JP2006080895A - Transmission system and its node device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission system capable of efficiently protecting traffic in a short period of time and its node device. <P>SOLUTION: A result of fault detection by a monitor of an input interface is notified upstream nodes through a different route in addition to fault detection by exchanging a hello message and Ack. Each node recognizes the occurrence of a fault on the basis of a result of these notification. This can shorten a period required for fault detection. The result of fault detection is notified not only adjacent nodes on an upstream side but also a far node located across a link for one hop. Consequently, a link fault and a node fault can be separately recognized on the basis of each notification combination so that link protection with low resources consumption can surely be carried out. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a transmission system having a mesh topology and a node device provided in the transmission system.

  In recent information transmission systems, a plurality of nodes are often connected in a mesh form via a link to form a mesh network. In order to allocate transmission resources of a mesh network to a plurality of communication paths, a method of searching for an optimum route by a routing algorithm has been applied conventionally. Various studies have also been made on the protection method for the assigned communication path.

  By the way, the failure is roughly classified into either a failure occurring in the node (node failure) or a failure occurring in the link (link failure) depending on the occurrence location. When a failure occurs in an existing transmission system, regardless of the location of the failure, the traffic passing through the failure location is uniformly diverted from the node immediately before the failure location to the next two nodes. Yes. That is, the traffic is diverted toward the node that is two nodes ahead of the failed link or the node that is one node ahead of the failed node. Such a traffic protection mode is referred to as (Next-Next-Hop Protection).

  However, this form may require a plurality of traffic detours, which is disadvantageous in terms of network scalability. At least for link failures, traffic should be protected by a single detour protection (referred to as Next-Hop Protection) towards the next node on the failed link.

  Further, the presence / absence of a failure is recognized by transmitting a Hello message from each node to the adjacent downstream node and monitoring reception of an Ack message. When an Ack message is no longer received at a certain node, it can be recognized that a failure has occurred in the direct link or the direct node. However, this process takes time, and link failure and node failure cannot be distinguished.

A related technique is disclosed in Patent Document 1 below. This document discloses an apparatus for maintaining a connection through an optimum route corresponding to the occurrence and recovery of a failure on a connection-oriented network. However, the technique of this document cannot solve the above problem.
Japanese Patent Laid-Open No. 2001-197071

As described above, the traffic protection method in the existing transmission system has room for further study from the viewpoint of efficiency and time required.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a transmission system and its node device capable of protecting traffic efficiently and in a short time.

  In order to achieve the above object, according to one aspect of the present invention, in a transmission system in which a plurality of nodes are connected in a mesh shape via a link, each of the plurality of nodes is located downstream in the traffic transmission direction. Inquiry means for sending an inquiry message (for example, Hello) to an adjacent node, monitor means for monitoring a transmission signal received from a link adjacent on the upstream side in the traffic transmission direction, and failure of the transmission signal by this monitoring means Is detected, notification means for notifying failure detection information to the opposite node across the link adjacent to the upstream side, presence / absence of a response message (for example, Ack) to the inquiry message, and the failure detection information Recognizing means for recognizing a failure state according to presence / absence, and traffic protection operation according to the failure state Protection means for performing, when the response message is not present and there is no failure detection information, the recognition means recognizes the occurrence of a node failure that is a failure of a node adjacent to the downstream side, and the protection means Is configured to perform node protection that bypasses the traffic to a node adjacent to the downstream side of the node adjacent to the downstream side when the occurrence of a node failure is recognized by the recognition unit. A system is provided.

  Particularly in the present invention, when the transmission means detects the failure of the transmission signal, the notifying means is connected to the node adjacent to the upstream side of the node facing the link adjacent to the upstream side. The failure detection information is notified, and the recognition means has the failure detection information from the node adjacent to the downstream side, and if there is no failure detection information from the node adjacent further downstream of the node, the downstream Recognizing the occurrence of a link failure, which is a link failure between the node adjacent to the node and the own node, and the protection means recognizes the occurrence of a link failure by the recognition means. It is characterized in that link protection is performed to bypass the traffic to an adjacent node.

  By taking such measures, in addition to the existing failure detection by exchanging Hello and Ack, each node can check whether there is a failure in the system based on failure detection information notified via the transmission plane or control plane. Can be detected. This makes it possible to quickly recognize a failure. Furthermore, by notifying not only the adjacent upstream node but also the node connected further upstream, the failure detection information can be recognized individually for each node by verifying the presence / absence of each node. Is possible. Accordingly, link protection can be implemented, and traffic can be efficiently protected.

  ADVANTAGE OF THE INVENTION According to this invention, the transmission system and its node apparatus which can protect traffic efficiently and in a short time can be provided.

  FIG. 1 is a system diagram showing an embodiment of a transmission system according to the present invention. FIG. 1 shows a form in which node devices (hereinafter referred to as nodes) 1 according to the present embodiment are connected in a mesh form via a link L. The node 1 (1-1 to 1-19) is, for example, a cross-connect device or a router device used in a digital signal transmission system compliant with a standardized method such as SDH (Synchronous Digital Hierarchy) or SONET (Synchronous Optical Network). Realized. The link L is an optical fiber, for example, and transmits an optical signal. The transmission signal need not be limited to light, and each node 1 may be connected by an electrical interface.

  The node 1 is connected to another node 1 through a link L to construct a network having a mesh topology. In a mesh topology, each node can be adjacent to a plurality of nodes, thereby providing traffic detours with various routes. This is a great advantage of the mesh topology, and it is difficult to obtain such an advantage in a system in which the number of adjacent nodes is limited to two, such as a ring network. The present invention realizes a protection function that takes full advantage of the mesh topology. Next, the protection function according to the present invention will be described in more detail.

  FIG. 2 is a functional block diagram showing an embodiment of the node 1 of FIG. The node 1 includes a high-speed interface unit (HS I / F) 7, a low-speed interface unit (LS I / F) 3, a cross connect 4, a storage unit 5, and a control unit 6.

  The high-speed interface unit 7 separates the multiplexed transmission signal introduced through the link L into each channel and inputs it to the cross connect 4, and multiplexes each channel signal given from the cross connect 4 to link L To send. The low speed interface unit (LS I / F) 3 accommodates the client interface via the low speed line 200.

  The cross-connect 4 arbitrarily sets channels of transmission signals given from the high-speed interface unit 7, the standby high-speed interface unit 2, and the low-speed interface unit 3, and forms a transmission path in the network. The storage unit 5 stores various programs and data necessary for the operation of the control unit 6. The control unit 6 executes various control functions based on the data stored in the storage unit 5.

  The control unit 6 includes an inquiry processing unit 6a, a monitor processing unit 6b, a notification processing unit 6c, a recognition processing unit 6d, a protection processing unit 6e, and a detour route setting unit 6f. The inquiry processing unit 6a sends a hello message to a node adjacent downstream in the traffic transmission direction. The monitor processing unit 6b receives a transmission signal transmitted from a link adjacent to the upstream side in the traffic transmission direction, and monitors its state.

  When the monitor processing unit 6b detects a transmission signal failure, the notification processing unit 6c notifies failure detection information to the opposite node across the link adjacent to the upstream side. The recognition processing unit 6d recognizes a failure state according to the presence / absence of an Ack message for the hello message and the presence / absence of failure detection information. The protection processing unit 6e performs a traffic protection operation according to the recognized failure state. The detour route setting unit 6f calculates and reserves a route for detouring traffic in advance when the network is configured in FIG. A detour route may be set at the time of failure detection. Each of these processing units is realized as a functional object by software.

FIG. 3 is a diagram illustrating a traffic detour route when a link failure occurs in the existing system. In the figure, (x) marks indicate failures. When attention is paid to the node immediately below the failure in the transmission direction of the transmission traffic, the traffic is detoured from the node immediately before the failure point to the node two nodes ahead. Due to the mesh topology, a bypass route can be easily secured.
FIG. 4 is a diagram showing a traffic detour path when a node failure occurs in the existing system. Even in this case, a detour route similar to that in FIG. 3 is secured.

  FIG. 5 is a diagram illustrating a more ideal detour route at the time of a link failure. As shown in FIG. 5, in the case of a link failure, the detour to the second node as shown in FIG. This is because it is sufficient that only the failed link can be avoided, and more efficient network operation can be expected. In the following, a method for realizing such detour processing will be described.

  FIG. 6 is a schematic diagram illustrating the function of a node in the present embodiment. A node periodically transmits a hello message to an adjacent node via a downstream link. The node that has received the hello message returns an Ack message to the upstream transmission source node. If Ack is not received for a certain period, it is determined that a failure has occurred in the downstream link, and the protection operation is activated. The message is not limited to Ack, and any other message may be used as long as it indicates the normality of the link.

  The node monitors the transmission signal received via the high-speed interface unit 7 and, when a signal failure is detected, notifies the failure detection information to all nodes one upstream and two upstream of the interface. The failure detection information to one upstream and the message indicating the normality of the link can be notified by using a low layer interface such as SONET / SDH overhead. In addition, a control plane formed by a network dedicated to network control may be used. Two upstream failure detection information is notified using the control plane.

Table 1 is a table in which combinations of the presence / absence of Ack and the presence / absence of failure detection information for a Hello message are associated with a node failure or a link failure. In the present embodiment, the failure notification information is notified from the node that has detected the failure to all the nodes upstream and two upstream, so the following Table 1 can be created as a logical consequence. .

  The node collects the failure detection information and the Ack notification from the first node facing each other across the transmission link of the failure location, and the failure detection information notification from the second node, and protects according to the conditions shown in Table 1. Perform the action. The link protection detour route and the node protection detour route are set in advance before the occurrence of a failure.

  The node that has received the failure detection information notification from the downstream node becomes the activation main body (main node (own node)) of the protection operation. The failure detection information notification from the downstream node means that there is no failure detection information notification from the next node or a reply (Ack) to the hello message issued by the main node, or failure detection from the second node This is when an information notification is received.

(Case 1) and (Case 3)
If there is no failure detection information notification from the next node and Ack is returned, it is determined that transmission between the main node and the next node is normally performed, and thus the protection operation is performed. Absent.

(Case 2) and (Case 4)
If there is no failure detection information notification from the one node ahead, but Ack is not returned, there is a suspicion that the one node is not operating normally. The transferred data is relieved by node protection. Since node protection is not possible when the data destination is one node ahead, link protection to a detour route to the node ahead is performed.
FIG. 7 is a schematic diagram showing node protection. In node protection, two links are skipped. For this reason, network utilization efficiency tends to be sacrificed.

(Case 5)
If there is a failure detection information notification from the next node and no failure detection information notification from the second node, it is determined that there is a link failure between the main node and the next node. can do. Therefore, the data that has been transferred from the main node to the next node through the failure section is transferred to the next node through another route by link protection.
FIG. 8 is a schematic diagram showing link protection. In link protection, it is sufficient to skip only the faulty link, so that the consumption of transmission resources can be minimized, which is advantageous from the viewpoint of scalability.

(Case 6)
When there is a failure detection information notification from the next node and a failure detection information notification from the second node, the link between the main node and the next node and the next node It can be determined that a failure has occurred in each of the links between the two nodes. That is, the occurrence of a double link failure can be recognized. In this case, node protection is performed, and the data that has been transferred from the main node to the next node through the failure section is switched to another route that jumps over the next node and transfers it to the next node. .

  Further, Case 5 and Case 6 may be simultaneously established on the same subject node and one node ahead. In this case, as shown in FIG. 9, the two protections operate independently. In case 6, the state of case 5 may be temporarily routed. In this case, after performing the link protection operation, the process proceeds to the node protection operation.

  As described above, in this embodiment, in addition to detecting a failure by sending and receiving a Hello message and an Ack, the result of the failure detection by monitoring the input interface is notified to the upstream node through another route. Each node recognizes the occurrence of a failure based on the result of these notifications. As a result, the time required for failure detection can be shortened. In addition, the failure detection result is notified not only to the node adjacent to the upstream side, but also to the node that is further past the link for one hop. This makes it possible to recognize link failures and node failures separately based on the combination of notifications, and to reliably execute link protection with low resource consumption. Accordingly, it is possible to provide a transmission system and its node device that can efficiently protect traffic in a short time.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

1 is a system diagram showing an embodiment of a transmission system according to the present invention. The functional block diagram which shows embodiment of the node 1 of FIG. The figure which shows the traffic detour route when a link failure arises in the existing system. The figure which shows the traffic detour route when a node failure arises in the existing system. The figure which shows the more ideal detour route at the time of a link failure. The schematic diagram which shows the function of the node in embodiment of this invention. The schematic diagram which shows a node protection. The schematic diagram which shows a link protection. The schematic diagram which shows the state in which node protection and link protection operate | moved independently.

Explanation of symbols

  L ... Link, 1 ... Node device, 3 ... Low speed interface unit, 4 ... Cross connect, 5 ... Storage unit, 6 ... Control unit, 6a ... Inquiry processing unit, 6b ... Monitor processing unit, 6c ... Notification processing unit, 6d ... Recognition processing unit, 6e ... protection processing unit, 6f ... detour route setting unit, 7 ... high speed interface unit, 200 ... low speed line

Claims (12)

In a transmission system in which a plurality of nodes are connected in mesh via a link,
Each of the plurality of nodes is
Inquiry means for sending an inquiry message to a node adjacent downstream in the traffic transmission direction;
Monitoring means for monitoring a transmission signal received from a link adjacent upstream in the traffic transmission direction;
A notification means for notifying failure detection information to nodes facing each other across a link adjacent to the upstream side when a failure of the transmission signal is detected by the monitoring means;
Recognizing means for recognizing a failure state according to presence / absence of a response message to the inquiry message and presence / absence of the failure detection information;
Protection means for performing a traffic protection operation according to the failure state,
The recognition means is
When there is no response message and no failure detection information, it recognizes the occurrence of a node failure that is a failure of a node adjacent to the downstream side,
The protection means includes
When the recognition unit recognizes the occurrence of a node failure, the transmission system is characterized in that node protection is performed to bypass the traffic to a node adjacent further downstream of the node adjacent to the downstream side. The notification means notifies the failure detection information to a node adjacent to an upstream side of a node opposed to each other across a link adjacent to the upstream side when a failure of the transmission signal is detected by the monitoring unit. ,
The recognition means is
If there is failure detection information from a node adjacent to the downstream side, and there is no failure detection information from a node adjacent to the downstream side of this node, between the node adjacent to the downstream side and the own node Recognize the occurrence of link failure, which is a link failure,
The protection means includes
2. The transmission system according to claim 1, wherein when the occurrence of a link failure is recognized by the recognizing unit, link protection is performed to bypass the traffic to a node adjacent to the downstream side. The recognition means is
When there is failure detection information from a node adjacent to the downstream side, and there is failure detection information from a node adjacent to the downstream side of this node, between the node adjacent to the downstream side and the own node Recognizing the occurrence of a double link failure, which is a failure of a link and a link between a node adjacent to the downstream side and a node adjacent to the downstream side of the node;
The protection means includes
The transmission system according to claim 2, wherein when the occurrence of a double link failure is recognized by the recognition means, the node protection is performed. The transmission system according to any one of claims 1 to 3, wherein the notification unit notifies the other party of the failure detection information via a transmission plane that transmits the transmission signal. The transmission system according to any one of claims 1 to 3, wherein the notification unit notifies the other party of the failure detection information via a control plane different from a transmission plane that transmits the transmission signal. 3. The detour route setting means for preliminarily reserving a traffic detour route for the node protection and a traffic detour route for the link protection prior to failure detection. Transmission system. In the node device provided in a transmission system in which a plurality of node devices are connected in a mesh shape via a link,
Inquiry means for sending an inquiry message to a node device adjacent downstream in the traffic transmission direction;
Monitoring means for monitoring a transmission signal received from a link adjacent upstream in the traffic transmission direction;
A notification means for notifying failure detection information to a node device that is opposed across the link adjacent to the upstream side when a failure of the transmission signal is detected by the monitoring means;
Recognizing means for recognizing a failure state according to presence / absence of a response message to the inquiry message and presence / absence of the failure detection information;
Protection means for performing a traffic protection operation according to the failure state,
The recognition means is
When there is no response message and no failure detection information, it recognizes the occurrence of a node failure that is a failure of a node device adjacent to the downstream side,
The protection means includes
A node protection device that, when a node failure is recognized by the recognizing unit, performs node protection that causes the node device adjacent to the downstream side of the downstream side device to bypass the traffic. apparatus. When the transmission unit detects a failure in the transmission signal, the notification unit sends the failure detection information to a node device adjacent to the upstream side of a node device facing the link adjacent to the upstream side. Notify
The recognition means is
If there is failure detection information from a node device adjacent to the downstream side and there is no failure detection information from a node device adjacent further downstream of the node device, the node device adjacent to the downstream side and its own node Recognizing the occurrence of a link failure, which is a link failure with the device,
The protection means includes
8. The node device according to claim 7, wherein when the occurrence of a link failure is recognized by the recognizing unit, link protection is performed so that the node device adjacent to the downstream side bypasses the traffic. The recognition means is
When there is failure detection information from a node device adjacent to the downstream side, and there is failure detection information from a node device adjacent to the downstream side of this node device, the node device adjacent to the downstream side and its own node Recognizing the occurrence of a double link failure, which is a failure between a link between the device and a node device adjacent to the downstream side and a node device adjacent to the downstream side of the node device;
The protection means includes
9. The node device according to claim 8, wherein when the occurrence of a double link failure is recognized by the recognition unit, the node protection is performed. The node device according to claim 7, wherein the notification unit notifies the other party of the failure detection information through a transmission plane that transmits the transmission signal. The node device according to claim 7, wherein the notification unit notifies the other party of the failure detection information through a control plane different from a transmission plane that transmits the transmission signal. 8. The detour path setting means for preliminarily reserving a traffic detour path for the node protection and a traffic detour path for the link protection prior to failure detection. Node equipment.

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