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Description  |
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TECHNICAL FIELD
This invention relates to network systems, and particularly public network
systems, such as the Internet. More particularly, this invention relates
to methods which improve distribution of streaming continuous data (e.g.,
audio and video data) from a content provider over a network to a
subscriber's computer or other content rendering unit.
BACKGROUND OF THE INVENTION
Public networks, and most notably the Internet, are emerging as a primary
conduit for communications, entertainment, and business services. The
Internet is a network formed by the cooperative interconnection of
computing networks, including local and wide area networks. It
interconnects computers from around the world with existing and even
incompatible technologies by employing common protocols that smoothly
integrate the individual and diverse components.
The Internet has recently been popularized by the overwhelming and rapid
success of the World Wide Web (WWW or Web). The Web is a graphical user
interface to the Internet that facilitates interaction between users and
the Internet. The Web links together various topics in a complex,
non-sequential web of associations which permit a user to browse from one
topic to another, regardless of the presented order of topics. A "Web
browser" is an application which executes on the user's computer to
navigate the Web. The Web browser allows a user to retrieve and render
hypermedia content from the WWW, including text, sound, images, video, and
other data.
One problem facing the continued growth and acceptance of the Internet
concerns dissemination of streaming continuous data, such as video and
audio content. Data is delivered and rendered to users in essentially two
formats. The first format, referred to as "block data," entails
downloading the entire data set to local storage and then rendering the
data from the locally stored copy. A second delivery format, known as
"streaming data," entails sending bits of data continuously over the
network for just-in-time rendering.
Computer network users have been conditioned through their experiences with
television and CD-ROM multimedia applications to expect instantaneous
streaming data on demand. For technical reasons, however, the Internet is
often unable to deliver streaming data. This inability is most pronounced
for video data. In the Internet context, there is often long delays
between the time video content is requested and the time when the video
content actually begins playing. It is not uncommon to wait several
minutes for a video file to begin playing. In essence, for factors
discussed below, video data is traditionally delivered as "block data"
over the Internet and thus requires that the entire file be downloaded
prior to rendering.
The inability to provide streaming data is a result of too little bandwidth
in the distribution network. "Bandwidth" is the amount of data that can be
moved through a particular network segment at any one time. The Internet
is a conglomerate of different technologies with different associated
bandwidths. Distribution over the Internet is usually constrained by the
segment with the lowest available bandwidth.
FIG. 1 shows a model of a public network system 20, such as the Internet.
The network system 20 includes a content server 22 (e.g., a Web server)
which stores and serves multimedia data over a distribution network 24.
The network system 20 also has regional independent service providers
(ISPs) or point of presence (POP) operators, as represented by ISP 26,
which provide the connectivity to the primary distribution network 24.
Many users, as represented by subscriber computers 28, 30, and 32, are
connected to the ISP 26 to gain access to the Internet.
The ISP 26 is connected to the distribution network 24 with a network
connection 34. In this example illustration, the network connection 34 is
a "T1" connection. "T1" is a unit of bandwidth having a base throughput
speed of approximately 1.5 Mbps (Megabits per second). Another common high
bandwidth connection is a T3 connection, which has a base throughput speed
of approximately 44.7 Mbps. For purposes of explaining the state of the
technology and the practical problems with providing real-time streaming
data over the Internet, it is sufficient to understand that there is also
a limited bandwidth connection between the content server 22 and the
distribution network 24.
The subscriber computers 28, 30, and 32 are connected to their host ISP 26
via home entry lines, such as telephone or cable lines, and compatible
modems. As examples of commercially available technology, subscriber
computer 28 is connected to ISP 26 over a 14.4K connection 36 which
consists of a standard telephone line and a V.32bis modem to enable a
maximum data rate of 14.4 Kbps (Kilobits per second). Subscriber computer
30 is connected to the ISP 26 with a 28.8K connection 38 (telephone line
and V.34 modem) which supports a data rate of 28.8 Kbps. Subscriber
computer 32 is connected to the ISP 26 with an ISDN connection 40 which is
a special type of telephone line that facilitates data flow in the range
of 128-132 Kbps. Table 1 summarizes connection technologies that are
available today.
TABLE 1
Connection Technologies and Throughput
Connection Type Base Speed (Kbps)
V.32bis modem 14.4
V.34 modem 28.8
56K Leased Line 56
ISDN BRI (1 channel) 56-64
ISDN BRI (2 channels) 128-132
Frame Relay 56-1,544
Fractional T1 256-1,280
ISDN PRI 1,544
Full T1 (24 channels) 1,544
ADSL 2,000-6,000
Cable Modem 27,000
T3 44,736
With a T1 connection to the primary distribution network 24, the ISP 26 can
facilitate a maximum data flow of approximately 1.5 Mbps. This bandwidth
is available to serve all of the subscribers of the ISP. When subscriber
computer 28 is connected and downloading data files, it requires a 14.4
Kbps slice of the 1.5 Mbps bandwidth. Subscriber computers 30 and 32
consume 28.8 Kbps and 128 Kbps slices, respectively, of the available
bandwidth.
The ISP can accommodate simultaneous requests from a number of subscribers.
As more subscribers utilize the ISP services, however, there is less
available bandwidth to satisfy the subscribers requests. If too many
requests are received, the ISP becomes overburdened and may not be able to
adequately service the requests in a timely manner, causing frustration to
the subscribers. If latency problems persist, the ISP can purchase more
bandwidth by adding additional capacity (e.g., upgrading to a T3
connection or adding more T1 connections). Unfortunately, adding more
bandwidth may not be economically wise for the ISP. The load placed on the
ISP typically fluctuates throughout different times of the day. Adding
expensive bandwidth to more readily service short duration high-demand
times may not be profitable if the present capacity adequately services
the subscriber traffic during most of the day.
The latency problems are perhaps the most pronounced when working with
video. There are few things more frustrating to a user than trying to
download video over the Internet. The problem is that video requires large
bandwidth in comparison to text files, graphics, and pictures.
Additionally, unlike still images or text files, video is presented as
moving images which are played continuously without interruption. Video
typically requires a 1.2 Mbps for real-time streaming data. This 1.2 Mbps
throughput requirement consumes nearly all of a T1 bandwidth (1.5 Mbps).
Accordingly, when multiple subscribers are coupled to the ISP and one
subscriber requests a video file, there is generally not enough capacity
to stream the video in real-time from the content server 22 over the
Internet to the requesting subscriber. Instead, the video file is
typically delivered in its entirety and only then played on the subscriber
computer. Unfortunately, even downloading video files in the block data
format is often inconvenient and usually requires an excessive amount of
time.
Consider the following example. Suppose a subscriber wishes to access the
CNN Web site on the Internet for an account of recent news. As part of the
news materials, CNN provides a twenty second video clip of an airplane
hijacking incident. At 1.2 Mbps, the 20 second video clip involves
downloading a 24 Mbyte file over the Internet. If the user has a modest
14.4 Kbps connection, it would take approximately 28 minutes to download
the entire file.
Now, assume that the subscriber/ISP connection is sufficiently large to
handle real-time video streaming of the video file, meaning that the
subscriber computer can render the video data as it is received from the
ISP. Despite the bandwidth of the subscriber/ISP connection, real-time
video streaming may still be unachievable if the T1 connection 34 between
the ISP 26 and the distribution network 24 is unable, or unwilling due to
policy reasons, to dedicate 1.2 Mbps of its bandwidth to the video file.
Requests for the CNN video clip made during peak traffic times at the ISP
most certainly could not be accommodated by the ISP/network connection.
Since adding more bandwidth may be a poor investment for the ISP, the ISP
may have no economic incentive to remedy the latency problem. The result
is that some users might be inconvenienced by the lack of ability to
receive streaming video despite their own connection to the ISP being
capable of accommodating streaming video.
The latency problem is further aggravated if the connection between the
content server 22 and the distribution network 24 is equally taxed. The
lack of sufficient bandwidth at the content server/network link could also
prevent real-time video streaming over the Internet, regardless of the
bandwidths of the network/ISP link or the ISP/subscriber link. If all
links lack sufficient bandwidth, the latency problem can be compounded.
One solution to this problem is to provide local cache storage at the ISP.
As subscribers request files from the Internet, the ISP caches the files
locally so that subsequent requests are handled in a more expeditious
manner. This process is known as "on-demand caching." Local on-demand
caching methods improve the ability to deliver video content over the
Internet. When the first subscriber requests the CNN video clip of the
airplane hijacking incident, the ISP requests the video clip from the CNN
server, and facilitates delivery of the video clip to the requesting
subscriber. The ISP also caches the video clip in its own memory. When any
subsequent subscriber requests the same CNN video clip, the ISP serves the
local version of the video clip from its own cache, rather than requesting
the clip from the CNN server. If the subscriber computer has a high
bandwidth connection with the ISP, the locally stored video clip can be
served as continuous streaming video data for instantaneous rendering on
the subscriber computer.
A drawback of the on-demand caching method is that the first requesting
subscriber is faced with the same latency problems described above. All
subsequent subscribers have the benefit of the cached version. However, if
the initial delay is too long, there may not be any subscriber who is
willing to assume the responsibility of ordering the video file and then
waiting for it to download.
Accordingly, there remains a need to develop improved techniques for
facilitating distribution of streaming video over public networks, such as
the Internet.
SUMMARY OF THE INVENTION
This invention provides improved methods for delivering large amounts of
data, such as streaming audio and video data, over a network, such as the
Internet. According to one aspect, the method involves an intelligent,
pre-caching and pre-loading of frequently requested content to the local
service provider (e.g., ISP or LAN network server) prior to peak demand
times when the content is likely to be requested by the subscribers. In
this manner, the frequently requested content is already downloaded and
ready to be served to the subscribers before they actually request it.
When the content is finally requested, the data is streamed continuously
in real-time for just-in-time rendering at the subscriber. This eliminates
the latency problems of prior art systems because the subscribers do not
have to wait for the downloading of video and audio files over the
Internet. Moreover, intelligently pre-caching content before peak demand
times is more effective than traditional on-demand caching because the
content is available to the first subscriber who requests it.
In one implementation, the network system includes a content provider
connected to local service providers via a distribution network. The local
service providers facilitate delivery of the content from the content
provider to multiple subscribers. The local service providers are
configured to request certain content from the content provider prior to a
peak time when the subscribers are likely to request the content. The
content is downloaded from the content provider during non-peak hours and
cached at the local service providers for serving to the subscribers
during the ensuing peak time.
The local service provider includes a processing control unit, a cache
memory, and a continuous media server. A hit recording module executes on
the processing control unit to record requests for particular content from
the subscribers. In the Internet context these requests are submitted in
the form of URLs (universal resource locators) for target resources
located on the Web. A pattern recognizer detects behavior patterns based
on subscriber requests to determine which content the subscribers are most
likely to request and when. A scheduler then schedules requests for the
frequently requested content from the content provider at a selected time
prior to the peak demand time for that content. These requests are posted
to the content provider at their scheduled times, and the content provider
downloads the content during the off-hours prior to the peak time.
When the content is received from the content provider, the local service
provider stores the content in the cache memory. For instance, the content
might be a Web page from a frequently visited Web site. Web pages are
typically designed as hypermedia documents to provide rich multimedia
presentations which blend text, images, sound, and video. If the Web page
references or includes continuous data files, such as audio or video
files, these files are stored in a continuous media server. The target
specifications embedded in the Web page to reference the continuous data
files are modified to reference the local copy of the continuous data
files, as opposed to the original location of the files at the Web site.
During the ensuing peak time, the processing control unit serves the target
resources maintained in the cache memory to the subscribers. If any
subscriber clicks on or otherwise activates a link to an audio or video
file, the requested file is served as a continuous stream of data from the
continuous media server at the ISP. In this manner, the continuous video
or audio data stream can be rendered just-in-time by the subscriber.
Another aspect of this invention involves supplementing the primary
Internet connection owned by the ISP with a delivery of content over a
secondary network. This supplemental delivery effectively increases
bandwidth between the content provider and the local service provider. In
the described implementation, the content provider broadcasts additional
content over a broadcast satellite network to the local service provider.
The broadcast communication link offers additional bandwidth at a fraction
of the cost that would be incurred if the local service provider installed
additional Internet connections, such as T1 or T3 connections. The
broadcasted content is stored at the local service provider and served
during peak times to afford continuous audio streaming to the subscribers.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic illustration of a network system which is used to
explain the present state of Internet technology.
FIG. 2 is a diagrammatic illustration of a network system constructed
according to one implementation of this invention.
FIG. 3 is a diagrammatic illustration of a network system constructed
according to another implementation of this invention.
FIG. 4 is a block diagram of the functional components in a local service
provider in the network system.
FIG. 5 is a flow diagram of a method for operating the local service
provider.
FIG. 6 is a diagrammatic illustration of a network system according to
still another implementation of this invention.
The same reference numbers are used throughout the figures to reference
like components and features.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 2 shows a public network system 50. It includes multiple content
servers, as represented by content server 52, which store and serve
content over a network 54. The content server 52 serves content in the
form of text, audio, video, graphic images, and other multimedia data. In
the Internet context, the content servers might represent Web sites which
serve or multicast content in the form of hypernmedia documents (e.g., Web
page) which link text, images, sounds, and actions in a web of
associations that permit a user to browse through related topics,
regardless of the presented order of the topics. The content server 52
might alternatively represent headend servers for a cable company which
transmit video content over a cable network, or an audio server for a
radio station that sends audio data over the network. The content server
52 might further represent servers for educational institutions, public
agencies, libraries, merchants, or any other public or private
organizations which serve or multicast information over the network.
The network 54 is a high-speed, high-bandwidth interactive distribution
network and can be representative of the Internet. Traffic over the
network 54 is organized according to protocols which define how and when
data is moved. One example protocol is the transmission control
protocol/Internet protocol (TCP/IP) which forms the backbone of the
Internet. The network 54 might be implemented using various physical
mediums, including wirebased technologies (e.g., cable, telephone lines,
etc.) and wireless technologies (e.g., satellite, cellular, infrared,
etc.). The network is operated according to high-speed switching services,
including connection-oriented network services (e.g., frame relay,
asynchronous transfer mode (ATM), etc.) and connectionless services (e.g.,
switched multimegabit data service, etc.). These switching services
support connection speeds of several Megabits per second (Mbps), up to
Gigabits per second (Gbps). At these speeds, the network 54 is capable of
supporting streaming video data which requires 1.2 Mbps.
Many independent service providers (ISPs), as represented by ISP 56,
function as terminal connections or "on-ramps" to the high-speed network
54. The ISP 56 acts as an intermediary between the subscribers 58 and 60
and the network 54. The ISP 56 has a network port 62 which provides a
high-speed, high-bandwidth connection 64 to the network 54. The ISPs
segment and rent portions of the bandwidth to the multiple subscribers 58
and 60 so that the subscribers do not individually need to purchase and
maintain their own network connections. The ISPs 56 may also be referred
to as point of presence (POP) servers, and the names "ISP" and "POP" are
used interchangeably in this disclosure.
The subscriber personal computers (PCs) 58 and 60 are individually
connected to the ISP 56 by permanent or sessional dial-up connections.
Conventional telephone or cable lines and compatible modems are used to
form the connections 66, 68. Examples of suitable technologies include
HFC, ISDN, POTS, and ADSL. The ISP 56 has network terminal switching
equipment 70 to accommodate the connections to the subscriber PCs 58, 60.
The ISP 56 also has a cache server 72 and a continuous media server (CMS)
74. The cache server 72 is configured as a conventional database server
having processing capabilities, including a CPU (not shown), and storage
78. As one example, the cache server 72 is implemented as a SQL (Structure
Query Language) database. The cache server 72 caches Internet resources,
such as those requested by subscriber computers 58, 60, that have been
downloaded from the content provider 52 to allow localized serving of
those resources.
The CMS 74 is a server designed particularly for serving continuous data
streams, such as video data and audio data, in an ordered and
uninterrupted manner. As one example implementation, the continuous media
server is configured as a disk array data storage system consisting of
many large capacity storage disks with video and audio data streams stored
digitally thereon. The locations of the video and audio data streams are
kept in a memory map and each video and audio data stream is accessed
through pointers to the particular memory location. To serve the audio or
video data, the processor grabs the pointer to the video stream and begins
retrieving the video from the storage disk 82 and streaming it over the
communication line 66, 68 to the requesting subscriber computing unit.
FIG. 3 shows a network system 90 which is implemented in a local area
network (LAN) configuration. This implementation is exemplary of how a
company or multi-user organization might be connected to the Internet. The
network system 90 differs from the system of FIG. 2 in that the local
service provider which facilitates the on-ramp connection to the
high-speed, high-bandwidth network 54 is itself a local server 92 on a LAN
94. The LAN 94 can be constructed using conventional network topologies,
such as Ethernet. The LAN network server 92 has a network port 96 which
enables a high-speed, high-bandwidth connection 98 to the network 54. The
cache server 72 and CMS 74 are connected to the LAN 94. Workstations or
other computing units 100, 102 are connected to the LAN 94 and are served
by the LAN network server 92 in regards to Internet access. In this
configuration, the LAN users of workstations 100, 102 have access to the
Internet through their enterprise LAN 94 and the LAN network server 92.
It is noted that both implementations of FIGS. 2 and 3 are shown and
described as suitable examples for implementing various aspects of the
invention. However, the network system might be implemented in a variety
of arrangements. In addition, the illustrations show the subscriber units
as being personal computers or work stations. However, the subscriber
units can be implemented in other forms which are capable of rendering
content received over the network. As examples, the subscriber computing
units might include televisions, computers, game devices, handheld
devices, and the like.
As explained in the Background section, conventional techniques for
delivering video and audio content over the Internet is plagued with
latency problems. An aspect of this invention is to provide an improved
method for delivering streaming audio and video content over a network
system. The technique involves an intelligent, pre-caching and pre-loading
of certain content at the local service provider (e.g., ISP, POP, LAN
network server) prior to optimal or peak demand times when the content is
likely to be requested by the subscribers. In this manner, the frequently
requested content is already downloaded and ready for access from the
subscribers before they actually request it. When it is finally requested,
the data can be streamed continuously in real-time for just-in-time
rendering from the local service provider to the subscriber. This
eliminates the latency problems of prior art systems. Moreover,
intelligently pre-caching content before peak demand times is more
-effective than traditional on-demand caching because the content is
available to the first subscriber who requests it.
FIG. 4 shows a functional block diagram of a local service provider 110
according to one implementation which enables intelligent pre-caching and
pre-loading. At its most fundamental level, the local service provider 110
provides an on-ramp connection to the Internet for its subscribers. The
subscribers send requests to the local service provider 110 for content
available on the Internet. The local service provider acts as an
intermediary facilitator which communicates the requests to the
appropriate content server and then returns the requested content to the
appropriate subscribers.
The local service provider 110 has a request handler 111 which manages
requests received from the subscribers. In the Web context, the subscriber
computers run Web browser applications which generate requests in the form
of universal resource locators (URLs). A URL describes everything about a
particular resource that a Web browser needs to know to request and render
it. The URL describes the protocol a browser should use to retrieve the
resource, the name of the computer it is on, and the path and file name of
the resource. The following is an example of a URL:
http://www.microsoft.com/upgrades The "http://" portion of the URL
describes the protocol. The letters "http" stand for HyperText Transfer
Protocol, the set of rules that a browser will follow to request a
document and the remote server will follow to supply the document. The
"www.microsoft.com" portion of the URL is the name of the remote host
computer which maintains the document. The last portion "/upgrades" is the
path and file name of the document on the remote host computer.
When the request handler 111 receives a request, the local service provider
110 first looks to its own cache memory 124 to determine if a proxy copy
of the target resource referenced by the URL is stored locally. The cache
memory 124 serves as a quasi-temporary local storage for holding proxy
copies of often used and requested target resources. The cache memory 124
can be implemented using different types of memory, including RAM, storage
disks (optical, magnetic, etc.), and the like. If a proxy copy is stored
in the cache memory 124, the target resource is served locally from the
cache memory 124. If there is no proxy copy, the local service provider
110 uses the URL request to locate the target resource from a content
provider and to request delivery of the target resource over the Internet.
The local service provider 110 passes the target resources on to the
requesting subscriber and may also cache the target resource in the cache
124 if the policy rules governing the cache are met.
The local service provider 110 has a hit recorder 112 which is coupled to
receive the URLs submitted by the subscribers. For each URL, the hit
recorder 112 records hit information in a URL hit database 114. The hit
information includes the date/time of the request, the subscriber who made
the request, and other information. The hit recorder 112 also triggers a
pattern recognizer 116 which draws on information in the URL hit database
114 to detect repetitive access behavior patterns based on subscriber
requests. The pattern recognizer 116 performs statistical analyses using
hit data from the URL hit database to determine usage patterns that help
the local service provider be more responsive to the needs of its
clientele. For instance, in the preferred implementation, the pattern
recognizer 116 determines which-URLs, and hence which Internet resources,
are being requested most often and least often, and the time of day when
the most requests are received. The pattern recognizer 116 is also
responsive to operator input to allow adjustment or tuning by the operator
for specialized analysis.
A scheduler 118 uses the pattern results generated by the pattern
recognizer 116 to schedule requests for specific URLs of target resources
on the Internet. The requests are scheduled to be filled at pre-selected
times prior to the peak times when the highest number of users are most
likely to request the content found at the URLs. Administrative tools 120
permit the operator to configure various operating parameters.
The pattern recognizer 116 and scheduler 118 cooperate to enable
intelligent pre-caching of frequently requested content. The operation of
the local service provider 110 to perform this intelligent pre-cacing
according to an aspect of this invention is described in conjunction with
reference to the flow diagram of FIG. 5. The local service provider is
programmed to perform the computer-implemented steps of FIG. 5 to
alleviate the problems of providing streaming video and audio data over
the Internet. The steps are presented in the illustrated order for
discussion purposes, but are not restricted to this sequence.
The pattern recognizer 116 monitors the patterns of the subscriber requests
to determine which content is most frequently requested and when (step 150
in FIG. 5). From these patterns, the pattern recognizer 116 can identify
peak times in subscriber traffic and the relation of the peak times to
specific requested content (step 152). For instance, suppose that a high
number of subscribers frequently request the CNN Web page during the
morning hours of 6:30 AM to 8:00 AM. These requests translate into a high
number of URL hits for the CNN Web page which are recorded by hit recorder
112 in the URL hit database 114. The pattern recognizer 116 recognizes
this recurring pattern of requests for the CNN Web page and identifies the
peak time for this Web page to be between 6:30 AM and 8:00 AM.
Using the patterns identified by the pattern recognizer 116, the scheduler
118 schedules delivery of the content at a selected time prior to the peak
time (step 154 in FIG. 5). In this example, the scheduler 118 might
schedule delivery of the CNN Web page at a time prior to 6:30 AM. For
instance, the scheduler 118 might schedule a request for the CNN Web page
at 6:00 AM to provide sufficient time to download that page before the
earliest subscribers are expected to begin asking for it, yet not too
early to ensure that the latest news is included.
At the scheduled time, a media loader 122 sends a request to the content
server on the Internet and receives the content from that content server
(step 156 in FIG. 5). The content is stored locally at the local service
provider (step 158). More particularly, the data comprising the target
resource is stored as a proxy file in the cache memory 124, and any
continuous data content (e.g., audio or video data) is stored in the
continuous media server 126. In the Web context, the content might be in
the form of a Web page or other hypermedia document that has hyperlinks to
various data items, such as audio and/or video clips. The hypermedia
document itself is stored in the cache memory 124, while the audio and
video clips referenced by the hyperlinks are stored in the CMS 126. The
target specifications corresponding to the links in the cached hypermedia
document are modified to reference the audio and video files in the CMS
126, as opposed to the files maintained at the Web site (step 160 in FIG.
5). As an alternative to modifying the target specifications, a conversion
table can be constructed which converts requests from referencing the
files at the Web site to referencing the files in the CMS 126.
In our CNN example, the local service provider 110 sends a request to the
CNN Web site seeking to download the CNN Web page at 6:00 AM. The CNN Web
page is downloaded over the Internet and stored in the cache memory 124.
If the CNN Web page contains links to any audio or video clips of recent
news, these data files are also downloaded and stored in the CMS 126. The
links within the cached Web page are modified to reference the audio and
video files stored locally in the CMS 126, instead of the files maintained
at the CNN Web site.
The media loader 122 loads the locally stored content just before the peak
time so that it is ready to serve during the peak time (step 162 in FIG.
5). When the first subscriber requests the CNN Web page at, for example,
6:40 AM, the local service provider 110 serves the Web page from the
cached memory 124. If the subscriber activates a link to a video or audio
file, the local service provider 110 immediately serves the data stream
from the CMS 126 for just-in-time rendering on the subscriber's computer.
Accordingly, the video file is served as streaming data to even the first
subscriber who requests it, rather than making that subscriber wait for
the file to be retrieved over the Internet.
The intelligent pre-caching method obviates the latency problems associated
with streaming video and audio over the Internet, and is a further
improvement to traditional on-demand caching techniques. However, it is
noted that the network system does not accommodate data streaming for
every video and audio file on the Internet, but instead only selected
files. The system makes an intelligent choice as to which content is
likely to be requested by its subscribers and then makes only this content
readily available to the subscribers. In this way, the method seeks to
optimize the physical computing resources of the local service provider in
a manner which best services the majority of the clientele.
It is noted that the content servers serve many local service providers
over the Internet. These local service providers, in turn, serve many
different users. Due to varying demographics, the local service providers
will generally differ in the content that it most often serves to its
clientele. For example, a service provider in Seattle, Wash., might have
many requests for content on entertainment or news local to Seattle. The
pattern recognizer for a Seattle-based service provider might therefore
schedule proportionally more Seattle related content than, say, a
London-based service provider. As a result, the sets of pre-cached content
may differ significantly from one service provider to another depending
upon the results of the local hit recorder and pattern recognizer.
The system and method described above places the authority for deciding
which content is pre-cached at the local service provider. This allows the
local service provider to adapt to the often changing patterns of its
clientele. However, in another implementation, the content servers can be
given the governing authority of deciding when and what content to
download to the ISPs prior to peak times. For instance, the content server
can maintain a schedule of when to download different sets of content to
various ISPs in timely fashion before the sets of content are requested by
the respective users who are serviced by the ISPs.
With continuing reference to FIG. 4, in this implementation, the local
service provider 110 also includes a policy manager 128 which defines and
administers rules that determine which documents or resources are cached
in the cache memory 124. For instance, caching rules might call for
caching resources that are routinely requested by many subscribers, but
foregoing caching resources that are rarely or infrequently requested. The
policy rules also coordinate cache maintenance by deciding when documents
are out-of-date and how these documents are deleted from the cache memory
124.
According to another aspect of this invention, time-to-live (TTL) tags are
assigned to the content to assist in determining when the content should
be refreshed or disposed. The TTL tags can be assigned by the content
server as part of the content itself. The server can attach an expiration
tag which represents the publisher's best estimate as to how long it will
be before the content is updated.
Alternatively, the local service providers might compute the TTL tags for
the content it caches in cache memory 124. The computation is based upon a
theory that older content is less likely to change. Content that changed
only 10 minutes ago is statistically more likely to change within the next
24 hours than content that last changed one month ago. In one
implementation, an approximate TTL is computed as a percentage of time
since the content is known to have last changed. The percentage is an
operator controlled parameter. Suppose a 10% value is selected. Content
that last changed 72 hours ago is assigned a TTL tag of 7.2 hours. If the
content is not updated within 7.2 hours, it is given a new value of 7.9
hours (i.e., (72 hours+7.2hours).times.10%=7.9 hours). As the content
ages, it is checked less often. The TTL tags can be kept in a separate
table of the cache 124 to correlate the tags and their content.
Deletion policies are a function of the content itself (e.g., its TTL
tags), the subscriber patterns (e.g., how frequently the content is
requested), the cost to request newer updated content, and the constraints
imposed by capacity limitations of the cache memory.
The local service provider 110 also maintains a subscriber database 130
which stores lists of subscribers (or LAN users in the LAN configuration)
and pertinent information about them (e.g., routing addresses, billing
addresses, etc.). A usage reporter 132 uses the URL hit information from
the URL hit database 114 and subscriber information from the subscriber
database 130 to generate reports on subscriber usage patterns. These
reports can be used by the operator to efficiently allocate computer
resources to best satisfy the needs of its clientele. The reports can also
be used by content providers to help them assess the popularity of their
Web sites and the type of subscribers who visit them.
In a preferred implementation, the functional components described with
respect to FIG. 4 are implemented in software which executes on the host
computer of the local service provider. It is noted that the functional
layout is provided for explanation purposes. The subscriber database 130,
the URL hit database 114, and the cache memory 124 can be implemented as
one database server. Other implementation variations may also be made.
In the above system, the local service providers (e.g., ISPs, LAN Web
servers) initiate the requests for content so that it may be pre-cached
prior to peak demand times when the content is most likely to be
requested. This system can be referred to as a "pull-caching" system in
that content is pulled over the Internet upon request of the local service
providers. The method of intelligently pull-caching data prior to peak
times enables delivery of streaming video and audio data to Internet
users.
FIG. 6 shows a network system 200 according to another aspect of this
invention. The network system 200 attacks the latency problem of streaming
video and audio data by supplementing the primary Internet distribution
network with a second network which is not reliant on the Internet/ISP
connection. The Internet/IISP connection is often the bottleneck for
streaming data and is typically the connection least likely to be upgraded
due to economic factors surrounding the business of the ISP. Although not
required, in this implementation, the content may be pushed top down from
the content provider over the Internet and thus, the system may be
referred to as a "push-caching" system.
Network system 200 is similar to the configuration of the FIG. 2 network
system 50 in that it has a content server 52 which serves content over a
high-speed, high-bandwidth network 54, via local ISPs 56, to end users 58
and 60. The difference between the two systems is that network system 200
of FIG. 6 has an additional, secondary network 202 for distributing
content from the content server 52 to the ISPs 56. In the illustrated
implementation, the secondary network 202 is a broadcast satellite
network. The content provider 52 has a transmitter 204 which sends signals
to an orbiting satellite 206, which redirects the signals to an ISP-based
receiver 208.
The secondary satellite network 202 affords a supplemental bandwidth for
delivery of content to participating ISPs in addition to the content
delivered over the interactive network connection 62. For instance, using
present DSS (digital satellite service) technology, the satellite network
202 provides an additional 6 Mbps bandwidth to deliver content to the ISP
56. This extra bandwidth is made available at a fraction of the cost of
buying T1/T3 connections.
The supplemental-caching technique allows the content provider to download
more information in a timely manner. To continue the above CNN example,
the CNN content provider might transmit the CNN Web page over the
satellite system 202 minutes before the peak time of 6:30 AM to 8:00 AM.
The ISP receives the Web page from its satellite receiver 208 and caches
the Web page for serving during the peak time. The CNN Web page is thereby
efficiently made available for real-time streaming to the subscribers,
without tying up or consuming any of the bandwidth provided by the network
connection 62.
In a preferred implementation, the supplemental satellite network 202 is
uni-directional, in that data is broadcast from the content provider 52 to
the ISP 56. It is a low cost solution increasing the bandwidth of the
pipeline to the ISP, without requiring significant investment on the part
of the ISP. In addition to satellite technologies, the broadcast network
202 can be implemented as other wireless systems, such as RF or cellular
technologies.
In another embodiment, the secondary network 202 can be implemented as an
second data communications network whereby supplemental content is
multicasted to participating ISPs prior to the peak time.
In compliance with the patent statutes, the invention has been described in
language more or less specific as to structure and method features. It is
to be understood, however, that the invention is not limited to the
specific features described, since the means herein disclosed comprise
exemplary forms of putting the invention into effect. The invention is,
therefore, claimed in any of its forms or modifications within the proper
scope of the appended claims appropriately interpreted in accordance with
the doctrine of equivalents and other applicable judicial doctrines.
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