JP2013009184A - Time synchronous system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably supply a reference time and frequency with high accuracy to a base station such as a mobile phone or a wireless sensor terminal via an optical burst switch network.
The present invention provides an optical delay device when an optical burst switching device (OBS) that outputs an optical burst signal with an appropriate delay applied thereto when transferring a Sync message and a DelayReq message in a time synchronization protocol. The delay setting data is recorded in association with the message, the node on the slave clock side acquires the recorded delay setting data, and corrects the time synchronization error based on the acquired delay setting data.
[Selection] Figure 1

Description

  The present invention relates to a time synchronization system, and more particularly to a time synchronization system for synchronizing a reference time and frequency supplied to a base station such as a mobile phone or a wireless sensor terminal via an optical burst switch network.

  In response to the increase in traffic on the network in recent years, an optical burst switch (OBS) that efficiently performs switching processing in the optical domain has attracted attention. A configuration example of this OBS is shown in FIG. The optical burst signal input from the input port 1-1 is branched in part by the optical splitter 2-1. The branched optical burst signal is converted into an electric signal by an optical-electric conversion unit (O / E) 3-1. The optical switch control circuit 4 analyzes the label included in the electrical signal and controls the N × N optical switch 6 based on the destination information to send the optical burst signal to an appropriate port of the output ports 7-1 to 7-n. To output. The same applies to the optical burst signals input from the input ports 1-2 to 1-N. Here, when the optical burst signals input from the input ports are output to the same output port, a collision of the optical burst signals occurs. By giving an appropriate delay to each optical burst signal using the optical delay units 5-1 to 5-N, collision of the optical burst signals can be avoided.

  A configuration example of the optical delay devices 5-1 to 5-N is shown in FIG. The delay for the optical burst signal is given by K types of fiber delay lines (FDL) 8-1 to 8-K. Here, if D is the unit delay amount (the maximum length of the optical burst signal), the delay amount of FDL 8-1 is D0 (fixed delay amount necessary for label analysis etc.), and the delay amount of FDL 8-2 is D0 + The delay amount of D and FDL 8-3 is D0 + 2D, and the delay amount of FDL 8-K is D0 + (K −1) * D. The 1 × K optical switch 9 and the K × 1 optical switch 10 select an appropriate FDL according to the control signal from the optical switch control circuit 4 so that the optical burst signals do not collide. Although optical loss increases, a configuration using an optical splitter instead of the 1 × K optical switch 9 or a configuration using an optical combiner instead of the K × 1 optical switch 10 is also possible.

  A base station of a mobile phone or a wireless sensor terminal requires highly accurate time or frequency. Therefore, time synchronization via an optical burst switch network configured by OBS is required. Here, a case is considered in which time synchronization is performed based on IEEE 1588 (for example, see Non-Patent Document 1) via an optical burst switch network. FIG. 3 shows an IEEE 1588-based time synchronization mechanism. In the figure, a node 101 has a master clock 102 and a node 103 has a slave clock 104.

  The configuration of the node 101 in FIG. 3 is shown in FIG. The node 101 includes a packet interface 20, an optical burst conversion unit 21, a time synchronization message processing unit 22, a time information interface 23, a time stamper 24, and an optical burst interface 25. The packet interface 20 is a connection interface with a packet network (IP network or Ethernet). The optical burst conversion unit 21 converts single or plural (transferred to the same destination node) IP packet or Ethernet frame input from the packet interface 20 into an optical burst signal format. Further, the received optical burst signal is converted into an IP packet or an Ethernet frame and output from the packet interface 20. The time synchronization message processing unit 22 transmits and receives a time synchronization message. The time stamper 24 acquires time information from the master clock 102 via the time information interface 23, and outputs the time information when the optical burst signal including the time synchronization message passes through the time stamper 24 to the time synchronization message processing unit 22.

  FIG. 5 shows the configuration of the node 103 in FIG. The same components as those in FIG. 4 are denoted by the same reference numerals, and description thereof is omitted. The configuration shown in FIG. 5 is almost the same as that of the node 101 (the time stamper 24 acquires time information from the slave clock 104 via the time information interface 23). A slave clock control unit 26 that controls the slave clock 104 is controlled based on the frequency and phase of the slave clock 104 via the clock control interface 27.

When performing time synchronization, a Sync message is transmitted from the node 101 to the node 103. Here, the time at which the node 101 transmits the Sync message is measured by the time stamper 24 based on the master clock 102 and is defined as T1. The Sync message reaches the node 103 via the OBS 200-1 to OBS 200-M. Here, the time at which the node 103 receives the Sync message is measured by the time stamper 24 based on the slave clock 104, and is defined as T2. Node 103 stores T2. Next, a Follow-up message is transmitted from the node 101 to the node 103. The time T1 is written in the Follow-up message. The Follow-up message reaches the node 103 via the OBSs 200-1 to 200-M. The node 103 receives the Follow-up message and stores the time T1. The node 103 that has received the Follow-up message transmits a DelayReq message to the node 101. Here, the time at which the node 103 transmits the DelayReq message is measured by the time stamper 24 based on the slave clock 104, and is set as T3. Node 103 stores time T3. The DelayReq message reaches the node 101 via the OBSs 200-M to 200-1. Here, the time when the node 101 transmits the DelayReq message is measured by the time stamper 24 based on the master clock 102, and is set as T4. The node 101 that has received the DelayReq message transmits a DelayResp message to the node 103. The time T4 is written in the DelayResp message. The DelayResp message reaches the node 103 via the OBSs 200-1 to 200-M. The node 103 receives the DelayResp message and stores the time T4. Through the above message exchange, the slave clock control unit 26 of the node 103 stores four time data of T1, T2, T3, and T4. If the error between the master clock 102 and the slave clock 104 is δ, the delay time of the Sync message is ΔT1, and the delay time of the DelayReq message is ΔT2,
T2 + δ = T1 + ΔT1
T4 -δ = T3 + ΔT2
Than,
δ = (T1-T2-T3 + T4 + ΔT1-ΔT2) / 2
Is established. Here, assuming that ΔT1 = ΔT2, the error δ between the master clock 102 and the slave clock 104 is
δ = (T1-T2-T3 + T4) / 2
Given in. Here, time synchronization between the master clock 102 and the slave clock 104 can be established by controlling the slave clock 104 so that δ becomes zero.

  Up to this point, it has been assumed that ΔT1 = ΔT2 holds, but this assumption often does not hold in an actual network. As described above, each OBS 200-i uses the optical delay unit 5-i to avoid the collision of optical bursts, and the OBS delay time required for the Sync message to reach the node 103 from the node 101 This is because the delay time of the OBS required for the DelayReq message to reach the node 101 from the node 103 is generally different.

DL_0: Transmission path delay between node 101 and OBS200-1
DL_1: Transmission line delay between OBS200-1 and OBS200-2
DL_2: Transmission line delay between OBS200-2 and OBS200-3…
DL_M: Assuming transmission line delay between OBS200-M and node 103,
ΔT1 = ΣDL_i + Σ (D0 + K_i * D)
ΔT2 = ΣDL'_i + Σ (D0 + K'_i * D)
(Σ represents the sum of i = 0 to M for transmission line delays DL_i and DL′_i, and i = 1 for intra-switch delays D0 + K_i * D and D0 + K′_i * D. Represents the sum of ~ M. The same applies below)
(ΔT1 -ΔT2) = (ΣDL_i -ΣDL'_i + ΣK_i * D -ΣK'_i * D) / 2
Given in. Here, DL_i and D0 + K_i * D are the transmission path delay and intra-device delay for the Sync message, and DL′_i and D0 + K′_i * D are the transmission path delay and intra-device delay for the DelayReq message. Assuming that there is no change in the transmission path length due to temperature fluctuation between the Sync message transfer and the DelayReq message transfer,
DL_i = DL'_i
Therefore, the time synchronization error is
(ΔT1 -ΔT2) = (ΣK_i -ΣK'_i) * D2
It becomes. However, since K_i and K′_i differ for each optical burst, this difference remains as an error and degrades the time synchronization accuracy. Further, since the error varies with time, the time synchronization stability is deteriorated.

A solution to this problem is to use round trip time (RTT).
RTT = (T4-T1)-(T3-T2)
The minimum value (ie, the value when the optical burst is transferred with only the fixed delay time D0 in all OBS) is extracted from many RTTs, and only the values of T1 to T4 at this time are time It can be used for synchronization. However, when a lot of traffic is flowing through the network, the optical burst tends to concentrate on the same output port, so the probability that the RTT will be the minimum value is low. In order to increase the number of samples for obtaining the minimum value of RTT, the frequency of synchronous message exchange per unit time must be increased, or the number of samples should be increased over a long period of time, but the former wastes network bandwidth. In the latter case, it is necessary to use an expensive highly stable oscillator (which is sufficiently stable for a long time to acquire a large number of samples) as a slave clock. In order to solve such a problem, a transparent clock is introduced in IEEE 1588 (Non-Patent Document 1). This is because the switch that the message is passing through also has a clock function, and the difference between the time when the switch received the Sync message and DelayReq message and the time when it was sent (the delay time within the switch) is displayed in the correction field of the Sync message and DelayReq message. Time synchronization accuracy can be improved by a method such as writing and correcting the delay time at the end node (called E2E-TC).

"IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems", IEEE 1588-2008.

  However, even if the transparent clock disclosed in IEEE 1588 (Non-Patent Document 1) is introduced and the time synchronization accuracy can be improved, the optical burst is transferred without electrical processing in OBS. It is difficult to use a technique such as this transparent clock.

  The present invention has been made in view of the above points, and a time at which a reference time and frequency can be stably supplied with high accuracy to a base station such as a mobile phone or a wireless sensor terminal via an optical burst switch network. It aims to provide a synchronization system.

In order to solve the above problems, the present invention (Claim 1) includes a first time supply means,
First communication means having a function of obtaining time data from the first time supply means and obtaining a transmission time and a reception time of the message;
A second time supply means;
Second communication means having a function of obtaining time data from the second time supply means to obtain a transmission time and a reception time of a message and a function of controlling the time or frequency of the second time supply means;
A time synchronization system comprising at least one message transfer means for transferring a message between the first communication means and the second communication means,
The message transfer means comprises message delay means for delaying messages in order to avoid collision of messages;
The first communication means writes the transmission time T1 in the first message and transfers it to the second communication means,
The message transfer means records the message delay data D1 in the message delay means when transferring the first message in the delay data storage means,
The second communication means that has received the first message holds the transmission time T1 written in the first message and the reception time T2 that has received the first message in a second storage means. And
The second communication means transmits a second message to the first communication means, holds a transmission time T3 of the second message in the second storage means,
The message transfer means records the message delay data D2 in the message delay means in the delay data storage means when transferring the second message,
The first communication means that has received the second message holds the reception time T4 of the second message in the first storage means,
The first communication means notifies the reception time T4 to the second communication means,
The second communication means acquires the message delay data D1 and D2 recorded by the message transfer means from the delay data storage means,
The second communication means includes the first time supply means and the first time supply based on the transmission time T1, the reception time T2, the transmission time T3, the reception time T4, and the message delay data D1 and D2. Calculate the error δ with the time supply means of 2,
The second communication means controls the second time supply means so that the error δ becomes a constant value.

The present invention (Claim 2) includes a first time supply means,
First communication means having a function of obtaining time data from the first time supply means and obtaining a transmission time and a reception time of the message;
A second time supply means;
Second communication means having a function of obtaining time data from the second time supply means to obtain a transmission time and a reception time of a message and a function of controlling the time or frequency of the second time supply means;
A time synchronization system comprising at least one message transfer means for transferring a message between the first communication means and the second communication means,
The message transfer means comprises message delay means for delaying messages in order to avoid collision of messages;
The first communication means transfers a first message to the second communication means;
Notifying the second communication means of the transmission time T1 of the first message;
The message transfer means records the message delay data D1 in the message delay means when transferring the first message in the delay data storage means,
The second communication means that has received the first message stores the transmission time T1 notified from the first communication means and the reception time T2 from which the first message has been received in a second storage means. Hold and
The second communication means transmits a second message to the first communication means, holds a transmission time T3 of the second message in the second storage means,
The message transfer means records the message delay data D2 in the message delay means in the delay data storage means when transferring the second message,
The first communication means that has received the second message holds the reception time T4 of the second message in the first storage means,
The first communication means notifies the reception time T4 to the second communication means,
The second communication means acquires the message delay data D1 and D2 recorded by the message transfer means from the delay data storage means,
The second communication means includes the first time supply means and the first time supply based on the transmission time T1, the reception time T2, the transmission time T3, the reception time T4, and the message delay data D1 and D2. Calculate the error δ with the time supply means of 2,
The second communication means controls the second time supply means so that the error δ becomes a constant value.

The present invention (Claim 3) includes the first time supply means,
First communication means having a function of obtaining time data from the first time supply means and obtaining a transmission time and a reception time of the message;
A second time supply means;
Second communication means having a function of obtaining time data from the second time supply means to obtain a transmission time and a reception time of a message and a function of controlling the time or frequency of the second time supply means;
A time synchronization system comprising at least one message transfer means for transferring a message between the first communication means and the second communication means,
The message transfer means comprises message delay means for delaying messages in order to avoid collision of messages;
The second communication means writes a transmission time T1 in the first message and transfers it to the second communication means,
The message transfer means records the message delay data D1 in the message delay means when transferring the first message in the delay data storage means,
The first communication means that has received the first message holds the transmission time T1 written in the first message and the reception time T2 that has received the first message in the first storage means. And
The first communication means transmits a second message in which the transmission time T1, the reception time T2, and the transmission time T3 are written to the second communication means,
The message transfer means records the message delay data D2 in the message delay means in the delay data storage means when transferring the second message,
The second communication means that has received the second message holds the reception time T4 of the second message in the second storage means,
The second communication means acquires the message delay data D1 and D2 recorded by the message transfer means from the delay data storage means,
The second communication means includes the first time supply means and the first time supply based on the transmission time T1, the reception time T2, the transmission time T3, the reception time T4, and the message delay data D1 and D2. Calculate the error δ with the time supply means of 2,
The second communication means controls the second time supply means so that the previous error δ becomes a constant value.

The present invention (Claim 4) includes the first time supply means,
First communication means having a function of obtaining time data from the first time supply means and obtaining a transmission time and a reception time of the message;
The second time supply means;
Second communication means having a function of obtaining time data from the second time supply means to obtain a transmission time and a reception time of a message and a function of controlling the time or frequency of the second time supply means;
A time synchronization system comprising at least one message transfer means for transferring a message between the first communication means and the second communication means,
The message transfer means comprises message delay means for delaying messages in order to avoid collision of messages;
The second communication means writes the transmission time T1 in the first message and transfers it to the second communication means, and holds the transmission time T1 in the second storage means,
The message transfer means records the message delay data D1 in the message delay means when transferring the first message in the delay data storage means,
The first communication means that has received the first message holds the reception time T2 in the first storage means,
The first communication means transmits a second message to the second communication means, holds a transmission time T3 in the first storage means,
The first communication means transmits the reception time T2 and the transmission time T3 to the second communication means,
The message transfer means records the message delay data D2 in the message delay means in the delay data storage means when transferring the second message,
The second communication means that has received the second message holds the reception time T4 of the second message in the second storage means,
The second communication means acquires the message delay data D1 and D2 recorded by the message transfer means from the delay data storage means,
The second communication means includes the first time supply means and the first time supply based on the transmission time T1, the reception time T2, the transmission time T3, the reception time T4, and the message delay data D1 and D2. Calculate the error δ with the time supply means of 2,
The second communication means controls the second time supply means so that the error δ becomes a constant value.

Further, according to the present invention (Claim 5), in the above Claim 1 or 2, the first communication device is
Creating identification information for uniquely identifying a combination of the first communication device and the second communication device;
The message transfer means includes:
Linking the identification information to the message delay data D1 and D2 in the message delay means,
The second communication device acquires the message delay data D1 and D2 associated with the delay data storage unit based on the identification information.

Further, according to the present invention (Claim 6), in Claim 3 or 4, the second communication device is:
Creating identification information for uniquely identifying a combination of the first communication device and the second communication device;
The message transfer means includes:
Linking the identification information to the message delay data D1 and D2 in the message delay means,
The second communication device is:
Based on the identification information, the message delay data D1 and D2 associated with the delay data storage means are acquired.

  As described above, according to the present invention, the delay setting data of the OBS is recorded according to the message exchanged between the nodes in time synchronization, and the recorded delay setting data is read out by the node on the slave clock side. A time synchronization error can be corrected in combination with a message transmission time and reception time in a standard time synchronization protocol. As a result, the reference time and frequency can be supplied to the base station of the mobile phone or the wireless sensor terminal via the optical burst switch network with extremely high accuracy and stability.

It is a structural example of the conventional optical burst switch. It is a structural example of the conventional optical delay device. IEEE1588 based time synchronization mechanism. It is a block diagram of the conventional node 101. FIG. It is a block diagram of the conventional node 103. FIG. It is a block diagram of the time synchronization system in the 1st Embodiment of this invention. It is a block diagram of the node 103 in the 1st Embodiment of this invention. It is a structural example of the optical burst switch in the 1st Embodiment of this invention. It is a block diagram of the time synchronization system in the 2nd Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  The present invention records the delay setting data of the optical delay unit when the OBS transfers the Sync message or DelayReq message in association with the message, so that the delay setting data can be obtained from the node on the slave clock side, The recorded delay setting data is acquired at the node on the slave clock side, and the time synchronization error is corrected based on the delay setting data.

[First embodiment]
This embodiment corresponds to claims 2 and 5.

  FIG. 6 shows the configuration of the time synchronization system according to the first embodiment of the present invention.

  In the figure, the same components as those in FIG. In FIG. 6, a management information transfer network 105 is connected to each OBS 200 in the configuration of FIG. 3, and a delay data collector 106 is connected to the management information transfer network 105.

  FIG. 7 shows the configuration of the node 103 in the first exemplary embodiment of the present invention. The configuration of the node 103 shown in the figure is almost the same as that shown in FIG. 5, but has a management information transfer interface 28 for transferring to the management information transfer network 105.

  FIG. 8 shows the configuration of OBSs 200-1 to 200-M in the first embodiment of the present invention. The configuration shown in the figure is almost the same as that shown in FIG. 1, but has a management information transfer interface 29 for transferring to the management information transfer network 105. Each node has a memory for holding transmission time and reception time, not shown.

  A flag and a field of message identification information are provided in the label of the optical burst transmitted by the node. If the optical burst includes a Sync message or a DelayReq message, the flag is “1”; otherwise, the flag is “0”. As message identification information, ID and SN (sequence number) are used. The ID is uniquely defined in the master clock side node 103 with respect to the combination of the master clock side node 101 and the slave clock side node 103 (simply a combination of the address of the node 101 and the address of the node 103 may be used. New values may be defined). The SN is incremented for each node every time a time synchronization message is transmitted.

  Each OBS 200 receives the header of the optical burst, and if the flag is “1”, the message identification information and the delay setting data are written to the delay data table of the delay data collector 106 via the management information transfer interface 29. Although each OBS 200 can manage the delay data table individually, in this embodiment, the delay data collector 106 centrally manages the delay data table via the management information transfer network 105.

  The node 101 transmits a Sync message (ID = A, SN = X) to the node 103, and stores the transmission time T1 in the memory. The flag of the optical burst label carrying the Sync message is “1”, and the OBSs 200-1 to 200-M perform message transfer, and the delay data table of the delay data collector 106 is transferred via the management information transfer interface 29. Write as follows: The node 103 receives the Sync message and stores the reception time T2 in the memory.

次に、ノード101からノード103にSyncメッセージ送信時刻T1を書き込んだFollow-upメッセージを送信する。Follow-upメッセージを運ぶ光バーストのラベルのフラグは"０"になっており、OBS200-1〜200-Mはメッセージ転送だけを行う。ノード103はFollow-upメッセージを受信し、Syncメッセージ送信時刻T1をメモリに保存する。

Next, the Follow-up message in which the Sync message transmission time T1 is written is transmitted from the node 101 to the node 103. The flag of the label of the optical burst carrying the Follow-up message is “0”, and the OBSs 200-1 to 200-M only perform message transfer. The node 103 receives the Follow-up message and stores the Sync message transmission time T1 in the memory.

  Next, a DelayReq message (ID = A, SN = Y) is transmitted from the node 103 to the node 101, and the transmission time T3 is stored in the memory. The flag of the optical burst label carrying the DelayReq message is “1”, and the OBSs 200-1 to 200-M perform message transfer, and the delay data collector 106 receives the delay data table via the management information transfer interface 29. Add as follows. The node 101 receives the DelayReq message and stores the reception time T4 in the memory.

次に、ノード101からノード103にDelayReqメッセージ受信時刻T4を書き込んだDelayRespメッセージを返信する。DelayRespメッセージを運ぶ光バーストのラベルのフラグは"０"になっており、OBS200-1〜200-Mはメッセージ転送だけを行う。ノード103はDelayReqメッセージの送信時刻T4をメモリに保存する。

Next, a DelayResp message in which the DelayReq message reception time T4 is written is returned from the node 101 to the node 103. The flag of the label of the optical burst carrying the DelayResp message is “0”, and the OBSs 200-1 to 200-M only perform message transfer. The node 103 stores the transmission time T4 of the DelayReq message in the memory.

After a series of message exchanges, the node 103 is removed from the table of the delayed data collector 106.
(ID = A) and (SN = X)
and
(ID = A) and (SN = Y)
The data matching the above condition is read, and the error δ between the master clock 102 and the slave clock 104 is
δ = {T1-T2-T3 + T4 + (ΣK_i -ΣK'_i) * D} / 2
By controlling the slave clock 104 so that δ becomes 0, time synchronization between the master clock 102 and the slave clock 104 can be established.

  In the present embodiment, the Follow-up message and the DelayResp message are transmitted and received using optical bursts, but T1 and T3 may be separately notified to the node 103 using the management information transfer network 105.

[Second Embodiment]
This embodiment corresponds to claims 3 and 6.

  FIG. 9 shows a configuration of a time synchronization system according to the second embodiment of the present invention.

  In the first embodiment described above, the time synchronization protocol has been described on the basis of IEEE 1588 (Non-Patent Document 1), but NTP (Network Time Protocol, IETF RFC 1305) (Reference 1: DL Mills, “Network Time Protocol”). (Version 3) Specification, Implementation and Analysis ", IETF RFC-1305.) And SNTP (Simple Network Time Protocol, IETF RFC 4330) (Reference 2: DL Mills," Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6) and OSI ", IETF RFC-4330.

  In the case of NTP or SNTP base, the ID is uniquely defined in the slave clock side node (client) for the combination of the master clock side node (server) and slave clock side node (client). This is different from the embodiment.

  A query message (ID = A, SN = X) is transmitted from the node 103. The transmission time T1 is written in the Query message. The flag of the label carrying the Query message is “1”, and the OBSs 200-1 to 200-M transfer the Query message and write it in the delay data table of the delay data collector 106 as follows.

次に、ノード101からReplyメッセージ（ID = A、SN = Y）を返信する。Replyメッセージには、Queryメッセージ送信時刻T1、Queryメッセージ受信時刻T2、Replyメッセージ送信時刻T3が書き込まれている。Replyメッセージを運ぶ光バーストのラベルのフラグは"１"になっており、OBS200-1〜200-MはReplyメッセージを転送し、遅延データコレクタ106の遅延データテーブルに以下のように追記する。なお、遅延データテーブルには、第１の実施の形態と同様に、管理情報転送用インタフェース29を介して書き込むものとする。

Next, a Reply message (ID = A, SN = Y) is returned from the node 101. In the Reply message, Query message transmission time T1, Query message reception time T2, and Reply message transmission time T3 are written. The flag of the label of the optical burst that carries the Reply message is “1”, and the OBSs 200-1 to 200-M transfer the Reply message and add it to the delay data table of the delay data collector 106 as follows. The delay data table is written via the management information transfer interface 29 as in the first embodiment.

一連のメッセージ交換の後、ノード103は遅延データコレクタ106のテーブルから
(ID = A) and (SN = X)
および
(ID = A) and (SN = Y)
の条件に合致するデータを読み出し、マスタクロック102とスレーブクロック104の誤差δを、
δ = {T1 - T2 - T3 + T4 + (ΣK_i -ΣK'_i)*D}/2
で計算し、δが0になるように、スレーブクロック104を制御することにより、マスタクロック102とスレーブクロック104の時刻同期を確立できる。

After a series of message exchanges, the node 103 is removed from the table of the delayed data collector 106.
(ID = A) and (SN = X)
and
(ID = A) and (SN = Y)
The data matching the above condition is read, and the error δ between the master clock 102 and the slave clock 104 is
δ = {T1-T2-T3 + T4 + (ΣK_i -ΣK'_i) * D} / 2
By controlling the slave clock 104 so that δ becomes 0, time synchronization between the master clock 102 and the slave clock 104 can be established.

  In this embodiment, the transmission time and the reception time are transmitted and received using a Query message and a Reply message, but T2 and T3 may be separately notified to the node 103 using the management information transfer network 105.

  In addition, the operation of each component of the nodes 101, 103 and OBS 200 in the above embodiment is constructed as a program and installed and executed on a computer used as the node or OBS, or distributed via a network. Is possible.

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

1 Input port
2 Optical splitter
3 Opto-electric converter (O / E)
4 Optical switch control circuit
5 Optical delay
6 N × N optical switch
7 Output port
20 Packet interface
21 Optical burst converter
22 Time synchronization message processor
23 Time information interface
24 Time Stamper
25 Optical burst interface
26 Stay clock controller
27 Clock control interface
28 Management information transfer interface
29 Management information transfer interface
101,103 nodes
102 Master clock
104 Slave clock
105 Management information transfer network
106 Delayed data collector
200 Optical burst switch (OBS)

Claims (6)

First time supply means;
First communication means having a function of obtaining time data from the first time supply means and obtaining a transmission time and a reception time of the message;
A second time supply means;
Second communication means having a function of obtaining time data from the second time supply means to obtain a transmission time and a reception time of a message and a function of controlling the time or frequency of the second time supply means;
A time synchronization system comprising at least one message transfer means for transferring a message between the first communication means and the second communication means,
The message transfer means comprises message delay means for delaying messages in order to avoid collision of messages;
The first communication means writes the transmission time T1 in the first message and transfers it to the second communication means,
The message transfer means records the message delay data D1 in the message delay means when transferring the first message in the delay data storage means,
The second communication means that has received the first message holds the transmission time T1 written in the first message and the reception time T2 that has received the first message in a second storage means. And
The second communication means transmits a second message to the first communication means, holds a transmission time T3 of the second message in the second storage means,
The message transfer means records the message delay data D2 in the message delay means in the delay data storage means when transferring the second message,
The first communication means that has received the second message holds the reception time T4 of the second message in the first storage means,
The first communication means notifies the reception time T4 to the second communication means,
The second communication means acquires the message delay data D1 and D2 recorded by the message transfer means from the delay data storage means,
The second communication means includes the first time supply means and the first time supply based on the transmission time T1, the reception time T2, the transmission time T3, the reception time T4, and the message delay data D1 and D2. Calculate the error δ with the time supply means of 2,
The time synchronization system, wherein the second communication means controls the second time supply means so that the error δ becomes a constant value. First time supply means;
First communication means having a function of obtaining time data from the first time supply means and obtaining a transmission time and a reception time of the message;
A second time supply means;
Second communication means having a function of obtaining time data from the second time supply means to obtain a transmission time and a reception time of a message and a function of controlling the time or frequency of the second time supply means;
A time synchronization system comprising at least one message transfer means for transferring a message between the first communication means and the second communication means,
The message transfer means comprises message delay means for delaying messages in order to avoid collision of messages;
The first communication means transfers a first message to the second communication means;
Notifying the second communication means of the transmission time T1 of the first message;
The message transfer means records the message delay data D1 in the message delay means when transferring the first message in the delay data storage means,
The second communication means that has received the first message stores the transmission time T1 notified from the first communication means and the reception time T2 from which the first message has been received in a second storage means. Hold and
The second communication means transmits a second message to the first communication means, holds a transmission time T3 of the second message in the second storage means,
The message transfer means records the message delay data D2 in the message delay means in the delay data storage means when transferring the second message,
The first communication means that has received the second message holds the reception time T4 of the second message in the first storage means,
The first communication means notifies the reception time T4 to the second communication means,
The second communication means acquires the message delay data D1 and D2 recorded by the message transfer means from the delay data storage means,
The second communication means includes the first time supply means and the first time supply based on the transmission time T1, the reception time T2, the transmission time T3, the reception time T4, and the message delay data D1 and D2. Calculate the error δ with the time supply means of 2,
The time synchronization system, wherein the second communication means controls the second time supply means so that the error δ becomes a constant value. First time supply means;
First communication means having a function of obtaining time data from the first time supply means and obtaining a transmission time and a reception time of the message;
A second time supply means;
Second communication means having a function of obtaining time data from the second time supply means and obtaining a transmission time and a reception time of the message, and a function of controlling the time or frequency of the second time supply means;
A time synchronization system comprising at least one message transfer means for transferring a message between the first communication means and the second communication means,
The message transfer means comprises message delay means for delaying messages in order to avoid collision of messages;
The second communication means writes a transmission time T1 in the first message and transfers it to the second communication means,
The message transfer means records the message delay data D1 in the message delay means when transferring the first message in the delay data storage means,
The first communication means that has received the first message holds the transmission time T1 written in the first message and the reception time T2 that has received the first message in the first storage means. And
The first communication means transmits a second message in which the transmission time T1, the reception time T2, and the transmission time T3 are written to the second communication means,
The message transfer means records the message delay data D2 in the message delay means in the delay data storage means when transferring the second message,
The second communication means that has received the second message holds the reception time T4 of the second message in the second storage means,
The second communication means acquires the message delay data D1 and D2 recorded by the message transfer means from the delay data storage means,
The second communication means includes the first time supply means and the first time supply based on the transmission time T1, the reception time T2, the transmission time T3, the reception time T4, and the message delay data D1 and D2. Calculate the error δ with the time supply means of 2,
The time synchronization system, wherein the second communication means controls the second time supply means so that the previous error δ becomes a constant value. The first time supply means;
First communication means having a function of obtaining time data from the first time supply means and obtaining a transmission time and a reception time of the message;
The second time supply means;
Second communication means having a function of obtaining time data from the second time supply means and obtaining a transmission time and a reception time of the message, and a function of controlling the time or frequency of the second time supply means;
A time synchronization system comprising at least one message transfer means for transferring a message between the first communication means and the second communication means,
The message transfer means comprises message delay means for delaying messages in order to avoid collision of messages;
The second communication means writes the transmission time T1 in the first message and transfers it to the second communication means, and holds the transmission time T1 in the second storage means,
The message transfer means records the message delay data D1 in the message delay means when transferring the first message in the delay data storage means,
The first communication means that has received the first message holds the reception time T2 in the first storage means,
The first communication means transmits a second message to the second communication means, holds a transmission time T3 in the first storage means,
The first communication means transmits the reception time T2 and the transmission time T3 to the second communication means,
The message transfer means records the message delay data D2 in the message delay means in the delay data storage means when transferring the second message,
The second communication means that has received the second message holds the reception time T4 of the second message in the second storage means,
The second communication means acquires the message delay data D1 and D2 recorded by the message transfer means from the delay data storage means,
The second communication means includes the first time supply means and the first time supply based on the transmission time T1, the reception time T2, the transmission time T3, the reception time T4, and the message delay data D1 and D2. Calculate the error δ with the time supply means of 2,
The time synchronization system, wherein the second communication means controls the second time supply means so that the error δ becomes a constant value. The first communication device is
Creating identification information for uniquely identifying a combination of the first communication device and the second communication device;
The message transfer means includes:
Linking the identification information to the message delay data D1 and D2 in the message delay means,
The time synchronization system according to claim 1 or 2, wherein the second communication device acquires the message delay data D1 and D2 associated with the delay data storage unit based on the identification information. The second communication device is:
Creating identification information for uniquely identifying a combination of the first communication device and the second communication device;
The message transfer means includes:
Linking the identification information to the message delay data D1 and D2 in the message delay means,
The second communication device is:
5. The time synchronization system according to claim 3, wherein the message delay data D1 and D2 associated with the delay data storage unit are acquired based on the identification information.

Images