Abstract:
A traceless midplane contains substantially no traces, pins, or active components and includes a front portion and a back portion. The front portion includes first connectors. The back portion includes second connectors arranged in a grid pattern. Each of the second connectors includes electrically-conductive conduits that connect the second connector to a corresponding one of the first connectors through the midplane. The second connectors include data connection points, ground connection points, and clock connection points. At least some of the data connection points are separated from each other and from the clock connection points by the ground connection points.

Description:
BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     The present invention relates generally to routing systems and, more particularly, to a traceless midplane that interconnects multiple boards of a network device. 
     B. Description of Related Art 
     Conventional network devices include multiple processing and/or switching boards that communicate with one another. Often, a backplane or midplane interconnects these boards so that they can communicate. These backplanes and midplanes, however, typically include traces (i.e., internal or external wires that interconnect connection points on the backplanes or midplanes), connection pins, and/or active circuitry to facilitate the communication between the boards. As the complexity of the network devices increases, the number of the traces in the backplanes and midplanes and the amount of pins and active circuitry required to manage the connections also increase, making it increasingly difficult to manufacture the backplanes and midplanes. 
     Also, a problem arises when an electrical fault occurs in the complex traces, pins, or active circuitry. The remedy usually takes the form of completely emptying the network device and replacing and/or troubleshooting the backplane or midplane. 
     Therefore, a need exists for an interconnecting mechanism that is easy to manufacture and permits communication between boards of a network device without suffering from electrical faults. 
     SUMMARY OF THE INVENTION 
     Systems and methods, consistent with the present invention, address this and other needs by providing a traceless midplane that facilitates the interconnection and communication of the boards of a network device. The traceless midplane contains no traces, pins, or active components, but only conduits that provide direct electrical connections between pins of the boards. Therefore, the midplane is easy to manufacture and less prone to electrical faults than midplanes that contain traces, pins, and/or active components. 
     In accordance with the purpose of the invention as embodied and broadly described herein, a traceless midplane, which contains substantially no traces, active components, or pins, includes a front portion and a back portion. The front portion includes first connectors. The back portion includes second connectors arranged in a grid pattern. Each of the second connectors includes electrically-conductive conduits that connect the second connector to a corresponding one of the first connectors through the midplane. The second connectors include data connection points, ground connection points, and clock connection points. At least some of the data connection points are separated from each other and from the clock connection points by the ground connection points. 
     In another implementation consistent with the present invention, a network device includes packet processor boards that include first pins, input/output control boards that include second pins, and a traceless midplane. The midplane interconnects the first pins of the packet processor boards and the second pins of the input/output control boards. The packet processor boards and the input/output control boards connect to the midplane in an orthogonal pattern. The midplane includes multiple connectors. Each of the connectors include multiple conductive conduits. Each of the conduits interconnects one of the first pins and one of the second pins through the midplane. 
     In a further implementation consistent with the present invention, a method for manufacturing a traceless midplane that contains no traces, active components, or pins, includes obtaining a printed circuit board; drilling holes to create conduits through the printed circuit board, where multiple conduits form one of the connectors; and placing electrically-conductive material in each of the conduits. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, explain the invention. In the drawings, 
     FIG. 1 is a diagram of an exemplary network device in which a passive midplane consistent with the present invention may be implemented; 
     FIGS. 2A-2C are exemplary views of a midplane configuration consistent with the present invention; 
     FIGS. 3A and 3B are exemplary front and side cross section views of the midplane of FIGS. 2A-2C according to implementation consistent with the present invention; and 
     FIG. 4 is an exemplary diagram of a pin connection layout on the midplane of FIGS. 3A and 3B according to an implementation consistent with the present invention; and 
     FIG. 5 is an exemplary flowchart of processing procedures for manufacturing a midplane in a manner consistent with the present invention. 
    
    
     DETAILED DESCRIPTION 
     The following detailed description of the invention refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims and equivalents. 
     Systems and methods, consistent with the present invention, provide interconnectivity between boards of a network device via a midplane. The midplane contains no traces, pins, or active components, but instead contains conduits that provide direct electrical connections between pins of the interconnecting boards. Such a construction is easy to manufacture and minimizes electrical faults in the midplane and, therefore, minimizes the need to replace or troubleshoot the midplane. 
     EXEMPLARY NETWORK DEVICE CONFIGURATION 
     FIG. 1 is a diagram of an exemplary network device in which systems and methods consistent with the present invention may be implemented. In this particular implementation, the network device takes the form of a router  100 . 
     The router  100  may include a routing engine  110  and a packet forwarding engine  120 . The routing engine  110  may perform routing updates and system management operations for the router  100 . The routing engine  110  may include one or more routing tables  112  and a forwarding table  114 . The routing table(s)  112  may consolidate routing information learned from routing protocols in the network. From the routing table(s)  112 , the routing engine  110  determines the active routes to network destinations and records these routes in the forwarding table  114 . 
     The packet forwarding engine  120  may make packet forwarding decisions for the router  100 . The packet forwarding engine  120  may include programmable interface cards (PICs)  122 , flexible PIC concentrators (FPCs)  124 , one or more packet processors  126 , and a forwarding table  128 . The PICs  122  receive and transmit packets for the router  100 . The PICs  122  may include media-specific logic that performs, for example, framing and checksum verification. Different types of PICs  122  may operate according to different transmission rates, such as OC- 192  and OC- 48  transmission rates, and protocols, such as the Synchronous Optical Networking (SONET), Asynchronous Transfer Mode (ATM), and Ethernet protocols. 
     The FPCs  124  may include input/output control logic that directs and manages the packets received and transmitted by the PICs  122 . The FPCs  124  may, for example, count packets and bytes, apply class-of-service rules to packets, prioritize packets, and perform basic packet integrity checks. The packet processor(s)  126  may include logic that determines how to route the packets. The packet processor(s)  126  may operate upon packet header information received from the FPCs  124  to identify the PIC  122  to output the packet. The packet processor(s) may use the forwarding table  128  to make this determination. The forwarding table  128  may obtain a copy of the forwarding table  114  from the routing engine  110 . 
     The routing engine  110  and packet forwarding engine  120  may be configured as a number of circuit boards in the router  100 . For example, the packet forwarding engine  120  may include separate circuit boards for the packet processors  126  and the FPCs  124  interconnected by a midplane. 
     FIG. 2A is an exemplary diagram of a midplane configuration consistent with the present invention. In this example, the midplane  210  interconnects circuit boards  220  which implement the packet processors  126  with circuit boards  230  which implement the FPCs  124 . The midplane  210  may include a traceless circuit board that interconnects the packet processor boards  220  and the FPC boards  230  in an orthogonal (i.e., cross-hatch or cross-connect) pattern. 
     As shown in FIG. 2A, the packet processor boards  220  may connect to the midplane  210  in a vertical direction via pins  225  and the FPC boards  230  may connect to the midplane  210  in a horizontal direction via pins  235 . The directions of the boards  220  and  230  may be reversed or different directions may be used in other implementations consistent with the present invention. With such a connection as shown in FIG. 2A, each of the packet processor boards  220  may be electrically connected with each of the FPC boards  230  through the midplane  210 . 
     FIG. 2B is an exemplary diagram of a front view of the midplane  210 . As shown, each of the packet processor boards  220  connect to the midplane  210  in a vertical direction. FIG. 2C is an exemplary diagram of a back view of the midplane  210 . As shown, each of the FPC boards  230  connect to the midplane  210  in a horizontal direction. 
     FIGS. 3A and 3B are exemplary front and side cross section views of the midplane  210 , respectively, according to an implementation consistent with the present invention. As shown in FIG. 3A, the midplane  210  may include multiple connectors  310  arranged in a grid pattern. The connectors  310  permit the packet processor boards  220  and the FPC boards  230  to communicate. Each of the connectors  310  may include multiple connection points  320 . 
     As shown in FIG. 3B, each of the connection points  320  may include an electrically-conductive conduit  330 , such as a copper tunnel, configured to connect a pin  225  of a packet processor board  220  and a pin  235  of a FPC board  230 . The pins  225  of the packet processor boards  220  and the pins  235  of the FPC boards  230  need not physically touch each other. The conductive material (e.g., copper) in the conduit  330  completes the connection and acts as a direct connection to facilitate the transmission of signals between the pins. The midplane connections between the boards  220  and  230  are designed such that no traces, pins, or active components are needed to transmit signals between the pins  225  and  235  on the boards  220  and  230 , respectively. 
     FIG. 4 is an exemplary diagram of a connector  310  according to an implementation consistent with the present invention. The connector  310  may include an AMP 2 mm hard metric connector with eight columns and ten rows of connection points  320 . Different numbers of rows and columns may be used in other implementations consistent with the present invention. 
     The connector  310  may include different types of connection points  320 , such as data (D) connection points  410 , ground (G) connection points  420 , and clock (C) connection points. The data connection points  410  convey data signals, such as high speed data signals, between boards. The ground connection points  420  provide ground connections between the boards. The clock connection points  430  convey clock signals between the boards. To minimize interference, the rows of data connection points  410  and clock connection points  420  may be separated from each other by rows of ground connection points  430 . 
     METHOD OF MANUFACTURING MIDPLANE 
     FIG. 5 is an exemplary flowchart of processing for manufacturing a midplane in a manner consistent with the present invention. Processing may begin by obtaining a circuit board for the midplane [act  510 ]. The circuit board may be made of standard materials of a desired size. The layout of the connectors on the circuit board may then be designed [act  520 ]. The designing of the connectors may be an automated, manual, or partially automated process. 
     The conduits for the connectors may then be drilled in the circuit board [act  530 ]. Conventional drilling techniques may be used to create the conduits. Conductive material, such as copper, may then be placed in the conduits using conventional techniques [act  540 ]. 
     While a series of acts have been described, the order of acts may differ in other implementations consistent with the present invention. 
     CONCLUSION 
     Systems and methods, consistent with the present invention, provide an interconnection mechanism that permits circuit boards to communicate. The interconnection mechanism may include a traceless midplane that contains no traces, pins, or active components. Instead, the interconnection mechanism uses only electrical conduits to provide direct connections between pins of the circuit boards. As a result, the interconnection mechanism is easy to manufacture. Also, the possibility of defects or faults associated with the interconnection mechanism is minimized. 
     The foregoing description of preferred embodiments of the present invention provides illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. For example, while the midplane  210  has been described in the context of a network device, it may be used in other complex systems in other implementations consistent with the present invention. 
     Also, the midplane  210  has been described as containing no traces, pins, or active components. In other implementations consistent with the present invention, the midplane  210  contains substantially no, or very few, traces, pins, or active components. 
     The scope of the invention is defined by the claims and their equivalents.