JP4555989B2 - Time stamp device and time stamp packet generation device - Google Patents

Description

  The present invention relates to a time stamp apparatus that inserts highly accurate time stamp information into a predetermined data packet on a network, and a time stamp packet generating apparatus that generates a data packet for storing highly accurate time stamp information. More specifically, the present invention provides high accuracy for data packets on a network for the purpose of non-invasive measurement of the network, that is, measurement processing such as high-accuracy monitoring and analysis with minimal influence on fluctuations in transmission delay. The present invention relates to a time stamp device for giving time stamp information such as time and time, and a data packet generation device.

  The time required to transmit the smallest Ethernet frame (72 bytes = MAC 22 bytes + Network PDU 46 bytes + CRC 4 bytes) on 1 gigabit Ethernet is 576 nanoseconds. In order to enable measurement of such a high-speed broadband network, high-accuracy time stamp processing in units of 10 nanoseconds is required.

  As a time stamp process for IP packets on Ethernet, there is a time stamp option in the header portion of the IP packet (see RFC781). The accuracy with this timestamp option is only on the order of milliseconds. Furthermore, insertion of a time stamp into the header portion of an IP packet is accompanied by a change in packet length, resulting in a variation in transmission delay, and thus is not suitable for time stamp processing for highly accurate network measurement.

  Various improvements have been made to improve the accuracy of time stamp processing. For example, as a time stamp process only by software, there is a method of providing a time stamp function in a network device driver and inserting time stamp information using a CPU time stamp counter, and the accuracy is improved to nearly 1 microsecond. ing.

However, since the frequency of the crystal oscillation circuit in the computer (PC) changes depending on the temperature, there is a problem that the fluctuation of the frequency reduces the accuracy of the time stamp information. Therefore, there is an improved technique for compensating for the frequency fluctuation of the crystal oscillation circuit by software. There is also an improved technique that uses a cesium atomic clock with improved stability instead of a crystal oscillator circuit. For example, in a network measurement system based on hardware called DAG, hardware time stamp processing using a cesium atomic clock is performed (see Non-Patent Document 1).
Jorg Micheel, Stephen Donnelly, and Ian Graham, "Precision timestamping of network packets" pp 54-97, In proceedings of the ACM SIGCOMM Internet Measurement Workshop, San Francisco, November 2001.

  Various network applications such as network measurement and time synchronization require highly accurate time information. For example, in Gigabit Ethernet, the network transit time per byte is 8 nanoseconds, and in 10 Gigabit Ethernet, it is only 0.8 nanoseconds.

  The accuracy of the hardware time stamp apparatus of the DAG system disclosed in Non-Patent Document 1 is about 100 nanoseconds at maximum. This is because scintillation in the atmosphere fluctuates the GPS signal and further changes the cesium electronic clock on the GPS. On the other hand, jitter (transmission delay fluctuation) in a Gigabit Ethernet LAN is less than 100 nanoseconds. Therefore, a hardware time stamp device using GPS is not suitable for such high-speed network measurement.

  Further, since the time stamp apparatus of the DAG system of Non-Patent Document 1 has a structure in which time stamp information is taken into the host PC separately from the packet, the time information inserted at a plurality of transit points on the network is made into one packet. It cannot be stored and transferred.

  An object of the present invention is to provide a time stamp device that provides highly accurate time information in order to enable non-invasive measurement that does not change the transmission delay in high-speed network measurement.

  Another object of the present invention is to provide a time stamp packet generation device that stores high-accuracy time information and generates data packets that do not cause fluctuations in transmission time.

To achieve the above object, the present invention provides a time-stamping device for inserting time information to the data packets on the network, 1) time synchronization signal generating means for generating a synchronization signal and the time signal from the external clock signal 2) time counting means for counting time at predetermined intervals using the time signal; 3) first network interface means for converting a data signal received from the network into a bit stream; and 4) the bit stream. a second network interface over face means for transmitting converted data signal to the network, 5) using the synchronization signal, passes between said first network interface unit and the second network interface means the Process the bitstream using the cut-through method And a packet processing means.

The packet processing means detects a data packet having predetermined identification information and having a fixed payload portion from the data packet converted into a bit stream by the first network interface means , a process of storing the time count information generated Ri by said time counting means to the payload portion of the detected data packet, checksum calculation result of the time count information is stored data packet to the data packet and it calculates a checksum compensation values for the checksum value set, and a process of storing the trailer part of the data packet the calculated checksum compensation value.

  The time stamp apparatus of the present invention uses, for example, a 10 MHz clock signal of a cesium atomic clock as a high-precision external clock signal. The time counting means includes a 64-bit counter, for example, and performs time counting at a predetermined interval using a time signal of 100 MHz obtained by amplifying the clock signal. This time count information (counter value) is used as time stamp information.

  A data signal on the network is converted into a bit stream by the first network interface means, passes through the packet processing means, is converted to a data signal by the second network interface means, and is sent out on the network. The Further, the packet processing means performs the following processing on the passing bit stream by the cut-through method.

  The packet processing means detects a data packet for a specific time stamp using predetermined identification information of the data packet configured by a bit stream. Then, the time count information (counter value) supplied by the time count means is stored in the fixed-size payload portion of the data packet in which the identification information is detected. Further, a compensation value is calculated so that a checksum calculation result performed after storing the time count information becomes a predetermined checksum value set in the data packet, and the compensation value is added to a predetermined portion at the end of the data packet. Store.

  Thereafter, the data packet processed by the packet processing means is converted into a data signal by the second network interface means and sent to the network.

  The bit stream for which no identification information has been detected is sent as it is to the network by the second network interface means.

  In the time stamp device of the present invention, the time counting means uses, for example, a unit of 10 nanoseconds using an arbitrary frequency amplified based on a high-accuracy external clock signal such as a 10 MHz clock signal of a cesium atomic clock. The packet processing means stores time stamp information using highly accurate time count information in a specific packet by a cut-through method instead of a store-and-forward method. In the time stamp apparatus of the present invention, the processing target of the packet processing means is a data packet having a payload portion having an arbitrary fixed data size in which predetermined identification information is set. For example, a datagram such as UDP Use type data packets.

  Thereby, in the measurement of a high-speed network, the highly accurate measurement of the transmission time using highly accurate time stamp information is realizable. In addition, since a change in transmission delay due to a change in packet size or a change in buffering time does not occur, noninvasive measurement that does not affect transmission delay jitter can be realized.

  Further, when the time count information is stored in the payload portion of the packet data, the packet processing means stores the time count information in addition to the stored time count information. As a result, time stamp information at a plurality of transit points can be stored and transferred in one data packet, so that the transmission time of the network can be monitored and measured with one data packet.

  The packet processing means detects a predetermined mode value from the data packet, and stores predetermined time stamp information including at least time count information in the payload portion according to the mode value. For example, a mode for sequentially storing time count information (counter value) at each waypoint, a mode for storing a parameter for converting the counter value into time information together with the counter value, and a mode for storing predetermined data such as a measured value together with the counter value Etc. can be specified. Thereby, highly accurate time stamp information can be used not only for network measurement but also for transfer of measurement data that requires accurate time management.

  The packet processing means further includes a packet capture means for capturing the bit stream and storing it in a data storage means. As a result, the bit stream passing over the network can be stored and used for network monitoring and analysis.

  The present invention also relates to a time stamp packet generating device for generating a time stamp data packet. 1) A time stamp packet storing device having a predetermined data size for storing time information and storing predetermined identification information. A packet generation unit that generates a datagram type data packet; and 2) a network interface unit that converts the data packet into a data signal and transmits the data signal to a network.

  The time stamp packet generator of the present invention further includes 3) time synchronization signal generating means for generating a synchronization signal and a time signal from a highly accurate external clock signal, and 4) a predetermined interval using the time signal. And 5) time stamp giving means for storing time count information by the time counting means in the payload portion of the data packet.

  Thereby, a data packet to be processed by the time stamp device can be provided.

  Further, the network interface means of the time stamp packet generating device sends the data packet to the network at an arbitrary interval. Thereby, a packet corresponding to an accurate time signal or a 1 pps (packet per second) signal can be transmitted or broadcast.

  According to the time stamp apparatus of the present invention, it is possible to realize a process of giving time stamp information with higher accuracy (for example, 10 nanoseconds rms) than the accuracy of 100 nanoseconds of the conventional time stamp processing. High-precision measurement for high-speed networks is possible.

  Further, according to the time stamp apparatus of the present invention, highly accurate time stamp information can be stored for a specific data packet passing by a cut-through method, and non-invasive measurement for a high-speed network becomes possible.

  In addition, the time stamp packet generator of the present invention can send packets storing high-accuracy time stamp information at an arbitrary interval. For example, a 1 pps packet can be used to set the clock of network home appliances and information devices. It is possible to transmit and provide accurate time information to precision measuring instruments and synchronization systems that require 1 pps signals.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  The time stamp apparatus 1 of the present invention is an apparatus that inserts high-precision time stamp information into a predetermined data packet that passes through a network, or creates a data packet for inserting time stamp information.

  The time stamp information provided by the time stamp device 1 is a counter value counted up at a predetermined interval based on a highly accurate external clock signal. The predetermined interval is GTS (Generalize Time Stamp), and in this example, the counter value is 10 nanoseconds. The reason why the value inserted as the time stamp information is not the power of nanoseconds but the number of counts of a predetermined interval (GTS) is that the processing cost can be reduced and the jitter can be reduced.

  A predetermined data packet to be processed by the time stamp device 1 or a data packet to be generated is a UDP (User Datagram Protocol) packet having a specific port number and corresponds to both IPv4 and IPv6. To do. Details of the format of this specific data packet will be described later.

  FIG. 1 is a diagram showing a configuration example of a time stamp apparatus according to the present invention.

  The time stamp device 1 is implemented based on a PCI (Peripheral Component Interconnect) standard card size FPGA, and includes a network interface unit 10, a time synchronization information generation unit 20, a time counter unit 30, a packet processing unit 40, and a host interface unit 50. Is provided.

  The network interface unit 10 has two ports having a 1 gigabit Ethernet interface, and converts a data signal on the network into a bit stream, or converts the converted bit stream into a data signal and sends the data signal to the network Is a means for performing full-duplex operation.

  Specifically, the network interface unit 10 includes the port # 1 of the connector (RJ45) 11-1 and the physical layer processing unit (PHY) 12-1, the connector (RJ45) 11-2, and the physical layer processing unit (PHY), respectively. ) Two 1000Base-T interfaces consisting of 12-2 port # 2 are provided, and an IP packet passes between the two interfaces (port # 1 and port # 2).

  The time synchronization information generation unit 20 includes an external signal input unit 21 and a phase synchronization unit (PLL) 22. The high-precision reference clock signal input by the external signal input unit 21 is amplified by the phase synchronization unit 22 and has a predetermined frequency. The processing means for generating the synchronization signal and the time signal.

The external signal input unit 21 uses a 10 MHz clock signal of a cesium electronic timepiece as a highly accurate reference clock signal. Alternatively, a clock signal of an oven type crystal oscillation circuit (not shown) provided in the rubidium atomic oscillator and the time stamp apparatus 1 may be used. Note that the oven-type crystal oscillation circuit in the apparatus has a performance capable of maintaining an accuracy of 10 ⁻⁸ in a temperature-controlled room without using an external 10 MHz signal.

  The external signal input unit 21 can input a highly accurate 1 pps signal (1 second pulse).

  The phase synchronization unit 22 amplifies the high-accuracy reference clock signal input from the external signal input unit 21, and outputs a 25 MHz synchronization signal to the physical layer processing units 12-1 and 12-2 and the packet processing unit 40. A 100 MHz synchronization signal or a 1 pps time signal is sent to the counter unit 30. In addition, a 40 MHz synchronization signal is sent to the host interface unit 50.

The time counter unit 30 has a 64-bit time counter and counts up at a predetermined interval (GTS) using a synchronization signal and a time signal. One count is in units of 10 nanoseconds, and the maximum number is 2 ²⁷ × 10 nanoseconds.

  In addition, the time counter unit 30 resets the counter value to 0 when the time stamp device 1 is turned on or for the first 1 pps time signal. Each time the 1 pps time signal reaches the power of 2, a value obtained by dividing the time stamp value by the 1 pps number is calculated, and the 64-bit calculation result is held as the counter rate.

  The packet processing unit 40 selects a GTS packet having a predetermined specific port number from among IP packets (bitstreams) passing through the pipeline between the two ports # 1 and # 2 of the network interface unit 10. Processing means for processing by a cut-through method.

  The packet processing unit 40 includes a time stamp assigning unit 41, a checksum compensation unit 42, a packet capture unit 43, and a packet generation unit 44.

  The time stamp assigning unit 41 detects a predetermined position of the passing IP packet, and for only a GTS packet having a specific port number, according to the mode designation set in the predetermined position of the payload part, the predetermined time stamp It is a processing means for storing information in a GTS packet. The time stamp giving unit 41 uses, as time stamp information, the counter value counted up by the time counter unit 30 when the head of the Ethernet frame of the GTS packet arrives at the connectors 11-1 and 11-2.

  After storing the time stamp information, the checksum compensation unit 42 computes a compensation value for the CRC (Cyclic Redundancy Check) checksum computation result to be a checksum value set in the header part of the GTS packet. It is a processing means stored in the trailer.

  The packet capture unit 43 is a processing unit that captures an Ethernet frame (bit stream) that passes through two ports of the network interface unit 10 and stores it in a predetermined data storage unit, for example, in the tcpdump format. The packet capture unit 43 captures 10 million or more Ethernet frames at a wire rate.

  The packet generation unit 44 is a processing unit that includes a payload portion having a predetermined data size for storing time stamp information, and generates a datagram type data packet in which a predetermined port number is set, that is, a GTS packet. The packet generator 44 sends the generated GTS packet to the network at an arbitrary interval through the network interface unit 10.

  The packet processing unit 40 passes the IP packet other than the GTS packet as it is without performing any processing.

  A GTS packet to be processed by the packet processing unit 40 has a payload portion having a predetermined data size. As for the format of the payload part, version number (Ver #), mode (mode), number of TS (n), serial number (serial #) are set to 0 to 7 bytes, and time stamp information is stored after 8 bytes. Configured.

  The version number is a field indicating the version of the format of the GTS packet, the mode is a field indicating the type of time stamping process, the TS number is a field indicating the number of hops that is the number of time stamps stored in the payload portion, and the serial number is a series This field indicates the order of the GTS packet. Each value is stored in network byte order or big-endian.

  2 to 4 show the format of the payload portion of the GTS packet in each mode.

  The mode designation includes, for example, a passing mode (0x02), a time conversion mode (0x04), and an event time stamp mode (0x10, 0x11).

[Passing mode]
The passing mode is a mode in which time stamp information of a plurality of waypoints can be stored in the payload portion.

  As shown in FIG. 2A, it is assumed that a packet is transmitted from the computer TX to the computer RX through the network N. The time stamp devices 1-1 and 1-2 are installed on the computer TX side and the computer RX side, respectively, and GTS packets transmitted from the computer TX to the computer RX are used in the passing mode.

  The time stamp device 1-1 stores time stamp information (timestamp # 0) in the GTS packet in the passing mode, and the time stamp device 1-2 stores time stamp information (timestamp # 1) in the same packet.

  Thereby, the transmission time of the network N between the computer TX and the computer RX can be measured with one GTS packet.

  FIG. 2B is a diagram showing the format of the payload portion specifying the passing mode.

  When the time stamp assigning unit 41 detects the designation of the passing mode (xxxxxxxx = 00000010) as the mode designation, the time stamp assigning unit 41 determines the predetermined storage location (8 *) of the payload part from the value of the number of TSs (hops) n (yyyyyyyy) in the payload part. The time stamp information is stored in the (yyyyyyyy + 1)) byte, and the TS number (hop number) n (yyyyyyyy) is incremented by one. If the size of the GTS packet is less than “8 * (yyyyyyyy + 1)” bytes, the time stamp information is stored in the last 8 bytes of the packet.

[Time conversion mode]
The time conversion mode is a mode for storing a GTS counter value and a value for converting the counter value into time information as time stamp information.

  In the present invention, the counter value by the time counter unit 30 is used as time stamp information in order to suppress processing costs and jitter. The counter value c can be easily converted to time t in the second unit system by the following equation (1).

t = c / r + o (1)
In the time conversion mode, a set of parameters necessary for conversion to the count value of the time counter unit 30 and time t is stored as time stamp information in the payload portion.

  FIG. 3 is a diagram showing the format of the payload portion for specifying the time conversion mode.

  When the time stamp adding unit 41 detects the specification of the time conversion mode (xxxxxxxx = 00000100) as the mode specification, the counter value (c) of the time counter unit 30 as the time stamp information, and the counter rate indicating the count number rate for one second (Rate (r)), offset (offset (o)) indicating the time when the counter is set to 0, and a unit of time (time) calculated from the counter value are set to a predetermined position (16th byte) of the payload portion Store.

  Thus, the host computer that has acquired the GTS packet in the time conversion mode can calculate the time t from the counter value c.

[Event timestamp mode]
The event time stamp mode is a mode for storing a GTS counter value and predetermined data as time stamp information.

  FIG. 4 is a diagram illustrating a format example of the payload portion for designating the event time stamp mode.

  When the time stamp assigning unit 41 detects the designation of the unlocked state (xxxxxxxx = 00010000) in the time conversion mode as the mode designation, the time stamp assigning unit 41 sets the counter value by the time counter unit 30 and a predetermined measurement value as time stamp information. And the mode is rewritten to the time conversion lock state (xxxxxxxx = 00010001).

  On the other hand, when the time stamp assigning unit 41 detects the designation of the locked state (xxxxxxxx = 00010001) of the time conversion mode as the mode designation, it does not store the time stamp information in the payload part.

  As a result, when data measured by the host computer is transferred to another computer via Ethernet, the counter value and the set of data to be transferred are stored in the payload portion of the GTS packet in the event time stamp mode. Accurate time stamps can be given to data.

  In any mode, the processing performance of the packet processing unit 40 is irrelevant to the packet length and is substantially constant at 400 nanoseconds. However, jitter of up to 20 nanoseconds (11 nanoseconds r.m.s) occurs. This is because the Fast Ethernet transmission frequency is 25 MHz.

  FIG. 5 shows an example of a measurement result of jitter of a 100M Ethernet GTS packet according to the present invention. It can be seen that the carrier of the 100M Ethernet network is 25 MHz, and that the present invention accurately measures the expected range of jitter.

  The host interface unit 50 is a processing unit that exchanges data and control with the host computer in which the time stamp device 1 is inserted by PCI. The host interface unit 50 supplies power via the PCI bus, and sets or resets each processing unit of the time stamp apparatus 1.

  The host computer can confirm the status of each processing means such as the clock of the phase synchronization unit 22 of the time stamp device 1 and the presence of a 10 MHz external clock signal through the host interface unit 50, and can remotely update the firmware.

  Hereinafter, application examples of the present invention will be described. The present invention is applied to each process of measurement of transfer jitter of a network device, evaluation of time stamp processing in a computer, and evaluation of network usage rate.

[Measurement of transfer jitter of network devices]
FIG. 6 is a diagram for explaining transfer jitter measurement of a network device to which the present invention is applied. As shown in FIG. 6A, when a packet is transmitted from the computer TX to the computer RX through the network device ND, the packet transfer jitter of the network device ND is measured. In order to measure several GbE switching hubs and L2 / 3 switches, the time stamp devices 1-1 and 1-2 are respectively installed on the computer TX side and the computer RX side across the measurement target. A GTS packet in passing mode was transmitted to

  The measurement result shown in FIG. 6B shows that the jitter of the switching hub is about 40 nanoseconds, and the jitter of the L2 / 3 switch is 100 to 200 nanoseconds. From this result, it can be seen that in some switching hubs, the jitter of transmission delay in the connected LAN does not exceed 100 nanosecond units. 100 nanosecond jitter is the limit of time synchronization by GPS. Thus, it can be seen that time synchronization of less than 100 nanoseconds in a wired network can be achieved without using GPS.

[Evaluation of time stamp processing in computers]
FIG. 7 is a diagram for explaining evaluation of time stamp processing in a computer to which the present invention is applied.
Assume that a packet is transmitted from the computer TX to the computer RX as shown in FIG.

  Computers with programmability and versatility are often used to time stamp packets. There are two typical techniques for improving the accuracy of time stamp processing using a computer.

  One approach is to use a processor cycle counter instead of the gettimeofday () function. Recent MPUs include a high-accuracy counter that increments the clock cycle of each CPU, and this counter corresponds to GTS.

  The other is a method of implementing a time stamp function in a device of a network interface. The device driver is the final stage in the program, and the time stamp processing in the device driver is hardly affected by the process schedule.

  Therefore, the time stamp apparatus 1 was connected to the entrance / exit of the network of the computer TX, and the accuracy of the time stamp processing by the above method in the computer TX was evaluated. That is, processing using the gettimeofday () function in the user program area (user land), processing by RDTSC in the user program area (an instruction to read a processor cycle counter in a certain MPU), and a network interface driver (NIC) The treatment with RDTSC was evaluated.

  The computer TX to be tested is a 2.4 GHz MPU and FSB 400 MHz bus, the operating system is Linux 2.4.20, and the network interface driver is tulip-0.9.14. The computer TX is driven by a cesium electronic timepiece.

  FIG. 7B shows the evaluation results. From this evaluation result, it can be seen that the accuracy of time stamp processing by RDTSC in the NIC is 100 nanoseconds or better than the time stamp processing of GPS-based hardware. Since the time during which high accuracy is maintained depends on the crystal oscillation circuit in the computer, it is necessary to replace the crystal oscillation circuit in order to maintain long-term stable processing accuracy.

[Estimation of network usage]
FIG. 8 is a diagram for explaining estimation of a network usage rate to which the present invention is applied.

  As shown in FIG. 8A, in order to estimate the usage rate of the line between the hub A and the hub B on the network, the time stamp devices 1-1 and 1-2 are respectively connected to the hub A and the hub B. The GTS packet was sent as a probe packet from the time stamp device 1-1 to the time stamp device 1-2, and traffic from the hub A to the hub B was measured.

  From the transmission delay of the probe packet, it can be confirmed whether the packet is waiting to be transferred. For example, assuming that the background traffic packet size is a constant P and the communication speed of the line is R, as shown in the upper part of FIG. 8B, in the background traffic transmitted from the hub A to the hub B, Packet occupies the line.

  In that case, as shown in the lower part of FIG. 8B, the delay due to waiting is uniform from zero to P / R, and if the probe packet is not in a waiting state, the transmission delay should be minimized. It is. Therefore, the ratio of packets included in the minimum capacity indicates the line non-use rate.

  FIG. 8C shows the waiting time for actual measurement of the probe packet when the occupation ratio of the background packet with the packet size P = 1500 bytes is 50% on the 1 Gbps line. This histogram is generally similar to the theoretical histogram shown at the bottom of FIG. 8 (B), while the estimated value of 50.2% is quite close to the actual traffic.

  As mentioned above, although this invention was demonstrated by the embodiment, it cannot be overemphasized that a various deformation | transformation is possible for this invention in the range of the main point. For example, the two ports of the network interface unit 10 of the time stamp device 1 may be ports of a 10 Gigabit Ethernet interface using an XENPAC specification optical module. The clock signal input by the external signal input unit 21 is not limited to 10 MHz.

It is a figure which shows the structural example of the time stamp apparatus of this invention. It is a figure which shows the format of the payload part of the GTS packet of passing mode specification. It is a figure which shows the format of the payload part of the GTS packet of time conversion mode specification. It is a figure which shows the format of the payload part of the GTS packet of event time stamp mode specification. It is a figure which shows the example of the measurement result of the jitter of the GTS packet of 100M Ethernet. It is a figure for demonstrating the measurement of the transfer jitter of the network device to which this invention is applied. It is a figure for demonstrating evaluation of the time stamp process in the computer to which this invention is applied. It is a figure for demonstrating the estimation of the utilization factor of the network to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Time stamp apparatus 10 Network interface part 11-1, 11-2 Connector 12-1, 12-2 Physical layer processing part 20 Time synchronization information generation part 21 External signal input part 22 Phase synchronization part 30 Time counter part 40 Packet processing part 41 Time stamp assignment unit 42 Checksum compensation unit 43 Packet capture unit 44 Packet generation unit 50 Host interface unit

Claims (7)

A time stamp device for inserting time information into a data packet on a network,
Time synchronization signal generating means for generating a synchronization signal and a time signal from an external clock signal;
Time counting means for counting time at predetermined intervals using the time signal;
First network interface means for converting a data signal received from the network into a bit stream;
Second network interface means for converting the bitstream into a data signal and sending it to a network;
Packet processing means for processing the bit stream passing between the first network interface means and the second network interface means by a cut-through method using the synchronization signal;
The packet processing means detects a data packet having predetermined identification information and having a fixed payload part from the data packet converted into a bit stream by the first network interface means;
Processing for storing the time count information generated by the time count means in the payload portion of the detected data packet;
A checksum compensation value is calculated so that a checksum calculation result of the data packet storing the time count information becomes a checksum value set in the data packet, and the calculated checksum compensation value is calculated as the data. A time stamp device characterized by performing processing for storing in a packet trailer section. When the time count information is stored in the payload portion of the packet data converted into the bit stream, the packet processing means is generated by the time count means at a position subsequent to the stored time count information. The time stamp apparatus according to claim 1, wherein the time count information is stored. The packet processing means detects a predetermined mode value from the data packet converted into the bit stream, and at least predetermined information including time count information generated by the time counting means according to the detected mode value Is stored in the payload portion of the data packet. The time stamp device according to claim 1 or 2, wherein: Data storage means for storing the bitstream converted by the first network interface means;
It said packet processing means, any one of claims 1 to 3, characterized in that capturing the bit stream converted by the first network interface comprises a packet capture means for storing in said data storage means The time stamp apparatus as described in the item. A time synchronization signal generating means for generating a synchronization signal and a time signal from an external clock signal; a time counting means for counting time at a predetermined interval using the time signal; and a data signal received from the network for converting to a bit stream. Network interface means, second network interface means for converting the bit stream into a data signal and sending it to the network, and using the synchronization signal, the first network interface means and the second network interface. While processing the bit stream passing between the means by a cut-through method, a data packet having predetermined identification information and having a fixed payload portion is detected from the data packet converted into the bit stream. ,in front A packet that stores time count information in the payload portion of the detected data packet, calculates a checksum compensation value for the checksum value of the data packet after storing the time count information, and stores it in the trailer portion of the data packet A time stamp packet generating device for generating a time stamp data packet to be processed by a time stamp device comprising processing means ,
A packet generation means for generating a datagram type data packet having a fixed length data size and having a payload portion for storing time count information, and storing predetermined identification information;
And a network interface means for converting the data packet into a data signal and sending the data packet to a network. Time synchronization signal generating means for generating a synchronization signal and a time signal from an external clock signal;
Time counting means for counting time at predetermined intervals using the time signal;
6. The time stamp packet generation device according to claim 5 , further comprising: a time stamp assigning unit that stores the time count information generated by the time count unit in a payload portion of the data packet generated by the packet generation unit. . The time stamp packet generation device according to claim 5 or 6 , wherein the network interface means transmits the data packet to a network at an arbitrary interval.

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