US-12621185-B2 - Transmission method and transmission apparatus in ring network

US12621185B2US 12621185 B2US12621185 B2US 12621185B2US-12621185-B2

Abstract

According to the transmission method, labels to be used at the failure occurrence are previously and individually set to links in respective directions among all nodes on the one directional link connecting between adjacent nodes basis, and when a failure occurs, a failure notifying message is sent out onto a same directional ring from a termination node of a failed block, to be sequentially transferred to each downstream node, and a label table for connecting the links in cooperative with the reception of the failure notifying message is created in each node, and also, a bypassing path is formed by turning back the rings at both end nodes of the failed block. Thus, in a ring network of label switching system, it becomes possible to easily perform the label table management and also to set a bypassing path in a short time at the failure occurrence.

Inventors

Yuji Tochio

Assignees

Yuji Tochio

Dates

Publication Date: 20260505
Application Date: 20090326
Priority Date: 20080627

Claims (16)

1 . A transmission method for performing an avoidance control at a failure occurrence in a ring network which applies a label switching system among a plurality of nodes connected in a ring shape to transmit a packet bidirectionally, comprising the processes of: previously and individually setting only labels to be used at the failure occurrence to links in respective directions among all nodes, each of the links connecting adjacent nodes with one direction; when a failure occurs in a ring in either direction, in a node positioned on a termination point of a failed block, sending out a failure notifying message which notifies the failure occurrence to the ring in the same direction, and at the same time, connecting between an output port on the same directional ring side in an own node which sends the failure notifying message and an input port on the opposite directional ring side in the own node to thereby form a path for turning back the rings of respective directions, and also, rewriting a label table of the own node corresponding to the formed path in accordance with the labels to be used at the failure occurrence, to store the label table; sequentially transferring the failure notifying message sent out onto the ring in the same direction by each node on a downstream side from the node which sent the failure notifying message, and at the same time, in each node transferred the failure notifying message, for the labels to be used at the failure occurrence, creating a label table for connecting together two links adjacent to an own node which transfers the failure notifying message on the opposite directional ring side in accordance with the labels to be used at the failure occurrence, to store the label table; terminating the failure notifying message sequentially transferred by each downstream node at the node positioned on a starting point of the failed block, and at the same time, in the node at which the failure notifying message is terminated, connecting between an input port on the same directional ring side in an own node which terminates the failure notifying message and an output port on the opposite directional ring side in the own node to thereby form a path for turning back the rings of respective directions, and also, rewriting a label table of the own node corresponding to the formed path in accordance with the labels to be used at the failure occurrence, to store the label table; and during the failure occurrence, in each node, label switching the packet that has reached the failed block in accordance with the label table stored in each node to transmit it, thereby making the packet bypass the failed block.
2 . A transmission method according to claim 1 , further comprising the processes of: when the ring is restored from the failure, in the node positioned on the termination point of the failed block, stopping the failure notifying message sent to the ring in the same direction, and also, forming a path connecting the input and output ports on the same directional ring side in the own node and rewriting the label table in the own node corresponding to the formed path, to store the label table; and when the failure notifying message is stopped, in each node that has been transferred the failure notifying message, releasing the connection of the two links for the labels to be used at the failure occurrence, and also, in the node at which the failure notifying message is terminated, forming a path connecting between the input and output ports on the same directional ring side in the own node and rewriting the label table of the own node corresponding to the formed path, to store the label table.
3 . A transmission method according to claim 1 , wherein the failure notifying message contains information relating to labels corresponding to the failed block, and the node positioned on the starting point of the failed block terminates the failure notifying message, based on the information relating to the labels corresponding to the failed block, which is contained in the failure notifying message.
4 . A transmission method according to claim 1 , wherein each downstream node that has received the failure notifying message returns a response signal to the failure notifying message, and the node positioned on the termination point of the failed block judges the node positioned on the starting point of the failed block based on the response signal from each downstream node, to resend the failure notifying message to the node positioned on the starting point of the failed block.
5 . A transmission method according to claim 1 , wherein the node positioned on the termination point of the failed block detects the failure in the link adjacent thereto on an upstream side to send the failure notifying message.
6 . A transmission method according to claim 1 , wherein the node positioned on the termination point of the failed block detects the failure in the node adjacent thereto on an upstream side to send the failure notifying message.
7 . A transmission method according to claim 1 , wherein each node that has been transferred the failure notifying message creates, for the labels to be used at the failure occurrence, the label table for connecting the two links adjacent to the own node on the opposite directional ring side as well as the two links adjacent to the own node on the same directional ring side, to stored the label table.
8 . A transmission method according to claim 1 , wherein when priorities are set to packets transmitted over the rings in respective directions, the process of previously and individually setting the labels to be used at the failure occurrence sets a plurality of labels to be used at the failure occurrence to each of the links in respective directions among all nodes, and each node that has been transferred the failure notifying message creates, for the labels to be used at the failure occurrence, the label table for connecting priority-correspondent two links adjacent to the own node on the opposite directional ring side, to store the label table.
9 . A transmission method according to claim 1 , wherein when the ring network has a configuration in which a plurality of rings corresponding to the bidirectional transmission is connected to each other, the failure notifying message contains a ring ID enabling the discrimination of the ring in which the failure occurs among the plurality of rings, and a shared node on the plurality of rings, when the failure notifying message is received, transfers the failure notifying message to each node on a downstream side from the node which sent the failure notifying message on the ring in which the failure occurs, according to the ring ID contained in the failure notifying message.
10 . A transmission apparatus applied to each of a plurality of nodes in a ring network for applying a label switching system among the plurality of nodes connected in a ring shape to transmit a packet bidirectionally, comprising: two sets of input and output ports respectively connected to rings in respective directions; a switch which changes over signal paths between the two sets of input and output ports; a switch control section configured to control the switch; a failure detecting section configured to detect whether a failure occurs on the rings in respective directions, based on states of input signals to the respective input ports; a failure notifying message extracting section configured to extract a failure notifying message which notifies of the failure occurrence, sent out from a different node, based on the signals input to the respective input ports; a label table storing section configured to store a label table; a label table managing section in which only labels to be used at the failure occurrence are previously and individually set to links in respective directions among all nodes, each of the links connecting adjacent nodes with one direction, and the label table managing section is configured to manage the label table in the label table storing section; a label processing section configured to add, replace or remove the labels to the packet in accordance with the label table in the label table storing section; and a control message processing section configured to generate the failure notifying message which notifies of the failure occurrence, when the failure occurrence on the ring in either direction is detected by the failure detecting section, to send the failure notifying message onto the same directional ring, and also, configured to generate a switch change-over message which instructs connection of the output port on the same directional ring side and the input port on the opposite directional ring side to thereby form a path for turning back the ring in each direction, to output the switch change-over message to the switch control section, and configured to generate a label processing message which instructs rewriting of the label table corresponding to the formed path, to output the label processing message to the label table managing section; and when the failure notifying message from the different node is extracted by the failure notifying message extracting section, if an own node of the transmission apparatus is not positioned on a starting point of a failed block, configured to transfer the failure notifying message from the different node to the node on a downstream side from the own node on the same directional ring, and also, for the labels to be used at the failure occurrence, configured to generate a label processing message which instructs creation of the label table connecting the two links adjacent to the own node on the opposite directional ring side, to output the label processing message to the label table managing section, and if the own node is positioned on the starting point of the failed block, configured to terminate the failure notifying message from the different node, and also, configured to generate a switch change-over message which instructs connection of the input port on the same directional ring side and the output port on the opposite directional ring side to thereby form a path for turning back the ring in each direction, to output the switch change-over message to the label table managing section, and also, configured to generate a label processing message which instructs the rewriting of the label table corresponding to the formed path, to output it-the label processing message to the label table managing section.
11 . A transmission apparatus according to claim 10 , wherein when the restoration from the failure is detected by the failure detecting section, the control message processing section stops the failure notifying message sent to the same directional ring, and also, generates a switch change-over message which instructs to form a path connecting between the input and output ports on the same directional ring side, to output the switch change-over message to the switch control section and generates a label processing message which instructs to rewrite the label table corresponding to the formed path, to output the label processing message to the label table managing section; and when the failure notifying message from the different node is not extracted by the failure notifying message extracting section, if the own node is not positioned on the starting point of the failed block, the control message processing section generates a label processing message which instructs to release the connection of the two links for the labels to be used at the failure occurrence, to output the label processing message to the label table managing section, and if the own node is positioned on the starting point of the failed block, the control message processing section generates a switch change-over message which instructs to form a path connecting the input and output ports on the same directional ring side, to output the switch change-over message to the switch control section and generates a label processing message which instructs to rewrite the label table corresponding to the formed path, to output the label processing message to the label table managing section.
12 . A transmission apparatus according to claim 10 , wherein the control message processing section generates the failure notifying message containing information relating to the labels corresponding to the failed block, to output the failure notifying message to the same directional ring.
13 . A transmission apparatus according to claim 10 , wherein the control message processing section sends out the failure notifying message to the same directional ring, and thereafter, judges the node positioned on the starting point of the failed block based on a response signal to the failure notifying message returned from each node on a downstream side from the own node, to resend out the failure notifying message to the node positioned on the starting point of the failed block.
14 . A transmission apparatus according to claim 10 , wherein when the failure notifying message from the different node is extracted by the failure notifying message extracting section, if the own node is not positioned on the starting point of the failed block, the control message processing section generates a label processing message which instructs to create, for the labels to be used at the failure occurrence, the label table for connecting the two links adjacent to the own node on the opposite directional ring side as well as the two links adjacent to the own node on the same directional ring side, to output the label processing message to the label table managing section.
15 . A transmission apparatus according to claim 10 , wherein when priorities are set for packets transmitted over the rings in respective directions, the label table managing section registers therein a plurality of labels to be used at the failure occurrence according to set numbers of the priorities, and the control message processing section, when the failure notifying message from the different node is extracted by the failure notifying message extracting section, if the own node is not positioned on a starting point of the failed block, generates a label table processing message which instructs to create, for the labels to be used at the failure occurrence, a label table for connecting priority-correspondent two links adjacent to the own node on the opposite directional ring side, to output the label table processing message to the label table managing section.
16 . A transmission apparatus according to claim 10 , wherein when the ring network has a configuration in which a plurality of rings corresponding to the bidirectional transmission is connected to each other, the control message processing section, when the failure occurrence is detected by the failure detecting section, generates the failure notifying message containing a ring ID enabling the discrimination of the ring in which the failure occurs among the plurality of rings, to send the failure notifying message to the same directional ring; and when the failure notifying message from the different node is extracted by the failure notifying message extracting section, if the own node corresponds to a shared node on the plurality of rings and is not positioned on the starting point of the failed block, transfers the failure notifying message to the node on a downstream side from the own node on the ring in which the failure occurs, according to the ring ID contained in the extracted failure notifying message.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2008-168605, filed on Jun. 27, 2008, the entire contents of which are incorporated herein by reference. FIELD The embodiments discussed herein are related to a transmission method and a transmission apparatus for performing an avoidance control for when a failure occurs in a ring network applied with a label switching system. BACKGROUND In recent years, with the advancement of a packet technology, the application of packet to a carrier domain has been progressed. Further, a ring network is available as a network form capable of effectively interconnecting transmission paths. Therefore, an emphasis is placed on the application of packet technology to the ring network. In order to cope with such a situation, there has been proposed a ring network applied with a label switching system in which a packet added with a label, such as a MPLS (Multi-Protocol Label Switching) or the like, is transmitted and exchanged among nodes on a path. Further, with the extension of packet technology in the carrier domains, an avoidance control technology (to be referred to as a protection technology, hereunder) for restoring in a short time a state where the packet transmission is suspended due to the failure occurrence becomes important, and in particular, a protection system without the necessity of getting help from an operator is desirable to be realized. Such a protection system can be applied not only when the failure occurs, but also when the network is extended on the basis of a ring form or when a plurality of rings is interconnected. As a conventional protection system in the ring network applied with the label switching system, as illustrated in FIG. 18, there has been proposed a system in which, separately from an active path through which user data is transmitted over a ring in one direction, a loop redundant path in which the data flow is opposite to that in the active path is previously set, and at the failure occurrence, the label matching (label table) in nodes adjacent to a failed block (node #4 and node #5 in the example in the figure) is changed to thereby switch between the active path and the redundant path, so that the user data bypasses the failed block (refer to Japanese Laid-open Patent Publication No. 2002-344493). However, in the conventional protection system in the ring network applied with the label switching system as described above, there is a problem in that if the number of nodes on the ring or the number of links among nodes is increased, the label table of redundant path-compliant prepared for each node becomes complicated and the management thereof becomes hard. For example, in a network as illustrated in FIG. 19 in which six nodes are connected in a ring-shape, in order to realize the protection at an arbitrary site for a clockwise active path, since each node is required to verify the circularity of the redundant path, there are set six counterclockwise redundant paths each of which starting point/termination point is set at each node (arrow lines in the ring in FIG. 19). Further, similarly to this, for a counterclockwise active path, six clockwise redundant paths are set (arrow lines outside the ring in FIG. 19). Thus, it becomes necessary to set a label table corresponding to each of the 12 redundant paths in each node on the ring. Namely, the label tables of four times the number of nodes are set for one node, and therefore, if the number of nodes (or the number of links) on the ring is increased, the label management becomes complicated in the entire network. In order to solve the above problems, for setting only one redundant path for one directional active path to perform the effective protection, in the conventional technology, it is necessary to verify the connectivity of a bypassing path when the active path/redundant path switching processing is performed at the failure occurrence. This verification of connectivity is normally performed by a turning-back test (a loopback test), and therefore, a control signal for the test reciprocates the bypassing path for one time. A time required for the one time reciprocation of the control signal increases a switching processing time of the active path/redundant path, and therefore, it becomes hard to realize the protection in a short time. Thus, when the setting number of the redundant paths is reduced (efficiently improved) to achieve the easy of label management, there is also a problem of how the path switching processing time containing the connectivity verification of the bypassing path is shortened. SUMMARY According to an aspect of the invention, a transmission method for performing an avoidance control at the failure occurrence in a ring network which applies a label switching system among a plurality of nodes connected in a ring shape to transmit a packet in bidirectional, includes