1. Field of the Invention
The present invention relates to a computer network system in which communication is realized by using a communication protocol address assigned to a computer and decided in accordance with its connecting location on a network. In particular, according to the present invention, even when the communication protocol address is to be changed dynamically due to movement of a computer, etc., communication is possible without variously affecting existing application programs from that change in the communication protocol address.
2. Related Art
Conventionally, in the network system of the Internet, there is used a domain name system (hereinafter, abbreviated to "DNS") which provides a communication protocol address (IP address) of a computer in accordance with an inquiry based on a name (domain name) uniquely assigned to that computer. In the DNS, names of computers and their communication protocol addresses are registered in a database in advance so that a communication protocol address can be searched for from a name of a computer.
In the environment of the network system using the DNS, when a communication protocol address assigned to a computer should be changed in accordance with a change of a connecting location of that computer due to movement of that computer, etc., the communication protocol address searched for using the name of the computer registered in the search database of the DNS is changed in that database. After the revision of the database, the changed communication protocol address of that computer to communicate with can be obtained using the name of the computer. Accordingly, in an application program (hereinafter, briefly referred to as "AP"), communication is possible even if a communication protocol address of a communication partner's computer is changed.
Conventionally, the search database of the DNS has been revised manually using a database editing program. Recently, the IETF (Internet Engineering Task Force), a group for standardization on the Internet, has promoted standardization work for a dynamic DNS (hereinafter, referred to as "DDNS") protocol, by which a search database of DNS can be revised on-line, dynamically. This DDNS includes a DDNS server computer, which has a search database and a function for allowing access to the search database from a client terminal. Accordingly, a user can access the search database of the DDNS server computer to change a communication protocol address.
Further, the above-described IETF work group has proposed a method in which, when a computer is moved and connected with another network, a server, etc. of the DHCP (Dynamic Host Configuration Protocol) assigns a new address to the moved host computer, and another host computer's communication with this host computer assigned with a new address is supported by mounting the VIP (Virtual Internet Protocol) on a router device or the host computers.
Another example of the system for communication of a mobile computer is described in Japanese Patent Application Laid-Open (KOKAI) No. 7-170286. This conventional technique realizes a function of supporting communication with a host computer assigned with a new address, in a network system including a mobility supporting border router (MSBR), and a mobility supporting router (MSR).
As a similar and known example, Japanese Patent Application Laid-Open (KOKAI) No. 7-129488 describes a mobile terminal administration device. In this conventional technique, communication with a mobile computer is supported by a home location administration device, a visitor location administration device, and a private location administration device.
Thus-described conventional techniques have the following problems.
In the above-described DDNS, an application program provided in a computer must have a logic for making a search of a communication protocol address, using a name of a computer of a communication partner. In another words, when an AP is not a software adapted for the DDNS, it cannot utilize the DDNS.
Further, in the mobile computer described in the above-described 7-170286 and 7-129488, an operating system of the computer must be remade, and a network transit device such as an existing router must be changed.