JP2019146079A - Station side termination device, subscriber side termination device, communication system, station side program, and subscriber side program - Google Patents

Abstract

To provide a station side termination device, subscriber side termination device, communication system, station side program, and subscriber side program that can prevent an increase in storage capacity of a buffer for defragmentation of the station side termination device in the communication system in which the subscriber side termination device performs fragmentation processing.SOLUTION: A station side termination device that is connected to a plurality of subscriber side termination devices, and receives frames from the respective subscriber side termination devices and transmits them to a higher-level network includes a first queue for storing a first frame which has a predetermined frame length and a plurality of second queues for storing each of a plurality of second frames into which the first frame is divided in association with the respective subscriber side termination devices.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a station-side termination device, a subscriber-side termination device, a communication system, a station-side program, and a subscriber-side program. In particular, the present invention relates to a buffer configuration and a buffer control method necessary for defragmenting a fragment frame in a station-side terminal device.

  2. Description of the Related Art In recent years, a service called FTTH (Fiber To The Home) using an optical fiber as a transmission path has been widespread for the purpose of providing high-speed and broadband broadband services to general private homes. For providing broadband services by FTTH, an optical access network called a passive optical network (PON) is often used.

  The PON is composed of one station-side terminal device (OLT: Optical Line Terminal) and a plurality of subscriber-side terminal devices (ONU: Optical Network Unit) using an optical passive element called an optical splitter (optical coupler). The optical cable is branched and connected in a one-to-many manner. In PON, an FTTH service can be economically provided by sharing an optical fiber, an OLT, and the like with a plurality of subscribers.

  There exists what is called NG (Next Generation) -PON2 in PON (for example, refer nonpatent literature 1). In the PON described in this Non-Patent Document 1, TDMA (Time Division Multiple Access) technology is used for communication (uplink communication) from the ONU to the OLT, and collision of signals from each ONU is avoided. . Further, it is an optical access network system that can construct a plurality of PONs on one infrastructure using WDM (Wavelength Division Multiplexing) technology and can cope with future increase in communication demand.

  As an application of NG-PON2 shown in Non-Patent Document 1, for example, there is application to a packet transfer network such as Ethernet (registered trademark), but when transferring an Ethernet frame in NG-PON2, XGEM ( XG-PON Encapsulation Method) frame is encapsulated and transferred. In addition, in NG-PON 2, in order to avoid collision of signals from each ONU with respect to uplink communication, uplink communication from the ONU is performed by an instruction of a transmission time and a transmission permission amount from the OLT.

  The ONU outputs an Ethernet (registered trademark) specification frame (hereinafter referred to as an “ether frame”) that can be output by the instructed transmission permission amount from the transmission time instructed by the OLT as an XGEM frame. If the Ethernet frame cannot be transmitted with the amount of transmission permission remaining in the XGEM frame, a plurality of XGEM frames are generated by dividing the Ethernet frame into a transmittable size, and the first XGEM frame remains The remaining XGEM frames are transmitted according to a transmission instruction from the next time on the transmission permission amount. Dividing an Ether frame into a transmittable size is generally called “fragmentation” (hereinafter, “fragment”), and each of the divided frames is called a “fragment frame”. Hereinafter, the process of dividing into fragments is referred to as “fragment processing”.

  The OLT converts the received XGEM frame into an Ethernet frame and outputs it. When the OLT is divided into a plurality of XGEM frames, the head and intermediate XGEM frames are held in a buffer (hereinafter referred to as “defragment buffer”). When the last XGEM frame is received, all the divided frames are integrated, converted into an ether frame, and output. Restoring the original frame by integrating the fragment frames is called “defragmentation” (hereinafter “defragmentation”). Hereinafter, the process of integrating the fragment frames and reproducing the original frame is referred to as “defragment process”.

  As a related art related to fragments, for example, a station side device disclosed in Patent Document 1 is known. The station-side device disclosed in Patent Document 1 permits transmission to each of the plurality of subscriber devices in the first period in the station-side device connected to the plurality of subscriber-side devices via an optical splitter. Based on the dynamic bandwidth allocation unit that determines the data length, and the data length that permits the transmission determined by the dynamic bandwidth allocation processing unit, determine the order of the plurality of subscriber side devices, in the determined order, A data transmission permission unit that determines transmission timings of data in a plurality of second periods shorter than the first period in a plurality of subscriber-side devices, respectively; That is, in the station side device disclosed in Patent Document 1, in the bandwidth allocation from the OLT to the ONU, by controlling the bandwidth allocation amount to each ONU, it is possible to prevent the occurrence of fragments in each ONU, or to reduce the probability of occurrence. Reduced.

JP 2008-283323 A

ITU-T G. 989.3 (10/2015) 40-Gigabit-capable passive optical network (NG-PON2): Transmission Convergence Layer Specification

  Here, the OLT in NG-PON 2 as described above requires a buffer (hereinafter referred to as “defragment buffer”) that temporarily stores fragment frames for the maximum ether frame length when converting from an XGEM frame to an ether frame. become. The maximum length of a normal ether frame is 1522 bytes, but in order to support a frame called a jumbo frame, a buffer amount of about 9 kilobytes is required. In addition, since fragmentation may occur simultaneously in all ONUs, defragment buffers corresponding to the total number of ONUs are required. For this reason, when the number of ONUs to be accommodated is large, a memory having a large storage capacity is required for the defragmentation processing in the OLT, which is a problem in terms of the feasibility of the optical communication system.

  In this regard, the station-side device disclosed in Patent Document 1 has a problem with fragment generation itself, but the station-side device disclosed in Patent Document 1 also actually considers the occurrence of fragments. It is considered necessary to provide a defragmentation buffer (queue). Even in this case, Patent Document 1 does not disclose the suppression of the increase in the storage capacity of the defragment buffer (queue) in the station side device.

  The present invention has been made in view of the above-described problems, and suppresses an increase in the storage capacity of a defragmentation buffer in a station-side terminal device in a communication system in which fragmentation processing is performed in a subscriber-side terminal device. It is an object of the present invention to provide a station-side terminator, a subscriber-side terminator, a communication system, a station-side program, and a subscriber-side program that can be used.

  In order to achieve the above-described object, a station-side termination device according to the present invention is a station connected to a plurality of subscriber-side termination devices and receiving a frame from each of the plurality of subscriber-side termination devices and sending it to an upper network. A side termination apparatus, wherein each of a first queue for accumulating a first frame having a predetermined frame length and a second frame obtained by dividing the first frame into a plurality of frames are connected to the subscriber side termination apparatus. And a plurality of second queues that are stored in correspondence with each other.

  In order to achieve the above-described object, a subscriber-side terminal device according to the present invention includes a receiving unit that receives the band allocation signal from the station-side terminal device, and a frame that is transmitted to the station-side terminal device includes the band allocation signal. In the case where the allocation band indicated by the signal is exceeded, when the permission signal is added to the band allocation signal, the division is performed to generate the second frame, and the prohibition signal is added In some cases, frame generation means for stopping the division is included.

  In order to achieve the above-described object, a communication system according to the present invention is a master device that receives a frame from a slave device, and includes a first queue that stores a first frame having a predetermined frame length, A second queue for storing each second frame obtained by dividing one frame into a plurality of frames corresponding to the slave device, a signal indicating an allocated band of a transmission frame for the slave device, and permission for permitting the division A master device including a generation unit that generates a band allocation signal including either a signal or a prohibition signal to be prohibited, a reception unit that receives the band allocation signal, and the permission signal is included in the band allocation signal The second frame is transmitted by executing the division in some cases, and the division is executed when the prohibition signal is included. A slave device including a frame generating means have, is intended to include.

  In order to achieve the above-described object, a station-side program according to the present invention is a station-side program that is connected to a plurality of subscriber-side termination devices and receives frames from each of the plurality of subscriber-side termination devices and sends them to a higher-level network. A terminating device, each of a first queue for storing a first frame having a predetermined frame length and a second frame obtained by dividing the first frame into a plurality of frames, is provided to the subscriber-side terminating device. A program for controlling a station-side terminator including a plurality of second queues stored correspondingly, wherein the computer is configured to transmit the first of the frames transmitted from each of the plurality of subscriber-side terminators. Allocating frames to the first queue, and allocating the second frame to the second queue corresponding to the subscriber-side terminating device that transmitted the second frame; Read control means for sending the first frame stored in the first queue to the upper network each time it is stored, and sending the first frame to the higher network when each of the second frames is stored in the second queue; , To function as.

  In order to achieve the above-described object, a subscriber-side program according to the present invention is a subscriber-side program of a subscriber-side termination device that is connected to a station-side termination device and transmits a frame to the station-side termination device, Receiving means for receiving a bandwidth allocation signal for transmitting the frame from the station-side termination device, and a frame to be transmitted to the station-side termination device for the computer installed in the subscriber-side termination device. When the allocation band shown in FIG. 1 is exceeded, if the permission signal for permitting the division of the frame is given to the band allocation signal, the division is performed and the divided frame is transmitted, and the division of the frame is prohibited. When the prohibition signal is given, the frame generation means does not execute the division and functions as a frame generation means.

  According to the present invention, in a communication system in which fragmentation processing is performed at a subscriber-side termination device, a station-side termination device that can suppress an increase in the storage capacity of a defragmentation buffer of the station-side termination device, a subscriber side It is possible to provide a terminal device, a communication system, a station side program, and a subscriber side program.

It is a block diagram which shows an example of a structure of the communication system which concerns on this Embodiment. (A) is a diagram for explaining a fragment, (b) is a diagram for explaining a fragment frame sequence, and (c) is a state transition diagram showing defragmentation processing in a station side terminal device. It is a flowchart which shows the transmission control process in a station | side terminal apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the drawings are merely schematically shown to the extent that the present invention can be understood. In the following, a preferred configuration example of the present invention will be described. However, numerical conditions and the like are merely preferred examples. Therefore, the present invention is not limited to the following embodiments, and many changes or modifications that can achieve the effects of the present invention can be made without departing from the scope of the configuration of the present invention.

  With reference to FIG. 1 to FIG. 3, a station-side termination device (OLT), a subscriber-side termination device (ONU), a communication system, a station-side program, and a subscriber-side program according to the present embodiment will be described. In this embodiment, an NG-PON2 system will be described as an example of a communication system.

  As shown in FIG. 1, the NG-PON 2 system according to the present embodiment includes an OLT 10 and a plurality of ONUs 40-1, 40-2,..., 40- m (hereinafter collectively referred to as “ONU 40”), an optical splitter 30, a plurality of optical fibers 32-1, 32-2,..., 32-m (m is illustrated in FIG. 1). Hereinafter, the term “optical fiber 32”) and the optical fiber 34 are collectively included. The OLT 10 is connected to the optical splitter 30 via an optical fiber 34, and each of the ONUs 40 is connected to the optical splitter 30 via an optical fiber 32.

  The OLT 10 includes an OSU 14, an optical receiver 16, and an OLT control unit 28. The OSU 14 is a termination device of the OLT 10 and faces the ONU 40 via the optical receiver 16. The OSU 14 has various functions for terminating the ONU 40. In FIG. 1, only the defragmentation buffer 12 directly related to the present embodiment is illustrated, and the other functions are not illustrated.

  The optical receiver 16 receives the upstream optical signal transmitted from each of the ONUs 40 via the optical transmission path (the optical fiber 32, the optical splitter 30, and the optical fiber 34), and converts it into an electrical signal. The OSU 14 also includes an optical transmitter that transmits a downstream optical signal to each of the ONUs 40, but is not shown in FIG. The optical transmitter corresponds to a “transmission unit” according to the present invention, and transmits a “band allocation signal” according to the present invention indicating an allocated band to which either a permission signal or a prohibition signal described below is given. In the present embodiment, a single OSU 14 is described as an example, but a plurality of OSUs 14 may be mounted on the OLT 10.

  The OLT control unit 28 performs overall control of the entire OLT 10. In the OLT control unit 28, a “bandwidth allocating unit” according to the present invention for calculating an allocated band for each of the plurality of ONUs 40, and a permission signal for permitting a fragment (“dividing” according to the present invention) for a part of the ONU 40 , And “signal generation means” according to the present invention for generating a prohibition signal for prohibiting fragmentation of the other parts of the plurality of ONUs 40.

  On the other hand, each of the ONUs 40 includes an optical transmitter 42 and a frame generation unit 44. The optical transmitter 42 faces the optical receiver 16 via the optical transmission path, and transmits an upstream optical signal toward the OLT 10. The ONU 40 also includes an optical receiver that receives the downstream optical signal from the OLT, but is not shown in FIG. The frame generation unit 44 which is a “frame generation unit” according to the present invention generates a frame signal to be transmitted from the ONU 40 to the OLT 10.

  Here, referring to FIGS. 2A and 2B, fragment processing executed in each of the ONUs 40 will be described. FIG. 2A shows a requested bandwidth DBW when transmitting a frame from the ONU 40 to the OLT 10, allocated bandwidths PBW (1), PBW (2) and PBW (3) actually allocated from the OLT 10, and from the ONU 40. This shows the relationship between the transmission frames. In the example shown in FIG. 2A, the ONU 40 requests the requested bandwidth DBW to transmit the frames Fr1 to Fr7. On the other hand, as shown in FIG. 2A, the bandwidth allocated by the OLT 10 is PBW (1) for the first allocated bandwidth, PBW (2) for the second allocated bandwidth, and PBW (3 for the third allocated bandwidth). In order to transmit the frames Fr1 to Fr6, the PBW (1) is less than the required bandwidth.

  In this case, the ONU 40 performs fragment processing. That is, in the first allocated band PBW (1), frames Fr1 to Fr5 can be transmitted, and therefore are set as transmission candidates. Next, the ONU 40 divides the remaining frame Fr6 by the amount that can be sent with the remainder of the allocated bandwidth PBW (1), and generates a fragment frame FFr1. In the first transmission, frames Fr1 to Fr5 (hereinafter “non-fragmented frame”) and fragment frame FFr1 are transmitted. In the second allocation band PBW (2), there is insufficient bandwidth to transmit the remaining divided frame Fr6, so the remaining divided frame Fr6 is divided by the amount that can be transmitted by PBW (2), and fragmented. A frame FFr2 is generated. In the second transmission, the fragment frame FFr2 is transmitted. Since there is a band for transmitting the remaining divided frames Fr6 and FR7 in the third allocated band PBW (3), fragment frames FFr3 and Fr7 are transmitted in the third transmission.

  FIG. 2B shows fragment frames FFr1 to FFr3 that are transmitted from a certain ONU 40 and are to be integrated by the OLT 10. That is, the fragment frames FFr1 to FFr3 shown in FIG. 2A are arranged in the order of arrival at the OLT 10, and are set as a fragment frame sequence DFrt as a target of defragmentation in the OLT 10. Although FIG. 2B shows a case where there are three fragment frames FFr, the number of fragment frames FFr may be any number. The first fragment frame FFr1 is a frame transmitted during the first transmission described above, and the fragment frames FFr2 to FFr3 are frames transmitted during the second and third transmissions.

  As shown in FIG. 2B, each fragment frame FFr has a fragment bit FB (“identifier” according to the present invention) indicating whether or not it is the last fragment frame. That is, the value of the fragment bit FB is such that the logical value of the last previous fragment frame FFr2 from the first fragment frame FFr1 is FB = 0, the logical value of the last fragment frame is FB = 1, and the last fragment frame is It is configured so that it can be identified. Of course, this logical value should be determined by the specification and may be reversed. The fragment bit FB may be a fragment bit provided as standard in the overhead (OH) of the XGEM frame.

  Next, the defragmentation buffer 12 included in the OLT 10 according to the present embodiment will be described with reference to FIG. The defragment buffer 12 is a part that integrates the fragment frames FFr and reproduces the original frame data. As shown in FIG. 1, the defragmentation buffer 12 includes a buffer unit 13, a frame distribution unit 18, a read control unit 20, and an allocation table 26. Further, the buffer unit 13 includes one or more defragmentation queues 22-1, 22-2,..., 22-n (in FIG. 1, the case of n is illustrated. Fragment queue 22 ") and through queue 24. Although there may be a plurality of through queues 24, the present embodiment will be described by exemplifying one case. In the present embodiment, the number n of defragmentation queues 22 is smaller than the number m of ONUs 40 (n <m).

  The frame distribution unit 18 is a part that sends the fragment frame FFr to the defragmentation queue 22 and sends the non-fragment frame Fr to the through queue 24. On the other hand, the read control unit 20 is a part that reads frames (non-fragment frame Fr, fragment frame FFr) from the defragmentation queue 22 and the through queue 24. The allocation table 26 is a table that holds the correspondence between the ONU 40 and the defragmentation queue 22.

  Next, the defragmentation process and the transmission control process executed in the OLT 10 will be described with reference to FIG.

  When the frame sent from the ONU 40 is a non-fragment frame Fr, the frame sorting unit 18 sends the frame to the through queue 24. The through queue 24 outputs a transmission request to the read control unit 20. The read control unit 20 reads the non-fragment frame Fr from the through queue 24 where the transmission request is generated, converts it into an Ether frame, and outputs it.

  On the other hand, when the frame sent from the ONU 40 is the fragment frame FFr, the frame sorting unit 18 sends the frame to one of the defragmentation queues 22. The defragmentation queue 22 is selected corresponding to the ONU 40, and the correspondence between the two is stored in the allocation table 26.

  As described above, the fragment frame FFr input to the frame sorting unit 18 has a fragment bit FB that is an identifier indicating whether or not the fragment frame FFr is the last fragment frame of the fragment frame sequence DFrt. In this embodiment, the fragment bit FB of the last fragment frame (FFr3) is set to FB = 1, and the fragment bit FB of the first fragment frame (FFr1) or the intermediate fragment frame (FFr2) is set to FB = 0. Yes. Note that the fragment bit FB of the non-fragment frame Fr is always set to BF = 1.

  With reference to the state transition diagram shown in FIG. 2C, the defragmentation process (frame distribution process) executed by the frame distribution unit 18 will be described in more detail. By this processing, the frame distribution unit 18, when the frame sent to the OLT 10 is the fragment frame FFr, the non-fragment frame Fr, or the fragment frame FFr, the fragment frame FFr (that is, FFr1 to FFr3). ) Is a first fragment frame and an intermediate fragment frame, or a last fragment frame. This determination is performed for each ONU 40 of the transmission source.

  As shown in FIG. 2C, when the upstream frame from each ONU 40 received by the OLT 10 is input to the frame distribution unit 18, the state 1 is first set to the initial state. If the fragment bit FB of the received frame is FB = 1, it is determined that the received frame is a non-fragmented frame in the determination T1, and the state transitions to state 1.

  On the other hand, when the fragment bit FB of the received frame is FB = 0, it is determined that the received frame is the fragment frame in the determination T2, and the first fragment frame (FFr1) is determined, and the state transitions to state 2. At that time, the frame distribution unit 18 searches for an unused queue among the plurality of defragmentation queues 22, selects one of them, and sends the frame to the selected defragmentation queue 22. If there is no unused defragmentation queue 22, the frame is discarded.

  In the state 2, when the fragment bit FB is FB = 0, the frame sorting unit 18 determines that the frame received in the determination T3 is an intermediate fragment frame. The frame distribution unit 18 searches the defragmentation queue 22, selects the defragmentation queue 22 that holds the fragment frame from the transmission source ONU of the fragment frame, and enters the defragmentation queue 22 that selected the frame. send. If there is no defragmentation queue 22 that holds a fragment frame from the transmission source ONU 40 of the frame, the frame is discarded. Thereafter, the state transits again to state 2.

  On the other hand, when the fragment bit FB is FB = 1 in the state 2, the frame sorting unit 18 determines that the frame received in the determination T4 is the last fragment frame. When the frame allocation unit 18 receives the last fragment frame, it searches the defragmentation queue 22 in use, selects the defragmentation queue 22 that holds the fragment frame from the transmission source ONU 40 of the frame, The frame is sent to the selected defragmentation queue 22. If there is no defragmentation queue 22 that holds a fragment frame from the transmission source ONU 40 of the frame, the frame is discarded. After that, the state transits to 1.

  The defragmentation queue 22 to which the last fragment frame has been sent outputs a transmission request to the read control unit 20. The read control unit 20 reads all the fragment frames (the first fragment frame FFr1 to the last fragment frame FFr3) from the defragmentation queue 22 where the transmission request is generated, converts them into Ether frames, and outputs them. In other words, if each of the first fragment frame (FFr1), the intermediate fragment frame (FFr2), and the last fragment frame (FFr3) is accumulated in the defragmentation queue 22, before being divided in the ONU 40 from these fragment frames. The frame (Fr6) can be restored. Here, “state 1” and “state 2” shown in FIG. 2C are configured to hold the states of “0” and “1” by storage means such as a latch circuit.

  By adopting the configuration of the defragment buffer 12 and the defragment processing described in detail above, it is only necessary to mount the number of defragmentation queues 22 required for the number of ONUs 40 as many as the number of ONUs 40 that generate fragments. Therefore, the number of defragmentation queues 22 can be reduced.

  Next, a transmission control process associated with the defragment process in the OLT 10 will be described with reference to FIG. In the defragmentation buffer 12 according to the present embodiment shown in FIG. 1, when the number of ONUs 40 that simultaneously generate fragments becomes larger than the number of defragmentation queues 22, the Ethernet frame cannot be normally transferred. Therefore, in the OLT 10 according to the present embodiment, transmission control is performed for each ONU 40 so that the number of ONUs that simultaneously generate fragments does not exceed the number of defragmentation queues 22.

  As shown in FIG. 3, the transmission control process according to the present embodiment is composed of three phases. In FIG. 3, the number of ONUs is None (m shown in FIG. 1), the number of defragmentation queues 22 is Nque (n shown in FIG. 1), and None> Nque. The transmission control process shown in FIG. 3 is executed by, for example, the OLT control unit 28, and the relationship between the defragmentation queue 22 and the ONU 40 may be determined with reference to the allocation table 26 at that time.

  Phase 1 is processing for completing the transmission of the fragment frame by the ONU 40 that is in the process of defragmenting.

  In step S10, the defragmentation queue 22 is examined to determine whether there is a defragmentation queue 22 in which fragment frames remain. If the determination is affirmative, the process proceeds to step S12. If the determination is negative, the process exits phase 1 and proceeds to phase 2 (step S22).

  In step S12, if a fragment frame remains, a bandwidth (transmission permission amount, “allocated bandwidth” according to the present invention) is assigned to the transmission source ONU 40 of the fragment frame by designating prohibition of fragmentation.

  In step S14, since the ONU 40 that prohibits the fragment is increased by 1, the counter n is incremented by 1, and the process proceeds to step S16.

  In step S16, it is determined whether n ≧ (Non-Nque). If the determination is affirmative, the number of bandwidth-allocated ONUs 40 is equal to or greater than the difference between the total number of ONUs (Nonu) and the number of defragmentation queues (Nque) (Non-Nque). Complete phase one. On the other hand, if the determination is negative, the process proceeds to step S18.

  In step S18, the defragment queue number counter i is incremented by 1, and the process proceeds to step S20.

  In step S20, it is determined whether i ≧ Nque. If the determination is negative, the process returns to step S10. If the determination is affirmative, the process proceeds to phase 2 (step S22). That is, the process of allocating a band by prohibiting fragments is repeated for the number of defragmentation queues 22.

  Phase 2 is a process of permitting a fragment and assigning a bandwidth to the ONU 40 that was previously prohibited from fragmenting. That is, in phase 2, among ONUs 40 to which no band is allocated in phase 1, ONUs 40 corresponding to the number (Nque) of defragmentation queues 22 are instructed to permit fragmentation (bandwidth allowed for transmission, that is, allocated bandwidth). ).

  In step S22, a fragment is permitted to one of the ONUs 40 to which no band is allocated and a band is allocated.

  In the next step S24, the number of ONUs 40 that permit fragmentation has increased by one, so the counter m is incremented by 1, and the flow proceeds to step S26.

  In step S26, it is determined whether m ≧ (Non-n). If the determination is affirmative, if the number of ONUs 40 to which no band is allocated in Phase 1 (Non-n) is equal to or less than Nque, that is, the allocation of bands to all ONUs 40 that permit fragmentation has been completed. This transmission control process is terminated. On the other hand, if the determination is negative, the process proceeds to step S28.

  In step S28, it is determined whether m ≧ Nque. If the determination is negative, the process returns to step S22. If the determination is positive, the process proceeds to phase 3 (step S30). That is, the process is repeated for the number of defragmentation queues 22.

  In phase 3, fragment prohibition is instructed to the ONU 40 to which no band is allocated in phase 1 and phase 2, and a band (transmission permission amount, that is, an allocated band) is allocated.

  In step S30, one of the ONUs 40 to which no band is allocated is allocated a band with fragment prohibition, and the process proceeds to step S32.

  In step S32, the number of ONUs 40 for instructing fragment prohibition and allocating a band is increased by 1. Therefore, the counter m is incremented by 1, and the process proceeds to step S34.

  In step S34, it is determined whether m ≧ (Non-n). If the determination is affirmative, the number of ONUs 40 to which bandwidth is allocated has reached the number of ONUs 40 to which bandwidth is not allocated in Phase 1 and Phase 2, and thus this transmission control process is terminated. On the other hand, if the determination is negative, the process returns to step S30, and bandwidth allocation is continued.

  By performing the above transmission control processing, it is possible to control the number of ONUs 40 in which fragments are generated simultaneously to be equal to or less than the number of defragmentation queues 22. Further, a bandwidth is allocated with the current fragment prohibition to the ONU 40 that permitted the previous fragment, and a bandwidth is allocated with the current fragment permission to the ONU 40 that prohibited the previous fragment. That is, when viewed from a certain ONU 40, fragment permission and prohibition are alternately specified, and there is an effect that fragment permission is fair among the ONUs 40.

  According to the defragmentation process and the transmission control process described in detail above, the number of ONUs 40 that simultaneously generate fragments is limited, and the number of defragmentation queues 22 that hold fragment frames is made smaller than the number of accommodated ONUs 40. be able to. Further, since the number of fragment queues is reduced, the amount of memory required for the fragment queue can be reduced.

  In the above embodiment, the embodiment in which the present invention is applied to the NG-PON2 system has been described as an example, but the present invention is not limited to this. The defragmentation processing and transmission control processing according to the present invention can be applied to a general network in which frame fragment processing is performed and communication is performed between the master device and the slave device while performing transmission control.

1 NG-PON2 system 10 OLT
12 Defragmenter buffer 13 Buffer unit 14 OSU
16 Optical receiver 18 Frame distribution unit 20 Read control unit 22, 22-1, 22-2, 22-n Defragmentation queue 24 Through queue 26 Allocation table 28 OLT control unit 30 Optical splitter 32, 32-1, 32- 2, ..., 32-m optical fiber 34 Optical fibers 40, 40-1, 40-2, ..., 40-m ONU
42 optical transmitter 44 frame generation unit DFrt fragment frame sequence FB fragment bit "
Fr Non-fragment frame FFr Fragment frame DBW Request bandwidth PBW Allocation bandwidth

Claims (12)

A station-side terminal device connected to a plurality of subscriber-side terminal devices, receiving a frame from each of the plurality of subscriber-side terminal devices and sending the frame to an upper network;
A first queue for accumulating a first frame having a predetermined frame length;
A plurality of second queues each storing a second frame obtained by dividing the first frame into a plurality of second frames corresponding to the subscriber-side terminal device; The station side termination device according to claim 1, wherein the number of the plurality of second queues is smaller than the number of the plurality of subscriber side termination devices. Of the frames transmitted from each of the plurality of subscriber-side termination devices, the first frame is distributed to the first queue, and the second-frame is transmitted to the second frame. Frame allocating means for allocating to the second queue corresponding to
Read control means for sending the first frame stored in the first queue to the upper network each time it is stored, and sending it to the upper network when each of the second frames is stored in the second queue; The station-side termination device according to claim 1, further comprising: Each of the plurality of second frames has an identifier indicating whether or not it is the last second frame among the divided frames,
When the identifier is an identifier indicating that the identifier is the last second frame among the divided frames, the read control unit can store each of the second frames and restore the state before the division. The station-side terminating device according to claim 3. A bandwidth allocation means for calculating a bandwidth to be periodically allocated to each of the plurality of subscriber-side termination devices;
A signal generation means for generating a permission signal for permitting the division for a part of the plurality of subscriber-side termination devices, and a prohibition signal for prohibiting the division for the other part of the plurality of subscriber-side termination devices;
Transmitting means for transmitting, to each of the plurality of terminal devices on the subscriber side, a band allocation signal in which either the permission signal or the prohibition signal is added to the allocation band calculated by the band allocation means; The station side termination device according to any one of claims 1 to 4. The station-side terminating device according to claim 5, wherein the number of the parts is equal to the number of the plurality of second queues. The signal generation means generates the prohibition signal this time for the subscriber-side terminating device that has permitted the division at the time of generation of the previous band allocation signal, and at the time of generation of the previous band allocation signal The station-side termination device according to claim 5 or 6, wherein the permission signal is generated this time for the subscriber-side termination device that is prohibited from being divided. Receiving means for receiving the band allocation signal from the station-side terminating device according to any one of claims 5 to 7,
When the frame to be sent to the station side terminal device exceeds the allocated band indicated by the band allocated signal,
Frame generation means for generating the second frame by performing the division when the permission signal is given to the band allocation signal and stopping the division when the prohibition signal is given And a subscriber-side terminating device. A master device that receives a frame from a slave device, wherein a first queue for storing a first frame having a predetermined frame length, and a second frame obtained by dividing the first frame into a plurality of frames A second queue to be stored corresponding to the slave device, a signal indicating an allocation band of a transmission frame for the slave device, and a band allocation signal including any of a permission signal for permitting the division and a prohibiting signal for prohibition are generated. A master device comprising a generating means;
The receiving means for receiving the band allocation signal, and when the permission signal is included in the band allocation signal, the division is performed to transmit the second frame and the prohibition signal is included. A slave device including frame generation means that does not perform the division in the case,
A communication system including: The master device is a station-side terminal device;
The slave device is a plurality of terminal devices on the subscriber side;
An optical splitter connected to the station side termination device by an optical fiber transmission line;
The communication system according to claim 9, further comprising: the plurality of subscriber-side termination devices connected to each of the plurality of optical fiber transmission lines connected to the optical splitter. A station-side terminator connected to a plurality of subscriber-side terminators and receiving frames from each of the plurality of subscriber-side terminators and sending it to a higher-level network, storing a first frame having a predetermined frame length And a plurality of second queues each storing a second frame obtained by dividing the first frame into a plurality of second queues corresponding to the subscriber-side terminal device. A program for controlling a device,
Computer
Of the frames transmitted from each of the plurality of subscriber-side termination devices, the first frame is distributed to the first queue, and the second-frame is transmitted to the second frame. Frame allocating means for allocating to the second queue corresponding to
Read control means for sending the first frame stored in the first queue to the upper network every time it is stored, and sending it to the upper network when each of the second frames is stored in the second queue When,
Station side program to function as A subscriber-side program of a subscriber-side termination device that is connected to a station-side termination device and transmits a frame to the station-side termination device, and a computer mounted on the subscriber-side termination device,
Receiving means for receiving a band allocation signal for transmitting the frame from the station-side terminal device;
When the frame to be transmitted to the terminal device on the station side exceeds the allocated band indicated by the band allocation signal, the division is performed when the band allocation signal is given a permission signal for permitting the division of the frame. A frame generating means for transmitting the divided frame and not performing the division when a prohibition signal for prohibiting the division of the frame is given,
As a subscriber-side program.