JP6539627B2 - Intra-office optical termination device and time synchronization method - Google Patents

Description

  The present invention relates to time synchronization of an intra-office optical termination device in a passive optical network.

  As an economical optical access system, there is a passive optical network (PON: Passive Optical Network) 10 as shown in FIG. In the PON 10, one in-station optical termination unit (OLT: Optical Line Terminal) and two or more in-home optical termination units (ONU: Optical Network Unit) 12-1, ..., 12-k (where k is a natural number) Is a network that performs point-to-multipoint communication via an optical fiber transmission line and a 1-to-k optical splitter 13. Hereinafter, the ONUs 12-1, ..., 12-k are collectively referred to as "ONU 12".

  As a representative standard of PON 10, there are Gigabit class 1G-EPON (Ethernet (registered trademark) PON) and 10 Gigabit class 10G-EPON standardized by IEEE 802.3ah. These are collectively called EPON.

  In the PON 10, the communication direction from the OLT 11 to the ONU 12 is generally called the downstream direction, and the opposite side is called the upstream direction. In the PON 10, since the ONUs 12-1, ..., 12-k share one optical fiber transmission line, there is a possibility that signals in uplink communication may collide. In order to prevent such signal collision, uplink communication is performed by, for example, time division multiple access. That is, the OLT 11 transmits a signal transmitted by a certain ONU 12-x (here, x = 1,..., K) and an ONU 12-y other than the ONU 12-x (here, y = 1,. , K, y ≠ x) prevents the collision of the signals by controlling the transmission timing of the ONU 12 so that the signals do not overlap.

  A communication protocol called MPCP (Multi-Point Control Protocol) defined in IEEE 802.3ah (see, for example, Non-Patent Document 1) will be described for a mechanism in which the OLT 11 controls the transmission timing of the ONU 12 in the PON 10.

  FIG. 8 is a sequence diagram showing an outline of this MPCP. The ONUs 12-1 and 12-2 describe the amount of upstream user data waiting for transmission in the buffer in a transmission request signal (hereinafter, referred to as "REPORT message") and transmit it to the OLT 11. The OLT 11 calculates the transmission start time and the transmission time for each of the ONUs 12-1 and 12-2 with reference to the transmission request amount acquired from the received REPORT message. The OLT 11 generates transmission permission signals (hereinafter referred to as “GATE messages”) in which the transmission information and the current time (hereinafter referred to as “time stamp values”) are imprinted, and the ONUs 12-1 and 12-2 generate the transmission information. Toward the terminal (steps S01 and S02).

  When receiving the GATE message, the ONUs 12-1 and 12-2 synchronize their time with the OLT 11 by first matching their clocks based on the time stamp value of the OLT 11 described in the GATE message. (Steps S03 and S04).

  After that, the ONUs 12-1 and 12-2 wait until the designated transmission start time (steps S05 and S06), and transmit the user data message stored in the upstream buffer together with the REPORT message (steps S07 and S08). . At this time, the ONUs 12-1 and 12-2 may transmit only the user data message, and the REPORT message may be transmitted at another timing.

  A period from the transmission of the GATE message to all the ONUs 12-1, ..., 12-k to the reception of the REPORT message is defined as a DBA (Dynamic Bandwidth Allocation) cycle.

  Conventionally, most functions of the OLT have been implemented by hardware in order to guarantee communication quality. However, hardware implementation is difficult to change or add to functions, and is considered to be a bottleneck when attempting to deploy various network services at high speed.

  Therefore, it is considered effective to implement the functions of the OLT as software operating on an OS (Operating System) (see, for example, Non-Patent Document 2). However, it is conceivable that the processing delay and fluctuation related to communication may be increased by making the function into software as compared with the hardware implementation.

  As described above, the ONU performs time synchronization with the OLT based on the timestamp value described in the GATE message received from the OLT. At this time, the OLT may cause fluctuation in the time from the time when the time stamp value is described to the time when transmission from the transmission port is completed due to the occurrence of an interrupt or the like. Due to the influence of the fluctuation, a shift occurs in the synchronization time of each ONU.

  Also, the OLT measures the RTT (Round-Trip Time) between the OLT and the ONU by subtracting the transmission time of the ONU described in the REPORT message from the reception time of the REPORT message, and refers to the RTT. Then, the transmission start time of the upstream signal of the ONU is calculated. However, since the OLT implemented by software fluctuates in time from reception of the REPORT message at the reception port to acquisition of the reception time in the software, it is difficult to measure an accurate RTT. Due to these factors, the OLT can not instruct the respective ONUs on accurate upstream signal transmission timing, which may cause collisions of upstream signals and significantly reduce the throughput in the upstream direction. Hereinafter, the process of describing the transmission time of the GATE message and the process of acquiring the reception time of the REPORT message will be referred to as “time stamp process”.

  As a prior art for such a subject, as shown in FIG. 9, there exists a thing which performs a time stamp process in the time stamp auxiliary | assistant apparatus hardware-implemented near transmission / reception physical ports, such as NIC (Network Interface Card). . The timestamp assistant describes the transmission time in the timestamp of the GATE message. The timestamp assistant describes the reception time in the padding portion of the REPORT message. As a result, the time from when the transmission time is described as time stamp processing to when it is sent from the transmission port, and the time from when it is received from the reception port to when the reception time acquisition processing is performed as time stamp processing The influence can be reduced (see, for example, Non-Patent Document 3). In the above, time stamp processing by hardware implementation has been described, but the implementation method is not limited to hardware implementation. For example, by preparing software dedicated to time stamps that secures real-time property separately from software that fulfills OLT functions, time stamp processing is performed on packets immediately after receiving a REPORT message and immediately before transmitting a GATE message. Similar effects can be expected. Hereinafter, hardware auxiliary devices that perform time stamp processing and software auxiliary mechanisms are collectively referred to as “time stamp auxiliary devices”.

IEEE 802.3ah-2012 Tadokoro, 3 others, "Examination of application of virtualization technology to optical access NW", Technical Report 115 (123), pp. 85-89, 2015 Ohly et. Al., "Hardware Assisted Precision Time Protocol Design and Case Study", Proc. Of the 9th LCI International Conference on High-Performance Clustered Computing, pp. 121-131, 2008 Assi et. Al., "Dynamic Bandwidth Allocation for Quality-of-Service Over Ethernet PONs", IEEE Journal on selected areas in communications, vol. 21 (9), pp. 1467-14, 2003

  However, the above-mentioned prior art has the following problems. In order to apply the prior art to the software implementation of the OLT, it is necessary to synchronize the time between a software process (hereinafter referred to as "OLT" process) that performs processing of the OLT function and the time stamp auxiliary device. As a general synchronization method, use of protocols such as NTP (Network Time Protocol) and PTP (Precision Time Protocol) can be considered.

  Even when time synchronization is performed between the OLT process and the time stamp auxiliary device, a transmission delay occurs between the OLT process and the time stamp auxiliary device. FIG. 10 is a sequence diagram illustrating a transmission delay occurring between the OLT process and the time stamp auxiliary apparatus. The OLT process writes 10:05 as the transmission start time, and sends a GATE message with a blank time stamp value. A transmission delay occurs between the OLT process and the time stamp auxiliary device. The time stamp auxiliary device describes 10:10, which is the transmission time of the GATE message, as a time stamp value in the GATE message. In such a case, the transmission start time described in the GATE message in the OLT process may be smaller than the time stamp value described in the GATE message by the time stamp auxiliary device. That is, due to the transmission delay generated between the OLT process and the time stamp auxiliary device, the magnitude of the transmission start time and the time stamp value is reversed. The ONU sets the Local clock to 10:10 based on the timestamp value. The transmission start time described in the GATE message is 10:05, which is a time (preceding time) smaller than 10:10, which is a timestamp value. Therefore, when the transmission start time is smaller than the time stamp value, the ONU can not start transmission of the user data message, and is in the worst link down state.

  The present invention has been made in view of the above circumstances, and the purpose thereof is the transmission start time described in the GATE message in the OLT process due to the transmission delay occurring between the OLT process and the time stamp auxiliary device. It is an object of the present invention to provide an intra-office optical termination device and a time synchronization method capable of reducing the possibility that R.sub.2 becomes smaller than the time stamp value described in the GATE message in the time stamp auxiliary device.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided a process of softwareizing at least a part of functions of an intra-office optical termination device connected with two or more in-home optical termination devices in a passive optical network; Time stamp assistance for adding information about time to a clock for the process, a transmission permission signal to be sent from the intra-office optical termination unit to the intra-office optical termination unit, and a transmission request signal received from the intra-office optical termination unit An intra-office optical termination device comprising an apparatus, wherein the time stamp auxiliary device transmits the time at which the time stamp auxiliary device sends the transmission permission signal to the home optical termination device in response to the transmission permission signal Means for adding as information on time, and in response to the transmission request signal, the time stamp auxiliary device performs the transmission request signal to the home optical termination Means for adding the time received from the device as information on the reception time, the process comprising: means for calculating a transmission delay time between the process and the time stamp auxiliary device; And a means for correcting the reception time to the time obtained by adding the transmission delay time.

  According to a second aspect of the present invention, in the first aspect, the means for calculating the transmission delay time sends the reception request time to the in-station optical termination device, and the reception time and the in-home optical termination device The transmission delay time is calculated using the time when the process sent the transmission permission signal, and the time when the process received the transmission request signal.

  According to a third aspect of the present invention, in the first aspect, the time stamp auxiliary device copies the transmission permission signal received from the process and outputs the copied transmission permission signal to the process. Means for calculating the transmission delay time using the time at which the process sent the transmission grant signal and the time at which the process received the transmission grant signal copied from the process The delay time is calculated.

  According to a fourth aspect of the present invention, in the first aspect, the means for calculating the transmission delay time includes the transmission time, the reception time, and a time when the process transmits the transmission permission signal. The transmission delay time is calculated using the time when the process receives the transmission request signal.

  According to a fifth aspect of the present invention, there is provided a fifth aspect of the present invention, there is provided a process of softwareizing at least a part of functions of an intra-office optical termination apparatus connected with two or more home optical termination apparatuses in a passive optical network; An intra-office optical termination comprising: a transmission permission signal transmitted from the intra-office optical termination device to the intra-home optical termination device and a time stamp auxiliary device for adding information on time to the transmission request signal received from the intra-home optical termination device. A time synchronization method performed by a device, wherein the time stamp auxiliary device transmits the time when the time stamp auxiliary device transmits the transmission permission signal to the home optical termination device in response to the transmission permission signal. Adding the information as the information on the time stamp auxiliary device, the time stamp Adding the time when the transmission request signal is received from the in-home optical termination unit as reception time information, and the process calculating a transmission delay time between the process and the time stamp auxiliary apparatus. Correcting the time of the clock to a time obtained by adding the transmission delay time to the reception time.

  According to the present invention, the transmission delay occurring between the OLT process and the time stamp auxiliary device causes the transmission start time described in the GATE message in the OLT process to be a time stamp value described in the GATE message in the time stamp auxiliary device. It is possible to provide an intra-office optical termination device and a time synchronization method capable of reducing the possibility of becoming smaller.

FIG. 1 is a block diagram illustrating a system including a time stamp assisting apparatus according to a first embodiment. FIG. 2 is a sequence diagram illustrating the operation of the system of FIG. 1; FIG. 5 is a block diagram illustrating a system including a time stamp assisting apparatus according to a second embodiment. FIG. 5 is a sequence diagram illustrating the operation of the system of FIG. 3; FIG. 7 is a block diagram illustrating a system including a time stamp assisting apparatus according to a third embodiment. FIG. 6 is a sequence diagram illustrating the operation of the system of FIG. 5; FIG. 2 is a block diagram showing a schematic configuration of a general PON. The sequence diagram which shows the outline | summary of general MPCP. The sequence diagram which shows the outline | summary of MPCP using a time stamp auxiliary | assistance apparatus. FIG. 7 is a sequence diagram illustrating transmission delay occurring between an OLT process and a time stamp auxiliary device.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
In the following, the use in a passive optical network (PON) as illustrated in FIG. 7 is assumed. Further, the transmission permission signal (GATE message) and the transmission request signal (REPORT message) are those defined in the above-mentioned MPCP.

  Also, in the following, “describe time in message” and “add time information to signal” have the same meaning, and both may be read mutually.

First Embodiment
(Constitution)
In FIG. 1, a block diagram of a system including a time stamp assisting apparatus 100 according to the first embodiment is illustrated. The system is an intra-office optical termination device comprising the time stamp assisting device 100 and the server 200. The server 200 comprises an OLT process 210 and a clock 220 for the OLT process 210. The server 200 may configure the optical termination device integrally with the time stamp assisting device 100. In addition, a configuration in which the time stamp auxiliary device 100 and the OLT process 210 are integrated may be used as the optical termination device. The solid arrows in FIG. 1 particularly indicate the flow of the MPCP message (GATE message / REPORT message). The dotted lines represent the flow of control signals in the time stamp auxiliary apparatus 100 and the server 200.

  The time stamp auxiliary apparatus 100 performs time stamp processing in cooperation with an OLT process 210 in which at least a part of the functions of the OLT connected to two or more ONUs in the PON is software-implemented. As an example, as a process used to perform time synchronization with the OLT process 210, the time stamp auxiliary apparatus 100 generates a GATE message generated by the OLT process 210 and sent from the intra-office optical termination apparatus to the ONU, and a REPORT received from the ONU Write the time for the message. The REPORT message is generated by the ONU and is a response to the GATE message. The time stamp auxiliary apparatus 100 has a structure that can be inserted into, for example, a transmission / reception port (not shown) of the server 200.

  The time stamp auxiliary apparatus 100 includes a PON side port unit 110, a REPORT message processing unit 120, a server side port unit 130, and a GATE message processing unit 140. Further, the REPORT message processing unit 120 includes a reception time clocking unit 121. The GATE message processing unit 140 further includes a transmission time clocking unit 141 and a transmission start time correction unit 142. The transmission start time correction unit 142 includes a transmission delay calculation GATE determination unit 143 and a correction processing unit 144. Equipped with The time stamp auxiliary apparatus 100 has a high-precision clock (not shown), and uses this clock to obtain high-precision transmission and reception times and to describe transmission and reception times in GATE messages and REPORT messages. The GATE message processing unit 140 is implemented by hardware and does not perform processing such as queuing. Thereby, it is possible to suppress the time synchronization deviation between each ONU and to prevent the collision of the upstream signals.

  The PON port unit 110 receives a REPORT message, upstream user data, and other control signals from an ONU (not shown) via the PON line, and outputs only the REPORT message to the reception time clocking unit 121. User data and other control signals are transferred to the server-side port unit 130 through another path (not shown). Also, the PON port unit 110 receives the GATE message from the correction processing unit 144, and outputs the GATE message to the ONU through the PON line. Furthermore, the PON side port unit 110 receives user data and other control signals from the server side port unit 130 via a separate path (not shown) from the server side port unit 130 and outputs the user data and other control signals to the ONU via the PON line.

  The reception time stamping unit 121 receives the REPORT message from the PON port unit 110. The reception time stamping unit 121 describes the time when the time stamp auxiliary apparatus 100 receives the REPORT message from the ONU as the reception time in the REPORT message. When the time at which the ONU has transmitted the REPORT message (hereinafter referred to as “ONU transmission time”) is described at the designated position of the REPORT message, the reception time memory unit 121 describes the ONU transmission time. The reception time is described at a position different from the one at The reception time clocking unit 121 outputs the REPORT message in which the reception time is described to the server side port unit 130.

  The server side port unit 130 receives the REPORT message in which the reception time is described from the reception time clocking unit 121, and outputs the REPORT message to the OLT process 210. Also, the server-side port unit 130 receives the GATE message from the OLT process 210 and outputs the GATE message to the transmission time stamping unit 141. Furthermore, the server-side port unit 130 receives other control signals and upstream user data from the PON-side port unit 110 and outputs them to the OLT process 210. In addition, the server-side port unit 130 outputs the other control signals and downstream user data received from the OLT process 210 to the PON-side port unit 110.

  The transmission time stamping unit 141 receives the GATE message from the server side port unit 130. The transmission time stamping unit 141 describes the time at which the time stamp auxiliary apparatus 100 sends the GATE message to the ONU as the transmission time in the GATE message. The transmission time stamping unit 141 describes the current time (time stamp value) as the transmission time at a designated position of the GATE message. The transmission time clocking unit 141 outputs a GATE message describing the time stamp value to the transmission start time correction unit 142.

  The transmission delay calculation GATE determination unit 143 plays a role of assisting time synchronization between the OLT process 210 and the time stamp auxiliary apparatus 100. In the GATE message in which the transmission time counting unit 141 describes the time stamp value, the transmission delay calculation GATE determining unit 143 determines that the transmission start time, which is the time when the ONU starts transmitting the REPORT message corresponding to the GATE message, is Determine if it is described. A GATE message in which the transmission start time is not described when the time stamp auxiliary apparatus 100 receives from the OLT process 210 may be referred to as a transmission delay calculation GATE message. When the transmission start time is described in the GATE message, the transmission delay calculation GATE determination unit 143 sends the GATE message in which the time stamp value is described to the PON side port unit 110 to the correction processing unit 144. And give instructions. When the transmission start time is not described in the GATE message, the transmission delay calculation GATE determination unit 143 recognizes the GATE message as a transmission delay calculation GATE message. The transmission delay calculation GATE determination unit 143 instructs the correction processing unit 144 to describe the transmission start time in the transmission delay calculation GATE message. The transmission delay calculation GATE determining unit 143 does not necessarily have to determine the GATE message in which the time stamp value is described, and may determine, for example, the GATE message in which the time stamp value is not described. .

  The correction processing unit 144 receives from the transmission time stamping unit 141 the GATE message in which the time stamp value is described. When the transmission start time of the REPORT message is described in the GATE message, the correction processing unit 144 outputs the GATE message in which the time stamp value and the transmission start time are described to the PON-side port unit 110. When the transmission start time of the REPORT message is not described in the GATE message, the correction processing unit 144 describes the transmission start time in the transmission delay calculation GATE message in which the time stamp value is described. The specific transmission start time described in the transmission delay calculation GATE message by the correction processing unit 144 will be described later. The correction processing unit 144 outputs the transmission delay calculation GATE message in which the time stamp value and the transmission start time of the REPORT message are described to the PON side port unit 110.

  The OLT process 210 includes an OLT function unit 211, a time synchronization control unit 212, and a clock correction unit 213. The OLT process 210 can exchange the GATE message and the REPORT message with the time stamp auxiliary apparatus 100 through the server side port unit 130. The OLT process 210 can be configured by, for example, one or more CPUs (Central Processing Units), and the respective units of the OLT process 210 are configured to be mutually communicable.

  The OLT function unit 211 has, for example, a general OLT function (such as a DBA function or an MPCP function). The OLT function unit 211 receives the REPORT message in which the reception time is described from the server side port unit 130 via the time synchronization control unit 212. Also, the OLT function unit 211 receives from the propagation delay time between the OLT process 210 and the ONU, the upstream user data amount, and the clock 220 calculated using the ONU transmission time described in the REPORT message and the reception time in the time stamp auxiliary apparatus 100. The bandwidth allocation calculation is performed based on the received time information, and a GATE message in which the transmission permission amount and the transmission start time are described for each ONU is created. The OLT function unit 211 can calculate an accurate RTT with less fluctuation by subtracting the ONU transmission time described in the REPORT message from the reception time of the time stamp auxiliary apparatus 100. The OLT function unit 211 outputs the created GATE message to the time synchronization control unit 212. The OLT function unit 211 may create a transmission delay calculation GATE message not describing the transmission start time.

  The time synchronization control unit 212 receives the REPORT message in which the reception time is described from the server side port unit 130, and outputs the REPORT message to the OLT function unit 211. Further, the time synchronization control unit 212 acquires and records the time when the GATE message is output from the OLT process 210 to the time stamp auxiliary apparatus 100. Further, the time synchronization control unit 212 measures the time when the REPORT message corresponding to the GATE message is received from the time stamp auxiliary apparatus 100. The time synchronization control unit 212 calculates a packet propagation delay time (hereinafter referred to as a transmission delay time) between the OLT process 210 and the time stamp auxiliary apparatus 100. The time synchronization control unit 212 uses at least the time when the GATE message is output from the OLT process 210 and the time when the REPORT message is received by the OLT process 210. A specific method of calculating the transmission delay time D will be described later. The time synchronization control unit 212 outputs the transmission delay time D to the clock correction unit 213.

  The clock correction unit 213 receives the transmission delay time D from the time synchronization control unit 212. The clock correction unit 213 corrects the clock 220 based on the transmission delay time D. The specific correction method will be described later.

(Operation)
In FIG. 2, an operation relating to time synchronization between the OLT process 210 and the time stamp auxiliary apparatus 100 by a system including the time stamp auxiliary apparatus 100 is illustrated. This operation is time synchronization using a transmission delay calculation GATE message. This operation transmits, for example, to the ONU for which the bandwidth request was zero, in order for the OLT process 210 to calculate the transmission delay between the OLT process 210 and the time stamp auxiliary apparatus 100 every few DBA cycles. Send a GATE message for transmission delay calculation with a blank start time. In the following, the operation of each unit will be described in chronological order.

  The OLT process 210 outputs a transmission delay calculation GATE message to the time stamp auxiliary apparatus 100 (time t1). At this time, the OLT process 210 generates a GATE message for transmission delay calculation without describing the transmission start time. Further, the time synchronization control unit 212 holds time t1 when the OLT process 210 sends the transmission delay calculation GATE message to the time stamp auxiliary apparatus 100.

  For the transmission delay calculation GATE message, the time stamp assistance device 100 determines a time stamp value (time T1) corresponding to the transmission time from the time stamp assistance device 100 and a predetermined time as the transmission start time to the time stamp value T1. The time (T1 + ΔT) to which the length ΔT is added is described, and is transmitted to the ONU. The predetermined time length is, for example, the minimum time until the ONU receives the GATE message for calculation of the transmission delay and the uplink transmission becomes possible.

  The ONU describes the ONU transmission time (T1 + ΔT) corresponding to the transmission start time (T1 + ΔT) described in the transmission delay calculation GATE message in the REPORT message for returning, and transmits the REPORT message to the OLT process 210. Do. The time stamp auxiliary apparatus 100 receives a REPORT message in which the ONU transmission time (T1 + ΔT) is described (time T2). At this time, the reception time stamping unit 121 describes the reception time T2 of the time stamp auxiliary apparatus 100 in the REPORT message.

  The time stamp auxiliary apparatus 100 outputs, to the OLT process 210, a REPORT message in which the ONU transmission time (T1 + ΔT) and the reception time T2 are described. The time synchronization control unit 212 receives, from the time stamp auxiliary apparatus 100, a REPORT message in which the ONU transmission time (T1 + ΔT) and the reception time T2 are described (time t2). The time synchronization control unit 212 measures time t2 when the REPORT message is received from the time stamp auxiliary apparatus 100.

  After exchanging the GATE message and the REPORT message, the time synchronization control unit 212 corresponds to the reception time T2 at which the time stamp auxiliary apparatus 100 receives the REPORT message from the ONU and the transmission start time (T1 + ΔT), and the ONU carries the REPORT message. ONU transmission time (T1 + ΔT) sent to the intra-office optical termination unit, time t1 when the OLT process 210 sent a GATE message for transmission delay calculation to the time stamp auxiliary apparatus 100, and the OLT process 210 time stamped the REPORT message The transmission delay time D between the OLT process 210 and the time stamp auxiliary apparatus 100 is calculated using the time t2 received from the apparatus 100. As a specific example, the time synchronization control unit 212 calculates a transmission delay time D (= {(t2-t1)-(T2-T1-ΔT)} / 2). The time synchronization control unit 212 outputs the transmission delay time D to the clock correction unit 213.

  The clock correction unit 213 corrects the time of the clock 220 to a time (T2 + D) obtained by adding the transmission delay time D to the reception time T2. The transmission delay time D may be a value calculated by one measurement, or an average value or a maximum value of values calculated by two or more measurements.

(effect)
As described in detail above, in the first embodiment, the intra-office optical termination apparatus measures the transmission delay time D between the OLT process 210 and the time stamp auxiliary apparatus 100 using the transmission delay calculation GATE message, and transmits The clock 220 can be set to an advanced (advanced) time based on the delay time D. Thereby, the intra-office optical termination apparatus can reduce the possibility that the transmission start time described in the GATE message in the OLT process 210 becomes smaller than the time stamp value described in the GATE message in the time stamp auxiliary apparatus 100. .

  Furthermore, the measurement of the transmission delay time between the OLT process 210 and the time stamp auxiliary apparatus 100 is all performed by the GATE message and the REPORT message. Therefore, the OLT process 210 and the time stamp auxiliary apparatus 100 do not need to newly correspond to the time synchronization protocol. Further, since it is not necessary to exchange messages regarding the time synchronization protocol between the OLT process 210 and the time stamp auxiliary apparatus 100, it is possible to perform transmission delay measurement while maintaining the bandwidth utilization efficiency.

Second Embodiment
(Constitution)
In FIG. 3, a block diagram of a system including a time stamp assisting apparatus 300 according to the second embodiment is illustrated. The time stamp auxiliary device 300 of FIG. 3 is configured based on the time stamp auxiliary device 100 according to the first embodiment, and the description of the common parts is omitted. The second embodiment differs from the first embodiment in that the transmission delay time D between the OLT process 210 and the time stamp auxiliary apparatus 300 is measured without using a transmission delay calculation GATE message.

  The time stamp auxiliary apparatus 300 includes a PON side port unit 110, a REPORT message processing unit 120, a server side port unit 150, and a GATE message processing unit 160. Further, the REPORT message processing unit 120 includes a reception time clocking unit 121, the server side port unit 150 includes a packet copying unit 151, and the GATE message processing unit 160 includes a transmission time clocking unit 161.

  The server side port unit 150 receives the REPORT message in which the reception time is described from the reception time clocking unit 121, and outputs the REPORT message to the OLT process 210. The server-side port unit 150 also receives the GATE message from the OLT process 210 and outputs the GATE message to the transmission time clocking unit 161.

  Every time the server side port unit 150 receives a GATE message from the OLT process 210, the packet copying unit 151 copies the received GATE message. The packet copying unit 151 outputs the copied GATE message to the OLT process 210 in a form of looping back.

  The GATE message processing unit 160 does not include the transmission start time correction unit 142 described in the first embodiment. Therefore, the transmission time imprinting unit 161 is different from the transmission time imprinting unit 141 described in the first embodiment in that the GATE message in which the time stamp value is described is output to the PON side port unit 110.

  The time synchronization control unit 212 receives the time when the OLT process 210 sends the GATE message to the time stamp auxiliary apparatus 100 and the time when the OLT process 210 receives the GATE message copied by the packet copying unit 151 from the time stamp auxiliary apparatus 300 The transmission delay time D between the OLT process 210 and the time stamp auxiliary apparatus 300 is calculated using As an example, the time synchronization control unit 212 receives from the time stamp auxiliary device 300 the time when the OLT process 210 sent the GATE message to the time stamp auxiliary device 100 and the GATE message copied by the OLT process 210 by the packet copying unit 151. The transmission delay time D is calculated based on the difference from the time of day. The OLT process 210 discards the copied GATE message after acquiring the time when the copied GATE message is received from the packet copying unit 151.

(Operation)
In FIG. 4, the operation of the system including the time stamp assistant 300 is illustrated. In the following, the operation of each unit will be described in chronological order.

  The OLT process 210 outputs the GATE message to the time stamp auxiliary apparatus 300 (time t1). The time synchronization control unit 212 holds time t1 at which the OLT process 210 sends the GATE message to the time stamp auxiliary apparatus 300. The packet copying unit 151 copies the GATE message received by the time stamp auxiliary apparatus 300 from the OLT process 210, and outputs the copied GATE message to the OLT process 210. The OLT process 210 receives the copied GATE message from the time stamp auxiliary device 300 (time t2). The time synchronization control unit 212 measures time t2 when the OLT process 210 receives the GATE message copied by the packet copying unit 151 from the time stamp auxiliary apparatus 300. The time synchronization control unit 212 calculates the transmission delay time D between the OLT process 210 and the time stamp auxiliary apparatus 300 based on the difference between the time t1 and the time t2. Specifically, the time synchronization control unit 212 calculates the transmission delay time D (= (t2-t1) / 2). The time synchronization control unit 212 outputs the transmission delay time D to the clock correction unit 213.

  The clock correction unit 213 corrects the time of the clock 220 to a time (T2 + D) obtained by adding the transmission delay time D to the reception time T2. The transmission delay time D may be a value calculated by one measurement, or an average value or a maximum value of values calculated by two or more measurements.

  In the above operation, when the GATE message is looped back, it is conceivable to compress the upstream band which is the direction from the ONU (or the timestamp auxiliary device 300) to the OLT process 210. However, in the basic DBA algorithm, the period during which the OLT process 210 is transmitting a GATE message is a band in which the ONU can not transmit upstream user data (uplink non-transmittable bandwidth) (for example, see Non-Patent Document 4) ). That is, the operation of returning the GATE message in the packet copying unit 151 is considered to have little influence on the upstream band.

(effect)
As described above in detail, in the second embodiment, the intra-office optical termination apparatus measures the transmission delay time D based on the difference between the transmission and reception times of GATE messages in the OLT process 210, and the clock 220 based on the transmission delay time D. Can be set to the time advanced (advanced). As a result, the intra-office optical termination apparatus can reduce the possibility that the transmission start time described in the GATE message in the OLT process 210 becomes smaller than the time stamp value described in the GATE message in the time stamp auxiliary apparatus 300. . Further, since the band in which the GATE message is returned is a band in which the uplink user data is not used, the intra-office optical termination apparatus can obtain the transmission delay time D used for time synchronization while maintaining the band use efficiency.

Third Embodiment
(Constitution)
In FIG. 5, a block diagram of a system including a timestamp assistance device 500 according to the third embodiment is illustrated. The time stamp auxiliary device 500 of FIG. 5 is configured based on the time stamp auxiliary device 100 according to the first embodiment, and the description of the common parts is omitted. The third embodiment differs from the first embodiment in that the transmission delay time D between the OLT process 210 and the time stamp auxiliary apparatus 500 is measured without using a transmission delay calculation GATE message.

  The time stamp auxiliary apparatus 500 includes a PON side port unit 110, a server side port unit 130, a REPORT message processing unit 170, and a GATE message processing unit 180. In addition, the REPORT message processing unit 170 includes a reception time stamping unit 171 and a transmission / reception interval imprinting unit 172, and the GATE message processing unit 180 includes a transmission time stamping unit 181.

  The reception time stamping unit 171 differs from the reception time stamping unit 121 in FIG. 1 and FIG. 3 in that it outputs a REPORT message in which the reception time is described to the transmission / reception interval stamping unit 172.

  The GATE message processing unit 180 does not include the transmission start time correction unit 142 described in the first embodiment. Therefore, the first point in time is that the transmission time imprinting section 181 outputs the GATE message describing the time stamp value to the PON side port section 110, and further outputs the time stamp value to the transmission / reception interval imprinting section 172. It differs from the transmission time imprinting unit 141 described in the embodiment. In the third embodiment, a time stamp value corresponding to a transmission time at which the time stamp auxiliary apparatus 500 sends a GATE message is referred to as a module transmission time. Also, the reception time at which the timestamp auxiliary device 500 receives the REPORT message is referred to as a module reception time.

  The transmission / reception interval imprinting unit 172 holds the module transmission time received from the transmission time imprinting unit 181 for each ONU. The transmission / reception interval imprinting unit 172 receives the REPORT message in which the module reception time is described from the reception time imprinting unit 171, and acquires the reception time from the REPORT message. The transmission / reception interval imprinting unit 172 calculates the difference between the module transmission time and the module reception time in the time stamp auxiliary apparatus 500. The transmission / reception interval transcribing unit 172 describes the transmission / reception difference between the module transmission time and the module reception time in the time stamp auxiliary device 500 in the empty area of the REPORT message in which the module reception time is described and sends it to the server side port unit 130. Output.

(Operation)
In FIG. 6, the operation by the system including the time stamp assistant 500 is illustrated. In the following, the operation of each unit will be described in chronological order.

  The OLT process 210 outputs the GATE message to the time stamp auxiliary apparatus 500 (time t1). At this time, the time synchronization control unit 212 holds time t1 at which the OLT process 210 sends the GATE message to each ONU.

  The time stamp auxiliary apparatus 500 describes the module transmission time T1 as a time stamp value in the GATE message, and transmits the GATE message in which the module transmission time T1 is described to the ONU. At this time, the transmission / reception interval imprinting unit 172 holds each module transmission time T1 described in the GATE message sent to each ONU.

  The ONU transmits a REPORT message to the OLT process 210 at the transmission start time described in the GATE message. The ONU describes ONU transmission time T3 corresponding to the transmission start time in a REPORT message for returning, and transmits the REPORT message to the OLT process 210. The time stamp auxiliary apparatus 500 receives the REPORT message from the ONU (time T2). At this time, the reception time stamping unit 171 describes the module reception time T2 in the time stamp auxiliary device 500 in the REPORT message. The transmission / reception interval imprinting part 172 describes the transmission / reception difference (T2-T1) between the module transmission time T1 and the module reception time T2 in the time stamp auxiliary device 500 in the empty area of the REPORT message. The transmission / reception difference (T2-T1) corresponds to the RTT of the ONU.

  The time stamp auxiliary apparatus 500 outputs the REPORT message in which the transmission / reception difference (T2-T1) is described to the OLT process 210. The OLT process 210 receives from the time stamp auxiliary apparatus 500 a REPORT message in which the transmission / reception difference (T2-T1) is described (time t2). The time synchronization control unit 212 measures time t2 when the REPORT message is received from the time stamp auxiliary apparatus 500.

  After exchanging the GATE message and the REPORT message, the time synchronization control unit 212 causes the module transmission time T1 in which the time stamp auxiliary device 500 sends the GATE message to the ONU, and the module in which the time stamp auxiliary device 500 receives the REPORT message from the ONU The OLT process 210 using the reception time T2, the time t1 when the OLT process 210 sends the GATE message to the time stamp auxiliary apparatus 500, and the time t2 when the OLT process 210 receives the REPORT message from the time stamp auxiliary apparatus 500. A transmission delay time D between the time stamp auxiliary device 100 and the time stamp auxiliary device 100 is calculated. As a specific example, the time synchronization control unit 212 calculates a transmission delay time D (= {(t2-t1)-(T2-T1)} / 2). The time synchronization control unit 212 outputs the transmission delay time D to the clock correction unit 213.

  The clock correction unit 213 corrects the time of the clock 220 to a time (T2 + D) obtained by adding the transmission delay time D to the module reception time T2. The transmission delay time D may be a value calculated by one measurement, or an average value or a maximum value of values calculated by two or more measurements.

(effect)
As described above in detail, in the third embodiment, the intra-office optical termination apparatus holds the module transmission time of the GATE message by the time stamp auxiliary apparatus 500, and acquires the module reception time of the REPORT message corresponding to the GATE message. Thus, the transmission delay time D between the OLT process 210 and the time stamp auxiliary apparatus 500 can be measured, and the time of the clock 220 can be set to the advanced (advanced) time based on the transmission delay time D. As a result, the intra-office optical termination apparatus can reduce the possibility that the transmission start time described in the GATE message in the OLT process 210 becomes smaller than the time stamp value described in the GATE message in the time stamp auxiliary apparatus 500. . Note that the intra-office optical termination device can be used to calculate the transmission delay time for any GATE message.

  The present invention is not limited to the above embodiment. In short, the present invention is not limited to the above embodiment as it is, and at the implementation stage, the constituent elements can be modified and embodied without departing from the scope of the invention. In addition, various inventions can be formed by appropriate combinations of a plurality of components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components in different embodiments may be combined as appropriate.

  DESCRIPTION OF SYMBOLS 10 ... Passive optical network, 11 ... Office optical termination device, 12 ... Home optical termination device, 13 ... Optical splitter, 100, 300, 500 ... Time stamp auxiliary device, 110 ... PON side port part, 120, 170 ... REPORT message processing Parts, 121, 171 ... Reception time stamping part 130, 150 ... Server side port part, 140, 160, 180 ... GATE message processing part 141, 161, 181 ... Transmission time stamping part 142 ... Transmission start time correction Unit: 143: GATE determination unit for transmission delay calculation; 144: correction processing unit; 151: packet copy unit; 172: transmission / reception interval imprinting unit; 200: server; 210: OLT process; 211: OLT function unit; Synchronous control unit, 213: clock correction unit, 220: clock.

Claims (5)

A softwareized process of at least part of the functions of the in-station optical termination unit connected to two or more in-home optical termination units in the passive optical network;
A clock for the process;
An intra-office optical termination comprising: a transmission permission signal transmitted from the intra-office optical termination device to the intra-premises optical termination device; A device,
The time stamp auxiliary device
A means for adding, as transmission time information, a time at which the time stamp auxiliary device sends the transmission permission signal to the home optical termination device with respect to the transmission permission signal;
Means for adding the time at which the time stamp auxiliary apparatus received the transmission request signal from the in-home optical termination apparatus to the transmission request signal as reception time information;
The process is
Means for calculating a transmission delay between the process and the time stamp aiding device;
Means for correcting the clock time to a time obtained by adding the transmission delay time to the reception time.   The means for calculating the transmission delay time includes the reception time, the time when the in-house optical termination unit sends the transmission request signal to the in-station optical termination unit, and the time when the process sends the transmission permission signal. The intra-office optical termination system according to claim 1, wherein the transmission delay time is calculated using the time when the process receives the transmission request signal. The time stamp assisting apparatus further comprises means for copying the transmission permission signal received from the process and outputting the copied transmission permission signal to the process.
The means for calculating the transmission delay time calculates the transmission delay time using the time when the process sent the transmission permission signal and the time when the transmission permission signal to which the process was copied is received. The intra-office optical termination device according to claim 1.   The means for calculating the transmission delay time uses the transmission time, the reception time, the time when the process sent the transmission permission signal, and the time when the process receives the transmission request signal. The intra-office optical termination apparatus according to claim 1, wherein the transmission delay time is calculated. A softwareized process of at least part of the functions of the in-station optical termination unit connected to two or more in-home optical termination units in the passive optical network;
A clock for the process;
An intra-office optical termination comprising: a transmission permission signal transmitted from the intra-office optical termination device to the intra-home optical termination device; and a time stamp auxiliary device for adding information about time to the transmission request signal received from the intra-home optical termination device. A time synchronization method performed by the device,
The time stamp auxiliary device adds, to the transmission permission signal, a time at which the time stamp auxiliary device sends the transmission permission signal to the home optical termination device as transmission time information;
The time stamp auxiliary apparatus adds, to the transmission request signal, the time when the time stamp auxiliary apparatus receives the transmission request signal from the home optical termination apparatus as reception time information;
Said process calculating a transmission delay time between said process and said time stamp aiding device;
Correcting the time of the clock to a time obtained by adding the transmission delay time to the reception time;
A time synchronization method comprising: