JP2010016753A - Pon system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PON system in which high-speed transfer of multicast packets can be performed and an optical line terminal (OLT) can control the transfer of the multicast packets all together. <P>SOLUTION: The OLT 4 distributes the multicast packets transferred from a multicast router 7 for MCB or a multicast router 8 for SCB to a plurality of optical network units ONUs 2a, 2b and 2c, and controls the transfer object of the multicast packets in the ONUs 2a, 2b and 2c. If the multicast packets distributed from the OLT 4 in the ONUs 2a, 2b and 2c are the transfer object multicast packets, the multicast packets are distributed to terminal devices 1a, 1b and 1c. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a PON (Passive) in which a station side device (OLT: Optical Line Terminal) and N subscriber side devices (ONU: Optical Network Unit) are connected by an optical fiber and perform Ethernet (registered trademark) communication. In particular, the present invention relates to a PON system that realizes transfer of multicast packets to a plurality of terminal devices accommodated in an ONU.

In the PON system, several methods for transferring a downlink multicast packet to a plurality of terminal apparatuses accommodated in a plurality of ONUs are known.
FIG. 15 is a block diagram showing a conventional PON system. In FIG. 15, the PON system is composed of an OLT and three ONUs, and the OLT and the three ONUs pass through an optical fiber and an optical splitter which are optical transmission media. An example of connection is shown.
The upper network connected to the OLT is composed of a multicast router, the Internet, and a video distribution server.
Although FIG. 15 shows an example in which there are three ONUs, the number of ONUs may be four or more.

16 to 18 are sequence diagrams showing multicast transfer in the conventional PON system.
In particular, FIG. 16 shows an MCB (Multiple Copy Broadcast) system in which a multicast router copies and forwards a downstream multicast packet as necessary (see, for example, Patent Document 1 below).
FIG. 17 shows an SCB (Single Copy Broadcast) method in which a multicast router transfers a downlink multicast packet without copying it (see, for example, Patent Document 2 below).
FIG. 18 shows an improvement of the SCB method in FIG. 17 (see, for example, Patent Document 3 below).

First, with reference to FIG. 16, the unicast transfer performed by the terminal device # 1 and the Internet will be described (S101).
First, when the terminal device # 1 transfers a unicast packet to the OLT via the ONU # 1 (S102), the OLT adds a VLAN (Virtual Local Area Network) tag to the unicast packet and multicasts the unicast packet. Transfer to the router (S103).
Here, the VLAN tag allows the upper network to identify which ONU the packet is transferred from, and a unique VLAN-ID is assigned to each ONU in advance in the OLT.
When receiving the unicast packet from the OLT, the multicast router performs a routing process on the unicast packet and transfers the unicast packet to the Internet (S104).

On the other hand, when the multicast router receives a unicast packet from the Internet (S105), the multicast router performs a routing process on the unicast packet, assigns a VLAN-ID indicating the destination ONU to the unicast packet, and transmits the unicast packet. The packet is transferred to the OLT (S106).
The OLT has a function of identifying the destination ONU from the VLAN-ID assigned to the unicast packet, and an LLID (Logical Link Identifier) indicating the ONU in the PON section is assigned to the unicast packet. Then, the unicast packet is distributed to all ONUs # 1, # 2, and # 3 (S107).
The ONUs # 1, # 2, and # 3 discard the unicast packet if the LLID assigned to the unicast packet is not its own LLID, and if the LLID is its own LLID, Deliver to.
In the example of FIG. 16, only ONU # 1 distributes the unicast packet to terminal device # 1 (S108).

Next, an example in which multicast packets are transferred from the video distribution server to the terminal devices # 2 and # 3 by the MCB method will be described (S109 in FIG. 16).
First, the video distribution server distributes the multicast packet to the multicast router (S110).
However, at this stage, since no multicast packet viewing request is transmitted from any terminal device, even if the multicast router receives the multicast packet from the video distribution server, in order to omit unnecessary transfer processing, The multicast packet is not transferred to the OLT.

Next, when the terminal devices # 2 and # 3 transmit a multicast control signal, which is a request for viewing a multicast packet, to the ONUs # 2 and # 3, the ONUs # 2 and # 3 transfer the multicast control signal to the OLT (S111, S112).
This multicast control signal corresponds to IGMP (Internet Group Management Protocol) or MLD (Multicast Listener Discovery), which is commonly used in IP multicast communication, and the group address for which viewing is requested is included in the multicast control signal. include.

When the OLT receives the multicast control signal from the ONUs # 2 and # 3, the OLT attaches the VLAN tag to the multicast control signal and forwards the multicast control signal to the multicast router (S113, S114).
When the multicast router receives the multicast control signal from the OLT, the multicast router updates the management table for managing the destination of the multicast packet according to the multicast control signal.

When the multicast router identifies the ONUs # 2 and # 3 containing the terminal devices # 2 and # 3 that are transmission sources of the viewing request with reference to the management table, the multicast router transmits the multicast packet distributed from the video distribution server to the ONU. In order to transfer to # 2 and # 3, the multicast packet is copied into two, VLAN-ID indicating ONU # 2 and # 3 is assigned to each multicast packet, and the two multicast packets are transferred to the OLT. (S115).
The OLT has a function of identifying the destination ONU from the VLAN-ID assigned to the two multicast packets, and assigns the LLID indicating the ONU to the multicast packet in the PON section, and all the two multicast packets are Are distributed to ONUs # 1, # 2, and # 3 (S116).

The ONUs # 1, # 2, and # 3 discard the multicast packet if the LLIDs assigned to the two multicast packets are not their own LLID, and send the multicast packet to the terminal device if they are their own LLID. To deliver.
In the example of FIG. 16, ONU # 2 distributes the multicast packet to terminal device # 2, and ONU # 3 distributes the multicast packet to terminal device # 3 (S117).
As described above, the MCB method has an advantage that the OLT and the ONU do not need to be equipped with a special function for multicast transfer. However, since the multicast router copies and forwards the multicast packet, the system consumes extra bandwidth. Have the disadvantages.

Next, an example in which a multicast packet is transferred from the video distribution server to the terminal devices # 2 and # 3 by the SCB method will be described (S121 in FIG. 17).
First, the video distribution server distributes the multicast packet to the multicast router (S122).
However, at this stage, since no multicast packet viewing request is transmitted from any terminal device, even if the multicast router receives the multicast packet from the video distribution server, in order to omit unnecessary transfer processing, The multicast packet is not transferred to the OLT.

Next, when the terminal devices # 2 and # 3 transmit a multicast control signal, which is a request for viewing a multicast packet, to the ONUs # 2 and # 3, the ONUs # 2 and # 3 receive the multicast control signal (S123, S124). Then, after snooping the multicast control signal (acquiring the group address included in the multicast control signal), the multicast control signal is transferred to the multicast router via the OLT (S125, S126).
When all the ONUs # 1, # 2, and # 3 receive the multicast control signal from the terminal devices # 1, # 2, and # 3, the group address included in the multicast control signal is used in the layer 2 When the destination MAC address is converted and registered, and a multicast packet is received from the OLT, a filtering function is provided that allows only the multicast packet related to the registered destination MAC address to pass.

When receiving the multicast control signal from the OLT, the multicast router transfers the multicast packet distributed from the video distribution server to the OLT (S127).
The OLT has a function of identifying a multicast packet. When a multicast packet is received from a multicast router, all ONUs # 1, # 2, and # 3 can receive the multicast packet in the PON section. LLID (= 0xFFFF) indicating broadcast delivery is assigned to the multicast packet, and the multicast packet is broadcast to all ONUs # 1, # 2, and # 3 (S128).

When all ONUs # 1, # 2, and # 3 receive a multicast packet from the OLT, if the multicast packet is a multicast packet related to a destination MAC address registered in advance by the filtering function, the multicast packet is transmitted to the terminal. Transfer to device # 1, # 2, # 3.
In the example of FIG. 17, ONU # 2 distributes the multicast packet to terminal device # 2, and ONU # 3 distributes the multicast packet to terminal device # 3 (S129).

As described above, in the case of the SCB method, the OLT has an advantage that high-speed transfer of the multicast packet can be realized only by broadcasting the multicast packet to all the ONUs # 1, # 2, and # 3. There is a disadvantage that the ONU needs to be equipped with routing, which is not economical.
In addition, the OLT cannot operate the service status of the subscriber and the start / stop of the service, and considering the multicast forwarding service, there is a problem that the OLT cannot be collectively managed.

In FIG. 18, the shortcomings of the SCB method in FIG. 17 are eliminated (S131 in FIG. 18).
First, the video distribution server distributes the multicast packet to the multicast router (S132).
However, at this stage, since no multicast packet viewing request is transmitted from any terminal device, even if the multicast router receives the multicast packet from the video distribution server, in order to omit unnecessary transfer processing, The multicast packet is not transferred to the OLT.

Next, when the terminal devices # 2 and # 3 transmit a multicast control signal, which is a request for viewing a multicast packet, to the ONUs # 2 and # 3, the ONUs # 2 and # 3 receive the multicast control signal, and the multicast control signal Is transferred to the OLT (S133, S134).
When the OLT receives the multicast control signal from the ONUs # 2 and # 3, the OLT snooping the multicast control signal to generate a multicast management table necessary for multicast transfer, and the filtering information is sent to the ONU # 2 by the following method. After remotely setting to # 3, the multicast control signal is transferred to the multicast router (S135, S136).

Remote setting of filtering information (1) For each multicast group address, the multicast LLID is associated one-to-one, and the multicast LLID is placed on the control signal used in the PON section and set to the ONU.
(2) For each multicast group address, the multicast VLAN-ID is associated one-to-one, and the multicast VLAN-ID is placed on the control signal used in the PON section and set to ONU.

When receiving the multicast control signal from the OLT, the multicast router transfers the multicast packet distributed from the video distribution server to the OLT (S137).
When the OLT receives a multicast packet from the multicast router, the destination address of the multicast packet is compared with the multicast management table, and if they match, the corresponding multicast LLID or multicast VLAN-ID is assigned to the multicast packet. Then, it is distributed to all ONUs # 1, # 2, and # 3 (S138).
In the case of VLAN-ID, LLID (= 0xFFFF) indicating broadcast delivery is added to the multicast packet.

When the ONUs # 1, # 2, and # 3 receive a multicast packet from the OLT, the multicast LLID or multicast VLAN-ID assigned to the multicast packet and the filtering information (multicast multicast previously set by the OLT) are transmitted. (LLID for multicast, VLAN-ID for multicast) is determined. If they match, the multicast packet is transferred to terminal apparatuses # 1, # 2, and # 3.
In the example of FIG. 18, ONU # 2 distributes the multicast packet to terminal device # 2, and ONU # 3 distributes the multicast packet to terminal device # 3 (S139).

As described above, the OLT performs snooping and generates the multicast management table, thereby eliminating the shortcomings of the SCB method in FIG. 17 and obtaining the advantage that the OLT can perform batch management.
However, there is a problem that the OLT needs to perform processing such as adding a multicast identifier (multicast LLID, multicast VLAN-ID) to the multicast packet, and processing delays correspondingly occur.

JP 2004-357200 A JP 2004-343243 A JP-T-2001-521716

Since the conventional PON system is configured as described above, if the SCB method of FIG. 17 is adopted, the OLT simply broadcasts multicast packets to all ONUs # 1, # 2, and # 3. High-speed transfer of multicast packets can be realized. However, since filtering of multicast packets is entrusted to the ONU, the OLT cannot collectively manage the multicast packet viewing request in the terminal device, and the OLT cannot sufficiently manage the multicast packet transfer service. was there.
If the SCB method of FIG. 18 is adopted, the OLT can collectively manage the multicast packet viewing request in the terminal device, but the OLT needs processing such as adding a multicast identifier to the multicast packet. There was a problem that processing delay occurred by the amount.

  The present invention has been made in order to solve the above-described problems. It is an object of the present invention to obtain a PON system that can realize high-speed transfer of multicast packets and can manage the transfer of multicast packets in a batch. Objective.

  The PON system according to the present invention includes a first multicast router that duplicates a multicast packet distributed from a first distribution server as necessary and forwards it to a station side device, and a multicast distributed from a second distribution server. A second multicast router for transferring the packet to the station side device, and the station side device distributes the multicast packet transferred from the first multicast router or the second multicast router to the plurality of subscriber side devices, Controls the multicast packet transfer target in multiple subscriber-side devices, and if the multicast packet distributed from the station-side device to multiple subscriber-side devices is the multicast packet to be transferred, distributes the multicast packet to the terminal device It is what you do.

  According to the present invention, the multicast packet distributed from the first distribution server is copied as necessary and transferred to the station side device, and the multicast packet distributed from the second distribution server is transmitted. A second multicast router that forwards to the station side device, the station side device distributes the multicast packet forwarded from the first multicast router or the second multicast router to the plurality of subscriber side devices, and a plurality of The multicast packet transfer target in the subscriber side device is controlled, and if the multicast packet distributed from the station side device by the plurality of subscriber side devices is the multicast packet to be transferred, the multicast packet is distributed to the terminal device. So that high-speed forwarding of multicast packets It is possible to present, the optical line terminal has an effect that can collectively manage the forwarding of multicast packets.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a PON system according to Embodiment 1 of the present invention. In the figure, terminal devices 1a, 1b, and 1c (terminal devices # 1, # 2, and # 3) are personal computers used by subscribers. A terminal such as a portable information terminal.
The ONUs 2a, 2b, and 2c (ONUs # 1, # 2, and # 3) that are subscriber-side devices are devices that accommodate the terminal devices 1a, 1b, and 1c.
When the ONUs 2a, 2b, and 2c receive the multicast control signal that is a multicast packet viewing request from the terminal devices 1a, 1b, and 1c, the ONUs 2a, 2b, and 2c distribute the multicast control signal to the OLT 4, and the multicast packet distributed from the OLT 4 If the unicast packet is a packet to be transferred, a process of distributing the multicast packet or unicast packet to the terminal devices 1a, 1b, and 1c is performed.

The optical splitter 3 is a device that branches an optical fiber that is an optical transmission medium.
The OLT 4 that is a station side device is connected to the ONUs 2a, 2b, and 2c via optical fibers, and performs Ethernet communication with the ONUs 2a, 2b, and 2c.
The OLT 4 distributes multicast packets and the like transferred from the MCB multicast router 7 or SCB multicast router 8 through the layer 2 switch 6 to the ONUs 2a, 2b, and 2c, as well as multicast packets in the ONUs 2a, 2b, and 2c. Implement processing to control the transfer target.

The upper network 5 is connected to the OLT 4 and distributes multicast packets and unicast packets.
The layer 2 switch 6 distributes the unicast packet, the multicast control signal, etc. transmitted from the OLT 4 to the MCB multicast router 7 or the SCB multicast router 8, while transferring the unicast packet transmitted from the MCB multicast router 7 or the SCB multicast router 8. A process of transferring a cast packet or a multicast packet to the OLT 4 is performed.

When the MCB multicast router 7 receives the multicast packet from the MCB video distribution server 10, the MCB multicast router 7 duplicates the multicast packet as necessary, and also assigns the unicast VID set by the OLT 4 to the multicast packet. When the unicast packet is received from the Internet 9, the unicast VID set by the OLT 4 is added to the unicast packet, and the unicast packet is transferred to the layer 2 switch. The process of transferring to 6 is performed. The MCB multicast router 7 constitutes a first multicast router.
When the multicast router 8 for SCB receives the multicast packet from the video distribution server 11 for SCB, the broadcast VID set by the OLT 4 is added to the multicast packet, and the multicast packet is transferred to the layer 2 switch 6. To do. The SCB multicast router 8 constitutes a second multicast router.

The Internet 9 is connected to the MCB multicast router 7 and transmits and receives unicast packets.
The MCB video distribution server 10 is connected to the MCB multicast router 7 and is a device for distributing multicast packets. The MCB video distribution server 10 constitutes a first distribution server.
The SCB video distribution server 11 is connected to the SCB multicast router 8 and is a device that distributes multicast packets. The SCB video distribution server 11 constitutes a second distribution server.

Although FIG. 1 shows an example in which three terminal apparatuses and three ONUs are installed, the number of terminals need not be three in particular, and for example, four or more terminal apparatuses and ONUs may be installed.
Also, an example is shown in which one set of MCB multicast router 7 and MCB video distribution server 10 is installed for MCB, and one set of SCB multicast router 8 and SCB video distribution server 11 is installed for SCB. However, it is not limited to one set, and two or more sets may be installed.

2 and 3 are sequence diagrams showing multicast transfer in the PON system according to Embodiment 1 of the present invention.
2 shows an operation sequence between the terminal devices 1a, 1b, 1c and the OLT 4, and FIG. 3 shows an operation sequence between the OLT 4 and the upper network 5.

Next, the operation will be described.
First, unicast transfer between the terminal device 1a (terminal device # 1) and the Internet 9 will be described (S1).
First, when the terminal device 1a transfers a unicast packet to the OLT 4 via the ONU 2a (ONU # 1) (S2), the OLT 4 attaches a VLAN (Virtual Local Area Network) tag to the unicast packet, and the unicast packet. Is transferred to the layer 2 switch 6 (S3).
Here, the VLAN tag enables the upper network 5 to identify from which ONU the packet is transferred. In the OLT 4, a unique unicast VID (VLAN-ID) is assigned to each ONU in advance. Allocated.

When the layer 2 switch 6 receives the unicast packet from the OLT 4, the layer 2 switch 6 confirms the VLAN tag attached to the unicast packet. If the VLAN tag is a unicast VID, the layer 2 switch 6 transmits the unicast packet to the MCB multicast router. 7 (S4).
When receiving the unicast packet from the layer 2 switch 6, the MCB multicast router 7 performs a routing process on the unicast packet and transfers the unicast packet to the Internet 9 (S5).

On the other hand, when the MCB multicast router 7 receives a unicast packet from the Internet 9 (S6), it performs a routing process on the unicast packet, assigns the unicast VID to the unicast packet, and sends the unicast packet to the unicast packet. The data is transferred to the OLT 4 via the layer 2 switch 6 (S7).
The OLT 4 has a function of identifying a destination ONU from a unicast VID given to a unicast packet, and a unicast LLID (Logical Link Identifier) that is an identifier indicating the ONU in a PON section is a unicast packet. And the unicast packet is distributed to all ONUs 2a, 2b, 2c (ONU # 1, # 2, # 3) (S8).

The ONUs 2a, 2b, and 2c discard the unicast packet if the unicast LLID assigned to the unicast packet is not its own LLID and the unicast LLID is not ALL1 (= 0xFFFF). The case of LLID = 0xFFFF (hereinafter referred to as “broadcast LLID”) will be described later.
If the unicast LLID is its own LLID, the unicast packet is distributed to the terminal devices 1a, 1b, and 1c (terminal devices # 1, # 2, and # 3).
In the example of FIG. 2, only the ONU 2a distributes the unicast packet to the terminal device 1a (S9).

Next, a viewing request sequence for multicast transfer will be described (S10).
First, the MCB video distribution server 10 distributes the multicast packet to the MCB multicast router 7 (S11).
The SCB video distribution server 11 distributes the multicast packet to the SCB multicast router 8 (S12).
However, at this stage, since no multicast packet viewing request is transmitted from any of the terminal devices, even if the multicast router 7 for MCB and the multicast router 8 for SCB receive the multicast packet, useless transfer processing is performed. In order to omit it, the multicast packet is not transferred to the layer 2 switch 6.

Next, when the terminal devices 1a and 1b (terminal devices # 1 and # 2) transmit a multicast control signal which is a multicast packet viewing request to the ONUs 2a and 2b (ONU # 1 and # 2), the ONUs 2a and 2b perform multicast control. The signal is transferred to the OLT 4 (S13, S14).
This multicast control signal corresponds to IGMP (Internet Group Management Protocol) or MLD (Multicast Listener Discovery), which is commonly used in IP multicast communication, and the group address for which viewing is requested is included in the multicast control signal. include.

When the OLT 4 receives the multicast control signal from the ONUs 2a and 2b, if the multicast control signal is a signal related to a request for viewing a multicast packet distributed from the MCB video distribution server 10, the multicast control signal is the MCB multicast router. The VLAN tag is added to the multicast control signal so that the layer 2 switch 6 can identify that the packet is to be transferred to.
On the other hand, if the multicast control signal is a signal related to a request for viewing a multicast packet distributed from the SCB video distribution server 11, the layer 2 indicates that the multicast control signal is transferred to the SCB multicast router 8. A VLAN tag is added to the multicast control signal so that the switch 6 can identify it.

Note that the OLT 4 is a signal related to a request for viewing a multicast packet distributed from the MCB video distribution server 10 when the multicast control signal transmitted from the ONU 2 is simultaneously transmitted to the multicast packet distributed from the SCB video distribution server 11. In the case of a signal relating to a viewing request, each control signal is extracted from the multicast control signal and two multicast control signals are assembled. Alternatively, one multicast control signal is copied to two.
Then, a VLAN tag is assigned to each of the two multicast control signals, one multicast control signal is transferred to the MCB multicast router 7, and the other multicast control signal is transferred to the SCB multicast router 8.

FIG. 4 is an explanatory diagram showing a VLAN-ID distribution management table used when the OLT 4 distributes multicast control signals.
In the VLAN-ID distribution management table of FIG. 4, group addresses of multicast packets distributed from the SCB video distribution server 11 are stored.
For example, there are those in which broadcast VIDs “V1” and “V2” corresponding to the group addresses G1 and G2 are set individually, such as group addresses G1 and G2, and G3 to G4. There are some groups in which a range of continuous group addresses is registered and one broadcast VID “V3” corresponding to the range is set.

At this time, V1, V2, and V3 of the broadcast VID may be set to the same value. However, when applying the VLAN-ID distribution management table of FIG. 4, it is necessary to satisfy the following conditions.
(1) Group addresses G1 to G4 should not overlap with the group addresses used in the MCB video distribution server 10. (2) Broadcast VIDs V1 to V3 should not overlap with unicast VIDs.

  As described above, when the OLT 4 receives the multicast control signal from the ONUs 2a and 2b, the OLT 4 determines whether the multicast control signal is a signal related to a request for viewing the multicast packet distributed from the MCB video distribution server 10, or the SCB video distribution. It is determined whether the signal is a request for viewing a multicast packet distributed from the server 11, and a VLAN tag is added. Specifically, the group address included in the multicast control signal, The group addresses registered in the VLAN-ID distribution management table are compared, and a group address that matches the group address included in the multicast control signal is registered in the VLAN-ID distribution management table of FIG. Broadcast VI corresponding to the group address. It was given to the multicast control signal, and transfers the multicast control signal to the layer 2 switch 6 (S16).

If the group address that matches the group address included in the multicast control signal is not registered in the VLAN-ID distribution management table in FIG. 4, the OLT 4 performs unicast as in the case of unicast packet transfer. The VID is assigned to the multicast control signal, and the multicast control signal is transferred to the layer 2 switch 6 (S15).
In the example of FIGS. 2 and 3, the broadcast VID is added to the multicast control signal transmitted from the ONU 2 b, and the multicast control signal is transferred to the layer 2 switch 6.
Further, a unicast VID is given to the multicast control signal transmitted from the ONU 2 a, and the multicast control signal is transferred to the layer 2 switch 6.

When the layer 2 switch 6 receives the multicast control signal from the OLT 4, if the VLAN tag attached to the multicast control signal is a unicast VID, the layer 2 switch 6 transfers the multicast control signal to the MCB multicast router 7 (S17). .
On the other hand, if the VLAN tag attached to the multicast control signal is a broadcast VID, the multicast control signal is transferred to the SCB multicast router 8 (S18).

The MCB multicast router 7 has a multicast management table necessary for multicast transfer. When the multicast control signal is received from the layer 2 switch 6, the MCB multicast router 7 refers to the unicast VID assigned to the multicast control signal, The terminal device 1a (terminal device # 1) that is the transmission source of the multicast packet viewing request is confirmed.
Since the MCB multicast router 7 distributes the multicast packet # 1 distributed from the MCB video distribution server 10 to the terminal device 1a, the unicast VID of the ONU 2a (ONU # 1) accommodating the terminal device 1a is used. It is added to the multicast packet # 1, and the multicast packet # 1 is transferred to the OLT 4 via the layer 2 switch 6 (S19).
Here, since there is only one terminal device that transmits the viewing request, the multicast packet # 1 is transferred to the layer 2 switch 6 without duplicating the multicast packet # 1, but the viewing request is not transmitted. If there are a plurality of terminal devices that are transmitting, a plurality of multicast packets # 1 are copied and the plurality of multicast packets # 1 are transferred to the layer 2 switch 6.

  The SCB multicast router 8 has a multicast management table necessary for multicast transfer. Upon receiving a multicast control signal from the layer 2 switch 6, the SCB multicast router 8 checks the broadcast VID assigned to the multicast control signal, The same broadcast VID as the broadcast VID is assigned to the multicast packet # 2 distributed from the SCB video distribution server 11, and the multicast packet # 2 is transferred to the OLT 4 via the layer 2 switch 6 (S20).

  The OLT 4 has a function of identifying the destination ONU from the unicast VID assigned to the multicast packet. When the OLT 4 receives the multicast packet # 1 from the MCB multicast router 7 via the layer 2 switch 6, the PON section Then, a unicast LLID indicating the ONU is assigned to the multicast packet, and the multicast packet is distributed to all the ONUs 2a, 2b, 2c (ONU # 1, # 2, # 3) (S21).

The ONUs 2a, 2b, and 2c discard the unicast packet if the unicast LLID assigned to the multicast packet is not its own LLID and the unicast LLID is not ALL1 (= 0xFFFF).
If the unicast LLID is its own LLID, the unicast packet is distributed to the terminal devices 1a, 1b, and 1c (terminal devices # 1, # 2, and # 3).
In the example of FIG. 2, only the ONU 2a distributes multicast packets to the terminal device 1a (S22).

  When the OLT 4 receives the multicast packet # 2 from the SCB multicast router 8 via the layer 2 switch 6, since the broadcast VID is assigned to the multicast packet # 2, all the ONUs 2a, 2b, 2c are multicast packets. Broadcast LLID indicating broadcast distribution is assigned to multicast packet # 2 so that # 2 can be received, and multicast packet # 2 is distributed to all ONUs 2a, 2b, 2c (S23).

The ONUs 2a, 2b, and 2c have a filtering function. When the multicast packet # 2 is received from the OLT 4, the ONUs 2a, 2b, and 2c filter the multicast packet # 2, thereby transmitting the multicast packet viewing request to the terminal device. Then, the multicast packet # 2 is transferred.
In the example of FIG. 2, only the ONU 2b distributes multicast packets to the terminal device 1b (S24).

The OLT 4 obtains information necessary for filtering of multicast packets in the ONUs 2a, 2b, and 2c from the multicast control signal of S14 transmitted from the terminal device 1b, and obtains the necessary information from IEEE (Institut of Electric Engineering and Electronic Engineers). ) It is set remotely on the corresponding ONU by placing it on an OAM (Operations, Administration, and Maintenance) frame used for control of the PON section defined in 802.3ah.
Hereinafter, the filtering operation by the ONU and the filter setting operation by the OLT 4 will be described.

First, the filtering operation by the ONU will be described.
FIG. 7 is a block diagram showing ONUs 2a, 2b, and 2c of the PON system according to Embodiment 1 of the present invention.
When receiving the unicast packet or multicast control signal from the terminal devices 1a, 1b, and 1c, the LLID adding unit 20 of the ONUs 2a, 2b, and 2c adds its own unicast LLID to the unicast packet or multicast control signal. A process of transferring a cast packet or a multicast control signal to the OLT 4 is performed.
When the LLID identification unit 21 receives a packet (unicast packet, multicast packet) from the OLT 4 and the LLID assigned to the packet is its own unicast LLID, the LLID identification unit 21 forwards the packet to the OAM frame termination unit 22. If the LLID assigned to the packet is a broadcast LLID, a process of transferring the packet to the MAC address filter unit 23 is performed.
The LLID identifying unit 21 discards the packet when the LLID assigned to the packet is not its own unicast LLID or broadcast LLID.

The OAM frame termination unit 22 terminates only the OAM frame among the packets output from the LLID identification unit 21, and sets the MAC address stored in the OAM frame and the registration / deletion of the MAC address. A process of transferring the flag to the MAC address filter unit 23 is performed.
The MAC address filter unit 23 performs a filtering process on the packet output from the LLID identification unit 21 using a MAC address. If the MAC address has an I / G (Individual / Group) bit of “1” in advance, , All are set to be discarded.

The I / G bit is the least significant bit of the first byte of the MAC address. When the bit is “1”, the I / G bit is a multicast packet. However, since the control signals Query and Report used in the next IGMP and MLD need to be transferred constantly regardless of the filter, they are excluded from being discarded because a unique MAC address is defined. ing.
The MAC address filter unit 23 refers to the MAC address and setting flag output from the OAM frame termination unit 22 and controls registration and deletion of the MAC address with respect to the internal discard filter.

Next, the filter setting operation by the OLT 4 will be described.
The OLT 4 has a multicast management table necessary for multicast transfer. For example, when a multicast control signal is received in S14 of FIG. 2, the multicast management table is updated according to the group address included in the multicast control signal. To do.
FIG. 5 is an explanatory diagram showing a multicast management table.
In FIG. 5, LLID is an identifier for identifying ONUs 2a, 2b, and 2c. In the multicast management table, a multicast group address and a destination MAC address (hereinafter referred to as a destination MAC address) in which the group address is mapped to layer 2 using LLID as a key. , Referred to as “multicast MAC address”).

FIG. 6 is an explanatory diagram showing a multicast management table in which the multicast management table of FIG. 5 is rearranged using a multicast group address as a key.
In the multicast management table of FIG. 6, in addition to managing the multicast MAC address and the LLID participating in the group address, the presence / absence of remote setting for the ONU is managed.
The reason why the presence / absence of remote setting for the ONU is managed is that the multicast address distributed from the SCB video distribution server 11 is transferred to the terminal device by multicasting to the MAC address filter unit 23 of the ONU in FIG. This is because it is necessary to remotely set the MAC address.

When a group address is added by a request for viewing a new multicast packet and the multicast management table in FIGS. 5 and 6 is updated, the multicast MAC address and setting flag are set to OAM only when remote setting for the ONU is required. Remote setting is performed by placing the frame and transmitting it to the corresponding ONU.
Here, the multicast MAC address is a MAC address in which a multicast group address is mapped to layer 2 in order to perform multicast transfer at the layer 2 level.

As this mapping method, in IPv4, 01-00-5E-00-00-00 to 01-00-5E-7F-FF-FF is the multicast MAC address, and the lower 23 bits of the multicast IP address are the MAC address. The address is mapped to the lower 23 bits.
In IPv6, it is 33-33-00-00-00-00 to 33-33-FF-FF-FF-FF, and the lower 24 bits of the IP address are mapped to the lower 24 bits of the MAC address.

Next, a sequence in which the terminal device 1c (terminal device # 3) makes a viewing request for the multicast packet # 2 distributed from the SCB video distribution server 11 will be described with reference to FIGS.
When the terminal device 1c transmits a multicast control signal, which is a request for viewing the multicast packet # 2, to the ONU 2c (ONU # 3), the ONU 2c transfers the multicast control signal to the OLT 4 (S25).

When the OLT 4 receives the multicast control signal from the ONU 2c, the multicast control signal is a signal related to a request for viewing a multicast packet distributed from the MCB video distribution server 10, or the multicast distributed from the SCB video distribution server 11 It is discriminated whether the signal relates to a packet viewing request, and a VLAN tag is attached.
That is, the OLT 4 compares the group address included in the multicast control signal with the group address registered in the VLAN-ID distribution management table of FIG. 4, and the group address included in the multicast control signal. 4 is registered in the VLAN-ID distribution management table of FIG. 4, the broadcast VID corresponding to the group address is assigned to the multicast control signal, and the multicast control signal is sent to the layer 2 switch 6. Transfer (S26).
The group address included in the multicast control signal transmitted from the terminal device 1c (terminal device # 3) is the group address included in the multicast control signal of S14 transmitted from the terminal device 1b (terminal device # 2). Is the same.

When the OLT 4 receives the multicast control signal from the ONU 2c, the OLT 4 updates the multicast management table of FIGS. 5 and 6 so that the group address included in the multicast control signal is added.
The OLT 4 remotely sets the multicast MAC address in which the added group address is mapped to layer 2 and the setting flag in the OAM frame and transmits the OAM frame to the corresponding ONU 2c.

When the layer 2 switch 6 receives the multicast control signal from the OLT 4, if the VLAN tag attached to the multicast control signal is a broadcast VID, the layer 2 switch 6 transfers the multicast control signal to the SCB multicast router 8 (S27). .
The SCB multicast router 8 has a multicast management table necessary for multicast transfer. When a multicast control signal is received from the layer 2 switch 6, the multicast management table is updated according to the multicast control signal.
Also, the SCB multicast router 8 confirms the broadcast VID assigned to the multicast control signal, and multicast packet # 2 in which the same broadcast VID as the broadcast VID is distributed from the SCB video distribution server 11. The multicast packet # 2 is transferred to the OLT 4 via the layer 2 switch 6 (S28).

  When the OLT 4 receives the multicast packet # 2 from the SCB multicast router 8 via the layer 2 switch 6, since the broadcast VID is assigned to the multicast packet # 2, all the ONUs 2a, 2b, 2c are multicast packets. Broadcast LLID indicating broadcast distribution is assigned to multicast packet # 2 so that # 2 can be received, and multicast packet # 2 is distributed to all ONUs 2a, 2b, and 2c (S29).

The ONUs 2a, 2b, and 2c have a filtering function. When the multicast packet # 2 is received from the OLT 4, the ONUs 2a, 2b, and 2c filter the multicast packet # 2, thereby transmitting the multicast packet viewing request to the terminal device. Then, the multicast packet # 2 is transferred.
In the example of FIG. 2, the ONUs 2b and 2c distribute multicast packets to the terminal devices 1b and 1c (S30 and S31).
That is, in the ONU 2c, as described with reference to FIG. 7, when the corresponding MAC address is removed from the discard filter by the MAC address filter unit 23, the multicast packet # 2 transferred from the OLT 4 is transferred to the terminal device 2c. Become so.
In the ONU 2b, the multicast packet # 2 transferred from the OLT 4 is continuously transferred to the terminal device 2b.

Next, the multicast transfer withdrawal request sequence will be described (S40).
When the terminal device 1a (terminal device # 1) transmits a multicast control signal, which is a request for leaving a multicast packet, to the ONU 2a (ONU # 1), the ONU 2a transfers the multicast control signal to the OLT 4 (S41).
When the OLT 4 receives the leaving multicast control signal from the ONU 2a, the OLT 4 distributes from the SCB video delivery server 11 whether the multicast control signal is a signal related to a multicast packet withdrawal request delivered from the MCB video delivery server 10. A VLAN tag is attached by determining whether the signal is a signal relating to a request to leave a multicast packet to be transmitted.

  In other words, the OLT 4 compares the group address included in the leaving multicast control signal with the group address registered in the VLAN-ID distribution management table of FIG. 4, and is included in the multicast control signal. If a group address that matches the group address is registered in the VLAN-ID distribution management table of FIG. 4, a broadcast VID corresponding to the group address is assigned to the multicast control signal, and the multicast control signal is assigned to layer 2. In this case, the group address that matches the group address included in the multicast control signal for leaving is not registered in the VLAN-ID distribution management table of FIG. It is added to the multicast control signal and its multicast Transferring a control signal to the layer 2 switch 6 (S42).

When the layer 2 switch 6 receives the multicast control signal for leaving from the OLT 4, the VLAN tag attached to the multicast control signal is a unicast VID, so the multicast control signal is transferred to the MCB multicast router 7. (S43).
When the MCB multicast router 7 receives the multicast control signal for leaving from the layer 2 switch 6, the MCB multicast router 7 refers to the unicast VID assigned to the multicast control signal and is the terminal that is the source of the multicast packet leave request The device 1a (terminal device # 1) is confirmed.
Since the MCB multicast router 7 stops the distribution of the multicast packet # 1 to the terminal device 1a, the multicast management table necessary for the multicast transfer is updated, and the multicast packet # 1 distributed from the MCB video distribution server 10 is updated. Distribution is stopped (S44).

Next, when the terminal device 1b (terminal device # 2) transmits a multicast control signal, which is a multicast packet withdrawal request, to the ONU 2b (ONU # 2), the ONU 2b transfers the multicast control signal to the OLT 4 (S45).
When the OLT 4 receives the leaving multicast control signal from the ONU 2b, the group address that matches the group address included in the multicast control signal is registered in the VLAN-ID distribution management table of FIG. The broadcast VID corresponding to the group address is assigned to the multicast control signal, and the multicast control signal is transferred to the layer 2 switch 6 (S46).

When the layer 2 switch 6 receives the leaving multicast control signal from the OLT 4, the VLAN tag attached to the multicast control signal is a broadcast VID, and therefore the multicast control signal is transferred to the SCB multicast router 8. (S47).
When the multicast router 8 for SCB receives the multicast control signal for leaving from the layer 2 switch 6, it updates the multicast management table according to the multicast control signal, and multicast packet # 2 distributed from the video distribution server 11 for SCB. In order to determine whether or not it is possible to stop the transfer of the packet, a confirmation is made that a broadcast VID is given to check whether a terminal device other than the terminal device 1b is viewing the multicast packet of the group address. The multicast control signal for use is transferred to the OLT 4 via the layer 2 switch 6 (S48).

When the OLT 4 receives a confirmation multicast control signal from the SCB multicast router 8 via the layer 2 switch 6, since the broadcast control VID is given to the multicast control signal, all the ONUs 2a, 2b, 2c confirm Broadcast LLID indicating broadcast distribution is added to the multicast control signal so that the multicast control signal can be received, and the multicast control signal is distributed to all ONUs 2a, 2b, and 2c (S49).
When the ONUs 2a, 2b, and 2c receive the multicast control signal for confirmation from the OLT 4, the multicast control signal is a control signal such as Query, and therefore forwards the multicast control signal to the terminal devices 1a, 1b, and 1c as it is ( S50).

When the terminal devices 1a, 1b, and 1c receive the confirmation multicast control signal from the ONUs 2a, 2b, and 2c, the terminal devices 1a, 1b, and 1c send a response multicast control signal via the ONUs 2a, 2b, and 2c if they participate in the group address. Transfer to OLT4.
Here, since only the terminal device 1c (terminal device # 3) participates in the group address, the terminal device 1c transfers a multicast control signal for response to the OLT 4 via the ONU 2c (S51).

When the OLT 4 receives the multicast control signal for response from the ONU 2c, the group address that matches the group address included in the multicast control signal is registered in the VLAN-ID distribution management table of FIG. The broadcast VID corresponding to the group address is assigned to the multicast control signal, and the multicast control signal is transferred to the layer 2 switch 6 (S52).
When the layer 2 switch 6 receives the response multicast control signal from the OLT 4, the VLAN tag attached to the multicast control signal is a broadcast VID, and therefore the multicast control signal is transferred to the SCB multicast router 8. (S53).

  When receiving the response multicast control signal from the layer 2 switch 6, the SCB multicast router 8 updates the multicast management table according to the response multicast control signal and also distributes the multicast packet distributed from the SCB video distribution server 11. After confirming that the terminal device 1c viewing # 2 exists, the multicast packet # 2 is continuously transferred to the OLT 4 via the layer 2 switch 6 (S54).

  When the OLT 4 receives the multicast packet # 2 from the SCB multicast router 8 via the layer 2 switch 6, since the broadcast VID is assigned to the multicast packet # 2, all the ONUs 2a, 2b, 2c are multicast packets. Broadcast LLID indicating broadcast distribution is assigned to multicast packet # 2 so that # 2 can be received, and multicast packet # 2 is distributed to all ONUs 2a, 2b, 2c (S55).

The ONUs 2a, 2b, and 2c have a filtering function. When the multicast packet # 2 is received from the OLT 4, the ONUs 2a, 2b, and 2c filter the multicast packet # 2, thereby transmitting the multicast packet viewing request to the terminal device. Then, the multicast packet # 2 is transferred.
In the example of FIG. 2, only the ONU 2c distributes the multicast packet to the terminal device 1c (S56).

In the above leaving sequence, when the OLT 4 receives the multicast control signal for leaving S45 from the ONU 2b, the OLT 4 corresponds to the unicast LLID of the ONU 2b, the multicast group address corresponding to the unicast LLID, and the unicast LLID. The multicast management tables in FIGS. 5 and 6 are updated so that the multicast MAC address is deleted.
Further, since the OLT 4 needs to be remotely set for the ONU 2b, the OLT 4 sets the multicast MAC address and a setting flag indicating registration in the OAM frame and transmits the setting to the ONU 2b.
As a result, in the ONU 2b, as described in FIG. 7, the MAC address filter unit 23 re-registers the MAC address in the discard filter, so that the multicast packet # 2 transferred from the OLT 4 is transmitted to the terminal device 2c. It is discarded without being transferred.
In the ONU 2c, since the remote setting from the OLT 4 is not changed, the multicast packet # 2 transferred from the OLT 4 is continuously transferred to the terminal device 2c.

  As is apparent from the above, according to the first embodiment, the multicast packet distributed from the MCB video distribution server 10 is duplicated as necessary and transferred to the OLT 4 and the SCB video. An SCB multicast router 8 for transferring the multicast packet distributed from the distribution server 11 to the OLT 4 is provided, and the multicast packet transferred from the MCB multicast router 7 or the SCB multicast router 8 by the OLT 4 is sent to a plurality of ONUs 2a, 2b, 2c. If the multicast packets distributed from the OLT 4 are multicast packets to be transferred, the multicast packets are controlled by the ONUs 2a, 2b, 2c. The multicast packet terminal device 1a, 1b, and then, is delivered to 1c, it is possible to realize a high-speed transfer of a multicast packet, an effect that can OLT4 to collectively manage the transfer of a multicast packet.

That is, according to the first embodiment, when the OLT 4 refers to the VLAN-ID distribution management table, the multicast control signal transmitted from the ONUs 2a, 2b, and 2c is transmitted to the MCB multicast router 7 or the SCB multicast router 8. Can be sorted.
In addition, the multicast packet distributed from the MCB video distribution server 10, the multicast packet distributed from the SCB video distribution server 11, and the unicast packet distributed from the Internet 9 are turned on by the OLT 4 using only the VLAN-ID in the packet. Hybrid high-speed multicast transfer that can be transferred to

  In addition, the OLT 4 updates the multicast management table according to the group address included in the multicast control signal, and transmits the multicast MAC address in which the group address is mapped to the layer 2 to the ONUs 2a, 2b, and 2c on the OAM frame. As a result, the multicast MAC address is remotely set in the ONUs 2a, 2b, and 2c, and the ONUs 2a, 2b, and 2c update the MAC address filter in accordance with the multicast MAC address, and a viewing request is received from the terminal devices 1a, 1b, and 1c. Only certain multicast packets can be transferred. Therefore, it is possible to realize multicast transfer in which two types of multicast transfer and unicast transfer are aggregated.

Embodiment 2. FIG.
In the first embodiment, the OLT 4 uses the multicast management table that manages the correspondence relationship between the LLID, the group address, and the multicast MAC address. However, as shown in FIG. When the valid flag is managed, even if the OLT 4 receives the multicast control signal from the ONU 2 in which the multicast valid flag is invalid, the multicast control signal may be discarded.
Specifically, it is as follows.

In the multicast management table of FIG. 8, the multicast valid flag is managed for each LLID of the ONU managed by the OLT 4 in the PON section.
The processing contents when receiving a multicast control signal from an ONU whose multicast valid flag is valid are the same as those in the first embodiment.
On the other hand, when receiving a multicast control signal from an ONU whose multicast validity flag is invalid, the OLT 4 discards all the multicast control signals of the transmission source from the terminal device accommodated in the ONU and updates the multicast management table. Do not implement.

As a result, the MAC address filter unit 23 in the ONU does not update the discard filter and discards all multicast MAC addresses that are in the initial state (except for the query and report control signals).
For this reason, a multicast packet is not transferred from the ONU regardless of whether or not there is a viewing request from the terminal device.

In the multicast management table of FIG. 8, the multicast limit number is further managed for each LLID of the ONU managed by the OLT 4 in the PON section.
The multicast limit number N (N ≧ 0) indicates the maximum number of multicast group addresses that can be registered, and the processing contents when the number of registered group addresses is equal to or less than the multicast limit number N are described in the above embodiment. Same as 1.
On the other hand, if the number of already registered group addresses has reached the multicast limit number N, the multicast control signal is discarded even if a new multicast control signal is received.
That is, the registration of the (N + 1) th group address is restricted, and even when the OLT 4 receives the (N + 1) th multicast control signal from the ONU, the multicast control signal is discarded and the multicast management table is not updated. Like that.

As a result, the MAC address filter unit 23 in the ONU does not update the (N + 1) th discard filter, but discards the (N + 1) th multicast MAC address (except for the query and report control signals).
For this reason, even if there is a viewing request exceeding the multicast limit number from the terminal device, multicast packets are not transferred due to the viewing request exceeding the multicast limit number.
When the multicast limit number N = 0, the processing contents are the same as when the multicast validity flag is invalid.

The multicast management table of FIG. 8 shows that the multicast valid flag is managed for each LLID of the ONU managed by the OLT 4 in the PON section. As shown in FIG. Even if a weight is managed and a multicast control signal is received from a certain ONU, the multicast control signal may be discarded if the total value of the group address weights reaches the multicast limit number.
That is, a weight is set for each multicast group address, and the OLT 4 controls updating of the multicast management table so that the total weight of the registered group addresses does not exceed the multicast limit number N shown in FIG. As a result, the number of viewing channels can be limited by the bandwidth and importance of each viewing channel.

  According to the second embodiment, the multicast valid flag, the multicast limit number N, and the weight of the group address are added to the multicast management table managed by the OLT 4, so that the multicast transfer is a request for viewing from the terminal device. There is an effect that the OLT 4 enables collective management without being influenced only by the presence or absence.

Embodiment 3 FIG.
FIG. 10 is a block diagram showing ONUs 2a, 2b, and 2c of the PON system according to Embodiment 3 of the present invention.
When receiving the unicast packet or multicast control signal from the terminal devices 1a, 1b, and 1c, the LLID adding unit 30 of the ONUs 2a, 2b, and 2c adds its own unicast LLID to the unicast packet or multicast control signal, and the unicast packet or multicast control signal. A process of transferring a cast packet or a multicast control signal to the OLT 4 is performed.
When the LLID identifying unit 31 receives a packet (unicast packet, multicast packet) from the OLT 4 and the LLID assigned to the packet is its own unicast LLID or broadcast LLID, the LLID identifying unit 31 identifies the packet as an OAM frame termination unit 32. Forward to.
The LLID identifying unit 31 discards the packet when the LLID assigned to the packet is not its own unicast LLID or broadcast LLID.

The OAM frame termination unit 32 terminates only the OAM frame among the packets output from the LLID identification unit 31, and sets the MAC address stored in the OAM frame and the MAC address indicating registration / deletion. The flag is transferred to the MAC address filter unit 33, and the MAC address update process of the filtering process in the MAC address filter unit 33 is performed by the MAC address and the setting flag.
The MAC address filter unit 33 performs a filtering process on the packet transferred from the OAM frame termination unit 32 with the MAC address.

FIG. 11 is a configuration diagram showing an internal filter of the MAC address filter unit 33.
The MAC address filter unit 33 includes a discard filter 34 that discards all MAC addresses whose I / G bits are “1” in advance.
The discard filter 34 includes a control signal MAC address transmission filter 35 and a MAC address transmission filter 36 that transmits an arbitrary MAC address.
However, since the Query and Report control signals used in IGMP and MLD must always be transmitted regardless of the discard filter, the control signal has a unique destination MAC address defined. The MAC address transmission filter 35 for control signals is set from the beginning.
The arbitrary MAC address transparent filter 36 can update addition / deletion by a MAC address transferred from the OAM frame termination unit 32 and a setting flag.

FIG. 11 shows an example in which the MAC address filter unit 33 includes the discard filter 34 including the MAC address transmission filter 35 and the MAC address transmission filter 36 for the control signal. However, as shown in FIG. A discard filter 37 may be mounted.
The MAC address filter unit 33 in FIG. 12 includes a MAC address discard filter 37 that discards a specified MAC address. The MAC address discard filter 37 is initially in a state without a discard filter. In other words, all MAC addresses are transparent.
The MAC address discard filter 37 can update the addition / deletion based on the MAC address transferred from the OAM frame termination unit 32 and the setting flag, and can discard the designated MAC address.

FIG. 13 is an explanatory diagram showing a multicast management table in the case where the MAC address filter unit 33 of the ONUs 2a, 2b, and 2c of FIG. 10 has the configuration of FIG.
The multicast management table in FIG. 13 is a simple modification of the multicast management table in FIG.

The ONUs 2a, 2b, and 2c in FIG. 7 according to the first embodiment receive the multicast packet (multicast packet to which the unicast LLID is assigned by the MCB multicast router 7) distributed from the MCB video distribution server 10, and the SCB. 7 receives the multicast packet distributed from the video distribution server 11 (multicast packet to which the broadcast LLID is assigned by the SCB multicast router 8), the LLID identifying unit 21 in FIG. 7 only receives the multicast packet to which the broadcast LLID is assigned. Is transferred to the MAC address filter unit 23.
Therefore, only the MAC address of the multicast packet distributed from the SCB video distribution server 11 needs to be set in the MAC address filter unit 23 (see the multicast management table in FIG. 6).

On the other hand, in the ONUs 2a, 2b, and 2c in FIG. 10, both the multicast packet distributed from the MCB video distribution server 10 and the multicast packet distributed from the SCB video distribution server 11 are sent to the MAC address filter unit 33. Therefore, if the MAC addresses of both multicast packets are set, it can be handled.
For this reason, the multicast MAC address in which the group addresses of the viewing request and the leaving request from the terminal devices 1a, 1b, and 1c are mapped to layer 2 may be placed on the OAM frame and remotely set in the ONU.
Therefore, operations other than the multicast management table may be the same as those in the first embodiment.

FIG. 14 is an explanatory diagram showing a multicast management table in the case where the MAC address filter unit 33 of the ONUs 2a, 2b, and 2c of FIG. 10 has the configuration of FIG.
In this case, it is defined that the filter number N of the MAC address discard filter 37 of FIG. 12 mounted in the ONUs 2a, 2b, and 2c of FIG. 10 is the same as the number of multicast packets used in the PON system of FIG. The total number of video channels distributed from the video distribution server is defined, and the multicast management table in FIG. 14 manages the multicast MAC address in which a fixed value of a predetermined group address is mapped to layer 2.

In the multicast management table of FIG. 14, all the unregistered states “x” are initially registered for the LLID, and at the initial stage when the ONUs 2a, 2b, and 2c are connected to the OLT 4, the OLT 4 registers with all the multicast MAC addresses. The setting flag shown is placed on the OAM frame and transmitted to the ONUs 2a, 2b, and 2c to perform remote setting.
In the ONUs 2a, 2b, and 2c, all the multicast packets used in the PON system in FIG. 1 are discarded by registering all the multicast MAC addresses remotely set by the OLT 4 in the MAC address discard filter 37 in FIG. It becomes a state.

Thereafter, when a viewing request is transmitted from the terminal devices 1a, 1b, and 1c, the MAC address of the corresponding LLID in the multicast management table of FIG. 14 is changed from “×” to “O”, and the changed multicast MAC Remote setting is performed by placing a setting flag indicating an address and deletion on the OAM frame and transmitting the flag to the ONUs 2a, 2b, and 2c.
In the ONUs 2a, 2b, and 2c, the corresponding MAC address is deleted from the MAC address discard filter 37 of FIG. 12, and the multicast packet that the user wants to view is transferred to the terminal devices 1a, 1b, and 1c.
In the case of a withdrawal request, the description is omitted because it is the reverse of the above description. In this way, the operation is the same as that of the first embodiment except that only the multicast management table is changed.

  According to the third embodiment, it is possible to realize multicast transfer in the PON system by changing the configuration of the multicast management table even for ONUs having different filtering methods in the ONUs 2a, 2b, and 2c. .

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the PON system by Embodiment 1 of this invention. It is a sequence diagram which shows the multicast transmission of the PON system by Embodiment 1 of this invention. It is a sequence diagram which shows the multicast transmission of the PON system by Embodiment 1 of this invention. It is explanatory drawing which shows the VLAN-ID distribution management table used when OLT4 distributes a multicast control signal. It is explanatory drawing which shows a multicast management table. It is explanatory drawing which shows the multicast management table rearranged using the multicast group address as a key. It is a block diagram which shows ONU2a, 2b, 2c of the PON system by Embodiment 1 of this invention. It is explanatory drawing which shows a multicast management table. It is explanatory drawing which shows a multicast management table. It is a block diagram which shows ONU2a, 2b, 2c of the PON system by Embodiment 3 of this invention. 4 is a configuration diagram showing an internal filter of a MAC address filter unit 33. FIG. 4 is a configuration diagram showing an internal filter of a MAC address filter unit 33. FIG. 12 is an explanatory diagram showing a multicast management table when the MAC address filter unit 33 of the ONUs 2a, 2b, and 2c in FIG. 10 has the configuration in FIG. 13 is an explanatory diagram showing a multicast management table when the MAC address filter unit 33 of the ONUs 2a, 2b, and 2c in FIG. 10 has the configuration in FIG. It is a block diagram which shows the conventional PON system. It is a sequence diagram which shows the multicast transmission in the conventional PON system. It is a sequence diagram which shows the multicast transmission in the conventional PON system. It is a sequence diagram which shows the multicast transmission in the conventional PON system.

Explanation of symbols

  1a, 1b, 1c Terminal device, 2a, 2b, 2c ONU (subscriber side device), 3 optical splitter, 4 OLT (station side device), 5 upper network, 6 layer 2 switch, 7 MCB multicast router (first Multicast router), 8 SCB multicast router (second multicast router), 9 Internet, 10 MCB video distribution server (first distribution server), 11 SCB video distribution server (second distribution server), 20 LLID adding unit, 21 LLID identifying unit, 22 OAM frame terminating unit, 23 MAC address filter unit, 30 LLID adding unit, 31 LLID identifying unit, 32 OAM frame terminating unit, 33 MAC address filter unit, 34 discard filter, 35 control signal MAC address transparent filter, 3 MAC address transmission filter, 37 MAC address waste filter.

Claims (11)

  In a PON system in which a plurality of subscriber-side devices accommodating terminal devices and a station-side device connected to the plurality of subscriber-side devices via an optical transmission medium communicate with each other, a first distribution server A first multicast router that replicates the multicast packet distributed from the network as needed and forwards it to the station side device; and a second multicast router that forwards the multicast packet distributed from the second distribution server to the station side device. A multicast router, and the station side device distributes the multicast packet transferred from the first multicast router or the second multicast router to the plurality of subscriber side devices, and the plurality of subscriber side devices. The multicast packet transfer target in the network is controlled, and the plurality of subscriber side devices are managed by the station side device. If a multicast packet of a multicasting packet transfer target, PON system characterized by distributing the multicast packet to the terminal device.   The first multicast router transfers the unicast packet distributed from the Internet to the station side device, and the station side device distributes the unicast packet transferred from the first multicast router to the plurality of subscriber side devices. 2. The unicast packet is delivered to a terminal device if the unicast packet delivered from the station side device is a unicast packet to be transferred by the plurality of subscriber side devices. PON system.   When the station side device receives a multicast control signal that is a multicast packet viewing request from the subscriber device, the station side device is a signal related to a multicast packet viewing request distributed from the first distribution server, If the multicast control signal is transmitted to the first multicast router and the multicast control signal is a signal related to a request for viewing a multicast packet distributed from the second distribution server, the multicast control signal is transmitted to the second multicast router. The PON system according to claim 1 or 2, wherein the transmission is performed.   When the station side device receives a multicast control signal which is a multicast packet viewing request from the subscriber device, the station side device includes a group address included in the multicast control signal, an identifier indicating the subscriber device, and the group address. 4. The PON system according to claim 3, wherein a multicast management table indicating a correspondence relationship with the destination MAC address mapped to 2 is updated.   When the station side device receives the multicast control signal that is a request for viewing the multicast packet distributed from the second distribution server, the station side device receives the terminal device that is the transmission source of the multicast control signal. 5. The PON system according to claim 4, wherein the multicast packet is included in a transfer target by remotely setting a destination MAC address in which a group address included in the multicast control signal is mapped to layer 2.   The subscriber side device updates the MAC address filter according to the destination MAC address remotely set by the station side device, and filters only the multicast packet transferred by the second multicast router using the MAC address filter. The PON system according to claim 5.   The subscriber side device updates the MAC address filter according to the destination MAC address remotely set by the station side device, and the multicast transmitted by the first multicast router or the second multicast router using the MAC address filter. 6. The PON system according to claim 5, wherein packets are filtered.   8. The PON according to claim 7, wherein the subscriber side device has a fixed number of discard filters in the MAC address filter, and updates the discard filter according to a destination MAC address remotely set by the station side device. system.   The station side device discards the multicast control signal even if it receives a multicast control signal from a subscriber side device whose multicast validity flag is invalid when the multicast management table manages the multicast validity flag. The PON system according to any one of claims 4 to 8.   When the multicast management table manages the multicast limit number, the station side device has already received the multicast control signal from the subscriber side device, but the number of group addresses corresponding to the identifier indicating the subscriber side device is already The PON system according to any one of claims 4 to 8, wherein the multicast control signal is discarded if the multicast limit number is reached.   If the station side device manages the weight of the group address in the multicast management table, even if the station side device receives the multicast control signal from the subscriber side device, the total value of the group address weight does not reach the multicast limit. 11. The PON system according to claim 10, wherein the multicast control signal is discarded.

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