JP2000332751A - Method for broadcasting communication and recording medium wherein broadcasting communication program is recorded - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable all client computers to receive information sent from a server computer by multicasting by dividing respective client computers as transmission destinations into multicast groups, according to receiving capacity information and broadcasting requested information by using transfer rates which are independent of one another by the multicast groups. SOLUTION: A server computer 10 takes reception information inputted from each client computer 12 into account and divides the client computers 12 into multicast groups. For example, when client computers 12(C1) and 12(C2) have low receiving capacity and client computers 12(C3) and 12(C4) have high reception capacity, the client computers 12(C1) and 12(C2) are put in a multicast group (1) with a relative low transfer rate to transfer information, and the client computers 12(C3) and 12(C4) are put in a multicast group (2) with a relatively high transfer rate to transfer the information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcast communication method and a recording medium on which a broadcast communication program is recorded. The broadcast communication method according to the present invention is used for performing a general client-driven information delivery service such as WWW (World Wide Web) or FTP (File Transfer Protocol) in a client / server data communication system. It is used for transfer rate control when broadcasting (multicast communication) is performed from a server computer to a large number of client computers. As a method of delivering information, there are generally unicast and multicast. In the case of unicast, data is delivered from the transmission side to one specific user. In the case of multicast, a plurality of users are defined as a multicast group, and data is simultaneously delivered to all users belonging to this multicast group. The recording medium on which the broadcast method and the broadcast program of the present invention are recorded assumes only multicast communication.

[0002]

2. Description of the Related Art Conventionally, there are two types of information transfer services for multicast transmission as follows. In the first service mode, the server computer prepares a multicast group in advance. Then, each client computer performs an operation to enter a multicast group prepared by the server computer, so that the client computer is registered in the server computer as a target of multicast transmission.

In the second service mode, when a plurality of client computers make a request for transmission of the same information to a server computer, the server computer issues a request for transmission of the same information to the plurality of client computers each time. Is assigned to a multicast group, and data transmission to the plurality of client computers is performed by multicast.

In the first service mode, for example, a data transfer amount (transfer rate) per unit time for a multicast group is determined in advance by a server. In this method, the multicast group is fixed without regard to the receiving capability of each client computer, and the server computer performs multicast transmission at a constant transfer rate. The method of fixing the transfer rate in this way is effective when the contents to be multicast-transmitted are predetermined and a high transfer rate is not required.

In the first service mode, a method is also known in which a plurality of multicast groups are prepared in advance in a server computer, and independent different transfer rates are determined for each multicast group. According to this method, when the data amount of the transmission content is large, a client computer having a high receiving ability can efficiently receive data by selecting a multicast group having a high transfer rate. In addition, a client computer having a low receiving ability can receive all data by selecting a multicast group having a low transfer rate. In this case, the transfer rate for each client computer is determined by a user's multicast group selection operation.

In the present invention, a second service mode is assumed in which a server computer side dynamically creates a multicast group based on an information transfer request from a client computer. In the second service mode, conventionally, the difference in the receiving capability of each client computer has not been considered.

[0007]

When a single multicast communication path is used, there is a problem that a client computer having a lower receiving capacity than a transfer rate specified for the communication path cannot receive the multicast communication. In order to enable all the client computers to receive the multicast communication, the transfer rate may be determined according to the client computer having the lowest reception capability among all the client computers belonging to the multicast group. However, in that case, there is a problem that a client computer having a high receiving ability cannot exhibit the receiving ability.

When a plurality of multicast communication paths having different transfer rates are prepared in advance, the number of client computers belonging to each multicast group varies, so that the bandwidth of the entire communication path is effectively used. There is a problem that it is not available. For example, 1
Assuming that 0 client computers are connected to the server computer, 1 out of 10 client computers
When only one unit has a very high receiving capacity, if one independent multicast communication path is assigned to one client computer with a high receiving ability, only one client computer occupies most of the bandwidth of the communication path. Therefore, the bandwidth of the communication path that can be used by the remaining nine client computers is reduced, and the utilization efficiency of the bandwidth is deteriorated.

According to the present invention, there is provided a broadcast communication method for performing multicast transmission in the second service mode and a recording medium on which a broadcast program for realizing the same is recorded. An object of the present invention is to enable reception by all client computers having a reception capability and to effectively use the bandwidth of the entire communication path.

[0010]

A first aspect of the present invention utilizes a communication system in which a server computer and a plurality of client computers are connected to each other via a network capable of broadcasting, and responds to a request from the client computer. And transmitting the requested information to the plurality of client computers requested by the server computer. In the broadcast communication method, the server computer relates to the reception capability from each of the transmission target client computers. Receiving the receiving capability information, allocating the plurality of client computers to be transmitted to a plurality of multicast groups according to the receiving capability information that has been received, and transmitting the requested information using a transfer rate independent of each multicast group. Information transmission.

The receiving capability of the client computer corresponds to the amount of data that can be received by the client computer per unit time. This receiving capability is determined by factors such as the capacity of the memory device provided in the client computer and the performance of the CPU device. According to the first aspect, the server computer can know the receiving capability of the client computer from the receiving capability information received from the client computer. Further, the server computer distributes a plurality of transmission target client computers to a plurality of multicast groups according to the received reception capability information, so that it is possible to prevent the occurrence of a client computer that cannot receive the multicast transmission data from the server computer. .

That is, after allocating a plurality of client computers to a plurality of multicast groups in accordance with the reception capability information received, the transfer rate of each multicast group is changed to the client computer having the lowest reception capability belonging to the multicast group. If it is determined together, the client computer having the lowest receiving capability can receive the multicast transmission data.

Since the server computer can know the receiving capability of each client computer, it can distribute the client computers so that the number of multicast groups and the number of client computers belonging to each multicast group are optimized.

According to a second aspect of the present invention, in the broadcast method of the first aspect, the server computer arranges the receiving capability information of all the client computers to be transmitted in the order of their sizes, and then arranges the arranged receiving capability information group. At least one position in the middle is divided into a plurality of groups, and each of the divided groups is associated with the multicast group.

According to the second aspect, the reception capability information group arranged in the order of the size is divided into a plurality of groups at intermediate positions, so that the plurality of multicast groups are divided according to the magnitude of the reception capability. For example, the maximum reception capability information included in a multicast group having a low reception capability is smaller than the minimum reception capability information included in a multicast group having a high reception capability.

Therefore, since the difference between the maximum receiving ability and the minimum receiving ability is relatively small in each multicast group, the transfer rate of each multicast group should be close to the receiving ability of each client computer belonging to that group. Is possible. According to a third aspect, in the broadcast method of the second aspect, the server computer calculates difference information corresponding to a difference between adjacent reception capability information for each of the reception capability information arranged in the order of magnitude. The reception capability information group is divided into a plurality of groups at the position of the difference information specified according to the order of the size of the calculated difference information.

According to the third aspect, the reception capability information group is divided into a plurality of groups at the position of the difference information specified in accordance with the order of the size of the difference information, so that those having similar reception capabilities are assigned to the same multicast group. Can be. In other words, the difference between the pieces of reception capability information adjacent to each other is large at the position where the group is to be divided, so that the position to be divided can be specified by the size of the difference information. In addition,
As the difference information, a ratio (floor ratio) between adjacent reception capability information and a difference may be used.

According to a fourth aspect of the present invention, in the broadcast method according to the third aspect, when a plurality of pieces of difference information having the same size exist in the server computer, the difference is determined by a central position in the arrangement of the reception capability information group. It is characterized in that near difference information is preferentially selected. By preferentially selecting the difference information closer to the center position of the arrangement of the reception capability information group and dividing the group at the position of the selected difference information, the number of client computers belonging to each of the divided groups can be increased. Be even. Therefore, it is useful to efficiently use the bandwidth of the entire communication path.

According to a fifth aspect of the present invention, in the broadcast method of the third aspect, the server computer adds a value obtained by adding a transfer rate associated with the minimum reception capability information belonging to each of the divided groups to all the groups. The method is characterized in that the group is compared with the bandwidth of the network and the division of the group is repeated until the comparison result satisfies a predetermined condition. Claim 5 assumes a case where the transfer rate of each multicast group is associated with the minimum reception capability information belonging to that group. As long as the total transfer rate of each multicast group is within the network bandwidth, the division of the multicast group is repeated to increase the number of multicast groups within a range where transmission of all multicast groups can be performed simultaneously. The entire road bandwidth can be used efficiently.

A sixth aspect of the present invention uses a communication system in which a server computer and a plurality of client computers are connected to each other via a network capable of broadcasting, and the server computer responds to a request from the client computer. A recording medium storing a broadcast communication program for broadcasting requested information to a plurality of client computers that have made a request, wherein the broadcast communication program includes a server computer, A procedure for receiving reception capability information related to the reception capability from each client computer, and a server computer allocating to a plurality of multicast groups according to the reception capability information that has received a plurality of transmission target client computers, The server computer uses an independent transfer rate for each multicast group. The information requested Te characterized by comprising a step of transmitting broadcast.

When the server computer reads the broadcast program from the recording medium storing the broadcast program according to claim 6, the broadcast method according to claim 1 can be carried out on the server computer. According to a seventh aspect of the present invention, in the recording medium storing the broadcast program of the sixth aspect, the reception capability information of all the client computers to be transmitted is arranged in the broadcast program of the server computer in the order of their sizes. And dividing the arranged reception capability information group into a plurality of groups at at least one position in the middle thereof, and associating each of the divided groups with the multicast group.

The server computer reads the broadcast program from a recording medium storing the broadcast program according to claim 7 so that the server computer can implement the broadcast method according to claim 2. According to an eighth aspect of the present invention, in the recording medium storing the broadcast communication program according to the seventh aspect, the reception capability information adjacent to the reception capability information arranged in the order of the size is stored in the broadcast program of the server computer. Calculating the difference information according to the difference from the received information, and dividing the reception capability information group into a plurality of groups at the position of the difference information specified according to the order of the size of the calculated difference information. .

When the server computer reads the broadcast program from a recording medium on which the broadcast program of claim 8 is recorded, the server computer can implement the broadcast method of claim 3 on the server computer. According to a ninth aspect of the present invention, in the recording medium storing the broadcast program of the eighth aspect, when the broadcast program of the server computer includes a plurality of pieces of difference information having the same size, the reception capability information The method is characterized in that a procedure for preferentially selecting difference information closer to the center position of the group arrangement is provided.

When the server computer reads the broadcast program from the recording medium storing the broadcast program according to the ninth aspect, the broadcast method according to the fourth aspect can be performed on the server computer. According to a tenth aspect of the present invention, in the recording medium storing the broadcast program according to the eighth aspect, all the transfer rates associated with the minimum reception capability information belonging to each divided group are stored in the broadcast program of the server computer. And comparing the value added for the group with the bandwidth of the network and repeating the division of the group until the comparison result satisfies a predetermined condition.

The server computer reads the broadcast program from a recording medium on which the broadcast program of claim 10 is recorded, whereby the server computer reads the broadcast program.
Broadcast method can be implemented.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a recording medium storing a broadcast communication method and a broadcast communication program according to the present invention will be described with reference to FIGS. This form corresponds to all claims.

FIG. 1 is a flowchart showing processing of the server computer according to the embodiment. FIG. 2 is a flowchart showing the contents of the processing for determining the optimum transfer rate group. FIG. 3 is a block diagram illustrating a configuration example of a communication system. FIG. 4 is a block diagram showing a configuration example of a server computer and a client computer. FIG. 5 is a block diagram illustrating an example of a transfer rate of broadcast transmission according to the embodiment. FIG. 6 is a flowchart showing a modified example of the processing of the server computer. FIG.
FIG. 4 is a schematic diagram showing an example of an operation of determining a transfer rate group.

In this embodiment, it is assumed that a file distribution service is provided in a communication system as shown in FIG. The communication system shown in FIG.
0, four client computers 12, and a broadcast network 11 connecting them. Of course, the number of client computers 12 connected to the broadcast network 11 is changed as needed.

As the broadcastable network 11, an asymmetric network combining a satellite broadcast line and a point-to-point line, a CSMA / CDLAN, a CS
A bus type network such as MA / ACKLAN can be used. The broadcast capable network 11 is required to be able to broadcast at least in a direction from the server computer 10 to the client computer 12.

In this example, as shown in FIG. 4, a file distribution service (transmission) 21, a broadcast communication function 22, and a driver 23 are stored in the server computer 10 as software.
Is provided. A file distribution service (reception) is provided as software inside the client computer 12.
31, a broadcast communication function 32 and a driver 33 are provided.

The drivers 23 and 33 are connected to the server computer 1
0 and the client computer 12 are software for connecting to the broadcastable network 11, for example, UN
This is a functional element corresponding to a network device in an operating system such as IX. The broadcast functions 22 and 33 are software necessary for broadcast communication, and are functional elements corresponding to IP multicast in an operating system such as UNIX.

The file distribution service 21 is software for transmitting file data requested by the client, and the file distribution service 31 is software for receiving file data transmitted from the server. File distribution services 21 and 31
Corresponds to an FTP program in an operating system such as UNIX, for example.

When implementing the present invention, the broadcast method of the present invention and the broadcast program for implementing the method are incorporated in the broadcast function 22 of the server computer 10. The broadcast program is read from a recording medium such as a CD-ROM or a floppy disk, and is loaded into an internal memory of the server computer 10 and executed. The receiving capability of each client computer 12 is determined according to factors such as the capacity of a memory device included in the client computer 12 and the performance of a CPU device. The reception capability is the amount of data that can be received in a unit time.

By the way, as shown in FIGS. 5 and 9, for example, the receiving capability of the client computer 50 differs for each computer. In the example of FIGS. 5 and 9, each client computer 5
0 and the receiving capability of the server computer 51 are represented by the thickness of the pipe indicated by a virtual line, and the magnitude of the transfer rate is represented by the thickness of the thick arrow. In the example of FIG. 9, the reception capability of the two client computers 50 (C1, C2) is relatively low, and the other two client computers 50 (C3, C4)
The receiving ability of is high.

As shown in FIG. 9, when all four client computers 50 (C1, C2, C3, and C4) are assigned to the same multicast group and transmitted from the server computer 51 for multicast transmission, the reception capability is the lowest. It is necessary to determine the transfer rate below the transfer rate that the client computer 50 (C1) can tolerate, that is, the receiving capacity of the client computer 50 (C1).

Therefore, as shown in FIG. 9, the client computer 50 (C3, C4) can only receive data at a transfer rate much lower than its own receiving capability.
The client computers 50 (C3, C4) cannot exhibit their capabilities. Therefore, in this embodiment, the server computer 10 executes a process as shown in FIG. In the example of FIG. 1, it is assumed that each client computer 12 inputs reception capability information indicating its own reception capability to the server computer 10 at the same time as a data transfer request.

As shown in FIG. 1, four client computers 12 (C 1) and 12 (C
When a transfer request for the same information (A) is input from 2), 12 (C3), and 12 (C4), the processing of the server computer 10 proceeds from step S21 to S22. In this case, in step S22, the four client computers 12 (C1), 12 (C2), 12 (C3), 12 (C
It decides to process the transfer of information (A) for 4) at the same opportunity. That is, the transfer of the information (A) is processed as multicast.

In the next step S23, the multicast group is divided in consideration of the reception capability information input from each client computer 12. For example, in the example of FIG. 5, two client computers 12 (C1) and 12 (C
Since the receiving capability of 2) is low and the receiving capabilities of the remaining two client computers 12 (C3) and 12 (C4) are high,
The multicast group used for distribution of the information (A) is divided into two groups, and the client computers 12 (C1) and 12 (C1)
For (C2), information (A) is simultaneously distributed in one multicast group (1), and to the client computers 12 (C3) and 12 (C4), another multicast group (2) is simultaneously distributed. Information (A) is distributed.

In each multicast group, the transfer rate is determined according to the receiving capability of the client computer 12 of each transfer destination. As shown in FIG. 1, after executing the step S23, the server computer 10 notifies each client computer 12 of the multicast group to which it belongs. Then, information (A) is transferred for each multicast group. The server computer 10 processes the transfer of the information (A) regarding the two multicast groups at the same opportunity.

Each client computer 12 receives only the information (A) of the multicast group notified in advance from the server computer 10 among the information (A) of the plurality of multicast groups transferred via the broadcast network 11. do it. In the example of FIG. 5, the information is transferred to the two client computers 12 (C1) and 12 (C2) by the multicast group (1) having a relatively low transfer rate corresponding to their reception capabilities. The information can be reliably received even by the client computer 12 having a low number. Further, the client computers 12 (C3) and 12 (C
In 4), the information is transferred by the multicast group (2) having a relatively high transfer rate corresponding to the receiving capability, so that the client computer 12 having high receiving capability can fully utilize the capability and efficiently transmit the information. Can be received.

Incidentally, in order to effectively use the bandwidth of the broadcast network 11 (including the transmission capability of the server computer 10), the number of multicast groups to be divided in step S23 in FIG. The assignment of each client computer 12 is very important. For example, if there is a large variation in the number of client computers 12 belonging to each of a plurality of multicast groups, a small number of client computers 12
Since the bandwidth occupied by the multicast group to which the group belongs becomes excessive, the transfer efficiency to other client computers 12 decreases, and the bandwidth cannot be used efficiently as a whole network.

Therefore, in step S23 of FIG. 1, the processing shown in FIG. 2 is performed to determine the number of multicast groups to be divided and the transfer rate of each multicast group so as to be optimized. In the example of FIG. 2, it is assumed that information is multicast-distributed to n client computers 12. In step S10,
Reception capability information x of all clients that have requested transfer
(1), x (2), x (3), x (4),..., X (n) are arranged and input in descending order. Here, it is assumed that the following relationship is established.

X (1) ≧ x (2) ≧ x (3) ≧ x (4) ≧... ≧ x (n) (1) The transfer rate of the multicast communication is described here for simplicity. , To the minimum value of the reception capability presented by the client computers 12 belonging to each multicast group. If all the client computers 12 communicate as a single multicast group, only one transfer rate corresponding to the minimum reception capability x (n) is required. Conversely, there are n multicast groups, and each multicast group has 1
If it is determined that one client computer 12 belongs,
Same as for unicast. That is, the transfer rate of each multicast group is x (1), x
(2), x (3), x (4), ..., x (n), and the required bandwidth is x (1), x (2), x (3), x (4) , ...
, X (n).

When n client computers 12 each having x (i) reception capability are divided into m multicast groups (i = 1 to n), the transfer rate of each multicast group is represented by X (j). It is desirable that (j = 1 to m) and (x (i) / X (j)) be as small as possible.
That is, the sum of (x (i) / X (j)) is minimized under the constraint that the sum of the transfer rates X (j) is limited within the bandwidth B (constant) of the broadcastable network 11. If the number m of multicast groups and the transfer rate X (j) of each multicast group are determined so that the bandwidth utilization efficiency of the broadcastable network 11 can be optimized.

However, it is necessary to assign those having similar receiving capabilities to the same multicast group.
Therefore, in step S10 of FIG. 2, the receiving capability information is input in the order of its size. If the multicast group is divided on the way while maintaining this arrangement order, those having similar reception capabilities are assigned to the same multicast group.

In step S11 of FIG. 2, the set χ is initialized. The content of the set 意味 means the transfer rate of each multicast group. Initially, there is only one multicast group, and as a result of the initialization in step S11, only the minimum reception capability information x (n) is assigned to the set χ. In step S12, (i = 1, 2, 3,...,
The floor ratio y (i) is obtained for each i of (n-1).
The floor ratio y (i) is expressed by the following equation.

Y (i) = x (i) / x (i + 1) (2) The magnitude of the floor ratio y (i) represents the ratio of two adjacent reception capabilities. In other words, a large floor ratio y (i) means that the difference between two adjacent reception capabilities is large.
If a set of reception capability information x (i) is divided at a position where the difference in reception capability is large, those that are close to each other are assigned to the same group.

In step S13, the bandwidth Bc occupied by all the multicast groups in the current state is calculated. That is, the sum of all the reception capability information x (i) (that is, the transfer rate) belonging to the current set χ is obtained as the bandwidth Bc. In step S14, step S1
The bandwidth Bc obtained in step 3 is compared with the bandwidth B of the broadcastable network 11. If (Bc <B), the process proceeds from step S14 to S16; otherwise, the process proceeds to step S1.
Go to 9.

In step S15, (i = 1, 2, 3,
.., N-1), the largest one among the floor ratios y (i) is detected as the maximum floor ratio ymax. However, before the maximum floor ratio ym
Those adopted as ax are excluded from detection targets. In step S16, it is determined whether or not a plurality of floor ratios have been simultaneously detected as the maximum floor ratio ymax in the immediately preceding step S15. If the maximum floor ratio ymax is one, the process proceeds to step S18, and if there is more than one, the process proceeds to step S17.

In step S17, the immediately preceding step S1
6, among the plurality of floor ratios y (i) detected as the maximum floor ratio ymax, only one that is closer to the (n / 2) -th position, which is the center position of the reception capability information belonging to the multicast group, is the last. Is selected as the optimal maximum ratio ymax. As a result, the number of client computers 12 belonging to each divided multicarrier group is equalized.

In step S18, the reception capability information x (ymax) at the position corresponding to the single maximum ratio ymax detected in step S15 or the single maximum ratio ymax selected in step S17 is added to the set χ. . The position corresponding to the single maximum ratio ymax detected in step S15 or the single maximum ratio ymax selected in step S17 corresponds to the division position of the multicast group, and the reception capability information x ( ymax) corresponds to the transfer rate of the new multicast group after division (same as the minimum receiving capability in the group).

The processes in steps S13 to S18 are repeated until the bandwidth Bc obtained in step S13 reaches the limit of the bandwidth B of the broadcastable network 11. That is, the division of the multicast group is repeated. When the bandwidth Bc obtained in step S13 reaches the bandwidth B of the broadcastable network 11, the process proceeds to step S13.
The process proceeds from S14 to S19. In step S19, the current set χ is returned as the result of the processing. That is, the transfer rate of each multicast group generated by the division is returned as a result of the processing in FIG.

One specific example will be described with reference to FIG. In this example, ten client computers 12
, The same information is distributed by multicast, so that ten pieces of reception capability information x (1) to x (1)
Handle 0). In order to simplify the explanation, FIG. 7 shows the order of the magnitudes instead of the floor ratio y (i).

In the initial state, ten pieces of reception capability information x (1) to x (1) corresponding to ten client computers 12 are set.
0) is assigned to a single multicast group,
Only the minimum reception capability information x (10) among them is assigned to the set と し て as the initial value of the transfer rate.

In the first processing of steps S13 to S18 in FIG. 2, reception capability information x (4) corresponding to the position where the order of magnitude of floor ratio y (i) is the first is added to set χ. . That is, since the difference between the two pieces of reception capability information x (4) and x (5) is the largest, the multicast group is divided into two at that position. In this case, the multicast group having the higher transfer rate has four pieces of reception capability information x (1) to x (4).
, And the client group 12 corresponding to the six pieces of reception capability information x (5) to x (10) is assigned to the multicast group having the lower transfer rate.

Since the receiving capacity information x (4) is assigned to the transfer rate of the multicast group having the higher transfer rate, all four client computers 12 belonging to this multicast group have the receiving capacity equal to or higher than the transfer rate. are doing. In the second processing, the floor ratio y (i)
Attention is paid to the second position in the order of the size of. In the example of FIG. 7, since two pieces of reception capability information x (2) and x (7) exist at the position where the order of the magnitude of the floor ratio y (i) is the second, (1
One piece of reception capability information x (7) closer to the fifth position (0/2). Then, the reception capability information x (7) is added to the set χ.

At the stage where the second processing is completed, three multicast groups are formed, and the first multicast group includes client computers 12 corresponding to four pieces of reception capability information x (1) to x (4). Assigned, second
Of the three receiving capability information x
Client computers 12 corresponding to (5) to x (7) are allocated, and client computers 12 corresponding to three pieces of reception capability information x (8) to x (10) are allocated to the third multicast group.

In the third processing, the receiving capability information x (2) at the second position in the order of the magnitude of the floor ratio y (i) not adopted in the second processing is selected. Then, the reception capability information x
(2) is added to the set χ.

Similarly, in the fourth processing, the reception capability information x existing at the position where the order of the magnitude of the floor ratio y (i) is the fourth position
(9) is added to the set χ. When the server computer 10 performs the processing shown in FIGS.
As shown in (1), the same information can be distributed from the server computer 10 to the client computers 12 by using a plurality of multicast groups divided according to the reception capability of each client computer 12.

In the example of FIG. 9, it is necessary to match the transfer rate with the client computer 50 having the lowest receiving capacity. However, in the example of FIG. 5, the transfer rate can be determined for each of the divided multicast groups. By assigning 12 to a multicast group with a high transfer rate, information can be transferred efficiently.

In the processing shown in FIG. 1, each client computer 12 sends a
2 It is assumed that the receiving capability information is input to the server computer 10, but a client that does not transmit the receiving capability information may be used. In such a case, the processing may be changed as shown in FIG. In the process of FIG. 6, when a transfer request from the client computer 12 is received, the process proceeds from step S31 to S32, and the presence or absence of reception capability information is identified. If there is no reception capability information from the client computer 12, the server computer 10 requests the client computer 12 to transmit the reception capability information in step S33.

When the server computer 10 receives the reception capability information after this request, the processing of FIGS. 1 and 2 is performed according to the reception capability information. If the reception capability information has not been received, the process proceeds from step S34 to S35, and a specified value is adopted as the reception capability information of the client computer 12. As the specified value, for example, the lowest value of the reception capability information received from another client computer 12 so far may be used.

When the present invention is compared with the conventional system, for example, there is a difference in capability as shown in FIG. In the present invention, since the distribution of the same information is divided into a plurality of multicast distributions, the transmittable amount for each multicast distribution of the broadcast network 11 is reduced, but the transfer amount of information actually received by each client computer is It is improved to an amount close to the receiving capacity.

[0064]

According to the present invention, a plurality of client computers to be transmitted are allocated to a plurality of multicast groups according to the reception capability information received from the client computers by the server computer. It is possible to prevent the occurrence of unreceivable client computers. In addition, since information can be efficiently transferred to a client computer having a high receiving capability by using a high transfer rate, each client computer can sufficiently exhibit its capability.

Further, by dividing the reception capability information group arranged in the order of size into a plurality of groups at intermediate positions, the difference between the maximum reception capability and the minimum reception capability in each multicast group is reduced. Relatively small.
This makes it possible to make the transfer rate of each multicast group close to the receiving capability of each client computer belonging to that group.

Further, by dividing the reception capability information group into a plurality of groups at the position of the difference information specified according to the order of the size of the difference information, those having similar reception capabilities can be assigned to the same multicast group. . Also, when there are a plurality of pieces of difference information having the same size, the difference information closer to the center position of the reception capability information group is preferentially selected, and the group is divided at the position of the selected difference information. By doing so, the number of client computers belonging to each of the divided groups is further equalized.

Also, while the sum of the transfer rates of each multicast group is within the network bandwidth, the division of the multicast group is repeated, so that the transmission of all the multicast groups can be performed simultaneously. The number can be increased, and the bandwidth of the entire communication path can be used efficiently.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating processing of a server computer according to an embodiment.

FIG. 2 is a flowchart illustrating a process of determining an optimum transfer rate group;

FIG. 3 is a block diagram illustrating a configuration example of a communication system.

FIG. 4 is a block diagram illustrating a configuration example of a server computer and a client computer.

FIG. 5 is a block diagram illustrating an example of a transfer rate of broadcast transmission according to the embodiment;

FIG. 6 is a flowchart illustrating a modification of the processing of the server computer.

FIG. 7 is a schematic diagram illustrating an example of an operation of determining a transfer rate group.

FIG. 8 is a graph showing a comparative example of the capabilities of the present invention and the conventional system.

FIG. 9 is a block diagram showing a transfer rate of broadcast transmission in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Server computer 11 Broadcastable network 12 Client computer 21 File distribution service 22 Broadcast communication function 23 Driver 31 File distribution service 32 Broadcast communication function 33 Driver 50 Client computer 51 Server computer

Claims (10)

[Claims] 1. A server computer and a plurality of client computers utilize a communication system connected to each other via a broadcast-capable network, and respond to requests from the client computers in response to requests from the server computers. In a broadcast communication method of broadcasting information requested to a plurality of client computers, the server computer receives reception capability information related to the reception capability from each of the transmission target client computers,
Distributing to a plurality of multicast groups according to the receiving capability information received a plurality of client computers of the transmission target, and broadcasts the requested information using a transfer rate independent from each other for each multicast group, Broadcast method to do. 2. The broadcast communication method according to claim 1, wherein the server computer arranges the receiving capability information of all the client computers to be transmitted in the order of their sizes, and then arranges the arranged receiving capability information group in the middle thereof. A broadcast method, comprising: dividing at least one location into a plurality of groups; and associating each of the divided groups with the multicast group. 3. The broadcast communication method according to claim 2, wherein the server computer calculates difference information according to a difference between adjacent reception capability information for each reception capability information arranged in the order of magnitude. And dividing the reception capability information group into a plurality of groups at the position of the difference information specified according to the order of the size of the calculated difference information. 4. The broadcast communication method according to claim 3, wherein in the server computer, when there are a plurality of pieces of difference information having the same size, a server closer to a central position in the arrangement of the reception capability information group. A broadcast communication method characterized by preferentially selecting difference information. 5. The broadcast method according to claim 3, wherein the server computer adds a value obtained by adding a transfer rate associated with the minimum reception capability information belonging to each of the divided groups for all the groups to the band of the network. A broadcast communication method comprising comparing a width with a width and repeating group division until the comparison result satisfies a predetermined condition. 6. A server computer and a plurality of client computers utilize a communication system connected to each other via a broadcast-capable network, and respond to requests from the client computers in response to requests from the server computers. Recording a broadcast program for broadcasting the requested information to a plurality of client computers, wherein the broadcast program includes a server computer, each of which is a client to be transmitted. A step of receiving reception capability information related to the reception capability from the computer, a step of the server computer distributing the plurality of transmission target client computers to a plurality of multicast groups according to the reception capability information received, , Using a transfer rate independent of each other for each of the multicast groups. Recording medium for recording a broadcast program, characterized in that a procedure for information broadcast transmission that. 7. A recording medium on which the broadcast program according to claim 6 is recorded, wherein the receiving capability information of all the client computers to be transmitted is arranged in the broadcast program of the server computer in the order of its size. And a step of dividing the arranged reception capability information group into a plurality of groups at at least one position in the middle thereof, and associating each of the divided groups with the multicast group. Recording medium on which is recorded. 8. A recording medium on which the broadcast program according to claim 7 is recorded, wherein the broadcast program of the server computer includes, for each of the reception capability information arranged in order of magnitude, adjacent reception capability information. Calculating the difference information according to the difference from the received information, and dividing the reception capability information group into a plurality of groups at the position of the difference information specified according to the order of the size of the calculated difference information. A recording medium on which a broadcast program is recorded. 9. The recording medium storing the broadcast program according to claim 8, wherein when the broadcast program of the server computer includes a plurality of pieces of difference information having the same size, the reception capability information is used. A recording medium storing a broadcast program, characterized by comprising a procedure for preferentially selecting difference information closer to the center position of the group arrangement. 10. The recording medium on which the broadcast program according to claim 8 is recorded, wherein the broadcast program of the server computer includes all transfer rates associated with the minimum reception capability information belonging to each divided group. Recording a broadcast program, characterized by comprising a step of comparing the value added for the group with the bandwidth of the network and repeating group division until the comparison result satisfies a predetermined condition.