Abstract:
A bulk Soft Permanent Virtual Circuit (SPVC) trace processor is provided. The bulk SPVC trace processor receives notifications of newly established SPVCs and SPVC re-routing instances. The bulk SPVC trace processor submits SPVC connection trace commands to corresponding trace source network nodes, and retrieves trace transit list information therefrom. The aggregate SPVC transport path information derived from trace transit list information is stored and provided to higher network management and service provisioning functions. The bulk SPVC trace processor may also be employed to trace SPVC portions of Hybrid SPVCs. As SPVC connection tracing is necessary subsequent to a failure, load balancing techniques are used to spread SPVC connection tracing over time, network resources, and network partitions to prevent weighting down the network. Network planning and design functions previously built for Permanent Virtual Circuit (PVC) provisioning may be seamlessly upgraded in migrating to (H)SPVC connectivity.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates to communication networks, and in particular to methods and apparatus for tracing soft permanent virtual circuit connections.  
         BACKGROUND OF THE INVENTION  
         [0002]    Asynchronous Transfer Mode (ATM) technologies have been developed to derive combined benefits from packet-switched technologies and circuit-switched technologies. Packet-switched technologies benefit from an efficient utilization of bandwidth. Circuit-switched technologies benefit from a high quality-of-service. ATM technologies employ fixed sized packets, known as cells, which are switched in an ATM network to follow Virtual Circuit (VC) transport paths.  
           [0003]    [0003]FIG. 1 is representative of an ATM network  100  which includes ATM network nodes  102  and interconnecting links  104 . Legacy ATM cell transport includes the use of pre-established Permanent Virtual Circuits (PVCs)  106  in the ATM network  100  provisioned over selected interconnecting links  104 . The establishment of a PVC  106  is performed by a call manager entity  110  which has access to knowledge regarding: the topology of the managed ATM network, cell processing capacities of each managed network node, transport bandwidth capacities of each managed interconnecting link, etc. The call manager  110  makes use of a network configuration database  112  to store and track provisioning information about the network  100 .  
           [0004]    If a connection is needed between any two ATM network nodes  102 , a request  120  for establishing the connection is provided to the call manager  110 . The request  120  includes a network address specification corresponding to the source network node  102 -S requesting the establishment of the connection and a network address specification corresponding to the destination network node  102 -D. The request may also specify resource utilization requirements including, but not limited to: a required average bandwidth, a maximum transport latency, a maximum jitter, etc.  
           [0005]    The call manager  110 , upon receiving the request  120  for establishing a connection, parses the request  120  to extract the source and destination network node addresses, and the resource utilization requirements. Based on the extracted information, and information held in the network configuration database  112 , the call manager  110  attempts to determine  122  a transport path, of network nodes  102  and interconnecting links  104 , which will have enough spare cell processing capacity at the network nodes  102 , and enough transport bandwidth on the interconnecting links  104 , to accommodate the new connection in the network  100 . Once the transport path is determined  122 , various commands are sent, via signaling messages  124 , to the network nodes  102  in the transport path to reserve resources for PVC  106  to be established therebetween. Once all network nodes  102  in the transport path confirm the resource reservations, via return setup complete signaling messages  126 , the PVC  106  is said to be established. The call manager  110  also updates  128  the network configuration database  112  with the particulars of the new PVC transport path.  
           [0006]    Via a Network Management System (NMS)  140 , network administrators  130  may be provided with a visual display  132  of all PVCs  106  in use in the network  100 . The provisioning of the visual display  132  is possible due to the fact that all PVC transport path provisioning information is available centrally via the network configuration database  112 . The availability of PVC transport path information stored in the network configuration database  112  enables micro-management of network resources.  
           [0007]    Should any network infrastructure failures occur, network nodes  102  connected to the affected failed interconnecting links  104  or failed network nodes  102 , inform the call manager  110  thereof, via signaling messages (not shown). The call manager  110  updates  128  the network configuration database  112  to reflect the failed equipment, determines the PVCs  106  which were provisioned via the failed network infrastructure, and the call manager  110  begins to reprovision ( 122 ,  124 ,  126 ,  128 ) all the affected PVCs  106  around the failed network infrastructure one-by-one in the same fashion presented above. Besides the deleterious effects of the infrastructure failure, a large amount of bandwidth is needed for the conveyance of signaling messages  124 / 126 / 128  to effect the reprovisioning of the affected PVCs.  
           [0008]    A person of ordinary skill in the art understands that ATM technologies were devised to provision a large number of PVCs  106  in order to deliver high transport capacities. An infrastructure failure therefore affects a large number of PVCs  106  which the call manager  110  will have to reroute in a short period of time following the infrastructure failure to reduce cell loss.  
           [0009]    There has been a trend towards conveying cells at ever increasing transport bandwidths over the interconnecting links  104 , and employing network nodes  102  of higher and higher cell processing capacities. The processing requirements imposed on the call manager  110  can quickly stress the call manager entity to its processing limits especially when network failures occur. As the call manager  110  is associated with a network node  102 -CM, an abnormal amount of signaling traffic processing is experienced by the network node  102 -CM although the network node  102 -CM may not be closely associated with the failed network infrastructure. The sequential transport path re-determination in healing the affected network  100  is considered very slow and typically leads to excessive cell loss.  
           [0010]    In referring to FIG. 2, recent developments have brought about intelligent ATM network nodes  202  which led to intelligent networks  200 . Intelligent ATM network nodes  202  use Private Network-Node Interface (PNNI) signaling to perform some of the tasks related to connection establishment, and connection rerouting in response to network failures. The transport path determination and reconfiguration performed by the intelligent network nodes  202  themselves, is enabled via the use of Soft Permanent Virtual Circuits (SPVC)  206 . In the event of a network failure  208 , benefits are derived from parallel transport path rerouting  210  which reduces the probability of cell loss. The use of SPVCs  206  provides connectivity resiliency by distributing SPVC connection re-routing processing overheads over many intelligent network nodes  202  in the network  200 . For this reason SPVCs are also know colloquially as Smart PVCs.  
           [0011]    In using SPVCs  206  to provision connectivity, the call manager  110  only keeps track of SPVC connectivity states at a high level—the task of ensuring low level physical SPVC connectivity being performed by the intelligent network nodes  202  themselves. The result is that the call manager  110  is informed  226  of the establishment of SPVCs  206  but not of the transport path used by the SPVCs. Therefore, in using SPVCs  206 , the call manager  110  and the network configuration database  112 , no longer have access to detailed connectivity information. Network administrators  130  can only engage in macro-management of network resources because the visibility of detailed connectivity information is diminished compared to what was previously enjoyed by using PVCs. As a result there is a reluctance to employ SPVCs  206  in provisioning connections over ATM infrastructure.  
           [0012]    There is a strong demand to provide SPVC configuration visibility akin to PVC provisioning to enable micro-management of SPVC connections.  
           [0013]    An extension to PNNI signaling has been described in af-cs-0141.000, “PNNI Addendum for Path and Connection Trace”, Version 1.0, March 2000, which is incorporated herein by reference. Provisions are made for SPVC path tracing in troubleshooting connection establishment, and for SPVC connection tracing for discovering the transport path used by already established SPVC connections.  
           [0014]    The very recent adoption of the af-cs-0141.000 extension to PNNI signaling has only benefited from a limited implementation. Prior art implementations enable a network administrator  130  to manually select  230 , via a network management system  140  having access to the network configuration database  112 , a single SPVC connection, and to manually issue a single SPVC connection trace command  232  to a single source trace node  202 -S. The SPVC trace results are provided via a trace transit list and stored at the source trace node  202 -S. The network administrator  130  needs to manually connect to the source trace node  202 -S via an element management interface, manually retrieve the trace transit list, and interpret it. This implementation is inadequate in providing network-wide visibility of all active SPVC connectivity because of the large number (millions) of SPVCs  206  typically intended to be used.  
           [0015]    There therefore is a need to address the above mentioned issues.  
         SUMMARY OF THE INVENTION  
         [0016]    In accordance with an aspect of the invention, a bulk SPVC connection trace processor is provided. The bulk SPVC connection trace processor includes an information store, an accumulator, a dispatcher, and a collector. The information store tracks SPVC connection status change reports for a plurality of SPVC connections. The accumulator gathers a group of SPVC connection status change reports. The dispatcher is triggered by the accumulator to initiate the issuance of a plurality of SPVC connection trace commands to trace source network nodes corresponding to SPVC connections associated with in the group of SPVC connection status change reports. The collector accesses the trace source network nodes to retrieve trace transit list information and provides consolidated SPVC transport path information derived from the retrieved trace transit list information. The tracking of SPVC connection status change reports provides a dynamic response to SPVC connectivity changes in a managed network.  
           [0017]    In accordance with another aspect of the invention, the bulk SPVC connection trace processor further includes a control interface to receive SPVC connection tracing requests for a selection of SPVC connections.  
           [0018]    In accordance with a further aspect of the invention, a method of tracing a plurality of SPVC connections is provided. Received SPVC connection status change reports corresponding to a multitude of SPVC connections are tracked. A group of received SPVC connection status change reports is accumulated. SPVC connection tracing commands are dispatched to a group of trace source network nodes provisioning SPVC connections corresponding to the group of accumulated SPVC connection status change reports. And, trace transit list information is collected from the group of trace source network nodes. The tracking of received SPVC connection status change reports provides a dynamic response to SPVC connectivity changes in a managed network.  
           [0019]    In accordance with yet another aspect of the invention, the trace transit list information for each traced SPVC is stored to provide connectivity information akin to that typically available for PVCs.  
           [0020]    The advantages are derived by network administrators, higher network management and service provisioning functions, being provided with the same level of transport path information detail previously enjoyed in using PVCs. Network planning and design functions previously built for PVC provisioning may be seamlessly upgraded in migrating to SPVC connectivity.  
           [0021]    By engineering the execution of bulk SPVC connection tracing, a minimized effect is felt by the network management and service provisioning tasks, enabling a large number of SPVC connections to be traced and thereby removing a major roadblock to large scale SPVC deployment.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    The features and advantages of the invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached diagrams wherein:  
         [0023]    [0023]FIG. 1 is a schematic diagram showing elements implementing an exemplary ATM network and exemplary signaling used in provisioning PVC connections;  
         [0024]    [0024]FIG. 2 is a schematic diagram showing elements implementing an exemplary intelligent ATM network and exemplary PNNI signaling used in provisioning SPVC connections;  
         [0025]    [0025]FIG. 3 is a schematic diagram showing, in accordance with an exemplary embodiment of the invention, interacting elements providing bulk SPVC connection tracing;  
         [0026]    [0026]FIG. 4 is a schematic flow diagram showing process steps implementing bulk SPVC connection tracing, in accordance with various exemplary implementations of the invention; and  
         [0027]    [0027]FIG. 5 is a schematic diagram showing elements providing processing load distributed bulk SPVC connection tracing, in accordance with various exemplary implementations of the invention.  
         [0028]    It will be noted that in the attached diagrams like features bear similar labels. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0029]    A dual benefit is sought: that of a reduced processing overhead derived by using SPVCs, and that of having access to full network-wide PVC-style transport path information for provisioned SPVCs. As contradicting requirements as these may seem in view of the current state of the art, an exemplary solution is described herein:  
         [0030]    [0030]FIG. 3 is a schematic diagram showing interacting elements providing bulk SPVC connection tracing.  
         [0031]    In accordance with a preferred embodiment of the invention, the reporting functionality  226  (see FIG. 2), used by intelligent network nodes  202  to inform the call manager  110  of the establishment of each new SPVC connection and/or of the re-routing of each SPVC connection affected by network failures, is tapped and used to trigger the issuing of SPVC connection trace commands. Trace transit list information is retrieved to derive SPVC transport path information therefrom.  
         [0032]    It is important to minimize the involvement of the call manager  110  in SPVC connection tracing due to a time critical operation thereof. The call manager  110  is (preferably) only involved in updating SPVC provisioning states in the network configuration database  112 . A change notifier  310  is exemplary associated with the call manager  110 , monitors signaling traffic conveyed to the call manager  110 , and generates SPVC status change notifications  312  for each SPVC connection status change report  226 . Therefore, SPVC connection status change notifications  312  are generated for each new SPVC connection establishment report and/or for each SPVC connection rerouting report.  
         [0033]    The SPVC connection status change notifications  312  are provided to a Bulk Connection Trace (BCT) processor  320  which is adapted to send ( 406 ) SPVC connection trace commands  232  to trace source network nodes  202 -S, retrieve trace transit lists from the respective trace source network nodes  202 -S, and store ( 412 ) the trace transit list information. In accordance with another exemplary implementation, the BCT processor  320  is also notified  312  of SPVC trace completions.  
         [0034]    The use of the BCT processor  320  ensures the use of minimal processing resources from the call manager  110 . The BCT processor  320  may be implemented as part of the network management system  140 . Alternatively the BCT processor  320  may be implemented on an off-board independent platform to ensure minimal processing resource utilization from time critical operation of the call manager  110 , and/or the network management system  140 . The implementation choice is not intended to limit the invention. Both the NMS  140 , call manager  110 , and the BCT processor  320  will have response time requirements, resource utilization requirements, etc. which factor into design choices. The BCT processor  320  may include a BCT software application implementing bulk SPVC connection trace logic.  
         [0035]    [0035]FIG. 4 is a schematic flow diagram showing process steps implementing bulk SPVC connection tracing.  
         [0036]    The overall process  400  performed by the BCT processor  320  (shown in solid outlined process steps) involves, waiting for the receipt of notifications  312 , which is exemplary shown at  402 . Once a notification  312  is received, the BCT processor  320  determines, in step  404 , whether the notification  312  corresponds to an SPVC connection status change report.  
         [0037]    Regardless of whether the SPVC connection status change notification  312  corresponds to a new SPVC establishment report  226  or an SPVC reconfiguration report  226 , the operation of the BCT processor  320  results in sending  406  a SPVC connection trace command ( 232 ) to a trace source network node ( 202 -S) corresponding to the changed SPVC. In sending  406  the SPVC connection trace command, the BCT processor  320  (either directly or indirectly through the network management system  140 ) may consult the network configuration database  112  to determine at least a network address of the trace source network node  202 -S, if not already specified in the notification  312 .  
         [0038]    If the notification  312  corresponds to an SPVC trace completion report of a previously sent SPVC connection trace command  232 , fact ascertained in step  408 , the BCT processor  310 , retrieves  410  the trace transit list information from the source trace network node  202 -S corresponding to the traced SPVC connection.  
         [0039]    The BCT processor  320  also stores  412  the retrieved trace transit list information in retrievable storage. Making reference to FIG. 3, the implementation of step  412  may employ a file  322 . The file  322 , without limiting the invention, includes a text file having a human readable format. A time stamp may be stored in the file  322 , along with SPVC transport path information, the value specified by the time stamp corresponding to the network time when the file  322  was last updated. The actual format of the file  322  is left to design choice which typically conforms to requirements imposed by further use of the file  322 , may include the use of binary files formats, and described elsewhere.  
         [0040]    In accordance with an exemplary implementation of the invention, the step  412  may involve the storage of the retrieved trace transit list information in the network configuration database  112  more particularly in corresponding SPVC records  330  (also known generically as call records), to track the transport path information. The stored SPVC transport path information may be equivalent to PVC transport path information. Populating SPVC records  330  with trace transit list information, enables network administrators  130  to have access to combined PVC and SPVC transport path information and therefore provides access to detailed network resource utilization and routing of connections in support of micro-management.  
         [0041]    The network configuration database  112  therefore, as far as SPVC connectivity information is concerned, will be updated in close to real-time.  
         [0042]    In accordance with another embodiment of the invention, an engineered response is provided in performing bulk SPVC connection tracing. As mentioned, network failures lead to a high level of PNNI signaling exchange. Burdening the network with SPVC connection tracing in bulk at the same time the network attempts to heal itself from the network failure, would further negatively impact the operation of the network  300 . Therefore, there is a need for a less intrusive solution as uncontrolled bulk SPVC connection tracing may lead to very intensive use of the available signaling bandwidth.  
         [0043]    In accordance with an exemplary implementation of the invention, each SPVC record  330  in the network configuration database  112  has a corresponding special purpose SPVC connection traced specifier  332 . Various implementations of the SPVC connection traced specifier  332  may be employed without limiting the invention thereto; for example a single bit register, also referred to as a flag, may be used.  
         [0044]    In accordance with another exemplary implementation of the invention, the BCT processor  320  makes use of storage resources  324  associated therewith in tracking SPVC connections for tracing purposes to minimize access to the network configuration database  112 . The structure of the information held in the storage  324  is not intended to limit the invention, nor is the actual type of information stored. At least specifiers  332  are stored in the storage  324  to identify SPVC connections to be traced. In accordance with another implementation of the invention the storage  324  may simply buffer SPVC related information stored in the network configuration database  112 .  
         [0045]    Referring to FIG. 4 and making additional reference to process steps shown in heavy interrupted outline, upon receiving an SPVC connection status change notification  312  from the change notifier  310 , step  404 , the BCT processor  320  accesses the network configuration database  112  ( 324 ), based on the SPVC identified in the notification  312 , to reset  420  the corresponding SPVC traced flag  332 . If a bit register is employed, a logic low value stored therein would signify that the SPVC connection needs to be traced. Conversely, a logic high value would signify that the SPVC connection has been traced (at least recently).  
         [0046]    When an SPVC connection trace complete notification  312  is received, step  408 , either from the source trace network node  202 -S, for example, or by other means without limiting the invention thereto, and the trace transit list is stored  412 , the BCT processor  320 , sets  422  the corresponding SPVC traced flag  332 . The assertion of the SPVC traced flag  332  signifies that the SPVC connection has been traced and that the connectivity information available (either in the network configuration database  112 , in the file  332 , or in the retrievable storage  324 ) corresponds to SPVC physical connectivity in the network  300 .  
         [0047]    Provisions may also be made for resetting the SPVC traced flag  332  when each SPVC record  330  is created: for example by ascribing a default logic low value thereto. Therefore on start-up or restart of the solution, all active SPVCs in the network  300  would be retraced to update all SPVC records  330 .  
         [0048]    Having provided for the identification of SPVC records  320  requiring transport path information updates via the use of the SPVC traced flags  332 , the BCT processor  320 , in providing the engineered response, is therefore enabled to accumulate SPVC status change notifications  312 .  
         [0049]    In accordance with an exemplary implementation of the invention, sending out SPVC connection trace commands  406  is delayed for a waiting period during which the network  300  is expected to heal itself from network failures ( 208 ). The speed at which a network is expected to heal itself is a combination of: the number of interconnecting links  104  affected, the number of nodes  102 / 202  affected, the number of connections  106 / 206  affected, etc. (It is envisioned that PVCs and SPVCs may be used concurrently.) Tolerated network-down time is also typically specified in service level agreements.  
         [0050]    In accordance with an exemplary implementation and making reference to both FIG. 4 and FIG. 5, the delay in sending out  406  SPVC trace commands  232  is provided via a delay counter  524 . The delay counter  524  is reset to zero  430  with each SPVC status change notification received ( 404 ) and incremented  432  during BCT processor  320  idling periods. If the value of the delay counter  524  reaches a predetermined “Wait” delay threshold time value, as ascertained in step  434 , then SPVC connection trace commands  232  are sent  406  for each flagged SPVC ( 332 ). The delay threshold time value is a design choice. Without limiting the invention, typical delay threshold time values would be in the order of minutes.  
         [0051]    It would be apparent to a person skilled in the art, that a lot of SPVC connection status change notifications  312  would be accumulated, without performing any SPVC connection tracing, if a long period of intense SPVC connection status change notification  312  receipts is experienced. Depending on the required response of the BCT processor  320 , the use of the delay counter  524  may be augmented with, or replaced by, the use of a notification accumulation counter  526 . Only once the BCT processor  320  has gathered a predetermined number (accumulation threshold) of received SPVC connection status change notifications  312  would the BCT processor  320  send  406  the SPVC connection trace commands ( 232 ) for each flagged  322  SPVC record  330 .  
         [0052]    In accordance with another implementation of the invention, SPVC connection tracing may be aged ( 552 ). At the expiration of a predefined information aging time period, the BCT processor  320  may be triggered  560  to update all SPVC connections in the network  300 . As mentioned above network-wide SPVC connection tracing may involve upwards of a million SPVCs  206  and may take a few hours to complete. The completion time is dependent on the processing power of the BCT processor  320 , the spare signaling bandwidth available in the network  300 , the available bandwidth in accessing the network configuration database  112 , etc.  
         [0053]    In accordance with the exemplary embodiment of the invention, the engineered response takes into account the facts that long bulk SPVC connection tracing jobs typically generated by: network failures, the above mentioned solution restarts, and large SPVC connection tracing requests, if not controlled, all lead to large bursts of signaling traffic in the network  300  (either immediate or delayed).  
         [0054]    In accordance with another exemplary embodiment of the invention, the BCT processor  320  makes further use of multiple BCT workers  540 , to employ a divide-and-conquer approach in spreading the bulk SPVC trace processing over combinations of time, processing resources, network nodes, and/or managed network domains/partitions. The use of the BCT processor  320  and BCT workers  540  in combination enables the BCT processor  320  to fully concentrate on processing received notifications  312  and to pace SPVC tracing by delegating SPVC connection tracing  450  to BCT workers  540  appropriately. In accordance with a further enhancement, each BCT worker  540  may further be adapted to send SPVC trace commands  232  at an adjustable rate  542 . Typically each BCT worker  540  may be implemented as an executable software application. The use of BCT workers  540  enables topology aware and/or weighted processing of SPVC connection tracing commands providing load balancing.  
         [0055]    The accumulation of notifications  312 , enables each BCT worker  540  to be given a group of SPVCs  206  to trace, the engineered response is therefore provided via effecting control over: the extent of the accumulation of notifications  312 , the grouping of SPVCs  206  requiring tracing, timely spawning  450  each BCT worker  540 , the rate  542  at which BCT workers  540  send  406  SPVC connection trace commands  232 , etc. The grouping of SPVCs  206  for delegated processing by BCT workers  540 , without limiting the invention, may be implemented in accordance with trace source network node associativity and/or network partition associativity. Having a group of SPVC connections  206  to be traced, the actual combined SPVC connection tracing may be performed serially or in parallel.  
         [0056]    On sending out all SPVC connection trace commands  232 , each BCT worker  540  may be adapted to generate the above mentioned SPVC connection traced notification(s)  312 , for example by issuing a “done” signal. It is recognized that the sending of the done signal may not be correlated with the availability of trace transit lists at source trace nodes  202 -S. It is intended that in sending of the done signal, after all SPVC connection trace commands  232  have been dispatched ( 406 ), sufficient time has been given for at least the first SPVC connections  206  in the delegated SPVC group to have completed connection tracing.  
         [0057]    In accordance with the exemplary embodiment of the invention the BCT workers  540  may be entrusted with the retrieval  410  of trace transit lists, the storage  412  of the SPVC transport path information, and the setting  422  of corresponding SPVC traced flags.  
         [0058]    In accordance with a further embodiment of the invention, an analysis module  550  may be employed for interacting  560  with the BCT processor  320 , and the BCT processor  320  may further implement an interface having control parameters for interaction therewith, in tailoring the operation of the BCT processor  320 .  
         [0059]    Without limiting the invention, the analysis module  550  may be concerned less with attending to notifications  312  and perhaps more concerned with correlations that may be derived from SPVC connections status changes. The exemplary analysis module  550  may have independent access to the network configuration database  112 . The above mentioned exemplary aging function  552 , may be implemented in the analysis module logic.  
         [0060]    The interface implemented by the BCT processor  320  may include the processing of messages  560  requesting the tracing of a specific group of SPVC connections  206  regardless of the current status of the SPVC traced flags  332 . The aging function  552  therefore may be implemented by requesting tracing of the group of all provisioned SPVCs. Care must be taken in issuing such a command to the BCT processor  320  as such an SPVC connection tracing request may involve millions of SPVC connections  206  and it is suggested that such SPVC tracing be limited to a day.  
         [0061]    The change notifier  310  presented above was described as being associated with the call manager  110 . The described association is not intended to limit the invention thereto. As shown in FIG. 5, a more generic purpose change notifier  310  may be associated with the network configuration database  112  to track changes to network configuration database records including SPVC records  330 . The BCT processor  320  would register with the generic change notifier  310  to receive the notification  312 .  
         [0062]    A person of skill in the art would understand that the apparatus and methods presented herein above apply equally well to Hybrid SPVCs (HSPVCs). An HSPVC is a hybrid connection which has at last one PVC portion and at least one SPVC portion. The transport path information regarding the PVC portion is held in the network configuration database  112  including the PVC-end network nodes  102 / 202 . HSPVC connection tracing involves issuing the connection trace command(s)  232  to PVC end-network node(s)  202 -S of the SPVC connection portion(s).  
         [0063]    The embodiments presented are exemplary only and persons skilled in the art would appreciate that variations to the above described embodiments may be made without departing from the spirit of the invention. The scope of the invention is solely defined by the appended claims.