(54) DYNAMIC PERFORMANCE BASED SERVER
`SELECTION
`(75) Inventor: Bruce A. Young, LeMars, IA (US)
`(73) Assignee: Gateway, Inc., Poway, CA (US)
`(*) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`21) Appl. No.: 09/329,620
`Filed
`o 1999
`(22) Filed:
`Jun. 10,
`(51) Int. Cl. ................................................ G06F 17/30
`(52) U.S. Cl. ............................. 707/2; 707/10, 707/201;
`707/203; 707/1; 707/3; 707/100; 709/224;
`709:248
`(58) Field of Search ................................. 709/224, 248;
`707/10, 1, 3, 100, 20, 201, 203
`
`(56)
`
`FOREIGN PATENT DOCUMENTS
`98/18076
`4/1998 ............. GO6F/9/46
`OTHER PUBLICATIONS
`E.P.O.'....","...");
`XP000787863, 650–653, (1/97).
`Katz, E.D., et al., “A Scalable HTTP server: the NCSA
`ss
`prototype', Computer Networks and ISDN Systems, North
`Holland Publishing, vol. 27, No. 2, XP004037986, 155–164,
`(1994).
`* cited by examiner
`Primary Examiner Diane D. Mizrahi
`Assistant Examiner Thuy Pardo
`(74) Attorney, Agent, or Firm-Scott Charles Richardson;
`Schwegman, Lundberg, Woesner & Kluth
`(57)
`ABSTRACT
`Downloading of Internet files is optimized based on which
`of multiple locations is most efficient in providing the files.
`Identical or contiguous portions of a file are downloaded
`References Cited
`from different Servers, and performance data Such as a bit
`rate for each Site is used to then Select the optimal Server to
`U.S. PATENT DOCUMENTS
`complete the download. An applet intercepts the request for
`5,049,873 A 9/1991 Robins et al. ......... 340/825.06
`the file from a web browser and determines the best server
`5,261,044 A 11/1993 Dev. et al. .................. 395/159
`to provide the file. When the request is intercepted, it reads
`5,572,643 A 11/1996 Judson et al. ..
`... 395/793
`a list of available file transfer protocol (ftp) locations from
`5,687.292 A 11/1997 Boda et al. ................... 395/11
`which to download the file. The applet or other type of
`5,744,669 A 6/1998 George et al. ......... 395/20054
`5:52, A go Stylist .. 35i program pings each site to prioritize the list based on
`5771226. A 6/1998 R al. . . . . . . . . . . . . . . . . . . 370/232
`Shortest response time. The throughput of the finally Selected
`5774,660 A 6/1998 Brendeletal. .395/20031
`server is tracked as the file is downloaded. If the throughput
`5,774,668. A
`6/1998 Choquier et al... 395/20053
`drops below a desired throughput, the next best Server is
`5,838,906 A 11/1998 Doyle et al. ........... 395/200.32
`Selected from the previous list, or the Selection and tracking
`5.974,460 A * 10/1999 Maddalozzo, Jr. et al. .. 709/224
`process is started again to determine if a faster Server has
`6,138,155. A * 10/2000 Davis et al. ................ 709/224
`become available due to changes in demand on the Servers.
`6.212,571 B1 * 4/2001 Kikuchi et al.
`... 709/248
`6,223,221 B1
`4/2001 Kunz ......................... 709/224
`24 Claims, 2 Drawing Sheets
`
`(12) United States Patent
`Young
`
`USOO6477522B1
`(10) Patent No.:
`US 6,477,522 B1
`(45) Date of Patent:
`Nov. 5, 2002
`
`WO
`
`
`
`210 - NTERCEPT REQUEST FOR FILE
`
`200
`/
`
`215.
`
`OBTAN LST OF SERVERS
`
`220-
`
`PRIORITIZE ST
`
`225 dOWNLOAD ORTIONS OF FE
`FROM EACH SERVER
`
`230-
`
`MONTOR THROUGHPUT
`
`235
`
`SELECT BEST SERVER To
`COMPLE FILE TRANSFER
`
`24-O-
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`MONTOR THROUGHT
`
`245
`
`HROUGHPUT
`BELOW DESIRED RATE
`
`NO
`
`YES
`
`250 -
`
`SELECT NEXT BEST SERVER
`TO COMPLETE OR MEASURE
`EACH HROUGHUT AGAIN
`
`-1-
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`Amazon v. Audio Pod
`US Patent 10,735,488
`Amazon EX-1008
`
`

`

`U.S. Patent
`
`Nov. 5, 2002
`
`Sheet 1 of 2
`
`US 6,477,522 B1
`
`FIG. 1
`
`102 - PROCESSOR
`
`1 OO
`1
`
`11 O
`
`style
`CACHE ... li. DART
`
`CONTROLLER
`
`12O
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`124
`of connector
`IDE conNECTOR
`scs connector
`scs conNECTOR
`USB PORT
`USB PORT
`126
`
`122
`
`I/O
`BRIDGE
`
`121 - PC CONNECTOR
`
`127
`GRAPHICS
`CONTROLLER
`
`PC CONNECTOR
`weaport(s)
`VGA PORT(S)
`129
`
`VIDEO
`128 Moy
`
`130
`
`BUFFER - 132
`
`140
`
`
`
`144
`REAL TIME KEYBOARD/
`CLOCK
`MOUSE
`|CONTROLLER
`KEYBOARD/145
`BIOS ROM
`
`SYSTEM | 12
`BIOS ROM
`.
`I/O
`CONTROLLER
`
`151 - ISA CONNECTOR
`
`131- ISA CONNECTOR
`
`151 - ISA CONNECTOR
`154
`155
`156
`
`SERAL PORT
`R
`SERAL PORT
`PARALLEL PORT
`
`57 1
`FDD CONNECTOR
`
`
`
`-2-
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`

`

`U.S. Patent
`
`Nov. 5, 2002
`
`Sheet 2 of 2
`
`US 6,477,522 B1
`
`210 - INTERCEPT REQUEST FOR FILE
`
`2OO
`/
`
`215
`
`OBTAIN LIST OF SERVERS
`
`22O
`
`PRIORITIZE LIST
`
`225
`
`DOWNLOAD PORTIONS OF FILE
`FROM EACH SERVER
`
`230
`
`MONITOR THROUGHPUT
`
`235
`
`SELECT BEST SERVER TO
`COMPLETE FILE TRANSFER
`
`240
`
`MONITOR THROUGHPUT
`
`245
`THROUGHPUT
`BELOW DESIRED RATE
`p
`
`SELECT NEXT BEST SERVER
`TO COMPLETE OR MEASURE
`EACH THROUGHPUT AGAIN
`
`
`
`
`
`
`
`
`
`
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`250
`
`FIG. 2
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`-3-
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`

`

`1
`DYNAMIC PERFORMANCE BASED SERVER
`SELECTION
`
`US 6,477,522 B1
`
`FIELD OF THE INVENTION
`The present invention relates to networked computer
`Systems and in particular to the Selection of a Server for
`desired information based on performance.
`
`BACKGROUND
`Networks, Such as the Internet contain information that a
`user desires to obtain. The information is contained in files
`that may be specified by uniform resource locators (URLs)
`which are essentially addresses which specify the computer
`and the location of the file on that computer. Many times,
`Several computers, referred to as Servers will have the same
`file available for retrieval by a user. Each such file has a
`different URL. In some cases, multiple servers may be
`connected together to appear as a single site and have Several
`individual Servers having the same file for increased overall
`throughput. In Such cases, a manager of the Servers trans
`parent to the user System Selects which individual Server or
`Servers should provide the file given a client/user request.
`The manager may Select the Server to balance the load
`between the servers. However, most files on the Internet are
`located on Separate Servers and are identified with Separate
`URLS.
`When a user tries to access a file, a Site is Selected, and the
`file transfer is requested through a browser when a user
`clicks on highlighted text or image which is associated with
`the URL, or types in the URL directly. This link identifies
`only one site, which may be very busy. The user will usually
`Select a site which is geographically closest to the user. This
`may or may not be the best choice. There is no easy ability
`for a user to Select a different site, other than to Stop the
`transmission of the file after noticing that it is taking a long
`time, then Searching for a different Site with the same file and
`initiating a new transfer. Some sites do offer multiple Sites
`from which to obtain the information, but the user still must
`make the decision as to which Site to use, and if not satisfied,
`Stop the transmission and Start over by Selecting another site.
`A further method of determining which Site might respond
`faster involves the use of a program which will ping a group
`of Selected Sites to see which will respond the fastest. A ping
`is a well known method of Sending a message to a server,
`essentially asking “are you there'?” The server will then
`respond that they are there. While this gives a good indica
`tion of the length of time for a download of a file to begin,
`it provides little information regarding the Speed at which
`Such a download will proceed. There is a need for an easier
`and more informative way to determine which server will
`provide the fastest download of a file. There is also a need
`for downloading information or files more quickly.
`
`SUMMARY
`Downloading of files is optimized based on which of
`multiple locations is most efficient in providing the files. In
`one implementation of the invention, portions of a file are
`downloaded from different Servers, and performance data
`Such as a bit rate for each Site is used to then Select the
`optimal Server to complete the download.
`In a further embodiment, an applet intercepts the request
`for the file from the browser and determines the best server
`to provide the file. When the request is intercepted, the
`applet reads a list of available file transfer protocol (ftp)
`
`2
`locations from which to download the file. The list may be
`hidden text in an hypertext markup language (HTML) page,
`or may actually be provided by a link on a Server. The applet
`or other type of program then may ping each site to prioritize
`the list based on Shortest response time. A first portion of the
`file is downloaded from one site, and throughput measure
`ments tracked. Using a reconnect internet protocol com
`mand to identify where the first download ended, a Second
`portion of the file is downloaded from the next site on the
`list, again with throughput measurements tracked. This
`process is repeated for further portions of the file, and the
`location with the best throughput is Selected to complete the
`file transfer. In Still further embodiments, a Same portion
`Such as the first portion is read from each Server to ensure
`consistent throughput measurements.
`In yet a further embodiment of the invention, the through
`put of the finally Selected Server is tracked as the file is
`downloaded. If the throughput drops below a desired
`throughput, the next best Server is Selected from the previous
`list, or the Selection and tracking proceSS is started again to
`determine if a faster Server has become available due to
`changes in demand on the Servers.
`The present invention provides improved information
`regarding the best Server from which to obtain a desired file,
`and the ability to download files quickly.
`
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`DESCRIPTION OF THE FIGURES
`FIG. 1 is a block diagram of a typical computer System in
`accordance with the present invention.
`FIG.2 is a flow chart of a module which determines which
`Server to use for a file transfer.
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`DETAILED DESCRIPTION
`In the following description, reference is made to the
`accompanying drawings which form a part hereof, and in
`which is shown by way of illustration specific embodiments
`in which the invention may be practiced. These embodi
`ments are described in Sufficient detail to enable those
`skilled in the art to practice the invention, and it is to be
`understood that other embodiments may be utilized and that
`Structural, logical and electrical changes may be made
`without departing from the Scope of the present invention.
`The following description is, therefore, not to be taken in a
`limited Sense, and the Scope of the present invention is
`defined by the appended claims.
`A Standard personal computer System is first described,
`followed by description of a module, Such as an applet that
`intercepts requests from a browser running on the computer
`System and determines which Server from a list of multiple
`servers is best to provide the file. The applet may also be a
`module or modules within the browser itself
`FIG. 1 shows a block diagram of a personal computer
`system 100 according to the present invention. In this
`embodiment, a processor 102, a System controller 112, a
`cache 114, and a data-path chip 118 are each coupled to a
`host bus 110. Processor 102 is a microprocessor Such as a
`486-type chip, a Pentiumrn(R), Pentium IICR) or other suitable
`microprocessor. Cache 114 provides high-Speed local
`memory data (in one embodiment, for example, 512 kB of
`data) for processor 102, and is controlled by System con
`troller 112, which loads cache 114 with data that is expected
`to be used Soon after the data is placed in cache 112 (i.e., in
`the near future). Main memory 116 is coupled between
`system controller 114 and data-path chip 118, and in one
`embodiment, provides random-acceSS memory of between
`
`-4-
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`

`

`3
`16 MB and 128 MB of data. In one embodiment, main
`memory 116 is provided on SIMMs (Single In-line Memory
`Modules), while in another embodiment, main memory 116
`is provided on DIMMs (Dual In-line Memory Modules),
`each of which plugs into Suitable Sockets provided on a
`motherboard holding many of the other components shown
`in FIG. 1. Main memory 116 includes standard DRAM
`(Dynamic Random-Access Memory), EDO (Extended Data
`Out) DRAM, SDRAM (Synchronous DRAM), or other
`Suitable memory technology. System controller 112 controls
`PCI (Peripheral Component Interconnect) bus 120, a local
`bus for system 100 that provides a high-speed data path
`between processor 102 and various peripheral devices, Such
`as graphics devices, Storage drives, network cabling, etc.
`Data-path chip 118 is also controlled by system controller
`112 to assist in routing data between main memory 116, host
`bus 110, and PCI bus 120.
`In one embodiment, PCI bus 120 provides a 32-bit-wide
`data path that runs at 33 MHz. In another embodiment, PCI
`bus 120 provides a 64-bit-wide data path that runs at 33
`MHz. In yet other embodiments, PCI bus 120 provides
`32-bit-wide or 64-bit-wide data paths that runs at higher
`speeds. In one embodiment, PCI bus 120 provides connec
`tivity to I/O bridge 122, graphics controller 127, and one or
`more PCI connectors 121 (i.e., sockets into which a card
`edge may be inserted), each of which accepts a standard PCI
`card. In one embodiment, I/O bridge 122 and graphics
`controller 127 are each integrated on the motherboard along
`with system controller 112, in order to avoid a board
`connector-board Signal-crossing interface and thus provide
`better speed and reliability. In the embodiment shown,
`graphics controller 127 is coupled to a video memory 128
`(that includes memory such as DRAM, EDO DRAM,
`SDRAM, or VRAM (Video Random-Access Memory)), and
`drives VGA (Video Graphics Adaptor) port 129. VGA port
`129 can connect to industry-standard monitorS Such as
`VGA-type, SVGA (Super VGA)-type, XGA-type (eXtended
`Graphics Adaptor) or SXGA-type (Super XGA) display
`devices. Other input/output (I/O) cards having a PCI inter
`face can be plugged into PCI connectorS 121.
`In one embodiment, I/O bridge 122 is a chip that provides
`connection and control to one or more independent IDE
`connectors 124-125, to a USB (Universal Serial Bus) port
`126, and to ISA (Industry Standard Architecture) bus 130. In
`this embodiment, IDE connector 124 provides connectivity
`for up to two standard IDE-type devices such as hard disk
`drives, CDROM (Compact Disk-Read-Only Memory)
`drives, DVD (Digital Video Disk) drives, or TBU (Tape
`Backup Unit) devices. In one similar embodiment, two IDE
`connectors 124 are provided, and each provide the EIDE
`(Enhanced IDE) architecture. In the embodiment shown,
`SCSI (Small Computer System Interface) connector 125
`provides connectivity for up to seven or fifteen SCSI-type
`devices (depending on the version of SCSI supported by the
`embodiment). In one embodiment, I/O bridge 122 provides
`ISAbus 130 having one or more ISA connectors 131 (in one
`embodiment, three connectors are provided). In one
`embodiment, ISA bus 130 is coupled to I/O controller 152,
`which in turn provides connections to two serial ports 154
`and 155, parallel port 156, and FDD (Floppy-Disk Drive)
`connector 157. In one embodiment, ISA bus 130 is con
`nected to buffer 132, which is connected to Xbus 140, which
`provides connections to real-time clock 142, keyboard/
`mouse controller 144 and keyboard BIOS ROM (Basic
`Input/Output System Read-Only Memory) 145, and to sys
`tem. BIOS ROM 146.
`Computer system 100, or other suitable computer system
`having a different configuration well known in the art is
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`many times used to run a common browser application
`which is used to acceSS and properly display information
`Stored on a network Such as the Internet. The information
`may be referred to as a file, which contains multimedia data,
`or just plain text. Some of the text contains a link or address
`to other files which may be stored on one or more servers
`attached to the network. When a user of computer system
`100 uses the browser to select the link, an applet indicated
`generally at 200 in FIG.2 may be configured to intercept the
`user's request for the file as indicated at 210. FIG. 2 is a
`flowchart of the applet 200, which may be run in the browser
`and set to look for file transfer protocol (ftp) requests or
`other types of file transfer requests. Each of the blocks or
`combinations of the blocks describe functionality that may
`be implemented in one or more Software modules which can
`easily be written by one skilled in the art with reference to
`the flowchart. The applet may automatically intercept Such
`requests and obtain a list of servers at 215 which contain the
`desired file by scanning hidden HTML text surrounding the
`link, or actually Scan the current file which contained the
`link for other visibly rendered links to multiple servers
`where the information or files may be obtained. In a further
`embodiment, a user may select a number of Server locations
`from which to obtain the file and provide them directly at
`215 without the need for automatic interruption at 210. This
`can be done by first invoking the applet 200 and then
`clicking on each of the desired links. Once all the links have
`been Selected, the applet may be requested to process the list.
`In still a further embodiment, the applet 200 obtains the list
`of possible servers from the server identified by the initial
`link.
`Once the applet 200 obtains the list, it reads the list, and
`Sends a "ping to each Server at 220, keeping track of the
`amount of time for each server to respond. This provides an
`indication of which Server responds the fastest, and may be
`a good candidate from which to obtain the file in the fastest
`manner. The list may then be prioritized in one embodiment,
`or may be used as is without any attempt to provide an initial
`prioritization.
`At 225, a first portion of the file is requested from the
`highest priority Server. The throughput of Such Server is
`tracked at 230, such as by a bits per second indication. The
`time for ping response obtained in initially prioritizing the
`list of servers is Subtracted from the time it takes to down
`load the first portion in one embodiment to obtain a better
`indication of true bit rate. After the first server has completed
`delivering the first portion of the file, a reconnect internet
`protocol (IP) command is used to indicate to the Second
`server that a file transfer was interrupted. With some well
`known handshaking, a starting address is provided to the
`Second Server, and a Second portion of the file is transferred
`from the Second Server. Throughput of this transfer is also
`tracked and the rest of the Servers are contacted in the same
`manner to obtain further consecutive or contiguous portions
`of the file. Once all the servers in the list have completed, the
`performance as measured by throughput is ranked, and the
`rest of the file is requested at 235 from the highest through
`put Server which is Selected as the optimal Server.
`The throughput may further be monitored at 240 from the
`optimal Server. This is done because performance may
`change over time for very large files. If the performance falls
`below a desired rate at 245, a different server may be
`Selected. Either the next server on the previously generated
`performance ranked list may be selected for continuation of
`the transmission, or the performance of each Server may be
`redetermined Starting again at 225. If the performance does
`not fall below a desired rate, the transfer is completed with
`the elected optimal Server.
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`

`S
`The desired rate for decision block 245 may be estab
`lished as a desired percentage of the throughput as deter
`mined at step 230, such as 75%. In this manner, if reselection
`if performed at 250, the desired percentage of throughput is
`again determined based on the measured throughput of the
`Server which is Selected to complete the transmission. A
`Sliding average may be used to Smooth out short term
`variations in transmission rates to prevent frequent Switch
`ing of Servers.
`It is to be understood that the above description is
`intended to be illustrative, and not restrictive. Many other
`embodiments will be apparent to those of skill in the art
`upon reviewing the above description. Downloading of files
`is optimized based on which of multiple locations is most
`efficient in providing the files. In one implementation of the
`invention, portions of a file are downloaded from different
`Servers, and performance data Such as a bit rate for each Site
`is used to then Select the optimal Server to complete the
`download. The size of the portions may be either temporal
`in nature, Such as one or more Seconds, or may be based on
`a predetermined number of bytes or blocks of data. In one
`embodiment, the first 500 bits are selected as the first
`portion, the Second 500 as the Second portion and So on. For
`Small files of a few thousand or more bits, the selection
`proceSS may be bypassed if desired. Embedded pictures may
`also be specified by indicating that an entire block should be
`obtained if encountered prior to completing a Specified
`portion.
`The applet may be Software Stored on computer readable
`media, and may be written in any of Several languages, Such
`as Java (trademark of Sun Microsystems of Palo Alto, Calif.)
`or other languages. The functionality of the applet may be
`provided in many of multiple forms, and may be built into
`the browser itself or as a separate application, or even as part
`of the operating System. It may be fully automated, or may
`present the results of the Server throughput to the user for
`user Selection. It is usually Stored on computer readable
`medium such as cache 114, main memory 116 or disk drives
`which are coupled to IDE connector 124, SCSI connector
`125 or USB port 126. Further, a carrier wave may be used
`as a computer readable medium to transmit the applet. The
`scope of the invention should, therefore, be determined with
`reference to the appended claims, along with the full Scope
`of equivalents to which Such claims are entitled.
`What is claimed is:
`1. A System for downloading a desired file from a network
`of multiple servers which have a copy of the file, the system
`comprising:
`means for identifying the locations of the desired file at
`each Server;
`means for estimating a throughput rate of transfer of the
`desired file from each Server, and
`means for Selecting the Server having the best estimated
`throughput rate for completing transfer of the desired
`file;
`wherein Said means for estimating further comprises:
`means for initiating the transfer of Selected portions of the
`file from each Server, and
`means for determining the time to receive the Selected
`portions of the file from each server.
`2. The system of claim 1, wherein the selected portions of
`the file comprise consecutive portion of the file.
`3. The system of claim 1 wherein the selected portions of
`the file comprise substantially the same portion of the file
`from each Server.
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`4. The System of claim 1 and further comprising:
`means for estimating latency of each Server; and
`means for Subtracting the latency during the measuring of
`the throughput of each Server.
`5. A system for downloading a desired file from a network
`of multiple servers which have a copy of the file, the system
`comprising:
`means for identifying the locations of the desired file at
`each Server;
`means for measuring a latency for each Server;
`means for measuring a time taken to transfer Selected
`portions of information from each Server,
`means for Subtracting the latency from Such time taken
`and to provide a throughput rate; and
`means for Selecting the Server having the best measured
`throughput rate for completing transfer of the desired
`file;
`wherein the Selected portions of information comprise
`Substantially the same portion of the desired file from
`each Server.
`6. The system of claim 5 wherein the selected portions of
`information comprise consecutive portions of the desired
`file.
`7. A computerized System for downloading desired files
`from a network of multiple Servers, Some of which have a
`copy of the file, the System comprising:
`a module that obtains a list of Servers having a copy of a
`desired file;
`a download module that initiates downloading of Selected
`portions of the desired file from multiple servers; and
`a module that measures the throughput from each of Said
`Server and Selects an optimal Server for completion of
`downloading of the file, and
`further comprising a module for monitoring the through
`put of the Selected optimal Server and Selecting a new
`optimal server if the throughput falls below a desired
`level.
`8. The system of claim 7 wherein the module that obtains
`the list comprises an applet that intercepts file transfer
`requests from a browser.
`9. The system of claim 7 wherein the selected portions
`comprise consecutive portions of the file.
`10. The system of claim 9 wherein the download module
`issues a reconnect IP command to obtain each consecutive
`portion by identifying a beginning address of the file.
`11. A method of downloading desired files from a network
`of multiple Servers, Some of which have a copy of the file,
`the method comprising:
`obtaining a list of Servers having a copy of a desired file,
`downloading Selected portions of the desired file from
`multiple different servers;
`measuring the throughput from each Server; and
`Selecting an optimal Server for completion of the down
`load of the desired file,
`further comprising monitoring the throughput of the
`Selected optional Server; and
`further comprising Selecting a new optimal Server if the
`throughput of the selected optimal server falls below a
`desired level.
`12. The method of claim 11 and further comprising:
`measuring a time for response to a message from each
`SCWC.
`13. The method of claim 12 wherein the message com
`prises a ping.
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`7
`14. The method of claim 12 wherein the time for response
`from each server is Subtracted from the time measured for
`downloading each portion from each corresponding Server.
`15. The method of claim 11 wherein the new optimal
`Server is Selected based on previously measured throughput
`from each Server.
`16. The method of claim 11 wherein the new optimal
`Server is Selected based current measurement of throughput
`as in claim 14.
`17. The method of claim 11 wherein the selected portions
`comprise the same portion.
`18. The method of claim 11 wherein the selected portions
`comprise consecutive portions of the desired file.
`19. The method of claim 11 wherein the size of the
`Selected portions is based on a predetermined number of
`bits, or on a predetermined time for downloading.
`20. A computer readable medium having instructions
`Stored thereon for causing a computer to implement a
`method of downloading desired files from a network of
`multiple Servers, Some of which have a copy of the file, the
`method comprising:
`obtaining a list of Servers having a copy of a desired file;
`downloading Selected portions of the desired file from
`multiple different servers;
`measuring the throughput from each Such Server; and
`Selecting an optimal Server for completion of the down
`load of the desired file; and
`further comprising monitoring the throughput of the
`Selected optimal Server and Selecting a new optimal
`server if the throughput falls below a desired level;
`completing downloading of the file.
`21. A computer readable medium having instructions
`Stored thereon for causing a computer to implement a
`method of downloading desired files from a network of
`multiple Servers, Some of which have a copy of the file, the
`method comprising:
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`1O
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`15
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`25
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`35
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`US 6,477,522 B1
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`8
`obtaining a list of Servers having a copy of a desired file;
`downloading Selected portions of the desired file from
`multiple different servers;
`measuring the throughput from each Such Server;
`Selecting an optimal Server for completion of the down
`load of the desired file;
`monitoring the throughput as the Selected optimal Server
`downloads the rest of the file; and
`redetermining an optimal Server if the throughput of the
`selected optimal server falls below a desired level.
`22. A computer implemented method of Selecting a Server
`for downloading a desired file from a network of multiple
`Servers which have a copy of the file, the method compris
`ing:
`identifying the locations of the desired file at each Server;
`measuring a latency for each Server;
`measuring a time taken to transfer Selected portions of
`information from each Server;
`Subtracting the latency from Such time taken and to
`provide a throughput rate; and
`Selecting the Server having the best measured throughput
`rate for completion of transfer of the desired file;
`wherein the Selected portions of information comprise
`Substantially the same portion of the desired file from
`each Server.
`23. The method of claim 22 and further comprising:
`transferring remaining portions of the file from the
`Selected Server.
`24. A computer readable medium having instructions
`Stored thereon for causing a computer to perform the method
`of claim 22.
`
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