Electrical computers and digital processing systems: multicomput – Distributed data processing – Client/server
Reexamination Certificate
1999-06-09
2004-11-30
Meky, Moustafa M. (Department: 2157)
Electrical computers and digital processing systems: multicomput
Distributed data processing
Client/server
C709S217000
Reexamination Certificate
active
06826593
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to communications networks, generally, and more particularly to a method of communication within such communication networks and apparatuses for practicing the method.
BACKGROUND OF THE INVENTION
Many emerging environments in the field of computer technology are increasingly facing a problem in that the data and computational requirements of software applications easily outstrip the system resources. The problem is particularly acute in multimedia environments such as intranets, the Internet (a communications network) or the World Wide Web (Web) as well as in many data intensive applications such as online analytical processing (OLAP) and multimedia databases.
The Web is essentially a distributed depository of files. The files are stored on Web servers connected by the Internet. Users of the Web may request transfer of files to their own computers, i.e., Web clients, for viewing, storing or printing. Each server stores files identified by a unique electronic address known as a universal resource locator (URL). A URL points to a particular server and identifies the location of a file on that server. Many of the files stored on Web servers are documents written in a standard programming language known as hypertext mark-up language (HTML). HTML files are translated for viewing, printing or storing by a Web browser (a computer program designed to display HTML files and communicate with Web servers). Using HTML, an author of such a file (Web page) can associate a hyperlink with a specific word, phrase or image in a document. While some files are stored on Web servers in HTML format, other files are available in non-standard formats which may not be translated for viewing, printing or storing by a standard Web browser. While some Web clients may be capable of translating such non-standard formats, others may not be so capable. Due to the vast heterogeneity of client resources, many files are available in formats that can only be translated by a subset of all clients while other files are stored in a plurality of formats to ensure translatability by most clients.
Users may access the World Wide Web in a variety of ways. Some users are fortunate enough to connect to the Internet with dedicated high-speed, high-bandwidth connections (e.g., T1, T3 or ISDN lines). However, many users, particularly users accessing the Internet from their homes, have only dial-up access to the Internet. In a dial-up arrangement, the user's computer typically has a modem for dialing and communicating with an Internet Service Provider to which the user subscribes. The Internet Service Provider typically maintains a proxy computer which is attached to the Internet via a dedicated communications line. The proxy intervenes between the Web server and Web client as described below.
Requests for file transfer, usually in the form of a GET URL HTTP request including a URL in the World Wide Web context, originate with the client and are forwarded to the proxy via the user's dial-up connection. The proxy then relays the request over the Internet to the appropriate Web server. The Web server responds by transmitting the requested file to the proxy. The proxy then relays that file to the client.
The user typically accesses files stored on the Web using Web browser software running on a Web client connected to the Internet. Typically, this is achieved by the user's selection of a hyperlink (typically displayed by the Web browser as an image, or a bold word or phrase) within a document being viewed with the Web browser. Each hyperlink is associated with an electronic address which uniquely identifies the file associated with the hyperlink indicating the file's location on a Web server. The electronic address is in the form of a URL. A user's selection of a hyperlink acts as a user's request for transmission of the file associated with the hyperlink to the client. The Web browser then issues a hypertext transfer protocol (HTTP) request for the requested file to the Web server identified by the requested file's URL. In response, the designated Web server returns the requested document to the Web browser, also using HTTP, provided that the file identified in the URL is present at the server identified in the URL at the location identified in the URL.
The standard HTML syntax of Web pages and the standard HTTP communications protocol supported by the Web guarantee that a Web browser can communicate with any Web server. The Javascript programming language and Javascript applets provide platform independent application programs over the Internet and the World Wide Web which can be run on any Web client.
Web pages typically are predominantly graphical in nature. The graphical images comprising each Web page are generally much larger in size (bytes) than even lengthy simple text documents. Such large graphics files slow the response time for users of the Web. The delay is referred to herein as latency. Latency is primarily a function of the size of the file transmitted and the bandwidth of the connection over which the file is transmitted. As an ever increasing number of users, both individual and corporate in nature, use the Internet and the Web, response times have even further slowed.
FIG. 1
is a symbolic diagram of a simplified Web topology of the prior art. In the example of
FIG. 1
, the Web client
6
is the user's computer. The client may connect to the Internet Service Provider (not shown) over a communications line
10
, using a modem in the client
6
. The Internet Service Provider typically controls the proxy
16
which has a dedicated connection over a transmission link
20
to the Internet
26
. The Internet
26
essentially is a sub-network of switching nodes and transmission links. A Web server
36
is connected to the Internet
26
by transmission link
30
. In actuality, the Internet
26
is comprised of numerous servers, clients, proxies, transmission links, etc. between the proxy
16
and the Web server
36
.
Using Web browser software running on the Web client C, the user requests an image, document, multimedia or other file (herein referred to collectively as “file”) by submitting a request in the form of a URL. In a typical Web topology, the URL is transmitted to the proxy
16
, which then forwards it over transmission link
20
to the Web server
36
via the Internet
26
and transmission link
30
. The Web server
36
responds to the request by transmitting the file via the Internet
26
to the proxy
16
which then forwards the file to the client
6
for viewing, storing or printing. In such a Web architecture, the link between the client and the proxy is typically the critical bottleneck, i.e., a low bandwidth connection relative to the bandwidth of network connections between the proxy and the server.
In an effort to reduce latency, Internet Service Providers frequently provide a memory cache on their proxy computers. Generally, the cache is capable of storing a file so that a subsequent requests from the same or a different client for the same file may be fulfilled by the proxy without having to wait for transmission of the file from the server. A proxy
16
having a memory cache
18
is shown in FIG.
1
. The cache stores a copy of a file requested by a client
6
and returned by the Web server
36
although it also forwards a copy of the file to the client
6
. As referred to above, this has helped in decreasing latencies, from the client's standpoint, between requesting a file and receiving the requested file. This is achieved by checking the cache
18
for the requested file at the proxy
16
each time a URL request is received from a client
6
. In a typical arrangement, if a copy of the file is resident in the cache
18
, the file is forwarded to the client
6
provided that the file in the cache
18
is not stale, i.e., the copy in the cache is current because the file has not been updated on the server. Methods for determining whether a cached file is current are well-known in the art. This is determi
Acharya Swarup
Korth Henry F.
Poosala Viswanath
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