JPH07240751A - Overlapped address check system - Google Patents

Abstract

PURPOSE:To perform the check of an MAC address where LLC sub-layers are overlapped, regardless of the control system of the MAC sub-layer in a LAN. CONSTITUTION:The subscription/connection of a LAN is performed, an XID command where a group address is preliminarily set is transmitted an opposite party and the XID command where the MAC address of its own device is set is transmitted to a transmission origin, in order to confirm whether other device having the same MAC address as its own device already exists or not (S21). The opposite party receiving the MIXD command transmits an XID response when the MAC address of the transmission origin is the same as the MAC address of its own device (D21, 22). Because the transmission side of the XID command receives two times XID responses of the XID response (S24) that its own device (LLC1) transmits and the XID response that the opposite device (LLC2) transmit, the transmission side cancels the both of the responses and leaves from the LAN because the device having the same MAC address as its own device already exists (S26).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a duplicate address check method, and in particular, when a new device is added to or connected to a LAN, it is checked whether or not a device having the same media access control (hereinafter referred to as MAC) address exists. Duplicate address check method for

[0002]

2. Description of the Related Art Conventionally, this type of duplicate address check method has been standardized by ISO in the LAN model as OSI.
The data link layer of the reference model is divided into a logical link control sublayer (LLC sublayer) and a MAC sublayer.
The LC sub-layer controls transmission / reception of frames, and the MAC sub-layer controls the transmission of data to a common transmission line and detects an abnormality in the transmission line. A device or station is newly added to the LAN. LLC when subscribing / connecting
When the sub-layer checks a duplicate address, the checking side issues a duplicate address check command in which the MAC address of the own device is set to the MAC address of the other device and the own device, and the other device with the same MAC address A duplicate address is checked depending on the presence or absence of a response.

[0003]

The above-mentioned conventional duplicate address check method has no problem when the MAC sublayer does not perform loopback control, but when the MAC sublayer performs loopback control, the LLC When the sub-layer sets the MAC address of its own device to the MAC address of the other device and issues a duplicate address check command, the frame due to loopback cannot be distinguished from the frame of the response command from the other device. However, since the check command is prohibited from being issued from the MAC sublayer, the LLC sublayer cannot check duplicate addresses.

[0004]

The duplicate address check method of the present invention is a logical link in the ISO standard duplicate address check method for checking whether or not a device having the same MAC address as its own device exists in a LAN. The control sub-layer is the LAN that is preset to the destination address.
Group address unique to the
The duplicate address check command sending means for sending the duplicate address check command in which the P bit of the control unit having the C address is "1", and the second duplicate address check response after sending the duplicate address check command is within the specified time. When the duplicate address check command is not received, the duplicate address check command is sent again. Even if the duplicate address check command is sent a prescribed number of times and the second duplicate address check response cannot be received, L
If there is no existing device with the duplicate address on the AN and LA receives the second duplicate address check response, LA
A determination means for recognizing that an existing device with a duplicate address exists on N, and discards this command if the source address is different from the own MAC address when the duplicate address check command is received, and the source address is the own MAC address. When the same as the above, it has a duplicate address check response sending means for sending the duplicate address check response in which the group address is set as the destination address and the F bit of the control unit having the own MAC address as the source address is set to "1". It is composed of

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 shows a data structure of a command used by the LLC sublayer in the duplicate address check in one embodiment of the present invention. FIG. 1A shows a duplicate address check command (XID- PD
FIG. 1B shows the data structure of the duplicate address check response (XIDRSP-PDU) 2 on the side where the duplicate address check is performed. In FIG. 1, the DA generally sets the partner address, but the group address is used in the duplicate address check, and the SA uses the own station MAC address as the source address. Further, DSAP is a destination sup address and SSAP is a source sup address. The source uses 00H and the destination uses 00H and 01H, respectively. The control unit is a control field defined by ISO.

FIG. 2 is a sequence diagram when XID-PDU is transmitted and there is no other device having the same MAC address as the own device. The sequence in this case will be described with reference to FIG. In FIG. 2, LLCI and MAC1 are the LLC sublayer and MAC sublayer on the side that performs duplicate address checking, and MAC2 and LLC
Reference numeral 2 denotes the MAC sublayer and the LLC sublayer on the side where the duplicate address check is performed.

On the side performing the duplicate address check, LA
In order to confirm whether or not a device having the same MAC address as its own device already exists when joining / connecting to N, the group address is set in the DA of the XID-PDU shown in FIG. Is set to the MAC address of its own device. The group address set in DA is a hexadecimal 12-digit value set separately from the MAC address of a device connectable to the LAN. The LLC1 first sends a duplicate address check command (XID) in which the P bit of the control unit is set to "1" (S11). Then LLC
1 receives the XID by the loopback control of MAC1 (S12), issues the XID response (XIDRSP-PDU) for this XID reception (S13), and receives the XID response as the loopback again.
It is discarded as the XID response for the second time (S14). L
The LC1 waits for the reception of the second XID response after discarding the first XID response, but since it has not arrived, the XID is issued again after a specified time (S15), and the processing from S11 onwards is repeated. If the XID response is not received twice within the specified time even after the XID is issued again, the same MAC address as that of the own device is used unless the XID is reissued the specified number of times and the XID response is not received twice. Assuming that there is no other device that has it, it joins and connects to the LAN as it is (S16).

On the other hand, the X transmitted from the MAC1 to the transmission path
Since the DA group address is specified in the ID-PDU, any MAC2 receives this XID-PDU and passes it to each LLC2.
Since the SA of U is different from its own MAC address, this XI
D reception is discarded (D1), and XID response is not sent. Subsequent XID-PDU transmitted from MAC1
Similarly, discard.

FIG. 3 is a sequence diagram when an XID-PDU is transmitted and there is another device having the same MAC address as the own device. The sequence in this case will be described with reference to FIG. LLC1, MAC1, in FIG.
MAC2 and LLC2 are the same as in FIG.
The contents of the XID-PDU sent from LC1 are the same as in the case of FIG. LLC1 first sends the XID (S
21). Then, LLC1 receives the XID (S22), X
Issue an ID response (XIDRSP-PDU) (S
23), the looped back XID response is received, but is discarded as the first XID response (S
24). Therefore, LLC1 prepares to issue the XID again if the second XID response does not come within the specified time, but this time it receives the second XID response (S25), so it has the same MAC address as its own device. Assuming that the device already exists, the device leaves the LAN (S2
6).

On the other hand, X transmitted from MAC1 to the transmission line
The ID-PDU is the XID-PDU of any MAC2.
Is received and passed to each of the LL2s (D21), but one of the LLCs 2 receives the XID of the P bit “1” having the same MAC address as the own device at the destination address SA, and thus the duplicate MAC The XID of the address is recognized, the group address is set in DA, the MAC address of the own device is set in SA, and the XID response of F bit "1" is sent (D22). MAC2 for LLC2
Received this XID response looped back in (D
23) and the reception of the XID response transmitted from MAC1 (D24) are obtained, but both are discarded.

[0012]

As described above, according to the present invention, a duplicate address check is performed using a preset group address, so that regardless of the control method of the MAC sublayer,
The duplication address check command can be transmitted / received, and the presence of a device having the same MAC address as its own device on the same transmission path can be checked.

[Brief description of drawings]

FIG. 1 is a diagram showing a data structure of a duplicate address check command used in an embodiment of the present invention.

FIG. 2 is a sequence diagram of processing using the duplicate address check command of FIG. 1 when there is no duplicate MAC address.

FIG. 3 is a sequence diagram of processing when there is a duplicate MAC address using the duplicate address check command of FIG.

[Explanation of symbols]

1 Duplicate address check command (XID-PD
U) 2 Duplicate address check response (XIDRSP
-PDU)

Claims (1)

[Claims] 1. In the ISO standard duplicate address check method for checking whether or not a device having the same media access control (hereinafter referred to as MAC) address as its own device exists in a LAN, the logical link control sublayer sends a message. A duplicate address check command sending means for sending a duplicate group address check command in which a group address peculiar to the LAN, which is set in advance as a destination address, and a P bit of a control unit having a source MAC address as a source address is set to "1", If the second duplicate address check response is not received within the specified time after the duplicate address check command is sent, even if the duplicate address check command is sent again and the duplicate address check command is sent the specified number of times The second check response is received When it is not possible, it is recognized that there is no existing device with the duplicate address on the LAN, and when the second duplicate address check response is received, it is judged that there is an existing device with the duplicate address on the LAN. When a duplicate address check command is received, this command is discarded if the source address is different from the own MAC address, and if the source address is the same as the own MAC address, the group address is set as the destination address and the source address is set as the source address. A duplicate address check response sending means for sending a duplicate address check response in which the F bit of the control unit having its own MAC address is set to "1".