Abstract:
A method of checking communication-path data in a system, in which a router connecting first and second networks operating on different protocols is connected to a switch of the second network, includes the steps of changing the router and the switch from a normal mode to a test mode, checking consistency between router communication-path data controlled by the router and switch communication-path data controlled by the switch by sending the router communication-path data to the switch during the test mode, and checking communication between the router and the switch by sending cells from the router to the switch and returning the cells from the switch to the router during the test mode.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a method of checking communication-path data in an MPLS (multi protocol label switching) communication scheme, and relates to a router a switch, and a communication system operating based on such a method. The present invention particularly relates to a method of checking communication-path data in an MPLS communication scheme for the purpose of checking integrity of label data controlled by a MPLS router and switch data controlled by a trunk switch, and relates to a router, a switch, and a communication system operating based on such a method. 
     2. Description of the Related Art 
     In the MPLS communication system that uses ATM (asynchronous transfer mode) switches as trunk switches, data for communication control purposes are maintained as label data controlled by an MPLS router and switch data controlled by an ATM switch. 
     FIG. 1 is an illustrative drawing showing a system based on the MPLS communication scheme. 
     An MPLS router  11  converts an IP packet  12  into an ATM cell  21  when the IP packet  12  is supplied from an IP (internet protocol) network  10 , and supplies the ATM cell  21  to an ATM network  20 . The ATM cell  21  is transferred to an MPLS router  31  via ATM switches  22  and  24  and the like through ATM switching based on PVC (permanent virtual circuit). 
     The MPLS, router  31  extracts an IP packet  32  from an ATM cell  25  supplied from the ATM network  20 , and supplies the IP packet  32  to an IP network  30 . 
     The MPLS communication scheme will be described further in detail in the following. 
     FIG. 2 is an illustrative drawing for explaining a principle of the MPLS communication system. 
     In FIG. 2, an MPLS router  40  is provided with label data  41 , which indicates correspondences between destination IP addresses and VPI/VCI (virtual path identifier/virtual channel identifier). An ATM switch  50  is provided with switch data  51  that is used for ATM switching. 
     The MPLS router  40  converts IP packets  42  and  43  supplied from the IP network into ATM cells  44  and  45  by utilizing the label data  41 , and supplies the ATM cells  44  and  45  to the ATM switch  50 . For example, when the IP packet  42  is supplied, the MPLS router  40  refers to a destination IP address “164.69.15.2” of the IP header, and reads VPI/VCI “1/10” from the label data  41  that corresponds to this destination IP address. Then, the MPLS router  40  generates the ATM cell  44  by using the obtained VPI/VCI and the IP packet  42 . 
     The ATM switch  50  performs ATM switching on the ATM cells  44  and  45  supplied from the MPLS router  40  where the switch data  51  is used for such ATM switching. By switching, the ATM switch  50  transfers the ATM-cells  44  and  45  to an MPLS router  60  or an MPLS router  61 . For example, when the ATM cell  44  is supplied, the ATM switch  50  refers to the VPI/VCI “1/10”, and reads VPI/VCI “2/15” and an output-communication-line number  1  from the switch data  51  as they correspond to the VPI/VCI “1/10”. Then, the ATM switch  50  generates an ATM cell  52  by utilizing the obtained VPI/VCI, and outputs the ATM cell  52  to the communication line of the output-communication-line number  1 . 
     The MPLS router  60  extracts an IP packet  62  from the ATM cell  52  supplied from the ATM switch  50 , and outputs the IP packet  62  to an IP network. 
     In this manner, data necessary for communication control in the MPLS communication scheme are kept in storage as the label data  41  controlled by the MPLS router and the switch data  51  controlled by the trunk switch. 
     When there is a need to identify a fault point during a setup of communication or upon detection of communication fault, the label data  41  and the switch data  51  have to be checked as to their contents. Further, in such a situation, the ATM communication lines need to be monitored to check whether the MPLS router  40  is operating normally to perform ATM-cell conversion as well as to check whether the ATM switch is receiving ATM cells without trouble. 
     In order to check the label data controlled by the MPLS router and the switch data controlled by the trunk switch, a visual inspection of the data is necessary. When the MPLS router and the trunk switch are located at physically distanced places or maintained by different administrators, such a visual inspection may be difficult. 
     Namely, in such cases, a check on the label data and the switch data cannot be made promptly, thereby making it difficult to promptly identify a fault point. 
     Further, apart from monitoring the communication lines, there is no other way of checking whether the MPLS router is correctly converting protocol data for the trunk switch and checking whether the protocol data converted by the MPLS router is correctly supplied to the trunk switch. 
     Accordingly, there is a need for a method for checking communication-path data in the MPLS communication system where the method can help to identify a fault point promptly and easily and help to make a prompt recovery. 
     SUMMARY OF THE INVENTION 
     It is a general object of the present invention to provide a method for checking communication-path data that substantially obviates one or more of the problems caused by the limitations and disadvantages of the related art. 
     Features and advantages of the present invention will be set forth in the description which follows, and in part will become apparent from the description and the accompanying drawings, or may be learned by practice of the invention according to the teachings provided in the description. Objects as well as other features and advantages of the present invention will be realized and attained by a method, a router, and a switch particularly pointed out in the specification in such full, clear, concise, and exact terms as to enable a person having ordinary skill in the art to practice the invention. 
     To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a method of checking communication-path data in a system in which a router connecting first and second networks operating on different protocols is connected to a switch of the second network. The method includes the steps of changing the router and the switch from a normal mode to a test mode, checking consistency between router communication-path data controlled by the router and switch communication-path data controlled by the switch by sending the router communication-path data to the switch during the test mode, and checking communication between the router and the switch by sending cells from the router to the switch and returning the cells from the switch to the router during the test mode. 
     In the method described above, the communication-path data controlled by the router and the communication-path data controlled by the switch are checked as to whether they are consistent with each other, and cells transmitted from the router to the switch are returned from the switch to the router so as to allow a check to be made as to communication between the router and the switch, so that a consistency check of the communication-path data, a cell-transparency check, and a connection check between the router and the switch can be easily made. 
     Accordingly, the method of checking communication-path data according to the present invention can help to identify a fault point easily and promptly in the communication system. In other words, when the communication system suffers a fault, it is possible to decide which one of the trunk switch and the router is suffering the fault, thereby separating the fault point from the rest of the system. 
     According to another aspect of the present invention, test signals are used for reporting results of the consistency check and results of the communication check. Therefore, the check results can be promptly and easily collected, which allows a fault point to be readily identified in a short time period. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an illustrative drawing showing a system based on the MPLS communication scheme; 
     FIG. 2 is an illustrative drawing for explaining a principle of the MPLS communication system; 
     FIG. 3 is a block diagram of a communication system according to an embodiment of the present invention; 
     FIG. 4 is an illustrative drawing for explaining a method of checking communication-path data in the MPLS-communication scheme according to the present invention; 
     FIG. 5 is an illustrative drawing for explaining test signals used in the MPLS-communication scheme of the present invention; 
     FIG. 6 is a block diagram of another embodiment of the communication system according to the present invention; 
     FIG. 7 is a sequence chart showing an example of operation of the communication system according to the present invention; and 
     FIG. 8 is an illustrative drawing for explaining an example of a test signal used in the communication system of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, embodiments of the present invention will be described with reference to the accompanying drawings. 
     In the embodiments disclosed herein, a description will be given with reference to an MPLS communication system based on ATM switches operating as trunk switches. It should be noted, however, that the present invention is not limited to such a particular configuration. For example, frame relays, a CDMA scheme, etc., may be used as trunk switches. 
     FIG. 3 is a block diagram of a communication system according to an embodiment of the present invention. 
     In FIG. 3, a communication system of FIG. 3 includes a maintenance terminal  70 , a terminal  71 , an MPLS router  80 , an ATM switch  90 , and an ATM-switch-maintenance terminal  72 . 
     Details of this communication system are as follows. The MPLS router  80  includes a central-processing apparatus  81  and an MPLS-communication apparatus  82 . The central-processing apparatus  81  includes an IP-packet-communication-control unit  83 , a control-data-management unit  84 , a communication-path-data-management unit  85 , and a communication-path-data-check unit  86 . The MPLS-communication apparatus  82  includes a subscriber-line-connection unit  87  and an ATM-communication-line-connection unit  88 . 
     The ATM switch  90  includes a central-processing apparatus  91  and a communication-line-control apparatus  92 . The central-processing apparatus  91  includes an ATM-data-management unit  93 , a maintenance-message-output unit  94 , and a communication-path-data-check unit  95 . The communication-line-control apparatus  92  includes a communication-line-connection unit  96  and a switch unit  97 . 
     In the following, the operation of the communication system of FIG. 3 will be described. FIG. 4 is an illustrative drawing for explaining a method of checking communication-path data in the MPLS-communication scheme according to the present invention. FIG. 5 is an illustrative drawing for explaining test signals used in the MPLS-communication scheme of the present invention. 
     The IP-packet-communication-control unit  83  is equipped with a function of receiving IP packets supplied from the maintenance terminal  70  or the terminal  71 , a function of converting the received IP packets into ATM cells, a function of transmitting the converted ATM cells to the ATM switch  90 , a function of receiving ATM cells supplied from the ATM switch  90 , a function of converting the received ATM cells into IP packets, and a function of transmitting the converted IP packets to the maintenance terminal  70  or the terminal  71 . 
     The IP-packet-communication-control unit  83  sends a switch request to the control-data-management unit  84  to change the IP-address-operation mode toga test mode when a signal  104  indicative of a start of a test is supplied from the maintenance terminal  70  as shown in FIG.  4 . When receiving an IP packet  100  from the terminal  71 , the IP-packet-communication-control unit  83  checks with the control-data-management unit  84  to learn the IP-address-operation mode, and sends a test-start request to the communication-path-data-check unit  86  if the IP-address-operation mode is a test mode. 
     When receiving a test-completion message from the communication-path-data-check unit  86 , the IP-packet-communication-control unit  83  sends a switch request to the control-data-management unit  84  to change the IP-address-operation mode to a normal-operation mode. The control-data-management unit  84  is equipped with a function of managing and controlling an IP-address-operation mode for each one of IP addresses. 
     The communication-path-data-management unit  85  is provided with a function of managing and controlling ATM-path data VPI/VCI corresponding to IP addresses. This function is implemented by use of label data  101  shown in FIG.  4 . During a period when the IP-address-operation mode indicates a normal operation mode, the communication-path-data-management unit  85  converts the IP packets into ATM cells. 
     When the IP-address-operation mode is a test mode, the communication-path-data-management unit  85  can generate OAM (operation, administration, and maintenance) cells  102  having ATM-path data VPI/VCI corresponding to a tested IP address. The OAM cells  102  are used for identifying a fault position, for example, and are characterized by their nature to return to their source position through backward transmission. 
     The communication-path-data-check unit  86  is provided with a test-processing-control function, a test-signal-control function, and a test-cell-exchange-control function. The test-processing-control function takes care of test-processing operations  105  through  109  as shown in FIG.  4 . The test-signal-control function takes care of exchanges of test signals between the MPLS router  80  and the ATM switch  90 . For example, the test signals that are exchanged may be that shown in FIG.  5 . The test-cell-exchange-control function takes care of exchanges of OAM cells  102 . 
     In the following, a description will be given with regard to a test signal with reference to FIG.  5 . 
     A test signal  110  includes control-information portion  112  and a set of information elements  114 . The control-information portion  112  includes a signal type  116 . The test signal  110  includes varying data in the set of information elements  114  that depends on the signal type  116 . 
     When the signal type  116  indicates that the signal is a test-start message, the set of information elements  114  is comprised of a set of information elements  120  that includes a test identifier and ATM-path data. The test signal  110  including the set of information elements  120  is transmitted from the MPLS router  80  to the ATM switch  90  during the test-processing operation  105  as shown in FIG.  4 . 
     When the signal type  116  indicates that the signal is a response to a test-start message, the set of information elements  114  is comprised of a set of information elements  121  that includes a test identifier, a test-start-operation result, and a consistency-check result. The test signal  110  including the set of information elements  121  is transmitted from the ATM switch  90  to the MPLS router  80  during the test-processing operation  106  as shown in FIG.  4 . 
     When the signal type  116  indicates that the signal is a test-completion message, the set of information elements  114  is comprised of a set of information elements  122  that includes a test identifier. The test signal  110  including the set of information elements  122  is transmitted from the MPLS router  80  to the ATM switch  90  during the test-processing operation  108  as shown in FIG.  4 . 
     When the signal type  116  indicates that the signal is a response to a test-completion message, the set of information elements  114  is comprised of a set of information elements  123  that includes a test identifier, a test-completion-operation result, and a connection-check result. The test signal  110  including the set of information elements  123  is transmitted from the ATM switch  90  to the MPLS router  80  during the test-processing operation  109  as shown in FIG.  4 . 
     With reference to FIG. 3 again, a description of the communication system will be further given in the following. 
     The ATM-data-management unit  93  is provided with a function of managing and controlling connections between ATM-path data controlled by the communication-path-data-management unit  85  and ATM-path data of an ATM communication partner. Namely, the ATM-data-management unit  93  is provided with the switch data. 
     The communication-path-data-check unit  95  is equipped with a test-processing-control function, a test-signal-control function, and a test-cell-monitor-control function. The test-processing-control function controls test-processing operations that are performed on the side of the ATM switch  90  among the test-processing operations  105  through  109  as shown in FIG.  4 . The test-signal-control function controls exchange of test signals between the ATM switch  90  and the MPLS router  80 . 
     The test-cell-monitor-control function controls exchange of the OAM cells  102  that are transmitted from the MPLS router  80 . The maintenance-message-output unit  94  supplies a message to the ATM-switch-maintenance terminal  72  connected to the ATM switch  90  where the message reports events that occurred in the ATM switch  90 . 
     In the following, details of the communication system according to the present invention will be described with accompanying drawings. 
     FIG. 6 is a block diagram of another embodiment of the communication system according to the present invention. FIG. 7 is a sequence chart showing an example of operation of the communication system according to the present invention. FIG. 8 is an illustrative drawing for explaining an example of a test signal used in the communication system of the present invention. In FIG. 6, the same elements as those of FIG. 3 are referred to by the same numerals, and a description thereof will be omitted. 
     When a test for checking communication-path data is to be started, an administrator uses a remote terminal such as the maintenance terminal  70  to access the MPLS router  80 , and requests a change of the IP-address-operation mode to a test mode. The request is sent to the control-data-management unit  84  via the IP-packet-communication-control unit  83 , and the control-data-management unit  84  changes the IP-address-operation mode to a test mode. 
     The sequence chart of FIG. 7 shows processing that is performed after the IP-address-operation mode is changed to a test mode. In FIG. 7, at a step S 10 , an administrator arranges to send an IP packet from any terminal such as the terminal  71  to the MPLS router  80 . At a step S 12 , the IP-packet-communication-control unit  83  checks with the control-data-management unit  84  to learn the IP-address-operation mode. If the IP-address-operation mode is a test mode, the IP-packet-communication-control unit  83  sends a test-start request to a communication-path-data-check-control unit  130 . 
     At a step S 14 , the communication-path-data-check-control unit  130  obtains a test identifier, and, thereafter, requests the communication-path-data-management unit  85  to read ATM-path data that corresponds to the specified IP address. At a step S 16 , the communication-path-data-management unit  85  supplies the requested ATM-pass data to the communication-path-data-check-control unit  130 . 
     At a step S 18 , the communication-path-data-check-control unit  130  requests a router-side-signal-control unit  131  to send a test-start request based on the ATM path data and the test identifier. At a step S 20 , the router-side-signal-control unit  131  generates a test signal  150  including a set of information elements  155  as shown in FIG. 8 based on the supplied ATM-path data and the test identifier. The test signal  150  is supplied to the ATM switch  90  from the MPLS router  80 . 
     When the test signal  150  is transmitted from the MPLS router  80  to the ATM switch  90 , a switch-side-signal-control unit  141  receives the test signal  150 , and, then, extracts the test identifier and the ATM-path data. At a step S 22 , the switch-side-signal-control unit  141  notifies a switch-side-check-control unit  140  of the test identifier and the ATM-path data. 
     At a step S 24 , the switch-side-check-control unit  140 , when capturing resources for test control that correspond to the test identifier, keeps the ATM-path data, and, then, sends an output request to the maintenance-message-output unit  94  to output the test-start message. The maintenance-message-output unit  94  notifies the administrator at the ATM-switch-maintenance terminal  72  that a test is going to be conducted. At a step S 26 , the maintenance-message-output unit  94  sends a response to the output request to the switch-side-check-control unit  140 . 
     At a step S 28 , the switch-side-check-control unit  140  sends a check request to check if the extracted ATM-path data is registered in the ATM-data-management unit  93 . At a step S 30 , the ATM-data-management unit  93  checks if the extracted ATM-path data is registered, and reports check results to the switch-side-check-control unit  140 . 
     At a step S 32 , the switch-side-check-control unit  140  sends a cell-monitor request to a test-cell-monitor unit  142 . At a step S 34 , the test-cell-monitor unit  142  sends a response to the call-monitor request to the switch-side-check-control unit  140 . Further, the test-cell-monitor unit  142  sends a request for received-ATM-cell check to the communication-line-control apparatus  92 , thereby placing the ATM switch  90  in a state of reception monitoring. 
     After reception monitoring begins, at a step S 36 , the switch-side-check-control unit  140  requests the switch-side-signal-control unit  141  to transmit a response to the test-start request based on results of test-start operation and the results of ATM-path-data-consistency check. At a step S 38 , based on the results of test-start operation and the results of ATM-path-data-consistency check, the switch-side-signal-control unit  141  generates the test signal  150  having a set of information elements  156  as shown in FIG. 8, and transmits the test signal  150  from the ATM switch  90  to the MPLS router  80 . 
     Upon receiving the test signal  150  from the ATM switch  90 , the communication-path-data-check-control unit  130  extracts the test identifier, the results of test-start operation, causes of anomaly in the results of test-start operation, and the results of consistency check. 
     If the results of test-start operation and the results of consistency check are normal, at a step S 40 , the communication-path-data-check-control unit  130  sends an OAM-cell-test-start request to a test-cell-exchange-control unit  132 . If the results of test-start operation and the results of consistency check indicate presence of anomalies, the communication-path-data-check-control unit  130  informs the maintenance terminal  70  of this fact via the IP-packet-communication-control unit  83 . Then, the test procedure comes to an end. 
     Upon receiving the OAM-cell-test-start request, the test-cell-exchange-control unit  132  requests the MPLS-communication apparatus  82  to transmit OAM cells. The MPLS-communication apparatus  82  generates OAM cells corresponding to the extracted VPI/VCI, and transmits the OAM cells to the ATM switch  90 . 
     Upon receiving the OAM cells, the communication-line-control apparatus  92  of the ATM switch  90  notifies the test-cell-monitor unit  142  of information on the received cells, and sends back the OAM cells to the MPLS router  80 . At a step S 42 , the test-cell-monitor unit  142  sends the information on the received cells to the switch-side-check-control unit  140 . 
     At a step S 46 , having received the cell information, the switch-side-check-control unit  140  checks connections to find no anomalies, and keeps results of the check. Further, the switch-side-check-control unit  140  sends an output request to the maintenance-message-output unit  94  to output a message indicative of reception of the OAM cells. In response, the maintenance-message-output unit  94  informs the administrator at the ATM-switch-maintenance terminal  72  that the OAM cells have been received. At a step S 48 , the maintenance-message-output unit  94  sends a response to the output request to the switch-side-check-control unit  140 . 
     The OAM cells returning from the communication-line-control apparatus  92  are received by the MPLS-communication apparatus  82 . The MPLS-communication apparatus  82  matches the returned OAM cells with the transmitted OAM cells, and finds no anomalies in the cell-transparency check between the MPLS router  80  and the ATM switch  90 . The MPLS-communication apparatus  82  reports the results of the check to the test-cell-exchange-control unit  132 . 
     At a step S 44 , the test-cell-exchange-control unit  132  sends the results of the cell-transparency check to the communication-path-data-check-control unit  130 . At a step S 50 , the communication-path-data-check-control unit  130  requests the router-side-signal-control unit  131  to transmit a test-completion request based on the test identifier. At a step S 52 , the router-side-signal-control unit  131  generates a test signal  150  having a set of information elements  157  shown in FIG. 8 based on the test identifier, and transmits the test signal  150  from the MPLS router  80  to the ATM switch  90 . 
     When the test signal  150  is sent from the MPLS router  80  to the ATM switch  90 , the switch-side-signal-control unit  141  receives the test signal  150 , and extracts the test identifier. At a step S 54 , the switch-side-signal-control unit  141  informs the switch-side-check-control unit  140  of the extracted test identifier. 
     At a step S 56 , the switch-side-check-control unit  140 , when successfully capturing resources for test control corresponding to the test identifier, sends an output request to the maintenance-message-output unit  94  to output a test-completion message. The maintenance-message-output unit  94  notifies the administrator at the ATM-switch-maintenance terminal  72  that the test is completed. At a step S 58 , the maintenance-message-output unit  94  sends a response to the output request to the switch-side-check-control unit  140 . 
     At a step S 60 , the switch-side-check-control unit  140  sends a request for completion of cell monitoring to the test-cell-monitor unit  142 . At a step S 62 , the test-cell-monitor unit  142  sends a response to the request for completion of cell monitoring to the switch-side-check-control unit  140 . Further, the test-cell-monitor unit  142  notifies the communication-line-control apparatus  92  of the completion of received-ATM-cell monitoring, thereby prompting the ATM switch  90  to get out of the state of reception monitoring. 
     At a step S 64 , the switch-side-check-control unit  140  requests the switch-side-signal-control unit  141  to transmit a response to the test-completion request based on results of test-completion operation and results of connection check. At a step S 66 , the switch-side-signal-control unit  141 , based on the results of the test-completion operation and the results of connection check, generates the test signal  150  having a set of information elements  158  as shown in FIG. 8, and sends the test signal  150  from the ATM switch  90  to the MPLS router  80 . 
     At steps S 68  and S 70 , the test signal  150  having the set of information elements  158  is sent from the ATM switch  90  to the MPLS router  80 , and the communication-path-data-check-control unit  130  generates test results based on the results of cell-transparency check, the results of connection check, etc., and sends the test results to the IP-packet-communication-control unit  83 . The IP-packet-communication-control unit  83  forwards the test results to the maintenance terminal  70 . 
     In this manner, the communication system of the present invention can help to identify a fault point easily and promptly in the MPLS communication scheme. In other words, when the communication system suffers a fault, it is possible to decide which one of the trunk switch and the MPLS router is suffering the fault, thereby separating the fault point from the rest of the system. 
     Accordingly, prompt recovery can be made in the router, switch, or the communication system where the method of checking communication-path data according to the present invention is employed, thereby providing reliable, better service. 
     In the claims, a unit for checking consistency corresponds to the steps S 14  through S 38 , and a unit for checking communication corresponds to the steps S 40  through S 48 . Further, the communication-path data controlled by the router corresponds to the label data  41 , and the communication-path data controlled by the trunk switch corresponds to the switch data  51 . 
     Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention. 
     The present application is based on Japanese priority application No. 11-310135 filed on Dec. 29, 1999, with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.