Method and apparatus for multi-layer network in sonet /sdh

ES 2 356 992 T3

DESCRIPTION

PROCEDURE AND APPARATUS FOR A MULTILAYER NETWORK IN SONET / SDH TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to telecommunications network control processing, and more particularly to a method and system for multilayer network routing.

BACKGROUND OF THE INVENTION

The calculation of a route through a network is based on link attributes reported by each node in the network. Several link attributes are known that can be reported by the nodes 12 of a telecommunications network 10. These link attributes include the traffic engineering metric, the maximum or total bookable bandwidth, the unreserved bandwidth, the class / resource color, link protection type, and shared risk link group. The traffic engineering metric specifies the link metric for traffic engineering purposes. The maximum or total bookable bandwidth specifies the maximum bandwidth that can be reserved on this link in one direction. Unreserved bandwidth specifies the amount of unreserved bandwidth still on the link in one direction. The resource class / color specifies administrative group membership for this link. The link protection type specifies the protection capability that exists for the link. The shared risk link group attribute identifies a set of links that share a resource whose failure can affect all links in the set.

The link state notification may also include an interface switching capability descriptor. The interface switching capability descriptor describes the switching capability for an interface where the link is defined as being connected to a node through an interface. For example, an interface connecting a given link to a node may not be able to switch individual packets, but instead can switch

ES 2 356 992 T3 channels in a synchronous optical network (SONET) payload. The interfaces at each end of a link may not have the same switching capabilities. For bidirectional links, the link switching capabilities are defined to be the same in both directions for data entering and leaving the node through that interface. For a unidirectional link, the interface switching capability descriptor at the far end of the link is assumed to be the same as at the near end of the link. A unidirectional link is required to have the same interface switching capabilities at both ends of the link.

The interface switching capacity descriptor can specify a switching capacity, an encoding type, a maximum and minimum bandwidth of the labeled switch path (LSP), and a maximum interface transmission unit. The switching capability descriptor specifies whether the interface can support layer 2, packet, time division multiplexing, lambda, or fiber, and also specifies whether the interface supports more than one of these types. The maximum LSP bandwidth specifies the lesser of the unreserved bandwidth and the maximum reservable bandwidth by priority. The minimum bandwidth LSP specifies the minimum amount of bandwidth that can be reserved. The interface maximum transmission unit descriptor defines the maximum size of a packet that can be transmitted on this interface without being fragmented. Descriptors other than the switching capacity descriptor depend on the type of switching capacity defined in the switching capacity descriptor.

The link attribute and interface switching capability descriptor mentioned above are reported by a node for its own egress interface only and require route calculations to find the reverse notification for a bi-directional link in order to determine endpoint capabilities. of a neighbor of the link. This unnecessarily complicates the route calculation

ES 2 356 992 T3 and adds the limitation that unidirectional links have the same capabilities at both ends.

Document US 2001/033548 discloses a technique to provide a virtual path between the nodes of a network having a common topology. A common protocol is used throughout the network for communications between nodes.

EP 1 146 682 discloses a system and method for combining mesh restoration and logical ring protection mechanisms for recovery from faults in bonded nodes of optical networks. SUMMARY OF THE INVENTION

From the foregoing, those skilled in the art can appreciate that there is a need for a technique to provide link status notifications in a telecommunications network in order to facilitate multilayer routing. In accordance with the present invention, a method and system for multilayer network routing are provided that substantially eliminate or greatly reduce the disadvantages and problems associated with conventional routing techniques.

According to one aspect of the present invention, there is provided a method for routing in a multilayer network according to claim 1.

According to another aspect of the invention, there is provided a network for the communication of transport signals according to claim 11.

According to a further aspect of the invention, there is provided a computer-readable medium including code to perform routing in a multilayer network according to claim 16.

The present invention provides several technical advantages over conventional data management techniques. Some of these technical advantages are shown and described in the description of the present invention. Embodiments of the present invention may present

ES 2 356 992 T3 some, all or none of these advantages. Other technical advantages may be readily apparent to those skilled in the art from the following figures, the description, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

To provide a more complete understanding of the present invention and of the characteristics and advantages thereof, reference is made to the following together with the attached figures, in the like references represent description parts, taken as similar numbers, and that: the

FIGURE illustrates a telecommunications network diagram;

the

Simplified FIGURE

<td>in</td><td>the</td>

<td>of</td><td>a</td>

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illustrates a simplified telecommunications multiple connection routing layer configuration diagram;

the network of the

FIGURE illustrates determined and reported type attributes of the connecting network of each telecommunications node;

the figures

4A

4C illustrate a link status notification of FIGURES

5A

5B illustrate generated example of at each node;

process for implementing connection;

route the

FIGURE a flow generating a calculation of the type attributes illustrates an additional step involved in the generation of candidate nodes carried out during the calculation of the route;

the

FIGURE illustrates a stage the generation of during the additional calculation involved in the candidate nodes of the route;

the

FIGURE

DESCRIPTION illustrates a layer-isolated connection routing approach for a multilayer network.

DETAILED OF THE INVENTION

FIGURE 1 is a simplified diagram of a network of

ES 2 356 992 T3 telecommunications 10. The telecommunications network 10 includes a plurality of nodes or switching points 12 interconnected by links 14. Each node 12 can be operated to transfer telecommunications signals using one or more signal types. Examples of signal types include digital service level 1 (DS1), DS3, virtual tributary level 1.5 (VT1.5), synchronous transport signal level 1 (STS-1), STS-3c, and level 3 optical carrier (OC-3). The nodes 12 can also support other conventional signal types readily known to those of skill in the art. Each type of signal represents a different connection routing layer in the telecommunications network 10. For each signal carried in the telecommunications network 10 a route to its intended destination is determined. The determination of the route through the telecommunications network 10 can be done at a source node 12, a node 12 that acts as a monitoring or control node, or at a centralized management node 16 according to a desired design for the network. telecommunications 10. The determination of a route and the generation of related information associated with the nodes 12 of the telecommunications network 10 can be carried out by means of suitable processing modules.

To automatically provide a signal through the telecommunications network 10, a route is calculated and a connection establishment is obtained from the route calculated for the information nodes 12. The route identifies the switching equipment at the nodes 12 and the Appropriate links 14 that the signal traverses in order to reach a destination node 12 from a source node 12. Once the route has been calculated, connection establishment signaling is carried out to the appropriate nodes 12 of the telecommunications network 10 in order to establish the intermediate switching connections necessary to provide an end-to-end service for the signal. Alternatively, connections can be configured from a central source or by other means

ES 2 356 992 T3 according to desired implementations. Signaling for connection establishment is performed by standard techniques known to those skilled in the art.

FIGURE 2 shows an exemplary layered view of telecommunications network 10. Routing of transport network signals through telecommunications network 10 can be achieved by layer isolated connection routing or multilayer connection routing. . A layer is an abstraction that contains the switch points and links that operate on one type of signal. For the example shown in FIGURE 2, layer 20 is associated with the DS1 signal type, layer 22 is associated with the DS3 signal type, and layer 24 is associated with the STS-1 signal type. A client layer is considered to be the originally requested network layer and a server layer provides trunk capacity for the client layer. Other layers may also be present in telecommunications network 10, where one layer is present for each type of signal supported by telecommunications network 10.

Layer isolated connection routing provides a separate routing instance that exists for each layer supported by the telecommunications network 10. These routing instances operate independently of each other. Therefore, each layer does not know the potential connectivity available in the other layers. By not knowing the connectivity available in other layers, the client layer cannot optimally determine a point to request a server layer connection between two points in the client layer. In this way, the client layer can choose non-optimal points to request a server layer connection in order to complete the route at the client layer. Also, the paths available at the server layer may not meet certain service requirements. If the client layer cannot identify the characteristics of an available server layer connectivity before making a request for a connection

ES 2 356 992 T3 trunk line, the client layer must wait for the route calculation to complete before determining whether the service requirements can be satisfied. If the service requirements cannot be satisfied, the client layer will need to consider the route it has taken and try to find another route that will satisfy the service requirements. Although the server layer can provide a list of connection possibilities with their respective attributes to the client layer, creating a list of paths and attributes in the client layer for each destination in the server layer will require a lot of effort to part of the processor and memory when a network has a high number of paths between the endpoints in the server layer and each path can have a different set of attributes. The present invention provides an embodiment for effectively utilizing layer isolated connection routing in a multilayer connection routing environment.

Multilayer routing provides a single routing instance that is responsible for connection routing at multiple layers of the telecommunications network 10. This routing instance allows you to view the status and attributes of all links at multiple layers and allows you to determine better routes with fewer processor cycles and less memory. The conventional link notification is not sufficient to support a route calculation that requires adaptation to multiplexed and correlated server layers and does not allow different costs to be allocated to link connections at different network layers on the same reported link. Typically, there is not enough information to determine acceptable routes in multilayer networks unless all border nodes can switch at all network layers, which may not be possible in a network design. In addition, current routing practices do not support routing through pooled resources for adaptation and / or interworking functions and do not address all types of problems.

ES 2 356 992 T3 routing constraints that are necessary for effective route calculation in multilayer networks. The present invention provides an embodiment that turns these disadvantages into advantages to efficiently provide multilayer routing.

The routes are calculated through the use of an algorithm. A common algorithm used in calculating a route through a network is known as the Dijkstra algorithm. Dijkstra's algorithm is a standard subroutine to find the shortest paths from a source node to a destination node, taking into account different weightings or costs involved in the route of the network. A variation of the Dijkstra algorithm, referred to as the Dijkstra extended algorithm or restricted first shortest path (CSPF) algorithm, takes into account attributes of a link, availability guarantees, and economic costs that are used to determine whether the link can satisfy the routing constraints provided in a routing request for a specified destination node. In this way, geographic diversity of a signal can be provided, the economic cost for a connection can be minimized, or other desirable routing behaviors can occur. In order to perform routing in a multilayer network, each node determines link states and reports these link states throughout the entire telecommunications network 10. At each layer supported by the telecommunications network 10, each node reports various attributes to neighboring nodes. These link state notifications are used to perform route calculations using the Dijkstra algorithm or other route determination techniques.

FIGURE 3 shows connection type attributes that can be supported by one node and reported to a neighboring node. These connection type attributes add efficiency and flexibility to route calculations not available with conventional attribute notifications. Connection type attributes include transit 30, source 31, collector

ES 2 356 992 T3

32, free egress 34, free ingress 35, free source 36 and free collector 37. The connection type transit 30 represents the ability of the notifying and neighboring node to receive transport network signals from a node and to forward the network signals transport to the next node in the path. The source connection type 31 represents the ability of the reporting node to create transport network signals in the current layer and the ability of a neighboring node to forward the transport network signals to the next node in the path. The collector connection type 32 represents the ability of the reporting node to forward the transport network signals to the neighboring node for termination. The free egress connection type 34 represents the ability of the reporting node to adapt the transport network signals from the current connection routing layer to a server connection routing layer. The free ingress connection type represents the ability of a neighboring node to receive transport network signals at the current connection routing layer from a server connection routing layer. The free source connection type 36 represents the ability of a reporting node to create transport network signals at the current connection routing layer and to adapt the source transport network signals to a server connection routing layer. The free collector connection type 37 represents the ability of a neighboring node to receive transport network signals at the current connection routing layer from a server connection routing layer and to terminate the current transport network signals.

In physical media layers, free relationships are not possible since the medium is assumed to be connected to the neighboring node and the physical media is not subject to adaptation to other server layers. In physical signal layers, the equipment inserted in the physical link between the nodes may have properties that are more restrictive than the switching equipment at the ends of the link. For example, two transparent crossovers can

ES 2 356 992 T3 be connected by means of a stretch of fibers that includes a SONET repeater. This will limit the link to SONET clients, whereas switching equipment does not have this limitation. In this case, the limiting properties of the span can be projected to the switches in a way that accurately indicates the type of connectivity available. The limitation is adopted by the nodes as a characteristic of the reported link even though the switching equipment themselves are not the source of the limitation.

FIGURES 4A to 4C show an example of a notification performed by a node 12 according to the present invention. FIGURE 4A shows the unreserved bandwidth and maximum LSP bandwidth attributes. These attributes can be reported once per link. The conventional attribute of maximum or total bookable bandwidth is not necessary as oversubscription can be handled by simply adjusting the unreserved bandwidth attribute to an appropriate fraction of the bandwidth reservation for each assigned link-state protocol. to the link.

FIGURE 4B shows a Connectivity Attribute Group (CAG) that can be reported as required. The CAG includes the signal type, the supported and available connection types, the availability of the server signal type and the associated adaptation cost, the availability of the client signal type and the associated adaptation cost, and the affinity of server endpoint. Each node determines the neighboring nodes with which it communicates during an operation identification phase. Then a capacity exchange phase is carried out so that a node can know the various capacities of each of its neighboring nodes. With this information, a node can create CAG for each link with each neighboring node. Alternatively, these phases can be provided at the installation of the nodes.

A CAG is formed and reported for each type of signal supported by the node. The signal type identifies the layer

ES 2 356 992 T3 for the link being advertised. The connection type identifies one or more of the connection types shown in FIGURE 3. The availability of the server signal type indicates that the node has the ability to adapt the current signal type to an identified server layer and that the Source connectivity is available at that server layer at this link. The adaptation cost identifies the cost involved in extending free egress connectivity in order to move towards the identified server layer.

Client signal type availability indicates that the neighboring node has the ability to adapt the current signal type to an identified client layer and that free connectivity is available at the identified client layer on this link. The adaptation cost identifies the cost involved in expanding the collector connectivity in order to move towards the identified client layer. The Server Affinity field identifies an endpoint list of router identifiers that indicate which nodes should have preferential treatment for terminating a server trail originating from this node while this type of signal is being routed.

Connection types and associated availability are displayed as bit fields with one bit position for each connectivity type defined above. These fields indicate if each connectivity is supported and is currently available for this link. Although displayed in this way, the link status notification can take any desired form for the communication of this information. If a connection type is reported as currently available for a link, this indicates that at least one link connection of that type is available. To support the establishment of multiple connections routed together, the reported information can be expanded to include the number of available connections of each type. However, the benefit of this expansion is not enough to justify the resulting increase in the size of

ES 2 356 992 T3 databases as automatic backward rerouting can be used to deal with relatively rare cases where the reported information is not sufficient to ensure that the calculated route is acceptable.

FIGURE 4C shows additional attributes that can be reported for each link. These attributes can be repeated as needed before the CAG to which they apply. These attributes include resource class / color, link protection type, and shared risk link group. These attributes refer to various routing restrictions. If not included, default values ​​apply. Any of these attributes can be individually repeated with a new value in order to set that value for subsequent CAGs.

FIGURES 5A and 5B show an example process for determining a route calculation using the reported CAG information. The process shows how Dijkstra's algorithm is modified to use CAG information to obtain a path extension through multiplexed and mapped server paths. Although changes in Dijkstra's algorithm are shown, such changes are shown by way of example only as the reported CAG information can be implemented in other link-state-based routing techniques and are not limited to its application in the algorithm. of Dijkstra. In the process shown, each node has an associated node identifier and a signal stack to uniquely identify the node. The signal stack is a stack of signal types that represent the current layers for the connection that is being routed at this node. Like all stacks, new values ​​are added to or pushed in at the top of the stack, and values ​​are pulled in or out from the top of the stack.

The calculation performed by the process of FIGURES 5A and 5B provides a set of routes within an area associated with an area, Area A. A tree of shorter trajectories is determined by a node that calculates the route

ES 2 356 992 T3 using a specified node in the network topology as a root. The formation of the shortest trajectory tree is carried out in two phases. In the first phase, only the links between the nodes of a single client layer are considered. In the second phase, the links of one or more server layers are considered. In each iteration of the algorithm there is a list of candidate nodes. The paths from the root to these candidate nodes have been determined, but the shortest paths have yet to be defined. The paths to the candidate node closest to the root are guaranteed to be the shortest. A path is said to be the shortest if it has the smallest link-state cost. The link state cost of a path is the sum of the costs of the links that make up the path when they are present in the layered network (ie, CAG). After identification, a candidate node is added to the tree of shortest paths and removed from the list of candidate nodes. The nodes adjacent to the candidate node added to the shortest path tree are examined for possible addition in the candidate node list and in the shortest path tree. The algorithm keeps iterating until the candidate node list is empty.

In FIGS. 5A and 5B, the process flow begins at block 50, where the algorithm data structures are initialized and candidate nodes are cleared. A shorter path tree is initialized by first adding a node, for example node V, which represents the root with a signal stack containing the requested signal to be routed. The shortest path tree is then updated to include new nodes that satisfy the desired routing constraints. The transit capacity of area A is set to false. At block 52 the link status notification of node V added to the shortest path tree is examined. Each link described by the link status notification provides signal types and costs to neighboring nodes. For each link

ES 2 356 992 T3 described that begins in block 54, if the attributes of the link between node V and a neighboring node, for example a node W, do not satisfy the requested routing restrictions, the examined link is discarded and the following link. If the routing constraints are satisfied, the process flow proceeds to block 56, where the link status notification from node W is examined. At block 57, if the link status notification for node W does not exist, has reached a maximum duration, or does not include a link back to node V, then the next link is parsed in the node's link status notification V. Otherwise, the process flow advances to block 58 for an analysis of each AGC on the link. In block 59, if the attributes of the CAG do not satisfy the routing constraints, the next CAG in the link is analyzed. If the routing constraints are satisfied in this case, the process flow proceeds to block 60, where the AGC signal type is compared to the top of the V node signal stack. look at the next CAG on the link.

If there is a match with a signal type, the process flow proceeds to block 62, where the CAG connection types are examined in order to generate new candidate nodes. If transit connectivity is available, an instance of node W is formed with the current signal stack to specify the uniqueness of one instance of node W relative to another. The reported cost of each instance is set at the transit cost for the CAG. If collector connectivity is available, the signal stack for node V has more than one input and any type of client signal from the AGC matches the second type of signal from the signal stack for node V, an instance of node W is formed for collector connectivity to the current signal stack excluding the top element of the signal stack for uniqueness and the reported cost is set to the AGC adaptation cost for that type of client signal. Yes

ES 2 356 992 T3 free egress connectivity is available, an instance of node W is formed with the current signal stack for free egress and for each type of CAG server signal. The reported cost is set at the CAG adaptation cost for each type of server signal. For each generated node W instance, the process flow proceeds to block 64 to determine if the newly generated node W instance is already in the shortest path tree. If so, it proceeds to the next generated instance of node W. If not, the process flow proceeds to block 66, where the link state cost is calculated for the path from root to node W. The link state cost is the sum of the link state cost of the shortest path to node V and the reported cost. At block 68, if the link state cost is greater than or equal to the value that already appears for node W in the candidate node list, then the next CAG is examined. If the link state cost is less than the value that appears for node W in the candidate node list or if node W does not yet appear in the candidate node list, then, at block 69, an entry from the list of candidate nodes for node W is set to the calculated link state cost and the next generated node W is examined.

After all the generated W nodes for each CAG for each link have been examined, the process flow proceeds to block 70, where the node from the candidate node list that is closest to the root is selected and added to the shorter trajectory tree. At block 72, if the node added to the shortest path tree presents a link status notification indicating that the destination is directly connected or available and the signal stack for the added node contains an input equal to the requested destination signal , then the route calculation ends. The path is obtained by tracing back from this added node to the root of the shortest path tree. If the path is not complete, the process flow returns to block 52 to examine the

ES 2 356 992 T3 link status notification for the newly added node.

When determining a route for a subnetwork connection for a signal across a network, it is desirable to move from a client layer, where the signal originates, to a server layer and back. However, although the destination node may be accessible through the client layer and the server layer, the destination node may not support the adaptation function necessary to support the client signal on all its interfaces at the server layer. . As a result, the path calculation creates a path that uses an adaptation function to return the connection to the signal source layer before completing the path. This behavior is supported through the collector connection type. Since the type of collector connection has an associated signal type, the type of collector connection may be required to match the type of the signal being routed. In the event that a particular client signal type is not supported on an interface, the restrictive mapping function will invalidate the collector connection as a candidate to complete signal routing. Afterwards, the route calculation will continue with the evaluation of other candidates. This behavior is also preferable when the destination node for which a route is being calculated is not the termination node but a border node that connects this route calculation domain with another domain. A link can be identified as a border by examining the type of notification found in the supporting routing protocol.

When the path of a signal through telecommunications network 10 is determined, the adaptation functions reported on a link become candidates for extending that path through a server layer. This candidate will be evaluated along with other candidates that are within the same layer as the signal is routed. The cost of the adaptation function, or adaptation cost, becomes a determining factor in the extent to which a server layer connection will be required to complete the

ES 2 356 992 T3 route for the signal. There may be times when you want to control the points at which server layer scaling will be allowed in the route calculation. This does not change the fact that there is an adaptation function, which is not removed from the notification described above. Instead, a special adaptation cost, such as 0xffff, can be used to indicate that such a path extension through a server layer is prohibited for the signal.

FIGURE 6 shows the change in the process of FIGURES 5A and 5B to implement this special adaptation cost. Since the adaptation cost is listed as part of the CAG associated with passing a signal from a client layer to a server layer, the adaptation cost is considered at the time the adaptation is applied to the path of the sign. The availability of the adaptation is also checked during the transition from the server layer to the client layer. Therefore, the return from the server layer to the client layer involves a reverse check of the availability of the adaptation function from client layer to server layer. If the reverse check fails during route calculation, then the return to the client layer cannot take place at this point and a new candidate will then be evaluated. The special adaptation cost check occurs during the generation of the new candidate nodes. During the check of the availability of a collector or the availability of free egress, if the adaptation cost has the special adaptation cost value, in this case 0xffff, then a candidate node is not generated. If the adaptation cost is not the special adaptation cost value, then a candidate node is added to the list of candidate nodes.

FIGURE 7 shows an exemplary change to the process of FIGURES 5A and 5B that implements an affinity cost adjustment for path extensions through multiplexed server trails. When a route is extended

ES 2 356 992 T3 through a free egress followed by a server layer source connection, a special candidate route is created that has an added endpoint constraint that must reach a matching server layer collector connection in a node that is already a neighbor of the current node for the link that contains transit connections at the client layer that is being routed. The cost of this special candidate path is adjusted by reducing or eliminating the cost of adaptation for the server layer. The endpoint constraint applies to this route candidate, and any route candidate that is generated from it, as the route calculation continues. The endpoint constraint for the special candidate route is determined by identifying all neighbors of the current node on links that support transit connection types in the layer being routed regardless of whether or not these links currently have available transit connections. For the collector connectivity check of block 62, the added limitation in generating a node W is that the top of the signal stack for node V has either a NULL endpoint constraint or the endpoint constraint includes a node W. For the free-egress connectivity check, a node W is generated with both an endpoint constraint and a NULL endpoint constraint. The reported cost for the first generated node W is set to the CAG transit cost and the reported cost for the second generated node W is set to the CAG adaptation cost. The endpoint constraint is a list of affinity endpoints that can be used to terminate the server layer trail and obtain the costs associated with the path to node V. Any signal in the signal stack, except the lowest signal, can be associated with a single-ended point constraint. This procedure can be extended to create special candidate routes with different cost discounts depending on the number and size of existing trunk lines to each current neighbor node.

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FIGURE 8 shows the implementation of layer isolated connection routing in a multilayer network. Through the effective reporting and route calculation described above, efficient multilayer network routing can be obtained. However, there may be situations where it may be beneficial to provide per-layer isolated connection routing in a multilayer network. A major limitation of the layer isolated connection routing described above is the inability to account for the potential connectivity that can be provided by server layer connections through links to the client layer where the signal is to be routed. This limitation can be removed by assigning a node identifier to a fictitious node, or pseudo node 80, which serves to represent the potential connectivity provided by a server layer between switching equipment operating at the client layer.

Typically, a node identifier is assigned to a network node. The node identifier serves to correlate all reported links related to that node in the sense that they have a common switch point through which signals can be routed. In multilayer networks, there may be resources that can be used to create additional connectivity or new links between nodes by creating new paths in a server layer of the network. However, notifying all possible new links will not suffice due to the large number of possibilities. Instead, the potential connectivity provided by a server layer can be effectively concentrated through the pseudo node. The pseudo node provides the ability for any node at the edge of the server layer to connect to any other node. The pseudo node represents the potential server layer connectivity that supports the client layer without the need to show the details of the server layer connectivity.

For each client layer node connected to a layer

ES 2 356 992 T3 server, one or more links will be included in the link state database to represent this connectivity. These bindings will be included in the node's link status notification at the client layer. Route calculations may take into account the possibility of creating new paths in the server layer by traversing links to and from the pseudo node. The cost of these can be set according to the desired policy regarding links with the preference to be provided to use the existing links in the client layer over the newly created links towards the pseudo node using the server layer.

Link notification must also be generated from the pseudonode. Generally, each node on the network reports its outgoing links. However, the pseudonode is fictitious.

To solve this, the content of a link notification can be independent of its source. In distributed flood protocols, the neighbor node from which a node receives a link notification is not normally the node that creates that link notification.

Taking advantage of this feature of flood protocols, a client layer node can notify a link from the node itself to the pseudo node and further notify the corresponding link from the pseudo node to the node itself. This notification is created as if it had been generated by the pseudonode and then it spreads to the rest of the network like any other binding notification. This allows distributed network implementations to use pseudo-nodes without the added complexity of creating a separate pseudo-node routing protocol entity.

Although pseudo nodes have been used in the past, the present invention can apply pseudo node techniques to multilayer transport networks. The pseudonode information being reported does not require a designated router choice or other coordination between proxy reporters. The use of pseudo nodes in a multilayer network provides the ability to control, through provisioning, the communities connected to a pseudo node

ES 2 356 992 T3 given to apply routing policies. In addition, the ability is provided for nodes to notify a connection to a pseudo-node to recognize the pseudo-node on routes and request a connection through the main network to substitute pseudo-node hops on the route.

In summary, efficient routing can be carried out in a multilayer network through the notification of appropriate link state information and through the use of the link state information during route calculation. Link state information includes connection type attributes that not only specify how a node can carry information in a layer and between layers of a network, but also identify optimal points for movement between layers and which nodes provide access to a network. desired layer of the network. Routing in a multilayer network can also be represented in a layer-isolated connection routing approach through the use of pseudo nodes.

The techniques performed by the present invention can be implemented in software, hardware, or a combination of both. For example, each node can present individual modules that can identify the different signal types and connection routing layers associated with the node, determine the connection types and availabilities corresponding to each connection routing layer at the node, and broadcast the link status notification, either in different modules or different functions can be combined in the same module. The modules can also be provided to calculate a route through the network and to determine the various transit and adaptation costs associated with connections in the network. These modules can provide the network structure to carry out the functionality of the present invention.

Although the present invention has been described in detail with reference to particular embodiments, it should be understood that various changes, substitutions, and alterations may be made therein without departing from the

ES 2 356 992 T3 scope of the present algorithm others the present invention. By invention has been described with de Dijkstra, in the present invention routing calculations with the same locations or operations described a plurality of components the processing of as well as any suitable. Those with the system of only one didactic, where it is to conceive other alterations and covers all said alterations and scope of the present invention, not any statement in which it is not reflected in the in the applications can be used suitable that facilitate various types of formats, hardware or software spirit or example, although reference to can be used effectively. In addition, previously potentially information on object, element, provisions described telecommunications configuration of being able to appropriate

The changes, modifications, changes, modifications claims are the accompanying claims specification.

above together they provide example used for purposes of making substitutions and modifications and according to particular needs. Substitutions, variations, and the present invention substitutions, variations, can be found in the art.

Furthermore, the limited in no way by del