JP4479601B2 - Multicast route calculation method and apparatus, program, and storage medium storing program - Google Patents

Description

  The present invention relates to a multicast path calculation method and apparatus, a program, and a storage medium storing the program, and in particular, in a communication network in which a multicast transmission apparatus and a unicast transmission apparatus are mixed, a link from a transmission transmission apparatus to a reception transmission apparatus. The present invention relates to a multicast route calculation method and apparatus used for obtaining a route that minimizes the cost, a program, and a storage medium storing the program.

  Conventionally, in a communication network, as shown in FIG. 20, the multicast route is calculated from the topology information 10 collected by the topology information collecting mechanism and the route setting restriction conditions 11 such as the transmission transmission device, the reception transmission device, and the necessary bandwidth. A multicast route calculation device 12 that outputs the calculation result to the route setting mechanism 13 is used.

  Here, a multicast route calculation apparatus using the Dijkstra multicast route calculation method according to the prior art will be described with reference to FIG.

  When the topology information including the connection relationship and the link cost as shown in FIG. 21A and the conditions of the transmission transmission device / reception transmission device are input, the link cost from the transmission transmission device to the reception transmission device is minimized. Calculate a multicast route such that

  Next, as shown in FIG. 5B, the link cost from the transmission transmission apparatus A to the adjacent transmission apparatuses (B, I) is calculated and set as a candidate apparatus. Next, the one with the lowest link cost from the transmission transmission device is selected from the candidate devices. In this topology, B having a link cost of “2” is selected, and a route from the transmission transmission apparatus A to B is determined. B is removed from the candidate devices, and is a visited device. The transmission apparatus adjacent to the determined transmission apparatus is searched. At that time, the device A immediately before the determined transmission device is not included in the adjacent devices. As shown in FIG. 6C, the link cost from the transmission transmission apparatus via the determined transmission apparatus is calculated for each adjacent transmission apparatus, and is set as a candidate apparatus.

  Similarly, as shown in FIG. 22D, I is a visited device, and transmission devices E and H adjacent to I are candidate devices.

  Next, from the candidate devices, the one with the lowest link cost from the transmission transmission device is selected. If there are a plurality of candidate devices, one is selected using other route setting restriction conditions. In this example, G is selected and G is the visited device. Further, when a route adjacent to the transmission device G is selected as a candidate, if the adjacent device is already a candidate device or a visited transmission device, the link cost from the transmission transmission device already calculated, The link cost from the transmission transmission apparatus via the determined transmission apparatus G is compared, and the smaller one is set as a route to the adjacent apparatus. Accordingly, in FIG. 22 (e), H is a candidate device from I, but by comparing the link costs from the transmission transmission device (comparison of (d) and (e) in the figure), H is Candidate device from G. F is a candidate device from B because the link cost from the transmission transmission device via G is large.

  Subsequently, as shown in FIG. 22 (f), F is removed from the candidate devices in the route to F as in the previous case, and is set as a visited device. Further, the route to E is determined, E is removed from the candidate devices, and the visited device is set. As shown in FIG. 23 (g), an adjacent device E is a candidate device D.

  After searching for all devices, the route is determined from the candidate devices in ascending order of link cost from the transmission transmission device.

  As a result, as shown in FIG. 23 (h), a multicast route including all the reception transmission devices input from the transmission transmission device has been found. As shown in FIG. 23 (i), an unnecessary route that does not reach the receiving transmission device is deleted from the route and output to the route setting mechanism 13.

In this output result, a branch has occurred in B which is a unicast transmission apparatus. In this way, in the prior art, a plurality of candidate devices are determined from the search target device using only the link cost without considering the difference between the multicast transmission device and the unicast transmission device. A route that branches in the transmission device is output (for example, see Non-Patent Document 1).
WIDE 2002 Internet Architecture 6th Lecture Materials http://www.soi.wide.ad.jp/class/20020022/materials_for_student/06/na-06.pdf (10 pages, 11 pages)

  In the technology shown above, a multicast route that minimizes the link cost from the transmitting transmission device to each receiving transmission device is calculated from the input topology information and route setting restriction conditions, and is output to the route setting mechanism. Can do.

  However, in the existing technology, in a communication network in which a multicast transmission device and a unicast transmission device are mixed, route calculation is performed without considering the difference between them. There is a problem that such a multicast route is output. As a result, the route setting mechanism cannot set the route normally and cannot communicate.

  The present invention has been made in view of the above points. Even in a communication network in which a multicast transmission apparatus and a unicast transmission apparatus are mixed, the link cost from the transmission transmission apparatus to each reception transmission apparatus is reduced, and the unicast transmission apparatus is reduced. An object of the present invention is to provide a multicast route calculation method and apparatus and program capable of outputting a multicast route that does not cause a branch in the cast transmission device, and a storage medium storing the multicast route calculation program.

  FIG. 1 is a diagram for explaining the principle of the present invention.

The present invention (Claim 1) applies a Dijkstra multicast route calculation method using topology information and route setting constraint conditions of an input communication network in a communication network in which multicast transmission devices and unicast transmission devices are mixed. A multicast route calculation method for calculating a multicast route,
A Dijkstra route calculation step (Step 1) in which all transmission devices in the communication network are regarded as multicast transmission devices, a multicast route is calculated by the Dijkstra multicast calculation method, and stored in the search route storage means;
Using the route output from the searched route storage means, the number of receiving devices that can be reached by each route in the unicast transmission device is calculated and stored in the receiving device number storage means (step 2). When,
An initial setting step (step 3) in which the transmission transmission device is stored in the visited storage means and is set as a search target device;
A multicast determination step (step 4) for determining whether the search target device is a unicast transmission device or a multicast transmission device;
In the multicast determination step, when it is determined as a unicast transmission device, one of the neighboring devices on the path having the maximum number of reception devices stored in the reception device number storage unit is set as a candidate device in the candidate device storage unit. A candidate device determination step (step 5) for storing the unicast device;
In the multicast determination step, when the search target device is a multicast transmission device, if the candidate device selected from the neighboring devices of the search target device is a candidate device already selected from the unicast transmission device, Candidate device for multicast device that re-selects candidate device from neighboring devices of cast transmission device, stores in candidate device storage means, and stores link cost and route to re-selected candidate device in search route storage means A decision step (step 6);
A search target device determination step (step 7) for selecting a candidate device with the lowest link cost from candidate devices stored in the candidate device storage means and storing it in the visited device storage means as a visited device;
When all the receiving devices are set in the visited device storage means (step 8), an output step (step 9) for outputting the route stored in the searched route storage means is performed.

The present invention (Claim 2) applies the Dijkstra multicast route calculation method using the topology information and route setting constraint conditions of the input communication network in a communication network in which multicast transmission devices and unicast transmission devices are mixed. A multicast route calculation method for calculating a multicast route,
A Dijkstra route calculation step in which all transmission devices in the communication network are regarded as multicast transmission devices, a multicast route is calculated by the Dijkstra multicast calculation method, and stored in the search route storage means;
A first receiving device number counting step of calculating the number of receiving devices that each route in the unicast transmission device can reach using the route output from the searched route storing means, and storing the number in the receiving device number storing means; ,
An initial setting step of storing the transmission transmission device in the visited storage means to be a search target device;
A multicast determination step for determining whether the search target device is a unicast transmission device or a multicast transmission device;
In the multicast determination step, when it is determined that the device is a unicast transmission device, one of the neighboring devices on the path having the maximum number of reception devices stored in the reception device number storage unit is selected as a candidate device, and a candidate is selected. A candidate device determination step for a unicast device to be stored in the device storage means;
Steps for resuming all transmission devices as multicast transmission devices and calculating multicast routes by the Dijkstra multicast route calculation method and storing them in the search route storage means for the topology that is disconnected except for the route to the selected candidate device When,
A second receiving device number counting step of calculating the number of receiving devices that each route in the unicast transmission device can reach using the route output from the searched route storing means, and storing the number in the receiving device number storing means; ,
If it is determined in the multicast determination step that the device is a multicast transmission device, if the candidate device selected from the neighboring devices of the search target device is a candidate device that has already been selected from the unicast transmission device, the unicast transmission device Candidate device for multicast device that re-selects candidate device from neighboring devices of cast transmission device, stores in candidate device storage means, and stores link cost and route to re-selected candidate device in search route storage means A decision step;
A search target device determination step of selecting a candidate device with the lowest link cost from candidate devices stored in the candidate device storage means, and storing it in the visited device storage means as a visited device;
An output step of outputting a route stored in the searched route storage means when all the receiving devices are set in the visited device storage means.

  FIG. 2 is a principle configuration diagram of the present invention.

The present invention (Claim 3) applies the Dijkstra multicast route calculation method using the topology information and route setting constraint conditions of the input communication network in a communication network in which multicast transmission devices and unicast transmission devices are mixed, A multicast route calculation device for calculating a multicast route,
Search route storage means 112 for storing the route to each transmission device to the transmission device and the link cost;
Visited device storage means 111 for storing the searched transmission device as a visited device;
Candidate device storage means 113 for storing candidate devices;
Receiving device number storage means 114 for storing the counted number of receiving devices;
Dijkstra route calculation means 120 that regards all transmission devices in the communication network as multicast transmission devices, calculates a multicast route by the Dijkstra multicast calculation method, and stores it in the search route storage means 112;
Using the route output from the search route storage unit 112, the number of receiving devices that each route in the unicast transmission device can reach is calculated and stored in the receiving device number storage unit 114; ,
An initial setting unit 103 which stores the transmission transmission device in the visited storage unit 111 and sets it as a search target device;
Multicast determination means 104 for determining whether the search target device is a unicast transmission device or a multicast transmission device;
When the multicast determination unit 104 determines that the device is a unicast transmission device, one of the neighboring devices on the path having the maximum number of reception devices stored in the reception device number storage unit 114 is stored as a candidate device. Unicast device candidate device determination means stored in the means 113;
In the multicast determination means 104, when the search target device is a multicast transmission device, if the candidate device selected from the neighboring devices of the search target device is a candidate device already selected from the unicast transmission device, A multicast device that reselects a candidate device from neighboring devices of a unicast transmission device, stores it in the candidate device storage means 113, and stores the link cost and route to the reselected candidate device in the search route storage means 112 Candidate device determining means 106,
A search target device determination unit 108 that selects a candidate device with the lowest link cost from candidate devices stored in the candidate device storage unit 113 and stores the selected device in the visited device storage unit 111 as a visited device;
A route completion determination unit 109 that outputs a route stored in the searched route storage unit 112 when all the reception devices are set in the visited device storage unit 111;

The present invention (Claim 4) applies a Dijkstra multicast route calculation method using topology information and route setting constraint conditions of an input communication network in a communication network in which multicast transmission devices and unicast transmission devices are mixed. A multicast route calculation device for calculating a multicast route,
Search route storage means for storing the route to each transmission device to the transmission device and the link cost;
Visited device storage means for storing the searched transmission device as a visited device;
Candidate device storage means for storing candidate devices;
Receiving device number storage means for storing the counted number of receiving devices;
Dijkstra route calculation means that regards all transmission devices in the communication network as multicast transmission devices, calculates a multicast route by the Dijkstra multicast calculation method, and stores it in the search route storage means;
First receiving device number counting means for calculating the number of receiving devices that each route in the unicast transmission device can reach using the route output from the searched route storing means, and storing in the receiving device number storing means; ,
An initial setting unit that stores the transmission transmission device in the visited storage unit and sets it as a search target device;
Multicast determination means for determining whether the search target device is a unicast transmission device or a multicast transmission device;
When the multicast determination means determines that the device is a unicast transmission device, it selects one of the neighboring devices on the path having the maximum number of reception devices stored in the reception device number storage means as a candidate device, and Unicast device candidate device determination means for storing in the device storage means;
Routes for which topology other than the route to the selected candidate device is disconnected, all transmission devices are regarded as multicast transmission devices again, multicast routes are calculated by the Dijkstra multicast route calculation method, and stored in the search route storage means Recalculation means;
Second receiving device number counting means for calculating the number of receiving devices that each route in the unicast transmission device can reach using the route output from the searched route storing means, and storing in the receiving device number storing means; ,
When the multicast determination means determines that the device is a multicast transmission device, if the candidate device selected from the neighboring devices of the search target device is a candidate device already selected from the unicast transmission device, the unicast transmission device Candidate device for multicast device that re-selects candidate device from neighboring devices of cast transmission device, stores in candidate device storage means, and stores link cost and route to re-selected candidate device in search route storage means A determination means;
A search target device determining unit that selects a candidate device having the lowest link cost from candidate devices stored in the candidate device storage unit, and stores the selected device in the visited device storage unit as a visited device;
Route completion determining means for outputting a route stored in the searched route storage means when all the receiving devices are set in the visited device storage means.

The present invention (Claim 5) includes a computer having a search route storage unit, a visited device storage unit, a candidate device storage unit, and a reception device number storage unit.
A multicast route calculation program that functions as a multicast route calculation apparatus having the means according to claim 3 or 4.

The present invention (Claim 6) includes a computer having a search route storage means, a visited device storage means, a candidate device storage means, and a reception device number storage means.
A storage medium storing a program that functions as a multicast route calculation apparatus having the means according to claim 3.

  As described above, according to the present invention, in a system in which multicast transmission apparatuses and unicast transmission apparatuses are mixed on a communication network, first, all transmission apparatuses are regarded as multicast transmission apparatuses and are routed by Dijkstra. In the case of a multicast transmission device, branching is performed so that the link cost from the transmission transmission device is minimized, and for a unicast transmission device, reception that can be reached from among the branch routes of the route calculation result Select a route with a large number of transmission devices. Thereby, suppression of branching in the unicast transmission apparatus and selection of a route with low transmission cost can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 3 shows the configuration of the route calculation apparatus according to the first embodiment of the present invention.

  The route calculation apparatus shown in the figure includes a topology information storage unit 101, a constraint condition storage unit 102, an initial setting unit 103, a multicast determination control unit 104, a multicast determination unit 105, a multicast device candidate device determination unit 106, and a unicast device. Candidate device determination unit 107, search target device determination unit 108, route completion determination unit 109, reception device count unit 110, visited device storage unit 111, search route storage unit 112, candidate device storage unit 113, reception device number storage unit 114. Among these, the topology information storage unit 101, the constraint condition storage unit 102, the visited device storage unit 111, the search route storage unit 112, the candidate device storage unit 113, and the reception device number storage unit 114 are stored in a storage medium such as a memory or a hard disk. Assume that it is stored.

  The topology information storage unit 101 stores the input connection relationship between devices, the multicast distribution capability of each device, the link cost between devices, and the like.

  The constraint condition storage unit 102 stores a constraint condition of a route to be output from a transmission device, a reception device, or the like.

  In the initial setting unit 103, information on the transmission device (for example, device ID) is extracted from the constraint condition storage unit 102 and stored in the visited device storage unit 111. In addition, information on the transmission device (for example, device ID) is sent to the multicast determination control unit 104 as a search target device.

  The multicast determination control unit 104 receives information (for example, device ID) of the search target device from the initial setting unit 103, and controls the multicast determination unit 105 to “recognize all devices as multicast transmission devices” and the search target device. Information (for example, device ID) is sent. Further, a signal is sent to the search path storage unit 112 so as to be output to the receiving device count unit 110 after the calculation is completed. In addition, when receiving a signal indicating that the number of received transmission devices is set from the reception transmission device count unit 110, the data in the visited device storage unit 111, the searched route storage unit 112, and the candidate device storage unit 113 are reset to A restart control signal is sent to the setting unit 103.

  When the multicast determination unit 105 receives a control signal from the multicast determination control unit 104, the multicast determination unit 105 sends the received information on the search target device (for example, device ID) to the multicast device candidate device determination unit 106. When the control signal is not received, the multicast capability is read from the topology information storage unit 101, it is determined whether the search target device is a unicast device from the multicast device, and the search target device is determined as a unicast device candidate device based on the determination result. The data is sent to the determination unit 107 or the multicast candidate device determination unit 106.

  The unicast candidate device determination unit 107 acquires the neighboring device of the search target device from the topology information storage unit 101. The number of receiving devices of each neighboring device in the search target device is acquired from the receiving device number storage unit 114, one neighboring device having the largest number of receiving transmission devices is selected, and that device is set in the candidate device storage unit 113. In addition, the link cost and route from the transmission transmission device to the selected candidate device are set in the search route storage unit 112.

  The multicast candidate device determination unit 106 acquires, from the topology information storage unit 101, link costs between adjacent devices and adjacent devices of the search target device. The link cost of each neighboring device via the search target device is calculated, and if it is not set in the search path storage unit 112 or smaller than the set link cost, information on the neighboring device (for example, device ID) is obtained. Candidate device storage unit 113 is set. At this time, when the information on the candidate device is already set in the candidate device storage unit 113 and is a candidate device from another unicast transmission device, the information on the unicast transmission device (for example, the device ID) is changed to the unicast transmission device. This is sent to the cast candidate device determination unit 107.

  The search target device determination unit 108 reads out the candidate device with the lowest link cost set in the candidate device storage unit 113, sets it as the search target device, and sends information about the device (for example, device ID) to the route completion determination unit 109. send. Further, the device information (for example, device ID) is deleted from the candidate device storage unit 113 and stored in the visited device storage unit 111.

  The route completion determination unit 109 determines whether all the receiving devices in the constraint condition storage unit 102 are set in the visited device storage unit 111. If all the reception devices are included, the route completion determination unit 109 determines that the route is completed, and stores it in the search route storage unit 112. Send a completion signal. If not all are included, the received information on the search target device is sent to the multicast determination unit 105.

  The search route storage unit 112 receives a completion signal from the route completion determination unit 109 and outputs the stored route. When the control signal is received from the multicast determination control unit 104, the signal is output to the receiving device count unit 110. When the control signal is not received, the route is output and the process ends normally.

  The reception device count unit 110 searches the received multicast route with reference to the search route storage unit 112 and the constraint condition storage unit 102, and counts the reception transmission devices that can be reached in each route of all unicast transmission devices. The number is set in the receiving device number storage unit 114. Also, after the setting is completed, a signal indicating the completion of setting the number of receiving transmission devices is transmitted to the multicast determination unit 105.

  4 to 8 are flowcharts of operations in the first embodiment of the present invention.

  In the following flowchart, s indicates a transmission transmission device, and v indicates a search target transmission device (usually a transmission device whose path has just been determined).

  Step 101) All devices are regarded as multicast in advance, and a route is calculated by the Dijkstra method and stored in the searched route storage unit 112.

  Step 102) The calculated route of the search route storage unit 112 is searched in advance, and the number of reception devices that can be reached through the next hop device of the unicast device is stored in the reception device number storage unit 114.

  Step 103) In the initial setting unit 103, the transmission transmission device s is set as a search target transmission device v.

  Step 104) The multicast determination unit 105 refers to the topology information storage unit 101 to determine whether the search target device v is a multicast transmission device. If it is a multicast transmission apparatus, the process proceeds to step 105; otherwise, the process proceeds to step 200 [Process 3].

  Step 105) Let f be a transmission apparatus that is adjacent to the search target apparatus v and is not the transmission apparatus immediately preceding v on the determined path. If no f exists, the following processing is not executed.

  The multicast device candidate device determination unit 106 calculates the link cost between the transmission device s and the transmission device f via the search target device v, and sets the value as df.

  Step 106) The multicast device candidate determination unit 106 acquires the link cost df of the transmission device f, refers to the visited device storage unit 111 and the candidate device storage unit 113, and determines that the transmission device f is a visited device or It is determined whether it is a candidate device of another device.

  If it is not a visited device, the process proceeds to step 108, and if it is a visited device, the process proceeds to step 107.

  Step 107) If it is a visited device, it is determined whether the already calculated link cost is larger than the link cost df calculated in Step 105. If it is larger, the process proceeds to Step 109. 114.

Step 108) The multicast candidate device determination unit 106 stores the route and link cost via the search device v from the transmission transmission device s to the transmission device f in the search route storage unit 112, and sets f as a candidate device. [Process 2]
Step 109) The multicast candidate apparatus determining unit 106 sets p as the transmission apparatus immediately preceding f in the path stored in the searched path storage unit 112.

  Step 110) The same operation as in the above step 108 is performed.

  Step 111) The multicast determination unit 105 determines whether the transmission device p is a multicast transmission device. If the transmission device p is a multicast transmission device, the process proceeds to step 114.

  Step 112) If it is not a multicast transmission device, let p be a search device v.

  Step 113) Steps 200 to 207 [Process 3] described later are performed.

  Step 114) If it is a multicast transmission device, the candidate device determination unit 107 for unicast refers to the candidate device storage unit 113 to determine whether there is a candidate device, and if it exists, proceeds to Step 120. .

  Step 115) If no candidate device exists, the search target device determination unit 108 sets i as the candidate device with the lowest link cost from the transmission transmission device s. If there are multiple, select one using other conditions. A route to the i is determined, i is deleted from the candidate device storage unit 113, and i is stored in the visited device storage unit 111 as a visited device.

  Step 116) The candidate device i is set as the search device v.

  Step 117) The route completion determination unit 109 determines whether all the receiving transmission devices are included in the route determined with reference to the visited device storage unit 111. If included, the processing proceeds to Step 118. If not included, the process proceeds to step 104.

  Step 118) The route completion determination unit 109 deletes the route that does not communicate with the receiving device from the searched route storage unit 112.

  Step 119) The route of the searched route storage unit 112 is output as the determined route.

  Step 120) “No solution” is output and the process is forcibly terminated.

[Process 3: Step 200 to Step 207]
Step 200) The candidate device determination unit 107 for the unicast device sets a transmission device adjacent to the search target transmission device v to be f.

  Step 201) It is determined whether or not there is a plurality of f. If there are f, the process proceeds to Step 202, and if not, the process proceeds to Step 205.

  Step 202) The candidate device determination unit 107 for the unicast device refers to the reception device number storage unit 114, selects one transmission device having a large number of stored reception devices, and there are a plurality of the same number. It is determined by prioritization conditions using the number of physical links, multicast distribution capability, and the like.

  Step 203) The process of Step 105 described above is performed.

  Step 204) The processing of Step 108 described above is performed, and the routine proceeds to Step 114.

  Step 205) In step 201, if there is not a plurality of f, it is determined whether one f is present. If one f is present, the process proceeds to step 206, and if none is present, Control goes to step 114.

  Step 206) The process of Step 105 described above is performed.

  Step 207) The processing of Step 108 described above is performed, and the routine proceeds to Step 114.

[Second Embodiment]
FIG. 9 shows the configuration of the route calculation apparatus according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same component as the structure of FIG. 3 in the above-mentioned 1st Embodiment.

  The route calculation apparatus shown in the figure includes a topology information storage unit 101, a Dijkstra topology information storage unit 201, a constraint condition storage unit 102, an initial setting unit 103, a Dijkstra control unit 202, a multicast determination unit 105, and a multicast device candidate device determination. Unit 106, unicast candidate device determination unit 107, search target device determination unit 108, route completion determination unit 109, reception device count unit 110, visited device storage unit 111, Dijkstra visited device storage unit 203, search route The storage unit 112, the Dijkstra search path storage unit 204, the candidate device storage unit 113, the Dijkstra candidate device storage unit 205, and the reception device number storage unit 114 are configured. Among these, the topology information storage unit 101, the constraint condition storage unit 102, the visited device storage unit 111, the searched route storage unit 112, the candidate device storage unit 113, the reception device number storage unit 114, the Dijkstra visited device storage unit 203, The Dijkstra search path storage unit 204 and the Dijkstra candidate device storage unit 205 are assumed to be stored in a storage medium such as a memory or a hard disk.

  The topology information storage unit 101 stores the input connection relationship between devices, the multicast distribution capability of each device, the link cost between devices, and the like.

  The Dijkstra topology information storage unit 201 stores topology information used for Dijkstra, and sets the same information as the topology information storage unit 101 for the first time.

  The constraint condition storage unit 102 stores a constraint condition for a route to be output, such as a transmission device or a reception device.

  The initial setting unit 103 takes out the transmission device from the constraint condition storage unit 102 and stores it in the visited device storage unit 111. Also, information on the transmission device (for example, device ID) is sent to the Dijkstra control unit 202 as a search target device.

  When the Dijkstra control unit 202 receives the search target device from the initial setting unit 103 for the first time or receives the control signal from the unicast transmission device candidate device determination unit 107, the Dijkstra control unit 202 instructs the multicast determination unit 105 to “all A control signal and information on a search target device (for example, device ID) are sent so that the device is regarded as a multicast transmission device. Further, a signal is sent to the search path storage unit 112 so as to be output to the receiving device count unit 110 after the calculation is completed. A control signal is sent to the multicast candidate device determination unit 106, the search target device determination unit 108, and the route completion determination unit 109 so as to operate in Dijkstra.

  In addition, when the Dijkstra control unit 202 receives a signal indicating the completion of the setting of the number of received transmission devices from the receiving device number counting unit 110, the Dijkstra visited device storage unit 203, the Dijkstra search path storage unit 204, and the Dijkstra candidate The device storage unit 205 is reset, and a restart control signal is transmitted to the initial setting unit 103 for the first time, and a restart control signal is transmitted to the unicast device candidate device determination unit 107 for the second and subsequent times.

  When receiving a control signal from the Dijkstra control unit 202, the multicast determination unit 105 sends the received information on the search target device (for example, device ID) to the multicast device candidate device determination unit 106. When the control signal is not received, the multicast capability is read from the topology information storage unit 101, it is determined whether the search target device is a multicast device or a unicast device, and the search target device is determined as a unicast device candidate based on the determination result. The data is sent to the device determination unit 107 or the multicast candidate device determination unit 106.

  The unicast candidate device determination unit 107 acquires the neighboring device of the search target device from the topology information storage unit 101. The number of receiving devices of each neighboring device in the search device is acquired from the receiving device number storage unit 114, one neighboring device having the largest number of receiving transmission devices is selected, and that device is set in the candidate device storage unit 113. In addition, the link cost and route from the transmission transmission device to the selected candidate device are set in the search route storage unit 112. The link that has not been selected is deleted from the Dijkstra topology information storage unit 201. A signal is transmitted to the Dijkstra control unit 202 to start Dijkstra calculation. Further, when the Dijkstra route calculation completion signal is received from the Dijkstra control unit 202, the process proceeds to the search target device determination unit 108.

  When the multicast candidate device determination unit 106 has not received a control signal from the Dijkstra control unit 202, the multicast information is obtained from the topology information storage unit 101 between the adjacent devices of the search target device and the adjacent devices. The link cost of each adjacent device via the search target device is calculated, and if the link cost is not set in the search route storage unit 112 or smaller than the set link cost, the adjacent device is set in the candidate device storage unit 113. . At this time, if the candidate device is already set in the candidate device storage unit 113 and is a candidate device from another unicast transmission device, information on the unicast transmission device (for example, device ID) is used for unicast. This is sent to the candidate device determination unit 107.

  Further, when the multicast candidate device determination unit 106 receives a control signal from the Dijkstra control unit 202, the multicast candidate device determination unit 106 acquires the link cost between the adjacent device of the search target device and the adjacent device from the Dijkstra topology information storage unit 201. . The link cost of each neighboring device via the search target device is calculated, and if it is not set in the Dijkstra search path storage unit 204 or is smaller than the set link cost, the neighboring device is stored as a Dijkstra candidate device. Set in the unit 205.

  If no control signal is received from the Dijkstra control unit 202, the search target device determination unit 108 sets the candidate device with the lowest link cost set in the candidate device storage unit 113 as the call target search target device, and performs the call target search. Information on the target device (for example, device ID) is sent to the route completion determination unit 109. Further, the device information (for example, device ID) is deleted from the candidate device storage unit 113 and stored in the visited device storage unit 111.

  In addition, when the search target device determining unit 108 receives a control signal from the Dijkstra control unit 202, the search target device determining unit 108 calls a candidate device with the lowest link cost set in the Dijkstra candidate device storage unit 205, and Then, information on the search target device (for example, device ID) is sent to the route completion determination unit 109. In addition, the device information (for example, device ID) is deleted from the Dijkstra candidate device storage unit 205 and stored in the Dijkstra visited storage unit 203.

  When the route completion determination unit 109 has not received a control signal from the Dijkstra control unit 202, the route completion determination unit 109 determines whether all the receiving devices in the constraint condition storage unit 102 are set in the visited device storage unit 111, and all of them are included. If it is, the route is completed, and a completion signal is transmitted to the searched route storage unit 112. If all are not included, the received information on the search target device (for example, device ID) is sent to the multicast determination unit 105.

  When control information is received by the Dijkstra control unit 202, it is determined whether all the receiving devices in the constraint condition storage unit 102 are set in the visited device storage unit 203 for Dijkstra. The completion signal is transmitted to the Dijkstra search path storage unit 204. If all are not included, the received information on the search target device (for example, device ID) is sent to the multicast determination unit 105.

  The search route storage unit 112 receives a completion signal from the route completion determination unit 109 and outputs the stored route.

  The Dijkstra search route storage unit 204 receives the completion signal from the route completion determination unit 109 and outputs the stored route to the receiving device count unit 110.

  The receiving device number counting unit 110 searches the received multicast route, counts the receiving transmission devices that can be reached in each route of all unicast transmission devices, and sets the number in the receiving device number storage unit 114. Also, after the setting is completed, a signal indicating the completion of setting the number of receiving transmission devices is transmitted to the Dijkstra control unit 202.

  Next, the operation in the above configuration will be described.

  10 to 14 are flowcharts of operations in the second embodiment of the present invention.

  In the following flowchart, s indicates a transmission transmission device, and v indicates a search target transmission device (usually a transmission device whose path has just been determined).

[Process 4: Step 301 to Step 303]
Step 301) The Dijkstra control unit 202 resets the data in each of the Dijkstra storage units and the storage unit number storage unit 114.

  Step 302) All devices are regarded as multicast using the Dijkstra topology in the Dijkstra topology information storage unit 201, and a route is calculated by the Dijkstra method.

  Step 303) The calculated route is searched, and the number of receiving devices that can be reached through the next hop device of the unicast device is set in the receiving device number storage unit 114.

  Step 304) The transmission transmission device s is set as a search target transmission device v.

  Step 305) The multicast determination unit 105 determines whether the search target transmission device v is a multicast transmission device. If the multicast transmission device is a multicast transmission device, the process proceeds to step 306. If not, the process proceeds to step 400. .

  Step 306) Here, let f be a transmission apparatus that is adjacent to the search target transmission apparatus v and is not the transmission apparatus immediately preceding v on the determined path. If no f exists, the following processing is not executed.

[Process 1: Step 307]
Step 307) The multicast device candidate device determination unit 106 calculates the link cost between the transmission transmission devices s and f via the search target transmission device v and sets it as df.

  Step 308) Referring to visited device storage unit 111 and candidate device storage unit 113, it is determined whether f is a visited device. If it is a visited device or a candidate device of another device, go to step 309. If it is determined that the apparatus is not a visited apparatus or a candidate apparatus of another apparatus, the process proceeds to step 310.

  Step 309) The multicast device candidate apparatus determination unit 106 determines whether the already calculated link cost is larger than df, and if it is larger, the process proceeds to Step 311; otherwise, the process proceeds to Step 316.

[Process 2: Step 310]
Step 310) The route via v from s to f and the link cost are stored in the candidate device storage unit 113, and f is a candidate device. Control goes to step 316.

  Step 311) Let p be the transmission device immediately preceding f in the route stored in the searched route storage unit 112.

  Step 312) The same processing as in the above step 310 is performed.

  Step 313) The multicast determination unit 105 determines whether the transmission device p is a multicast transmission device. If the transmission device p is a multicast transmission device, the process proceeds to step 316; otherwise, the process proceeds to step 314.

  Step 314) Let p be a search target transmission device v.

  Step 315) The processing of Step 400 to Step 409 [Process 3] is performed.

  Step 316) The following processing is executed for all f.

  Step 317) The multicast device candidate device determination unit 106 refers to the candidate device storage unit 113 to determine whether f exists. If it exists, the process proceeds to step 318. If not, the process proceeds to step 323. Transition.

  Step 318) The search target device determination unit 108 sets i as a candidate device having the minimum link cost from s. If there are multiple, select one using other conditions. The route to i is determined, and i is deleted from the candidate device storage unit 113. i is stored in the visited device storage unit 111 as a visited device.

  Step 319) The search target device determination unit 108 sets i as the search target transmission device v.

  Step 320) The path completion determination unit 109 determines whether all the receiving devices are included in the determined path. If included, the process proceeds to step 321. If not included, the process proceeds to step 305. .

  Step 321) The route that does not communicate with the receiving device is deleted from the searched route storage unit 112.

  Step 322) The route determined by the searched route storage unit 112 is output, and the process is terminated.

  Step 323) If there is no candidate in Step 317, “no solution” is output and the process is forcibly terminated.

[Process 3: Steps 400 to 409]
Step 400) When it is determined in step 305 that v is not a multicast transmission apparatus, the unicast candidate apparatus determination unit 107 sets a transmission apparatus adjacent to v to f.

  Step 401) It is determined whether or not there are a plurality of fs. If there are a plurality of fs, the process proceeds to Step 402.

  Step 402) Referring to the reception device number storage unit 114, one transmission device having a large number of stored reception devices is selected. If there are a plurality of the same number, it is determined by the prioritization condition using the number of physical links, multicast distribution capability, and the like.

  Step 403) The topology in which the link between the undecided device and v is cut is stored in the Dijkstra topology information storage unit 201 as the Dijkstra topology.

  Step 404) Step 301 to Step 303 [Process 4] are performed.

  Step 405) Step 307 [Process 1] is performed.

  Step 406) Step 310 [Process 2] is performed.

  Step 407) In step 401, when f is not plural, it is determined whether there is one f. If there is one, the process proceeds to step 408, and if none exists, the process proceeds to step 317.

  Examples of the present invention will be described below.

[First embodiment]
The first embodiment will be described with reference to FIGS.

  In the following example, description will be made assuming that the transmission transmission device is {A} and the reception transmission device is {B, I, K, L}.

  Each of the transmission apparatuses A, B, D, E, F, G, I, J, K, and L shown in FIGS. 15 and 16 is a multicast transmission apparatus, and C and H are unicast transmission apparatuses.

  The topology information including the connection relationship and the link cost shown in FIG. 15A and the input of the transmission transmission device and the reception transmission device are received.

  (1) All transmission apparatuses are regarded as multicast transmission apparatuses, and multicast paths are calculated by the Dijkstra method. The number of receiving transmission devices on each route of all unicast routes is counted according to the route (FIG. 15 (b)).

  Since the route from the unicast transmission apparatus C to E leads to I, K, and L, the number of reception transmission apparatuses is three. The route to D is 0. Similarly, the route from H to J leads to K and L, so the number of receiving transmission devices is 2, and the route to I is 1.

  (2) The transmission transmission apparatus A is a visited apparatus and a search target apparatus, the candidate apparatus, the visited apparatus, the searched path, etc. are reset, and the multicast path calculation is restarted.

  (3) The search target device A is a multicast transmission device, and B and C are candidate devices (FIG. 15C).

  (4) Let B be the next device to be searched and the visited device.

  (5) Since no candidate device exists from B, C is set as the next search target device and is a visited device.

  (6) Since C is a unicast transmission apparatus, one candidate apparatus is selected using the number of reception transmission apparatuses. In this case, E is the largest in the number of receiving transmission devices 3, and E is a candidate device.

  (7) Of the candidate devices, E is the next device to be searched and is a visited device (FIG. 15 (d)).

  (8) Since E is a multicast transmission device, G and H are candidate devices (FIG. 16 (e)).

  (9) Let G be the next device to be searched and the visited device.

  (10) Since no candidate device exists in G, H is set as the next search target device and is a visited device.

  (11) Since H is a unicast transmission apparatus, one candidate transmission apparatus is selected as the number of reception transmission apparatuses, and the largest J is selected as the number of reception transmission apparatuses 2 (FIG. 16 (f)).

  (12) The search proceeds in the same manner, and the route of FIG. 16 (g) is calculated.

  (13) An unnecessary route (between E and G) is deleted, and FIG.

[Second Embodiment]
A second embodiment will be described with reference to FIGS.

  In the following description, it is assumed that the transmission transmission device is {A} and the reception transmission device is {C, D, G}.

  Each of the transmission apparatuses A, C, D, E, and G shown in FIGS. 17 to 19 is a multicast transmission apparatus, and B, F, H, and I are unicast transmission apparatuses.

  (1) All transmission apparatuses are regarded as multicast transmission apparatuses, and multicast paths are calculated by the Dijkstra method. The number of receiving transmission devices on each route of all unicast routes is counted according to the route (FIG. 17B).

  Since the route from the unicast transmission apparatus I to E leads to D, the number of reception transmission apparatuses is one. The route to H is 0. Similarly, since the route from B to C leads to C, the number of receiving transmission devices is 1, and the route to G is 1.

  (2) The transmission transmission apparatus A is a visited apparatus and a search target apparatus, the candidate apparatus, the visited apparatus, the searched path, etc. are reset, and the multicast path calculation is restarted.

  (3) The search target A is a multicast transmission device, and B and C are candidate devices (FIG. 17C).

  (4) B with the lowest link cost is set as the next search target device, and is a visited device.

  (5) Since B is a unicast transmission apparatus, one candidate apparatus is selected using the number of reception transmission apparatuses. In this case, C and G are the largest in the number of receiving transmission devices 1, but C is a candidate device depending on the number of physical links and the like (FIG. 18D).

  (6) For the topology in which G and F that are not selected as candidate devices in B are cut, calculation is performed using the Dijkstra method, and the number of receiving transmission devices is reset again (FIG. 18 (e)).

  (7) The search is resumed again, and I is set as the next search target device and the searched device.

  (8) Since I is a unicast transmission apparatus, a candidate apparatus is selected using the number of reception transmission apparatuses. In this case, H and E have the same number of receiving transmission apparatuses, but H is a candidate apparatus based on the number of physical links and the like (FIG. 18 (f)).

  (9) A route is calculated by Dijkstra using the topology in which the link between I and E is deleted, and the number of receiving transmission devices is reset (FIG. 19 (g)).

  (10) Let C be the next device to be searched and a visited device.

  (11) Let G be the next device to be searched and a visited device (FIG. 19 (h)).

  (12) The search proceeds in the same manner, and FIG. 19 (i) is output.

  Also, the initial setting unit 103, multicast determination control unit 104, multicast determination unit 105, multicast device candidate device determination unit 106, unicast device candidate device determination unit 107, search target device shown in FIGS. The route calculation processing using the determination unit 108, the route completion determination device 109, the reception device count unit 110, and the Dijkstra route calculation method may be constructed as a program and executed by a computer or distributed via a network. Is possible.

  Further, the constructed program can be stored in a portable storage medium such as a hard disk device, a flexible disk, or a CD-ROM, and installed in a computer to be executed or distributed.

  The present invention is not limited to the above-described embodiments and examples, and various modifications and applications can be made within the scope of the claims.

  The present invention is applicable to a technique for setting a multicast route for a communication network in which a multicast transmission apparatus and a unicast transmission apparatus are mixed, such as the MPLS technique.

It is a figure for demonstrating the principle of this invention. It is a principle block diagram of this invention. It is a block diagram of the route calculation apparatus in the 1st Embodiment of this invention. It is a flowchart (the 1) of the operation | movement in the 1st Embodiment of this invention. It is a flowchart (the 2) of the operation | movement in the 1st Embodiment of this invention. It is a flowchart (the 3) of the operation | movement in the 1st Embodiment of this invention. It is a flowchart (the 4) of the operation | movement in the 1st Embodiment of this invention. It is a flowchart (the 5) of the operation | movement in the 1st Embodiment of this invention. It is a block diagram of the path | route calculation apparatus in the 2nd Embodiment of this invention. It is a flowchart (the 1) of the operation | movement in the 2nd Embodiment of this invention. It is a flowchart (the 2) of the operation | movement in the 2nd Embodiment of this invention. It is a flowchart (the 3) of the operation | movement in the 2nd Embodiment of this invention. It is a flowchart (the 4) of the operation | movement in the 2nd Embodiment of this invention. It is a flowchart (the 5) of the operation | movement in the 2nd Embodiment of this invention. It is FIG. (1) for demonstrating a series of operation | movement in 1st Example of this invention. FIG. 6 is a diagram (No. 2) for describing a series of operations in the first example of the invention. It is FIG. (1) for demonstrating a series of operation | movement in 2nd Example of this invention. It is FIG. (2) for demonstrating a series of operation | movement in 2nd Example of this invention. It is FIG. (3) for demonstrating a series of operation | movement in 2nd Example of this invention. It is a figure for demonstrating a multicast route calculation apparatus. It is FIG. (1) for demonstrating a prior art. It is FIG. (2) for demonstrating a prior art. It is FIG. (3) for demonstrating a prior art.

Explanation of symbols

101 topology information storage unit, topology information storage unit 102 constraint condition storage unit, constraint condition storage unit 103 initial setting unit, initial setting unit 104 multicast determination control unit 105 multicast determination unit, multicast determination unit 106 candidate device determination unit for multicast device, Candidate device determination unit for multicast device 107 Candidate device determination unit for unicast device, Candidate device determination unit for unicast device 108 Search target device determination unit, Search target device determination unit 109 Route completion determination unit, Route completion determination unit 110 Receiver Number counting unit, receiving device number counting unit 111 Visited device storage unit, visited device storage unit 112 Search route storage unit, search route storage unit 113 Candidate device storage unit, candidate device storage unit 114 Receiving device number storage unit 120 Dijkstra route Calculation means 20 Dijkstra for topology information storage section 202 Dijkstra controller 203 Dijkstra for visited apparatus memory unit 204 Dijkstra for searching route storage unit 205 Dijkstra for candidate device storage unit

Claims (6)

A multicast route calculation method for calculating a multicast route by applying the Dijkstra multicast route calculation method using topology information and route setting constraint conditions of the input communication network in a communication network in which multicast transmission devices and unicast transmission devices are mixed Because
A Dijkstra route calculation step in which all transmission devices in the communication network are regarded as multicast transmission devices, a multicast route is calculated by a Dijkstra multicast calculation method, and stored in a search route storage unit;
Using the route output from the search route storage means, calculate the number of receiving devices that each route in the unicast transmission device can reach, and store the number in the receiving device number storage means,
An initial setting step of storing the transmission transmission device in the visited storage means to be a search target device;
A multicast determination step for determining whether the search target device is a unicast transmission device or a multicast transmission device;
If it is determined as a unicast transmission device in the multicast determination step, one of the neighboring devices on the path having the maximum number of reception devices stored in the reception device number storage unit is selected as a candidate device and stored as a candidate device. A candidate device determination step for a unicast device that stores the link cost and route to the candidate device in the search route storage unit,
In the multicast determination step, when the search target device is a multicast transmission device, if the candidate device selected from neighboring devices of the search target device is a candidate device that has already been selected from the unicast transmission device, A candidate device determination step for multicast device that re-selects a candidate device from neighboring devices of a unicast transmission device and stores the candidate device in the candidate device storage means;
A search target device determining step of selecting a candidate device having a minimum link cost from candidate devices stored in the candidate device storage means, and storing the selected device as a visited device in the visited device storage means;
An output step of outputting a route stored in the searched route storage means when all receiving devices are set in the visited device storage means;
A multicast route calculation method characterized by: A multicast route calculation method for calculating a multicast route by applying the Dijkstra multicast route calculation method using topology information and route setting constraint conditions of the input communication network in a communication network in which multicast transmission devices and unicast transmission devices are mixed Because
A Dijkstra route calculation step in which all transmission devices in the communication network are regarded as multicast transmission devices, a multicast route is calculated by a Dijkstra multicast calculation method, and stored in a search route storage unit;
A first receiving device number counting step of calculating the number of receiving devices that each route in the unicast transmission device can reach using the route output from the searched route storing means and storing the number in the receiving device number storing means When,
An initial setting step of storing the transmission transmission device in the visited storage means to be a search target device;
A multicast determination step for determining whether the search target device is a unicast transmission device or a multicast transmission device;
In the multicast determination step, when it is determined that the device is a unicast transmission device, one of the neighboring devices on the path having the maximum number of reception devices stored in the reception device number storage unit is selected as a candidate device. The candidate device determination step for unicast device to be stored in the candidate device storage means,
With respect to the topology in which the route other than the route to the selected candidate device is disconnected, all transmission devices are regarded as multicast transmission devices again, multicast routes are calculated by the Dijkstra multicast route calculation method, and stored in the search route storage means. Steps,
Using the route output from the searched route storage means, the number of receiving devices that each route in the unicast transmission device can reach is calculated, and stored in the receiving device number storage means. Steps,
When it is determined in the multicast determination step that the device is a multicast transmission device, if the candidate device selected from the neighboring devices of the search target device is a candidate device that has already been selected from the unicast transmission device, A multicast device that reselects a candidate device from neighboring devices of a unicast transmission device, stores the candidate device in the candidate device storage means, and stores the link cost and route to the reselected candidate device in the search route storage means Candidate device determination step,
A search target device determining step of selecting a candidate device having a minimum link cost from candidate devices stored in the candidate device storage means, and storing the selected device as a visited device in the visited device storage means;
An output step of outputting a route stored in the searched route storage means when all receiving devices are set in the visited device storage means;
A multicast route calculation method characterized by: Multicast route calculation device for calculating multicast route by applying Dijkstra multicast route calculation method using topology information of input communication network and route setting restriction condition in communication network where multicast transmission device and unicast transmission device are mixed Because
Search route storage means for storing the route to each transmission device to the transmission device and the link cost;
Visited device storage means for storing the searched transmission device as a visited device;
Candidate device storage means for storing candidate devices;
Receiving device number storage means for storing the counted number of receiving devices;
All transmission devices in the communication network are regarded as multicast transmission devices, Dijkstra route calculation means for calculating a multicast route by a Dijkstra multicast calculation method and storing it in the searched route storage means;
Using the route output from the searched route storage means, calculate the number of receiving devices that each route in the unicast transmission device can reach, and store the number of receiving devices in the receiving device number storage means;
An initial setting means for storing the transmission transmission device in the visited storage means and making it a search target device;
Multicast determination means for determining whether the search target device is a unicast transmission device or a multicast transmission device;
When the multicast determination unit determines that the device is a unicast transmission device, one of the neighboring devices on the path having the maximum number of reception devices stored in the reception device number storage unit is selected as a candidate device and stored as a candidate device. Unicast device candidate device determining means to be stored in the means;
In the multicast determination means, when the search target device is a multicast transmission device, if the candidate device selected from the neighboring devices of the search target device is a candidate device that has already been selected from the unicast transmission device, A multicast device that reselects a candidate device from neighboring devices of a unicast transmission device, stores the candidate device in the candidate device storage means, and stores the link cost and route to the reselected candidate device in the search route storage means Candidate device determination means,
A search target device determining unit that selects a candidate device with the lowest link cost from candidate devices stored in the candidate device storage unit, and stores the selected device as a visited device in the visited device storage unit;
A route completion determination unit that outputs a route stored in the searched route storage unit when all receiving devices are set in the visited device storage unit;
A multicast route calculation apparatus comprising: Multicast route calculation device for calculating multicast route by applying Dijkstra multicast route calculation method using topology information of input communication network and route setting restriction condition in communication network where multicast transmission device and unicast transmission device are mixed Because
Search route storage means for storing the route to each transmission device to the transmission device and the link cost;
Visited device storage means for storing the searched transmission device as a visited device;
Candidate device storage means for storing candidate devices;
Receiving device number storage means for storing the counted number of receiving devices;
All transmission devices in the communication network are regarded as multicast transmission devices, Dijkstra route calculation means for calculating a multicast route by a Dijkstra multicast calculation method and storing it in the searched route storage means;
Using the route output from the searched route storage means, the number of receiving devices that each route in the unicast transmission device can reach is calculated, and stored in the receiving device number storage means. Means,
An initial setting means for storing the transmission transmission device in the visited storage means and making it a search target device;
Multicast determination means for determining whether the search target device is a unicast transmission device or a multicast transmission device;
When the multicast determination unit determines that the device is a unicast transmission device, one of the neighboring devices on the path having the maximum number of reception devices stored in the reception device number storage unit is selected as a candidate device. Unicast device candidate device determination means for storing in the candidate device storage means;
With respect to the topology in which the route other than the route to the selected candidate device is disconnected, all transmission devices are regarded as multicast transmission devices again, multicast routes are calculated by the Dijkstra multicast route calculation method, and stored in the search route storage means. Route recalculation means;
Using the route output from the searched route storage means, the number of receiving devices that each route in the unicast transmission device can reach is calculated, and stored in the receiving device number storage means. Means,
When the multicast determination means determines that the device is a multicast transmission device, if the candidate device selected from the neighboring devices of the search target device is a candidate device already selected from the unicast transmission device, A multicast device that reselects a candidate device from neighboring devices of a unicast transmission device, stores the candidate device in the candidate device storage means, and stores the link cost and route to the reselected candidate device in the search route storage means Candidate device determination means,
A search target device determining unit that selects a candidate device with the lowest link cost from candidate devices stored in the candidate device storage unit, and stores the selected device as a visited device in the visited device storage unit;
A route completion determination unit that outputs a route stored in the searched route storage unit when all receiving devices are set in the visited device storage unit;
A multicast route calculation apparatus comprising: A computer having search route storage means, visited device storage means, candidate device storage means, and reception device number storage means;
A computer is caused to function as a multicast route calculation apparatus having the means according to claim 3 or 4 to function as a multicast route calculation apparatus having the means according to claim 3 or 4. Multicast route calculation program to do. A computer having search route storage means, visited device storage means, candidate device storage means, and reception device number storage means;
5. A storage medium storing a multicast route calculation program storing a program that functions as a multicast route calculation apparatus having the means according to claim 3 or 4.

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