JP2013251778A - Communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress repetition of mail transmission trial to a mail server where failures occur at each time of transmitting mail when failures occur at some mail servers of a destination domain of mail transmission, which occurs in a conventional mail gateway system.SOLUTION: A communication system includes: collecting convergence statistical information having hierarchical structure for each MX record and each host; and determining an IP address of the host having high possibility that mail transmission is successful using the collected convergence statistical information.

Description

  The present invention relates to a technique for selecting a destination mail server when a failure occurs in a destination mail server or a communication path in a mail gateway system.

A conventional mail gateway system performs name resolution of a mail transmission destination domain by a DNS (Domain Name Service) inquiry. The DNS inquiry is performed by first making an MX (MailXchange) record inquiry, making an inquiry about the A record of the MX record having the highest priority (preference value) among the obtained MX records, and obtaining the obtained host (IP address). Send mail to any mail server in the group.
In a conventional mail gateway, when a counter mail server failure occurs, as described in Patent Document 1, for example, congestion control is performed on a plurality of destination mail servers for each domain, and transmission restriction and cancellation are performed. For example, in Patent Document 2, congestion control is performed by lowering the priority of a server in which a failure of the MX record held in the internal DNS occurs.

JP2010-287987 JP2001-086152

  In the conventional mail gateway system, when a failure occurs in some mail servers in the mail transmission destination domain, the mail gateway system repeatedly provides mail transmission attempts to the mail server in which the failure occurs each time mail is sent. There is a possibility that the mail delivery service will affect the delivery delay. Further, the MX record of the mail transmission destination domain has a priority, but since the master is managed by the external DNS, the priority cannot be changed by the mail gateway. In addition, the host associated with the MX record has no priority, and if a failure occurs in some servers of a large communication system having a plurality of MX records and hosts, there is a host that can transmit, There is a problem that mail transmission is repeatedly delayed after repeated mail transmission attempts to the fault mail server.

  In the mail gateway system, when a failure occurs in some mail servers or communication paths in the destination domain, the mail transmission to the failed mail server is regulated for the domain in which the failure has occurred, and healthy mail is sent. The challenge is to provide a mail delivery service that is less affected by failures that occur in the destination domain by preferentially sending mail to the server.

 As an example, the communication system according to the present invention reads a mail transmitted from a communication terminal, reads the mail from the storage, obtains a plurality of MX records corresponding to the destination domain of the mail, and Congestion statistics information for each MX record is searched using the MX record as a key to determine a destination MX record, a plurality of IP addresses corresponding to the destination MX record are obtained, and a congestion statistics for each host is obtained using the plurality of IP addresses as a key. A mail relay processing unit that searches information to determine a destination host and forwards the mail to the destination host.

  Even when a failure occurs in some mail servers in the mail transmission destination domain, it is possible to determine a host server having a relatively high possibility of successful transmission from the mail server group, and to minimize the influence of the mail delivery failure.

1 is a block diagram of a system configuration example showing an embodiment of the present invention. Figure of mail gateway block logical configuration example The figure of the example of a sequence of congestion control by this mail gateway system. Congestion statistics information example for each MX record Example of congestion statistics for each host Transmittable MX record determination flowchart example Sendable host determination flowchart example

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing an example of an embodiment of a mail gateway system. In FIG. 1, 101 is a communication terminal capable of sending mail, 102 is a wireless network connecting 101 and 103, 103 is a carrier equipment network (core network) managed by a communication carrier, and connects 102, 104 and 106, 104 is In the Internet, 105 is a mail server group of mail transmission destinations connected via 104, 107 is a DNS server connected via 104, 106 is a mail gateway system, and 108 is 106 for monitoring operation via 103. It is an operation monitoring server.
FIG. 2 shows a logical configuration of the mail gateway system. In FIG. 2, 201 is a mail reception process processing unit that receives mail from a communication terminal via 103, 202 is a message queue (first storage unit) that stores the mail received in 201, and 204 is mail stored in 202. Is a mail relay process processing unit that transmits the message to the forwarding mail server via 103. Reference numeral 207 denotes a retransmission queue (second storage unit) for storing mail when 204 fails to send mail. A DNS communication process processing unit 205 performs name resolution of the destination domain requested from 204. A command I / F process processing unit 206 relays the operation command from 108 to 204. Reference numeral 203 denotes a congestion statistical information processing unit that processes statistical information regarding the processing by 204.
Next, name resolution control by this mail gateway system will be described according to the sequence of FIG. Upon receiving the mail 301 from the communication terminal having the mail client function, the mail reception process processing unit stores the mail 302 in the message queue, and transmits a normal response 304 to the communication terminal when the success response 303 is received. The message relay process processing unit reads the mail 305 stored in the message queue, makes a sendable domain determination 306, and sends an MX record inquiry 307 about the destination domain of the mail read from the message queue to the DNS server. The mail relay process processing unit receives the MX record 308 as a response to the MX record inquiry 307 from the DNS server.

  Next, the mail relay process processing unit searches the congestion statistical information 320 for each MX record stored in the congestion statistical information processing unit 203 using the received MX record as key information. Details of the congestion statistical information 320 for each MX record are shown in FIG. In this search, key information 402 that matches the received MX record is searched, and failure determination counter information 404, failure breakdown information 405, and priority information 407 corresponding to the matching key information 402 are searched. Based on these search results, a transmittable MX record determination 309, which will be described in detail later, is performed.

  The mail relay process processing unit transmits the host name inquiry 310 to the DNS server using the MX record determined as the transmission destination MX record in 309, and receives the IP address 311 from the DNS server as a response to the host name inquiry 310.

  The mail relay process processing unit searches the congestion statistical information 321 for each host (IP address) stored in the congestion statistical information processing unit 203 using the destination MX record and the received IP address as key information. Details of the IP address congestion statistics information 321 are shown in FIG. In this search, key information (IP address) 502 and option storage area (MX record) 507 are searched using the received IP address and MX record as keys, and corresponding failure determination counter 504 information and failure breakdown 505 information are searched. . Based on these search results, a transmittable host determination 312 is described in detail later. A search may be performed using only key information (IP address) as a key.

The mail relay process processing unit transmits (transfers) the mail 313 to the transmission destination mail server to the transmission destination host (transmission destination host IP address) determined in 312. After receiving the transmission result 314 of 313, the mail relay process processing unit performs a transmission result determination 315, reflects the result in 320 and 321, and updates the congestion statistical information 316.
Next, an example of congestion statistical information for each MX record collected by the mail gateway system will be described with reference to FIG. The congestion statistical information for each MX record includes mail transmission failure information for each MX record. For example, for each unique ID 401, key information (MX record), counter information 403 for counting the number of successful email transmissions, failure determination count information 404 for counting the number of failed email transmissions, and email transmission failure This is a table for storing failure breakdown information 405 for counting the number of times for each error cause, update date and time information 406, and priority information 407 received from DNS. For example, when reusing mail transmission connections, the number of connections in use may be stored together. Further, the number of emails sent per unit time, the average message size of emails sent, and the average response time of email transmission requests may be aggregated.
Next, an example of congestion statistical information for each IP address collected by the mail gateway system will be described with reference to FIG. The congestion statistical information for each IP address includes failure information for mail transmission for each IP address. For example, for each unique ID 501, key information (IP address), counter information 503 that counts the number of times mail transmission has been successful, failure determination count information 504 that counts the number of times mail transmission has failed, and mail transmission failure This is a table for storing failure breakdown information 505 for counting the number of times for each error cause when the failure has occurred, update date and time information 506, and the original MX record 507. For example, when reusing mail transmission connections, the number of connections in use may be stored together. Further, the number of emails sent per unit time, the average message size of emails sent, and the average response time of email transmission requests may be aggregated.
Next, transmittable MX record determination will be described with reference to FIG. In the sendable MX record determination, it is determined whether or not the MX record obtained by the DNS inquiry of the destination domain exists in the congestion statistics information 320 for each MX record in 601. If there is no MX record, MX obtained by the DNS inquiry is determined. Select an MX record with a high record priority. Here, a plurality of MX records are generally obtained in response to a DNS inquiry in the destination domain. Therefore, if there is a plurality of MX records obtained by the DNS inquiry of the destination domain in the congestion statistical information 320 for each MX record, an MX record with few failures is selected in 602.

  An MX record with few failures is an MX record that is judged to have the smallest number of failures among a plurality of MX records. For example, the failure record counter has the smallest ratio to the counter information. The failure determination counter information can have the smallest numerical value, or the failure breakdown information can have the smallest failure numerical value for a specific failure factor.

In the selection of 602, for example, a method of selecting a MX record having a high priority for an MX record having a failure rate (a ratio of the failure determination counter to the counter information) below a certain value by setting a threshold value is possible. In addition, when the mail transmission connection is used repeatedly, a method of selecting an MX record with a small number of effective connections is also possible. Also, the method of selecting the MX record with the smallest number of emails sent per unit time, the method of selecting the MX record with the smallest average message size of sent emails, and the average response time of email transmission requests A method of selecting a small MX record or a method of selecting a plurality of methods with priority may be used. In the determination of 602, the threshold value, expiration date, and determination priority can be changed by a command operation from the operation monitoring terminal. For the MX record selected in 602, the expiration date of the update date is determined in 603. If the expiration date has expired, the corresponding information is deleted from the congestion statistics information in 604, and the MX record is selected from “Start”. Try again.
Next, transmission possible host determination will be described with reference to FIG. In the transmission possible host determination, it is determined in 701 whether the IP address obtained by the DNS inquiry response of the MX record selected in the transmission possible MX record determination exists in the congestion statistics information 321 for each host (IP address). , Arbitrarily select from IP addresses obtained by DNS inquiry.

  Here, a plurality of IP addresses are generally obtained in response to DNS inquiry of MX record. Therefore, when there are a plurality of IP addresses obtained by the MX record host name inquiry response in the congestion statistics information 321 for each host (IP address), an IP address with few failures is selected in 702.

  An IP address with few failures is an IP address that is judged to have the smallest number of failures among a plurality of IP addresses. For example, the failure determination counter has the smallest ratio to the counter information. The failure determination counter information can have the smallest numerical value, or the failure breakdown information can have the smallest failure numerical value for a specific failure factor.

  In the selection of 702, for example, a method is possible in which a threshold value is set and an IP address having a failure rate (a ratio of the failure determination counter to the counter information) of a certain value or less is selected. In addition, when a mail transmission connection is used repeatedly, a method of selecting an IP address with a small number of effective connections is also possible. Also, the method of selecting the IP address with the smallest number of emails sent per unit time, the method of selecting the IP address with the smallest average message size of sent emails, and the average response time of email transmission requests A method of selecting a small IP address or a method of selecting a plurality of methods with priority may be used. In the determination of 702, the threshold, the expiration date, and the expiration date can be changed by a command operation from the operation monitoring terminal. For the IP address selected in 702, the expiration date of the update date / time is determined in 703. If the expiration date has expired, the corresponding information is deleted from the congestion statistical information in 704, and the IP address is selected from “Start”. Try again.

Claims (6)

A storage unit for storing mail transmitted from the communication terminal;
Reading the mail from the storage unit, obtaining a plurality of MX records corresponding to the destination domain of the mail, determining the destination MX record by searching the congestion statistical information for each MX record using the plurality of MX records as a key, Mail that obtains a plurality of IP addresses corresponding to the destination MX record, searches for congestion statistics information for each host using the plurality of IP addresses as a key, determines a destination host, and forwards the mail to the destination host A communication system having a relay processing unit.   The mail relay processing unit communicates with a DNS server for the mail destination domain to obtain the plurality of MX records, and communicates with the DNS server for the destination MX record to obtain a plurality of IP addresses. The communication system according to claim 1.   The communication system according to claim 1, wherein the mail relay processing unit determines a destination host IP address by searching for congestion statistics information for each host using the plurality of IP addresses as keys.   4. The congestion statistical information for each MX record includes failure information for mail transmission for each MX record, and the congestion statistical information for each host includes failure information for mail transmission for each IP address. Communication system.   The mail relay processing unit searches the congestion statistical information for each MX record, sets the MX record with the least number of mail transmission failures among the plurality of MX records as the destination MX record, and congestion for each host. 5. The communication system according to claim 4, wherein statistical information is searched to make an IP address with the least number of mail transmission failures among the plurality of IP addresses as the destination host.   The mail relay processing unit receives the mail transmission result from the destination host, and updates the MX record congestion statistics information and the host congestion statistics information based on the transmission result. The communication system according to claim 1.

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