ES2377087B1 - METHOD, SYSTEM AND LOCKER AVOIDING ROADER IN AN INTERCONNECTION NETWORK. - Google Patents

Abstract

Method, system and blocking avoidance router in an interconnection network. # The method comprises: #a) detecting a situation prone to a blockage; e # b) identify a routing cycle involved in the situation prone to a blockade detected, by performing the following sub-stages by a router (r {sup, i}), using an intra-asynchronous search mechanism Router and inter-routers that do not require the use of timers: # b1) Compose and send an identification message from an input buffer (to {sup, i} {sub, j}) of the router (r {sup, i} ) to an output buffer (b {sup, h} {sub, k}) of another router (r {sup, h}); and # b2) receive the identification message in the output buffer (b {sup, i} {sub, k}) associated with said input buffer (a {sup, i} {sub, j}) of the router (r {sup, i}) that composed it, after its retransmission by at least another router (r {sup, h}) from an input buffer (a {sup, h} {sub, j}) of the same. # The system and the router are adapted to implement the method proposed by the invention.

Description

Method, system and blocking avoidance router in an interconnection network.

Technical sector

The present invention generally concerns, in a first aspect, a method of preventing blockages in an interconnection network based on the identification of routing cycles involved in situations prone to a blockage, and more particularly a method comprising carrying carry out said identification through a mechanism that does not require the use of timers.

The invention belongs to the field of parallel computer interconnection networks and focuses on the area of fault tolerance for high speed interconnection networks.

The object of the present invention is to identify cycles of resource dependencies in high-speed interconnection networks asynchronously intra-router and inter-routers. The purpose of the identification is to prevent the occurrence of faults in the network devices from generating blocking situations in the interconnection network, thus allowing the completion of the applications that are running in the parallel computer.

A second aspect of the invention concerns a block avoidance system in an interconnection network adapted to implement the method of the first aspect.

A third aspect of the invention concerns a router intended for the implementation of the method of the first aspect of the invention.

Prior art

The performance of the latest generation parallel computing systems is closely related to the performance of the interconnection network that communicates its computing elements. This interrelationship attaches vital importance to the fault tolerance mechanisms of the interconnection network since, ultimately, it is the network that allows the operation of such computers as coherent and cohesive entities.

Under these circumstances, the occurrence of only one network failure is capable of generating potentially harmful anomalies in the computer system, and preventing the correct termination of the applications that are running in said system. Among these anomalies, the blocking scenarios, "deadlocks", are perhaps the most likely to occur because most of the current computer systems use routing algorithms that were not designed to tolerate failures (a situation that increases probability of occurrence of blockages in these systems). This problem becomes critical in situations where the computer system must deal with failures that appear randomly, that is, with dynamic failures. Some examples may be the banking transaction systems or the systems used for geological studies and natural disasters, among others.

In the context of interconnection networks, blockages occur when at least one message cannot reach its destination, because in its path it requests resources that are not available, more specifically, storage space in the queue of a device Network This situation results in total system blocking because the messages do not release the resources that other messages need, while requesting resources that are in possession of other messages. This leads to a group of messages being permanently blocked, causing the entire computer system to be out of order. Unfortunately, the appearance of blockages is frequent in situations in which one or more network devices fail. This is because even a relatively low number of failures can generate cyclic resource dependencies, derived from changes in the characteristics of the network, mainly in the topology.

During the last decades, several authors have proposed solutions to the problem of blockages in interconnection networks, among which are: limit the injection of messages in the network [1], [2]; use virtual channels [3], [4]; and modify the network devices and routing algorithms [5], [6], [7], Unfortunately, all the solutions proposed so far have been designed to avoid blockages in fault-free networks, so their applicability in the The scope of fault tolerance is very small.

The presence of network failures causes the vast majority - if not all - of the current blockage avoidance mechanisms to be seriously affected and limited, even not being effective. These limitations relate to important aspects of the general theory of fault tolerance, such as the timing and manner of occurrence of failures, the number of failures to tolerate, the duration of failures, the characteristics of the systems used, etc.

The way in which the fault occurs is the most important aspect to consider because it is closely related to the applicability and suitability of blockage avoidance techniques. If a static fault mode is assumed, it is essential to know in advance the location of such failures in the network. In contrast, when assuming a dynamic fault mode, the errors appear at random times and locations during system execution. The static failure model allows simpler solutions to be implemented, but the dynamic failure model clearly defines the behavior of the failures in real computer systems.

If the simplest routing algorithms are used, those based on static failure mode, it is impossible to avoid dynamic failures because such algorithms do not allow (by themselves) the use of alternative and adaptive paths. In contrast, the more complex routing algorithms, the adaptive ones, allow alternative paths to be used to avoid failures. Even so, despite profiling as a very promising solution, from the point of view of fault tolerance, the adaptive algorithms approach presents a new and important problem: the appearance of blockages or deadlocks. This problem becomes critical in situations where the computer system must deal with failures that appear randomly throughout the execution of the system, that is, with dynamic failures.

Currently, the vast majority of block avoidance techniques capable of tolerating failures in interconnection networks use virtual channels to break the cyclic dependencies of resources between messages. The use of virtual channels limits the scalability of these techniques because the number of virtual channels needed is directly proportional to the number of failures to tolerate. For this reason, most of the proposed techniques are based on static failure models, in order to reduce the number of virtual channels required. Another group of commonly used techniques is based on the concept of limiting the injection of packets, avoiding the hoarding of network resources in order to avoid indefinite blocking situations. However, these techniques are useful for routing algorithms based on the use of minimum paths, which makes it difficult or simply impossible to tolerate a medium or high number of failures. Virtually all of these methods and techniques to avoid blockages are based on different types of cycle identification mechanisms. Unfortunately, most of these methods were designed to operate in the absence of failures, so they become inapplicable to the occurrence of network failures.

From the point of view of the state of the art, the closest antecedent to the invention proposed here is a three-stage blockage avoidance mechanism, called "Non-blocking Adaptive Cycles" (NAC), proposed by the present authors. invention in [8] and [9]. From the explanation of the method and its application environment, it is possible to infer directly that the NAC method presents a series of synchronization problems that limit its application in high-speed interconnection networks. More specifically, NAC uses a “best effort” type cycle identification mechanism, which is applied step by step serially and is based on the control of router clock cycles to try to avoid situations known as “fake negative. " That is, the method uses the clocks of the routers to avoid situations in which a routing cycle prone to generate blockages is not correctly identified, despite the existence of it. In this method, identification is performed serially from the first router that detects the preset or trigger conditions. During this process, the identification on a buffer is applied, then, when a time predefined by the clock expires, the identification is made on the next input buffer, and so on. This situation makes it impossible to apply the mechanism proposed in [8] and [9] in high-speed interconnection networks because its application is restricted to cases in which the synchronization of router clocks is not lost. This is due to the fact that in NAC situations may occur in which more than one router starts the identification process on the same dependency cycle. In this situation, each router handles the requests serially, so that the responses to the identification requests may suffer certain delays of varying duration. In cases where the accumulation of delays causes the identification time to exceed the threshold value of the clock, at least one router will reach the wrong conclusion that there is no dependency cycle, so the corresponding actions will not be applied and It will generate a permanent blocking or “deadlock” situation in the network. In summary, the identification mechanism proposed in [8] and [9] can reach both blocking situations as well as "false negative" situations. Additionally, the block avoidance mechanism proposed in [9] has other restrictions that make its application very expensive, although not impossible. These limitations are based on the logical arrangement of the block avoidance elements, more specifically of the block avoidance buffers, which are in the critical path of the network devices, which considerably slows down the operation of the router since it is It is necessary to constantly carry out checks on which of the two physical paths connected to the input buffer should be used, both in the presence and in the absence of situations prone to generate blockages in the interconnection network.

Explanation of the invention.

It seems necessary to offer an alternative to the state of the art that covers the gaps found therein, and that in particular overcomes the aforementioned limitations of those proposed in [8] and [9].

To this end, the present invention provides, in a first aspect, a method of preventing blockages in an interconnection network, which comprises sequentially performing the following steps:

a) detect at least one situation prone to blockage; and

b) identify at least one routing cycle involved in said situation prone to a detected blockage, also known as a resource dependency cycle, by performing the following steps by a router of said interconnection network:

b1) composing and sending an identification message from an input buffer of said router to at least one output buffer, of at least one other router, connected thereto; Y

b2) receiving said identification message in the output buffer associated with said input buffer of said router that composed it, after its retransmission by at least said other router from an input buffer thereof.

Unlike the method disclosed in [9], which requires the use of timers, the method proposed by the present invention comprises performing said step b) by means of an asynchronous intra-router and inter-router search mechanism that does not require the use of timers

The term buffer should be understood herein as that corresponding to a storage device used to compensate for differences that may occur in the rate of data transmission between devices, as well as in the time of occurrence of such transmission events.

The method proposed by the first aspect of the invention is an asynchronous and scalable method, compatible with current network technologies, capable of identifying and cycling cyclic dependencies of resources asynchronously intra-router and inter-routers, to ensure the avoidance of blockages in interconnection networks with multiple dynamic failures.

According to an exemplary embodiment, the method comprises, in order to identify a plurality of routing cycles involved in situations prone to a block, performing, in parallel, a plurality of stages b) by said router, initiated by a corresponding plurality of stages b1) of composition and sending, in parallel, of a plurality of said identification messages from respective input buffers, and finalized by a corresponding plurality of stages b2) of receiving said identification messages in the output buffer associated with said input buffer of said router. This exemplary embodiment is possible thanks to the intra-router asynchronousness characteristics that the search mechanism used by the method of the invention uses, which allows for an input buffer of a router to initiate an identification process is not necessary. that another identification process initiated by another input buffer ends, both of which can be carried out in parallel.

For an exemplary embodiment, said asynchronous intra-router and inter-router search mechanism is an amplitude search mechanism, or BFS ("Breadth First Search").

Said step a) comprises, according to one embodiment, locally assessing in each input buffer of said router operating conditions whose compliance establishes that the router is in a state prior to a blocking situation, which is interpreted as said detection of a situation prone to blockage.

The method comprises, by at least said other router, in general by several other routers, carrying out step a) for their input buffers and performing said retransmission of the message or identification messages received through the buffer or input buffers where said operating conditions are met, before being received or received, in said sub-step b2), in the output buffer or buffers of the router that composed the message or identification messages sent.

Also, for another embodiment, the method comprises at least initiating a corresponding sub-stage b1) by said other router or at least one router of said plurality of routers, during the realization of step b) by said router. That is to say that it is possible for a router involved in an identification process initiated by another router to initiate his or her own identification process before it ends the one in which it is involved since, although this implies accumulation of delays , thanks to the inter-router asynchronousness characteristics that the search mechanism used by the method of the invention uses, no router will reach the wrong conclusion that there is no dependency cycle even if the reception of the sub-message is delayed step b2), since, unlike what is proposed in [9], said reception is not limited to any time threshold value.

For an exemplary embodiment, the method comprises, after identifying a routing cycle in step b) associated with an input buffer and an output buffer of said router, freeing a space in said input buffer by moving a first message of said buffer of entry to a block avoidance buffer attached to it outside its critical path.

The method comprises, after said release of a space in the input buffer of said router, to initiate a protocol for gradual recovery of message movement that guarantees the movement of messages in said routing cycle identified in step b).

According to an exemplary embodiment, the method comprises initiating a plurality of said gradual message movement recovery protocols, in parallel, for a corresponding plurality of routing cycles identified in step b).

The method proposed by the first aspect of the invention constitutes a method of identifying and monitoring cycles of resource dependencies fault tolerant for high-speed interconnection networks, based on a novel technique that allows parallel and distributed priority searches. in breadth. The proposed method is to identify asynchronously the cycles of resource dependencies through an identification process applied in the opposite direction to that used in the process of allocating resources for the routing of messages through the network.

The purpose of the method is to provide interconnection networks with an asynchronous cycle identification mechanism, scalable and easy to implement by means of hardware solutions in current network devices, to avoid situations of blockages in the event of one or more failures in the network devices In summary, the new method proposed here is a non-blocking asynchronous cycle identification mechanism that, unlike previous proposals, dispenses with the use and control of router clocks and allows parallel application of searches in breadth.

By dispensing with these controls, the new mechanism can be applied asynchronously to any circumstance and network topology. In addition, this new mechanism allows both identification processes and recovery processes to be applied in parallel, which represents a novel advance in terms of resource optimization that allows to improve the total system performance under all operating conditions of the system. interconnection network

The method proposed by the first aspect of the invention allows searching:

one.

Asynchronous: since the router clocks are not used during the process of identifying resource dependency cycles, the method does not depend on any type of inter-router synchronization. Unlike the previous methods, the invention proposed here does not present problems in situations in which more than one router can initiate the process of identifying cycles simultaneously or almost simultaneously on the same cycle of resource dependencies;

2.

In parallel: since the intra-router replication of the cycle identification packets can be performed in parallel and simultaneously on all the input buffers that meet the pre-established conditions. Unlike the previous methods, which apply the serial identification process, the proposal presented here allows parallel identification, without the use of clocks in the routers;

3.

Non-blocking: because it differentiates blocking situations from congestion situations in the interconnection network without the need to use router clocks as time limits. This contribution of the invention prevents the cycle identification process from being blocked under any circumstances (as opposed to the previously published methods).

Thanks to the structural modification consisting in the relocation of the block avoidance buffers to the side of the critical path of the router, carried out for an embodiment, it prevents the operation of the router from blocking and / or slowing down during the process of identification and treatment of resource dependency cycles.

A second aspect of the invention concerns a block avoidance system in an interconnection network, comprising two or more routers provided for the implementation of the method of the first aspect, with input buffers, output buffers and a unit of control suitable for performing said detection of said stage a) and said identification of said stage b).

For an exemplary embodiment, at least one of said two routers comprises a block avoidance buffer attached to an input buffer thereof outside its critical path, its control unit being provided to implement the method of the first aspect according to the example of embodiment explained above with reference to the release of a space in the router's input buffer.

Also, according to an embodiment of the system of the second aspect, said control unit is intended to execute at least one protocol for gradual recovery of message movement by implementing the method of the first aspect.

A third aspect of the invention concerns a block avoidance router in an interconnection network, intended for the implementation of the first aspect method, comprising input buffers, output buffers and a control unit capable of detecting of stage a) and the identification of stage b).

According to an embodiment, the router proposed by the third aspect of the invention comprises a block avoidance buffer attached to an input buffer thereof outside its critical path, said control unit being provided to implement the first aspect method. according to the exemplary embodiment explained above with reference to the release of a space in the router's input buffer.

Said control unit is provided, according to an exemplary embodiment, to execute at least one protocol for gradual recovery of message movement by implementing the method of the first aspect.

Brief description of the drawings

The foregoing and other advantages and features will be more fully understood from the following detailed description of some embodiments with reference to the attached drawings, which should be taken by way of illustration and not limitation, in which:

Figure 1 is a summary table of the notation and the operators used in the description of the present invention;

Figure 2 is a diagram of the simplified architecture of the router or network device proposed by the third aspect of the invention;

Figure 3 illustrates the detail of the activation and deactivation process of the cycle identifiers in a router, according to an example of embodiment of the method proposed by the first aspect of the invention;

Figure 4 is a graph representation of two resource dependency cycle identifications in the interconnection network based on the network device of Figure 2, for an exemplary embodiment of the method proposed by the first aspect of the invention;

Figure 5 is a graphic representation of the three stages that make up the method proposed by the first aspect of the invention, for an exemplary embodiment;

Figure 6 illustrates two interconnected routers that include the proposed notation for the description of some embodiments that will be performed in the following section with respect to the method proposed by the first aspect of the invention;

Figure 7A illustrates the interconnection network of Figure 6, where a router has three input buffers full and one output buffer also full and connected to an input buffer full of a second router, and Figure 7B is a representation of graphs of said interconnection network;

Figure 8 is a graphic representation of the conditions for detecting situations prone to generate blockages to be detected according to step a) the method proposed by the first aspect of the invention, illustrated on the scheme of Figure 6; Y

Figure 9 is a graphical representation, on the scheme of Figure 6, of the recovery conditions in which, by applying the method proposed by the first aspect of the invention for an embodiment, a space has been released in the buffer of input of one of the routers illustrated as a previous step to the beginning of a protocol of gradual recovery of message movement.

Detailed description of some embodiments

The notation used in this section for the description of the invention is detailed in the table of Figure 1, as well as in the interconnection network illustrated in Figure 6.

Likewise, a simplified diagram of the architecture of a network device or router based on the postulates of the invention presented here is shown in Figure 2, including the inbound (ACKe) and outgoing (ACKs) Acknowledge lines, which represents , for an exemplary embodiment, both the router of the third aspect of the invention, and those included in the system of the second aspect, as well as the one used by the method of the first aspect.

In said Figure 2 the input buffers such as Be and the output buffers as Bs, a switch as C, and a series of input link controllers such as CEE and a series of output link controllers have been generically referenced as CES, all of them conventional elements in the kind of network device illustrated.

Likewise, following Figure 2, the block avoidance buffers such as DAB and the routing and arbitration unit such as EA have been indicated. The function of these elements will be described later.

The novelty of the proposal made by the present invention is based on the use of an asynchronous intra-router and inter-router search mechanism that allows to identify in real time the appearance of cyclic dependencies in the allocation of routing resources, as well as to perform said identification in a parallel and distributed manner.

The cycle identification mechanism proposed in the invention is, for an exemplary embodiment, an original extension of the amplitude priority search processes or "Breadth-First Search" (BFS), based on the parallel application of distributed searches in each of the network devices that are part of the resource dependency cycle. During the search, a series of actions are applied in a parallel and asynchronous way starting from a network device, or router, in charge of initiating the cycle identification process.

Said network device, indicated in Figures 6 to 9 as the ri node, constitutes the initial point of the identification process and is the device that sends the identification messages through at least one input buffer there that does not have storage space. available and, in turn, need to access a bik output buffer of the same device that also does not have available space, that is to say that it complies with the aforementioned operating conditions whose compliance establishes that the ri router is in a previous state to a blocking situation. These actions are part of the intra-router identification process.

The rh network devices (see Figure 9) that are physically connected to the input buffers aij of the ri network device, for which the identification messages are sent, repeat the same procedure applied in the ri device, that is, they replicate the identification message to the network devices connected to their input buffers ahj that meet the conditions detailed above, extending the identification process to the inter-router search space. Otherwise, the rh network devices that do not have ahj input buffers that meet these conditions drain - remove - the identification messages instead of replicating them. In other words, the network devices that replicate the identi fi cation messages activate in a distributed and asynchronous manner the indicators of the existence of cycles, while the network devices that drain the messages deactivate them. This process is exemplified in Figure 3, where the gray circles correspond to the activated indicators and the white circles to the deactivated indicators.

In said Figure 3 five nodes ry, rh, rz, ri, rm are illustrated, and it can be seen that the central node ri has four input buffers ai1, ai2, ai3, ai4 and four output bi1, bi2, bi3, bi4 and that it has initiated three cycles of identification in parallel through three respective input buffers ai1, ai3, ai4 in which the three operating conditions previously referred to and indicative of a state prior to a blocking situation were met, and which they are respectively connected to an output buffer b and b of node ry, an output buffer bh3 of node rh and an output buffer bz1 of node rz for the transmission of respective cycle identification messages.

The cycles are identified when the ri network device that initiated the identification and tracking process receives the corresponding cycle identification message by the correct bik output buffer, which in the case illustrated by Figure 3 is the bi3 buffer, which has said identification message received through the input buffer am3 of the rm node.

This last process is exemplified in the diagram of Figure 4, which shows two processes for identifying cycles applied asynchronously on the same cycle of resource dependencies, from the ri and rh network devices, respectively. Explained colloquially, the method of identifying and monitoring cycles consists of illuminating the path step by step (dependency cycles), lighting (activating) light bulbs (cycle indicators) along the path. As the network devices themselves - both those that replicate and those that drain the messages - are responsible for activating and deactivating the cycle indicators, the invention proposed here allows the cycle identification method to be applied in a distributed and asynchronous manner. throughout the cycle of resource dependencies.

This asynchronous distributed search approach in amplitude has not been previously proposed or applied by any method of blocking avoidance.

The new identification method proposed by the present invention in its first aspect is composed, for an exemplary embodiment, by three stages, graphically represented in Figure 5:

one.

The first identification of the resource dependency cycle, initiated by the first router ri (corresponding to node 1 of Figure 5 as 1) that detects the buffer occupation conditions explained above. This stage ends when the router rou receives the corresponding cycle identification message through the correct bik output buffer. These actions correspond to stage 1 of Figure 5;

2.

The secondary identi fi cations, which are carried out on the same cycle of resource dependencies but are initiated by at least one other router rh from an input buffer ahj thereof. These actions correspond to stage 2 of Figure 5, illustrated for four of said secondary identi fi cations initiated from four respective routers (or nodes 2, 3,4 and 5 in Figure 5);

3.

The propagation of the "recovery" signal, initiated by the ri router immediately after the end of step 1. The use of the recovery signal is explained in detail below, for an example of application of the invention. These actions (R1 to R5) correspond to stage 3 of Figure 5.

The demonstration of the applicability and suitability of the cycle identification mechanism pertaining to the invention presented here is based on the fact that one of the purposes of BFS searches is to “find cycles in a graph or prove that such cycles do not exist " Said BFS type search approach is based on the mathematical concepts from which the architecture of a network can be represented as a graph (abstract representation of a set of vertices or nodes and edges) where vertices represent network devices

or processing, as appropriate, and the edges represent the links that connect the devices [11]. If the input (aij) and output (bik) buffers that make up the logical buffers (ci, mk, j) in Figure 6 are considered as nodes, and the connections of the ACK fl ow control system and signals - with origin and completion in the routing and arbitration unit EA-of the network device such as edges, an equivalent representation of the network can be obtained as a graph, as exemplified in Figures 7a and 7b, respectively. From this graph, asynchronous and parallel intra-router and asynchronous and distributed inter-router BFS type searches can be performed, according to the method proposed in the invention presented herein.

In order to improve the compression of the invention, an example of application of the cycle identification and monitoring method proposed herein is described below. The application example includes the detection of situations prone to generate blockages, and the identification and monitoring of the routing cycles involved in said situations, which is the object of the present invention.

Conceptually, the proposal is based on preventing the fulfillment of two of the four main conditions that cause blockages: the “hold-and-wait” condition, and the “circular wait” condition (“ circular wait ”) [10]. To achieve this objective and thus avoid the appearance of blockages, a DAB block avoidance buffer (by the English name "Deadlock Avoidance Buffer") is included attached to each input buffer as exemplified in Figure 2, and the application of a group of simple actions when accessing and using the output buffers that do not have available free space. It is important to clarify that these actions are only applied under specific circumstances directly related to the space available in the buffers of certain network devices, as explained above.

In order to be able to detect what are the situations that have the capacity to generate blockages in the network, three operating conditions are proposed (illustrated in Figure 8, and indicated as (1), (2) and (3)) that they act as triggers for blockage avoidance mechanisms. The situation described by these conditions is that of an input buffer of any node that does not have available storage space (Condition (3)) and tries to choose as an next step an output buffer (within the same network node) that neither It has available space (Condition (2)) and is physically linked to another network node whose corresponding input buffer also has no available space (Condition (1)).

These three conditions are evaluated locally on each ri network device before each message routing cycle. If all three of the above conditions are met, the network device is in a state prior to a blocking situation (since there are still resources available in DAB buffers). In these circumstances, the network device in which these conditions arise (which is the ri node in Figure 8) applies the following actions:

one.

Stops the injection of messages in the logical buffer (ci, mk, j);

2.

It stops the injection of new messages from the input buffer connected to the local processing node (if necessary), that is, from the input buffer of the gray-marked ri node.

After applying these two actions, the ri network device must identify and follow the routing cycles between origin-destination pairs likely to generate blockages. This process is responsible for identifying the start and end of the routing cycles between origin-destination pairs in each network device involved in a possible blocking situation. Note that this process corresponds to stages 1 and 2 of Figure 5. The identification of resource dependency cycles can be performed asynchronously and parallel intra-router and asynchronous and distributed inter-routers, making the identification in the opposite direction the one used in the process of allocating resources for routing messages through the network. This process is intended to ensure access to the last free resources in a routing cycle by the correct input buffer.

The necessary steps for the identification and monitoring of routing cycles applied by a network device are:

one.

Compose a new identification message that includes as information: the identifier of the ri network device that created it; the identification of the input buffer there where the trigger conditions were met; and the identifier of the output buffer bik through which the message should be received if it is part of the routing cycle;

2.

Send the identification message in the opposite direction to the message routing address, by the point-to-point flow control mechanism of the network device ri. The message is sent to the output buffers (bhk E ch, ik, j) of the rh network devices (see Figure 9) physically connected to the input buffers aij that meet the firing conditions.

Upon receiving one of these identification messages, each rh network device must verify the conditions and, if at least one of the ahj input buffers meets these conditions, the network device replicates (retransmits) this identification message to the buffers appropriate. Otherwise, the network device drains (deletes) the message. The first identification stage of the cycle of Figure 5 concludes when the identification message arrives at the network device that composed it ri through the correct bik output buffer, as illustrated by the arrow of the gray line of Figure 4 for the node ri or that of the black for the rh node.

Once the input and output buffers aij, bik that are part of the cycle, have been identified, a space is released in the input buffer aij through the move operation (aij, dij). This operation is the one that finally introduces a new free space in the routing cycle by moving the first message from the input buffer aij to the DAB buffer dij (see Figure 9), unlocking the semi-blocking situation of the input buffer aij and allowing cycle messages move to their respective destinations. The cases in which the identification does not end are due to the fact that the identification message has been sent through the correct input buffer aij but there is at least one rx network device throughout the cycle in which the conditions are not met So the identification message is deleted. In this case, the routing cycle is not blocked but congested.

As a first step, the network device ri in which the risk situation was identified must compose and send (in the opposite direction to the routing of application messages) the recovery signal corresponding to step 3 of Figure 5, in order to that the network device rh that precedes it in the routing cycle initiates the protocol of gradual movement recovery. This signal is used to alert previous network devices that the new space generated in their bhk output buffer is actually a space generated from the use of the DAB buffer. This signal allows the rh network device to distinguish between the following two situations:

•

The new space was generated by the disappearance of the situation prone to generate a blockade;

•

The new space was generated by the use of the DAB buffer in the network device connected to its bhk output buffer.

After receiving the recovery signal, the network device rh uses the information obtained from its own identification process (one of the secondary identifications of step 2 of Figure 5) to locally identify which of the input buffers ( ahj) belongs to the routing cycle. This action is critical since each network device that is part of the routing cycle must apply the move (ahj, dhj) operation on the correct ahj input buffer. Once the routing cycles involved in situations prone to generating blockages are identified, a set of actions that guarantee the movement of the messages in said cycles must be applied without blocking situations occurring. This set of actions has as its starting point the stage of secondary identi fi cations of Figure 5, in which at least one rh router starts its own identification of the dependency cycle to know which of its ahj input and bhk output buffers are involved. in the cycle and then be able to ensure the gradual recovery of message movement until the normal operating conditions of the network are reached, that is, that at least one of the conditions in Figure 9 is not met (indicated as (4) , (5), (6) and (7)). If any of these four conditions is not met, the protocol for gradual recovery of message movement must be finalized since this implies that the network has returned to its normal operating conditions. As a first step, the message injection in the logical buffer (ch, ik, j) is restarted by the start_st (bhk) action (giving priority to the messages stored in the DAB buffers). Finally, the injection of messages from the local processing node is again allowed by the start_fw (ahj) action.

Possible industrial application and production of the invention:

The goal of the invention is to achieve its incorporation, use and implementation - at industrial and production level - in high-performance interconnection networks. It is for this reason that the invention seeks to provide a method of blocking avoidance that allows a high-speed interconnection network to tolerate one or more faults in its components. The scheme of Figure 2 represents a possible starting point for the design of devices compatible with the invention, although it is only illustrative and not limiting.

A person skilled in the art could introduce changes and modifications in the described embodiments without departing from the scope of the invention as defined in the appended claims.

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Claims (19)

1. Method of avoiding blockages in an interconnection network, which comprises sequentially performing the following steps: a) detect at least one situation prone to blockage; and b) identify at least one routing cycle involved in said situation prone to a blockade detected, by performing the following sub-stages by a router (ri) of said interconnection network: b1) composing and sending an identification message from an input buffer (aij) of said router (ri) to at least one output buffer (bhk), of at least one other router (rh), connected thereto; Y b2) receiving said identification message in the output buffer (bik) associated with said input buffer (aij) of said router (ri) that composed it, after its retransmission by at least said other router (rh) from a input buffer (ahj) thereof; the method being characterized in that it comprises performing said step b) by means of an asynchronous intra-router and inter-router search mechanism that does not require the use of timers.

2.

Method according to claim 1, characterized in that, to identify a plurality of routing cycles involved in situations prone to a blockage, the method comprises carrying out, in parallel, a plurality of stages b) by said router (ri), initiated by a corresponding plurality of sub-stages b1) of composition and sending, in parallel, of a plurality of said identification messages from respective input buffers (ai1, ai2, ai3, ai4), and finalized by a corresponding plurality of stages b2 ) of receiving said identification messages in the output buffer (bi1, bi2, bi3, bi4) associated with said input buffer (ai1, ai2, ai3, ai4) of said router (ri).

3.

Method according to any one of the preceding claims, characterized in that said asynchronous intra-router and inter-router search mechanism is an amplitude search mechanism.

Four.

Method according to any one of the preceding claims, characterized in that said identification message includes at least information concerning the identifier of the router (ri) that created it, the identification of the input buffer (aij) for which it was sent and the identifier. of the output buffer (bik) for which the identification message should be received if it is part of the routing cycle.

5.

Method according to any one of the preceding claims, characterized in that said step a) comprises assessing in each input buffer (ai1, ai2, ai3, ai4) of said router (ri) operating conditions whose compliance establishes that the router (ri ) is in a state prior to a blocking situation, which is interpreted as said detection of a situation prone to a blocking.

Method according to claim 5, characterized in that it comprises, on the part of at least said other route hhh nador (rh), carry out said step a) for its input buffers (ah1, a2, a3, a4) and perform said retransmission hhh of the message or identification messages received through the buffer or input buffers (ah1, a2, a3, a4) where said operating conditions are met. 7. Method according to claim 6, characterized in that it comprises performing said message retransmission or identification messages through a plurality of routers (rh, ry, rz, rm), for their input buffers that meet said operating conditions, before being received or received, in said sub-stage b2), in the buffer or output buffers (bik) of said router (ri) that composed the sent message or identification messages.

8.

Method according to claim 5, characterized in that said operating conditions describe a situation in which an input buffer (aij) of a router (ri) does not have available storage space and attempts to choose an output buffer (bik) as the next step , of the same router (ri), which also does not have available space and is physically linked to the input buffer (amj) of another router (rm) that also has no available space.

9.

Method according to any one of the preceding claims, characterized in that it comprises at least initiating a corresponding sub-stage b1) by at least said other router (rh) or at least one router of said plurality of routers (rh, rm), during the realization of step b) by said router (ri).

10.

Method according to any one of the preceding claims, characterized in that, after identifying a routing cycle in said stage b) associated with an input buffer (aij) and an output buffer (bik) of said router (ri), freeing a space in said input buffer (aij) by moving a first message from said input buffer (aij) to a block avoidance buffer (dij) attached thereto outside its critical path.

eleven.

Method according to claim 10, characterized in that, after said release of a space in the input buffer (aij) of said router (ri), to initiate a protocol for gradual recovery of message movement that guarantees the movement of messages in said cycle of routing identified in step b).

12.

Method according to claim 11, characterized in that it comprises initiating a plurality of said protocols for gradual recovery of message movement, in parallel, for a corresponding plurality of routing cycles identified in step b).

13.

Block avoidance system in an interconnection network, characterized in that it comprises at least two routers (ri, rh) provided for the implementation of the method according to any one of the preceding claims, with input buffers (aij, ahj), buffers output (bik, bhk) and a control unit suitable for performing said detection of said stage a) and said identification of said stage b).

14.

System according to claim 13, characterized in that at least one (ri) of said two routers (ri, rh) comprises a block avoidance buffer (dij) attached to an input buffer (aij) thereof outside its critical path, its control unit being provided to implement the method according to claim 9 to perform said release of a space in said input buffer (aij).

fifteen.

System according to claim 14, characterized in that said control unit is provided to execute at least one protocol for gradual recovery of message movement by implementing the method according to claim 11 or 12.

16.

Block avoidance router in an interconnection network, characterized in that it is provided for the implementation of the method according to any one of claims 1 to 12, comprising input buffers (aij), output buffers (bik) and a unit of control suitable for performing said detection of said stage a) and said identification of said stage b).

17.

Router according to claim 16, characterized in that it comprises a block avoidance buffer (dij) attached to an input buffer (aij) thereof outside its critical path, said control unit being provided to implement the method according to claim 10 for perform said release of a space in said input buffer (aij).

18.

Router according to claim 17, characterized in that said control unit is provided to execute at least one protocol for gradual recovery of message movement by implementing the method according to claim 11 or 12.

SPANISH OFFICE OF PATENTS AND BRANDS SPAIN REPORT ON THE STATE OF THE TECHNIQUE 51 Int. Cl. G06F11 / 34 (2006.01) twenty-one Application No. 201101048 22 Date of submission of the application: 22.09.2011 32 Date of priority: RELEVANT DOCUMENTS

 Category

 @ Documents cited  Claims Affected

x

GONZALO ALBERTO ZARZA, "Multipath Fault-tolerant Routing Policies to deal with Dynamic Link 1-18

Failures in High Speed Interconnection Networks "- Autonomous University of Barcelona, School

of Engineering - Dept. of Computer Architecture and Operating Systems. Chapter 4,

pages 53-66.

URL: // http://www.tesisenred.net/bitstream/handle/10803/51494/gaz1de1.pdf?sequence=1

  Category of the documents cited x: of particular relevance Y: of particular relevance combined with other / s of the same category A: reflects the state of the art O: refers to unwritten disclosure P: published between the priority date and the date of priority submission of the application E: previous document, but published after the date of submission of the application

  This report has been produced � for all claims � for claims No:

 Date of realization of the report 08.03.2012

 Examiner B. Perez Garcia  Page 1/4

TECHNICAL STATUS REPORT Application NO .: 201101048 Minimum documentation sought (classification system followed by classification symbols) G06F, H04L Electronic databases consulted during the search (name of the database and, if possible, terms of search used) INVENES, EPODOC, WPI, INSPEC State of the Art Report Page 2/4  WRITTEN OPINION Application NO .: 201101048 Date of Written Opinion: 08.03.2012 Statement

Novelty (Art. 1 LP 11/198)

Claims YES

Claims 1-18

NO

Inventive activity (Art. 8.1 LP11 / 198)

Claims YES

Claims

NO

The application is considered to comply with the industrial application requirement. This requirement was evaluated during the formal and technical examination phase of the application (Article 31.2 Law 11/1986).  Basis of Opinion.- This opinion has been made on the basis of the patent application as published. State of the Art Report Page 3/4  WRITTEN OPINION Application NO .: 201101048 1. Documents considered.- Below are the documents pertaining to the state of the art taken into consideration for the realization of this opinion.

Document

Publication or Identification Number Publication Date

D01

GONZALO ALBERTO ZARZA, "Multipath Fault-tolerant Routing Policies to de al with D ynamic Link Failures in H igh S peed Interconnection Networks" -Universidad Aut6noma de Barcelona, School of Engineering -Dept. of Computer Architecture and Operating Systems. Chapter 4, pages 53-66. 07.15.2011

2. Statement motivated according to articles 29. and 29.7 of the Regulations for the execution of Law 11/198, of March 20, on Patents on novelty and inventive activity; quotes and explanations in support of this statement The submitted application is described in full and detailed form in document D01, doctoral thesis of the applicant and which was disclosed prior to the date of submission of the application. This document D01 contains all the technical characteristics defined in the claims and has not been found. no difference. Therefore, the disclosure of D01 cancels the novelty of the application filed, according to Article 6 of the Spanish Patent Law. State of the Art Report Page 4/4