Electrical computers and digital processing systems: multicomput – Distributed data processing – Client/server
Reexamination Certificate
1999-03-02
2001-10-02
Harrell, Robert B. (Department: 2152)
Electrical computers and digital processing systems: multicomput
Distributed data processing
Client/server
Reexamination Certificate
active
06298373
ABSTRACT:
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.32 bis 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 Tl
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
Burns Gregory
Leach Paul J.
Harrell Robert B.
Lee & Hayes PLLC
Microsoft Corporation
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