Electrical computers and digital processing systems: multicomput – Distributed data processing – Client/server
Reexamination Certificate
1998-10-06
2003-01-28
Sheikh, Ayaz (Department: 2155)
Electrical computers and digital processing systems: multicomput
Distributed data processing
Client/server
C709S241000, C709S224000, C709S228000, C709S229000
Reexamination Certificate
active
06513061
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a server-client network system, and more particularly to the network technique which is arranged to-curtail loads burdened on the network and a server and provide a comfortable working environment to each client.
Before describing the invention, the following four known arts will be described.
(1) Domain Name System (DNS)
The internet employs a system that uses a domain name represented by hierarchically setting each logical group called a domain and delimiting the logical group with a period.
The correspondence between a domain name and an IP address, (which corresponds to a network address in the internet, for example, the address being represented by figures delimited with some periods) is managed by a DNS server. The DNS server operates to swap information with another DNS server if necessary. The swapping operation results in making it possible to correspond all the domain names to the IP addresses included in the internet.
A client makes access to a destination server for providing the target service the client would like to reach through the use of the internet. For this purpose, in actual, the client uses the IP address that is a physical address in place of the host name. It means that the client has to obtain the IP address of the server for providing the target service the client would like to reach.
If, therefore, the client does not know the IP address of the server for providing the target service, the client indicates the domain name of the target server to the DNS server pre-registered as its own server for inquiring the IP address of the target server. In response to the inquiry, the DNS server searches the corresponding IP address to the domain name of the target service server and notifies the client of the IP address.
In addition, if the DNS server of inquiry cannot obtain the IP address of the service server, the DNS server inquires the upper DNS server of it.
(2) Proxy Server
Between a network inside of an organization that needs high security and the internet located outside of the network, a firewall for access control is normally built. The proxy server is a proxy gateway developed in effect when the communications inside or outside of the organization are prohibited by the firewall.
For example, inside of a local area network (referred to as an LAN), a user cannot directly communicate with a wide area network (referred to as a WAN). To overcome the inconvenience, a segment area called “Barrier Segment” is provided between the LAN and the WAN, so that the client user temporarily has to do remote log-in to the server operating on the barrier segment and then makes access to the server on the WAN side.
This method, however, needs to prepare many user accounts (right of use given in the user registration) in the server operating on the barrier segment. This disadvantageously leads to increasing the security holes.
Under these circumstances, a proxy server has been developed which allows the server or the client of the network inside of the organization to access a resource or data of Gopher, WWW or the like without having to prepare any user account for the server operating on the barrier segment.
The proxy server is operated on the firewall. The proxy server keeps special ports open so that it can receive messages from plural clients. Then, the proxy server operates to transfer the received messages to the server for providing the target service the client would like to reach. It thus serves to be proxy for the client.
The proxy server receives a message from the client without user authentication. The proxy server uses the IP address that corresponds to the physical address of the client for the communications with the client, so that the log-in of the client to the proxy server is unnecessary if not specified.
The proxy server has a function of relaying a client's access to the resource or the data of the Gopher or the WWW, for example. The client just communicates with only the proxy server without direct communications with the server on the WAN side.
This proxy server eliminates the necessity of directly exchanging the message between the LAN and the WAN, thereby making it impossible for the WAN side to unjustly attack the LAN side.
(3) Proxy Cache Server
When developing the foregoing proxy server, a proxy server provided with a cache function has been developed as its byproduct.
The proxy server has been developed for the purpose of relaying the client's access to the resource or the data. Hence, highly plausibly, two or more clients on the LAN side may refer to the data at a time.
If two or more requests for referring to the data takes place, the proxy server refers to the data of the server on the WAN side and gives back the data to the clients on the LAN side who have issued the referring requests.
As mentioned above, the proxy server may operate to temporarily cache the resource or the data referenced once by itself in a storage medium such as a disk and give back the data temporarily cached in the disk to the clients on the LAN side who have issued the referring requests without having to access the server on the WAN side if two or more requests for referring to the resource or the data given by the clients take place at a time. The proxy server provided with this type of function is referred to as a proxy cache server.
The proxy cache server helps to curtail the traffic on the WAN. It is more advantageous to the user, because the communications on the WAN is lower in speed and higher in cost than those on the LAN.
Moreover, the reduction of the access times given from the client on the LAN to the server on the WAN makes great contribution to lessening the load burdened on the server. Further, the user on the LAN can reuse the resource or the data cached in the proxy cache server that is a local server, so that the user may enjoy a comfortable response to the access.
In addition, the proxy cache server may make sure of a time stamp of the resource or the data cached in a storage medium such as a disk so that it may access the server on the WAN again about the resource or the data having the previous time stamp than a given period. This operation allows the proxy cache server to obtain the resource or the data of the latest version.
(4) Client-Store System
As an inexpensive internet access device of the next generation, an inexpensive terminal is designed wherein only the internet function and protocol to be supported as minimum level are mounted.
This type of terminal has to support as minimum functions many internet communications protocols such as Web and FTP (File Transfer Protocol) and a networking standard service of a network sharing system, a UDP (User Datagram Protocol), a TCP (Transmission Control Protocol), a DHCP (Dynamic Host Configuration Protocol), a BOOTP (Bootstrap Protocol), and the like.
Unlike personal computers, it is preconditioned that this type of terminal requires the server to concentratively manage all the applications and the promotion. However, this type of terminal does not include a harddisk. Hence, each time it is started, the application program has to be downloaded from the server. This results in disadvantageously increasing the load burdened on the server and the network.
In place of this type of terminal, a system is also provided for reducing distribution of the application program from the server to a minimum through the use of the harddisk of the existing personal computer.
When the resource is transferred from the server, this type of system operates to record the resource in the harddisk and reuse the resource recorded in the harddisk if necessary.
This system does not need to constantly read the resource from the server. Further, in using the resource or periodically, the system is operated to check change of the resource on the server. It thus has an advantage that the resource of the latest version may be constantly started on the client side. On the other hand, however, this type of system would be more disadvantageous in portab
Ebata Tomoichi
Ito Hiromichi
Kamata Yoshihiro
Saito Masato
Antonelli Terry Stout & Kraus LLP
Jean Frantz B.
Sheikh Ayaz
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