JP2002044127A - Network abnormality countermeasure method and node unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a network abnormality countermeasure method that addresses an abnormal state caused by erroneously transmitting topology data in a network adopting the dynamic routing method. SOLUTION: All node units record a snap shot of topology data 28 at the same time according to an instruction from an NMS(Network Management System). Each node informs the NMS about the result of acquisition of the snap shot in a stable state where only a Hello packet is received for a prescribed period. When a network abnormality is detected in the case that all nodes obtain the snap shot, the topology data are replaced with the snap shot and routing processing is continued until the fault is recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a network employing a dynamic routing system,
The present invention relates to a method for coping with an abnormal state of the entire network and a node device therefor.

[0002]

2. Description of the Related Art OSPF (Open Shertest Path First) and A in IP (Internet Protocol) networks
PNNI (Private Network-Network Interface) in TM (Asynchronous Transfer Mode) network
For example, a dynamic routing method using a link state algorithm is used to create and update a network topology database for creating a routing table (route table).

[0003]

In this method, each node automatically updates its network topology database held by each node by transmitting its own link state to the network periodically and when the configuration is changed. There are advantages such as "short convergence time" and "hard routing loop". However, according to the principle of operation, if a node in the network operates abnormally and an incorrect link state flows through the network, it affects the topology database of the entire network and paralyzes the routing operation of the network. Can happen.

Accordingly, an object of the present invention is to provide a network employing a dynamic routing method,
An object of the present invention is to provide a method for coping with an abnormal state of the entire network and a node device therefor.

[0005]

According to the present invention, a plurality of nodes in a network exchange the link state of each node with each other so that each node holds the same topology data and performs routing. A method for coping with a network abnormality in a network used for control, wherein a snapshot of topology data when the network is in a stable state is recorded at the same time in each node, and while the network is in an abnormal state, a snapshot of each node is recorded. , A method comprising using the snapshot as topology data for routing control.

According to the present invention, by exchanging the link state of each node among a plurality of nodes included in the network, each node holds the same topology data and uses it for routing control in a network. Means for recording a snapshot of topology data when the network is in a stable state at the same time as another node, and a node device for coping with the abnormality while the network is in an abnormal state. Means for using as a topology data for routing control.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the present invention, a dynamic routing method in an OSPF in an IP network or a PNNI in an ATM network will be described. In the network configuration shown in FIG. 1, the network A is connected to the network C via the node 2.
It is connected to the. Here, a router corresponds to a node in an IP network, and an ATM switch corresponds to a node in an ATM network. Network C is further connected to network D via node 1. More specifically, network C is directly connected to port 1 of node 1 and network D is directly connected to port 0 of node 1.

Each node exchanges link states indicating which networks are directly connected to each node according to a link state algorithm, thereby constructing a topology database storing topology data as shown in FIG. Each node creates a routing table (route table) based on this topology data, and the routing of IP packets or ATM cells is performed according to the table. FIG. 3 shows a routing table of the node 1 in the example of FIG. According to the routing table of FIG. 3, for example, an IP packet or an ATM cell whose destination network has reached the node 1 is A,
Routed from port 1 to node 2.

The packets or cells include general user data packets or cells and routing protocol packets or cells. The user data packet or cell is routed according to the routing table as described above. In the case of a packet or cell for a routing protocol, the operation varies depending on the type, but in the case of a packet or cell carrying the above link state, it is transferred to another node and stored in the topology database as topology data shown in FIG. , A new routing table is created based on it.

FIG. 4 shows an example of a network configuration to which the present invention is applied. In FIG. 4, each node 10 is mutually connected via a network 12, and manages the entire network by an NMS (Network Management).
System 14). FIG. 5 shows a configuration of the node device 10 according to an embodiment of the present invention. The node device corresponds to, for example, a router in an IP network and an ATM switch in an ATM network. In FIG. 5, the NMS control unit 20 is the NM of FIG.
The port controller 22 exchanges data with the S. The port controller 22 routes packets or cells input and output from the port 24 in accordance with the routing table 25. The port control unit 22 corresponds to an ATM switch in the case of an ATM exchange. When the arriving packet or cell is a routing protocol packet or cell, the packet or cell is also sent to the main processor 26. If the link state is included in the packet or cell for the routing protocol, the topology data 28 is updated accordingly, and a new routing table 25 is created based on the updated topology data 28. The snapshot 30 will be described later.

In the embodiment described below, it is assumed that the times of all nodes under the NMS including the NMS completely match, so if the times do not match (not shown here) To match) in an appropriate way.
This time synchronization check is performed at an appropriate cycle, and the time is always matched between the nodes. FIG. 6 is a flowchart of a snapshot collection process in the main processor 26 of the node device 10. When the maintenance person instructs the NMS 14 to take a snapshot of the network, the NMS 14 designates a time for each node under the network, and at this time, copies the topology data held by each node. Prompt. When the time indicated by the NMS 14 is reached (Step 1000), each node 10 copies the topology data (Step 1002), and at the same time, verifies whether the data is sufficiently stable from the exchange of the topology data until immediately before by the following method. Then, the result is notified to the NMS (step 1008).

In general, packets used in the link state algorithm include a database description packet that carries network configuration information and a Hello packet indicating that the own node is available. Hello of the latter
Packets always flow on the network link at a certain interval when the own node is operating, but the former database description packet has a change in network configuration and is synchronized between each node Only used sometimes. From this fact, if only Hello packets are flowing on the link of the network for a certain period of time, then the network can be regarded as stable (synchronous).

FIG. 7 is a flowchart of a stable state determination process. In FIG. 7, when a packet is received (step 1100), it is determined whether or not the packet is a Hello packet (step 1102). If the packet is not a Hello packet, the stability timer is initialized (step 110).
4), the state is set to "unstable" (step 1106).
When the received packet is a Hello packet,
If the timer has expired (step 1108), the state is set to "stable" (step 1110).

[0014] The time (grace time) until it can be regarded as stable is the time held by each node, or
This is the time according to the instruction from the NMS, and each node may select one of these two methods. N
The MS 14 waits for notifications from all nodes, and checks whether or not sufficiently stable data has been obtained in all nodes. Through a series of these operations, all nodes in the network can hold a copy (snapshot) of the topology data at a certain time.

When creating a snapshot, the NMS
All nodes may autonomously collect snapshots at a fixed time without receiving the instruction of 14. In this case, the processing of the other parts is the same as described above. From now on,
Each node regularly checks the normality of the network according to the procedure shown in FIG. Each node calculates a value such as a call loss rate for connection-type connection and a packet loss rate for connectionless-type connection (step 1202). However, at the time of this calculation, the fault caused by the hardware installed therein is subtracted, and only the fault generated purely as a result of routing by software is calculated. When a specific route becomes unusable due to a hardware failure, the routing protocol itself is automatically excluded from the routing target, and there is no continuous call loss or packet loss. When the value thus calculated exceeds a certain reference value (step 1204), the network is determined to be in an abnormal state, and a notification to that effect is sent to the NMS (step 1206).

The reference value may be a value held unique to each node or a value specified by an NMS, and each node may select one of these two methods. FIG. 9 shows a process of the NMS when a notification of an abnormal state is received from any node. Upon receiving the abnormal state, the NMS instructs each node to discard the currently used topology data at the designated time and use the topology data saved as a snapshot (step 1302). . When each node instructed by the NMS reaches the designated time,
The topology data that is abnormal data is discarded, the routing table is regenerated from the held topology data, and the call processing operation is continued using this data. During this time, the cause of the abnormality is identified, recovered, and the topology data considered to be normal is completed by the link state algorithm, and then the NMS is notified (step 1).
304). The NMS receives this and notifies each node again of the return time to the normal mode (step 1306), and each node shifts to the normal mode according to the instruction. FIG. 10 shows an operation sequence of the NMS and the node when an abnormality is detected.

(Supplementary Note 1) By exchanging the link state of each node among a plurality of nodes included in the network, each node holds the same topology data with each other and causes a network abnormality in a network used for routing control. (A) snapshots of the topology data when the network is in a stable state are recorded at the same time in each node, and (b) while the network is in an abnormal state, Using the snapshot as topology data for routing control. (1) (Supplementary Note 2) In step (a), (i) the stability of the network is determined at each node, (ii) snapshots are created at the same time in each node, and (ii)
i) The method according to Appendix 1, comprising a sub-step of notifying each node to the network management system (NMS) when the creation of the snapshot when the network is determined to be stable is successful. (2) (Appendix 3) The sub-steps (a) and (ii) instruct the NMS to create a snapshot at a designated time from each node, and in each node, issue topology data at a designated time according to the instruction from the NMS. 3. The method of claim 2 including the sub-step of copying as a snapshot.

(Supplementary note 4) The method according to supplementary note 2, wherein in each of the sub-steps (a) and (ii), each node copies the topology data as a snapshot at a predetermined time regardless of an instruction from the NMS. (Supplementary note 5) The method according to Supplementary note 2, wherein in sub-steps (a) and (i), the network is determined to be stable when no link state is received from an adjacent node within a predetermined grace period.

(Supplementary note 6) The method according to supplementary note 5, wherein the grace time is set uniquely for each node. (Supplementary note 7) The method according to supplementary note 5, wherein the grace time is specified by an NMS. (Supplementary Note 8) In step (b), (i) in each node, the normality of the network is determined. (Ii) When it is determined that the network is abnormal, the node notifies the NMS to that effect. iii) The method of Appendix 1, including a sub-step of instructing each node to switch the topology data to a recorded snapshot at a specified time in response to the notification that the network is abnormal. (3) (Supplementary note 9) The supplementary note 8 described in Supplementary note 8, wherein, in the sub-steps (b) and (i), when the call blocking rate and / or the packet discarding rate excluding those due to the hardware failure exceed a predetermined threshold, it is determined that the network is abnormal. Method.

(Supplementary note 10) The method according to supplementary note 9, wherein the threshold value is set uniquely for each node. (Supplementary Note 11) The threshold is specified by NMS.
The described method. (Supplementary Note 12) In order to cope with a network abnormality in a network used for routing control by mutually exchanging the link state of each node among a plurality of nodes included in the network and each node holding the same topology data with each other and performing routing control Means for recording a snapshot of topology data when the network is in a stable state at the same time as another node, and routing the snapshot as topology data while the network is in an abnormal state. A node device comprising: a unit used for control. (4) (Supplementary Note 13) The snapshot recording means includes means for determining the stability of the network, means for creating a snapshot at the same time as the other nodes, and means for determining that the network is stable. 13. The node device according to supplementary note 12, further comprising: means for notifying the NMS when the snapshot has been successfully created. (5) (Supplementary note 14) The snapshot creation means receives the snapshot creation instruction at the designated time from the NMS, and copies the topology data as the snapshot at the designated time according to the instruction from the NMS. 14. The node device according to supplementary note 13, including means.

(Supplementary note 15) The node device according to supplementary note 13, wherein the snapshot creating means copies the topology data as a snapshot at a predetermined time regardless of an instruction from the NMS. (Supplementary Note 16) The network stability determining unit determines that the network is stable when a link state is not received from an adjacent node within a predetermined delay time.
The described node device.

(Supplementary note 17) The node device according to supplementary note 16, wherein the grace time is set uniquely for each node. (Supplementary note 18) The node device according to supplementary note 16, wherein the grace time is specified by an NMS. (Supplementary Note 19) The snapshot using means includes a means for determining the normality of the network, a means for notifying the NMS when the network is determined to be abnormal, and a topology in response to an instruction from the NMS. Data
13. The node device according to claim 12, further comprising: means for switching to a recorded snapshot at a designated time.

(Supplementary note 20) The node device according to supplementary note 19, wherein the network normality determining unit determines that the network is abnormal when the call loss rate and / or the packet discard rate excluding those due to hardware failures exceed a predetermined threshold. (Supplementary note 21) The node device according to supplementary note 20, wherein the threshold is set uniquely for each node.

(Supplementary note 22) The node device according to supplementary note 20, wherein the threshold is specified by an NMS.

[0025]

As described above, according to the present invention, it is possible to prevent the worst situation in which the entire network is paralyzed due to the failure of one node and the service cannot be provided. Communication between nodes can be continued and availability can be maintained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a network configuration.

FIG. 2 is a diagram showing topology data in the network configuration of FIG. 1;

FIG. 3 is a diagram showing a routing table of a node 1 generated from the topology data of FIG. 2;

FIG. 4 is a diagram showing an example of a network configuration to which the present invention is applied.

FIG. 5 is a block diagram illustrating a hardware configuration of a node device.

FIG. 6 is a flowchart of a snapshot collection process.

FIG. 7 is a flowchart of a stable state determination process.

FIG. 8 is a flowchart of a node operation normality confirmation process.

FIG. 9 is a flowchart of an operation of the NMS when an abnormality occurs.

FIG. 10 is a sequence diagram showing operations of the NMS and each node when an abnormality occurs.

Claims (5)

[Claims] 1. A method for exchanging the link state of each node among a plurality of nodes included in the network to cope with a network abnormality in a network used for routing control by each node holding the same topology data. The method comprises: (a) recording a snapshot of topology data when the network is in a stable state at each node at the same time; and (b) performing a snapshot at each node while the network is in an abnormal state. Using the shots as topology data for routing control. 2. The step (a) comprises: (i) determining the stability of the network at each node; (ii) creating snapshots at the same time at each node; and (iii) stabilizing the network. If it is determined that the snapshot has been successfully created, the respective nodes notify the network management system (NM)
2. The method according to claim 1, comprising the substep of notifying S). 3. The step (b) includes: (i) determining the normality of the network at each node; and (ii) notifying the NMS from the node when it is determined that the network is abnormal, 3. The method of claim 1, further comprising: (iii) in response to the notification that the network is abnormal, instructing each node from the NMS to switch the topology data to the recorded snapshot at the specified time. . 4. A plurality of nodes included in the network exchange the link state of each node with each other, so that each node holds the same topology data and copes with a network abnormality in a network used for routing control. Means for recording a snapshot of the topology data when the network is in a stable state at the same time as the other nodes, and using the snapshot as topology data while the network is in an abnormal state. A node device comprising: means used for routing control. 5. A snapshot recording means, means for determining the stability of the network, means for creating a snapshot at the same time as another node, and snapshot when the network is determined to be stable. 5. The node device according to claim 4, further comprising means for notifying the NMS when the shot is successfully created.