JP2001036528A - Multipoint repeater for multipoint communication - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A terminal without a multicast packet transmission / reception function, a terminal connected via a low-speed line, a terminal without a token-linked rate control function, and can receive information other than the speaker. Be able to participate in multipoint communication. When performing multipoint communication using multicast, a terminal without a multicast function, a terminal connected via a low-speed line, and a terminal without a token interlocking rate control function are sent to a multipoint via a multicast relay device. Participate in communications.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an apparatus for realizing multipoint communication by three or more users on a communication network.
In particular, the present invention relates to a technology for assisting a function of a terminal participating in multipoint communication.

[0002]

2. Description of the Related Art (Multipoint Communication System) A communication system for exchanging information between persons at three or more remote locations is called a multipoint communication system. FIG.
FIG. 2 is a diagram illustrating a multipoint communication system. The function required for the multipoint communication system is a function for realizing information transmission and reception among three or more terminals on the assumption that any terminal can be a speaker terminal. Furthermore, it is desired that more multipoint communication can be realized with better quality by effectively utilizing the transmission path bandwidth of the network.

(Regarding the multicast function of the packet switching device) As a method for realizing a multipoint communication system, a method using a multicast function of a packet switching network such as an IP network can be considered. First, the multicast function of the IP network will be described.

The IP network is a network generally used as a communication means between computers, and a packet switching device called an IP router transfers packets.
In the IP network, each terminal is assigned an address called an IP address.

In order to enable a certain terminal to communicate with a plurality of terminals at the same time, a value called a port number is added to an address to form a logical address. FIG. 10 is a diagram illustrating packet communication using an IP network. FIG.
At 0, the terminal T1 and the terminal T4 are communicating, but the terminal T1 has an IP address of t1 and uses a port number of a for communication with T4, and the terminal T4 is at t4.
For communication with the terminal T1
Port number is used.

The terminal writes the logical address used by itself as the source address, writes the logical address used by the communication partner terminal as the destination address, and sends the packet to the IP router. The IP router identifies the destination address written in the packet and forwards the packet to an appropriate output port. As shown in FIG. 10, a wide area IP network is constructed by connecting a plurality of IP routers.

Many IP routers have a function of copying a packet and transferring the same packet to a plurality of destinations. This is called multicast. FIG. 11 is a diagram illustrating multicast transfer by an IP router. In this case, a multicast address is used as the destination address of the packet as shown in FIG.
A multicast address and a list of a plurality of packet transfer destinations corresponding to the multicast address are registered in the multicast group table of the IP router.

[0008] Upon receiving a packet whose destination address is a multicast address, the IP router transfers the packet to a packet transfer destination corresponding to the multicast address. Meanwhile, packet transfer from one terminal to one terminal is called unicast. A packet whose destination address is a unicast address is called a unicast packet, and a packet whose destination address is a multicast address is called a multicast packet.

FIG. 12 is a diagram for explaining a multicast function (realizing a mesh connection) of the IP network. Multicasting by a plurality of connected IP routers enables multicasting to a plurality of IP routers connected to a wide area IP network. A feature of the multicast by the IP network is that any terminal of the multicast group can be a transmission terminal. Such communication means between terminals will be referred to as a mesh connection channel.

(Multipoint Communication System Using Multicast Function of Packet Switching Network) It is considered that a packet switching apparatus having a multicast function can realize the aforementioned multipoint communication system. That is, when an IP router is used as the packet switching device, one mesh connection channel may be set for the multipoint communication group. FIG. 13 is a diagram illustrating multipoint communication using the multicast function of the packet switching network. Terminals T1, T2, T3,
When T4 performs multipoint communication, one multicast address for this multipoint communication is assigned.

The address is g1. Since information from each terminal is broadcast to the same multicast address, a port number is assigned to each terminal, and when each terminal broadcasts information, the port number assigned to itself is set as the destination. I will broadcast it. In the example of FIG. 13, a, b, and b are respectively assigned to terminals T1, T2, T3, and T4.
Port numbers c and d are assigned. An important feature of this method for the later description is that information from terminals other than the speaker is also broadcast by multicast, and each terminal can receive information other than the speaker.

The following problems and their solutions exist in the multipoint communication system using the multicast function. (1) Support for networks that do not allow multicast There are many networks that do not allow multicast communication due to reasons such as bandwidth management. A solution to this problem is MBone packet tunneling. FIG.
4 is MBone to a network that does not support multicast
FIG. 4 is a diagram for explaining the correspondence by packet tunneling. This is a terminal that supports multicast communication and L
This is a technique for solving a case where a relay network connecting an AN (Local Area Network) does not support multicast. In this method, MBo is connected to each connected LAN.
Ne router is installed. The MBone router provides a function of wrapping a multicast packet in a LAN with a unicast packet and transferring it to a relay network, thereby realizing multicast communication between LANs.

The points that should be noted as the differences from the present invention are as follows. In the MBone packet tunneling, the terminal needs to support multicast. (2) The problem that the required bandwidth is proportional to the number of participants In a TV conference or the like, images of all participants are transmitted to the network regardless of who is speaking. Therefore, the total amount of packets flowing in the network increases in proportion to the number of participants. As a technique for solving this problem, the present applicant has proposed a token-linked rate control method in Japanese Patent Application No. 11-046762. FIG. 15 is a diagram comparing a conventional multicast multipoint conference with a token-linked rate controlled multipoint conference. In this method, the allocation rate for multipoint communication is determined, and the information transmission rate allocation for each terminal is dynamically allocated on the condition that the sum of the information transmission rates from each terminal is equal to or less than the rate allocated for multipoint communication. Change to By updating the rate allocation so that the allocation rate of the speaker to the terminal increases in accordance with the change of the speaker, it is possible to increase the communication quality achievable under a certain rate constraint.

[0014] The applicant of the present invention filed Japanese Patent Application No. 11-0467.
No. 82 proposed a multipoint communication system that broadcasts only the speaker. FIG. 16 is a diagram illustrating a multipoint communication system in which only the speaker performs multicast broadcasting. This method is a method using multicast communication for relaying information between conference terminal devices, and is a method for multicasting only the speaker. In this method, a device called an edge device that transmits and receives information to and from each other by multicast communication is provided. The edge device transmits and receives information to and from the terminal by unicast, broadcasts information from the speaker terminal to another edge device by multicast communication, and transmits information received by multicast communication to the terminal. A point to be noted as a difference from the present invention is that, in this method, the information broadcasted by the multicast communication is only the information of the speaker, and the edge device selects and processes the data stream broadcasted by the multicast communication. Instead of delivering to terminals.

[0015]

The above-mentioned method of multicasting only the speaker does not require the terminal to have a multicast function, but broadcasts only information from the speaker. Even if a TV conference or the like is performed in this manner, only the image of the speaker is delivered and the user cannot grasp the appearance of other participants, so that the convenience is low. For this reason, it is desirable to realize multipoint communication in which information from terminals other than the speaker is also broadcast. However, a multicast communication system capable of receiving information from terminals other than the speaker has the following problems.

(Problem 1: A terminal without a multicast receiving function cannot participate in multipoint communication) Some terminals do not have a function of receiving a multicast packet. These terminals cannot participate in multipoint communication using the multicast function. This problem cannot be solved because packet tunneling using MBone also requires the terminal to have a multicast function.

(Problem 2: It is difficult for a terminal connected by a low-speed line to participate in multipoint communication)
As described above, in a TV conference or the like, image information is transmitted from all terminals, and image information from all terminals is distributed to each terminal. This is as shown in FIG.
For this reason, information of a rate equal to the number of conference participants multiplied by the stream rate per terminal arrives at the terminal.
However, some conference participant terminals participate in a conference through a low-speed continuous line such as ISDN. In order for such terminals to be able to participate in the multicast conference, the constraint is that the sum of the stream rates from all terminals will be less than or equal to the connection line speed, even if the token-linked rate control method described above is used. Need to do rate allocation. However, if the audio / video stream rate is set low in accordance with such a condition, the communication quality for other terminals that are not connected via a low-speed line will also deteriorate.

(Problem 3: It is difficult for a terminal that does not have a multicast packet transmission function or a token-linked rate control to participate in multipoint communication) A terminal that does not have a multicast packet transmission function uses the multicast function. Can not participate in the multipoint communication that was. In addition, many of the TV conference terminals that have already become widespread do not support token-linked rate control. These terminals cannot participate in multipoint communication that makes effective use of bandwidth with token-linked rate control.

Therefore, the present invention solves the above problems,
Enables terminals without multicast packet transmission / reception functions, terminals connected via low-speed lines, terminals without token-linked rate control functions, and multipoint communication that can receive information other than the speaker The purpose is to: This aims to increase the number of users who can participate in multipoint communication by multicast communication.

[0020]

The main feature of the present invention is to configure a device called a multicast relay device to solve the above problems 1, 2, and 3.

FIG. 17 is a diagram for explaining the realization of the participation of the terminal in the multipoint communication by the multicast relay device. FIG.
As shown in, when performing multipoint communication using multicast, terminals without a multicast function, terminals connected via a low-speed line, and terminals without a token interlocking rate control function, We will participate in communication. For the sake of explanation, a terminal participating in multipoint communication via a multicast relay device will be referred to as a relay connection terminal. However, as a usage form, there are cases where a terminal with a multicast function participates in multipoint communication via a multicast relay device as a relay connection terminal, such as when the terminal has a multicast function but is connected by a low-speed line. It is possible.

(Provision of Downstream Relay Function) When the relay connection terminal does not have the multicast reception function or is connected to the network through a low-speed line, the multicast relay device has the following characteristics. Provides functions. That is, the multicast relay device selects a data stream to be relayed by some means from the multicast stream addressed to the address assigned to the multipoint communication, receives the selected data stream, and converts the received data stream by unicast. Sent to the relay connection terminal. At this time, only the selected data stream is transferred. The following can be considered as a specific method for selecting a data stream to be transferred.

Method specified by terminal: A message indicating a stream to be received (stream selection message) is transmitted from the relay connection terminal to the multicast relay device. The multicast relay device selects the stream indicated in the stream selection message and transfers the stream to the relay connection terminal.

Method for transferring a speaker: A message (token control message) indicating a terminal having the floor has to be transmitted from a terminal (chair terminal) operated by the chairman of the multipoint communication. The multicast relay device receives the token control message, selects a data stream from a terminal having the floor, and transfers the data stream to the relay connection terminal.

When a plurality of terminals are participating in multipoint communication via one multicast relay device,
The stream to be transferred is selected independently for each terminal.

Further, as a part of the downstream function, the multicast relay device desirably has a means for rate-converting the received multicast stream in accordance with the connection line speed of the relay connection terminal, the reception capability of the relay connection terminal, and the like.

As a method of determining the target value of the rate conversion, the stream rate selection message may indicate the converted target rate, and the downstream conversion means may use this value as the target rate.

(Provision of Upstream Relay Function) When the relay connection terminal does not have a multicast transmission function or does not have a token interlocking rate control function, the multicast relay device provides an upstream relay function characterized by the following. I do. That is, the multicast relay device receives the data stream from the relay connection terminal by unicast, converts the rate of the received data stream, and sets the data stream after the rate conversion to the multicast address assigned to the multipoint communication. To be transmitted using a multicast packet. As a method of determining the target value of the rate conversion, a method is considered in which the multicast relay apparatus receives a message (rate allocation message) indicating the allocation rate for each terminal, and uses the value indicated by the message as the target rate.

The difference from the above-described method of multicasting only the speaker is that in the present invention, the data stream to be multicasted is not limited to the speaker only. The difference is that it is performed for each relay connection terminal. In addition, the aforementioned MBone
The difference from the tunneling method is that the terminal can transmit and receive information by unicast.

As a realization mode, the data stream relayed by the multicast relay device is not limited to audio and video, but may be another data stream relayed.

As a realization form, a multicast relay device having the characteristics of the present invention only for the downstream and a multicast relay device having the characteristics of the present invention only for the upstream can be considered.

(Device Configuration of Multicast Relay Device for Providing Downstream Relay Function) The features of the device configuration of the multicast relay device for providing the downstream relay function are as follows. That is,
The multicast relay device selects a stream to be transferred from a multicast stream addressed to the multicast address assigned to the multipoint communication (stream selecting unit), and receives a multicast stream selected by the stream selecting unit (multicast). Stream receiving means) and means for transmitting the received multicast stream to the relay connection terminal by unicast (unicast stream transmitting means).

It is desirable that the multicast relay device includes a means (stream message receiving means) for receiving a stream selection message from the relay connection terminal. It is assumed that the multicast relay device having this has a function of selecting the stream indicated in the received stream selection message by the stream selection means.

It is preferable that the multicast relay device includes a unit for receiving a floor right notification message (a floor right notification message receiving unit). It is assumed that the multicast relay device provided with this has a function of selecting the stream of the speaker indicated by the floor right notification message by the stream selecting means.

Further, it is preferable that the multicast relay device includes means for converting the rate of the received multicast stream (downstream rate conversion means). Further, in one implementation of the multicast relay device including the same, the stream selection message includes a target value for rate conversion, and the downstream rate conversion means performs rate conversion using the value indicated in the message as a target value. Function.

(Device Configuration of Multicast Relay Device for Providing Upstream Relay Function) The features of the device configuration of the multicast relay device for providing the upstream relay function are as follows. That is,
Means for receiving a data stream from a relay connection terminal by unicast (unicast stream receiving means), means for converting the received data stream (upstream rate converting means),
It is characterized by comprising means (multicast stream transmitting means) for transmitting a received data stream by means of a multicast packet addressed to a multicast address assigned to multipoint communication.

It is preferable that the multicast relay device has a means for receiving a message (rate assignment message) indicating the assigned rate to the terminal. The upstream rate conversion means of the multicast relay device provided with this has a function of setting the allocation rate to the relay connection terminal indicated by the rate allocation message as a target value for rate conversion.

It should be noted that the upstream function according to the present invention and the downstream function according to the present invention can be realized separately and independently, and the feature of the present invention is only for either the upstream or the downstream as a form of implementation of the multicast relay device. Is also conceivable.

(Operation of Downstream Relay Function) Multicast communication information distributed by multicast is transmitted to the relay connection terminal by unicast by the multicast stream receiving means and the unicast stream transmitting means. As a result, it becomes possible for the relay connection terminal to participate in a conference using multicast without having the multicast reception function. Furthermore, the stream selection means of the multicast relay device relays, to the relay connection terminal, only the data stream from the speaker terminal or the data stream from the terminal selected by the relay connection terminal, instead of the data stream from all terminals. Becomes possible. As a result, only the selected data stream flows on the connection line of the relay connection terminal.

That is, thanks to the data stream selection means, the restriction on the rate control of keeping the sum of the data stream rates from all the terminals below the connection line speed of the terminals is eliminated. The rate control condition is that the data stream rate of each terminal is equal to or less than the connection line and that the sum of the data stream rates from all terminals is equal to or less than the rate assigned to multipoint communication. Constraints are relaxed. In other words, the restriction on the band that occurs when a terminal connected via a low-speed line participates in multipoint communication is relaxed by the data stream conversion unit.

Further, since the data stream selection is performed independently for each relay connection terminal, the user of the relay connection terminal can select a data stream according to his / her own interest, and the receivable data stream is the information from the speaker. It is not limited to. In other words, the provision of the data stream selecting means solves the problem of the method of multicasting only the speaker, that is, the inability to grasp the state other than the speaker.

Further, when the rate of the data stream broadcast by the multicast communication is higher than the connection line speed of the relay connection terminal, the data stream rate is reduced to the connection line speed by the downstream rate conversion means. Thus, the data stream can be relayed. This eliminates the restriction on rate control that keeps the sum of the data stream rates from all terminals below the connection line speed of the terminals. The restriction on rate control is that the sum of the data stream rates from each terminal is equal to or less than the rate assigned to multipoint communication, and there is no terminal that participates through a low-speed connection line. Is the same. In other words, the restriction on the bandwidth caused by the terminal connected by the low-speed line participating in the multipoint communication is eliminated by the downstream rate conversion means.

(Operation of Upstream Relay Function) The unicast stream receiving means and the multicast stream transmitting means transmit the data stream generated by the relay connection terminal by unicast to the multicast stream addressed to the multipoint communication. . As a result, the relay connection terminal having no multicast transmission function can participate in multipoint communication by multicast. Further, the upstream rate conversion means converts the rate of the data stream issued by the relay connection terminal with the target rate set for the relay connection terminal indicated by the rate allocation message. As a result, a terminal without a token-linked rate control function can also participate in multipoint communication by token-linked rate control.

When the multicast relay device provides both the downstream relay function and the upstream relay function, the relay connection terminal can participate in the multipoint communication using the multicast even if it has only the unicast function. It becomes possible.

That is, a user having a unicast terminal can participate in multicast multipoint communication without having to change the device for multicast multipoint communication.

[0046]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a multicast relay apparatus for multipoint communication according to an embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a diagram showing a device configuration of a multicast relay device according to an embodiment of the present invention.

The present invention relates to a multicast relay apparatus for multipoint communication. The feature of the present invention is that, as shown in FIG. 1, a multicast address assigned to a multipoint communication is set as a destination address. A stream selecting means 1 for selecting a data stream to be received from a data stream of packets, a multicast stream receiving means 2 for receiving the data stream selected by the stream selecting means 1, and a data stream received by the multicast stream receiving means 2. There is provided a unicast stream transmitting means 4 for converting a data stream of a multicast packet into a data stream of a unicast packet and transmitting the converted data stream to a data distribution destination terminal.

At this time, there is provided a stream selection message receiving means 9 for receiving a message including the data stream information desired to be received from the data distribution destination terminal. Select the data stream desired to be received by the data distribution destination terminal corresponding to each data distribution destination terminal.

Also, there is provided a token control message receiving means 8 for receiving a message indicating the speaker terminal, and the stream selecting means 1 selects a data stream from the speaker terminal indicated by the message indicating the speaker terminal. You can also.

Further, there is provided downstream rate conversion means 3 for converting the transmission rate of the data stream.

At this time, the downstream rate conversion means 3 can also convert the transmission rate according to the rate conversion request transmitted from the distribution destination terminal.

The above is the configuration for processing the downstream. Next, the configuration for processing the upstream will be described.

As shown in FIG. 1, a configuration for processing an upstream includes a unicast stream receiving means 7 for receiving a data stream of a unicast packet transmitted from a data distribution destination terminal, and a unicast stream receiving means. Means 7 for converting a unicast packet of the data stream received by step 7 into a packet addressed to the multicast address assigned to the multipoint communication, and transmitting the data stream of the converted and generated multicast packet. 5 is provided.

At this time, there are provided a rate assignment message receiving means 10 for receiving a message indicating an assignment rate for each terminal participating in the multipoint communication, and an upstream rate conversion means 6 for converting a data stream transmission rate. Stream rate conversion means 6
Converts the transmission rate according to the message indicating the assigned rate.

In FIG. 1, the interface of the relay connection terminal example and the interface of the multicast terminal side are separately provided, but in an actual implementation example, these interfaces may be realized by the same physical interface.

Next, the operation of the multicast relay device for multipoint communication according to the embodiment of the present invention will be described. FIG. 2 shows a system configuration in the embodiment of the present invention. In this embodiment, the terminals T1, T2, and T3 are terminals having a multicast function, and the terminals T4 and T5 are not provided with a multicast transmission / reception function or a token interlocking rate control function.
It is a terminal connected by a line with a low speed of bps. The multicast relay device provides both the downstream relay function and the upstream relay function according to the present invention.

FIG. 3 is a diagram showing a protocol stack for transmitting and receiving voice / image information between the terminals T4 and T5. The relay connection terminals (T4, T5) transmit and receive information using the protocol stack shown in FIG. That is, the terminal has a function of transmitting and receiving voice and image streams packetized by RTP using UDP / IP packets. At this time, audio and video are transmitted and received using different UDP / IP packets.

FIG. 4 shows the format of a stream selection message. A stream selection message is generated in the message format shown in FIG.
A stream selection message is sent to the multicast relay device by P / IP. The relay connection terminal continuously transmits and receives images and voices by unicast to and from the multicast relay device, and sends a stream selection message to the multicast relay device when a user inputs a stream selection command.

Terminals other than the relay connection terminal also transmit and receive voice and images using the same protocol stack as the relay connection terminal.
The terminal used by the chair (chair terminal) has the function of sending a token control message. FIG. 5 is a diagram showing a protocol stack of the chair terminal. FIG. 6 is a diagram showing a format of the token control message. The protocol stack in this case is as shown in FIG. 5, and the token control message of the format shown in FIG. 6 is transmitted by UDP / IP. As shown in FIG. 6, in the present embodiment, the token control message also includes the rate assigned to the multipoint communication participating terminal, also serving as the rate assignment message. At this time, the destination address is a multicast address assigned to the multipoint communication, and the port number is a port number assigned for token control. The chair terminal sends a token control message when the chair user inputs a command specifying the speaker.

FIG. 7 is a diagram showing a protocol stack of the multicast relay device. The multicast relay device transmits and receives information according to the protocol stack shown in FIG. That is, audio and images are restored up to the RTP layer,
The packet is retransmitted by a UDP / IP packet having another destination address. The multicast relay device has a function of receiving a token control message and a function of receiving a stream selection message. The multicast relay device has a control parameter table shown in Table 1 as means for storing operation settings.

[0061]

[Table 1] That is, for each relay connection terminal to which the relay function is provided,
Downstream information and upstream information are to be stored, and the downstream and upstream information elements include a transmission address, a port number,
The receiving address, port number, and rate are stored. For explanation, the unicast address / port number for downstream transmission is AddrUniSend, and the multicast address / port number for downstream reception is AddrMultiR.
ecv, the downstream rate is represented as RateDown, the multicast address / port number for upstream transmission is AddrMultiRecv, the unicast address / port number for upstream reception is AddrUniSend, and the upstream rate is RateUp.

The multicast relay apparatus sets RateUp as the target rate for the upstream, and
Convert the stream rate using RateDown as the target rate. A plurality of specific methods of rate conversion can be considered, but a method of thinning out information on a frame basis is considered as a simple mounting method. The marker bit of the RTP header is 1 in the last packet of the frame. By utilizing this, it is possible to realize the information thinning in a frame unit. That is, each time a packet having a marketbit of 1 in the RTP header arrives, the rate conversion means determines whether to discard or forward the subsequently arriving packet, and discards or forwards the arriving packet based on this determination. The discard or transfer may be determined by determining the frame rate based on the average information amount per frame and the target rate, and based on this frame rate. For example, a target rate of 32 kbps is a 128 kbps image having an information amount per frame of 12.8 kbit and a frame rate of 10 frames per second.
In the case of rate conversion as above, discarding 3 frames and transferring 1 frame may be repeated with a cycle of 4 frames.
In this embodiment, audio is transferred without rate conversion. As another implementation example, it is conceivable to reduce the rate by temporarily decoding and re-encoding the audio and the image.
In this case, the voice can also be rate-converted.

FIG. 8 shows the operation of the multicast relay device. FIG. 8 is a flowchart showing the operation of the multicast relay device. First, at the time of activation, a unicast transmission / reception address, a multicast transmission address, a stream selection message reception address, and a token control message reception address are set, and a packet reception wait is started. When the token control message is received, the multipoint communication is identified from the multipoint communication address in the message, and AddrMultiRecv for the relay connection terminal participating in the multipoint communication is changed to the port number of the speaker.
Also, RateUp for the relay connection terminal participating in the multipoint communication is updated based on the assigned rate information in the token control message. When a stream selection message is received, it is determined which relay connection terminal is sent from the sender address of the message, the AddrMultiRecv for the relay connection terminal is changed to the specified address, and RateDown is set to the specified rate. Update to It should be noted that whenever AddrMutliRecv is changed, the multicast packet reception wait is reset each time.
When a packet is received at the multicast waiting address, a search is made for a relay connection terminal with the multicast address and the port number of the received packet set to AddrMultiRecv, and for each relay connection terminal, selective discard of the packet and transmission of a unicast packet . At this time, selective discarding of packets is performed with RateDown of each relay connection terminal as a target rate, and transmission of unicast packets is performed with AddrUniSend of each relay connection terminal as a destination. If a packet is received with a unicast listening address, search for a terminal with the destination address and port number of the received packet as AddrUniRecv, select and discard the packet with RateUp for the relay connection terminal as the target rate, and forward it. The packet is transmitted as a multicast packet having AddrMultiSend for the relay connection terminal as a destination address.

In the implementation example, the audio and the image are separated from each other by UD.
Although transmitted / received as P / IP packets, the multicast relay device transfers the packet with the port number for audio when receiving the packet with the port number for audio, and transfers the packet with the port number for image when receiving the packet with the port number for image. It is assumed that packets are transferred by number.

As another embodiment, a form in which the multicast relay device provides only the upstream function according to the present invention can be considered. In this embodiment, the relay connection terminal directly receives the multicast stream issued by another terminal, but transmits the stream to the multicast relay device by unicast. This mode is useful when the relay connection terminal has a multicast function but does not have a token-linked rate control function.

As another embodiment, a form in which the multicast relay device provides only the downstream function according to the present invention can be considered. In this embodiment, the relay connection terminal transmits a stream by multicast, but receives a stream through a multicast relay device. This mode is useful when the relay connection terminal has a multicast function and a token-linked rate control function, but is connected to the network via a low-speed line.

[0067]

As described above, the multicast relay apparatus for multipoint communication according to the present invention can also be applied to terminals having no multicast function, terminals connected via a low-speed line, and terminals not having a token interlocking rate control function. It is possible to participate in multipoint communication by multicast communication. That is, according to the present invention, the number of users who can participate in multipoint communication by multicast communication can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a multicast relay device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a system configuration according to an embodiment of the present invention.

FIG. 3 is a diagram showing a protocol stack for transmitting / receiving audio / image information of terminals T4 and T5.

FIG. 4 is a diagram showing a format of a stream selection message.

FIG. 5 is a diagram showing a protocol stack of a chair terminal.

FIG. 6 is a diagram showing a format of a token control message.

FIG. 7 is a diagram showing a protocol stack of the multicast relay device.

FIG. 8 is a flowchart showing the operation of the multicast relay device.

FIG. 9 illustrates a multipoint communication system.

FIG. 10 is a diagram illustrating packet communication using an IP network.

FIG. 11 is a diagram illustrating multicast transfer by an IP router.

FIG. 12 is a diagram illustrating a multicast function (realizing a mesh connection) of the IP network.

FIG. 13 is a view for explaining multipoint communication using a mesh connection channel.

FIG. 14 is a diagram illustrating an MB to a non-multicast network.
The figure explaining the correspondence by packet tunneling of one.

FIG. 15 is a diagram comparing a conventional multicast multipoint conference with a token-linked rate-controlled multipoint conference.

FIG. 16 is a diagram illustrating a multipoint communication system in which only a speaker performs multicast broadcasting.

FIG. 17 is a view for explaining the realization of multipoint communication participation of a relay connection terminal by a multicast relay device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stream selection means 2 Multicast stream reception means 3 Downstream rate conversion means 4 Unicast stream transmission means 5 Multicast stream transmission means 6 Upstream rate conversion means 7 Unicast stream reception means 8 Token control message reception means 9 Stream selection message reception means 10 Rate allocation message receiving means T1 to T4 Terminal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K030 HA08 HB11 LD04 LD05 LD06 LD08 9A001 CC02 CC09 CZ04 JJ12 JJ18 JZ23

Claims (7)

[Claims] 1. A means for selecting a data stream to be received among data streams of a multicast packet having a multicast address assigned to a multipoint communication as a destination address, and a data stream selected by the selecting means. Means for receiving; means for converting a data stream of a multicast packet received by the means for receiving into a data stream of a unicast packet; and a data stream converted to a unicast packet by the means for converting. Transmitting means for transmitting data. Multicast relay device for multipoint communication. 2. A method for receiving a message including data stream information desired to be received from the data distribution destination terminal, wherein the selecting means determines whether each data distribution destination terminal is in accordance with the desired data stream information. 2. The multicast relay device for multipoint communication according to claim 1, further comprising means for selecting a data stream desired to be received for each data distribution destination terminal. 3. The apparatus according to claim 1, further comprising means for receiving a message indicating the speaker terminal, wherein said selecting means includes means for selecting a data stream from the speaker terminal indicated by the message.
The multicast relay device for multipoint communication according to the above. 4. The multicast relay device for multipoint communication according to claim 1, further comprising means for converting a transmission rate of the data stream. 5. The multicast relay device for multipoint communication according to claim 4, wherein said converting means includes means for converting a transmission rate in accordance with a rate conversion request transmitted from a data distribution destination terminal. 6. A means for receiving a data stream of a unicast packet transmitted from a data source terminal, and a unicast packet of the data stream received by the receiving means assigned to multipoint communication. A multicast relay device for multipoint communication, comprising: means for converting an address into a packet having a destination; and means for transmitting a data stream of a multicast packet generated by the converting means. 7. A system comprising: means for receiving a message indicating an assigned rate for each terminal participating in multipoint communication; and means for converting a transmission rate of a data stream, wherein the converting means includes a message indicating the assigned rate. 7. The multicast relay device for multipoint communication according to claim 6, further comprising means for converting a transmission rate according to the following.