Multicast communication method and apparatus

• US 6,532,233 B1
• Filed: 10/19/1999
• Issued: 03/11/2003
• Est. Priority Date: 10/19/1998
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Momona, Morihisa, Matsunaga, Yasuhiko
• Primary Examiner(s): Rao, Seema
• Assistant Examiner(s): Duong, Frank
• Application Number:
  US09/421,065
• Time in Patent Office: 1,239 Days
• Field of Search: 370/467, 370/469, 370/408, 370/489, 370/238, 370/254, 370/255, 370/256, 370/257, 370/390, 370/392, 370/401, 370/402, 370/432
• US Class Current: 370/390
• CPC Class Codes: H04L 12/185 with management of multicast group membership
• CPC Class Codes: H04L 12/1859 adapted to provide push services, e.g. data channels

Abstract

A multicast communication apparatus includes a center station and subscriber stations. Each station includes input/output ports, and a section for layer-2 bridging between the ports in a 7-layer OSI model. Each station includes a transfer control table for holding group addresses, and an address converting section. Each section also includes a section for transferring a multicast packet to corresponding ports, a section for analyzing the layer-3 message received from each port, a section for checking registration of layer-3 group addresses corresponding to subscription requests, transferring or not transferring the messages depending on whether the group addresses are registered, registering the corresponding group addresses, a section for transferring subscription state query messages and generating/outputting layer-3 multicast subscription request messages destined to acquired layer-3 group addresses, and a section for deleting a layer-3 group address from the table if the corresponding multicast subscription request message is not received for a predetermined period of time, and deleting a layer-2 group address if the corresponding layer-3 group address is not present. A multicast communication method is also disclosed.

Claims

1. A multicast communication apparatus comprising a center station or subscriber station in a two-way CATV network, said center station or subscriber station including:

a plurality of ports for inputting/ou tputting packets;

means for performing layer-2 bridging between said ports in a 7-layer OSI model;

a transfer control table for holding layer-2 and layer-3 group addresses for each of said ports in the 7-layer OSI model;

means for converting th e layer-3 group address into the layer-2 group address;

means for transferring a multicast packet to a corresponding port upon reception of the multicast packet from an arbitrary one of said ports only when a layer-2 group address of a destination of the multicast packet is registered in said table corresponding to each of said ports other than said port through which the multicast packet has been received;

means for analyzing the layer-3 message received from each of said ports, and extracting the message if the message is a management message indicating a subscription request for a layer-3 multicast group or subscription state query;

means for, when the extracted management message is a multicast subscription request, checking whether the layer-3 group address corresponding to the subscription request has been registered in said table corresponding to said port through which the subscription request message has been received, not transferring the subscription request message to said other ports if the layer-3 group address has been registered, transferring the subscription request message to all said ports other than said port through which the message has been received if the layer-3 group address has not been registered, registering the layer-3 group address corresponding to the subscription request in said table corresponding to said port through which the subscription request message has been received, and also registering a layer-2 group address corresponding to the registered layer-3 group address if the layer-2 group address has not been registered in said table;

means, when the extracted management message is a multicast subscription state query, transferring the subscription state query message to all said ports other than said port through which the message is received, acquiring layer-3 group addresses registered in said transfer control tables corresponding to all said ports other than said port through which the message is received, generating layer-3 multicast subscription request messages destined to the respective acquired layer-3 group addresses, and outputting the subscription state query message to said port through which the message is received; and

means for, when a multicast subscription request message destined to a layer-3 group addresses registered in said table through said port for a predetermined period of time, deleting the corresponding layer-3 group address from said table, and, when no layer-3 group address corresponding to a layer-2 group address registered in said table is left as a result of deletion, deleting the corresponding layer-2 group address from said table.

2. A multicast communication apparatus comprising a center station or subscriber station in a two-way CATV network, said center station or subscriber station including:

a plurality of ports for inputting/outputting packets;

means for performing layer-2 bridging between said ports in a 7-layer OSI model;

a transfer control table for holding layer-2 and layer-3 group addresses for each of said ports in the 7-layer OSI model;

means for converting the layer-3 group address into the layer-2 group address;

means for transferring a multicast packet to a corresponding port upon reception of the multicast packet from an arbitrary one of said ports only when a layer-2 group address of a destination of the multicast packet is registered in said table corresponding to each of said ports other than said port through which the multicast packet has been received;

means for analyzing the layer-3 message received from each of said ports, and extracting the message if the message is a management message indicating a subscription request for a layer-3 multicast group or subscription state query;

means for, when the extracted management message is a multicast subscription request, checking whether the layer-3 group address corresponding to the subscription request has been registered in said table corresponding to said port through which the subscription request message has been received, not transferring the subscription request message to said other ports if the layer-3 group address has been registered, transferring the subscription request message to all said ports other than said port through which the message has been received if the layer-3 group address has not been registered, registering the layer-3 group address corresponding to the subscription request in said table corresponding to said port through which the subscription request message has been received, and also registering a layer-2 group address corresponding to the registered layer-3 group address if the layer-2 group address has not been registered in said table;

means for, when a multicast subscription state query message is received from said port, not transferring the message to said other ports, acquiring layer-3 group addresses registered in said transfer control tables corresponding to all said ports, other than said port through which the message is received, by looking up said transfer control tables, generating multicast subscription request messages destined to the respective acquired layer-3 group addresses, and outputting a multicast subscription state query message from said port through which the message is received;

means for periodically transmitting multicast subscription state query messages from an arbitrary one of said ports; and

means for, when a multicast subscription request message destined to a layer-3 group addresses registered in said table through said port for a predetermined period of time, deleting the corresponding layer-3 group address from said table, and, when no layer-3 group address corresponding to a layer-2 group address registered in said table is left as a result of deletion, deleting the corresponding layer-2 group address from said table.

3. A multicast communication apparatus comprising a center station or subscriber station in a two-way CATV network, said center station or subscriber station including:

a first port for inputting a downstream packet and outputting a upstream packet;

a second port for outputting a downstream packet and inputting a upstream packet;

means for performing layer-2 bridging between said first and second ports in a 7-layer OSI model;

a transfer control table for holding layer-2 and layer-3 group addresses of a destination of a downstream multicast packet to be used for transfer from said first port to said second port;

means for converting the layer-3 group address into the layer-2 group address;

means for transferring a downstream multicast packet received from said first port to said second port only when a layer-2 group address of a destination of the downstream multicast packet is registered in said table, and discarding the downstream multicast packet if the layer-2 group address is not registered;

means for analyzing types of layer-3 messages received from said first and second ports;

means for, when a multicast subscription request message is received from said second port, checking whether a layer-3 group address corresponding to the subscription request has been registered in said table, not transferring the subscription request message to said first port if the layer-3 group address has been registered, transferring the subscription request message to said first port if the layer-3 group address has not been registered, and registering a layer-2 group address corresponding to the registered layer-3 group address if the layer-2 group address has not been registered in said table;

means for periodically transmitting multicast subscription state query messages from said second port;

means for, when a multicast subscription state query message is received from said first port, not transferring the message to said second port, acquiring layer-3 group addresses registered in said table, generating layer-3 multicast subscription request messages destined to the respective acquired layer-3 group addresses, and outputting the messages from said first port; and

means for, when a multicast subscription request message destined to a layer-3 group addresses registered in said table is not received from said second port for a predetermined period of time, deleting the corresponding layer-3 group address from said table, and, when no layer-3 group address corresponding to a layer-2 group address registered in said table is left as a result of deletion, deleting the corresponding layer-2 group address from said table.

4. A multicast communication method in a center station or subscriber station in a two-way CATV network, which includes a transfer control table for each input/output port of said center station or subscriber station to hold layer-2 and layer-3 group addresses to be used for transfer, transfers a multicast packet, when receiving the multicast packet from an arbitrary port, to a port other than said port through which the packet is received if a group address of a destination of the received packet at layer 2 is registered in said table corresponding to said port other than said port through which the packet is received, and discards the received packet if the group address is not registered, thereby performing filtering to obtain only a multicast packet destined to a group address desired to be used for distribution by a subordinate terminal, comprising the steps of:

when the multicast packet received through said port is a multicast management message and the management message is a multicast subscription request, checking whether a layer-3 group address corresponding to the subscription request has been registered in said table corresponding to said port through which the packet is received, updating an expiration time of the layer-3 group address in said table without transferring the subscription request message to other ports if the layer-3 group address has been registered, transferring the received subscription request message to all said ports other than the reception port if the layer-3 group address has been registered, also registering the layer-3 group address corresponding to the subscription request in said table, converting the layer-3 group address into the layer-2 group address, and registering the layer-2 group address in said table corresponding to said port through which the message is received if the layer-2 group address has not be registered in said table; and

when the received multicast management message is a multicast subscription state query message, transferring the subscription state query message to all said ports other than said port through which the message is received, acquiring layer-3 group addresses registered in said tables corresponding to all said ports other than said port through which the message is received, generating layer-3 multicast subscription request messages destined to the respective acquired layer-3 group addresses, and outputting the subscription state query message to said port through which the message is received.

5. A method according to claim 4, further comprising the step of setting a predetermined expiration time for each of layer-3 and layer-2 group addresses registered in said table, updating the expiration time every time the multicast subscription request message is received, deleting the layer-3 group address registered in said table if no multicast subscription request message destined to the layer-3 group address is received for a predetermined period of time, and, if no layer-3 group address corresponding to the layer-2 group address is left as a result of deletion of the layer-3 group address, deleting the corresponding layer-2 group address from said table.

6. A multicast communication method in a center station or subscriber station which includes a first port for inputting a downstream packet and outputting a upstream packet, a second port for outputting a downstream packet and inputting a upstream packet, and a transfer control table for holding a layer-2 group address and layer-3 group address of a destination of a downstream multicast packet to be transferred from said first port to said second port, transfers a downstream multicast packet received from said first port to said second port only when a layer-2 group address of a destination of the downstream multicast packet is registered in said table, and discards the received packet if the layer-2 group address is not registered, thereby performing filtering to obtain only a multicast packet destined to a group address desired to be used for distribution by a subordinate terminal, comprising the steps of:

periodically transmitting multicast subscription state query messages from said second port, not transferring a multicast subscription request message received from said second port to said first port if a layer-3 group address corresponding to the subscription request has been registered in said table, transferring the subscription request message to said first port if the layer-3 group address has not been registered, registering the layer-3 group address corresponding to the subscription request in said table, and also registering a layer-2 group address corresponding to the registered layer-3 group address in said table if the layer-2 group address has not been registered in said table; and

when a multicast subscription state query message is received from said first port, acquiring layer-3 group addresses registered in said table without transferring the message to said second port, generating layer-3 multicast subscription request messages destined to the respective acquired layer-3 group addresses, and outputting the subscription request messages from said first port.

7. A method according to claim 6, further comprising the step of, when no multicast subscription request message destined to a layer-3 group address registered in said table is received from said second port for a predetermined period of time, deleting the corresponding layer-3 group address from said table, and, if no layer-3 group address corresponding to the layer-2 group address is left, deleting the corresponding layer-2 group address from said table.