Patent Publication Number: US-9904027-B2

Title: Rack assembly structure

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 14/236,583, which is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/US2014/011643, filed Jan. 15, 2014, entitled “A RACK ASSEMBLY STRUCTURE”, which designated, among the various States, the United States of America, and also claims priority to U.S. Provisional Applications 61/752,963 and 61/752,966, filed on Jan. 15, 2013. The Specification of the PCT/US2014/011643 and U.S. patent application Ser. No. 14/236,583 Applications are hereby incorporated by this reference. 
    
    
     FIELD 
     Embodiments of the present disclosure generally relate to data center architecture, and more particularly, to using disaggregated rack structure in compute environment including data centers. 
     BACKGROUND 
     A computing data center may include one or more computing systems including a plurality of compute nodes that may comprise various compute structures (e.g., servers) and may be physically located on multiple racks. The servers and/or nodes comprising the servers may be interconnected, typically via one or more switches, forming different compute structures. 
     However, currently used data center structures that employ multiple racks may require substantial operation costs, energy consumption, complex management, and substantial maintenance, due to difficulties associated with accessing, servicing, and interconnecting different network and compute components (e.g., nodes) residing on the racks. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements. Embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings. 
         FIG. 1  schematically illustrates an example rack assembly that may be used in a data center architecture, in accordance with some embodiments. 
         FIG. 2  schematically illustrates an example network connectivity model for the rack assembly described in reference to  FIG. 1 . 
         FIG. 3  is a block diagram illustrating one example network connectivity model for the rack assembly, implementing a 3-stage Clos-ring hybrid scheme, in accordance with some embodiments. 
         FIG. 4  schematically illustrates an example optical patch panel implementation, in accordance with some embodiments. 
         FIG. 5  illustrates a perspective view of a tray that may be included in a rack assembly, in accordance with some embodiments. 
         FIG. 6  illustrates a perspective view of a tray that may be included in a rack assembly, with an optical communication system configured to provide communicative connection for the rack assembly, some elements of which are shown in greater detail, in accordance with some embodiments. 
         FIG. 7  is a block diagram illustrating an example disaggregated compute system that may be employed in a data center, in accordance with some embodiments. 
         FIG. 8  is a block diagram illustrating another example disaggregated compute system  800  that may be employed in a data center, in accordance with some embodiments. 
         FIG. 9  is a block diagram of a compute module comprising a compute node that may be similar to compute nodes used in the rack assembly of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure include configurations for compute environment such as a data center or a server farm. The configurations may include one or more racks containing compute nodes, storage, and networking components that may be disposed within the racks in a disaggregated fashion. 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof, wherein like numerals designate like parts throughout, and in which are shown by way of illustration embodiments in which the subject matter of the present disclosure may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments is defined by the appended claims and their equivalents. 
     For the purposes of the present disclosure, the phrase “A and/or B” means (A), (B), or (A and B). For the purposes of the present disclosure, the phrase “A, B, and/or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C). 
     The description may use perspective-based descriptions such as top/bottom, in/out, over/under, and the like. Such descriptions are merely used to facilitate the discussion and are not intended to restrict the application of embodiments described herein to any particular orientation. 
     The description may use the phrases “in an embodiment,” or “in embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments of the present disclosure, are synonymous. 
     The term “coupled with,” along with its derivatives, may be used herein. “Coupled” may mean one or more of the following. “Coupled” may mean that two or more elements are in direct physical, electrical, or optical contact. However, “coupled” may also mean that two or more elements indirectly contact each other, but yet still cooperate or interact with each other, and may mean that one or more other elements are coupled or connected between the elements that are said to be coupled with each other. The term “directly coupled” may mean that two or more elements are in direct contact. 
     It is to be noted that, although some embodiments have been described in reference to particular implementations, other implementations are possible according to some embodiments. Additionally, the arrangement and/or order of circuit elements or other features illustrated in the drawings and/or described herein need not be arranged in the particular way illustrated and described. Many other arrangements are possible according to some embodiments. 
       FIG. 1  schematically illustrates an example rack assembly  100  that may be used in a compute environment, such as a data center or a system of servers, in accordance with some embodiments. In some embodiments, multiple rack assemblies may be included in a compute environment. The rack assembly  100  may include one or more (e.g., a set of) trays, for example, trays  102  and  104 , in the rack assembly  100 . Tray  102  may be communicatively connected within the rack assembly  100  by a power connector  118  providing power to the tray  102 . The tray  102  may include a plurality of sleds such as a sled  142 , with each sled having one or more compute nodes  110 . The compute nodes  110  may provide a compute, storage, networking function, or a combination thereof, for the data center having the rack assembly  100 . The compute node  110  may include at least one central processing unit (CPU), a memory and/or other components as needed or a combination thereof. The compute node structure is described in reference to  FIG. 9 . In general, the sled  142  may contain different types of compute, even over successive generations, providing for flexible compute. 
     While not explicitly described, the tray  104  may include communicative connections and components similar to tray  102 . In some embodiments, trays  102  and  104  may include at least some dissimilar communicative connections/components. 
     The compute nodes  110  included in the sled  142  in the tray  102  may be communicatively connected with one or more other components of the rack assembly  100  and other rack assemblies comprising a compute environment (e.g., a data center) by an optical communication system configured to carry incoming and outgoing network (e.g., Ethernet) traffic. The communications between the compute nodes  110  included in the sled  142  on the tray  102  and other components of the compute environment (e.g., data center including the rack assembly  100 ) may be managed by one or more networking elements  112  disposed in the tray  102 . The optical communication system providing the communication links between the tray  102  and the other components of the rack assembly  100  will be described below in detail. The sled  142  may be communicatively connected to the networking element  112  via communicative connections  120 . 
     In some embodiments, the networking element  112  may include or be included in (e.g., reside on) a mezzanine card. In some embodiments, a mezzanine card may comprise a small board where electrical signals, such as Peripheral Component Interconnect Express (PCIe) or Ethernet signals, may be aggregated prior to transmission via an optical module (e.g., optical module  124  described below). The networking element  112  may include a switch  122  (e.g., a switch chip) and a control unit  126  (e.g., CPU control module) configured to manage communicative connections provided by the switch  122 . An embodiment in which the networking element  112  includes or is included in a mezzanine card is described in greater detail in reference to  FIG. 4 . 
     The optical communication system configured to connect the sled  142  with other components of the rack assembly  100  may include one or more optical modules  124  residing on the networking element  112  and an optical jumper cable  128  communicatively coupling the optical modules  124  with an optical connector  114 . The optical module  124  may comprise an optical transceiver capable of both transmitting and receiving optical data streams. The optical connector  114  may be configured to communicatively couple the optical modules  124 , via the jumper cable  128 , with an external optical cable  116 . The external optical cable  116  may provide a communicative connection of the tray  102  to other components of the rack assembly  100  and to other rack assemblies (not shown) via a rack resource component  130 . The rack resource component  130  may include, for example, a patch panel. 
     As described above, the networking element  112  may be disposed separately from the compute nodes  110  residing on the sled  142 , such as may reside on a mezzanine card, while the compute nodes (e.g., CPUs) may reside on the sled  142  that may be configured to be physically removable via front access to the rack assembly  100 . In other words, the sled  142  within the tray  102  ( 104 ) may allow for compute nodes to be removed and replaced without changing the network elements  112 , due to the communicative connections provided by the optical communication system comprising parallel optics. The optical communication system is described in greater detail in reference to  FIG. 5 . 
     The networking element  112  disposed on the tray  102  to provide communicative connections for the tray  102  ( 104 ) via the optical communication system, may be integrated (e.g., on a mezzanine card) or may be distributed throughout the rack assembly  100 . This distribution may allow the networking elements  112  within the rack assembly  100  to be managed and controlled as a single network entity. Using the connectivity provided by the optical communication system, the compute nodes  110  of the sled  142  may be interconnected using a passive connectivity element, for example a passive patch panel (described in greater detail in reference to  FIGS. 2 and 6 ), thus removing the need for a discrete networking element in the rack assembly  100 . A discrete networking element (e.g., a switch shown in  FIG. 1  as optional tray  106 ) may be used to increase the networking bandwidth between compute nodes (as described in detail in reference to  FIG. 7 ), but may not be required. In summary, the rack assembly  100  disaggregated as described above may provide network flexibility, matching the network with application workload demands, and may be updated over time separately from the compute nodes  110  comprising the rack assembly  100 . 
       FIG. 2  is a block diagram illustrating an example network connectivity model  200  for the rack assembly  100  of  FIG. 1 , in accordance with some embodiments. In some embodiments, the connectivity model  200  may be implemented within a physical patch panel, such as a patch panel  230 . In some embodiments, the patch panel  230  may comprise a passive patch panel. As shown, the trays  102 ,  104 , and  106  may be communicatively connected to components of the rack assembly  100  via the patch panel  230  using different connection topologies that may provide a varying degree of bandwidth between compute nodes  110  within the rack assembly  100 . By using the connectivity within the patch panel  230 , each compute node  110  in the tray  102  may be interconnected to all other compute nodes, for example, compute nodes of tray  104 , as well as to other rack assemblies that may constitute a data center, without adding a discrete networking element (such as tray  106 ) into the rack assembly  100 . The topologies in different implementations may include an N-dimensional (N-D) ring, Clos (a multi-stage circuit switching network representing an idealization of multi-stage telephone switching systems), or a combination thereof (e.g., a hybrid topology), as indicated in  FIG. 2 . A varying number of links within the parallel optics comprising an optical communication system may be used to build the intra-rack and inter-rack connectivity. 
     In general, any computer network may be represented as a graph of vertices (switches) and edges (links). The switch integrated into the tray with the parallel optics may enable at least some (e.g., majority) of the networking function to be distributed, with the switching being performed first in  112  and then further and optionally in a second set of switches. For example, there may be switches disposed above the patch panel in  106 . The benefit of such structure is in reducing the cost associated with the second level of switches, while maintaining one optical cable per tray. Any topology may be feasible in this architecture, including circulant graph, paylay graph, or Clos. 
       FIG. 3  is a block diagram  300  illustrating one example network connectivity model for the rack assembly  100 , implementing a 3-stage Clos-ring hybrid scheme, in accordance with some embodiments. The diagram  300  includes a ring  302  and the 2-stage Clos models  304  and  306  built on top of the ring  302 . The scheme&#39;s elements include multiple switches  310  (similar to the switch  122 ) and optical modules  312  (similar to the optical module  124 ), connected via optical communication links  314 . In a 2-stage Clos model, a butterfly pattern of connectivity between the leaf nodes (first stage) and the spine nodes (second stage) may be used. For example, for a 4-port switch ( 122 ), in order to have a Clos model six switches may be used, namely four leaves and two spines, and each leaf may be connected to each spine. Half of the ports from the leaf go down into the network. This structure may result in an 8-port total switch, thus doubling the port count. 
     To build a 3-stage Clos model, at least 8 ports in the switch  310  may be used, having two rows of leaf switch (4 ports down, 4 ports up) and the third row may comprise spines at the top. Accordingly, there may be 8 first stage leaves, 8 second stage leaves, and 4 spines, which may result in a 128 port switch. 
     For radix R, a 2-stage Clos model may provide a maximum of R{circumflex over ( 0 )}2/2 ports. A 3-stage Clos model may provide a maximum of R{circumflex over ( 0 )}3/4 ports. More generally, an n-stage Clos may provide R{circumflex over ( 0 )}n/(2(n−1)) ports. Clos model may be used to get to a high port count overall, wherein chips consumed may be calculated as (2n−1)/2(n−1)*R{circumflex over ( 0 )}2. Thus, a Clos model may consume a quadratic number of chips in the number of stages. It may be desirable to reach as high radix as possible in the number of stages. By implementing the bottom stage as a load balancing ring, the overall port count or scale of a Clos model may be increased, whether the model comprises two or three stages. In general, designs may be implemented that reduce the number of stages, or make one of the stages based on a higher radix effective switch. 
       FIG. 4  illustrates an example optical patch panel  230  implementation, in accordance with some embodiments. The optical patch panel  230  comprises a passive optical connection, connecting the optical channels from the compute nodes and other elements, such as input-output (I/O) subsystems and/or switches via uplinks, forming fabric topology within the rack assembly  100  and/or between rack assemblies. The optical patch panel  230  includes multiple optical cables  402 ,  406 ,  406 ,  408 ,  410 , etc. comprising external optical cables  116 , providing communicative connections between the trays (e.g., trays  1 ,  2 ,  3 ,  4 ,  5 , N) included in a rack assembly as described in reference to  FIG. 1 . The optical patch panel  230  further includes uplink cable  412  providing a communicative connection with other rack assemblies. The optical patch panel  230  comprises a ring model and allows for an external connection between the patch panel  230  and the subsystems included in the rack assembly  100  and a compute environment comprising the rack assembly  100 . It should be appreciated that multiple fabric connectivity topologies may be implemented; the illustrated implementation is not limited to the ring example shown in  FIG. 4 . Such topologies may include, but may not be limited to, two-dimensional (2D) and three-dimensional (3D) Torus, and other mesh type configurations. 
       FIG. 5  illustrates a perspective view of the tray  102  in accordance with some embodiments. It should be understood that the tray  102  may comprise a sub-rack level of aggregation and distribution for the rack assembly  100 . The tray  102  may include a midplane board  502  into which planar circuit boards  504  (e.g., sleds such as sled  142 ) may be plugged through co-planar or perpendicular connectors (not shown). A mezzanine card (e.g., mezzanine card  506 , which may include or be included in the networking element  112 ) may plug into the midplane board  502 , e.g., through a riser connector (not shown). An enlarged view  560  of the mezzanine card  506  is shown in  FIG. 5 . 
     The planar circuit boards  504  may also be configured to serve as a base for vertical cartridges. A parallel optical connector  512  (similar to  114 ) may be a part of the tray  102  housing, and not attached directly to any of the coplanar, vertical, or mezzanine cards or boards. The optical connector  512  is described in greater detail in reference to  FIG. 6 . An optical fiber segment  528  (similar to the optical jumper  128 ) may connect the optical connector  512  to the mezzanine card  506 . Other signals, such as power signal, may connect (not shown) through the tray midplane board  502 . 
     A rack assembly, such as the rack assembly  100 , may be configured with bussed power available to all trays (e.g.,  102 ) in the rack assembly  100 , a patch panel (e.g., passive patch panel  230 ), and cabling between the patch panel  230  and each tray  102 . This configuration allows for upgrade of the tray  102  independently from the rack assembly  100 . 
     As described in reference to  FIG. 5 , the tray  102  inserting into the rack assembly  100  may include a midplane board  502  to interconnect power, networking, storage, management, and server/compute. Each of these elements may be independent of the other. The networking subsystem may include the networking circuitry and cabling in a co-planar mezzanine module (e.g., mezzanine card  506 ) that may be pluggable into the tray  102 . The networking subsystem may be upgraded by removing the cable connections to the mezzanine card  506  and replacing the mezzanine card  506 . 
     Because the server/compute subsystem may be independent of the networking subsystem, the server/compute subsystem may be upgradable independently of the networking subsystem. As indicate by arrow  570 , the tray  102  may be removable at its front end  572 , and may attach to the rack assembly at its back end  574 . 
       FIG. 6  illustrates a perspective view the tray  102  with some connectivity elements shown in greater detail in accordance with some embodiments. 
     As described in reference to  FIG. 1 , the optical communication system may include the components  124 ,  128 ,  114 , and  116 , some of which are described herein in greater detail. As discussed above, some of the optical communication system components may reside on the mezzanine card  506 . For example, optical modules  124  may comprise silicon photonic (SiP) modules with a number (e.g., N) of fiber connections interfacing to a mezzanine multi-fiber cable, such as the optical jumper cable  128 , via an optical connector  606 . The mezzanine multi-fiber cable such as the optical jumper cable  128  may provide for the optics to be embedded in the system while still allowing an optical connection in the front or rear of the rack chassis with a single multi-fiber bulkhead connection. This may allow the compute or input-output trays (e.g., tray  102 ) to be accessible from the front for easy removal. 
     The optical jumper cable  128  may communicatively connect with the external optical cable  116  via the optical connector  114 . The optical connector  114  may include a connector receptacle  630  that may be attached around the front end  572  of the tray  102 . The receptacle  630  may provide a reference for a photonic connector mated pair formed by the receptacle  630  from the internal fiber jumper and a photonic connector plug  632  of the external optical cable  116 . The optical connector  114  may be configured to support up to 4 rows of 16 fibers each for a total scalable solution of 64 optical fibers, which may result in a fiber density of greater than one fiber per square millimeter. As shown, the photonic connector plug  632  may include a fiber ferrule  622  and a ferrule housing  624 . The mechanical alignment tolerance may be provided by the mechanical alignment pins  648  and the latching mechanism  650 . 
       FIG. 6  shows an implementation of the photonic connector plug  632  with 24 fibers arranged in 3 rows of 8 each, represented by the lenses in the fiber ferrule  622  portion of the design. This particular implementation is shown for illustrative purposes only; other implementations according to the described design may be accomplished. As described above, the external optical cable  116  coupled with the photonic connector plug  632  may make the optical connection between the server/compute subsystem and the patch panel (e.g.,  230 ) or discrete networking element (e.g.,  106 ) such as a Top-of-Rack (TOR) switch. The external optical cable configured with the connector plug  632  may provide a 1:1 optical connection of each optical channel to the patch panel  230 . 
       FIG. 7  is a block diagram illustrating an example disaggregated compute system  700  that may be employed in a data center, in accordance with some embodiments. The example system  700  may include one or more components of the rack assembly  100  discussed in  FIGS. 1-6 . 
     The example system  700  includes one or more trays  702  (similar to  102 ) that may contain one or more CPUs  710  and the associated memory  712  coupled via an interface  720  such as double data rate (DDR) synchronous dynamic random-access memory interface (SDRAM), and control and boot support (not shown). In some embodiments, the compute nodes comprising the tray  702  may form a server. 
     Communications may be aggregated between the trays  702  through a silicon photonics module  718  (similar to optical module  124 ) to a switch, such as a Top of Rack (ToR) switch  704 , which may be configured to provide communications interconnections for the compute nodes and other devices. The ToR switch  704  may communicate to the individual compute nodes in the trays  702  elements through a Network Interface Chip (NIC)  714  via an optical cable  730 , and also support an array of Solid State Disk Drives (SSDs)  716 . This configuration may allow for the modular upgrade of the computing and memory infrastructure. It should be appreciated that other configurations for the disaggregated compute system architecture are possible, for example, including the disaggregation of the memory system. 
       FIG. 8  is a block diagram illustrating another example disaggregated compute system  800  that may be employed in a data center, in accordance with some embodiments. As shown, the system  800  may include one or more trays  702  discussed in reference to  FIG. 7 , as well as a remote storage  802 . As shown, the compute and network functions may be distributed between the system components, as indicated by numerals  810  and  812  respectively. A switch  802  (e.g., integrated in a switch chip) may be configured to support aggregation of data streams between the trays  702  to reduce overall fiber and cabling burden as well as a distributed switching functionality. This approach may allow for a granular deployment of resources throughout the data center infrastructure, and may support a granular approach to upgradability and re-partitioning of the architecture in such a way that system resources may be shared between different compute elements. It should be understood that the components  810  and  812  in this example system  800  may be swapped dynamically and asymmetrically so that improvements in bandwidth between particular compute nodes of trays  702  may be upgraded individually. 
       FIG. 9  is a block diagram of a compute module comprising a compute node  900  that may be similar to compute nodes used in the rack assembly  100  of  FIG. 1 . (Hereinafter, the terms compute node and compute module will be used interchangeably.) The compute node  900  may be used, for example, to form various compute structures (e.g., servers) for a data center, in accordance with embodiments described in reference to  FIGS. 1-9 . The compute module  900  may comprise, for example, a laptop computer, desktop computer, tablet computer, mobile device, server, or blade server, netbook, a notebook, an ultrabook, a smartphone, a personal digital assistant (PDA), an ultra mobile PC, a printer, a scanner, a monitor, a set-top box, an entertainment control unit, a digital camera, a portable music player, or a digital video recorder, among others. In further implementations, the compute module  900  may be any other electronic device that processes data. 
     In some examples, a compute module or compute node is any device that is capable of communicating across the multi-node system to another module. Accordingly, in some examples, the multi-node system is a network of modules, where each module is any device capable of communicating across the network. Additionally, in some examples, the multi-node is a server in a rack server system. The compute module  900  may include a central authority coupled to a plurality of nodes and containing management firmware for the plurality of nodes in a data center or server farm. 
     The compute module  900  may include a host central processing unit (CPU)  902  that is configured to execute stored instructions, as well as a memory device  904  that stores instructions that are executable by the host CPU  902 . The host CPU  902  may be coupled to the memory device  904  by a bus  906 . Additionally, the host CPU  902  may be a single core processor, a multi-core processor, a computing cluster, or any number of other configurations. In some cases, the host CPU  902  and other components of the compute module  900  may be implemented as a system on chip (SOC). Furthermore, the compute module  900  may include more than one host CPU  902 . The memory device  904  may include random access memory (RAM), read only memory (ROM), flash memory, or any other suitable memory systems. For example, the memory device  904  may include dynamic random access memory (DRAM). 
     The compute module may be communicatively connected to a baseboard  908 . The baseboard  908  may contain a central authority  910 . The central authority is used to manage each node connected to the baseboard. Additionally, each compute module may also include a plurality of sensors  912 . The sensors may collect data regarding its respective node. For example, sensors may collect system management information for each node. The data may include power management data, humidity control data, cooling control data, workload provisioning data, storage servicing data, I/O data, throughput data and the like. The system management data is transmitted to a central authority. 
     Each compute module also includes logic  914 . The logic  914  enables monitoring of system management data for each node. System management data may be passed to the central authority  910  through the logic  914 . In some cases, system management data is gathered through several different interfaces. For example, a general purpose input\output (GPIO) interface may be used to enable access to power control, reset, and status information of the compute module  900  from the host CPU  902 . A low pin count (LPC) or enhanced serial peripheral interface (eSPI) bus may be used to support various embedded controllers of the compute module  900 . Additionally, a platform environment control interface (PECI) may be used to manage thermal sensors within the compute module  900 . The logic  914  may obtain system management information from various interfaces and transmit this data to the central authority. Similarly, the central authority may manage the compute module  900  by transmitting information to the logic  914 . The logic  914  may transmit the necessary information to the host CPU  902 . In this manner, a standardized set of interfaces may be used to communicate with the host CPU  902 . 
     The block diagram of  FIG. 9  is not intended to indicate that the compute module  900  is to include all of the components shown in  FIG. 9 . Further, the compute module  900  may include any number of additional components not shown in  FIG. 9 , depending on the details of the specific implementation. Moreover, the compute module  900  may include fewer components than those illustrated in  FIG. 9 . For example, the compute module  900  may include a GPU, I/O device interface, or display interface. 
     The embodiments described herein may be further illustrated by the following examples. Example  1  is tray to be disposed in a rack assembly, the tray comprising: a plurality of sleds with individual sleds including one or more compute nodes; and a networking element coupled with a sled of the plurality of sleds and configured to communicatively connect the sled to one or more other components of the rack assembly via an optical communication system, wherein the optical communication system includes an external optical cable configured to communicatively connect the networking element with the rack assembly. 
     Example 2 may include the subject matter of Example 1, and further specifies that the networking element includes a switch component configured to communicatively connect the sleds to the optical communication system. 
     Example 3 may include the subject matter of Example 2, and further specifies that the networking element includes a control unit configured to manage communicative connections provided by the switch component. 
     Example 4 describes a rack assembly comprising the tray of claim  2  and the optical communication system, wherein the optical communication system further includes an optical module configured to communicatively connect the networking element with the rack assembly via the switch component to transmit and receive optical data streams. 
     Example 5 may include the subject matter of Example 4, and further specifies that the optical module is configured to communicatively connect with the external optical cable via an optical jumper cable. 
     Example 6 may include the subject matter of Example 5, and further specifies that the rack assembly further comprises a patch panel, wherein the at least one external optical cable is configured to communicatively connect the networking element with the patch panel of the rack assembly. 
     Example 7 may include the subject matter of Example 6, and further specifies that the patch panel is a passive patch model configured to provide communicative connections within the rack assembly or between the rack assembly and another rack assembly, the communicative connections forming a connectivity model. 
     Example 8 may include the subject matter of Example 7, and further specifies that the connectivity model includes an n-dimensional (N-D) ring topology, Clos topology, or a combination thereof. 
     Example 9 may include the subject matter of Example 6, and further specifies that the tray comprises a front end and a back end, wherein the tray is disposed in the rack assembly with the back end facing a frame of the rack assembly. 
     Example 10 may include the subject matter of Example 9, and further specifies that the external optical cable is communicatively connected with the optical jumper cable with a parallel optics connector disposed at the front end of the rack assembly. 
     Example 11 may include the subject matter of Example 9, and further specifies that the networking element comprises a mezzanine card disposed in the back end of the tray. 
     Example 12 may include the subject matter of any of Examples 4 to 11, and further specifies that the sled is configured to be removable from the tray without removing the tray from the rack assembly. 
     Example 13 may include the subject matter of any of Examples 4 to 11, and further specifies that the compute node comprises a central processing unit. 
     Example 14 may include the subject matter of any of Examples 4 to 11, and further specifies that the compute node comprises a memory. 
     Example 15 is a method for forming a rack assembly, comprising: forming a tray including: a plurality of sleds, with individual sleds including one or more compute nodes; and 
     a networking element coupled with a sled of the plurality of sleds and configured to communicatively connect the sled to one or more components of the rack assembly via an optical communication system; and communicatively connecting the tray to the rack assembly with the optical communication system, wherein the optical communication system includes an external optical cable configured to communicatively connect the networking element with the rack assembly. 
     Example 16 may include the subject matter of Example 15, and further specifies that forming a tray further includes assembling the networking element, including adding a switch component configured to communicatively connect the sleds to the optical communication system, and coupling the switch component with a network interface component configured to provide network connection for the tray. 
     Example 17 may include the subject matter of Example 15, and further specifies that forming a tray further includes: assembling the optical communication system, including providing an optical module configured to communicatively connect the networking element with the one or more components of the rack assembly via the switch component to transmit and receive optical data streams; and communicatively connecting the optical module to an external optical cable via an optical jumper cable, the external optical cable configured to communicatively connect the networking element with a patch panel of the rack assembly. 
     Example 18 may include the subject matter of Example 17, and further specifies that forming a tray further includes: disposing a parallel optics connector about a front end of the tray; and communicatively connecting the optical jumper with the external optical cable via the parallel optics connector. 
     Example 19 may include the subject matter of Example 18 and further specifies that the method further comprises disposing the tray on the rack assembly, with a back end of the tray facing a frame of the rack assembly and the front end of the tray facing outward. 
     Example 20 may include the subject matter of any of Examples 15 to 19, and further specifies that the compute node comprises a central processing unit and/or a memory. 
     Various operations are described as multiple discrete operations in turn, in a manner that is most helpful in understanding the claimed subject matter. However, the order of description should not be construed as to imply that these operations are necessarily order dependent. Embodiments of the present disclosure may be implemented into a system using any suitable hardware and/or software to configure as desired. 
     Although certain embodiments have been illustrated and described herein for purposes of description, a wide variety of alternate and/or equivalent embodiments or implementations calculated to achieve the same purposes may be substituted for the embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the embodiments discussed herein. Therefore, it is manifestly intended that embodiments described herein be limited only by the claims and the equivalents thereof.