Abstract:
Embodiments of the invention are directed to extended psuedowire groups in a packet switched network. Embodiments associate a pseudowire to one or more groups at each provider edge device across which the pseudowire traverses. When a pseudowire set-up request message traverses across various provider edge devices, each provider edge device typically adds one or more local group membership information elements into the pseudowire set-up request message. In that way the grouping assigned by each provider edge device that the pseudowire traverses is made available to all other provider edge devices traversed by the pseudowire. Advantageously, this availability pseudowire grouping information allows any of these provider edge devices to initiate a wildcard message to notify other provider edge devices with respect to pseudowires in any of its local groups, as well as allowing a pseudowire to be bound to multiple groups based on various requirements.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention is directed to groups of pseudowires in a packet switched network (PSN), particularly to establishing and managing the groups and conveying information in connection with the groups to devices in the PSN. 
       BACKGROUND 
       [0002]    Pseudowire (PW) is a mechanism that emulates the essential attributes of a telecommunications service (Frame Relay, Asynchronous Transfer Mode, Ethernet) over a Packet Switched Network (PSN). These Layer 2 services can be emulated over an MPLS backbone by encapsulating the layer 2 Protocol Data Units (PDU) and transmitting them with MPLS labels that identifies a PWs. Label Distribution Protocol (LDP) is used as the default protocol for Pseudowire Setup and Maintenance as per Internet Engineering Task Force (IETF) RFC 4447. 
         [0003]    The terminology used herein includes PE for “Provider Edge Device” and CE for “Customer Edge Device”. A PSN tunnel is established to provide a data path for the PW between two provider edge devices. PW traffic is not distinguishable to the core network, and the core network is transparent to the CEs. Native data units (bits, cells, or packets) arrive via the respective Attachment Circuit (AC) between each PE and its CE, are encapsulated in a PW PDU, and are carried across the underlying network via the PSN tunnel. The PEs perform the necessary encapsulation and decapsulation of PW PDUs and handle any other functions required by the PW service, such as sequencing or timing. 
         [0004]    A Multi-Segment Pseudowire (MS-PW) is a set of two or more contiguous PW segments that behave and function as a single point-to-point PW. A MS-PW enables providers to extend the reach of PWs across multiple transport PSN domains. The terminology used herein includes S-PE for “Switching” PE Device where two segments of a MS-PW are stitched together. PW Labels are switched by S-PE between two PW segments. 
         [0005]    RFC4447 describes a concept of PW grouping that represents an arbitrary group of PWs specific to a “Terminating” PE (T-PE) device. T-PE stands for the PE device where a PW terminates. When label mapping messages are exchanged between two PW emulation points, those messages carry a PW grouping TLV that identifies a PW group local to the sender T-PE. The T-PE at the other end (receiver of the label mapping) maintains a database of PWs that map to the PW group at sender T-PE. 
         [0006]    The PW grouping allows “wildcard” messaging from the sender T-PE on the entire group when any event common to the group requires notifications to the other end T-PE—such as wildcard label withdrawals or wildcard status notification messages. A single message can be sent with the PW grouping identifier (ID) to notify action on all member PWs in a group. For example, a PW grouping ID can be used as a port index and can be assigned to all PWs that have ACs bound to that port. Use of PW grouping ID enables a PE to send one single wildcard label withdrawal message or PW status notification message specifying the group ID in the event of port failure. Such wildcard messaging provides significant reduction of per PW messaging overhead and makes the PW Operations Administration and Maintenance (OAM) Status notifications very efficient. 
         [0007]    The existing method of PW grouping imposes the restriction that a PW can belong to only one group across the T-PEs. Further with MS-PW, it is not possible that a PW can belong to the same group across the T-PEs since the MS-PW traverses across one or more S-PEs and such PW grouping is meaningful across a single PW segment. 
         [0008]    A set of PWs originating in a first T-PE can be bound to the same local port. It is not necessary that all member PWs are bound to the same PSN tunnel between the first T-PE and a first S-PE since the PSN requirements of the PWs may vary based on diverse Quality of Service (QoS) or diverse next-hop S-PEs requirements, etc. Two PWs of the group may share the same local port but may be routed to different S-PEs. This requires a PW to assign at least two groups at the sender T-PE:
       1. An “access” group based on port id or other attributes on the attachment circuit (AC) for triggering a wildcard PW status message on various fault/status transitions associated with the AC.   2. A “network” group based on the PSN tunnel used to reach the first S-PE for triggering wildcard PW status message on various PSN fault/status transitions associated with the PSN tunnel.       
 
         [0011]    The grouping association may also change at each S-PE along the MS-PW. For example, the first S-PE may receive a PW set-up request for both PWs, which have the same grouping ID “G”, but may route each of the PWs to different S-PEs or the same S-PE but over different PSN tunnels based on diverse QoS/Policy requirements of each of the PWs. However in both cases, if the first S-PE detects a PSN tunnel fault towards another S-PE, it cannot use wildcard messaging to notify the fault to all PEs of the member PWs that are affected. Further, when an S-PE receives a wildcard message with group G, it cannot transparently forward the wildcard message to next-hop S-PE(s) since grouping ID is meaningful only for a single PW hop. 
         [0012]    For efficiency and scalability of PW maintenance, it is required that wildcard messaging be possible from any T-PE or S-PE that can be seamlessly notified across all T-PE or S-PE devices through which the PWs that belong to the group traverse. Hereinafter this document at times may use PE to specify a T-PE or an S-PE. LDP is a Transmission Control Protocol (TOP) based protocol which is prone to signaling delays due to congestion control in TCP. In Dynamic MS-PW, a PW status message traverses through control planes of each of the S-PEs of the MS-PW since that is a requirement of PW OAM Message Mapping, according to IETF RFC6310. Efficiency and performance of PW status signaling is a very important factor for PW OAM Message Mapping, PW Redundancy, PW applications such as Virtual Private Local Area Network Service (VPLS) Media Access Control (MAC) Address Flush for example according to IETF RFC4762. When PW scaling requirements are high (e.g. 128,000 PWs) the resulting high volume of PW status signaling may impact the operational efficiency of LDP and SLA (Service Level Agreement) of the PW service, 
         [0013]    Therefore, an efficient way of establishing and managing the PW groups and conveying information in connection with the groups to devices in the PSN is desired. 
       SUMMARY 
       [0014]    Embodiments of the invention are directed to extended psuedowire groups in a packet switched network. Some embodiments associate a pseudowire to one or more groups at each provider edge device across which the pseudowire traverses. When a pseudowire set-up request message traverses across various provider edge devices, each provider edge device typically adds one or more local group membership information elements into the pseudowire set-up request message. In that way the grouping assigned by each provider edge device that the pseudowire traverses is made available to all other provider edge devices traversed by the pseudowire. Advantageously, this availability of pseudowire grouping information allows any of these provider edge devices (T-PE or any of the S-PEs) to initiate a wildcard message to notify other provider edge devices with respect to pseudowires in any of its local groups, as well as allowing a pseudowire to be bound to multiple groups based on various requirements. The invention describes this PW grouping as “Extended Groups”. 
         [0015]    According to an aspect of the invention a method of learning a pseudowire extended group is provided. The method comprises performing the following steps by a provider edge device: receiving a pseudowire setup request message that includes a pseudowire label and extended group information; extracting the extended group information and the pseudowire label from the pseudowire setup request message; adding the extracted extended group information to a database in the provider edge device; and adding the pseudowire label to a record in the database that includes the extracted extended group information. 
         [0016]    According to another aspect of the invention a method of initiating a wildcard pseudowire status message is provided. The method comprises performing the following steps on a provider edge device: detecting a change in status of a resource associated with the provider edge device; determining if a pseudowire is affected by the change in status; determining, responsive to a pseudowire being affected by the change in status, a pseudowire group of the pseudowire; forming a wildcard pseudowire status message that includes an indication of the pseudowire group; and forwarding the wildcard pseudowire status message to a next hop of the provider edge device in a path of the pseudowire. 
         [0017]    According to yet another aspect of the invention a method of responding to a wildcard pseudowire status message is provided. The method comprises performing the following steps on a provider edge device: receiving a wildcard pseudowire status message over a pseudowire; determining, from the pseudowire status message, an affected pseudowire group; determining an affected pseudowire of the affected pseudowire group; and taking an action with respect to the affected pseudowire. 
         [0018]    According to a further aspect of the invention a device for implementing a pseudowire extended group is provided. The device comprises: a data port operable to receive and transmit pseudowire protocol data unit traffic; storage having memory that has been adapted by a program of instructions; and a processor in communication with the storage and the data port. Execution of the program by the processor causes the device to perform a function associated with a pseudowire extended group. 
         [0019]    The function performed by the device may include: receiving a pseudowire setup request message that includes a pseudowire label and extended group information; extracting the extended group information and the pseudowire label from the pseudowire setup request message; adding the extracted extended group information to a database in the provider edge device; and adding the pseudowire label to a record in the database that includes the extracted extended group information. 
         [0020]    Additionally or alternatively the function performed by the device may further include: detecting a change in status of a resource associated with the provider edge device; determining if a pseudowire is affected by the change in status; determining, responsive to a pseudowire being affected by the change in status, a pseudowire group of the pseudowire; forming a wildcard pseudowire status message that includes an indication of the pseudowire group; and forwarding the wildcard pseudowire status message to a next hop of the provider edge device in a path of the pseudowire. 
         [0021]    Further additionally or alternatively the function performed by the device may further include: performing the following steps on a provider edge device: receiving a wildcard pseudowire status message over a pseudowire; determining, from the pseudowire status message, an affected pseudowire group; determining an affected pseudowire of the affected pseudowire group; and taking an action with respect to the affected pseudowire. 
         [0022]    According to yet a further aspect of the invention a packet switched network is provided. The packet switched network comprises: a first device for implementing a pseudowire extended group, the first device including a first database; and a second device for implementing a pseudowire extended group, the second device including a second database. The first and second devices have been provisioned to enable communication between them via a pseudowire. The first database includes an identifier of the second device in association with the pseudowire and a second pseudowire group, and the second database includes an identifier of the first device in association with the pseudowire and a first pseudowire group. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of the preferred embodiments, as illustrated in the appended drawings, where: 
           [0024]      FIG. 1  depicts a prior art PW emulation reference model. 
           [0025]      FIG. 2  depicts a prior art reference model for MS-PW. 
           [0026]      FIG. 3  depicts devices and messaging used to assign and convey PW extended groups for MS-PWs according to a first embodiment of the invention. 
           [0027]      FIG. 4  depicts a PW extended group type length value (TLV) message according to a second embodiment of the invention. 
           [0028]      FIG. 5  depicts a PW group element of the message in  FIG. 4 . 
           [0029]      FIG. 6  is a flowchart depicting a method of learning a PW extended group according to a third embodiment of the invention. 
           [0030]      FIG. 7  is a flowchart depicting a method of initiating a wildcard PW status message according to a fourth embodiment of the invention. 
           [0031]      FIG. 8  is a flowchart depicting a method of responding to a wildcard PW status message according to a fifth embodiment of the invention. 
           [0032]      FIG. 9  depicts a device for implementing a pseudowire extended group according to a sixth embodiment of the invention. In the figures like features are denoted by like reference characters. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]      FIG. 1  depicts a prior art PW emulation reference model. As depicted, two PEs (PE1, PE2) provide two PWs (PW1, PW2) on behalf of their client CEs (CE1 and CE2) to enable the client CEs to communicate over a PSN. A PSN tunnel is established to provide a data path for the PWs (PW1, PW2) between the two PEs (PE1, PE2). The PW traffic is indistinguishable from other traffic to the core network, and the core network is transparent to the CEs. Native service data units (e.g. bits, cells, or packets) arrive via the Attachment Circuits (AC1, AC2), are encapsulated in respective pseudowire PDUs (PW PDUs), and are carried across the underlying network via the PSN tunnel. The PEs perform encapsulation and decapsulation of PW PDUs and handle any other functions required by the PW service, such as sequencing or timing. 
         [0034]      FIG. 2  depicts a prior art reference model for MS-PW. A Multi-Segment Pseudowire (MS-PW) is a set of two or more contiguous segments that behave and function as a single point-to-point PW. A MS-PW enables providers to extend the reach of PWs across multiple transport PSN domains. 
         [0035]    Referring to  FIG. 2 , a switching point PE (S-PE) (SPE1) runs two separate control planes: one toward a first tunnel endpoint PE (TPE1), and one toward a second tunnel endpoint PE (TPE2), The PW switching point (SPE1) is configured to connect a first segment of a first pseudowire (PW1 Segment  1 ) carried over a first PSN tunnel (PSN Tunnel  1 ) and a second segment of the first pseudowire (PW1 Segment  2 ) carried over a second PSN tunnel (PSN Tunnel  2 ) together to complete the multi-segment PW between the first and second tunnel endpoint PEs (TPE1, TPE2). The first and second segments of the first pseudowire (PW1 Segment  1 , PW1 Segment  2 ) must be of the same PW type, but the first and second PSN tunnels (PSN Tunnel  1 , PSN Tunnel  2 ) need not be the same technology. In the latter case, if the PW is switched to a different technology, the PEs must adapt the PDU encapsulation between the different PSN technologies. In the case where the first PSN tunnel (PSN Tunnel  1 ) and the second PSN tunnel (PSN Tunnel  2 ) are the same technology, the PW PDU does not need to be modified, and PDUs are then switched between the first and second segments of their respective pseudowires at the PW label level. 
         [0036]      FIG. 3  depicts a system  10  capable of assigning a PW extended group for a MS-PW and conveying information about the extended group to all PEs in the path of the MS-PW according to a first embodiment of the invention. The system is similar to that of  FIG. 2  with at least one distinguishing feature that the PEs (TPE1, SPE1, TPE2) have been adapted to implement a new concept of PW “extended” groups to enable seamless wildcard messaging across the span of the MS-PW. When a PW is set-up, PW extended group information is carried along with a set-up request message used to set-up the PW. The set-up request message is processed in a control plane  12  of the PEs. Each S-PE along the path of the MS-PW adds the extended group information assigned locally by the S-PE before forwarding the PW set-up request to next-hop PE device. The PW extended group contains multiple PW group elements to which the PW belongs. Each PW group element is described by a PE identifier and group Identifier (PE-ID, Group-ID) tuple. A PE may bind a PW to one or more groups unique to that PE, each such group being represented by a PW group element. Thus a PW group element has local significance to a PE, but the information is propagated to all other PEs along with the path over which the set-up request message of that specific PW travels. 
         [0037]    Each PE maintains a mapping  14  of PW group elements that it has learned from it neighboring PE devices. A PE device learns the various PW groups assigned by another PE device from PW extended group information received in a PW set-up request message. Although a PW group is unique to a PE device, each PE device receiving such information maintains the mapping, e.g. as a record in a database on the PE, of PW group elements based on the neighboring PE device from which the PW group elements were learned. This is important since a wildcard message is typically received through a specific neighbor PE device. 
         [0038]    A mapping record of a PW group element contains the list of its member PWs. The PW extended grouping allows any PE device to initiate a wildcard message based on one or more local PW group elements. A receiving PE device takes appropriate action on member PWs as per the PW group element mapping record with respect to the sender PE. If the receiving device is an S-PE for a set of PWs that belong to the specified group (or groups) then the wildcard message is seamlessly forwarded to all next-hop S-PE and/or T-PE of the member PWs. 
         [0039]    An example is as follows based on the MS-PW shown in  FIG. 3 .
       1. Both the first pseudowire (PW1) and the second pseudowire (PW2) share the same local port and thus are assigned a group (TPE1, G1) in the first tunnel endpoint PE (TPE1).   2. The first and second pseudowires (PW1, PW2) are both routed to the same next-hop, which is the switching point PE (SPE1), but are assigned different transport tunnels, those being the first PSN tunnel (PSN Tunnel  1 ) and the second PSN tunnel (PSN Tunnel  2 ), respectively. The first tunnel endpoint PE (TPE1) assigns group G2 to all PWs sharing the first PSN tunnel (PSN Tunnel  1 ) and G3 to all PWs sharing the second PSN tunnel (PSN Tunnel  2 ). Thus the first pseudowire (PW1) is assigned the groups (TPE1, G1)+(TPE1, G2) and the second pseudowire (PW2) is assigned the groups (TPE1, G1)+(TPE2, G3).   3. After the switching point PE (SPE1) receives a first PW set-up request message  16  for the first and second pseudowires (PW1, PW2), the switching point PE (SPE1) learns the following PW grouping information and stores it as a mapping  14  of PW group elements:       
 
       Neighbor T-PE1:   
     Port 
       [0000]    
       
         
           
             (TPE1, G1)---&gt;PW1, PW2 
           
         
       
     
       Tunnel 
       [0000]    
       
         
           
             (TPE1, G2)----&gt;PW1 
             (TPE1, G3)----&gt;PW2 
             4. The switching point PE (SPE1) decides to route both the first and second pseudowires (PW1, PW2) to the same next-hop, which is the second tunnel endpoint PE (TPE2) over the same PSN tunnel, which is a third PSN tunnel (PSN Tunnel  3 ). The switching point PE (SPE1) assigns the group G1 to all PWs sharing the third PSN tunnel (PSN Tunnel  3 ). Thus a second set-up request message  18  for the first pseudowire (PW1) is forwarded to the second tunnel endpoint PE (TPE2) with the groups (TPE1, G1)+(TPE1, G2)+(SPE1, G1). A third set-up request message  20  for the second pseudowire (PW2) is forwarded to the second tunnel endpoint PE (TPE2) with the groups (TPE1, G1)+(TPE1, G3)+(SPE1, G1). 
             5. On receiving the second and third set-up request messages  18 ,  20  for the first and second pseudowires (PW1, PW2) respectively, the second tunnel endpoint PE (TPE2) forms the following and stores it as a mapping  14  of PW group elements: 
           
         
       
     
       Neighbor T-PE1:   
     Port 
       [0000]    
       
         
           
             (TPE1, G1)----&gt;PW1, PW2 
           
         
       
     
       Tunnel 
       [0000]    
       
         
           
             (TPE1, G2)----&gt;PW1 
             (TPE1, G3)----&gt;PW2 
             (SPE1, G1)----&gt;PW1, PW2 
           
         
       
     
         [0052]    Based on the PW set-up above some of the PW status/failure procedures would be as follows. 
         [0053]    When local port status changes at the first tunnel endpoint PE (TPE1), the first tunnel endpoint PE (TPE1) initiates a wildcard PW status message  22  with group (TPE1, G1) and sends the message  22  to the switching point PE (SPE1). Upon receiving the message  22 , the switching point PE (SPE1) takes action on the first and second pseudowires (PW1, PW2) based on membership information available on the group (TPE1, G1). The switching point PE (SPE1) forwards the wildcard PW status message  22  to the next-hop (or next-hops) of the member PWs, which is the second tunnel endpoint PE (TPE2). Upon receiving the message  22 , the second tunnel endpoint PE (TPE2) takes action on the first and second pseudowires (PW1, PW2) based on the membership information it had learned about the group (TPE1, G1). Such actions taken by the switching point PE (SPE1) and the second tunnel endpoint PE (TPE2) may include raising an alarm, diverting traffic carried by the first and second pseudowires (PW1, PW2) to other pseudowires, and/or rerouting the first and second pseudowires (PW1, PW2). 
         [0054]    When status of the third PSN tunnel (PSN Tunnel  3 ) changes at the switching point PE (SPE1), the switching point PE (SPE1) initiates a wildcard PW status message  24  with the group (SPE1, G1) and sends it to the next-hop (or next-hops) of all PWs that share that group, which is the second tunnel endpoint PE (TPE2) in this case. On receiving the wildcard PW status message  24 , the second tunnel endpoint PE (TPE2) takes action on the first and second pseudowires (PW1, PW2) based on membership information available in its database  14 . Such action taken by the second tunnel endpoint PE (TPE2) may include raising an alarm, diverting traffic carried by the first and second pseudowires (PW1, PW2) to other pseudowires, and/or rerouting the first and second pseudowires (PW1, PW2). 
         [0055]      FIG. 4  depicts a PW extended group type length value (TLV) message  50  according to a second embodiment of the invention. A PW extended group TLV  56  occupying bits  2  to  15  in the message  50  carries a list of PW group elements, each PW group element  60   a,    60   n  being a multiple of 32 bits in length. Bits  0  and  1  of the PW extended group TLV message  50  are set to 1 and 0, respectively. Bits  16  to  31  of the PW extended group TLV message  50  hold a length value  58  corresponding to the length of the message  50 . The definition of the PW extended group TLV message  50  is compliant with the requirements of IETF LDP specification RFC5036. The LDP specification RFC5036 allows Vendor Private TLV space which can be used to assign the TLV type space assigned to the Vendor. For inter-operability among vendors, the TLV type can also be standardized with the Internet Address and Naming Authority (IANA). 
         [0056]      FIG. 5  depicts a PW group element  60  of the PW extended group message  50  in  FIG. 4 . A PW group element  60  includes an element type field  102  occupying bits  0  to  7 , a length field  104  occupying bits  8  to  15  that specifies the length of the PW group element  60 , one or more variable length value fields  106   a,    106   m  occupying the remaining bits of the PW group element  60 . 
         [0057]    The following PW group element Types  102  are defined in this document: 
         [0000]    Type  1 —Value field  106  contains the following:
       32 bit Group ID,   IP address identifying the PE device to which the Group ID belongs.
 
Type  2 —Value field  106  contains the following:
   32 bit Group ID,   Identifier of the PE device in S-PE addressing format as specified in Dynamic Multi-segment PW specification.       
 
         [0062]      FIG. 6  is a flowchart depicting a method  200  of learning an PW extended group according to a third embodiment of the invention. The method  200  may be performed by a PE, which as already stated includes S-PE and TPE devices. The following description of the method  200  references features of the foregoing drawings as examples by the reference characters of the features. The method  200  begins by receiving  202 , at a PE (TPE1, SPE1, TPE2), a PW setup request message ( 16 ,  18 ,  20 ) that identifies a PW to be setup, e.g. by an MPLS PW label, The PE determines  204  whether or not the PW setup request message ( 16 ,  18 , and  20 ) includes PW extended group information such as a PW extended group TLV  56 . If such PW extended group information is not included in the PW setup request message the method  200  ends  212 , otherwise execution of the method  200  proceeds to a step of extracting  206 , from the PW setup request message ( 16 ,  18 ,  20 ) one or more PW group elements  60 . 
         [0063]    The extracted PW group elements  60  are added  208  to the group mapping database  14  of the PE if they are not already present in the group mapping database  14 . This adding  208  could be done in several ways, for example a check could be made first to see if a particular PW group element  60  is already in the group mapping database, e.g. by using the PW group element tuple (PE-ID, group-ID) as an index to search for records in the database already having that tuple, or an attempt to add the PW group element  60  could be made and the actual adding simply skipped if an error was returned indicating that the tuple already exist in the group mapping database  14 . 
         [0064]    The method  200  then proceeds to adding  210  the PW label of the PW being setup to records in the group mapping database  14  that include the PW group elements extracted from the PW extended TLV  56 . The method  200  then ends  212 . 
         [0065]      FIG. 7  is a flowchart depicting a method  300  of initiating a wildcard PW status message  22  according to a fourth embodiment of the invention. The method  300  may be performed by a PE, which as already stated includes S-PE and TPE devices. The following description of the method  300  references features of the foregoing drawings as examples by the reference characters of the features. The method  300  begins by detecting  302 , at a PE, a change in status of a resource associated with the PE. Such resource could be a port of the PE or a PSN tunnel (e.g. PSN Tunnel  1 ) over which the PE is conveying PW PDUs or otherwise using or monitoring the resource. The change in status may include a change from operational to non-operational status of the resource, a change from alarm-free to alarmed status of the resource, a change from error-free operational to non-error-free operational status of the resource, etc. After a change in status of the resource is detected  302 , execution of the method proceeds to a step of determining  304  which PW or PWs, if any, are affected by the change in status. This could be done for example by the PE checking its records of MPLS label provisioning (e.g. as would exist in typical PEs) for PWs that are associated with the resource in question. If no PWs are affected by the change in resource status the method  300  ends  312 , otherwise execution of the method  300  proceeds to a step of determining  306  groups of the affected PW or PWs. 
         [0066]    Recall that during the method  200  of learning an PW extended group that a PW is associated with includes storing, in a record of the group mapping database  14 , the PW label and a PW group element  60 . Further recall that a PW group element  60  comprises a tuple that includes a PE-ID and a group-ID. The step of determining  306  groups of one or more affected PWs can be achieved by using the PW label of each affected PW as an index to lookup PW group elements in the PE&#39;s group mapping database  14  that correspond to that PW. Execution of the method  300  then proceeds to forming  308  a wildcard message  22  that includes an indication of the affected PW groups. This forming  308  comprises creating a PW extended group TLV  50  that includes the PW group elements  60  of the affected PW groups that were looked up in the PE&#39;s group mapping database  14 . Execution of the method  300  then proceeds to forwarding  310  that wildcard message  22  to next hop devices in the path of the affected PW or PWs. The method  300  then ends  312 . 
         [0067]      FIG. 8  is a flowchart depicting a method  400  of responding to a wildcard PW status message  22  according to a fifth embodiment of the invention. The method  400  may be performed by a PE, which as already stated includes S-PE and TPE devices. The following description of the method  400  references features of the foregoing drawings as examples by the reference characters of the features. The method  400  begins by receiving  402  a wildcard PW status message  22  at a PE over a PW (e.g. PW1). The PE then determines  404  which PW groups are affected from the PW status message  22 . This is done by reading the group-ID from the one or more tuples included in the PW group elements  60  of the wildcard PW status message  22 . Execution of the method  400  then proceeds to determining  406  affected PW of the affected PW groups. The PE may perform this step for example by using the tuples of the one or more affected group-IDs as an index to read, from the PE&#39;s group mapping database  14 , the label of each PW associated with the affected PW groups. The method  400  then proceeds to the step of the PE taking  408  an action with respect to the affected PWs. Taking  408  an action may include initiating another wildcard PW status message  22  in accordance with the method  300  previously described, as well it may include raising an alarm, diverting traffic carried by the PW to another PW, and/or rerouting the PW. The method  400  then ends  410 . 
         [0068]      FIG. 9  depicts a device  500  for implementing an pseudowire extended group according to a sixth embodiment of the invention. The device may take the form of a PE as previously described. The device  500  includes a processor  502 , storage  504 , and one or more data ports  506 . The processor is in communication with the storage  504  and the data ports  506 . The data ports are used to receive and transmit PW PDU traffic of the type previously described, including PW setup request messages ( 16 ,  18 ,  20 ) and wildcard PW status messages ( 22 ,  24 ). The storage  504  includes memory that stores a program  508  that embodies one or more of the methods  200 ,  300 ,  400  previously described. That is, the storage  504  has been configured by the program  508 , so that the device  500  is operable to perform one or more of them methods  200 ,  300 ,  400 . For example, the program  508  would typically include executable instructions that when executed by the processor  500  cause the steps of one or more of the described methods  200 ,  300 ,  400  to be performed by the device  500 . For that purpose the storage  504  also includes memory  510  that has been adapted to store, and in operation typically stores, information contained in the group mapping database  14  previously described. 
         [0069]    Advantageously, PW extended grouping procedures previously described can be applicable for the following scenarios: wildcard withdrawal of PW label mappings, PW status signaling including all OAM message mappings, PW applications as such MAC flush for VPLS, etc. 
         [0070]    Numerous modifications, variations and adaptations may be made to the embodiments of the invention described above without departing from the scope of the invention, which is defined in the claims.