JP2000253065A - Method and system for multi-cast routing and recording medium recording its program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To select a multiple address link as part of a multi-cast tree when use of the multiple access link is effective in a network which contains multiple access/non-multiple access nodes. SOLUTION: On the occurrence of a participation request from a node (j) to a multi-cast communication (k), the node (j) informs a routing decision section 4 in a multi-cast routing controller 2 of a participation request to the multi-cast communication (k). Then, based on the request of the routing decision section 4, an information management section 3 informs the routing decision section 4 of node information having already taken participation to the multi-cast communication (k). Then the routing decision section 4 calculates a virtual cost of all multiple address nodes according to a formula of a cost of multiple address node (i)/max [number of non-multiple address nodes belonging to the multiple address node (i) and having already taken participation -1], compares the virtual cost of the multiple address node that is calculated with a link cost of the non-multiple address nodes having already taken participation and selects a node at the least cost as a connection destination node of a newly participation node.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a routing technique for performing multicast communication on a communication network in which broadcast nodes and non-broadcast nodes coexist, and in particular, connects a new participating node to a connection destination node having the lowest cost. The present invention relates to a multicast routing method and apparatus for performing the method, and a recording medium on which the program is recorded.

[0002]

2. Description of the Related Art A multicast communication service provided on a communication network can simultaneously deliver the same information to a plurality of recipients. With multicast communication, without increasing the load on the network,
Information can be transmitted to multiple recipients simultaneously. In a multicast on a network that does not have a broadcast link such as a terrestrial network, information from a source copies information at a node serving as a branch point, and the information is copied to a link corresponding to a route of a node to which a receiver is connected. Is forwarded. Also, in the multicast service, it is stipulated that a participant dynamically joins or leaves the multicast communication, and it is possible for the participant to join or leave on the Internet or ATM. The node here means a switching node on the network, and individual terminal nodes connected under the switching node are omitted.

[0003] Further, it is being studied to realize a multicast service not only on a network connecting specific nodes by links but also on a broadcast node mixed network including nodes that broadcast to a plurality of nodes. For example, there is a satellite / terrestrial integrated network as a broadcast node mixed network.

FIG. 6 shows an example of a network having a broadcast node based on an integrated satellite / terrestrial network. In the figure, the satellite broadcasts to a plurality of nodes and thus functions as a broadcast node. In a satellite / terrestrial integrated network, nodes connected by a terrestrial network are also connected by a satellite line. Note that a ground node on the ground network functions as a non-broadcast node. At this time, the cost when using the broadcast link of the satellite, which is the broadcast node, can be considered constant regardless of the number of ground nodes on the receiving side of the satellite node. In addition, when performing multicast communication, if there are a large number of nodes on the receiving side of satellite broadcasting, using satellite broadcasting reduces costs. However, when the number of nodes participating in the multicast communication is small and the number of nodes that receive satellite broadcasts is small, performing the multicast using only the terrestrial network may be lower cost.

[0005] From the viewpoint of cost, the conventional multicast routing method generates a minimum cost tree (Steiner Tree) approximately based on the cost assigned to each link, and a shortest path tree (Shortest Path Tree). Tree). The minimum cost tree aims at minimizing the cost of the entire multicast tree, but is an approximate method because it is difficult to create an optimal minimum cost tree. A typical example is the Greedy algorithm. In this method, if there is a new participating node, the node that can connect at the lowest cost among the nodes that have already received or relay the multicast communication is selected and connected. Is done.

On the other hand, in the shortest path tree, when there is a new participating node, a link that is the shortest path to the source (or core) is selected. But,
In this case, the cost of the multicast tree is larger than the cost of the minimum cost tree.

[0007]

However, in a network in which broadcast nodes and non-broadcast nodes coexist as shown in FIG. 6, the multicast routing described above may form a low-cost multicast tree. Can not. Because a broadcast link is inexpensive because it is used simultaneously by multiple non-broadcast nodes, the broadcast link is not included in the multicast tree from the viewpoint of a non-broadcast node newly joining the multicast communication. If not, the broadcast link is always determined to be expensive and is hardly used.

[0008] The present invention has been made in view of such circumstances, and an object of the present invention is to use a broadcast link in a network in which broadcast nodes and non-broadcast nodes coexist. It is to provide a multicast routing technique in which a broadcast link is selected as part of a multicast tree.

[0009]

The multicast routing method of the present invention is a routing method with minimum cost, and applies a multicast routing model in a normal broadcast node / non-broadcast node. Then, when there is a new joining node newly participating in the multicast communication between the broadcast node and the non-broadcast node, the virtual cost of the broadcast node calculated from the node cost of the broadcast node is compared with the existing participating non-multicast node. The multicast routing method is characterized by comparing the link cost of the information node with the link cost and selecting a node having the lowest cost as a connection destination node of the new joining node.

That is, in the multicast routing method according to the first aspect, a broadcast node having a link capable of broadcasting to a plurality of nodes and a non-broadcast node having a link for performing communication between specific nodes coexist. In a multicast routing method capable of dynamically providing a multicast service, a connection request to a multicast communication is generated from a new participating node when nodes participating in / leaving from the multicast communication are sequentially generated on a communication network that performs communication. A process of receiving participation request information from a new participating node; obtaining information on nodes already participating in multicast communication and network configuration information based on the participation request information; and calculating a virtual cost for the broadcast node. Process, calculated virtual cost and existing participating non-broadcast nodes Comparing the link cost with the new joining node, and selecting the node having the lowest cost as the connection destination node of the new joining node as a result of the comparison, and connecting the new joining node to the selected joining destination node. It is characterized by having.

A multicast routing method according to a second aspect of the present invention is the multicast routing method according to the first aspect, wherein the total cost of the broadcast link at the broadcast node is regarded as the cost of the broadcast node itself, and Assuming that the cost is 0 and that each asynchronous node belongs to a broadcast node that can be connected at the lowest cost, the virtual cost of the broadcast node is the cost of broadcast node i / max [belonging to broadcast node i and existing. The number of participating non-broadcast nodes -1]. However, the number of participating non-broadcast nodes includes the source and the newly participating nodes.

According to a third aspect of the present invention, there is provided a multicast routing apparatus in which a broadcast node having a link capable of broadcasting to a plurality of nodes and a non-broadcast node having a link for performing communication between specific nodes coexist. A multicast routing apparatus capable of dynamically providing a multicast service when nodes connected to each node on the network via the network and participating / leaving in the multicast communication are sequentially generated. An information management means for managing nodes participating in each multicast communication, and a request for participation in a newly generated multicast communication from a new participating node, and based on the information of the participation request, from the information management means, Nodes participating in multicast communication related to the new joining node Acquires and de information and network configuration information, calculates a virtual cost for broadcast node,
Routing decision means for comparing the virtual cost and the link cost to the existing participating non-broadcast node, and notifying the new participating node of the node of the lowest cost among them,
Connecting means for connecting a new participating node to a connection destination node having the lowest cost in response to a notification from the routing determining means.

According to a fourth aspect of the present invention, in the multicast routing apparatus according to the third aspect, the total cost of the broadcast link in the broadcast node is regarded as the cost of the broadcast node itself, and the cost of the broadcast link is considered. Is assumed to be 0 and each asynchronous node belongs to a broadcast node that can be connected at the lowest cost, the virtual cost of the broadcast node is the cost of broadcast node i / max [belonging to broadcast node i and existing The number of participating non-broadcast nodes -1]. However, the number of participating non-broadcast nodes includes the source and the newly participating nodes.

According to a fifth aspect of the present invention, there is provided a recording medium storing a multicast routing program, comprising: a broadcast node having a link capable of broadcasting to a plurality of nodes; and a non-broadcast having a link for performing communication between specific nodes. When a node that participates in or leaves multicast communication sequentially occurs on a communication network in which nodes are mixed, a recording medium that records a multicast routing program capable of dynamically providing a multicast service includes:
When a connection request to the multicast communication is issued from a new joining node, the joining request information received from the new joining node and, based on the joining request information, information on nodes already participating in the multicast communication and network configuration information, The calculated virtual cost information of the broadcast node, comparison information that compares the calculated virtual cost with the link cost to the existing participating non-broadcast node, and, as a result of the comparison, the node with the lowest cost as the new participating node A multicast routing program including selection information to be selected as a connection destination node and connection information for connecting a new participating node to the connection destination node based on the selection result is recorded.

According to a sixth aspect of the present invention, in the recording medium storing the multicast routing program, the total cost of the broadcast link at the broadcast node is regarded as the cost of the broadcast node itself. When it is assumed that the cost of the broadcast link is 0 and each asynchronous node belongs to a broadcast node that can be connected at the lowest cost, the virtual cost information includes the virtual cost of the broadcast node.
A recording of a multicast routing program characterized in that it is recorded that it is calculated by the cost of broadcast node i / max [the number of non-broadcast nodes that belong to the broadcast node i and have already joined] -1. Medium. However, the number of participating non-broadcast nodes includes the source and the newly participating nodes.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the multicast routing technique of the present invention will be described.
The features of the present invention will be described. In other words, the multicast routing technique of the present invention, when a non-broadcast node newly participating in multicast communication selects a connection destination node on a node weighted graph that models a broadcast node mixed network, The lowest possible multicast tree is constructed by considering the cost to the broadcast nodes due to the arrangement of the already joined non-broadcast nodes on the network in addition to the link cost to the non-broadcast nodes It is characterized by doing.

In the conventional multicast routing based on cost, a network is modeled as a graph, link costs are used as branch weights, and node costs are regarded as zero. On the other hand, the modeling of the multicast routing in the broadcast node / non-broadcast node of the present invention does not change the link cost and the node cost for the non-broadcast node, but the broadcast link cost and the node cost for the broadcast node. Is different from the conventional one.

That is, the broadcast link cost is aggregated at the node of the broadcast node as the node cost of the broadcast node.
Therefore, the broadcast link cost is set to 0. This allows
If the broadcast link is included in the multicast tree, a certain cost is added irrespective of the number of ground nodes using the broadcast link. If there is a link between the broadcast nodes, there is a weighted branch as a link cost for establishing a link between the broadcast nodes in addition to the node cost of each broadcast node. Think.

The multicast routing method of the present invention is a routing method with a minimum cost, and uses the above-mentioned multicast routing model in the broadcast node / non-broadcast node. Then, when there is a new joining node newly participating in the multicast communication between the broadcast node and the non-broadcast node, the virtual cost of the broadcast node calculated from the node cost of the broadcast node is compared with the existing participating non-multicast node. This is a multicast routing method that compares the link cost of the information node with the link cost and selects the node with the lowest cost as the connection destination node of the new joining node.

In calculating the virtual cost of a broadcast node,
Instead of using the virtual cost as the node cost itself of the broadcast node, the node cost of the broadcast node is obtained by dividing the node cost of the broadcast node by “the existing non-broadcast node belonging to the broadcast node-1”. The reason is as follows. That is, in a multicast network of broadcast nodes and non-broadcast nodes, the node cost of a broadcast node is much higher than the link cost of each non-broadcast node. Therefore, if there is a new participating node first, a non-broadcast node is usually selected.
If the virtual cost is the node cost itself of the broadcast node for the purpose of immediately recovering the cost of the broadcast node from the participating node, the broadcast node is not selected forever.

Therefore, by utilizing the cost borne by each participating node in the ideal state where all the participating nodes have selected the broadcast node, the link cost to the existing participating non-broadcast node is reduced. The apparent cost required to connect to the broadcast node, i.e., the virtual cost, is lower, thereby increasing the chances of a newly joining node choosing a broadcast node.

When a new participating node first selects a broadcast node, a cost corresponding to the cost of the broadcast node cannot be obtained from the new participating node. However, as the number of new participating nodes increases, the broadcast node is selected. As the number increases, it becomes possible to obtain a cost corresponding to the cost of the broadcast node or more. That is, in other words,
A newly joined non-broadcast node may be connected to a non-broadcast node, and the existing participating non-broadcast node may be connected to any It is considered that connecting to an existing participating broadcast node can connect to an existing multicast tree at lower cost. And
If many non-broadcast nodes belonging to the broadcast node participate in the multicast communication, the cost of the broadcast node is determined to be low, and the broadcast link is more easily used.

In calculating the virtual cost of a broadcast node, "the number of non-broadcast nodes belonging to the broadcast node and existing and participating"
Instead, the reason is obtained by dividing by "the number of existing participating non-broadcast nodes belonging to the broadcast node-1". That is, if all existing participating non-broadcast nodes belonging to broadcast node i use broadcast node i, and non-broadcast nodes not belonging to broadcast node i do not use broadcast node i, Any existing non-broadcast node belonging to the broadcast node i functions as a transmitting node with respect to the broadcast node i. Therefore, the number of non-broadcast nodes sharing the downlink broadcast link is always “the number of existing participating non-broadcast nodes−
1 ".

Here, the number of non-broadcast nodes of the existing participant here includes a new participant node in addition to the transmitting side node and the so-called existing participant node. If the transmitting node belongs to another broadcast node and the broadcast node to which the new participating node belongs does not have an existing participating node, the “number of existing participating non-broadcast nodes−1” is 0. Therefore, it is set to 1 in this case.

Further, the present invention is directed to a multicast service in which each node sequentially joins and leaves the multicast communication. The joining and leaving are as follows. That is, for the nodes that have already participated in the multicast communication, the information transmission path from the source to the node is not changed until the node leaves the multicast communication.

The means as a multicast routing device has the following configuration. That is, this device is a multicast routing control device connected to each node on a communication network in which broadcast nodes and non-broadcast nodes coexist with each other via a control signal network. The multicast routing control device includes an information management unit and a routing determination unit.

The information management unit is means for managing network configuration information including costs and nodes participating in each multicast communication. In addition, the routing determination unit attaches a request for participation in a newly generated multicast communication from the newly participating node, and based on the information,
From the information management unit, information on nodes participating in the multicast communication relating to the new participating node and network configuration information are obtained. Means for calculating a virtual cost for the broadcast node, comparing the virtual cost with the link cost to the existing participating non-broadcast node, and notifying the new participating node of the connection destination node having the lowest cost among them. It is.

Further, each node is connected to the multicast routing controller via a control signal network, and notifies the multicast routing controller of a newly generated request for participation in multicast communication, and the lowest request for the request is sent to the multicast routing controller. It has a function of receiving notification of the cost connection destination node from the multicast routing control device and connecting to the notified connection destination node.

Next, specific embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a network and a multicast routing control device according to a first embodiment of the present invention, and the first embodiment will be described with reference to FIG. The network 1 includes a multicast routing control device 2, a broadcast node and a synchronization link between the broadcast nodes, and a non-broadcast node and a link between the non-broadcast nodes. The multicast routing control device 2 includes an information management unit 3 and a routing determination unit 4 and is a device that manages nodes participating in multicast communication, and is provided in the network 1.
The multicast routing control device 2 is connected to all nodes via a control signal network.

The information management unit 3 is a device for managing network configuration information including costs and nodes participating in each multicast communication. The routing determining unit 4 is a device that determines a route based on a request for joining a multicast communication newly generated from a node.

Next, a multicast routing method when a request for joining a multicast communication is newly issued from a node will be described with reference to a flowchart. FIG.
FIG. 2 is a flowchart showing a processing flow of a multicast routing method in the configuration diagram of FIG. 1. First, node j
As a result, a request for participation in the multicast communication k is generated (step S1, hereinafter, steps are omitted). Next, the node j notifies the routing determination unit 4 in the multicast routing control device 2 of a request to join the multicast communication k (S2). Then, the routing determination unit 4 requests the information management unit 3 for information on the nodes that have already participated in the multicast communication k (S3). Further, the information management unit 3 notifies the routine determination unit 4 of information on the nodes already participating in the multicast communication k (S4).

Next, the routing determination unit 4 calculates the virtual cost of all broadcast nodes by the cost of the broadcast node i / max [the number of non-broadcast nodes that belong to the broadcast node i and have participated-1]. (S5). However, the number of existing participating nodes includes the source and new participating nodes.

Based on the calculated virtual cost of the broadcast node and the link cost that has already been set, an existing participating node other than the newly joining node that can be connected with the lowest cost is calculated from the newly participating node. . In calculating the virtual cost, depending on the network configuration,
There is also a method in which the calculation is performed only for the broadcast node to which the new participating node belongs, not for all the broadcast nodes.

Next, the routing determining unit 4 notifies the information managing unit 3 and the node j of the calculated node.
(S6). Then, the node j issues a connection setting request to the node indicated by the routing determining unit 4 via the shortest path (S7).

In FIG. 1, since the number of non-broadcast nodes belonging to and participating in the broadcast node 1 at the time of the new participating node is 4, the virtual cost of the broadcast node 1 is 10 /(4-1)=3.33... Similarly, the virtual cost of broadcast node 2 is 9 / (1-1) =
9 is calculated. The denominator (1-1) = 0 is set to 1 as described above.

The existing participating node that can be connected at the lowest cost for the new participating node is the non-broadcast node # 1, the node # 2, or the source that can be connected via the broadcast node 1. The cost of the route is 3.33..., And the cost of the other route, for example, the route from the new joining node to the non-broadcast node # 1, is 4,
It can be seen that passing through the broadcast node 1 has the lowest cost. Therefore, the new participating node is connected to any of those nodes via the broadcast node 1 and its broadcast link. Further, when the node J leaves the multicast communication, the node j notifies the information management unit 3 of the release from the multicast communication k. Then, the information management unit 3 updates the node information regarding the multicast communication k and ends the processing.

Next, a second embodiment of the present invention will be described. FIG. 3 is a configuration diagram of a network and a multicast routing control device according to the second embodiment of the present invention. This embodiment shows a case where the broadcast nodes are connected by a non-broadcast link in the first embodiment. Therefore, in FIG. 3, the broadcast node 1 and the broadcast node 2 are connected by a non-broadcast link.

That is, a case will be described in which a multicast tree as shown in FIG. 3 has already been created and a new joining node exists in the multicast tree. At this time, since the number of non-broadcast nodes belonging to the broadcast node 1 and already participating is 4, the virtual cost of the broadcast node 1 is 10 / (4-
1) = 3.33... Similarly, broadcast node 2
Is calculated as 9 / (1-1) = 9.
The denominator (1-1) = 0 is set to 1 as described above.

For the new joining node, the existing joining node which can be connected at the lowest cost passes through the broadcast node 2 and further, the non-broadcast which can be connected from the broadcast node 2 via the broadcast node 1. Node # 1 or non-broadcast node # 2 or source. In order to connect to these nodes, the total cost of this new route is 13.33..., And other routes, such as the new participating node → non-broadcast node # 4 → non-broadcast node # 2 It can be seen that the cost is the lowest as compared with the above. Therefore,
The new participating node goes to the non-broadcast node # 1, the non-broadcast node # 2, or any of the source nodes via the broadcast node 2, and further from the broadcast node 2 via the broadcast node 1. Connected.

Next, evaluation results of the multicast routing method according to the present invention will be described. The multicast routing method according to the present invention was simulated to evaluate how effective the multicast routing method was based on the simple Greedy algorithm. FIG. 4 shows the simulation results.
That is, FIG. 4 shows an evaluation result of the multicast tree cost of the present invention based on the simulation. FIG. 5 shows parameter values based on the evaluation model of the multicast routing method according to the present invention.

In FIG. 4, the horizontal axis represents the average number of nodes participating in the multicast group, and the vertical axis represents the average tree cost. Here, the average tree cost is an average of the sum of the link cost and the broadcast node cost for each tree. Note that the simulation results here are expressed as an average of the results obtained for ten different networks. In addition, the number of events of joining and leaving nodes of 20,000 is set as one simulation run, and up to 2,000 of the initial number of events of the run is excluded in order to eliminate the influence of the initial state.

As can be seen from FIG. 4, in a situation where the number of recipients is large as a whole, the cost of the multicast tree of the multicast routing method according to the present invention is lower than that of the multicast routing method using the simple Greedy algorithm. . This allows a simple Gr
It can be seen that the multicast routing method according to the present invention is easier to select than the multicast routing method using the eedy algorithm. In the simulation, parameter values as shown in FIG. 5 were used on the premise of an evaluation model as described below.

Next, an evaluation model of the multicast routing method according to the present invention will be described. As an evaluation model for a non-broadcast node, a random graph used in the evaluation of the conventional multicast routing method is used. In the random graph, when nodes of N non-broadcast nodes are arranged on a plane and the pair of nodes is (u, v), the occurrence rate of the node pair is given by the following equation (1).

[0044]

(Equation 1) Here, e is the average number of links protruding from a certain node,
k is a parameter that determines the average distance of the node pair, d
(U, v) is the Euclidean distance between u and v, L is d
The maximum Euclidean distance that (u, v) can take, β and α
Are parameters, and 0 <β <1 and 0 <α <1.
Also, let the cost of the branch be the Euclidean distance d between u and v
(U, v).

Further, an evaluation model when a broadcast node and a broadcast link are added to the network of non-broadcast nodes in the above evaluation model is as follows. In other words, Ns nodes as broadcast nodes, like non-broadcast nodes,
Place them randomly on a plane. The presence or absence of a link between a broadcast node and each non-broadcast node is given by the probability Pd regardless of the distance between the broadcast node and the non-broadcast node.

The cost of the broadcast link is as follows. That is, the value obtained by dividing the total link cost of each non-broadcast node connected to the node selected as a broadcast node by h is taken as the cost of that broadcast node, and the cost of each broadcast link is Set to 0. h is a parameter for adjusting the sum. The sum of the link costs of the non-broadcast nodes connected to the node selected as the broadcast node is adjusted by the adjustment parameter without using the cost of the node of the broadcast node. are doing. The reason is that, when a broadcast node is selected, many nodes can share a broadcast link so that the degree of the structure at which the entire tree is reduced in cost can be selected by simulation.

The probability of a node joining and leaving the multicast communication participating in the multicast communication is given by the following equation (2).

(Equation 2) Here, q is the number of nodes participating in the multicast communication at that time. γ (0 ≦ γ ≦ 1) is a parameter for determining the number of nodes participating in the multicast communication in the parallel state, and the average number of participating nodes on the horizontal axis in FIG. 4 is γN. The broadcast node itself works only as a relay node without participating in or leaving the multicast communication.

Next, an evaluation model of a multicast routing method using a simple Greedy algorithm will be described. The evaluation model of the multicast routing method by the simple Greedy algorithm is different from the evaluation model of the multicast routing method according to the present invention in that the cost of the broadcast node is regarded as the cost of the node as it is, that is,
The broadcast link cost required by the new participating node when a new participating node occurs is fixed, and its value differs in that it is the node cost of the broadcast node, but the other conditions are the same.

[0049]

As described above, according to the multicast routing technique of the present invention, by using a selection algorithm in consideration of a broadcast node, when it is effective to use a broadcast link, broadcast is performed. The link will be selected as part of the multicast tree. As a result, it is possible to provide a multicast routing method and an apparatus for configuring a low-cost multicast tree and a recording medium on which the program is recorded.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a network and a multicast routing control device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a processing flow of a multicast routing method in the configuration diagram of FIG. 1;

FIG. 3 is a configuration diagram of a network and a multicast routing control device according to a second embodiment of the present invention.

FIG. 4 is an evaluation result of a multicast tree cost of the present invention based on a simulation.

FIG. 5 shows parameter values based on an evaluation model of the multicast routing method according to the present invention.

FIG. 6 is an example of a network having a broadcast node based on a satellite / terrestrial integrated network.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Network 2 Multicast routing control device 3 Information management unit 4 Routing determination unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) H04Q 7/30 F term (reference) 5K030 GA20 LB05 LD02 5K067 AA41 CC00 CC14 DD23 EE02 EE07 EE10 EE16 GG11 HH21 JJ00 JJ11 JJ43 9A001 CC06 GG19

Claims (6)

[Claims] 1. A participant in multicast communication on a communication network in which a broadcast node having a link capable of broadcasting to a plurality of nodes and a non-broadcast node having a link for performing communication between specific nodes coexist. In a multicast routing method capable of dynamically providing a multicast service when nodes that leave / join sequentially occur, when a connection request to the multicast communication is issued from a new joining node, a joining request is issued from the new joining node. Receiving information, and, based on the participation request information, obtaining information on nodes already participating in the multicast communication and network configuration information, and calculating a virtual cost for the broadcast node. Comparing said virtual cost with a link cost to an existing participating non-broadcast node Selecting a node having the lowest cost as a connection destination node of the new participation node as a result of the comparison, and connecting the new participation node to the selected connection destination node. Multicast routing method. 2. The multicast routing method according to claim 1, wherein a total cost of the broadcast link in the broadcast node is regarded as a cost of the broadcast node itself, and a cost of the broadcast link is regarded as 0; Assuming that each asynchronous node belongs to a broadcast node that can be connected at the lowest cost, the virtual cost of the broadcast node is: cost of broadcast node i / max [non-broadcast that belongs to broadcast node i and has already joined The number of nodes minus 1]. However, the number of participating non-broadcast nodes includes the source and the newly participating nodes. 3. Nodes and networks in a communication network in which a broadcast node having a link capable of broadcasting to a plurality of nodes and a non-broadcast node having a link for performing communication between specific nodes are mixed. A multicast routing device capable of dynamically providing a multicast service when nodes connected and participating / leaving in the multicast communication occur sequentially. Receiving a request for participation in a newly generated multicast communication from a newly joining node, and receiving information relating to the newly joining node from the information managing means based on the information of the joining request. Information on nodes participating in multicast communication And calculate the virtual cost for the broadcast node, compare the virtual cost with the link cost to the existing participating non-broadcast node, and determine the connection destination node having the lowest cost among the new participating nodes. A multicast routing apparatus, comprising: a routing determining unit that notifies the new joining node to a connection destination node having the lowest cost based on a notification from the routing determining unit. 4. The multicast routing apparatus according to claim 3, wherein a total cost of the broadcast link in the broadcast node is regarded as a cost of the broadcast node itself, and a cost of the broadcast link is regarded as 0, Assuming that each asynchronous node belongs to a broadcast node that can be connected at the lowest cost, the virtual cost of the broadcast node is: cost of broadcast node i / max [non-broadcast that belongs to broadcast node i and has already joined The number of nodes minus 1] is calculated. However, the number of participating non-broadcast nodes includes the source and the newly participating nodes. 5. A participant in multicast communication on a communication network in which a broadcast node having a link capable of broadcasting to a plurality of nodes and a non-broadcast node having a link for performing communication between specific nodes coexist. When a node that leaves / separates sequentially, in a recording medium that records a multicast routing program capable of dynamically providing a multicast service, when a connection request to the multicast communication is generated from a newly joining node, Based on the participation request information received from the new participating node, and based on the participation request information, virtual cost information of the broadcast node calculated based on information on nodes already participating in the multicast communication and network configuration information. The virtual cost and the link cost to the existing participating non-broadcast node. Comparison information, selection information for selecting a node having the lowest cost as a connection destination node of the new participation node as a result of the comparison, and connection information for connecting the new participation node to the connection destination node based on the selection result. A recording medium characterized by recording a multicast routing program comprising: 6. A recording medium on which a multicast routing program according to claim 5 is recorded, wherein a total cost of a broadcast link at the broadcast node is regarded as a cost of the broadcast node itself, and a cost of the broadcast link is considered. Is assumed to be 0, and if each asynchronous node belongs to a broadcast node that can be connected at the lowest cost, the virtual cost information indicates that the virtual cost of the broadcast node is the cost of broadcast node i / max [ A recording medium recording a multicast routing program, characterized in that it is recorded that the number of non-broadcast nodes belonging to the broadcast node i and calculated by the number of participating non-broadcast nodes-1] is recorded. However, the number of participating non-broadcast nodes includes the source and the newly participating nodes.