Abstract:
A backplane includes at least one central slot, a first plurality of slots on a first side of the central slot(s) and a second plurality of slots on an opposite side of the central slot(s). The backplane also includes a plurality of inter-slot connections, including a first subplurality between each of the slots of the first plurality and the central slot(s), a second subplurality between each of the slots of the second plurality and the central slot(s), and a third subplurality between each slot of the first plurality and each slot of the second plurality.

Description:
BACKGROUND  
       [0001]     The Peripheral Component Interconnect Industrial Computer Manufacturers Group 3.0 Advanced Telecommunications Computing Architecture (“PICMG 3.0 AdvancedTCA”) specification has been accepted as a standard for the backplane architecture for computing/telecommunications equipment. The PICMG 3.0 AdvancedTCA specification defines connector architecture for backplane slots, as well as certain connection topologies that may be provided by the backplane between slots. However, it may be desirable to provide more efficient and/or higher bandwidth capabilities than are provided by the topologies set forth in the PICMG 3.0 AdvancedTCA specification. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0002]      FIG. 1  is a schematic illustration of an item of computing/telecommunications equipment provided according to some embodiments.  
         [0003]      FIG. 2  is a schematic illustration of a configuration of a backplane component of the equipment shown in  FIG. 1 .  
         [0004]      FIG. 3  schematically illustrates a portion of the connection topology provided in the backplane of  FIG. 2 .  
         [0005]      FIG. 4  schematically illustrates another portion of the connection topology provided in the backplane of  FIG. 2 .  
         [0006]      FIG. 5  is a table that shows an example channel mapping to implement the connection topology shown in  FIGS. 3 and 4 .  
     
    
     DETAILED DESCRIPTION  
       [0007]      FIG. 1  is a schematic illustration of an item  100  of computing and/or telecommunications equipment provided according to some embodiments.  
         [0008]     The item of equipment  100  includes a backplane  102  having slots (not separately shown) that may conform to the PICMG 3.0 AdvancedTCA specification. In addition, the backplane provides interconnections (by signal traces/vias that are not separately shown) among slots to implement a connection topology that is described below.  
         [0009]     The item of equipment  100  includes a number of electronic device cards  104 , each of which may be installed in a respective one of the backplane slots. The backplane  102  and the cards  104  may be held in a conventional chassis and/or housing, schematically represented at  106 .  
         [0010]      FIG. 2  is a schematic illustration of a configuration of the backplane  102 . The backplane  102  includes four central slots indicated at  202 , and configured as two pairs of slots given logical slot designations  1 A,  1 B (first pair) and  2 A,  2 B (second pair). Each pair of the central slots is configured to receive a respective double-width switching card to implement a dual star connection topology described below with reference to  FIG. 3 . The double-width switching cards are schematically represented by hollow arrows  204 ,  206 .  
         [0011]     The backplane  102  also includes five slots (indicated at  208 ) to the left side of the central slots  202  and given the logical numbering 3, 4, 5, 6, 7. Each of the slots  208  may be suitable for receiving a respective line card (each schematically represented by an arrow  210 ).  
         [0012]     On the opposite side of the central slots  202  (i.e., on the right side of the central slots) are five more slots, which are indicated at  212  and are given the logical numbering 8, 9, 10, 11, 12. Each of the slots  212  may be suitable for receiving a respective line card (each schematically represented by an arrow  214 ). In some embodiments, service cards may be installed in the slots  212  in place of some or all of the line cards  214 . Alternatively, in some embodiments, service cards may be installed in the slots  208  in place of some or all of the line cards  210 . (As would be understood by those who are skilled in the art, a line card provides a physical input/output interface to a data transmission line, whereas a service card performs processing on data received via a line card.)  
         [0013]      FIG. 3  schematically illustrates a portion of the connection topology provided in the backplane  102 . In particular,  FIG. 3  shows a conventional dual star inter-slot connection topology which is implemented as a portion of the connection topology provided by the backplane  102 .  
         [0014]     In  FIG. 3 , each of the larger circles  302  represents one of the two pairs of central slots  202  ( FIG. 2 ). The five smaller circles (indicated at  304  in  FIG. 3 ) at the left side of  FIG. 3  each represent one of the left side slots  208  ( FIG. 2 ). The five smaller circles (indicated at  306  in  FIG. 3 ) at the right side of  FIG. 3  each represent one of the right side slots  212  ( FIG. 2 ). The lines indicated at  310  in  FIG. 3  represent inter-slot conductive signal connections between each of the left side slots  304  and each pair  302  of the central slots. Each of the lines  310  may represent four 10 Gbs (gigabit per second) channels. The lines indicated at  312  represent inter-slot conductive signal connections between each of the right side slots  306  and each pair  302  of the central slots. Again each of the lines  312  may represent four 10 Gbs channels. Similarly, a connection is provided (represented by line  314 ) between the central slot pairs. It will be noted that considering this dual star topology alone, no connection is present between any of the slots indicated at  304 ,  306 . Rather any connection between the slots  304 ,  306  must be made via switching at one of the central slots  302  (again considering just the dual star topology).  
         [0015]      FIG. 4  schematically illustrates another portion of the connection topology provided in the backplane  102 . As in  FIG. 3 , the five circles  304  each represent one of the left side slots  208  ( FIG. 2 ) and the five circles  306  each represent one of the right side slots  212  ( FIG. 2 ). The lines indicated at  402  represent inter-slot conductive signal connections between each of the left side slots  304  and each of the right side slots  306 . Thus  FIG. 4  shows a “half mesh” connection topology provided in the backplane  102  according to some embodiments in addition to the dual star topology shown in  FIG. 3 . Each of the lines  402  may represent four 10 Gbs channels. (The central slots do not enter into the half mesh connection topology.)  
         [0016]     It will be noted that no slot of the left side slots  304  is connected to any other slot of the left side slots, and no slot of the right side slots  306  is connected to any other slot of the right side slots. For a “full mesh” topology to be implemented every one of the slots in the groups  304 ,  306  would have to be connected to every other one of the slots in those two groups. However, for the number of slots and the number of connectors provided in each slot, full mesh topology cannot be implemented to provide 40 Gbs of bandwidth between all pairs of slots.  
         [0017]     The half mesh topology shown in  FIG. 4  allows for “semi-random” direct datapath closure between slots that are on opposite sides of the array of slots. This may be useful for direct, full bandwidth, low latency ring closure and “one-plus-one” operation, without requiring complex fabric management or fabric bandwidth. It is also not necessary for the two connected slots to be adjacent as would be the case for update channels as referred to in the PICMG 3.0 AdvancedTCA specification.  
         [0018]     The half mesh topology may also allow for direct, full bandwidth, low latency connections between line cards and service feature cards without using fabric bandwidth. For example, the cards in the five left side slots may all be line cards and the cards in the five right hand slots may all be service cards (or there may be fewer than five service cards), with each service card having a direct connection to up to five of the line cards on the left side.  
         [0019]      FIG. 5  is a table that shows an example channel mapping to implement the connection topology shown in  FIGS. 3 and 4 . It will be noted that “zone 3” of the connectors (indicated as “user definable” in the PICMG 3.0 AdvancedTCA specification) is employed to provide data connection channels (fabric channels or “FCs”)  16 - 29  as well as fabric management (“FM”) channels  1 - 7 ).  
         [0020]     In the column entries in the “logical slot” columns (designated  1 A,  1 A,  2 A,  2 B through  12 ), the numeral before the hyphen (“-”) in each entry corresponds to the destination slot, and the numeral after the hyphen corresponds to the destination data connection channel in that slot. In addition to the data channel mapping and the fabric management channel mapping,  FIG. 5  also shows the base interface mapping (at the bottom of the table).  
         [0021]     (As used herein and in the appended claims “zone 2” and “zone 3” have the meanings as defined in the PICMG 3.0 AdvancedTCA specification, and correspond to regions of the connectors provided in the slots.)  
         [0022]     The mapping shown in  FIG. 5  is only an example of the numerous ways in which the combined dual star/half mesh topology may be realized. In the particular mapping shown in  FIG. 5 , most of the data connection channels of the central slots  1 A,  1 B,  2 A,  2 B are used for the dual star portion of the topology (the other data connection channels in the central slots are unused) and the data connection channels  1 ,  2 ,  8 ,  9 ,  21 ,  22 ,  23  and  24  of the left and right side slots are also used for the dual star portion of the topology. The other data connection channels of the left and right side slots are used for the half mesh portion of the topology, except for channel  15  which is not used.  
         [0023]     It should be noted that the combined dual star/half mesh topology may also be implemented on backplanes having fewer than the 14 PICMG 3.0 AdvancedTCA slots illustrated in  FIG. 2 .  
         [0024]     In some embodiments, the dual star topology may be replaced by a single star topology (e.g., slots  2 A,  2 B and the switching card installed therein may be eliminated). In other embodiments, the half mesh topology may be provided without either a dual star or a single star topology being present. For example, the topology of  FIG. 4  may be present without the topology of  FIG. 3  being present. I.e., the backplane may have only ten slots, interconnected as in  FIG. 4 , with the central slots  1 A,  1 B,  2 A,  2 B having been eliminated. It will be noted that the two groups of slots  3 - 7  and  8 - 12  are not interspersed with each other. As suggested by the previous paragraph, the half mesh topology may also be implemented with more or fewer than ten total slots. The two disjoint, half-mesh-connected connected groups of slots need not be equal to each other in terms of the number of slots in each group.  
         [0025]     The several embodiments described herein are solely for the purpose of illustration. The various features described herein need not all be used together, and any one or more of those features may be incorporated in a single embodiment. Therefore, persons skilled in the art will recognize from this description that other embodiments may be practiced with various modifications and alterations.