JP2887806B2 - Network system and mail gateway - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a network system in which electronic mail is exchanged between devices communicating according to different protocols.

[Conventional technology]

As shown in FIG. 5, a conventional network system comprises a logical network system 1 comprising workstations (WS) 2 and 3 having a protocol 1 connected to a network 1, and a network 4
If a logical network system 2 composed of workstations (WS) 5 and 6 having a protocol 2 connected to a different system is configured using a different protocol, the workstations having different protocols are mutually connected. In order to transfer mail (e-mail) between the workstations, a special application program for performing protocol conversion such as a mail format is prepared in the workstation on the sending side and the receiving side, and the gateway 7 connecting both networks prepares electronic mail. The mail is passed (relayed), and the e-mail from the transmitting side is transmitted to the designated receiving side.

In this case, after executing the special application program on the sending side and converting the protocol, transfer the mail, or execute the special application program on the receiving side and convert the input mail to the protocol, Whether to perform mail data processing is determined in advance by an agreement between the transmitting side and the receiving side.

As described above, information resources are effectively used by converting electronic mail between devices (workstations) that perform data processing according to different protocols.

[Problems to be solved by the invention]

By the way, in the above-mentioned conventional network system, in order to perform mail transfer, each workstation must be provided with a special application program for converting a protocol such as a mail format.

Therefore, as the number of logically identical network systems capable of communicating according to different protocols increases, application programs corresponding to the number of network systems must be provided for workstations existing in the network systems. ,
Also, when the contents of the protocol are changed, the application programs provided on all the workstations must be changed to correspond to the changed contents, and mail between the workstations having different protocols must be changed. The exchange process is complicated, so that information cannot be easily exchanged and memory resources cannot be used effectively.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a network system capable of solving the above-mentioned drawbacks, easily exchanging e-mails, and effectively using memory resources, and a mail gateway used in the network system. .

[Means for solving the problem]

According to a first aspect of the present invention, there is provided a first apparatus for transmitting and receiving mail according to a first mail protocol, and a second apparatus for transmitting and receiving mail according to a second mail protocol different from the first mail protocol. In a network system having at least, a format of at least a destination of mail addressed to the second device transmitted by the first device is converted from a format according to a first mail protocol to a format according to a second mail protocol. In this case, a mail protocol conversion device for converting a mail protocol and transmitting the mail protocol to the second device is provided.

Also, in the second invention, when the mail protocol conversion device receives a mail addressed to the first device transmitted by the second device, the mail protocol conversion device converts at least a destination format of the mail into a second mail protocol. Is converted from a format according to the first mail protocol to a format according to the first mail protocol.

In a third aspect, a first communication means for transmitting / receiving a mail conforming to a first mail protocol to / from a first device, and a second mail protocol different from the first mail protocol. Communication means for transmitting and receiving the received mail to and from a second device, and first conversion means for converting a destination address according to the first mail protocol into a destination address according to the second protocol. And control means for converting the address of the mail addressed to the second device received from the first device using the first conversion means.

Further, the fourth invention further comprises a second conversion means for converting a destination address according to the second mail protocol into a destination address according to the first protocol,
The control means performs address conversion of the mail addressed to the first device received from the second device using the second conversion means.

[Action]

The present invention relates to a first device for handling mail according to a first mail protocol such as the STMP protocol.
When a mail addressed to a second device that handles mail according to a second mail protocol such as the XNS mailing protocol is transmitted, the destination conversion of the mail is performed by a mail protocol conversion device (mail gateway). For this reason, it is not necessary to provide a special application for each device that joins the network, thereby improving the flexibility of the network system and effectively using the memory resources.

In the present invention, the first mail protocol and the second mail protocol are used.
Perform bidirectional conversion between mail protocols. Therefore, the flexibility of the network system can be further improved.

〔Example〕

Hereinafter, embodiments of a network system according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing one embodiment of a network system according to the present invention. In FIG. 1, a communication protocol (hereinafter, referred to as a protocol) 1 has a host computer for processing data such as e-mail according to the protocol, a processing device 11 such as a workstation, and a protocol 2. A host computer for processing data such as e-mail according to the protocol, a processing device 12 such as a workstation, and a gateway 13 having the above-mentioned protocols 1 and 2 and performing protocol conversion between the respective protocols are logically connected to each other. Connected on the same network 14. In addition,
In the embodiment, the network 14 is set to Ethernet (local area network).

FIG. 2 shows the network system in more detail.

In FIG. 2, a TCP host computer (hereinafter, referred to as TCP host) 21, an XNS workstation (hereinafter, referred to as XNS WS) 22, an XNS mail server 23, and a gateway 24 are connected to a network 20.

The TCP host 21 is, for example, a network architecture TCP / IP (Transmission Control) as a protocol 1.
ol Protocol / Internet.Protocol), and performs data processing such as electronic mail according to this protocol.

The XNS WS 22 has, for example, a protocol in the network architecture XNS (Xerox Network System) as the protocol 2, and performs data processing such as e-mail according to this protocol.

The XNS mail server 23 has the above-described protocol 2 and performs mail transfer with the gateway 24, and the XNS WS22
And mail transfer. Also, the XNS mail server 23 has
A user name registered as a user connected to the network 20 and capable of accessing a device that communicates according to Protocol 2 and a mailbox for storing an e-mail to the user name are registered in correspondence.

Gateway 24 is OSI (Open Systems Interconnect)
ion: open system interconnection) A protocol (corresponding to the first and second layers in the reference model), and a single unit (not shown) for transmitting and receiving data such as electronic mail between the TCP host 21 and the XNS mail server 23. One interface unit, SMTP module unit 25 and XNS Mailing module unit 26
And a processing unit 27.

The SMTP module unit 25 performs mail transfer with the TCP host 21 according to the SMTP protocol described later. XNS Mailing
The module unit 26 performs mail transfer with the XNS mail server 23 according to the XNS Mailing protocol described later.

The processing unit 27 includes an SMTP (Simple Mail Transfer Protocol), which is an upper layer protocol of the TCP / IP (protocol 1).
l) Protocols (protocols corresponding to the fifth to seventh layers in the OSI reference model) and XNS Mailing protocol (protocol corresponding to the seventh layer in the OSI reference model) which is an upper layer protocol of the above XNS (protocol 2) And a mail storage unit (not shown) that temporarily stores queued mail. Refer to the storage contents of the protocol storage unit (not shown). Then, the mail stored in the mail storage unit is protocol-converted.

In addition to the above protocol information, the gateway 24 is the third type of the OSI reference model in TCP / IP (protocol 1).
It has protocol information corresponding to the layers corresponding to the layers 4 to 4 and protocol corresponding to the layers 3 to 6 of the OSI reference model in the XNS (protocol 2). And each module unit (not shown) for executing the protocol of each layer.

Protocols corresponding to the third and fourth layers of the OSI reference model in the TCP / IP (protocol 1) were input via Ethernet (protocols corresponding to the first and second layers of the OSI reference model). In order to transfer data to the fifth or higher layer of the OSI reference model, highly reliable data transfer is performed.

A protocol corresponding to the third layer of the OSI reference model in XNS (protocol 2) is for transmitting data to the upper layer in units of Internet packets, and a protocol corresponding to the fourth layer is corresponding to the above layer. And a protocol corresponding to the fifth and sixth layers converts data from the fourth layer into data that can be interpreted by an upper application layer (seventh layer). Things.

The e-mail and the like from the TCP host 21 are sent to the interface unit (not shown), the module unit (not shown) for executing a protocol corresponding to the third and fourth layers of the OSI reference model in the TCP / IP protocol, and the SMTP module unit. 25 and the processing unit 27, where the protocol conversion is performed. XNS Mailing
The module unit 26 executes the respective protocols corresponding to the third layer, the fourth layer, and the fifth to sixth layers of the OSI reference model in the XNS protocol. Sent over network 20.

In Protocols 1 and 2, the first and second layers of the OSI reference model include the contents including the Ethernet. Therefore, the use of the Ethernet as in this embodiment makes it possible to use the first and second layers. The two layers can be a common protocol.

Meanwhile, when exchanging e-mails on the network 20 described above, as shown in FIG. 3, an e-mail composed of a header section 52 including a destination 52A and the like and a text 53 in which a message is described is provided. Is transmitted.

The designation of the destination 52A in the above SMTP protocol is performed in accordance with the format 61 shown in the solid frame shown in FIG. 4 (a), and the destination 52a in the XNS Mailing protocol is specified.
Is specified in the format 62 shown in the solid frame shown in FIG. 4 (b).
Perform according to.

Next, an e-mail transfer operation in the network system will be described.

Here, an operation in the case where an e-mail is transferred from the TCP host 21 to the XNS WS 22 will be described.

The TCP host 21 transmits an e-mail having a destination specified in accordance with the protocol of the e-mail system of the protocol 1 and configured as shown in FIG.

In this case, when specifying the destination 52A according to the format 61 shown in FIG. 4 (a), the TCP host 21 uses the user name portion as the content of the format 62 shown in FIG. 4 (b).

In FIG. 4A, the destination machine name (name of the gateway) is set as the host name. In FIG. 4 (b), an area generally refers to a group composed of a plurality of workstations and servers on the same network, and an organization refers to a group of a plurality of the groups.

The gateway 24 sends the e-mail sent to the gateway 24 (that is, the machine name (gateway name) in the destination 52A column in the header section 52) to the processing section 27 via the interface section and the SMTP module section 25 (not shown). Is done. The input e-mail is sent to the processing unit 27
Once queued.

The processing unit 27 converts the queued mail from the SMTP protocol to the XNS Mailing protocol. For example, for the destination set by the TCP host 21 in accordance with the format 61 shown in FIG. 4A, the processing unit 27 of the gateway 24 refers to the user name in the format 61 destination, and the destination is set in FIG. It is converted into the content according to the format 62 shown.

The gateway 24 that has converted the protocol transfers the e-mail to the XNS mail server 23. This protocol converted email is sent to the XNS Mailing module part 2
6. The data is transferred to the XNS mail server 23 via the interface unit (not shown) and the network 20.

The XNS mail server 23 refers to the header 52 of the transferred e-mail, and refers to the user name 61A,
That is, the user 62A is obtained, and the electronic mail is stored in a mailbox corresponding to the user name.

The user on the receiving side operates the XNS WS 22 to inquire the XNS mail server 23 as to whether or not the e-mail has arrived in his / her own mailbox, and access the desired e-mail if it has arrived. . The accessed e-mail is transferred from the XNS mail server 23 to the XNS WS 22.

In the embodiment shown in FIG.
I explained the process of transferring email to WS22,
Next, a process of transferring an electronic mail from the XNS WS 22 to the TCP host 21 will be described.

First, an e-mail from the XNS WS 22 having the protocol 2 passes through the XNS mail server 23, and then is sent to the network 20,
The data is input to the processing unit 27 via the interface unit (not shown) and the XNS Mailing module unit 26, where the protocol is converted. The email that has undergone protocol conversion is
A TC having a protocol 1 via the SMTP module 25, the interface (not shown) and the network 20.
Transferred to P host 21.

In this case, in the XNS WS 22, when the destination is specified in the format as shown in FIG. 4B, the part of the user name 62A has the content of the format 61 as shown in FIG. 4A.

In the above embodiment, the protocol 1 is set to the protocol content in the network architecture TCP / IP, and the protocol 2 is set to the protocol content in the network architecture XNS. However, the present invention is not limited to this. , The protocol contents corresponding to the first and second layers of the OSI reference model are the same,
Any protocol 1 and protocol 2 having different protocol contents corresponding to the third to seventh layers can be applied.

Further, in the above embodiment, the transfer of the e-mail when the number of different protocols is two has been described. However, the present invention is not limited to this, and the number of different protocols is three.
One or more of them can all be applied.

In this case, it is necessary to provide the gateway with a program (module) capable of performing protocol conversion of an upper layer protocol of the third layer or higher of the OSI reference model between different protocols.

According to the above embodiment, electronic mail exchange can be easily performed between devices that communicate according to different protocols that are logically connected on the same network.

Also, when a device that communicates according to a protocol different from the existing protocol is newly connected to a network to which devices that communicate according to the existing protocol are connected, e-mail is exchanged. Should be provided, as in the past, for devices connected on the network,
There is no need to provide a special application program that performs conversion with the new protocol.

Therefore, the flexibility of the network system can be improved and the memory resources can be effectively used.

〔The invention's effect〕

As described above, according to the present invention, when the first device that handles mail according to the first mail protocol transmits mail addressed to the second device that handles mail according to the second mail protocol, Since the mail destination conversion is performed by a mail protocol conversion device (mail gateway), there is no need to provide a special application for each device that joins the network, thereby improving the flexibility of the network system and reducing memory resources. Can be used effectively.

In the present invention, the first mail protocol and the second mail protocol are used.
The configuration is such that bidirectional conversion between mail protocols is performed, so that the flexibility of the network system can be further enhanced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a network system according to the present invention, FIG. 2 is a configuration diagram showing the network system shown in FIG. 1 in more detail, and FIG. FIG. 4 is a configuration diagram showing a configuration, FIG. 4 is an explanatory diagram for explaining an example of a description format of a destination of each protocol, and FIG. 5 is a schematic configuration diagram showing a conventional network system. 11, 12… Processing unit, 13, 24… Gateway, 14, 20
…… Network, 21 …… TCP host computer, 22
…… XNS workstation, 23 …… XNS mail server,
25 ... SMTP module part, 26 ... XNS Mailing module part, 27 ... Processing part.

Claims (4)

(57) [Claims] At least a first device for transmitting and receiving mail according to a first mail protocol and a second device for transmitting and receiving mail according to a second mail protocol different from the first mail protocol are provided. Converting at least the destination format of the mail addressed to the second device transmitted by the first device from a format according to a first mail protocol to a format according to a second mail protocol. A network system, comprising: a mail protocol conversion device that converts a mail protocol and transmits the mail protocol to the second device. 2. When the mail protocol conversion device receives a mail addressed to the first device transmitted by the second device, the mail protocol conversion device changes at least the destination format of the mail to a second format.
The network system according to claim 1, wherein a format according to the first mail protocol is converted into a format according to the first mail protocol. 3. A first communication means for transmitting and receiving a mail according to a first mail protocol to and from a first device, and a mail according to a second mail protocol different from the first mail protocol. Second communication means for transmitting and receiving to and from a second device; first conversion means for converting a destination address according to the first mail protocol into a destination address according to the second protocol; Control means for converting the address of the mail addressed to the second device received from the first device using the first conversion means. 4. The apparatus according to claim 2, further comprising: a second conversion unit configured to convert a destination address according to the second mail protocol into a destination address according to the first protocol. The mail gateway according to claim 3, wherein the mail received from the first device and addressed to the first device is converted using the second converting means.