NETWORK MANAGEMENT SYSTEM UTILIZING NOTIFICATION BETWEEN FAULT MANAGER FOR PACKET SWITCHING NODES OF THE HIGHER-ORDER NETWORK LAYER AND FAULT MANAGER FOR LINK OFFERING NODES OF THE LOWER-ORDER NETWORK LAYER

In a network management system performing a fault management process in a hierarchical network, an upper layer fault manager performs a fault management of an upper layer of a hierarchical network, a lower layer fault manager performs a fault management of a lower layer of the network, an inter-layer node connecting information storage portion manages connecting information between packet switching nodes composing the upper layer and link offering nodes composing the lower layer, and an inter-layer fault notifying portion notifies the upper layer fault manager, upon receiving a notification of a link fault which has occurred on a link between the link offering nodes from the lower layer fault manager, that the packet switching nodes affected by the fault are faulted, based on the connecting information.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a network management system, and in particular to a network management system performing a fault management process in a hierarchical network.

2. Description of the Related Art

A fault restoration process in a prior art hierarchical (layered) network management system is performed closed in each layer, in many cases. Specifically, in an Internet Protocol (IP) network which has been used increasingly in recent years, a method of performing an independent fault management in each layer is generally known due to a historical background that management entities or managers for an IP layer and a lower layer thereof are different.

FIG. 11shows a schematic diagram of the prior art network management system. ATM switches SW1-SW3composing a lower layer L2of a hierarchical network NW, which is an IP network, are respectively connected to routers RT1-RT3composing an upper layer L3.

The ATM switches SW1-SW3are mutually connected with information lines for passing user data. The ATM switches SW1-SW3are connected to an L2fault manager200with control lines (indicated by dotted lines) for notifying fault information apart from these information lines.

Also, a computer10is connected to the router RT1, computers21and22are connected to the router RT2, and a computer30and an L3fault manager100are connected to the router RT3.

InFIG. 11, because of no cooperative function between the L3fault manager100and the L2fault manager200, an individual layer fault management is respectively performed.

Generally, in a fault management method of an IP layer (upper layer), connection confirmation data packets are periodically exchanged between packet switching nodes over the network so that if the connection confirmation data packets are not received within a fixed number of trials, it is determined that there is a fault at the other node or a link fault toward the other node. The fault is dealt with by selecting another route (next node) for transmitting the data packets.

Moreover, in case the packet switching node performs a packet transmission according to a quality policy such as a priority, the fault manager of the IP layer which has received fault information from a certain packet switching node extracts a packet switching node on an alternate route (hereinafter referred to as an alternate node), and resets the priority to each alternate node to realize an end-to-end priority process.

This operation will be specifically described referring to FIG.12.

FIG. 12shows a fault management in the upper layer L3as a performance example of the above-mentioned independent layer fault management. InFIG. 12, the routers RT1-RT3are the packet switching nodes composing the upper layer L3of the network NW. The L3fault manager100which performs the fault management of this upper layer L3is composed of a fault detector101, a node setting portion102, a fault process determining portion103, an L3connecting information storage portion104, and a priority information storage portion105.

The routers RT1-RT3are mutually exchanging connection confirmation data packets periodically. For example, if a fault occurs between the routers RT1and RT2as shown inFIG. 12, the following processes (1)-(5) are performed:

(1) Since the exchange of the connection confirmation data packets between the routers RT1and RT2is disabled, the router RT1or RT2detects the fault (it is assumed in the following description that the router RT1detects the occurrence of the fault). Simultaneously with the fault detection, the router RT1starts alternate routing the data to the router RT3.

(2) The router RT1notifies the L3layer fault manager100of a trap (i.e. fault information).

(3) In the L3fault manager100, the following processes are performed:(3-1) The fault notification is received from the router RT1at the fault detector101. Based on the contents of the fault notification, the fault process determining portion103refers to the L3connecting information storage portion104to extract the node RT3on the alternate route.(3-2) The fault process determining portion103compares the settings of the routers RT1and RT3, and determines that a quality policy is unset in the router RT3.(3-3) The fault process determining portion103extracts priority information required to be set in the router RT3from the priority information storage portion105, and instructs the node setting portion102to set the priority information in the router RT3.

In order to describe the contents of the L3connecting information storage portion104, a connection state of the upper layer L3in the network NW ofFIG. 11is shown inFIG. 13, in which the routers RT1-RT3are mutually connected with virtual links VL1-VL3.

In the L3connecting information storage portion104, the connection (virtual link) between the routers RT1and RT2is stored, in the form of data, as the virtual link VL1from a port1of the router RT1(RT1/port1) to a port1of the router RT2(RT2/port1).

In the same way, the virtual links VL2and VL3are respectively stored as the virtual link from a port2of the router RT2(RT2/port2) to a port1of the router RT3(RT3/port1), and the virtual link from a port2of the router RT1(RT1/port2) to a port2of the router RT3(RT3/port2).

It is to be noted that the L2fault manager200also performs a management similar to the L3fault manager100, and includes L2connecting information storage portion204corresponding to the L3connecting information storage portion104. However, since the priority setting is performed only in the upper layer L3, the L2fault manager200is not provided with a portion corresponding to the priority information storage portion105.

This will be described referring toFIG. 14which shows only the lower layer L2in the network NW of FIG.11. It is to be noted that inFIG. 14, the ATM switches SW1-SW3are mutually connected with links LK1-LK3.

The L2connecting information storage portion204stores the connection (link) between the ATM switches SW1and SW2as the link LK1from a port1of the ATM switch SW1(SW1/port1) to a port1of the ATM switch SW2(SW2/port1).

In the same way, the links LK2and LK3are respectively stored as the link from a port2of ATM switch SW2(SW2/port2) to a port1of the ATM switch SW3(SW3/port1), and the link from a port2of the ATM switch SW1(SW1/port2) to a port2of the ATM switch SW3(SW3/port2).

It is to be noted that the L2fault manager200differs from the L3fault manager100connected to the routers RT1-RT3with the information lines for passing the user data in that the L2fault manager200is connected to the ATM switches SW1-SW3with the control lines (indicated by dotted lines) apart from the information lines for passing the user data. Therefore, it is made possible to separately manage the fault of the ATM switch itself and the link fault.

FIG. 15shows an upper layer L3as a network state before the fault occurrence in the network of FIG.11. In this case, it is assumed that the priority information as the quality policy is set in the routers RT1and RT2so that data from the computer10addressed to the computer21are transmitted with a high priority while data from the computer10addressed to the computer22are transmitted with a low priority. However, this quality policy (priority information) is not set in the router RT3.

A case where a fault occurs on the link LK1inFIGS. 11 and 14will now be considered. The link LK1offers a physical link between the ATM switches SW1and SW2respectively connected to the routers RT1and RT2. The occurrence of a fault on this link LK1will lead to the fault of the virtual link VL1shown in FIG.15.

The fault of the link LK1is immediately notified to the L2fault manager200. However, because of no cooperative function between the L2fault manager200and the L3fault manager100, the L3fault manager100cannot detect the fault of the virtual link VL1until the fault notification is received from the router RT1or RT2by the above-mentioned general fault management method in the IP network. Therefore, it takes time from the occurrence of the fault on the link LK1to the fault detection by L3fault manager100.

This will be described referring to FIG.16.

FIG. 16shows a network state in case a fault occurs after the state of FIG.15. The router RT1starts alternate routing to the router RT3simultaneously with a fault detection (see FIG.16(1)), and notifies to the L3fault manager100that a fault has occurred at the RT1/port1(see FIG.16(2)).

However, since the quality policy is not set in the router RT3, it is not possible to provide the service according to the determined quality policy for the data packets passing through the router RT3until the L3fault manager100re-sets the quality policy in the router RT3(see FIG.16(3)).

It may be considered to make the router RT1store (buffer) the data packets until the quality policy setting in the router RT3is completed as a measure to observe the quality policy. However, since the disconnected time is prolonged in this case, the deterioration of the communication quality over the entire network cannot be avoided.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a network management system which is able to shorten a time required up to detecting a fault after the occurrence of the fault and to reduce a network communication quality deterioration in a network management system performing a fault restoration process in a hierarchical network.

For the achievement of the above object, the network management system according to claim1comprises, as shown inFIG. 1, an L3fault manager100, which is an upper layer fault manager, for performing a fault management of an upper layer L3of a hierarchical network NW, an L2fault manager200, which is a lower layer fault manager, for performing a fault management of a lower layer L2of the network NW, an inter-layer node connecting information storage portion300for managing connecting information between packet switching nodes RT1-RT3composing the upper layer L3and link offering nodes SW1-SW3composing the lower layer L2, and an inter-layer fault notifying portion400for notifying the upper layer fault manager100, upon receiving a notification of a link fault which has occurred on a link between the link offering nodes from the lower layer fault manager, that the packet switching nodes affected by the fault are faulted, based on the connecting information.

Namely, for example, if a link fault occurs on a link LK1between the link offering nodes SW1and SW2of the lower layer L2inFIG. 1, the inter-layer fault notifying portion400receives the notification of the link fault from the L2fault manager200, and notifies the L3fault manager100that the packet switching nodes affected by the fault (i.e. the routers RT1and RT2) are faulted, based on the connecting information stored in the inter-layer node connecting information storage portion300.

As a result, a cooperative function of the fault management between the lower layer L2and the upper layer L3can be established so that it is made possible to shorten the time required up to the fault detection in the upper layer after the fault occurrence in the lower layer compared with the prior art network management system where the upper layer L3detects the fault independently of the lower layer L2.

Also, according to claim2, the inter-layer fault notifying portion400in the present invention of claim1shown inFIG. 1may retrieve the link offering nodes affected by the link fault from lower layer connecting information stored in an L2connecting information storage portion204provided in the L2fault manager200, and may recognize the packet switching nodes affected by the link fault by retrieving the information of the inter-layer node connecting information storage portion300with the affected link offering nodes.

InFIG. 1, the L3fault manager100and the L2fault manager200have the same arrangements as those in the prior art, and are respectively composed of, for example, fault detectors101and201, node setting portions102and202, fault process determining portions103and203, and connecting information storage portions104and204as in FIG.12. The L3fault manager100further includes a priority information storage portion105.

Also, the links LK1-LK3and the link offering nodes (i.e. the ATM switches SW1-SW3) at the opposite ends of the links are associated by the L2connecting information storage portion204included in the L2fault manager200, and the link offering nodes and the packet switching nodes (i.e. the routers RT1-RT3) are associated or made corresponding to each other by the inter-layer node connecting information storage portion300.

Namely, in order to recognize, for example, that the packet switching nodes affected by the fault of the link LK1are the routers RT1and RT2, the inter-layer fault notifying portion400firstly refers to the L2connecting information storage portion204included in the L2fault manager200.

Then, after retrieving the link offering nodes (i.e. the ATM switches SW1and SW2) at the opposite ends of the link LK1, the inter-layer fault notifying portion400retrieves the routers RT1and RT2from the inter-layer node connecting information storage portion300.

Thus, the inter-layer fault notifying portion400can retrieve the information of the inter-layer node connecting information storage portion300using the L2connecting information stored in the L2connecting information storage portion204.

Also, according to claim3, the present invention according to claim2may further comprise an affected node information storage portion for preliminarily associating each link with the packet switching nodes affected by the link fault based on respectively stored information of the lower layer connecting information storage portion and the inter-layer node connecting information storage portion, and the inter-layer fault notifying portion may extract the packet switching nodes affected by the link fault from the affected node information storage portion without using the respectively stored information of the lower layer connecting information storage portion and the inter-layer node connecting information storage portion.

Each link and the packet switching nodes affected by the fault of the link can be preliminarily associated using the L2connecting information storage portion204and the inter-layer node connecting information storage portion300shown inFIG. 1whereby the affected node information storage portion500can be added to the arrangement ofFIG. 1instead of the L2connecting information storage portion204and the inter-layer node connecting information storage portion300.

Namely, inFIG. 2, by providing the affected node information storage portion500, when the inter-layer fault notifying portion400receives the link fault from the L2fault manager200, the packet switching node affected by the link fault can be extracted directly from the affected node information storage portion500without referring to the L2connecting information storage portion204and the inter-layer node connecting information storage portion300.

Therefore, the packet switching nodes affected by the link fault can be notified promptly to the L3fault manager100.

Also, according to claim4, the present invention of claim1may further comprise an alternate route information storage portion where each link is associated with a packet switching node on an alternate route at a time of the link fault, and the inter-layer fault notifying portion may instruct the upper layer fault manager to set predetermined information related to a communication quality to the packet switching node on the alternate route extracted from the alternate route information storage portion at the time of the link fault.

Namely, instead of the affected node information storage portion500ofFIG. 2, an alternate route information storage portion600is provided, as shown inFIG. 3, which associates each link with the packet switching node (alternate node) on the alternate route at the time of the link fault.

In this case, the inter-layer fault notifying portion400can extract the alternate node from the alternate route information storage portion600and instruct the L3fault manager100to set the predetermined information related to the communication quality to the alternate node.

As a result, it is . made possible to immediately perform the predetermined setting related to the communication quality to the packet switching node on the alternate route according to the link fault in the lower layer.

Therefore, it is made possible to shorten the period when the communication quality is not maintained because the predetermined setting related to the communication quality is not set in the packet switching node on the alternate route so that the deterioration of the communication quality of the network can be reduced.

Also, according to claim5, when a fault occurs in the lower layer in the present invention of claim1, the inter-layer fault notifying portion does not necessarily notify the upper layer fault manager of the fault in case an alternate routing at a link offering node in the lower layer is performed.

Namely, even if the fault occurs in the lower layer, when performing the alternate routing at the link offering node in the lower layer to prevent the upper layer from being affected by the fault, the inter-layer fault notifying portion need not notify the fault to the upper layer fault manager.

Thus, an unnecessary fault notification can be avoided so that the fault management cooperation between the lower layer L2and the upper layer L3can be performed more promptly.

Also, in claim4, the predetermined information may comprise priority information.

Thus, it is made possible to shorten the period when the required priority information is not set in the alternate node at the time of the fault occurrence when the priority process is performed in the upper layer and to reduce the deterioration of the communication quality of the network.

Also, in claim4, the predetermined information may comprise bandwidth guaranteeing information.

Thus, it is made possible to shorten the period when the required bandwidth guaranteeing information is not set in the alternate node at the time of the fault occurrence when the bandwidth guarantee is performed in the upper layer, and to reduce the deterioration of the communication quality of the network.

Also, in claim4, when a plurality of alternate routes exist for an arbitrary link, the alternate route information storage portion may store a shortest alternate route where a hop count becomes minimum in correspondence with the link.

Namely, when a plurality of alternate routes exist for an arbitrary link, the alternate route information storage portion can preliminarily calculate the shortest alternate route where the hop count becomes minimum to store only the shortest alternate route associated with the link.

Thus, the alternate route at the time of the link fault occurrence can always be the shortest route.

In this case, the shortest alternate route may be obtained using a Dijkstra algorithm.

Throughout the figures, like reference numerals indicate like or corresponding components.

DESCRIPTION OF THE EMBODIMENTS

FIG. 4shows an embodiment of the connecting information of the nodes of the lower layer L2(L2nodes) and the upper layer L3(L3nodes) stored in the inter-layer node connecting information storage portion300in the network management system according to the present invention schematically shown in FIG.1. For example, inFIG. 4, the SW1/port1of the L2node is associated with or made corresponding to the RT1/port1of the L3node in the form of a table.

An operational embodiment when using such an inter-layer node connecting information storage portion300will be described herebelow referring to FIG.5.

Firstly, the arrangement of the hierarchical network NW inFIG. 5is basically the same as that of the network NW shown in FIG.11.

Namely, the ATM switches SW1-SW3composing the lower layer L2are respectively connected to the routers RT1-RT3composing the upper layer L3.

Also, the computer10is connected to the router RT1, the computers21and22are connected to the router RT2, and the computer30and the L3fault manager100are connected to the router RT3.

Moreover, the L2fault manager200is connected to the ATM switches SW1-SW3.

It is to be noted that the arrangements of the L3fault manager100and the L2fault manager200are the same as that shown in FIG.1.

While the inter-layer fault notifying portion400and the inter-layer node connecting information storage portion300shown inFIG. 1are illustrated as not being included in the L3fault manager100and the L2fault manager200, it is assumed in this embodiment that they are included in the L2fault manager200.

Also, information stored in the L3connecting information storage portion104provided in the L3fault manager100and the L2connecting information storage portion204provided in the L2fault manager200are respectively the same as those shown inFIGS. 12 and 13.

When a fault occurs on the link LK1as shown inFIG. 5, the ATM switch SW1notifies the L2fault manager200of the fault of the link LK1(see FIG.5(1)).

The inter-layer fault notifying portion400in the L2fault manager200retrieves the L2connecting information storage portion204in the L2fault manager200shown inFIG. 14with the information of the link LK1to obtain the SW1/port1and the SW2/port1as the information of the nodes at the opposite ends of the link LK1.

Based on this information, the inter-layer fault notifying portion400further retrieves the inter-layer node connecting information table shown inFIG. 4to obtain the RT1/port1and the RT2/port1respectively corresponding to the SW1/port1and the SW2/port1as information of the affected L3nodes.

Then, the L2fault manager200notifies the fault of the routers RT1and RT2to the L3fault manager100from the inter-layer fault notifying portion400(see FIG.5(2)). The L3fault manager100having received this notification performs a prior art fault restoration process

In this case, it is made possible to shorten the time for the router RT1or RT2to independently detect the fault in the prior art.

FIG. 6shows an embodiment of a link-affected node correspondence table stored in the affected node information storage portion500in the network management system according to the present invention schematically shown in FIG.2. In this table, each faulted link is preliminarily associated with the affected packet switching nodes (L3nodes) based on the L2connecting information shown in FIG.14and the information of the inter-layer node connecting information table shown in FIG.4.

Therefore, for example, the faulted link LK1is associated with RT1/port1and RT2/port1as shown in FIG.6.

An operational embodiment when using such an affected node information storage portion500will be described below, also referring to FIG.5.

Also in this case, although the affected node information storage portion500inFIG. 2is illustrated as not being included in the L3fault manager100and the L2fault manager200, in the same way as the above-mentioned inter-layer fault notifying portion400and the interlayer node connecting information storage portion300, the affected node information storage portion500storing the table shown inFIG. 6is included in the L2fault manager200shown inFIG. 5

Firstly, as for the fault which has occurred on the link LK1, the L2fault manager200receives the fault notification from the ATM switch SW1(see FIG.5(1)).

Next, the inter-layer fault notifying portion400in the L2fault manager200retrieves only the table ofFIG. 6with the information of the link LK1, recognizes that the affected packet switching nodes are the RT1/port1and the RT2/port1, and notifies the L3fault manager100of the fault of the routers RT1and RT2(see FIG.5(2)).

Therefore, it is made possible to further shorten the time up to the L3fault manager100receives the fault notification after the occurrence of the link fault.

FIG. 7shows an embodiment of a link-setting node correspondence table stored in the alternate route information storage portion600in the network management system according to the present invention schematically shown in FIG.3. This table preliminarily associates the links LK1-LK3with the alternate nodes (routers RT3, RT1, and RT2, respectively) upon the fault occurrence as the setting node requiring the setting of the quality policy.

The operational embodiment when using such an alternate route information storage portion600will be described herebelow, also referring to FIG.5.

Also in this case, although the alternate route information storage portion600inFIG. 3is illustrated as not being included in the L3fault manager100and the L2fault manager200, the alternate route information storage portion600storing the table shown inFIG. 7is assumed to be included in the L2fault manager200shown inFIG. 5, in the same way as the above-mentioned inter-layer fault notifying portion400, the inter-layer node connecting information storage portion300, and the affected node information storage portion500.

Firstly, as for a fault which has occurred on the link LK1, a fault notification is received from the ATM switch SW1(see FIG.5(1)).

Next, the inter-layer fault notifying portion400in the L2fault manager200recognizes the necessity of the setting of the quality policy to the router RT3, which is set for the alternate route in case of the fault of the link LK1, by retrieving the table of FIG.7.

Then, the inter-layer fault notifying portion400instructs the L3fault manager100by a command input to set the quality policy equivalent to the router RT1in the router RT3(see FIG.5(2)).

In case the quality policy is a priority, i.e. when L3fault manager100includes the priority information storage portion shown inFIG. 1, the priority information equivalent to the router RT1is set in the router RT3.

In this case, it means that the L2fault manager200plays a role of an administrator to the L3fault manager100concerning the setting of the quality policy. As a result, it is made possible to shorten the time required up to setting the quality policy to the alternate node after the link fault occurrence.

It is to be noted that apart from the priority, the bandwidth guarantee can also be set for the quality policy.

FIG. 8shows another embodiment of the link-setting node correspondence table stored in the alternate route information storage portion600in the network management system according to the present invention schematically shown in FIG.3.

The table shown inFIG. 8is different from the table shown inFIG. 7in that not only the router RT2but also the router RT3is associated as the setting node for the faulted link LK3.

This is because the network on which the table shown inFIG. 7is based has only a single router of the upper layer connected to a single ATM switch of the lower layer, whereas in the network on which the table shown inFIG. 8is based, the routers RT3and RT4are connected to the single ATM switch SW3as shown in FIG.9.

As forFIG. 9, when the fault occurs on the link LK1, the alternate routings are required for the affected routers RT1and RT2. As the alternate routes in this case, “RT1→RT4→RT3→RT2” and “RT1→RT3→RT2” exist, but the route of “RT1→RT3→RT2” has a fewer hop count and assumes the shortest route.

Also, as the alternate routes of the routers RT2and RT3affected by the fault of the link LK2, “RT2→RT1→RT4→RT3” and “RT2→RT1→RT3” exist, and “RT2→RT1→RT3” assumes the shortest route.

Thus, when a plurality of alternate routes exist for an arbitrary link, the alternate route information storage portion can be made to store only the node on the shortest route as the setting node.

Also, the routers affected by the fault of the link LK3are the routers RT1, RT3and RT4. In this case, the alternate route between RT1and RT3is “RT1→RT2→RT3” and the alternate route between RT1and RT4is “RT1→RT2→RT3→RT4”.

Therefore, in case of the network arrangement shown inFIG. 9, in the link-setting node correspondence table stored in the alternate route information storage portion600, the setting nodes are the router RT3in case of the fault on the link LK1, the router RT1in case of the fault on the link LK2, and the routers RT2and RT3in case of the fault on the link LK3as shown in FIG.8.

It is to be noted that, for example, a Dijkstra algorithm (E.W.Dijkstra, A note on two problems in connection with graphs, Numer. Math., 1(1959), pp. 269-271) can be used for a method of obtaining the shortest route.

In the description of the above-mentioned embodiments, it is assumed that a fault which has occurred in the lower layer always affects the upper layer. However, for example, the routers RT1and RT2are not affected if the alternate routing within the lower layer (SW1→SW3→SW2) is performed when a fault occurs on the link LK1in FIG.5.

If information of whether or not to perform such an alternate routing in the lower layer is preliminarily set in an alternate route setting table shown in FIG.10and provided, for example, in the L2fault manager200shown inFIG. 3so as to be referred by the inter-layer fault notifying portion400included in the L2fault manager200, it is made possible that the fault notification is not given to the L3fault manager100if the notified link is the link LK1which has the alternate route setting while being given to the L3fault manager100if it is the link LK2or LK3which has no alternate route setting.

As described above, the network management system according to the present invention is arranged such that an upper layer fault manager performs a fault management of an upper layer of a hierarchical network, a lower layer fault manager performs a fault management of a lower layer of the network, an inter-layer node connecting information storage portion manages connecting information between packet switching nodes composing the upper layer and link offering nodes composing the lower layer, and an inter-layer fault notifying portion notifies the upper layer fault manager, upon receiving a notification of a link fault which has occurred on a link between the link offering nodes from the lower layer fault manager, that the packet switching nodes affected by the fault are faulted, based on the connecting information. Therefore, it is made possible to shorten a time required up to detecting a fault after occurrence of the fault.

Also, the present invention is arranged such that an alternate route information storage portion associates each link with a packet switching node on an alternate route at a time of the link fault, and the inter-layer fault notifying portion instructs the upper layer fault manager to set predetermined information related to a communication quality to the packet switching node on the alternate route extracted from the alternate route information storage portion at the time of the link fault. Therefore, it is made possible to reduce a network communication quality deterioration.