the length of the reserve link and the time it takes for a signal to travel through the reservation link, without the signal routing components; and combining the delayed time originated by each of the signal routing components and the time it takes for the signals to travel along the length of the reserve link, to determine the total time. The method according to claim 1, further comprising the steps of: prohibiting the broadcasting of any other signal on the reservation link while the reservation link is receiving a signal. 4. The method according to claim 1, further comprising the steps of: generating the respective respective times P1 61 7 / 97MX taking into account the delay time caused by the signal routing components, along the reserve link, in a signal that travels through them and the time it takes for the signal to travel to through the length of the reserve link. 5. In a telecommunications network having a plurality of nodes, a method for preventing messages from being flooded by two nodes towards a reserve link sandwiched thereon, at substantially the same time, comprising the steps of: providing a first period of time at the end of which a message must have crossed from one of the nodes to the other; provide a second period of time at the end of which a message should have crossed from one node to the other; and deciding that the one node has reserved the reservation link for its use if the one node has sent a message to the other node and has not received a message from that other node before the completion of the first time period. The method according to claim 5, further comprising the step of: deciding that the other node has reserved the reservation link for its use, if the other node has sent a message to a node and has not received a message from that P1 1 Í / 97MX a node before the end of the second period of time. The method according to claim 5, further comprising the step of: prohibiting the broadcast of any of the other signals on the reservation link while the link is receiving a signal. The method according to claim 5, wherein each of the steps of providing comprises the steps of: combining the time it takes for a signal to travel through the reserve link and any time delay caused to the signal by the equipment placed along the reserve link for the transmission or reception of messages. 9. The method according to claim 5, wherein the stages of providing further comprise the steps of: generating the first and second periods of time, taking into account the delay time originated in a signal, by the equipment placed along the reserve link, and the time It takes the signal to travel through the length of the reserve link. 10. A method to decide if a node is entitled to the exclusive use of a reservation link that is P161 / 97MX connects to a remote node, when both nodes, the node and the remote node, are disputing the reserve link, which comprises the stages of: defining a predetermined period of time that it takes a message to travel through from the reservation link from the node to the remote node; the decision that the node has exclusive use of the reserve link if the amount of time elapsed since sending your message, through the reservation link, to the remote node has exceeded the predetermined time period and if no received any message by the node, coming from the remote node. The method according to claim 10, further comprising the steps of; prohibit the sending of any other message to the booking link while the booking link has already sent you a message. The method according to claim 10, wherein the definition step further comprises the steps of: measuring the inherent characteristics of the components placed along the reserve link, which adds delay to the time it takes a message to travel along the reservation link; measure the length of the reserve link; P16] 7 / 97MX equalize the length of the reserve link with an amount of time it takes a message to travel through the booking link; and combining the delay time due to the components and the equalization time of the reserve link to determine the predetermined time period. The method according to claim 10, wherein the definition step further comprises the steps of: generating the predetermined time period taking into account the delay time caused by the components, placed along the reserve link, in a message that travels through them, and the time it takes for the message to travel through the length of the reservation link. 14. In a telecommunications network having a plurality of multiple nodes and links including reservation links connecting the nodes, an apparatus for deciding whether a node is entitled to the exclusive use of a reservation link connecting to a node with a remote node, when the two nodes are disputing the reservation link, comprising: means for defining a predetermined period of time that it takes a message to travel through the reservation link from the node to the remote node, and P-6 -7 / 97MX means to decide that the node is entitled to the exclusive use of the reserve link, if the amount of time elapsed since the node sent its message through the reserve link to the remote node has exceeded the predetermined time period and the node has not detected any message from the remote node. 15. Apparatus according to claim 14, further comprising: means for prohibiting any other message from being sent to the reservation link while the reservation link has already received a message. Apparatus according to claim 14, wherein the means of determination further comprise: means for measuring the inherent characteristics of the components placed along the reserve link, which adds delay to the time it takes a message to travel to length of the reserve link; means for measuring the length of the reserve link; means to equalize the length of the reservation link with an amount of time it takes for a message to travel through the reservation link; and means for combining the delay time due to the components and the equalization time of the reserve link to determine the predetermined time period. P1617 /; M, 17. Apparatus according to claim 14, wherein the definition means further comprise: a timer for generating the predetermined time period taking into account the delay time caused by the components, placed along the reservation link, in a message that travel through them, and the time it takes for the message to travel through the length of the booking link. 18. System for the arbitration of which of the two adjacent nodes of a telecommunications network has the right to use a reserve link to restore traffic suspended due to a network failure, if both adjacent nodes are disputing the reservation link, comprising: a first timer to define a predetermined first time that it takes a signal to travel along the reservation link from one of the adjacent nodes to the other adjacent node; a second stopwatch to define a predetermined first time that it takes a signal to travel along the reserve link from one of the nodes to the other; and a processor means for making the decision that the reservation link will be dedicated for the use of the other node if it is determined that the signal sent by the one node arrives at the other node before the signal sent by the Pl -7/97; i another node is received by the one node; the processor means further decides whether the reserve link will be dedicated for the use of the other node if it is determined that the signal sent by that other node arrives at a node before the signal sent by the one node is received by that other node . 19. System according to claim 18, further comprising: means for measuring the delay time caused by each component placed along the reserve link, in a signal passing through it; means for measuring the length of the reserve link and the time it takes for a signal to travel through the reservation link, between each of the components; and means for combining the delayed time caused by each of the components- and the time it takes the signals to travel along the length of the reserve link, to determine the predetermined time defined by each stopwatch. The system according to claim 18, further comprising: means for prohibiting the ultiemission of any other signal in the reservation link while receiving P1617 / 97MX a signal. The system according to claim 18, wherein each of the first and second measurement means generates the respective total times taking into account the delay time caused by the components placed along the reserve link, in a traveling signal. through them and the time it takes for the signal to travel through the length of the reservation link. 22. In a telecommunications network having a plurality of nodes that are connected by multiple circuits including reserve links, an apparatus for preventing messages from being flooded by two nodes towards a reserve link sandwiched between them, practically at the same time, which comprises: means to provide a first period of time at the end of which a message should have crossed from one node to the other; means to provide a second period of time at the end of which a message should have traversed from one node to the other; and means for deciding that the one node has reserved the reservation link for use if the one node has sent f a message to the other node and has not received a message from that other node before the completion of the first time period. PK- 17 / 97MX 23. Apparatus according to claim 22, wherein the decision elements further decide that the other node has reserved the reserve link for its use, if the other node has sent a message to a node and has not received a message from that one node before the termination of the other period of time. 24. Apparatus according to claim 22, further comprising: elements for prohibiting the broadcasting of any of the other signals in the reservation link while the reservation link is receiving a signal. 25. Apparatus according to claim 22, wherein each of the means for providing combines the time it takes for a signal to travel through the reserve link and any time delay caused to the signal by the equipment placed along the reservation link for the transmission or reception of messages, to generate the one or the other time periods .. 26. Apparatus according to claim 22, further comprising: at least one stopwatch to generate the one and the other periods of time, taking into account the delay time caused by the equipment, along the reserve link, in a signal and the time it takes for the signal to travel through the length of the reserve link. F161 / 97 X