JP2000278657A - Multicast method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent plural reports reporting the same multicast address from being sent to a multicast router by permitting private modem to receive a packet having information showing that the packet is sent to it itself among packets arrived from a cable television network. SOLUTION: Private modem 13 connects a cable television network 15 and a private network 17 and repeats data. Private modem 13 has a first multicast address table for holding what kind of host group exists in a connected private network 17-side and a second multicast address table holding which report message from what kind of host group is received against an inquiry message from a multicast router 12. Private modem 13 receives a packet having information showing that the packet is sent to it itself among packets for cable television network, which are arrived from the cable television network 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicast method in a system for communicating Internet Protocol (IP) packets using a cable television network.

[0002]

2. Description of the Related Art In recent years, the use of the Internet has begun to permeate not only businesses but also households. However, the connection to the Internet at home is usually made by using a public telephone network to connect to each Internet service provider, and the line speed is only tens of kilobits per second at most. Also, in order to connect by telephone, it is necessary to pay a telephone fee separately from the fee paid to the Internet service provider.

As one method of solving the above, a system (cable modem system) for transmitting IP packets transparently using an existing cable television network has been proposed, and some of them have begun to be put into practical use. By using a cable television network, a high-speed line speed can be obtained, and there is no need to pay telephone charges.

[0004] In IP, unicast to be transmitted to individual destinations, broadcast to be transmitted to all destinations, and multicast to be transmitted to arbitrary plural destinations are defined. In terms of full support of IP communication and effective use of lines, it is important to enable multicast communication transparently even in a cable modem system.

First, a generally used method for multicast communication will be described. In IP, the first 4 bits of a 32-bit IP address of 1110 are assigned for multicast, and are called class D addresses. This corresponds to 224.0.0.0 to 239.255.255.255. One class D address corresponds to one host group, and an IP packet destined for a certain class D address is transmitted to all hosts belonging to the host group.

[0006] When a multicast-capable router (multicast router) receives a multicast packet, it transmits the packet to a connected sub-network. In this case, it is not efficient to relay the multicast packet to a subnetwork where no host receives the multicast packet. Therefore, in order to relay the multicast packet only to the subnetwork where the host receiving the multicast packet exists, the multicast router needs to know which host of the connected subnetwork belongs to which host group.

According to the Internet Group Management Protocol (IGMP) described in RFC 1122, a multicast router periodically sends a query message (Query).
To find out what host groups each host on the subnetwork comprises. This Query
Is sent to all host groups (224.0.0.1). The TTL (Time to Live) field of the IP header is set to 1 so that the query closes within the subnetwork. Each host on the subnetwork reports all host groups on the interface that received the query in response to this Query, and reports the report message (Report).
Report using In this case, all hosts
If you respond immediately to the ery, network traffic can be very high, and RFC1122 offers two solutions to address this.

[0008] 1. The host receiving the query starts a timer using a random number for each host group to which the interface that has received the query belongs. A Report is sent when each timer expires.

[0009] 2. The report destination IP address is the same as the class D address of the host group of the report content. As a result, each host can intercept a Report from another host belonging to the same host group. If such a Report is intercepted before the timer expires, the host stops the timer and stops sending reports for that host group. Also, the TTL of the IP header of the report is set to 1 so that the report is closed in the sub-network.

No report is created for all host groups (224.0.0.1).

[0011] "Data-Over-Cable Service Interface Specificati", an industry standard for cable modems in the United States
ons, Radio Frequency Interface Specification "and" Radio Frequency (RF) Interface Management Infor
According to the “MIME Base (MIB)”, a management server is placed on the cable television station side, and the management server notifies each home modem of the destination address of the IP packet to be relayed. Multicast (class D) address Are also notified to the home modems by the management server, and each home modem has an IP address having the notified multicast address.
When a packet including a P packet is received from the cable television network, the packet is transmitted to the connected home network.

[0012] The management server intercepts the exchange of IGMP between the user terminal and the multicast router, and holds a combination of the identifier of the home modem and the multicast address. One cable modem system includes thousands to tens of thousands of home modems, and the management server manages multicast addresses for all of them. You need to build a server. Also, due to centralized management on the management server, if the management server fails,
Multicast cannot be performed in the entire system.

[0013]

According to the present invention, in the cable modem system, when the management server manages the multicast address, the load on the management server becomes extremely large, and a high-performance and expensive management server is required. In consideration of the problem that the management server becomes centralized and multicasting cannot be performed in the entire system when the management server fails due to centralized management by the management server, an expensive management server is required even if there are many home modems. It is another object of the present invention to provide a multicast method in which the multicast communication of the entire system is not stopped even when the management server fails.

Further, as described above, in IGMP, in order to reduce the traffic volume and the load on the multicast router, two or more Reports that report the same multicast address for one Query. Avoid being reported as much as possible. In the cable modem system, communication between the in-home modems may be restricted in consideration of the fact that each in-home modem is placed in a general home. In this case, the user terminal connected to the home modem cannot intercept a report from another user terminal connected to another home modem, and a plurality of reports reporting the same multicast address are sent to the multicast router.

According to the present invention, in the above cable modem system, in consideration of the problem that a plurality of reports reporting the same multicast address are transmitted to the multicast router, a plurality of reports reporting the same multicast address are transmitted to the multicast router. It is an object of the present invention to provide a multicast method for preventing such a situation.

[0016]

In order to solve the above-mentioned problems, a first invention (corresponding to claim 1) is to provide an Internet protocol packet in data communication using a cable television network with a plurality of destinations. A multicast method for transmitting to the cable television network, a line controller and a plurality of home modems are connected, the line controller is connected to a center network, and the home modems are each connected to a home network. The line control device, if the Internet Protocol packet is a multicast Internet Protocol packet, including the Internet Protocol packet, generates a cable television network packet having information indicating that it is addressed to all home modems, To the cable TV network, and the home modem Among cable television network packet arriving from Bull television network, a multicast method characterized by receiving the cable television network packet having information indicating that it is their destined.

Further, the second invention (corresponding to claim 2) provides:
What is claimed is: 1. A multicast method for transmitting an Internet protocol packet in a data communication using a cable television network to an arbitrary plurality of destinations, wherein a line controller and a plurality of home modems are connected to the cable television network. Is connected to the home network, each of the home modems is connected to the home network, and the line control device, upon receiving an Internet protocol packet from the center network, notifies that one or more home modems are addressed. And generating a packet for the cable television network having information indicating the information and transmitting the packet to the cable television network. The in-home modem transmits an Internet protocol packet received from the in-home network connected to the in-home modem to a report of the Internet group management protocol. Observe if it ’s a message If the report message, the multicast address reported in the report message is recorded, if the destination address of the Internet Protocol packet included in the cable TV network packet received from the cable TV network is a multicast address, the multicast A multicast method, wherein the Internet protocol packet is transmitted to a home network only when the address is an address recorded by the home modem.

A third aspect of the present invention (corresponding to claim 3) is:
What is claimed is: 1. A multicast method for transmitting an Internet protocol packet in a data communication using a cable television network to an arbitrary plurality of destinations, wherein a line controller and a plurality of home modems are connected to the cable television network. Is connected to an in-center network, the in-home modems are each connected to an in-home network, and the line control device sends a cable television network packet received from the cable television network to the in-center network as the Internet protocol packet. The home modem sends the Internet Protocol packet received from the home network to the cable TV network as a cable TV network packet, and the home modem or the line control device respectively transmits the home network or the cable TV network. Received from If packet is a report message Internet Group Management Protocol, a multicast method, wherein the report message is sent to the report message not overlap.

A fourth aspect of the present invention (corresponding to claim 4) is:
If the Internet protocol packet received from the home network is a report message of the Internet Group Management Protocol, the home modem does not duplicate the report message reported through itself.
The multicast method according to the third aspect of the present invention is characterized in that the line control device having received the message does not duplicate the report messages reported from each home modem.

A fifth aspect of the present invention (corresponding to claim 5) is:
If the packet received from the cable television network is a report message of the Internet Group Management Protocol, the line control device transmits the report message after receiving an inquiry message corresponding to the report message from the center network. The third or fourth invention, wherein the report message is sent to the network in the center only when the reported multicast address is the first multicast address received, so that the report message is not duplicated. Is a multicast method described in 1.

A sixth aspect of the present invention (corresponding to claim 6) is:
If the packet received from the home network is an Internet Group Management Protocol report message, the home modem may send an Internet Group Management Protocol inquiry message corresponding to the report message included in the cable TV network packet from the cable TV network. Transmitting the report message to the cable television network only when the multicast address reported in the report message is the first multicast address received since receiving the report message so that the report message is not duplicated. The multicast method according to the third or fourth invention, characterized in that:

[0022]

FIG. 1 is an example of a communication system to which the present embodiment is applied. Reference numeral 11 denotes a line control device which connects to the center network 14 and the cable television network 15 and relays data. The line control device 11 has a multicast address table that holds the report from which host group the query has been received from the multicast router 12. A multicast router 12 connects the external network 16 and the center network 14 and relays data. Reference numeral 13 denotes a home modem, which is a cable television network 15.
And the home network 17 and relay the data. The home modem 13 has a first multicast address table for storing what host group is on the connected home network 17 side, and from what host group in response to the inquiry message from the multicast router 12 The second that holds whether the report message of the second is received
Of the multicast address table. Reference numeral 18 denotes a user terminal, which exchanges data with a server or the like existing in an external network 16 via a home network 17, a home modem 13, a cable television network 15, a line control device 11, a center network 14, and a multicast router 12. . Many home modems 13 are connected to the cable television network 15, and a plurality of user terminals 18 are connected to the home network 17.

Each of the above devices and each network constitutes an IP network. That is, it is assumed that there is an ability to exchange IP packets. The multicast router 12 and the user terminal 18 can exchange IGMP packets described in RFC1122. The in-center network 14 and the in-home network 17 are also assumed to be IEEE802.3 networks defined by the IEEE802.3 committee. The communication from the line controller 11 to the home modem 13 is “downstream”,
The communication from the network controller 11 to the line controller 11 is called “up”.

FIG. 2 shows a line controller 11 and a home modem 13.
2 shows a packet structure of a communication protocol used between the server and the server. This packet structure is common to the upstream and downstream. Each home modem 13 is assigned a unique address (32 bits). This address is called a cable address. The cable address system is independent of the IP address system used in the IP network. 3
A cable address in which all two bits are 1 is called a broadcast cable address, and a packet to which this cable address is assigned in the downstream is sent to all the in-home modems 13. Upstream packets must not have a broadcast cable address. The line control device 11 holds a set of a cable address of each in-home modem 13 and an IP address of a user terminal 18 connected to the in-home modem 13.

As shown at 21 in FIG. 2, a cable address is assigned to the head of each packet. The cable address indicates the source home modem 13 on the upstream and the destination home modem 13 on the downstream. Reference numeral 22 denotes a control field including the type and length of the packet. In the description of the present invention, "data" is sufficient as the packet type, but it is considered that there are other packet types used for checking the state of the in-home modem 13, adjusting the output level, and the like. It is not described here. The length indicates the length of the entire packet. When the type of the packet is “data” in the data section 23, the line controller 11 receives the packet from the center network 14 (in the case of downlink) or the home modem 13 receives the packet from the home network 17 (in the case of uplink). ), IEEE802.
Three frames are copied as they are. FIG. 2 shows an example.

FIG. 3 is a flowchart showing the operation of the line controller 11. The line controller 11 is the network 1 in the center.
It is observed whether or not an IEEE802.3 frame has been received from Step 4 (Step 1). If there is a reception, the destination IP address is observed and it is determined whether or not it is a broadcast address (step 2). If it is a broadcast address, the packet having the IEEE802.3 frame in the data section is generated such that the cable address is a broadcast cable address (step 6) and relayed to the cable television network 15 (step 7). In step 2, if the destination IP address is not a broadcast address, it is determined whether it is a multicast address (class D address) (step 3). If it is a multicast address, it is determined whether it is an IGMP Query (step 4). If not Query, proceed to Step 6. Q
If uery, the multicast address table is cleared (step 5), and the process proceeds to step 6. If it is not a multicast address in step 3, it is checked whether the IP address is registered (step 8), and a packet is generated using the cable address as the cable address corresponding to the destination IP address (step 9). ), And proceed to Step 7.

If there is no reception from the center network 14 in step 1, the line control device 11
To see if there is a packet from
1). If there is a received packet, its type is observed (step 12). If the type is other than "data", control packet processing is performed (step 18). The details of the control packet processing are out of the scope of the present invention, and a description thereof will be omitted. If the type is "data" in step 12, it is confirmed whether or not the IP packet included in the data portion is an IGMP Report (step 13). If not Report, IEEE802.
Only three frames are taken out and relayed to the center network 14 (step 16). If it is Report, it is confirmed whether the multicast address reported there is described in the held multicast address table (step 14). If not described, the multicast address reported in the Report is added to the multicast address table (step 15), and the process proceeds to step 16. If not, the packet is discarded (step 17).

FIG. 4 is a flowchart showing the operation of the home modem 13. The in-home modem 13 is the cable television network 1
Observe whether there is a packet from 5 (step 1). If there is a received packet, it is checked whether the cable address of the packet is its own cable address (step 2). If so, the type is confirmed (step 3). If the type is other than "data", control packet processing is performed (step 5). The details of the control packet processing are out of the scope of the present invention, and a description thereof will be omitted. If the type is "data" in step 3, the IEEE 802.3 frame included in the data portion of the received packet is relayed to the home network 17 (step 4).

If the cable address is not its own cable address in step 2, it is determined whether it is a broadcast cable address (step 6). If so, the type is confirmed (step 7). If the type is other than "data", go to step 5. If the type is "data", the IP packet included in the data part is IGMP
It is determined whether the query is a query (step 8). Que
If it is ry, the contents of the second multicast table are copied to the first multicast table (step 9), and the second multicast table is cleared (step 10).

If it is not a query in step 8, the IP
It is determined whether the address is held in the first multicast address table (step 1).
1). If so, an IEEE802.3 frame included in the data portion is extracted and relayed to the home network 17 (step 4). If the IP address is not held in step 11, it is determined whether or not it is a broadcast address (step 12). If it is a broadcast address, go to step 4. Otherwise, the received packet is discarded (step 13).

If there is no reception from the cable television network 15 in step 1, it is determined whether there is reception from the home network 17 (step 14). If there is a received IEEE802.3 frame, it is determined whether it is an IGMP Report (step 15). If it is Report, it is checked whether the reported multicast address is included in the second multicast address table (step 1).
6) If not included, add the multicast address to the second multicast address table (step 17). In step 15, if the received IEEE802.3 frame is not Report, the IEEE802.3 frame is used as a data portion, and a packet whose type is data and whose cable TV address is its own cable TV address is generated. 15 (step 18). If the multicast address of the report is described in the second multicast address table in Step 16, the frame is discarded (Step 1).
9). At step 15, the received IEEE802.3 frame is
If not t, proceed to step 18 for the cable television network 1
Relay to 7.

As described above, in the present embodiment, each home modem 13 is connected to the multicast router 12 and the user terminal 1.
By observing the exchange of IGMP packets between the eight,
The multicast packet can be filtered by the home modem 13 without the intervention of the management server. In addition, the line controller 11 and the in-home modem 1
No. 3 discards reports other than the first one when two or more reports reporting the same multicast address are observed for the same Query. As a result, an increase in traffic due to IGMP packets and a processing load on the multicast router 12 in the intra-center network 14 and the cable television network 15 are reduced.

In the present embodiment, the line controller 11 adds the cable address to the IEEE802.3 frame from the center network 14 and transmits the frame to the cable television network 15, but without adding the cable address, May be sent. In this case, the line controller 11 does not broadcast the multicast packet to the in-home modem 13.
In this case, each home modem 13 is connected to the cable TV network 15.
It is determined whether or not a multicast packet is included in the packet for the cable television network from the server. If the packet is a multicast address, the packet is received once, and the processing after step 8 in FIG. 4 is performed. By doing so, the processing load on the in-home modem 13 slightly increases, but the processing load on the line controller 11 decreases.

[0034]

As is apparent from the above description, according to the present invention, the load on the management server can be reduced, and a high-performance and expensive management server can be eliminated. It is possible to provide a multicast method capable of avoiding a situation where multicast communication cannot be performed.

Also, it is possible to provide a multicast method capable of reducing the increase in traffic due to IGMP packets and the processing load on the multicast router.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a cable modem system to which an embodiment of the present invention is applied;

FIG. 2 is a diagram illustrating a packet format on a cable television network used in the embodiment of the present invention;

FIG. 3 is a flowchart showing the operation of the line control device according to the embodiment of the present invention;

FIG. 4 is a flowchart showing the operation of the home modem according to the embodiment of the present invention;

[Brief description of reference numerals]

 DESCRIPTION OF SYMBOLS 11 Line control apparatus 12 Multicast router 13 Home modem 14 Center network 15 Cable TV network 16 External network 17 Home network 18 User terminal

Claims (6)

[Claims] 1. A multicast method for transmitting an Internet Protocol packet in data communication using a cable television network to a plurality of arbitrary destinations, wherein a line controller and a plurality of home modems are connected to the cable television network. The line controller is connected to a center network; the home modems are each connected to a home network; the line controller includes the Internet protocol packet if the Internet protocol packet is a multicast Internet protocol packet; A cable television network packet having information indicating that the packet is destined for all the home modems is generated and transmitted to the cable television network. The home modem includes a cable television network packet arriving from the cable television network. Be addressed to yourself Multicast method characterized by receiving the cable television network packet having information indicating a. 2. A multicast method for transmitting an Internet protocol packet in a data communication using a cable television network to a plurality of arbitrary destinations, wherein a line controller and a plurality of home modems are connected to the cable television network. The line controller is connected to an in-center network; the in-home modems are each connected to an in-home network; the line controller is configured to receive one or more in-home modems upon receiving an Internet Protocol packet from the in-center network. A packet for a cable television network having information indicating the destination is generated and transmitted to the cable television network. The in-home modem transmits an Internet protocol packet received from the in-home network connected to the in-home modem to the Internet. Group management protocol report message Observe whether the message is the report message, and record the multicast address reported in the report message. If the destination address of the Internet Protocol packet included in the cable television network packet received from the cable television network is the multicast address In some cases, the Internet protocol packet is transmitted to the home network only when the multicast address is an address recorded by the home modem. 3. A multicast method for transmitting an Internet protocol packet in a data communication using a cable television network to a plurality of arbitrary destinations, wherein a line controller and a plurality of home modems are connected to the cable television network. The line controller is connected to a network in a center, the home modems are each connected to a home network, and the line controller is a cable for a cable television network received from the cable television network as the Internet protocol packet in the center. The home modem transmits the Internet protocol packet received from the home network to the cable TV network as a cable TV network packet, and the home modem or the line control device is connected to the home network, respectively. Or the cable tele When the packet received from the network is a report message of the Internet Group Management Protocol, the report message is transmitted without duplicating the report message. 4. The home modem, when the Internet protocol packet received from the home network is an Internet Group Management Protocol report message, prevents the report message reported through itself from being duplicated, and receives the received report message. 4. The multicasting method according to claim 3, wherein the line controller does not duplicate the report messages reported from each of the home modems. 5. When the packet received from the cable television network is a report message of the Internet group management protocol, the line control device may determine whether the inquiry message corresponding to the report message from the network in the center is received. Transmitting the report message to the center network only when the multicast address reported in the report message is the first multicast address received, so that the report message is not duplicated. Item 3. The multicast method according to Item 3 or 4. 6. The in-home modem, when the packet received from the in-home network is an Internet group management protocol report message, the Internet group corresponding to the report message included in the cable television network packet from the cable television network. By transmitting the report message to the cable television network only when the multicast address reported in the report message is the first multicast address received since receiving the query message of the management protocol, the report message is duplicated. 5. The multicast method according to claim 3, wherein the multicast method is not performed.