JP2946193B2 - Multicast connection path selection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicast connection path selection method, and more particularly to a multicast connection path for a multicast connection in which a plurality of terminals are connected / released simultaneously via a communication network composed of a plurality of switching nodes. It concerns the selection method.

[0002]

2. Description of the Related Art A voice having CBR (Constant Bit Rate) traffic characteristics in which data is transmitted to a network at an equal speed using a communication network composed of a plurality of switching nodes, and a large amount of data in a short period of time. When transmitting computer-processed image information and the like having bursty traffic characteristics to be transmitted to a network to a plurality of terminals at once, in response to a virtual channel (VC) connection request from the calling terminal It is necessary to select a route connecting the originating terminal and each destination terminal, and reserve a band based on the required transmission capacity.

Conventionally, when such a multicast connection path is selected, an optimum path connecting the originating terminal and each destination terminal is determined for each destination terminal, and a portion of the optimum path commonly used is used. A method of extracting and sharing a route is conceivable. FIG. 7 is an explanatory diagram showing an example of a communication network composed of a plurality of switching nodes.
T is a calling terminal, LF1 and LF2 are called terminals, and a to g are switching nodes for connecting and connecting the calling terminal RT and each of the called terminals LF1 and LF2 in a net-like manner via a link.

In a communication network as shown in FIG. 7A, when selecting a multicast connection path for connecting a calling terminal RT and called terminals LF1 and LF2, first, the calling terminal RT and each called terminal LF1 and LF2 are connected. Are respectively determined. For the destination terminal LF1, a
The route composed of -bc is the optimal route with the least number of switching nodes and links.

[0005] Further, regarding the destination terminal LF2, ad-d-
The route composed of e is the optimal route with the least number of switching nodes and links. In this way, FIG.
As shown in (1), after an optimal route is obtained for each destination terminal, a partial route commonly used by these optimal routes is extracted. In this case, the link connecting between the switching nodes other than the RT-a is not commonly used, and the link is not shared.

[0006]

However, in such a conventional multicast connection route selection method, an optimum route connecting the originating terminal and each destination terminal is determined for each destination terminal, and a common route among these optimum routes is determined. Since the shared paths are extracted and shared, the share of switching nodes and links tends to be low,
There is a problem that a multicast connection path that can efficiently use network resources cannot be selected. For example, as shown in FIG. 7B, in the multicast connection path selected by the above-described conventional method,
The number of exchange nodes from the originating terminal to all destination terminals is 5, and the number of links used is 4.

However, as shown in FIG. 7 (c), for example, a multicast connection path such as abcce or adcec is a partial path abc or ad.
−e can be shared by the destination terminals LF1 and LF2, the number of switching nodes is 4, and the number of links is 3. Therefore, the conventional multicast connection path selection method cannot select such a multicast connection path that efficiently uses network resources. There was a problem that sometimes. The present invention has been made to solve such a problem, and an object of the present invention is to provide a multicast connection path selection method capable of efficiently using network resources and selecting a multicast connection path with a small propagation delay. I have.

[0008]

In order to achieve the above object, a multicast connection path selection method according to the present invention is directed to a method for selecting the number of switching nodes via an MC tree candidate for multicast connection between a calling terminal and all called terminals. MC tree configuration node selection processing for selecting the MC tree configuration node in order of decreasing order, and for each of these MC tree candidates, an MC tree configuration for determining an arc connecting the originating terminal and the destination terminal farthest from the originating terminal with the least number of via links An arc determination process is executed. Therefore, MC tree candidates for multicast connection between the originating terminal and all the destination terminals are selected in ascending order of the number of switching nodes via the nodes.
For the C-tree candidate, the arc that connects the originating terminal and the destination terminal farthest from the originating terminal with the least number of via links is determined.

In the MC tree configuration node determination process, for each MC tree candidate in the state being searched, all the node candidates in the state are searched, and a switching for accommodating a destination terminal of any of the node candidates is performed. A search of the MC tree is performed by sequentially storing what has reached or has reached the node in the MC tree candidate being searched, and all the switching nodes in which the searching MC tree candidate accommodates each destination terminal are executed. , The search is terminated at each point, and each search end tree is output as a desired MC tree candidate. Therefore, in the MC tree configuration node determination process, each M
With respect to the C-tree candidates, all node candidates in the state are searched, and those that have reached or are likely to reach the switching node accommodating any of the terminating terminals are searched for the MC tree candidates. The search is terminated when the MC tree candidate being searched reaches all the switching nodes accommodating each destination terminal, and each search end tree is output as a desired MC tree candidate.

Further, if the number of exchange nodes of the MC tree candidate being searched is not smaller than the number of exchange nodes of each search end tree, it is determined whether or not the number of search end trees is equal to or more than a predetermined number. If you have more than
This is to end the MC tree configuration node determination processing. Therefore, if the number of exchange nodes of the MC tree candidate being searched is not smaller than the number of exchange nodes of each search end tree, it is determined whether or not the number of search end trees has been obtained by a predetermined number or more. If so, the MC tree configuration node determination processing ends.

[0011] In the MC tree configuration arc determination process, the switching nodes of the MC tree under search which are closest to the terminating terminal are respectively selected and included in the MC tree under search among the switching nodes constituting the MC tree candidate. Arcs from the remaining switching nodes to the switching nodes adjacent to the selected switching node are sequentially selected, an arc search to be included in the MC tree being searched is performed, and all switching nodes accommodating each destination terminal are searched. Is terminated in the MC tree during search, and the arc search end tree is output as a desired MC tree. Therefore, in the MC tree configuration arc determination process, the switching nodes from the switching terminal of the searching MC tree which are closest to the destination terminal are selected, and are not included in the searching MC tree among the switching nodes forming the MC tree candidate. Arcs from the remaining switching nodes to switching nodes adjacent to the selected switching node are sequentially selected and included in the searching MC tree, and all switching nodes accommodating each destination terminal are included in the searching MC tree. The arc search is terminated at the point when the
Output as a tree.

[0012]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing a processing procedure of a multicast connection path selection method according to one embodiment of the present invention. In a network composed of a plurality of switching nodes, this processing is performed in response to a predetermined connection request from an arbitrary terminal. A communication network is selected to select a multicast connection path for simultaneous multicast (MC: Multi Cast) connection between a calling terminal (RT) and a plurality of called terminals (LF) specified by a connection request from the calling terminal. It is executed in advance by a predetermined switching node to be managed or in response to a connection request.

In performing the multicast connection path selection process, the switching node performs various types of connection information such as a network configuration to be processed, ie, switching nodes, links connecting the switching nodes, and switching nodes accommodating each terminal. Is assumed. Here, an ATM switching node will be described as an example of means for switching and connecting each link. However, this switching node may include a subnetwork composed of a plurality of switching nodes. In this case, each subnetwork is managed. The multicast connection selection process is executed by the subnet manager that performs the connection.

In the switching node, a multicast connection selection process for connecting a predetermined originating terminal and a plurality of destination terminals includes:
The processing as shown in FIG. 1 is executed. First, a plurality of switching nodes required for multicast connection between a calling terminal and all destinations are determined as MC tree candidates, and MC tree candidates composed of these switching nodes are output in ascending order of the number of switching nodes passed. Therefore, an MC tree configuration node determination process (step 10) is executed. Since the shape of the multicast connection path has a tree structure, the path pattern of the multicast connection path is hereinafter referred to as an MC tree.

Therefore, in this case, the switching nodes forming the MC tree for multicast connection between the calling terminal and all the called terminals are output as MC tree candidates in ascending order of the number of transit switching nodes. It should be noted that even if the same number of switching nodes
When a tree can be configured, a switching node group is selected as an MC tree candidate for each MC tree.

Next, it is determined whether or not an MC tree candidate for connecting the originating terminal and a plurality of destination terminals has been output by the MC tree configuration node determining process (step 11).
If no C-tree candidate is output (step 1
1: NO), it is determined that there is no MC tree for connecting these calling terminals and a plurality of called terminals (step 13), and the process ends.

On the other hand, if any MC tree candidate is output by the MC tree configuration node determination processing (step 11: YES), for each MC tree candidate, a calling terminal and its calling terminal are transmitted via the switching node group. In order to connect the destination terminal furthest from the terminal with the least number of via links, an MC tree configuration arc determination process is performed (step 12). An arc is an arbitrary route (branch) in a tree structure, and is actually composed of links connecting switching nodes.

Therefore, here, for each MC tree candidate having a small number of switching nodes, a link group forming an MC tree for multicast connection between the originating terminal and each destination terminal via the least number of via links is determined. Becomes If the MC tree can be constructed from different link groups even with the same number of links, the MC tree is selected as a different MC tree.

As described above, after selecting MC tree candidates for multicast connection between a predetermined calling terminal and all called terminals in ascending order of the number of transit switching nodes, for each of these MC tree candidates, the destination most distant from the calling terminal is selected. Since the arc to be connected with the least number of via links to the terminal is determined, the optimal route connecting the calling terminal and each destination terminal is determined for each destination terminal as in the past, and among these optimal routes, Compared with the method of extracting and sharing commonly used partial routes, it is possible to reliably select the multicast connection route with the least number of switching nodes and transit links, and efficiently use network resources And
In addition, the propagation delay can be reduced.

Next, referring to FIG. 2, the MC according to the present invention will be described.
The tree configuration node determination processing will be described. FIG.
10 is a flowchart illustrating a C-tree configuration node determination process, which is an example of a process corresponding to step 10 of FIG. 1 described above. Here, for the MC tree candidate in an arbitrary searching state, all the node candidates in the state are searched, and the node that has reached or is likely to reach the switching node that accommodates the destination terminal, that is, the LF accommodation node. The tree search is performed by sequentially storing those in the MC tree candidate.

Further, when all the LF accommodation nodes have been reached, the search is terminated, and among these search end trees, the desired MC tree candidates are output in ascending order of the number of exchange nodes. In the following description, the number of exchange nodes indicating MC tree candidates to be searched and the set of exchange nodes are denoted by mtn (), and the set of remaining LF accommodating nodes not reached by mtn () is denoted by mtn (). l
n.

Further, the switching node group mtn () indicating the MC tree candidate in the searching state and the corresponding remaining LF
A set holding the accommodating node group ln () in the order of the number of exchange nodes is Q, and a set holding the search end tree in the order of the number of exchange nodes is MTN. Further, a set including all node candidates in the MC tree candidate in an arbitrary searching state is defined as an.

FIG. 3 is an explanatory diagram showing the transition of the MC tree configuration node determination process, which has the same configuration as the network described above (FIG. 7). First, as an initialization process, a switching node group indicating an MC tree candidate including only the switching node accommodating the calling terminal, that is, the RT accommodating node is mtn
(1) is stored in Q (step 20), and the remaining LF accommodation nodes of the MC tree candidate are stored as ln (1) to store all LF accommodation nodes (step 21).

As a result, Q = {mtn (1) = {1 + 2, a}, ln (1) = {c, e}} is stored as the candidate MC tree under search. In mtn (), the first element indicates the minimum number of exchange nodes required to construct each MC tree candidate in an arbitrary search state.
Here, it is the sum of the number “1” indicating the RT accommodation node a and the number “2” indicating the LF accommodation nodes c and e.

Next, in steps 22 to 33, a tree search process is performed for each MC tree candidate.
First, an MC tree candidate under search is extracted from the top of Q (step 22). In this case, as described later, M in Q
Since the C-tree candidates are stored in the order of the number of individual switching nodes, the searching MC tree candidate with the smallest number of switching nodes is always selected from Q here.

The retrieved MC tree candidates during search are stored in processing variables mtn and ln, and Q
Becomes empty. mtn = mtn (1) = {1 + 2, a} ln = ln (1) = {c, e} Q = {

Subsequently, whether the number of exchange nodes, which is the first element of mtn, is smaller than the number of exchange nodes of each MC tree candidate in the search end tree group MTN, or whether there is no search end tree in the MTN. Is determined (step 23). Here, when the number of exchange nodes, which is the first element of mtn, is smaller than the number of exchange nodes of each MC tree candidate in the search end tree group MTN, or when there is no search end tree in the MTN (step 23: YE
S), the following node search processing and storage determination processing are started.

First, an arbitrary LF accommodating node from all the switching nodes of mtn and all of the switching nodes that may reach the arbitrary LF accommodating node are searched (step 24). Here, the node search method will be described with reference to FIG. FIG. 4 is an explanatory diagram showing a node search method, where ND1 to ND18 are switching nodes. In particular, ND1 (hatched hatching) is an RT accommodation node, ND
8, ND9, ND14-16, ND18 (thick line) are LF
It is an accommodation node.

In this case, ND1 is the only element (RT accommodation node) that constitutes mtn, and all node candidates from ND1 are searched. First, mtn
Then, among the nodes adjacent to each element in, an LF accommodation node or a node having three or more owned arcs is selected (condition 1). In the case of FIG. 4, ND15 and ND16 are selected as LF accommodation nodes adjacent to ND1, and ND2 is selected as a node having three or more owned arcs.

Next, among the nodes adjacent to each element in mtn, the other nodes other than the nodes in mtn that have two arcs and are connected by the arc are selected. This is repeated until the node of condition 1 appears (condition 2). In the case of FIG. 4, ND3 and ND4, and ND13 and ND
14 are collectively selected as node candidates.

In condition 2, if the destination node is LF
If the node is not the accommodation node and the number of owned arcs is one, it is not selected as a node candidate (condition 3). In FIG. 4, ND10, ND11 and ND12 correspond to this. Furthermore, in condition 2, the destination node is mtn
If it is a node included as an element in, it is not selected as a node candidate (condition 4). In FIG. 4, ND5 and ND6 correspond to this.

In condition 2, when a node which is an element in mtn is reached via the LF accommodation node, among arcs from the element in mtn to the LF accommodation node, an arc having a smaller number of transit nodes is used. Is preferentially selected (condition 5). In FIG. 4, for example, ND
If 3 and ND4 are already included in mtn, N
From the arc passing from D4 to ND8 via ND7,
The node corresponding to the arc going from ND4 directly to ND8 is selected.

Thus, in step 24, mt
n optional LF accommodating nodes connected to each switching node,
And all the switching nodes that can reach any LF accommodation node are retrieved. Therefore, FIG.
In (a), three node candidates, that is, bc as an (1), de as an (2), and fc as an (3) are searched from the RT accommodation node a, and It is stored in the group set an. an = {(b, c), (d, e), (f, g, c)}

Subsequently, it is determined whether or not there is a node candidate searched by the node search processing (step 2).
5) If one or more node candidates have been searched (step 25: YES), arbitrary node candidates are sequentially selected from the node candidates (step 26), and the selected node candidates correspond to the selected node candidates. The storage node is subjected to mtn storage determination processing (steps 27 to 31). First, it is determined whether the node newly connected by the selected arbitrary node candidate is the LF accommodation node (step 27).

Here, in the case of the LF accommodation node,
Since one of the desired LF accommodation nodes has been reached, the LF accommodation node is deleted from the remaining accommodation node group ln of the mtn (step 28). Further, it is determined whether or not the remaining accommodation nodes have disappeared (step 29). If the remaining accommodation nodes have disappeared, it is determined that mtn has reached all desired LF accommodation nodes, and the selected node candidate is included. mtn is stored in the MTN as a search end tree in the order of the number of exchange nodes (step 30).

On the other hand, in step 27, if the node newly connected by the selected arbitrary node candidate is not the LF accommodation node (step 27: NO), and if the remaining accommodation node still exists in step 29 (step 29) : NO), a new mtn including the selected node candidate is generated and stored in Q in the order of the number of exchange nodes (step 31).

Therefore, in FIG. 3A, when an (1) is selected as a node candidate, the LF accommodating node c is deleted from ln (step 28), and a new mtn is stored in Q. . an (1) = (b, c) ln = ln- (c) = {e} mtn = mtn + an (1) = {1 + 3, a, b, c} Q = {mtn (1) = {1 + 3, a, b, c}, ln (1) = {e}}

These steps 30 and 31
Is performed, it is determined whether or not there is an unselected node candidate in the node candidate group an (step 32). If there is an unselected node candidate (step 32: YES), the process returns to step 26 described above. . Therefore, an (2) is selected as the next node candidate, and an (2) = (d, e) ln = ln− (e) = {c} mtn = mtn + an (2) = {1 + 3, a, d, e｝ Q = ｛mtn (1) = ｛1 + 3, a, b, c｝, ln (1) = ｛e｝ mtn (2) = ｛1 + 3, a, d, e｝, ln (2) = ｛c ｝｝.

Further, an (3) is selected as a node candidate, and an (3) = (f, g, c) ln = ln- (c) = {e} mtn = mtn + an (3) = {1 + 4, a , F, g, c} Q = {mtn (1) = {1 + 3, a, b, c}, ln (1) = {e} mtn (2) = {1 + 3, a, d, e}, ln ( 2) = {c} mtn (3) = {1 + 4, a, f, g, c}, ln (3) = {e}

When all the node candidates have been selected (step 32: NO), another mtn is included in Q.
It is determined whether or not there is (step 33). If there is another mtn (step 33: YES), the process returns to step 22 described above. Therefore, mtn (1) from the top of Q
Is selected, and since the search termination tree is not stored in the MTN, as shown in FIG. 3B, an (1) is selected as a node candidate of mtn (1).

Mtn = mtn (1) = {1 + 3, a, b, c} ln = ln (1) = {e} Q = ｛mtn (2) = {1 + 3, a, d, e}, ln (2 ) = {C} mtn (3) = {1 + 4, a, f, g, c}, ln (3) = {e}}

An = {e} an (1) = (e) ln = ln− (e) = ｛｝ mtn = mtn + an (1) = ｛1 + 3, a, b, c, e｝ MTN = ｛MTN (1 ) = {1 + 3, a, b, c, e}}

Subsequently, mtn (2) is selected from the top of Q. Here, the number of exchange nodes “1 + 3” is not smaller than the number of exchange nodes “1 + 3” of each MC tree candidate in the search end tree group MTN (step 23: N
O), the search termination tree in the MTN has the desired communication quality QO
It is determined whether or not a predetermined number or more determined by S or the like is stored (step 34). If a predetermined number or more are stored (step 34: YES), it is determined that the desired number of MC tree candidates have been obtained, and the series of tree configuration node determination processing ends.

If the MTN does not contain a predetermined number or more of search end trees (step 34: N
O) The process proceeds to step S24 to continue the process. Therefore, as shown in FIG. 3C, an (1) is selected as a node candidate of mtn (2). mtn = mtn (2) = {1 + 3, a, d, e} ln = ln (2) = {c} Q = {mtn (3) = {1 + 4, a, f, g, c}, ln (3) ＝ {e}｝

An = {c} an (1) = (c) ln = ln− (c) = ｛｝ mtn = mtn + an (1) = {1 + 3, a, d, e, c} MTN = ｛MTN (1 ) = {1 + 3, a, b, c, e} MTN (2) = {1 + 3, a, d, e, c}}

Further, if mtn (3) is selected from Q, two MC tree candidates are stored in the MTN, but if the predetermined number is not satisfied, step 24 is executed.
Then, the same arc selection processing as in FIG. 3B is performed. mtn = mtn (3) = {1 + 4, a, f, g, c} ln = ln (3) = {e} Q = ｛｝ an = ｛e｝ an (1) = (e)

Ln = ln− (e) = ｛｝ mtn = mtn + an (1) = ｛1 + 4, a, f, g, c, e｝ MTN = ｛MTN (1) = ｛1 + 3, a, b, c, e｝ MTN (2) = {1 + 3, a, b, e, c} MTN (3) = {1 + 4, a, f, g, c, e}

Thereafter, at step 33, another mt is added to Q.
Since there is no n (step 33: NO), the set MTN already determined is set as a desired MC tree candidate group, and a series of MC tree configuration node determination processing ends.

As described above, in the MC tree configuration node determination processing, for each MC tree candidate in the state being searched, all the node candidates in the state are searched, and the switching node that accommodates the destination terminal, that is, the LF accommodation node The tree search process is performed by sequentially storing, in the MC tree candidate, those that have reached or have reached.

Further, the tree search processing is terminated when all the destination terminals are reached, and these search end trees are output as desired MC tree candidates. Therefore, by outputting these search end trees as MC tree candidates in ascending order of the number of switching nodes, it is possible to surely establish MC tree constituent nodes for multicast connection by sharing a large number of links connecting a predetermined originating terminal and a plurality of destination terminals. Can be obtained.

If the number of exchange nodes of the MC tree candidate being searched extracted from Q is not smaller than the number of exchange nodes in the search end tree group MTN, the number of search end trees is stored in the MTN in a predetermined number or more. It is determined whether or not the connection is established, and if a predetermined number or more is stored, the MC tree configuration node determination process is terminated. Therefore, for example, the multicast connection specified by a desired communication quality QOS or the like as the predetermined number is performed. By setting the number of repetitions at the time of unsuccess, it becomes possible to omit unnecessary MC tree candidate search processing and to obtain a number of MC tree candidates satisfying the communication quality in the order of the number of exchange nodes. .

Further, as a node search method, among nodes adjacent to each element in mtn, an LF accommodation node or a node having three or more owned arcs is selected (condition 1).
In addition, among the nodes connected by the arc and having two arcs, the other nodes other than the nodes in mtn are selected, and this node is repeatedly selected until the node of condition 1 appears (condition 2) As a result, nodes having no change in the mtn configuration can be selected collectively, and the time required for processing can be reduced.

In condition 2, if the destination node is LF
If it is not the accommodation node and the number of owned arcs is one (condition 3), furthermore, in condition 2,
When the node is included as an element in n (condition 4)
Does not select as a node candidate, and in condition 2, when reaching a node which is an element in mtn via an LF accommodation node, among arcs from an element in mtn to the LF accommodation node, Since a node corresponding to an arc having a small number of passing nodes is preferentially selected (condition 5), unnecessary arcs are deleted, and the time required for the subsequent mtn storage determination process for each selected node candidate Can be shortened.

Next, referring to FIG. 5, the MC according to the present invention will be described.
The tree configuration arc determination processing will be described. FIG.
9 is a flowchart illustrating a C-tree configuration arc determination process, which is an example of a process corresponding to step 12 of FIG. 1 described above. Here, for each MC tree candidate selected by the above-described MC tree configuration node determination process (step 10), a connection route with the smallest number of links via via from the originating terminal to the farthest terminal is determined.

FIGS. 6A and 6B are transition diagrams showing an MC tree configuration arc determination process, wherein FIG. 6A shows the configuration of an MC tree candidate selected by the MC tree configuration node determination process, and FIG. (C) shows an MC tree when an arc is determined based on the depth-first search method and an arc is determined based on the width-first search method of the present invention. In FIG. 6, ND1 to ND7 are switching nodes, and especially ND1 is a (shaded hatching) RT accommodation node,
ND3 to ND5 and ND7 (thick lines) are LF accommodation nodes.

First, as initialization processing, the RT accommodation node is stored in a desired MC tree (step 50). Next, from the MC tree, the switching node group LN
() Is extracted (step 51), and one of the switching nodes LN (i) is selected (step 52).

Subsequently, as an arc search process for LN (i), among the remaining switching nodes not included in the MC tree under search, switching node group MNL () directly connected to LN (i) via a link. ) (Step 5)
3), one of the switching nodes MLN (k)
Is selected (step 54). Here, it is determined whether or not MLN (k) exists (step 55). If it exists (step 55: YES), MLN (k) is converted from MLN (i) to MLN (k).
Arc to (k), here link and MLN (k)
Is stored in the MC tree during the search (step 56).

Thereafter, the flow returns to step 54 to execute another ML.
If N (k) is selected and MLN (k) no longer exists (step 55: NO), it is determined whether or not all LN (i) have been selected (step 57). Here, if another LN (i) exists (step 57: N
O), returning to step 52, selecting a new LN (i) and performing the arc search processing described above (steps 53 to 53).
56).

On the other hand, if all LN (i) have been selected (step 57: YES), it is determined whether or not there are any remaining switching nodes not included in the MC tree being searched (step 58). If there are still remaining switching nodes (step 58: YES), the flow returns to step 51 to newly extract a switching node group LN () from the most-destination terminal from the MC tree being searched, and to perform a search for each LN ( The arc search processing for i) is performed.

When all the switching nodes are included in the MC tree and there are no remaining switching nodes (step 58: NO), a series of MC tree configuration arc determination processing ends. Therefore, in the MC tree candidate of FIG. 6A, ND1 which is the RT accommodation node is first selected as NL (i), and ND2 and ND6 are respectively MNL.
(K) is stored in the searching MC tree.

Subsequently, ND2 and ND6 are NL (i)
And for ND2, ND3 and ND
4 is selected as MNL (k) and stored in the searching MC tree, and for ND6, ND5 and ND7 are selected as MNL (k) and stored in the searching MC tree, and the remaining switching nodes are exhausted. Then, the process ends. Thereby, the MC as shown in FIG.
The tree is determined.

On the other hand, by a general depth-first search method,
If an arc is selected repeatedly until an arbitrarily selected arc reaches an LF accommodation node having no more arcs, an MC tree as shown in FIG. 3B is obtained. That is, for example, when ND2 is selected from ND1, after ND3 is selected, ND4 is returned to ND2 and ND4 is selected.
D5, ND6 and ND7 will be selected.

Accordingly, in comparison with the case where the number of via links from ND1 to ND7 is 5 as in this case, the number of via links to all LF accommodation nodes is within 2 in FIG. Multicast connection can be performed with a small number of via links, and the propagation delay from the originating terminal to each destination terminal can be reduced.

[0064]

As described above, according to the present invention, an MC tree constituting node determining process for selecting an MC tree candidate for multicast connection between an originating terminal and all destination terminals in order of decreasing number of switching nodes via the nodes is executed. For each of these MC tree candidates, an MC tree configuration arc determination process for determining an arc that connects the destination terminal farthest from the originating terminal with the least number of via links is performed. The optimal route connecting the destination terminal and each destination terminal is determined for each destination terminal, and the number of exchange nodes and the number of exchange nodes are compared with those obtained by extracting and sharing a common partial route among these optimum routes. It is possible to select the multicast connection route with the fewest number of links via links reliably, to use network resources efficiently and to reduce propagation delay. The ability.

In the MC tree configuration node determination process, for each MC tree candidate in the state being searched, all the node candidates in the state are searched, and a switching terminal accommodating the destination terminal of any of the node candidates is searched. A search of the MC tree is performed by sequentially storing what has reached or has reached the node in the MC tree candidate being searched, and all the switching nodes in which the searching MC tree candidate accommodates each destination terminal are executed. The search is terminated at the time when the search destination is reached, and each of these search end trees is output as a desired MC tree candidate. Therefore, the link for connecting a predetermined calling terminal and a plurality of receiving terminals is more shared and multicast connection is performed. It is possible to reliably obtain the MC tree configuration node that performs the above operation.

Further, if the number of exchange nodes of the MC tree candidate being searched is not smaller than the number of exchange nodes of each search end tree, it is determined whether or not the number of search end trees is equal to or more than a predetermined number. If you have more than
Since the MC tree configuration node determination processing is ended, for example, by setting the number of repetitions at the time of unsuccessful multicast connection specified by a desired communication quality QOS or the like as a predetermined number, unnecessary MC tree candidates are searched. The processing can be omitted, and the number of MC tree candidates satisfying the communication quality in the order of the number of exchange nodes can be obtained.

In the MC tree configuration arc determination process, the switching nodes closest to the destination terminal are selected from among the switching nodes of the MC tree being searched, and are included in the searching MC tree among the switching nodes constituting the MC tree candidate. Arcs from the remaining switching nodes to the switching nodes adjacent to the selected switching node are sequentially selected and searched. An arc search to be included in the MC tree is executed, and all switching nodes accommodating each destination terminal are searching. The arc search is terminated at the time when the arc search is included in the MC tree.
Since the output is performed as a C-tree, all the destination terminals can be connected by multicast with a smaller number of via links, and the propagation delay from the source terminal to each destination terminal can be reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a processing procedure of a multicast connection path selection method according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an MC tree configuration node determination process.

FIG. 3 is an explanatory diagram showing transition of MC tree configuration node determination processing.

FIG. 4 is an explanatory diagram showing a node search method.

FIG. 5 is a flowchart showing an MC tree configuration arc determination process.

FIG. 6 is an explanatory diagram showing a transition of an MC tree configuration arc determination process.

FIG. 7 is an explanatory diagram showing a conventional multicast connection path selection method.

[Explanation of symbols]

11: MC tree configuration node determination processing, 13: MC tree configuration arc determination processing, RT: Calling terminal, LF1, LF2
... destination terminals, a to g, ND1 to ND18 ... switching nodes.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-8-242226 (JP, A) 1988 Fall Meeting of IEICE, B-147, p. B-2-23 1990 Spring Meeting of IEICE, B -587, p.3-165 1995 General Meeting of IEICE, B-825, p.271 1995 General Meeting of IEICE, SB-4-1, p. 639 (58) Field surveyed (Int.Cl. ⁶ , DB name) H04L 12/18

Claims (4)

(57) [Claims] 1. Multicast connection path selection for selecting a connection path when performing a multicast connection for simultaneously connecting a predetermined originating terminal and a plurality of destination terminals via a communication network composed of a plurality of switching nodes. A method for multicast connection between a calling terminal and all called terminals
An MC tree configuration node determination process is performed to select the C tree candidates in the order of the number of transit switching nodes in ascending order. A multicast connection path selection method, wherein an MC tree configuration arc determination process for determining an arc to be connected is performed. 2. The method for selecting a multicast connection path according to claim 1, wherein in the MC tree configuration node determining process, for each MC tree candidate in a state being searched, all node candidates in the state are searched. A search of the MC tree is performed by sequentially storing, in the MC tree candidate under search, those that have reached or are likely to reach the switching node accommodating any one of the terminating terminals. A multicast connection path selecting method, wherein the search is terminated when the candidate reaches all the switching nodes accommodating each destination terminal, and each search end tree is output as a desired MC tree candidate. 3. The multicast connection path selection method according to claim 2, wherein, if the number of exchange nodes of the MC tree candidate being searched is not smaller than the number of exchange nodes of each search end tree, the number of search end trees is predetermined. A method for selecting a multicast connection path, characterized in that it is determined whether or not a predetermined number or more is obtained, and if a predetermined number or more is obtained, the MC tree configuration node determination process is terminated. 4. The method for selecting a multicast connection path according to claim 1, wherein, in the MC tree configuration arc determining process, the switching nodes closest to the destination terminal are selected from among the switching nodes of the MC tree being searched, and the MC tree candidates are selected. Searching MC among switching nodes to configure
From the remaining switching nodes not included in the tree, arcs to switching nodes adjacent to the selected switching node are sequentially selected, and an arc search to be included in the MC tree being searched is performed. Wherein the arc search is terminated when the switching node is included in the searching MC tree, and the arc searching end tree is output as a desired MC tree.