JP2005286641A - Communication device, communication system, and receiving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that duplication or missing of frames can occur in the communication device that uses Ethernet (R) for connection with double transmission paths because there exists no such means as absorbing a delay difference of data inputted from two transmission paths. <P>SOLUTION: The communication device comprises a medium access control means, first and second encoding/decoding means, a memory for holding reception data, and a signal conversion means. The first and second encoding/decoding means assigns a consecutive number to the region between transmission frames when transmitting, while extracting the consecutive number at receiving to adjust transmission delay difference between the reception data. In the receiving method, the data containing the consecutive number assigned to the region between the frames is received from two transmission paths, and the consecutive number is extracted from the reception data to adjust transmission delay difference between the reception data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a communication device, a communication system, and a reception method, and more particularly, to switching of a transmission path of a communication apparatus that performs communication via two transmission paths.

  In a communication system in which a working transmission line and a spare transmission line are arranged between communication apparatuses, when trouble occurs in one transmission line, it is necessary to switch the transmission line as quickly as possible or without interruption. Various methods have been proposed for this purpose. Recently, for example, two virtual paths are set between nodes of an ATM network, the switching control management cells are transmitted in parallel and intermittently from the transmitting node, the sequence numbers of the cells are compared and collated, A method of switching virtual paths has been proposed (see Patent Document 2).

  On the other hand, in recent years, Ethernet (registered trademark) has been applied not only to LAN (Local Area Network) but also to networks including MAN (Metropolitan Area Network) / WAN (Wide Area Network). In this case as well, a provider who provides MAN and WAN to the user is attempting to duplicate the subscriber transmission path and the transmission path within the service provider in order to improve reliability. However, in Ethernet (registered trademark) standardized by IEEE802.3, there is no mechanism for duplexing the transmission path except for 10G-WAN-PHY. For this reason, for example, a technique has been proposed in which the transmission path is switched using the detection of the interruption of the received light or electrical signal as a trigger (see Patent Document 2).

JP 08-237253 A (page 4-5, FIGS. 1 and 2) Japanese Patent Laying-Open No. 2003-209527 (page 3-9, FIG. 1, FIG. 2, FIG. 3)

  However, in the redundant transmission line communication device using the Ethernet (registered trademark), there is a possibility that duplication or omission of frames may occur. This is because there is no means for absorbing the delay difference between the data input from the two transmission lines. Another reason is that it takes a predetermined time from the occurrence of an optical input interruption or an electric input interruption of a received signal until the input interruption is detected, and the failure occurrence timing cannot be specified in the transmission line selection block. One.

  In order to solve the above-described problems, an object of the present invention is to provide a communication device, a communication system, and a reception method capable of switching without interruption to a backup transmission line in units of frames.

  A communication apparatus according to the present invention is a communication apparatus that performs communication via a plurality of transmission paths, and includes medium access control means, first encoding / decoding means, second encoding / decoding means, A memory for holding received data and signal converting means, and the first and second encoding / decoding means assign a code to a region between transmission frames at the time of transmission and extract the code at the time of reception Adjust the transmission delay difference of the received data. In this case, for example, an Ethernet (registered trademark) frame can be used as the frame. Further, the first and second encoding / decoding means can add a code to the preamble area of the transmission frame at the time of transmission. The frame in this case can use a MAC frame.

The encoding / decoding means can adjust the timing of frame output to the medium access control means by adjusting the read timing of the received data held in the memory at the time of reception. The encoding / decoding means receiving data from the working transmission line outputs a reception abnormality notification when detecting a code violation of the received data, and the medium access control means receives the abnormality notification and encodes the other encoding. / Receiving data from decoding means The communication system of the present invention is a communication system including communication devices connected by a plurality of transmission paths, the communication device comprising medium access control means and a first code Encoding / decoding means, second encoding / decoding means, a memory for holding received data, and signal conversion means, and the first and second encoding / decoding means transmit at the time of transmission. A code is assigned to an area between frames, and at the time of reception, the code is extracted to adjust a transmission delay difference of received data. As this frame, an Ethernet (registered trademark) frame can be used. The other communication system of the present invention has the same configuration as that of the communication system described above, but the first and second encoding / decoding means of the communication apparatus assign a code to the preamble region of the transmission frame. In this case, a MAC frame can be used as the frame. In the above communication system, the encoding / decoding means adjusts the read timing of the received data held in the memory at the time of reception to match the timing of frame output to the medium access control means.

  The invention of the receiving method of the present invention is a receiving method for receiving data from two transmission paths, each receiving data including a frame and a code assigned to each inter-frame area from the two transmission paths, and receiving the data. The code is extracted from the data to adjust the transmission delay difference between the received data. The frame in this case is an Ethernet (registered trademark) frame. The assigned code is extracted by the data decoding means. Also, the received data is held in the memory, the read timing of the received data is adjusted, and the timing for outputting the frame from the decoding means is matched. Further, when a code violation of the received data is detected, the data is received from a transmission path different from the transmission path through which the data is transmitted. The code may be assigned to the preamble part of the frame. The frame in that case is a MAC frame.

  According to the above-described invention, when a failure occurs in the working transmission line, it is possible to receive a frame from the backup transmission line without interruption in units of frames without using the data use area.

  FIG. 1 shows a block diagram of an embodiment of a communication apparatus of the present invention. In FIG. 1, between the communication apparatuses 10 and 11, two transmission lines, active and spare (indicated by networks 12a and 12b in FIG. 1), are arranged. FIG. 1 shows the communication device 10 as a transmission device and the communication device 11 as a reception device for convenience. Further, this example is a case where it is applied to 1000BASE-X of Gigabit Ethernet (registered trademark), and the communication devices 10 and 11 are assumed to have a function standardized by IEEE802.3. Each of the communication devices 10 and 11 includes medium access control means (Media Access Control, hereinafter referred to as MAC) 1t and 1r. Furthermore, the communication devices 10 and 11 include encoding / decoding means (physical coding sublayer (hereinafter, referred to as PCS)) and serial / parallel conversion means (physical medium attachment (physical medium attachment)) corresponding to two transmission paths. A physical medium attachment (hereinafter referred to as PMA), and an electrical / optical conversion means (physical medium dependent sub-layer, hereinafter referred to as PMD). The memories 5a and 5b hold reception data input from the PCS 2ra and PCS 2rb, respectively.

  MAC1t and MAC1r frame data and determine how the communication apparatus schedules and transmits data. The PCS 2t performs 8B / 10B encoding on the data input from the MAC 1t and outputs the data to the PMA 3ta and the PMA 3tb. PCS2ra and PCS2rb decode 8B / 10B data inputted from PMA3ra and PMA3rb, respectively. PMA3ta and PMA3tb of the communication device 10 perform parallel / serial conversion of data, and PMA3ra and PMA3rb of the communication device 11 perform serial / parallel conversion of data and clock recovery. Furthermore, PMD4ta and PMD4tb perform electrical / optical conversion, and PMD4ra and PMD4rb perform optical / electrical conversion. The networks 12a and 12b are transmission paths. Although different types of communication devices can be arranged on these transmission paths, the communication devices need to be able to transfer data output from PMDs 4ta and 4tb including the IFG area described later.

  In the communication apparatus of the above-described embodiment, the PCS 2t assigns a code (for example, a sequence number) to an inter-frame region (Inter Frame Gap, hereinafter referred to as IFG) or a preamble region of a frame when encoding transmission data. Output to the heavy transmission line. The sequence number is preferably a serial number such as a number or alphabet. However, the sequence number may be a code that allows communication devices to recognize each other by matching the mutual positional relationship of the area, even if it is not a serial number. On the other hand, the PCS 2ra and the PCS 2rb extract the sequence number from the IFG area or the preamble, and transmit / receive information indicating the sequence number and the head of the data to each other. As a result, the transmission delay difference between the two received data is determined. Further, based on the determination result, the PCS 2ra and PCS 2rb adjust the read timing from the memories 5a and 5b, respectively, and control the output timing of the frame to the MAC 1r at the same time.

  Assume that MAC1r is receiving a frame from PCS2ra. If an abnormality occurs in the network 12a at this time, the PCS 2ra detects the abnormality by detecting an 8B / 10B code violation. At this time, the PCS 2ra discards the frame that was being written to the memory 5a, and temporarily stops writing to the memory 5a thereafter. Further, the PCS 2ra reads the frame that has been normally written and the immediately following IFG, and updates the sequence number of the IFG. Further, the PCS 2ra outputs an IFG end pulse, and sets the reception abnormality flag that was L before abnormality detection to H. The MAC 1r selects a frame from the PCS 2ra and performs frame reception processing. However, when the MAC 1r detects the reception abnormality flag H from the PCS 2ra, the MAC 1r selects a frame input from the PCS 2rb and performs reception processing. Since the same frame is input to the MAC 1r from the PCS 2ra and the PCS 2rb at the same timing, the MAC 1r can execute frame selection switching without overlapping or missing frames.

  FIG. 2 is a time chart showing the operation of the communication apparatus of the present invention. This time chart shows an operation in which when the network 12a is operated, a failure occurs in the network 12a and the operation state changes to the network 12b side. Hereinafter, the operation of the present invention will be described along this time chart. FIG. 2 shows an example in which the transmission delay difference of data via two transmission paths is small.

  First, in the communication device 10 on the transmission side, the PCS 2t performs 8B / 10B encoding on data output from the MAC 1t. At this time, a sequence number is assigned to a series of IFG areas. It is also possible to assign the sequence number to the preamble area of the MAC frame. The data is converted from parallel to serial by PMA3ta and PMA3tb, and further converted to electrical / optical by PMD4ta and PMD4tb. This data is output to the networks 12a and 12b serving as transmission paths.

  Next, in the receiving side communication device 10, the transmitted data is optical / electrically converted by PMD4ra and PMD4rb, and serial / parallel converted by PMA3ra and PMA3rb. FIG. 2A shows data received by the PCS 2ra. A sequence number (1) is assigned to the IFG between the frames F0 and F1. FIG. 2B shows data received by the PCS 2rb. This data is slightly behind the data in FIG. FIG. 2C shows a frame output by the PCS 2ra, and FIG. 2G shows a frame output by the PCS 2rb. Here, the PCS 2ra and the PCS 2rb extract the sequence number assigned to the IFG area while performing 8B / 10B decoding. The sequence number is managed in association with the previous and subsequent frames. The received data is stored in the memory 5a and the memory 5b, read after a predetermined time Ta, and only the frame is output to the MAC 1r. At this time, L is output to the IFG area. Both the PCS 2ra and the PCS 2rb transmit and receive a sequence number and a signal indicating the end of the IFG, and adjust the time Ta so that the MAC 1r matches the timing of frame output of the PCS that is selecting data.

  When the PCS 2ra continuously detects the 8B / 10B code violation while receiving the frame F2, the PCS 2ra discards the frame being written to the memory 5a and temporarily stops writing to the memory 5a thereafter. The resumption of writing to the memory 5a is performed after the completion of the reading of the normal frame that has been written to the memory 5a and when the head of the normal frame is detected.

  The PCS 2ra reads the frame F1 that has been normally written and the IFG immediately after that. Thereafter, the PCS 2ra updates the sequence number of the IFG output to the MAC 1r and the PCS 2rb. FIG. 2F shows a sequence number detected by the PCS 2ra. Further, as shown in FIG. 2E, the PCS 2ra outputs a pulse indicating the end of IFG to the MAC 1r and the PCS 2rb, and updates the reception abnormality flag to H. FIG. 2D shows the reception abnormality flag H. The reception abnormality flag H is updated immediately before transmitting the frame, and is transmitted to the MAC 1r and the PCS 2rb. When the MAC 1r selects a frame from the PCS 2ra and performs a reception process, and detects a reception abnormality flag H from the PCS 2ra, the MAC 1r selects a frame from the PCS 2rb and performs a frame reception process. In this case, since the same frame is input from the PCS 2ra and PCS 2rb to the MAC 1r at the same timing, the MAC 1r can continue the reception process without duplication or omission of frames by switching data selection.

  Note that FIG. (H) is a signal indicating an abnormality in the output data of the PCS 2rb. Here, since there is no abnormality, L is output. FIG. (I) shows the end of the IFG of the data output from the PCS 2rb. This signal is output to MAC1r and PCS2ra. FIG. (J) shows a sequence number assigned to the IFG detected by the PCS 2rb. FIG. (K) shows the result of the MAC 1r selecting a frame input from the PCS 2ra and the PCS 2rb.

  When an 8B / 10B violation occurs in the IFG area, the following processing is performed. When the sequence number is extracted, the PCS 2ra outputs 12 bytes after the last normal frame is output, outputs the extracted sequence number, outputs the IFG end pulse, and sets the reception abnormality flag to H. Update. The PCS 2rb continues processing. Before extracting the sequence number, the PCS2ra waits for 12 bytes after outputting the last normal frame, increments and outputs the last extracted sequence number, outputs the IFG end pulse, and reception error Update the flag to 'H'. The PCS 2rb continues processing. The MAC 1r detects the abnormality flag H received from the PCS 2ra and switches the data selection. Since the switching is performed in the IFG area, the reception process can be continued without overlapping or missing frames.

  Next, an operation example when the difference in transmission delay of data passing through two transmission paths is large will be described with reference to the time chart of FIG. Each time chart corresponds to the figure. Also in this case, the operation when the PCS 2ra detects a code violation is the same as in FIG. FIG. 3A shows data received by the PCS 2ra, and FIG. 3B shows data received by the PCS 2rb. Thus, when the transmission path delay difference between the two is large, the PCS 2ra adds a delay that can discard the frame when an 8B / 10B code violation is detected in the maximum frame (1518 bytes in IEEE 802.3), and then the memory 5a Read from. The PCS 2rb stops outputting the frame to the MAC 1r and the PCS 2ra based on the data read from the memory 5b and outputting the IFG end pulse. However, as shown in FIG. 3J, the IFG sequence number is updated. When the PCS 2rb receives the reception abnormality flag H from the PCS 2ra, the PCS 2rb determines a frame to start output to the MAC 1r from the IFG end flag and sequence number received last from the PCS 2ra. This is as shown in FIG. 3 (e) to FIG. 3 (i). The PCS 2rb starts output to the MAC 1r from the next frame of the IFG in which the IFG sequence number of the received data matches the above value. When the MAC 1r receives the reception abnormality flag H from the PCS 2ra, the MAC 1r changes the data selection to data input from the PCS 2rb. As shown in FIG. 3 (k), the MAC 1r continues the IFG reception process until data transmission from the PCS 2rb is started. By subsequently receiving a frame transmitted from the PCS 2rb, it is possible to continue the reception process without duplication or omission of the frame. Even when the phase of the working frame in which the code violation has occurred is delayed as compared with the standby system, it is possible to receive the frame from the standby system without interruption by operating in the same manner as described above. Further, when the 8B / 10B code violation is continuously detected in the standby system, it can be left as it is. However, it is possible to switch to the third transmission system (if installed), or to perform a survey on the standby system while continuing the current communication.

  FIG. 4 shows a method of assigning sequence numbers to the IFG area. FIG. 4A shows an outline of a frame format of communication conforming to IEEE802.3. A MAC frame is composed of a 72 to 1518 byte Ethernet (registered trademark) frame, a 7 byte preamble, and a 1 byte SFD (Start of Frame Delimiter). After this, an IFG of 12 bytes or more is arranged, and it is stipulated that the next MAC frame is transmitted.

  FIG. 4B shows an example of a state in which the IFG region and the preamble region are 8B / 10B encoded. In the IFG area, encoding is performed to / I2 / indicating an idle period after / T / and / R / indicating the end of a frame. In the preamble area, the first or second byte is encoded to / S / indicating the start of the MAC frame, and the rest is encoded to / D /.

  FIG. 4C shows an example in which a sequence number is assigned to the IFG area. Sequence numbers SN_H and SN_L are assigned to each D16.2 portion of two consecutive / I2 /. For the sequence number, 16-bit data is divided into 8 bits and 8B / 10B converted to SN_H and SN_L. However, in order to identify the sequence number, a data code not defined as an order set is used in combination with K28.5 from the data codes (D0.0 to D31.7). In the figure, it is inserted immediately after / T / and / R /, but is inserted instead of two consecutive / I2 /.

  FIG. 4D shows another example in which a sequence number is assigned to the IFG area. Use two consecutive / I2 /. D16.2 at the head / I2 / is combined with K28.5 to form an 8B / 10B code not defined as an order set (for example, D10.2), and the next two 8B / 10B codes are sequence numbers SN_H , SN_L. The next two data codes (D0.0 to D31.7) are used as sequence numbers. In this case, there is no data code that cannot be used. In the figure, it is inserted immediately after / T / and R /, but it is inserted in place of two consecutive / I2 /.

  FIG. 4E shows an example in which a sequence number is assigned to the preamble area instead of the IFG area. In the preamble area, the first or second byte is / S /, and is encoded by 8B / 10B with / D /. The 2 bytes immediately after / S / are defined and used as a sequence number. In the figure, it is inserted in the 2 bytes immediately after / S /, but it may be two consecutive bytes.

  The present invention is also applicable to 10 Gigabit Ethernet (registered trademark) (10G-LAN-PHY) that converts data to a combination of a control code and a data code such as an 8B / 10B code and transfers the data. Can do.

The block diagram of the Example of the communication apparatus of this invention is shown. The time chart which shows the operation example of the communication apparatus of this invention. The time chart which shows the other operation example of the communication apparatus of this invention. The frame structural example which shows the allocation method of the sequence number to the IFG area | region of this invention.

Explanation of symbols

1t, 1r MAC
12a, 12b network 2ra, 2rb PCS
5a, 5b memory

Claims (20)

A communication device that performs communication via a plurality of transmission paths, a medium access control unit, a first encoding / decoding unit, a second encoding / decoding unit, and a memory that holds received data And a signal conversion means,
The first and second encoding / decoding means allocate a code to an area between transmission frames at the time of transmission, and extract the code at the time of reception to adjust a transmission delay difference of received data. Communication device. A communication device that performs communication via a plurality of transmission paths, a medium access control unit, a first encoding / decoding unit, a second encoding / decoding unit, and a memory that holds received data And a signal conversion means,
The first and second encoding / decoding means allocate a code to a preamble area of a transmission frame at the time of transmission, and extract the code at the time of reception to adjust a transmission delay difference of received data. Communication device. The communication apparatus according to claim 1, wherein the frame is an Ethernet (registered trademark) frame. The communication apparatus according to claim 2, wherein the frame is a MAC frame. 5. The communication apparatus according to claim 1, wherein the encoding / decoding unit adjusts a read timing of received data held in the memory at the time of reception to match a frame output timing to the medium access control unit. . The encoding / decoding means receiving data from the working transmission line outputs a reception abnormality notification when detecting a code violation of the received data, and the medium access control means receives the notification, and the other encoding / decoding means 6. The communication apparatus according to claim 1, wherein the communication apparatus receives data from the means. The communication apparatus according to claim 1, wherein the encoding / decoding unit performs 8B / 10B encoding / decoding. A communication system including a communication device connected by a plurality of transmission paths, the communication device comprising: a medium access control unit; a first encoding / decoding unit; a second encoding / decoding unit; A memory for holding received data and signal converting means, and the first and second encoding / decoding means assign a code to a region between transmission frames at the time of transmission and extract the code at the time of reception And adjusting a transmission delay difference of received data. The communication system according to claim 8, wherein the frame is an Ethernet (registered trademark) frame. A communication system including a communication device connected by a plurality of transmission paths, the communication device comprising: a medium access control unit; a first encoding / decoding unit; a second encoding / decoding unit; The first and second encoding / decoding means allocate a code to the preamble area of the transmission frame at the time of transmission and extract the code at the time of reception; And adjusting a transmission delay difference of received data. The communication system according to claim 10, wherein the frame is a MAC frame. 12. The communication system according to claim 8, wherein the encoding / decoding unit adjusts a read timing of received data held in the memory at the time of reception to match a frame output timing to the medium access control unit. . A receiving method for receiving data from a plurality of transmission paths,
Data including a frame and a code assigned to each inter-frame region is received from each of the two transmission paths, and the code is extracted from the received data to adjust a transmission delay difference between the received data. Reception method. 14. The receiving method according to claim 13, wherein the serial number is extracted by data decoding means. 15. The reception method according to claim 14, wherein the reception data is held in a memory, the read timing of the reception data is adjusted, and the timing for outputting a frame from the decoding means is matched. 16. The receiving method according to claim 15, wherein when a code violation of the received data is detected, the data is received from a transmission path different from the transmission path through which the data is transmitted. A receiving method for receiving data from two transmission paths,
Receiving data including a frame and a code assigned to a preamble area of each frame from the two transmission paths, extracting the code from the received data, and adjusting a transmission delay difference between the received data, To receive. 18. The receiving method according to claim 17, wherein the serial number is extracted by a data decoding unit. 19. The receiving method according to claim 18, wherein the received data is held in a memory, the read timing of the received data is adjusted, and the timing for outputting a frame from the decoding means is matched. 20. The receiving method according to claim 19, wherein when a code violation of the received data is detected, the data is received from a transmission path different from the transmission path through which the data is transmitted.

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