Abstract:
A redirected USB device that does not fall within well-defined device-classes requires special treatment as redirection software will not always permit the servicing of universal serial bus request blocks (URB) on the same thread that the URBs are received. This results in the redirected USB device not functioning properly. A virtual USB bus driver may intercept the URBs so that a temporary kernel buffer can be created. The temporary kernel buffer stores the data necessary for processing the URBs. The temporary kernel buffer is queued along with the URB so that regardless of the thread for processing the URB, the data associated with the URB is preserved so that the vendor-specific application at the client may properly service any request.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates generally to information handling systems and, more particularly, to URB preserving data associated with universal serial bus block requests so that the vendor-specific application at the client may properly service any request. 
       BACKGROUND 
       [0002]    As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more information handling systems, data storage systems, and networking systems. 
         [0003]    A thin client, or as it is sometimes referred to a lean client or a slim client, is an information handling system or an executable software program running on an information handling system. A thin client generally relies on another information handling system, such as a server, to fulfill at least some of the requested computational roles. For example, a user can access applications or other computational support services from a server by logging into the server from a thin client, for example, a terminal device. Multiple users may log into the same server from multiple terminal devices and may simultaneously request services from the server. 
         [0004]    A user may connect a particular universal serial bus (USB) device to a local client device. Many USB devices fall within well-defined device classes, for example, mass storage devices. When devices fall within these well-defined classes, the operating system drivers or equivalent provide all necessary support for the USB device functionalities at the kernel-level itself. When the USB device does not fall within one of the well-defined device classes, the vendor for the USB device provides the necessary support for the USB device either through one or more applications, kernel drivers, etc. Many times the vendor will provide the necessary support via an application and a minimal driver. In general, the application will communicate with the USB device by issuing certain USB request block (URB) commands to the USB device driver. The driver posts the request associated with the command to the USB device from the same thread initiated by the application. That is, the application memory associated with the command and the USB device remains valid. 
         [0005]    A problem arises when a USB device is connected by a user that is not within a well-defined class and that USB device is redirected to a server where the USB device is virtualized. When such vendor-specific USB devices are redirected, all the requests associated with the USB device will be queued and serviced in an arbitrary thread. This results in the USB device not functioning properly with the USB redirection/virtualization software. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    For a more complete understanding of the present invention and its features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
           [0007]      FIG. 1  is a block diagram of selected elements of an information handling system. 
           [0008]      FIG. 2  is an example of a network environment of one embodiment according the present disclosure. 
           [0009]      FIG. 3  is an example of a driver stack for one embodiment according to the present disclosure. 
           [0010]      FIG. 4  is an example of a method for one embodiment according to the present disclosure. 
           [0011]      FIG. 5  is an example of a method for one embodiment according to the present disclosure. 
           [0012]      FIG. 6  is an example of a method for one embodiment according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The detailed description set forth below is intended as a description of various configurations of the subject technology and is not intended to represent the only configurations in which the subject technology may be practiced. The appended drawings are incorporated herein and constitute a part of the detailed description. The detailed description includes specific details for the purpose of providing a thorough understanding of the subject technology. However, it will be apparent to those skilled in the art that the subject technology may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring the concepts of the subject technology. 
         [0014]    In the following description, details are set forth by way of example to facilitate discussion of the disclosed subject matter. It should be apparent to a person of ordinary skill in the field, however, that the disclosed embodiments are exemplary and not exhaustive of all possible embodiments. 
         [0015]    For the purposes of this disclosure, an information handling system may include an instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize various forms of information, intelligence, or data for business, scientific, control, entertainment, or other purposes. For example, an information handling system may be a personal computer, a PDA, a consumer electronic device, a network storage device, or another suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include memory, one or more processing resources such as a central processing unit (CPU) or hardware or software control logic. Additional components or the information handling system may include one or more storage devices, one or more communications ports for communicating with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling system may also include one or more buses operable to transmit communication between the various hardware components. 
         [0016]    Herein, a computer-readable non-transitory storage medium or media may include one or more semiconductor-based or other integrated circuits (ICs) (such, as for example, field-programmable gate arrays (FPGAs) or application-specific ICs (ASICs)), hard disk drives (HDDs), hybrid hard drives (HHDs), optical discs, optical disc drives (ODDs), magneto-optical discs, magneto-optical drives, floppy diskettes, floppy disk drives (FDDs), magnetic tapes, solid-state drives (SSDs), RAM-drives, SECURE DIGITAL cards or drives, any other suitable computer-readable non-transitory storage media, or any suitable combination of two or more of these, where appropriate. A computer-readable non-transitory storage medium may be volatile, non-volatile, or a combination of volatile and non-volatile, where appropriate. 
         [0017]    Particular embodiments are best understood by reference to  FIGS. 1-6 , wherein like numbers are used to indicate like and corresponding parts. 
         [0018]      FIG. 1  illustrates an example information handling system  100 . In particular embodiments, one or more information handling systems  100  perform one or more steps of one or more methods described or illustrated herein. In particular embodiments, one or more information handling systems  100  provide functionality described or illustrated herein. In particular embodiments, software running on one or more information handling systems  100  performs one or more steps of one or more methods described or illustrated herein or provides functionality described or illustrated herein. Particular embodiments include one or more portions of one or more information handling systems  100 . Herein, reference to an information handling system may encompass a computing device, and vice versa, where appropriate. Moreover, reference to an information handling system may encompass one or more information handling systems, where appropriate. 
         [0019]    This disclosure contemplates any suitable number of information handling systems  100 . This disclosure contemplates information handling system  100  taking any suitable physical form. As example and not by way of limitation, information handling system  100  may be an embedded information handling system, a system-on-chip (SOC), a single-board information handling system (SBC) (such as, for example, a computer-on-module (COM) or system-on-module (SOM)), a desktop information handling system, a laptop or notebook information handling system, an interactive kiosk, a mainframe, a mesh of information handling systems, a mobile telephone, a personal digital assistant (PDA), a server, a tablet information handling system, or a combination of two or more of these. Where appropriate, information handling system  100  may include one or more information handling systems  100 ; be unitary or distributed; span multiple locations; span multiple machines; span multiple data centers; or reside in a cloud, which may include one or more cloud components in one or more networks. Where appropriate, one or more information handling systems  100  may perform without substantial spatial or temporal limitation one or more steps of one or more methods described or illustrated herein. As an example and not by way of limitation, one or more information handling systems  100  may perform in real time or in batch mode one or more steps of one or more methods described or illustrated herein. One or more information handling systems  100  may perform at different times or at different locations one or more steps of one or more methods described or illustrated herein, where appropriate. 
         [0020]    In particular embodiments, information handling system  100  includes a processor  102 , memory  104 , storage  106 , an input/output (I/O) interface  108 , a communication interface  110 , and a bus  112 . Although this disclosure describes and illustrates a particular information handling system having a particular number of particular components in a particular arrangement, this disclosure contemplates any suitable information handling system having any suitable number of any suitable components in any suitable arrangement. 
         [0021]    In particular embodiments, processor  102  includes hardware for executing instructions, such as those making up a computer program. As an example and not by way of limitation, to execute instructions, processor  102  may retrieve (or fetch) the instructions from an internal register, an internal cache, memory  104 , or storage  106 ; decode and execute them; and then write one or more results to an internal register, an internal cache, memory  104 , or storage  106 . In particular embodiments, processor  102  may include one or more internal caches for data, instructions, or addresses. This disclosure contemplates processor  102  including any suitable number of any suitable internal caches, where appropriate. As an example and not by way of limitation, processor  102  may include one or more instruction caches, one or more data caches, and one or more translation lookaside buffers (TLBs). Instructions in the instruction caches may be copies of instructions in memory  104  or storage  106 , and the instruction caches may speed up retrieval of those instructions by processor  102 . Data in the data caches may be copies of data in memory  104  or storage  106  for instructions executing at processor  102  to operate on; the results of previous instructions executed at processor  102  for access by subsequent instructions executing at processor  102  or for writing to memory  104  or storage  106 ; or other suitable data. The data caches may speed up read or write operations by processor  102 . The TLBs may speed up virtual-address translation for processor  102 . In particular embodiments, processor  102  may include one or more internal registers for data, instructions, or addresses. This disclosure contemplates processor  102  including any suitable number of any suitable internal registers, where appropriate. Where appropriate, processor  102  may include one or more arithmetic logic units (ALUs); be a multi-core processor; or include one or more processors  102 . Although this disclosure describes and illustrates a particular processor, this disclosure contemplates any suitable processor. 
         [0022]    In particular embodiments, memory  104  includes main memory for storing instructions for processor  102  to execute or data for processor  102  to operate on. As an example and not by way of limitation, information handling system  100  may load instructions from storage  106  or another source (such as, for example, another information handling system  100 ) to memory  104 . Processor  102  may then load the instructions from memory  104  to an internal register or internal cache. To execute the instructions, processor  102  may retrieve the instructions from the internal register or internal cache and decode them. During or after execution of the instructions, processor  102  may write one or more results (which may be intermediate or final results) to the internal register or internal cache. Processor  102  may then write one or more of those results to memory  104 . In particular embodiments, processor  102  executes only instructions in one or more internal registers or internal caches or in memory  104  (as opposed to storage  106  or elsewhere) and operates only on data in one or more internal registers or internal caches or in memory  104  (as opposed to storage  106  or elsewhere). One or more memory buses (which may each include an address bus and a data bus) may couple processor  102  to memory  104 . Bus  112  may include one or more memory buses, as described below. In particular embodiments, one or more memory management units (MMUs) reside between processor  102  and memory  104  and facilitate accesses to memory  104  requested by processor  102 . In particular embodiments, memory  104  includes random access memory (RAM). This RAM may be volatile memory, where appropriate. Where appropriate, this RAM may be dynamic RAM (DRAM) or static RAM (SRAM). Moreover, where appropriate, this RAM may be single-ported or multi-ported RAM. This disclosure contemplates any suitable RAM. Memory  104  may include one or more memories  104 , where appropriate. Although this disclosure describes and illustrates particular memory, this disclosure contemplates any suitable memory. 
         [0023]    In particular embodiments, storage  106  includes mass storage for data or instructions. As an example and not by way of limitation, storage  106  may include a hard disk drive (HDD), a floppy disk drive, flash memory, an optical disc, a magneto-optical disc, magnetic tape, or a USB drive or a combination of two or more of these. Storage  106  may include removable or non-removable (or fixed) media, where appropriate. Storage  106  may be internal or external to information handling system  100 , where appropriate. In particular embodiments, storage  106  is non-volatile, solid-state memory. In particular embodiments, storage  106  includes read-only memory (ROM). Where appropriate, this ROM may be mask-programmed ROM, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), electrically alterable ROM (EAROM), or flash memory or a combination of two or more of these. This disclosure contemplates mass storage  106  taking any suitable physical form. Storage  106  may include one or more storage control units facilitating communication between processor  102  and storage  106 , where appropriate. Where appropriate, storage  106  may include one or more storages  106 . Although this disclosure describes and illustrates particular storage, this disclosure contemplates any suitable storage. 
         [0024]    In particular embodiments, I/O interface  108  includes hardware, software, or both, providing one or more interfaces for communication between information handling system  100  and one or more I/O devices. Information handling system  100  may include one or more of these I/O devices, where appropriate. One or more of these I/O devices may enable communication between a person and information handling system  100 . As an example and not by way of limitation, an I/O device may include a keyboard, keypad, microphone, monitor, mouse, printer, scanner, speaker, still camera, stylus, tablet, touch screen, trackball, video camera, another suitable I/O device or a combination of two or more of these. An I/O device may include one or more sensors. This disclosure contemplates any suitable I/O devices and any suitable I/O interfaces  108  for them. Where appropriate, I/O interface  108  may include one or more device or software drivers enabling processor  102  to drive one or more of these I/O devices. I/O interface  108  may include one or more I/O interfaces  108 , where appropriate. Although this disclosure describes and illustrates a particular I/O interface, this disclosure contemplates any suitable I/O interface. 
         [0025]    In particular embodiments, communication interface  110  includes hardware, software, or both providing one or more interfaces for communication (such as, for example, packet-based communication) between information handling system  100  and one or more other information handling systems  100  or one or more networks. As an example and not by way of limitation, communication interface  110  may include a network interface controller (NIC) or network adapter for communicating with an Ethernet or other wire-based network or a wireless NIC (WNIC) or wireless adapter for communicating with a wireless network, such as a WI-FI network. This disclosure contemplates any suitable network and any suitable communication interface  110  for it. As an example and not by way of limitation, information handling system  100  may communicate with an ad hoc network, a personal area network (PAN), a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), or one or more portions of the Internet or a combination of two or more of these. One or more portions of one or more of these networks may be wired or wireless. As an example, information handling system  100  may communicate with a wireless PAN (WPAN) (such as, for example, a BLUETOOTH WPAN), a WI-FI network, a WI-MAX network, a cellular telephone network (such as, for example, a Global System for Mobile Communications (GSM) network), or other suitable wireless network or a combination of two or more of these. Information handling system  100  may include any suitable communication interface  110  for any of these networks, where appropriate. Communication interface  110  may include one or more communication interfaces  110 , where appropriate. Although this disclosure describes and illustrates a particular communication interface, this disclosure contemplates any suitable communication interface. 
         [0026]    In particular embodiments, bus  112  includes hardware, software, or both coupling components of information handling system  100  to each other. As an example and not by way of limitation, bus  112  may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT) interconnect, an Industry Standard Architecture (ISA) bus, an INFINIBAND interconnect, a low-pin-count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCIe) bus, a serial advanced technology attachment (SATA) bus, a Video Electronics Standards Association local (VLB) bus, or another suitable bus or a combination of two or more of these. Bus  112  may include one or more buses  112 , where appropriate. Although this disclosure describes and illustrates a particular bus, this disclosure contemplates any suitable bus or interconnect. 
         [0027]      FIG. 2  illustrates an example configuration of networked information handling systems (for example, client devices and servers). In particular embodiments, one or more client devices  220  and one or more servers  240  are connected via network  210 . Network  210  may be a public network or a private (for example, corporate) network. Additionally, network  210  may, for example, be a Local Area Network (LAN), a Wide Area Network (WAN), a wireless network, the Internet, an intranet or any other suitable type of network. In particular embodiments, network  210  may include one or more routers for routing data between client devices  220  and/or servers  240 . A device (for example, a client device  220  or a server  240 ) on network  210  may be addressed by a corresponding network address including, for example, an Internet protocol (IP) address, an Internet name, a Windows Internet name service (WINS) name, a domain name or other system name. In particular embodiments, network  210  may include one or more logical groupings of network devices such as, for example, one or more sites (for example, customer sites) or subnets. As an example, a corporate network may include potentially thousands of offices or branches, each with its own subnet (or multiple subnets) having many devices. One or more client devices  220  may communicate with one or more servers  240  via any suitable connection including, for example, a modem connection, a LAN connection including the Ethernet or a broadband WAN connection including DSL, Cable, Ti, T3, Fiber Optics, Wi-Fi, or a mobile network connection including GSM, GPRS, 3G, or WiMax. 
         [0028]    Client device  220  may be a desktop computer, a laptop computer, a tablet computer, a handheld device, a mobile phone, a kiosk, a vending machine, a billboard, or any suitable information handling system. In particular embodiments, a client device  220  is an embedded computer and may have flash memory (for example, a solid state drive) instead of a hard disk drive. In particular embodiments, a client device  220  is a thin client having limited processing capabilities and limited storage, and such a thin client may require minimal management and updates. A client device  220  may communicate with a server  240  via one or more protocols such as Hypertext Transfer Protocol (HTTP), Hypertext Transfer Protocol Secure (HTTPS), File Transfer Protocol (FTP), Common Internet File System (CIFS), Independent Computing Architecture (ICA) protocol (developed by Citrix Systems, Inc.), Remote Desktop Protocol (RDP) (developed by Microsoft Corporation), or any suitable protocol or combination of protocols. 
         [0029]    A server  240  may include one or more of: a computing device, a desktop computer, a laptop computer, a database, a corporate server, a repository server, a configuration application server, a domain name system (DNS) server, a dynamic host configuration protocol (DHCP) server, a virtual machine (for example, VMware® Virtual Machine), a desktop session (for example, Microsoft Terminal Server), a published application (for example, Microsoft Terminal Server), or any suitable information handling system. As an example, a private (for example, corporate) network may include a device manager server and a repository server each configured to communicate with multiple client devices  220  across one or more domains, sites, or subnets of network  210 . In particular embodiments, a server  240  may include one or more servers, or functions of one or more servers. A client device  220  may access software resources provided by a server  240  such as, for example, operating systems, add-ons, content, or any other suitable data, applications, or images. In particular embodiments, a client  220  may access resources provided by a server  240  only after providing suitable authentication information. Alternatively, a server  240  may provide software or other resources automatically to one or more client devices  220 . 
         [0030]    It may be desirable, in the case of a private (for example, corporate) network including multiple sites or subnets to deploy software (including, for example, all or part of one or more operating systems, applications, add-ons, or data) to one or more client devices  220  across one or more sites or subnets. The client devices  220  may, for example, be located remotely from one or more servers  240  (including, for example, device managers or resource repositories), and as such, there may be challenges in deploying software or other resources to the client devices. As an example, limited connectivity or limited speed due to bandwidth constraints or network latencies may create delays in deploying software. As another example, remote sites or subnets may not include managed components or may not have any personnel with information technology expertise necessary to implement software deployment to client devices at the sites or subnets. Additionally, as the size of operating system images or other content (for example, videos) increases, deploying software or other data to remote sites or subnets may be further delayed. These issues may be further exacerbated in the case of embedded computers such as thin clients, which may have limited processing capability and limited storage space. Traditional approaches involving using a static remote software repository for each subnet or site may not be feasible due to cost or management and monitoring requirements. 
         [0031]    In particular embodiments, one or more servers  240  of a network  210  may include a device manager that may manage one or more client devices  220  (for example, thin clients) of one or more sites or subnets of the network. The device manager may, for example, be a software-based management tool that allows for software imaging, software updates, and software configurations to be deployed to the clients from one or more servers. The device manager may also perform any other suitable management function to manage client devices including, for example, enabling or performing (for example, automatically) device discovery, tracking of assets (for example, hardware or software inventory) at client devices, monitoring the status or health of client devices, applying one or more policies to client devices (including, for example, network settings of the client devices), or remote administration and shadowing of client devices. The device manager may deliver any suitable resources including, for example, operating systems, add-ons, content, or any other suitable data, applications, or images to one or more thin client devices  220  of network  210 . 
         [0032]    In particular embodiments, a client device such as client device  220  may be designed with minimal or limited storage capacity (for example, in a hard disk). The client device may be required, however, to run an operating system such as WINDOWS EMBEDDED or WINDOWS SERVER, but the footprint of such an operating system may grow over time with newer releases or updates. Hence, client devices may, over time, begin to run low on free storage space (for example, in the hard disk). Unwanted files may be deleted or full volume compression of the storage medium (for example, the hard disk) may be implemented to increase available storage space. However, full volume compression may introduce performance shortcomings (for example, increased number of instruction cycles required to compress/uncompress data in the volume) from the point of view of an end user of the client device. In particular embodiments, optimized volume compression may be implemented to reduce effective disk usage on a client device while minimizing impact on system performance. 
         [0033]    In particular embodiments, client device  220  (for example, a thin client, a slim client, or a lean client) or one or more software components associated with client device  220  may depend on server  240  to fulfill its computational roles. As an example of a Virtual Desktop Infrastructure (VDI) and not by way of limitation, client device  220  may provide one or more terminal services to one or more users of client device  220 . As such, the users of client device  220  may login to the same server  240  and perform tasks on the same server  240  substantially at the same time. In the VDI, one or more I/O devices  260  may be connected to client device  220 . In particular embodiments, in order for the I/O devices  260  to work seamlessly, communications associated with the I/O devices  260  may be redirected to a Virtual Desktop (VD) operating system (OS) or a Virtual Machine (VM) OS (for example, WINDOWS SERVER 2003) of the VDI. Furthermore, communications for one or more of the I/O devices  260  may be restricted (for example, limited) only to a particular user session, as in session-level-restriction (SLR) or session-isolation. 
         [0034]    SLR may be implemented for many types of I/O devices  260  such as for example, printers, scanners, and storage devices (for example, mass storage, pen drive, hard drive, compact disc (CD), digital video disc (DVD), and BLU-RAY disc). As an example and not by way of limitation, SLR may be implemented for an I/O device  260  that is being operated by a current user or a current user session in a VM OS. In particular embodiments, a third-party kernel filter driver may be layered (for example, loaded) on top of every device class of the I/O device. Accordingly, one or more of the symbolic links in the driver stack for the I/O device  260  at the server  240  may be moved from global namespace to a pre-determined namespace of the user session. Furthermore, the third-party kernel filter driver may block other user sessions (for example, I/O requests of the other user sessions) operating in the VM OS from accessing the device stack. As such, the I/O device  260  may only be accessible by the current user or the current user session. 
         [0035]      FIG. 3  illustrates communication between the driver stack  380  and the USB vendor specific application  340  at the client  220  shown generally at  300 . In particular embodiments, a driver stack  380  may comprise a USB minimal driver  310 , optional filter drivers  320 , and virtual USB bus driver  330  and any other components known to one of ordinary skill in the art. In particular embodiments, an SLR-enabled I/O device  260  may include a single device class (for example, driver) stack  380 . As an example and not by way of limitation, a SLR-enabled USB printer may be associated with a printer device driver stack  380  or a printer class stack (for example, WINDOWS Printer Class). As such, the third-party kernel filter driver may only handle the printer device driver stack  380 . Herein, reference to a third-party kernel filter driver may encompass a SLR filter driver, or vice-versa, where appropriate. Herein, reference to a device class stack may encompass a driver stack, or vice-versa, where appropriate. In particular embodiments, a SLR-enabled I/O device  260  may have two or more driver stacks  380 . Furthermore, the driver stacks  380  may be handled in a coordinated manner. As an example and not by way of limitation, an SLR-enabled USB storage device may include a disk driver stack and a volume driver stack. 
         [0036]    In one embodiment, the driver stack  380  comprises a USB minimal driver  310  provided by the vendor of an I/O device  260 . For example, a vendor may supply a USB minimal driver  310  for a USB device, such as I/O device  260 , when the USB device is not identified with a well-defined device-class. The vendor may also supply an application  340  located at the client  220 . The vendor supplied minimal driver  310  may communicate with the application  340  via input/output control (IOCTL) commands. The minimal driver  310  along with the application  340  provide the necessary functionality sustain the operability of I/O device  260 . 
         [0037]    When the I/O device  260  is redirected, the virtual USB bus driver  330  creates a virtual USB device  280  at the server  240  with the same characteristics of as that of the I/O device  260 . In a particular embodiment, the virtual USB bus driver  330  is a Dell Wyse Virtual USB driver. One of ordinary skill in the art would understand that virtual USB bus driver  330  may be any virtual USB bus driver. The virtual USB bus driver  330  will load all the necessary drivers associated with the virtual USB device  280 . The virtual USB bus driver  330  services requests to virtual USB device  280  through the USB minimal driver  310 . In addition, this USB minimal driver  310  receives the memory of the ‘command or data’ from the USB vendor specific application  340 . These commands or data are posted to the virtual USB bus driver  330  by forming URB of type URB_FUNCTION_VENDOR_DEVICE. The payload of this URB will store the memory address of the ‘command or data’. Whenever the virtual USB bus driver  330  receives a URB type URB_FUNCTION_VENDOR_DEVICE request, the virtual USB bus driver  330  creates a temporary buffer. The temporary buffer may be a temporary kernel buffer that is created and stored at the server  240 . This temporary kernel buffer stores ‘command or data’ that is referenced in the URB&#39;s payload or transfer buffer contents. When the request from the USB vendor&#39;s application is queued, this temporary buffer is also queued so that the memory associated with the request remains with the request. That is, when an I/O device  260  is redirected, the thread does not remain the same when another user or client  220  attempts to access the virtual USB device  280  which causes any memory associated with the request to become invalid. Queuing the request and the temporary buffer maintains the integrity of the memory so that the USB vendor specific application  340  will operate according to the proper data. When a notification is received that an I/O device  260  has been connected to a client  220 , the virtual USB bus driver  330  creates a virtual USB device  260  with the same properties as the associated real I/O device (for example, I/O device  260 .) For example, if a printer is connected to the parallel port of client  220 , the virtual USB bus driver  330  will create a virtual USB printer with the same properties that the local USB printer has that is coupled to client  220 . These optional filter drivers shall provide some form of optimization to the device like power saving, encryption, etc. 
         [0038]    Shown generally at  400  of  FIG. 4  is one embodiment according to the present disclosure for handling URBs received by the upper layers of the driver stack  380 . The USB minimal driver  310  receives the memory of the ‘command or data’ from the USB vendor specific application  340 . These commands or data are posted to the virtual USB bus driver  330  by forming URB of type URB_FUNCTION_VENDOR_DEVICE. The payload of this URB is stored in the memory address of the ‘command or data’. 
         [0039]    At step  402 , the virtual USB bus driver  330  receives the URB from its upper driver layers, for example, USB minimal driver  310  and optional filter drivers  320 . At step  404 , it is determined if the URB is a vendor specific command. For example, an I/O device  260  may be a vendor specific USB device that is not within a well-defined device-class. This vendor-specific USB device  160  may have vendor specific drivers installed and may have an application installed at the client  220  to provide support in processing commands to/from the vendor-specific USB device  260 . If the URB is not a vendor-specific command, the method proceeds to step  412 . 
         [0040]    If it is determined that the URB is a vendor-specific command, then at step  406  a temporary buffer is created in the kernel of the server  240 . At step  408 , the contents of the URB are copied to the temporary buffer. Then, at step  412 , the URB and the temporary buffer are queued. 
         [0041]    Shown generally at  500  of  FIG. 5  is one embodiment according to the present disclosure for servicing queued URBs. At step  502  a queued URB is received. A different thread in the Virtual USB Bus Driver  330  walks through the URB queue, de-queues one by one and request the ‘URB handler function/method’ to handle it. Here, the ‘URB handler function/method’ receives these queued URBs.  FIG. 5  explains a scenario happening within this ‘URB handler function/method’. This ‘URB handler function/method’ is responsible for transferring these URBs over a network, such as network  210  to the I/O device  260  at the client  220 . 
         [0042]    At step  504  it is determined if the URB is a vendor-specific command. If the URB is a vendor specific command, then at step  508  the temporary buffer created at steps  406  and  408  of  FIG. 4  is used to copy/write data for servicing of the URB. If the URB is not a vendor-specific command, then at step  510 , the transfer buffer associated with the URB is used. A temporary buffer is not necessary at step  510  as the operating system at the server will be able to handle processing any URB as the virtualized USB device does not require any vendor-specific drivers and thus does not proceed with servicing the URB on a different thread. Steps  508  and  510  proceed to step  512  where the URB is sent to the I/O device  260  at the client  220  (the client  220  coupled to the I/O device  260  associated with the particular virtual USB device  280 ). 
         [0043]    Shown generally at  600  of  FIG. 6  is one embodiment according to the present disclosure for completing the serviced URBs. The serviced URB is received from the client  220  at step  604 . Once a URB is posted to the I/O device  260  it returns back the URB with appropriate data and/or response. Such URBs are called ‘serviced URBs’. At step  606 , the temporary buffer created at steps  406  and  408  of  FIG. 4  is deleted. At step  608  the URB is sent to the upper layers USB minimal driver  310  and optional filter drivers  320  and finally it reaches the USB vendor specific application  340 . 
         [0044]    Those of skill in the art would appreciate that items such as the various illustrative blocks, modules, elements, components, methods, operations, steps, and algorithms described herein may be implemented as hardware, computer software, or a combination of both. 
         [0045]    To illustrate the interchangeability of hardware and software, items such as the various illustrative blocks, modules, elements, components, methods, operations, steps, and algorithms have been described generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application. 
         [0046]    In one aspect, “means,” a block, a module, an element, a component or a processor may be an item (for example, one or more of blocks, modules, elements, components or processors) for performing one or more functions or operations. In one aspect, such an item may be an apparatus, hardware, or a portion thereof. In one example, an item may have a structure in the form of, for example, an instruction(s) encoded or stored on a machine-readable medium, on another device, or on a portion thereof. An instruction(s) may be software, an application(s), a subroutine(s), or a portion thereof. The instructions(s) may be for performing the function(s) or operation(s). The instruction(s) may be executable by one or more processors to perform the function(s) or operation(s). One or more processors may execute the instruction(s) by, for example, transferring or copying and instructions into an executable memory space and executing the instructions. In one example, an item may be implemented as one or more circuits configured to perform the function(s) or operation(s). A circuit may include one or more circuits and/or logic. A circuit may be analog and/or digital. A circuit may be electrical and/or optical. A circuit may include transistors. In an example, one or more items may be implemented as a processing system (for example, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), etc.), as a portion(s) of any of the foregoing, or as a combination(s) of any of the foregoing. Those skilled in the art will recognize how to implement the instructions, circuits, and processing systems. 
         [0047]    In one aspect of the disclosure, when actions or functions (for example, hooking, modifying, intercepting, redirecting, determining, traversing, obtaining, creating, operating, deleting, removing, receiving, providing, generating, converting, displaying, notifying, accepting, selecting, controlling, transmitting, reporting, sending, or any other action or function) are described as being performed by an item (for example, one or more of blocks, modules, elements, components or processors), it is understood that such actions or functions may be performed, for example, by the item directly. In another example, when an item is described as performing an action, the item may be understood to perform the action indirectly, for example, by facilitating such an action (for example, assisting, allowing, enabling, causing, or providing for, such action to occur; or performing a portion of such an action). For example, determining can refer to facilitating determination, attaching can refer to facilitating attaching, and receiving can refer to facilitating receiving. In one aspect, performing an action may refer to performing a portion of the action (for example, performing a beginning part of the action, performing an end part of the action, or performing a middle portion of the action). 
         [0048]    A reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” For example, a client may refer to one or more clients, a server may refer to one or more servers, an operation may refer to one or more operations, and a signal, message, or communication may refer to one or more signals, messages, or communications. 
         [0049]    Unless specifically stated otherwise, the term “some” refers to one or more. Pronouns in the masculine (for example, his) include the feminine and neuter gender (for example, her and its) and vice versa. Headings and subheadings, if any, are used for convenience only and do not limit the invention. 
         [0050]    A phrase such as an “embodiment” does not imply that such embodiment is essential to the subject technology or that such embodiment applies to all configurations of the subject technology. A disclosure relating to an embodiment may apply to all embodiments, or one or more embodiments. An embodiment may provide one or more examples. A phrase such an embodiment may refer to one or more embodiments and vice versa. A phrase such as a “configuration” does not imply that such configuration is essential to the subject technology or that such configuration applies to all configurations of the subject technology. A disclosure relating to a configuration may apply to all configurations, or one or more configurations. A configuration may provide one or more examples. A phrase such a configuration may refer to one or more configurations and vice versa. 
         [0051]    In one aspect, unless otherwise stated, all measurements, values, ratings, positions, magnitudes, sizes, and other specifications that are set forth in this specification, including in the claims that follow, are approximate, not exact. In one aspect, they are intended to have a reasonable range that is consistent with the functions to which they relate and with what is customary in the art to which they pertain. 
         [0052]    In one aspect, the term “coupled” or the like may refer to being directly coupled. In another aspect, the term “coupled” or the like may refer to being indirectly coupled or communicatively coupled. 
         [0053]    Various items may be arranged differently (for example, arranged in a different order, or partitioned in a different way) all without departing from the scope of the subject technology. In one aspect of the disclosure, the elements recited in the accompanying claims may be performed by one or more modules or sub-modules. For example, a local link creation module and a local link deletion module may be combined into one module. 
         [0054]    It is understood that the specific order or hierarchy of steps, operations or processes disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps, operations or processes may be rearranged. Some of the steps, operations or processes may be performed simultaneously. Some or all of the steps, operations, or processes may be performed automatically, without the intervention of a user. The accompanying method claims, if any, present elements of the various steps, operations or processes in a sample order, and are not meant to be limited to the specific order or hierarchy presented. 
         [0055]    The disclosure is provided to enable any person skilled in the art to practice the various aspects described herein. The disclosure provides various examples of the subject technology, and the subject technology is not limited to these examples. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. 
         [0056]    All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.” Furthermore, to the extent that the term “include,” “have,” or the like is used, such term is intended to be inclusive in a manner similar to the term “comprise” as “comprise” is interpreted when employed as a transitional word in a claim. 
         [0057]    The Title, Background, Summary, Brief Description of the Drawings and Abstract of the disclosure are hereby incorporated into the disclosure and are provided as illustrative examples of the disclosure, not as restrictive descriptions. It is submitted with the understanding that they will not be used to limit the scope or meaning of the claims. In addition, in the Detailed Description, it can be seen that the description provides illustrative examples and the various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed subject matter requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed configuration or operation. The following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter. 
         [0058]    The scope of this disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments described or illustrated herein that a person having ordinary skill in the art would comprehend. The scope of this disclosure is not limited to the example embodiments described or illustrated herein. Moreover, although this disclosure describes and illustrates respective embodiments herein as including particular components, elements, feature, functions, operations, or steps, any of these embodiments may include any combination or permutation of any of the components, elements, features, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would comprehend. Furthermore, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative.