Patent Publication Number: US-10765031-B1

Title: Modular cage enclosure system

Description:
This application is a divisional of U.S. application Ser. No. 15/388,769, filed Dec. 22, 2016, the entire contents of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to data centers, and more specifically, to customer cage enclosures within a co-location facility. 
     BACKGROUND 
     A facility such as a data center includes a data center storage space storing numerous electronic devices that produce heat, including network, server, and storage gear, as well as power distribution units for distributing power to devices within the facility. In some examples, a network services exchange provider or co-location provider (a “provider”) may employ a communication facility, such as a data center or warehouse, in which multiple customers of the network services exchange provider locate network, server, and storage gear and interconnect to a variety of telecommunications and other network service provider(s). The overall data center storage space may be shared by the multiple customers. 
     SUMMARY 
     In general, the disclosure describes a modular cage enclosure system. The modular cage enclosure system is based on a specific planning grid, to provide flexibility in configuring and reconfiguring colocation space within the data center to easily accommodate changing needs for customers colocated within the data center. The modular cage enclosure system includes a plurality of posts and a plurality of cage panels removably coupled to the posts. Different cage panels may have different widths, but each of the cage panels has a nominal width that is a modular increment value, meaning that any of the nominal widths divided by the modulus has a remainder of zero. In some examples, the value of the modulus may be selected based on dimensions of infrastructure in the data center colocation space, such as a length or width of server cabinets in the colocation space, dimensions of tiles in a floor of the data center colocation space, and dimensions of support structure undergirding the floor of the data center colocation space. The modular cage enclosure system may avoid a need to manufacture custom-sized cage enclosure panels that may later be unusable for future customer needs. 
     In one example, a system includes a data center colocation space comprising a floor, the floor comprising a plurality of floor tiles, a plurality of posts arranged with a center of each post aligned with an adjoining edge of at least two of the plurality of floor tiles, and each post perpendicular to the floor, and a plurality of cage panels, wherein the plurality of cage panels and the plurality of posts are arranged to form at least one cage enclosure within the data center colocation space, wherein each of the cage panels is removably coupled to one or more of the plurality of posts, wherein a nominal width of each of the cage panels is congruent based on a modulus equal to a width of the floor tiles, wherein each of the cage panels has an actual width less than its nominal width. 
     In another example, a method includes installing, within a data center, a customer cage enclosure having first dimensions, the customer cage enclosure comprising: a plurality of posts; and a plurality of cage panels, wherein each of the cage panels is removably coupled to one or more of the plurality of posts, wherein a nominal width of each of the cage panels is congruent based on a modulus, wherein an actual width of each of the cage panels is equal to a difference between the nominal width of the cage panel and the width of one of the plurality of posts, and wherein any combination of a subset of the plurality of cage panels coupled in a common orientation to a subset of the plurality of posts has a combined width, between respective centers of end posts of the subset of the plurality of posts, that is congruent based on the modulus, wherein installing comprises arranging one or more of the plurality of cage panels and two or more of the plurality of posts to form a perimeter partition of the customer cage enclosure. The method also includes reconfiguring a portion of the perimeter partition of the customer cage enclosure to adjust a dividing partition of the customer cage enclosure perpendicular to at least a portion of the perimeter partition, by replacing at least a first cage panel of the plurality of cage panels in the perimeter partition with at least a second cage panel of the plurality of cage panels, the first cage panel having a first nominal width and the second cage panel having a second nominal width different than the first nominal width. 
     In a further example, a system includes a plurality of posts, each of the plurality of posts having a base plate for attaching the post to a floor of a data center colocation space, and a plurality of cage panels, wherein each of the cage panels is removably coupled to one or more of the plurality of posts, wherein a nominal width of each of the cage panels is congruent based on a modulus, wherein an actual width of each of the cage panels is equal to a difference between the nominal width of the cage panel and the width of one of the plurality of posts, and wherein any combination of a subset of the plurality of cage panels coupled in a common orientation to a subset of the plurality of posts has a combined width, between respective centers of end posts of the subset of the plurality of posts, that is congruent based on the modulus. 
     In a further example, a system includes a data center colocation space comprising a floor, a plurality of posts arranged with each post perpendicular to the floor, and a plurality of cage panels, wherein the plurality of cage panels and the plurality of posts are arranged to form at least one cage enclosure within the data center colocation space, the cage enclosure enclosing a plurality of cabinets, wherein each of the plurality of the posts is arranged with a center of each post aligned with an edge of at least two of the plurality of cabinets, wherein each of the cage panels is removably coupled to one or more of the plurality of posts, wherein a nominal width of each of the cage panels is congruent based on a modulus equal to a width of the cabinets, wherein each of the cage panels has an actual width less than its nominal width. 
     The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating a planview of an example data center colocation space of a data center, having a modular cage enclosure system installed in a first configuration, in accordance with one or more techniques of the disclosure. 
         FIG. 2  is a block diagram illustrating a plan view of an example data center having a modular cage enclosure system installed in a second configuration, in accordance with one or more techniques of the disclosure. 
         FIG. 3  is a block diagram illustrating a plan view of an example data center having a modular cage enclosure system in a third configuration, in accordance with one or more techniques of the disclosure. 
         FIGS. 4-6  are block diagrams illustrating example configurations of a module cage enclosure system, in accordance with one or more techniques of the disclosure. 
         FIG. 7  is a schematic diagram illustrating an axonometric view of an example door and cage panel assembly, in accordance with one or more techniques of the disclosure. 
         FIG. 8  is a schematic diagram illustrating an elevation of the example door and cage panel assembly of  FIG. 7 , in accordance with one or more techniques of the disclosure. 
         FIG. 9  is a schematic diagram illustrating in further detail how a cage panel is connected to a post in the assembly of  FIGS. 7 and 8 , in accordance with one or more techniques of the disclosure. 
         FIG. 10  is a schematic diagram illustrating an example isometric view of a post assembly, in accordance with one or more techniques of the disclosure. 
         FIG. 11  is a flowchart illustrating example installation and reconfiguration of an example modular cage enclosure system, in accordance with the techniques of this disclosure. 
     
    
    
     Like reference characters denote like elements throughout the figures and text. 
     DETAILED DESCRIPTION 
     A data center may store numerous electronic devices that produce heat, including the network, server, and storage gear, as well as power distribution units (PDUs) for distributing power to devices within the facility. The data center may be a co-location facility in which multiple customers co-locate their network equipment. Customers may require security measures to ensure that only they have access to their equipment. To ensure the proper level of security, the provider of the data center facility may provide customer cage enclosures that provide secure locations for customer equipment. The customer cage enclosures may have lockable doors with security features, such as biometric access controls, for example. 
     Data center storage needs of co-location facility customers may change over time. For example, an existing customer may later require a larger customer cage enclosure than initially obtained. As another example, a customer requiring a larger enclosure may leave the co-location facility, and the co-location facility provider may wish to replace the larger enclosure with multiple smaller enclosures to house multiple other customers. The disclosure describes a modular cage enclosure system based on a specific planning grid, to provide flexibility in configuring and reconfiguring colocation space within the data center to easily accommodate changing customer needs. The modular cage enclosure system may avoid a need to manufacture custom-sized cage enclosure panels that may later be unusable for future customer needs. 
       FIG. 1  is a block diagram illustrating a plan view of an example data center colocation space  10  of a data center, having a modular cage enclosure system installed in a first configuration, in accordance with one or more techniques of the disclosure. Data center colocation space  10  may be shared by multiple customers (or “tenants”) of the data center. The first configuration includes an eight-tile wide dual row arrangement, where “dual row” refers to two rows of cabinets  20 . 
     A floor of the data center colocation space may include a plurality of floor tiles  12 . In some examples, the floor may be a raised floor that provides a structural floor elevated above a solid base material. The space between the structural floor and the base material can be used for passage of mechanical or electrical services, cool air distribution, or other features. In these examples, the structural floor may include floor tiles  12 , pedestal supports, and a metal framework forming a grid, upon which the floor tiles are removably positioned. In other examples, a raised floor system may not be used and the floor may be a concrete slab without floor tiles. 
     The modular cage enclosure system includes a plurality of posts  14  and a plurality of cage panels removably coupled to the posts  14 . In some examples, posts  14  may be hollow, to receive post extensions. Posts  14  are installed such that they extend vertically outward from the floor (perpendicular to the plane of a horizontal floor). Posts  14  may be, for example, 2-inch square posts. Posts  14  may include base plates for affixing the posts  14  to a floor of the data center colocation space  10 , and top mounting plates for affixing the posts  14  to a ceiling structure of the data center colocation space  10 . In some examples, posts  14  may include symmetric base plates and asymmetric top mounting plates. Posts  14  may be, for example, 2 inch by 2 inch by 14 gauge square steel tubes with a 2 inch by 7 inch by ¼ inch steel flat base plate punched to accept two ⅜ inch diameter anchors. 
     The plurality of cage panels includes at least a first plurality of cage panels  16 A having a first nominal width n, and a second plurality of cage panels  16 B having a second nominal width 2n, where n is a modular value (modulus). In the example of  FIG. 1 , the nominal width of the cage panels  16 B is double the nominal width of the cage panels  16 A. In a system having at least two posts and a panel, the center line of a first post to the center line of a second post is on the modular increments. The nominal width of a cage panel may be obtained based on an actual measurement from a center of the first post, across the width of the panel, to a center of the second post. 
     In some examples, the modular cage enclosure system includes only two different panel widths. In other examples, the modular cage enclosure system may include more than two panel widths. That is, although shown for purposes of example in  FIG. 1  as including only nominal width n and nominal width 2n, in other examples, a modular cage enclosure system may include panels having other nominal widths also based on the modular increment. 
     Cage panels  16 A- 16 B (“cage panels  16 ”) have nominal widths that are modular increments, meaning that each of the nominal widths are congruent modulo n and any of the nominal widths divided by the modulus n has a remainder of zero. In other words, the nominal widths of each of cage panels  16  is congruent based on the modulus n. In some examples, the value of the modulus may be selected based on dimensions of infrastructure in the data center colocation space, such as a length or width of server cabinets in the storage space, or the dimensions of tiles in a floor of the data center colocation space, for example. Each of cage panels  16  along the width dimension makes up part of the perimeter of at least one customer cage area. In some cases, multiple customer cages may define respective perimeters that share a cage panel, with a first face of the cage panel facing a first customer cage area and a second face of the cage panel facing a second customer cage area. Because it divides one customer cage area from another customer cage area, such a shared cage panel may be referred to as a “dividing panel.” Any combination of a subset of the plurality of cage panels coupled in a common orientation to a subset of the plurality of posts has a combined width, between respective centers of end posts of the subset of the plurality of posts, that is congruent based on the modulus. 
     Where the modulus is n, the nominal width of cage panels  16 A is n, and the nominal width of cage panels  16 B is 2n. The nominal width of any panel is greater than its actual width, such that a panel having a nominal width of 2n could be replaced in the same space with one post and two panels having nominal width n. Thus, the actual width of each panel  16 A,  16 B is based on the nominal width of the panel minus the width of one post. That is, the actual width of a panel having nominal width n is n−p, where p is the width of a post. The actual width of cage panel  16 B is 2n−p. Thus, the actual width of cage panels  16 B may be replaced by one post and two of cage panels  16 A, because 2n−p=p+2(n−p). Similarly, a panel having nominal width of 3n could be replaced in the same space with three panels each having nominal width of n and two posts. Alternatively, a panel having nominal width of 3n could be replaced in the same space with one post, one panel having nominal width of n, and one panel having nominal width of 2n. The term “actual width” refers to the actual physical width of the panel as measured by any typical measuring apparatus. 
     As one example, where the nominal widths of the cage enclosure panels are selected based on 24-inch by 24-inch floor tiles (60.96 cm), the modulus may be chosen as twenty-four inches. In some examples, the dimensions of the floor tiles may refer to nominal dimensions of the floor tiles, while in other examples, the dimensions of the floor tiles may refer to actual dimensions of the floor tiles. In this example, where posts are two inches square, cage panels  16 A may have a nominal width of twenty-four inches, and an actual width of twenty-two inches. In some examples, the actual post widths may be slightly greater than 2 inches, requiring the actual dimension n to be slightly less than 22 inches to compensate, to avoid an “dimensional creep” effect in continuous runs of panels and posts. Cage panels  16 B may have a nominal width of forty-eight inches (121.92 cm) and an actual width of forty-six inches (116.84 cm). In this example, the modular cage enclosure system described herein provides the ability to replace a cage panel  16 B having a nominal width of forty-eight inches with a post and two cage panels  16 A having nominal widths of twenty-four inches in the same space. 
     As another example, where the nominal widths of the cage enclosure panels are selected based on 600 mm by 600 mm floor tiles, the modulus may be chosen as 600 mm. In this example, where posts  14  are 50 mm square, cage panels  16 A may have a nominal width of 600 mm, and an actual width of 550 mm. Cage panels  16 B may have a nominal width of 1200 mm and an actual width of 1150 mm. Cage panels  16 B may similarly be replaced with a post and two cage panels  16 A in the same space. 
     In this manner, when the customer cage enclosures  18  are installed in a data center colocation space  10 , a center of each post  14  can be aligned with an edge of one or more floor tiles  12 , such as the adjoining edge of two neighboring floor tiles  12 . For example, the center of a post  14  may be located at an intersection point of corners of four floor tiles  12 . Selecting the cage panel dimensions for a modular cage enclosure system based on the size of floor tiles may have one or more advantages. For example, where the floor is a raised floor, using cage panels with widths that correspond to floor tile dimensions may allow the weight of cage posts and panels to be aligned with raised floor support structures. This may allow for improved distribution of weight across the data center floor, and may potentially improve overall structural integrity of the data center colocation space. 
     As another example, the modulus for the modular cage enclosure system may be selected as a function of dimensions of server cabinets  20 . For example, the modulus n may be selected such that 2n=5w, where w is the width of a server cabinet. In this example, for server cabinets having a width of 24 inches, the modulus may be n=60 inches (5 feet (152.4 cm)). The width of the server cabinets may refer to a nominal width of the server cabinets. Panels in such a system may have nominal widths of 5 feet or 10 feet (n or 2n), and actual widths of 58 inches and 118 inches. This may allow for easy construction of cage enclosures that can accommodate at least five server cabinets, with the ability to swap out 10-foot panels with two nominal 5-foot panels and one two-inch post. This can allow for a cage enclosure having first dimensions to be divided into two cage enclosures having second (smaller) dimensions, because a dividing partition can be added to the newly added two-inch post. The dividing partition may be perpendicular to the orientation of the 5-foot panels. 
     Because any combination of a subset of the plurality of cage panels coupled in a common orientation to a subset of the plurality of posts has a combined width that is a modular increment of the modular value, the modular cage enclosure system described herein provides flexibility for data center administrators or customers to build any cage size having dimensions divisible by the modular increment (e.g., 24-inch increments). Further, data center colocation space  10  can easily be repurposed to fit different customer needs and accommodate multiple co-located customers, without requiring the use of customized cage enclosure components. For example, the modular cage enclosure system provides the ability to easily add or remove the dividing partitions between back-to-back cages, and to easily move the location of the existing dividing partitions between back-to-back cages, to change dimensions of the customer cage enclosures. The addition, removal, or adjustment of dividing partitions may be simplified because the modular dimensions of the panels enable adjusting as few as two of the side panels in the back-to-back customer cage enclosures while leaving the remainder of the side panels untouched. 
     Customer cage enclosures  18 A- 18 D (“customer cage enclosures  18 ”) are installed in data center colocation space  10  based on needs of data center administrators and/or customers/tenants of the data center. In some examples, each of customer cage enclosures  18  is leased by a different customer of the data center. Customer cage enclosures  18  securely contain network equipment owned or leased by the respective customers. Each of customer cage enclosures  18  may include a door assembly  22 . Door assemblies  22  may include a door and an adjacent door panel configured to include a biometric security device and an in-mesh demarcation panel, for example. Door assemblies  22  may have a width of 3n, in some examples. In this way, a door assembly  22  could be replaced with a 2n-width panel, a post, and an n-width panel. In some examples, both the strike and hinge posts  14  in door assembly  22  may include openings to accommodate the strike box and wiring for the biometric reader and electrified hinge. One example of such a post is described in further detail with respect to  FIG. 10 . 
     In the example of  FIG. 1 , customer cages  18  are installed in an arrangement corresponding to an eight-tile wide dual row of server cabinets  20 . In this example, customer cage enclosure  18 A is installed with a first side having a width of four cage panels, each of the cage panels having a nominal 2n width, to span a combined width aligned with eight floor tiles. A second side of customer cage enclosure  18 A, opposite the first side, has two cage panels of nominal 2n width, one cage panel of nominal 1n width, and a 3n wide door assembly  22  consisting of a door, post and a biometric reader/demarcation panel section. Customer cage enclosure  18 A has a third side having a combined width made up of two cage panels of nominal 2n width and one cage panel of nominal 1n width, to span a combined width aligned with five floor tiles. Customer cage enclosure  18 A has a fourth side, opposite the third side, having the same configuration as the third side. 
     Customer cage enclosures  18  house a plurality of cabinets  20 . In some examples, cabinets  20  may be 600 mm wide (twenty-four inch nominal width). Cabinets  20  may have depths between 1000 mm (40 inch nominal depth) and 1200 mm (48 inch nominal depth). Cabinets having other widths and/or depths may also be used. Cabinets  20  (sometimes also called “racks”) may be server cabinets, network cabinets, or other cabinets, and typically include frames for mounting one or more types of equipment, such as servers, switches, routers, patch panels, uninterruptible power supplies (UPSs), monitors, and other equipment. 
     Data center colocation space  10  is part of an overall data center. Data center colocation space  10  may store network and/storage gear or any other suitable electronic or supporting devices. The data center may additionally include one or more cooling units that cool and supply air to data center colocation space  10 . When in use, server exhaust is released from servers in cabinets  20 . Warm air, including server exhaust is returned as return air to be cooled and recirculated by the cooling unit. The data center may be situated in a stand-alone building used primarily or exclusively for the data center, or may be situated in a portion of a larger building used for other uses including office space, residential space, retail space, or any other suitable use. The data center may be in an urban, suburban, or rural location or any other suitable location with any suitable climate. The data center may provide an operating environment for co-location, interconnection, and/or other services. For example, the data center may provide an operating environment for any number of services that may be categorized according to service types, which may include, for example, applications/software, platforms, infrastructure, virtualization, and servers and data storage. The names of service types are often prepended to the phrase “as-a-Service” such that the delivery of applications/software and infrastructure, as examples, may be referred to as Software-as-a-Service (SaaS) and Infrastructure-as-a-Service (IaaS), respectively. 
     Servers housed by cabinets  20  may be systems that respond to requests across a computer network to provide, or help to provide, a network or data service. Each of the servers may include one or more processors that execute software that is capable of accepting requests from clients. Requests from clients may be to share data, information, or hardware and software resources. The servers may include one or more of a database server, file server, storage server, mail server, print server, web server, gaming server, application server, communication server, compute server, media server, or any other suitable type of server that may be employed by a data center provider or tenant of the data center provider, according to particular needs. The servers may be specialized or general-purpose devices. The servers may represent x86 or other real or general-purpose servers configured to apply and/or offer services to customers. The servers may also include special-purpose appliances or controllers for providing interconnection services between customers of a co-location facility provided by the data center or for providing any other suitable services according to particular needs. 
     Customer cage enclosure  18 A encloses six cabinets  20  arranged in two rows of three cabinets  20 . Customer cage enclosure  18 B encloses twelve cabinets  20  arranged in four rows of three cabinets  20 . Customer cage enclosure  18 C encloses ten cabinets  20  arranged in two rows of five cabinets  20 . Customer cage enclosure  18 D encloses twenty cabinets  20  arranged in four rows of five cabinets  20 . 
     In some examples, the data center may employ a cooling air supply system delivering the cooling air as a horizontal stream, or a vertical downflow from a ceiling or a higher level, or as vertical upflow from a raised floor, for cooling electronic devices within the data center. Servers and other equipment may pull cool air from streams of cool air in relatively cooler “cold aisles”  21  as needed and discharge warm server exhaust into contained “hot aisles”  23  that are relatively hotter. Hot aisles  23  are formed by hot air containment units that separate the hot and cold aisles  21  and include air containment doors. The air containment doors provide access to hot aisles  23 . In some examples, the ceiling structure may be a dropped ceiling structure that forms a plenum between the dropped ceiling and an actual ceiling of the data center colocation space. The plenum may collect hot air from the hot aisles  23 , for example. The warm server exhaust may be returned to a cooling unit as return air for cooling and recirculation in cool air streams in the cold aisles  21 . Alternatively or in addition, cool outdoor air may be supplied as a portion of the cool air streams supplied by the cooling unit to the cold aisles. In the example of  FIG. 1 , cool air may be returned to cold aisles  21  by perforated floor tiles between the rows of cabinets  20 . 
       FIG. 2  is a block diagram illustrating a plan view of an example data center colocation space  10  having a modular cage enclosure system installed in a second configuration, in accordance with one or more techniques of the disclosure. The second configuration is a nine-tile wide dual row arrangement. Customer cage enclosures  25 A,  25 B, and  25 C each enclose six cabinets arranged in two rows of three cabinets. The nine-tile wide arrangement may allow for a larger cabinet size than in an eight-tile wide arrangement. Customer cage enclosure  25 D encloses ten cabinets arranged in two rows of five cabinets. Customer cage enclosure  25 E encloses twenty cabinets arranged in four rows of five cabinets. The example of  FIG. 2  illustrates a cage enclosure layout in which the perimeter partitions that extend in one direction (here, north-to-south) are offset from the edges of the perforated floor tiles, to allow the rows of perforated floor tiles in the cold aisles  21  to remain unobstructed by the cabinets  20 . 
     In  FIG. 2 , for example, the modular cage enclosure system of  FIG. 1  may have been modified (e.g., partially uninstalled and reinstalled) to convert from an eight-tile wide dual row of  FIG. 1  to the nine-tile wide dual row configuration of  FIG. 2 . For example, customer cage enclosure  18 A of  FIG. 1  may be modified to form customer cage enclosure  25 A of  FIG. 2  by replacing a nominal 24-inch panel next to the door assembly with a nominal 48-inch door panel, and adding a new nominal 24-inch panel to a south perimeter partition of customer cage enclosure  18 A to increase the width of the south perimeter partition by from eight floor tiles to nine floor tiles. 
     As another example, the single customer cage enclosure  18 B of  FIG. 1  may be modified to form two customer cage enclosures  25 B and  25 C of  FIG. 2  in a similar manner, by replacing each of the nominal 24-inch panel next to the door assemblies with nominal 48-inch panels, and adding two new nominal 24-inch panels to the south perimeter partition of customer cage enclosure  18 B to increase the width of the south perimeter partition by from sixteen floor tiles to eighteen floor tiles. In addition, a new partition  26  made up of multiple panels removably attached to new or existing posts of customer cage enclosure  18 B may be added to divide customer cage enclosure  18 B of  FIG. 1  into the two customer cage enclosures  25 B and  25 C of  FIG. 2 . In some examples, customer cage enclosures  25 B and  25 C of  FIG. 2  may be used to house equipment of two different customers of the data center. 
     The modular cage system described herein may be particularly useful during a cage design phase, because its modular nature allows for straightforward modification using the basic planning grid of the modularity. In some cases, it may not be practical to change the overall width of customer cage enclosures after installation, other than by removing dividing partitions, because the overall perimeter of the cage space is typically fixed by corridors and walls within the colocation facility, so any width increase in one case results in a decrease in an adjoining cage (which may be currently occupied by another customer and thus not changeable). There may also be fixed items such as structural columns, remote power panels, lighting, ducts, perforated floor tiles, and cable tray and air containment systems, for example, which may interfere with making certain changes to customer cage perimeter wall dimensions. 
       FIG. 3  is a block diagram illustrating a plan view of an example data center colocation space  10  having a modular cage enclosure system in a third configuration, in accordance with one or more techniques of the disclosure. The third configuration includes cage enclosures in a ten-tile wide dual row arrangement (e.g., customer cage enclosures  30 C and  30 H), and cage enclosures in a five-tile wide single row arrangement (e.g., customer cage enclosures  30 A,  30 B,  30 D,  30 E,  30 F,  30 G,  30 I, and  30 J). 
     For example, the modular cage enclosure system of  FIG. 1  may have been modified (e.g., partially uninstalled and reinstalled) to convert from an eight-tile wide dual row of  FIG. 1  or the nine-tile wide dual row of  FIG. 2  to the the-tile wide dual row and five-tile wide single row configuration of  FIG. 2 . The configuration of  FIG. 3  uses the same modular cage enclosure system basic building blocks of posts, nominal 1n panels, and nominal 2n panels. The modular cage enclosure system provides a flexible, adaptable system for customer cage enclosures that can be modified to meet changing customer needs. 
       FIGS. 4-6  are block diagrams illustrating example configurations of a module cage enclosure system, in accordance with one or more techniques of the disclosure.  FIG. 4  illustrates twelve different example configurations that may be installed in the same data center colocation area footprint using the modular cage enclosure system described herein. 
     Because servers and/or other devices stored in cabinets of the data center colocation space operate more efficiently and/or reliably within a specific temperature range, it may be desirable to keep air in portions of the data center colocation space within the temperature range. Cabinets storing servers may be arranged in rows within the data center colocation space. Rows may be positioned between “cold aisles” for supplying cool supply air to servers and “hot aisles” for collecting server exhaust and diverting server exhaust to an exhaust plenum. In the view of  FIGS. 4-6 , cabinets are viewed as oriented such that an exhaust side of the servers is directed out the right-hand side of the cabinets. In the example of  FIGS. 4-6 , where the right-hand side of the cabinets is contained, the arrangement is referred to as a hot-aisle containment (HAC) arrangement in which a hot aisle collects and diverts exhaust from the servers. Where the left-hand side of the cabinets is contained, the arrangement is referred to as a cold-aisle containment (CAC) arrangement in which temperature of a cold aisle is maintained within a suitable temperature range by the introduction of cooled air, and the rest of the space in the cage is hotter due to exhaust from the servers being released outside the containment area. 
     Row  40  illustrates ten-foot wide, single row hot-aisle containment (HAC) arrangements having 600 mm by 1000 mm (nominal twenty-four-inch by forty-inch) cabinets. Arrangement  41 A illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures securely separated by a dividing partition  46 , a first customer cage enclosure enclosing six cabinets and a second customer cage enclosure enclosing seven cabinets. Arrangement  41 B illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing five cabinets and a second customer cage enclosure enclosing eight cabinets. Arrangement  41 C illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing four cabinets and a second customer cage enclosure enclosing nine cabinets. Arrangement  41 D illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing three cabinets and a second customer cage enclosure enclosing ten cabinets. For example, to reconfigure the customer cage enclosures in  41 A to those of arrangement  41 B, only the panels adjacent to the dividing partition  46  need to be re-arranged, by swapping the 2n panels and the n panels on either side of the dividing partition  46  and moving the existing dividing partition  26  panels to the new post locations corresponding to the new 2n panels, n panels arrangement. The rest of the panels in the customer cage enclosures need not be adjusted. 
     Row  42  illustrates ten-foot wide, single row cold aisle containment (CAC) arrangements having 600 mm by 1000 mm (nominal twenty-four-inch by forty-inch). Arrangement  43 A illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing six cabinets and a second customer cage enclosure enclosing seven cabinets. Arrangement  43 B illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing five cabinets and a second customer cage enclosure enclosing eight cabinets. Arrangement  43 C illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing four cabinets and a second customer cage enclosure enclosing nine cabinets. Arrangement  43 D illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing three cabinets and a second customer cage enclosure enclosing ten cabinets. 
     Row  44  illustrates ten-foot wide, single row cage arrangements having 600 mm by 1200 mm (nominal twenty-four-inch by forty-eight-inch). Arrangement  45 A illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing six cabinets and a second customer cage enclosure enclosing seven cabinets. Arrangement  45 B illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing five cabinets and a second customer cage enclosure enclosing eight cabinets. Arrangement  45 C illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing four cabinets and a second customer cage enclosure enclosing nine cabinets. Arrangement  45 D illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing three cabinets and a second customer cage enclosure enclosing ten cabinets. Arrangements  41 A- 41 D,  43 A- 43 D, and  45 A- 45 D each have a plurality of cage panels and a plurality of posts arranged to form perimeter partitions of the customer cage enclosures. The perimeter partitions can be reconfigured to adjust the dividing partition (e.g., dividing partition  46 ) by replacing cage panels in the perimeter partition with other cage panels having different nominal widths, or swapping the order of the cage panels in the perimeter partition to move a location of the dividing partition  46  coupled to a post between the swapped cage panels. 
       FIG. 5  illustrates ten different example configurations that may be installed in the same data center colocation area footprint using the modular cage enclosure system described herein. Row  50  includes eighteen-foot wide, dual row cold-aisle containment (CAC) cages having 600 mm by 1200 mm (nominal twenty-four-inch by forty-eight-inch) and a centered cold aisle location. Arrangement  51 A illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing twelve cabinets and a second customer cage enclosure enclosing twelve cabinets. Arrangement  51 B illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing ten cabinets and a second customer cage enclosure enclosing fourteen cabinets. Arrangement  51 C illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing eight cabinets and a second customer cage enclosure enclosing sixteen cabinets. Arrangement  51 D illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing six cabinets and a second customer cage enclosure enclosing eighteen cabinets. Arrangement  51 E illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing four cabinets and a second customer cage enclosure enclosing twenty cabinets. 
     Row  52  includes eighteen-foot wide, dual row hot-aisle containment (HAC) cages having 600 mm by 1200 mm (nominal twenty-four-inch by forty-eight-inch) cabinets and a centered cold aisle location. Arrangements  53 A- 53 E are identical to those of  51 A- 51 E, as far as numbers of cabinets per customer cage enclosure in the various arrangements. Only the quantities and locations of the air containment doors have changed. 
     Row  60  of  FIG. 6  illustrates five different example configurations that may be installed in the same data center colocation area footprint using the modular cage enclosure system described herein. Row  60  includes eighteen-foot wide, dual row hot-aisle containment (HAC) cages having 600 mm by 1200 mm (nominal twenty-four-inch by forty-eight-inch) and a centered hot aisle location. Arrangement  61 A illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing twelve cabinets and a second customer cage enclosure enclosing twelve cabinets. Arrangement  61 B illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing ten cabinets and a second customer cage enclosure enclosing fourteen cabinets. Arrangement  61 C illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing eight cabinets and a second customer cage enclosure enclosing sixteen cabinets. Arrangement  61 D illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing six cabinets and a second customer cage enclosure enclosing eighteen cabinets. Arrangement  61 E illustrates how the modular cage enclosure system may be used to configure two customer cage enclosures, a first customer cage enclosure enclosing four cabinets and a second customer cage enclosure enclosing twenty cabinets. 
     Row  62  of  FIG. 6  illustrates another five different example configurations that may be installed in the same data center colocation area footprint using the modular cage enclosure system described herein. Row  62  includes sixteen-foot wide, dual row cold-aisle containment (CAC) cages having 600 mm by 1000 mm (nominal twenty-four-inch by forty-inch) and a centered cold aisle location. Arrangements  63 A- 63 E are identical to those of  61 A- 61 E, as far as numbers of cabinets per customer cage enclosure in the various arrangements. The only difference is that location of the hot and cold aisles have been reversed. 
       FIG. 7  is a schematic diagram illustrating an axonometric view of an example door and cage panel assembly  70 , in accordance with one or more techniques of the disclosure. Door and cage panel assembly  70  includes door  72 , biometric reader/demarcation panel assembly  74 , panel  76 , posts  80 A- 80 D (“posts”), and post extensions  78 . 
     Posts  80  are hollow, to receive post extensions  78 . Posts  80  may be, for example, 2-inch square posts. Post  80 C may be a gate tube post, configured to receive electrical wiring for components of door  72 , such as a biometric panel and electrified hinges, for example. Door  72  may be attached to gate tube post  80 C by hinges. 
     Posts  80  include symmetric base plates  86 . Base plates  86  include a pair of symmetrically arranged plate extensions that can be affixed to a floor of the data center colocation space. The plate extensions of base plates  86  may have holes to accommodate anchors for fastening to concrete slabs or screws for affixing the base plates  86  of posts  80  to the raised floor assembly by screwing into one or more floor tiles, pedestals, stringers or other structural supports located below the floor tiles. 
     In the example of  FIG. 7 , base plates  86  are symmetric, and the symmetric plate extensions may be oriented perpendicular to a plane of the panel attached to the post  80 . The symmetric base plates  86  may provide stability to a cage partition and help avoid overturning in response to a force applied laterally to the cage partition. In some examples, base plates  86  may have dimensions of two inches by seven inches by ¼ inch. 
     Post extensions  78  may be inserted within the hollow posts  80 , and may enable posts  80  to have adjustable height. Post extensions  78  may be attached to (e.g., screwed into) a ceiling of the data center colocation space. In some examples, posts  80  may be two inches square and ⅛ inch thick. Post extensions  78  have smaller dimensions than posts  80 , such as 1¾ inches square. In some examples, in may be recommended that post extensions  78  be inserted at least six inches into posts  80 . 
     Post extensions  78  include asymmetric top mounting plates  87  having a single, asymmetrically arranged plate extension for attaching the post to a ceiling of the data center colocation space. The plate extension of top mounting plates  87  may have holes to accommodate bolts or screws for affixing the post  80  to a ceiling grid or structure of a data center colocation space. Post extensions  78  may be rotated relative to posts  80  before insertion such that the most suitable orientation of asymmetric top mounting plates  87  for the space may be chosen. The asymmetric shape of the top mounting plates  87  can enable the posts  80  to be installed in a corner of a data center colocation space without requiring any modification of the post extension, such as cutting off a portion of the top mounting plates. In contrast, one plate extension of symmetric base plates  86  may need to be cut off for posts  80  to fit into a corner of a data center colocation space. In some examples, asymmetric top mounting plates may have dimensions of two inches by six inches by ¼ inch. 
     In some examples, after the post extension  78  is inserted and the desired height of the post extension  78  is reached, post extensions  78  may be fastened to posts  80 . In other examples, post extensions  78  may not be fastened to posts  80 , but may be fastened only to the ceiling. The use of post extensions  78  allow posts to be easily installed in spaces having various heights. Post extensions  78  also accommodate situations where the height of the ceiling or roof structure varies within the data center colocation space. Moreover, post extensions  78  can allow for flexibility in height in the event of settling or deflection of the ceiling structure or roof structure to which the post extensions are coupled. Post extensions may be, for example, 1¾ inch by 1¾ inch by 14 gauge square tubes, welded to 2 inch by 6 inch by ¼ inch top plate. 
     In some examples, there may not be a post extension  78  attached to each post  80 . In this case, a top support or top capping bars (not shown) may be attached between the tops of posts  80  to provide additional lateral support for the cage panel assembly  70 . In some examples, the top capping bars may be 2 inch by ⅛ inch by 9 foot, ten inch long hot-rolled steel flat bar with holes 5 inches from each end and then 12 inches o.c. in between; 2¼ inch by 1 inch and 3½ inch by 1 inch cold-rolled steel channels. Capping channel, if required, may be installed with legs up to allow for installation of demarcation box aligned with top of cage panels. 
     In some examples, the cage panel assemblies may include horizontal panel stiffeners (not shown). Horizontal panel stiffeners may include, for example, two of ½ inch by 1 inch by ⅛ inch cold-rolled steel channels, bolted or riveted toe to toe with wire woven through; or ¼ inch by ¾ inch thick hot rolled flat stock, located where indicated on the drawings and welded to wire mesh and vertical frames. In some examples, cage panels may be attached to a wall of data center colocation space  10  by wall cops, such as near the top and bottom of the cage panels. 
       FIG. 8  is a schematic diagram illustrating an elevation of the example door and cage panel assembly  70  of  FIG. 7 , in accordance with one or more techniques of the disclosure. Panel  76  has a nominal width that is a modular increment, meaning that any of the nominal widths divided by the modulus has a remainder of zero. In some examples, the value of the modulus may be selected based on dimensions of infrastructure in the data center colocation space, such as a length or width of server cabinets in the colocation space, or dimensions of tiles in a floor of the data center colocation space. Panel  76  has a nominal width of 2n. 
     As one example, where the nominal widths of the cage enclosure panels are selected based on 24-inch by 24-inch floor tiles, the modulus may be chosen as twenty-four inches. In this example, where posts are two inches square, panel  76  may have a nominal width of forty-eight inches and an actual width of forty-six inches. The door assembly that includes panel  72 , post  80 C, and panel  74  may have a nominal total width of seventy-two inches, and an actual total width of seventy inches. In some examples, panel  74  alone may have an actual width 24⅛ inches wide, and door panel  72  may have an actual width of 43⅞ inches. 
     As another example, where the nominal widths of the cage enclosure panels are selected based on 600 mm by 600 mm floor tiles, the modulus may be chosen as 600 mm. In this example, where posts are 50 mm square, panel  76  may have a nominal width of 1200 mm and an actual width of 1150 mm. The door assembly that includes panel  72 , post  80 C, and panel  74  may have a nominal width of 1800 mm, and an actual width of 1750 mm. 
     Panels  74 ,  76  may be 7 feet, 9 inches high, in some examples. In some examples, the panels may be mounted to posts such that the panels are elevated 3 inches above the floor, such that the top of the panels is 8 feet above the floor. When installed, a top of door may be aligned with the top of adjacent panels. For doors that do not extend full height of partition, a transom may be provided over the door, fabricated from same mesh and framing as partition panels. Hinges may be, for example, 4½ inch by 4½ inch, 2 pairs per door; welded or screwed to door and jamb; removable at electrified locations. 
     In some examples, a removable portion of panel  74  may be removed and a demarcation point cabinet may be installed in its place, as described in U.S. Pat. No. 8,650,805, entitled “SYSTEMS AND METHODS FOR DMARC IN A CAGE MESH DESIGN,” issued Feb. 18, 2014, the entire contents of which are incorporated by reference herein. The demarcation point cabinet provides network connectivity between network equipment in the cage and one or more networks, including for connecting to one or more exchanges, such as an Internet Exchange, Ethernet Exchange, or Cloud Exchange, for example. One or more cross-connects may be installed from the network(s) through the demarcation point cabinet to network wiring of the customers, such as to one or more customer cabinets within the cage. In examples where the demarcation point cabinet is slightly smaller than the removable portion of panel  74 , an additional infill panel piece is also installed to fill the remaining open gap. 
       FIG. 9  is a schematic diagram illustrating in further detail how a cage panel  76  is connected to a post  80 A in the assembly of  FIGS. 7 and 8 , in accordance with one or more techniques of the disclosure. Post  80 A is a two-inch by two-inch panel tube post. Panel  76  includes a woven wire  94  attached to a frame  90 . In some examples, wire  94  may be tack welded to an angle frame. In some examples, wire  94  may be clinched to framing. The wire  94  may be 10 gauge wire (0.135-inch diameter) (e.g., steel wire), spaced 1-inch by 1-inch. The angle frame may be 1¼ inch by 1¼ inch, for example. 
     In some examples, the woven wire  94  has an intermediate crimp, in which wires pass over one and under the next adjacent wire in both directions, with wires crimped before weaving and with extra crimps between the intersections. In some examples, the woven wire  94  has a lock crimp, with deep crimps at points of the intersection that lock wires securely in place. 
     The frame  90  of panel  76  may be fastened to post  80  by fastening means  96 , such as screws, bolts, nails, staples, welding, or the like. In some examples, panel  76  may be fastened to post  80  by ¼ inch by ¼ inch screws. An angle aligner tab  92  may be attached to panel  76  and post  80 A to facilitate proper alignment of the panel  76  relative to post  80 A. 
       FIG. 10  is a schematic diagram illustrating an example isometric view of an example post assembly  100 , in accordance with one or more techniques of the disclosure. The post assembly  100  may a gate tube post such as gate tube post  80 C of  FIGS. 7 and 8 , and may be on the hinge side of a door such as door  72 . Post assembly  100  includes a hollow post  80 C having a symmetric base plate  86  with screw holes, and an asymmetric top mounting plate  87  with screw holes. The top mounting plate  87  may also include a hole, such as 1¼ inches in diameter, for passage of line voltage for electrified hinges. The post assembly includes an extension tube post  78  that inserts into the tube post with an unrestricted slip fit. The extension tube post may insert up to six inches into the tube post, in some examples. In some examples, the extension tube post is 14-gauge metal, and the tube post is 12-gauge metal. The tube post may include holes to receive electrified hinges, and holes for electrified hinge wire harness clearance (not shown in  FIG. 10 ). The tube post may also include a notch opposite the holes for a wire chase to the biometric panel (not shown in  FIG. 10 ). The tube posts may be cold-formed structural-steel tubing, in some examples. 
     Example design details for the cage mesh partitions are described below. These examples may be applied to any of the foregoing examples. In some examples, various elements of the cage panels and posts may be made of steel. Some elements may be metallic-coated steel sheets, such as commercial steel with G60 zinc (galvanized) or A60 zinc-iron-alloy (galvannealed) coating designation. In some examples, elements may have seismic bracing, i.e., angles with legs not less than 1¼ inch wide, formed from 0.04-inch-thick, metallic-coated steel sheet; with bolted connections and ¼-inch-diameter bolts, as required. In some examples, panel-to-post fasteners may include one or more of steel bolts, nuts, screws and washers. 
     In some examples, such as where the modular cage enclosure system is installed on a concrete slab floor (rather than a raised floor) posts may be installed using expansion anchors in concrete having capability to sustain, without failure, load imposed within factors of safety indicated. The anchors may include drop-in anchors, and may be zinc-plated carbon steel, for example. In some examples, posts may be installed using powder-actuated fasteners in concrete, which may include a fastener system of type suitable for application indicated and fabricated from corrosion-resistant materials; with clips or other accessory devices for attaching hangers of type indicated, and with capability to sustain, without failure, a load equal to 10 times that imposed by wire mesh construction. However, in some cases powder-actuated fasteners would not be used to attach cage mesh system components to floor surfaces other than concrete slabs. Post base plate fasteners at raised floor tiles may include steel bolts, nuts, screws, plates and washers as required for base plate attachment to top and bottom of floor tiles and/or stringers. 
       FIG. 11  is a flowchart illustrating example installation and reconfiguration of an example modular cage enclosure system, in accordance with the techniques of this disclosure. A method includes installing, within a data center, a customer cage enclosure having first dimensions, the customer cage enclosure comprising a plurality of posts, and a plurality of cage panels ( 150 ), wherein each of the cage panels is removably coupled to one or more of the plurality of posts, wherein a nominal width of each of the cage panels is congruent based on a modulus, wherein an actual width of each of the cage panels is equal to a difference between the nominal width of the cage panel and the width of one of the plurality of posts, and wherein any combination of a subset of the plurality of cage panels coupled in a common orientation to a subset of the plurality of posts has a combined width, between respective centers of end posts of the subset of the plurality of posts, that is congruent based on the modulus, wherein installing comprises arranging one or more of the plurality of cage panels and two or more of the plurality of posts to form a perimeter partition of the customer cage enclosure. The method also includes reconfiguring a portion of the perimeter partition of the customer cage enclosure to adjust a dividing partition of the customer cage enclosure perpendicular to at least a portion of the perimeter partition, by replacing at least a first cage panel of the plurality of cage panels in the perimeter partition with at least a second cage panel of the plurality of cage panels, the first cage panel having a first nominal width and the second cage panel having a second nominal width different than the first nominal width ( 152 ). 
     In some examples, reconfiguring the perimeter partition of the customer cage enclosure to adjust the dividing partition includes replacing the first cage panel, a third cage panel of the plurality of cage panels having the first nominal width, and a post coupled to the first cage panel and the third cage panel, with the second cage panel, and removing the dividing partition, wherein the dividing partition comprises at least a fourth cage panel coupled to the post coupled to the first cage panel and the third cage panel. 
     In some examples, reconfiguring the perimeter partition of the customer cage enclosure to adjust the dividing partition comprises converting the customer cage enclosure to two smaller customer cage enclosures, wherein converting includes replacing the second cage panel with: the first cage panel, a third cage panel of the plurality of cage panels having the first nominal width, and a post coupled to the first cage panel and the third cage panel, and adding the dividing partition, wherein the dividing partition comprises at least a fourth cage panel coupled to the post coupled to the first cage panel and the third cage panel. 
     In some examples, reconfiguring the perimeter partition of the customer cage enclosure to adjust the dividing partition comprises moving the dividing partition, wherein moving the dividing partition includes replacing the second cage panel with: the first cage panel, a third cage panel of the plurality of cage panels having the first nominal width, and a post coupled to the first cage panel and the third cage panel, wherein the dividing partition comprises at least a fourth cage panel coupled to the post coupled to the first cage panel and the third cage panel. 
     In some examples, the method also includes affixing the posts to floor tiles of a data center colocation space such that a center of each of the posts is aligned with adjacent edges of the floor tiles. In some examples, installing also includes affixing the cage panels to the posts. 
     In some examples, installation may include one or more of the following example aspects. The posts are anchored to the floor. The panels are attached to the posts, such as using steel bolts, nuts, screws and washers. In some examples the panels are attached to the posts before the posts are anchored to the floor, while in other examples, the posts are anchored to the floor first, and the panels are then attached to the posts. Anchoring the posts to the floor where the floor is a concrete slab may include anchoring with ⅜-inch diameter, post-installed expansion anchors through the holes in base plates  86  of each post, and adjusting wire mesh partition posts in floor shoes to achieve level and plumb installation. Anchoring the posts to the floor where the floor is a concrete slab may include anchoring with ⅜-inch diameter bolts with washers through base plates  86  and the access floor. 
     In some examples, an installer may anchor wire mesh partitions to walls at 12 inches o.c. through back corner panel framing and as follows: For concrete and solid masonry anchorage, use drilled-in expansion shields and hanger or lag bolts. For hollow masonry anchorage, use toggle bolts. For steel-framed gypsum board assemblies, use hanger or lag bolts set into wood backing between studs. Coordinate with stud installation to locate backing members. Install temporary shims at gaps between panels and vertical supports to provide uniform spacing. Secure top capping bar (where occurs) to top framing channels with ¼-inch-diameter “U” bolts spaced not more than 28 inches o.c. Provide line posts at locations indicated or, if not indicated, as follows: For partitions that are 7 to 9 feet high, spaced at 15 to 20 feet o.c. For partitions that are 10 to 12 feet high, located between every other panel. For partitions that are more than 12 feet high, located between each panel. Install post extensions connected to unistrut ceiling grid at locations indicated, or if not indicated, at 10 feet o.c. maximum. Provide a minimum 6″ overlap inside primary post. Post extensions may not be fastened to the primary post sleeve order to allow for vertical deflection of overhead building structural supports. May provide seismic supports and bracing as required for code compliance and stability, extending and fastening members to supporting structure. Install doors and hinges. Weld or bolt sheet metal bases to wire mesh partitions and doors where indicated. Bolt accessories to wire mesh partition framing. 
     Although the foregoing examples have been illustrated as being used to allow configuration and reconfiguration of customer cages in a data center colocation space, the assembly may be used in a variety of different applications requiring modular enclosure systems. 
     Various examples have been described. These and other examples are within the scope of the following claims.