JP2012209844A - Multicast system, multicast tree construction method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multicast system, a multicast tree construction method, and a program that can quickly and flexibly control variations in delivery delay.SOLUTION: The multicast system includes means for setting a delivery delay, and means for constructing a multicast tree so as to maximize the number of nodes where delay control for reducing a delay variation from the delivery delay set by the setting means is unnecessary.

Description

  The present invention relates to a multicast system, a multicast tree construction method, and a program. In particular, the present invention relates to a multicast system, a multicast tree construction method, and a program for controlling data delivery delay time.

  There is a multicast system that distributes update information of a WEB server or data generated by a sensor or the like to a large number of devices using a multicast tree having a data distribution source as a root.

  This multicast tree is a logical network composed of nodes that use the data, and may be created for each distribution source or may share one multicast tree. Data is transferred between nodes according to the structure of the multicast tree.

  Regarding the multicast tree construction method, several means for constructing a multicast tree for distributing data in real time to a large number of users have been proposed.

  For example, in Patent Document 1, by exchanging information such as CPU usage rate, memory usage rate, CPU specification, physical proximity, and survival time of a node with surrounding nodes, a plurality of pieces of information received from the surroundings are compared and evaluated. A means for constructing a multicast tree is disclosed. The “physical proximity” can be obtained by measuring the response time of the peer-to-peer connection operation between the nodes. In addition, “survival time” can be defined as the average connection time of the terminal connected to the network in one connection.

  Patent Document 2 discloses means for evaluating a hop count (stage count) or an estimated value of a sequence number of an arrival packet at a certain time to construct a multicast tree.

  Further, Patent Document 3 is a multicast transfer route calculation method for obtaining a multicast transfer route from a given start node to a plurality of end nodes in a network composed of a plurality of nodes, and includes network topology information and Using the delay information, a minimum delay path from the start node to the end node is obtained for each end node, and a node on one delay minimum path among a plurality of minimum delay paths to the start node and each end node is determined. , Select as a candidate node of the aggregation point node in multicast forwarding, and for each candidate node, calculate a minimum delay path from the candidate node to the end node for each end node, and a plurality of minimum delay paths for each end node Find the difference between the maximum and minimum values of the delay, and select the candidate node with the smallest error as the aggregation node To select it, and minimum delay paths from the start node to the aggregation point node, and outputs the respective minimum delay path from the aggregation point node to each end node as a multicast forwarding path. According to the above-mentioned patent document 3, it is described that the calculation speed of the multicast transfer route can be improved and the delay dispersion between users can be reduced.

JP 2005-252596 A JP 2004-246790 A JP 2004-208289 A

  The following analysis is given by the present invention.

  With the above-described conventional technology, it is difficult to set a multicast tree quickly and flexibly so that there is no variation in distribution delay in the multicast system.

  In general, nodes participating in a multicast tree have different timings for receiving data depending on positions on the multicast tree. As a result, the dispersion of the distribution delay in the multicast tree becomes large. Patent Document 3 describes a method for selecting a route so as to suppress a variation in distribution delay. However, in order to suppress a variation in distribution delay by selecting a route, an optimal route is selected from a large number of routes in all nodes. Adjustment to select the route is required. As a result, adjustment takes time, and it is not possible to set a multicast tree quickly and flexibly so that there is no variation in delivery delay.

  The present invention has been made in view of such circumstances, and a first object of the present invention is to reduce the delay adjustment for reducing the variation and to reduce the variation in the distribution delay of the nodes participating in the multicast tree. The object is to provide a multicast system capable of building a small multicast tree quickly and flexibly.

  According to the first aspect of the present invention, it is not necessary to adjust the delay amount for reducing the delay variation with respect to the delivery delay amount set by the means for setting the delivery delay amount and the delivery delay amount set by the setting means. And a means for configuring the multicast tree to maximize the number of nodes.

  According to the second aspect of the present invention, a step of receiving a participation request message from a node attempting to participate in the multicast tree, a step of confirming the current multicast tree configuration, and a delay with respect to a predetermined delivery delay amount Determining the connection destination node of the node that sent the participation request message so that the number of nodes that do not require adjustment of the delay amount to reduce variation is maximized, and for the node that sent the participation request message And a step of transmitting a participation response message including information of the connection destination node.

  According to a third aspect of the present invention, there is provided a program for causing a computer to execute the multicast tree construction method according to the second aspect.

  According to a fourth aspect of the present invention, a delay amount setting function unit that is a root node of a multicast tree and sets a distribution delay amount to be protected by the multicast tree, and a delivery delay set by the delay amount setting function unit Provided by a root node of a multicast tree having a tree configuration calculation function unit that configures a multicast tree so that the number of nodes that do not require adjustment of delay amount to reduce delay variation with respect to the amount is maximized Is done.

  According to each aspect of the present invention, it is possible to quickly and flexibly construct a multicast tree in which the delay adjustment for reducing the variation is reduced and the distribution delay of the nodes participating in the multicast tree is small. The reason is that by configuring the multicast tree so that there are as many nodes as possible that do not need to adjust the delay amount to reduce the delay variation, the node of the specified delivery delay amount, that is, the adjustment amount is This is because the number of nodes that become 0 can be maximized.

It is a conceptual diagram which shows the structural example of the multicast tree 1 by one Embodiment of this invention. It is a conceptual diagram which shows the structural example of the multicast tree 1 by one Embodiment. 4 is a diagram illustrating a process of building a multicast tree in the order of (a), (b), and (c) according to an embodiment. It is a block diagram which shows the structure of the root node by one Embodiment. It is a block diagram which shows the structure of the node by one Embodiment. 6 is a flowchart illustrating a process in which a root node changes the topology of a multicast tree when there is a node requesting participation in an embodiment. 6 is a flowchart illustrating a process in which a root node changes the topology of a multicast tree when there is a leaving node in an embodiment.

  An outline of an embodiment of the present invention will be described. Note that the reference numerals of the drawings attached to this summary are merely examples for facilitating understanding, and are not intended to be limited to the illustrated embodiments.

  A multicast system (see FIG. 1) according to an embodiment of the present invention includes a means (115) for setting a delivery delay amount, and a delay for reducing delay variation with respect to the delivery delay amount set by the setting means. And means (114) for configuring the multicast tree so that the number of nodes that do not require adjustment of the amount is maximized. The multicast tree is configured so that the number of nodes that do not require delay adjustment to reduce delay variation is maximized with respect to the set delivery delay amount, so the participating nodes can leave the multicast tree. Even when a node occurs, it is possible to reduce the adjustment of the delay to reduce the variation.

  As shown in one embodiment, the means (114) constituting the multicast tree deepens the shape of the tree until the set delivery delay amount, and exceeds the set delivery delay amount in order from the deepest position. The number of nodes that do not require adjustment of the delay amount may be maximized by connecting the nodes in order so that there is no maximum delivery delay amount.

  Further, as shown in one embodiment, the means (114) constituting the multicast tree increases the number of child nodes of one node until the set delivery delay amount, and among the child nodes, By increasing the number of child nodes for the child node so that it does not exceed the set delivery delay amount from the child node with the largest delivery delay amount, the number of nodes that do not require adjustment of the delay amount is maximized. It may be made to become.

  Furthermore, when a node participating in the multicast tree leaves, the means (114) constituting the multicast tree reconnects the last connected node to the parent position of the isolated node due to the node leaving. It is preferable to configure the multicast tree so that the This is because the last connected node has no child nodes, and therefore, reconnection does not affect other nodes.

  The description of the outline has been completed, and more specific embodiments will be described in detail below with reference to the drawings.

[First Embodiment]
FIG. 1 is a conceptual diagram illustrating a configuration example of a multicast tree 1 according to the first embodiment.
In FIG. 1, a multicast tree 1 has a root node 100 and a plurality of nodes 200, and constitutes a logical network. The root node 100 is represented by a square symbol, and the nodes 200 other than the root node are represented by a circular symbol.

  FIG. 2 shows the IDs of the root node 100 and each node 200 for the multicast tree 1 of FIG. As shown in FIG. 2, the root node 100 (node n2) is a vertex, the node 200 is a node n8, a node n35, a node n47, and a node n31, and the node n8 is a node n3 and a node n31. n29 and node n44 are connected in a tree structure state.

  Each node 200 is connected to the root node 100 and / or one or more nodes 200. Each node 200 transfers data to the downstream node 200 in the multicast tree 1 when data is received from the root node 100 connected to the upstream or the node 200.

  FIG. 3 is a diagram for explaining a process of constructing the multicast tree 1 by adding nodes in the first embodiment. In FIG. 3, the multicast tree 1 is constructed by adding the nodes 200 in the order of FIGS. 3 (a), 3 (b), and 3 (c). In FIG. 3, nodes are added so as to minimize the adjustment for reducing the variation in distribution delay.

  In FIG. 3, the symbols shown in each node are “node ID”, “distribution delay amount”, “additional node estimated delay amount”, and “delay adjustment amount” in order from the left. Here, the “distribution delay amount” is a delay amount of data distribution. The “additional node estimated delay amount” is the estimated delay amount of the newly connected node when a new node is connected to the node, and the node newly connected to the multicast tree is connected. This is a numerical value used as a guide when selecting the destination. The “delay adjustment amount” is a delay adjustment amount that can be expressed by a difference between the designated delay amount and the delivery delay amount in order to obtain the designated delay amount.

  In the example of FIG. 3, the target delay amount is 4, for example, n9 has a distribution delay amount of 4 and adjustment is unnecessary, so the delay adjustment amount is 0, and the distribution delay amount of n8 is 1, so the difference from the target delay amount 4 3 is the delay adjustment amount. By making this adjustment, the node 200 connected to the multicast tree 1 can adjust the data processing timing with little delay variation.

The distribution delay amount of a certain node i is D_i, the processing delay amount for distributing data to the jth node under the first generation is DP_ij, and the network delay between the node i and the jth node under the one generation is DN_ij Then, the delivery delay amount D_ij of the j-th node one generation below the node i can be expressed by Equation 1.
D_ij = D_i + DP_ij + DN_ij (Formula 1)

Here, P_i0 is the intra-node transfer processing delay from when node i receives the packet from the parent node of node i until it transmits data to the first subordinate node, and P_ij is subordinate j at node i. Deliver data to the jth node under the 1st generation when the intra-node transfer processing delay from sending data to the node under the 1st generation to sending data to the subordinate j + 1st generation node The processing delay amount DP_ij for
DP_ij = DP_i (j-1) + P_i (j-1)
DP_i1 = P_i0
Can be written.

At this time, if there is no difference in data transmission processing between subordinate nodes in node i and subordinate nodes, Equation 1 can be simplified. Further, the intra-node transfer processing delay from the time when node i receives a packet from the parent node of node i to the time when the data is transmitted to the subordinate first generation node is the intra-node transfer processing to other subordinate nodes. Considering that it is sufficiently small compared to the delay. In particular,
P_i0 = 0,
And P_i1 = P_i2 = P_i3,
And DN_i1 = DN_i2 = DN_i3 = DN_i4 ...
When we can assume
Equation 1 can be simplified as Equation 2.
D_ij = D_i + DP_i * (j-1) + DN_i (Formula 2)

  In Expression 2, DP_i is a processing delay required for one data transfer in the node i. DN_i is a network delay to a node one generation lower in node i. This value is calculated statically or dynamically from, for example, the actual processing delay, distribution delay, node processing capacity (CPU speed, CPU utilization), the value of a representative subordinate node or one generation higher node. To do.

In addition, at any node participating in the multicast tree,
DP_1 = DP_2 = ... = DP,
And DN_1 = DN_2 = ... = DN
Can be further simplified. That is, it can be expressed as Equation 3.
D_ij = D_i + DP × (j−1) + DN (Formula 3)

  In Expression 3, DP is a processing delay required for one data transfer. DN is a network delay to a node one generation below. This value is calculated statically or dynamically from, for example, actual processing delay, delivery delay, node processing capability (CPU speed, CPU utilization), and arbitrary node value.

  In the example of FIG. 3, the distribution delay amount of the root node n2 is set to 0, Expression 3 is applied, and DP = DN = 1. For example, the root node n2 is 0, the subordinate first node n8 is 1, and the node n3 that receives data subsequently is 2.

Specifically, the “additional node estimated delay amount” is defined as an estimated delay amount of a newly connected node when a new node is connected to the node. For a newly connected node or a node whose connection destination is changed, the distribution delay is smaller when the node is newly connected to a node with a small amount of distribution delay. When the estimated delay amount of a newly connected node is expressed by an expression, assuming that the newly connected node is the nth child of node i, the delivery delay amount of a certain node i is newly connected to D_i and node i Assuming that the estimated delay amount of a node is D_in, the estimated value of processing delay until data is distributed to the node when the new node is connected is DP_in, and the estimated value of the network delay when the new node is connected is DN_in. 4 can be expressed.
D_in = D_i + DP_in + DN_in (Formula 4)

Here, as in the derivation of Equation 1 to Equation 2, Equation 4 can be simplified if there is no difference in data transmission processing between subordinate nodes in node i and subordinate nodes. Further, the intra-node transfer processing delay from the time when node i receives a packet from the parent node of node i to the time when the data is transmitted to the subordinate first generation node is the intra-node transfer processing to other subordinate nodes. Considering that it is sufficiently small compared to the delay. In particular,
P_i0 = 0,
And P_i1 = P_i2 = P_i3,
And DN_i1 = DN_i2 = DN_i3 = DN_i4 ...
Can be simplified as equation 5.
D_in = D_i + DP_i * (n-1) + DN_i (Formula 5)

Furthermore, as in the derivation of Equation 2 to Equation 3, at any node participating in the multicast tree,
DP_1 = DP_2 = ... = DP,
And DN_1 = DN_2 = ... = DN
In Equation 5, when the number of current child nodes is further simplified as c, Equation 6 is obtained.
D_in = D_i + DP × c + DN (Formula 6)

  In the example of FIG. 3, when the distribution delay amount of the root node n2 is 0, Expressions 3 and 6 are applied, and DP = DN = 1, the distribution delay amount is within 4 and the distribution delay amount varies. In this example, the multicast tree 1 is configured so that as many nodes as possible do not need to be adjusted to reduce the number of nodes. As a configuration method, there are a configuration method that prioritizes the depth of the multicast tree 1, a configuration method that prioritizes the number of child nodes, and a combination of the two. In FIGS. 3A to 3C, priority is given to the depth. The configuration method is shown.

  Specifically, the depth-first configuration method means that the tree shape is deepened until the specified delivery delay amount is reached, and the maximum delivery delay amount that does not exceed the specified delivery delay amount in order from the deepest position. Nodes are connected in order from the position that is the delivery delay amount. In FIG. 3, first, the depth is increased to n2, n8, n3, n18, and n9. This state is shown in FIG. In FIG. 3A, since the delivery delay amount 4 specified by n9 has reached the designated delivery delay amount 4, the next node n23 is located at a position where the estimated delay amount of a newly connected node is as deep as possible, that is, n3. Is connected to n23 (see FIG. 3B). The next node n29 is connected to a node under which the estimated delay amount of the newly connected node is 3 because the estimated delay amount of the newly connected node is not 4. That is, n29 is connected under n8. Then, the estimated delay amount of the newly connected nodes n8 and n29 becomes 4. Since the next node n15 gives priority to depth, it is connected under n29. The next node n44 is connected under n8.

  Specifically, the configuration method that gives priority to the number of child nodes is to increase the number of child nodes of one node until the specified delivery delay amount is reached, and then specify the specified delivery delay in order from the end of the child. Nodes are connected in order from the position where the maximum delivery delay amount does not exceed the amount. When the configuration method that gives priority to the number of child nodes is taken, in FIG. 3C, the order in which new nodes are connected to the root node n2 is shown as follows: n2 → n8 → n35 → n47 → n31 → n5 → n20 → n22 → n11 → n3 → n29 → n44 → n15 → n18 → n23 → n9. That is, after the fourth child node n31 of the root node n2 is provided, the child node n8, n35, n47, n31 of the child nodes n8, n35, n47, n31 is not increased in the range of the delivery delay time to the root node n2. A child node will be provided for either. Among the child nodes n8, n35, n47, and n31, n8 has the largest number of child nodes. In this embodiment, from n31 that is the last child (child node having the largest delivery delay amount), n31 → The connection of child nodes is examined in the order of n47 → n35 → n8, and the nodes are connected in order from the position where the maximum delivery delay amount does not exceed the designated delivery delay amount.

  When a certain node leaves, when an isolated node is generated by the removal, the node connected last is reconnected to the parent position of the isolated node due to the node leaving. Since the last connected node has no child nodes, no problem occurs even if the connection position is moved, and the configuration of the multicast tree 1 does not change significantly. By reconfiguring in this way, the characteristics of the multicast tree can be maintained even when the node leaves.

In this method, there is a limit to the number of nodes in the multicast tree 1 that satisfy the specified delivery delay amount. When Expression 3 and Expression 6 are applied and DP = DN = 1, assuming that the maximum number of nodes that can satisfy a certain delivery delay amount i (i> 0) is Ni,
Ni = 2 to the power of i.

At this time, the number of nodes Mi with an adjustment amount of 0 that does not require adjustment is
Mi = 2 to the power of (i−1).

  Since Ni and Mi are the maximum numbers in the above model, this is not the case when there is a limit to the actual delivery delay amount or the number of nodes that can be connected per node.

  By configuring the multicast tree 1 in such a manner that there are as many nodes as possible that do not require adjustment of the delay amount to reduce delay variation, a node having a specified delivery delay amount, that is, Since the number of nodes having the adjustment amount of 0 is maximized, the multicast tree 1 can be configured with less adjustment for reducing delay variation.

  FIG. 4 is a block diagram illustrating a configuration of the root node 100 according to the first embodiment. In FIG. 4, the root node 100 includes a main control unit 110, a network interface 120, and a node information database 121. The main control unit 110 is a main part of a computer composed of a CPU, a RAM, an OS, and the like. The main control unit 110 operates a program that causes the computer to function as a root node of the multicast system. The control unit 110 can function as a transmission / reception unit 111, a participation reception function unit 112, a withdrawal reception function unit 113, a tree configuration calculation function unit 114, and a delay amount setting function unit 115. The node information database is stored in the storage unit of the computer. The program can be recorded on a recording medium such as a nonvolatile semiconductor storage device such as a flash memory, a magnetic recording medium such as a hard disk, and an optical recording medium such as a DVD or a Blu-ray disc.

  The node information database 121 stores node information in the multicast tree 1. The node information is information necessary for transmitting / receiving a message to / from another node 200 such as a node ID, IP address, and port number that uniquely identifies the node 200. The node information of all the nodes 200 in the tree structure of the multicast tree 1 Information. The node information database 221 also stores the delivery delay amount of each node, the estimated delay amount of the newly connected node (added node estimated delay amount), the delay adjustment amount, and the date and time when it joined the multicast tree 1.

  The transmission / reception unit 111 receives a message from the node 200 via the network interface 120, sees the message type, and sends the message to the participation reception function unit 112 or the withdrawal reception function unit 113.

  In addition, the transmission / reception unit 111 receives a message from the participation reception function unit 112 or the withdrawal reception function unit 113, and transmits the message to the node 200 that is the destination described in the message via the network interface 120.

  The participation reception function unit 112 processes a participation request message from a node newly participating in the multicast tree 1. Specifically, when a participation request message is received from the node 200, the message is sent to the tree configuration calculation function unit 114, and the calculation result is included in the participation response message and returned. Here, the participation request message includes node information of the newly participating node 200. Further, the participation response message includes node information of the node 200 that is a connection destination of the newly participating node 200.

  The leave acceptance function unit 113 processes a leave request message from a node already participating in the multicast tree 1. Specifically, when a leave request message is received from the node 200, a leave response message is returned. Further, a message is sent to the tree structure calculation function unit 114, and if an isolated node exists due to the node 200 leaving, the last connected node is reconnected to the parent position of the isolated node due to the node leaving Therefore, a movement request message is transmitted to the corresponding node 200. Thereafter, when a movement response message is received from the node 200, the message is sent to the tree structure calculation function unit 114. Here, the leave request message includes node information of the node 200 to leave. Further, the leaving response message includes information indicating message acceptance. The movement request message includes the node information of the node 200 that requests movement and the node information of the node 200 that is the movement destination. Further, the movement response message includes information indicating movement completion.

  The tree configuration calculation function unit 114 manages the configuration of the multicast tree 1 and calculates the configuration of the multicast tree 1 when the configuration needs to be changed. Specifically, when a participation request message is received from the participation reception function unit 112, the node information is read from the node information database 121 and the configuration of the multicast tree is confirmed. Thereafter, the connection destination of the newly participating node 200 is determined by the configuration method that prioritizes the depth, the configuration method that prioritizes the number of child nodes, or a combination of both, and becomes the connection destination of the newly participating node 200. The node information of the node 200 is returned to the participation reception function unit 112. Further, the node information database 121 including the connection destination information is updated for the node information of the newly participating node 200. Here, when the connection destination of the newly participating node 200 is determined, the designated delay amount from the delay amount setting function unit 115 is used for the calculation.

  Further, when receiving a leave request message from the leave acceptance function unit 113, the tree structure calculation function unit 114 reads the node information from the node information database 121 and confirms the configuration of the multicast tree. At this time, if there is no isolated node as the configuration of the multicast tree 1, the node information database 121 is updated with respect to the node information of the detached node 200, and the completion of the process is returned to the leaving acceptance function unit 113. When there is an isolated node as a configuration of the multicast tree 1, the node information database 121 searches for the node 200 that last joined the multicast tree 1 from the node information database 121 and requests its movement. Then, the node information of the node 200 as the movement destination is returned to the leave acceptance function unit 113. Thereafter, when a movement response message is received from the leaving acceptance function unit 113, the node information database 121 is updated in order to reflect the latest multicast tree configuration in the node information database 121.

  The delay amount setting function unit 115 sets a delivery delay amount that the multicast tree 1 should protect. Specifically, the system user determines the delivery delay amount and receives an input of the numerical value.

  FIG. 5 is a block diagram illustrating a configuration of the node 200 according to the first embodiment. In FIG. 5, the node 200 includes a main control unit 210, a network interface 220, and a node information database 221. The main control unit 210 is a main part of a computer that includes a CPU, a RAM, an OS, and the like. By operating a program that causes the computer to function as a node of the multicast system in the main control unit 210, the main control unit 210 is connected to the transmission / reception unit 211, the participation request function unit 212, and the withdrawal request function unit 213. The function unit 214 can function.

  The node information database 221 is equivalent to the node information database in the root node 100, and is node information of nodes above and below the own node in the tree structure of the multicast tree 1. The node information database 221 is stored in the storage unit of the computer.

  Since the transmission / reception unit 211 is equivalent to the transmission / reception unit 111 in the root node 100, the description thereof is omitted.

  The participation request function unit 212 has a function of requesting the root node 100 to participate when newly joining the multicast tree 1. Specifically, when a participation request message is transmitted to the root node 100 and a participation response message is received from the root node 100, the node information of the connection destination node described in the participation response message is passed to the connection function unit 214.

  The leave request function unit 213 has a function of requesting the root node 100 to leave when leaving the multicast tree 1. Specifically, when a leave request message is transmitted to the root node 100 and a leave response message is received from the root node 100, a disconnection request message is transmitted to one or a plurality of nodes in connection. Subsequently, when a disconnection response message is received from the node that sent the disconnection request message, the node information of the node that is in the connection relationship is deleted from the node information database 221.

  The connection function unit 214 has a function of establishing a connection relationship with other nodes. Specifically, when node information of the connection destination node is received from the participation request function unit 212 or when a movement request message is received from the root node 100 and node information of the connection destination node is received, the connection destination node is obtained. Send a connection request message to the node. Subsequently, when a connection response message is received from a node as a connection destination, the node information database 221 is updated. If a movement request message has been received from the root node 100, a movement response message is transmitted to the root node 100.

  Furthermore, when the connection function unit 214 receives a connection request message from another node, the connection function unit 214 transmits a connection response message and updates the node information database 221. Furthermore, when the connection function unit 214 receives a disconnection request message from another node, the connection function unit 214 transmits a disconnection response message and updates the node information database 221.

  Next, a particularly characteristic part of the operation of the present embodiment will be described. FIG. 6 is a flowchart illustrating an operation when the root node 100 according to the present embodiment accepts a participation request from a node 200 that newly participates in the multicast tree 1. When the operation is started, first, the transmission / reception unit 111 enters a state of waiting for communication from another node 200 or the main control unit 110 in the root node 100 (hereinafter referred to as an idle state) (step S300).

  In the idle state (step S300), the root node 100 receives the participation request message from the node 200 (step S301), refers to the node information database 121, and confirms the current configuration of the multicast tree 1 (step S302). . Subsequently, the configuration of the multicast tree 1 is determined by any one of the configuration method that prioritizes the depth described above, the configuration method that prioritizes the number of child nodes, or a combination of the two (step S303). A participation response message including the node information of the node 200 that is the connection destination is transmitted to the node 200 that has transmitted the participation request message so as to have the determined configuration of the multicast tree 1 (step S304). Is updated (step S305), and the process returns to the idle state.

  FIG. 7 is a flowchart showing an operation in the case where the root node 100 according to the present embodiment accepts a leave request from the nodes 200 participating in the multicast tree 1.

  In the idle state (step S300), the root node 100 receives a leave request message from the node 200 (step S311), and transmits a leave response message (step S312). Subsequently, the node information database 121 is referred to and the current configuration of the multicast tree 1 is confirmed (step S313). At this time, when this leaving node occurs, it is confirmed whether or not there is an isolated node as a configuration of the multicast tree 1 (step S314). In step S314, when there is no isolated node (No in step S314), the node information database 121 is updated (step S318), and the process returns to the idle state. On the other hand, if an isolated node exists in step S314 (Yes in step S314), the node 200 that last joined the multicast tree 1 is searched from the node information database 121 (step S315), and the node 200 is requested to move. Therefore, a movement request message is transmitted to the node 200 that requests the movement (step S316). Thereafter, when a movement response message is received (step S317), the node information database 121 is updated (step S318), and the process returns to the idle state.

  6 and 7 can be configured to be executed as a program that operates on a computer (main control unit) provided in advance in the root node 100.

  As described above, by configuring the multicast tree so that there are as many nodes as possible that do not need to adjust the delay amount to reduce delay variation, the node of the specified delivery delay amount, that is, the adjustment Since the number of nodes whose amount is 0 is maximized, the multicast tree 1 can be configured with less adjustment to reduce delay variation.

  A part or all of the above embodiments can be described as in the following supplementary notes, but is not limited thereto.

(Appendix 1)
A delay amount setting function unit for setting a delivery delay amount;
Tree configuration for calculating the configuration of the multicast tree so that the number of nodes that do not require adjustment of the delay amount to reduce delay variation is maximized with respect to the delivery delay amount set by the delay amount setting function unit A calculation function unit;
With
A multicast system, wherein a multicast tree is constructed based on a calculation result of the tree configuration calculation function unit.

(Appendix 2)
The tree configuration calculation function unit includes:
The tree is deepened until the set delivery delay amount is reached, and nodes are connected in order from the deepest position so that the maximum delivery delay amount does not exceed the set delivery delay amount. The multicast system according to supplementary note 1, wherein:

(Appendix 3)
The tree configuration calculation function unit includes:
The number of child nodes of one node is increased until the set delivery delay amount is reached, and the set delivery delay amount is not exceeded from the child node having the largest delivery delay amount among the child nodes. The multicast system according to appendix 1, wherein the number of child nodes for the child node is increased as described above.

(Appendix 4)
The tree configuration calculation function unit includes:
The tree is deepened until the set delivery delay amount is reached, and nodes are connected in order from the deepest position so that the maximum delivery delay amount does not exceed the set delivery delay amount. Algorithm and
The number of child nodes of one node is increased until the set delivery delay amount is reached, and the set delivery delay amount is not exceeded from the child node having the largest delivery delay amount among the child nodes. And an algorithm for increasing the number of child nodes for the child node,
The multicast system according to appendix 1, wherein the configuration of the multicast tree is calculated such that the number of nodes that do not require adjustment of the delay amount for reducing the delay variation by combining the above is maximized.

(Appendix 5)
The tree configuration calculation function unit includes:
When a node participating in the multicast tree leaves, the multicast tree configuration is calculated so that the last connected node is reconnected to the parent position of the isolated node when the node leaves. The multicast system according to any one of supplementary notes 1 to 4.

(Appendix 6)
A node information storage unit for storing node information in the multicast tree;
The multicast system according to any one of appendices 1 to 5, further comprising:

(Appendix 7)
The multicast system according to appendix 6, wherein the node information storage unit stores information on the order in which each node participates in the multicast tree.

(Appendix 8)
The multicast system according to appendix 6 or 7, wherein the node information storage unit stores information related to a date and time when each node participates in the multicast tree.

(Appendix 9)
The node information storage unit stores in advance an additional node estimated delay amount that is an estimated delay amount when a node is newly connected immediately below the node for each node, and the tree configuration calculation function unit includes the additional node The multicast system according to any one of appendices 6 to 8, wherein a connection destination of a node to be newly connected is determined using a node estimated delay amount.

(Appendix 10)
The multicast system according to any one of appendices 1 to 6, wherein the delay amount setting function unit and the tree configuration calculation function unit are provided in a root node of the multicast tree.

(Appendix 11)
11. The multicast system according to appendix 10, wherein the root node further includes a participation request function unit that receives a connection request from a node that newly participates in the multicast tree.

(Appendix 12)
12. The multicast system according to appendix 10 or 11, wherein the root node further includes a leave accepting function unit for accepting a leave request from the multicast tree.

(Appendix 13)
When there is a new node that wants to participate in the multicast tree, the number of nodes that do not require adjustment of the delay amount to reduce delay variation with respect to the predetermined distribution delay amount is maximized. Determining a node to which a node wishing to join is connected;
Notifying the node that wishes to join the node to be connected;
A method for constructing a multicast tree, comprising:

(Appendix 14)
The step of determining the connection destination node deepens the shape of the tree until the predetermined delivery delay amount, and in order from the deepest position, the maximum delivery delay amount not exceeding the predetermined delivery delay amount 14. The multicast tree configuration method according to appendix 13, wherein the node to be the connection destination is determined by connecting nodes in order.

(Appendix 15)
The step of determining the connection destination node includes:
The number of child nodes of one node is increased until the predetermined delivery delay amount is reached, so that the predetermined delivery delay amount is not further exceeded from the child node having the largest delivery delay amount among the child nodes. 14. The multicast tree configuration method according to appendix 13, wherein the node to be the connection destination is determined by increasing the number of child nodes with respect to the child node.

(Appendix 16)
The step of determining the connection destination node includes:
An algorithm that deepens the shape of the tree until the predetermined delivery delay amount is reached, and sequentially connects nodes so that the maximum delivery delay amount does not exceed the predetermined delivery delay amount in order from a deep position. ,
The number of child nodes of one node is increased until the predetermined delivery delay amount is reached, so that the predetermined delivery delay amount is not further exceeded from the child node having the largest delivery delay amount among the child nodes. An algorithm for increasing the number of child nodes for the child node;
14. The multicast tree construction method according to appendix 13, wherein a node to be the connection destination is determined by combining

(Appendix 17)
The method of claim 13 further comprising the step of reconnecting the last connected node to the parent position of the isolated node when a node participating in the multicast tree leaves and an isolated node is generated. The method for constructing a multicast tree according to any one of 1 to 16.

(Appendix 18)
A computer program for causing a computer included in a multicast system to construct a multicast tree,
A delay amount setting process for setting a delivery delay amount;
Tree configuration for calculating the configuration of the multicast tree so that the number of nodes that do not require adjustment of the delay amount to reduce delay variation is maximized with respect to the delivery delay amount set by the delay amount setting function unit Arithmetic processing,
Including
A program for constructing a multicast tree based on a computation result of the tree configuration computation processing.

(Appendix 19)
The tree structure calculation process is:
The tree is deepened until the set delivery delay amount is reached, and nodes are connected in order from the deepest position so that the maximum delivery delay amount does not exceed the set delivery delay amount. The program according to appendix 18, characterized by the above.

(Appendix 20)
The tree structure calculation process is:
The number of child nodes of one node is increased until the set delivery delay amount is reached, and the set delivery delay amount is not exceeded from the child node having the largest delivery delay amount among the child nodes. The program according to appendix 18, wherein the number of child nodes for the child node is increased.

(Appendix 21)
The tree structure calculation process is:
The tree is deepened until the set delivery delay amount is reached, and nodes are connected in order from the deepest position so that the maximum delivery delay amount does not exceed the set delivery delay amount. Processing,
The number of child nodes of one node is increased until the set delivery delay amount is reached, and the set delivery delay amount is not exceeded from the child node having the largest delivery delay amount among the child nodes. Process to increase the number of child nodes for the child node,
The program according to appendix 18, wherein the configuration of the multicast tree is calculated so as to maximize the number of nodes that do not require adjustment of the delay amount for reducing the delay variation by combining.

(Appendix 22)
The tree structure calculation process is:
When an isolated node occurs when a node participating in the multicast tree leaves, the configuration of the multicast tree is calculated so that the last connected node is reconnected to the parent position of the isolated node. The program according to any one of appendices 18 to 21, characterized in that:

(Appendix 23)
A program that causes a computer to build a multicast tree,
When there is a new node that wants to participate in the multicast tree, the number of nodes that do not require adjustment of the delay amount to reduce delay variation with respect to the predetermined distribution delay amount is maximized. Determining a node to which a node wishing to join is connected;
Notifying the node that wishes to join the node to be connected;
A program comprising:

(Appendix 24)
The step of determining the connection destination node deepens the shape of the tree until the predetermined delivery delay amount, and in order from the deepest position, the maximum delivery delay amount not exceeding the predetermined delivery delay amount The program according to appendix 23, wherein the node as the connection destination is determined by connecting the nodes in order.

(Appendix 25)
The step of determining the connection destination node includes:
The number of child nodes of one node is increased until the predetermined delivery delay amount is reached, so that the predetermined delivery delay amount is not further exceeded from the child node having the largest delivery delay amount among the child nodes. The program according to appendix 23, wherein the node to be the connection destination is determined by increasing the number of child nodes for the child node.

(Appendix 26)
Item 23. The method according to claim 23, further comprising the step of reconnecting the last connected node to a parent position of the isolated node when a node participating in the multicast tree leaves and an isolated node is generated. The program in any one of thru | or 25.

(Appendix 27)
A recording medium on which the program according to any one of appendices 18 to 26 is recorded.

(Appendix 28)
A recording medium on which the program according to the third aspect is recorded.

  Within the scope of the entire disclosure (including claims and drawings) of the present invention, the examples and the examples can be changed and adjusted based on the basic technical concept. In addition, various combinations or selections of various disclosed elements are possible within the scope of the claims of the present invention. That is, the present invention naturally includes various modifications and changes that could be made by those skilled in the art according to the entire disclosure including the claims and the drawings, and the technical idea.

1: Multicast tree 100: Root node 200: Node 110, 210: Main control unit 120, 220: Network interface 121, 221: Node information database 111, 211: Transmission / reception unit 112: Participation reception function unit 113: Departure reception function unit 114 : Tree configuration calculation function unit 115: Delay amount setting function unit 212: Participation request function unit 213: Leave request function unit 214: Connection function unit

Claims (10)

A means for setting a delivery delay amount;
Means for configuring the multicast tree so that the number of nodes that do not require adjustment of the delay amount for reducing delay variation is maximized with respect to the delivery delay amount set by the setting means;
A multicast system comprising: The means for configuring the multicast tree includes:
The tree is deepened until the set delivery delay amount is reached, and nodes are connected in order from the deepest position so that the maximum delivery delay amount does not exceed the set delivery delay amount. The multicast system according to claim 1. The means for configuring the multicast tree includes:
The number of child nodes of one node is increased until the set delivery delay amount is reached, and the set delivery delay amount is not exceeded from the child node having the largest delivery delay amount among the child nodes. The multicast system according to claim 1, wherein the number of child nodes for the child node is increased. The means for configuring the multicast tree includes:
When a node participating in the multicast tree leaves, the multicast tree is configured so that the last connected node is reconnected to the parent position of the isolated node due to the node leaving The multicast system according to any one of claims 1 to 3. Receiving a join request message from a node attempting to join the multicast tree;
Checking the current multicast tree configuration;
Determining a connection destination node of the node that transmitted the participation request message so that the number of nodes that do not require adjustment of the delay amount to reduce delay variation for a predetermined delivery delay amount is maximized;
Transmitting a participation response message including information of the connection destination node to the node that has transmitted the participation request message;
A multicast tree construction method comprising: Receiving a leave request message from a node participating in the multicast tree;
Sending a leave response message;
Confirming the configuration of the multicast tree before leaving,
Checking whether or not a node isolated from the multicast tree occurs due to the leaving; and
Searching for the node that last joined the multicast tree when the isolated node occurs;
Sending a move request message to the node where the leave occurred to the node that last joined the multicast tree;
Receiving a move response message;
The multicast tree construction method according to claim 5, further comprising:   A program causing a computer to execute the multicast tree construction method according to claim 5 or 6. The root node of the multicast tree,
A delay amount setting function unit for setting a delivery delay amount to be protected by the multicast tree;
Tree configuration calculation function that configures a multicast tree so that the number of nodes that do not require adjustment of the delay amount to reduce delay variation is maximized with respect to the delivery delay amount set by the delay amount setting function unit And
A root node of the multicast tree, characterized in that   Processes a participation request message received from a node wishing to participate in the multicast tree and transmits it to the tree configuration calculation function unit, and information on a node to which the node desiring to participate determined by the tree configuration calculation function unit is connected The multicast tree root node according to claim 8, further comprising: a participation reception function unit that generates a response message including: A leave acceptance function unit that processes a leave request message received from a node participating in the multicast tree and transmits the message to the tree configuration calculation function unit,
The tree structure calculation function unit determines whether or not there is an isolated node due to the leaving when the leave request message is transmitted, and if an isolated node occurs, the last connected node is determined by the leaving. Decide to reconnect to the parent position of the isolated node,
9. The leaving acceptance function unit transmits a message requesting movement to a position to be reconnected to the last connected node based on the determination of the tree configuration calculation function unit. Or the root node of the multicast tree according to 9.

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