Abstract:
A method for solving communication failure includes transmitting user traffic over an automatic protection switching (“APS”) connection between a near network node and a far network node, determining that a protect path on the APS connection has failed, sending a message to the far network node that the protect path has failed, and switching user traffic to the working path at the near network node.

Description:
RELATED APPLICATION 
       [0001]    This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application Ser. No. 61/438,125 filed Jan. 31, 2011, entitled “METHOD AND SYSTEM FOR SOLVING COMMUNICATION FAILURE AND TRAFFIC LOSS IN SERVICE PROTECTION NETWORKS.” 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to networked communications and, more particularly, to a method and system for solving communication failure and traffic loss in service protection networks. 
       BACKGROUND 
       [0003]    Ethernet automatic protection switching under the G.8031 standard may use protected paths, one active and one backup, to communicate between virtual local area networks. The paths are monitored, and if one of the paths is detected as faulty, the backup path may take over and traffic continues to flow. The G.8031 standard has heretofore dictated the specific protocol for switching traffic between the paths in a variety of circumstances. 
       SUMMARY 
       [0004]    In one embodiment, a method for solving communication failure includes transmitting user traffic over an automatic protection switching (“APS”) connection between a near network node and a far network node, determining that a protect path on the APS connection has failed, sending a message to the far network node that the protect path has failed, and switching user traffic to the working path at the near network node. 
         [0005]    In another embodiment, an article of manufacture includes a computer readable medium and computer-executable instructions carried on the computer readable medium. The instructions are readable by a processor. The instructions, when read and executed, cause the processor to transmit user traffic over an APS connection between a near network node and a far network node, determine that a protect path on the APS connection has failed, send a message to the far network node that the protect path has failed, and switch user traffic to the working path at the near network node. 
         [0006]    In yet another embodiment, a switch system includes a near switch and an automatic protection switching (“APS”) connection communicatively coupled to the near switch. The switch includes a computer readable medium, a processor coupled to the computer readable medium, and computer-executable instructions carried on the computer readable medium. The instructions are readable by the processor. The instructions, when read and executed, cause the processor to transmit user traffic over the APS connection between the near switch and a far switch, determine that a protect path on the APS connection has failed, send a message to the far network node that the protect path has failed, and switch user traffic to the working path at the near network node. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    For a more complete understanding of the present invention and its features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
           [0008]      FIG. 1  is an example embodiment of a system for solving communication failure and traffic loss in service protection networks; 
           [0009]      FIG. 2  is an example illustration of the operation of the system during normal operation; 
           [0010]      FIG. 3  is an illustration of the operation of the system during conditions that may cause a loss of user traffic; 
           [0011]      FIG. 4  is an illustration of the operation of the system after switches have detected a loss in automatic protection switching (“APS”) message traffic over a protect path; 
           [0012]      FIG. 5  is an illustration of the operation of the system after a switch has sent an APS message to another switch indicating a failure a protect path in the switch; and 
           [0013]      FIG. 6  is an example embodiment of a method for solving communication failure and traffic loss in service protection networks by monitoring for APS communication interruptions. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  is an example embodiment of a system  100  for solving communication failure and traffic loss in service protection networks. In one embodiment, system  100  may be configured to solve communication failure and traffic loss associated with automatic protection switching (“APS”) message failure. In another embodiment, system  100  may be configured to solve communication failure and traffic loss in G.8031 service protection networks. Such a network may include a one-to-one (1:1) protected configuration. System  100  may include some or all of a one-to-one bidirectional G.8031 network. System  100  may include a network entity such as switch  102  communicatively coupled to another network entity such as switch  108 . Switch  102  and switch  108  may be communicatively coupled to exchange information, and to transport user traffic between network destinations such as those found in network  106  or network  112 . 
         [0015]    Switch  102  and switch  108  may be communicatively coupled through a network, sub-network, local-area-network, wide-area-network, an intranet, then Internet, various network entities, or any suitable combination thereof. Switch  102  may include one or more virtual groups of transmission tunnels. Such a group may include an Ethernet service protection group (“SVCPG”)  104 . Switch  108  may include one or more virtual groups of transmission tunnels. Such a group may include an SVCPG  110 . SVCPGs  104 ,  110  may be communicatively coupled to each other. SVCPGs  104 ,  110  may be implemented as logical entities within switches  102 ,  108  respectively. SVCPGs  104 ,  110  may include paths  118 ,  120 , as well as any other suitable resource. System  100  may be configured to prevent traffic loss caused by concurrent bidirectional wait-to-restore mechanisms in either SVCPG  104 ,  110 , occurring during networked communication between the two. 
         [0016]    Network  106  may comprise any suitable network—for example, a local-area-network, wide-area-network, a network of metro Ethernet switches, virtual-local-area-network, an intranet, or a portion of the Internet. Network  112  may comprise any suitable network—for example, a local-area-network, wide-area-network, a network of metro Ethernet switches, virtual-local-area-network, an intranet, or a portion of the Internet. 
         [0017]    Switch  102  may be communicatively coupled to switch  108  through SVCPG  104 . Switch  108  may be communicatively coupled to switch  102  through SVCPG  110 . 
         [0018]    System  100  may include an operator  122  communicatively coupled to one or more portions of the network of system  100 , such as switch  102 . System  100  may include additional operators, such as operator  123  communicatively coupled to other portions of the network of system  100 , such as switch  108 . In one embodiment, operator  122  and/or operator  123  may include an electronic device configured to receive information about the operation of system  100 . Operator  122  and/or operator  123  may include an electronic device configured to make changes in system  100  in response to information about the operation of system  100 . For example, operator  122  and/or operator  123  may be configured to set the state of operation of switch  102  or switch  108 . Operator  122  and/or operator  123  may be configured to make some of such changes automatically. In another embodiment, operator  122  and/or operator  123  may include interfaces for human administrators of the system  100  to receive information regarding the operation of system  100 , and to enter desired changes in system  100  in response to the information. 
         [0019]    Switch  102  may include a processor  114  coupled to a memory. Processor  114  may comprise, for example, a microprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), or any other digital or analog circuitry configured to interpret and/or execute program instructions and/or process data. Switch  102  may interpret and/or execute program instructions and/or process data stored in memory  116 . Memory  116  may comprise any system, device, or apparatus configured to hold and/or house one or more memory modules. Each memory module may include any system, device or apparatus configured to retain program instructions and/or data for a period of time (e.g., computer-readable media). 
         [0020]    In one embodiment, switch  108  may include a processor  124  coupled to a memory  126 . Processor  124  may comprise, for example, a microprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), or any other digital or analog circuitry configured to interpret and/or execute program instructions and/or process data. Switch  108  may interpret and/or execute program instructions and/or process data stored in memory  126 . Memory  126  may comprise any system, device, or apparatus configured to hold and/or house one or more memory modules. Each memory module may include any system, device or apparatus configured to retain program instructions and/or data for a period of time (e.g., computer-readable media). 
         [0021]    Switch  102  may be configured to solve APS communication failure and traffic loss in G.8031 service protection networks according to some or all of the teachings of this disclosure. In one embodiment, switch  108  may be implemented in the same way as switch  102  with regards to solving APS communication failure and traffic loss in G.8031 service protection networks. In such an embodiment, switch  108  and switch  102  may be implemented in the same or related makes or models of switches. In another embodiment, switch  108  may not be implemented in the same way as switch  102  with regards to solving APS communication failure and traffic loss in G.8031 service protection networks. In such an embodiment, switch  108  may be implemented with only features conforming to the G.8031 standard. Switch  108  may thus be of a different makes or models of switches. In such a case, switch  108  may be provided by a third party. 
         [0022]    Switch  102  and switch  108  may communicate using linear protected switching. Switch  102  and switch  108  may be communicatively coupled through a linearly protected switching connection. The linearly protected switching connection may include a protected path. In one embodiment, the protected path may form a portion of a G.8031 protected path. In a further embodiment, the protected path may comprise a working path  118  and a protect path  120 . Each of working path  118  and protect path  120  may include routes through a number of network entities between switch  102  and switch  108 . Each of working path  118  and protect path  120  may include two transmission media. Such transmission media may include any suitable media such as fiber or copper. In one embodiment, two of such transmission media may interface with each of SVCPG  104  and SVCPG  110  to form a transmission tunnel and a reception tunnel. Switch  102  and switch  108  may be communicatively coupled through SVCPG  104  and SVCPG  110  over working path  118  and protect path  120 . One of paths  118 ,  120  may be designated as active, wherein a switch using paths  118 ,  120  for user traffic will transmit and receive packets making up the user traffic over the active path, but ignore such user traffic on the other path. User traffic may include customer traffic originating and travelling to destinations in network  106  and network  112 . User traffic may flow on working path  118  or protect path  120 , depending upon the configuration of switches  102  and  108 . Such a configuration may determine which of the paths is active and thus carrying user traffic. In one embodiment, user traffic may be transmitted on either the working path  118  or on the protection path  120 , but not on both paths simultaneously. Thus if the two switches  102 ,  108  transmit user traffic on different paths, user traffic may be lost. The switches  102 ,  108  may monitor the protection path  120  for control and status messages, such as APS messages. APS messages may implement a control packet. APS messages may include protocol messages. APS messages may include property and state information of an originating SVCPG. In one embodiment, the working path  118  may be initially configured as the active path. If working path  118  is down or otherwise unavailable, then protect path  120  may be configured as the active path for user traffic. In another embodiment, switch  102  and switch  108  may exchange user traffic over the active path, but only exchange APS messages over protect path  120 . In such an embodiment, if protect path  120  is unavailable then APS messages may be lost. APS messages and user traffic may thus be able to be transmitted at times on the same protect path  120 . System  100  may thus be configured to transport user traffic between various networked entities in system  100 , such as between those in network  106  and in network  112 . 
         [0023]    Switch  102  may be configured to receive a packet of information of user traffic from a network entity in network  106 , and forward the information across working path  118  and/or protect path  120  to switch  108  for delivery to a network entity in network  112 . Switch  102  may be configured to exchange control information, statuses, or other messages regarding the communication itself with switch  108 . Switch  102  may be configured to exchange such information over protect path  120 . Such information may be in the form of APS messages. 
         [0024]    Switch  108  may be configured to receive a packet of information of user traffic from switch  102  for delivery to a destination address in network  112 . Switch  108  may be configured to receive control information, statuses, or other messages regarding the communication itself from switch  108  and take appropriate action based on such information. Switch  102  may be configured to exchange such information over protect path  120 . Such information may be in the form of APS messages. 
         [0025]    Switches  102 ,  108  may be configured to operate in pre-determined states of operation, depending upon the conditions encountered. Pre-determined states of operation may indicate any suitable information about operational settings or conditions encountered. For example, pre-determined states of operation may indicate to switches  102 ,  108  which path  118 ,  120  should be used for communication of user traffic given the occurrence of a particular event. 
         [0026]    Switch  102  may be configured to notify operator  122  regarding any change in the status of communication between switch  102  and switch  108 . For example, if encountering communication difficulties on a particular path  118 ,  120  switch  102  may take corrective action to resume communication with switch  108  to minimize the loss of information. In such a case, switch  102  may notify operator  122  of actions taken, conditions observed, and may implement subsequent actions required by operator  122 . Switch  102  may be configured to make state changes based on information or instructions received from operator  122 . 
         [0027]    Switch  108  may be configured to notify operator  123  regarding any change in the status of communication between switch  102  and switch  108 . For example, if encountering communication difficulties on a particular path  118 ,  120  switch  108  may take corrective action to resume communication with switch  108  to minimize the loss of information. In such a case, switch  108  may notify operator  123  of actions taken, conditions observed, and may implement subsequent actions required by operator  123 . Switch  108  may be configured to make state changes based on information or instructions received from operator  123 . 
         [0028]    Switch  102  and switch  108  may be configured to periodically exchange APS messages. Such messages may be exchanged in both directions. Switch  102  and switch  108  may be configured to exchange APS messages on protect path  120 . 
         [0029]    Conditions may arise that may cause one or both of switch  102  and switch  108  to lose communication of the APS messages. Such conditions may include, for example, congestion in the network on protect path  120 , the deletion of one of the SVCPGs  104 ,  110 , or disabling G.8031 protection in one of the SVCPGs  104 ,  110 . Such conditions may affect the transmission of APS messages in one direction. For example, switch  108  may be able to receive APS messages sent by switch  102 , but switch  102  may not be able to receive APS messages sent by switch  108 . The loss of APS messages, without additional action, may adversely affect one or more services being carried on the network connection as described below. 
         [0030]    In addition to such a loss of APS messages, a decision may be made at one of the switches to switch traffic from working path  118  to protect path  120 . For example, for maintenance reasons operator  123  may instruct switch  108  to switch user traffic to protect path  120  using a MAN/FORCE command. Switch  108  may not be aware of the problems that switch  102  is encountering in receiving APS messages from switch  108 . Thus, without any such notifications from switch  102 , switch  108  may transition user traffic to be transported over protect path  120 . Switch  108  may send an APS message to switch  102  with information about the change in user traffic. However, since switch  102  may be having difficulty receiving APS messages from switch  108 , switch  102  may not be informed of the impending change in paths, and may instead continue to transmit and monitor for user traffic on working path  118 . As a consequence, a complete traffic loss in the user traffic may result. Such a situation may arise under these or similar circumstances if switches  102 ,  108  implement the G.8031 standard. However, one or both of switches  102 ,  108  may be configured as described below to handle these and other situations. 
         [0031]      FIG. 2  is an example illustration of the operation of system  100  during normal operation. Switch  102  may be configured to exchange user traffic with switch  108  over working path  118 , which may be acknowledged by both switches as active. Protect path  120  may be reserved as a backup path. Switch  102  and switch  108  may exchange APS messages in each direction over protect path  120 . 
         [0032]      FIG. 3  is an illustration of the operation of system  100  during conditions that may cause a loss of user traffic. Conditions may arise such that the receiving tunnel of switch  102  at the protect path becomes congested or otherwise unusable. Switch  102  may not receive APS messages from switch  108 . In addition, conditions may arise that cause switch  108  to switch transmission of user traffic from working path  118  to protect path  120 . 
         [0033]    Switch  102  may be configured to monitor protect path  120  for APS message traffic. Switch  102  may be configured to use a countdown timer to determine for how long APS messages have not been received. Any suitable countdown period may be used by switch  102  to monitor protect path  120  for APS messages. The period may vary between different SVCPGs, according to priority, physical distance, quantity of network entities between the SVCPGs, speed of connections, kinds of traffic to be handled, the expected flow of data, or any other suitable criteria. The period may be set by operator  122 . In one embodiment, a countdown period of three times the APS communication period may be used. In another embodiment, the APS communication period may be five seconds. Upon receipt of an APS message, switch  102  may be configured to reset the countdown timer for the SVCPG through which the APS message was received. The countdown timer may be implemented in memory  116 , or in any other suitable mechanism. If the countdown expires, switch  102  may be configured to determine that the APS traffic has been interrupted. 
         [0034]      FIG. 4  is an illustration of the operation of system  100  after switches  102  has detected a loss in APS message traffic over protect path  120 . Even though switch  108  may still be receiving APS message traffic over protect path  120  and thus the protect path  120  may at least be partially in working order, switch  102  may be configured to send a message to switch  108  indicating that the protect path has failed. Such a message may normally indicate to switch  108  that the protect path has failed, and switch  108  may take standard operating procedures in accordance with such a status. In one embodiment, switch  108  may be configured to switch user traffic to working path  118  upon receipt of a message that protect path  120  has failed. 
         [0035]    To send a message to switch  108  claiming that the protect path  120  has failed, switch  102  may generate an “SF-P” event and place it within an APS message to be sent to switch  108 . Switch  102  may be configured to move traffic to working path  118 , send the APS message on the protection path  120  to switch  108 , and send an alarm to operator  122 . 
         [0036]      FIG. 5  is an illustration of the operation of system  100  after switch  102  has sent an APS message to switch  108  with an “SF-P” event, or otherwise indicated a failure in protect path to switch  102 . Switch  108  may be configured to receive a signal failure message such as one containing “SF-P” from switch  102 . Switch  108  may be configured to evaluate the instruction in the APS message against any current states of execution of switch  108 , to determine whether the received message may overrule the presently executing state. Such a determination may be made by consulting a hierarchy of command or state priorities. For example, switch  108  may be configured to accept the actions implied by the “SF-P” signal over a previously received instruction from an operator to manually switch user traffic from working path  118  to protect path  120 . Switch  108  may be configured to move its traffic to the working path  118  in accordance with the received instruction. In one embodiment, switch  108  may be in a lockout state when receiving the message from switch  102 , and may ignore the message. In another embodiment, switch  108  may be configured to ignore the message when switch  108  is already transmitting user traffic on the working path  118 . 
         [0037]    Consequently, even if switch  108  is implemented using only the G.8031 standard, switch  102  may be configured to solve one-to-one bidirectional APS communication failure and traffic loss in G.8031 service protection networks. In addition, switch  102  may be configured to solve one-to-one bidirectional APS communication failure and traffic loss in G.8031 service protection networks without any information as to the status of switch  108 . Switch  108  may be transmitting user traffic on either path  118 ,  120 . 
         [0038]    In operation, switch  102  may be receiving user traffic on working path  118  from another entity such as switch  108  through SVCPG  110 . Switch  102  may reset a countdown timer each time an APS message is received via a given SVCPG, such as SVCPG  104 . Switch  102  may receive settings for the countdown timer from operator  122 . If the countdown timer expires, switch  102  may determine that an interruption in APS traffic has occurred on protect path  120 . 
         [0039]    Switch  102  may send a failure indication such as “SF-P” in an APS message to switch  108  on the protect path  120 . Switch  102  may move user traffic to working path  118 , if such user traffic is not already being transmitted on working path  118 . Switch  102  may send an alarm to operator  122 . 
         [0040]    Upon receipt of a message such as “SF-P” from switch  102 , switch  108  may move to the corresponding state of operation. For example, if “SF-P” was received as part of the APS message, switch  108  may move user traffic to the working path  118 . Switch  108  may evaluate the message against any existing statuses before implementing or ignoring the message. 
         [0041]      FIG. 6  is an example embodiment of a method  600  for solving communication failure and traffic loss in service protection networks by monitoring for APS communication interruptions. In step  605 , a path may be monitored for control messages. In one embodiment, the path may be one portion of a G.8031 protected path. In another embodiment, the path may be the receiving tunnel of a protect path. In yet another embodiment, the path may be monitored for APS messages from another network entity. 
         [0042]    In step  610 , it may be determined whether any of the monitored-for traffic has been encountered on the observed path. In one embodiment, it may be determined whether any APS messages have been received on the receiving tunnel of the protect path. If such traffic has been received, in step  615  a timer may be reset to a maximum value, and the method  600  may resume monitoring at step  605 . 
         [0043]    If no such traffic has been received, then in step  617  the timer may be decremented. In step  620  it may be determined whether the timer has reached zero. If the timer has not reached zero, then the countdown may be updated and the method  600  may resume monitoring the active path at step  605 . 
         [0044]    If the timer has reached zero, then in step  625  it may be determined that APS messages on the receiving tunnel of the protect path has been interrupted. A signal failure on the protect path may be declared. Such a signal failure may be designated by “SF-P.” In step  630 , an APS message with an SF-P even may be sent over the protect path. Such a message may indicate to other entities to switch to a different state of operation, which may include communicating over a different path. Such a message may be sent to a network entity with which user traffic has been exchanged. In step  635 , an alarm may be sent to an operator indicating the path and the type of failure that has been encountered. 
         [0045]    In step  640 , user traffic may be moved to working path, if necessary. After step  640 , the method  600  may resume monitoring in step  605 . 
         [0046]    Although  FIG. 6  discloses a particular number of steps to be taken with respect to an example method  600 , method  600  may be executed with more or fewer steps than those depicted in  FIG. 6 . In addition, although  FIG. 6  discloses a certain order of steps to be taken with respect to method  600 , the steps comprising method  600  may be completed in any suitable order. 
         [0047]    Method  600  may be implemented using the system of  FIGS. 1-5  or any other system, network, or device operable to implement method  600 . In certain embodiments, method  600  may be implemented partially or fully in software embodied in computer-readable media. 
         [0048]    For the purposes of this disclosure, computer-readable media may include any instrumentality or aggregation of instrumentalities that may retain data and/or instructions for a period of time. Computer-readable media may include, without limitation, storage media such as a direct access storage device (e.g., a hard disk drive or floppy disk), a sequential access storage device (e.g., a tape disk drive), compact disk, CD-ROM, DVD, random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), and/or flash memory; as well as communications media such wires, optical fibers, and other electromagnetic and/or optical carriers; and/or any combination of the foregoing. 
         [0049]    Although the present disclosure has been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereto without departing from the spirit and the scope of the disclosure as defined by the appended claims. For example, in some embodiments the operations of switch  102  may also be conducted by switch  108 , and vice-versa.