JP2000036838A - Path setting retrieval device for communication network, and recording medium recorded with path setting retrieval program for communication network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a method for reducing the scale of a node of a two-layer structure shown below with respect to traffic band between nodes provided as a band table to solve a problem of a larger scale node device as capacity of transmission lines increases in a communication network through investigation of a configuration for reducing the capacity of a router by adding an exchange to set a path of a large capacity on the router that apply line concentration/edit to traffic in a detailed unit. SOLUTION: If the total sum of request bands of all paths passing through a block on a network is more than a prescribed path setting threshold level, the block is used for a path setting available block. A path is set sequentially to the path setting available block that has a highest via node number among the path setting available blocks. The traffic contained in the path is eliminated from the band table. The path setting increasing the path average via node number to a degree that is possible is obtained by repeating the processing aboves until all request bands on the band table is zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a path setting search device and a recording medium for recording a path setting search program in a communication network.

[0002]

2. Description of the Related Art In response to the recent increase in communication traffic,
Optical transmission lines are being laid in public trunk networks. In addition, wavelength multiplexing technology that dramatically increases the capacity of an optical transmission line has also been introduced at the commercial network level. With an increase in the capacity of a transmission line, an increase in throughput of a switching device installed in a station is also required. In a circuit-switched network,
Traffic is transmitted through a fixed-capacity transmission channel spanned from an input node to an output node. Such a transmission channel is called a path. The path setting of each path is performed by the switching device. Here, the path of the path is defined by all nodes and transmission paths through which the path passes, and the order in which they pass. The purpose of the route setting by the switching device is to distribute traffic for each destination and to set a bypass route in the event of a network failure.

When the ratio between the unit switching capacity of the switching device and the transmission line capacity increases, it may be more economical to hierarchize the switching units in the switching device. For example, in a network in which traffic is switched by an electric switch (switching unit is about 50 Mb / s), when the input traffic to the node is more than a certain level, if an optical switching device using an optical switch having a large switching unit capacity is used, the hardware of the node becomes harder. Ware scale has been shown to be effectively reduced (for example, R. Rama
swami and KN Sivarajan, "Optical Networks", Mo
rgan Kaufmann Pub. (1998) (Reference 1)). However, since the introduction of a new traffic management layer usually results in the addition of redundant transmission path capacity, the increase or decrease in hardware cost of the entire network is not always obvious.

For a given traffic, the required scale of the node device depends on the path setting. The term “path setting” used herein refers to an operation of determining the number of paths to be set for each path and generally each of a plurality of paths corresponding to each start / end node pair. Methods for optimizing the path setting for the required bandwidth given between the nodes have been studied by various research institutions. For example, N. Wauters and P. De
meester, "Design of the Optical Path Layer in Multi
wavelength Cross-Connected Networks ", IEEE Journal
of Selected Areas in Communications, Vol. 14, No.
5, pp.881-893, June 1996. (Reference 2), in an optical path network in which wavelengths correspond to paths in a wavelength division multiplexing network, a path setting that minimizes the total path length or the number of wavelengths as much as possible is obtained. A method is given.

In Reference 2, the required bandwidth is given in path units. However, the actual traffic between each source / destination node pair is generally a continuous value. For example, if the method of Reference 2 is applied when the traffic is smaller than the path capacity, redundant transmission path capacity and node size are assumed. , Can not design the network with the lowest cost. B. Mukherjee, D. Banerjee, S. et al. Find a path setting that achieves the maximum throughput when given a continuous value of traffic.
Ramamurthy, and A. Mukherjee, "Some Principles for
Designing a Wide-Area WDM Optical Network ", IEEE /
ACM Transactions on Networking, Vol.4, No.5, pp.68
4-696, October 1996. Reference 3 considers only minimizing the node scale as much as possible, and does not consider the transmission path cost. Miyamoto, Harai, Murata, Miyahara, "Optical path accommodation design method in WDM / TDM path network", IEICE technical report SSE97-142, pp.13-24 (1997) (Reference 4)
Has provided a method of determining a path setting that minimizes the transmission path capacity for continuous value traffic, but does not consider reducing the node cost as much as possible.

[0006]

FIG. 1 shows a configuration example of a node device in a circuit switching network to which the present invention is applied. The switching device sets a path, and the router concentrates and edits traffic in units of smaller capacity than the path. A plurality of paths are multiplexed and accommodated in the transmission path via a separator / multiplexer. The terminating device terminates the path and separates and multiplexes traffic in units of editing in the router.

In the node shown in FIG. 1, in order to set a route to bypass a router by using a switching device without adding redundant transmission capacity, the traffic passing through the node needs to be equal to or larger than the path capacity. Here, the path capacity is the maximum traffic capacity that can be accommodated in a path switched by the switching device. The path capacity depends on the transmission rate, overhead, bandwidth margin, etc. of the terminating device,
Generally, the amount is determined by the user. However, even if there is more than one path of bypass traffic, if they are distributed and accommodated in multiple input paths, those multiple paths will have the bypass traffic accommodated and the traffic originating or ending at that node. Must be terminated to separate. Therefore, in order to efficiently bypass the traffic through the router, it is necessary to perform path setting such that the passing traffic is collectively accommodated in one path at each node. It is assumed that in the network considered here, in addition to the node including the switching device, there may be a node that does not include the switching device and performs the concentration and editing of the traffic only by the router.

An object of the present invention is to determine a path setting that can reduce the hardware scale as much as possible with respect to a traffic accommodating band (required band) required between nodes.
The hardware constituting the network is a transmission path and a node. Among them, for the transmission path, a method of selecting a traffic path between each node so as to minimize the cost for a given required bandwidth is described in, for example, D. Bertsekas and
R. Gallager, "DataNetworks", Prentice Hall (1992)
(Reference 5). In general, there are a plurality of routes corresponding to a certain start / end node pair. In Reference 5, when a required bandwidth between each start / end node pair is given, the distribution of traffic to all routes corresponding to each start / end node is given. As a result, the required bandwidth for each path, which is optimized to minimize the transmission path cost, is provided. Hereinafter, the correspondence table between each route determined by some method and the required bandwidth is referred to as a bandwidth table. The present invention provides a method for obtaining a path setting that minimizes node cost while maintaining a minimum necessary transmission capacity uniquely determined from the band table and the path capacity when a band table is provided. . The path setting is performed for a section in the network. A section is a route passing only through a node including a switching device.

Given the bandwidth table, the capacity of the input / output transmission line in FIG. 1 is uniquely determined, so that the number of input ports and output ports of the switching device is determined. Therefore, the difference in the node cost due to the path setting is caused by the difference in the number of terminating devices in the node. The smaller the number of terminating devices in the entire network, that is, the smaller the total number of paths, the lower the node cost in the entire network. Therefore, in the present invention, a path setting that accommodates the passing traffic in each node as much as possible in a common path and avoids unnecessary path termination is obtained. Since the total extension of all paths is uniquely determined from the number of transmission paths of the entire network obtained from the bandwidth table, reducing the number of paths is equivalent to increasing the average path length (the number of nodes through which the paths pass). .

[0010]

A means is provided for searching for a path setting that reduces the cost of a node device while keeping the transmission path cost at a uniquely determined minimum value from a given band table.

In the present invention, a computer program for obtaining a path setting is recorded on a storage medium. The program recorded on the storage medium performs the following operation when all sections and a bandwidth table in which a path may be set on the target network are given.

First, a path that accommodates only traffic whose start point and end point match the path is set. Such a path is called a dedicated path. The dedicated path is (x _p /
n) ↓ Set this. That is, a dedicated path is not set for a route whose required bandwidth is n or less. Where a ↓ is the largest integer less than or equal to a. Further, _xp is a required bandwidth for the path p. n is the path capacity, which is the upper limit of the transmission rate of the traffic accommodated in one path. FIG. 2 shows a conceptual diagram of setting a dedicated path.

Next, consider a path setting problem in a state where the traffic accommodated in the dedicated path is removed from the traffic of each route. As an example, FIG. 3A shows a state in which the traffic accommodated in the dedicated path is removed from the state of FIG. In this state, only traffic with a rate less than the path capacity exists on any route. Therefore, a middle section common to a plurality of different routes is searched, and a path accommodating the traffic of those routes is set in the shared section. Such a path is called a shared path. In FIG. 3, traffic that can be accommodated in the shared path is shown by surrounding it with a black frame. Here, the path setting that minimizes the node cost of the entire network is:
The setting is such that the total number of passes is minimized. This is because the number of input / output ports of the switching device is uniquely determined by the bandwidth table in the node of FIG. 1, but the number of merge / segment ports is equal to the number of paths terminated at the node. Reducing the number of paths is equivalent to increasing the average path length (the number of transmission paths through which the paths pass). This is realized by searching for a shared section having the maximum number of links for which a path can be set. In other words, a setting that accommodates a long path as much as possible is given priority to individual traffic. However, the meaning of “path setting possible” means that the total traffic including the shared section in the route exceeds a predetermined path setting threshold value. That is, the path setting threshold is the amount of traffic that one path should contain at a minimum. If the path setting threshold is equal to or more than (S _i / n) max and equal to or less than n (path capacity), the transmission path capacity necessary to accommodate all the set paths is uniquely determined by the bandwidth table. Is kept. Therefore, the path setting threshold may be arbitrarily set within this range. However S _i is the traffic amount of the transmission line i is accommodated, (S _i / n) max is the S _i and n ratio of the transmission path that the ratio of S _i and n is the maximum.

After setting a path in a certain shared section, the traffic contained in the path is removed, and the section having the maximum number of links is searched again. If all of the transmission paths included in the target section have only traffic of a path passing through the section and the traffic is less than a threshold value, one path is set in the section. This is repeated until there is no more traffic, thereby completing the path setting. In the above description, the path setting threshold is fixed, but a calculation using a variable path setting threshold that updates the threshold every time the bandwidth table is updated is also possible. When a variable path setting threshold is used, a setting with a smaller number of paths may be required than when a fixed path capacity is used. For example, if the path setting threshold is set smaller than the path capacity when determining the possibility of setting a path in a long section, a path that is shorter than the path capacity but longer can be set, and as a result, the average path length may increase. . Of course, there is no problem even if the fixed path setting threshold value is used.

By the way, a dedicated path can be considered as a special shared path in which traffic to be accommodated belongs to only one route. Therefore, it is not always necessary to separate the dedicated path setting procedure and the shared path setting procedure. However, the method treated separately here is introduced because the calculation time may be shorter. .

FIG. 4 is a flowchart showing the procedure up to this point.

Next, an example of an actual procedure of data manipulation performed in the present invention will be described. The bandwidth table records the required bandwidth corresponding to each route. In the first dedicated path setting, a path to which a required bandwidth equal to or larger than the path capacity is assigned is extracted from the bandwidth table, and each of the paths p
If there is a section that matches, the number of paths corresponding to that section recorded in the path table (the initial value is 0)
To the currently recorded value plus (x _p / n) ↓. On the other hand, the required bandwidth on the bandwidth table corresponding to the route corresponding to the section in which the number of paths has been updated is updated to a value obtained by subtracting the product of x _p / n ↓ and n from the currently recorded value.
This state corresponds to FIG.

Next, the longest section in which a shared path can be set is searched. This is realized, for example, by examining the path setting possibility in order from the longest section existing in the target network. In this case, the section for which it is determined that the path can be set first is the longest path settable section. For the section to be considered, the determination of the path setting possibility and the updating of the bandwidth table and the path table accompanying the path setting are performed as follows.

First, all the routes passing through the section q are extracted from the bandwidth table. Find the total s _q required bandwidth corresponding to the extracted route, if s _q is less than the path capacity n in the path setting threshold T or more, the path corresponding to the duration recorded in the path table Update the number to the current value plus one. When s _q is n or more, the number of passes corresponding to the period recorded in the path table is set to the current value.
Update to the value obtained by adding (s _q / n) ↓.

In updating the bandwidth table, the extracted routes are classified into three types. Classify route 1 that matches section q, Classify route that matches start or end point of section q
2. Routes that do not match the section q with both the start point and end point are classified as category 3. These are further prioritized. The priority is
Of the three classifications, Class 1 is the smallest and Class 3 is the largest. Further, among the classifications, a route having a shorter route length has a lower priority.

When s _q is equal to or more than T and less than n, the required bandwidths of all the extracted routes are updated to zero. When s _q is equal to or more than n, the requested bandwidths are added in order from the route with the lowest priority, and the route having the lowest priority whose sum is n · {(s _q / n) ↓} or more is added to p _j , and the corresponding priority is j. The required bandwidth of the route up to the priority j-1 is updated to 0 (FIG. 3B).
When the total sum m _{j of the} updated required bandwidth is smaller than n · [{(s _q / n) ↓} -1] + T, the required bandwidth of the path p _j is m _j + x _j- [n
-It is updated to the value obtained by subtracting {(s _q / n) ↓}] (Fig. 3c). Here, x _j is the required bandwidth of p _j before updating. Otherwise, the required bandwidth of p _j is not updated.

Next, a surplus route is defined for each route whose required bandwidth has been updated in the above procedure. Path pk with priority _k
The remainder path, a starting point the origin of the path p _k, the starting point of the section q as a starting point the end point of the path, and the section q, as an end point, the end point of the path p _k a path such that the end point, The route is such that all of the transit nodes are included in _pk . For such a remainder route, referred to as p _k with the main path. The required bandwidth of the remaining route of each route whose required bandwidth has been updated is the difference between the required bandwidth of the corresponding main route before the update and the required bandwidth after the update,
The value is updated to the value added to the current value (Fig. 3d).

Up to this point, the update of the path table and the bandwidth table accompanying the path setting to the section q is completed. This situation is shown in FIG. 3e. In the example of the figure, since the surplus route of the route of the priority 3 and the surplus route of the route of the priority j are equal, the traffic of these routes is added by the band table updating operation. From this state, the longest section in which a path can be set is searched again. This series of operations is repeated until the required bandwidth for all the paths becomes zero.

[0024]

FIG. 5 shows a first embodiment of the present invention. The path setting search device includes a memory device, a recording medium, an input unit, a processor unit, and an output unit,
Each element is connected by a data bus. The memory device includes an area for accommodating the band table and the path table. A path setting search program is recorded on the recording medium. When the user gives a program execution command from the input device or receives a call from another program, the processor unit reads and executes the path setting search program of the recording medium via the data bus. The path table at the end of the program is transmitted to another device by the output unit.

FIG. 6 shows a second embodiment of the present invention. The switching device sets a route for the path. The bandwidth table is input to the path setting detection device, and the path setting detection device outputs a path table. The path table is sent to the controller of each node, and the switching device receiving the control signal from the controller stores the path table in the path table. Therefore, connection setting is performed.

FIG. 7 shows a third embodiment of the present invention. The bandwidth table is input to the path setting detection device, and the path setting detection device outputs a path table. The path table is sent to the controller of each node. The connection between the input / output ports connected to the working input / output transmission line is set according to the table. The remaining part is used for switching to a spare transmission line for transmitting traffic when a transmission line or a node fails, and does not respond to path table information from the controller.

[0027]

In the communication network, it is possible to obtain a path setting that can reduce hardware costs as much as possible for a traffic accommodation band required between each node. It is effective for designing low-cost communication networks.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a node configuration of a communication network to which the present invention is applied.

FIG. 2 is a diagram schematically illustrating a concept of a dedicated path setting introduced in the present invention.

FIG. 3 is a diagram schematically illustrating the concept of setting a shared path introduced in the present invention;

FIG. 4 is a flowchart showing execution steps of a program recorded on a recording medium of the present invention.

FIG. 5 is a diagram showing a first embodiment of the present invention.

FIG. 6 is a diagram showing a second embodiment of the present invention.

FIG. 7 is a diagram showing a third embodiment of the present invention.

Claims (6)

[Claims] 1. A memory device for storing a bandwidth table in which a required bandwidth is associated with each route on a communication network and a path table in which a predetermined identification code is associated with each section. If, for a section, the required bandwidths corresponding to all the routes passing through the section are extracted from the bandwidth table, the total of the extracted required bandwidths is calculated, and the total exceeds the input path setting threshold. A path having a means for searching for a section having the largest number of via nodes from among the path settable sections, extracting an identification code corresponding to the searched section from the path table, and outputting the identification code. Setting search device. 2. A memory device for storing a bandwidth table in which a required bandwidth is associated with each route on a communication network and a path table in which a predetermined identification code is associated with each section. On the bandwidth table, if there is a route to which a required bandwidth equal to or greater than a predetermined path capacity is associated, the route is extracted, and the required bandwidth corresponding to the extracted route is a value recorded in the bandwidth table. The bandwidth table is updated so that the remainder is divided by the path capacity.For a certain section, required bandwidths corresponding to all routes passing through the section are extracted from the bandwidth table, and a total of the extracted required bandwidths is calculated. If the sum is greater than the input path setting threshold, the section is set as a path settable section, and the section with the largest number of via nodes among the path settable sections Succinate, retrieved path setting retrieval apparatus comprising means for outputting the extracted from the path table an identification code corresponding to the section. 3. A recording medium recording a search program for obtaining a path setting on a communication network by a computer, wherein the search program stores a band table in which a requested band is associated with each path on the communication network. Write the path table in which the initial values correspond to each section on the network to the memory device. (A) For a certain section, the required bandwidth corresponding to all the paths passing through the section is a band table. Calculate the sum of the extracted required bandwidth, the sum exceeds a predetermined path setting threshold, or includes the transmission path included in the section,
If there is no route other than the route passing through the section or includes the transmission path included in the section, and the required bandwidth of any route other than the route passing through the section is 0,
The section is set as a path settable section, and the path settable section is searched for the one with the largest number of passing nodes, and the quotient obtained by dividing the total capacity passing through the section by a predetermined path capacity is set as an increment,
However, if the quotient is 0, the increment is set to 1, and the path table is updated so that the number of paths in the section is changed to a value obtained by adding the increment to the number of paths in the section recorded in the path table. (B) the sum of the required bandwidths corresponding to all the routes passing through the section is greater than the sum of the required bandwidth values recorded in the bandwidth table, at least the product of the increment and the path setting threshold, Update the bandwidth table so that it becomes smaller by a value equal to or less than the product of the increment and the path capacity. (C) The operation including the procedures of (a) and (b) is performed when the required bandwidth recorded in the bandwidth table is 0. A recording medium storing a communication network path setting search program characterized by being repeated until the path setting search program is completed. 4. A recording medium storing a search program for obtaining a path setting on a communication network by a computer, wherein the search program stores a band table in which a requested band is associated with each path on the communication network. Write to the device, write a path table in which an initial value is made to correspond to each section on the network to the memory device, and, on the band table, there is a route corresponding to a required band of a predetermined path capacity or more. If they are extracted, the bandwidth table is updated so that the required bandwidth corresponding to the extracted route is a remainder obtained by dividing the value recorded in the bandwidth table by the path capacity. , Extract the required bandwidth corresponding to all the routes passing through the section from the bandwidth table, calculate the total of the extracted required bandwidth, Including the transmission path whose sum exceeds a predetermined path setting threshold or is included in the section,
If there is no route other than the route passing through the section or includes the transmission path included in the section, and the required bandwidth of any route other than the route passing through the section is 0,
The section is set as a path settable section, and the path settable section is searched for the one with the largest number of passing nodes, and the quotient obtained by dividing the total capacity passing through the section by a predetermined path capacity is set as an increment,
However, if the quotient is 0, the increment is set to 1, and the path table is updated so that the number of paths in the section is changed to a value obtained by adding the increment to the number of paths in the section recorded in the path table. (B) the sum of the required bandwidths corresponding to all the routes passing through the section is greater than the sum of the required bandwidth values recorded in the bandwidth table, at least the product of the increment and the path setting threshold, Update the bandwidth table so that it becomes smaller by a value equal to or less than the product of the increment and the path capacity. (C) The operation including the procedures of (a) and (b) is performed when the required bandwidth recorded in the bandwidth table is 0. A recording medium storing a communication network path setting search program characterized by being repeated until the path setting search program is completed. 5. A recording medium recording a search program for obtaining a path setting on a communication network by a computer, the search program comprising: (a) a band in which a required band is made to correspond to each route on the communication network; Writing a table into the memory device, and writing a path table in which the initial values correspond to each section on the network into the memory device,
(B) If there is a route on the bandwidth table that corresponds to a required bandwidth equal to or greater than a predetermined path capacity, those routes are extracted, and the required bandwidth corresponding to the extracted route is recorded in the bandwidth table. Updating the bandwidth table so that the remainder is obtained by dividing the value by the path capacity, and (c) extracting, from the bandwidth table, required bandwidths corresponding to all routes passing through the section for a certain section, and extracting the extracted request. Calculate the sum of the bandwidths, whether the sum exceeds a predetermined path setting threshold, includes the transmission path included in the section, and does not include any path other than the path passing through the section, or includes the path in the section. If the required bandwidth of any route other than the route passing through the section is 0, the section is set as a path settable section, and the path settable section having the largest number of passing nodes is The quotient obtained by dividing the total capacity passing through the section and the predetermined path capacity is set as an increment. However, when the quotient is 0, the increment is set to 1, and the number of paths of the section recorded in the path table is set. The path table is updated so that the number of paths in the section is changed to a value obtained by adding this increment to
(D) Among the routes passing through the section, class 1 matches the section that matches the section, class 2 matches the section that matches the start point or end point, and classifies the path that does not match the section matches the start / end node. Of the three, Class 1 is the smallest, Class 3 is the largest,
In addition, among the routes belonging to each classification, the priority is set so that the smaller the number of passing nodes, the smaller the priority. (E) The initial value 0 is written in the buffer area of the memory device. The requested bandwidth in the bandwidth table is updated in order from the set route with the smallest priority, and the updated value is added to the value. (F) Is the value of the buffer equal to or larger than the product of the increment obtained in (c) and the path capacity? Or, when the bandwidths of all the paths passing through the section have been added to the buffer, the buffer update is interrupted, and when the buffer update is interrupted, the value of the buffer becomes equal to the increment obtained in (c) above and the path capacity. If the product is larger than the product, the bandwidth table is updated so that the required bandwidth of each path corresponding to a priority lower than the priority corresponding to the required bandwidth last added in (e) becomes 0, and the buffer update is interrupted. With If the value of the fa is equal to or less than the increment obtained in (c) and the path capacity, the required bandwidth of each route corresponding to the priority equal to or less than the priority corresponding to the required bandwidth last added in (e) is 0. The bandwidth table is updated so that (g) the sum of the requested bandwidths from the route with the lowest priority to the route one priority lower than the route corresponding to the requested bandwidth last added to the buffer in (e). If “A” is smaller than the product of the value obtained by subtracting 1 from the increment obtained in (c) and the path capacity, and the path setting threshold is added, the buffer is finally added in (e). Update the bandwidth table so that the required bandwidth is a value obtained by subtracting “A” from the product of the increment and the path capacity from the value recorded in the bandwidth table,
(H) Each of the routes belonging to the categories 2 and 3 and having the required bandwidth updated in (f) and (g) is set as a main route for the section, and the origin node of the main route in the section is the origin node. ,
A route in which all of the transit nodes are included in the transit nodes of the main route, and a route where all the transit nodes are included in transit nodes of the main route, and A table is stored in the memory device, in which both of the nodes, all of which are included in the transit nodes of the main route, are stored in the memory device as a surplus route of the main route. (I) The table belongs to the categories 2 and 3, and ),
The required bandwidth of each of the remaining routes of the main route whose required bandwidth has been updated in (g) is the required bandwidth of the main route before being updated in (f) and (g) and the required bandwidth of the main route after being updated. The bandwidth table is updated so that the difference between the required bandwidth and the required bandwidth of the surplus path recorded in the bandwidth table is added. (J) For all the paths, the required bandwidth recorded in the bandwidth table is 0 and (C), (d), (e), (f), (g),
(H) A recording medium recording a communication network path setting search program characterized by repeating (i). 6. The recording medium according to claim 2, further comprising a step of updating a path setting threshold capacity each time a bandwidth table is updated by a recorded program. A recording medium that records a communication network path search program.