JP2006101259A - Method and system for transmitting data and network repeater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent bands from being wasted by multiple transmission of broadcasting contents of the same channel. <P>SOLUTION: In response to broadcasting service viewing requests of the same channel from two or more ONUs 40-1 to 40-3 installed in user's houses, an OLT 32 transmits the first viewing request to an edge router 30 and blocks viewing requests after the second one. The OLT 32 broadcasts, to the plurality of ONUs 40-1 to 40-3, traffic of a broadcasting service distributed from the edge router 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a data transmission method and system corresponding to a broadcast service, and a network relay device.

  A so-called PON (Passive Optical Network) system is known as a data transmission system compatible with broadcasting services. The PON system has a configuration in which a center side optical terminator OLT (Optical Line Terminal) and each user's optical terminator ONU (Optical Network Unit) are connected by an optical transmission line composed only of passive optical elements. That is, a 1: n optical coupler is disposed between the optical fiber connected to the center-side optical terminator and the optical fiber connected to the optical terminator ONU of each user.

  Broadcasting services that use IP networks are attracting attention. FIG. 2 shows a schematic block diagram of an IP multicast network for a broadcast service.

  The media server 10 outputs a data signal carrying the requested content to the edge router 12. Data output from the media server 10 enters the network 14 via the edge router 12, exits from the edge router 16, and is input to the center-side termination device (OLT) 18 of the PON system. The network 14 is normally operated as an IP multicast network.

  Multicast routing protocols such as PIM-SM (Protocol Independent Multicast-Sparse Mode) and PIM-DM (Protocol Independent Multicast-Dense Mode) are used between routers in an IP multicast network. IGMP (Internet Group Management Protocol) is used between the edge router and the user apparatus.

  The OLT 18 converts the data from the edge router 16 into an optical signal and outputs it to the optical fiber 20. The optical splitter 22 divides the optical signal from the optical fiber 20 into n pieces, and outputs the divided optical signals to the optical fibers 24-1 to 24-n. Each optical signal divided by the optical splitter 22 is input to optical terminal units (ONUs) 26-1 to 26-n at user's homes via optical fibers 24-1 to 24-n. Each ONU 26-1 to 26-n converts an input optical signal into an electric signal, takes in data addressed to itself, and discards the others. Each of the ONUs 26-1 to 26-n supplies the fetched data to a requesting device under its control, for example, the set top boxes 28-1 to 28-n.

  In a broadcast service on an IP network, a device that receives a broadcast, for example, the set top boxes 28-1 to 28-n transmits the request to the edge router 16 by an IGMP JOIN message. The OLT 18 and the ONUs 26-1 to 26-n of the PON system snoop the IGMP message and store it in a predetermined transfer table, so-called snooping table. When the requested broadcast data is input, the OLT 18 refers to its own forwarding table, and if the identifier of the broadcast traffic is registered in the forwarding table, that is, if it is addressed to itself, the subordinate ONUs 26-1 to 26- broadcast to n and discard if not registered. After each of the ONUs 26-1 to 26-n converts the input optical signal to an electrical signal, it determines whether or not it is addressed to itself based on its own forwarding table, like the OLT 18, and takes in only the traffic addressed to itself. Discard traffic. As an identifier of broadcast traffic, that is, multicast traffic, a MAC address in layer 2 or an IP address in layer 3 is used.

  For example, when the user stops viewing ch1, the set-top boxes 28-1 to 28-n transmit an IGMP Leave message that means leaving the viewing group of ch1 to the edge router 16. When the edge router 16 receives an IGMP Leave message from a user device, for example, the set top boxes 28-1 to 28-n, the edge router 16 immediately transmits a GSQ (Group-Specific Query) message to the OLT 18. The OLT 18 sends GSQ messages to all ONUs 26-1 to 26-3 and thus to all user equipments 28-1 to 28-n. The edge router 16 also transmits the GSQ message to all user devices again with the same contents one second after transmitting the GSQ message. If there is no response to these GSQ messages indicating continuation of viewing within a certain period, it is considered that viewing has been stopped, and transmission to the user device is stopped.

  In the E-PON system (IEEE 802.3ah), whose standardization was completed in June 2004, a logical link on an optical transmission line using a logical link identifier (LLID) placed in the preamble portion of the MAC frame. Can be set.

  A logical link in the E-PON system will be briefly described. The LLID is roughly classified into a unicast LLID and a broadcast LLID. The unicast LLID is an LLID used for transferring unicast traffic, and realizes a logical one-to-one connection between the OLT and a specific ONU. On the other hand, the broadcast LLID is an LLID used for transfer of broadcast traffic, and is used to broadcast data from the OLT to all ONUs. In other words, all ONUs are permitted to capture a frame to which a broadcast LLID is assigned.

  When a broadcast type service is provided by multicast technology in the PON system, multicast traffic is transferred from the OLT 18 to all ONUs 26-1 to 26-n using the broadcast LLID, and each ONU 26-1 to 26-n transmits the captured traffic. Transfer to a subordinate requesting terminal, for example, a computer or set-top box 28-1 to 28-n. One or a plurality of communication devices can be connected to each user's ONUs 26-1 to 26-n. Communication devices that can be connected to the ONU typically include a computer, a set-top box for receiving TV viewing or a video-on-demand service, an IP telephone, and a video recorder with a network connection function.

  The ONUs 26-1 to 26-n detect whether or not a terminal that requests data transmitted by multicast traffic is under control by sniffing the request signal by IGMP (Internet Group Management Protocol) snooping. In IGMP snooping, the exchange of IGMP between the user apparatus and the upper router is snooping, the multicast address is held in the IGMP snooping table, and this is updated as needed. Thereby, the ONU can know the request source of the multicast traffic, and transmits the multicast traffic received from the OLT to the terminal under the request source.

  The OLT 18 also performs IGMP snooping. When multicast traffic that is not registered in the IGMP snooping table is input from the upper edge router 16, the traffic is discarded, and the multicast traffic registered in the IGMP snooping table is the upper edge. When input from the router 16, the traffic is transferred to the subordinate ONUs 26-1 to 26 -n.

  In recent years, virtual local area networks (LANs) have been rapidly adopted for such broadcast services. VLAN is to set up a virtual group of terminals independently of the physical connection form, and to group each terminal according to the MAC address, IP address or protocol used by the terminal. Used. There is an advantage that the network configuration can be changed without worrying about the physical location of the terminal. The VLAN may also be used for the purpose of evenly allocating the transmission band to terminals connected to the same LAN, or for the purpose of hindering communication between users connected to the same network.

  When a VLAN is used, an identifier called a VLAN tag for identifying each VLAN is added to each frame. Even if the traffic transmits the same data, if the VLAN tag is different, the OLT 18 treats them as different MAC frames. When a VLAN tag is added to a frame input from the edge router 16 to the OLT 18, a frame to which a different VLAN tag is assigned even if the content to be transferred, that is, the multicast traffic is the same (for example, ch1) Treat as different frames.

  In a combination of a multicast broadcast service and a VLAN, a transmission band may be wasted. As described above, the conventional OLT treats frames with different VLAN tags as different frames, and therefore may be transmitted redundantly even though they are frames that transmit the same content. Consider a case where a VLAN is set between the edge router 16 and the set top boxes 28-1 to 28-n. When the VLAN is distinguished by the unicast LLID on the transmission path between them, even if the frames or packets transmitting the same content are different, if the LLID is different, these are transmitted separately. The same content is transmitted repeatedly, and bandwidth is wasted. In addition, when transferring using the broadcast LLID, it is necessary to transfer the frame with the VLAN tag, and therefore, it is handled as a different frame. Similar to the method of transferring using the unicast LLID, the same content is duplicated and transmitted, and bandwidth is wasted.

One method for solving this is described in Patent Document 1. User terminals that request the same content belong to the same group of VLANs, and one multicast packet with a VLAN tag is transmitted from the edge router to the lower router, and the lower router copies the received packet, Send to user terminal.
JP 2003-032287 A

  In the method described in Patent Document 1, user terminals that request the same content need to belong to the same VLAN group. In other words, when user terminals belonging to different VLAN groups request the same content, waste of bandwidth cannot be saved.

  For example, when a set-top box under the control of three ONUs requests viewing of the same channel, the OLT multicasts three frames that differ only in VLAN tags that deliver the content of the designated channel to all ONUs. In practice, this means that the transmission capacity for two frames is wasted.

  An object of the present invention is to provide a data transmission method and system and a network relay device that eliminate such waste.

  The data transmission method according to the present invention optically transmits a center-side optical termination device, a plurality of user-side optical termination devices arranged at each user's home, the center-side optical termination device, and the plurality of user-side optical termination devices. The present invention is applied to a data transmission system having optical transmissions connected to each other. In response to a broadcast service viewing request for the same channel from two or more user-side optical termination devices, the center-side optical termination device distributes the first viewing request to the host device and blocks the second and subsequent viewing requests. To do. The center-side optical termination device broadcasts the traffic on the same channel distributed from the higher-level device to the plurality of user-side optical termination devices.

  A data transmission system according to the present invention optically transmits a center-side optical termination device, a plurality of user-side optical termination devices arranged at each user's home, the center-side optical termination device, and the plurality of user-side optical termination devices. In the data transmission system comprising the optical transmission lines to be connected to each other, the center side optical termination device stores a broadcast service viewing request and a channel from the plurality of user side optical termination devices, and the plurality of the transmission tables. In response to a broadcast service viewing request from the user-side optical terminal device, a table updating means for updating the transfer table and a broadcast service viewing request for the same channel from two or more user-side optical terminal devices Transfer control means for distributing the viewing request to the host device and blocking the second and subsequent viewing requests, and the same channel distributed from the host device. The channel traffic is characterized by comprising a broadcasting means for broadcasting to the plurality of user-side optical termination unit.

  A network relay device according to the present invention is a network relay device that mediates data transfer between a host device connected to a network and a plurality of terminal devices, and requests for viewing broadcast services and channels from the plurality of terminal devices In response to a broadcast service viewing request from the plurality of terminal devices, a table updating means for updating the transfer table, and a broadcast service viewing request for the same channel from two or more terminal devices. A transfer control unit that distributes the first viewing request to the host device and blocks the second and subsequent viewing requests; and a broadcasting unit that broadcasts the traffic of the same channel distributed from the host device to the plurality of terminal devices. It is characterized by comprising.

  According to the present invention, it is not necessary to waste a transmission band between the edge router and the center side optical termination device and between the center side optical termination device and a plurality of user side optical termination devices.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic block diagram of a PON system according to an embodiment of the present invention.

  The edge router 30 is arranged at a position corresponding to the edge router 16 of the IP network shown in FIG. The OLT 32 of the PON system is connected to the edge router 30 and is also connected to the optical splitter 36 via the optical fiber 34. The optical splitter 36 divides the optical signal from the optical fiber 34 into three, and outputs the divided optical signals to the optical fibers 38-1 to 38-3. Each optical signal divided by the optical splitter 36 is input to the ONUs 40-1 to 40-3 at the user's home via the optical fibers 38-1 to 38-3. Each ONU 40-1 to 40-3 converts an input optical signal into an electric signal, takes in data addressed to itself, and discards the others. Each of the ONUs 40-1 to 40-3 supplies the fetched data to the subordinate requesting device, for example, the set top boxes 42-1 to 42-3. For explanation, only the set top boxes 42-1 to 42-3 are shown, but other information devices such as personal computers can be connected to the ONUs 40-1 to 40-3.

  For convenience of explanation, three ONUs 40-1 to 40-3 are shown, but it is possible to connect four or more ONUs to the optical splitter 36.

  Although details will be described later, the OLT 32 stores and manages the multicast address and the correspondence relationship between the VLAN and the LLID in which the viewing request is received from the subordinate ONUs 40-1 to 40-3 in the address management table 58, and the ONUs 40-1 to 40- 3 stores and manages the relationship between the multicast address for which a viewing request is received from a subordinate user device and the device for which viewing is requested, in a VLAN / address management table 76 described later. The address management table 58 is a transfer table that stores information related to transfer of data passing through the OLT 32. In other words, the VLAN / address management table 76 is a transfer table that stores information related to transfer of data passing through the ONUs 40-1 to 40-3.

  Since the purpose of this embodiment is to prevent wasted bandwidth when a plurality of users request the same broadcast channel, here, the set top boxes 42-1 to 42-3 are viewing the same channel, for example, ch1. The operation will be described assuming the case of requesting. Of course, each set top box 42-1 to 42-3 can request the media server to view ch1 at different timings.

  In the present embodiment, a case where a frame with a VLAN tag is used and a case where a frame with a VLAN tag is used between the ONUs 40-1 to 40-3 and user devices under the ONUs 40-1 to 40-3, for example, set top boxes 42-1 to 42-3 will be considered. FIG. 3 shows a case where a frame with a VLAN tag is not used between the ONUs 40-1 to 40-3 and the set top boxes 42-1 to 42-3, and each set top box 42-1 to 42-3 has the same ch1. The signal flow in the case of wishing to watch FIG. 4 shows a case where a VLAN tagged frame is used between the ONUs 40-1 to 40-3 and the set top boxes 42-1 to 42-3, and each set top box 42-1 to 42-3 has the same ch1. The signal flow in the case of wishing to watch

  First, with reference to FIG. 3, a characteristic operation for the broadcast service of the present embodiment will be described. In the operation shown in FIG. 3, each of the ONUs 40-1 to 40-3 belongs to different VLANs, VLAN-ID = 1 for identifying the VLAN is assigned to the ONU 40-1, and the VLAN to the ONU 40-2. It is assumed that -ID = 2 is assigned and VLAN-ID = 3 is assigned to the ONU 40-3. In addition, for logical identification in unicast communication in the PON section between the OLT 32 and each ONU 40-1 to 3, LLID = 1 is used for the unicast communication between the OLT 32 and the ONU 40-1, and the unicast communication between the OLT 32 and the ONU 40-2. LLID = 2 is used, and LLID = 3 is used for unicast communication between the OLT 32 and the ONU 40-3.

  The set-top box 42-1 outputs a JOIN message (S1) of the protocol IGMPv2 to the ONU 40-1 as a signal requesting viewing of ch1. The network interface 70 of the ONU 40-1 applies this request signal (S1) from the set top box 42-1 to the ONU control device 72 and the VLAN tag control device 74. In the operation example shown in FIG. 3, the ONU control device 72 snoops the IGMP message. When the ONU control device 72 is a JOIN message, the device (in this case, the set top) receives the broadcast service viewing request source in the VLAN / address management table 76. Box 42-1) and the requested channel (here, ch1) are additionally recorded in association with each other. In other words, the VLAN / address management table 76 is a transfer table that stores information related to transfer of data passing through the ONU 40-1.

  The JOIN message (S 1) from the network interface 70 contains the LLID for unicast communication between the ONU 40-1 and the OLT 32, that is, LLID = 1, in the preamble portion, and is applied to the E / O converter 78. The E / O converter 78 converts the electrical signal from the VLAN tag control device 74 into an optical signal at a timing instructed by the OLT 32, and outputs the optical signal to the WDM optical coupler 80. The WDM optical coupler 80 outputs the optical signal from the E / O converter 78 to the optical fiber 38-1. The optical signal (S2) from the ONU 40-1 to the optical coupler 36 on the optical fiber 38-1 carries a JOIN message (S1) with LLID = 1 added to the preamble portion.

  Similarly, the set-top boxes 42-2 and 42-3 respectively send JOIN messages (S3 and S5) for requesting viewing of ch1 to the ONUs 40-2 and 40-3 at a timing independent of the set-top box 42-1. Output to. The ONU 40-2 outputs an optical signal (S4) carrying the JOIN message (S3) with LLID = 2 added to the preamble portion to the optical fiber 38-2 by the same processing as the ONU 40-1. The ONU 40-3 outputs an optical signal (S6) carrying the JOIN message (S5) with LLID = 3 added to the preamble portion to the optical fiber 38-2.

  The ONUs 40-1 to 40-3 output the optical signals (S2, S4, S6) so as not to overlap each other on the time axis. The optical signals (S2, S4, S6) are input to the OLT 32 via the optical coupler 36 and the optical fiber 34.

  In the OLT 32, the WDM optical coupler 50 applies an optical signal input from the optical fiber 34 to the O / E converter 52. The O / E converter 52 converts the input optical signal into an electric signal, and applies the electric signal to the OLT control device 54 and the VLAN tag control device 56. The OLT control device 54 manages the correspondence between the LLID assigned to the ONUs 40-1 to 40-3 under the OLT 32 and the VLAN-ID, and the channel information requested to be viewed by the ONUs 40-1 to 40-3. An address management table 58 is used. Specifically, the address management table 58 stores the correspondence of the LLID, VLAN-ID, MAC address, and IP address for each device (ONU 40-1 to 40-3) to which the LLID is assigned. The address management table 58 stores channel information requested for viewing from the subordinate ONUs 40-1 to 3, that is, the MAC or IP multicast address and the VLAN-ID.

  When the OLT control device 54 detects a JOIN message requesting viewing of a broadcast service, the OLT control device 54 checks whether or not the channel requested by the JOIN message has already been requested. If it has not been requested, the OLT control device 54 adds a VLAN tag of VLAN-ID = 1 corresponding to LLID = 1 to the JOIN message, or responds to all JOIN messages from the OLT device 54 to the edge router. The representative VLAN-ID to be assigned is determined in advance, a VLAN tag having the representative VLAN-ID value is assigned, and the VLAN tag control device 56 is controlled so as to output it. The VLAN tag control device 56 is instructed to shut off.

  In the example shown in FIG. 3, since the JOIN message from the set top box 42-1 is the first request for viewing ch1, the VLAN tag control device value 56 is only an electrical signal corresponding to the optical signal (S2). And the electric signal corresponding to the optical signal (S4, S6) is cut off.

  The network interface 60 supplies the signal (S7) output from the VLAN tag control device 56 to the edge router 30.

  Thus, in this embodiment, the OLT 32 transfers only one of the signals to the edge router 30 even if there are a plurality of signals requesting the same channel. Therefore, when viewed from the edge router 30 and the upstream media server, only one user device appears to be viewing one channel. Edge router 30 transmits a single traffic for the requested channel. Thereby, waste of bandwidth between the edge router 30 and the OLT 32 can be prevented.

  Upon receiving the JOIN message (S7), the edge router 30 requests the IP multicast network to which it belongs to transfer the requested channel (here, ch1). The media server that owns the channel ch1 connects to another edge router of the IP multicast network, and transmits the requested ch1 traffic to the OLT 32 via the multicast network and the edge router 30. The frame of the ch1 traffic (S8) transmitted from the edge router 30 to the OLT 32 includes the same VLAN tag given to the JOIN message, an identifier indicating ch1, that is, a MAC or IP multicast address, and the contents of ch1. Transport.

  The traffic (S8) is input to the OLT control device 54 and the traffic / VLAN tag control device 62 via the network interface 60 of the OLT 30. When the input traffic is multicast traffic, the OLT control device 54 checks whether or not the multicast address of the traffic is registered in the address management table 58. If the input traffic is registered, the OLT control device 54 checks the traffic / VLAN tag control device 62. The VLAN tag is deleted at, the broadcast LLID is added to the preamble portion, and the E / O converter 64 is output. If the multicast address of the traffic is not registered in the management table 58, the traffic / VLAN tag control device 62 discards the traffic.

  The E / O converter 64 converts the output signal of the traffic / VLAN tag control device 62 into an optical signal (S9). The WDM optical coupler 50 outputs the output optical signal from the E / O converter 64 to the optical fiber 34.

  Note that the user apparatus that views ch1 can also be identified by the ONUs 40-1 to 40-3. Therefore, regardless of whether the requesting apparatus of ch1 is one or more, the OLT 32 transmits the traffic of ch1 to all ONUs 40-1 to 40-. 3 may be broadcast.

  The optical splitter 36 divides the signal light (S9) from the OLT 32 into three. The divided optical signals (S9-1, S9-2, S9-3) propagate through the optical fibers 38-1 to 38-3 and are input to the ONUs 40-1 to 40-3.

In the ONU 40-1, the WDM optical coupler 80 supplies the optical signal (S9-1) from the optical fiber 38-1 to the O / E converter 82. The O / E converter 82 converts the input optical signal into an electric signal, and applies the electric signal to the ONU controller 72 and the traffic / VLAN control device 84.
When the input traffic is multicast traffic, the ONU control device 72 checks whether or not the multicast address of the traffic is registered in the VLAN / address management table 76, and if it is registered, the traffic / VLAN control is performed. Control device 84 to cause the requesting device to forward the traffic. Multicast traffic that is not registered in the VLAN / address management table 76 is discarded.

  In the conventional example, a viewing request message of the same channel having a different VLAN tag, that is, a JOIN message is transmitted from the OLT to the edge router, and the multicast traffic of the same content to which the different VLAN tag is attached is transferred from the edge router. As a result, the bandwidth between the edge router and the OLT and between the OLT and the ONU was wasted, but in this embodiment, even if there is a broadcast viewing request for the same channel from a device with a different VLAN, the edge router 30 Since the broadcast content of the channel is transmitted in a single multicast frame from the OLT 32 to the OLT 32 and from the OLT 32 to all the ONUs 40-1 to 40-3, the bandwidth is not wasted.

  Note that the viewing channel and viewing device correspondence data recorded in the VLAN / address management table 76 of the ONUs 40-1 to 40-3 and the address management table 58 of the OLT 32 is the result of the viewing device stopping viewing or the GSP message. When the viewing confirmation message for the inquiry is not received within a predetermined time, it is deleted from the tables 76 and 58.

  The OLT 32 collects viewing requests from the plurality of ONUs 40-1 to 40-3 together and transmits them to the edge router 30. Similarly, the OLT 32 collectively transmits viewing requests to the edge router 30. That is, when the response to continue viewing in response to the GSQ message includes the identifiers of the ONUs 40-1 to 40-3, the OLT 32 sends a single viewing continuation response including the identifier of any one of the ONUs that continue viewing to the edge router 30. Reply to

  As described above, in this embodiment, when a channel request is issued from the OLT 32 to the upper edge router 30, one VLAN tag for the channel, that is, the first requested VLAN, or a predetermined request is determined in advance. The channel request from the OLT 32 to the edge router 30 and the channel transfer from the edge router 30 to the OLT 32 are performed using the existing VLAN. Between the OLT 32 and the edge router 30, there is only a channel request signal with one VLAN tag and multicast traffic, so that the problem of multiple copies of the same content does not occur.

  When multicast traffic with the VLAN tag is input from the edge router 30 to the OLT 32, the OLT 32 deletes the VLAN tag and then forwards the traffic to all ONUs 40-1 to 40-3 using the broadcast LLID. To do. Each ONU 40-1 to 40-3 forwards the received multicast frame to the user apparatus if the channel is registered in the forwarding table. This avoids the problem of multiple copying of VLAN tagged multicast frames in the PON section.

  When allowing communication of VLAN untagged frames between the edge router 30 and the OLT 32, the OLT 32 may send an untagged Join message to the edge router 30 to request the untagged multicast traffic from the edge router 30. .

  In this embodiment, a representative VLAN is used for communication between the edge router 30 and the OLT 32. At this time, a response to the IGMP GQ (General Query) message for inquiring the viewing state and the GSQ message output corresponding to the Leave message is performed using the representative VLAN. The OLT 32 aggregates the responses from the respective user apparatuses with respect to the GQ message and the GSQ message, and sends it back to the edge router 30 using the representative VLAN.

  Next, the operation in the case of the signal flow shown in FIG. 4 will be described. In the operation shown in FIG. 4, the set top boxes 42-1 to 42-3 belong to different VLANs, and the ONUs 40-1 to 40-3 set the traffic broadcast from the OLT 32 to the set that requested this traffic. A VLAN tag is attached to the top boxes 42-1 to 42-3 and transferred. For this purpose, each ONU 40-1 to 40-3 stores and manages in the VLAN / address management table 76 which subordinate user device belongs to which VLAN and which broadcast content is requested. In FIG. 3, the section between the edge router 30 and the OLT 32 is a section with a VLAN tag, but in FIG. 4, there is also a connection between the ONUs 40-1 to 40-3 and the set top boxes 42-1 to 42-3. This is a section with a VLAN tag.

  An operation between the ONU 40-1 and the set top box 42-1 will be described. The set-top box 42-1 outputs to the ONU 40-1 an IGMPv2 JOIN message (S1a) to which a VLAN tag having the ID of the VLAN to which the set top box 42-1 belongs is assigned as a signal for requesting viewing of ch1. The network interface 70 of the ONU 40-1 applies this request signal (S1a) from the set top box 42-1 to the ONU control device 72 and the VLAN tag control device 74. The ONU control device 72 snoops the IGMP message, and when it is a JOIN message, the request / request device of the broadcast service (here, the set-top box 42-1) and the request are stored in the VLAN / address management table 76. The channel (ch1 in this case) is additionally recorded in association with it, and the VLAN tag control device 74 is instructed to output the input signal (S1a) in the same format.

  The VLAN tag control device 74 refers to the VLAN / address management table and embeds an LLID corresponding to the VLAN-ID, that is, LLID-1 in the preamble portion of the JOIN signal (S1a) from the network interface 70, and Applied to the O converter 78. The E / O converter 78 converts the electrical signal from the VLAN tag control device 74 into an optical signal at a timing instructed by the OLT 32, and outputs the optical signal to the WDM optical coupler 80. The WDM optical coupler 80 outputs the optical signal from the E / O converter 78 to the optical fiber 38-1. The optical signal (S2) directed from the ONU 40-1 to the optical splitter 36 on the optical fiber 38-1 substantially carries the JOIN message (S1a) itself output from the set top box 42-1.

  Similarly, the set top boxes 42-2 and 42-3 each request viewing of ch1 to which a VLAN tag having a VLAN-ID to which the set top boxes 42-1 belong is attached at a timing independent from the set top box 42-1. Messages (S3a, S5a) are output to ONUs 40-2, 40-3. The ONUs 40-2 and 40-3 embed each LLID in the preamble part of the JOIN message (S3a, S5a) and process the optical signals (S4, S6) with the optical fibers 38-2, 38 by the same processing as the ONU 40-1. To -3.

  Processing until the JOIN message reaches the edge router 30 from the ONUs 40-1 to 40-3 via the optical coupler 36 and the OLT 32, and the traffic of the broadcast service output from the edge router 30 are ONUs 40-1 and 40-. The processing up to reaching 2, 40-3 is the same as that in FIG. Through these processes, the ch1 traffic output from the media server enters the ONUs 40-1, 40-2, and 40-3 as optical signals (S9-1, S9-2, and S9-3), respectively.

  In the ONU 40-1, the WDM optical coupler 80 supplies the optical signal (S9-1) from the optical fiber 38-1 to the O / E converter 82. The O / E converter 82 converts the input optical signal into an electric signal, and applies the electric signal to the ONU controller 72 and the traffic / VLAN control device 84. When the input traffic is multicast traffic, the ONU control device 72 refers to the VLAN / address management table 76 to check the device that requested the content, and obtains the VLAN-ID of the requested device from the VLAN / address management table 76. Read and apply to traffic / VLAN controller 84. The traffic / VLAN controller 84 adds a VLAN tag having a VLAN-ID indicating the request source set-top box 42-1 of the frame carried by the optical signal (S9-1), that is, VLAN-ID = 1. To the network interface 70. The output signal (S10a) of the traffic / VLAN control device 84 is transmitted to the set top box 42-1 via the network interface 70.

  Similarly, the ONU 40-2 has assigned a VLAN tag having a VLAN-ID indicating the request source set-top box 42-2 of the frame carried by the optical signal (S9-2), that is, VLAN-ID = 2. The signal (S11a) is supplied to the set top box 42-2. The ONU 40-3 transmits a VLAN tag having a VLAN-ID indicating the set top box 42-3 that is a request source of the frame carried by the optical signal (S9-3), that is, a signal to which a VLAN tag having VLAN-ID = 3 is attached (S12a). ) To the set top box 42-3.

  Although the invention has been described with reference to specific illustrative embodiments, various modifications and alterations may be made to the above-described embodiments without departing from the scope of the invention as defined in the claims. This is obvious to an engineer in the field to which the present invention belongs, and such changes and modifications are also included in the technical scope of the present invention.

It is a schematic block diagram of one Example of this invention. It is a schematic block diagram of a prior art example. FIG. 3 is a schematic diagram showing a signal flow of a first operation of the present example. It is a schematic diagram which shows the signal flow of the 2nd operation | movement of a present Example.

Explanation of symbols

10: Media server 12: Edge router 14: Network 16: Edge router 18: Center-side terminal device (OLT)
20: Optical fiber 22: Optical splitters 24-1 to 24-n: Optical fibers 26-1 to 26-n: Optical terminator (ONU)
28-1 to 28-n: set top box 30: edge router 32: OLT
34: Optical fiber 36: Optical splitters 38-1 to 38-3: Optical fibers 40-1 to 40-3: ONU
42-1 to 42-3: set top box 50: WDM optical coupler 52: O / E converter 54: OLT controller 56: VLAN tag controller 58: address management table 60: network interface 62: traffic / VLAN tag control Device 64: E / O converter 70: Network interface 72: ONU control device 74: VLAN tag control device 76: VLAN / address management table 78: E / O converter 80: WDM optical coupler 82: O / E converter 84 : Traffic / VLAN tag control device

Claims (10)

Center-side optical termination device (32), a plurality of user-side optical termination devices (40-1 to 40-3) arranged at each user's home, the center-side optical termination device (32), and the plurality of user sides In a data transmission system comprising optical transmission lines (34, 36, 38-1 to 38-3) for optically connecting optical termination devices (40-1 to 40-3),
In response to the broadcast service viewing request for the same channel from two or more user-side optical termination devices, the center-side optical termination device (32) distributes the first viewing request to the host device (30) and the second Block future viewing requests,
The data transmission method, wherein the center-side optical termination device (32) broadcasts the traffic of the same channel distributed from the higher-level device (30) to the plurality of user-side optical termination devices.   In response to the same channel viewing continuation request from two or more user side optical termination devices that continue to view the same channel, the center side optical termination device transmits a single viewing continuation request to the host device (30). The data transmission method according to claim 1, wherein:   Each of the user side optical termination devices (40-1 to 40-3) adds an identifier for identifying the user device that has requested the traffic to the traffic broadcast from the center side optical termination device (32), The data transmission method according to claim 1 or 2, wherein the data is unicast to the user apparatus.   The data transmission method according to any one of claims 1 to 3, wherein the two or more user-side optical terminal devices that request viewing of the same channel broadcast service belong to different virtual LANs.   The at least two user devices connected to any of the two or more user-side optical terminal devices that request viewing of the same channel broadcast service belong to different virtual LANs. The data transmission method according to any one of the above. Center-side optical termination device (32), a plurality of user-side optical termination devices (40-1 to 40-3) arranged at each user's home, the center-side optical termination device (32), and the plurality of user sides A data transmission system comprising optical transmission lines (34, 36, 38-1 to 38-3) for optically connecting optical termination devices (40-1 to 40-3),
The center side optical termination device (32) includes a transfer table (58) for storing broadcast service viewing requests and channels from the plurality of user side optical termination devices (40-1 to 40-3), In response to a broadcast service viewing request from the user side optical terminal devices (40-1 to 40-3), the table updating means (54) for updating the transfer table (58) and two or more user side optical terminal devices. In response to a broadcast service viewing request for the same channel, a transfer control means (54, 56) that distributes the first viewing request to the host device (30) and blocks the second and subsequent viewing requests, and the host device ( 30) broadcast means (62) for broadcasting the traffic of the same channel distributed from (30) to the plurality of user side optical terminal devices (40-1 to 40-3); Data transmission system characterized by comprising.   The transfer control means (54, 56) sends a single viewing continuation request to the higher-level device (30) in response to a viewing continuation request for the same channel from two or more user-side optical terminal devices that continue viewing the same channel. 8. The data transmission system according to claim 6, wherein   Each of the user-side optical terminal devices (40-1 to 40-3) stores a broadcast service viewing request, a channel, and the requested user device from one or more user devices (42-1 to 42-3) under its control. A second forwarding table (76) that transmits the traffic broadcast from the center-side optical terminal device (32) with reference to the second forwarding table, and transmitting the traffic to the user device that requested the traffic The data transmission method according to claim 6 or 7, further comprising: A network relay device that relays data transfer between a host device (30) connected to a network and a plurality of terminal devices (40-1 to 40-3),
A transfer table (58) for storing broadcast service viewing requests and channels from the plurality of terminal devices (40-1 to 40-3);
Table updating means (54) for updating the transfer table (58) in accordance with a broadcast service viewing request from the plurality of terminal devices (40-1 to 40-3);
Transfer control means (54, 56) that distributes the first viewing request to the host device (30) and blocks the second and subsequent viewing requests in response to broadcast service viewing requests on the same channel from two or more terminal devices. )When,
Broadcast means (62) for broadcasting the traffic of the same channel distributed from the higher-level device (30) to the plurality of termination devices (40-1 to 40-3)
A network relay device comprising:   The network repeater according to claim 9, wherein the network repeater is a center-side optical terminator of the PON system.

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