JP2000232481A - Bypassing method and system in data communication network without communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish bypass control technique for economically realizing a rapid and flexible bypass control function which can be applied even to a wide range and large scale network. SOLUTION: Each repeater 1 reads the contents of the incoming side address (DA) in an incoming PDU(protocol data unit), retrieves a route information table 2 and discriminates the presence of output routes which are not in a clogged state. When the output routes which are not in a clogged state exist, the most preferential output route among the ones which are not in the clogged state concerning DA is selected and PDU is transferred to the selected route. Unless the output routes which are not in a clogged state exist, the PDU is abandoned, its incoming route is discriminated and a 'network state report message (clogging)' is transmitted to the opposing device of the incoming route of PDU. Thus, a route change-over processing is executed by the device of a preceding stage one by one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connectionless data communication network which is capable of quickly and economically recovering the degradation of availability and performance of network services even in the event of network failure or congestion. About the detour method.

[0002]

2. Description of the Related Art In a data communication network, when a failure or congestion occurs, a network operator is provided with a network to cope with such actions as detouring, repairing a failed part, and redesigning / reconstructing the network. There is a need for a means for notifying information about the abnormal state of the device. As such notification means, an out-channel notification method using a control communication network different from the main data communication network and an in-channel notification method using the main data communication network are conventionally used.

Further, as an example of the in-channel notification method, there is a method of notifying by redistributing route information updated when a failure is detected in a routing protocol in an autonomous system in an autonomous distributed data communication network. Method for notifying information about the network status to the source of data found in the control message protocol in a mobile data communication network, asynchronous transfer mode (ATM: As
OAM (Operatio) seen in asynchronous TransferMode
n And Maintenance) There is an alarm transfer function.

[Conventional method 1] In the out-channel notification method, a control communication network is constructed separately from the main data communication network, and information on network status is transmitted and received together with various control information via the control communication network. Since the control communication network is generally constituted by a low-speed line, a certain delay or more occurs as compared with the in-channel notification method.

[Conventional method 2] In a routing protocol in an autonomous system in an autonomous decentralized data communication network, a device that detects a failure sequentially notifies neighboring devices of new route information or network configuration information reflecting the failure. As a result, failure notification is realized by a method in which failure information is distributed throughout the entire network. In this method, the route calculation process and the failure information notification process are performed simultaneously in parallel, so in a large-scale network, a certain delay or more occurs until the route information of the entire network matches, and the network becomes temporarily inoperable. May be in a stable state. In addition, in the application to a wide-area large-scale network, the consumption of bandwidth due to exchange of routing information or network configuration information cannot be ignored.

[Conventional method 3] In a control message protocol in an autonomous decentralized data communication network, when there is no reachability to a destination host or network, a protocol data unit (hereinafter referred to as PDU) is sent from a relay device that is finally determined as unreachable. ) Is sent to the sender address (SA). This method expects the sender or terminal of the PDU to perform an operation such as searching for and repairing a faulty part or changing terminal settings. Even if there is sufficient redundancy in the network, the redundancy is not required. Cannot be quickly and fully exploited by network functions.

[Conventional method 4] O in ATM communication system
In the AM alarm transfer function, a network abnormality state is notified to an adjacent device using a preset logical transmission path, that is, a channel on a connection. In order to realize the same mechanism in the connectionless communication network, it is necessary to set up a virtual connection on the network abnormal state search path.
It is difficult to implement this mechanism to support the entire network economically.

[0008]

In a connectionless data communication network, there are the following four methods for notifying a network abnormal state for the purpose of detour control. (1) Out-channel notification method by control communication network. (2) Redistribution of routing information or network configuration information by a routing protocol. (3) Notification of unreachability to SA by control message protocol. (4) Realization of a mechanism equivalent to the OAM alarm transfer function in ATM.

In the method (1), the delay in the notification of the network abnormality state and the detour control becomes relatively large, and is not suitable for the detour control in the event of a network abnormality requiring immediacy.

In the method (2), the notification / propagation of the network abnormal state and the route optimization calculation are performed simultaneously and in parallel, so that the convergence time until the route information of the entire network matches and the bandwidth required for fault information notification. There is a problem from the viewpoint of applicability to a wide area large scale network.

In the method (3), since information on the network abnormal state is directly returned to the sender of the PDU, it is difficult to flexibly cope with the network abnormal state by the function of the network.

In order to apply the method (4) to a connectionless communication network, it is necessary to set a virtual connection for searching for and notifying a network abnormal state. Not be able to take advantage of the economic benefits that exist.

The present invention has been made to solve the above-mentioned problems, and has a detour control technique for economically realizing a quick and flexible detour control function applicable to a wide-area large-scale network. The purpose is to establish.

[0014]

In order to solve the above problems, according to the present invention, a terminal device or a relay device in a connectionless data communication network is provided with, for example, means as shown in FIG. , Notification of recovery from a network error, detour control in the event of a network error, and switchback control in the event of a network error recovery.

The terminal device or the relay device 1 is connected in multiple stages by a plurality of physical or logical transmission lines to form a connectionless data communication network. The route information table 2 is a table in which information for each terminal device or the relay device 1 to use for route selection is set.

The failure detecting section 3 is a means for detecting a self-accommodated transmission line failure, a self-device failure, and a neighboring device failure. The congestion detection unit 4 is means for detecting congestion in the self-contained transmission line. The route closing unit 5 is a unit that closes a route related to a detection route in the route information table 2 when a network abnormal state is autonomously detected.

The failure recovery detecting unit 6 is provided with a
This is a means for detecting recovery from a failure in the own device and a failure in an adjacent device. The congestion mitigation detecting unit 7 is means for detecting congestion mitigation in the self-contained transmission line. The route block release unit 8 is a unit that, when autonomously detecting the recovery of the network abnormal state, releases the blocked route among the routes related to the detection route in the route information table 2.

The PDU DA reading unit 9 is a means for reading a destination address (hereinafter, referred to as DA) of the PDU. The route information table search unit 10 is a means for searching the route information table 2 based on DA. Route selection unit 11
Is a means for selecting, from the route information table 2, a route having the highest priority among routes that are not in the closed state. PDU
The discarding unit 12 is a unit that discards the PDU when a route that is not in the blocked state cannot be found in the route information table 2.

The blocking notification unit 13 is a means for transmitting a network abnormal status notification message (blocking) to an incoming route of the PDU when a route that is not blocked is not found in the route information table 2. The block release notification unit 14 detects a return from an abnormal state such as a failure recovery or a congestion alleviation in the self-contained transmission line, the adjacent device, or the own device, or is instructed by the adjacent device to release the block of the route. This is a means for sending a network abnormal state notification message (blockage release) to the adjacent device when the state of the route to the DA changes from a state in which all blocks are blocked to a state in which some or all of the paths are not blocked.

The Anycast address writing unit 15
A special address (An
ycast address). PDU (Anyc
ast address) receiving unit 16 stores A
This is a means for interpreting the nycast address and receiving the PDU.

The route blocking unit 17 based on the blocking message
When the network abnormal state notification message (blocking) is received, this is a means for blocking the path related to the DA. The route block release unit 18 based on the block release message is means for releasing the block related to the DA when a network abnormal state notification message (block release) is received.

According to the present invention, a highly reliable connectionless data communication network having a quick detour control mechanism can be easily realized according to the present invention. Because a simple message protocol is used to notify the network abnormal state,
This has the effect of suppressing the processing load related to the band required for notification and the bypass control.

Further, by causing the network abnormal state detecting device to execute the route switching process one by one in the device at the preceding stage, the redundancy at the transmission line level of the network can be sufficiently utilized.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows a network configuration according to an embodiment of the present invention. Here, 1-1 and 1-2 are terminal devices for transmitting and receiving PDUs via a network, 21,
22, 23, 24, 25, and 26 are relay devices that select a transfer destination route hop-by-hop based on the DA of the PDU and transfer the PDU, 101, 102, 103, 104,
105, 106, 107, 108, 109, 110, 1
Reference numeral 11 denotes a physical or logical transmission path.

The PDU sent from the terminal device 1-1 to the terminal device 1-2 is transferred via a relay device and a transmission line on the way. The terminal device is a device having the same function as the relay device with respect to the PDU transfer mechanism except that the terminal device becomes the start point or the end point of the communication.

FIG. 3 is a diagram in which route information to be performed by a PDU addressed to the terminal device 1-2 is extracted from a route information table in the relay device and the terminal device constituting the network. The route information table used by the relay device and the terminal device to determine the transfer destination route of the PDU includes a “DA field” serving as a search key, an “outgoing route field” storing next transfer destination information, and the same DA. "Priority field" that describes the priority in the transfer to
And the "block flag field" indicating the block status of the route
Is composed of the following four fields. For one DA,
A plurality of routes having different priorities can be set. In addition, by setting a blocking flag of a record related to a route recognized as being in an abnormal state to a value other than 0 in response to a notification from an adjacent device or failure information or congestion information obtained by autonomous detection, the corresponding record is set. Can be disabled. Hereinafter, the state of the “blocking flag $ 0” is referred to as a path blocking state. Resetting the route blocking flag to 0 is called blocking release.

In this embodiment, a network status notification message (blockage) and a network status notification message (blockage release) are used to notify a network abnormal state.

The network status notification message (blockage) is generated by detecting an abnormal state such as a failure or congestion in the self-contained transmission line, the adjacent device, or the own device, or instructing the adjacent device to close the route. When the relay device having all the routes to the relay device receives the PDU addressed to the DA, the relay device notifies or instructs the preceding relay device not to transfer the subsequent PDU addressed to the DA to its own device. Used for

The network status notification message (blockage) is received and interpreted by the opposite device in the message transmission line of the message transmission device, and is used as a trigger for closing the route information table of the message reception device. This message notifies information of “target DA”, “instruction content (blockage)”, and “instruction reason (failure, congestion, etc.)”, but may include other additional information. If there is no particular problem, a message used for another purpose such as an unreachable message may be used instead.

The network status notification message (block release) is used to detect a return from an abnormal state such as failure recovery or congestion mitigation in the self-contained transmission line, the adjacent device, or the own device, or instruct the route release from the adjacent device. As a result, when a path for a certain DA changes from a state in which all routes are blocked to a state in which some or all routes are not blocked, it is used to notify an adjacent device of release of blocking.

The network status notification message (block release) is received and interpreted by the opposite device on the message transmission line of the message transmitting device, and is used as a trigger for releasing the block of the routing information table of the message receiving device. This message notifies the information of “target DA”, “instruction content (block release)”, and “instruction reason (failure recovery, congestion alleviation, etc.)”, but may include other additional information.
If there is no particular problem, a message used for another purpose such as an unreachable message may be used instead.

These messages are special addresses (Anycast addresses) that are uniquely defined in the network and represent “the other device on the transmission line” or “all devices on the transmission line”.
Is sent to A device that receives a PDU addressed to an Anycast address indicating "another device on the transmission line" or "all devices on the transmission line" interprets the contents of the PDU without transferring the PDU to an adjacent device, and responds to the contents. Action must be performed.

FIG. 4 shows P in the relay device and the terminal device.
4 shows a flow of a DU transfer process. The outline of the process in the relay device related to the transfer of the PDU is as follows. Step S1: Read the contents of DA of the incoming PDU. Step S2: The route information table 2 is searched for the DA, and it is determined whether or not there is an outgoing route that is not in the closed state. A. When there is a departure route that is not in a blocked state • Step S3: A top priority route is selected from the departure routes that are not in a blocked state for the DA. Step S4: Transfer the PDU to the selected route. B. When there is no outgoing route that is not in the blocked state. Step S5: Discard the PDU. Step S6: Determine an incoming route of the PDU. Step S7: Send a “network status notification message (blocked)” to the opposite device on the incoming route of the PDU.

The processing relating to the blockage of the route in the network device will be described below.

(1) When the device autonomously detects a failure by some means such as monitoring a link down or a transmission line failure alarm, the route related to the failed transmission line in the routing information table is set to the closed state.

(2) When the device autonomously detects congestion by some means such as counting the number of cell discards or PDUs discarded, the route related to the congested transmission line in the route information table is closed.

(3) When a network status notification message (blockage) is received from an adjacent node,
The route related to the message receiving route among the routes for the DA notified by the message is set to the closed state.

Processing related to release of blockage of a route in the network device will be described below.

(1) If the device autonomously detects a fault recovery by any means such as monitoring of a link up or a transmission line fault alarm, the device is in a blocked state among the routes related to the fault-recovered transmission line in the route information table. Release the closed state of the thing.

(2) If the device autonomously detects congestion mitigation by any means such as counting the number of cell discards or PDU discards, it is in a blocked state among the routes related to the congestion-relieved transmission line in the route information table. Release the closed state of the thing.

(3) When a network status notification message (block release) is received from an adjacent node, the route to the DA notified by the message in the route information table is related to the message receiving route and is in the blocked state. Release the closed state for.

An example of abnormal state notification and detour processing when a transmission line is in an abnormal state such as failure or congestion in communication from the terminal device 1-1 to the terminal device 1-2 in the network of FIG. 2 will be described below. Show.

If there is no abnormality in the network, the PDU sent from the terminal device 1-1 to the terminal device 1-2 is as shown in FIG.
According to the path information table of “terminal device 1-1 → transmission line 101 → relay device 21 → transmission line 102 → relay device 22”
The data is transferred along the path of “transmission path 103 → relay device 23 → transmission line 104 → terminal device 1-2”.

When the transmission line 104 is in an abnormal state, the relay device 23 detects the transmission line abnormality and closes the route related to the transmission line 104, so that the route information table of the relay device is as shown in FIG. As a result, the PDU transmitted from the terminal device 1-1 to the terminal device 1-2 is “the terminal device 1-1”.
→ Transmission path 101 → Relay apparatus 21 → Transmission path 102 → Relay apparatus 22 → Transmission path 103 → Relay apparatus 23 → Transmission path 107 →
The data is transferred through the route of “the relay device 26 → the transmission path 111 → the terminal device 1-2”.

Further, when the transmission line 103 becomes abnormal, the relay device 22 detects the transmission line abnormality and
The route related to 3 is closed. As a result, the route information table of the relay device becomes as shown in FIG. 6, and the PDU transmitted from the terminal device 1-1 to the terminal device 1-2 is "terminal device 1-1 → transmission line 101 → relay device 21 → transmission Road 10
2 → relay device 22 ". However, the relay device 2
2 has no path to the terminal device 1-2 that is not in the closed state, the PDU is discarded. At the same time, the relay device 22 sends a network status notification message (blockage) to the opposing device on the transmission line 102, which is the input route of the PDU, using the Anycast address.

The network status notification message (blocked) is received by the relay device 21 which is the opposite device on the transmission line 102, and the record using the transmission line 102 in the route information on the terminal device 1-2 is set to the blocked state. I do. As a result, the route information table of the relay device becomes as shown in FIG.
After the next PDU addressed to the terminal 2, the terminal device 1-1 → transmission line 10
1 → Relay 21 → Transmission path 105 → Relay 24 → Transmission path 109 → Relay 25 → Transmission 110 → Relay 26
→ Transmission path 111 → Terminal device 1-2 ”.

Hereinafter, a method of switching back when the network state is recovered from the detour state will be described. When the path information table is in the state of FIG. 7 and the abnormal state of the transmission line 103 is recovered, the relay device 22 detects the recovery of the abnormal state of the transmission line 103, and the transmission line in the path information table of the relay device 22 is detected. By releasing the blocked state of the route related to 103, the route information table of the device becomes as shown in FIG. At the same time, the relay device 22 notifies the opposing device on the transmission line 102 and the opposing device on the transmission line 106 of the network status notification message (block release ) Is sent.

The network status notification message (block release) is received by the relay device 21 and the relay device 25. In the relay device 21 having a route that is blocked in a route related to the transmission path that has received the network status notification message, By releasing the blockage of the route, the route information table of the relay device becomes as shown in FIG.
After U, “terminal device 1-1 → transmission path 101 → relay apparatus 21 → transmission path 102 → relay apparatus 22 → transmission path 103 → relay apparatus 23 → transmission path 107 → relay apparatus 26 → transmission path 11
1 → terminal device 1-2 ".

Further, when the abnormal state of the transmission line 104 is recovered, the relay device 23 detects the recovery of the abnormal state of the transmission line 104 and the closed state of the route related to the transmission line 104 in the route information table of the relay device 23. Is canceled, the route information table of the device becomes as shown in FIG. At the same time, the relay device 23 informs the neighboring node of the release of the blockage of the route related to the transmission path 104 to the neighboring device on the transmission line 103 and the partner device on the transmission line 107 (network release notification message). Is sent.

The network state notification message (block release) is received by the relay devices 22 and 26,
Since neither of the relay devices has a blocked route in the route related to the transmission route that has received the network status notification message, the blocking flag in the route information table is not rewritten. After the next PDU addressed to the terminal device 1-2, “terminal device 1-1 → transmission path 101 → relay apparatus 21 → transmission path 102 → relay apparatus 22 → transmission path 103 → relay apparatus 23” according to the path information table of FIG. → Transmission path 104 → Terminal device 1-2 ”.

In this embodiment, an example of one-to-one unidirectional transmission from the terminal device 1-1 to the terminal device 1-2 has been described. However, the route information can be defined independently for each DA, and can be defined on the network. By installing a plurality of terminal devices and setting a plurality of routes with priorities for each terminal device, the present invention can be applied to the bypass control at the time of failure in the many-to-many bidirectional communication. Also, the explanation has been given assuming that one or two prioritized routes are set in each device.
In actual application, it is possible to improve network redundancy by setting n (n> 2) prioritized routes in each device.

[0053]

According to the present invention, it is possible to economically realize a highly reliable network by quick and flexible detour control by making full use of the redundancy at the transmission path level. By using a simple message protocol for the notification of the abnormal state of the network, it becomes possible to suppress the processing load related to the bandwidth consumption and the bypass control required for the notification.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a terminal device or a relay device according to the present invention.

FIG. 2 is a diagram illustrating a network configuration according to an embodiment of the present invention.

FIG. 3 is a diagram showing initial setting values of a route information table according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a PD in a relay device according to an embodiment of the present invention.
It is a figure showing a U processing flow.

FIG. 5 is a diagram showing a route information table at the time of failure of the transmission line 104 according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating a path information table before transmission / reception of a network state notification message when a failure occurs in the transmission path 104 and the transmission path 103 according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a route information table after transmission and reception of a network status notification message when a failure occurs in the transmission line 104 and the transmission line 103 according to an embodiment of the present invention.

FIG. 8 is a diagram showing a route information table at the time of recovery from the failure of the transmission line 103 according to an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 terminal device (relay device) 2 route information table 3 failure detection unit 4 congestion detection unit 5 route blocking unit 6 failure recovery detection unit 7 congestion mitigation detection unit 8 route blocking release unit 9 PDU DA reading unit 10 routing information table search unit 11 Route selection unit 12 PDU discard unit 13 Block notification unit 14 Block release notification unit 15 Anycast address writing unit 16 PDU (Anycast address) reception unit 17 Route block unit by block message 18 Route block release unit by block release message

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaharu Hashiba Nippon Telegraph and Telephone Corporation 3-9-1-2 Nishishinjuku, Shinjuku-ku, Tokyo (72) Inventor Hiroyuki Ichikawa 3-192-3 Nishishinjuku, Shinjuku-ku, Tokyo No. Nippon Telegraph and Telephone Corporation F-term (reference) 5K030 HA08 KA05 LA03 LB08 LB18 MB01 MD02

Claims (5)

[Claims] 1. A detour method in a connectionless communication network comprising a terminal device and a relay device for selecting a route using a route information table and a plurality of physical or logical transmission lines connecting these devices in multiple stages. When the terminal device or the relay device detects an abnormality of the own device, the self-accommodated transmission line, or an opposite device on the self-accommodated transmission line, the terminal device or the relay device closes the abnormal transmission line or the route related to the abnormal device in the route information table, and a certain destination address. In the transfer of the protocol data unit transmitted to the destination, the transfer of the protocol data unit transferred using the blocked path is stopped according to the path information on the destination address, and the apparatus does not transmit the destination data with respect to the destination address. When an alternative route via the abnormal transmission path is not set, the protocol data unit Notify the opposing device on the upstream transmission path concerned that the protocol data unit addressed to the destination address is not transferable to the device, and the notified device sets the transmission path on which the notification was received with respect to the destination address. A detour method in a connectionless data communication network, characterized by recognizing an abnormal state and blocking a related path. 2. A detour method in a connectionless communication network comprising a terminal device and a relay device for performing route selection using a route information table and a plurality of physical or logical transmission lines connecting these in multiple stages. When the terminal device or the relay device detects the recovery from the abnormal state of the own device, the self-contained transmission line, or the opposite device on the self-contained transmission line, the transmission line or the device recovered from the abnormal state in the path information table of the device is determined. Of the relevant routes,
Releases the blockage of the path that was previously blocked as an abnormal state, notifies the adjacent device that the protocol data unit via the unblocked route can be transferred to the device direction, and the notified device A detour method in a connectionless data communication network, characterized by recognizing that a transmission path that has received a notification has recovered from an abnormal state, and releasing the blocked path among the related paths. 3. A detour method in a connectionless data communication network according to claim 1 or 2, wherein a protocol data unit is transferred using a highest priority path in a normal state, and an alternative path is used in a network abnormality. A detour method in a connectionless communication network, wherein detour control is performed at the time of network abnormality for transferring a protocol data unit. 4. A detour method in a connectionless data communication network according to claim 1, wherein the protocol data unit transferred by using the highest priority path in normal times is replaced by a network abnormality. A connectionless communication network characterized in that when a network error is recovered, a rerouting control at the time of network error recovery is performed, in which the protocol data unit is transferred again using the highest priority route when the network error is recovered. Detour method in. 5. A detour system in a connectionless communication network comprising a terminal device and a relay device for selecting a route using a route information table and a plurality of physical or logical transmission lines connecting these devices in multiple stages. The relay device, when detecting an abnormality in the own device, the self-accommodated transmission line, or an opposing device on the self-accommodated transmission line, means for closing the abnormal transmission line or the route related to the abnormal device in the route information table; Means for stopping transfer of a protocol data unit transmitted using a closed path by following path information on the destination address in the transfer of the protocol data unit transmitted to the destination address; If an alternative route via the non-abnormal transmission path is not set for the address, the protocol Means for notifying the opposing device on the upstream transmission line relating to the data data unit that the protocol data unit addressed to the destination address is not transferable to the device, and the notified device sets the transmission line on which the notification was received to Means for recognizing the destination address as being in an abnormal state and closing a related path; and detecting a recovery from the own apparatus, the self-contained transmission path, or a counterpart apparatus on the self-contained transmission path from the abnormal state. Of the transmission line or device-related route that has been recovered from the abnormal state in the path information table of the above, via the means to release the blockage of the path that was previously blocked as the abnormal state, and via the path that was released from the block by the adjacent device Means for notifying that the protocol data unit to be transferred can be transferred to the device, and the notified device to turn the transmission path receiving the notification from an abnormal state. Bypass system in connectionless data communication network, characterized in that it comprises a means for releasing a blockage of a path in a closed state of the path associated with recognized as.