JP2010288043A - Communication system and switching method in the communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system which performs relieving by a backup link at a failure of an active link, without having to use an expensive layer 2 switch for first communications equipment. <P>SOLUTION: The communication system includes the first communications equipment; and second communications equipment which performs switching of frames between two arbitrary links, wherein the first communications equipment and the second communications equipment are connected to each other via one or more active links and one backup link, the first communications equipment is provided with: a first means corresponding to each active link; and a multiplex means corresponding to the backup link, and in a direction of going from the first communications equipment to the second communications equipment; the first means is considered as any one of the configurations for transmitting a frame to be transmitted to the second equipment only to a corresponding active link, configuration for transmitting the frame only to the backup link, and configuration for transmitting the frame to both the corresponding active link and the backup link; and the multiplex means multiplexes frames which each of the first means outputs to be transmitted to the backup link. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a traffic relief technique when a failure occurs in a communication system. More specifically, the present invention relates to a technique for detouring traffic to a spare link prepared in advance when a failure occurs in a working link.

  FIG. 14 is a system configuration diagram of a PON (Passive Optical Network) system. The PON system includes a plurality of ONUs 7 (Optical Network Units) installed in a subscriber's house and a plurality of ONUs 7 installed on a station side. The optical termination device 5 is connected to a node device 6 such as a layer 2 switch.

  As shown in FIG. 14, the optical termination device 5 includes a plurality of OSU (Optical Subscriber Unit) units 51. One OSU unit 51 is composed of one or more pieces of hardware, usually called a package or a card, that can be inserted into and removed from the optical terminator 5, and the optical terminator 5 is based on the OSU unit 51 as a unit. Expansion is possible.

  Each OSU unit 51 converts an optical signal received from the ONU 7 into an electrical signal, performs necessary processing on the received frame, converts the signal again into an optical signal, and transmits it to the node device 6. After the optical signal received from the node device 6 is converted into an electrical signal, necessary processing is performed on the received frame, and the optical signal is converted again and transmitted to the ONU 7.

  As shown in FIG. 14, the node device 6 includes an optical termination device side interface unit 61, a layer 2 switch unit 62, and a network side interface unit 63. The optical termination device side interface unit 61 performs processing necessary to transmit / receive signals to / from the optical termination device 5, and the network side interface unit 63 performs processing necessary to transmit / receive signals to / from the network, and performs a layer 2 switch. The unit 62 has a function of performing frame switching so that the frame is output from the optical link corresponding to the destination. The optical terminal unit side interface unit 61 and the network side interface unit 63 are configured by one or more pieces of hardware, usually called packages or cards, that can be inserted into and removed from the node device 6.

  In the configuration shown in FIG. 14, there is no redundant system. Therefore, there is a failure in the OSU unit 51, the optical termination unit side interface unit 61, and the optical link connecting the OSU unit 51 and the optical termination unit side interface unit 61. If it occurs, service interruption continues until the fault is recovered. Therefore, redundancy is required from the viewpoint of service reliability and maintenance operability.

  For this reason, the structure which made the communication area of the optical terminal device 5 and the node apparatus 6 redundant is proposed (for example, refer patent document 1, nonpatent literature 1, nonpatent literature 2, and nonpatent literature 3). . FIG. 15 is a switching configuration diagram according to the prior art. In the configuration shown in FIG. 15, the OSU unit 51 in FIG. 14 includes a part (displayed as an ONU side IF unit in FIG. 15) that performs processing necessary to send and receive frames with a plurality of ONUs 7, and the node device 6. It is divided into parts (indicated as a node-side IF unit in FIG. 15) that perform processing necessary to transmit and receive frames, and the layer 2 switch unit 62 of the node device 6 is between the ONU-side IF unit and the node-side IF unit. The layer 2 switch part which has the function equivalent to is provided.

  In the configuration shown in FIG. 15, the layer 2 switch units of the optical termination device 5 and the node device 6 are made redundant, and the switching is performed by the layer 2 switch unit. The route passing through the node-side IF unit displayed as WA and WB is a working link, and the route passing through the node-side IF unit displayed as PA and PB is a backup link and passes through the WA. When the working link fails, a protection link via PA is used, and when the working link via WB fails, a protection link via PB is used.

  In the configuration shown in FIG. 15, the reception end switching method (1 + 1 switching method), the transmission / reception end switching method (1: 1 switching method), the transmission end switching method (described in Non-Patent Document 2 and Non-Patent Document 3) Link Aggregation) is available. The 1 + 1 switching method is a method in which the same frame is transmitted to both the working link and the backup link in the layer 2 switch unit on the transmission side, and the frame from one of the links is selected in the layer 2 switch unit on the reception side. is there.

  In the 1: 1 switching method, the transmission side layer 2 switch unit normally transmits a frame only to the working link, and transmits a frame to the protection link only when a failure occurs in the working link. It is a method. In this system, the layer 2 switch unit on the reception side and the layer 2 switch unit on the transmission side need to work together, so that a control signal for switching is sent between the optical terminal device 5 and the node device 6. It is necessary to send and receive. For this reason, the device configuration is more complicated than the 1 + 1 switching method that does not require transmission / reception of control signals. However, in a normal state, a frame of a low priority class can be transmitted / received by using a spare link, and a plurality of working It is also possible to share one spare link with the link, so that traffic can be accommodated efficiently. In addition, Link Aggregation means that a layer 2 switch unit on the receiving side is configured to select both frames received from both the working link and the backup link, and the layer 2 switch unit on the transmitting side The frame is transmitted.

  The frame overhead, that is, management information includes a VLAN (Virtual LAN) tag for identifying the traffic of each user, and switching control is performed in units of user traffic, that is, in units of VLAN.

JP 2002-218008 A

ITU-T G. 984.1, “14 Protection on the PON section”, March 2008 ITU-T G. 8031 / Y. 1342, “10.6 Protection switching models”, June 2006 IEEE802.1ax, “5.2 Link Aggregation Operation”, November 2008

  The configuration in the prior art is that the optical termination device 5 is also provided with a layer 2 switch unit. However, the layer 2 switch unit that performs frame forwarding and switching between arbitrary ports is expensive, and this is used as an optical termination unit. It is uneconomical to implement in the device 5 as well. On the other hand, in order to perform switching without increasing the cost, a port-based switch that switches signals between two ports may be used. However, since only switching control can be performed in units of ports, 1 can be used with a plurality of working links. The book's spare link cannot be shared. Therefore, when a plurality of working links simultaneously fail, it is impossible to realize a configuration in which high priority traffic accommodated in each working link is relieved with one spare link.

  Accordingly, an object of the present invention is to provide a communication system and a switching method that do not use an expensive layer 2 switch unit in an optical termination device. It is another object of the present invention to provide a communication system and a switching method capable of sharing only one spare link among a plurality of working links and selecting only a high priority class frame for repair.

According to the communication system of the present invention,
A first communication device, and a second communication device that performs frame switching between any two links, wherein the first communication device and the second communication device include one or more active links In the communication system connected by one spare link, the first communication device includes first means corresponding to each active link and multiplexing means corresponding to the spare link, In the direction from the communication device to the second communication device, the first means transmits a frame to be transmitted to the second communication device only to the corresponding working link and a configuration to transmit only to the backup link. And a corresponding transmission link to both the working link and the protection link, and the multiplexing means multiplexes the frames output by each first means for transmission to the protection link. Reserve phosphorus And transmits to.

According to another embodiment of the communication system in the present invention,
A priority is set for the management information included in each frame, and the first communication device has a frame whose priority is equal to or lower than a predetermined value among frames output by each first means for transmission to the protection link. It is also preferable to further include filter means for discarding.

According to another embodiment of the communication system of the present invention,
The first communication device further includes second means for determining a first means of an output destination of the frame based on management information included in a frame received from the backup link, and the second communication In the direction from the device to the first communication device, the first means selects and outputs only the frame received from the corresponding working link, and selects and outputs only the frame received from the backup link. It is also preferable that it can be set to either a configuration for selecting and outputting a frame received from both the corresponding working link and the protection link.

Furthermore, according to another embodiment of the communication system of the present invention,
The second communication device switches only frames whose priority is higher than a predetermined value to the protection link, or, among frames switched to the protection link, transmits a frame having a priority lower than the predetermined value before transmission to the protection link. It is also preferable to have a filter means for discarding.

Furthermore, according to another embodiment of the communication system of the present invention,
The second communication apparatus further includes means for adding an identifier to the management information of each frame transmitted to the first communication apparatus, and the second means outputs a frame received from a backup link. It is also preferable to use the identifier for the determination of the first means.

According to the method of the present invention,
A first communication device, and a second communication device that performs frame switching between any two links, wherein the first communication device and the second communication device include one or more active links A switching method in the case of a working link failure in a communication system connected by one backup link, wherein the first communication device includes a switching unit corresponding to each working link, and the first communication device In the direction from the second communication device to the second communication device, each switching unit outputs a frame to be transmitted to the second communication device only to the first port reaching the corresponding working link, and a spare link. Can be set to either the second configuration that outputs only to the second port leading to, or the third configuration that outputs to both the first port and the second port, and each switching unit uses a spare link If so, the second configuration or Serial to the third configuration, otherwise, characterized in that it is set to the first configuration or the third configuration.

According to another embodiment of the method in the present invention,
A priority is set for the management information included in each frame, and the first communication device has a priority among frames output to the second port in the second configuration or the third configuration. It is also preferable to discard frames whose degrees are below a predetermined value and transmit the remaining frames to the protection link.

Also, according to another embodiment of the method in the present invention,
The first communication device determines a working link corresponding to the frame based on management information included in a frame received from a backup link, and outputs the frame to a switching unit corresponding to the determined working link, In the direction from the second communication device to the first communication device, each switching unit outputs only the frame received from the third port reaching the corresponding working link to the fifth port that is the transmission destination. A fourth configuration, a fifth configuration for outputting only frames received from the fourth port reaching the backup link to the fifth port, and frames received from the third port and the fourth port. Both can be set to any of the sixth configurations that output to the fifth port, and each switching unit can be set to the fifth configuration or the sixth configuration when using a spare link. Except In this case, the second communication device is set to the fourth configuration or the sixth configuration, and when the spare communication link is used, the second communication device transmits a frame to be transmitted to the working link to the spare link. It is also preferable to do.

Furthermore, according to another embodiment of the method in the present invention,
The second communication device switches only frames whose priority is higher than a predetermined value to the protection link, or, among frames switched to the protection link, transmits a frame having a priority lower than the predetermined value before transmission to the protection link. It is also preferable to discard.

Furthermore, according to another embodiment of the method in the present invention,
The first communication device adds a first identifier to the management information of each frame transmitted to the second communication device, and the second communication device uses the working link corresponding to the frame received from the backup link. The second identifier is added to the management information of each frame to be transmitted to the first communication device, and the first communication device It is also preferable to use the second identifier for determining the working link corresponding to the frame received from the protection link.

  The first communication device uses only the first means for performing small port-based switching and the multiplexing means for performing frame-based multiplexing, and is capable of forwarding and switching frames between arbitrary ports. This is economical because a single large-capacity layer 2 switch is not used. Further, in the present invention, even if a plurality of working links simultaneously fail, the high priority class traffic transmitted / received through the plurality of working links can be relieved with a single spare link. It is possible to improve reliability.

It is a block diagram of the communication system by this invention. It is a block diagram of an OSU part. It is a block diagram of a demultiplexing part. It is a block diagram of an optical terminal unit side interface part. It is a block diagram of a network side interface part. It is a figure which shows a frame structure. It is a figure which shows the frame structure after giving an identifier. It is a figure explaining the operation | movement of the up direction in a transmission / reception end switching system. It is a figure explaining the operation | movement of the downlink direction in a transmission / reception end switching system. It is a figure explaining the operation | movement of the uplink direction by a transmission end switching system. It is a figure explaining operation | movement of the down direction by a transmission end switching system. It is a figure explaining the operation | movement of the uplink direction by a receiving end switching system. It is a figure explaining the operation | movement of the downlink direction by a receiving end switching system. It is a system configuration figure of a PON system. It is a switching block diagram by a prior art.

  EMBODIMENT OF THE INVENTION The form for implementing this invention is demonstrated in detail below using drawing. FIG. 1 is a block diagram of a communication system according to the present invention. The communication system includes, in the PON system, an optical termination device 1 which is a device installed on the station side, and a node device 2 such as a layer 2 switch. The optical termination device 1 and the node device 2 include one or more optical termination devices 1 and 2. It is connected to the working link with one spare link.

  As shown in FIG. 1, the optical termination device 1 includes a plurality of OSU units 11 and a demultiplexing unit 12. Note that one OSU unit 11 is composed of one or more pieces of hardware, usually called a package or a card, that can be inserted into and removed from the optical termination device 1. The OSU unit 11 receives a signal conforming to the PON system standard from the optical link on the ONU side, performs a predetermined process, and then transmits each frame to the optical link on the node equipment 2 side, that is, the working link. After a predetermined process is performed on a signal including a frame received from the optical link on the node device 2 side, a signal conforming to the standard of the PON system is generated and transmitted from the optical link on the ONU side. In the configuration shown in FIG. 1, each OSU unit 11 provides a function of transmitting and receiving a pair of optical signals to the ONU side and the node device 2 side, but the number of links to be provided is arbitrary. is there.

  FIG. 2 is a block diagram of the OSU unit 11. The PON terminator has a function of generating a signal conforming to the PON system standard, outputting the signal to the first optical transceiver, and extracting a frame from the signal conforming to the PON system standard input from the first optical transceiver. The first optical transmission / reception unit transmits / receives an optical signal conforming to the standard of the PON system. The identifier assigning unit assigns an identifier for identifying each frame in the switching section to frame overhead, that is, management information and outputs the identifier to the switching unit, and the identifier removing unit identifies each frame in the switching section. Are removed from the management information of the frame.

  The switching unit has a function of switching on a port basis. Specifically, in the transmission direction to the node device 2, a configuration in which all frames input from the identifier assigning unit are output only to the first port to the first frame processing unit, the second frame processing unit It is possible to set to either a configuration that outputs only to the second port or a configuration that outputs to both ports to the first frame processing unit and the second frame processing unit. In addition, in the direction of receiving from the node device 2, a configuration in which only a frame input from the third port connected to the first frame processing unit is selected and output to the fifth port connected to the identifier removing unit, Select only the frame input from the fourth port connected to the second frame processing unit and output to the fifth port, select both the third port and the frame input from the fourth port It is possible to set to any of the configurations that output to the fifth port. The switching control unit performs control such as collection of failure information serving as a start trigger of the switching operation, switching processing of the switching unit, and the like.

  The first and second frame processing units each perform processing necessary for a frame transmitted / received to / from the node device 2. The first frame processing unit processes frames transmitted / received on the working link, the second frame processing unit processes frames transmitted / received on the backup link, and the second optical transmitting / receiving unit is a node device. 2 transmits / receives an optical signal to / from the working link connected to 2. In addition, the filter unit has a function of allowing only high priority frames to pass and discarding low priority frames. The priority level can be determined by a CoS (Class of Service) value included in the frame management information. In this embodiment, the priority is two levels, high or low. However, when a plurality of levels are used as the priority, the priority below a predetermined level is set to low and other priority levels are set. The present invention is applied at a high degree.

  Note that, as an identifier for identifying each frame in the switching section, for example, an S tag defined by IEEE 802.1ad can be used. Specifically, the identifier adding unit adds an S tag to the frame shown in FIG. 6 and outputs the frame shown in FIG. 7, and the identifier removing unit removes the S tag from the frame shown in FIG. The frame shown in FIG. 6 is output. The C tag in FIGS. 6 and 7 is a VLAN tag.

  If the working link is different, the same value can be used for the VLAN tag for different user traffic, but a frame using the same VLAN tag value accommodated in a different working link is relieved with one spare link. In this case, VLAN identification, that is, user traffic cannot be identified. For this reason, in the present invention, an identifier is assigned in the switching section to identify each VLAN. Therefore, the user traffic to which each frame belongs can be identified from the VLAN tag of the received frame and other values such as the VLAN tag value is not duplicated in all working links using a certain protection link. It is not necessary to assign an identifier to the ID, and in this case, an identifier assigning unit and an identifier removing unit are unnecessary.

  FIG. 3 is a block diagram of the demultiplexing unit 12. In FIG. 3, the multiplex processing unit multiplexes and outputs a frame from each OSU unit 11, and the separation processing unit receives the frame from the third optical transmission / reception unit and outputs the OSU unit 11 to which the frame is to be output. A determination is made based on a value specifying the VLAN of the frame, for example, the value of the VLAN tag, or the value and identifier of the VLAN tag, and is output to the determined OSU unit 11. The third optical transmission / reception unit transmits / receives an optical signal to / from the backup link connected to the node device 2.

  Returning to FIG. 1, the node device 2 includes an optical termination device side interface unit 21, a layer 2 switch unit 22, a network side interface unit 23, and a switching control unit 24. In addition, the optical terminal unit side interface unit 21 and the network side interface unit 23 are usually configured by one or more pieces of hardware called a package or a card. Further, the number of links accommodated by one optical terminal unit side interface unit 21 and network side interface unit 23 is arbitrary.

  FIG. 4 is a block diagram of the optical termination device side interface unit 21. The fourth optical transmission / reception unit transmits / receives an optical signal to / from the optical termination device 1, the frame processing unit performs processing necessary for a frame transmitted / received to / from the optical termination device 1, and the queue manager unit includes a buffer. The transmission speed difference between the layer 2 switch 22 side and the optical termination device 1 side is absorbed. Further, the filter unit is mounted only on the optical terminal unit side interface unit 21 that accommodates the backup link, and has a function of allowing only high-priority frames to pass and discarding low-priority frames. It should be noted that a filter unit capable of controlling whether or not to execute the filter function is mounted on all the optical termination device side interface units 21, and depending on whether or not the accommodated link is active. The configuration may also be such that the execution of the filter function is controlled. Further, when the layer 2 switch unit 22 recognizes the priority and can switch only the frame of the high priority class to the backup link, the filter unit can be omitted.

  FIG. 5 is a block diagram of the network side interface unit 23. The queue manager unit has a buffer and absorbs a transmission rate difference between the layer 2 switch 22 side and the network side. The frame processing unit performs processing necessary for a frame transmitted / received to / from the network. The transmission / reception unit transmits / receives an optical signal to / from the network. The identifier removing unit and the identifier adding unit add and remove an identifier for identifying which VLAN each frame belongs to in the switching section, as in the OSU unit 11. That is, a frame transmitted / received using the backup link adds and removes an identifier for identifying the working link that should be originally transmitted / received to / from the management information. If the working link corresponding to the frame received from the backup link can be determined without assigning the identifier, the identifier removing unit and the identifier assigning unit are not necessary as already described with respect to the OSU unit 11. .

  The layer 2 switch unit 22 is for switching frames between arbitrary links mounted on the node device 2, that is, to transmit a frame input to a certain link from a link corresponding to the destination. Switching is performed. It should be noted that the frame transmitted to the protection link can be transmitted simultaneously with the working link, that is, the same frame can be duplicated and transmitted simultaneously to two links. In addition, the switching control unit 24 collects necessary failure information and controls each unit for switching the protection link.

  Next, a specific switching operation will be described with reference to FIGS. In the following description, it is assumed that one working link is shared by three working links, and one that passes through the OSU unit 11-1 passes through the first working link and the OSU unit 11-2. Is called the second working link, and the one passing through the OSU unit 11-3 is called the third working link. Note that the backup link is a link connected to the demultiplexing unit 12. In addition, the direction from the optical terminal device 1 to the node device 2 is referred to as an upstream direction, and the direction from the node device 2 to the optical terminal device 1 is referred to as a downstream direction. Further, in FIGS. 8 to 13, L1 and H1 are low priority and high priority frames using the first working link, respectively, and L2 and H2 are low low using the second working link, respectively. The priority and high priority frames, and L3 and H3 are low priority and high priority frames that use the third working link.

  8 and 9 are diagrams for explaining the operation in the transmission / reception end switching method. FIG. 8 shows the operation in the upstream direction, and FIG. 9 shows the operation in the downstream direction. FIG. 8 (a) shows a state in the uplink direction during normal operation, that is, when no failure has occurred, and the switching units of the OSU units 11-1 to 11-3 The data is output to the first frame processing unit side in FIG. 2, that is, to the working link side. Accordingly, the frames input to the OSU units 11-1 to 11-3 are transmitted to the working link as they are, and the frames are switched by the layer 2 switch unit 22 of the node device 2 to be transmitted to a predetermined network side. Sent from the link.

  In this state, when a failure occurs in the second working link, as shown in FIG. 8B, the switching unit of the OSU unit 11-2 determines the output destination of the input frame as the second frame in FIG. Switch to the processing unit side. Of the frames output to the second frame processing unit, the low priority frame is removed by the filter unit, so the demultiplexing unit 12 transmits only the high priority frame to the backup link. In addition, due to the occurrence of a failure, the layer 2 switch unit 22 of the node device 2 changes the switching process for each VLAN so that the frame received from the second working link is received from the backup link. High priority traffic is saved. In FIG. 8B, the switching unit of the OSU unit 11-2 transmits a frame only to the protection link side, but may be configured to transmit a frame to both the working link and the protection link. .

  FIG. 9A shows a normal state in the downlink direction, and the switching unit of each OSU unit 11-1 to 11-3 selects the first frame processing unit, and thus the frame input from the working link. Is output to the ONU side. In this state, when a failure occurs in the second working link, as shown in FIG. 9B, the layer 2 switch unit 22 of the node device 2 uses the backup link for the frame transmitted from the second working link. As shown in FIG. However, since the filter unit is mounted on the optical terminal unit side interface unit 21 connected to the protection link, only the high priority frame is transmitted to the protection link. The demultiplexing unit 12 determines that the output destination of the received frame is the OSU unit 11-2 based on the received frame management information, and outputs the received frame to the OSU unit 11-2. The switching unit of the OSU unit 11-2 selects the second frame processing unit when a failure occurs in the second working link, and thus high priority traffic is relieved. As already described, the layer 2 switch unit 22 of the node device 2 performs switching in units of VLAN so that only the high priority class frame is transmitted to the protection link, and the filter unit of the optical terminal unit side interface unit 21 May be omitted. Further, in FIG. 9B, the node device 2 transmits the frame only to the protection link side, but may be configured to transmit the frame to both the second working link and the protection link.

  In this method, it is necessary to transmit and receive control information for switching control between the optical terminal device 1 and the node device 2. This control information transmission / reception uses, for example, a spare link, and exchanges values for specifying a switching cause and a VLAN to be switched. Here, the cause of switching is, for example, signal interruption, signal deterioration, forced switching, manual switching, etc., and the value for specifying the VLAN to be switched is the value of the VLAN tag, and further when an identifier is used Is a value including a combination of a VLAN tag value and an identifier. The control information may be exchanged using a control line other than the backup link.

  10 and 11 are diagrams for explaining the operation in the transmission end switching method. FIG. 10 shows the operation in the upstream direction, and FIG. 11 shows the operation in the downstream direction. In the following description, description of portions common to the 1: 1 switching method is omitted. FIG. 10A shows a normal uplink state, and the switching units of the OSU units 11-1 to 11-3 transfer the input frames to the first frame processing unit side in FIG. That is, it outputs to the working link side. Accordingly, the frames input to the OSU units 11-1 to 11-3 are transmitted as they are to the working link. Further, the node device 2 is configured so that not only the frame received from the working link but also the frame received from the backup link is transmitted to a predetermined network side link based on the value specifying the VLAN. 22 is configured.

  In this state, when a failure occurs in the second working link, as shown in FIG. 10B, the switching unit of the OSU unit 11-2 determines the output destination of the input frame as the second frame in FIG. Switch to the processing unit side. Of the frames output to the second frame processing unit, the low priority frame is removed by the filter unit, so the demultiplexing unit 12 transmits only the high priority frame to the backup link. Since the layer 2 switch unit 22 of the node device 2 is configured to transmit a frame received from the backup link in advance to a predetermined network side port based on a value specifying the VLAN, the optical terminal device High priority traffic can be relieved only by processing on one side.

  Further, FIG. 11A shows a normal state in the downward direction, and the switching unit of each OSU unit 11-1 to 11-3 selects and outputs both the first and second frame processing units. ing. In this state, when a failure occurs in the second working link, as shown in FIG. 11B, the layer 2 switch unit 22 of the node device 2 reserves a frame transmitted to the second working link. Switching is performed on a VLAN basis so that it is transmitted to the link. Accordingly, as described with reference to FIG. 9, only the high priority frame is transmitted to the protection link. The demultiplexing unit 12 outputs a value included in the management information, for example, a frame received based on the value of the identifier when the identifier is used, to the OSU unit 11-2. In this case, high priority traffic is relieved without performing special processing. As described above, in this embodiment, transmission / reception of control information can be omitted.

  12 and 13 are diagrams for explaining the operation in the receiving end switching method. FIG. 12 shows the operation in the upstream direction, and FIG. 13 shows the operation in the downstream direction. FIG. 12A shows a normal state in the upward direction, and the switching units of the OSU units 11-1 to 11-3 process the input frames respectively in the first and second frame processes of FIG. Output to both. Therefore, each frame input to each of the OSU units 11-1 to 11-3 is transmitted as it is to the working link, and a high priority frame is also transmitted to the backup link. However, the node device 2 switches only the frame from the working link and discards the frame from the backup link.

  In this state, when a failure occurs in the second working link, as shown in FIG. 12B, the layer 2 switch unit 22 of the node device 2 does not reserve the frame received from the second working link. Change the switching configuration to receive from the link.

  FIG. 13 (a) shows a normal state in the downlink direction, and the node device 2 transmits a layer transmitted from the first working link to the third working link so that the frame is also transmitted to the backup link. 2 switch part 22 is comprised. A high-priority frame transmitted from the first working link to the third working link is included in the protection link by filtering in the filter unit or by switching only the high-priority frame to the protection link. The same frames are transmitted, and these are respectively output from the second frame processing unit of the corresponding OSU unit to the switching unit. However, since the switching unit of each OSU unit 11-1 to 11-3 selects the first frame processing unit, the frame input from the working link is output to the ONU side. In this state, when a failure occurs in the second working link, as shown in FIG. 13 (b), the switching unit of the OSU unit 11-2 performs switching so as to select the second frame processing unit. High priority traffic will be rescued.

  In the present invention, a small-capacity port-based switching unit and a frame can be used without using a high-function single large-capacity layer 2 switch unit capable of frame forwarding and switching between arbitrary ports in the optical termination device 1. It is economical because only the base demultiplexer is used. Further, according to the present invention, switching control in service class units is possible, and it is economical because it is sufficient to reserve spare resources according to high priority class traffic that needs to be relieved when a failure occurs.

1, 5 Optical termination device 2, 6 Node device 7 ONU
11, 11-1, 11-2, 11-3, 51 OSU unit 12 Demultiplexing unit 21, 61 Optical terminal unit side interface unit 22, 62 Layer 2 switch unit 23, 63 Network side interface unit 24 Switching control unit

Claims (10)

A first communication device, and a second communication device that performs frame switching between any two links, wherein the first communication device and the second communication device include one or more active links A communication system connected by one spare link,
The first communication device includes first means corresponding to each working link and multiplexing means corresponding to a backup link,
In the direction from the first communication device to the second communication device, the first means transmits a frame to be transmitted to the second communication device only to the corresponding working link, and only the backup link. Can be set to either the configuration to transmit to the corresponding configuration and the configuration to transmit to both the corresponding working link and protection link,
The multiplexing means multiplexes the frames output by each first means for transmission to the protection link and transmits the multiplexed frames to the protection link.
Communications system. Priorities are set for the management information included in each frame,
The first communication device further includes filter means for discarding frames having a priority level equal to or lower than a predetermined value among frames output by each first means for transmission to the backup link.
The communication system according to claim 1. The first communication device further includes second means for determining a first means of an output destination of the frame based on management information included in the frame received from the backup link,
In the direction from the second communication device to the first communication device, the first means selects and outputs only the frame received from the corresponding working link, and only the frame received from the backup link. Can be set to either a configuration for selecting and outputting, and a configuration for selecting and outputting frames received from both the corresponding working link and protection link,
The communication system according to claim 1 or 2. The second communication device switches only frames whose priority is higher than a predetermined value to the protection link, or, among frames switched to the protection link, transmits a frame having a priority lower than the predetermined value before transmission to the protection link. Having filter means to discard,
The communication system according to claim 3. The second communication device further includes means for adding an identifier to management information of each frame to be transmitted to the first communication device,
The second means uses the identifier in the determination of the first means for outputting the frame received from the backup link.
The communication system according to claim 3 or 4. A first communication device, and a second communication device that performs frame switching between any two links, wherein the first communication device and the second communication device include one or more active links A switching method at the time of a working link failure in a communication system connected by one spare link,
The first communication device includes a switching unit corresponding to each working link,
In the direction from the first communication device to the second communication device, each switching unit outputs a frame to be transmitted to the second communication device only to the first port reaching the corresponding working link. Each of the switching units, the second configuration that outputs only to the second port that reaches the backup link, and the third configuration that outputs to both the first port and the second port. Is set to the second configuration or the third configuration when a spare link is used, and is set to the first configuration or the third configuration otherwise.
Switching method. Priorities are set for the management information included in each frame,
In the second configuration or the third configuration, the first communication device discards a frame having a priority level equal to or lower than a predetermined value from the frames output to the second port, and uses the remaining frames. Send to backup link,
The method of claim 6. The first communication device determines a working link corresponding to the frame based on management information included in a frame received from a backup link, and outputs the frame to a switching unit corresponding to the determined working link.
In the direction from the second communication device to the first communication device, each switching unit outputs only frames received from the third port reaching the corresponding working link to the fifth port that is the transmission destination. A fourth configuration that outputs only a frame received from the fourth port reaching the backup link to the fifth port, and a frame received from the third port and the fourth port. Can be set to any one of the sixth configurations that output to the fifth port, and each switching unit can be set to the fifth configuration or the sixth configuration when using a spare link, Otherwise, set to the fourth configuration or the sixth configuration,
When the second communication device uses the spare link, the second communication device sends a frame to be transmitted to the working link to the spare link.
The method according to claim 6 or 7. The second communication device switches only frames whose priority is higher than a predetermined value to the protection link, or, among frames switched to the protection link, transmits a frame having a priority lower than the predetermined value before transmission to the protection link. Discard,
The method of claim 8. The first communication device adds a first identifier to the management information of each frame transmitted to the second communication device, and the second communication device uses the working link corresponding to the frame received from the backup link. Using the first identifier in the determination of
The second communication device adds a second identifier to the management information of each frame transmitted to the first communication device, and the first communication device uses the working link corresponding to the frame received from the backup link. Using the second identifier in the determination of
10. A method according to claim 8 or 9.

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