Electrical computers and digital processing systems: multicomput – Distributed data processing – Client/server
Reexamination Certificate
2000-08-09
2002-12-31
Choules, Jack (Department: 2177)
Electrical computers and digital processing systems: multicomput
Distributed data processing
Client/server
C709S224000
Reexamination Certificate
active
06502125
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. Such delivery sites and servers are selected so as to increase network capacity, distribute server load, and reduce transmission delays between the server and the user.
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.
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 performance problems are exacerbated. Network bandwidth, or the data-carrying capacity of a particular network, is limited. Thus, packet loss and delays increase. Long delivery times consume a large amount of server capacity for a long time, decreasing the resources available to other users. Accordingly, because the network infrastructure becomes increasingly congested, packet loss and delays continue to increase, transmission times rise, and server load increases further.
This pattern exemplifies a “downward spiral” of network performance, which can be driven by the attempted transmission of large data files such as video clips. As long as network traffic remains within the limits imposed by network bandwidth, network performance will remain acceptable. However, whenever peak network loads exceed capacity, the downward spiral described above will begin, causing increasing periods of poor network performance.
As discussed above, a browser program 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, or more commonly, by “hotlinking” to Web pages. Common browsers are Lynx, NCSA Mosaic, Netscape Navigator, and Microsoft Internet Explorer. The desired Web page is specified by a uniform resource locator (“URL”), indicating the precise location of the file using the syntax “http://internet.address/directory/filename.html”.
Web pages are generally described, in terms of layout and content, by way of a language known as “HTML” (HyperText Markup Language). Any particular computer linked to the Internet can store one or more Web pages, i.e. computer files in HTML format, for access by users.
Hotlinking from one HTML Web page to another is accomplished as follows. The user first accesses a Web page having a known address, often on the computer located at the user's ISP (Internet Service Provider). The ISP is the organization providing Internet connectivity to the user. That Web page can contain, in addition to textual and visual data specified in HTML format, “links,” or embedded information (in the form of URLs) pointing to the Internet addresses of other Web pages, often on other computers throughout the Internet. The user, by selecting a link (often by pointing and clicking with a mouse), can then access other Web pages, which c
Karush Arnold
Kenner Brian
Akamai Technologies, Inc.
Choules Jack
Judson David H.
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