Electrical computers and digital processing systems: multicomput – Computer network managing – Computer network access regulating
Reexamination Certificate
1998-03-01
2002-07-16
Maung, Zarni (Department: 2152)
Electrical computers and digital processing systems: multicomput
Computer network managing
Computer network access regulating
C709S224000, C709S219000
Reexamination Certificate
active
06421726
ABSTRACT:
The invention relates to a system and method for distributed data storage and retrieval, and more particularly, to a system and method whereby a user can acquire network performance information for a dynamic and distributed multipurpose network, and use this information to identify and select optimum delivery sites or servers from which to receive computer data, specifically multimedia content, as well as to select the particular type of multimedia content viewable by the user. Such delivery sites, servers, and content type are selected so as to increase network capacity, distribute server load, reduce transmission delays between the server and the user, and reduce obstacles to viewing the multimedia content.
BACKGROUND OF THE INVENTION
The Internet is a loose network of connected computers spread throughout the world. A message can be sent from any computer on the Internet to any other by specifying a destination address and passing the message from computer to computer via a series of “hops.” Each computer, router, or “node” on the Internet has a unique Internet address. When an intermediate computer or router receives a message in transit, the computer checks the intended destination of the message and passes it along accordingly.
The Internet is growing, in terms of both size and sophistication, at a rapid rate. In the past, most users of the Internet were academic, research, or institutional users; the Internet was primarily used at that time to transmit and receive electronic mail and network news and to allow transfer of computer files. However, since the introduction of the World Wide Web (also known as the “Web” or the “WWW”) several years ago, the Internet has begun to host increasing amounts of other types of data of general interest, namely representations of images, articles, etc.
The Web protocol and language establish a graphical means to navigate the expanses of the Internet. “Web pages,” often consisting primarily of text and graphical material, are stored on numerous computers, known as “Web servers,” throughout the Internet. A software program known as a “browser” can be used to access and view Web pages across the Internet by specifying the location (i.e. Internet address) of the desired Web page. When a Web page is accessed, its information is transmitted from the remote computer (server or delivery site), wherever in the world it may be located, across the Internet, to the user.
In recent times, the Web has begun to host highly sophisticated types of multimedia content, such as audio and video data, and computer software. Compared to first generation Web content, namely text and still images, audio clips, video clips, and software programs have extremely high storage and bandwidth requirements.
Before a video clip can be transmitted over a computer network, the clip must be digitized by encoding the video's analog signal to “1s” and “0s.” In order to reduce the bandwidth required to transmit the digitized video, the video data stream is frequently compressed. Video compression is a process by which redundant data is eliminated from the video data stream so that the overall size of the data stream is reduced. There are many different compression formats which are used to reduce video data streams, e.g., MPEG, JPEG, H261, Indeo, Cinepak, AVI, Quicktime, TrueMotion and Wavelet.
Video clips received in a compressed format generally s must be decompressed before they can be viewed. Decompression of a video is commonly performed by a video player “CODEC” program, or COmpressor/DECompressor, often located at a user's multimedia terminal. Generally speaking, a single CODEC program can only recognize and decompress a single compression format.
When a video clip is stored for transmission in a format which can be decompressed by the CODEC at a user terminal, delivery of the video clip to the user can proceed smoothly. This is typically the situation where a subscription service provides video delivery over a confined network. The service provides a subscribing user with a preferred CODEC, and stores video clips in the compression format recognized by the provided CODEC.
However, when a service begins to make video clips available over the Internet, it is more likely that the video clips will be requested by a non-subscribing user whose multimedia terminal does not have the service provider's preferred CODEC. In this case, if the user wishes to view the video clips, he would be required to acquire or download a CODEC program capable of decompressing the desired video clip. Like video clip files, CODEC program files can be large files that take a long time to download. Moreover, a CODEC program can be difficult, time-consuming, or inconvenient to install onto the multimedia terminal. If a user is forced to download a CODEC program before he can play a video file, he may be discouraged from pursuing that particular video request any further.
At present, it is difficult, if not impossible, to provide sustained high-speed transmission of large audio/video files over a multi-node link on the Internet. Because the data is often transferred from afar, many factors can cause the delay or even loss of parts or all of a transmission. It is generally not critical if a user experiences minor delays in receiving small graphic or text files. However, it is recognized that real-time data such as video has very specific and stringent timing requirements for data transfer and display.
Unfortunately, the present design of traditional Internet-like data networks is based on the principle that delays and significant data transmission rate variations are acceptable for ordinary data (e.g. text and still images). Consequently, because of the high value of permitting access to text and graphical information from locations around the world, such transmission defects are considered acceptable, and the base capacity of the Internet is somewhat “oversubscribed” to reduce data transmission costs. In other words, the timeliness of network data transmission has been significantly compromised in order to render relatively insignificant the aggregate cost of long distance communication connections.
In order to successfully transfer audio-video data across a message-oriented network such as the Internet, for any more than a few users, network resources should be committed in a manner facilitating timeliness of transmittal. A system using committed network resources generally cannot take advantage of the existing pricing scheme of shared networks like the Internet, since it cannot participate in the sharing of network resources on a data packet by data packet basis. Video data must be transmitted to the exclusion of lower-priority data. Transmission costs thus become significant, especially when the connection is “long distance” or when the connection is continued over an extended period of time.
Another consequence of the timeliness vs. cost compromise discussed above has been the seemingly indiscriminate topographical design of the network. Since delays and throughput variations have traditionally been excused in favor of low cost, the configuration of the Internet infrastructure has also been driven by cost considerations. Accordingly, the interconnection efficiency of the network has rarely been considered. The rapid growth of real time data is changing this requirement.
It is recognized that inadequate data transfer performance of time-sensitive data on the Internet is typically caused by four factors: packet loss, excessive server utilization, the relatively low capacity of the network infrastructure, and inherent delays in the network hardware. Packet loss, in particular, is caused by inadequate infrastructure and lack of robustness in routing. The inherent delays are believed to be caused by, among other things, the lack of flow control between adjacent nodes in a multiple-node path on the Internet.
Unlike smaller text and graphic files, relatively large video files can take several minutes (or more) of “streaming,” or constant data flow. Consequently, the usual network perfo
Brownell Lonnie J.
Colby Kenneth W.
Kenner Brian
Weathersby Guy P.
Akamai Technologies, Inc.
Cardone Jason D.
Judson David H.
Maung Zarni
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