JP2008048114A - Route calculating method, route calculating program, route calculating device, and node - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To calculates the shortest route satisfying delay restriction value by route calculation where an inclusive route is specified. <P>SOLUTION: A route calculating device 1 divides the delay restriction value of a route from a start point node 2A, to a terminal point node 2D by a section (the section defined by relay nodes 2B and 2C), defined by inclusive route specification. For each section, a route (shortest route) which satisfies a divided delay restriction value and has the least link cost is searched for. For a section for which a route satisfying a divided delay restriction value is not found, however the delay restriction value is changed into a delay restriction value of a section which satisfies the delay restriction value. Then a route satisfying the changed delay restriction value is searched for again to find the route satisfying the delay restriction value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a route calculation technique considering a plurality of constraints.

  In recent years, audio / video streaming services have become widespread with the increase in network speed and capacity. Applications that provide these services need to be provided with QoS (Quality of Service) restrictions and sufficient bandwidth in order to prevent quality degradation due to delay and packet loss.

  Here, a server or router in the network is equipped with a Constrained Shortest Path First (CSPF) function in order to set up a route that can efficiently use a limited bandwidth and support the required QoS. . The CSPF function is a function that calculates a path of a path that satisfies a constraint based on a request from the outside such as a module that exchanges signaling information, and answers the path to the outside, that is, a shortest path with a constraint (link This is a function for calculating a route having the shortest cost.

  In addition, it is particularly important to satisfy delay constraint conditions in traffic that requires strict QoS such as audio and video streaming. For this reason, various algorithms for calculating paths that satisfy the delay constraint conditions have been proposed (see, for example, Non-Patent Documents 1 and 2). These algorithms calculate the shortest path satisfying a delay constraint condition (delay constraint value) based on link cost and delay information.

By the way, there are cases where a location that must be routed at the time of path setting is designated (inclusive route designation) due to the effective use of limited network resources, QoS control, or operational convenience of the operator. In order to calculate the route in consideration of this inclusive route specification, the start node and the specified node (the node specifying the inclusive route) 1, the specified node 1 and the specified node 2, and so on, the specified node N and the end node, and so on. Dividing into sections, route calculation is performed independently for each section, and finally, the end-to-end paths are obtained by adding the paths.
X Douglas S. Reeves, and Hussein F. Salama, “A Distributed Algorithm for Delay-Constrained Unicast Routing,” IEEE / ACM TRANSACTIONS ON NETWORKING, VOL.8, NO.2, APRIL2000. XinJin; Xiande Liu; Shiyuan Xiao, `` An effective algorithm for delay Constrained least cost unicast routing, '' Circuits and Systems, 2005.IEEE International Symposium on.

  However, none of the algorithms described above takes into consideration the constraints when inclusive route is specified. For this reason, when route calculation is performed for each section designated as an inclusive route, the total delay time in each section may not satisfy the end-to-end delay constraint value.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems and provide means for calculating the shortest path satisfying the end-to-end delay constraint value when an inclusive route is designated.

  In order to solve the above-described problem, in the route calculation device, the delay constraint value is divided into sections divided by the inclusive route specification, that is, sections divided by the inclusive node (relay node), and the section is divided into sections. In other words, the path that satisfies the delay constraint value and has the lowest link cost (shortest path) is calculated. In the route calculation apparatus, first, a route (shortest route) having the lowest link cost is calculated for each section. Then, the delay time when the entire section is the shortest route is calculated, and if the calculated delay time does not exceed the delay constraint value, the calculated route is output as the calculation result. On the other hand, when the total delay time value exceeds the delay constraint value, the route with the shortest delay time is calculated in order from the section with the highest link cost (or the section with the long delay time). And when the total value of the delay time satisfies the delay constraint value, the shortest path in the section is replaced with the path with the shortest delay time and output.

  That is, the invention described in claim 1 includes an input / output unit that controls input / output of various data, a communication unit that performs communication via a network, topology information of nodes that constitute the network, and links that connect the nodes. A route calculation control device comprising a storage unit that stores link cost information, and a processing unit that performs route calculation with reference to the topology information and the link cost information, in the route in the network via the input / output unit A relay node input step for accepting input of identification information of a relay node that passes between the start point node and the end point node, and an upper limit value of a delay time in communication from the start point node to the end point node via the input / output unit A delay constraint value input step for accepting an input of a certain delay constraint value; and A delay constraint value assigning step that assigns the route from the node to the end node divided into sections divided by the relay node, and obtains the actual delay time between the nodes via the communication unit, With reference to the acquired delay time stored in the storage unit, the acquired actual delay time between the nodes, the topology information, and the link cost information, the actual delay time in the section for each section The route calculation step of performing route calculation of a route that is equal to or less than the delay constraint value assigned to the section and that has the minimum link cost, and stores the calculated route in the storage unit is performed.

  According to a sixth aspect of the present invention, there is provided a route calculation device taking delay constraints into consideration, a storage unit for storing topology information of nodes constituting a network and link cost information of links connecting the nodes, and via the network A communication unit that performs communication in the network, a relay node input unit that receives input of identification information of a relay node that passes between a start point node and an end point node in a route in the network, and stores the input information in the storage unit; and the input / output A delay constraint value input unit that receives an input of a delay constraint value that is an upper limit value of a delay time in communication from the start point node to the end point node, and stores the delay constraint value input unit, and the input delay constraint value Is assigned a delay constraint value by dividing the route from the start node to the end node into sections divided by the relay node. A delay time acquisition unit that acquires an actual delay time between the nodes via the communication unit and stores the actual delay time between the nodes, the acquired actual delay time between the nodes, and the topology With reference to the information and the link cost information, for each of the sections, the actual delay time in the section is less than or equal to the delay constraint value assigned to the section, and the route calculation that minimizes the link cost is performed. And a route calculation unit that stores the calculated route in the storage unit.

  By doing in this way, the route calculation device can set the delay constraint value from the start node to the end node (delay constraint value in end-to-end) by each section, that is, the relay node delimited by the inclusive route specification. Divide into sections. Then, a route (shortest route) that satisfies the divided delay constraint value and has the lowest link cost is calculated for each section. Therefore, even when an inclusive route is specified, the shortest route that satisfies the end-to-end delay constraint value can be calculated.

  According to a second aspect of the present invention, in the route calculation method according to the first aspect, in the route calculation step, a route in which an actual delay time in the section is less than or equal to a delay constraint value assigned to the section in the route calculation step. When there is a first section that cannot be calculated, and a second section that is a section that can calculate a route that is less than or equal to the delay constraint value assigned to the section, the second section is assigned to the second section. The delay constraint value is distributed to the delay constraint value assigned to the first interval, the delay constraint value in the first interval stored in the storage unit is changed, and the changed delay constraint value is changed to the changed delay constraint value. Based on this, the route calculation of the first section is executed again.

  According to this method, the route calculation device distributes the delay constraint value of the interval in which the route that is less than or equal to the delay constraint value can be calculated to the interval that cannot calculate the route that is less than or equal to the delay constraint value. Since the route satisfying the changed delay constraint value is calculated again, it is easy to find a route satisfying the end-to-end delay constraint value.

  According to a third aspect of the present invention, there is provided an input / output unit that controls input / output of various data, a communication unit that performs communication via a network, topology information of nodes constituting the network, and link cost of a link connecting the nodes A route calculation control device comprising a storage unit for storing information and a processing unit for performing route calculation with reference to the topology information and the link cost information, via the input / output unit, a start node in a route in the network A relay node input step that receives an input of identification information of a relay node that is routed from the end point node to the end point node, and that is stored in the storage unit; A delay constraint value input step for receiving an input of a delay constraint value which is an upper limit value of time and storing the delay constraint value in the storage unit; Referring to the log information and the link cost information, for each section obtained by dividing the path from the start node to the end node by the relay node, calculate the shortest path that minimizes the link cost of the section, The shortest path calculation step stored in the storage unit, the actual delay time between the nodes is acquired via the communication unit, and the delay time acquisition step stored in the storage unit, between the acquired nodes A delay time determining step of calculating an actual delay time in each section from the actual delay time of the first delay time, and determining whether or not a total value of the calculated delay times exceeds the input delay constraint value; When the delay time determination step determines that the total value of the calculated actual delay times exceeds the input delay constraint value, the link A route calculation step of calculating a link cost of each section with reference to a list information, calculating a path having the shortest delay time in the section in order from the section with the largest link cost calculated; A route replacement step of replacing the stored route of the section with the route having the shortest calculated delay time, and the total value of the actual delay times of the sections after the route replacement is the input delay The method was executed until the value was less than the constraint value.

  According to a seventh aspect of the present invention, there is provided a route calculation device taking delay constraints into consideration, a storage unit for storing topology information of nodes constituting a network and link cost information of links connecting the nodes, and via the network A communication unit that performs communication in the network, a relay node input unit that receives input of identification information of a relay node that passes between a start point node and an end point node in a route in the network, and stores the input information in the storage unit; and the input / output A delay constraint value input unit that receives an input of a delay constraint value that is an upper limit value of a delay time in communication from the start node to the end node, and stores the delay constraint value input unit in the storage unit, the topology information, and the link cost Referring to the information, the route from the start node to the end node is divided for each section separated by the relay node. Calculating a shortest path that minimizes the link cost of the section, storing the path calculation unit in the storage unit, acquiring an actual delay time between the nodes, and storing a delay time acquisition unit in the storage unit; The actual delay time in each section is calculated from the acquired actual delay time between the nodes, and whether or not the total value of the calculated delay times exceeds the input delay constraint value. A delay time determination unit for determining, when the delay time determination unit determines that the total value of the calculated actual delay times exceeds the input delay constraint value , Referring to the link cost information, calculating the link cost of each section, calculating the path having the shortest delay time in the section in order from the section with the highest calculated link cost, Is replaced with a path having the shortest calculated delay time, and the total actual delay time of each section after the path replacement is less than or equal to the input delay constraint value. It was set as the structure performed until it becomes.

  Such a route calculation apparatus first calculates the shortest route of each section delimited by the inclusive route designation (delimited by the relay node). And it is confirmed whether the value which totaled the delay time for every area satisfy | fills a delay constraint value. That is, it is confirmed whether or not the delay time when the entire section is the shortest path satisfies the delay constraint value. When the delay time when the entire section is the shortest path satisfies the delay constraint value, the shortest path is output as a calculation result. Therefore, when the inclusive route is designated, it is possible to calculate the route with the lowest link cost (shortest route) while satisfying the end-to-end delay constraint value.

  According to a fourth aspect of the present invention, in the route calculation method according to the third aspect, in the delay time determining step, it is determined that a total value of the calculated actual delay times exceeds the input delay constraint value. In this case, the shortest path calculation step and the path replacement step are executed in order from the section in which the calculated actual delay time is long among the sections.

  According to an eighth aspect of the present invention, in the route calculation device according to the seventh aspect, in the route calculation unit, the delay time determination unit determines that the total value of the calculated actual delay times is the input delay. When it is determined that the constraint value is exceeded, the route with the shortest delay time in the interval is calculated in order from the calculated actual delay time, and the route of the interval stored in the storage unit is calculated. The calculated delay time is replaced with the shortest route, and the processing is executed until the total value of the actual delay times of the respective sections after the route replacement is equal to or less than the input delay constraint value.

  By doing in this way, the route calculation apparatus can calculate a route that satisfies the delay constraint value even when the total value of the delay times when all sections are made the shortest route does not satisfy the delay constraint value. At this time, since route recalculation is performed in order from the section with the largest link cost, the amount of calculation when calculating the shortest route satisfying the delay constraint value can be reduced as much as possible.

  According to a fifth aspect of the present invention, there is provided a route calculation program that causes the route calculation apparatus, which is a computer, to execute the route calculation method according to any one of the first to fourth aspects.

  By doing so, the computer can execute the route calculation method according to any one of claims 1 to 4.

  The invention according to claim 9 is a node having the function of the route calculation apparatus according to any one of claims 6 to 8.

  In this way, it is not necessary to provide a route calculation device separately from the node.

  According to the present invention, it is possible to calculate the shortest route satisfying the end-to-end delay constraint when an inclusive route is designated in route setting. Accordingly, it becomes easy for a network administrator or the like to set a desired route in traffic requiring strict QoS.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an “embodiment”) will be described by dividing it into a first embodiment and a second embodiment.

<< First Embodiment >>
First, the route calculation apparatus according to the first embodiment of the present invention will be described. This route calculation device is characterized by dividing and assigning an end-to-end delay constraint value to each section divided by the inclusive route specification, and calculating a route that satisfies the delay constraint value assigned to each section. To do.

  FIG. 1 is a diagram illustrating a route calculation apparatus according to the first embodiment. As shown in FIG. 1, the network includes a node 2 (2A, 2B, 2C, 2D) and a route calculation device 1 that performs route calculation of a path set between the node 2 and the node 2. . The node 2 and the route calculation apparatus 1 are connected to be communicable.

  This network is realized by a circuit switching network such as TDM (Time Division Multiplexing) and WDM (Wavelength Division Multiplexing), or IP (Internet Protocol), Ethernet (registered trademark), MPLS (Multi-Protocol Label Switching). Node 2 is realized by an MPLS router of an MPLS network, a router of a packet network, an optical cross-connect of an optical network, or the like. Here, a path (logical path) is set between the node 2A and the node 2D.

<Overview of operation>
Here, an outline of the operation of the route calculation apparatus 1 according to the first embodiment will be described with reference to FIG.

  First, the route calculation device 1 receives an instruction input from a relay node (nodes 2B and 2C) on a route from a start node (node 2A) to an end node (node 2D). In other words, it accepts an input of a node (inclusive node) to be routed in inclusive route specification. Further, the route calculation apparatus 1 accepts an input of an upper limit value of delay time (end-to-end delay constraint value) in the route from the node 2A to the node 2D. For example, an input of information “delay constraint value = 30 ms or less” is accepted.

  The route calculation apparatus 1 divides and assigns end-to-end delay constraint values to the sections # 1 to # 3 divided by the relay node. For example, the end-to-end delay constraint value is equally divided and assigned to each section by 10 ms. Then, the route calculation device 1 calculates a route that satisfies the delay constraint value assigned to each section. In other words, although illustration is omitted here, in the sections # 1 to # 3, nodes that are linked to each other are installed, and it is calculated (search) which link is required to satisfy the delay constraint value. ) As a result of the calculation, if a route satisfying the delay constraint value can be calculated for all the sections (if a route can be found), the route is output as a calculation result. On the other hand, if there is a section (first section) in which a route satisfying the delay constraint value cannot be calculated, the remaining delay constraint value is assigned to the section (second section) in which the path satisfying the delay constraint can be calculated. .

  For example, in the network illustrated in FIG. 1, the route calculation device 1 can find a route that satisfies the delay constraint value 10 ms for the interval # 1 and the interval # 3, but the delay constraint value 10 ms is set for the interval # 2. When a satisfying route cannot be found, the remaining delay constraint value in interval # 1 and interval # 3 (a value obtained by subtracting the actual delay time from the delay constraint value in that interval) is assigned to interval # 2. That is, when the delay constraint value is left by 5 ms in the interval # 1 and the interval # 2, this value is assigned to the interval # 2, and the delay constraint value in this interval is changed to 10 ms + 5 ms + 5 ms = 20 ms. As a result, the route calculation apparatus 1 calculates a route satisfying the end-to-end delay constraint value 20 ms for the section # 2.

<Configuration of route calculation device>
Next, the configuration of the route calculation apparatus 1 will be described in detail with reference to FIG. FIG. 2 is a block diagram showing the configuration of the route calculation apparatus of FIG.

  As illustrated in FIG. 2, the route calculation device 1 includes an input / output unit 11, a processing unit 12, a storage unit 13, and a communication unit 14.

  The input / output unit 11 is an interface such as an input device (not shown) such as a keyboard and a mouse connected to the path calculation device 1 and an output device (not shown) such as a liquid crystal monitor. The input / output unit 11 outputs information input from the input device to the processing unit 12 and outputs information processed by the processing unit 12 to the output device. The input / output unit 11 includes a relay node input unit 111 and a delay constraint value input unit 112. The relay node input unit 111 receives input of identification information of a relay node (inclusive node). Also, the delay constraint value input unit 112 receives an input of an end-to-end delay constraint value. The relay node identification information and the delay constraint value may be input via the communication unit 14.

  The processing unit 12 controls the entire route calculation apparatus 1 and controls the input / output unit 11 and the storage unit 13 and processes input information. The processing unit 12 divides the delay constraint value at the end-to-end by dividing the route constraint unit 121 that performs route calculation, the delay time acquisition unit 122 that acquires the delay time at each node 2, and assigns it to each section. Delay constraint value assignment unit 123, routing information acquisition unit 124 for acquiring link information of each node 2 and routing information such as topology information, and path control for outputting a path setting command based on the calculated route to node 2 Part 125.

  When the route calculation unit 121 receives a route calculation command via the input / output unit 11 or the communication unit 14, the route calculation unit 121 satisfies the delay constraint value assigned to the section for each section and has the minimum link cost. (Shortest path) is calculated. The calculation of the shortest path at this time may use a known algorithm such as a restricted dijkstra method. Further, the route calculation unit 121 includes a section in which a route satisfying the delay constraint value assigned to the section is not found (first section) and a section in which the route is found (second section). When there is, the delay constraint value assigned to the second interval is distributed to the delay constraint value assigned to the first interval, and the delay constraint value in the first interval is changed. Then, a route that satisfies the changed delay constraint value is recalculated.

  The delay time acquisition unit 122 acquires the delay time of each node 2 via the communication unit 14 and stores this delay time in the routing information storage unit 131. Note that the delay time may be acquired by the routing information acquisition unit 124 described later.

  The delay constraint value allocation unit 123 divides and allocates the end-to-end delay constraint value into each section. Then, the delay constraint value assigned to each section is stored in the path information storage unit 132.

  The routing information acquisition unit 124 acquires the link cost (such as the remaining bandwidth in each link) of each node 2 via the communication unit 14 and stores it in the routing information storage unit 131.

  When the path control unit 125 receives a path setting command from the input / output unit 11 or the communication unit 14, the path control unit 125 outputs a path calculation command to the path calculation unit 121. When the route calculation result from the route calculation unit 121 is received, a path setting command based on the route calculation result is output to each node 2 via the communication unit 14.

  The function of the processing unit 12 is realized by a predetermined program stored in the storage unit 13 by a CPU (Central Processing Unit) or the like.

  The storage unit 13 stores various data to be referred to when the processing unit 12 performs route calculation, in addition to a program for realizing the function of the route calculation device 1. The storage unit 13 includes a routing information storage unit 131 that stores routing information (link information and topology information), a path information storage unit 132 that stores a route (path) calculated by the route calculation unit 121, and an input end− and a constraint condition storage unit 133 that stores constraint conditions when performing route calculation, such as delay constraint values in to-end and relay node identification information. The storage unit 13 is realized by a storage device such as a RAM (Random Access Memory), a flash memory, and an HDD (Hard Disk Drive).

  The routing information storage unit 131 stores link information connecting each node 2 and network topology information. As illustrated in Table 1 below, this link information includes, for each link ID, the link cost, delay time, A-end node ID, A-end node IF (interface) ID, Z-end node ID, and Z-end of the link. This is information indicating the node IF ID and the like. The link cost value may be a value obtained from the remaining bandwidth of the link or may be a value obtained from the delay time. The node ID and IF ID are described by an IP address, for example.

  The topology information is information indicating identification information of the node 2 installed in the network and how the nodes are connected to each other.

  Here, the topology information and the link information are separate, but the above-described link information may be included in the topology information.

  The path information storage unit 132 stores the route (path) information calculated by the route calculation unit 121 as described above. Table 2 below illustrates the path information.

  For example, as illustrated in Table 2, the path information includes the path ID of the path (path) calculated by the path calculation unit 121, the start node ID of the path, the start node IF ID, the end node ID, the end node IF ID, This is information indicating a via link ID list, link cost, delay time (actual delay time), and the like.

  The path information may be prepared both for the end-to-end route and for each section obtained by dividing the route with the inclusive route designation. In that case, the path information for each section is, for example, as follows, for each path (path) path ID, the start point node ID, start point node IF ID, end point node ID, end point node in each section dividing the path This is information indicating an IF ID, a via link ID list, a link cost, a delay constraint value assigned to the section (delay constraint value sub-delay (k, i) described later), and the like. As the delay constraint value, the delay constraint value assigned to the section by the delay constraint value assignment unit 123 is written. The route link ID list, link cost, and delay time in the path information for each section are rewritten when the route calculation unit 121 recalculates the route in the section.

  As described above, the constraint condition storage unit 133 stores a constraint condition in route calculation. The constraint condition is information indicating, for each path ID, an end-to-end delay constraint value in that path, relay node identification information passing through the path, and the like as exemplified in Table 4 below.

  Information in the routing information storage unit 131, the path information storage unit 132, and the constraint condition storage unit 133 is referred to when the route calculation unit 121 performs route calculation.

  The communication unit 14 manages a communication interface with each node 2. The processing unit 12 acquires the delay time and routing information of each node 2 and outputs a path setting command to each node 2 via the communication unit 14.

<Operation of route calculation device>
Next, the operation of the route calculation apparatus 1 will be described with reference to FIG. FIG. 3 is a flowchart showing the operation of the route calculation apparatus of FIG. Note that the route calculation device 1 acquires the routing information of each node 2 and the delay time (actual delay time) generated between the nodes 2 before starting the route calculation, and stores it in the routing information storage unit 131. Shall be kept.

  First, the route calculation apparatus 1 accepts an input of inclusive route designation via the relay node input unit 111 (S301). That is, the input of the IDs of the start node and the end node and the ID (identification information) of the relay node that passes between the nodes is accepted. The number of relay nodes here is N, for example.

  In addition, an input of a delay constraint value from the start node to the end node is accepted via the delay constraint value input unit 112 (S302). The input relay node ID and delay constraint value are stored in the constraint storage unit 133.

  When the path control unit 125 receives a path setting command from the input / output unit 11 or the like, the path control unit 125 outputs a path calculation command to the path calculation unit 121. Then, the route calculation unit 121 uses this as a trigger to divide the route from the start node to the end node into N + 1 sections Ri (1 ≦ i ≦ N + 1) at the relay node. Next, the delay constraint value assigning unit 123 divides the delay constraint value input in S302 (delay constraint value in end-to-end) into N + 1 pieces, and in each section Ri delimited by the relay node, The divided delay constraint value sub-delay (0, i) is assigned (S303). The delay constraint value sub-delay (0, i) assigned to each section Ri is stored in the path information storage unit 132. Each value in parentheses of sub-delay indicates (the number of recalculations of the delay constraint value, the ID of the divided section).

  Next, the route calculation unit 121 searches (calculates) a route satisfying the delay constraint value sub-delay (0, i) for each section Ri (S304). The calculation result is recorded in the path information storage unit 132. Here, when a route satisfying the delay constraint value sub-delay (k, i) can be found for all the sections Ri to be calculated (Yes in S305), the route calculation unit 121 uses the calculated route as a calculation result. The data is output to the path control unit 125 or the input / output unit 11 (S308), and the process ends.

  On the other hand, the route calculation unit 121 could not find a route satisfying the delay constraint value sub-delay (k, i) for all the sections Ri to be calculated (No in S305), but any one or more sections When a route satisfying sub-delay (k, i) can be found for Ri (Yes in S306), that is, an interval where a route satisfying the delay constraint value sub-delay (k, i) was not found can be found. When there is a new section, the process proceeds to S309. Then, the delay constraint value assignment unit 123 sets a new delay constraint value sub-delay (k + 1, i) in a section in which a route satisfying the delay constraint value sub-delay (k, i) cannot be found (S309). ).

The new delay constraint value sub-delay (k + 1, i) at this time is calculated based on the following equation (1).
sub-delay (k + 1, i) = {Σ (delay time of sub-delay (k, j) −Rj) / number of sections not satisfying delay constraint value} + sub-delay (k, i) (1)
j: ID of the section in which a route satisfying the delay constraint value was found

  In other words, the delay constraint value assigning unit 123 assigns a delay time exceeding the actual delay time in the section (that is, the remaining delay time) to a section not satisfying the delay constraint value in the section satisfying the delay constraint value. Then, the delay constraint value assignment unit 123 stores the new delay constraint value sub-delay (k + 1, i) in the path information storage unit 132.

  Then, the path calculation unit 121 sets the new delay constraint value sub-delay (k + 1, i), that is, the delay constraint value sub-delay after the change for the interval Ri in which the delay constraint value is changed. A route satisfying (k + 1, i) is searched (S310). Thereafter, a route satisfying the delay constraint value sub-delay (k + 1, i) can be found for the section Ri whose delay constraint value is changed, and a route satisfying the delay constraint value is found for all the sections Ri to be calculated. When completed (Yes in S305), the calculated route is output as a calculation result (S308).

  When no route satisfying the delay constraint value is found for any section Ri to be calculated (No in S306), the route calculation unit 121 outputs that a route satisfying the delay constraint value cannot be found. (S307), and the process ends.

  When there is a section in which a route satisfying the delay constraint value sub-delay (k, i) cannot be found and a section in which a route satisfying the delay constraint value sub-delay (k, i) is found (No in S305 → Yes in S306). In step S309, the delay constraint value assignment unit 123 again sets a new delay constraint value sub-delay (k + 1, i) in a section in which a route satisfying the delay constraint value sub-delay (k, i) cannot be found. Is set (S309). Then, the route calculation unit 121 searches (calculates) a route satisfying the changed delay constraint value sub-delay (k + 1, i) (S310). When a route satisfying the changed delay constraint value sub-delay (k + 1, i) is found, the route is stored in the path information storage unit 132. The route calculation device 1 repeats such processing, and finally finds a route satisfying the delay constraint value sub-delay (k, i) for all the sections Ri to be calculated (Yes in S305). A result obtained by connecting the path information of each section stored in the path information storage unit 132 by end-to-end is output as a calculation result (S308).

  On the other hand, even if the delay constraint value allocation unit 123 repeats the distribution of the delay constraint values, when the route satisfying the delay constraint value sub-delay (k, i) cannot be found (No in S306), the delay constraint value is satisfied. The fact that the route could not be found is output to the input / output unit 11 or the path control unit 125 (S307), and the process ends.

  By doing in this way, the route calculation apparatus 1 can calculate the shortest route satisfying the end-to-end delay constraint when the inclusive route is designated.

  Note that the route searched by the route calculation unit 121 in S304 and S310 is preferably a route that satisfies the delay constraint value for each section and has the minimum link cost. That is, when a plurality of routes satisfying the delay constraint value are found, the route calculation unit 121 selects a route having the minimum link cost among them. By doing so, it is possible to find a route with the minimum link cost while satisfying the delay constraint value.

  Further, the division of the end-to-end delay constraint value in the delay constraint value assignment unit 123 may be equally divided into each section or may be divided in proportion to the link cost of each section. That is, the delay constraint value assignment unit 123 assigns a longer delay constraint value sub-delay (k, i) to a section where the link cost is large, and a shorter delay constraint value sub-delay to a section where the link cost is small. (K, i) may be assigned. By doing in this way, the calculation amount required for route calculation (route search) of each section can be reduced. Furthermore, the end-to-end delay constraint value may be divided in proportion to the delay time of each section (actual delay time). By doing in this way, when dividing a delay constraint value, it is possible to divide without using routing information.

  The route calculation unit 121 may calculate, for each section, a route that satisfies the delay constraint value assigned to the section and maximizes the link cost.

<< Second Embodiment >>
Next, a route calculation apparatus according to the second embodiment will be described. The route calculation apparatus according to the second embodiment has a high link cost when the total delay time of the shortest route in each section divided by the inclusive route specification exceeds the end-to-end delay constraint value. In order from the section, the route having the shortest delay time is recalculated, and a route that is equal to or less than the end-to-end delay constraint value is searched (calculated).

<Overview of operation>
FIG. 4 is a diagram illustrating a route calculation apparatus according to the second embodiment. Since the network configuration is the same as that of the first embodiment, the description thereof is omitted. Note that the end-to-end delay constraint value in the path from the node 2A to the node 2D will be described as 30 ms or less as in the first embodiment.

  First, the route calculation device 1a calculates the shortest route for each of the sections # 1 to # 3 divided by the relay node. Then, for each section, the actual delay time in the shortest path is calculated and totaled. That is, the actual delay time of the shortest path in end-to-end is obtained. Here, if the actual delay time of the shortest path at the end-to-end does not exceed the delay constraint value (30 ms), the shortest path is output as a calculation result. On the other hand, if the actual delay time of the shortest path in the end-to-end exceeds the delay constraint value, the following processing is performed.

  That is, the route calculation device 1a first performs route recalculation on the section with the highest link cost among the sections divided by the relay node. For example, for the section # 3 with the highest link cost, the path with the shortest delay time is calculated among the paths that can be taken in this section. Then, the path calculation device 1a checks whether the end-to-end delay time after the calculation is equal to or less than the delay constraint value, and the end-to-end delay time after the calculation is the delay constraint. If the value is less than or equal to the value, the route in section # 3 is replaced with the recalculated route.

  In the example shown in FIG. 4, for the interval # 3, a route passing through the node 2E (delay time: 10 ms × 2 = 20 ms) and a route passing through the nodes 2F and 2G (delay time: 5 ms × 3 = 15 ms) If there is, the route via the node 2E has a smaller number of hops, but the route via the nodes 2F and 2G has a shorter delay time. Therefore, a route passing through the nodes 2F and 2G is selected. Here, the total value (30 ms) of the delay time (15 ms) of the route passing through the nodes 2F and 2G and the delay time (10 ms + 5 ms) of other sections is equal to or less than the above-described end-to-end delay constraint value. (30 ms or less). Therefore, the path information of the section # 3 stored in the path information storage unit 132 is output by replacing the path via the node 2E with the path via the nodes 2F and 2G.

  On the other hand, when the total value of the delay time of the route passing through the nodes 2F and 2G and the delay time of the remaining section does not satisfy the delay constraint value (30 ms or less) in the end-to-end, the route calculation device 1a repeats the same route calculation in order from the section with the highest link cost (for example, section # 1) for the remaining sections, and stores the calculated paths in the path information storage unit 132. Then, when a path satisfying a delay constraint value (30 ms or less) in end-to-end is found, the calculation is terminated.

  In this way, the route calculation device 1a can obtain the shortest route that satisfies the end-to-end delay constraint and the inclusive route specification constraint.

<Configuration of route calculation device>
Next, the configuration of the route calculation apparatus 1a will be described in detail with reference to FIG. FIG. 5 is a block diagram showing a configuration of the route calculation apparatus of FIG. Constituent elements similar to those in the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.

  The route calculation device 1a includes a route calculation unit 121a that calculates a route (shortest route) that minimizes the link cost and a route that minimizes the delay time, instead of the route calculation unit 121 of FIG. Further, instead of the delay constraint value assigning unit 123 in FIG. 2, it is determined whether or not the total delay time of all sections exceeds the end-to-end delay constraint value stored in the constraint condition storage unit 133. A delay time determination unit 126 is provided.

  The route calculation unit 121a first calculates the shortest route of each section divided by the relay node. The calculation of the shortest path at this time may use a known algorithm such as a restricted dijkstra method. Then, in the delay time determination unit 126, the actual delay time in the shortest path is calculated for each section and totaled. Then, when it is determined that the total actual delay time exceeds the delay constraint value stored in the constraint condition storage unit 133, the route with the shortest delay time is recalculated in order from the section with the highest link cost. .

<Operation of route calculation device>
Next, the operation of the route calculation apparatus 1a will be described with reference to FIG. FIG. 6 is a flowchart showing the operation of the route calculation apparatus of FIG. The route calculation device 1a also acquires the routing information of each node 2 and the delay time (actual delay time) occurring between the nodes before storing the route calculation, and stores it in the routing information storage unit 131. Keep it.

  Since S601 and S602 are the same processes as S301 and S302 in FIG. 3 described above, the description thereof will be omitted, and the description will start from S603.

  The route calculation unit 121a calculates (searches) the shortest route (route with the lowest link cost) of each section Ri (1 ≦ i ≦ N + 1) divided by the relay node (S603). The shortest path for each section Ri is stored as a via link ID list in the path information storage unit 132.

  Then, the route calculation unit 121a calculates the delay time of each section Ri (actual delay time when the shortest route is taken in each section Ri) from the delay time for each link recorded in the routing information storage unit 131. . Then, the calculated delay times of the respective sections Ri are summed to calculate an end-to-end delay time (S604).

  Next, the delay time determination unit 126 determines whether or not the calculated delay time at end-to-end exceeds the delay constraint value stored in the constraint condition storage unit 133 (S605). If the calculated end-to-end delay time does not exceed the delay constraint value stored in the constraint condition storage unit 133 (No in S605), the route calculation unit 121a stores the path information storage unit 132 in the path information storage unit 132. The stored route is output as a calculation result (S610), and the process ends.

  On the other hand, when the calculated end-to-end delay time exceeds the delay constraint value stored in the constraint condition storage unit 133 (Yes in S605), the route calculation unit 121a refers to the routing information storage unit 131. Then, the link cost of each section Ri is calculated, and the path with the shortest delay time is calculated in the section Ri having the largest link cost (S606). Note that the link cost of each section Ri is calculated in consideration of, for example, the number of hops in addition to the delay time and the remaining bandwidth.

  Then, the route calculation unit 121a replaces the shortest route stored in the path information storage unit 132 with a route having the shortest delay time (S607), sums the delay times of the sections Ri after the route replacement, The end-to-end delay time is recalculated (S608), and the delay time determination unit 126 determines whether or not the total value of the delay times exceeds the delay constraint value (S609).

  Here, when the delay time determination unit 126 determines that the total value of the delay times does not exceed the delay constraint value (No in S609), the route calculation unit 121a stores the path information storage unit 132 in the path information storage unit 132. The route that has been stored is output as a calculation result (S610), and the process is terminated. That is, the route after route replacement is output as a calculation result.

  On the other hand, when the delay time determination unit 126 determines that the total value of the delay times exceeds the delay constraint value described above (Yes in S609), the path calculation unit 121a determines that i in the section Ri to be calculated. The value is incremented (+1) (S611), and if the incremented value of i is N + 1 or less (No in S612), the process returns to S606. Then, the route calculation unit 121a calculates the route having the shortest delay time for the section Ri having the highest link cost, excluding the section Ri that is the current calculation target, and replaces the route of the section Ri with the calculated route. .

  The route calculation unit 121a repeats the above processing for each section Ri until the total end-to-end delay time becomes equal to or less than the delay constraint value. When the total end-to-end delay time is equal to or less than the delay constraint value (No in S605), the process proceeds to S610, and the path of each section Ri after path replacement is output.

  Note that when the value of i exceeds N + 1 (Yes in S612), that is, when the calculation of the route with the shortest delay time for all the sections Ri is completed, the route calculation unit 121a uses the route designated by the inclusive route. The fact that the delay constraint value could not be found is output as a calculation result (S613), and the process is terminated.

  By performing the above processing, the route calculation device 1a can calculate the shortest route satisfying the end-to-end delay constraint even when the inclusive route is designated.

  In the embodiment described above, the route calculation unit 121a performs the route recalculation in order from the section Ri having the largest link cost. However, the route calculation unit 121a performs the route recalculation in order from the section Ri having the longest delay time. Alternatively, route recalculation may be performed in order from a section with a high link cost and a long delay time. Moreover, you may make it calculate in order from the area Ri with many path | routes other than the shortest path | route among each area Ri. This also makes it easier to find a route that satisfies the end-to-end delay constraint value when an inclusive route is specified.

  Furthermore, when the route calculation unit 121a does not find a route that satisfies the delay constraint value, a screen that prompts the output device connected to the route calculation device 1a to re-specify the inclusive route or reset the delay constraint value. You may make it display.

  Further, the route calculation unit 121a may calculate (search) a route that maximizes the link cost in each section Ri divided by the relay node in S603 of FIG. In this way, the route calculation device 1a can calculate a route that satisfies the delay constraint value and has the maximum link cost.

  Furthermore, in the above-described embodiment, the route calculation devices 1 and 1a have been described as devices separate from the node 2. However, the node 2 may function as the route calculation devices 1 and 1a.

  The route calculation apparatuses 1 and 1a according to the present embodiment can be realized by a computer program that executes the processing as described above, and the program is stored in a computer-readable storage medium (CD-ROM or the like). Can be provided. It is also possible to provide the program through a network.

It is a figure explaining the route calculation apparatus of 1st Embodiment. It is the block diagram which showed the structure of the route calculation apparatus of FIG. It is the flowchart which showed operation | movement of the route calculation apparatus of FIG. It is a figure explaining the route calculation apparatus of 2nd Embodiment. It is the block diagram which showed the structure of the route calculation apparatus of FIG. 6 is a flowchart showing the operation of the route calculation apparatus of FIG.

Explanation of symbols

1, 1a Route calculation device 2 (2A to 2G) Node 11 Input / output unit 12 Processing unit 13 Storage unit 14 Communication unit 111 Relay node input unit 112 Delay constraint value input unit 121, 121a Path calculation unit 122 Delay time acquisition unit 123 Delay Constraint value allocation unit 124 Routing information acquisition unit 125 Path control unit 126 Delay time determination unit 131 Routing information storage unit 132 Path information storage unit 133 Constraint condition storage unit

Claims (9)

An input / output unit that controls input / output of various data, a communication unit that performs communication via a network, a storage unit that stores topology information of nodes configuring the network, and link cost information of a link connecting the nodes; A route calculation apparatus comprising a processing unit that performs route calculation with reference to topology information and the link cost information,
A relay node input step for receiving input of identification information of a relay node that passes between a start point node and an end point node in a route in the network via the input / output unit;
A delay constraint value input step for receiving an input of a delay constraint value that is an upper limit value of a delay time in communication from the start node to the end node via the input / output unit;
A delay constraint value assigning step for assigning the input delay constraint value by dividing the route from the start node to the end node into sections divided by the relay node;
A delay time acquisition step of acquiring an actual delay time between the nodes via the communication unit and storing the actual delay time in the storage unit;
With reference to the acquired actual delay time between the nodes, the topology information, and link cost information, for each section, the actual delay time in the section is equal to or less than the delay constraint value assigned to the section. And a route calculation step of performing route calculation of a route with a minimum link cost and storing the calculated route in the storage unit;
The path calculation method characterized by performing. In the route calculation step, in each of the sections, a first section that is a section in which a path whose actual delay time in the section is less than or equal to the delay constraint value assigned to the section cannot be calculated, and the section When there is a second section that is a section in which a route that is less than or equal to the assigned delay constraint value can be calculated,
Distributing the delay constraint value assigned to the second interval to the delay constraint value assigned to the first interval, and changing the delay constraint value in the first interval stored in the storage unit; The route calculation method according to claim 1, wherein the route calculation of the first section is performed again based on the changed delay constraint value. An input / output unit that controls input / output of various data, a communication unit that performs communication via a network, a storage unit that stores topology information of nodes configuring the network, and link cost information of a link connecting the nodes; A route calculation apparatus comprising a processing unit that performs route calculation with reference to topology information and the link cost information,
Via the input / output unit, accepting input of identification information of a relay node that passes between a start point node and an end point node in a route in the network, and a relay node input step of storing in the storage unit;
A delay constraint value input step for receiving an input of a delay constraint value that is an upper limit value of a delay time in communication from the start point node to the end point node via the input / output unit;
Referring to the topology information and the link cost information, for each section obtained by dividing the path from the start node to the end node by the relay node, the shortest path that minimizes the link cost of the section is calculated. , The shortest path calculation step stored in the storage unit;
A delay time acquisition step of acquiring an actual delay time between the nodes via the communication unit and storing the actual delay time in the storage unit;
The actual delay time in each section is calculated from the acquired actual delay time between the nodes, and it is determined whether or not the total value of the calculated delay times exceeds the input delay constraint value. A delay time determination step,
Run
In the delay time determining step, when it is determined that the total value of the calculated actual delay times exceeds the input delay constraint value,
Referring to the link cost information, calculating the link cost of each section, and calculating the path with the shortest delay time in the section in order from the section with the large calculated link cost;
A route replacement step of replacing the route of the section stored in the storage unit with the route having the shortest calculated delay time;
The path calculation method is executed until a total value of actual delay times of the respective sections after the path replacement becomes equal to or less than the input delay constraint value. In the delay time determining step, when it is determined that the total value of the calculated actual delay times exceeds the input delay constraint value,
4. The route calculation method according to claim 3, wherein the shortest route calculation step and the route replacement step are executed in order from the interval in which the calculated actual delay time is long among the intervals.   5. A route calculation program that causes the route calculation device, which is a computer, to execute the route calculation method according to claim 1. A route calculation device taking delay constraints into account,
A storage unit for storing topology information of nodes constituting the network and link cost information of links connecting the nodes;
A communication unit for communicating via the network;
A relay node input unit that receives input of identification information of a relay node that passes between a start point node and an end point node in a route in the network, and stores the information in the storage unit;
A delay constraint value input unit that receives an input of a delay constraint value that is an upper limit value of a delay time in communication from the start node to the end node via the input / output unit, and stores the delay constraint value in the storage unit;
A delay constraint value assigning unit that assigns the input delay constraint value by dividing the route from the start node to the end node into sections divided by the relay node;
A delay time acquisition unit that acquires an actual delay time between the nodes via the communication unit, and stores the actual delay time in the storage unit;
With reference to the acquired actual delay time between the nodes, the topology information, and link cost information, for each section, the actual delay time in the section is equal to or less than the delay constraint value assigned to the section. And a route calculation unit that performs route calculation of a route with a minimum link cost, and stores the calculated route in the storage unit;
A route calculation apparatus comprising: A route calculation device taking delay constraints into account,
A storage unit for storing topology information of nodes constituting the network and link cost information of links connecting the nodes;
A communication unit for communicating via the network;
A relay node input unit that receives input of identification information of a relay node that passes between a start point node and an end point node in a route in the network, and stores the information in the storage unit;
A delay constraint value input unit that receives an input of a delay constraint value that is an upper limit value of a delay time in communication from the start node to the end node via the input / output unit, and stores the delay constraint value in the storage unit;
Referring to the topology information and the link cost information, for each section obtained by dividing the path from the start node to the end node by the relay node, the shortest path that minimizes the link cost of the section is calculated. A route calculation unit stored in the storage unit;
A delay time acquisition unit for acquiring an actual delay time between the nodes and storing the actual delay time in the storage unit;
The actual delay time in each section is calculated from the acquired actual delay time between the nodes, and it is determined whether or not the total value of the calculated delay times exceeds the input delay constraint value. A delay time determination unit,
With
The route calculation unit
In the delay time determination unit, when it is determined that the total value of the calculated actual delay times exceeds the input delay constraint value,
Referring to the link cost information, the link cost of each section is calculated, and the path with the shortest delay time in the section is calculated in order from the section with the highest link cost calculated and stored in the storage unit. The route of the section is replaced with the route having the shortest calculated delay time, and is executed until the total value of the actual delay times of the sections after the route replacement is equal to or less than the input delay constraint value. A route calculation apparatus characterized by: The route calculation unit
In the delay time determination unit, when it is determined that the total value of the calculated actual delay times exceeds the input delay constraint value,
In order from the section where the calculated actual delay time is large, the path with the shortest delay time in the section is calculated, and the path of the section stored in the storage unit is the path with the shortest calculated delay time. The route calculation apparatus according to claim 7, wherein the route calculation device is executed until a total value of actual delay times of the respective sections after the route replacement becomes equal to or less than the input delay constraint value.   A node comprising the function of the route calculation device according to any one of claims 6 to 8.

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