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RELATED PATENT APPLICATIONS
Related patent applications include commonly assigned copending patent
application U.S. Ser. No. 08/085,264 filed on filed on the same date as
the present application, entitled "SYSTEM AND METHOD FOR PROVIDING
MULTIMEDIA QUALITY OF SERVICE SESSIONS IN A COMMUNICATIONS NETWORK",
hereby incorporated by reference; commonly assigned copending patent
application U.S. Ser. No. 08/085,274 filed on the same date as the present
application, entitled "SYSTEM AND METHOD FOR BANDWIDTH RESERVATION FOR
MULTIMEDIA TRAFFIC IN COMMUNICATIONS NETWORKS" now U.S. Pat. No.
5,388,097, hereby incorporated by reference; and commonly assigned
copending patent application U.S. Ser. No. 08/085,275 filed on the same
date as the present application, entitled "MULTIMEDIA RESOURCE RESERVATION
SYSTEM", hereby incorporated by reference.
TECHNICAL FIELD
The present invention relates to data processing systems and more
particularly to data processing systems providing resource reservation to
assure a desired quality of service.
BACKGROUND ART
It has long been known to provide computer workstations interconnected by
digital communication networks whereby users of the individual
workstations may communicate with one another over the network for tasks
such as file serving from a host or server to client computers. This has
been previously common, for example, by means of a typed note, data or
program file transmitted to another user. More recently, users have
increasingly requested multimedia file services, desktop conferencing,
remote presentations, and other multimedia applications between network
users. However, such multimedia applications utilizing data-intensive
sound, voice, and video flows require performance guarantees for high disk
access and high bandwidth communication links between distributed
computing systems with minimal communication delay, maximum throughput,
and instantaneous burst communication capability. As a result, it has
become very difficult to schedule appropriate resources to meet the
requirements of such multimedia applications.
Prior art has recognized that certain data in a network, such as that
associated with multimedia, may require priority handling. Thus, for
example, a "quality of service " (QOS) or bandwidth has been defined in
the literature. Quality of service or bandwidth seeks to describe various
parameters which may be specified in an attempt to define certain minimum
requirements which must be met for transmission of given data types over
the network. See, for example, quality of service standards set forth in
the OSI TP4 Open System Interconnect Standard X.214 and the quality of
service standards defined in CCITTQ.931 (ISDN), Q.933 (frame relay), and
Q.93B (B-ISDN ATM) drafts. As yet another example there is an architected
priority mechanism in the IEEE 802.5 Token Ring. A station on the ring
with a high priority frame to send may indicate this in an access control
field of a passing frame. When a station sending the frame releases the
token, it releases the token at the priority of the AC field, and
eventually sets it back to its original priority as specified in an IEEE
802.5 medium access control protocol. The IEEE standard and
implementations thereof merely specify a protocol for increasing and
decreasing priority. However, the user of such a service, such as a
client-server file system, has to determine when service guarantees are
needed for certain file accesses. For example, multimedia file reads for
playing sound, voice, and video from a server to a client need certain
quality of service guarantees.
Allocating resources when a connection is made between digital computers,
such as for a client-server session, is known where memory is allocated to
hold information related to the session. Buffers are also commonly
reserved for file access on computers, such as on a server computer.
Buffers may also be reserved on the client computer for multimedia file
where a memory buffer must be large enough to store a reserve of file
elements so that variations in delay between the server and client are
absorbed. That is, there should be enough file elements stored in the
memory buffer so that the buffer will not go empty during the playback of
sound, voice or video. Otherwise, a glitch or jitter will occur causing a
deterioration in the quality of a presentation. For example, if the
maximum delay is two seconds and the multimedia flow averages 150
kilobytes per second, then a buffer at least 300 kilobytes in size is
needed to preserve quality of service.
Many types of files contain information in their header useful for
determining such quality of service parameters. Other types of files may
require that the file be read, parsed or scanned to determine such quality
of service parameters. However, in a general purpose client-server
environment, a very large variety of file types and formats exist and a
file server may not be programmed to determine quality of service
parameters in all cases. In addition, an application program, running on a
workstation in a client-server environment, may not recognize whether a
file being accessed is located on the workstation or on a remote file
server. If the file is located on the application program workstation,
then quality of service is generally met. However, if the file being
accessed is located on a remote server, then the file access must contend
for server resources such as disk cycles or bandwidth, disk controller
cycles, system bus resources, server processor resources, and network
resources. As a result, it is difficult to maintain quality of service in
a client-server environment for remote file accesses.
DISCLOSURE OF THE INVENTION
A method for providing files to a remote node including the steps of
determining whether bandwidth is available for transmitting across a
communications link a file requested by a remote node, reserving bandwidth
for the requested file if bandwidth is determined to be available, and
opening the requested file for transmission only if bandwidth is reserved.
In addition, an apparatus for providing files to a remote node including
apparatus for determining whether bandwidth is available for transmitting
across a communications link a file requested by a remote node, apparatus
for reserving bandwidth for the requested file if bandwidth is determined
to be available, and apparatus for opening the requested file for
transmission only if bandwidth is reserved.
A further understanding of the nature and advantages of the present
invention may be realized by reference to the remaining portions of the
specification and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a typical data processing system utilized by a
preferred embodiment of the invention;
FIG. 2 is an illustration of a data processing system including three
workstations interconnected by a network in accordance with the subject
invention;
FIG. 3 is a block diagram illustrating a multilayered computer
communication network model based upon the OSI layered reference model;
FIG. 4 is a block diagram of a preferred layered open systems
interconnection model showing the relationship of components of the
subject invention to the layers;
FIG. 5 is a flowchart illustrating initializing a host system with default
quality of service parameters for types of files;
FIG. 6 illustrates a default table generated by the process described in
FIG. 5;
FIGS. 7A-7C are a flowchart illustrating a preferred method for
individually determining quality of service parameters for files;
FIG. 8 is a block diagram of a reservation table utilized by the resource
reservation system to handle resource reservations according to a
preferred embodiment of the invention; and
FIGS. 9A-9B are a flowchart illustrating a preferred method for reserving a
desired quality of service of various resources.
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a block diagram of a typical data processing system 100 utilized
by a preferred embodiment of the invention. The data processing system
includes main processor(s) 110 coupled to a main memory 120 in computer
box 105 with input device(s) 130 and output device(s) 140 attached. Main
processor(s) 110 may include a single processor or multiple processors.
Input device(s) 130 may include a keyboard, mouse, tablet or other types
of input devices. Output device(s) 140 may include a text monitor, plotter
or other types of output devices.
The main processor may also be coupled to graphics output device(s) 210
such as a graphics display through a graphics adapter 200. Graphics
adapter 200 may be located in an adapter slot 160A. Graphics adapter 200
receives instructions regarding graphics from main processor 110 on bus
150, thereby rendering the desired graphics output from the main
processor.
A communications adapter 250 such as a modem or a network adapter for
networks such as token ring or ethernet may be located in slot 160C. The
slot provides communications with main processor 110 across bus 150.
Communications adapter 250 may communicate with other data processing
systems 270 across communications line 260. As a result, the main
processor may communicate with other data processing systems 270 via bus
150, slot 160C, communications adapter 250 and communications line 260.
A hard disk 255 may be located in slot 160D to provide additional memory
for use by the main processor. Computer readable removable media 290, such
as a magnetic diskette or a compact disc, may be inserted into an
input/output device 285, such as a disk drive or a CD-ROM (compact
disc--read only memory) drive. Data is read from or written to the
removable media by the I/O device under the control of the I/O device
controller 280. The I/O device controller communicates with the main
processor through slot 160E across bus 150. Main memory 120, hard disk 255
and removable media 290 are all referred to as memory for storing data for
processing by processor 110. One of the preferred implementations of the
present invention is as several sets of instructions in a code module
resident in the main memory 120. Until required by the computer system,
the sets of instructions may be stored in another computer memory, for
example, in a hard disk drive, or in a removable memory such as an optical
disk or floppy disk for eventual use in a CDROM or the floppy disk drive.
FIG. 2 illustrates a data processing system comprising a number of
workstations (here, three workstations 300, 320, and 330) interconnected
by a pair of data networks 310 and 340 (also referred to as communications
links), so as to permit communication between the workstations (also
referred to as nodes). It is assumed that the data processing shown in
FIG. 2 is of a type which permits concurrent real-time communication
between the users. The network operates according to a conventional
network protocol, such as the token ring protocol described in Token Ring
NetWork Architecture reference, SC30-3374, IBM, 1989.
FIG. 2 depicts only one possible hardware configuration for a data
processing network. Other configurations are possible. For example, the
data processing system could be based upon a star network, or a host
processor connected to a plurality of dumb terminals, or could further be
based upon a plurality of remote processors connected by a communication
network. the networks could also be based upon the telephone network, and
ISDN network, or any other "dial up" networks. Moreover, the workstations
could be located within the single workspace or within a local area, or
could be remote from one another. A source for detailing technical
planning information for configuring a network of workstations in
accordance with the invention, is the IBM Extended Services for OS/2
Example Scenarios Manual , 1991.
Multimedia computing is the processing of various media, such as video,
waveform audio, musical instrument digital interface (MIDI) streams,
animation, graphics, and text. Media processing includes the capture,
authoring (editing) and playback of media streams as well as other data
processing applications. Multimedia documents which are stored on some
non-volatile medium, such as a disk, are referred to as recorded
multimedia applications. There are also live multimedia applications in
which two or more people communicate with each other at the same time
using a computer. Live multimedia applications are normally conducted
across space and time indicating that live multimedia is inherently
distributed. Even recorded multimedia applications require distributed
file system services to share large volumes of stored media, such as video
disk, audio information, or computer-generated images. Thus, it is
critical that a prioritizing scheme in accordance with the invention for
multimedia applications includes support for a distributed environment.
To reduce design complexity, most networks are organized as a series of
layers, each one built upon its predecessor as described in Computer
Networks, Tannenbaum, Andrew S., Prentice Hall (1988) and OSI, A Model for
Computer Communications Standards, Black, Ulyess, Prentice Hall, 1991. The
number of layers, the name of each layer, contents, and function of each
layer differ from network to network. However, in each network, the
purpose of the layers is to offer certain services to the higher layers,
shielding those layers from the details of how the offered services are
actually implemented. The purpose, function, and details of each of the
layers and their interaction is set forth in the previously noted
references and is familiar to communication programmers ordinarily skilled
in the art.
Priority assurance is an important factor in ensuring bandwidth or quality
of service, and is enabled by operation of a component which may be
implemented in hardware logic or software. The component regulates access
to the priority queue or transmit channel that is attached to the shared
medium local area network section. Access to the priority queue or
transmit channel will pass through this component, thus subjecting all
communication transactions to rejection or tracking by the component. A
more detailed discussion of this component and the related station's
bandwidth manager component are described in commonly assigned copending
patent application U.S. Ser. No. 07/930,587, filed Aug. 17, 1992, entitled
"Network Priority Management" (IBM Docket No. AT9-92-089), hereby
incorporated by reference.
FIG. 3 is a block diagram illustrating a multilayered computer
communication network model based upon the OSI layered reference model.
Further detail of this OSI and related IEEE models may be found in OSI, A
Model for Computer Communications Standards, infra. A client system 20A is
shown communicating with a server system 20B across a communications link
30. The seven layers of the OSI model for each system are shown as
reference numerals 40-52. The lowest layer is physical layer 40A-40B which
is responsible for implementing a physical circuit between data terminal
equipment and data circuit terminating equipment.
A data link layer 42A-42B is responsible for transfer of data across the
link. A network layer 44A-44B specifies the interface of the user into a
network and also defines network switching/routing and communications
between networks. A transport layer 46A-46B provides an interface between
the data communications network and the upper three layers. This layer is
of particular interest because it provides the user options in obtaining
certain levels of quality, and is designed to keep the user isolated from
some of the physical and functional aspects of the network. A session
layer 48A-48B serves as a user interface into the transport layer below,
providing a means for exchange of data between users such as simultaneous
transmission, alternate transmission, checkpoint procedures and the like.
The remaining two layers, a presentation layer 50A-50B and an application
layer 52A-52B ensure that user applications can communicate with each
other and further concern the support of the end-user application process.
Please note that each of the client system layers is shown communicating
with the corresponding server system layers. Although each of the layers
perceives that these communications are direct, the communications are
shown as dotted lines because the only direct communications are performed
through the network.
It will be noted from FIG. 3 that there are other implementations in the
art of such an OSI reference model bearing varying degrees of similarity
thereto, a portion of one being depicted in the left part of FIG. 3 as the
IEEE model, a physical layer 60 may be seen corresponding to the physical
layer of the OSI model. The IEEE recognized a need to divide the data link
layer into two sublayers in order to handle different link configurations
and thus a medium access control (MAC) 62 and logical link control (LLC)
64 were provided for. The sublayer is protocol-specific (such as to a LAN
such as Ethernet) whereas the LLC serves as an interface to an upper layer
protocol, typically the network layer (and isolates the network layer from
the specific actions of the MAC sublayer). One purpose of depicting
varying forms of a multilayered computer communication network in FIG. 3
is to illustrate that the invention admits to implementations in any
number of such multilayered models, and is thereby not intended to be
limited to application to the OSI reference model emphasized in the
description herein.
FIG. 4 is a block diagram of a preferred layered open systems
interconnection model showing the relationship of components of the
subject invention to the layers and to the data processing system. An
application program 70 on a client system seeks a file to be accessed
through a file system application program interface (API) 72 to a
redirector 74. If the file is not located on the client system, then the
redirector determines which remote system, such as the server system, has
the desired file. If the file is located on the client system, then the
file is accessed on a local file system not shown. If the file is located
on the server system, then the redirector passes a request for access to
the desired file to the server system through a communications transport
76 (such as netbios or TCP/IP) to a network adapter device driver 78. The
network device driver then sends the request to the server system through
a network adapter 79 across a communications link 80 (such as ethernet or
token ring) to the server system network adapter 99 and network adapter
device driver 98. The network adapter device driver then passes the
request on to the communications transport 96. The communications
transport then passes the request on to a high performance file system
(HPFS) 94. The high performance file system then passes the file request
onto a resource reservation system (RRS) 92. The resource reservation
system then determines whether there are any quality of service parameters
for the requested file. If not, then the resource reservation system so
notifies the high performance file system. The high performance file
system then accesses the file on a local disk drive not shown. If the
resource reservation system determines that there are quality of service
parameters for the requested file, then the resource reservation system
then automatically reserves the appropriate resources to ensure that the
quality of service for the file is maintained. This process will be
described in detail below. The resource reservation system so notifies the
high performance file system. The high performance file system then opens
and accesses the file through a local file system to a local disk drive.
Access to the file is then provided to the requesting application program,
with quality of service guarantees if established, and the application
program is so notified. This notification occurs through communications
transport 96, network device driver 98, network adapter 99, communications
link 80, network adapter 79, network device driver 78, communications
transport 76, redirector 74, and file system API 72. Please note that the
elements of the client and server systems are shown corresponding to
layers of the OSI model described above. In addition, the elements of the
client and host systems correspond to the elements of the data processing
system described above. Elements 70-78 reside in memory of the client
system and are executed by the client system processor. Network adapters
79 and 99 are communications adapters for the client and hosts systems
respectively. In addition, portions of the network adapter device drivers
may reside on and be executed by the network adapters. Communications link
80 may be a network such as Ethernet or Token ring. Elements 92-98 reside
in memory of the host system and are executed by the host system
processor.
This system allows for easy access to the files across a network and also
provides the capabilities for an automatic resource reservation system as
will be described below.
Determining Quality of Service Parameters
There are many types of quality of service parameters known in the art. The
parameters of particular interest to a preferred embodiment of the
invention are throughput, burst, and delay. Throughput is the average
amount of information passed through the communications link in a given
period of time such as 150 kilobytes per second. Burst is the maximum
amount of information passed through the communications link in a short
period of time. Delay is the maximum amount of delay that can be
tolerated, typically due to buffer size in relation to throughput.
Default quality of service parameters may be provided for files for types
of files. That is, files are typically stored as XXXXXX.YYY where .YYY is
the extension of the file. The extension typically describes the type of
the file (e.g. .VOC for a voice file and .WAV for a wave file). These
default values may be provided.
FIG. 5 is a flowchart illustrating initializing a host system with default
quality of service parameters for types of files. In step 350, the user
provides to the high performance file system (HPFS) a quality of service
(QOS) file listing file types and quality of service parameters for each
file type. The user may provide this QOS file in a variety of ways. A soft
copy of a QOS file may be provided with a set of multimedia files by a
vendor and provided therewith for installation by the user or the vendor
may provide a software tool for the user to use to create the QOS file. In
addition, the user may respond to a set of queries from the host system.
In step 360, the first entry in the QOS file is read. In step 370, if end
of file is not reached, then processing continues to step 380. In step
380, a description of the file type and its quality of service parameters
are extracted from the record and added to a default table in memory. FIG.
6 illustrates a default table 392 generated by the process described in
FIG. 5. The default table may include values for file type 393, throughput
394, burst 395, and delay 396. Processing then returns to step 360 to read
the next record in the QOS file. If end of file is reached in step 370,
then the default table containing the file types and quality of service
parameters are provided to the resource reservation system (RRS) for later
use as will be described below.
FIGS. 7A-7C are a flowchart illustrating a preferred method for
individually determining quality of service parameters for files. There
are many types of files which may require quality of service and it is
preferable to obtain the quality of service parameters for an individual
file when that file is transferred to the host computer for storage on the
host computer. This individual determination of quality of service
parameters for files may be performed automatically for certain types of
files such as voice (VOC), wave (WAV), audio-visual (AVI), or other types
of multimedia files. These quality of service parameters may also be
obtained by querying the operator as the files are transferred and stored
in the host computer. In an alternative embodiment, the quality of service
parameters may be determined when a file is first used or at each use of a
file. In another alternative embodiment, the quality of service parameters
may be determined for an application by accumulating the quality of
service parameters of each file to be accessed by the application.
In step 400, the file is transferred to the host computer for storage. The
host computer may receive the file from an external media such as a CD-ROM
or floppy disk, or from another data processing system across a
communications adapter. In step 405, it is determined whether quality of
service parameters are to be calculated for the transferred file. The user
may request calculation of quality of service parameters by using a
particular command to transfer the file to the host system. In addition,
the host system may automatically calculate quality of service parameters
for certain types of files. If no parameters are to be calculated, then
processing ends. Otherwise, in step 410, a quality of service calculation
utility may be executed to determine the quality of service parameters for
the file. This utility may be executed at the request of the user storing
the file on the host system or the utility may be automatically executed
for certain types of predesignated files. In step 420 the extension of the
file is obtained. That is, files are typically stored as XXXXXX.YYY where
.YYY is the extension of the file. The extension typically describes the
type of the file (e.g. .VOC for a voice file and .WAV for a wave file).
Multimedia files are preferably distinguished into two types, fixed sample
or variable sample. Fixed sample files have fixed length sample records
and may include a header record describing the records. An example of a
fixed sample file is a voice (VOC) file which typically has a header
followed by a number of contiguous bytes, each byte being an eight sample.
The header provides information about the sampling rate (e.g. 8000, 11000
or 44000 samples per second) and the number of channels (e.g. one for
mono, two for stereo, more than two for multichannel). Variable sample
files have variable length sample records and require greater processing
to determine quality of service parameters according to the preferred
embodiment of the invention. An example of a variable sample file is a
digital video interactive (DVI) file which has a series of reference
frames with two or more delta frames interspersed between each pair of
reference frames. The size of the delta frames depends on the amount of
movement occurring between reference frames. In step 430, based on the
extension, if the file is a fixed sample file then processing continues to
the flowchart of FIG. 7B. If the file is a variable sample file, then
processing continues to the flowchart of FIG. 7C.
Once the quality of service parameters are obtained, then in step 440, the
quality of service parameters are preferably stored as extended attributes
of the file. That is, many operating systems such as OS/2 (trademark of
International Business Machines Corp.) have the capability of storing and
retrieving extended attributes for any file without requiring the file be
opened. Extended attributes are described in detail in the OS/2 2.0
Technical Library, Programming Guide, Volume 1, Version 2.00, hereby
incorporated by reference. As a result, the extended attributes may be
accessed to determine whether appropriate resources are available for
utilizing the file prior to opening the file. In alternative embodiments,
the quality of service parameters may be stored in the file or may be
stored in a table with reference to the file. If the quality of service
parameters are determined each time the file is used, then the parameters
do not need to be stored.
FIG. 7B is a flowchart illustrating a preferred method for determining
quality of service parameters for fixed sample files (that is, files that
have fixed length records for each sample and typically have a header
record describing the records). In step 500, the file header is read. If a
file header is not available, then the first record in the file is read.
In step 510, information for determining quality of service is extracted
from the file header or the first record. For fixed sample records, the
number of concurrent channels or data streams, the frequency of sampling
data, and the sample size are extracted from the file.
In step 520, the quality of service parameters are calculated from the
information obtained from the file. These parameters are determined for
reading the files. However, the parameters could also be determined for
writing to the files. The quality of service parameters typically
determined are rea | | |
