JP4769239B2 - COMMUNICATION SYSTEM, COMMUNICATION DEVICE, AND COMMUNICATION CONTROL METHOD - Google Patents

Description

  The present invention is connected to a subscriber termination device when multicasting an Ethernet (registered trademark) frame from a single station communication device to a plurality of subscriber termination devices connected to the station communication device. The present invention relates to a communication system capable of multicast distribution of frames to a specific terminal device, a communication device constituting the communication system, and a communication control method.

  In a network system that connects a single station-side communication device and a plurality of subscriber termination devices, IEEE (Institute of Electrical and Electronic Engineers) from the station-side communication device to all subscriber termination devices connected thereto A conventional control procedure for transmitting an Ethernet (registered trademark) frame (hereinafter simply referred to as a frame) to which an 802.1Q-compliant VLAN (Virtual Local Area Network) tag is attached will be described below.

  Here, a control procedure in the case of a PON system connected by a PON (Passive Optical Network) topology standardized by IEEE 802.3ah will be described. In the following description, unicast transfer refers to a transfer method from a single station-side communication device to a specific subscriber termination device, and broadcast transfer refers to transmission from a single station-side communication device to all subscriber termination devices. Indicates the transfer method. Multicast transfer refers to a transfer method that is intended for a plurality of subscriber termination devices from a single station-side communication device and is not intended for all subscriber termination devices. Further, it is assumed that a terminal device is connected to each subscriber termination device.

  First, a control procedure in a network system using unicast transfer (a network system corresponding to unicast transfer) is shown as a control procedure by the subscriber terminal device. When the station side communication device receives a frame from the higher level network, the VID (VLAN-ID) value existing in the VLAN tag is set to a predetermined VID value for the frame in which the VLAN tag exists. After rewriting, an LLID (Logical Link Identifier) value indicating the destination subscriber terminal device is assigned and broadcasted to all subscriber terminal devices.

  When each subscriber terminal device (unicast subscriber terminal device) receives a frame delivered from the station side communication device, the subscriber terminal device checks the value of the LLID given to the received frame, and the value indicates itself. If it is an LLID value or an LLID value indicating broadcast delivery (= 0xFFFF), it further checks whether the frame is a control frame based on the TPID value, and if it is not a control frame, the terminal connected to itself Transfer the received frame to the device. That is, since frames other than the control frame are transferred to the terminal device, the frame multicast-transferred from the station side communication device is also transferred to the terminal device.

  Patent Document 1 below shows a control procedure in a network system corresponding to multicast transfer and unicast transfer realized by extending the control procedure described above. More specifically, the station side communication apparatus confirms whether or not the frame is a target of multicast transfer when a VLAN tag is present in the frame received from the upper network.

  If it is a multicast transfer target, the VID value in the VLAN tag is rewritten to a preset multicast VID value, and then the broadcast delivery LLID value (= 0xFFFF) indicating all subscriber termination devices is addressed. ) To the frame and broadcast to all the subscriber terminal devices. On the other hand, if it is not a target for multicast transfer, after rewriting the VID value in the VLAN tag to a preset unicast VID value, an LLID value indicating a specific single subscriber terminating device corresponding to the destination Is added to the frame and broadcasted to all subscriber terminal devices.

  Each subscriber terminal device has an LLID value given to the frame received from the station side communication device as an LLID value indicating itself or an LLID value (= 0xFFFF) indicating broadcast delivery, and based on the TPID value. If it is determined that the received frame is not a control frame, it is checked whether the TPID value is a value indicating a VLAN tag (= 0x8100). If the VLAN tag is indicated, it is determined whether to transfer the received frame to the terminal device connected to itself based on the VID value included in the VLAN tag.

  As described above, the station side communication apparatus of the network system corresponding to the multicast transfer and the unicast transfer sets a different VID value between the case of performing the multicast transfer and the case of performing the unicast transfer, and transfers the frame. On the other hand, each subscriber termination device determines whether or not to transfer the received frame to the terminal device according to the content of the VID of the received frame. Thereby, it is possible to unicast transfer and multicast transfer a frame with a VLAN tag attached to each subscriber termination device from the station side communication device, and to a specific terminal connected to the subscriber termination device A frame can be multicasted only to the device.

JP 11-33137 A

  As described above, in the network system corresponding to the unicast transfer, a frame can be transferred from the station-side communication device to each subscriber termination device by unicast transfer and multicast transfer (broadcast delivery). When multicast transfer is performed, a frame is unconditionally distributed to all terminal devices (all terminal devices in the system) connected to each subscriber termination device. On the other hand, in the network system corresponding to the multicast transfer and the unicast transfer, it is possible to distribute the multicast transferred frame only to a specific terminal device in the system.

  However, in the control method applied to the conventional network system corresponding to multicast transfer and unicast transfer, among the plurality of subscriber termination devices connected to the station side communication device, the unicast subscriber termination device (above-mentioned) It did not consider the case where a network system subscriber terminal equipment supporting unicast transmission) coexists. For this reason, the station side communication device is connected to the terminal device connected to the unicast subscriber termination device that does not have the function of determining whether to transfer the frame based on the content (VID value) of the received frame. In a system in which multicast-transferred frames are distributed, that is, in a system in which subscriber termination devices for unicast are mixed, there is a problem that control for multicast transfer only to an intended terminal device cannot be realized.

  The present invention has been made in view of the above, and is a unicast subscriber termination device (a subscriber termination device that does not have a function of determining whether to forward a multicast frame to a terminal device) When subscriber termination devices (subscriber termination devices having a function to determine whether or not to forward a multicast frame to a terminal device) are mixed and connected to a single station-side communication device In addition, communication for performing multicast transfer control only for a terminal device connected to a multicast-compatible subscriber terminal device, and controlling so that multicast traffic is not transferred to a terminal device connected to a unicast subscriber terminal device It is an object to obtain a system and a communication control method for realizing the system.

  In order to solve the above-described problems and achieve the object, the present invention includes a station-side communication apparatus and a plurality of subscriber-side communication apparatuses that communicate with the station-side communication apparatus, and the subscriber-side communication apparatus Each of which is a communication system in which a terminal device is connected, and the station side communication device determines whether a frame received from an upper network is a target of multicast transfer based on determination information included in the frame Multicast determination means, frame type rewriting means for rewriting the frame type of the frame included in the frame determined to be multicast transfer target by the multicast determination means to a value indicating a control frame, and multicast transfer by the multicast determination means The network to which the frame included in the frame determined to be The network ID of the work is rewritten by a network ID rewriting unit that rewrites the predetermined value used in the multicast transfer process corresponding to the determination information, the frame type rewriting unit, and the network ID rewriting unit. Transfer means for multicast forwarding the received frame to the subscriber-side communication device, and the plurality of subscriber-side communication devices include the frame type rewriting included in the frame received from the station-side communication device. Transfer determination means for determining whether to transfer the frame to a terminal device connected to itself based on the frame type after being rewritten by the means and the network ID after being rewritten by the network ID rewriting means; It is characterized by providing.

  According to the present invention, when the station-side communication device multicasts a frame to the subscriber-side communication device (subscriber termination device), the TPID value of the frame to be transferred is defined as a value indicating the control frame. In addition, the VID value is changed to a value determined in advance as a value to be used at the time of multicast transfer, and broadcast distribution is made to each subscriber terminal device. The subscriber-side communication device that determines whether or not to transfer the frame based on the TPID value and VID value existing therein can correctly receive the multicast-transferred frame and execute transfer processing according to the contents. On the other hand, the subscriber-side communication device that unconditionally transfers the received frame determines that the multicast-transferred frame is an undefined (unrecognizable) control frame and does not execute the transfer process. That is, it is possible to realize a communication system capable of multicasting a frame only to a subscriber-side communication device that determines whether to transfer the frame based on the TPID value and VID value present in the received frame. Play.

  Embodiments of a communication system according to the present invention will be described below in detail with reference to the drawings. In the following description, an example in which the station side communication apparatus transmits a frame to which a VLAN tag compliant with IEEE 802.1Q is transmitted to a subscriber terminal apparatus connected to the station side communication apparatus will be described. Note that the present invention is not limited to the embodiments.

Embodiment.
The communication system according to the present embodiment includes a single station-side communication device and a plurality of subscriber termination devices connected thereto, and a terminal device can be connected to the subscriber termination device. In addition, in a plurality of subscriber termination devices, when receiving a frame that has been multicast-transmitted (transferred) from the station-side communication device, the reception process assuming only a unicast-transmitted frame is performed. A conventional subscriber termination device that unconditionally transfers the received frame to the terminal device may be included.

  FIG. 1 is a diagram showing a configuration example of a communication system according to the present invention. This system includes a single station-side communication device 1, a plurality of multicast-compatible subscriber termination devices 2, and a unicast subscriber termination device 3 (conventional subscriber termination device). The optical fiber 6-1 connected to the optical fiber 6-1 is branched into a plurality of fibers 6-2 by the optical branching unit 5, each of which is a subscriber termination device (multicast-compatible subscriber termination device 2, unicast subscriber termination device 3). )It is connected to the. The station-side communication device 1 is connected to a network, and a terminal device 4 can be connected to each subscriber termination device. FIG. 1 shows a case where the terminal device 4 is connected to only one multicast-compatible subscriber terminal device 2. FIG. 1 shows a configuration example in which two multicast-compatible subscriber termination devices 2 and two unicast subscriber termination devices 3 are connected to the station-side communication device 1. Good.

  Here, first, a control operation when a conventional subscriber terminating device receives a frame from a station side communication device will be described with reference to the drawings. FIG. 2 is a diagram illustrating a configuration example of a system including a conventional subscriber termination device (hereinafter referred to as a unicast subscriber termination device). This system includes a single station-side communication device 101 (conventional station-side communication device) and a plurality of unicast subscriber termination devices 102, and an optical fiber 105-connected to the station-side communication device 101. 1 is branched into a plurality of optical fibers 105-2 by an optical branching unit 104, and each is connected to each unicast subscriber terminating device 102. The station-side communication apparatus 101 is connected to a network, and a terminal apparatus 103 can be connected to each unicast subscriber termination apparatus 102. FIG. 2 shows a case where the terminal device 103 is connected to only one unicast subscriber termination device 102.

  The station-side communication device 101 has a function of broadcasting a frame received from the network to all the unicast subscriber termination devices 102. When each unicast subscriber terminating device 102 receives the frame distributed from the station side communication device 101, it determines whether it can be transferred from the information in the received frame to the terminal device 103 connected to itself, If transfer is possible, the frame is transferred to the terminal apparatus 103 without confirming whether the frame has been multicast-transmitted. If transfer is not possible, the received frame is discarded.

  FIG. 3 is a diagram illustrating a configuration example of the station-side communication device 101. The station-side communication device 101 includes a VLAN tag recognition unit 110, a VID rewriting unit 111, a VID setting unit 112, and an LLID adding unit 113.

  FIG. 4 is a diagram illustrating a configuration example of the unicast subscriber termination device 102, and the unicast subscriber termination device 102 includes an LLID processing unit 120 and a TPID determination unit 121.

  FIG. 5 is a flowchart showing an example of frame transmission control in the conventional system shown in FIG.

  A frame transmission control operation in the conventional system shown in FIG. 2 will be described with reference to FIGS. In the station side communication apparatus 101 shown in FIG. 3, the VLAN tag recognition unit 110 receives a frame transmitted from the network side. The VLAN tag recognition unit 110 checks whether or not a VLAN tag exists in the received frame (step S101 in FIG. 5). In addition, as a means for recognizing whether a VLAN tag exists, IEEE 802.1Q defines a specific position in a frame as a TPID (Tag Protocol Identifier) area, and the TPID value stored in this TPID area is 0x8100. In this case, since the frame is defined to be recognized as a frame with a VLAN tag, this is used. That is, if the TPID value of the received frame is 0x8100, the VLAN tag recognition unit 110 determines that the VLAN tag is attached to the frame.

  As a result of executing step S101, if it is determined that a VLAN tag is attached to the received frame, the frame is passed to the VID rewriting unit 111 (Yes in step S101), while it is determined that the VLAN tag is not attached. If so, the received frame is discarded (No in step S101).

  The VID rewriting unit 111 has a VID value for overwriting set in advance from the VID setting unit 112, and rewrites the VID value existing in the VLAN tag attached to the received frame to the overwriting VID value, and the LLID adding unit 113. (Step S102). The LLID assigning unit 113 has a function of determining the destination of the received frame, and assigns an LLID value indicating a specific single subscriber terminal device corresponding to the destination of the frame (step S103). Then, the station side communication device 101 broadcasts the frame to which the LLID value is assigned by the LLID assigning unit 113 to all the unicast subscriber termination devices 102 (step S104).

  In the unicast subscriber terminating device 102 shown in FIG. 4, the LLID processing unit 120 receives the frame distributed from the station side communication device 101. Then, the LLID processing unit 120 confirms the LLID value given to the received frame, and if it is the LLID value indicating the address of the own device or the LLID value (= 0xFFFF) indicating the broadcast distribution, the LLID processing unit 121 (Yes in step S105). On the other hand, if the LLID value given to the received frame does not indicate that the device is addressed to itself and does not indicate broadcast delivery, the frame is discarded (No in step S105).

  The TPID determination unit 121 confirms whether or not the TPID value stored in the TPID area in the received frame is a value indicating a control frame. If the value indicates a control frame (Yes in step S106), The process of regarding the received frame as a control frame is started. For example, in the IEEE 802.3ah system, when the TPID value is 0x8808, the received frame is regarded as an MPCP (Multi-point MAC Control) frame that is a control frame, and control of the PON system is started. On the other hand, when the TPID value is not a value indicating a control frame (No at Step S106), the TPID determination unit 121 transfers the frame to the terminal device 203.

  As described above, in the system shown in FIG. 2, a frame having a VLAN tag can be unicast-transferred and multicast-transferred from the station-side communication device to each unicast subscriber termination device. In addition, the VID value existing in the VLAN tag can be rewritten to an arbitrary value and transmitted to the terminal device. However, when receiving a multicast-transferred frame, the unicast subscriber terminating device transfers it unconditionally to the terminal device without recognizing whether or not it is a multicast-transferred frame.

  In addition, when a multicast frame is received, it is possible to determine whether to forward the frame to the terminal device based on information in the received frame, which is different from the unicast subscriber termination device. The operation of the apparatus will be described with reference to the drawings. FIG. 6 is a diagram illustrating a configuration example of a system including a subscriber termination device (hereinafter referred to as a multicast-compatible subscriber termination device) capable of determining whether or not to forward a frame transmitted by multicast transmission. This system includes a single multicast-compatible station-side communication device 201 (a conventional station-side communication device different from the above-mentioned station-side communication device 101), and a plurality of multicast-compatible subscriber termination devices 202. The optical fiber 205-1 connected to the side communication device 201 is branched into a plurality of optical fibers 205-2 by the optical branching unit 204, and each is connected to each multicast corresponding subscriber termination device 202. The multicast-compatible station communication device 201 is connected to a network, and a terminal device 203 can be connected to each multicast-compatible subscriber termination device 202.

  FIG. 7 is a diagram illustrating a configuration example of the multicast-compatible station communication device 201. The multicast-compatible station communication device 201 includes a VLAN tag recognition unit 210, a multicast determination unit 211, a multicast VID rewriting unit 212, and a unicast. A VID rewriting unit 213, a multicast VID setting unit 214, a unicast VID setting unit 215, and an LLID adding unit 216 are provided.

  FIG. 8 is a diagram illustrating a configuration example of the multicast-compatible subscriber termination device 202. The multicast-compatible subscriber termination device 202 includes an LLID processing unit 220, a TPID determination unit 221, a VID filter unit 222, and a VID registration unit 223. .

  FIG. 9 is a flowchart showing an example of frame transmission control in the conventional system shown in FIG.

  The transmission control operation in the conventional system shown in FIG. 6 will be described based on FIGS. In the multicast-compatible station communication device 201 shown in FIG. 7, the VLAN tag recognition unit 210 receives a frame transmitted from the network side. The VLAN tag recognizing unit 210 checks whether or not the VLAN tag is present in the received frame (FIG. 9, step S201), and if the VLAN tag is present, passes the received frame to the multicast determination unit 211 (step S201). If not, the received frame is discarded (No in step S201). Whether or not the VLAN tag exists is determined by the same method as that of the station side communication apparatus 101 of the system shown in FIG.

  The multicast determination unit 211 determines whether the received frame is a multicast transfer target (step S202). The determination of whether or not this is a multicast transfer target can be made based on the contents of an arbitrary area in the received frame. For example, whether or not the VID value existing in the VLAN tag attached to the frame is a multicast VID value. Judgment by. When the multicast determination unit 211 determines that the received frame is a target for multicast transfer, the multicast determination unit 211 passes the frame to the multicast VID rewriting unit 212 (step S202, Yes), while it is not a target for multicast transfer (that is, unicast transfer). Is transferred to the unicast VID rewriting unit 213 (No in step S202).

  The multicast VID rewriting unit 212 has the multicast VID value set in advance from the multicast VID setting unit 214, and rewrites the VID value existing in the VLAN tag attached to the received frame to the multicast VID value. To the LLID assigning unit 216 (step S203). On the other hand, the unicast VID rewriting unit 213 has a unicast transfer VID value set in advance from the unicast VID setting unit 215, and the unicast VID rewriting unit 213 converts the VID value present in the VLAN tag attached to the received frame into a unicast. The data is rewritten to the casting VID value and transferred to the LLID adding unit 216 (step S205).

  The LLID assigning unit 216 has a function of specifying a destination of a frame received from the multicast VID rewriting unit 212 and the unicast VID rewriting unit 213, a function of transferring the frame to all multicast-compatible subscriber termination devices 202, When a frame is received from the multicast VID rewriting unit 212, a LLID value for broadcast delivery (= 0xFFFF) indicating all multicast-capable subscriber termination devices 202 is assigned to the frame, and all multicast Broadcast distribution to the subscriber terminal device 202 (steps S204 and S207). On the other hand, when a frame is received from the unicast VID rewriting unit 213, the destination of the frame is determined and corresponding to the destination as in the case of the LLID adding unit 113 of the station side communication apparatus 101 shown in FIG. An LLID value indicating a single multicast-capable subscriber termination device 202 is assigned and broadcasted to all multicast-capable subscriber termination devices 202 (steps S206 and S207).

  In the multicast compatible subscriber terminating device 202 shown in FIG. 8, the LLID processing unit 220 receives the frame distributed from the multicast compatible station side communication device 201. Then, the LLID processing unit 220 confirms the LLID value given to the received frame. If the LLID value is an LLID value indicating that the device is addressed or an LLID value indicating broadcast delivery (= 0xFFFF), the LLID processing unit 220 determines the received frame as a TPID determination unit. 221 (Yes in step S208). On the other hand, if the LLID value given to the received frame does not indicate that the device is addressed to itself and does not indicate broadcast delivery, the frame is discarded (No in step S208).

  The TPID determination unit 221 confirms whether or not the TPID value stored in the TPID area in the received frame is a value indicating a control frame. If the value is a value indicating a control frame (Yes in step S209), A process in which the frame is regarded as a control frame is executed. Whether the TPID value is a value indicating a control frame is determined by a method similar to that of the TPID determination unit 121 of the unicast subscriber terminating device 102 shown in FIG. On the other hand, when the TPID value is not a value indicating a control frame (step S209, No), it is further checked whether the TPID value of the frame is a value indicating a VLAN tag (= 0x8100). The frame is passed to the VID filter unit 222 (step S210, Yes). On the other hand, if the TPID value is not 0x8100, the frame is discarded (No in step S210).

  The VID filter unit 222 is registered in advance with a plurality of VID values that can be transferred from the VID registration unit 223 to the terminal device, and the VID values in the frame received from the TPID determination unit 221 are a plurality of VIDs registered in advance. If it matches one of the values, the frame is transferred to the terminal device 203 (step S211, Yes). On the other hand, if the VID value does not match any registered VID value, the frame is discarded (No in step S211).

  As described above, in the system shown in FIG. 6, it is possible to perform unicast transfer and multicast transfer of a frame with a VLAN tag to each multicast-compatible subscriber terminal device from the multicast-compatible station side communication device. In addition, when a multicast-terminated subscriber terminal receives a multicast-transferred frame, it can determine whether to transfer the frame to the terminal device and transfer only a specific frame. That is, in the system shown in FIG. 6, a frame can be multicasted to a specific terminal device.

  However, since the unicast subscriber terminating device 102 shown in FIG. 2 transfers the received frame unconditionally, the multicast compatible station side communication device 201 of the system shown in FIG. When the unicast subscriber terminating device 102 of the system shown is connected, a terminal device (a unicast subscriber terminating device 102 is not intended for a multicast-transmitted frame from the multicast-compatible station communication device 201). (Ie, connected terminal devices), that is, a problem arises in that multicast transfer targeting a specific terminal device cannot be realized.

  Therefore, in the communication system (see FIG. 1) according to the present invention, this problem is solved by applying the following configuration and control procedure.

  FIG. 10 is a diagram illustrating a configuration example of the station-side communication device 1 of the communication system according to the present invention. The station-side communication device 1 includes a VLAN tag recognition unit 10, a multicast determination unit 11, a TPID rewriting unit 12, and a TPID setting. Unit 13, multicast VID rewriting unit 14, multicast VID setting unit 15, unicast VID rewriting unit 16, unicast VID setting unit 17, LLID adding unit 18, and VLAN tag setting unit 19.

  The VLAN tag recognizing unit 10, the multicast determining unit 11, the multicast VID rewriting unit 14, the unicast VID rewriting unit 16, the unicast VID setting unit 17 and the LLID adding unit 18 are respectively compatible with the conventional multicast described above. It corresponds to the VLAN tag recognition unit 210, the multicast determination unit 211, the multicast VID rewriting unit 212, the unicast VID rewriting unit 213, the unicast VID setting unit 215, and the LLID adding unit 216 of the station side communication apparatus 201. Therefore, detailed description of these parts is omitted.

  The TPID rewriting unit 12 rewrites the TPID value of the received frame with a multicast TPID value (a TPID value used in the case of multicast transfer), and passes it to the multicast VID rewriting unit 14. When a multicast group is registered in the station side communication device 1, the TPID setting unit 13 acquires the TPID used at the time of multicast transfer to the multicast group from the station side communication device 1 and sets it in the TPID rewriting unit 12.

  When a multicast group is registered in the station side communication apparatus 1, the multicast VID setting unit 15 acquires a VID used when multicast is transferred to the multicast group and sets the multicast VID in the multicast VID rewriting unit 14.

  The VLAN tag setting unit 19 notifies each multicast corresponding subscriber termination device 2 of multicast group information obtained when a multicast group is registered in the station side communication device 1.

  The multicast group refers to a group specified by information as shown in FIG. 11, for example. In this embodiment, this information is called multicast group information, and includes a group VID, a multicast VID and a multicast TPID associated therewith. A VID value existing in a VLAN tag attached to a frame multicast-transmitted from the network is defined as a “group VID”. Then, the station side communication device 1 determines whether or not the frame is subject to multicast transfer based on the VID in the VLAN tag attached to the frame transferred from the network. In the following, description will be made using the example of FIG. 11 in which a multicast group is configured by “group VID”. However, a destination multicast MAC (Media Access Control) address or a destination multicast IP (Internet Protocol) address is used instead of the group VID. It is also possible to configure a multicast group using general identifiers indicating that the target is multicast transfer.

  FIG. 12 is a diagram showing a configuration example of the multicast compatible subscriber termination device 2 of the communication system according to the present invention. This multicast-compatible subscriber termination device 2 has a different configuration from the above-described conventional multicast-compatible subscriber termination device 202 (see FIG. 8), and includes an LLID processing unit 20, a TPID determination unit 21, a TPID registration unit 22, and a VID filter. Unit 23 and VID registration unit 24. The LLID processing unit 20, the TPID determination unit 21, and the VID filter unit 23 correspond to the LLID processing unit 220, the TPID determination unit 221, and the VID filter unit 222 of the multicast-compatible subscriber terminal device 202, respectively. Therefore, detailed description of these parts is omitted.

  The TPID registration unit 22 extracts multicast TPID information (a combination of the multicast TPID value and the group VID) from the multicast group information (see FIG. 11) notified from the station side communication device 1, and uses the extracted TPID information as the TPID. Register in the determination unit 21.

  The VID registration unit 24 extracts multicast VID information (a combination of the multicast VID value and the group VID) from the multicast group information notified from the station side communication device 1 and registers the extracted VID information in the VID filter unit 23. To do.

  FIG. 13 is a diagram illustrating a configuration example of the unicast subscriber termination device 3 of the communication system according to the present invention. The unicast subscriber termination device 3 includes an LLID processing unit 30 and a TPID determination unit 31. The unicast subscriber termination device 3 corresponds to the above-described conventional unicast subscriber termination device 102 (see FIG. 4). That is, the LLID processing unit 30 is the same as the LLID processing unit 120, and the TPID determination unit 31 is the same as the TPID determination unit 121. Therefore, detailed description of the unicast subscriber termination device 3 is omitted.

  Next, a control operation in the communication system when the station-side communication apparatus 1 receives a frame from the network and transfers the received frame will be described with reference to the drawings.

  First, an operation when registering multicast group information used in a process of multicast forwarding a received frame to a specific terminal device 4 in the communication system in the station side communication device 1 and the multicast corresponding subscriber termination device 2 (see FIG. 10). Will be described with reference to FIG. FIG. 14 is a flowchart showing an example of a multicast group information registration procedure in the communication system shown in FIG.

  When a multicast group is registered in the station side communication device 1, it is necessary from multicast group information (information including a group VID indicating a multicast group, and a multicast VID and a multicast TPID corresponding to this one-to-one). Information is extracted and registered in the TPID rewriting unit 12. Specifically, the TPID setting unit 13 extracts the correspondence relationship between the group VID value and the multicast TPID value from the multicast group information, and uses the extracted correspondence relationship (combination of the group VID value and the multicast TPID value) as the TPID rewriting unit 12. (Step S1). Similarly, information extracted from the multicast group information is also registered in the multicast VID rewriting unit 14. Specifically, the multicast VID setting unit 15 extracts the correspondence relationship between the group VID value and the multicast VID value from the multicast group information, and uses the extracted correspondence relationship (the combination of the group VID value and the multicast VID value) for multicast. Registration is made in the VID rewriting unit 14 (step S2).

  Further, the VLAN tag setting unit 19 generates a remote control frame including the multicast group information and transmits it to all the multicast compatible subscriber termination devices 2 (step S3). The remote control frame including the multicast group information is not transmitted to the unicast subscriber termination device 3.

  In the multicast-compatible subscriber termination device 2 (see FIG. 12) that has received the remote control frame transmitted from the station side communication device 1, the multicast group information contained in the frame is stored in the TPID registration unit 22 and the VID registration unit 24. Passed to. Then, the TPID registration unit 22 extracts TPID information from the received multicast group information and registers it in the TPID determination unit 21 (step S4). The TPID information indicates a multicast TPID value (a combination of a group VID value and a multicast TPID value) that is associated with the group VID included in the multicast group information in a one-to-one relationship. Further, the VID registration unit 24 extracts VID information from the received multicast group information and registers it in the VID filter unit 23 (step S5). The VID information indicates a multicast VID value (a combination of the group VID value and the multicast VID value) that is associated with the group VID included in the multicast group information on a one-to-one basis. In addition, when receiving a frame from the station-side communication device 1, the multicast corresponding subscriber terminating device 2 compares the VID value of the received frame with the VID value registered in the VID filter unit 23, and based on the comparison result, It is determined whether to transfer the frame to the terminal device 4.

  Next, the control operation in the communication system according to the present invention will be described with reference to FIGS. 15A to 15C are flowcharts illustrating an example of frame transmission control in the communication system illustrated in FIG.

  In the station side communication apparatus 1, when the VLAN tag recognition part 10 receives the flame | frame transmitted from the network side, the transmission control shown to FIGS. 15-1 is performed. Specifically, the VLAN tag recognition unit 10 checks whether or not the VLAN tag exists in the received frame (step S11), and if the VLAN tag exists, passes the received frame to the multicast determination unit 11. (Step S11, Yes), if not, the received frame is discarded (No at Step S11).

  Here, when a means for recognizing whether a VLAN tag exists is shown, IEEE 802.1Q defines a specific position in a frame as a TPID area, and when the TPID value stored in this TPID area is 0x8100, Is used as a VLAN-tagged frame. Specifically, when the TPID value of the received frame is 0x8100, the VLAN tag recognition unit 10 recognizes that the VLAN tag is attached to the frame.

  FIG. 16 is a diagram showing a configuration of an Ethernet (registered trademark) frame with a VLAN tag (hereinafter referred to as a VLAN tag frame) defined by IEEE 802.1Q and an MPCP frame defined by IEEE 802.3ah. This shows an example of a frame used in the present embodiment. As shown in FIG. 16, a frame with a VLAN tag includes a preamble area in which information is set for timing setting, a destination MAC address area in which the destination MAC address of the frame is set, and the transmission source of the frame Consists of a source MAC address area in which a MAC address is set, a TPID area in which information indicating whether or not the frame includes a VLAN tag header, a TCI area, and a data area in which user data is set Is done. The TCI area is used to identify a user priority area (an area where “P” is described), a CFI (Canonical Format Identifier) area (an area where “C” is illustrated), and a VLAN in which priority information is set. It is constituted by a VID area in which a VID value used as an identifier is registered. In IEEE 802.1Q, when a frame with a VLAN tag is indicated, the value stored in the TPID area is defined as 0x8100.

  The MPCP frame includes a preamble area in which information is set for timing setting, a destination MAC address area in which the destination MAC address of the frame is set, and a transmission source in which the MAC address of the transmission source of the frame is set. A MAC address area, a TPID area in which information indicating whether or not the frame is an MPCP frame, an Opcode area indicating the type of the MPCP frame, and a data area in which the processing content of the MPCP frame is set It is comprised by. IEEE 802.3ah stipulates that the value stored in the TPID area is 0x8808 when an MPCP frame is indicated.

  Returning to the description of FIG. 15A, the multicast determination unit 11 has a function of determining whether or not the received frame received is a multicast transfer target. In this embodiment, the determination as to whether or not this is a multicast transfer target is performed using a group VID registered as multicast group information. Specifically, if the VID value present in the VLAN tag in the received frame matches any one of the group VIDs included in the multicast group information, it is determined as a multicast transfer target and does not match. In this case, it is determined that the target is unicast transfer. When the multicast determination unit 11 determines that the received frame is a target for multicast transfer, the multicast determination unit 11 outputs the frame to the TPID rewriting unit 12 (Yes in step S12), whereas when it determines that the received frame is a target for unicast transfer Is transferred to the unicast VID rewriting unit 16 (No in step S12).

  The TPID rewriting unit 12 that has received the frame determined to be the target of the multicast transfer uses the VID value (group VID value) existing in the VLAN tag in the frame from the rewriting TPID set in advance by the TPID setting unit 13. TPID corresponding to) is selected. Then, the TPID value of the frame (0x8100, which is a TPID value indicating a VLAN tag) is rewritten to the selected TPID value and passed to the multicast VID rewriting unit 14 (step S13). As shown in FIG. 11, in the present embodiment, the TPID value is rewritten to 0x8808 (a value indicating a control frame).

  When the multicast VID rewrite unit 14 has a multicast VID value set in advance from the multicast VID setting unit 15 and receives a frame from the TPID rewrite unit 12, the multicast VID rewrite unit 14 corresponds to the group VID value existing in the VLAN tag. The multicast VID value is rewritten and passed to the LLID adding unit 18 (step S14). On the other hand, when the unicast VID rewriting unit 16 has a unicast transfer VID value set in advance from the unicast VID setting unit 17 and receives a frame from the multicast determination unit 11, The existing VID value is rewritten to the corresponding unicast VID value and passed to the LLID adding unit 18 (step S16).

  The LLID assigning unit 18 has a function of specifying the destination of the frame received from the multicast VID rewriting unit 14 and the unicast VID rewriting unit 16, a function of transferring the frame to all multicast-compatible subscriber termination devices 2, It comprises. When the LLID assigning unit 18 receives a frame from the multicast VID rewriting unit 14, the LLID assigning unit 18 assigns a broadcast delivery LLID value (= 0xFFFF) indicating all multicast-compatible subscriber termination devices 2 to the frame, Broadcast distribution is performed to all the multicast compatible subscriber termination devices 2 and the unicast subscriber termination device 3 (steps S15 and S18). On the other hand, when a frame is received from the unicast VID rewriting unit 16, the destination of the frame is specified, and a single multicast compatible subscriber termination device 2 or unicast subscriber termination device 3 corresponding to the destination is specified. And broadcast delivery to all multicast-compatible subscriber termination devices 2 and unicast subscriber termination devices 3 (steps S17 and S18).

  As shown in FIG. 16, the TCI area including the VID area in the frame with the VLAN tag and the Opcode area in the MPCP frame (control frame) exist at the same position. Therefore, when the TPID value is rewritten to x8808 (a value indicating a control frame), the conventional subscriber termination device (unicast subscriber termination device 3) has a control frame in which undefined information is written in the Opcode area. Are recognized.

  In the multicast compatible subscriber termination device 2, when the LLID processing unit 20 receives the frame distributed from the station side communication device 1, the LLID processing unit 20 executes the transmission control shown in FIG. Specifically, the LLID processing unit 20 confirms the LLID value given to the received frame, and if it is the LLID value indicating the address of the own device or the LLID value (= 0xFFFF) indicating the broadcast delivery, the received frame Is passed to the TPID determination unit 21 (Yes in step S21). On the other hand, if the LLID value assigned to the received frame does not indicate that the device is addressed to itself and does not indicate broadcast delivery, the frame is discarded (No in step S21).

  The TPID determination unit 21 confirms whether the TPID value stored in the TPID area in the received frame is a value indicating a control frame. If the value is a value indicating a control frame, the TPID determination unit 21 determines that the frame is a control frame. Is started (step S22, Yes). Whether the TPID value is a value indicating a control frame is determined as an MPCP frame when TPID = 0x8808 in accordance with the provisions of IEEE 802.3ah. That is, when the TPID value = 0x8808, it is determined that the received frame is a control frame (a value indicating a control frame). When processing that is regarded as a control frame is started, the TPID determination unit 21 further determines whether or not the TPID value (= 0x8808) determined as the value indicating the control frame is registered as the TPID value indicating the VLAN tag. (Whether or not the TPID value registered in advance by the TPID registration unit 22 includes a TPID value determined to be a value indicating the control frame) is confirmed, and the TPID value (= 0x8808) is not registered In the case (step S23, No), it is determined that a normal control frame has been received, and the processing is continued.

  When the TPID value determined as the value indicating the control frame is registered as the TPID value indicating the VLAN tag (step S23, Yes), the TPID determination unit 21 further selects the Opcode area in the frame (MPCP frame). It is checked whether or not the value in the Opcode area is a value defined by IEEE 802.3ah.

  As a result of the confirmation, if the value in the Opcode area is a value defined by IEEE 802.3ah (No in step S24), it is determined that a normal control frame has been received, and the processing is continued. On the other hand, when the value in the Opcode area is a value not defined by IEEE 802.3ah, the received frame is regarded as a multicast frame to which a VLAN tag is attached and is passed to the VID filter unit 23 (Yes in step S24). . That is, when the TPID value of the received frame is a value indicating a control frame (= 0x8808), the TPID determination unit 21 regards the frame as a VLAN-tagged frame (multicast frame) based on the value of the Opcode area. It is determined whether to execute a process to be passed to the VID filter unit 23 or to execute a process regarded as a control frame as in the conventional case.

  On the other hand, when the TPID value stored in the TPID area in the received frame is not a value indicating a control frame (No in step S22), the TPID determination unit 21 further indicates a value indicating the VLAN tag. Whether or not (= 0x8100) is confirmed. If the value indicates a VLAN tag, the frame is passed to the VID filter unit 23 (Yes in step S25). On the other hand, if the TPID value is not a value indicating a VLAN tag, the frame is discarded (No in step S25).

  The VID filter unit 23 has previously registered a plurality of VID values that can be transferred from the VID registration unit 24 to the terminal device 4, and the VID values in the frame received from the TPID determination unit 21 have a plurality of registered VID values. If it matches any one of the VID values, the frame is transferred to the terminal device 4 (Yes in step S26). On the other hand, if the VID value does not match any registered VID value, the frame is discarded (No in step S26).

  As described above, in the multicast corresponding subscriber terminating device 2 shown in FIG. 12, when 0x8808, which is a value indicating the control frame, is set in the TPID value of the frame received from the station side communication device 1, It is determined whether the received frame is a control frame based on the confirmation result. If it is determined that the control frame has been received, the same processing as before (processing at the time of receiving the control frame) is executed. On the other hand, if it is determined that a frame other than the control frame has been received, It is determined whether to transfer to the terminal device according to the existing VID value.

  In the unicast subscriber terminating device 3, when the LLID processing unit 30 receives the frame distributed from the station side communication device 1, the LLID processing unit 30 executes the transmission control shown in FIG. Specifically, the LLID processing unit 30 confirms the LLID value given to the received frame, and if it is an LLID value indicating the address of the own device or an LLID value (= 0xFFFF) indicating broadcast delivery, the received frame Is passed to the TPID determination unit 31 (Yes in step S31). On the other hand, if the LLID value given to the received frame does not indicate the address to the own apparatus and does not indicate the broadcast distribution, the frame is discarded (No in step S31).

  The TPID determination unit 31 checks whether or not the TPID value stored in the TPID area in the received frame is a value indicating a control frame. If the value is a value indicating a control frame, the TPID determination unit 31 determines that the frame is a control frame. Is started (step S32, Yes). Here, when TPID = 0x8808, it is determined that the value indicates a control frame. That is, it is determined that the received frame is an MPCP frame. When processing that is regarded as a control frame is started, the TPID determination unit 31 further confirms the value in the Opcode area in the frame, and if it is a value specified in IEEE 802.3ah (step S33). , No), it is determined that a normal control frame has been received, and the processing is continued. On the other hand, if the value is not defined in IEEE 802.3ah (Yes in step S33), it is determined that an undefined control frame (a control frame that cannot be recognized) is received, and the frame is discarded. Note that this operation is also performed in the conventional system.

  Further, when the TPID value stored in the TPID area in the received frame is not a value indicating the control frame (No in step S32), the TPID determination unit 31 transfers the frame to the terminal device 4.

  As described above, in the unicast subscriber terminating device 3 shown in FIG. 13, when the TPID value included in the frame transmitted from the station side communication device is a value indicating the control frame (= 0x8808), the Oocode area Whether the received frame is a control frame is determined based on the confirmation result. Specifically, when it is determined that the control frame has been received, the same processing as the conventional one (processing at the time of receiving the control frame) is executed. On the other hand, when it is determined that a frame other than the control frame has been received, Discard. Therefore, in the communication system having the configuration shown in FIG. 1, the multicast transfer frame set to TPID = 0x8808 is not transferred to the terminal device connected to the unicast subscriber termination device 3.

  As described above, in the present embodiment, when the station side communication apparatus executes multicast transmission of a frame, the TPID value of the multicast target frame is set to 0x8808 defined as a value indicating the control frame, The VID value is rewritten to a value determined (registered) in advance as a value to be used at the time of multicast transfer, and broadcasted to each subscriber termination device (multicast-compatible subscriber termination device, unicast subscriber termination device). The multicast-compatible subscriber termination device determines whether to transfer based on the TPID value and VID value present in the received frame from the station side communication device. As a result, when the unicast subscriber terminal receives a multicast frame, it recognizes that it received a control frame with an undefined value in Opcode, and discards the received frame. Multicast-transferred frames are not transferred to terminal devices connected to the unicast subscriber termination device. That is, it is possible to realize a communication system that can transfer a received frame from a network only to a specific terminal device connected to a multicast-compatible subscriber terminal device.

  Further, according to the present embodiment, a frame that is a target of unicast transfer is transferred to each subscriber terminal without changing the TPID value, with 0x8100 indicating a normal VLAN tag. That is, in unicast transfer, the multicast-compatible subscriber termination device and the unicast subscriber termination device have the same operation, and it is possible to perform unicast transfer according to the prior art.

  Further, according to the present embodiment, since the rewriting process is performed on the TPID value stored in advance in the frame, the length of the Ethernet (registered trademark) frame is not changed. That is, it is possible to transfer a multicast frame only to a terminal device connected to a multicast-compatible subscriber terminal device without causing deterioration in transmission efficiency due to an increase in the Ethernet (registered trademark) frame length.

  In addition, according to the present embodiment, the multicast TPID value registered in the multicast group can be set to 0x8100. In this case, the multicast transfer target frame is the TPID value defined in IEEE 802.1Q as in the prior art. Is transferred at 0x8100. That is, the unicast subscriber termination device can transfer the frame to the terminal device, and the unicast subscriber termination device can unconditionally transfer the multicast transfer frame as in the prior art. Furthermore, since the multicast TPID value can be set independently for each multicast group, it is possible to control whether or not the unicast subscriber termination device transfers for each multicast group.

  In the present embodiment, the transmission system has been described as an example of a PON system defined by IEEE 802.3ah connected by a PON topology. However, all devices that transmit Ethernet (registered trademark) frames typified by layer 2 switches are described. For the above, it is possible to realize a multicast transfer method using a TPID value according to the present invention. In other words, an Ethernet including both a conventional subscriber termination device that regards a frame having a certain TPID value as a control frame and a subscriber termination device according to the present invention that can regard a certain TPID value as a VLAN tag. The present invention can be applied to all systems that transmit (registered trademark) frames.

  As described above, the communication system according to the present invention is useful for realizing a system capable of multicast transfer of a frame with a VLAN tag to a specific terminal device. A state in which a plurality of first subscriber terminators to be transferred to the network and a plurality of second subscriber terminators to determine whether to transfer the received frame based on the contents of the VLAN-ID of the received frame are mixed Is suitable for a system that multicasts a frame to a specific terminal device connected to a second subscriber termination device.

It is a figure which shows the structural example of the communication system concerning this invention. It is a figure which shows the structural example of the system containing the conventional subscriber terminal device. It is a figure which shows the structural example of the station side communication apparatus for unicast. It is a figure which shows the structural example of the subscriber termination | terminus apparatus for unicast. It is a flowchart which shows an example of the frame transmission control in a conventional system. It is a figure which shows the structural example of the system containing the conventional subscriber terminal device which can determine whether the flame | frame transmitted by multicast transmission is transferred. It is a figure which shows the structural example of the multicast corresponding station side communication apparatus. It is a figure which shows the structural example of a subscriber terminal apparatus corresponding to a multicast. It is a flowchart which shows an example of the frame transmission control in a conventional system. It is a figure which shows the structural example of the station side communication apparatus of the communication system concerning this invention. It is a figure which shows the structural example of a multicast group. It is a figure which shows the structural example of a subscriber terminal apparatus corresponding to a multicast. It is a figure which shows the structural example of the subscriber termination | terminus apparatus for unicast. It is a flowchart which shows an example of the registration procedure of multicast group information. It is a flowchart which shows an example of frame transmission control. It is a flowchart which shows an example of frame transmission control. It is a flowchart which shows an example of frame transmission control. It is a figure which shows the structure of the frame with a VLAN tag prescribed | regulated by IEEE802.1Q, and the MPCP frame prescribed | regulated by IEEE802.3ah.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Station side communication apparatus 2 Subscriber termination apparatus corresponding to multicast 3 Subscriber termination apparatus for unicast 4, 103, 203 Terminal apparatus 5, 104, 204 Optical branching section 6-1, 6-2, 105-1, 105 -2, 205-1, 205-2 Optical fiber 10, 110, 210 VLAN tag recognition unit 11, 211 Multicast determination unit 12 TPID rewriting unit 13 TPID setting unit 14, 212 Multicast VID rewriting unit 15, 214 Multicast VID setting Unit 16, 213 Unicast VID rewriting unit 17, 215 Unicast VID setting unit 18, 113, 216 LLID adding unit 19 VLAN tag setting unit 20, 30, 120, 220 LLID processing unit 21, 31, 121, 221 TPID Determination unit 22 TPID registration unit 23, 222 V D filter unit 24 VID registration section 102 for unicast subscriber terminating device 111 VID rewriter 112,223 VID setting unit 201 multicast enabled station side communication device 202 multicast corresponding subscriber termination device

Claims (8)

A communication system including a station-side communication device and a plurality of subscriber-side communication devices that communicate with the station-side communication device, wherein a terminal device is connected to each of the subscriber-side communication devices,
The station side communication device is
Multicast determination means for determining whether or not a frame received from an upper network is a target of multicast transfer based on determination information included in the frame;
Frame type rewriting means for rewriting the frame type of the frame included in the frame determined to be subject to multicast transfer by the multicast determination means to a value indicating a control frame;
A network ID of a network to which the frame included in the frame determined to be multicast transfer target by the multicast determination unit is determined in advance, and is a predetermined value used in the multicast transfer process corresponding to the determination information On the other hand, the network ID of the network to which the frame included in the frame that has not been determined as the target of multicast transfer belongs is rewritten to a predetermined value used in the unicast transfer process. Network ID rewriting means;
Transfer means for adding an LLID corresponding to the network ID after rewriting to the frame rewritten by the network ID rewriting means, and delivering the same to the communication device on the subscriber side;
With
The plurality of subscriber side communication devices,
Transfer determining means for determining whether to transfer the frame to a terminal device connected to itself based on a frame type and a network ID included in the frame received from the station-side communication device;
Equipped with a,
The frame type rewriting means, a frame type that is included in the target determined frame of the multicast transfer, the rewriting Rukoto to 0x8808 value indicating MPCP frame is a control frame specified in IEEE802.3ah A featured communication system. The transfer determination means includes
When the frame type included in the frame indicates the MPCP frame, frame determination means for determining whether the frame is a multicast frame based on the information of the Opcode area included in the frame;
Check whether the network ID included in the frame determined to be a multicast frame by the frame determination means matches the network ID acquired in advance from the station-side communication device. Transfer necessity determination means for determining that transfer to the terminal device is necessary;
The communication system according to claim 1 , further comprising: The station side communication device further comprises:
Determining means for determining the predetermined value for uniquely associating the determination information with the corresponding multicast forwarding process;
With
The subscriber side communication device further comprises:
Obtaining means for obtaining a predetermined value determined by the determining means;
Communication system according to claim 1 or 2, characterized in that it comprises a. A station-side communication device that multicasts a predetermined frame to a subscriber-side communication device,
Multicast determination means for determining whether or not a frame received from an upper network is a target of multicast transfer based on determination information included in the frame;
Frame type rewriting means for rewriting the frame type of the frame included in the frame determined to be subject to multicast transfer by the multicast determination means to a value indicating a control frame;
A network ID of a network to which the frame included in the frame determined to be multicast transfer target by the multicast determination unit is determined in advance, and is a predetermined value used in the multicast transfer process corresponding to the determination information On the other hand, the network ID of the network to which the frame included in the frame that has not been determined as the target of multicast transfer belongs is rewritten to a predetermined value used in the unicast transfer process. Network ID rewriting means;
Transfer means for adding a LLID corresponding to the network ID after rewriting to the predetermined frame rewritten by the network ID rewriting means, and performing broadcast distribution;
Equipped with a,
The frame type rewriting means, a frame type that is included in the target determined frame of the multicast transfer, the rewriting Rukoto to 0x8808 value indicating MPCP frame is a control frame specified in IEEE802.3ah A communication device. A subscriber-side communication device that communicates with the station-side communication device according to claim 4 ,
Frame determining means for determining whether the frame is a multicast frame based on a frame type included in a frame received from the station-side communication device;
Check whether the network ID included in the frame determined to be a multicast frame by the frame determination means matches the network ID acquired in advance from the station-side communication device. A transfer necessity determination means for determining that it is necessary to transfer to a terminal device connected to itself;
A communication apparatus comprising: If the frame type indicates an MPCP frame that is a control frame defined by IEEE802.3ah, the frame determination means further determines whether the frame is a multicast frame based on the information of the Opcode area included in the frame. The communication device according to claim 5 , wherein the communication device is determined. A communication control method in a communication system including a station-side communication device and a plurality of subscriber-side communication devices that communicate with the station-side communication device, wherein a terminal device is connected to each of the subscriber-side communication devices. ,
As processing executed by the station side communication device,
A multicast determination step for determining whether or not a frame received from a higher-order network is a target of multicast transfer based on determination information included in the frame;
A frame type rewriting step of rewriting the frame type of the frame included in the frame determined to be a multicast transfer target in the multicast determination step to a value indicating a control frame;
The network ID of the network to which the frame included in the frame whose frame type has been rewritten in the frame type rewriting step is determined in advance to a predetermined value used in the multicast forwarding process corresponding to the determination information On the other hand, the network ID of the network to which the frame included in the frame that has not been determined as the target of multicast transfer in the multicast determination step has been determined in advance and used in the unicast transfer process A network ID rewriting step for rewriting the value;
A transfer step of adding an LLID corresponding to the network ID after rewriting to the frame rewritten in the network ID rewriting step, and broadcasting to the communication device on the subscriber side;
Including
As processing executed by the plurality of subscriber side communication devices,
A transfer determination step of determining whether to transfer the frame to a terminal device connected to itself based on a frame type and a network ID included in the frame received from the station-side communication device;
Only including,
In the frame type rewriting step, the frame type included in the frame determined to be the target of the multicast transfer is rewritten to a value 0x8808 indicating an MPCP frame that is a control frame defined in IEEE802.3ah. Communication control method. The transfer determining step includes:
When the frame type included in the frame indicates the MPCP frame, based on the information of the Opcode area included in the frame, a frame determination step of determining whether the frame is a multicast frame;
Check whether the network ID included in the frame determined as the multicast frame in the frame determination step matches the network ID acquired in advance from the station side communication device, and if the network ID matches, A transfer necessity determination step for determining that transfer to the terminal device is necessary;
The communication control method according to claim 7 , further comprising:

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