Abstract:
Methods and apparatus for allowing a dense wave division multiplexing (DWDM) line card w to function as an add/drop multiplexer (ADM), a transponder, and a muxponder are disclosed. According to one aspect of the present invention, a line card suitable for use in a network to aggregate signals of different line rates for transport includes a first arrangement having ADM functionality, a second arrangement having transponder functionality, and a third arrangement having muxponder functionality. The line card also includes hardware that facilitates communication between the arrangements, as well as a plurality of ports arranged to receive a signal and to provide the signal to the hardware.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of Invention  
         [0002]     The present invention relates generally to networks. More particularly, the present invention relates to a multi-functional dense wave division multiplexing line card that has add/drop multiplexer, transponder, and muxponder capabilities, and may be readily reconfigured to support additional traffic demands.  
         [0003]     2. Description of the Related Art  
         [0004]     The use of the Gigabit Ethernet (GbE) communications protocol is becoming more widely used in networking applications. As a result, synchronous optical network (SONET) or synchronous digital hierarchy (SDH) networks that were not designed to transport GbE signals must be augmented in order for GbE signals to be transported.  
         [0005]     Many optical networks are dense wave division multiplex (DWDM) based. DWDM-based networks may transmit data of substantially any protocol and any bit-rate. Hence, DWDM-based networks may transmit SONET, SDH, and Ethernet signals.  FIG. 1  is a block diagram representation of a network. A network  100  may be a wide area network that includes a local area network  102  with nodes  110   b - d  and links  114   a - d  which allow nodes  110   b - d  to communicate. Nodes  110   b - d  may be network elements such as switches, while links  114   a - d  may be wireless communications links or wired communications links such as fiber-optic cable. A node  110   a  may be a client which requests access to nodes  110   b - d  through a trunk  1   18 . Trunk  118  may be used to substantially interconnect nodes  110   a - d  to form network  110  from local area network  102  and node  110   a . In other words, trunk  118  may be considered to be a communications channel between local area network  102  and client  110   a.    
         [0006]     Local area network  102  may be a SONET/SDH network. As GbE is becoming more prevalent, the ability to carry GbE signals over local area network  102  that supports SONET/SDH is desirable. Hence, trunk  118  and node  110   a  may each include line cards which effectively allow GbE signals to be transported through network  100 .  
         [0007]     With reference to  FIG. 2 , line cards which are included in a client and a trunk will be described. A client  210  and a trunk  218  each include an add/drop multiplexer (ADM) line card  222   a ,  222   b , a transponder line card  226   a ,  226   b , and a muxponder line card  230   a ,  230   b . ADM line cards  222   a ,  222   b  are arranged to provide an interface between higher speed and lower speed signals. By way of example, a SONET ADM may extract lower rate signals from a higher rate multiplexed signal or insert lower rate signals into a higher rate multiplexed signal. A signal may be added or dropped substantially without disrupting the transmission of other signals included in a multiplexed signal. Transponder line cards  226   a ,  226   b  function as transmitters and responders, and are arranged to pick up and to respond to incoming signals. Transponder line cards  226   a ,  226   b  are typically modules that receive an incoming signal and convert the incoming signal to a wavelength to be optically multiplexed with other wavelengths. Muxponder line cards  230   a ,  230   b  have the combined functionality of multiplexers and transponders, and are arranged to enable multiple channels to share a single wavelength.  
         [0008]     Line cards associated with client  210  and line cards associated with trunk  218  are often different. For example, ADM line card  222   a  that is suitable for use as a part of client  210  may be different from ADM line card  222   b  that is suitable for use as part of trunk  218 . For client  210 , ADM line card  222   a  may be an ADM-on-a-blade line card.  
         [0009]     With reference to  FIG. 3 , the steps associated with configuring a trunk or a client to support particular traffic types will be described. A process  300  of configuring a trunk or a client begins at step  304  in which a current traffic type that is to be transported across a SONET/SDH network is identified. Once the current traffic type is identified, transponder line cards, muxponder line cards, and ADM line cards that support the current traffic type may be purchased or otherwise obtained in step  308 . Line cards are generally specific to line rates and protection schemes.  
         [0010]     In step  312 , the trunk or the client are configured to support the current traffic type. Configuring the trunk or the client often includes updating software associated with the trunk or the client. Then, the current traffic type is transported through the trunk or the client in step  316 . A determination is made in step  320  as to whether a different, or unsupported traffic type, is requested. That is, it is determined if a different traffic demand has been requested. A different traffic demand may correspond to a different line rate, or a different protection scheme. If it is determined that a different traffic demand has not been requested, process flow returns to step  316  in which the current traffic type continues to be transported.  
         [0011]     Alternatively, when the determination in step  320  is that a different traffic demand has been requested, then at least some of the line cards associated with the trunk or the client are replaced in step  324 . In other words, new transponder line cards, muxponder line cards, and ADM line cards which support the different traffic demand may be purchased or otherwise obtained. Once obtained, the new line cards are installed in the system, i.e., the trunk or the client, and the system is configured to support the different traffic demand in step  328 . After the system is configured to support the different traffic type, the different traffic type is transported as a current traffic type in step  322 . From step  332 , process flow returns to step  320  in which it is determined whether a different traffic type is requested.  
         [0012]     Although replacing transponder line cards, muxponder line cards, and ADM line cards as necessary is effective in enabling new traffic demands to be supported, replacing line cards is inefficient. Having to replace one or more line cards, and to reconfigure an overall system once one or more line cards have been replaced, may be both time-consuming and expensive. Further, the use and the maintenance of multiple line cards is also often expensive.  
         [0013]     While a network administrator may anticipate future traffic demands and configure a system accordingly, i.e., a network administrator may set up a system to support more than a set of initially demanded traffic types, future traffic demands are often difficult to predict. As a result, even line cards which account for future traffic demands are likely to have to be replaced when unanticipated traffic demands are requested.  
         [0014]     Therefore, what is needed is a system in which different traffic demands may be supported substantially without requiring that one or more line cards be replaced. That is, what is desired is a method and an apparatus that has the flexibility to allow new traffic demands to be supported without the need for replacing line cards.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:  
         [0016]      FIG. 1  is a block diagram representation of a network.  
         [0017]      FIG. 2  is a block diagram representation of line cards used with a trunk and line cards used with a client within a network that supports dense wave division multiplexing (DWDM) and synchronous optical network (SONET) or synchronous digital hierarchy (SDH) transmissions.  
         [0018]      FIG. 3  is a process flow diagram which illustrates steps associated with a method of upgrading a system to support a different traffic type.  
         [0019]      FIG. 4A  is a block diagram representation of the functionality associated with a multi-functional line card in accordance with an embodiment of the present invention.  
         [0020]      FIG. 4B  is a block diagram representation of a multi-functional line card in accordance with an embodiment of the present invention.  
         [0021]      FIG. 5A  is a block diagram representation of multi-functional line cards interfaced with a SONET/SDH network in accordance with an embodiment of the present invention.  
         [0022]      FIG. 5B  is a block diagram representation of multi-functional line cards, i.e., multi-functional line cards  510   a - b  of  FIG. 5A , in which small form factor pluggable components may be replaced in accordance with an embodiment of the present invention.  
         [0023]      FIG. 6  is a process flow diagram which illustrates steps associated with a method of upgrading a multi-functional line card to support a new traffic type in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0024]     The ability to efficiently upgrade a system to support a new traffic type or a new traffic demand that is to be transmitted through a synchronous optical network (SONET) network, a synchronous digital hierarchy (SDH) network, or a dense wave division multiplexing (DWDM) network is crucial. When one or more line cards needs to be replaced when a new traffic type is to be transported, the cost and the efficiency associated with supporting a new traffic type may be prohibitive.  
         [0025]     In one embodiment, a single optical module or line card acts as a transponder, a muxponder, and an add/drop multiplexer (ADM). Such a line card may be configured to be used as a part of both a client and a trunk. By allowing pluggable components such as small form factor pluggable (SFP) components to provide transponder, muxponder, and ADM functions in a module, upgrades may be readily made by replacing or adding appropriate SFPs to the module. Hence, by upgrading the module, different or additional traffic types may be supported without having to replace one or more line cards. As such, a system may be updated to support a new traffic demand relatively inexpensively and efficiently, and substantially without having to replace line cards.  
         [0026]      FIG. 4A  is a block diagram representation of the functionality associated with a multi-functional line card in accordance with an embodiment of the present invention. A multi-functional line card  400  is arranged to accept traffic  404  that is to be processed into traffic  406  that may be transported through a SONET/SDH network or a DWDM network. Multi-functional line card  400  is further arranged to accept traffic  406  from a SONET/SDH network or a DWDM network and to process traffic  406  to form traffic  404  which, in one embodiment, is either time-division multiplexed (TDM) or Ethernet traffic.  
         [0027]     Multi-functional line card  400  is generally a single board with components which provide different functionality, and is arranged to aggregate multiple types of traffic. In one embodiment, multi-functional line card  400  may be arranged to aggregate oc 3 , OC12, OC48, and gigabit Ethernet (GbE) traffic. While the functionality is generally provided by SFP components, it should be understood that the functionality may also be provided by other components, e.g., daughter boards. In general, multi-functional line card includes ADM functionality  410 , muxponder functionality  414 , and transponder functionality  418 . ADM functionality  410  may be provided as an ADM-on-a-blade.  
         [0028]     Protection schemes  422  may also be implemented by multi-functional line card  400 . Protections schemes  422  may be widely varied and may include, but are not limited to, 1+1 automatic protection switching (APS) schemes, Y-cable optical channel protection schemes, unidirectional path switched ring (UPSR) schemes, splitter optical channel protection schemes, and bidirectional line switched ring (BLSR) schemes.  
         [0029]     As mentioned above, functionality on multi-functional line card  400  is typically provided by pluggable components such as SFP or XFP components. In order to accommodate pluggable components, multi-functional line card  400  may include hardware and slots which facilitates the insertion and removal of pluggable components. With reference to  FIG. 4B , the general layout of a multi-functional line card will be described in accordance with an embodiment of the present invention. A multi-functional line card  450  is arranged to be used for many purposes, e.g., as both a trunk and a client. Interfaces associated with multi-functional line card  450  include an interface  460  for ADM capabilities, an interface  468  for transponder capabilities, and an interface  464  for muxponder capabilities. By reconfiguring software associated with a software interface  480 , multi-functional line card  450  may function as an ADM, a transponder, or a muxponder based on traffic flow and aggregation capability. It should be appreciated that hardware associated with an ADM, a transponder, and a muxponder may be upgraded or replaced.  
         [0030]     A client interface  482 , which may include a plurality of input and output ports, of multi-functional line card  450  allows inputs to and outputs from a client to be made when multi-functional line card  450  is part of the client. In one embodiment, client interface  482  is a pluggable interface that allows multi-functional line card  450  to function as a client. The pluggable interface may generally be arranged to accommodate any number of SFPs. Client interface  482  may include hardware that allows various signals to be received and transmitted. The received and transmitted signals may include, but are not limited to, Ethernet, SONET, and SDH signals. It should be appreciated that the actual signals may have any suitable line rates. By way of example, an Ethernet signal may be a GbE signal, while a SONET signal may have an OC3, an OC12, and OC48, or an OC192 line rate. A trunk interface  486 , which may be used when multi-functional line card  450  is used as a part of a trunk, includes hardware and a plurality of ports which may be arranged to allow a variety of signals to be received and transmitted. Trunk interface  486  may also be arranged to provide framing capabilities. Like client interface  482 , trunk interface  486  may be a pluggable interface.  
         [0031]     The number of ports associated with client interface  482  and trunk interface  486  may vary. In one embodiment, client interface  482  may include approximately sixteen ports with a total capacity of approximately ten Gigabits. The approximately sixteen ports may include approximately four ports arranged to accept OC48, OC12, and OC3 transmissions or approximately sixteen ports arranged to receive OC12 or OC3 transmissions. Alternatively, when GbE transmissions are supported, the approximately sixteen ports may include approximately eight to ten ports arranged to accept GbE transmissions.  
         [0032]     Cross-connect hardware  490  may also be included in multi-functional line card  450  to provide a switching fabric. In general, slots  460 ,  464 ,  468  are coupled to cross-connect hardware  490  such that functionality associated with slots  460 ,  464 ,  468  may be interfaced with each other and with cross-connect hardware  490 . A software interface  480  is arranged to allow multi-functional line card  450  to be configured to add additional traffic types or services associated with SFPs in slots  460 ,  464 ,  468 . Alternatively, functionality associated with slots  460 ,  464 ,  468  may be provided substantially in software. In addition, software interface  480  may be arranged to manage a DWDM layer as well as the functionality associated with the SFPs.  
         [0033]     The use of a multi-functional line card such as line card  400  of  FIG. 4A  or line card  450  of  FIG. 4B  replaces the need to use multiple line cards to allow TDM and Ethernet traffic to be transported through a SONET/SDH network.  FIG. 5A  is a block diagram representation of multi-functional line cards interfaced with a SONET/SDH network in accordance with an embodiment of the present invention. A multi-functional line card  510   a  which acts as a client and a multi-functional line card  510   b  which acts as a trunk may be in communication with a SONET/SDH network  520 . Line cards  510   a,    510   b  may be arranged to aggregate a plurality of different types of traffic into network  520 , as line cards  510   a,    510   b  include ADMs, transponders, and muxponders. In the described embodiment, line cards  510   a .  510   b  are arranged to support at least GbE traffic, although line cards  510   a .  510   b  may generally support any type of traffic.  
         [0034]     If a traffic type that is not supported by line cards  510   a .  510   b  is demanded, line cards  510   a .  510   b  may be upgraded or augmented to support the traffic type. As shown in  FIG. 5B , by adding new SFPs  554   a ,  554   b  to line cards  510   a,    510   b,  respectively, line cards  510   a .  510   b  may be configured to support the previously unsupported traffic type. By way of example, if SONET traffic with a 1+1 APS protection scheme is to be supported, then SFPs  554   a ,  554   b  with transponder and muxponder functionality that supports the desired protected SONET traffic may be added to line cards  510   a .  510   b.  In general, adding SFPs  554   a ,  554   b  may involve either replacing previously installed SFPs (not shown) or allowing SFPs  554   a ,  554   b  to be used in addition to the previously installed SFPs.  
         [0035]     Though line card  510   a  and line card  510   b  may be the same line card, i.e., though line card  510   a  which is used as a client line card and line card  510   b  which is used as a trunk line card may have the same underlying mother board, SFPs used on line card  510   a  and line card  510   b  may be different. That is, ADM, transponder, and muxponder SFPs on line card  510   a  may differ from ADM, transponder, and muxponder SFPs on line card  510   b.    
         [0036]      FIG. 6  is a process flow diagram which illustrates steps associated with a method of upgrading a multi-functional line card to support a new traffic type in accordance with an embodiment of the present invention. A process  600  of upgrading a multi-functional line card to support a new traffic demand begins at step  604  in which at least one current traffic type to be transported is identified. Traffic types, or traffic demands, may vary widely and may include, but are not limited to, GbE traffic, SONET traffic, and SDH traffic. The traffic types may also be unprotected or protected, e.g., protected using 1+1 automatic protection switching (APS) or a unidirectional path switched ring (UPSR).  
         [0037]     After at least one current traffic type to be transported is identified, then a multi-functional line card is configured to support the at least one current traffic type in step  608 . Configuring the multi-functional line card may include selecting and installing SFPs on the line card and configuring software associated with the line card to support the at least one current traffic type. The multi-functional line card may be configured, for example, as an ADM-on-a-blade, as a transponder, or as a muxponder using software. SFPs provide interface flexibility in hardware components that may be needed to support a particular software configuration. For example, if the multi-functional line card is to function as a transponder for one client using one trunk, approximately two SFPS that support the same rate may be plugged in such that one SFP is plugged into a client interface and another SFP is plugged into a trunk interface. Alternatively, if the multi-functional line card is to function as a muxponder for two or more clients multiplexed using one trunk, two or more lower bit rate SFPs may be plugged into a client interface while a higher rate SFP may be plugged into a trunk interface. In one embodiment, if the multi-functional line card is to function as an ADM with at least two low bit rate clients that are internally cross-connected to support SONET functionality over approximately two trunks with UPSR protection, multiple SFPS of a lower bit rate may be plugged into a client interface while approximately two SFPS of a higher bit rate may be plugged into a trunk interface.  
         [0038]     Once the multi-functional line card is configured in step  608 , the supported traffic types are transported in step  612  using the multi-functional line card. A determination is made in step  616  whether an unsupported traffic type is requested. In other words, it is determined in step  616  if a different traffic demand is requested.  
         [0039]     If the determination in step  616  is that no unsupported traffic type is requested, process flow returns to step  612  in which supported traffic types are transported. Alternatively, it the determination in step  616  is that an unsupported traffic type is requested, then in step  620 , at least one SFP component that may be used to provide support for the unsupported traffic type is obtained in step  620 . SFP components may include, but are not limited to, components with transponder functionality, components with muxponder functionality, and components with ADM functionality.  
         [0040]     Upon obtaining any new SFP components to be used to support the unsupported traffic type, the new SFP components may be installed onto the multi-functional line card in step  624 . Installing new SFP components may include removing previously installed SFP components and effectively replacing those SFP components with the new SFP components. However, it should be appreciated that the SFP components that support the unsupported traffic type may instead be added to the multi-functional line card to operate in conjunction with previously installed SFP components.  
         [0041]     Once any new SFP components are installed or otherwise coupled to the multi-functional line card, process flow proceeds to step  628  in which software associated with the multi-functional line card is configured to support the unsupported traffic type. After the software is configured to support the unsupported traffic type, then that traffic type becomes a supported traffic type, and process flow returns to step  612  in which the supported traffic types are transported.  
         [0042]     Although only a few embodiments of the present invention have been described, it should be understood that the present invention may be embodied in many other specific forms without departing from the spirit or the scope of the present invention. By way of example, although the ADM functionality, the transponder functionality, and the muxponder functionality on multi-functional line cards has been described as being provided by SFPs or other pluggable components, such functionality may be provided by substantially any suitable component.  
         [0043]     The types of traffic, the line rates associated with traffic, and protection schemes that are supported by a multi-functional line card may vary widely. Additionally, the networks with which multi-functional line cards are interfaced may also vary widely. While a SONET/SDH network has been described, a network to which multi-functional line cards are interfaced may instead be a DWDM ring.  
         [0044]     A module or a multi-functional line card is not limited to including transponders, muxponders, and ADMs. A multi-functional line card may include components that provide additional functionality. Alternatively, a multi-functional line card may include any subset of transponders, muxponders, or ADMs. By way of example, a multi-functional line card may include a transponder and a muxponder but not ADM, or an ADM and a transponder but not a muxponder.  
         [0045]     A multi-functional line card may have many features in addition to those described above. For instance, SONET management features such as section and line fault, configuration, and performance management may be incorporated into a line card. Similarly, GbE management features such as fault, configuration and performance management features may also be included in a line card.  
         [0046]     The steps associated with the methods of the present invention may vary widely. Steps may be added, removed, altered, combined, and reordered without departing from the spirit of the scope of the present invention. Therefore, the present examples are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims.