JP2015177235A - Traffic flow allocation method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a traffic flow allocation method and device for sharing a link band by making respective slices of SDN share one packet transfer queue for each physical link.SOLUTION: A minimum hop route calculation part 20 calculates a minimum hop route from all traffic flows. A virtual network candidate creation part 30 successively calculates such a traffic flow route as to minimize increase of a packet transfer scheduling cost expectation value between slices, thereby creating a plurality of virtual network candidates with different routes while meeting all the traffic flows for each slice. A traffic flow allocation calculation part 40 calculates, as a solution of an integer scheduling model, such a combination of virtual network candidates as to minimize packet transfer scheduling cost between slices for combinations of virtual network candidates as many as all slices which are selected one by one for each slice, out of a virtual network candidate group created for each slice.

Description

  The present invention relates to a traffic flow assignment method and apparatus for assigning a route on a network to a traffic flow group to which attributes such as arrival and departure nodes are given in advance. The present invention relates to a traffic flow allocating method and apparatus for realizing sharing of a link bandwidth by sharing a packet transfer queue between networks with a small amount of computing resources.

  Non-Patent Documents 1 and 2 disclose SDN as a technology for creating a virtual network by software. In SDN, since a number of completely independent virtual networks called “slices” can be constructed on one physical network, a unique network corresponding to a user's request can be constructed for each slice.

  Patent Document 1 discloses a traffic flow allocation method and apparatus for promoting sharing of a packet transfer queue and a link band between slices in an SDN to minimize a packet transfer scheduling cost.

  In Patent Document 2, a plurality of virtual network candidates having a tree topology are configured in advance for each slice of the SDN, and an integer programming model is solved to minimize the packet transfer scheduling cost. A traffic flow allocation method and apparatus for selecting a combination of the above is disclosed.

Japanese Patent Application No. 2013-262879 Japanese Patent Application No. 2013-269103

"Examination of Integrated State Collection and Analysis Mechanism for Control Plane Application Development and Operation Monitoring in Software Defined Network" IEICE Technical Report. NS, Network Systems 111 (408), 127-132, 2012-01- 19 "OpenFlow / SDN and Network Virtualization" IEICE Technical Report, vol. 112, no. 230, IN2012-96, pp. 115-119, October 2012, Shigenori Shindo

  Each slice of SDN can share each link of the physical network. However, if a unique link bandwidth is set for each slice, the link bandwidth cannot be used effectively. For example, if a 1G bandwidth is fixedly allocated to slices A and B for a physical link with a bandwidth of 2G, for example, even if slice A has a large traffic volume and slice B has a small traffic volume, slice A Cannot allocate the surplus bandwidth of slice B.

  On the other hand, if the bandwidth is allocated so that slices A and B share one packet transfer queue for each physical link, each slice A and B can allocate the surplus bandwidth to other slices. The link bandwidth can be effectively used without degrading the service quality of the slice. However, until now, it has not been studied that each slice of an SDN shares a link bandwidth by sharing one packet transfer queue for each physical link.

  In response to such a technical problem, the inventors of the present invention input the network topology information and traffic flow information as input, and assign traffic flow allocation that minimizes the sum of scheduling costs for packet transfer of all links to an integer plan. Calculated as a solution of the legal model, and for each ring of the network, among the slices with one priority class of traffic flow passing through the link, the link bandwidth is set between slices having the same priority class. A method and apparatus for calculating traffic flow allocation under shared conditions was invented and a patent application was filed (Patent Document 1).

  However, the direct solving method of the integer programming model disclosed in Patent Document 1 uses a large amount of computing resources, and thus has a technical problem that it is difficult to apply to a large-scale SDN.

  In response to such a technical problem, the inventors of the present invention further select a tree topology candidate that most reduces the packet transfer scheduling cost from a plurality of tree topology candidates given in advance in each slice. Only by solving the integer programming model, a traffic flow allocation method and apparatus that do not require a large amount of computational resources were invented and a patent application was filed (Patent Document 2).

  However, a virtual network having a tree topology in each slice does not always reduce the scheduling cost of packet transfer.

  An object of the present invention is to solve the above technical problem, to reduce the amount of calculation resources used, and to provide a traffic flow allocation method and apparatus capable of efficiently reducing the packet transfer scheduling cost. .

  In order to achieve the above object, the present invention has the following configuration in a traffic flow allocation apparatus that calculates traffic flow allocation that realizes sharing of a link bandwidth by sharing a packet transfer queue between slices of an SDN. There is a feature in the point.

  (1) Based on the network topology information and traffic flow information, the means to create multiple virtual network candidates with different paths for each slice and the combinations of virtual network candidates selected from each slice for the number of slices And a means for calculating, as a solution of the integer programming model, a combination that minimizes the sum of scheduling costs related to packet transfer of each link through which the traffic flow passes, and one type of priority class of traffic flow passing through each link Among a plurality of slices, a combination of virtual network candidates is calculated under a condition in which a link band is shared between slices having the same priority class.

  (2) The means for creating a virtual network candidate is a means for setting the cost of each link to an increase in the expected value of inter-slice scheduling cost when the path calculation target traffic flow is assumed to pass through the cost setting target link; Means for creating a plurality of route groups in which each route is different by satisfying all traffic flows for each slice according to each link cost, and by combining all the routes in each route group, a plurality of virtual networks for each slice A candidate was created.

  (3) The means for creating a plurality of types of route groups is to sequentially calculate the traffic flow route that minimizes the increase in the expected packet transfer scheduling cost between slices.

  According to the present invention, the following effects are achieved.

  (1) In SDN, traffic flow allocation that promotes sharing of packet transfer queues and link bandwidths between slices and minimizes scheduling costs of packet transfers can be realized. Further, since the sharing of the packet transfer queue and the link band between the slices is promoted, the utilization efficiency of the link band is improved.

  (2) Since virtual network candidates are configured in which the sequential increase in the expected value of the packet transfer scheduling cost between slices is minimized, it is possible to accurately realize traffic flow allocation that reduces the packet transfer scheduling cost between slices.

  (3) Since only a combination of virtual network candidates that reduce the packet transfer scheduling cost most is selected from a plurality of virtual network candidates with different paths created for each slice, the integer programming model is solved. It does not require a large amount of computing resources and can be applied to large-scale SDN.

It is the figure which showed the typical example of sharing of a link band by sharing of the packet transfer queue between slices by this invention. It is the figure which showed the example which is not suitable for sharing of a link band by sharing of a packet transfer queue because the priority class is set to the traffic flow. FIG. 11 is a diagram (part 1) illustrating an example suitable for sharing a link bandwidth by sharing a packet transfer queue even when a priority class is set for a traffic flow; FIG. 10 is a diagram (part 2) illustrating an example suitable for sharing a link bandwidth by sharing a packet transfer queue even when a priority class is set for a traffic flow; It is a figure for demonstrating the relationship between the number of slices which share a link, the packet transfer queue set to each slice, and scheduling cost. It is the functional block diagram which showed the structure of the principal part of the traffic flow allocation apparatus which concerns on one Embodiment of this invention. It is the flowchart which showed the procedure which produces a some virtual network candidate for every slice. It is the figure which showed the other example of sharing of a link band by sharing of the packet transfer queue between slices by this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, link bandwidth sharing by sharing packet transfer queues according to the present invention will be described, and then a traffic flow allocation method capable of minimizing scheduling cost by sharing link bandwidth will be described in detail.

  The scheduling cost noticed by the present invention is a processing cost required for each node to transfer a packet of each traffic flow with a priority according to its priority class. The scheduling cost depends on the number of slices sharing the link bandwidth and the number of packet transfer queues. Dependent.

  In the present invention, typically, as shown in FIG. 1, the packet transfer queues provided in the same physical link in a plurality of slices (here, two slices # 1 and # 2) are combined into one. By sharing a single packet transfer queue for multiple slices # 1 and # 2, the total of the link bandwidth allocated to each of slices # 1 and # 2 for that link is shared by slices # 1 and # 2 Traffic flow allocation is realized.

  On the other hand, in a slice in which a plurality of priority classes are provided in a traffic flow, band allocation that is relatively superior or inferior is generally performed according to the priority class. However, since such bandwidth allocation is based on contract service charges, etc., even if packet transfer opportunities with lower priority classes are lost as a result of the increase in packet transfers with higher priority classes, the quality of service is reduced. There is not much unfairness inside.

  However, as shown in FIG. 2, when the link bandwidth is shared by slices (# 3, # 4) in which a plurality of priority classes are provided in the traffic flow, one slice (here, slice # 4) If the traffic flow increases and the high-priority traffic flow increases, the bandwidth that should be allocated to the low-priority traffic flow of the other slice (here, slice # 3) is eroded, and the service quality is degraded. So unfairness arises.

  Therefore, in the present invention, the slices to be shared of the link bandwidth by sharing the packet transfer queue are limited to slices in which only a single and the same priority class traffic flow flows in each link.

  In addition, as shown in FIG. 1, the combination of slices includes not only the slices having a unique priority class as shown in FIG. 1, but also traffic flows having different priority classes as slices as shown in FIGS. However, in the link unit, slices in which only the high priority traffic flow flows (FIG. 3) and slices in which only the low priority traffic flow flows (FIG. 4) are also the same in the slices in which the priority class is unique. The slice is a link band sharing target.

  1 to 4, for the convenience of explanation, the packet transfer queue and link bandwidth sharing between two slices has been described as an example. However, as shown in FIG. The same applies to links shared by # 6. That is, the slices # 1 and # 2 are not shared because there are a plurality of priority classes of traffic flows. Slices # 3 and # 4 are shared because only the high-priority traffic flow passes through them. Slices # 5 and # 6 are shared because only the low-priority traffic flow passes.

  The present invention considers the realization of traffic flow allocation that promotes sharing of packet transfer queues and link bandwidths between slices and minimizes packet transfer scheduling costs between slices in the entire network. Here, the packet transfer scheduling cost between slices to be minimized is the sum of the scheduling costs between slices in each link. The inter-slice scheduling cost in each link is represented by the number of virtual machines that process packet transfer control in each slice, and is simply proportional to the number of slices after link bandwidth sharing. Therefore, in the example of FIG. 5, the number of virtual machines is 4, and the scheduling cost between slices is proportional to 4.

  FIG. 6 is a functional block diagram showing the configuration of the main part of the traffic flow allocation apparatus 1 according to one embodiment of the present invention. Such a traffic flow allocation apparatus 1 can be configured by installing an application (program) for realizing each function described later on a general-purpose computer or server. Alternatively, a part of the application may be configured as a dedicated machine or a single-function machine in which hardware or ROM is implemented.

  The input interface (I / F) 10 includes a topology information receiving unit 10a that receives and stores input of network topology information, and a traffic flow information receiving unit 10b that receives and stores input of traffic flow information. The minimum hop number route calculation unit 20 calculates the minimum hop number route of all traffic flows, and further calculates the average number of via hops.

  As will be described in detail later, the virtual network candidate creation unit 30 sequentially calculates a traffic flow route that minimizes an increase in the expected value of the packet transfer scheduling cost between slices. A plurality of virtual network candidates that satisfy the traffic flow and have different routes are created. In order to calculate the expected value of the packet transfer scheduling cost between slices, the value of the average number of hops in the traffic flow is necessary. Use this instead.

  In the virtual network candidate creation unit 30, the link cost setting unit 30a sets the cost of each link to the amount of increase in the expected value of the inter-slice scheduling cost when it is assumed that the path calculation target traffic flow passes through the cost setting target link. To do. The minimum cost route group calculation unit 30b sequentially calculates the minimum cost route of each traffic flow for each slice according to each set link cost, and repeats this to obtain a plurality of virtual network candidates with different routes. create.

  The traffic flow allocation calculation unit 40 performs packet transfer scheduling between slices for combinations of virtual network candidates corresponding to the total number of slices selected for each slice from a plurality of virtual network candidates created for each slice. The combination of virtual network candidates that minimizes the cost is calculated as the solution of the integer programming model. The traffic flow path constituting the virtual network candidate selected in each slice is output as a traffic flow allocation result that minimizes the scheduling cost of packet transfer.

  FIG. 7 is a flowchart showing a procedure in which the minimum cost route group creation unit 30b creates a plurality of virtual network candidates that satisfy all traffic flows for each slice and differ in each route. The belonging traffic flows are randomly selected one by one, and the routes of the selected traffic flows are sequentially calculated.

  In the present embodiment, a plurality of virtual network candidates with different routes are created by changing the order of traffic flows to be subjected to route calculation. Prior to route calculation for each traffic flow, the cost of each link is set to an increase amount of the expected value of inter-slice scheduling cost when the traffic flow to be calculated passes through the link.

  That is, in step S101, a list of slices to be shared with the link band is created. In step S102, one slice (target slice) of interest is extracted from the slice list. In step S103, “1” is set as the initial value in the virtual network candidate number Ncad.

  In step S104, the flow list of the target slice is created based on the traffic flow information. In step S105, one traffic flow is selected at random from the flow list and is set as the current traffic flow of interest, that is, the route calculation target traffic flow.

  In step S106, the link cost that the traffic flow passing through the link bears is set for each link. In this embodiment, as will be described in detail later with reference to equations (1) to (5), the cost of each link is assumed to be the inter-slice scheduling cost expectation when the traffic flow of interest passes through the cost setting link. It is set to the increment of the value (0-1).

  In step S107, the minimum cost route of the traffic flow of interest is calculated. In step S108, it is determined whether or not the allocation of the minimum cost path has been completed for all traffic flows registered in the flow list. If not completed, the process returns to step S105, and the allocation of the minimum cost path and the update of the link cost are repeated while switching the traffic flow of interest.

  Thereafter, when it is determined that the processing related to all the traffic flows registered in the flow list has been completed, the process proceeds to step S109, and a virtual network is configured by synthesizing all the minimum cost paths calculated in the current slice of interest. This is registered as one of the virtual network candidates related to the target slice. In step S110, the virtual network candidate number Ncad is incremented.

  In step S111, it is determined whether the virtual network candidate number Ncad has reached a predetermined number of candidates. If the predetermined number of candidates has not been reached, the process returns to step S104 and the above processes are repeated to further create another virtual network candidate for the current target slice.

  Thereafter, when it is determined in step S111 that a predetermined number of virtual network candidates have been acquired for the current attention slice, the process proceeds to step S112, and these virtual network candidates are registered as a virtual network candidate group of the attention slice.

  In step S113, it is determined whether or not extraction of the virtual network candidate group has been completed for all slices. If not completed, the process returns to step S102, and the above processes are repeated while switching the target slice, and Ncad virtual network candidate groups are extracted for each slice.

  Next, the link cost setting method in step S106 will be described in detail. In this embodiment, each link cost Cost in the calculation of virtual network candidates for each slice of interest increases the expected value of inter-slice scheduling cost (0 to 1) when it is assumed that the current traffic flow passes the cost setting link. It is set to a quantity and takes one of the following three values depending on the attribute of the link.

Case 1 Link without passing traffic flow: Cost = LC0
Case 2 A link through which only a traffic flow belonging to one priority class different from the traffic flow of interest passes: Cost = 1.0-LC0
Case 3 Other links: Cost = ε (ε is a sufficiently small value)

  That is, when the traffic flow of interest first passes from the state where no traffic flow passes through the link whose cost is to be set (case 1), if the total number of slices is S, a virtual network candidate is obtained. Of the S-1 slices other than the current slice of interest, i (= 0 to S-1) slices and the link can be expected to share the bandwidth for the link. The amount of increase is 1 / (i + 1).

  For example, if bandwidth sharing of the link with S-1 slices other than the current target slice for which a virtual network candidate is to be obtained cannot be expected (i = 0), the inter-slice scheduling cost in the link increases. The amount becomes 1 as it is.

  On the other hand, the slice that can share the link band is a slice in which only one or more traffic flows belonging to the same priority class as the traffic flow of interest pass through the link.

  Here, if the number of combinations for selecting n slices from m slices is mCn and the probability that only one or more traffic flows belonging to the same priority class as the traffic flow of interest passes through the link is P, The probability that the link bandwidth can be shared with i (= 0 to S-1) slices of S-1 slices other than the target slice for which a network candidate is to be obtained is expressed by the following equation (1). It can be expressed as

  Therefore, when the link bandwidth can be shared with i (= 0 to S-1) slices out of S-1 slices other than the target slice, the increase in the inter-slice scheduling cost is calculated by the formula (1) above. Since it is sufficient to average i (= 0 to S-1) using the result, it can be expressed by the following equation (2).

  On the other hand, regarding the probability P, if the average number of hops through traffic flows is H and the number of links is L, the probability that each traffic flow passes through a link whose cost is to be set is given by (H / L). However, in the present embodiment, the average via hop count H is substituted with the average via hop count of the minimum hop count route of all traffic flows obtained previously.

  If each slice contains Fs traffic flows, the probability that one or more i (= 1 to Fs) traffic flows out of the Fs traffic flows will pass through the link. And can be expressed by the following equation (3)

  In addition, i (= 1 to Fs) traffic flows pass through the link, and all i (= 1 to Fs) traffic flows that pass through the link have the same priority class as the traffic flow of interest. The probability of belonging can be expressed by the following equation (4), where K is the number of priority classes.

  From the above, in each slice, the probability P that only one or more traffic flows belonging to the same priority class as the traffic flow of interest passes through the link is obtained by taking the sum of i (= 1 to Fs) and calculating the following equation ( It can be expressed in 5). However, it is assumed that the number of traffic flows belonging to each priority class is equal.

  In case 2, if the traffic flow of interest passes through the link, at that time, the slice becomes an independent slice that cannot share the link bandwidth with other slices. Therefore, the increase amount of the inter-slice scheduling cost expectation value from the state where there is no traffic flow passing through the link is 1.0, and LC0 represents the cost immediately before the link.

  In the case 3, even if the traffic flow of interest passes through the link, the expected value of the scheduling cost between slices does not increase. Therefore, ε is a sufficiently small real number, for example, a number smaller than the reciprocal of the total link number L of the network.

  By calculating the minimum cost route under this link cost, it is possible to calculate a route that minimizes the increase in the expected value of the packet transfer scheduling cost between slices. When the route calculation of all the traffic flows belonging to the slice is completed, the virtual network candidates are configured by combining the routes of the traffic flows.

  Then, the traffic flow allocation calculation unit 40 solves an integer programming model having the topology information and virtual network candidate information of each slice as inputs, and minimizes the scheduling cost of packet transfer between slices. And the traffic flow allocation result are output.

The topology information of the network includes a node set and a link set constituting the network. The virtual network candidate information is information relating to a traffic flow path included in the slice, which constitutes each virtual network candidate. Constants and sets in the integer programming model are defined as follows:
Node: Node set
node: Node
s: Originating node
d: destination node
t: Relay node
Link: Link set
link
node inout: A set of links connected to the node node
Flow: Traffic flow set
f: Traffic flow
Pr: Priority class set
pr: Priority class
Sl: Slice set
sl: Slice
FPr (pr): Traffic flow set belonging to the priority class pr
FSl (sl): traffic flow set belonging to slice sl
MCad: Number of virtual network candidates in each slice
cad: Virtual network candidate.
X f, cad (link): When a virtual network candidate cad is selected in a slice including traffic flow f, a binary constant that is “1” when traffic flow f passes through link link and “0” otherwise.
A: Constant with a sufficiently large value

Each variable is defined as follows.
Y sl, cad: Binary variable that is “1” when virtual network candidate cad is selected in slice sl, and “0” otherwise
Q pr, sl (link): A binary variable whose traffic flow belonging to priority class pr in slice sl is “1” when passing through link link, and “0” otherwise.
Q1 sl (link): A binary variable that is “1” when a traffic flow belonging to one or more priority classes in the slice sl passes the link link, and “0” otherwise.
Q2 sl (link): A binary variable that is “1” when a traffic flow belonging to two or more priority classes in slice sl passes the link link, and “0” otherwise.
NQ pr (link): A binary variable that is “1” when only traffic flows belonging to the priority class pr pass through the link link and “0” otherwise.
SQ (link): A binary variable that is “1” when a traffic flow belonging to two or more slices passes through the link link, and “0” otherwise.

  In the integer programming model, the condition of the virtual network candidate selected in each slice is given by the following equation (6).

  The following equation (7) is a condition that traffic flows belonging to each priority class pass through each link in each slice, and Q pr, sl (link) is ΣΣ (X f, cad (link) × Y sl, cad ) Is 0 or less, it is “0”, and if it is 1 or more, it is “1”.

  The following equation (8) is a condition that traffic flows belonging to one or more priority classes pass through the link in each slice, and Q1 sl (link) is ΣQ pr, sl (link) is 0 or less “0”, “1” if 1 or more.

  The following equation (9) is a condition that traffic flows belonging to two or more priority classes pass through the link in each slice, and Q2 sl (link) is ΣQ pr, sl (link) -1 is 0 or less “0” if present, “1” if greater than or equal to “1”.

  The following equation (10) is a condition that only a traffic flow belonging to each priority class passes through the link in a certain slice.

  The following equation (11) is a condition that traffic flows belonging to two or more slices pass through the link, and SQ (link) is ΣQ2 sl (link) + ΣNQ pr (link) -1 if it is 0 or less “0”, “1” if 1 or more.

  The scheduling cost of packet transfer between slices to be minimized is expressed by the following equation (12).

  In the above equation (12), the constant W represents a proportional constant for converting the number of slices after the sharing of the link bandwidth into the inter-slice scheduling cost.

  In the term multiplied by the constant W, the first term (ΣQ2 sl...) Is the total number of slices in which a plurality of traffic flows having different priority classes flow in the same slice in the current target link link (∈Link), that is, the target This is the total number of slices that require independent inter-slice scheduling for the link, and corresponds to slices # 1 and # 2 in FIG.

  The second term (ΣNQ...) Is the total number of priority classes (pr) in which there is a slice in which only the traffic flow belonging to the priority class exists in the current link of interest (link), and the slice [# This corresponds to the priority class corresponding to [3 + # 4] and [# 5 + # 6]. That is, regarding the link of interest, the total number of slices after the sharing of the link bandwidth is represented for a slice that can be a link bandwidth sharing target in which only traffic flows belonging to one priority class flow.

  The assignment result of each traffic flow can be known from the values of the variables Y sl and cad representing the virtual network candidates selected in each slice by the values of the constants X f and cad (link).

  According to the present embodiment, in each slice of the SDN, an integer programming model is solved to select a virtual network candidate that reduces the packet transfer scheduling cost most from a plurality of virtual network candidates given in advance. Therefore, it does not require a large amount of computing resources and can be applied to large-scale SDN.

  In addition, according to the present embodiment, virtual network candidates are configured in which the sequential increase of the expected value of the packet transfer scheduling cost between slices is minimized, so traffic flow allocation that reduces the packet transfer scheduling cost between slices is performed. Can be realized with high accuracy.

  In the above-described embodiment, the slice set that is the target of sharing the link band is the same and the same slice of the priority class of the traffic flow passing through the link, and the slices through which a plurality of traffic flows of different priority classes pass. Was described as being out of scope for sharing.

  However, even if the slices pass through a plurality of traffic flows with different priority classes, as shown in FIG. 8, if the link band is fixedly assigned to each priority class in the slice, the corresponding priority is set. By summarizing and sharing the packet transfer queue between classes, the sum of the link bandwidths may be shared for each priority class. At this time, the bandwidth allocated to the corresponding priority class of each slice does not necessarily have to be the same.

  In this way, packets with the same priority class are treated fairly, and even if the high-priority traffic flow of one slice increases, the bandwidth to be allocated to the low-priority traffic flow of the other slice is secured. . Therefore, link bandwidth utilization efficiency can be improved without unfairly degrading service quality.

  DESCRIPTION OF SYMBOLS 1 ... Traffic flow allocation apparatus, 10 ... Input interface, 10a ... Topology information reception part, 10b ... Traffic flow information reception part, 20 ... Minimum hop number path | route calculation part, 30 ... Virtual network candidate creation part, 30a ... Link cost setting part , 30b ... minimum cost route calculation unit, 40 ... traffic flow allocation calculation unit

Claims (7)

In a traffic flow allocation device that calculates traffic flow allocation that realizes link bandwidth sharing by sharing packet transfer queues between each slice of SDN,
Means for creating a plurality of virtual network candidates with different paths for each slice based on network topology information and traffic flow information;
A method for calculating a combination that minimizes the sum of scheduling costs related to packet forwarding of each link through which traffic flows pass as a solution of an integer programming model for combinations of virtual network candidates selected from each slice. And
The means for calculating the combination is a virtual network candidate under a condition in which, among a plurality of slices having a single priority class of traffic flow passing through each link, a link band is shared between slices having the same priority class. A traffic flow allocation apparatus characterized by calculating a combination of The means for creating the virtual network candidate is:
Means for setting the cost of each link to an increase in the expected value of the inter-slice scheduling cost when the path calculation target traffic flow is assumed to pass through the cost setting link;
Means for satisfying all the traffic flows for each slice according to each link cost and creating a plurality of route groups in which each route is different,
2. The traffic flow allocation apparatus according to claim 1, wherein a plurality of virtual network candidates are created for each slice by synthesizing all paths in each path group.   The traffic flow allocation according to claim 2, wherein the means for creating the plurality of path groups sequentially calculates a traffic flow path that minimizes an increase in an expected value of a packet transfer scheduling cost between slices. apparatus.   4. The traffic flow allocation apparatus according to claim 2, wherein each path of the path group is a minimum cost path.   5. The traffic flow allocation apparatus according to claim 1, wherein the integer programming model does not share a link bandwidth among traffic flows having different priority classes. In a traffic flow allocation method for calculating traffic flow allocation that realizes sharing of a link bandwidth by sharing a packet transfer queue between slices of SDN,
Based on the network topology information and traffic flow information, creating a plurality of virtual network candidates with different paths for each slice;
A procedure for calculating a combination that minimizes the sum of scheduling costs related to packet forwarding of each link through which traffic flows pass as a solution of the integer programming model for combinations of virtual network candidates selected from each slice. Including
In the procedure for calculating the combination, a virtual network candidate is used under a condition in which, among a plurality of slices having one kind of priority class of traffic flow passing through each link, a link band is shared between slices having the same priority class. A traffic flow allocation method characterized by calculating a combination of The procedure for creating the virtual network candidate is as follows:
A procedure for setting the cost of each link to an increase in the expected value of the inter-slice scheduling cost when the path calculation target traffic flow is assumed to pass through the cost setting target link;
According to each link cost, creating a plurality of route groups that satisfy all traffic flows for each slice and each route is different,
The traffic flow allocation method according to claim 6, wherein a plurality of virtual network candidates are created for each slice by synthesizing all the routes in each route group.