Abstract:
Bandwidth on the Internet and intranets is highly variable and unreliable, two properties that can make streaming digital media content difficult. In a virtualization system (e.g., virtual desktop, remote desktop, remote application, and the like), this is especially so based on different bandwidths available to the session host and the session client. Methods and systems for emulating a bandwidth of a client device in a virtualization system are described. When the session host is executing an application (e.g., a digital media application), the session host may emulate the bandwidth of the session client by hooking into and throttling date over one or more APIs associated with the digital media application, thereby tricking the application into making a bandwidth determination based on the emulated bandwidth of the session client, rather than based on the bandwidth of the session host.

Description:
FIELD 
       [0001]    Aspects described herein relate to computer systems, computer networks, and virtualization of computer services. More specifically, aspects described herein relate to the optimization of services provided over a virtualization session based on available bandwidth between a session host and a session client. 
       BACKGROUND 
       [0002]    Traditionally, personal computers include combinations of operating systems, applications, and user settings, each managed individually by owners or administrators on an ongoing basis. However, many organizations are now using desktop virtualization to provide a more flexible option to address the varying needs of their users. In desktop virtualization, a user&#39;s computing environment (e.g., operating system, applications, and/or user settings) may be separated from the user&#39;s physical computing device (e.g., smartphone, laptop, desktop computer). Using client-server technology, a “virtualized desktop” may be stored in and administered by a remote server, rather than in the local storage of the client computing device. 
         [0003]    There are several different types of desktop virtualization systems. As an example, Virtual Desktop Infrastructure (VDI) refers to the process of running a user desktop inside a virtual machine that resides on a server. VDI and other server-based desktop virtualization systems may provide personalized desktops for each user, while allowing for centralized management and security. Servers in such systems may include storage for virtual desktop images and system configuration information, as well as software components to provide the virtual desktops and allow users to interconnect to them. For example, a VDI server may include one or more hypervisors (virtual machine managers) to create and maintain multiple virtual machines, software to manage the hypervisor(s), a connection broker, and software to provision and manage the virtual desktops. 
         [0004]    A virtual desktop might still require a client application (e.g., a thin client) executing on a client device to execute or perform various tasks. The client, in turn, may be constrained by an available network bandwidth between the client device and one or more networks on which the client device relies for network and/or Internet access. 
       SUMMARY 
       [0005]    In light of the foregoing background, the following presents a simplified summary of the present disclosure in order to provide a basic understanding of some aspects described herein. This summary is not an extensive overview, and is not intended to identify key or critical elements or to delineate the scope of the claims. The following summary merely presents various described aspects in a simplified form as a prelude to the more detailed description provided below. 
         [0006]    In order to address the above shortcomings and additional benefits that will be realized upon reading the disclosure, aspects herein describe new methods and systems of optimizing client device performance for hosted services based on the network bandwidth available to the client device. Bandwidth on the Internet and intranets is highly variable and unreliable, two properties that can make streaming digital media content difficult. In a virtualization system (e.g., virtual desktop, remote desktop, remote application, and the like), this is especially so based on different bandwidths available to the session host and the session client (e.g., session hosts regularly have higher available bandwidths than session clients). Methods and systems for emulating a bandwidth of a client device in a virtualization system are described herein. 
         [0007]    According to some aspects, when a session host is executing an application (e.g., a digital media application), the session host may emulate the bandwidth of the session client by hooking into and throttling data over one or more APIs associated with the digital media application, thereby tricking the application into making a bandwidth determination based on the emulated bandwidth of the session client, rather than based on the actual bandwidth of the session host. 
         [0008]    According to another aspect, methods and systems hook into (e.g., intercept) an application programming interface (API) on a session host in a virtualization system. The hook may be within a virtual desktop, and may further be only with respect to one or more particular processes executing within that virtual desktop. When the API is called, the session host (or virtual desktop) may intercept the API call, and return data to the API based on a bandwidth of a session client connected with the session host (e.g., the session client connected to that particular virtual desktop). 
         [0009]    According to some aspects, the API is determined by querying a database for a process name associated with a first application executing on the session host or executing within the virtual desktop. The API might be hooked only within the particular process, such that when the API is called by a second application executing on the session host, the API is executed without interception by the hook. The data returned to the hooked API may be same data as otherwise would be returned, however, the data may be throttled based on the bandwidth of the session client. The application may then perform a first action based on an analysis of the data returned via the API, e.g., selecting a particular bitrate for a video or digital media stream. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Having thus described aspects of the disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
           [0011]      FIG. 1  illustrates an example operating environment in which various aspects of the disclosure may be implemented. 
           [0012]      FIG. 2  illustrates a client device that may be used in accordance with one or more illustrative aspects described herein. 
           [0013]      FIG. 3  illustrates a client device that may be used in accordance with one or more illustrative aspects described herein. 
           [0014]      FIG. 4  illustrates a system architecture in accordance with one or more illustrative aspects described herein. 
           [0015]      FIG. 5  shows an illustrative flowchart for a method of emulating bandwidth according to one or more aspects described herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    In the following description of the various embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration various embodiments in which aspects described herein may be practiced. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope and spirit of the present disclosure. 
         [0017]    As will be appreciated by one of skill in the art upon reading the following disclosure, various aspects described herein may be embodied as a method, a data processing system, or a computer program product. Accordingly, those aspects may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, such aspects may take the form of a computer program product stored by one or more computer-readable storage media having computer-readable program code, or instructions, embodied in or on the storage media. Any suitable computer readable storage media may be utilized, including hard disks, CD-ROMs, optical storage devices, magnetic storage devices, and/or any combination thereof. In addition, various signals representing data or events as described herein may be transferred between a source and a destination in the form of electromagnetic waves traveling through signal-conducting media such as metal wires, optical fibers, and/or wireless transmission media (e.g., air and/or space). 
         [0018]      FIG. 1  illustrates an example block diagram of a generic computing device  101  (e.g., a computer server  106   a ) in an example computing environment  100  that may be used according to one or more illustrative embodiments of the disclosure. According to one or more aspects, generic computing device  101  may be a server  106   a  in a single-server or multi-server desktop virtualization system configured to provide virtual machines for client access devices. The generic computing device  101  may have a processor  103  for controlling overall operation of the server and its associated components, including random access memory (RAM)  105 , read-only memory (ROM)  107 , input/output (I/O) module  109 , and memory  115 . 
         [0019]    I/O module  109  may include a mouse, keypad, touch screen, scanner, optical reader, and/or stylus (or other input device(s)) through which a user of generic computing device  101  may provide input, and may also include one or more of a speaker for providing audio output and a video display device for providing textual, audiovisual, and/or graphical output. Software may be stored within memory  115  and/or other storage to provide instructions to processor  103  for enabling generic computing device  101  to perform various functions. For example, memory  115  may store software used by the generic computing device  101 , such as an operating system  117 , application programs  119 , and an associated database  121 . Alternatively, some or all of the computer executable instructions for generic computing device  101  may be embodied in hardware or firmware (not shown). 
         [0020]    The generic computing device  101  may operate in a networked environment supporting connections to one or more remote computers, such as terminals  140  (also referred to as client devices). The terminals  140  may be personal computers or servers that include many or all of the elements described above with respect to the generic computing device  101 . The network connections depicted in  FIG. 1  include a local area network (LAN)  125  and a wide area network (WAN)  129 , but may also include other networks. When used in a LAN networking environment, the generic computing device  101  may be connected to the LAN  125  through a network interface or adapter  123 . When used in a WAN networking environment, the generic computing device  101  may include a modem  127  or other network interface for establishing communications over the WAN  129 , such as computer network  130  (e.g., the Internet). It will be appreciated that the network connections shown are illustrative and other means of establishing a communications link between the computers may be used. 
         [0021]    Generic computing device  101  and/or terminals  140  may also be mobile terminals (e.g., mobile phones, smartphones, PDAs, notebooks, etc.) including various other components, such as a battery, speaker, and antennas (not shown). 
         [0022]    The disclosure is operational with numerous other general purpose or special purpose computing system environments or configurations. Examples of well-known computing systems, environments, and/or configurations that may be suitable for use with the disclosure include, but are not limited to, personal computers, server computers, hand-held or laptop devices, multiprocessor systems, microprocessor-based systems, set top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like. 
         [0023]    As shown in  FIG. 1 , one or more client devices  140  may be in communication with one or more servers  106   a - 106   n  (generally referred to herein as “server(s)  106 ”). In one embodiment, the computing environment  100  can include an appliance installed between the server(s)  106  and client machine(s)  140 . This appliance can manage client/server connections, and in some cases can load balance client connections amongst a plurality of backend servers  106 . 
         [0024]    The client machine(s)  140  can in some embodiment be referred to as a single client machine  140  or a single group of client machines  140 , while server(s)  106  may be referred to as a single server  106  or a single group of servers  106 . In one embodiment a single client machine  140  communicates with more than one server  106 , while in another embodiment a single server  106  communicates with more than one client machine  140 . In yet another embodiment, a single client machine  140  communicates with a single server  106 . 
         [0025]    A client machine  140  can, in some embodiments, be referenced by any one of the following terms: client machine(s)  140 ; client(s); client computer(s); client device(s); client computing device(s); local machine; remote machine; client node(s); endpoint(s); endpoint node(s); or a second machine. The server  106 , in some embodiments, may be referenced by any one of the following terms: server(s), local machine; remote machine; server farm(s), host computing device(s), or a first machine(s). 
         [0026]    In one embodiment, the client machine  140  may be a virtual machine. The virtual machine may be any virtual machine, while in some embodiments the virtual machine may be any virtual machine managed by a hypervisor developed by Citrix Systems, IBM, VMware, or any other hypervisor. In some aspects, the virtual machine may be managed by a hypervisor, while in particular aspects the virtual machine may be managed by a hypervisor executing on a server  106  or a hypervisor executing on a client  140 . 
         [0027]    The client machine  140  may execute, operate or otherwise provide an application that can be any one of the following: software; a program; executable instructions; a virtual machine; a hypervisor; a web browser; a web-based client; a client-server application; a thin-client computing client; an ActiveX control; a Java applet; software related to voice over internet protocol (VoIP) communications like a soft IP telephone; an application for streaming video and/or audio; an application for facilitating real-time-data communications (e.g., such as for an on-line video game); a HTTP client; a FTP client; an Oscar client; a Telnet client; or any other set of executable instructions. Still other embodiments include a client device  140  that displays application output generated by an application remotely executing on a server  106  or other remotely located machine. In these embodiments, the client device  140  can display the application output in an application window, a browser, or other output window. In one example, the application is a desktop, while in other examples the application is an application that generates a desktop. A desktop may include a graphical shell providing a user interface for an instance of an operating system in which local and/or remote applications can be integrated. Applications, as used herein, are programs that execute after an instance of an operating system (and, optionally, also the desktop) has been loaded. 
         [0028]    The server  106 , in some embodiments, executes a remote presentation client or other client or program that uses a thin-client or remote-display protocol to capture display output generated by an application executing on a server  106  and transmits the application display output to a remote client  140 . The thin-client or remote-display protocol can be any one of the following protocols: the Independent Computing Architecture (ICA) protocol manufactured by Citrix Systems, Inc. of Ft. Lauderdale, Fla.; or the Remote Desktop Protocol (RDP) manufactured by the Microsoft Corporation of Redmond, Wash. 
         [0029]    The computing environment can include more than one server  106 A- 106 N such that the servers  106 A- 106 N are logically grouped together into a server farm  106 . The server farm  106  can include servers  106  that are geographically dispersed and logically grouped together in a server farm  106 , or servers  106  that are located proximate to each other and logically grouped together in a server farm  106 . Geographically dispersed servers  106 A- 106 N within a server farm  106  can, in some embodiments, communicate using a WAN, MAN, SAN, or LAN, where different geographic regions can be characterized as: different continents; different regions of a continent; different countries; different states; different cities; different campuses; different rooms; or any combination of the preceding geographical locations. In some embodiments the server farm  106  may be administered as a single entity, while in other embodiments the server farm  106  can include multiple server farms  106 . 
         [0030]    In some embodiments, a server farm  106  can include servers  106  that execute a substantially similar type of operating system platform (e.g., Windows Server, manufactured by Microsoft Corp. of Redmond, Wash., UNIX, LINUX, iOS, or LION, etc.) In other embodiments, the server farm  106  can include a first group of servers  106  that execute a first type of operating system platform, and a second group of servers  106  that execute a second type of operating system platform. The server farm  106 , in other embodiments, can include servers  106  that execute different types of operating system platforms. 
         [0031]    The server  106 , in some embodiments, can be any server type. In other embodiments, the server  106  can be any of the following server types: a file server; an application server; a web server; a proxy server; an appliance; a network appliance; a gateway; an application gateway; a gateway server; a virtualization server; a deployment server; a SSL VPN server; a firewall; a web server; an application server or as a master application server; a server  106  executing an active directory; or a server  106  executing an application acceleration program that provides firewall functionality, application functionality, or load balancing functionality. In some embodiments, a server  106  may be a RADIUS server that includes a remote authentication dial-in user service. In embodiments where the server  106  comprises an appliance, the server  106  can be an appliance manufactured by any one of the following manufacturers: the Citrix Application Networking Group; Silver Peak Systems, Inc.; Riverbed Technology, Inc.; F5 Networks, Inc.; or Juniper Networks, Inc. Some embodiments include a first server  106   a  that receives requests from a client machine  140 , forwards the request to a second server  106   n , and responds to the request generated by the client machine  140  with a response from the second server  106   n . The first server  106   a  can acquire an enumeration of applications available to the client machine  140  as well as address information associated with an application server  106  hosting an application identified within the enumeration of applications. The first server  106   a  can then present a response to the client&#39;s request using a web interface, and communicate directly with the client  140  to provide the client  140  with access to an identified application. 
         [0032]    The server  106  can, in some embodiments, execute any one of the following applications: a thin-client application using a thin-client protocol to transmit application display data to a client; a remote display presentation application; any portion of the CITRIX ACCESS SUITE by Citrix Systems, Inc. like XENAPP, XENDESKTOP, METAFRAME or CITRIX PRESENTATION SERVER; MICROSOFT WINDOWS Terminal Services manufactured by the Microsoft Corporation; or an ICA client, developed by Citrix Systems, Inc. Another embodiment includes a server  106  that is an application server such as: an email server that provides email services such as MICROSOFT EXCHANGE manufactured by the Microsoft Corporation; a web or Internet server; a desktop sharing server; a collaboration server; or any other type of application server. Still other embodiments include a server  106  that executes any one of the following types of hosted servers applications: GOTOMEETING provided by Citrix Online Division, Inc.; WEBEX provided by WebEx, Inc. of Santa Clara, Calif.; or Microsoft Office LIVE MEETING provided by Microsoft Corporation. 
         [0033]    Client machines  140  can, in some embodiments, be a client node that seeks access to resources provided by a server  106 . In other embodiments, the server  106  may provide clients  140  or client nodes with access to hosted resources. The server  106 , in some embodiments, functions as a master node configured to communicate with one or more clients  140  or servers  106 . In some embodiments, the master node can identify and provide address information associated with a server  106  hosting a requested application, to one or more clients  140  or servers  106 . In still other embodiments, the master node can be a server farm  106 , a client  140 , a cluster of client nodes  140 , or an appliance. 
         [0034]    One or more clients  140  and/or one or more servers  106  can transmit data over a network  130  installed between machines and appliances within the computing environment  100 . The network  130  can comprise one or more sub-networks, and can be installed between any combination of the clients  140 , servers  106 , computing machines and appliances included within the computing environment  100 . In some embodiments, the network  130  can be: a local-area network (LAN); a metropolitan area network (MAN); a wide area network (WAN); a primary network  104  comprised of multiple sub-networks located between the client machines  140  and the servers  106 ; a primary public network  130  (e.g., the Internet) with a private sub-network; a primary private network  130  with a public sub-network; or a primary private network  130  with a private sub-network. Still further embodiments include a network  130  that can be any of the following network types: a point to point network; a broadcast network; a telecommunications network; a data communication network; a computer network; an ATM (Asynchronous Transfer Mode) network; a SONET (Synchronous Optical Network) network; a SDH (Synchronous Digital Hierarchy) network; a wireless network; a wireline network; or a network that includes a wireless link where the wireless link can be an infrared channel or satellite band. The network topology of the network  130  can differ within different embodiments, possible network topologies include: a bus network topology; a star network topology; a ring network topology; a repeater-based network topology; or a tiered-star network topology. Additional embodiments may include a network of mobile telephone networks that use a protocol to communicate among mobile devices, where the protocol can be any one of the following: AMPS; TDMA; CDMA; GSM; GPRS UMTS; or any other protocol able to transmit data among mobile devices. 
         [0035]    Illustrated in  FIG. 2  is an embodiment of a computing device  200 , where the client machine  140  and server  106  illustrated in  FIG. 1  may be deployed as and/or executed on any embodiment of the computing device  200  illustrated and described herein. Included within the computing device  200  is a system bus  250  that communicates with the following components: a central processing unit  221 ; a main memory  222 ; storage memory  228 ; an input/output (I/O) controller  223 ; display devices  224 ; an installation device  216 ; and a network interface  218 . In one embodiment, the storage memory  228  includes: an operating system, software routines, and a client agent  220 . The I/O controller  223 , in some embodiments, is further connected to a keyboard  226 , and a pointing device  227 . Other embodiments may include an I/O controller  223  connected to more than one input/output device  230 . 
         [0036]      FIG. 3  illustrates one embodiment of a computing device  300 , where the client machine  140  and server  106  illustrated in  FIG. 1  can be deployed as and/or executed on any embodiment of the computing device  300  illustrated and described herein. Included within the computing device  300  is a system bus  350  that communicates with the following components: a bridge  370 , and a first I/O device  330   a . In another embodiment, the bridge  370  is in further communication with the main central processing unit  321 , where the central processing unit  321  can further communicate with a second I/O device  330   b , a main memory  322 , and a cache memory  340 . Included within the central processing unit  321 , are I/O ports, a memory port  303 , and a main processor. 
         [0037]    Embodiments of the computing machine  300  can include a central processing unit  321  characterized by any one of the following component configurations: logic circuits that respond to and process instructions fetched from the main memory unit  322 ; or any combination of a microprocessor, a microcontroller, a central processing unit with a single processing core, a central processing unit with two processing cores, or a central processing unit with more than one processing core. 
         [0038]    While  FIG. 3  illustrates a computing device  300  that includes a single central processing unit  321 , in some embodiments the computing device  300  can include one or more processing units  321 . In these embodiments, the computing device  300  may store and execute firmware or other executable instructions that, when executed, direct the one or more processing units  321  to simultaneously execute instructions or to simultaneously execute instructions on a single piece of data. In other embodiments, the computing device  300  may store and execute firmware or other executable instructions that, when executed, direct the one or more processing units to each execute a section of a group of instructions. For example, each processing unit  321  may be instructed to execute a portion of a program or a particular module within a program. 
         [0039]    In some embodiments, the processing unit  321  can include one or more processing cores. For example, the processing unit  321  may have two cores, four cores, eight cores, etc. In one embodiment, the processing unit  321  may comprise one or more parallel processing cores. The processing cores of the processing unit  321 , may in some embodiments access available memory as a global address space, or in other embodiments, memory within the computing device  300  can be segmented and assigned to a particular core within the processing unit  321 . In one embodiment, the one or more processing cores or processors in the computing device  300  can each access local memory. In still another embodiment, memory within the computing device  300  can be shared amongst one or more processors or processing cores, while other memory can be accessed by particular processors or subsets of processors. In embodiments where the computing device  300  includes more than one processing unit, the multiple processing units can be included in a single integrated circuit (IC). These multiple processors, in some embodiments, can be linked together by an internal high speed bus, which may be referred to as an element interconnect bus. 
         [0040]    In embodiments where the computing device  300  includes one or more processing units  321 , or a processing unit  321  including one or more processing cores, the processors can execute a single instruction simultaneously on multiple pieces of data (SIMD), or in other embodiments can execute multiple instructions simultaneously on multiple pieces of data (MIMD). In some embodiments, the computing device  100  can include any number of SIMD and MIMD processors. 
         [0041]    The computing device  300 , in some embodiments, can include a graphics processor or a graphics processing unit (Not Shown). The graphics processing unit can include any combination of software and hardware, and can further input graphics data and graphics instructions, render a graphic from the inputted data and instructions, and output the rendered graphic. In some embodiments, the graphics processing unit can be included within the processing unit  321 . In other embodiments, the computing device  300  can include one or more processing units  321 , where at least one processing unit  321  is dedicated to processing and rendering graphics. 
         [0042]    One embodiment of the computing machine  300  includes a central processing unit  321  that communicates with cache memory  340  via a secondary bus also known as a backside bus, while another embodiment of the computing machine  300  includes a central processing unit  321  that communicates with cache memory via the system bus  350 . The local system bus  350  can, in some embodiments, also be used by the central processing unit to communicate with more than one type of I/O device  330 . In some embodiments, the local system bus  350  can be any one of the following types of buses: a VESA VL bus; an ISA bus; an EISA bus; a MicroChannel Architecture (MCA) bus; a PCI bus; a PCI-X bus; a PCI-Express bus; or a NuBus. Other embodiments of the computing machine  300  include an I/O device  330  that includes a video display  224  that communicates with the central processing unit  321 . Still other versions of the computing machine  300  include a processor  321  connected to an I/O device  330  via any one of the following connections: HyperTransport, Rapid I/O, or InfiniBand. Further embodiments of the computing machine  300  include a processor  321  that communicates with one I/O device  330   a  using a local interconnect bus and a second I/O device  330   b  using a direct connection. 
         [0043]    The computing device  300 , in some embodiments, includes a main memory unit  322  and cache memory  340 . The cache memory  340  can be any memory type, and in some embodiments can be any one of the following types of memory: SRAM; BSRAM; or EDRAM. Other embodiments include cache memory  340  and a main memory unit  322  that can be any one of the following types of memory: Static random access memory (SRAM), Burst SRAM or SynchBurst SRAM (BSRAM); Dynamic random access memory (DRAM); Fast Page Mode DRAM (FPM DRAM); Enhanced DRAM (EDRAM), Extended Data Output RAM (EDO RAM); Extended Data Output DRAM (EDO DRAM); Burst Extended Data Output DRAM (BEDO DRAM); Enhanced DRAM (EDRAM); synchronous DRAM (SDRAM); JEDEC SRAM; PC100 SDRAM; Double Data Rate SDRAM (DDR SDRAM); Enhanced SDRAM (ESDRAM); SyncLink DRAM (SLDRAM); Direct Rambus DRAM (DRDRAM); Ferroelectric RAM (FRAM); or any other type of memory. Further embodiments include a central processing unit  321  that can access the main memory  322  via: a system bus  350 ; a memory port  303 ; or any other connection, bus or port that allows the processor  321  to access memory  322 . 
         [0044]    One embodiment of the computing device  200 / 300  provides support for any one of the following installation devices  216 : a CD-ROM drive, a CD-R/RW drive, a DVD-ROM drive, tape drives of various formats, USB device, a bootable medium, a bootable CD, a bootable CD for GNU/Linux distribution such as KNOPPIX®, a hard-drive or any other device suitable for installing applications or software. Applications can in some embodiments include a client agent  220 , or any portion of a client agent  220 . The computing device  200 / 300  may further include a storage device  228  that can be either one or more hard disk drives, or one or more redundant arrays of independent disks; where the storage device is configured to store an operating system, software, programs applications, or at least a portion of the client agent  220 . A further embodiment of the computing device  200 ,  300  includes an installation device  216  that is used as the storage device  228 . 
         [0045]    The computing device  200 ,  300  may further include a network interface  218  to interface to a Local Area Network (LAN), Wide Area Network (WAN) or the Internet through a variety of connections including, but not limited to, standard telephone lines, LAN or WAN links (e.g., 802.11, T1, T3, 56 kb, X.25, SNA, DECNET), broadband connections (e.g., ISDN, Frame Relay, ATM, Gigabit Ethernet, Ethernet-over-SONET), wireless connections, or some combination of any or all of the above. Connections can also be established using a variety of communication protocols (e.g., TCP/IP, IPX, SPX, NetBIOS, Ethernet, ARCNET, SONET, SDH, Fiber Distributed Data Interface (FDDI), RS232, RS485, IEEE 802.11, IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, CDMA, GSM, WiMax and direct asynchronous connections). One version of the computing device  200 ,  300  includes a network interface  218  able to communicate with additional computing devices  200 ′,  300 ′ (not shown) via any type and/or form of gateway or tunneling protocol such as Secure Socket Layer (SSL) or Transport Layer Security (TLS), or the Citrix Gateway Protocol manufactured by Citrix Systems, Inc. Versions of the network interface  218  can comprise any one of: a built-in network adapter; a network interface card; a PCMCIA network card; a card bus network adapter; a wireless network adapter; a USB network adapter; a modem; or any other device suitable for interfacing the computing device  200 ,  300  to a network capable of communicating and performing the methods and systems described herein. 
         [0046]    Embodiments of the computing device  200 ,  300  include any one of the following I/O devices  230   a - 230   n : a keyboard  226 ; a pointing device  227 ; mice; trackpads; an optical pen; trackballs; microphones; drawing tablets; video displays; speakers; inkjet printers; laser printers; and dye-sublimation printers; or any other input/output device able to perform the methods and systems described herein. An I/O controller  223  may in some embodiments connect to multiple I/O devices  230   a - 230   n  to control the one or more I/O devices. Some embodiments of the I/O devices  230   a - 230   n  may be configured to provide storage or an installation medium  216 , while others may provide a universal serial bus (USB) interface for receiving USB storage devices such as the USB Flash Drive line of devices manufactured by Twintech Industry, Inc. Still other embodiments include an I/O device  230  that may be a bridge between the system bus  250  and an external communication bus, such as: a USB bus; an Apple Desktop Bus; an RS-232 serial connection; a SCSI bus; a FireWire bus; a FireWire  800  bus; an Ethernet bus; an AppleTalk bus; a Gigabit Ethernet bus; an Asynchronous Transfer Mode bus; a HIPPI bus; a Super HIPPI bus; a SerialPlus bus; a SCI/LAMP bus; a FibreChannel bus; or a Serial Attached small computer system interface bus. 
         [0047]    In some embodiments, the computing machine  200 ,  300  can connect to multiple display devices  224   a - 224   n , in other embodiments the computing device  100  can connect to a single display device  224 , while in still other embodiments the computing device  200 ,  300  connects to display devices  224   a - 224   n  that are the same type or form of display, or to display devices that are different types or forms. Embodiments of the display devices  224   a - 224   n  can be supported and enabled by the following: one or multiple I/O devices  230   a - 230   n ; the I/O controller  223 ; a combination of I/O device(s)  230   a - 230   n  and the I/O controller  223 ; any combination of hardware and software able to support a display device  224   a - 224   n ; any type and/or form of video adapter, video card, driver, and/or library to interface, communicate, connect or otherwise use the display devices  224   a - 224   n . The computing device  200 ,  300  may in some embodiments be configured to use one or multiple display devices  224 A- 224 N, these configurations include: having multiple connectors to interface to multiple display devices  224 A- 224 N; having multiple video adapters, with each video adapter connected to one or more of the display devices  224 A- 224 N; having an operating system configured to support multiple displays  224 A- 224 N; using circuits and software included within the computing device  200  to connect to and use multiple display devices  224 A- 224 N; and executing software on the main computing device  200  and multiple secondary computing devices to enable the main computing device  200  to use a secondary computing device&#39;s display as a display device  224 A- 224 N for the main computing device  200 . Still other embodiments of the computing device  200  may include multiple display devices  224 A- 224 N provided by multiple secondary computing devices and connected to the main computing device  200  via a network. 
         [0048]    In some embodiments, the computing machine  200  can execute any operating system, e.g., any WINDOWS-based, Unix, Linux, MacOS, iOS, OS/2, PalmOS, Android, Symbian, or any other embedded operating system, real-time operating system, open source operating system, proprietary operating system, operating systems for mobile computing devices, or any other operating system. In still another embodiment, the computing machine  200  can execute multiple operating systems. For example, the computing machine  200  can execute PARALLELS or another virtualization platform that can execute or manage a virtual machine executing a first operating system, while the computing machine  200  executes a second operating system different from the first operating system. 
         [0049]    The computing machine  200  can be embodied in any one of the following computing devices: a computing workstation; a desktop computer; a laptop or notebook computer; a server; a handheld computer; a mobile telephone; a portable telecommunication device; a media playing device; a gaming system; a mobile computing device; a netbook; a device of the IPOD family of devices manufactured by Apple Computer; any one of the PLAYSTATION family of devices manufactured by the Sony Corporation; any one of the Nintendo family of devices manufactured by Nintendo Co; any one of the XBOX family of devices manufactured by the Microsoft Corporation; or any other type and/or form of computing, telecommunications or media device that is capable of communication and that has sufficient processor power and memory capacity to perform the methods and systems described herein. In other embodiments the computing machine  100  can be a mobile device, smartphone, personal digital assistant, or the like. Any computing device regardless of different platforms, processors, operating systems, and input devices may be used that is capable of performing the methods and systems described herein. 
         [0050]    Moreover, the computing device  200  can be any workstation, desktop computer, laptop or notebook computer, server, handheld computer, mobile telephone, digital audio player (iPod, iPhone, Zune, RAZR, ROKR, etc.), any other computer, or other form of computing or telecommunications device that is capable of communication and that has sufficient processor power and memory capacity to perform the operations described herein. 
         [0051]      FIGS. 1-3  show a high-level architecture of illustrative virtualization systems. As shown, the desktop virtualization system may be single-server or multi-server system, including at least one virtualization server  106  configured to provide virtual desktops and/or virtual applications to one or more client access devices  140 . As used herein, a desktop refers to a graphical environment or space in which one or more applications may be hosted and/or executed. A desktop may include a graphical shell providing a user interface for an instance of an operating system in which local and/or remote applications can be integrated. Applications, as used herein, are programs that execute after an instance of an operating system (and, optionally, also the desktop) has been loaded. Each instance of the operating system may be physical (e.g., one operating system per device) or virtual (e.g., many instances of an OS running on a single device). Each application may be executed on a local device, or executed on a remotely located device (e.g., remoted). 
         [0052]    Having described in  FIGS. 1-3  various examples of virtualization systems, and certain software and functionality that may be included in such systems, it will be appreciated that other software and hardware may be used other than those which are identified above. In addition, the following paragraphs provide additional examples of various methods and systems relating to optimizing hosted services based on the available bandwidth between a session host and a session client. 
         [0053]    With reference to  FIG. 4 , one or more external client devices  405   a - 405   n  may communicate with a connection broker  430  via one or more networks  415 ,  435 . Network  415  may include a public network such as the Internet. Network  435  may include a private network such as a corporate LAN, WAN or the like, protected by firewall  420 . Any other networks may also be used. 
         [0054]    External client device  405  may communicate through firewall  420  via an edge device  425 , such as an access gateway, virtual private network (VPN) server, or the like. Web server  430  may include an externally facing aspect and an internally facing aspect for communicating with external client devices  405  and internal client devices  410 , respectively. Alternatively, a single logical web server may be adapted or configured to communicate with all client devices. Web server  430  communicates with connection broker  401  to handle requests for sessions with virtualized resources, as further described herein. In some aspects web server  430  and connection broker  401  are physically and/or logically separate devices. In other aspects web server  430  and connection broker  401  may be physically and/or logically combined. 
         [0055]    Connection broker  401  may receive login credentials from users at client devices  405 ,  410  (e.g., via a web server  430  or other client-server configuration), and then create and/or assign resources to authorized users, and provide management consoles to authorized administrators. Each resource, e.g., a hosted application, hosted resource, virtual machine, or the like, may be hosted by one or more session hosts  440   a - 440   n  (e.g., device  101 ,  106 ). 
         [0056]    When a session host for a hosted desktop or hosted application has high network bandwidth, and the session client has lower available bandwidth, problems may arise when the session host performs some action on behalf of the session client based on the higher bandwidth available to the session host rather than the lower bandwidth available to the session client.  FIG. 4  illustrates session hosts  440   a - 440   n  having high Internet bandwidth/pipe  450 , illustrated by a thick line. Session clients  405   a - 405   n  may have varying levels of bandwidth  455 - 465 , illustrated by lines of varying thickness. Session clients  410   a - 410   a , which in this example are located behind corporate firewall  420 , may have the same Internet bandwidth  450  as session hosts  440   a - 440   n . That is, corporate network  435  may be limited in bandwidth by connection  450  outside the corporate firewall  420 , but otherwise have Fast Ethernet or Gigabit Ethernet speeds, e.g., 100 Mbits/s, Gigabit/s or faster. 
         [0057]    In one example, web-based video content (on demand or real-time) may be encoded into multiple files or streams using different bitrates (e.g., multiple H.264 streams) so that a recipient of the video can select the optimal bitrate based on the network bandwidth available to the recipient. When the virtual desktop (session host) has high bandwidth, a bandwidth adaptive video player application running on the virtual desktop might fetch a high bitrate video based on the virtual desktop&#39;s available bandwidth  450 . However, that bitrate might not be appropriate (for instance, the video might have to be transcoded) if the client-side bandwidth  465  where the video will be decoded and rendered is low. Stated differently, the transcoding of video may occur at the session client device, despite being initially requested by the host device. In addition, the session host device may select a particular bitrate data stream to download based on the bandwidth determined to be available at the session host, rather than based on the bandwidth of the session client that will actually be performing the transcoding. The session client may thus suffer performance issues when constrained by the client&#39;s available bandwidth versus the bitrate of the incoming video stream. Similar problems may arise when a session host is running other data-intensive applications on behalf of the session client. 
         [0058]    There is presently no standard application programming interface (API) or methodology used to determine bandwidth. Each application typically uses its own set of APIs or techniques to determine bandwidth. Video applications in particular, e.g., Windows Media Player by Microsoft Corporation of Redmond, Wash., may independently determine bandwidth and dynamically alter the bitrate of a video stream based on the currently available bandwidth. Windows Media Player refers to this as Intelligent Streaming. Other video players or other high-bandwidth applications may use other techniques to determine bandwidth. 
         [0059]    According to one aspect, database  121  may store information regarding APIs that each application uses to determine bandwidth. For example, application A might use APIs X and Y to determine bandwidth, e.g., by sending or receiving some known quantity of data via those APIs and measuring the amount of time taken to send or receive the known quantity of data. Application B might use API Z to perform a similar calculation. By using one or more APIs, applications executing on the session host (or within a particular virtual desktop) determine the session host&#39;s bandwidth and make any subsequent decisions (e.g., a selection of which bitrate video stream to choose) based on the host device&#39;s bandwidth. However, the bandwidth available to the session client may present a subsequent, unaccounted for bottleneck. Thus, according to an illustrative embodiment, the session host (or the virtual desktop) may be configured to emulate the client device&#39;s network bandwidth by hooking in to one or more 
         [0060]    Patent Application API(s) identified in database  121  and throttling bandwidth based on the bandwidth of the client device. Hooking and throttling may be performed system-wide or on a per-process basis. 
         [0061]    With reference to  FIG. 5 , an illustrative method for emulating a client device&#39;s bandwidth is provided. Initially, in step  501 , an application is launched within the hosted session, e.g., a video player application may be launched based on user input or automatically based on the occurrence of some event or selection of an Internet link. In step  503 , the session host queries database  121  based on the process name of the application. If the process name is not in database  121 , then no hooks are created or established for any given APIs within that process, and the method skips to step  513 . A hook, as used herein, refers to the practice of intercepting an API call and returning a value other than from the originally called API. 
         [0062]    If, in step  503 , the query returns one or more known API(s) that the application uses to determine bandwidth, then the session host in step  505  creates new hooks for the identified APIs to intercept calls to those APIs. Session host may create the hook on a per-process basis, thereby intercepting API calls only from the launched application, while allowing other processes to still access the APIs unhindered. Alternatively, the hooks may be established on a system-wide basis. 
         [0063]    In step  507  the session host waits for the launched application to call one or more of the identified APIs. In step  509 , when one or more of the identified APIs are called, the session host checks, queries, or otherwise determines the current bandwidth of the session client device. There are various ways to determine the client device bandwidth, and the particular method used is secondary to the ability to determine the bandwidth. Stated differently, how the client device&#39;s bandwidth is determined does not matter, provided that there is some method or mechanism that can estimate or determine the client device&#39;s bandwidth. In one example, the client/server software executing the virtual desktop may include a software component or module that determines a current bandwidth between the session host and session client. In another example, session host may maintain a known or estimated bandwidth determine when the session was initially established between the session host and session client. In another example, the session host may query the session client, and the session client may in turn execute a bandwidth determination process, e.g., using any number of publicly available or accessible Internet bandwidth determination web sites or tools, etc. 
         [0064]    Regardless of how the client bandwidth is determined, the session host in step  511  artificially throttles the bandwidth of one or more of the identified APIs based on the determined bandwidth of the session client, thereby emulating the bandwidth of the session client. Next, in step  513 , the launched application makes a bandwidth determination based on the information/data returned from the API(s). If the API(s) are hooked in step  505 , then the information/data returned by the API(s) is the result of the artificial throttling that occurred in step  511 . The launched application will therefore determine the bandwidth to be consistent with the emulated bandwidth of the client device. However, if the APIs were not hooked (because the launched application was not included in database  121 ), then the launched application makes a truly independent bandwidth determination because the information/data returned from the API(s) is not based on artificially throttling to emulate the client bandwidth. Lastly, in step  515 , the launched application makes a decision, executes an event, selects an input or output, or otherwise performs some action based on the determined bandwidth. 
         [0065]    The method illustrated in  FIG. 5  may be altered without departing from the spirit or scope of the inventions described herein. For example, steps may be modified, combined, or split into further sub-steps, and may be performed in other than the recited order based on system design. 
         [0066]    Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as illustrative forms of implementing the claims.