Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1998-08-05
2001-08-28
Alam, Hosain T. (Department: 2771)
Data processing: database and file management or data structures
Database design
Data structure types
C709S219000, C713S152000
Reexamination Certificate
active
06282542
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
This invention relates generally to data transfer. More specifically, the invention relates to digital data transfer over a digital network.
II. Description of the Related Art
The bloom of the Internet has encouraged many companies and individuals to establish an Internet presence. For example, a company may create a web page which describes its products and services and allows a user to place a purchase order. These web pages are stored on web servers. A user may access a web page from the a web server using web browser software running on a computer. The web page may contain links to other information at the same site or other web sites.
FIG. 1
is a block diagram showing an Internet connection. A user originates a file request from a web browser
20
. The web browser
20
may comprise a personal computer, a network terminal or any other manner of digital user terminal capable of executing web browsing software. The request is passed through a series of routers
22
A-
22
N of the Internet
24
. The routers
22
A-
22
N do not examine the contents of the request but simply transfer the request to an appropriate web server
26
according to an address header. The web server
26
examines the contents of the request and responds with the requested file.
When a user would like to access information on the Internet, the user enters a uniform resource locator (URL) into the web browser. The URL is basically a pointer to the location of an object. For example, “http: \\www.internic.net\rfc\rfc1738.txt” is the URL address which points to a Request For Comment document which describes uniform resource locators. In the URL, the “http” indicates that the HyperText Transfer Protocol (HTTP) protocol is used to access the site. A double backslash indicates that a host name follows such as “www.internic.net”. A single backslash indicates that either a directory or a filename follows. In this case, “rfc” is a directory and “rfc1738.txt” is the file in that directory which is displayed when this URL is requested by the web browser
20
.
The World Wide Web is built on top of the Internet. HTTP is the client/server protocol used most commonly on the World Wide Web. HTTP is used to set up communication between a client and a server and pass commands and files between the two systems.
HTTP provides a means for a web browser to access a web server and request documents created using the HyperText Markup Language (HTML). HTML web pages can include images, sound clips, text files and other types of objects. Some of the objects may not be part of the original HTML parent file (the base component of the web document) requested by the web browser
20
. Instead, the HTML parent file contains external references to these inline objects, which are in the form of other data files on the server. When a user retrieves the HTML parent file on the web browser, the inline objects are also retrieved and inserted into the displayed of the document. Thus, an HTML document (or “page”) actually consists of the HTML parent file along with any additional sound, graphics and multimedia inline objects specified with the parent file. For example, the inline objects may include advertising banners, sliders, bullet listings, graphic images, sound clips or other such items.
FIG. 2
is a timing diagram showing data transfer to and from the web browser
20
. In
FIG. 2
, time progresses from left to right. The upward pointing arrows indicate outgoing messages from the web browser
20
intended for the web server
26
. Downward arrows indicate incoming messages received at the web browser
20
from the web server
26
. For simplicity of illustration, each incoming and outgoing message appears to be transferred instantaneously. In actual implementations, the transfer of each message typically requires a discernible amount of time.
An outgoing message
30
carries the initial URL request. In response, an incoming message
32
carries the first portion of a response to the request carried in the outgoing message
30
. An incoming message
34
and an incoming message
36
correspond to a second and third portion of the response.
Assume that the incoming message
32
contains an external reference to an inline object. The web browser
20
examines the incoming information and in response sends an outgoing message
38
which carries a request for the inline object. For illustration purposes, we shall assume that the inline object is a sound clip.
Following the outgoing message
38
, the web browser
20
receives an incoming message
40
containing additional information corresponding to the initial request carried in the outgoing message
30
. After reception of the incoming messages corresponding to the initial request, the web browser
20
begins to receive the sound clip within an incoming message
42
. In an incoming message
44
, the web browser
20
continues to receive information concerning the sound clip.
Assume that the incoming message
42
contains an external reference to an inline object which is an ad banner. An outgoing message
46
carries a request for the ad banner. Following the outgoing message
46
, the web browser
20
receives an incoming message
48
and an incoming message
50
containing additional information corresponding to the sound clip. Finally, in an incoming message
52
, the web browser
20
receives the information concerning the ad banner.
Each time that the web browser
20
requests information from the web server
26
, a delay is incurred. For example, notice that a time delay &agr;T
1A
elapses between the outgoing message
30
and the corresponding incoming message
32
. The delay includes two primary components: (i) the round-trip delay associated with connection to the web server
26
and (ii) the response time of the web server
26
. In the
FIG. 2
example, the transfers of the inline objects are delayed by transfers of previously requested objects and the parent file and the time delays &Dgr;T
2A
and &Dgr;T
3A
are, therefore, longer than the delay &Dgr;T
1A
.
As described in more detail below, because the HTTP protocol requires the web browser to examine the parent file and generate separate requests for the inline objects, the introduction of a link which introduces significant delay can greatly increase the amount of time required to fully retrieve and display a web page. For example, if the user's internet access channel includes a satellite link, the time required to retrieve a web page that includes a single inline object will be at least twice the round-trip delay of the satellite link. Further, the need to separately request inline objects produces unnecessary traffic over the communications link. The present invention seeks to overcome these problems without the need to modify the HTTP protocol.
SUMMARY OF THE INVENTION
The present invention addresses the above problems by providing a distributed system and method for prefetching inline objects of documents. In a preferred embodiment, the system is in the form of a distributed proxy server for use in an internet access system which includes a satellite link. The distributed proxy server includes an access point component which runs on the client (browser) side of the satellite link and communicates with web browsers, and includes a satellite gateway component which runs on the internet (web server) side of the satellite link and communicates with web servers. In operation, when a web server returns a parent file of a web page that has been requested by the user, the satellite gateway component parses the parent file to identify any references to inline objects, and prefetches these objects from the web server. The objects are thus requested without waiting for the browser to receive the parent file and generate requests for the inline objects.
The satellite gateway forwards the prefetched objects over the satellite link to the access-point component, which in-turn caches the inline objects until requested by the browser. If the access point compone
Carneal Bruce L.
Fish Ram A.
Guralnick Jeremy
Alam Hosain T.
Fleurantin Jean Bolte
Knobbe Martens Olson & Bear LLP
Tachyon, Inc.
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