JP2013110469A - Network reception device and reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct a communication system that is not strictly required for timing of redundant switching at a network side in a communication system having a redundant configuration and to make a device low in cost.SOLUTION: A network reception device is provided at each of redundant communication paths, and includes buffers 26, 27 for storing communication signals received from the communication paths and an extraction unit 51 for taking out the communication signals from the buffers 26, 27. A resource provided for the communication signals taken out by the extraction unit 51 is restricted to being shared by the communication signals taken out from the plurality of buffers 26, 27. The extraction unit 51 sets a preferential buffer, which should take priority, on the basis of at least one of the state of switching of the communication path and the state of the buffers 26, 27, and performs taking out the communication signal from the preferential buffer faster compared to taking out the communication signal from the subordinate buffer.

Description

  The present invention relates to a network receiving apparatus and a receiving method, and more particularly, to a network receiving apparatus and a receiving method for receiving a communication signal via a redundant communication path.

  In recent years, the Internet has become widespread, and users can access various information on sites operated in various parts of the world and obtain the information. Along with this, devices capable of broadband access such as ADSL (Asymmetric Digital Subscriber Line) and FTTH (Fiber To The Home) are rapidly spreading.

  In IEEE Std 802.3ah (registered trademark) -2004 (non-patent document 1), a plurality of home side devices (ONU: Optical Network Unit) share an optical communication line, and a station side device (OLT: Optical Line Terminal). One method of a passive optical network (PON), which is a medium-sharing communication that performs data transmission with the network, is disclosed. That is, EPON (Ethernet (registered trademark) PON) in which all information is communicated in the form of an Ethernet (registered trademark) frame, including user information passing through the PON and control information for managing and operating the PON, and EPON An access control protocol (MPCP (Multi-Point Control Protocol)) and an OAM (Operations Administration and Maintenance) protocol are defined. By exchanging MPCP frames between the station side device and the home side device, the home side device joins and leaves, and uplink access multiplexing control is performed. Non-Patent Document 1 describes a registration method for a new home device, a report indicating a bandwidth allocation request, and a gate indicating a transmission instruction using an MPCP message.

  In addition, IEEE 802.3av (registered trademark) -2009 is standardized as the next generation technology of GE-PON (Giga Bit Ethernet (registered trademark) Passive Optical Network), which is an EPON realizing a communication speed of 1 gigabit / second. Even in the 10 G-EPON, that is, the EPON corresponding to a communication speed of 10 gigabits / second, the access control protocol is premised on MPCP.

  By the way, in general, in a network service for business, in order to provide a high quality service, it is essential to make a system redundant (redundant). Also, a highly reliable system can be provided by using a duplex system in an audio / video distribution service. In the redundant system, a redundant configuration is adopted in which each of the devices, components, and network has an active system and a standby system as required. When a failure occurs in a part of the operating system, it is possible to make the system stop time due to the failure as short as possible by performing redundant switching from the active system to the standby system.

  Even if a failure has not become apparent, the module may be replaced proactively in consideration of the deterioration tendency of characteristics, the life of parts, and the like. If the system has a redundant configuration for the module, it is possible to shorten the system stop time due to such maintenance work as much as possible.

  Here, a PON system in which a service node interface (SNI) between a station-side device and a host network is duplicated is being studied. As an example of such a PON system, for example, Japanese Unexamined Patent Application Publication No. 2009-284179 (Patent Document 1) discloses the following technique. In other words, the optical access termination device includes a plurality of optical transmission / reception means for mutually converting electrical signals and optical signals, a plurality of PON protocol termination means for inserting and extracting PON control protocol information, and a plurality for connection to a higher level network. Service node interface. The optical access termination device further includes link monitoring means for monitoring normality / abnormality of communication related to the plurality of service node interfaces. A first electric circuit is disposed in an upstream signal path between the plurality of optical transmission / reception means and the plurality of PON protocol termination means. When the communication related to the plurality of service node interfaces is normal, the first electric circuit outputs an upstream signal input from each optical transmission / reception means to the PON protocol termination means corresponding to the optical transmission / reception means. . The first electrical circuit corresponds to an upstream signal input from an optical transmission / reception unit corresponding to an abnormal side and a normal side when communication related to any of the plurality of service node interfaces becomes abnormal. One of the uplink signals input from the optical transmission / reception means is dynamically selected and output to the PON protocol termination means corresponding to the normal side. In the first electric circuit, an upstream signal is temporarily stored in a buffer provided for each optical transmission / reception means, and then output to any PON protocol termination means.

IEEE Std 802.3ah (registered trademark) -2004

JP 2009-284179 A

  In a PON system in which SNI is made redundant, a station apparatus that receives a downstream frame from an upper network needs to be provided with a memory for temporarily storing the downstream frame before transmission to the PON line. . Since such a memory is normally required to have a large capacity, a common memory is provided in each SNI from the viewpoint of cost reduction.

  Here, in the device on the higher-level network side that transmits the downlink frame to the station-side device, it is difficult for the redundant switching source transmission unit and the redundant switching destination transmission unit to completely stop and stop operation. is there. For this reason, when switching the SNI for some reason, there is a moment when the station side apparatus simultaneously receives a downlink frame from the switching source SNI and the switching destination SNI, and the communication speed of the downlink frame to the station side apparatus is instantaneously normal. There are times when it becomes twice the time. For this reason, in the configuration in which a common memory is provided in each SNI as described above, a downlink frame may be lost.

  In addition, when the transmission time of the downstream frame from the higher level network after the redundant switching to the station side device becomes shorter than before the redundant switching, the downstream frame passing through the switching destination SNI is more than the downstream frame passing through the switching source SNI. May arrive at the station-side device first, resulting in overtaking of the downstream frame.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to construct a communication system that does not strictly require the timing of redundant switching on the network side in a communication system having a redundant configuration, and It is an object of the present invention to provide a network receiving apparatus and a receiving method capable of reducing the cost of the apparatus.

  In order to solve the above problems, a network receiver according to an aspect of the present invention is a network receiver capable of receiving a communication signal via a plurality of redundant communication paths, and is provided for each of the communication paths. A plurality of buffers for accumulating communication signals received from the communication path, and an extraction unit for extracting the communication signals from the buffer, provided for the communication signals extracted by the extraction unit. There is a restriction that the allocated resource is shared among the communication signals extracted from the plurality of buffers, and the extraction unit should give priority based on at least one of the switching state of the communication path and the state of the buffer. In addition to setting a priority buffer that is the buffer, taking out the communication signal from the priority buffer is inferior. Performed faster than the removal of the communication signal from the buffer.

  With such a configuration, it is possible to construct a system that allows a certain level of redundancy switching timing on the network side at a low cost. That is, even when the switching timing of the communication path cannot be strictly controlled between the higher-level devices of the station side device, the redundant switching can be performed without causing a communication signal loss. In addition, the communication signal can be received from any communication path, and the communication signal is received after the communication path to be prioritized is determined, so that redundant switching can be performed without prior notification for the occurrence of an abnormality. Even in such a case, the communication signal can be received via the inferior standby communication path. That is, even after the communication path is switched, the communication signal can be received via the switching source communication path. Thereby, the loss of communication signals can be minimized. Further, it is possible to perform redundant switching without causing communication signal loss without performing strict handshaking with the host device in order to switch the communication path in the network reception device. Therefore, in a communication system having a redundant configuration, it is possible to construct a communication system in which the timing of redundant switching on the network side is not strictly required, and to reduce the cost of the apparatus.

  Preferably, the extraction unit sets the buffer corresponding to the communication path to be switched as a priority buffer.

  With such a configuration, an appropriate buffer can be set as a priority buffer according to the switching state of the communication path.

  More preferably, the take-out unit is configured such that the state of the buffer corresponding to the switching source communication path satisfies a predetermined condition, and the state of the buffer corresponding to the switching destination communication path satisfies a predetermined condition. At least one of them is set as the priority buffer setting condition.

  With such a configuration, in addition to the switching state of the communication path, a more appropriate buffer can be set as a priority buffer according to the state of the switching source buffer or the switching destination buffer.

  More preferably, the take-out unit indicates that the accumulated amount of the buffer corresponding to the switching destination communication path is larger than the accumulated amount of the buffer corresponding to the switching source communication path. This is the setting condition.

  With such a configuration, a more appropriate buffer can be set as a priority buffer according to the comparison result of the accumulation amount of the switching source buffer and the accumulation amount of the switching destination buffer.

  More preferably, the extraction unit sets the priority buffer as a condition for setting the free capacity of the buffer corresponding to the switching destination communication path to be less than a predetermined value.

  With such a configuration, the communication signal can be extracted from the switching source buffer as much as possible in a state where the free space of the switching destination buffer is secured, so that the loss of the communication signal can be minimized.

  Preferably, the extraction unit sets the priority buffer based on an accumulation amount or a free capacity of the buffer.

  With such a configuration, even when a communication path switching command cannot be received for some reason, an appropriate buffer can be set as a priority buffer based on the state of the buffer, and communication signal loss can be minimized.

  More preferably, the extraction unit sets the buffer having an accumulation amount equal to or larger than a predetermined value as the priority buffer.

  With such a configuration, an appropriate buffer can be set as a priority buffer according to the accumulation amount of each buffer.

  Preferably, the resource is a memory for temporarily storing the communication signal before the communication signal is transmitted to another device or processed by the network reception device. The communication signal fetched from is stored in the memory.

  With such a configuration, the capacity of the memory for storing communication signals can be reduced, so that the cost of the apparatus can be reduced.

  Preferably, the extraction unit continuously extracts the communication signal from the priority buffer until the communication signal disappears from the priority buffer.

  With such a configuration, it is possible to increase the speed of extracting the communication signal from the priority buffer.

  In order to solve the above problems, a receiving method according to an aspect of the present invention is capable of receiving a communication signal through a plurality of redundant communication paths, provided for each of the communication paths, and from the communication path. A reception method in a network reception device including a plurality of buffers for storing received communication signals, wherein priority is given to the buffer to be prioritized based on at least one of the switching state of the communication path and the state of the buffer Including a step of setting a buffer and a step of extracting the communication signal from the buffer, and a resource provided for the communication signal extracted from the buffer is between the communication signals extracted from the plurality of buffers. In the step of extracting the communication signal, there is a restriction shared by the priority buffer. The extraction of the serial communication signals, at high speed as compared with taking out subordinated to the communication signal from the buffer.

  With such a configuration, it is possible to construct a system that allows a certain level of redundancy switching timing on the network side at a low cost. That is, even when the switching timing of the communication path cannot be strictly controlled between the higher-level devices of the station side device, the redundant switching can be performed without causing a communication signal loss. In addition, the communication signal can be received from any communication path, and the communication signal is received after the communication path to be prioritized is determined, so that redundant switching can be performed without prior notification for the occurrence of an abnormality. Even in such a case, the communication signal can be received via the inferior standby communication path. That is, even after the communication path is switched, the communication signal can be received via the switching source communication path. Thereby, the loss of communication signals can be minimized. Further, it is possible to perform redundant switching without causing communication signal loss without performing strict handshaking with the host device in order to switch the communication path in the network reception device. Therefore, in a communication system having a redundant configuration, it is possible to construct a communication system in which the timing of redundant switching on the network side is not strictly required, and to reduce the cost of the apparatus.

  According to the present invention, in a communication system having a redundant configuration, it is possible to construct a communication system in which the timing of redundant switching on the network side is not strictly required, and to reduce the cost of the apparatus.

It is a figure which shows schematic structure of the PON system which concerns on embodiment of this invention. It is a figure which shows the structure of the concentrating part in the station side apparatus which concerns on embodiment of this invention. It is a figure which shows the structure of OSU in the station side apparatus which concerns on embodiment of this invention. It is a flowchart which shows the operation | movement procedure at the time of OSU which switches the SNI port which concerns on embodiment of this invention. It is a figure which shows an example of the switching conditions of the priority buffer in OSU which concerns on embodiment of this invention. It is a figure which shows an example of the switching conditions of the priority buffer in OSU which concerns on embodiment of this invention. It is a figure which shows an example of the switching conditions of the priority buffer in OSU which concerns on embodiment of this invention. It is a figure which shows an example of the switching operation | movement of a SNI port in the OSU which concerns on embodiment of this invention, and the reception operation | movement of a downstream frame. It is a flowchart which shows the operation | movement procedure at the time of OSU which switches the SNI port which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Configuration and basic operation]
FIG. 1 is a diagram showing a schematic configuration of a PON system according to an embodiment of the present invention.

  Referring to FIG. 1, a PON system 301 includes a station side device (network receiving device) 201, m PON lines 1 to m (203-1 to 203-m) that are optical fibers, and m light beams. Couplers 204-1 to 204-m and a plurality of home units (ONUs) 202 are provided. The station apparatus 201 includes optical line units (hereinafter also referred to as OSUs (Optical Subscriber Units)) 1 to m (12-1 to 12-m) and a concentrator 11. Here, m is an integer of 1 or more. Further, the direction from the ONU to the upper network is referred to as an upstream direction, and the direction from the upper network to the ONU is referred to as a downstream direction.

  In the PON system 301, for example, each PON line corresponds to GE-PON, which is an EPON that realizes a communication speed of 1 gigabit / second, and 10G-EPON, which is an EPON that realizes a communication speed of 10 gigabit / second. The upper network corresponds to Ethernet (registered trademark) that realizes a communication speed of 10 gigabits / second. Also, for example, ONU registration, withdrawal, bandwidth allocation to the ONU, bandwidth request from the ONU, communication speed switching instruction, and sleep (operation stop) instruction to the ONU are performed by the MPCP frame.

  The station apparatus 201 accommodates a plurality of PON lines corresponding to GE-PON and 10G-EPON. One or a plurality of ONUs are connected to one PON line. The station-side apparatus 201 multiplexes data from these PON lines to the upper network. Further, the station-side device 201 distributes data from the upper network and transmits it to each ONU in each PON line. Further, the station side device 201 allocates the upstream band of the PON line to each ONU.

  More specifically, the station-side apparatus 201 is connected to m PON lines 1 to m, and terminates the m PON lines. Each OSU is provided corresponding to a PON line, and transmits / receives a communication signal including a frame to one or a plurality of ONUs connected to the corresponding PON line. The PON lines 1 to m are connected to the optical couplers 204-1 to 204-m, and are connected to the ONUs 202 through these optical couplers. Each ONU 202 and OSU 12 are connected via a PON line 203 and an optical coupler 204, and transmit / receive optical signals as communication signals to / from each other. In the PON system 301, optical signals from each ONU 202 to the OSU 12 are time-division multiplexed on a common PON line 203.

  The line concentrator 11 transmits the downstream frame received from the upper network to each ONU via a plurality of OSUs. Specifically, the concentrator 11 performs a process of distributing the downstream frame from the upper network to an appropriate OSU. Further, the line concentrator 11 transmits the upstream frame received from each ONU via a plurality of OSUs to the upper network.

  In the station apparatus 201, the SNI is multiplexed. That is, a plurality of SNIs are provided for each OSU for redundancy.

  More specifically, the OSU 12 can transmit / receive a frame to / from one or a plurality of ONUs 202, and can transmit a downlink frame received from the concentrator 11 to the ONU 202 via a plurality of redundant communication paths, that is, SNI ports. The upstream frame received from each ONU 202 can be transmitted to the concentrator 11 via a plurality of SNI ports.

  In addition, the OSU 12 includes a buffer provided for each SNI for accumulating downlink frames received from the upper network.

  FIG. 2 is a diagram showing the configuration of the concentrator in the station side apparatus according to the embodiment of the present invention.

  Referring to FIG. 2, the concentrating unit 11 includes switch units 41 and 42.

  The switch unit 41 switches whether to output the downlink frame received from the upper network to the SNI port A (SNI-A) or to output to the SNI port B (SNI-B) via the switch unit 42.

  The switch unit 42 switches whether to output the downlink frame received from the upper network to the SNI port B (SNI-B) or to output to the SNI port A (SNI-A) via the switch unit 41.

  For example, when SNI port A is the active system and SNI port B is the standby system, the downstream frame received by switch unit 41 is output to SNI port A, and the downstream frame received by switch unit 42 is the switch unit. 41 to the SNI port A. On the other hand, when the SNI port B is the active system and the SNI port A is the standby system, the downlink frame received by the switch unit 42 is output to the SNI port B, and the downlink frame received by the switch unit 41 is the switch unit. 42 to the SNI port B.

  Here, when the active system is switched from SNI port B to SNI port A, for example, the downstream frame received by the switch unit 41 is transmitted to the SNI port B through the route RT2 before switching, but after switching. Is transmitted to SNI port A through path RT1. Then, the transmission time of the downlink frame before switching includes the internal delay of the switch unit 42, but the transmission time of the downlink frame after switching does not include the internal delay of the switch unit 42.

  As a result, the downlink frame from the switching destination SNI arrives at the OSU 12 before the downlink frame from the switching source SNI, and the downlink frame may be overtaken.

  Further, even when the switch unit 41 and the switch unit 42 are completely synchronized and stopped and started, there is a case where the overtaking of the downstream frame may occur due to the difference in the transmission delay of the downstream frame as described above. is there.

  Note that the switching of the SNI port is performed due to various factors as described above, for example, a failure in the upstream direction, maintenance work, and the like.

  FIG. 3 is a diagram showing the configuration of the OSU in the station side apparatus according to the embodiment of the present invention.

  Referring to FIG. 3, OSU 12 includes a 1 GPON transmission / reception unit 21, a 10 GPON transmission / reception unit 22, an extraction unit 51, buffers 26 and 27, MAC (Media Access Control) processing units 28 and 29, and an SNI-A interface. Part 30 and SNI-B interface part 31. The extraction unit 51 includes a buffer control unit 23, a quality of service (QOS) unit 24, a multiplexer (MUX) 25, and a control unit 32. In addition, the station side device 201 includes a memory 91 provided outside the OSU 12. Here, the OSU 12 includes two SNI interface units, but the number of SNI interface units may be three or more. Further, the memory 91 may be provided inside the OSU 12.

  The 1 GPON transmission / reception unit 21 and the 10 GPON transmission / reception unit 22 are connected to one optical fiber which is a corresponding PON line as a master station side starting point of the PON line. The 1GPON transmission / reception unit 21 and the 10GPON transmission / reception unit 22 receive an upstream optical signal of a specific wavelength, for example, a 1310 nm band, and receive an electrical signal of 1 Gbps or 10 Gbps so that bidirectional communication can be performed with each ONU via this optical fiber. And the downstream frame is converted into a downstream optical signal of another wavelength. For example, the 1GPON transmission / reception unit 21 converts the frame received from the buffer control unit 23 into an electrical signal of 1 Gbps, and converts it into a downstream optical signal in the 1490 nm band. Further, the 10GPON transmission / reception unit 22 converts the frame received from the buffer control unit 23 into an electrical signal of 10 Gbps, and converts it into a downstream optical signal in the 1570 nm band.

  In the OSU 12, a buffer for accumulating downlink frames received from the upper network is provided for each SNI port. For example, the OSU 12 includes two buffers 26 and 27 provided for each of two SNI ports, that is, SNI interface units. The buffers 26 and 27 are, for example, FIFO (First in First Out).

  The line concentrator 11 performs predetermined communication processing with other devices in the upper network, distributes the downstream frames received from the upper network, and outputs them to the SNI-A interface unit 30 or the SNI-B interface unit 31.

  The SNI-A interface unit 30 and the SNI-B interface unit 31 perform predetermined communication processing with the line concentrator 11 to output the downlink frames received from the line concentrator 11 to the MAC processor 28 and the MAC processor 29, respectively. .

  The MAC processing unit 28 and the MAC processing unit 29 perform MAC layer processing on the downstream frames received from the SNI-A interface unit 30 and the SNI-B interface unit 31, respectively, and process the processed frames into the buffer 26 and the buffer 27. Accumulate in each.

  The extraction unit 51 extracts the downstream frame from the buffers 26 and 27. Here, in the OSU 12, the resources provided for the downlink frame extracted by the extraction unit 51 are limited to be shared between the downlink frames extracted from the buffers 26 and 27.

  Specifically, for example, the resource is a memory for temporarily storing a downstream frame before transmitting the downstream frame to the ONU 202 or processing the OSU 12.

  The extracting unit 51 stores the downstream frame extracted from each buffer in the memory. The extraction unit 51 intensively extracts downlink frames from the priority buffer, that is, continuously extracts downlink frames from the priority buffer until there are no more downlink frames from the priority buffer.

  More specifically, in the extraction unit 51, the control unit 32 sets one of the buffer 26 and the buffer 27 as a priority buffer, and notifies the multiplexer 25 of the setting content. The multiplexer 25 extracts the downstream frame from the buffer 26 and the buffer 27 in accordance with the setting contents notified from the control unit 32 and outputs it to the QOS unit 24. For example, when the downlink frames are accumulated in the priority buffer, the multiplexer 25 continuously extracts the downlink frames from the priority buffer without accessing the inferior buffer. When the priority buffer becomes empty, the multiplexer 25 accesses the inferior buffer, extracts the downstream frame stored in the inferior buffer, and accesses the priority buffer to check whether the downstream frame is newly stored. To do.

  The QOS unit 24 analyzes the downstream frame received from the multiplexer 25, and outputs the analysis result and the downstream frame.

  Based on the analysis result of the QOS unit 24, the buffer control unit 23 stores the downstream frame in the ONU 202 and the priority area set in the memory 91. When the transmission timing is reached, the buffer control unit 23 extracts the downstream frame from the memory 91 and outputs 1GPPON. The data is output to the transmission / reception unit 21 or the 10 GPON transmission / reception unit 22. The downlink frame extracted from the memory 91 by the buffer control unit 23 may be processed by the control unit 32, for example.

  The 1 GPON transmission / reception unit 21 and the 10 GPON transmission / reception unit 22 convert the downstream frame received from the buffer control unit 23 into an optical signal as described above and output the optical signal to the PON line.

  The control unit 32 performs station-side processing relating to control and management of the PON line such as MPCP and OAM. That is, by exchanging MPCP messages and OAM messages with each ONU connected to the PON line, ONU operation including upstream access control including ONU registration, withdrawal and bandwidth allocation, and sleep instruction to the ONU Perform management. The control unit 32 outputs a control frame including various control messages such as an MPCP gate frame to the 1 GPON transmission / reception unit 21 and the 10 GPON transmission / reception unit 22.

  The control unit 32 monitors the usage state such as the storage amount and free capacity of the buffers 26 and 27. For example, the control unit 32 sets the priority buffer by analyzing the switching command received from the concentrator 11 and determining the SNI port to be used.

  As described above, the OSU 12 can set an arbitrary buffer as a priority buffer in accordance with, for example, a switching instruction from the concentrator 11. Note that the switching command from the concentrator 11 may be generated in the concentrator 11 or may be generated in another device in the upper network.

[Operation]
Next, downlink frame reception operation in the OSU according to the embodiment of the present invention will be described with reference to the drawings.

  FIG. 4 is a flowchart showing an operation procedure when the OSU according to the embodiment of the present invention switches the SNI port. FIG. 4 shows an example in which the priority buffer is switched from the buffer 26 to the buffer 27.

  The extraction unit 51 sets a priority buffer that is a buffer to be prioritized based on at least one of the SNI port switching state and the buffer state. For example, the extraction unit 51 sets a buffer corresponding to the switching destination SNI port as a priority buffer. Then, as described above, the extraction unit 51 extracts the downstream frame from the priority buffer at a higher speed than the downstream frame extraction from the inferior buffer.

  Specifically, referring to FIG. 4, first, consider a state where SNI port A is the active system and SNI port B is the standby system. In this state, the control unit 32 sets the buffer 26 corresponding to the SNI-A interface unit 30 as a priority buffer. That is, the multiplexer 25 continuously retrieves the downstream frames from the buffer 26 when the downstream frames are accumulated in the buffer 26, and retrieves the downstream frames from the buffer 27 when the downstream frames are not accumulated in the buffer 26. Take out (step S1).

  Next, when receiving a switching instruction from the concentrator 11 to the SNI port B (YES in step S2), the controller 32 checks the states of the buffers 26 and 27 (step S3).

  The control unit 32 waits until the buffers 26 and 27 satisfy the predetermined condition. When the buffers 26 and 27 satisfy the predetermined condition (YES in step S3), the control unit 32 switches the priority buffer from the buffer 26 to the buffer 27. That is, the control unit 32 sets the buffer 27 corresponding to the SNI-B interface unit 31 as a priority buffer. The multiplexer 25 continuously extracts the downlink frames from the buffer 27 when the downlink frames are accumulated in the buffer 27, and extracts the downlink frames from the buffer 26 when the downlink frames are not accumulated in the buffer 27 ( Step S4).

  For example, the take-out unit 51 determines whether the state of the buffer corresponding to the switching source SNI port satisfies the predetermined condition and the state of the buffer corresponding to the switching destination SNI port satisfies the predetermined condition. This is the setting condition.

  Hereinafter, a specific example of the predetermined condition will be described.

  FIG. 5 is a diagram showing an example of priority buffer switching conditions in the OSU according to the embodiment of the present invention. In FIG. 5 to FIG. 7 below, F indicates a downstream frame.

  Referring to FIG. 5, the extraction unit 51 determines that the buffer storage amount corresponding to the switching destination SNI port is larger than the buffer storage amount corresponding to the switching source SNI port. The conditions are as follows.

  Specifically, the control unit 32 receives the switching command from the concentrating unit 11 to the SNI port B in the state where the buffer 26 is set as the priority buffer, and then compares the buffer 27 with the number of frames stored in the buffer 26. When the number of stored frames increases, the buffer 27 is set as a priority buffer.

  FIG. 6 is a diagram showing an example of priority buffer switching conditions in the OSU according to the embodiment of the present invention.

  Referring to FIG. 6, the extraction unit 51 sets the priority buffer setting condition that the free space of the buffer corresponding to the switching destination SNI port is less than a predetermined value.

  Specifically, the control unit 32 receives the switching command from the concentrating unit 11 to the SNI port B in the state where the buffer 26 is set as the priority buffer, and then the free capacity of the buffer 27 is less than the predetermined threshold Th1. Then, the buffer 27 is set as a priority buffer.

  Note that FIG. 6 can be considered as the following operation. That is, when the control unit 32 receives the switching command from the concentrating unit 11 to the SNI port B in a state where the buffer 26 is set as the priority buffer, and the accumulated amount of the buffer 27 becomes a predetermined threshold Th1 or more, The buffer 27 is set as a priority buffer.

  FIG. 7 is a diagram showing an example of priority buffer switching conditions in the OSU according to the embodiment of the present invention.

  Referring to FIG. 7, control unit 32 may add the following conditions in parallel with the conditions described in FIG. 6.

  That is, the control unit 32 sets the priority buffer setting condition that the number of accumulated frames in the buffer corresponding to the SNI port before switching becomes zero.

  Specifically, when the control unit 32 receives the switching command from the concentrating unit 11 to the SNI port B in the state where the buffer 26 is set as the priority buffer, the buffer 27 becomes empty when the buffer 26 becomes empty. Even if the capacity is not less than the predetermined threshold Th1, the buffer 27 is set as a priority buffer.

  FIG. 8 is a diagram showing an example of SNI port switching processing and downlink frame reception operation in the OSU according to the embodiment of the present invention.

  Referring to FIG. 8, a state is considered in which SNI port A is the active system and SNI port B is the standby system. In this state, the control unit 32 sets the buffer 26 corresponding to the SNI-A interface unit 30 as a priority buffer.

  Here, at the timing T1, switching of the SNI port is determined in the host network or the concentrator 11.

  Next, at timing T <b> 2, the control unit 32 receives a switching command from the concentrator 11 to the SNI port B. Thereby, the control part 32 sets the buffer 27 corresponding to the SNI-B interface part 31 as a priority buffer, when the buffers 26 and 27 satisfy | fill the predetermined condition. At this timing T2, the downstream frame is continuously transmitted from the concentrator 11 to the SNI port A, and the downstream frame is not yet transmitted from the concentrator 11 to the SNI port B. Therefore, the multiplexer 25 takes out the downstream frame from the buffer 26 because the buffer 27 is empty.

  Next, the concentrator 11 switches the SNI port that is the transmission destination of the downstream frame.

  Here, consider a case 1 in which a downstream frame starts to arrive at the SNI-B interface unit 31 after the downstream frame is not transmitted to the SNI-A interface unit 30.

  In Case 1, after the time k has elapsed since the 4th frame that is the last downlink frame to the SNI port A arrives at the SNI-A interface unit 30, the 5th frame that is the next frame after the 4th frame. Frame arrives at the SNI-B interface unit 31.

  In this case, the multiplexer 25 can extract the fifth and subsequent frames stored in the buffer 27 without any problem after extracting the fourth frame from the buffer 26.

  Therefore, in Case 1, the OSU 12 can correctly receive continuous downlink frames before and after switching of the SNI port. That is, the OSU 12 does not perform a downlink frame reception path, that is, SNI switching processing in a short period from when the fourth frame arrives at the SNI-A interface unit 30 until time k elapses. Can be received correctly.

  Next, consider a case 2 in which a downstream frame starts to arrive at the SNI-B interface unit 31 before the downstream frame is not transmitted to the SNI-A interface unit 30.

  In Case 2, before the 4th frame that is the last downlink frame to the SNI port A arrives at the SNI-A interface unit 30, the 5th frame that is the next frame of the 4th frame is SNI-B. Arrives at the interface unit 31.

  In this case, the multiplexer 25 takes out the fifth and subsequent frames accumulated in the buffer 27 before taking out the fourth frame from the buffer 26. Here, the multiplexer 25 can extract the downstream frame from the buffers 26 and 27 at a speed somewhat higher than the communication speed of the downstream frame. For this reason, the multiplexer 25 can extract the fourth frame from the buffer 26 between the extraction of the downstream frames from the buffer 27. Also, after the SNI port of the downlink frame transmission destination is switched in the concentrator 11, only a few frames remain in the buffer 26. In this example, only one frame remains. Does not occur, and there is no loss of downstream frames.

  Note that the control unit 32 is not limited to the configuration in which the priority buffer is set based on the switching command from the concentrator 11, and may be configured to autonomously select the priority buffer according to the state of the buffer.

  For example, the extraction unit 51 sets a priority buffer based on the accumulation amount or free space of the buffers 26 and 27.

  FIG. 9 is a flowchart showing an operation procedure when the OSU according to the embodiment of the present invention switches the SNI port.

  Referring to FIG. 9, control unit 32 periodically checks the states of buffers 26 and 27, for example (step S11), and when buffers 26 and 27 satisfy predetermined condition A (YES in step S12), 26 is set as a priority buffer (step S13).

  On the other hand, when the buffers 26 and 27 do not satisfy the predetermined condition A (NO in step S12) and satisfy the predetermined condition B (YES in step S14), the control unit 32 sets the buffer 27 as a priority buffer. (Step S15).

  If the buffers 26 and 27 do not satisfy the predetermined condition A (NO in step S12) and do not satisfy the predetermined condition B (NO in step S14), the control unit 32 sets the current priority buffer. To maintain.

  As a specific example of the predetermined condition illustrated in FIG. 9, for example, the extraction unit 51 sets a buffer having an accumulation amount equal to or greater than a predetermined value as a priority buffer. In this case, the conditions A and B shown in FIG. 9 are the same conditions.

  Note that the control unit 32 may use the same buffer state conditions as those described with reference to FIGS. 5 to 7 as the priority buffer switching conditions in FIG. 9.

  By the way, in the PON system in which the SNI is made redundant, when the SNI is switched for some reason, the station side device that receives the downstream frame from the upper network simultaneously transmits the downstream frame from the switching source SNI and the switching destination SNI. There is a moment of reception, and the communication speed of the downstream frame to the station side device may be instantaneously twice as fast as normal. For this reason, in a configuration in which a common memory is provided in each SNI, there is a possibility that a downlink frame may be lost. In addition, when the transmission time of the downstream frame from the higher level network after the redundant switching to the station side device becomes shorter than before the redundant switching, the downstream frame passing through the switching destination SNI is more than the downstream frame passing through the switching source SNI. May arrive at the station-side device first, resulting in overtaking of the downstream frame.

  Specifically, the OSU includes, for example, 10G-EPON and GE-PON interfaces. The rates of these interfaces are, for example, 9.7 Gbps and 1 Gbps, respectively. For this reason, the OSU only needs to be able to receive a 10 Gbps downstream frame via the SNI.

  However, for example, in a configuration in which an OSU has two SNIs for redundancy and two SNIs for 10 Gbps are provided, a frame of 20 Gbps may be instantaneously received as described above.

  In the station side device, for example, the input rate of data from the host network is 10 Gbps to 20 Gbps, while the output rate can be ensured only up to 9.7 Gbps, for example. For this reason, in order to provide the QOS function in the downlink direction in the station side device, it is necessary to buffer the downlink frame using a large-capacity external memory. As this buffering storage device, for example, an inexpensive DDR (Double Data Rate) memory is used.

  However, in such a configuration, it is very difficult to realize a memory controller with an input rate of 20 Gbps and an output rate of 9.7 Gbps from the viewpoint of cost.

  On the other hand, the OSU according to the embodiment of the present invention can receive a downstream frame via a plurality of redundant communication paths, that is, SNI ports. In this OSU, buffers 26 and 27 are provided for each SNI port, and accumulate downstream frames received from the SNI port. The extraction unit 51 extracts the downstream frame from the buffers 26 and 27. The resource provided for the downlink frame extracted by the extraction unit 51 has a restriction of being shared between the downlink frames extracted from the buffers 26 and 27. Then, the extraction unit 51 sets a priority buffer which is a buffer to be prioritized based on at least one of the SNI port switching state and the buffer state, and extracts the downstream frame from the priority buffer from the subordinate buffer. This is performed faster than the downstream frame extraction.

  Specifically, in the OSU, a downstream frame can be received from any SNI port between the SNI interface units 30 and 31 and the buffer control unit 23 and can be output to the buffer control unit 23. Control to prioritize receiving downstream frames from ports.

  With such a configuration, it is possible to construct at low cost a system in which the switch in the concentrator and the redundant switching timing in the host device in the concentrator are allowed to some extent. That is, even when the switching timing of the SNI port cannot be strictly controlled between the higher-level devices of the station side device, the redundant switching can be performed without causing the loss of the downlink frame.

  Also, when a frame can be received after determining the SNI port to be prioritized from any SNI port, and redundant switching is performed without prior notification due to occurrence of an abnormality. However, it is possible to receive the downstream frame via the subordinate standby SNI port. That is, even after switching the SNI port, it is possible to receive a downlink frame via the switching source SNI port. Thereby, the loss | deletion of a downstream frame can be suppressed to the minimum.

  Further, it is possible to perform redundant switching without causing loss of downstream frames without performing strict handshaking with the host device in order to switch the SNI port in the OSU.

  Therefore, in the OSU according to the embodiment of the present invention, in a communication system having a redundant configuration, a communication system in which the timing of redundant switching on the network side is not strictly required is constructed, and the cost of the apparatus is reduced. Can do.

  Further, in the OSU according to the embodiment of the present invention, the extraction unit 51 sets a buffer corresponding to the switching destination SNI port as a priority buffer.

  With such a configuration, an appropriate buffer can be set as a priority buffer according to the switching state of the communication path.

  Further, in the OSU according to the embodiment of the present invention, the extraction unit 51 satisfies that the state of the buffer corresponding to the switching source SNI port satisfies the predetermined condition, and the state of the buffer corresponding to the switching destination SNI port is predetermined. At least one of the conditions is set as a priority buffer setting condition.

  With such a configuration, in addition to the switching state of the communication path, a more appropriate buffer can be set as a priority buffer according to the state of the switching source buffer or the switching destination buffer.

  In the OSU according to the embodiment of the present invention, the extraction unit 51 has a larger buffer accumulation amount corresponding to the switching destination SNI port than the buffer accumulation amount corresponding to the switching source SNI port. Is a condition for setting the priority buffer.

  With such a configuration, a more appropriate buffer can be set as a priority buffer according to the comparison result of the accumulation amount of the switching source buffer and the accumulation amount of the switching destination buffer.

  Further, in the OSU according to the embodiment of the present invention, the extraction unit 51 sets the priority buffer setting condition that the free space of the buffer corresponding to the switching destination SNI port is less than a predetermined value.

  With such a configuration, it is possible to extract the downstream frame from the switching source buffer as much as possible in a state where the free space of the switching destination buffer is ensured, so that the loss of the downstream frame can be minimized.

  In the OSU according to the embodiment of the present invention, the extraction unit 51 sets a priority buffer based on the accumulation amount or free capacity of the buffers 26 and 27.

  With such a configuration, even when a communication path switching command cannot be received for some reason, an appropriate buffer can be set as a priority buffer based on the state of the buffer, and loss of downlink frames can be minimized.

  Further, in the OSU according to the embodiment of the present invention, the extraction unit 51 sets a buffer whose accumulated amount is a predetermined value or more as a priority buffer.

  With such a configuration, an appropriate buffer can be set as a priority buffer according to the accumulation amount of each buffer.

  Further, in the OSU according to the embodiment of the present invention, the resource is a memory for temporarily storing the downstream frame before transmitting the downstream frame to another device or processing the downstream frame. Then, the extracting unit 51 stores the downstream frame extracted from each buffer in the memory.

  With such a configuration, it is possible to reduce the capacity of the memory for accumulating the downstream frames, so that the cost of the apparatus can be reduced.

  Further, in the OSU according to the embodiment of the present invention, the extraction unit 51 continuously extracts downlink frames from the priority buffer until there are no downlink frames from the priority buffer.

  With such a configuration, it is possible to increase the speed of extracting the downstream frame from the priority buffer.

  In the OSU according to the embodiment of the present invention, two SNI ports A and B are provided and redundant switching between the SNI port A and the SNI port B is performed. However, the present invention is limited to this. is not. The OSU 12 may have a configuration in which three or more SNI ports are provided.

  Moreover, although the station side apparatus which concerns on embodiment of this invention was set as the structure provided with the concentrating part 11, it is not limited to this. The concentrator 11 may be provided not on the station side device 201 but on the higher network side. In this case, the transmission stop request is directly transmitted from the upper network to the OSU 12.

  Moreover, although the station side apparatus in the PON system was illustrated as an embodiment of the present invention, the present invention can be applied not only to the station side apparatus in the PON system but also to a network receiving apparatus that receives some communication signal from the network. Is possible.

  The above embodiment should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

11 Concentrator 12, 12-1 to 12-m Optical line unit (OSU)
21 1 GPON transmission / reception unit 22 10 GPON transmission / reception unit 23 Buffer control unit 24 QOS unit 25 Multiplexer 26, 27 Buffer 28, 29 MAC processing unit 30 SNI-A interface unit 31 SNI-B interface unit 32 Control unit 41, 42 Switch unit 51 Extraction unit 91 Memory 201 Station side device 202 Home side device (ONU)
203-1 to 203-m PON line 204-1 to 204-m optical coupler 301 PON system

Claims (10)

A network receiver capable of receiving communication signals via a plurality of redundant communication paths,
A plurality of buffers provided for each of the communication paths, for storing communication signals received from the communication path;
An extraction unit for extracting the communication signal from the buffer;
The resource provided for the communication signal extracted by the extraction unit has a restriction to be shared among the communication signals extracted from the plurality of buffers,
The extraction unit sets a priority buffer which is the buffer to be prioritized based on at least one of the switching state of the communication path and the state of the buffer, and subordinates the extraction of the communication signal from the priority buffer. A network receiver that performs at a higher speed than the extraction of the communication signal from the buffer.   The network receiving device according to claim 1, wherein the extraction unit sets the buffer corresponding to the communication path to be switched to as a priority buffer.   The take-out unit has at least one of a condition that the buffer corresponding to the switching source communication path satisfies a predetermined condition and a condition that the buffer corresponding to the switching destination communication path satisfies a predetermined condition, The network receiver according to claim 2, wherein the priority buffer is set as a condition.   The priority buffer setting condition is that the extraction unit has a larger storage amount of the buffer corresponding to the switching destination communication path than a storage amount of the buffer corresponding to the switching source communication path. The network receiving device according to claim 3.   The network receiving device according to claim 3, wherein the extraction unit sets the priority buffer setting condition that a free capacity of the buffer corresponding to the communication path to be switched to is less than a predetermined value.   The network reception device according to claim 1, wherein the extraction unit sets the priority buffer based on an accumulation amount or a free capacity of the buffer.   The network receiving device according to claim 6, wherein the extraction unit sets the buffer having an accumulation amount equal to or greater than a predetermined value as the priority buffer. The resource is a memory for temporarily storing the communication signal before the communication signal is transmitted to another device or processed by the network receiving device,
The network receiving device according to claim 1, wherein the extraction unit stores the communication signal extracted from each buffer in the memory.   9. The network reception device according to claim 1, wherein the extraction unit continuously extracts the communication signal from the priority buffer until the communication signal disappears from the priority buffer. 10. Reception in a network reception device capable of receiving communication signals via a plurality of redundant communication paths, and provided with a plurality of buffers provided for each of the communication paths and for storing communication signals received from the communication paths. A method,
Setting a priority buffer which is the buffer to be prioritized based on at least one of the switching state of the communication path and the state of the buffer;
Retrieving the communication signal from the buffer;
The resource provided for the communication signal extracted from the buffer has a restriction to be shared among the communication signals extracted from the plurality of buffers,
In the step of extracting the communication signal, the communication signal is extracted from the priority buffer at a higher speed than the extraction of the communication signal from the subordinate buffer.

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