JP2011146823A - Method for updating cache information, computer, program and storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide, in a hierarchized DNS (Domain Name System), a technique for changing old domain information held in a cache of each computer to new domain information without a time lag and without applying a load to a network when a domain of a certain computer is changed. <P>SOLUTION: Pieces of information on a domain name before change, an IP address before the change, a domain name after the change, an IP address after the change, and update time are received, and are stored in first to fifth storage areas of a cache table respectively, and when the update time comes, the domain name before the change in the first storage area is set to the domain name after the change in the third storage area, the IP address before the change in the second storage area is set to the IP address after the change of the fourth storage area, and pieces of information in the third to fourth storage area are set to NULL data. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a DNS (Domain name System), and more particularly to a technique for automatically updating a cache held by a computer in the DNS.

The DNS server is a server that performs name resolution. The DNS server has a hierarchical structure, and in principle requests a name resolution from the DNS server one level higher. However, as an exception, for the purpose of improving name resolution efficiency, the DNS server has a mechanism for storing the contents inquired by itself as a cache (see Non-Patent Document 1). DNS that received a name resolution request
The server first refers to the cache information, and if there is information corresponding to the cache information, responds to the request source according to the cache information. Therefore, even when the DNS information of a certain domain is changed, if the information before the change remains in the cache, there is a problem that the DNS server makes a wrong answer to the requester without malicious intention. The holding and holding period of the cache information is determined by each DNS server and cannot be changed from other servers. For this reason, other servers cannot improve possession of unauthorized cache information.

  As an improvement measure, there is a technique for notifying each DNS server of changes in DNS information and rewriting cache information (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 10-161921

2nd name resolution mechanism and zone file setting, basic operation of BIND, 2001/1/1, [online], [searched December 8, 2009], Internet <URL: http: // www .atmarkit.co.jp / flinux / rensai / bind02 / bind02.html>

  In Patent Document 1, a cache change notification cannot be made to DNS servers and terminals other than the same domain. In addition, since the time until the notification reaches the change notification sending destination DNS server and terminal from the change notification sending source depends on the line speed of the network, there is a problem that a time lag from notification to execution occurs. While the domain change time lag occurs, HP (homepage) and mail service using the changed domain cannot be provided to the end user. Therefore, for companies (organizations) whose business is providing services by HP or e-mail, it becomes a matter of concern that leads to reduced trust and loss of interest for end users.

  In addition to the normal name resolution process, a process for notifying the subordinate DNS server of the change is generated, so that the load on the network increases and the processing performance of the normal name resolution process may be degraded.

  The present invention has been made in view of the above circumstances, and in a hierarchical DNS, when a domain of a computer is changed, there is no time lag, and no load is imposed on the network. It is an object of the present invention to provide a technology capable of changing old domain information that is held to new domain information.

  One means for solving the above problem will be described. The present invention is a method for updating cache information in a computer connected via a network, the domain name before change, the Internet address before change, the domain name after change, and the Internet after change via the network. A process for receiving address and update time information, and a cache table for the domain name before the change, the Internet address before the change, the domain name after the change, the Internet address after the change, and the information about the change time, respectively. The first storage area, the second storage area, the third storage area, the fourth storage area, and the fifth storage area, the process of periodically referring to the update time, and the current time Is the update time, the domain name before the change in the first storage area is changed to the first storage area. The changed domain name in the storage area of the second storage area, the Internet address before the change in the second storage area as the changed Internet address of the fourth storage area, and the third to fourth storage areas. And a process for setting each of the information in NULL data.

According to the present invention, when a domain of a computer is changed in a hierarchical DNS, the old domain information held in the cache of each computer is updated with no time lag and no load on the network. Can be changed to domain information.

It is a figure which shows the hierarchical structure of DNS1 whole structure and name resolution which concerns on embodiment of this invention. It is a figure which shows the hardware structural example of the DNS server 2, 3, 4, 6, 7 which concerns on embodiment of this invention. It is a figure which shows the hardware structural example of the user terminals 5 and 9 which concern on embodiment of this invention. It is a figure which shows the data structural example of the cache tables 208 and 308 which concern on embodiment of this invention. Similarly, it is a figure which shows the example of a data structure of the cache tables 208 and 308 which concern on embodiment of this invention. It is a figure which shows the example of a data structure of the name resolution related information tables 205 and 305 which concern on embodiment of this invention. It is a figure which shows the flow of a process from name resolution which concerns on embodiment of this invention until it holds cache information. It is a figure which shows the flow of a process until it confirms and updates the possession cache information which concerns on embodiment of this invention. It is a flowchart which shows a flow from the name resolution which concerns on embodiment of this invention to a cache update.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing an overall configuration of DNS 1 and a hierarchical structure of name resolution. The DNS 1 is a computer system that includes a DNS server 2, a plurality of DNS servers 3 and 6, a plurality of DNS servers 4 and 7, a plurality of user terminals 5 and 9, and a time synchronization server 10. . The DNS server 2, the plurality of DNS servers 3 and 6, and the plurality of DNS servers 4 and 7 are connected to a network such as the Internet. The plurality of user terminals 5 and 9 and the time synchronization server 10 are connected to a local area network (LAN).

  In FIG. 1, a DNS server 2 is a server that manages a DNS server with a domain name (.jp) and a user terminal. When the domain information of the DNS server and user terminal with (.jp) added to the domain name is changed, the administrator of the DNS server 3, 4, 6, 7 or the user terminal 5, 9 The administrator of the DNS server 2 who applied for the change is requested to the administrator, and changes the corresponding management information in the DNS server 2. At this time, the administrator of the DNS server 2 also registers the update time of the domain information (time for reflecting the change information).

  The DNS server 3 is a server that manages servers and terminals with (.go.jp) added to the domain name, and is under the management of the DNS server 2. Similarly, the DNS server 6 is a server that manages a server and a terminal having a domain name with “.co.jp”, and is under the management of the DNS server 2.

  The DNS server 4 is a server that manages a terminal having a domain name with XX.go.jp, and is under the management of the DNS server 3. Similarly, the DNS server 7 is a server that manages a terminal having a domain name with YY.go.jp, and is under the management of the DNS server 3.

  The user terminal 5 is a terminal having a domain name of A.XX.go.jp and is under the management of the DNS server 4. Similarly, the user terminal 9 has a domain name Z. XX. go. a terminal having jp and under the management of the DNS server 4.

  The time synchronization server 10 is a server that has the domain name GD.XX.gp.JP and is the time synchronization source of the XX.go.jp domain.

  The DNS 1 has a hierarchical structure as shown in FIG. 1, so that, for example, the user terminal 5 is assigned to the DNS server 4, the DNS server 4 is assigned to the DNS server 3, and the DNS server 3 is assigned to the DNS server 2. It has a function of making a resolution request and responding to a name resolution request. Servers and terminals existing in the XX.go.jp domain, such as the user terminal 5, the user terminal 9, and the DNS server 4, make a time synchronization request to the time synchronization server 10.

  Next, the hardware configuration shown in FIGS. 2 and 3 and the functions of the stored program will be described.

  FIG. 2 is a diagram illustrating a hardware configuration example of the DNS server 2. The hardware configuration of the other DNS servers (3, 4, 6, 7) is the same as that of the DNS server 2.

  The DNS server 2 includes a storage unit 201, a display unit 210 such as a display, an input unit 211 such as a keyboard and a mouse, a control unit 212 such as a CPU, and a network interface unit 213 that transmits and receives information to and from the network. To do. Each part is connected by BUS or the like. Each DNS server is realized by a general computer.

  The storage unit 201 includes a cache update time confirmation function 202, a cache update function 203, a name resolution function 204, a cache holding function 206, a cache deletion function 207, a time synchronization function 209, a name resolution related information table 205, A cache table 208 is stored.

  The cache update time confirmation function 202 has a function of confirming the cache update time.

  The cache update function 203 has a function of updating information in the cache table 208.

  When the name resolution function 204 receives a name resolution request via the network, the name resolution function 204 has a function of referring to the cache table 208 held by itself and returning information on the record if there is a corresponding record.

  The cache holding function 206 has a function of holding a response obtained from the upper DNS server via the network in its own cache table 208.

  The cache deletion function 207 refers to a TTL (Transistor-Transistor Logic) 425 of the name resolution related information table 205, and deletes a record in the cache table 208 when the TTL value 425 has elapsed from the time when the cache table 208 is held. Have

  The time synchronization function 209 has a function of performing time synchronization via the network with respect to the time synchronization server 10 in the same LAN.

  The name resolution related information table 205 stores DNS server information of the name resolution request destination and its own domain information. The name resolution function 204 makes a name resolution request / reply according to the information.

  In the cache table 208, the domain name before the change, the Internet address before the change (for example, IP address), the domain name after the change (hereinafter referred to as a new domain name), the result after the name resolution answer, Information indicating an IP address (hereinafter referred to as a new IP address) and an update time is stored. The information in the cache table 208 is not stored permanently, but is deleted by the cache deletion function 207 when the TTL period stored in the name resolution related information table 205 has passed.

  FIG. 3 is a diagram illustrating a hardware configuration example of the user terminal 5. The hardware configuration of other user terminals 9 is the same as that of the user terminal 5. Each user terminal is realized by a general computer.

  Although not shown, the time synchronization server 10 includes a control unit such as a CPU, a storage unit, and a network interface unit, and receives a time synchronization request from a DNS server or a user terminal and responds with information on the current time. Have

  FIG. 4 is a diagram illustrating a data configuration example of the cache tables 208 and 308.

  The cache tables 208 and 308 indicate the cache No. 401, the domain name 402 before the change, the IP address 403 before the change, the domain name 404 after the change, the IP address 405 after the change, and the update time 406. Information is stored in association with each other.

  The cache No. 401 is information indicating the item number of the cache, and is assigned sequentially in the registered order. Each record can be identified by the cache NO 401. The domain name 402 is information indicating the domain name of the domain that has performed name resolution. The IP address 403 is information indicating the IP address of the domain that has performed name resolution. The new domain name 404 is information indicating the domain name after the change when the domain name of the domain subjected to name resolution is to be changed. The new IP address 405 is information indicating the IP address after the change of the domain when the IP address of the domain that has performed name resolution is to be changed. The update time 406 is information indicating the date and time when the domain name or IP address of the domain that has undergone name resolution is to be changed. These pieces of information are registered in the cache table when each server and terminal makes a name resolution request via the network and receives a response from the name resolution request destination.

  FIG. 5 is a diagram illustrating a data configuration example after the cache is updated, and is the same data configuration as FIG. 4.

  The cache No. 411 is information indicating a cache item number. It is given in sequential order in the registered order. The domain name 412 is information indicating the domain name after the cache is updated. The IP address 413 is information indicating the IP address after the cache is updated. The new domain name 404, the new IP address 405, and the update time 406 are set to NULL data when the cache is updated.

  FIG. 6 is a diagram illustrating a data configuration example of the name resolution related information tables 205 and 305.

  The domain name 421 is information indicating its own domain name. The IP address 422 is information indicating its own IP address. The upper DNS server 423 is information indicating the name resolution request destination DNS server. The lower DNS server 424 is information indicating a server and a terminal under the domain 421 of its own. The TTL 425 is information indicating a period in which the TTL 425 itself holds a cache.

  FIG. 7 is a diagram showing the flow of processing from name resolution to possession of cache information. Here, as a premise, it is assumed that the user terminal 5 performs name resolution. Also, if you want to change the domain information, in addition to the "domain name after change" and "IP address after change" when applying to the top DNS server administrator for the change of domain information, (Date and time) "is applied to the administrator of the highest DNS server 2, and the administrator registers the change information in the DNS server 2 (step S500).

  First, the name resolution function 304 of the user terminal 5 refers to the name resolution related information table 305 and makes a name resolution request to the DNS server (XX.go.jp management) 4 which is a higher level DNS server (step S501). . When making a name resolution request, the user terminal 5 passes domain information (domain name or IP address) to be resolved to a DNS server (XX.go.jp management) 4 which is a higher level DNS server. Upon receiving the name resolution request, the name resolution function 204 of the DNS server (XX.go.jp management) 4 searches the cache table 208 held by itself using the received domain name or IP address as a key. If the domain name or IP address as the key matches the domain name 402 or IP address 403 of the cache table 208, the name resolution function 204 returns the record information to the user terminal 5 (step S508). The user terminal 5 receiving the response stores the response result as a record in its own cache table 308 by the cache holding function 306 (step S509).

  In step S501, if there is no corresponding record, the name resolution function 204 of the DNS server 4 determines that the DNS server (.go.jp management) 3 is a higher DNS server of the DNS server (XX.go.jp management) 4. A name resolution request is made (step S502).

  When making a name resolution request, the DNS server (XX.go.jp management) 4 sends domain information (domain name or IP address) to be resolved to the DNS server (.go.jp management) 3 which is a higher level DNS server. )give. Upon receiving the name resolution request, the name resolution function 204 of the DNS server (.go.jp management) 3 searches the cache table 208 held by itself using the received domain name or IP address as a key. If the domain name or IP address as the key matches the domain name 402 or IP address 403 of the cache table 208, the name resolution function 204 of the DNS server (.go.jp management) 3 converts the record information into DNS. Reply to the server (.go.jp management) 3 (step S506). The DNS server (XX.go.jp management) 4 that has received the reply stores the reply result as a record in its own cache table 208 by the cache holding function 206 (step S507). If there is no corresponding record, the name resolution function 204 of the DNS server (.go.jp management) 3 sends to the DNS server (.jp management) 2 which is a higher DNS server of the DNS server (go.jp management) 3. A name resolution request is made (step S503).

  The name resolution function 204 of the DNS server (go.jp management) 3 refers to the name resolution related information table 205 and makes a name resolution request to the DNS server (go.jp management) 3 which is a higher DNS server (steps). S503). When making a name resolution request, the DNS server (go.jp management) 3 passes the domain information (domain name or IP address) to be resolved to the DNS server (.jp management) 2 which is the upper DNS server. The name resolution function 204 of the DNS server (.jp management) 2 that has received the name resolution request searches the cache table 208 held by itself using the received domain name or IP address as a key. If the domain name or IP address used as the key matches the domain name 402 or IP address 403 of the cache table 208, the name resolution function 204 of the DNS server (.jp management) 2 stores the record information in the DNS server ( go.jp management) 3 is answered (step S504). The DNS server (go.jp management) 3 that has received the reply stores the reply result as a record in its own cache table 208 by the cache holding function 206 (step S505).

  FIG. 8 is a diagram showing the flow of processing until the retained cache information is confirmed and updated. Here, as a premise, it is assumed that the server that performs the cache update is the DNS server (XX.go.jp management) 4. Further, it is assumed that the cache table 208 of the DNS server (XX.go.jp management) 4 has cache information that holds the corresponding update time as a value.

  First, the time synchronization function 209 of the DNS server (XX.go.jp management) 4 makes a time synchronization request to the time synchronization server 10 (step S601), and acquires information on the current time (step S602). The time synchronizer 2309 of the DNS server (XX.go.jp management) 4 compares the current time held by itself with the current time received from the time synchronization server 10 and performs time synchronization (step S603).

  Next, the cache update time confirmation function 202 of the DNS server (XX.go.jp management) 4 records records registered in its own cache table 208 using the current time at which time synchronization was performed in step S603 as a key. A search is performed (step S604), a record having an update time 406 equal to the current time is specified, and the current time of the search key is compared with the update time 406 of the specified record (step S605). Then, the cache update function 203 updates the information (cache information) of the record (step S606). Specifically, the cache update function 203 changes the domain name 402 in the cache table 208 to the new domain name 404 and the IP address 403 to the new IP address, respectively, the new domain name 404, the new IP address 405, the update time NULL data is set in 406.

  FIG. 9 is a flowchart showing a flow of processing from name resolution to cache update. In this case, it is assumed that the name resolution request source is the DNS server (XX.go.jp management) 4 and the name resolution request destination is the DNS server (.go.jp management) 3.

  The name resolution function 204 of the DNS server (XX.go.jp management) 4 sends domain information to be subjected to name resolution to the DNS server (.go.jp management) 3 which is a higher DNS server, and makes a name resolution request. (Step S701).

  Upon receipt of the request, the name resolution function 204 of the DNS server (.go.jp management) 3 searches the cache table 208 using the domain information received from the DNS server (XX.go.jp management) 4 as a key. A name resolution answer including record information (domain name, IP address, new domain name, new IP address, update time) is transmitted to the DNS server (XX.go.jp management) 4 (step S702).

  The cache holding function 206 of the DNS server (XX.go.jp management) 4 assigns a cache number to the received information (domain name, IP address, new domain name, new IP address, update time), and stores its own cache table. It is stored in 208 (step S703). The data after saving is the cache No. 401, the domain name 402, the IP address 403, the new domain name 404, the new IP address 405, and the update time 406, respectively.

  Thereafter, the time synchronization function 209 of the DNS server (XX.go.jp management) 4 periodically makes a time synchronization request to the time synchronization server 10 (step S704), acquires the current time, and acquires the acquired current time. It is set to its own time (step S705).

  Next, the cache update time confirmation function 202 of the DNS server (XX.go.jp management) 4 periodically compares the current time after synchronization with the update time 406 of the cache table 208 (step S706), and the same If there is something (YES in step S707), the cache update function 203 of the DNS server (XX.go.jp management) 4 sets the domain name 402 in the cache table 208 to the new domain name 404 and the new IP address 403. The IP address is changed to the IP address 405, and NULL data is set in the new domain name 404, the new IP address 405, and the update time 406 (step S708).

  If no identical item is found in step S707, the process is terminated (step S709).

  Although an example of the preferred embodiment of the present invention has been described above, according to the above-described embodiment of the present invention, when the domain of each DNS server or user terminal is changed in the hierarchical DNS 1, the time lag is changed. The old domain information held in the cache of each DNS server or user terminal can be changed to new domain information without any load on the network. As a result, each DNS server and user terminal can always keep the information in the cache tables 208 and 308 held up-to-date, and the information does not match between the cache tables 208 and 308 and the DNS server (.jp management) 3. It is possible to prevent incorrect name resolution answers. In addition, companies (organizations) that change DNS information do not have to worry about the suspension of HP and mail services due to the time lag of domain change. In addition, parallel operation of the new and current domain environment is not required to reduce the service stop time, and the work cost and work risk are reduced.

  As another embodiment, the TTL value is changed by adding the TTL time to the records of the name resolution related information tables 205 and 305, the cache retention period is shortened, and the cache information is updated. A method of keeping will be described. In order to use this method, each DNS server 2 or the like needs to have a TTL changing function. The TTL change function indicates a function of shortening the period during which each DNS server 2 or the like holds cache information by automatically changing the TTL value in the name resolution related information table 208. Here, it is assumed that the DNS server (XX.go.jp management) 4 receives a name resolution record including TTL and stores the value in the cache table 208 as a premise.

  First, the TTL change function of the DNS server (XX.go.jp management) 4 refers to the name resolution related information table 205 using the received TTL as a key, and rewrites the value of the TTL 425 to the received TTL. The cache deletion function 207 of the DNS server (XX.go.jp management) 4 deletes the cache information when the changed value of the TTL 425 has elapsed. As a result, the cache holding period of each DNS server 2 or the like can be changed from the outside, and the cache holding period can be made uniform.

  Also, the program executed in each of the DNS server and user terminal shown in FIG. 2 and FIG. 3 is recorded on a computer-readable recording medium, and the program recorded in this recording medium is read into a computer system and executed. As a result, the DNS 1 according to the embodiment of the present invention is realized. Further, the program may be provided to the DNS server and the user terminal via a network such as the Internet. The functions of the program may be realized by hardware.

    Further, the present invention is not limited to the above embodiment, and can be appropriately changed without departing from the gist of the present invention.

2, 3, 4, 6, 7 ... DNS server, 5, 9 ... user terminal, 10 ... time synchronization server, 201, 301 ... storage unit, 210, 310 ... display unit, 211, 311 ... input unit, 212, 312 ... control unit, 213, 313 ... network interface unit.

Claims (6)

A method for updating cache information in a computer connected via a network, comprising:
A process of receiving information on the domain name before the change, the Internet address before the change, the domain name after the change, the Internet address after the change and the update time via the network,
Information about the domain name before change, the Internet address before change, the domain name after change, the Internet address after change and the change time are respectively stored in a first storage area and a second storage area of the cache table. Storing in the third storage area, the fourth storage area, and the fifth storage area;
A process of periodically referring to the update time;
When the current time reaches the update time, the domain name before the change in the first storage area is changed to the domain name after the change in the third storage area, and the Internet before the change in the second storage area. A process of setting an address to the changed Internet address of the fourth storage area and information of the third to fourth storage areas to NULL data, respectively.
A cache information updating method characterized by the above. The first and second Internet addresses are IP addresses;
The DNS cache information update method according to claim 1, wherein: A computer connected via a network,
A cache table and a control unit;
The controller is
Via the network, the domain name before the change, the Internet address before the change, the domain name after the change, the Internet address after the change and the information of the update time are received,
Information about the domain name before change, the Internet address before change, the domain name after change, the Internet address after change and the change time are respectively stored in a first storage area and a second storage area of the cache table. , Store in the third storage area, the fourth storage area and the fifth storage area,
Periodically refer to the update time,
When the current time reaches the update time, the domain name before the change in the first storage area is changed to the domain name after the change in the third storage area, and the Internet before the change in the second storage area. An address is set to the changed Internet address of the fourth storage area, and information of the third to fourth storage areas is set to NULL data.
A computer characterized by that. The first and second Internet addresses are IP addresses;
The computer according to claim 3. A program executed by a computer connected via a network,
A process of receiving information on the domain name before the change, the IP address before the change, the domain name after the change, the IP address after the change and the update time via the network;
Information about the domain name before change, the IP address before change, the domain name after change, the IP address after change and the change time are respectively stored in a first storage area and a second storage area of the cache table. Storing in the third storage area, the fourth storage area, and the fifth storage area;
A process of periodically referring to the update time;
When the current time becomes the update time, the domain name before change in the first storage area is changed to the domain name after change in the third storage area, and the IP address before change in the second storage area. Causing the computer to execute a process of setting an address to the changed IP address of the fourth storage area and information of the third to fourth storage areas to NULL data, respectively.
A program characterized by that.   A computer-readable storage medium storing the program according to claim 5.

Images