Abstract:
Network service providers have largely addressed the growth in demand for communications networks in two ways: employing faster and more robust communications protocols through equipment upgrades and increasing use of Operations, Administrations, and Management (OAM) procedures for improved network performance. Typically, OAM operations procedures used by a network protocol are unique to that protocol and are not compatible with other network protocols. Service providers with networks that use multiple communications protocols, such as networks using legacy and newly installed equipment, can have difficulty ensuring optimal performance due to non-compatible OAM operations. A method, and corresponding apparatus, for supporting OAM interworking between first and second communications protocols used in an interworking circuit of a communications network is disclosed. The method, or corresponding apparatus, allows network service providers to ensure optimal network performance in a manner that does not affect customer traffic, is transparent to customers, and can be seamlessly integrated into existing interworking network nodes.

Description:
BACKGROUND OF THE INVENTION 
     To meet service demands of customers, service providers ensure performance of their communications networks, such as through the use of network operational activities, including fault detection, isolation, and notification. Network operational activities allow service providers to reroute traffic in an event of detection of a fault, thereby sustaining loss of traffic capacity along certain network routes and maintaining service demands of customers. To perform fault detection, isolation, and notification across disparate networks, service providers typically support a variety of service domains. Within a given service domain, network operational activities are monitored, and fault conditions are addressed, either through automated recovery procedures or manual recovery procedures. As a result of the network operational activities, service providers are generally able to demonstrate a robust network to their customers. 
     As demand for networks, such as the Internet, has grown, service providers have installed new equipment to existing networks. In order to support increased demand further, the newly added equipment often utilizes a faster and more robust communications protocols than legacy equipment. For continuity of service, it is useful that the newly added network equipment operate seamlessly with legacy equipment. 
     SUMMARY OF THE INVENTION 
     A method, and corresponding apparatus, for supporting Operation, Administration, and Maintenance (OAM) interworking between a first and a second communications protocol of an interworking circuit in a communications network is disclosed. The first and second communications protocols operate at a common communications layer of the communications network. Alternatively, the first and second communications protocols may operate at different layers. According to an example embodiment, the present invention may monitor the communications channels for state information and facilitate transparent awareness of the state of communications channels to support interworking between the first and second communications channels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention. 
         FIG. 1A  is a network block diagram illustrating a communications network that uses two different communications protocols connected by an interworking link and is divided into multiple protocol domains. 
         FIG. 1B  is a network diagram illustrating a communications network that uses two different communications protocols connected by an interworking link. 
         FIG. 2  is a block diagram illustrating an interworking node, within an interworking link, configured to monitor the state of communications channels and translate monitored state information from the first interface of the of the interworking node to the second interface and also from the second interface to the first interface. 
         FIG. 3  is a flow diagram of an example procedure performed by an interworking node. 
         FIG. 4  is a block diagram illustrating a one-to-one mapping of a first communications channel identifier in a first communications protocol to a second communications channel identifier in a second communications protocol. 
         FIG. 5  is a signal and timing diagram illustrating a procedure performed at an interworking node in a case of a synchronous one-to-one mapping of a first communications channel identifier in a first communications protocol to a second communications channel identifier in a second communications protocol. 
         FIG. 6  is a signal and timing diagram illustrating a procedure performed at a interworking node in a case of an asynchronous one-to-one mapping of a first communications channel identifier in a first communications protocol to a second communications channel identifier in a second communications protocol. 
         FIG. 7  is a block diagram illustrating the asynchronous frame relay port to Ethernet logical OAM group mapping of a first communications channel identifier in a first communications protocol to a second communications channel identifier in a second communications protocol. 
         FIG. 8  is a signal and timing diagram illustrating a procedure performed at an interworking node in a case of an asynchronous frame relay port to Ethernet logical group mapping of a first communications channel identifier in a first communications protocol to a second communications channel identifier in a second communications protocol. 
         FIG. 9  is a block diagram illustrating a mapping of a first communications channel identifier in a first communications protocol to a second communications channel identifier in a second communications protocol. 
         FIG. 10  is a signal and timing diagram illustrating the procedure performed at an interworking node in a case of a synchronous one-to-one mapping of a first communications channel identifier in a first communications protocol to a second communications channel identifier in a second communications protocol. 
         FIG. 11  is a signal and timing diagram illustrating the procedure performed at an interworking node in a case of an asynchronous one-to-one mapping of a first communications channel identifier in a first communications protocol to a second communications channel identifier in a second communications protocol. 
         FIG. 12  is a flow diagram of an example procedure performed by an interworking node. 
         FIG. 13  is a block diagram illustrating contents of a table that may be used in the method, or corresponding apparatus, for facilitating transparent state awareness of monitored channels of an interworking circuit in a communications network. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A description of example embodiments of the invention follows. 
     An example embodiment of the invention relates generally to communications over a communications network and more particularly to methods and apparatus supporting the interworking of operations, administration and maintenance (OAM) functions between heterogeneous control plane technologies in the communications network. 
     Operations, Administration, and Maintenance (OAM) procedures can be used for monitoring networks by network operators. OAM refers to a set of functions that can be used to enable the detection of network faults, measurement of network performance, and distribution of fault-related information. Typically, OAM functions used by a particular network protocol are unique to that protocol and are not compatible with other (i.e., different) protocols. As a result, networks using multiple communications protocols, such as networks using both legacy equipment running corresponding legacy protocols and newly installed equipment using modern protocols, can have limited OAM capabilities. In many cases, the OAM limitations exist because the legacy OAM functions are not compatible with the newer OAM functions. This results in OAM functionality of each subsection of the network being constrained to the portion of the network using the respective associated protocol. With constrained OAM capability, network service providers are limited in their abilities to address network faults, reroute traffic, and meet customer demand. Thus, it is useful to support OAM interworking in networks, such as carrier access networks or carrier core networks, using multiple communications protocols, possibly in isolated maintenance domains configurations. 
     At least one embodiment of the present invention is configured to operate in a communications network employing legacy equipment using, for example, a Frame Relay protocol and modern equipment using, for example, an Ethernet protocol. Throughout the following description, reference is made to Frame Relay and Ethernet protocols, but it should be understood that such protocols represent convenient example communications protocols and that alternative embodiments may be configured to support interworking of different communications protocols, currently known or developed in the future, operating at the same or different network communications layers, such as at Layers 2, 2.5, or 3 of the International Organization for Standardization (OSI) stack. Service providers often use Frame Relay encapsulation for all low speed connections to the Public Internet or layer three (L3) virtual private network (VPN) services. Low speed connections currently refer to those connections with data transfer rates less than that of digital signal three (DS3). Today, these low speed circuits terminate on Frame Relay/Asynchronous Transfer Mode (FR/ATM) switches for T1 service and are then passed on to a Public Internet Protocol (IP) or L3 VPN Provider Edge (PE) router as ATM ports. 
     Unfortunately, this network model cannot handle the enormous network traffic growth forecast for the coming years, and Frame Relay/ATM switch vendors are discontinuing manufacture certain hardware and ending support or charging very high support fees. Also, cost to support ATM ports on provider edge (PE) routers in comparison to Gigabit Ethernet ports is high. Traditional ATM switches, like the FR-ATM switches, are creating more and more bottlenecks (as compared to newer communications protocol switches) that limit the extent to which service providers can expand their networks using legacy equipment. To meet the forecast demand, service providers are building scalable, multiservice, IP networks with capacity to expand. A potential solution to the ATM switch bottleneck is to eliminate the intermediate conversion from Frame Relay to ATM protocol at the FR-ATM switch and convert Frame Relay directly to the Ethernet protocol used on the PE routers. Modern PE routers may employ gigabit Ethernet (GigE) trunks that are more efficient and cost effective than legacy ATM ports. 
     A capability to convert FR protocol to Ethernet protocol, using pseudowire emulation (PWE), for handoff to GigE trunks, currently exists. However, with the existing PWE technology, service providers lose visibility of FR OAM signaling. This greatly reduces fault detection and response capabilities, and, in turn, greatly reduces an ability to reroute traffic and meet customer service expectations. Thus, an embodiment of the present inventions supports OAM interworking in carrier access networks using Frame Relay and Ethernet protocols, or, more generally, in networks across any two different communications protocols. In the case of FR and Ethernet protocols, in order to monitor customer services effectively and provide necessary outage notifications, remote-side FR channel states are recognized, translated, and communicated to the core-side PE router over an Ethernet trunk. Likewise, channel states on the core-side Ethernet trunk are passed back to affected FR circuits. Effective monitoring enables stable network communications OAM interworking. 
     An embodiment of the present invention includes a method, and corresponding apparatus, for supporting Operation, Administration, and Maintenance (OAM) interworking between a first and a second communications protocol of an interworking circuit in a communications network. The first and second communications protocols operate at a common communications layer of the communications network. Alternatively, the first and second communications protocols may operate at different layers. According to an example embodiment, the present invention may monitor the communications channels for state information and facilitate transparent awareness of the state of communications channels to support interworking between the first and second communications channels. 
     For purposes herein, transparent awareness means that the interworking circuit and interworking activities are effectively imperceptible to the communications protocols on either side of the interworking circuit at least with respect to the OAM interworking. For example, transparent awareness can mean that OAM signals or OAM signaling on one side of the interworking is received on the other side of the interworking without modification to either communications protocol, optionally from traffic or OAM perspective(s). Moreover, transparent awareness activities may include observation of traffic or OAM channels within the interworking circuit or received at the interworking circuit without disruption or modification to traffic or OAM signals or OAM signaling therein. Further, in at least one embodiment, the transparent awareness can also operate autonomously and automatically such that activation or continued operation signaling is not required. Still further, the transparent awareness can occur with respect to OAM signals or OAM signaling, in accordance with the focus of embodiments disclosed herein, or with respect to other signals or signaling, whether traffic or otherwise, in which transparent awareness across an interworking circuit is useful. 
     Some example embodiments of the present invention can be configured to support OAM interworking between Frame Relay and Ethernet communications protocols, for example, and a multiple logical interfaces or subinterfaces corresponding to the channels. This embodiment of the present invention may monitor Frame Relay continuity messaging on a per-interface, data-link connection identifier (DLCI) basis, translate that messaging to the corresponding Ethernet continuity messaging, and notify the corresponding Ethernet virtual local area network with an identifier. This embodiment may further or alternately monitor Ethernet continuity messaging in a similar manner, translate that messaging to the corresponding Frame Relay continuity messaging, and notify the corresponding Frame Relay virtual local area network with an identifier. 
     Some example embodiments of the of the present invention can use a method, or corresponding apparatus, of mapping the first and second channels and associated states to the corresponding second and first channels, respectively, and the respective associated states. The example embodiments that use this method, or corresponding apparatus, facilitate transparent awareness of the state of communications channels of an interworking circuit based on the mapping. 
     A number of example embodiments of the present invention may use a method, or corresponding apparatus, of accessing a table to map the first and second channels and associated states to the corresponding second and first channels, respectively, and the respective associated states. The accessed table can contain identifiers identifying the first and second communications channels and states for each protocol interface, or can include translation information corresponding to states for each protocol of the interworking circuit. 
     Various example embodiments of the present invention may use a method, or corresponding apparatus, to monitor the state of communications channels using an Operations, Administration, and Management (OAM) procedure. The OAM procedure may be used to confirm operation, detect or isolate faults or failures, or notify the network of faults or failures of the channels of the interworking circuit. The OAM procedure used in these example embodiments can include another procedure to verify connectivity, detect faults, monitor performance, or observe alarm indications. 
     Numerous example embodiments of the present invention can use a method, or corresponding apparatus, to monitor the state of the communications channels, including quality of service attributes of the interworking circuit, and to notify the first and second channels of the quality of service attributes of the second and first channels, respectively, to support the facilitating of transparent awareness. The monitored quality of service attributes that the corresponding channels are notified of can include availability, change in status, frame delay, frame delay variation, sequence error, bad frames, or frame loss. 
     Further example embodiments of the present invention may include a non-transitory computer readable medium containing instructions that can be executed by a processor, and, when executed, cause the processor to monitor a state of communications channels on a first and a second interface using a first and second communications protocol, respectively, and to facilitate transparent awareness of the state of the communications channels to support an interworking circuit of a communications network. The communications channels of the interworking circuit may be operating at a common communications layer of the communications network, with the first and second interfaces being associated with the first and second protocols, respectively. 
     Specific communications protocols, such as IEEE 802.1ag, used as examples herein are for illustration purposes only. Similarly, any specific signaling or nomenclature described in reference thereto should not be construed as limiting embodiments of the present invention. Other embodiments within the context of supporting OAM interworking between any two communications protocols may be employed. 
       FIG. 1A  shows a block diagram illustrating an example of a communications network  100 . The network is divided into maintenance domains (MD)  101 ,  105   a ,  105   b  for network management purposes. Typically, MDs are configured in a hierarchal relationship, where a higher level MD  100   a  can include multiple lower level MDs  105   a ,  105   b . MDs are used by network providers to monitor the state of communications links within a MD by using, for example, a continuity messaging service. 
     Services are provided by a set of maintenance entities that are associated with service instances. This maintenance entity is shown as  108 . Traffic communications service instance examples include virtual private label switching (VPLS) service, Ethernet point-to-point circuit, or circuit bundle. 
     Nodes  110 , such as routers, at the edge of a maintenance domain are commonly contain a maintenance interface associate with each maintenance entity. A maintenance interface denotes the endpoints of a maintenance entity and resides on the boundaries of the MD within the network. Common protocol communications channels  115 , such as label switched paths (LSPs), communicatively connect provider edge nodes  110  together and provide such service instance capabilities, such as VPLS. Maintenance entities can be tied together, through PE nodes  110 , using circuit interface links  117 . Subdivisions of the network running different communications protocols can be tied together using an interworking link  120 . The interworking link supports the interworking of different communications protocols, and can include facilitating transparent awareness of the state of the communications channels using interworking channel state representations  122   a ,  122   b . An interworking link  120  can employ different types of circuit interface links  117 , which support the corresponding different types of communications protocols and an interworking node  125 . 
       FIG. 1B  shows a diagram illustrating a particular example of a communications network that uses both Frame Relay and Ethernet protocols in which an embodiment of the present invention may be used. Frame Relay services are provided by a Frame Relay network  108   a . Ethernet services are provided by an Ethernet network  108   b . Frame Relay protocol is used on the remote side  117   a  to support low speed customer service. 
     In the example network of  FIG. 1B , customers connect to the Frame Relay network  108   a  using Frame Relay equipment  110   a . Frame Relay circuit interface links  117   a  are used to connect Frame Relay equipment  110   a  to create Frame Relay networks  108   a . Ethernet PE routers  110   b  mark an edge of the Ethernet protocol network  108   b  within a core side  107   b  of the network. Similar to the Frame Relay domain of the network, Ethernet circuit interface links  117   b  are used to connect Ethernet PE routers  110   b  to create Ethernet protocol MAs  108   b . An interworking link  121  provides connections between the two domains of the network using the different protocols. For example, one domain may use the Frame Relay protocol and another domain may use the Ethernet protocol. The interworking link  121  supports Frame Relay interworking channel state representations  122   a . Examples of Frame Relay interworking channel state representations  122   a  may include local management connectivity messaging using a protocol such as local management interface (LMI). The interworking link  121  in this example network embodiment also supports Ethernet interworking channel state representations  122   b . Many Ethernet channel state representations exist, where some examples of which are connectivity check messages (CCM) or other forms of monitoring connectivity states within, between, or among network nodes within a given maintenance domain. The interworking circuit link  121  may include a Frame Relay circuit interface link  117   a  and Ethernet circuit interface links  117   b , along with an interworking node  126 . 
       FIG. 2  is a block diagram of an example of an interworking link  200  between first and second communications protocols. The interworking link  200  may monitor and facilitate transparent awareness of the state of communications channels between a first communications protocol domain  210   a  and a second communications protocol domain  210   b . The interworking link  200  may include a first communications protocol circuit interface link  217   a , second communications protocol circuit interface link  217   b , and interworking node  225 . The interworking node  225  may include a local interworking circuit  230 , first interface  235   a , second interface  235   b , monitoring module  240 , awareness module  245 , and interworking pseudowire (PWE)  250 . 
     In one embodiment, the interworking node  225  interfaces with the communications protocol of the first communications protocol domain  210   a  using an associated first interface  235   a , and, likewise, the interworking node  225  interfaces with the communications protocol of the second communications protocol domain  210   b  using an associated second interface  235   b . The first interface  235   a  establishes a connection with the first communications protocol domain  210   a , while the second interface  235   b  establishes a connection with the second communications protocol domain  210   b . The PWE  250  links the first and second interfaces  235   a, b  and forms the interworking node  225  section of an interworking circuit. It should be understood that the interfaces  235   a, b  can be physical or logical interfaces. 
     The channels of the interworking circuit are monitored by the monitoring module  240 . In one embodiment, messaging from the first communications protocol domain  210   a  destined for the second communications protocol domain  210   b , as well as messaging from the second communications protocol domain  210   b  destined for the first communications protocol domain  210   a , is automatically monitored by the monitoring module  240 . Select communications messages, such as interworking channel state representations,  255   a, b ,  256   a, b ,  257   a, b , and  258   a, b , are routed to the awareness module  245 . Each select communications message,  255   a, b ,  256   a, b ,  257   a, b , and  258   a, b  is routed to be automatically translated from the protocol of the domain from which it entered the interworking node  225  to the protocol of the domain to which is its destination to facilitate transparent awareness of the state of the communications channels of the interworking circuit. In this example embodiment, network traffic  252   a, b  and  253   a, b  not containing interworking channel state representations information would be automatically translated from the protocol of the domain from which it entered the interworking node  225  to the protocol of the domain to which it exited toward the traffic&#39;s destination, bypassing the monitoring module and the awareness module. 
     Traffic from the first communications protocol domain  210   a  destined for the second communications protocol domain  210   b  is represented by network traffic  252   a, b, c . The interworking link may contain network traffic  252   a, b, c  at different stages of protocol translation. Multiple packets of communications data, network traffic  252   a , are sent by network terminals that are part of the first communications protocol domain  210   a , are within the first communications protocol domain  210   a , and are destined for network terminals that are part of the second communications protocol domain  210   b . Network traffic  252   c , is sent by network terminals that are part of the first communications protocol domain  210   a , has started the procedure of translation from first communications protocol to the second communications protocol within the interworking node  225 , and is destined for network terminals that are part of the second communications protocol domain  210   b . Network traffic  252   b , is sent by network terminals that are part of the first communications protocol domain  210   a , has completed the procedure of translation from first communications protocol to the second communications protocol, is within the second communications protocol domain  210   b , and is destined for network terminals that are part of the second communications protocol domain  210   b.    
     Similarly, traffic from the second communications protocol domain  210   b  destined for the first communications protocol domain  210   a  is represented by network traffic  253   a, b, c . The interworking link may contain network traffic  253   a, b, c  at different stages of protocol translation. Multiple packets of communications data, network traffic  253   b , are sent by network terminals that are part of the second communications protocol domain  210   b , are within the second communications protocol domain  210   b , and are destined for network terminals that are part of the first communications protocol domain  210   a . Network traffic  252   c , is sent by network terminals that are part of the second communications protocol domain  210   b , has started the procedure of translation from second communications protocol to the first communications protocol within the interworking node  225 , and is destined for network terminals that are part of the first communications protocol domain  210   a . Network traffic  253   a , is sent by network terminals that are part of the second communications protocol domain  210   b , has completed the procedure of translation from the second communications protocol to the first communications protocol, is within the first communications protocol domain  210   a , and is destined for network terminals that are part of the first communications protocol domain  210   a.    
     Another example embodiment may embed interworking channel state representations  255   a, b ,  256   a, b ,  257   a, b , and  258   a, b  within network traffic  252   a, b, c , and  253   a, b, c . In this example embodiment, the network traffic  252   c  and  253   c  containing interworking channel state representations are automatically monitored and the interworking channel state representations are automatically translated to facilitate transparent awareness between the communications protocols of the adjacent (vertical or horizontal) maintenance domains. 
       FIG. 3  shows a flow diagram  300  illustrating a method by which a state of communications channels are monitored  340  and transparent awareness of the state is facilitated  345  to support interworking between first and second communications protocol, the method may be used by an interworking node, such as the interworking node  225  of  FIG. 2 . A state of communications channels process  340  may monitor channel state information while not monitoring non-state information traffic. A transparent awareness facilitation process  345  provides the monitored channel state information to the interworking circuit and the communications network, as appropriate, to support interworking. 
       FIG. 4  shows an interworking circuit  400  of a communications network defining a first communications protocol domain  410   a  and a second communications protocol domain  410   b , where one or more first communications channels  417   a  may be mapped to a corresponding one or more second communications channels  417   b . The first and second communications channels are respectively associated with the first and second communications protocols. A section of the second communications protocol domain is shown as a maintenance domain  405 . An interworking node  425  is situated between the first communications channels  417   a  and the second communications channels  417   b . The interworking node  425  can perform a method, such as that described in reference to  FIG. 3 , by which a state of the first communications channels  417   a  and the second communications channels  417   b  are monitored and transparent awareness of the state is facilitated to support interworking of the interworking circuit  400 . 
     The transparent awareness of the state of the communications channels can be facilitated by assigning identifiers, logical or physical, to each of the first communications channels  417   a  and to each of the second communications channels  417   b , and mapping each first communications channel  417   a  identifier to a corresponding second communications channel  417   b  identifier, optionally on a one-to-one basis. The mapping of each second communications channel  417   b  identifier to a corresponding first communications channel  417   a  identifier, on a one-to-one basis, for example, may be used in an alternative embodiment. Other example embodiments of the present invention can use bases other than a one-to-one basis for mapping first communications channel identifiers  417   a  to second communications channel identifiers  417   b , such as a one-to-one bases or many-to-one basis. 
     Another example embodiment of the present invention can include a first communications protocol of Frame Relay  410   a  and a second communications protocol of Ethernet. The example embodiment may also include multiple frame relay circuits  417   a . In this example embodiment the multiple frame relay circuits  417   a  represent multiple physical DS3 speed circuits which terminate on the interworking node  425 . The multiple frame relay circuits  417   a  may use one of the Frame Relay communications protocol local management interface (LMI) signaling methods to indicate the state of the individual circuits, with each virtual circuit identified by Frame Relay Data Link Connection Identifier(s) (DLCI). 
     The interwork node  425  converts the frame relay data stream to Ethernet frames for transmission to an attached Ethernet device  410   b  in communication therewith. The interworking node  425  may communicatively connect to a core network through an Ethernet link  417   b . The interworking node  425  may use an OAM protocol set, such as IEEE 802.1ag, to indicate state, in which case 802.1ag continuity check messages (CCM) are passed between the interworking node and the Ethernet device  410   b . Correct mapping of the DLCI, which identify Frame Relay communications channels, to corresponding Virtual Local Area Network (VLAN) channels, which identify Ethernet communications channels, in a one DLCI to one VLAN manner, ensure that signals are passed to the appropriate end points. 
       FIG. 5  is a signal timing diagram illustrating a process  500  for carrying out a method of supporting interworking between a first and a second communications protocol of an interworking circuit of a communications network. The interworking node  525 , using a local circuit  530 , which, in one example embodiment, can be logical, physical, or some combination thereof, interfaces with first communications channels associated with the first communications protocol, logical, physical or some combination thereof, using a first interface  353   a . The interworking node  525  also interfaces with second communications channels associated with the second communications protocol, likewise logical, physical, or some combination thereof, using a second interface  353   b.    
     The interworking node  525 , to monitor a state of the first communications channels and facilitate transparent awareness of the state to the second communications channels, uses a signal and timing process  550 . The signal and timing process  550  includes operations for receiving a first communications protocol status signal using the first protocol interface  535   a , automatically translating the received first communications protocol status signal and channel identifier to a corresponding second communications protocol status signal and channel identifier, and transmitting the translated status signal and channel identifier using the second interface  353   b.    
     The interworking node  525  uses another signal and timing procedure  560  to monitor a state of the second communications channels and facilitate transparent awareness of the state to the first communications channels. The signal and timing procedure  560  includes operations for of receiving a second communications protocol status signal using the second protocol interface  535   b , automatically translating the received second communications protocol status signal and channel identifier to a corresponding first communications protocol status signal and channel identifier, and transmitting the translated status signal and channel identifier using the first interface  353   a.    
     In an example embodiment of the present invention, the signal and timing procedures  550 ,  560  can be reciprocal procedures, but need not be. In another example embodiment of the present invention, the signal and timing procedures  550 ,  560  can be synchronous, but need not be. 
     In another example embodiment of the present invention,  FIG. 5  shows a view of the Frame Relay LMI to 802.1ag Ethernet OAM interworking. More details on specific message types that are passed, as well as the message path between devices and a proposal for timer intervals, are shown. The central two columns  552 ,  553  and  562 ,  563  show actions taking place within the Interworking node, while external columns  551 ,  554 ,  561  and  564  show the message path outside of the interworking node  545 . The columns  551 ,  554 ,  561  and  564  are self-evident to a person of ordinary skill in the art. 
       FIG. 6  is a signal timing diagram illustrating a procedure  600  for carrying out a method of supporting interworking between a first and a second communications protocol of an interworking circuit of a communications network. The procedure  600  illustrated is yet another example embodiment of the present invention, the example is an interworking of Frame Relay LMI to 802.1ag Ethernet OAM. More details on specific message types that are passed, as well as the message path between devices and a proposal for timer intervals, are shown. The central two columns  652 ,  652  and  662 ,  663  show actions taking place within an interworking node  625 , while external columns  651 ,  654 ,  661  and  664  show the message path outside of the interworking node  625 . The columns  651 ,  654 ,  661  and  664  are self-evident to a person of ordinary skill in the art. 
       FIG. 7  illustrates an example embodiment of the present invention, an interworking circuit  700  of a communications network defining a first communications protocol domain  710   a  and a second communications protocol domain  710   b , where one or more first communications channels  717   a  are mapped to a corresponding one or more second communications channels  717   b . The first and second communications channels are respectively associated with the first and second communications protocols. A section of the second communication protocol domain is shown as a maintenance domain  705 . An interworking node  725  is situated between the first communications channels  717   a  and the second communications channels  717   b . The interworking node  725  can perform a method, such as that described in  FIG. 3 , by which a state of the first communications channels  717   a  and the second communications channels  717   b  are monitored and transparent awareness of the state is facilitated to support interworking of the interworking circuit  700 . 
     In an example embodiment of the present invention, the first communications protocol domain  710   a  can be Frame Relay, and the second communications protocol domain  710   b  can be Ethernet. In the example network of  FIG. 7 , Frame Relay DLCI  717   a  are mapped to individual Ethernet Q-in-Q or, alternately, IEEE 802.1ad circuits  717   b . The interworking node  725  correlates, maps and transmits Frame Relay LMI and IEEE 802.1ag signals. 
       FIG. 8  is a signal timing diagram illustrating a procedure  800  for carrying out a method of supporting interworking between a first and a second communications protocol of an interworking circuit of a communications network. The procedure illustrated carries out yet another example embodiment of the present invention, for example, interworking of Frame Relay to Ethernet Q-in-Q or alternately IEEE 802.1ad. The central two columns  852 ,  853  and  862 ,  863  show actions taking place within an interworking node  825 , while external columns  851 ,  854 ,  861 , and  864  show the message path outside of the interworking node  825 . The columns  851 ,  854 ,  861 , and  864  are self-evident to a person of ordinary skill in the art. A benefit of the example embodiment of procedure  800  is the suppression of individual VLAN asynchronous updates. 
       FIG. 9  illustrates an example embodiment of the present invention, an interworking circuit  900  of a communications network comprised of a first communications protocol domain  910   a  and a second communications protocol domain  910   b , where one or more first communications channels  917   a  are mapped to a corresponding one or more second communications channels  917   b . The first and second communications channels are respectively associated with the first and second communications protocols. An interworking node  925  is situated between the first communications channels  917   a  and the second communications channels  917   b . The interworking node  925  can perform a method, such as that described in  FIG. 3 , by which a state of the first communications channels  917   a  and the second communications channels  917   b  are monitored and transparent awareness of the state is facilitated to support interworking of the interworking circuit  900 . 
     In an example embodiment of the present invention, the first communications protocol domain  910   a  can be Frame Relay, and the second communications protocol domain  910   b  can be Ethernet. Frame Relay DLCI  917   a  are mapped to individual Ethernet circuits  717   b , which can be logical or physical. The interworking node  925  correlates, maps, and transmits Frame Relay LMI and Ethernet-Local Management Interface (E-LMI) signals. 
       FIG. 10  is a signal timing diagram illustrating a procedure  1000  for carrying out a method of supporting interworking between a first and a second communications protocol of an interworking circuit of a communications network. The procedure illustrated carries out an example embodiment of the present invention, the example embodiment facilitating transparent awareness using FR LMI and E-LMI in a synchronous manner. The central two columns  1052 ,  1053 , and  1062 ,  1063  show actions taking place within the Interworking node  1025 , while external columns  1051 ,  1054 ,  1061 , and  1064  show the message path outside of the Interworking Node  1025 . The columns  1051 ,  1054 ,  1061 , and  1064  are self-evident to a person of ordinary skill in the art. 
       FIG. 11  is a signal timing diagram illustrating a procedure  1100  for carrying out a method of supporting interworking between a first and a second communications protocol of an interworking circuit of a communications network. The procedure illustrated carries out an example embodiment of the present invention, the example embodiment facilitating transparent awareness using FR LMI and E-LMI in an asynchronous manner. The central two columns  1152 ,  1153 ,  1162 ,  1063  show actions taking place within the Interworking node  1025 , while external columns  1151 ,  1154 ,  1161 , and  1164  show the message path outside of the Interworking Node  1125 . The columns  1151 ,  1154 ,  1161 , and  1164  are self-evident to a person of ordinary skill in the art. 
       FIG. 12  is a flow diagram that illustrates a procedure performed by an interworking node  1200 . The example interworking node  1200  may include a monitoring module  1205  and an awareness module  1210 . The monitoring module  1205  may include a first communications protocol procedure (submodule)  1215   a  and a second communications protocol procedure  1215   b . The awareness module  1210  may include two procedures (submodules): a state mapping procedure  1220  and a channel mapping procedure  1225 . 
     In one example embodiment, the monitoring module  1205  monitors a state of communications channels. The interworking node  1200  flow diagram begins with determining whether to monitor, or to continue to monitor, the state of communications channels  1230 . A determination to not monitor, or to not continue to monitor, the state of communications channels  1230  ends the interworking node  1200  procedure. A determination to monitor, or to continue to monitor, the state of communications channels  1230 , in an example embodiment, may result in parallel monitoring procedures for the first and second communications protocols, while other example embodiments may perform the motoring procedures in series (i.e., one after the other) or some combination of performing monitoring procedures in parallel and series. 
     For the sake of descriptive clarity, the example embodiment discussion is limited to the first communications protocol procedure  1215   a , but it should be understood that it applies to the first and second communications protocol procedures  1215   a, b . The interworking node  1200  originates a channel state inquiry message, such as the state channel representation  257   a  in  FIG. 2 , and transmits the channel state inquiry message from the interworking node  1200  at the first interface  1235   a  to the first communications protocol network domain  1240   a . The interworking node  1200  receives a channel state response message, such as the state channel representation  255   a  in  FIG. 2 , via the first interface  1245   a.    
     In the example embodiment, a determination is made as to whether this received signal is a channel state response message  1250   a . If the received signal is not a channel state response message, it is passed directly to the awareness module  1210 . At the awareness module, the channel mapping procedure  1225  occurs, where messages are mapped or otherwise directed from the first protocol to the second protocol  1275   a . On the other hand, if the received signal is a channel state response message, another determination is made. 
     In FR LMI and Ethernet 802.1ag protocols, remote FR and Ethernet devices proactively send updates (i.e., LMI and CCM messages), and it is by the process of not receiving these messages over several intervals that the interworking node realizes that the circuits are down and issues some sort of fault notification. Other networks may employ state inquiry messaging, such as in an example embodiment that determines whether the channel state response message is in response to the interworking node&#39;s  1200  originated channel state inquiry message or not  1255   a . In this latter embodiment, if the received signal is not a channel state response message to the interworking node&#39;s  1200  originated channel state inquiry message, it is passed directly to the awareness module  1210 . At the awareness module, the channel state mapping procedure  1220  occurs, where state messages are mapped from the first protocol to the second protocol  1270   a . On the other hand, if the received signal is a channel state response message to the interworking node&#39;s  1200  originated channel state inquiry message, a procedure of channel state checks or channel performance test  1250   a  occur. A similar determination can be made in the former embodiment in which remote FR and Ethernet devices proactively send updates or internal interworking node state inquiries are automatically provided. 
     The final operation of the procedure in this example embodiment is a determination of whether the results of the procedure of channel state checks or channel performance test(s)  1250   a  are new or useful to communicate to the second communications protocol channel  1240   b . If the result of the procedure of channel state checks or channel performance test(s)  1250   a  is not new or useful to communicate, the monitoring procedure starts anew with the determination of whether to monitor, or to continue to monitor, the state of communications channels  1230 . If the result of the procedure of channel state checks or channel performance test  1250   a  is new or useful to communicate, then it is passed directly to the awareness module  1210 . At the awareness, module the channel state mapping procedure  1220  occurs where state messages are mapped or otherwise directed from the first protocol to the second protocol  1270   a.    
     In the awareness module  1210 , all results for the channel state mapping procedure  1220  are input to the channel mapping procedure  1225 . The result of the procedure of mapping channel state of the first communications protocol to channel states of the second communications protocol  1270   a  is a possible input for the procedure of mapping channel identification of the first communications protocol to channel identification of the second communications protocol  1275   a , where channel identification can be logical or physical. The result of the procedure of mapping channel identification of the first communications protocol to channel identification of the second communications protocol  1275   a  is an input for transmitting a message to the second protocol domain of the communications network procedure  1235   b.    
     In this example embodiment, the second communications protocol division  1215   b  of the interworking node  1200  uses an identical procedure  1215   b  to the procedure  1215   a  just described in the above few paragraphs to monitor the state of communications channels of the second communications protocol. 
       FIG. 13  is a block diagram illustrating contents of a table  1300  optionally accessed during a mapping procedure, where the mapping procedure maps first and second channel and state associated with the channels, to a corresponding second and first channels and associated states, respectively, to facilitate transparent awareness of an interworking circuit of a communications network, the first and second channels being associated with first and second communications protocols. 
     It should be understood that the flow diagrams of  FIGS. 3 , and  12  and the signal flow and timing diagrams of  FIGS. 5 ,  6 ,  8 ,  10 , and  11  are examples that can include more or fewer components, be partitioned into subunits, or be implemented in different combinations. Moreover, the flow diagrams may be implemented in hardware, firmware, or software. If implemented in software, the software may be written in any software language suitable for use in networks as illustrated in  FIGS. 1A ,  1 B,  4 ,  7 , and  9 . The software may be embodied on any form of computer readable medium, such as RAM, ROM, or magnetic or optical disk, and loaded and executed by generic or custom processor(s). 
     The invention is applicable to any communications network protocol as long as two or more communications protocols, such as Frame Relay (FR) and Ethernet, are used. 
     While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.