Electrical computers and digital processing systems: multicomput – Computer network managing
Reexamination Certificate
2001-06-12
2004-06-29
Burgess, Glenton B. (Department: 2151)
Electrical computers and digital processing systems: multicomput
Computer network managing
C709S228000, C707S793000
Reexamination Certificate
active
06757726
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a cache server and a distributed cache server system and, more particularly, to a cache server and a distributed cache server system which reduce a traffic of an external network.
2. Description of the Related Art
Recently, as computer networks, such as the Internet, have developed, people have come to dispatch various sorts of information to computer networks, as well as browse various sorts of information from computer networks.
In the Internet, for example, large-amount information, such as moving images and music, has been increasingly furnished, and electronic commerce has become popular, partly due to the spread of information technology. Accordingly, the amount of data existing in the Internet is increasing day by day.
Conventionally, in order to deal with such an increasing amount of data, a cache server or a proxy server having a caching function is provided between an internal network such as a LAN (local area network) and an external network such as the Internet. The conventional cache server or the proxy server having a caching function (hereinafter generally referred to as a cache server) reduces the traffic between the internal network and the external network by temporarily caching data sent from the external network upon connection from the internal network to the external network.
FIG. 1
illustrates an example of a conventional cache server. A cache server
101
shown in
FIG. 1
is connected with client PCs
102
a
to
102
d
, constituting an internal network. For example, when the client PC
102
d
makes a request to connect to a Web page, the cache server
101
judges whether or not data of the requested Web page is cached. Then, if not cached, the cache server
101
connects to the Internet
100
. Subsequently, the cache server
101
sends data of the Web page sent from the Internet
100
to the client PC
102
d
as well as temporarily caches the data of the Web page.
Meantime, when the client PC
102
a
makes a request to connect to the Web page, the cache server
101
judges whether or not data of the requested Web page is cached. Then, if cached, the cache server
101
does not connect to the Internet
100
, but sends the cached data of the Web page to the client PC
102
a.
FIG. 2
illustrates an example of cache servers provided in a conventional large-scale computer network. In a large-scale computer network as of a corporation, for example, a cache server is provided for each of the head office and branch offices. Cache servers
103
a
to
103
c
shown in
FIG. 2
are provided respectively for the head office and branch offices, for example, and are connected with client PCs
104
a
to
104
c
, respectively, constituting an internal network. The cache servers
103
a
to
103
c
perform a process referred to as a mirroring that synchronizes cache data among the cache servers
103
a
to
103
c
so as to have the same cache data.
For example, when the client PC
104
a
makes a request to connect to a Web page, the cache server
103
a
judges whether or not data of the requested Web page is cached. Then, if not cached, the cache server
103
a
connects to the Internet
100
. Subsequently, the cache server
103
a
sends data of the Web page sent from the Internet
100
to the client PC
104
a
as well as temporarily caches the data of the Web page. Additionally, the cache server
103
a
performs the mirroring of the cached data of the Web page among the cache servers
103
a
to
103
c.
FIG. 3
illustrates another example of cache servers provided in a conventional large-scale computer network. Cache servers
105
a
to
105
c
shown in
FIG. 3
are connected with client PCs
106
a
to
106
c
, respectively, constituting an internal network. The cache servers
105
a
to
105
c
shown in
FIG. 3
do not perform the mirroring of data, but each of the cache servers
105
a
to
105
c
individually caches data.
For example, the cache server
105
a
temporarily caches only data of a Web page requested for connection by the client PC
106
a
. Likewise, the cache servers
105
b
and
105
c
temporarily cache only data of Web pages requested for connection by the client PCs
106
b
and
106
c
, respectively.
However, the cache servers
103
a
to
103
c
shown in
FIG. 2
cause the amount of cache data to increase by retaining the same cache data among the cache servers
103
a
to
103
c
by mirroring. Therefore, the cache servers
103
a
to
103
c
have a problem that a recording medium such as a hard disk suffers a heavy load from the increasing amount of cache data. Additionally, because the amount of cache data remarkably increases, the cache servers
103
a
to
103
c
are unable to operate effectively in a large-scale computer network.
On the other hand, the cache servers
105
a
to
105
c
shown in
FIG. 3
do not perform the mirroring of data, but each of the cache servers
105
a
to
105
c
individually caches data. Therefore, the amount of cache data decreases. As a result, there are more cases that the cache servers
105
a
to
105
c
have not cached data that is requested for connection by the client PCs
106
a
to
106
c
, and thus the cache servers
105
a
to
105
c
more often connect to the Internet
100
. Therefore, the cache servers
105
a
to
105
c
are unable to reduce the traffic of an external network effectively.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an improved and useful cache server and a distributed cache server system in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a cache server and a distributed cache server system in which, while the amount of cache data retained by each cache server is decreased, the traffic of an external network can be reduced.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a cache server provided in an internal network, the cache server comprising:
a cache-data-list table storing information concerning data retained by other cache servers on an individual cache server basis; and
a cache-data-list administrating unit receiving a data-inquiry request from one of the other cache servers, and searching the cache-data-list table for cache-server information indicating another one of the other cache servers retaining data regarding the data-inquiry request so as to send the cache-server information to the one of the other cache servers.
According to the present invention, the cache server can administrate information of data retained by other cache servers so that the other cache servers do not have to retain the same data as one another. This reduces the amount of cache data as a whole so as to lessen the task load imposed on a recording medium such as a hard disk. Furthermore, the other cache servers can obtain data from one another so as to alleviate the traffic of an external network.
Additionally, the cache server according to the present invention may further comprise:
a relative-position information table storing information indicating a distance between each two of the other cache servers; and
a control-data sending and receiving unit obtaining a distance between the one of the other cache servers and the said another one of the other cache servers from the relative-position information table so as to order the one of the other cache servers to retain the data regarding the data-inquiry request depending on the distance.
Additionally, in the cache server according to the present invention, the control-data sending and receiving unit orders the one of the other cache servers to retain the data regarding the data-inquiry request when the distance is larger than a predetermined distance.
According to the present invention, when one of the other cache servers makes a request to obtain data retained by another cache server that is several cache servers away therefrom, the one of the other cache servers can cache the data in itself so as not
Ikeda Hitoshi
Matsumoto Takesi
Shibata Keiichiro
Burgess Glenton B.
Dinh Khanh Quang
Fujitsu Limited
Katten Muchin Zavis & Rosenman
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