JP6301168B2 - Station side equipment - Google Patents

Description

  The present disclosure relates to a resource allocation technique in a passive optical network (PON).

  PON is used as an optical access system. In the PON, one station-side terminal device (OLT: Optical Line Terminal) communicates with one or more subscriber-side terminal devices (ONU: Optical Network Unit) via an optical coupler. At this time, the OLT allocates a transmission timing and a period of each ONU, that is, a resource, to each ONU so that optical signals transmitted by each ONU do not collide in communication in the upstream direction, that is, from the ONU to the OLT direction.

  This uplink resource allocation is performed in units of allocation cycles. Specifically, when there is transmission data, each ONU transmits a request signal including information indicating the transmission data amount to the OLT. Based on the request signal received during a predetermined period, the OLT determines a resource to be allocated to the ONU that has transmitted the request signal in the next allocation period based on the transmission data amount included in the request signal. Then, the allocated bandwidth is notified to each ONU by an allocation signal.

  Patent Document 1 discloses a wavelength allocation method in a configuration (TWDM-PON) in which wavelength multiplexing (WDM) is applied to a PON.

JP2013-207716A

  Conventionally, the PON is used as an access line such as the Internet, for example, and the service for the terminal has been centered on so-called best effort. However, in recent years, use of PON for connection between a base station and a core network in a mobile communication system has been studied. In such a case, an ONU that receives a service with the best effort and an ONU that receives a service with a low delay and a fixed bandwidth are mixed in the PON. The configuration described in Patent Document 1 does not assume a case where ONUs that receive services with best effort and ONUs that receive services with low delay and fixed bandwidth are mixed, and appropriate resource allocation in such an environment Can not do.

The present invention provides a passive optical network, there is provided a station-side termination equipment to allocate the appropriate resources to the subscriber side terminating device.

According to one aspect of the present invention, when a request signal is received from one or more subscriber-side terminal devices in a passive optical network station-side terminal device, a continuous fixed band included in the request signal is requested. According to the information on whether or not the allocation means for allocating the wavelength to the subscriber-side termination apparatus that transmitted the request signal, and the wavelength allocated by the allocation means to the subscriber-side termination apparatus that transmitted the request signal Notification means for notifying , wherein the allocating means classifies the subscriber-side termination device that requests a continuous fixed bandwidth as a first subscriber-side termination device, and does not require a continuous fixed bandwidth. The terminator is classified as a second subscriber-side terminator, and the first subscriber-side terminator and the second subscriber-side terminator are assigned wavelengths according to different criteria. Already assigned wavelength A first value corresponding to a vacant bandwidth that is a value obtained by subtracting a required bandwidth of each of the first subscriber-side termination devices, and a second value corresponding to the number of the second subscriber-side termination devices to which the wavelength is assigned. A wavelength is assigned to the second subscriber-side termination device based on the value .

  Appropriate resources can be allocated to the subscriber-side terminal device.

The block diagram of PON by one Embodiment. The sequence diagram of the registration process of ONU which requests | requires the fixed band by one Embodiment. The sequence diagram of the registration process of ONU which requests | requires best effort by one Embodiment. The flowchart of the registration process by one Embodiment. The flowchart of the wavelength change process by one Embodiment. Explanatory drawing of the resource allocation by one Embodiment. The flowchart of the registration process by one Embodiment. Explanatory drawing of the resource allocation by one Embodiment. 1 is a schematic configuration diagram of a station-side termination device according to an embodiment. FIG.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In the following drawings, components that are not necessary for describing the embodiment are omitted from the drawings. Moreover, the following embodiment is an illustration and does not limit the scope of the present invention to the content of the embodiment. Note that the following description relates to resource allocation for transmission in the upstream direction, that is, from the ONU to the OLT direction.

<First embodiment>
FIG. 1 is a configuration diagram of a PON according to an embodiment. In FIG. 1, a station-side terminator (OLT) 1 is connected to a plurality of subscriber-side terminators (ONU) 31, 32, 33 via a splitter 2. In this embodiment, an ONU that requests fixed band allocation (hereinafter referred to as a fixed band ONU) and an ONU that does not require fixed band allocation and requests a service at best effort (hereinafter, referred to as a fixed band ONU). Called “best effort ONU”). For example, the ONU 31 in FIG. 1 is a fixed band ONU, and the ONU 33 is a best effort ONU.

  First, the registration process of the fixed band ONU 31 will be described with reference to FIG. The OLT 1 broadcasts a transmission timing notification signal to each ONU at a predetermined timing. The transmission timing notification signal is, for example, a discovery gate signal, and is a signal for notifying an ONU newly connected to the PON of a reference timing. After receiving the transmission timing notification signal, the newly connected fixed band ONU 31 transmits to the OLT 1 a registration request signal including information indicating that a fixed band allocation with a low delay is requested. The registration request signal is a signal that the ONU requests to register its own device in the OLT 1, and the registration request signal includes information indicating the requested bandwidth. Note that, for example, the fact that the information indicating the requested bandwidth is included can be an indication to the OLT 1 that the registration request signal requests allocation of a fixed bandwidth. However, the registration request signal can explicitly include information indicating that a low-bandwidth and fixed band allocation is requested separately from the information indicating the requested band. The registration request signal is transmitted at a predetermined wavelength. When the OLT 1 receives the registration request signal, the OLT 1 determines whether or not the request band can be allocated to the fixed band ONU 31. The period is notified with an allocation signal. Here, the allocation signal is, for example, a gate signal. The wavelength to be used, the transmission timing, and the transmission period may be notified by a registration signal. When the fixed band ONU 31 receives the allocation signal, the fixed band ONU 31 transmits a response signal to the OLT 1.

  Thereafter, the fixed band ONU 31 uses the allocated wavelength without transmitting individual band requests to the OLT 1 and transmits data to the OLT 1 during the transmission period notified from the allocated transmission timing. be able to. Hereinafter, any one of the wavelength, transmission timing, transmission period, or combination thereof used for data transmission by the ONU is collectively referred to as a resource. In the present embodiment, the fixed band ONU 31 does not need to receive resource allocation individually from the OLT 1 as long as the allocated resource is used. However, when it is necessary to transmit additional data, a resource request signal can be transmitted to the OLT 1 to temporarily receive additional resource allocation. Although not shown in FIG. 2, if the request band cannot be assigned to the fixed band ONU 31, the OLT 1 transmits a rejection notification signal to the ONU 31.

  Next, the registration process of the best effort ONU 33 will be described with reference to FIG. After receiving the transmission timing notification signal, the newly connected best effort ONU 33 transmits to OLT 1 a registration request signal including information indicating that the service is requested for best effort. For example, information indicating that there is no information indicating the requested bandwidth or that the requested bandwidth is 0 can be used as information for requesting a service at the best effort. When the OLT 1 receives the registration request signal, the OLT 1 determines the wavelength used by the best effort ONU 33, notifies the determined wavelength to the ONU 33 by the registration signal, and then transmits an allocation signal to the best effort ONU 33. When receiving the allocation signal, the best effort ONU 33 transmits a response signal to the OLT 1.

  Thereafter, when data to be transmitted is generated, the best effort ONU 33 transmits a resource request signal to the OLT 1, and transmits data using the resource allocated to the best effort ONU 33 by the OLT 1 as a response to the request signal.

  FIG. 4 is a flowchart of ONU registration processing executed by the OLT 1 in this embodiment. Note that the registration process of FIG. 4 is also a resource allocation process for the fixed bandwidth ONU and the best effort ONU. For simplification of description, transmission of signals that are not necessary for explanation among signals shown in FIGS. 2 and 3 is omitted from the flowchart of FIG. In the following flowchart, N is the number of wavelengths used in the PON, and i (1 ≦ i ≦ N) is an index indicating the wavelength. In the present embodiment, there is an allocation order for wavelengths allocated to the fixed band ONU, and it is assumed that the smaller the value of i, the higher the allocation order.

By starting the process, the OLT 1 initializes the value C _i to 0 and the value B _i to the value B _o in S10. Here, the value C _i indicates the number of best effort ONUs to which the wavelength λ _i is assigned, and the value B _i has already been assigned to the fixed band ONU from the entire transmission band (transmission speed) at the wavelength λ _i . This is a free band obtained by subtracting the band (hereinafter, simply referred to as a free band), and the value B _o is the entire transmission band at the wavelength λ _i . Thereafter, the OLT 1 waits until a registration request signal is received from the ONU in S11. When the registration request signal is received from the ONU in S11, the OTL 1 determines whether the ONU is a best effort ONU or a fixed band ONU in S12. Note that the best-effort ONU or the fixed band ONU can be determined based on, for example, whether a fixed band is requested by a registration request signal. However, it may be determined from other information included in the registration request signal.

If the ONU is a fixed band ONU, the OLT 1 determines in S13 whether there is a wavelength λ _i having a free band B _i equal to or greater than the request band B of the fixed band ONU. If it does not exist, it is impossible to allocate a fixed band, so the OLT 1 transmits a rejection notification signal to the fixed band ONU in S17. On the other hand, if there is a wavelength λ _i having a free band B _i equal to or greater than the required band B, the OLT 1 selects a wavelength with the smallest index i in S14. That is, the wavelength with the highest allocation order is selected. Then, the OLT 1 notifies the fixed band ONU in S15 that the wavelength λ _i has been assigned together with the transmission timing and transmission period at the selected wavelength λ _i . In S15, the OLT 1 updates the free bandwidth B _{i so as} to reduce only the bandwidth B allocated to the fixed bandwidth ONU. Thereafter, the OLT 1 repeats the processing from S11 after performing the wavelength changing processing in S16. Details of the wavelength changing process will be described later.

On the other hand, in S12, the ONU is a best effort ONU, OLT 1 is a S18, for each wavelength lambda _i, computes the value _{(B i} / _C i), the maximum value _{(B i} / _C i) Select i. When there are a plurality of _i values that maximize the value (B _i / C _i ), any one is selected from them. Further, in the calculation of the value _(B i / _{C i),} if the value of _{B i} is 0, regardless of the value of _{C i,} the value _(B i / _{C i)} is assumed to be 0. Furthermore, when the value of B _i is not 0 and the value of C _i is 0, the value (B _i / C _i ) is assumed to be infinite. In S19, the OLT 1 decides to allocate the wavelength λ _i corresponding to i selected in S18 to the best effort ONU, and notifies the best effort ONU that the wavelength λ _i is allocated in S19. Further, OLT 1 updates the number _{C i} as is incremented by one.

The transition of assignment according to the flowchart of FIG. 4 will be described with reference to FIG. In the following description, N = 4, and the entire bandwidth of each wavelength is 10 Gbps. Further, the required bandwidth of the fixed bandwidth ONU is all 2.5 Gbps. In FIG. 6, LL indicates a fixed band ONU, and BE indicates a best effort ONU. Note that, under each wavelength, a number C _i and a free band B _i are shown.

FIG. 6A shows an initial state used for the description. The wavelength λ ₁ is assigned to four fixed band ONUs, the number C ₁ is 0, and the free band B ₁ is 0. The wavelength λ ₂ is assigned to two fixed band ONUs, the number C ₂ is 0, and the free band B ₂ is 5 Gbps. Further, the wavelength λ ₃ is assigned to one best effort ONU, the number C ₃ is 1, and the free band B ₃ is 10 Gbps. Further, the wavelength λ ₄ is assigned to one best effort ONU, the number C ₄ is 1, and the free band B ₄ is 10 Gbps.

In the state of FIG. 6A, it is assumed that registration request signals from two fixed band ONUs are received. In this embodiment, the allocation order of the wavelength λ ₁ is the highest, but the free band of the wavelength λ ₁ is zero. On the other hand, the empty band of the wavelength λ ₂ having the second highest allocation order is 5 Gbps, and can accommodate two fixed band ONUs. Therefore, the OLT 1 assigns the wavelength λ ₂ to the two fixed band ONUs and enters the state shown in FIG. 6B. Incidentally, free band _{B 2} is updated to 0. Thereafter, in the state of FIG. 6B, it is assumed that a registration request signal is received from one fixed band ONU. In the state of FIG. 6B, the vacant bands of the wavelengths λ ₁ and λ ₂ are both 0, and the vacant band of the wavelength λ ₃ having the next highest allocation order is 10 Gbps. Therefore, the OLT 1 assigns the wavelength λ ₃ to the fixed band ONU and enters the state shown in FIG. Incidentally, free band _{B 3} is updated to 7.5Gbps.

On the other hand, it is assumed that a registration request signal from one best effort ONU is received in the state of FIG. The value (B ₁ / C ₁ ) is 0, the value (B ₂ / C ₂ ) is infinite, and the value (B ₃ / C ₃ ) and the value (B ₄ / C ₄ ) are both 10. , The value (B ₂ / C ₂ ) is the largest. Therefore, the OLT 1 assigns the wavelength λ ₂ to this best effort ONU, and enters the state shown in FIG. Note that the number _{C 2} is updated to 1. Thereafter, it is assumed that registration request signals from two best effort ONUs are received in the state of FIG. Since the value (B ₁ / C ₁ ) is 0, the value (B ₂ / C ₂ ) is 5, and the value (B ₃ / C ₃ ) and the value (B ₄ / C ₄ ) are both 10, The OLT 1 assigns the wavelength λ ₃ to one best effort ONU. Therefore, the value (B ₃ / C ₃ ) is 5. Therefore, the wavelength λ ₄ is assigned to another best effort ONU. Therefore, the state shown in FIG. Thereafter, it is assumed that a registration request signal from one fixed band ONU is received in the state of FIG. In this case, the OLT 1 assigns the wavelength λ ₂ having the highest assignment order among the wavelengths having a free band of 2.5 Gbps or more, and the state shown in FIG. 6F is obtained.

As described above, in the present embodiment, the allocation is performed so that the fixed band ONU uses the same wavelength as much as possible. The reason why the wavelength allocated to the best effort ONU is determined by the value (B _i / C _i ) is to increase the bandwidth that can be used by the best effort ONU. Specifically, the value (B _i / C _i ) indicates an average band that can be used by one best effort ONU at the wavelength. Therefore, by assigning the wavelength having the largest average bandwidth to a new best effort ONU, the average bandwidth that can be used by the best effort ONU is prevented from greatly fluctuating for each wavelength.

  Next, the wavelength changing process in S16 of the flowchart of FIG. 4 will be described with reference to FIG. As described above, in this embodiment, the wavelength allocation to the best effort ONU is performed so that the average bandwidth that can be used by one best effort ONU is not biased. However, when a wavelength is assigned to the fixed band ONU, the vacant band of the wavelength is reduced, and thus the average available band of the best effort ONU to which the wavelength is assigned is reduced. Therefore, in this embodiment, after assigning a wavelength to the fixed band ONU, the wavelength changing process shown in FIG. 5 is performed, and another wavelength is assigned to the best effort ONU to which the wavelength is assigned depending on the conditions. This prevents the average band that can be used by the best effort ONU from being biased by assigning the wavelength to the fixed band ONU.

First, in S30 of FIG. 5, the OLT 1 calculates a value (B _i / (C _i −1)) for the wavelength λ _i assigned to the fixed band ONU in S15 of FIG. The value (B _i / (C _i −1)) is an average band that can be used by the best effort ONU at the wavelength when the best effort ONU to which the wavelength λ _i is assigned is reduced by one from the current state. is there. The OLT 1 calculates a value (B _j / (C _j +1)) for each j (1 ≦ j ≦ N and j ≠ i). The value (B _j / (C _j +1)) is an average band that can be used by the best effort ONU at the wavelength when the best effort ONU to which the wavelength λ _j is assigned is increased by one from the current state. . Thereafter, the OLT 1 determines in S30 whether or not j having a value (B _j / (C _j +1)) equal to or greater than the value (B _i / (C _i −1)) exists. If not, the OLT 1 decides not to change the wavelength assignment for the best effort ONU to which the wavelength λ _i is assigned, and ends the process. On the other hand, if present, the OLT 1 selects one of the best effort ONUs to which the wavelength λ _i is assigned in S31, and changes the assigned wavelength of the selected ONU from the wavelength λ _i to the wavelength λ _j . When there are a plurality of js that satisfy the condition of S30, j corresponding to the maximum value (B _j / (C _j +1)) is selected. Thereafter, the wavelength change is notified to the selected ONU, and the OLT 1 updates the numbers C _i and C _j in S32. In this embodiment, whether or not to change the wavelength is determined based on the value (B / C) after one of the best effort ONUs using the wavelength λ _i is moved to another wavelength. However, whether or not to change the wavelength may be determined based on the value (B / C) before the change.

<Second embodiment>
Next, the second embodiment will be described focusing on the differences from the first embodiment. FIG. 7 is a flowchart of ONU registration processing executed by the OLT 1 in this embodiment. The difference from the process shown in FIG. 4 is that S14 in FIG. 4 is replaced with the process in S44, and the other processes are the same as those in FIG.

In this embodiment, if there is an _i whose free band B _i is equal to or greater than the required band B of the fixed band ONU, the OLT 1 selects and fixes _i having the largest free band B _i in S44. It is determined that the wavelength λ _i is assigned to the band ONU. Therefore, unlike the first embodiment, the wavelength is assigned to the fixed band ONU so that the free band is not biased at each wavelength. When there are a plurality of _i having the maximum free bandwidth B _i , any one is selected. However, in order to reduce the influence on the best effort ONU, _i having the smallest number Ci may be selected.

Transition of assignment according to the flowchart of FIG. 7 will be described with reference to FIG. The preconditions in FIG. 8 are the same as those in FIG. FIG. 8A shows an initial state used for the description. Wavelength λ ₁ and wavelength λ ₂ are assigned to two fixed band ONUs, both number C ₁ and number C ₂ are 0, and are free. Band B ₁ and free band B ₂ are both 5 Gbps. The wavelength λ ₃ is assigned to one fixed band ONU and one best effort ONU, the number C ₃ is 1, and the free band B ₃ is 7.5 Gbps. The wavelength λ ₄ is the same as the wavelength λ ₃ .

Assume that registration request signals from two fixed band ONUs are received in the state of FIG. In this case, a wavelength λ ₃ and a wavelength λ ₄ having a large vacant bandwidth are assigned to the two fixed bandwidth ONUs, respectively. Therefore, the state shown in FIG. Thereafter, it is assumed that a registration request signal is received from one fixed band ONU in the state of FIG. Since the free bandwidth of all wavelengths is the same 5 Gbps, the OLT 1 selects an arbitrary wavelength and performs wavelength allocation. In the example of FIG. 8, the wavelength λ ₁ is selected and assigned. Therefore, the state shown in FIG.

On the other hand, it is assumed that a registration request signal from one best effort ONU is received in the state of FIG. In this case, since the value (B ₁ / C ₁ ) and the value (B ₂ / C ₂ ) are both infinite, the OLT 1 assigns the wavelength λ ₁ or the wavelength λ ₂ to this best effort ONU. In the example of FIG. 8, the wavelength λ ₂ is selected and assigned. Therefore, the state shown in FIG. Thereafter, in the state of FIG. 8D, it is assumed that registration request signals from two best effort ONUs have been received. Since the value (B ₁ / C ₁ ) is infinite, the wavelength λ ₁ is assigned to one best effort ONU. By assigning the wavelength λ _{1 to} the best effort ONU, the maximum value (B / C) is 7.5 at the wavelengths λ ₃ and λ ₄ , so the OLT 1 sets the wavelength λ ₃ or the wavelength λ ₄ to the other one. Assign to two best effort ONUs. In the example of FIG. 8, the wavelength λ ₄ is selected and assigned. Therefore, the state shown in FIG. Thereafter, it is assumed that a registration request signal is received from one fixed band ONU in the state of FIG. The maximum value of the free band B is 7.5 Gps of the wavelength λ ₃ or the wavelength λ ₄ , and the OLT 1 can assign the wavelength λ ₃ or the wavelength λ ₄ to this fixed band ONU. In the example of FIG. 8, the wavelength λ ₃ is selected and assigned. Therefore, the state shown in FIG.

  FIG. 9 is a schematic configuration diagram of the OLT 3 according to the present embodiment. When the allocation unit 11 receives the registration request signal, the allocation unit 11 determines whether the ONU that transmitted the registration request signal is a best effort ONU or a fixed band ONU. Then, as described above, the allocation unit 11 determines wavelengths to be allocated by applying different standards to the best effort ONU and the fixed band ONU. In the case of a fixed band ONU, the allocation unit 11 further determines a transmission timing and a transmission period in addition to the wavelength. The notification unit 12 notifies the assigned wavelength to the ONU that has transmitted the registration request signal, and further notifies the transmission timing and the transmission period in the case of a fixed band ONU.

  As described above, wavelength allocation is performed using different criteria for the fixed band ONU and the best effort ONU. With this configuration, it is possible to realize efficient resource allocation even in an environment where fixed bandwidth ONUs and best effort ONUs are mixed. For example, for the best effort ONU, the allocated wavelength can be determined based on the wavelength vacant band and the number of accommodated best effort ONUs. More specifically, the assigned wavelength can be determined based on the ratio between the wavelength vacant bandwidth and the number of accommodated best effort ONUs. Thereby, it is possible to prevent the average available bandwidth of the best effort ONU from being biased for each wavelength. For the fixed band ONU, the wavelength having the highest allocation order can be allocated among the wavelengths whose free band is equal to or greater than the required band. This configuration increases the probability that the best effort ONU can use the maximum wavelength band. On the other hand, for the fixed band ONU, among the wavelengths whose free band is equal to or greater than the required band, the wavelength having the maximum free band can be assigned. With this configuration, it is possible to prevent the vacant bandwidth of the wavelength from being biased for each wavelength and to prevent the bias of the average bandwidth that can be used by the best effort ONU.

  Further, when a wavelength is assigned to the fixed band ONU, the vacant band of the wavelength decreases, and the average band that can be used by the best effort ONU that uses the wavelength also decreases. Therefore, when the wavelength is assigned to the fixed band ONU, the wavelength changing process can be performed so as to prevent the deviation of the average band that can be used by the best effort ONU. In the wavelength change processing, whether or not to change the wavelength based on the average available bandwidth of the best effort ONU at each wavelength when the ONU using the wavelength allocated to the fixed band ONU is moved to another wavelength, and change Determine the change destination.

Claims (8)

A station-side termination device for a passive optical network,
When receiving a request signal from one or more subscriber-side termination devices, the subscriber-side termination device that has transmitted the request signal according to information on whether to request a continuous fixed band included in the request signal Assigning means for assigning wavelengths to
Notifying means for notifying the wavelength assigned by the assigning means to the subscriber-side terminating device that transmitted the request signal;
Equipped with a,
The allocating means classifies a subscriber-side termination device that requires a continuous fixed bandwidth as a first subscriber-side termination device, and a subscriber-side termination device that does not require a continuous fixed bandwidth as a second subscriber-side termination device. Classified as a device, assigning wavelengths to the first subscriber-side termination device and the second subscriber-side termination device according to different criteria,
The assigning means assigns a first value corresponding to a vacant band, which is a value obtained by subtracting the required bandwidth of each of the first subscriber-side terminating devices that have already assigned the wavelength from the entire wavelength band, and the wavelength. A station-side terminating device , wherein a wavelength is assigned to the second subscriber-side terminating device based on a second value corresponding to the number of the second subscriber- side terminating devices. The allocation means, by the ratio of said first value and said second value, the station-side termination apparatus according to claim 1, characterized in that allocating a wavelength to said second subscriber side terminating device. The station according to claim 2 or 3 , wherein the assigning means assigns a wavelength having a maximum value obtained by dividing the first value by the second value to the second subscriber-side terminating device. Side termination device. The allocating unit holds information indicating a wavelength allocation order, and allocates a wavelength having a highest allocation order to which a required bandwidth can be allocated to the first subscriber-side terminal device. The station-side termination device according to any one of 1 to 3 . The station side according to any one of claims 1 to 3 , wherein the allocating unit allocates a wavelength having a largest available band to which a requested band can be allocated to the first subscriber-side terminating device. Termination equipment. The assigning means, when assigning the first wavelength to the first subscriber-side terminating device, determines whether to change the assigned wavelength of the second subscriber-side terminating device to which the first wavelength is assigned. The station-side termination device according to any one of claims 1 to 5 , characterized in that: The assigning unit compares the ratio between the first value and the second value related to the first wavelength, and the ratio between the first value and the second value related to wavelengths other than the first wavelength. The station-side terminator according to claim 6 , wherein whether or not to change the assigned wavelength of the second subscriber-side terminator to which the first wavelength is assigned is determined. The assigning means is a ratio of a value obtained by subtracting 1 from the second value relating to the first wavelength to the first value, and a value obtained by adding 1 to the second value relating to a wavelength other than the first wavelength. And the ratio of the first value to determine whether to change the assigned wavelength of the second subscriber-side terminating device to which the first wavelength is assigned. The station side termination device according to claim 6 .

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