JP2011040992A - Sdh/sonet-packet conversion transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify processing of pointer calculation, in an SDH/SONET (Synchronous Digital Hierarchy/Synchronous Optical NETwork)-packet conversion transmitter. <P>SOLUTION: In the transmitter which transmits an SDH/SONET signal converted into a packet signal by a CEP (Circuit Emulation over Packet) packet, a transmitting device performs packetization according to a phase of the SDH/SONET signal to be input, and transmits packetized data excluding section overhead of the SDH/SONET signal of one frame stored into a fixed position of a data storage area of a CEP packet signal sequentially from the head (J1 byte) of the data. The receiving device stores received data of the packet signal into a memory, determines a pointer value based on a read-out phase of the memory and phase information of the section overhead of the SDH/SONET signal, converts the data read from the memory into the SDH/SONET signal of one frame, adds the pointer value to the SDH/SONET signal to be output. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an SDH / SONET-packet conversion / transmission apparatus, which converts a SDH / SONET (Synchronous Digital Hierarchy) / Synchronous Optical NETwork (Synchronous Optical NETwork) signal into a CEP (Circuit Emulation over Packet) packet. The present invention relates to an SDH / SONET-packet conversion / transmission apparatus for transmission.

  Conventionally, the SDH / SONET network and the packet network are completely separated, or the packet is converted into an SDH / SONET signal by EOS (Ethernet (registered trademark) Over SDH / SONET) and transmitted through the SDH / SONET network. In recent years, packet networks have rapidly developed and become popular, and systems that transmit SDH / SONET signals over packet networks are required. For such systems, RFC 4842 is used to packetize SDH / SONET signals. A packet transmission method based on CEP (Circuit Emulation over Packet) is specified.

  FIG. 4A shows the header format of the CEP packet. The header of the CEP packet includes “L” indicating whether or not an AIS (Alarm Indication Signal) of the SDH / SONET signal is present, “R” indicating CEP-RDI (Remote Defect Indication), and “N” indicating negative / positive tap. "NP", "FRG" indicating a 3-bit flag, "Length" indicating the packet length, "Sequence Number" indicating the packet sequence number, and a pointer indicating the data head position of the SDH / SONET signal and the tuff operation in the CEP packet It has an area of “Structure Pointer” for storing values.

  In the conventional SDH / SONET signal packetization, when the SDH / SONET signal is packetized on the transmission side, the packetization process is periodically performed without synchronizing the packetization process with the phase of the input SDH / SONET signal. Is going. FIG. 4B shows an example of packetization of a conventional SDH / SONET signal.

  In the conventional packetization shown in FIG. 4B, the data of the virtual container (VC-n) excluding the section overhead of the SDH / SONET signal is converted into the SDH / SONET signal in one frame period of the SDH / SONET signal. Packetize asynchronously with input phase. Therefore, as shown by a broken line in FIG. 4B, data from the middle of one frame of the SDH / SONET signal to the middle of the next one frame is packetized into one CEP packet.

  Therefore, information indicating the phase difference τ between the head byte of the SDH / SONET signal data (J1 byte in the example) and the head position of the CEP packet data is inserted into the header of the CEP packet as a pointer value and transmitted. To do. If the pointer value of the input SDH / SONET signal is a value indicating a stuff operation, the pointer value is inserted into the header of the CEP packet and transmitted.

  On the receiving side, the received CEP packet signal needs to be temporarily stored in a memory and then converted to an SDH / SONET signal. This is because the SDH / SONET signal is a continuous signal, whereas the packet signal has fluctuations in delay time during transmission, and the arrival time of each CEP packet becomes somewhat discrete. For this reason, the variation in arrival time of each CEP packet is absorbed, and the continuity when returning to the SDH / SONET signal is ensured.

  FIG. 5 shows an example of the functional block configuration of a conventional packet-SDH / SONET conversion process on the receiving side. On the receiving side, after the packet synchronization unit 1 performs packet synchronization on the received CEP packet, the pointer synchronization unit 2 performs pointer synchronization based on the pointer value in the header of the CEP packet, and performs control of the write control unit 3. Below, the payload data of the CEP packet is written into the first memory 4. At this time, the pointer value needs to be held in the second memory 5.

  Further, when a staff instruction is detected as a result of the pointer synchronization processing, it is necessary to notify the writing control unit 3 of the staff instruction and change the writing control. In the conversion to the SDH / SONET signal, the read control unit 6 reads the read phase of the first memory 4, the pointer value held in the second memory 5, and the phase information of the section overhead (SOH) to be multiplexed, It is necessary to calculate the pointer value to be added to the SDH / SONET signal by the pointer calculation unit 7, add the pointer value to the section overhead (SOH) of the SDH / SONET signal by the pointer addition unit 8, and output the SDH / SONET signal There is.

  Note that circuit emulation (CEP: Circuit Emulation over Packet) that realizes time-division multiplex transmission on a packet exchange network is described in, for example, Patent Document 1 below. Non-Patent Document 1 below describes packetization of SDH / SONET signals by CEP (Circuit Emulation over Packet).

JP 2008-124705 A

SONET / SDH Circuit Emulation over Packet (CEP) draft-ietf-pwe3-sinet-12

  In the conventional technique, when the SDH / SONET signal is packetized on the transmission side, the packetization is periodically performed regardless of the phase of the input SDH / SONET signal. Therefore, on the receiving side, after performing the packet synchronization processing, the pointer synchronization processing is performed, the pointer value is held in the memory, and the packet data read phase, pointer value, and section overhead (SOH) are converted into the SDH / SONET signal. ), The pointer value to be added is calculated and the pointer needs to be added, and the pointer calculation processing on the receiving side is complicated and enormous.

  For example, when a SDH / SONET signal of one frame of the VC-4 path is converted into one CEP packet, the data in the payload portion alone is 2349 bytes, and a standard packet size such as Ethernet (registered trademark) There is a problem that the packet size is larger than that of 1500 bytes, and transmission delay and delay time fluctuation increase.

  In addition, when one frame of data of the SDH / SONET signal is divided into a plurality of packets and packetized, if an alarm generated during packet transmission is reflected in units of packets, it is partially reflected in the SDH / SONET signal. There was a problem that. Further, in order to cope with the wander of the input SDH / SONET signal, there is a problem that a large-capacity memory must be used as a data storage memory in conversion of the SDH / SONET signal into packets. The present invention provides an SDH / SONET-packet conversion transmission apparatus that can solve the above-described problems. In the following description, the CEP packet is also simply referred to as a packet.

  The SDH / SONET-packet conversion transmission apparatus of the present invention converts an SDH / SONET signal into a packet signal by a CEP (Circuit Emulation over Packet) packet and transmits the packet signal on the transmission side. Packetization is performed according to the signal phase, and data excluding the section overhead of the SDH / SONET signal of one frame is stored in a fixed position in the data storage area of the packet signal in order from the beginning of the data to be packetized. Packet conversion means for receiving and storing the received packet signal data in the memory, and based on the read phase of the memory and the phase information of the section overhead of the SDH / SONET signal, the section of the SDH / SONET signal Determine the pointer value to insert into the overhead and Converting the data read from the Li into SDH / SONET signal frame, and the pointer value is obtained and an SDH / SONET signal converting means for outputting to impart to the SDH / SONET signal.

  The packet converting means includes means for dividing one frame data of the SDH / SONET signal into a plurality of CEP packets, and the SDH / SONET signal converting means includes a plurality of divided CEPs. Means for receiving a packet signal and storing data of the received CEP packet signal in a memory are provided.

  Further, on the receiving side, each CEP packet signal of the SDH / SONET signal transmitted in a divided manner is temporarily held, and alarm information generated in at least one packet transmission of the CEP packet signal is indicated by the CEP packet signal. The SDH / SONET signal is output by reflecting it in the alarm information of the SDH / SONET signal of one frame divided into two.

  On the receiving side, the data of the received packet signal is temporarily stored in the memory, and then sequentially read to construct the SDH / SONET signal, and the difference between the section overhead phase of the SDH / SONET signal and the read phase of the memory Is assigned as a pointer value, the amount of data held in the memory is monitored, and when the amount of retained data increases or decreases beyond a certain range, stuffing is performed using the pointer value assigned when the SDH / SONET signal is constructed. To do.

  According to the present invention, when the SDH / SONET signal is transmitted using the packet network, the position of the SDH / SONET signal in the packet is a fixed position. Can be Further, by dividing one frame of data of the SDH / SONET signal into a plurality of packets and transmitting them, it becomes possible to suppress transmission delay and fluctuation.

  Furthermore, even when one frame of data of the SDH / SONET signal is divided and transmitted into a plurality of packets, a partial alarm in packet transmission can be reflected in units of frames of the SDH / SONET signal. Further, even when the input SDH / SONET signal has a phase variation due to the influence of frequency deviation, wander, etc., the SDH / SONET signal to be reconstructed at the receiving side that has received the packetized data of the SDH / SONET signal. By performing stuffing on the SONET signal, it is possible to avoid a dropout (instantaneous interruption) of the signal due to a slip or the like.

It is a figure which shows the example of packetization of the SDH / SONET signal by this invention. It is a figure which shows the structural example of the packet-SDH / SONET conversion process of this invention. It is a figure which shows the Example of the packet-SDH / SONET conversion process of this invention. It is a figure which shows the example of packetization of the header format of a CEP packet, and the conventional SDH / SONET signal. It is a figure which shows the structural example of the conventional packet-SDH / SONET conversion process.

  In the present invention, packetization processing is performed in accordance with the phase of the SDH / SONET signal input on the transmission side. FIG. 1 shows an example of packet processing according to the present invention. In the example of FIG. 1, the virtual container (VC-n) data (data excluding the section overhead) of the SDH / SONET signal of one frame is stored in order from the first byte (J1 byte in the example) of the one frame. And packetize. Then, a fixed value (in this case, “0”) is inserted into the pointer value of the CEP header shown in FIG.

  Even if the pointer value of the input SDH / SONET signal is a pointer value indicating a stuff instruction, it is not transmitted as the pointer value of the CEP header, and the packetization timing cycle is set to about 1 byte according to the stuff instruction. By doing so, transmission timing adjustment substantially equivalent to the staff instruction is performed.

  That is, in a system that packetizes and transmits SDH / SONET signals by CEP, on the transmission side (side that converts SDH / SONET signals to packet signals), means for packetizing so that the pointer value is always a fixed value is provided. On the receiving side (the side that converts the packet signal into the SDH / SONET signal), the SDH / SONET signal position in the packet is always processed as a fixed position.

  On the receiving side, the packet signal is temporarily held in the memory. This is because the SDH / SONET signal is a continuous signal, but since the packet arrival time becomes discrete to some extent due to fluctuations during transmission, etc., the continuity of the SDH / SONET signal is reduced. Necessary to secure.

  FIG. 2 shows an example of the functional block configuration of the packet-SDH / SONET conversion process on the receiving side according to the present invention. On the receiving side, after the packet synchronization processing is performed on the received packet by the packet synchronization unit 1, the packet data is written to the first memory 4 under the control of the write control unit 3, but the SDH / SONET signal in the packet Therefore, it is not necessary to perform pointer synchronization as in the prior art, and the data phase of the SDH / SONET signal is fixedly recognized from the data storage position of the received packet.

  In the conversion to the SDH / SONET signal, the read control unit 6 reads the packet data from the first memory 4 and assigns it to the SDH / SONET signal from the read phase and the phase information of the section overhead (SOH) to be multiplexed. A pointer value to be calculated is calculated by the pointer calculation unit 7, the pointer value is added to the section overhead (SOH) of the SDH / SONET signal by the pointer adding unit 8, and an SDH / SONET signal is output.

  As described above, since packetization processing is performed in accordance with the phase of the SDH / SONET signal input on the transmission side, one frame of data of the SDH / SONET signal can be divided into a plurality of packets and transmitted. It becomes. By dividing and transmitting a plurality of packets, the packet size is reduced, and transmission delay and fluctuation can be suppressed.

  When one frame of data of the SDH / SONET signal is divided into a plurality of packets and converted, the phase information of each divided data is indicated using the header of the CEP packet and notified to the receiving side. As a first method for indicating the phase information, a part of “Sequence Number” indicating the sequence number in the header of the CEP packet can be used.

  For example, when the data of one frame of the SDH / SONET signal is divided into three, it is “01” indicating the first data, “10” indicating the second data, and the third data. 2 bits of information such as “11” indicating the “Sequence Number” may be assigned to the higher or lower 2 bits and notified to the receiving side.

  Further, as a second method for indicating the phase information of each divided data, it is possible to employ a configuration that indicates the phase information of each data by using “FRG” that indicates a 3-bit flag in the header of the CEP packet. . Further, as a third method for indicating the phase information, an area of “Structure Pointer” that stores a pointer value in the header of the CEP packet can be used.

  In the present invention, the start position in the SDH / SONET signal packet is a fixed position. Therefore, the pointer value of “Structure Pointer” is a fixed value (for example, “0”). In this case, the phase information of each divided data can be notified instead of the notification of the pointer value.

  Further, as a fourth method for indicating the phase information, a configuration in which the phase information of each divided data is notified by providing an area for writing the phase information in the payload area of the packet without using the CEP header. it can.

  Next, a description will be given of processing of an alarm generated in packet transmission when one frame of data of the SDH / SONET signal is divided and packetized. When one frame of data of the SDH / SONET signal is divided and packetized, the receiving side that has received the packet temporarily holds the received data of one frame of the SDH / SONET signal, and is one of the CEP packets. Is reflected in the alarm information of each CEP packet for one frame of the SDH / SONET signal, and the alarm information is reflected in one frame unit of the SDH / SONET signal to output the SDH / SONET signal. In this way, the alarm information can be reflected in the frame unit of the SDH / SONET signal, not the partial alarm of the SDH / SONET signal.

  Furthermore, when one frame of data of the SDH / SONET signal is divided and packetized, the receiving side that has received the packet temporarily holds the received data of a plurality of frames (for example, 3 frames) of the SDH / SONET signal. The SDH / SONET signal alarm information generated in one of the CEP packets is reflected in the SDH / SONET signal alarm information of a plurality of frames (for example, 3 frames) including the SDH / SONET signal of one frame divided into the CEP packet signal. / SONET signal is output. By doing so, it is possible to reflect the alarm information in a plurality of frames of the SDH / SONET signal, instead of reflecting a partial alarm of the SDH / SONET signal.

  Next, a description will be given of a processing example of assigning a pointer value when constructing an SDH / SONET signal on the receiving side. On the receiving side, the payload data of the CEP packet is temporarily stored in the first memory 4, and the section overhead of the SDH / SONET signal to be output when the SDH / SONET signal is constructed by sequentially reading the data from the first memory 4. The read phase of the first memory 4 is determined from the phase information of (SOH), and a fixed value can be assigned as the pointer value. By doing so, the calculation of the pointer value becomes unnecessary, and the processing can be simplified.

  Next, an example of processing for dealing with phase fluctuations caused by wander of the SDH / SONET signal input on the transmission side will be described. If the SDH / SONET signal input to the transmission side has a phase fluctuation due to the influence of frequency deviation, wander, etc., if no action is taken on the reception side, the reconstructed data of the SDH / SONET signal will be In some cases, data omission (instantaneous interruption) may occur due to slip or the like.

  Therefore, when the receiving side temporarily stores the packet data in the first memory 4 and sequentially reads the packet data from the first memory 4 to construct the SDH / SONET signal, the section overhead (SOH) of the SDH / SONET signal is established. And the difference between the read phase of the first memory 4 and the read phase of the first memory 4 as a pointer value, the packet data retention amount (the difference obtained by subtracting the read data amount from the write data amount in the first memory 4) is monitored. When the packet data retention amount increases or decreases beyond a certain range, stuffing is performed (the pointer value to be assigned and the read phase are controlled).

  That is, when the packet data holding amount exceeds the upper limit value in a certain range, a pointer value indicating negative stuff is generated and the read phase of the first memory 4 is accelerated. On the other hand, when the packet data holding amount is equal to or lower than the lower limit of the certain range, a pointer value indicating positive stuff is generated and the read phase of the first memory 4 is delayed. By doing so, it is possible to adjust the data holding amount on the receiving side and prevent the dropout (instantaneous interruption) in the reconstructed SDH / SONET signal.

  FIG. 3 shows an embodiment of conversion processing from a CEP packet to an SDH / SONET signal according to the present invention. The packet synchronizer 1 checks whether the sequence number of the header of the received CEP packet is correct (has no omission), whether alarm information such as CEP-AIS has been transferred, and the like, and needs to transfer the alarm information If there is, the alarm information is passed to the alarm transfer processing unit 10.

  Also, the packet synchronization unit 1 passes the information indicating the head of the payload in the case of normal reception to the write control unit 3, and skips the address for one packet when alarm information such as CEP-AIS is received. If a packet loss is detected, an instruction to skip the address for the lost packet and information indicating the beginning of the payload are passed.

  The write control unit 3 generates the address specified by the phase of the packet data and the write address of the memory 4 based on the information passed from the packet synchronization unit 1. Further, the generated write address is passed to the phase comparison unit 9 and the alarm transfer processing unit 10.

  The phase comparison unit 9 compares the memory write address from the write control unit 3 with the memory read address from the read control unit 6, and causes the read control unit 6 and the pointer calculation unit 7 to make the difference constant. Instruct positive / negative staff.

  The read control unit 6 generates a memory read address. When there is a stuff instruction from the phase comparison unit 9, the read control unit 6 controls reading in response to the instruction. That is, when a negative stuff instruction is issued, reading is performed at a phase corresponding to H3 bytes, and when a positive stuff instruction is issued, processing for stopping reading by 1 byte is performed at a phase immediately after corresponding to H3 bytes. The read control unit 6 passes the read address to the pointer calculation unit 7, the phase comparison unit 9, and the alarm transfer processing unit 10.

  The pointer calculation unit 7 compares the read address information from the read control unit 6 with the phase information of the section overhead (SOH) of the SDH / SONET signal, calculates the pointer value, and sends the pointer value to the pointer grant unit 8. hand over. Further, when there is a stuffing instruction from the phase comparison unit 9, it is converted into a pointer value indicating the stuff instruction, and the pointer value is passed to the pointer providing unit 8.

  The alarm transfer processing unit 10 calculates the read delay of the memory 4 from the write address of the write control unit 3 and the read address of the read control unit 6, and outputs the alarm information from the packet synchronization unit 1 at which timing SDH / It is determined whether to reflect in the SONT signal, and alarm information to be inserted and timing information to be reflected are passed to the alarm insertion unit 11. The alarm insertion unit 11 inserts alarm information and outputs an SDH / SONT signal based on these pieces of information passed from the alarm transfer processing unit 10. With the above configuration, the embodiment of the present invention can configure an SDH / SONET-packet conversion transmission apparatus with a reduced circuit scale compared to the conventional configuration example.

DESCRIPTION OF SYMBOLS 1 Packet synchronization part 2 Pointer synchronization part 3 Write control part 4 1st memory 5 2nd memory 6 Read control part 7 Pointer calculating part 8 Pointer assignment | providing part 9 Phase comparison part 10 Alarm transfer process part 11 Alarm insertion part

Claims (11)

In a transmission device that converts an SDH / SONET signal into a packet signal using a CEP (Circuit Emulation over Packet) packet and transmits it.
On the transmitting side, packetization processing is performed in accordance with the phase of the input SDH / SONET signal, and data excluding the section overhead of the SDH / SONET signal of one frame is stored in the data of the packet signal in order from the head of the data. Packet conversion means for storing and packetizing at a fixed position in the area;
On the receiving side, the received packet signal data is stored in the memory, and the pointer value to be inserted into the section overhead of the SDH / SONET signal based on the read phase of the memory and the phase information of the section overhead of the SDH / SONET signal SDH / SONET signal converting means for converting the data read from the memory into an SDH / SONET signal of one frame, and giving the pointer value to the SDH / SONET signal for output.
An SDH / SONET-packet conversion transmission device characterized by comprising:   The packet conversion means includes means for dividing one frame of data of the SDH / SONET signal into a plurality of CEP packets, and the SDH / SONET signal conversion means includes a plurality of divided CEP packet signals. The SDH / SONET-packet conversion / transmission apparatus according to claim 1, further comprising means for storing data of the received CEP packet signal in a memory.   When the transmitting side divides the SDH / SONET signal into a plurality of CEP packets and packetizes them, information indicating the phase information of each divided data of the SDH / SONET signal is stored in the header of the CEP packet and transmitted. 3. The SDH / SONET-packet conversion / transmission apparatus according to claim 2, wherein the receiving side recognizes the phase of each divided data of the SDH / SONET signal divided into a plurality based on the phase information. .   4. The SDH / SONET-packet conversion transmission according to claim 3, wherein the information indicating the phase information of each of the divided data is transmitted by being stored in a part of an area indicating a sequence number in a header of the CEP packet. apparatus.   4. The SDH / SONET-packet conversion / transmission apparatus according to claim 3, wherein information indicating the phase information of each of the divided data is stored and transmitted in an area indicating a flag in a header of the CEP packet.   4. The SDH / SONET-packet conversion / transmission apparatus according to claim 3, wherein information indicating phase information of each divided data is stored and transmitted in an area indicating a pointer value in a header of the CEP packet.   4. The SDH / SONET-packet conversion / transmission apparatus according to claim 3, wherein information indicating phase information of each of the divided data is stored in a payload area of the CEP packet and transmitted.   On the receiving side, each CEP packet signal of the SDH / SONET signal transmitted in a divided manner is temporarily held, and alarm information generated in at least one packet transmission of the CEP packet signal is divided into the CEP packet signals. 3. The SDH / SONET-packet conversion / transmission apparatus according to claim 2, wherein the SDH / SONET signal is output by reflecting it in the alarm information of the one-frame SDH / SONET signal.   On the receiving side, each CEP packet signal of the SDH / SONET signal transmitted in a divided manner is temporarily held, and alarm information generated in at least one packet transmission of the CEP packet signal is divided into the CEP packet signals. 3. The SDH / SONET-packet conversion according to claim 2, wherein the SDH / SONET signal is output in response to alarm information of a plurality of frames of SDH / SONET signals including one frame of SDH / SONET signals. Transmission equipment.   On the receiving side, after temporarily storing the received packet signal data in the memory, the data from the memory is read based on the phase information of the section overhead of the SDH / SONET signal when sequentially reading and constructing the SDH / SONET signal. 2. The SDH / SONET-packet conversion / transmission apparatus according to claim 1, wherein a read phase is determined and a fixed pointer value is added to a section overhead of the SDH / SONET signal.   On the receiving side, the data of the received packet signal is temporarily stored in the memory, and then sequentially read to construct the SDH / SONET signal, and the difference between the phase of the section overhead of the SDH / SONET signal and the read phase of the memory is pointed to When assigning as a value, the amount of data retained in the memory is monitored, and when the amount of retained data increases or decreases beyond a certain range, stuffing is performed using the pointer value that is assigned when the SDH / SONET signal is constructed. The SDH / SONET-packet conversion transmission apparatus according to claim 1.

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