PON system and Optical Network Unit

• US 20070264017A1
• Filed: 08/14/2006
• Published: 11/15/2007
• Est. Priority Date: 05/10/2006
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ashi, Yoshihiro, Kazawa, Tohru, Takase, Masayuki, Mizutani, Masahiko, Kobayashi, Masanobu, Shibata, Takeshi
• Granted Patent: US 7,630,637 B2
• Time in Patent Office: Days
• US Class Current: 398/72
• CPC Class Codes: H04J 3/1694 Allocation of channels in TDM/TDMA networks, e.g. distributed multiplexers Passive Optical Networks H04Q11/0062
• CPC Class Codes: H04L 12/185 with management of multicast group membership
• CPC Class Codes: H04Q 11/0066 Provisions for optical burst or packet networks
• CPC Class Codes: H04Q 11/0067 Provisions for optical access or distribution networks, e.g. Gigabit Ethernet Passive Optical Network (GE-PON), ATM-based Passive Optical Network (A-PON), PON-Ring
• CPC Class Codes: H04Q 2011/0073 Provisions for forwarding or routing, e.g. lookup tables
• CPC Class Codes: H04Q 2011/0079 Operation or maintenance aspects

Abstract

Provided is an ONU that suppresses transmission of a useless multicast control message to a PON section and enables a communication bandwidth of the PON section to be effectively used. The ONU of the PON system has a multicast group management table that shows a correspondence between a multicast group identifier and an address of a user terminal participating in a multicast group. When the ONU receives a request message of participation in the multicast group from the user terminal, the ONU registers the correspondence between the multicast group identifier indicated by the received message and the user terminal address. A new received message is deleted without being sent to the OLT if another user terminal address is registered already, along with a correspondence with the same multicast group identifier, in the multicast group management table.

Claims

1. An optical network unit (ONU) for a PON system that is connected to an optical local terminal (OLT) connected to a wide area network through a passive optical-network (PON) and selectively sends a downstream frame received from the optical local terminal to a user terminal, comprising:

a multicast group management table for showing a correspondence between a multicast group identifier and an address of the user terminal participating in a multicast group;

an upstream frame send controller that, when receiving a control message showing a request of participation in the multicast group from the user terminal, registers the correspondence between the multicast group identifier specified by the control message and the user terminal address in a multicast group management table and determines whether the control message needs to be sent to the optical local terminal according to the multicast group management table; and

a downstream frame send controller for controlling distribution of multicast data received from the passive optical network to a user terminal according to the multicast group management table,

wherein, when the upstream frame send controller receives a new control message of a request of participation in the multicast group, if the upstream frame send controller has already registered another user address, along with a correspondence with the multicast group identifier specified by the control message, in the multicast group management table, the upstream frame send controller deletes the control massage without sending it to the optical local terminal.

2. The optical network unit according to claim 1,

wherein, when the upstream frame send controller receives a control message of a request of secession from the multicast group from any of the user terminals, it deletes the correspondence between the multicast identifier indicated by the control message and the user terminal from the multicast group management table, and

wherein, when another user terminal address is registered already, along with a correspondence with the multicast group indicated by the control message, in the multicast group management table, the upstream frame send controller deletes the control message without sending it to the optical line terminal.

3. The optical network unit according to either claim 1 or claim 2,

wherein the multicast group management table stores first flag information showing response necessity to a confirmation message from a sender device of the multicast data, along with a correspondence with the multicast group identifier, and

wherein, when receiving a control message representing a response to the confirmation message from any of the user terminals, the upstream frame send controller determines whether the control message needs to be sent to the optical line terminal according to a state of the first flag corresponding to the multicast group identifier specified by the control message.

4. The optical network unit according to claim 3,

wherein, when the downstream frame send controller receives the confirmation message from the passive optical network, after re-setting the first flag information corresponding to the multicast group identifier specified by the confirmation message, the downstream frame send controller sends the confirmation message to a user terminal, and

wherein, when the upstream frame send controller receives a control message representing a response to the confirmation message from any of the user terminals, if the first flag information is the re-set state, the upstream frame send controller sends the control message to the optical line terminal and changes the first flag information to a set-up state, and if the first flag information represents already a set-up state, the upstream frame send controller deletes the control message without sending it to the optical line terminal.

5. The optical network unit according to either claim 3 or claim 4, comprising memory for storing second flag information indicating the presence/absence of a response obligation to a confirmation message from a sender device of the multicast data,

wherein, while the second flag information indicates the absence of response obligation to the confirmation message, the upstream frame send controller deletes all the control messages each representing a response to the confirmation message received from the user terminal.

6. The optical network unit according to claim 5,

wherein the second flag information is switched over to a state showing the presence of response obligation to the confirmation message by a flag control message issued from the optical line terminal.

7. The optical network unit according to any of claim 1 to claim 6,

wherein the upstream frame send controller includes:

a controller for performing registration and deletion of a table entry showing a correspondence between the multicast group identifier and the user terminal address in the multicast group management table; and

an upstream frame processing unit that, when receiving a control message of a specific protocol for participation and secession in and from the multicast group from a user terminal, sends the control message or its copy to the controller and determines whether the control message needs to be transmitted to the optical line terminal according to the multicast group management table, and

wherein the upstream frame send controller updating the multicast group management table according to the control message or its copy.

8. An optical network unit that is connected to an optical line terminal (OLT) connected to a wide area network via a passive optical network (PON) and selectively sends a downstream frame to a user terminal, comprising:

a multicast monitoring table showing a service state of multicast data in the passive optical network, along with a correspondence with a multicast group identifier; and

a multicast monitor for monitoring multicast data received from the passive optical network and updating the service state shown by the multicast monitoring table,

wherein, when receiving a control message indicating a request of participation in the multicast group from any of the user terminals, the optical network unit determining whether multicast data of the multicast group specified by the control message is in service according to the multicast monitoring table, and

wherein, when the multicast data is already in service, the optical network unit starting distribution of the multicast data to the sender user terminal of the control message without sending the control message to the optical line terminal.

9. The optical network unit according to claim 8, comprising:

a multicast group management table for showing a correspondence between the multicast group identifier and the address of a user terminal participating in the multicast group;

an upstream frame send controller that, when receiving a control message showing a request of participation in the multicast group from any of the user terminals, registers a correspondence between the multicast group identifier specified by the control message and the user terminal address in the multicast group management table and determines whether the control message needs to be sent to the optical line terminal according to the multicast group management table; and

an upstream frame send controller for controlling distribution of the multicast data received from the passive optical network to the user terminal according to the multicast group management table

wherein, when another user terminal address is registered already, along with a correspondence with the multicast group identifier specified by the control message, in the multicast group management table, the upstream frame send controller deletes the control message without sending it to the optical line terminal, and

wherein, when another user terminal address corresponding to the multicast group identifier specified by the control message is unregistered in the multicast group management table, the upstream frame send controller determines whether the control message needs to be sent to the optical line terminal according to the multicast monitoring table.

10. The optical network unit according to claim 9,

wherein, when the upstream frame send controller receives a control message showing a request of secession from the multicast group from any of the user terminals, the correspondence between the multicast group identifier and the user terminal address indicated by the control message is deleted from the multicast group management table, and

wherein, when another user terminal address is registered already, along with a correspondence with the multicast group identifier specified by the control message, in the multicast group management table, the control message is deleted without being sent to the optical line terminal.

11. The optical network unit according to either claim 9 or claim 10,

wherein the upstream frame send controller includes:

a controller for updating the multicast group management table;

an upstream frame processing unit that, when receiving a control message of a specific protocol for participation and secession in and from the multicast group from a user terminal, sends the control message or its copy to the controller and determines whether the control message needs to be sent to the optical line terminal according to the multicast group management table, and

wherein the controller performs registration and deletion of the correspondence between the multicast group identifier and the user terminal address in the multicast group management table according to the control message or its copy.

12. The optical network unit according to any of claim 8 to claim 11,

wherein the multicast monitoring table shows the service state, along with a correspondence with the group identifier for multicast data that unspecified users can receive freely.

13. A PON system in which a plurality of optical network units (ONUs) each accommodating a plurality of user terminals and an optical line terminal (OLT) connected to a wide area network are connected by an optical passive network (PON), the optical line terminal sends a downstream frame received from the wide area network to the plurality of optical network units via the passive optical network, and each of the optical network units selectively sends the downstream frame to the user terminals,

the each optical network unit having:

a multicast group management table showing a correspondence between a multicast group identifier and an address of the user terminal participating in a multicast group;

an upstream frame send controller that, when a control message indicating a request of participation in the multicast group is received from any of the user terminals, registers a correspondence between the multicast group identifier specified by the control message and the user terminal address in the multicast group management table and determines whether the control message needs to be sent to the optical line terminal according to the multicast group management table; and

a downstream frame send controller for controlling distribution of the multicast data received from the passive optical network to the user terminal according to the multicast group management table,

wherein, when the upstream frame send controller receives a new control message of a request of participation in the multicast group, if another user terminal address is registered already, along with a correspondence with the multicast group identifier specified by the control message, the upstream frame send controller deletes the control message without sending it to the optical line terminal, and

wherein the optical line terminal has a management table showing relay necessity determination information of the control message, along with a correspondence with the multicast group identifier and, when receiving a control message indicating a request of participation in the multicast group from any of the optical network units, controls sending of the control message to the wide area network according to the management table.

14. The PON system according to claim 13,

wherein the optical line terminal stores the user terminal address indicated by the control message of a request of participation in the multicast group sent from any of the optical network units as information whereby necessity of relaying the control message is determined.