JPH0983572A - Backup line connection/cut system for frame relay and backup communication system for frad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the processing of cut/connection in accordance with the state of an opposite station at the time of using a backup line in the backup line connection/cut system of a frame relay in constitution where a standard repeating line and the backup line are provided between exchanges. SOLUTION: The respective exchanges are provided with backup control parts 1 connecting the backup lines by the generation of a main cause for using the backup lines, monitoring frame transmission control parts 2 which periodically transmit backup monitoring frames provided with information displaying the presence/absence of the backup main causes of a self exchange- side through the connected backup lines and monitoring frame reception control parts 3 receiving the backup monitoring frames from an opposite party. The backup control parts 1 identify to which station the backup main cause exists between the self station or the other station and controls the cut of the backup line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frame relay backup line connection / disconnection system and a FRAD backup communication system.

[0002] In recent years, in the era of multimedia, the needs for high-speed communication of a large amount of data are increasing,
Expectations are rising for data communication networks such as frame relays as infrastructure that supports this.

The frame relay network is different from the packet network in which confirmation of data transmission / reception is carried out in the network, and the function of confirming data transmission / reception is left to the terminal by helping the improvement of the line quality and the high performance of the terminal. It realizes high-speed communication by largely omitting the data delivery confirmation process, and is composed of a frame relay exchange and a frame relay multiplexer (hereinafter referred to as FRAD).

In a data communication network, network failures, disasters such as earthquakes, fires, etc. are major factors that reduce the reliability of the network. In consideration of the degree of impact on network users, economic efficiency, etc. It is important to be prepared. In order to improve the network reliability, various measures can be considered from the viewpoint of the line configuration, communication device redundancy configuration, security, etc. However, since the frame relay network simplifies the delivery confirmation process, the line configuration Trouble-proof design is an important point for improving network reliability. As one of the countermeasures for the line configuration, there is a method of setting a backup line. This is a method to secure communication by setting a backup line (standby line) when the working line fails or is congested. Depending on the cost and communication volume, a backup dedicated line can be provided, or the ISDN public network can be used as a backup line. can do.

The present invention relates firstly to a technique for immediately and accurately performing control for connecting or disconnecting a backup line when a backup factor occurs in a relay line of a frame relay exchange or the like.

Further, the FRA is used as a device forming a frame relay network for performing communication by the frame relay system.
Although there is a D (Frame Assembly Disassembly), the exchange that accommodates the FRAD is a FRAD
If a failure occurs in the relay line between and, the backup line is used. In that case, if a PVC has been set with another exchange, it is necessary to accommodate the backup line in the link memory of the same control unit as the original relay line in order to communicate with the backup line using the PVC. .

The present invention secondly relates to a FRAD backup communication system in frame relay.

[0008]

2. Description of the Related Art (1) Description of Connection / Disconnection of Backup Line between Conventional Frame Relay Switches FIG. 12 shows an example of the configuration of a frame relay network. In the figure, 80 is a frame relay network, and in this configuration, a frame relay exchange A, a frame relay exchange B and a FRAD
(Frame multiplexer) is connected, and terminals are respectively accommodated in the frame relay exchange A and the FRAD. Between the frame relay exchanges A and B, a standard relay line a that is normally set and a backup relay line b that is used when a backup factor such as a line failure or line congestion of the standard relay line occurs are provided. There is. The backup relay line b uses a line similar to the standard relay line a (for example, a dedicated line), or as shown in FIG.
A line via the exchange of the DN network 81 may be used.

Backup connection method Backup due to line failure: When a line failure occurs in the standard relay line a,
When Frame Relay Switch A detects the line failure,
The frame relay exchange A performs a connection process to the backup relay line b.

Backup due to line congestion: When the frame relay exchange A increases the amount of communication to the standard relay line a and recognizes that it is line congestion, the frame relay exchange A performs connection processing for the backup relay line b in addition to the standard relay line a. To do. In this case, there are two relay lines between the frame relay exchange A and the frame relay exchange B.

Backup disconnection method Backup due to line failure: When the standard relay line is restored during backup of the relay line due to line failure and it is detected by the frame relay A, the frame relay exchange A transfers from the backup relay line b to the standard relay line a. The backup relay line b is disconnected.

Backup due to line congestion: Frame relay 4 exchange A during backup of trunk line due to line congestion
When the congestion state is released, the frame relay exchange A disconnects the backup relay line b. FIG. 13 shows an operation sequence of disconnection at the time of line congestion. Note that the stations A and B in FIG. 13 represent the exchange A and the exchange B, respectively.

(2) Description of Communication via FRAD of Conventional Frame Relay Network FIG. 17 is a block diagram of a frame relay network accommodating a conventional FRAD.
In FIG. 17, 90, 95 and 96 are terminal lines, 91,
Reference numerals 92 and 94 are relay lines, 93 is a FRAD relay line, and terminals 1 and 3 are frame relay compatible terminals and terminal 2 is a non-frame relay compatible terminal.

A FRAD (frame multiplexer) converts a frame from a frame relay terminal or data from a non-frame relay terminal into a frame relay format and multiplexes it on a relay line with the frame relay exchange to make a frame relay exchange. To send and receive.

In the case of FIG. 17, a PVC is connected between the terminal 1 directly connected to the frame relay exchange A and the terminal 2 connected under the FRAD via the frame relay exchange B.
(Permanent Virtual Circuit: Fixed connection with the other party) Communication is performed.

As shown in FIG. 17, each exchange and FRAD internally have a link memory for determining the transmission destination of the frame received from the terminal and the transmission destination of the frame received from the network to the own station. In the case of PVC (different from SVC (Switched Virtual Connection)), a certain number of link memories are prepared in advance in the exchange.

The structure of the link memory is shown in FIG.
A. As shown in, the link number (link memory number) of the terminal itself, the terminal line number, and the terminal DLCI (Data Link Connec
tion Identifier: Data link connection identifier), communication partner node (switch) number, partner link number (link memory number), terminal attribute, etc.

The link number of the self terminal and the link number of the communication partner among these are B.B. It is represented by the identification number of the call control unit accommodating the terminal line in the exchange and the link number in the call control unit as shown in FIG. In the case of PVC, the information in the link memory is registered in both exchanges accommodating each other's terminals that perform communication by the operation of a maintenance person or the like prior to the start of communication.

FIG. 19 shows the structure of the link memory and the line in the exchange. In FIG. 19, 90 is an exchange, 91 is a common processing unit, 92-94 are call control units, and 92a-9.
Reference numeral 4a is a link memory provided in each call control unit 92 to 94. The "call control unit" described here represents a processor that performs call control and routing control of the frame relay.

In this example, the call control unit 92 has a terminal line,
The FRAD relay line and the backup line are accommodated, and the link memory 92a corresponds to the PVC set in each of the plurality of lines and corresponds to A.A. Data having the contents shown in is stored.

Explaining the operation in the configuration as shown in FIGS. 17 to 19, the exchange on the transmitting side searches the link memory by the DLCI number in the reception frame from the terminal, and determines the accommodation node number and the link number of the other terminal. It is converted and transmitted in the network. In the receiving side exchange, conversely, from the link number to DLC
Converts to an I number and sends the frame to the registered partner line. If the partner terminal is a line accommodated in FRAD,
The line and the link number for FRAD (the DLCI number may be used) are registered in the link memory, and the frame is transmitted to the relay line for FRAD. Upon receiving the frame, the FRAD searches its own link memory to determine the destination terminal line, converts it into a DLCI number within the line, and transmits it to the terminal line.

[0022]

(1) Regarding connection / disconnection of a backup line between conventional frame relay exchanges FIG. 14 shows a sequence for discarding user frames. At the time of backup connection of the connecting relay line, etc., there is no link establishing means such as packets, and the user frame starts to be transmitted when the line of the local exchange is in use.
If the other side is not ready for reception (a state in which the connection by the backup line has not been completed), the user frame may be discarded.

Further, as a problem when the backup is disconnected due to the line congestion, there is a case shown in FIG. FIG. 15 is a backup disconnection sequence when the congestion of the partner station occurs.
In this case, even if congestion occurs at station A and a backup is connected and then congestion occurs at station B, if the congestion is released at station A after that, the backup line is disconnected. Since the congestion is not released at station B, the backup line is connected from station B, and there is a possibility that the congestion state will become worse due to the retention of transfer data due to the reduction of relay lines during disconnection / connection processing. .

Further, in the case of the abnormal sequence of the partner station shown in FIG. 16, if the backup line is not used normally due to an abnormality of the partner station, the line is put on hold even if communication is stopped unless the connection side detects an error. It In this case, if an ISDN line or the like of the public network is used as a backup line, the communication cost will increase and it will be uneconomical.

(2) Communication via FRAD of conventional frame relay network As shown in FIG. 19 above, when a normal frame relay terminal is accommodated in an exchange,
Since the number of lines that can be accommodated in one call control unit is limited due to the capacity of the exchange, multiple call control units are used to increase the line capacity. In this case, since the link memory is distributed among the call control units, the link number for identifying the link memory is the B. The number system is "call control number + call control unit serial number".

Therefore, for example, when communication is performed between the terminal 1 and the terminal 2 in FIG. 18, the link number of the partner FRAD set in the link memory of the exchange A is the accommodation position of the relay line for FRAD in the exchange B. It corresponded to.

In such an exchange, when a backup line is used as a line for FRAD in addition to the standard trunk line (used when the standard trunk line fails or is congested), it is the same as the standard trunk line as shown in FIG. It was necessary to connect a backup line to the call control unit. This is because if the call control unit is different, the link number will also be different, so it will be inconsistent with the link number of the other exchange, and the other exchange will not be able to send the frame transmitted by the previous link number, and communication will not be possible as it is. Is.

A first object of the present invention is to enable disconnection / connection processing according to the state of the partner station when the backup line is used. The present invention makes it possible to accommodate a relay line for FRAD and a backup line in different call control units in a frame relay network that accommodates FRAD, and to automatically switch and switch back the relay line and backup line. The second purpose.

[0029]

FIG. 1 is a diagram illustrating a first principle of the present invention. In FIG. 1, a backup line is provided between the A station (frame relay exchange A) and the B station (frame relay exchange B) in addition to the standard relay line. The same configuration is provided (the internal configuration of station B is not shown), and an example of an operation sequence between the two is shown.

In FIG. 1, 1 is a backup control unit, 2 is a supervisory frame transmission control unit, 3 is a supervisory frame reception control unit,
Reference numeral 4 is a monitoring frame, 4a is a display of the presence / absence of a factor requiring a backup line (congestion, line failure), and 4b is an authentication code of a partner station which is arranged in advance with the partner.

According to the first principle of the present invention, an exchange (station) connected by a backup line transmits a backup monitor frame to a partner station at a constant cycle, and at least a backup factor (congestion) is transmitted to the own station side. It is to set whether or not there is a line failure). Also, the authentication code of the partner station can be added to this monitor frame at the same time so that the partner station can be authenticated.

In the case of FIG. 1, the communication between the station A and the station B is congested and the backup line is connected (a in FIG. 1), and the backup control unit 1 transmits the supervisory frame via the backup line at regular intervals. A control frame including a cause is transmitted from the control unit 2 (b in FIG. 1). The backup control unit 1 of station B receives this by the supervisory frame reception control unit 3, and A
Recognize that the station has a backup factor. This time,
If the authentication code (ID code) agreed with the partner station in advance is added to the received monitoring frame, it is authenticated that the partner of the backup line is station A. When station B arrives, the station B also transmits a supervisory frame (including no cause) to station A (step c).

When this is received by the backup control unit 1 of station A, it is determined that station B has no backup factor. When the supervisory frame from this partner station is received, the link establishment status of the backup line can be confirmed, and communication (transmission of user frames) by the backup line is performed. After that, monitoring frames of similar contents are sent and received between station A and station B at fixed intervals (e, f in FIG. 1), and when congestion is released at station A, station B does not have a backup factor in advance. Is notified, station A disconnects the backup line (g in FIG. 1).

FIG. 2 is a diagram for explaining the second principle of the present invention.
In FIG. 2, 10 is a switch accommodating FRAD (frame relay switch, 11 is PVC data registering via FRAD, 12 is link memory control means, 13 is link memory determining means, 14 is link number change notifying means, 15,
16 is a call control unit, 150 and 160 are link memories, 17 is a standard trunk line, 18 is a backup line, 1
Reference numeral 9 is FRAD, 20 is an exchange (frame relay exchange) which does not accommodate FRAD, 21 is a link memory, and 22 is a link number changing means.

According to the second principle of the present invention, in the FRAD-accommodating exchange, at the time of PVC registration via FRAD, registration is made in the link memories of both the call control unit of the standard trunk line and the call control unit of the backup line, and the lines are connected. Alternatively, when disconnecting, the state of each link memory is set to active or inactive, the active line is detected when the relay line is used, the link memory to be used is determined, and the partner exchange is notified when switching.

The exchange 20 and the FRAD 19 are connected by a standard trunk line 17 and a backup line 18, each line is accommodated in different call control units 15 and 16, and when registering the PVC via FRAD, the PVC data via FRAD is registered. The link memory 15 of each call control unit 15 and 16 by the registration means 11
0 and 160 are registered respectively. At this time, the exchange 2
Information of the link memory of the call control unit accommodating the standard trunk line 17 is set in the link memory 21 of 0. When the line is connected (open) or disconnected (closed), the link memory control means 12 stores a call in which the active or disconnected relay line is accommodated in the link memory corresponding to the call control unit in which the connected relay line is accommodated. Inactivity is set in the link memory corresponding to the control unit, and the state is determined by the link memory determination means 13. When switching the trunk line to be used, the link memory control means 12 switches the state (active or inactive), the link number change notifying means 14 notifies the exchange 20 of a new link memory number, and the exchange 20 notifies this. Upon receipt, the link number changing means 22 changes the number set in the link memory 21 to the received number.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows a configuration of an embodiment centered on control of a backup line of a frame relay exchange. This configuration is provided in each station (exchange) shown in the first principle configuration of the present invention shown in FIG. 1, and the same configuration is also provided with a partner exchange connected by a trunk line.

In FIG. 3, reference numeral 30 is a backup control unit for setting the table of the backup factor of the local station, authentication of the connected remote station, and monitoring of frame reception from the remote station, and 31 is a frame for controlling the transmission of the user frame to the backup line. Transmission control unit (also controls transmission to the standard trunk line),
Reference numeral 32 is a line control unit for connecting / disconnecting the backup line, 33 is a supervisory frame transmission control unit for activating a supervisory frame transmission cycle, and setting a backup factor of the own station, and 34 is a table setting of a backup factor of the partner station, and no frame relay A supervisory frame reception control unit that performs reception monitoring and notification of reception and notification of a partner station authentication code, 35 is a congestion control unit that detects congestion / decongestion, and 36 is a presence / absence of a backup factor of the own station and the partner station. It is a backup factor existence table retained by

FIG. 4 shows the structure of the backup supervisory frame according to the present invention. Reference numeral 40 is a backup monitoring frame, in which 41 is a destination node number representing the partner exchange number, 42 is a source node number representing the originating exchange number, and 43 is
Is a frame type that is information for identifying a user frame (frame for transmitting user data) or a backup monitoring frame, and 44 is a self-station backup that indicates whether or not the self station currently has a backup factor (congestion or failure) Information about the presence / absence of a factor, 45 is an authentication code (different from the node numbers 41 and 42) that is a code for confirmation of the other party, which is arranged in advance with the other station, and other necessary information can be added.

5 to 7 show sequence examples 1 to 3 of the backup connection / disconnection by the monitoring frame. FIG.
11 is a sequence example 1 of backup disconnection by the monitoring frame shown in FIG. This sequence will be described with reference to FIGS.

When congestion shown at station A occurs,
This is detected by the congestion control unit 35 of the backup control unit 3
Notify 0. The backup control unit 30 sets the presence of the own station factor in the backup factor presence / absence table 36, and instructs the line control unit 32 to perform the backup connection. As a result, the backup connection is established as shown in FIG. In this case, the B station is not connected.
After that, the supervisory frame transmission control unit 33 of the station A activates the supervisory frame transmission cycle in response to the supervisory frame transmission start instruction from the backup control unit 30, and transmits the backup supervisory frame having the configuration shown in FIG. 4 (see FIG. 5). b). At that time, referring to the local factors in the backup factor presence / absence table 36, information 4 indicating the presence / absence of backup factors
Set the factor to 4.

At this time, even if the monitoring frame (b in FIG. 5) is transmitted from the A station, the backup line on the B station side is not connected, but when the connection is completed after that, the backup control section on the B station side. 30, the supervisory frame transmission control unit 33 activates a transmission cycle, and periodically transmits a backup supervisory frame (indicating no backup factor) having the configuration shown in FIG. 4 (c in FIG. 5). When the supervisory frame reception control unit 34 of the station A receives the supervisory frame from the partner station B, the supervisory frame reception notification and the received partner station authentication code are output to the backup control unit 30 and the backup factor presence / absence table 36 Set no factor as the information of the partner station. The backup control unit 30 receives the notification of frame reception from the connection partner station and the authentication code, recognizes the link confirmation when authenticating the partner station with the authentication code, and instructs the frame transmission control unit 31 to start user frame transmission. . In this way, communication via the backup line is performed (d in FIG. 5).

After this, the A station and the B station respectively transmit backup supervisory frames (e, f in FIG. 5). The backup monitor frame may be transmitted independently after the communication is started, or may be transmitted by being multiplexed with the user frame.

After that, when the congestion is released at station A as shown in FIG. 5, the congestion control unit 35 instructs the backup control unit 30 to release the congestion. Accordingly, the backup control unit 30 sets the setting content of the own station side in the backup factor presence / absence table 36 to no factor, and refers to the factor of the partner station in the backup factor presence / absence table 36 to set the partner station to no factor. Then, the supervisory frame transmission controller 33 is instructed to stop the transmission of the supervisory frame, and the line controller 32 is instructed to disconnect the backup, so that the backup line is disconnected (g in FIG. 5).

Next, FIG. 6 shows a sequence example 2 of backup connection / disconnection using the monitoring frame. In this example 2, as in FIG. 5 above, congestion occurs at station A, and a backup line is connected at station A (a in FIG. 6),
The transmission of the backup supervisory frame (b in FIG. 6) and the reception of the backup supervisory frame from the other station B (c in FIG. 6) confirm the link establishment and start the communication by the backup line (d in FIG. 6). ).

If congestion occurs at station B during communication via this backup line, the backup control unit 30 of station B sets its own station factor in the backup factor presence / absence table 36 of station B (at this time). , Factor of partner station is also A
When the supervisory frame is received from the station, the cause is set), and the supervisory frame sent periodically is set to have the cause and is transmitted to the station A (e in FIG. 6). Upon receiving this, station A also sets the factor of the partner station in the backup factor presence / absence table 36. After that, the congestion as shown in the A station is released, but since the cause of the partner station is set, unlike the example of FIG. 5, the backup line is not disconnected and the A station in the next cycle is not disconnected. No cause is set in the monitor frame transmitted from (g in FIG. 6). At the station B, after receiving this, when the congestion is released as shown in (h in FIG. 6), the backup factor of the own station and the partner station becomes zero, so the backup is disconnected (see FIG. 6).
I).

As described above, the disconnection / connection can be prevented from being repeated by considering the state of the partner station without disconnecting the backup line only by canceling the backup factor of the own station.

FIG. 7 is a sequence example 3 of backup connection / disconnection using the monitoring frame. In this example 3, as in the case of FIG.
The station establishes a link by connecting a backup line (a in FIG. 7), sending a backup supervisory frame (b in FIG. 7), and receiving a backup supervisory frame from the other station B (c in FIG. 7). Then, the communication via the backup line is started (d in FIG. 7). After this, station B sets no backup factor in the backup monitoring frame and sends it (see FIG. 7).
E), after receiving this at station A, if station B becomes abnormal and transmission from station B is lost as shown in step A, station A transmits a monitoring frame at a fixed cycle. (F, g in FIG. 7), nothing is transmitted from the partner station B.
This state is detected by monitoring the next monitoring frame from the B station by the time monitoring means (timer) activated every time the monitoring frame from the B station is received.

This monitoring is performed by the supervisory frame reception control unit 34 of FIG. 3, and if the next supervisory frame is not received within a fixed time, the supervisory frame reception control unit 34 notifies the backup control unit 30 that there is no frame indicating the partner abnormality. The reception is notified, and the backup control unit 30 thereby notifies the line control unit 3
Instruct 2 to disconnect. As a result, the line control unit 3
2 disconnects the backup line as indicated by h in FIG.

FIG. 8 is a diagram for explaining the operation of the main parts of the exchange that accommodates the FRAD and the other exchange according to the present invention. The configuration corresponds to the second principle configuration of the present invention shown in FIG. In FIG. 8, 50 is a terminal, 51 is an exchange A (or A station) accommodating the terminal 50, 52 is a common processing unit, 53
Is a call control unit (only one is shown, but a plurality exists), 54 is a link memory, and 55 is an exchange B (B
57-1 is a call control unit to which a standard trunk line is connected,
57-2 is a call control unit to which a backup is connected, 58-
Reference numerals 1 and 58-2 are link memories provided in the call control units 57-1 and 57-2, 59 is a standard relay line between the exchange B and FRAD, 60 is a backup line between the exchange B and FRAD, and 61 is FRAD. , 62 are terminals connected to the FRAD 61.

Although the terminal 50 is connected to the exchange A in FIG. 8, when the FRAD is connected instead of the terminal, or when the standard trunk line and the backup line are connected to the FAD.
The RAD may also be connected.

First, the exchange B (5
In 5), since the standard trunk line 59 and the backup line 60 are accommodated in different call control units 57-1 and 57-2, both call control units have a link memory in which the communication partner of FRAD is registered. Common processing unit 5 in that case
The processing executed in 6 will be described with reference to FIG.

FIG. 9 is a PVC registration processing flow. From terminal 50 shown in FIG. 8 to exchange A, exchange B, FRAD6
When registration of the PVC connected to the terminal 62 via 1 is started in the exchange B, it is determined whether or not there is an empty link memory on the standard trunk line side (S1 in FIG. 9). If not, the process ends abnormally. Next determines whether or not there is an empty link memory on the backup line side (at step S2). If there is no free link memory on the backup line side, it will end abnormally. If there is, there is a link memory on the standard relay line side (see Fig. 8).
No. 57-1) is hunted (S3 in FIG. 9), and the link memory (57-2 in FIG. 8) on the backup line side is hunted (S4 in FIG. 9).

Next, the data is registered in the link memory on the hunted standard trunk line side (S5 in FIG. 9), and then the data is registered on the link memory on the hunted backup line side (S6 in the same figure), and registered. The process ends.

On the other hand, in the exchange A (51) on the partner side, this PVC (between the terminal 50 and the terminal 62) is registered in the link memory 54, but the partner node number (number of the switch B) and the link of the standard trunk line are registered. Number (link memory 57-
The number 1) is registered.

FIG. 10 shows the structure of the link memory according to the present invention. The first 70 is the own link number (memory link number), 71 is the terminal line number, 72 is the DLCI number (data link connection identifier), 73 is the partner node number representing the number of the partner exchange, and 74 is the partner link number (partner link). Memory number). The following 75 to 78 are information provided by the present invention, and 75 is the line attribute (FR) of the link.
AD relay, FRAD backup, terminal distinction), 76
Indicates link status 1 (active / inactive distinction), 77 indicates link status 2 (used / unused distinction), 7
8 is the opposite link number (the other duplicated link memory number), which is the link number of the backup line when the own link is the standard trunk line, and the link of the standard trunk line when the own link is the backup line A number is set, and 79 is other information.

In the exchange B containing the FRAD 61 in the configuration shown in FIG. 8, the FRAD 61 has a standard trunk line 59.
When using the link status 1 (7) of the link memory 58-1 of the call control unit 55 corresponding to the standard trunk line 59,
6) is active, the link status 2 (77) is set to “use”, and the link status 1 of the link memory 58-2 of the call control unit 57-2 corresponding to the backup line 60 is inactive and the link status 2 Is set to "unused" and the link memory 58-1 corresponding to the standard relay line 59 is
To communicate with FRAD61. Further, the link number (the number of the link memory 58-1) corresponding to the standard trunk line 59 is registered in advance in the partner exchange A as the partner link number.

During communication in the above state, the standard relay line 59
Switch becomes a failure, the exchange B changes all the link memories corresponding to the standard trunk line 59 to the inactive state.
Also, when the backup line is opened, all the link memories corresponding to the backup line are changed to the active state, and the exchange B is used by using the backup line.
Communication with the FRAD 61. The link memory 58-1 corresponding to the standard relay line is in the inactive state and the link memory 58-2 corresponding to the backup line is
When it detects that the link number of the FRAD 61 has been changed, it transmits a "link number change notification" frame to the other exchange A. In this "link number change notification" frame, F
A link number corresponding to the backup line (number of the link memory 58-2) is set as a new link number of RAD.

FIG. 11 is a processing flow of link memory switching and change notification. In order to realize the above processing, the exchange B is used.
Is executed in the common processing unit of. This processing flow is started when a line open notification or line close notification occurs in response to a line failure or restoration. First, it is judged whether it is open or closed, and if it is closed (when the standard relay line is closed due to an obstacle, etc.), the process of changing the link memory state (making active inactive) is started (S2 in FIG. 11). ), The closed line is identified (S3), and if it is a FRAD backup line, it is terminated, and if it is a FRAD standard relay line, it is determined whether the backup link memory is in an unused state or active state (Same as above). S4). If this condition is not satisfied, the process ends. If it does, the link memory of the opened line is used as a new link number and a link memory change notification (same as the link number change notification) is sent to the other exchange (see the same S
5) Change the status of the link memory in the own exchange (change the standard trunk line side to the unused state and the backup line side to the used state) (at step S6).

In addition, in the step S1, when the notification is an open, the process of changing the link memory state (changing inactive to active) is started (see FIG. 1).
1 of S7), the opened line is identified (S8 of the same).
If the line is a FRAD backup line, it is determined whether the link memory of the standard trunk line is in use and inactive. If both conditions are not met, the process ends, but if both conditions are met, a link memory change notification is sent. Is transmitted to the partner exchange (S10 in FIG. 11). Then, the state of the link memory of the own exchange is changed (the standard trunk line side is unused and the backup line is used) (at step S11).

When it is determined in step S8 that the FRAD standard relay line has been opened, it is determined whether the own link memory is in the unused state (at step S12). In the case of, the link memory change notification is sent to the other exchange (at step S13), and at the same time, the state of the link memory of the own exchange is changed (the standard trunk line side is used and the backup line side is not used). (S14).

In the remote exchange A that has received the link memory (link number) change notification, the common processing unit 52 changes the partner link number in the corresponding link memory 54 to the notified link memory number.

In FIG. 8, the standard relay line 5 of FRAD
When 9 becomes an obstacle and is switched to the backup line 60, the link memory 58-2 of the exchange B becomes active and the partner link number of the exchange A is changed by the link number change notification. The user frame to be transmitted is transmitted to the link number corresponding to the backup line, and the detour communication using the backup line is automatically possible.

On the contrary, when the standard trunk line 59 is recovered and the backup line 60 is closed, the link memory 58-1 corresponding to the standard trunk line is activated and the link memory 58-2 corresponding to the backup line is deactivated. State. Then, a link number change notification frame is transmitted to the exchange A to notify that the link number of the FRAD 61 has been changed to the link number corresponding to the standard trunk line.

The transmission timing of the "link number change notification" frame when switching back from the backup line to the standard relay line is not fixed. Depending on the network, the standard trunk line may be used for communication as soon as the standard trunk line is restored. However, even if the standard trunk line is restored, the backup line may continue for a certain period of time.

[0066]

According to the first aspect of the present invention, when the backup line is used, the frame relay switch exchanges the link establishment state of the backup line by the monitoring frame and the presence / absence state of the backup factor of the partner station. This eliminates unnecessary load on the exchange due to disconnection and connection processing. Also, by ensuring a backup line, smooth data transfer is possible. In addition, when connecting to the backup line, check the authentication code agreed with the partner station in advance to check whether the public network with switching such as ISDN is used as the backup line and whether it is properly connected to the partner station. You can

With these, the data communication network in which the accommodated line speeds up and the communication data tends to increase,
In particular, it is possible to supply a stable communication path in a frame relay network, etc., whose delivery confirmation process is simplified, and to ensure high network reliability, including network security that prevents unauthorized connections by checking the authentication code with the partner station. Can be achieved.

According to the second configuration of the present invention, when the exchange accommodating the FRAD uses a backup line in addition to the standard trunk line as a relay line between the FRAD and the FRAD for use, different call control of the exchange is performed. It becomes possible to register in the department, and it is possible to automatically switch from the standard trunk line to the backup line and switch back.

Further, even if the call control unit accommodating the standard trunk line becomes unavailable due to a failure or the like, the communication on the backup line becomes possible.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a first principle of the present invention.

FIG. 2 is a diagram illustrating a second principle of the present invention.

FIG. 3 is a configuration diagram of an embodiment centered on control of a backup line of a frame relay exchange.

FIG. 4 is a diagram showing a configuration of a backup monitoring frame according to the present invention.

FIG. 5 is a diagram showing a sequence example 1 of backup connection / disconnection using a monitoring frame.

FIG. 6 is a diagram showing a second sequence example of backup connection / disconnection using a monitoring frame.

FIG. 7 is a diagram showing a third sequence example of backup connection / disconnection using a monitoring frame.

FIG. 8 is a diagram for explaining the operation of the main part of the exchange that accommodates the FRAD and the other exchange according to the present invention.

FIG. 9 is a diagram showing a processing flow of PVC registration.

FIG. 10 is a diagram showing a configuration of a link memory according to the present invention.

FIG. 11 is a diagram showing a processing flow of link memory switching and change notification.

FIG. 12 is a diagram showing a configuration example of a frame relay network.

FIG. 13 is a diagram showing an operation sequence of disconnection at the time of line congestion.

FIG. 14 is a diagram showing a sequence of discarding a user frame.

FIG. 15 is a diagram showing a sequence of backup disconnection at the time of congestion at the partner station.

FIG. 16 is a diagram showing a sequence of abnormality of a partner station.

FIG. 17 is a configuration diagram of a frame relay network accommodating a conventional FRAD.

FIG. 18 is a diagram showing a configuration of a link memory.

FIG. 19 is a diagram showing a configuration of a link memory and a line in the exchange.

[Explanation of symbols]

 1 Backup control unit 2 Monitoring frame transmission control unit 3 Monitoring frame reception control unit 4 Monitoring frame 4a Display of backup factor presence 4b Authentication code of partner station

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Shoji Oyoshi, 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa, Fujitsu Limited (72) Inventor Yukio Sone, 1015, Kamikodanaka, Nakahara-ku, Kawasaki, Kanagawa

Claims (7)

[Claims] 1. In a frame relay backup line connecting / disconnecting method in which a backup line is provided between the exchanges in addition to a standard trunk line, each exchange connects the backup line when a factor of using the backup line occurs. A backup control unit is provided, and the backup control unit periodically sends a backup supervisory frame including information indicating at least the presence or absence of a backup factor via a connected backup line, and a supervisory frame transmission control unit from a partner. A frame characterized by comprising a supervisory frame reception control unit for receiving a backup supervisory frame, wherein the backup control unit discriminates whether the backup factor is in its own station or another station and controls disconnection of the backup line. How to connect / disconnect relay backup line formula. 2. The frame relay backup line connection according to claim 1, wherein the station to which the backup line is connected transmits a user frame by receiving a monitor frame from a partner station.・ Cutting method. 3. The supervisory frame reception control unit of the backup control unit of the station which receives the backup supervisory frame by adding the identification code of the partner station to the supervisory frame, according to claim 1 or 2. A connection / disconnection method for a backup line of a frame relay, characterized in that the connection partner station is authenticated by the above identification code to check for incorrect connection. 4. The supervisory frame reception control unit according to claim 1, wherein the supervisory frame reception control unit starts timer monitoring when a backup supervisory frame is received from the other party, and the backup when the backup supervisory frame is not received from the other party within a fixed period. A method of connecting / disconnecting a backup line of a frame relay, which notifies the control unit and the backup control unit disconnects the backup line by the notification. 5. In a frame relay network accommodating a FRAD, the exchange accommodating the FRAD is an FR.
The standard trunk line for AD and the backup line are accommodated in separate call control units, and when the PVC is registered via FRAD, PVs are stored in separate link memories corresponding to the two call control units.
A FRAD backup communication method characterized by registering C data. 6. The link memory for registering PVC data of the standard trunk line and the backup line according to claim 5, wherein status information indicating whether the own line is active or inactive, and whether it is used or not is used. FRAD, characterized in that the exchange holds the state information indicating the state of the link memory corresponding to the standard trunk line and the backup line and determines the link memory to be used.
Backup communication method. 7. The exchange according to claim 5, wherein the exchange accommodating the FRAD is connected to the exchange to form a PVC when a use state of a standard trunk line or a backup line is changed as a relay line with the FRAD. In contrast,
The other exchange having the means for sending the link number change notification, and having received the link memory change notification, changes the link memory holding the registration data for PVC via the FRAD using the notified link number. FRAD backup communication system characterized by.