JP5713446B2 - Pass accommodation control method - Google Patents

Description

  The present invention relates to a technology for dynamically performing path accommodation control in an optical network that assigns wavelengths to paths using frequency slots.

  The traffic of the optical network that supports the current backbone network is increasing year by year. In order to meet such traffic demands, research and development for efficiently utilizing limited spectrum resources in optical fibers are being actively conducted.

  For example, Non-Patent Document 1 discloses a technique for improving the frequency utilization efficiency of an optical signal by performing optical modulation with multiple values. Patent Document 1 (WO 2010/032844) discloses a variable bandwidth communication technique that can increase or decrease a signal band according to demand by using an optical OFDM signal.

  Until now, in optical networks based on wavelength division multiplexing, wavelengths have been allocated to optical paths based on a frequency grid defined by ITU-T. Recently, more flexible and efficient resource allocation has been implemented. In order to make this possible, a method of allocating resources using frequency slots has been proposed (Non-Patent Document 2).

  An example of the frequency slot is shown in FIG. In FIG. 1A, the horizontal axis is frequency. Each frequency slot is assigned a number for identifying which frequency slot. The frequency width (bandwidth) of each frequency slot is the same. For example, the width of one frequency slot is 12.5 GHz. Using such frequency slots, for example, as shown in FIG. 1B, resource allocation is performed such that frequency slots 1 to 3 are allocated to path A and frequency slots 5 to 8 are allocated to path B. Here, when assigning a plurality of frequency slots to a certain path, the plurality of frequency slots must be continuous.

  Further, in the prior art, generally, a modulation scheme that allows transmission of all length optical paths with respect to the OSNR penalty (optical signal quality degradation amount) in the longest optical path is described in Non-Patent Document 2. In this technique, the modulation method is selected according to the OSNR penalty of the path route to be set.

  FIG. 2 shows the relationship between various modulation schemes and OSNR (Optical Signal to Noise Ratio) penalties. In the case of a modulation system with a low multi-level number of PSK (Phase Shift Keying) and QPSK (Quadrature Phase Shift Keying), the OSNR penalty is small, so it is suitable for transmission over a long distance or a path with a large number of nodes. 8PSK, 16QAM , 64QAM, the higher the multi-value number, the more the OSNR penalty increases, so the transmission distance and the number of nodes that can be transferred are reduced. On the other hand, as the multi-value number increases, the amount of information that can be transmitted with the same resource amount increases.

  Based on such characteristics, the technique of Non-Patent Document 2 realizes efficient resource allocation by selecting a modulation scheme according to the communication distance and bit rate and flexibly allocating frequency slots. FIG. 3 is a diagram illustrating an example of the effect of a technique for adaptively selecting a modulation scheme according to a communication distance or the like using a frequency slot as described in Non-Patent Document 2. As shown in FIG. 3, a modulation scheme (16QAM) having a large OSNR penalty (low noise immunity) but a large transmission information amount is assigned to a short path with a small band (3 slots), and conversely, the transmission information amount is small. However, it is possible to accommodate such that a modulation scheme (QPSK) having a small OSNR penalty (high noise resistance) is allocated to a larger band (5 slots). As a result, the resource utilization efficiency is greatly improved as compared with the case where wavelength allocation is performed using a frequency grid as in the conventional case (in the example of FIG. 3, 8 slots are required for the entire distance).

H. Goto et al., "Polarization-multiplexed 1 Gsymbol / s, 128 QAM (14Gbit / s) coherent optical transmission over 160 km using a 1.4 GHz Nyquist filter", OFC / NFOEC 2008, HThA45, 2008 M. Jinno, B. Kozicki, H. Takara, A. Watanabe, Y. Sone, T. Tanaka, and A. Hirano: Distance-Adaptive Spectrum Resource Allocation in Spectrum-Sliced Elastic Optical Path Network, "IEEE Comm. Mag. , Vol.48, No.8, pp.138-145, 2010.

WO2010 / 032844

  By allocating resources using frequency slots, the bandwidth can be set flexibly for each path. However, the frequency slots used in one path must be the same throughout the path (generally consisting of multiple links), and as described above, the frequency slots assigned to one path must be continuous. In an optical network that accommodates long and short paths, simply assigning a path to an empty slot causes many empty slots that cannot be used in each link, which hinders improvement in resource utilization efficiency. There is a problem that it may become.

  For example, in the optical network including four nodes A, B, C, and D shown in FIG. 4, when resources are defined as slots 1 to 8, slots 1 to 3 are assigned to path 1 of A-> B. In the case where slots 6 to 8 are allocated to the path 2 of A-> B-> C and slots 1 to 5 are allocated to the path 3 of B-> C-> D, it is assumed that C-> D Even if there is a request to allocate path 4 (requires two slots) of-> A-> B, the same 2 slots cannot be secured between AB and between CDs, so path 4 cannot be allocated. However, each link of C-> D, D-> A, and A-> B has at least two free spaces. In this way, an empty slot that cannot be used may occur.

  The present invention has been made in view of the above points, and an object thereof is to provide a technique for improving resource utilization efficiency in an optical network in which resources are allocated to paths using frequency slots.

The above problem is a path accommodation control method executed by a network management apparatus that performs processing related to path establishment and cancellation using a frequency slot in an optical network composed of a group of variable bandwidth communication apparatuses connected in a link.
In response to the reception of the path establishment request, among the paths that can be taken on the optical network as the path of the path related to the request, there is a path in which continuous frequency slots of the number of slots necessary for the path are vacant through the path. An empty determination step for determining whether or not there is,
In the vacancy determination step, when it is determined that there is a path in which the frequency slot is vacant, an allocation step of allocating the frequency slot to the path on the path;
A path rearrangement step for performing a path rearrangement process when it is determined in the empty determination step that there is no path in which the frequency slot is free;
The path rearrangement step includes:
A route extraction step of extracting one route from possible routes on the optical network as a route of the path related to the request;
On the extracted route that is the route extracted in the route extracting step, a relocation target path that is a path to which at least one frequency slot is allocated among consecutive frequency slots of the number of slots necessary for the path is extracted. Relocation target path extraction step;
It is determined whether or not the relocation target path can be relocated to a route different from the route in which the path is established, and relocation is performed if possible, by relocation, Allocating the continuous frequency slots vacated through the path to the path according to the request.

The present invention is a path accommodation control method executed by a network management apparatus that performs processing related to path establishment and cancellation using a frequency slot in an optical network including a group of band-variable communication apparatuses connected in a link,
Storing a request in a request storage means when a request related to a path is received;
A request processing step for performing processing according to the request for each request stored between the timing and the previous timing in response to the arrival of a predetermined timing.
The request processing step includes:
In the case where the request is a path establishment request, among the routes that can be taken on the optical network as the path of the path related to the request, there is a path in which continuous frequency slots of the number of slots necessary for the path are vacant through the path. An empty determination step for determining whether or not there is,
In the vacancy determination step, when it is determined that there is a path in which the frequency slot is vacant, an allocation step of allocating the frequency slot to the path on the path;
A path rearrangement step for performing a path rearrangement process when it is determined in the empty determination step that there is no path in which the frequency slot is free;
The path rearrangement step includes:
A route extraction step of extracting one route from possible routes on the optical network as a route of the path related to the path establishment request;
On the extracted route that is the route extracted in the route extracting step, a relocation target path that is a path to which at least one frequency slot is allocated among consecutive frequency slots of the number of slots necessary for the path is extracted. Relocation target path extraction step;
It is determined whether or not the relocation target path can be relocated to a route different from the route in which the path is established, and relocation is performed if possible, by relocation, Assigning the continuous frequency slots vacated through the route to the path according to the request may be configured as a path accommodation control method.

Further, the present invention is a path accommodation control method executed by a network management apparatus that performs processing related to path establishment and cancellation using a frequency slot in an optical network including a group of variable bandwidth communication apparatuses connected in a link,
A relocation step to be executed in response to receiving the path establishment request, and a slot allocation step to be executed thereafter,
The relocation step includes:
Searching for a link having a slot usage rate equal to or greater than a predetermined value on the optical network;
Relocating the path on the link to a different path from the path on which the path is established when the link exists;
The slot allocation step includes:
Among the paths that can be taken on the optical network as the path of the request, when there is a path in which continuous frequency slots of the number of slots necessary for the path are vacant through the path, the path is changed to the path. You may comprise as the path | pass accommodation control method which has the step which allocates the said frequency slot.

Further, the present invention is a path accommodation control method executed by a network management apparatus that performs processing related to path establishment and cancellation using a frequency slot in an optical network including a group of variable bandwidth communication apparatuses connected in a link,
When a request related to a path is received, the request is stored in the request storage means, and the timing is stored between the timing and the previous timing in response to the arrival of a predetermined timing. A request processing step for performing processing according to the request for each request;
In the case where the request is a path establishment request, the request processing step includes a rearrangement step and a slot allocation step to be executed thereafter,
The relocation step includes:
Searching for a link having a slot usage rate equal to or greater than a predetermined value on the optical network;
Relocating the path on the link to a different path from the path on which the path is established when the link exists;
The slot allocation step includes:
Among the paths that can be taken on the optical network as the path of the path relating to the path establishment request, when there is a path in which continuous frequency slots of the number of slots necessary for the path are vacant through the path, the path on the path A path accommodation control method may include a step of assigning the frequency slot to a path.

Further, the present invention is a path accommodation control method executed by a network management apparatus that performs processing related to path establishment and cancellation using a frequency slot in an optical network including a group of variable bandwidth communication apparatuses connected in a link,
A rearrangement step that is executed in response to the arrival of a predetermined timing, and a request processing step that is executed when a request related to a path is received;
The relocation step includes:
Searching for a link having a slot usage rate equal to or greater than a predetermined value on the optical network;
Relocating the path on the link to a different path from the path on which the path is established when the link exists;
The request processing step includes:
When the request is a path establishment request, among the routes that can be taken on the optical network as the path of the path relating to the path establishment request, continuous frequency slots of the number of slots necessary for the path are vacant through the route. When there is a route, the path accommodation control method may include a step of assigning the frequency slot to the path on the route.

  In the path accommodation control method, when one route is selected from the possible routes on the optical network as the route of the path related to the request, it is allocated with the same number of slots as the number of slots necessary for the route having the minimum OSNR penalty. A route may be selected only within a possible range, and a route having a small OSNR penalty may be preferentially selected.

  Also, when performing path relocation, the path selection range to be relocated is within the range in which the slot group on the path occupied by the path to be relocated is excluded from the optical network topology. It is also possible to preferentially select a path with a small OSNR penalty, with a range that can be allocated with the same number of slots as the number of slots occupied by the.

  In addition, a path to be rearranged may be preferentially selected from a path having a large number of via links, or a path to be rearranged may be preferentially selected from a path having a small number of via links. Good.

  Alternatively, a path to be rearranged may be preferentially selected from paths that have a large number of links that pass through links having a slot usage rate equal to or greater than a predetermined value. Furthermore, it is also possible to preferentially select a path with a large average number of congested links by dividing the number of paths to be rearranged by dividing the number of links whose slot usage rate is higher than a predetermined value by the number of via links. Good.

  It is possible to provide a technique for improving resource utilization efficiency in an optical network that allocates resources to paths using frequency slots.

It is a figure which shows the example of a frequency slot. It is a figure which shows the relationship between various modulation systems and OSNR penalty. It is a figure which shows the example of the effect of the technique which selects a modulation system adaptively according to a communication distance etc. using a frequency slot. It is a figure for demonstrating the subject of a prior art. 1 is a configuration diagram of a variable bandwidth communication system according to an embodiment of the present invention. 1 is a configuration example of a variable bandwidth communication device 10. 1 is a configuration diagram of a network management device 100. FIG. It is a figure which shows the example of the information stored in a path allocation information storage part. FIG. 3 is a diagram for explaining an outline of the operation of the network management apparatus 100. FIG. 3 is a diagram for explaining an outline of the operation of the network management apparatus 100. FIG. 3 is a diagram for explaining an outline of the operation of the network management apparatus 100. It is a figure which shows the outline | summary of the 1st operation example. It is a process flowchart of the network management apparatus 100 in a 1st operation example. It is a figure for demonstrating the process which concerns on a path rearrangement. It is a figure which shows the outline | summary of the 2nd operation example. It is a process flowchart of the network management apparatus 100 in a 2nd operation example. It is a figure which shows the outline | summary of the 3rd operation example. It is a process flowchart of the network management apparatus 100 in a 3rd operation example. It is a figure for demonstrating the example of the link etc. whose slot usage rate is more than a predetermined value. It is a figure which shows the outline | summary of the 4th operation example. It is a process flowchart of the network management apparatus 100 in a 4th operation example. It is a figure which shows the outline | summary of the 5th operation example. It is a process flowchart of the network management apparatus 100 in the 5th operation example. It is a process flowchart of the network management apparatus 100 in the 5th operation example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments.

(System configuration)
FIG. 5 shows a configuration diagram of the variable bandwidth communication system according to the embodiment of the present invention. As shown in FIG. 5, the variable bandwidth communication system according to the present embodiment includes an optical network 200 including a plurality of nodes and a network management apparatus 100. Each node constituting the optical network 200 has a function of setting a path (pass band between specific ports in the communication apparatus) based on a control signal from the network management apparatus 100, and performing transmission / reception of optical signals, cross-connection, and the like. This is a variable bandwidth communication device provided. In the optical network 200, each node is connected to another node by a link (specifically, an optical transmission line made of an optical fiber).

  FIG. 6 shows a configuration example of the variable bandwidth communication device 10 configuring the optical network 200. As shown in FIG. 6, the variable bandwidth communication apparatus 10 according to the present embodiment includes a variable bandwidth transmitter 11, a variable bandwidth receiver 12, a variable bandwidth path switcher 13, an optical amplifier 14, and a controller 15. Including.

  The transmission unit 11 is a functional unit that generates and transmits an optical signal, and the reception unit 12 is a functional unit that receives an optical signal. The path switching unit 13 has a path switching function for switching one or more output ports of light incident from the input port based on a control signal from the control unit 15 and a section passing from the input port to the output port through which the path passes. A band changing function for changing a possible frequency band is provided. The control unit 15 receives a control signal (such as a path establishment command) from the network management apparatus 100 and controls the transmission unit 11, the reception unit 12, and the route exchange unit 13. With these functions, it is possible to establish a path according to a command received from the network management apparatus 100.

  FIG. 7 shows a configuration diagram of the network management apparatus 100 according to the present embodiment. As shown in FIG. 7, the network management device 100 includes a request receiving unit 101, a request storage unit 102, a processing control unit 103, a path accommodation design unit 104, a path relocation processing unit 105, a communication device command unit 106, and a network information storage. Unit 107 and path allocation information storage unit 108.

  The request receiving unit 101 is a functional unit that receives a path establishment request, a path release request, and the like from, for example, an external communication device or a network administrator. The path establishment request includes a path start point node, an end point node, and a necessary bandwidth (bit rate). The path release request includes, for example, identification information of a path to be released. The request storage unit 102 is a functional unit that stores received requests.

  The processing control unit 103 is a functional unit that controls the path accommodation design unit 104, the path rearrangement processing unit 105, the communication device command unit 106, and the like so as to perform the operations shown in each operation example described later.

  The path accommodation design unit 104 includes a function for calculating the number of slots required for the path related to the request, a path route extraction, and the like, and a function for assigning a path / frequency slot to the path related to the request and the relocation destination path Part. The path rearrangement processing unit 105 is a functional unit that performs processing for path rearrangement. The communication device command unit 106 is a functional unit that transmits a command for establishing a path (including information on frequency slots to be allocated) and a command for canceling a path to the corresponding node.

  The network information storage unit 107 stores physical topology information of the optical network 200 (including node / link connection information and information for calculating an OSNR penalty such as a link length). The path allocation information storage unit 108 stores path information, allocation slot numbers, and the like for each set path.

  FIG. 8 shows an example of information stored in the path assignment information storage unit 108. Note that the example shown in FIG. 8 is for easy understanding of the contents of the information, and the data structure of the information stored in the path assignment information storage unit 108 is not limited to that shown in FIG. Each of the network information storage unit 107 and the path allocation information storage unit 108 or the entire database system constitutes a database system. For example, when a specific link is specified, which path is allocated to the link in which slot It is possible to immediately extract information on what is being done.

  The network management apparatus 100 can be realized by causing a computer to execute a program describing the processing contents described in the present embodiment. That is, the function of each unit of the network management apparatus 100 executes a program corresponding to the process executed by each unit using hardware resources such as a CPU and a memory built in the computer constituting the network management apparatus 100. This can be realized by doing so. Each storage unit in the network management apparatus 100 is realized by a storage unit such as a memory. In addition, the program is a computer-readable recording medium such as FD (Floppy (registered trademark) Disk), MO (Magneto-Optical disk), ROM (Read Only Memory), memory card, CD (Compact Disk)- ROM, DVD (Digital Versatile Disk) -ROM, BD (Blu-ray Disk) -ROM, CD-R, CD-RW, DVD-R, DVD-RW, BD-R, BD-RE, HDD, removable disk, etc. It can be recorded and stored or distributed. It is also possible to provide the program through a network such as the Internet or electronic mail.

(Operation of network management apparatus 100)
<Overview>
An outline of the operation of the network management apparatus 100 according to the present embodiment will be described with reference to FIGS.

  In the present embodiment, it is assumed that a path establishment request and a path release request arrive at the network management apparatus 100 every moment. The path establishment request and the path cancellation request are not limited to a request that needs to be immediately established / cancelled, such as telephone communication, and the path is established before the communication is actually used, for example, in the case of a video conference reservation. It is assumed to include such requests.

  As shown in FIG. 9A, a path 1 establishment request, a path 2 establishment request, and a path 3 establishment request arrive in sequence, and the network management apparatus 100 performs path design according to each request and assigns frequency slots. By making a setting request to the node, paths 1 to 3 are established.

  Thereafter, as shown in FIG. 9B, a pass 2 release request for releasing pass 2 arrives, pass 2 is released, and a pass 4 establishment request arrives. However, the path (D-> C) requested by the path 4 establishment request cannot be established because there are not enough frequency slots in the link D-> C.

  Therefore, in the present embodiment, as shown in FIG. 9C, the network management apparatus 100 rearranges the path 1, creates a free frequency slot in the section D-> C, and sets the freed frequency slot to the path 4 Assign to. With such an operation, the frequency utilization efficiency of the entire optical network is increased.

  Hereinafter, each operation example according to the present embodiment will be described in more detail.

<First operation example>
First, a first operation example will be described. In the first operation example, as shown in FIG. 10, each time a request arrives, path establishment / release and path relocation (post-path relocation) associated therewith are performed. In the present embodiment, the timing for performing path establishment / cancellation is referred to as path control timing, and the timing for performing path rearrangement is referred to as path rearrangement control timing.

  FIG. 11 is a process flowchart of the network management apparatus 100 in the first operation example. The operation of the network management apparatus 100 will be described along the procedure shown in FIG.

  The network management apparatus 100 receives the request (step 101). In this operation example, the timing at which the request is received becomes the path control timing and the path rearrangement control timing.

  The network management device 100 determines the type of request (step 102), and if the request is a path release request, performs a path release process (step 103). In other words, the frequency slot allocated to the corresponding path in the path allocation information storage unit 108 is released, and the path is released by transmitting a band release command corresponding to the frequency slot to each node on the corresponding path. .

If it is determined in step 102 that the request is a path establishment request, the process proceeds to step 104. In step 104, the network management apparatus 100 refers to the network information storage unit 107 and the path allocation information storage unit 108 to determine the number of slots necessary for the path related to the request, and further, the path related to the request (starting node) -> End point node) is extracted, and for each path, it is determined whether or not the number of frequency slots required for the path can be allocated through the path (whether or not available).
If allocation is possible with one path, a frequency slot is allocated to the path, the path allocation information storage unit 108 is updated, and a band setting command for the frequency slot is transmitted to each corresponding node, thereby establishing a path. Perform (step 105). If there are a plurality of assignable routes, for example, the route (minimum optical signal degradation) having the minimum OSNR penalty is selected, and the path is established in step 105. For example, the technique described in Non-Patent Document 2 is used for how many frequency slots are assigned to a path.

  Further, in the route extraction / assignment determination processing in step 104, routes are extracted only within a range that can be assigned with the same number of slots as the number of slots required for the route having the minimum OSNR penalty, and the OSNR penalty is small among them. A route may be preferentially selected and frequency slot allocation may be performed. A route having a small OSNR penalty is, for example, a route having a minimum OSNR penalty.

  For example, when it is determined that the number of slots required for the path having the minimum OSNR penalty is 3 (example: the number of 16QAM slots shown in FIG. 3), the range that can be allocated with the number of slots is 3 (example: shown in FIG. 3). Routes in the range of the number of hops corresponding to the 16QAM slot number) are extracted, and a route having a small OSNR penalty is preferentially selected from the routes.

  If it is determined in step 104 of FIG. 11 that there is no route to which a frequency slot for the requested path can be assigned, the process proceeds to step 106.

  In step 106, the network management apparatus 100 selects one route from the routes that can be taken by the path related to the request. Here, the criterion for selecting one route can be, for example, a route having a minimum OSNR penalty.

  Similarly to the above, a route is extracted only in a range that can be allocated with the same number of slots as the number of slots necessary for the route having the minimum OSNR penalty, and a route having a small OSNR penalty is preferentially selected. It is good.

  Subsequently, the network management device 100 extracts as many slot groups as the number of slots necessary for the requested path (step 107). For example, when the required number of slots is 3, slots 1 to 3 are extracted as a slot group. The slot group extracted here may be, for example, a slot group in which the number of links in which the slot for establishing a path becomes insufficient is the smallest in the route selected in step 106.

  Next, the network management apparatus 100 extracts a path to which at least one slot of the slot group extracted in step 107 has been assigned in the route selected in step 106 (step 108). For example, in the optical network shown in FIG. 12, when the route selected for the requested path is A-> B-> C and the extracted slot groups are slots 1 to 3, the D-> Assuming that slots 3 to 6 have already been assigned to the path X of A-> B, slots 1 to 3 cannot be assigned in the section AB, so that the path X is extracted in step 108.

  Subsequently, the network management apparatus 100 attempts to relocate the path extracted in step 108 to another path (step 109).

  In the relocation, for example, the path selection range to be relocated is occupied by the path in a range where the slot group on the route occupied by the relocation target path is excluded from the topology of the optical network. A range that can be allocated with the same number of slots as the number of existing slots may be selected, and a path with a small OSNR penalty may be preferentially selected. A route having a small OSNR penalty is, for example, a route having a minimum OSNR penalty. Note that the rearrangement method is not limited to this, and rearrangement may be performed by another method as long as the path can be appropriately set by another route.

  If rearrangement is possible as a result of the processing in step 109, path rearrangement is performed (step 110). That is, the slot group on the path before the rearrangement is made empty, the path allocation information is updated so that the slot group is allocated to the path after the rearrangement, and a bandwidth setting command is transmitted to each node. For example, in the example of FIG. 12, the path X is rearranged to become a path D-> C-> E-> B.

  When a plurality of paths are extracted in step 108, the processes of steps 109 and 110 are executed for each extracted path.

  Then, the network management device 100 performs slot allocation (update of the path allocation information storage unit 108) for the requested path and a bandwidth setting command for each node (step 111). If the rearrangement is impossible as a result of the processing in step 109, the path establishment request is regarded as communication failure (step 112).

<Second operation example>
Next, a second operation example will be described. In the second operation example, as shown in FIG. 13, path establishment / release and path relocation associated therewith are performed at predetermined time intervals. In addition, it is good also as performing at every predetermined time instead of a predetermined time interval.

  That is, in this operation example, processing is not performed for each request that arrives sequentially, but is performed as a batch process at a predetermined time interval. In this operation example, it is assumed that an incoming request does not require immediate processing.

  Hereinafter, a second operation example will be described along the procedure of FIG. The second operation example is different from the first operation example in the timing of processing, and the individual processing for path establishment / release and path relocation associated therewith is the same as the first operation example. The explanation will focus on the processing flow.

  When receiving the request (step 201), the network management apparatus 100 stores the request in the request storage unit 102 (step 202). The network management apparatus 100 determines whether or not a predetermined timing (that is, a path control timing and a path rearrangement control timing) has been reached (step 203). When the predetermined timing is reached, the request storage unit 102 ( One request is extracted from the previous timing (the request from the previous timing to the current timing is stored) (step 204), the type of the request is determined (step 205), and if the request is a path cancellation request, the path cancellation processing (Step 206).

In step 205, if the request is a path establishment request, the process proceeds to step 207. In step 207, the network management apparatus 100 refers to the network information storage unit 107 and the path allocation information storage unit 108 to extract the path of the path (start node → end node) related to the request, and for each path. Then, it is determined whether or not the number of frequency slots necessary for the path can be allocated through the path (whether or not available).
If there is a route that can be allocated, a frequency slot is allocated to the route, the path allocation information storage unit 108 is updated, and a band setting command for the frequency slot is transmitted to each corresponding node to establish a path. (Step 208).

  If it is determined in step 207 that there is no route to which a frequency slot for the requested path can be assigned, the process proceeds to step 209.

  In step 209, the network management device 100 selects one route from the possible routes of the path related to the request.

  Subsequently, the network management apparatus 100 extracts as many slot groups as the number of slots necessary for the requested path (step 210), and at least one of the slot groups extracted in step 210 in the route selected in step 209. A path to which one slot has already been assigned is extracted (step 211).

  Subsequently, the network management apparatus 100 tries to relocate the path extracted in step 211 to another path (step 212).

  If rearrangement is possible as a result of the processing in step 212, path rearrangement is performed (step 213). Then, the network management apparatus 100 performs slot allocation (update of the path allocation information storage unit 108) for the requested path and a bandwidth setting command to each node (step 214).

  If rearrangement is impossible as a result of the processing in step 212, the path establishment request extracted this time is regarded as communication failure (step 215).

  After steps 206, 208, 214, and 215, if there is no request that has not been processed yet, the processing at this timing is terminated and the processing returns to step 201 (No in step 216). When a request is received during execution of processing at the current timing, it may be handled as a request at the current timing or as a request at the next timing.

  If there is a request that has not yet been processed after steps 206, 208, 214, and 215, the process returns to step 204 to process the next request.

<Third operation example>
Next, a third operation example will be described. As shown in FIG. 15, in the third operation example, path relocation (referred to as pre-path relocation) is performed every time a request arrives, and then path establishment / cancellation is performed. Note that when the request is a path release, the path rearrangement may not be performed. The following operation example shows an example in which path relocation is not performed when the request is a path cancellation.

  Hereinafter, a third operation example will be described along the procedure of FIG. In the third operation example, the path establishment / cancellation process corresponding to the request itself is the same as in the first operation example. However, in the third operation example described below, the path rearrangement after the path establishment is attempted is not performed. Of course, in the third operation example (and the fourth and fifth operation examples by performing the pre-path rearrangement), the path rearrangement after attempting the path establishment is performed as in the first operation example. Also good. In the following, description will be made with emphasis on portions different from the first operation example.

  The network management device 100 receives the request (step 301). The network management device 100 determines the type of request (step 302), and if the request is a path release request, performs a path release process (step 303).

  If it is determined in step 302 that the request is a path establishment request, the process proceeds to step 304. In step 304, the network management apparatus 100 searches the path assignment information storage unit 108 for a link whose slot usage rate is equal to or greater than a predetermined value on the optical network. If there is a link whose slot usage rate is equal to or greater than a predetermined value, the process proceeds to step 305, and if not, the process proceeds to step 306.

  Regarding step 304, for example, in the optical network shown in FIG. 17, all slots are 1 to 8, the number of slots used for each link is as shown in FIG. 17, and a predetermined threshold is assumed to be 0.6. Then, the link of C-> D (slot usage rate 6/8 = 0.75) is extracted as a link whose slot usage rate is a predetermined value or more.

  In step 305, the path on the link extracted in step 304 is rearranged. For example, in the case of FIG. 17, a path X and a path Y are extracted as paths on the extracted link, and rearrangement is performed for these paths.

  As for which of the extracted paths to be rearranged, rearrangement is performed for at least the number of paths in which the slot usage rate for the corresponding link is less than a predetermined value. When there are a plurality of paths to be rearranged, the paths to be rearranged are preferentially selected from paths having a large number of via links, for example. That is, in the example of FIG. 17, the rearrangement of the path X is performed with priority. To perform rearrangement preferentially means to perform rearrangement first.

  When the scale of the network is large (for example, a network with a predetermined number of links or more), there are generally many path routes with a large number of via links. By doing so, it can be expected that the resource allocation is effectively distributed.

  Further, when the network size is not large, for example, a path to be rearranged may be preferentially selected from a path with a small number of via links.

  Furthermore, the paths to be rearranged may be preferentially selected from paths that have a large number of paths that pass through links whose slot usage rate is equal to or greater than a predetermined value. Alternatively, the path to be rearranged may be preferentially selected as a path with a large average number of congested links obtained by dividing the number of links whose slot usage rate is greater than or equal to a predetermined value by the number of via links. Good.

  By selecting the path to be relocated as described above, it is possible to effectively reduce links with a high slot usage rate, and improve the slot usage efficiency by distributing the slot usage rate of each link in the entire network. Can be made.

  The relocation processing of each path in step 305 is the same as the relocation processing in the first operation example. That is, for example, in a range in which a path selection range to be relocated is excluded from a slot group on a route occupied by a path to be relocated from the topology of the optical network, the slot occupied by the optical path is The range that can be allocated with the same number of slots as the number of channels is selected, and a route with the smallest OSNR penalty is preferentially selected. In addition, in a link through which a path after rearrangement passes, a link with a slot usage rate exceeding a predetermined value does not occur (or a link with a slot usage rate exceeding a predetermined value is minimized) The relocation destination path may be determined.

  When the rearrangement is not required or after the rearrangement is completed, a process for establishing a path related to the request is performed (steps 306 and 307). The processing here is the same as the path establishment processing in the first operation example, and the network management apparatus 100 refers to the network information storage unit 107 and the path allocation information storage unit 108 to thereby determine the path ( (Start node-> end point node) is extracted, and for each route, it is determined whether or not the number of frequency slots necessary for the path can be allocated through the route (whether or not available) (step 306). A frequency slot is allocated to an allocatable route, the path allocation information storage unit 108 is updated, and a path establishment command is transmitted to each corresponding node to establish a path (step 307).

  If it is determined in step 306 in FIG. 16 that there is no route to which a frequency slot can be assigned to the path related to the request, the communication related to the path establishment request is failed (step 308), and the process ends.

<Fourth operation example>
Next, a fourth operation example will be described. In the fourth operation example, as shown in FIG. 18, pre-path rearrangement and path establishment / cancellation are performed at predetermined time intervals. In addition, it is good also as performing at every predetermined time instead of a predetermined time interval.

  That is, in this operation example, processing is not performed for each request that arrives sequentially, but is performed as a batch process at a predetermined time interval. In this operation example, it is assumed that an incoming request does not require immediate processing. Individual pre-path relocation and path establishment processing in the fourth operation example are the same as those in the third operation example. The fourth operation example is different from the third operation example in the timing of processing. In the following, description will be made with an emphasis on the flow of processing with reference to the flowchart of FIG.

  When receiving the request (step 401), the network management apparatus 100 stores the request in the request storage unit 102 (step 402). The network management apparatus 100 determines whether or not a predetermined timing (that is, the pre-path relocation control timing and the path control timing) has been reached (step 403), and if the predetermined timing has been reached, the request storage unit One request is extracted from 102 (requests from the previous timing to the current timing are stored) (step 404), the type of the request is determined (step 405), and if the request is a path release request, the path Release processing is performed (step 406).

  If it is determined in step 405 that the request is a path establishment request, the process proceeds to step 407. In step 407, the network management apparatus 100 searches for a link having a slot usage rate equal to or higher than a predetermined value on the optical network. If there is a link whose slot usage rate is equal to or greater than a predetermined value, the process proceeds to step 408, and if not, the process proceeds to step 409. In step 408, the path on the link extracted in step 407 is rearranged.

  When the rearrangement is not required or after the rearrangement is completed, a process for establishing a path related to the request is performed (steps 409 and 410). The processing here is the same as the path establishment processing in the first operation example, and the network management apparatus 100 refers to the network information storage unit 107 and the path allocation information storage unit 108 to thereby determine the path ( (Start node-> end point node) is extracted, and for each route, it is determined whether or not the number of frequency slots necessary for the path can be allocated through the route (whether or not available) (step 409). A frequency slot is allocated to an allocatable route, the path allocation information storage unit 108 is updated, and a path establishment command is transmitted to each corresponding node to establish a path (step 410).

  If it is determined in step 409 in FIG. 19 that there is no route to which a frequency slot for the requested path can be allocated, the communication related to the path establishment request is failed (step 411).

  After Steps 406, 410, and 411, if there is no request that has not been processed yet, the processing at this timing is terminated and the processing returns to Step 401 (No in Step 412). When a request is received during execution of processing at the current timing, it may be handled as a request at the current timing or as a request at the next timing.

  After Steps 406, 410, and 411, if there is a request that has not been processed yet, the process returns to Step 404 to process the next request.

<Fifth operation example>
Next, a fifth operation example will be described. In the fifth operation example, as shown in FIG. 20, path establishment / cancellation is performed each time a request arrives. On the other hand, pre-path rearrangement is performed at predetermined time intervals. In addition, it is good also as performing prior path rearrangement for every predetermined time instead of a predetermined time interval.

  The path establishment / cancellation process corresponding to the request in the fifth operation example is the same as that in the first operation example. However, in the fifth operation example described below, the path rearrangement after the path establishment is attempted is not performed. Of course, in the fifth operation example, as in the first operation example, the path rearrangement after the path establishment may be performed. The pre-path rearrangement process itself is the same as in the third and fourth operation examples.

  Hereinafter, description will be made with an emphasis on the flow of processing with reference to the flowcharts of FIGS. 21A and 21B.

  FIG. 21A is a flowchart of path establishment / cancellation processing performed in response to a request.

  The network management apparatus 100 receives the request (step 501). The network management apparatus 100 determines the type of request (step 502), and if the request is a path release request, performs a path release process (step 503).

  In step 502, if the request is a path establishment request, the process proceeds to step 504. The processing in steps 504 and 505 is the same as the path establishment processing in the first operation example, and the network management apparatus 100 makes a request by referring to the network information storage unit 107 and the path allocation information storage unit 108. The route of the path concerned (start point node-> end point node) is extracted, and for each route, it is determined whether or not the number of frequency slots necessary for the path can be allocated through the route (whether it is empty) (step 504), assigning a frequency slot to an assignable route, updating the path assignment information storage unit 108, and transmitting a bandwidth setting request for the frequency slot to each corresponding node to establish a path (step 505). ).

  If it is determined in step 504 that there is no route that can be assigned a frequency slot for the path related to the request, the communication related to the path establishment request is failed (step 506), and the process is terminated.

  FIG. 21B is a flowchart of pre-path relocation processing performed at predetermined time intervals.

  The network management apparatus 100 determines whether or not a predetermined timing (that is, prior path rearrangement control timing) has been reached (step 511), and proceeds to step 512 when the predetermined timing has been reached. In step 512, network management apparatus 100 searches for a link whose slot usage rate is equal to or greater than a predetermined value on the optical network. If there is a link whose slot usage rate is equal to or greater than a predetermined value, the process proceeds to step 513. In step 513, the path on the link extracted in step 512 is rearranged. When the rearrangement is not required or after the rearrangement is completed, the process returns to step 511 and waits until the next timing.

  The present invention is not limited to the above-described embodiments, and various modifications and applications are possible within the scope of the claims.

DESCRIPTION OF SYMBOLS 10 Band variable communication apparatus 11 Band variable transmission part 12 Band variable reception part 13 Band variable path switching part 14 Optical amplifier 15 Control part 100 Network management apparatus 101 Request reception part 102 Request storage part 103 Processing control part 104 Path accommodation design Unit 105 path rearrangement processing unit 106 communication device command unit 107 network information storage unit 108 path allocation information storage unit 200 optical network

Claims (11)

A path accommodation control method executed by a network management device that performs processing related to path establishment and cancellation using a frequency slot in an optical network including a group of variable bandwidth communication devices connected by a link,
In response to the reception of the path establishment request, among the paths that can be taken on the optical network as the path of the path related to the request, there is a path in which continuous frequency slots of the number of slots necessary for the path are vacant through the path. An empty determination step for determining whether or not there is,
In the vacancy determination step, when it is determined that there is a path in which the frequency slot is vacant, an allocation step of allocating the frequency slot to the path on the path;
A path rearrangement step for performing a path rearrangement process when it is determined in the empty determination step that there is no path in which the frequency slot is free;
The path rearrangement step includes:
A route extraction step of extracting one route from possible routes on the optical network as a route of the path related to the request;
On the extracted route that is the route extracted in the route extracting step, a relocation target path that is a path to which at least one frequency slot is allocated among consecutive frequency slots of the number of slots necessary for the path is extracted. Relocation target path extraction step;
It is determined whether or not the relocation target path can be relocated to a route different from the route in which the path is established, and relocation is performed if possible, by relocation, Assigning the consecutive frequency slots vacated through the path to a path according to the request;
A path accommodation control method. A path accommodation control method executed by a network management device that performs processing related to path establishment and cancellation using a frequency slot in an optical network including a group of variable bandwidth communication devices connected by a link,
Storing a request in a request storage means when a request related to a path is received;
A request processing step for performing processing according to the request for each request stored between the timing and the previous timing in response to the arrival of a predetermined timing.
The request processing step includes:
In the case where the request is a path establishment request, among the routes that can be taken on the optical network as the path of the path related to the request, there is a path in which continuous frequency slots of the number of slots necessary for the path are vacant through the path An empty determination step for determining whether or not there is,
In the vacancy determination step, when it is determined that there is a path in which the frequency slot is vacant, an allocation step of allocating the frequency slot to the path on the path;
A path rearrangement step for performing a path rearrangement process when it is determined in the empty determination step that there is no path in which the frequency slot is free;
The path rearrangement step includes:
A route extraction step of extracting one route from possible routes on the optical network as a route of the path related to the path establishment request;
On the extracted route that is the route extracted in the route extracting step, a relocation target path that is a path to which at least one frequency slot is allocated among consecutive frequency slots of the number of slots necessary for the path is extracted. Relocation target path extraction step;
It is determined whether or not the relocation target path can be relocated to a route different from the route in which the path is established, and relocation is performed if possible, by relocation, Assigning the consecutive frequency slots vacated through the path to a path according to the request;
A path accommodation control method. A path accommodation control method executed by a network management device that performs processing related to path establishment and cancellation using a frequency slot in an optical network including a group of variable bandwidth communication devices connected by a link,
A relocation step to be executed in response to receiving the path establishment request, and a slot allocation step to be executed thereafter,
The relocation step includes:
Searching for a link having a slot usage rate equal to or greater than a predetermined value on the optical network;
Relocating the path on the link to a different path from the path on which the path is established when the link exists;
The slot allocation step includes:
Among the paths that can be taken on the optical network as the path of the request, when there is a path in which continuous frequency slots of the number of slots necessary for the path are vacant through the path, the path is changed to the path. A path accommodation control method comprising: assigning the frequency slot. A path accommodation control method executed by a network management device that performs processing related to path establishment and cancellation using a frequency slot in an optical network including a group of variable bandwidth communication devices connected by a link,
Storing a request in a request storage means when a request related to a path is received;
A request processing step for performing processing according to the request for each request stored between the timing and the previous timing in response to the arrival of a predetermined timing.
In the case where the request is a path establishment request, the request processing step includes a rearrangement step and a slot allocation step to be executed thereafter,
The relocation step includes:
Searching for a link having a slot usage rate equal to or greater than a predetermined value on the optical network;
Relocating the path on the link to a different path from the path on which the path is established when the link exists;
The slot allocation step includes:
Among the paths that can be taken on the optical network as the path of the path relating to the path establishment request, when there is a path in which continuous frequency slots of the number of slots necessary for the path are vacant through the path, the path on the path A path accommodation control method comprising: assigning the frequency slot to a path. A path accommodation control method executed by a network management device that performs processing related to path establishment and cancellation using a frequency slot in an optical network including a group of variable bandwidth communication devices connected by a link,
A rearrangement step that is executed in response to the arrival of a predetermined timing, and a request processing step that is executed when a request related to a path is received;
The relocation step includes:
Searching for a link having a slot usage rate equal to or greater than a predetermined value on the optical network;
Relocating the path on the link to a different path from the path on which the path is established when the link exists;
The request processing step includes:
When the request is a path establishment request, among the routes that can be taken on the optical network as the path of the path relating to the path establishment request, continuous frequency slots of the number of slots necessary for the path are vacant through the route. A path accommodation control method comprising: allocating the frequency slot to the path on a route when there is a route. When selecting one path from the possible paths on the optical network as a path path for the request, it is limited to a range that can be allocated with the same number of slots as the number of slots necessary for the path that has the minimum OSNR penalty. The path accommodation control method according to any one of claims 1 to 5, wherein a path is selected, and a path with a small OSNR penalty is preferentially selected. When relocating a path, the path selection range to be relocated is occupied by the path in the range excluding the slot group on the route occupied by the path to be relocated from the optical network topology. The path accommodation control method according to any one of claims 1 to 5, wherein a path that can be allocated with the same number of slots as the number of slots that are assigned is preferentially selected and a path with a small OSNR penalty is preferentially selected.   6. The path accommodation control method according to claim 3, wherein a path to be rearranged is preferentially selected from paths having a large number of via links.   6. The path accommodation control method according to claim 3, wherein a path to be rearranged is preferentially selected from paths having a small number of via links.   The path accommodation control method according to any one of claims 3 to 5, wherein a path to be rearranged is preferentially selected from paths having a large number of paths that pass through links having a slot usage rate equal to or greater than a predetermined value. .   6. The path to be rearranged is preferentially selected as a path with a large average number of congested links obtained by dividing the number of links whose slot usage rate passes through a predetermined value or more by the number of via links. The path accommodation control method according to any one of the above.

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