JP5678123B2 - Transmission apparatus, transmission path switching method, and program - Google Patents

Description

  The present invention relates to a transmission apparatus that switches between transmission paths in a communication network.

  In a transmission system that includes a transmission device on the transmission side and a transmission device on the reception side and connects them with multiple transmission lines, there is a conventional non-instantaneous transmission technology that switches between transmission lines without interruption. It is used for non-instantaneous transmission.

  As the conventional uninterruptible transmission technology, for example, as described in Patent Document 1, it is intended to eliminate the influence on the user by switching without instantaneous interruption when a transmission line failure or the like occurs. There is technology to do.

  In the conventional technology for realizing non-instantaneous switching at the time of transmission line failure, etc., the same signal is sent from the transmission side transmission device to a plurality of transmission lines (systems), and the reception side transmission device has a delay of each system. Are compared, and the phase of the signal of each system is matched with the phase of the signal of the most delayed system (also referred to as the long distance system) by inserting a delay into the early arrival system (also referred to as the short distance system). Then, when a failure occurs in the selected system in the receiving side transmission apparatus, the selected system is switched to another normal system.

  In such a conventional technique, since a long-distance delay is always inserted in a short-distance transmission path, there is a problem that the delay becomes larger than a line not having an uninterruptible function. In particular, when the line capacity is large, the influence of the delay time becomes significant. Further, when the signal transmission path passes through a plurality of sections, the delay of the long distance system in each section is integrated, so that the influence of the delay is noticeable. Therefore, there are many cases where the above-described conventional technology cannot be applied to applications sensitive to absolute delay such as voice calls and applications such as online games.

  Now, on long-distance transmission lines, the frequency of disconnection of routes (optical fibers, etc.) caused by planned roads, bridge construction, etc. is higher than the frequency of disconnection due to failures in lines and relay devices. There are many cases. In such a case, there is an idea that it is sufficient to realize non-instantaneous switching only in the case of frequent planned construction. In addition, there is a need for an uninterruptible switching transmission system with low delay that can be applied to applications sensitive to absolute delay such as voice calls.

  From this point of view, during normal operation without planned construction, the insertion of a delay in order to match the maximum delay system as described above is stopped, and instantaneous switching that is very unlikely to occur is allowed, There is a technique described in Patent Literature 2 as a conventional technique that applies switching without interruption only during planned construction.

  In the technique described in Patent Document 2, a delay is not inserted at the receiving side transmission apparatus during normal operation, but a delay is inserted only at the time of plan switching. Further, in order to reduce the influence on the application and the user as much as possible, the delay is gradually inserted when inserting the delay.

JP-A-9-135228 JP 2007-228282 A

  The conventional technique described in Patent Document 2 can solve the problem in the uninterruptible transmission method in which a delay is always inserted.

  However, since the prior art described in Patent Document 2 is a method of switching at the receiving side transmission apparatus, it is necessary to transmit packets in parallel from the transmission side transmission apparatus to a plurality of paths, and the occupied bandwidth is Necessary for the number of routes. In addition, the transmission apparatus on the receiving side needs to include a plurality of buffers for performing delay difference control, and there is a problem that the circuit becomes large-scale.

  In order to solve the above-mentioned problems, it is conceivable to employ a system that is normally operated in a short-distance system, and that a system to be selected in the transmission apparatus on the transmission side is switched from a short-distance system to a long-distance system when switching plans. However, this method has a problem that the order of packets is reversed when switching from the long-distance system to the short-distance system.

  The present invention has been made in view of the above points, and in a technique for switching without interruption for planned system switching, without further transmitting signals in parallel on a plurality of paths, the circuit of the transmission apparatus is further provided. The purpose is to provide a technology for switching without interruption without increasing the scale of the system. Regarding the present invention, the term “non-instantaneous” in this specification means that the signal sequence is not reversed before and after switching, and the continuity of the signal is maintained.

  The present invention is a transmission apparatus that receives a packet from an upstream apparatus, and transmits the packet to a transmission apparatus on the reception side via one transmission path of a selection system among a plurality of transmission paths, Output control means for sending a packet received from the upstream device to at least one selected transmission line of the first transmission line and the second transmission line, and storage means for holding a predetermined threshold time And when switching the transmission line of the selection system from the first transmission line to the second transmission line having a delay smaller than the delay of the first transmission line, packets from the upstream device are transferred. Control that performs switching of the selection system for the output control means when it is detected that the next packet has not been received before the threshold time elapses after reception and transmission via the output control means Means and It was example can be configured as a transmission apparatus according to claim.

  In addition, the present invention is a transmission apparatus that receives a packet from an upstream apparatus and transmits the packet to a transmission apparatus on the reception side via one transmission line of a selection system among a plurality of transmission lines. Output control means for sending a packet received from the upstream device to at least one selected transmission line of the first transmission line and the second transmission line, and receiving from the upstream apparatus The packet identification means for determining whether or not the packet type is a predetermined type and the transmission line of the selection system have a delay smaller than the delay of the first transmission line from the first transmission line. When switching to the second transmission path, when the packet identification unit determines that the packet received from the upstream device is the packet of the predetermined type, the packet is output. After sending via the control means may be configured as a transmission apparatus characterized by and a control means for performing switching of the selection system for said output control means.

  In addition, the present invention is a transmission apparatus that receives a packet from an upstream apparatus and transmits the packet to a transmission apparatus on the reception side via one transmission line of a selection system among a plurality of transmission lines. A delay control means for sending an instruction packet for temporarily interrupting the sending of the packet to the upstream apparatus, and a packet received from the upstream apparatus at least as a first transmission line and a second Output control means for sending out to one of the transmission lines of the selected transmission line, the delay of the first transmission line, and the delay of the second transmission line having a delay smaller than the delay When the storage means for holding the delay difference and the transmission line of the selection system are switched from the first transmission line to the second transmission line, a predetermined time based on the delay difference is given to the upstream device. Only to interrupt packet transmission An instruction packet after being sent to the delay control means may be configured as a transmission apparatus characterized by and a control means for performing switching of the selection system for said output control means.

  Further, when each of the transmission apparatuses includes a computer configuration including a CPU and a memory, the function of the control unit may be realized by causing the computer to execute a program. In addition, the program can be provided as the present invention.

  According to the present invention, there is provided a technique for switching transmission lines without instantaneous interruption without transmitting signals in parallel on a plurality of paths and further without increasing the scale of the circuit of the transmission apparatus as compared with the prior art. It becomes possible.

It is a block diagram of the transmission apparatus 10 in 1st Embodiment. It is a timing diagram of a packet in the first embodiment. 3 is a flowchart for explaining the operation of the transmission apparatus 10 in the first embodiment. It is a timing diagram of a packet in the first embodiment. It is a timing diagram of a packet for reference. It is an example of a configuration when switching of the interface is required on the receiving side. FIG. 10 is a packet timing diagram in the second embodiment. It is a flowchart for demonstrating the operation | movement in the modification of 2nd Embodiment. It is a timing diagram corresponding to the operation | movement based on 1st Embodiment. It is a flowchart for demonstrating operation | movement of the transmission apparatus 10 in 3rd Embodiment. FIG. 10 is a packet timing diagram according to the third embodiment. It is a figure which shows the example of TCP communication between a client and a server. It is a block diagram of the transmission apparatus 10 of the modification in 3rd Embodiment. It is a flowchart for demonstrating the modification in 3rd Embodiment. It is a block diagram of the transmission apparatus 10 in 4th Embodiment. It is an example of the delay difference information in 4th Embodiment. 14 is a flowchart for explaining an operation of the transmission apparatus 10 in the fourth embodiment. It is a frame structure of a PAUSE frame. It is a block diagram of the transmission apparatus 10 in 5th Embodiment. 10 is a flowchart for explaining the operation of the transmission apparatus 10 in the fifth embodiment.

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

<First Embodiment>
(Device configuration)
FIG. 1 shows the configuration of a transmission apparatus 10 according to the first embodiment of the present invention. The transmission apparatus 10 shown in FIG. 1 can be used as each transmission apparatus in a transmission system in which a plurality of transmission apparatuses are connected via a transmission path. The transmission apparatus 10 according to the embodiment of the present invention is a signal Since the configuration on the transmission side is characteristic, the transmission apparatus 10 in FIG. 1 shows a configuration for signal transmission, and a configuration for signal reception is not shown. In addition, the transmission device 10 may include a routing function for selecting a signal route, but is not illustrated.

  Also, FIG. 1 shows a receiving-side transmission device 20 that receives a signal transmitted from the transmission device 10 in the present embodiment and immediately sends it to the downstream side, and monitoring control of the transmission device 10 via a communication network. An operation system 30 for performing is shown. The transmission device 20 on the reception side can be any configuration as long as it can continuously receive packets that have passed through the switched transmission path when the transmission path is switched by the transmission device 10 on the transmission side. You may have.

  In the present embodiment, a “packet” that is a signal to be transmitted is used in a broad sense including ATM cells, Ethernet (registered trademark) frames, IP packets, TCP frames, and the like. Furthermore, in this embodiment, two transmission paths (path 1 and path 2) are used as an example. The transmission path of path 1 is longer than the transmission path of path 2, and the transmission path of path 1 is When the signal transmission delay is B and the signal transmission delay in the transmission path of path 2 is b, B> b is established. Hereinafter, a system corresponding to the path 1 is referred to as a long distance system, and a system corresponding to the path 2 is referred to as a short distance system.

  As illustrated in FIG. 1, the transmission apparatus 10 includes an interface unit 11 (IF_R1), a delay control unit 12 configured by a memory 121, an output destination selection unit 13, a control unit 14, an interface unit 15 (IF_S1), and an interface unit 16. (IF_S2).

  The interface unit 11 (IF_R1) is an interface that receives a packet from a communication device (including a terminal such as a PC) on the upstream side of the transmission device 10 and inputs the packet into the transmission device 10. The delay control unit 12 includes a memory 121. A packet input from the interface unit 11 (IF_R1) is written in the memory 121 based on the writing / reading control by the control unit 14, and is read with a delay as necessary, as will be described later. The data is output to the first selection unit 13.

  The output destination selection unit 13 is a functional unit that receives the packet output from the memory 121 and outputs the packet to the interface unit corresponding to the system instructed by the control unit 13. The output destination selection unit 13 is, for example, a selector, a switch, an output mechanism that refers to a route table, or the like.

  The interface unit 15 (IF_S1) is an interface that sends a packet to the transmission path of the route 1 (long distance system), and the interface unit 16 (IF_S2) sends a packet to the transmission path of the route 2 (short distance system). It is a functional part. Note that the output destination selection unit 13 and each output interface unit may be collectively referred to as an output control unit.

  The control unit 14 includes storage means such as a memory that holds information on a delay difference between paths and the like and holds a state of a selection system (long-distance system or short-distance system). The delay difference between the paths held by the control unit 14 may be measured by, for example, the transmission device 20 on the receiving side and transmitted to the control unit 14 via the operation system 30 or the transmission path, or the path length. The operation system 30 may notify the control unit 14 of the value calculated by the operation system 30 based on the above. Further, the information notified to the control unit 14 may be the delay difference itself or the delay amount of each transmission path. When the information notified to the control unit 14 is the delay amount of each transmission path, the control unit 14 calculates the delay difference and stores it in the storage unit.

  In this embodiment, the delay difference used at the time of system switching may be acquired by any method, and the method of acquiring the delay difference does not affect the system switching method.

  A system switching instruction as to which system to select is notified from the operation system 30 to the control unit 14. Of course, an operation terminal may be connected to the transmission apparatus 10 and a switching instruction may be issued from the operation terminal to the control unit 14, or a switching time may be reserved and set in the control unit 14 of the transmission apparatus 10 in advance. Switching may be performed when the time comes. Further, the switching trigger may be received via a transmission line connected to the transmission apparatus 10, and is not limited to an operation system or an operation terminal.

  The control unit 14 also has a function of instructing the output destination selection unit 13 to perform system switching, a function of performing packet writing and reading control with respect to the delay control unit 12 (memory 121), and the like.

  The transmission apparatus 10 includes, for example, a program corresponding to an operation executed by the control unit 14 described in the embodiment on a transmission apparatus such as a router or a switch including a computer configuration including a CPU and a storage device. It can be realized by mounting. The same applies to other embodiments. Of course, the transmission apparatus 10 can also be realized by a hardware circuit. The program may be stored in a recording medium such as a portable memory and installed in the transmission device from the recording medium, or downloaded from a server on a communication network to which the transmission device is connected and installed in the transmission device. May be.

(Operation of Transmission Device 10)
Hereinafter, the operation of the transmission apparatus 10 in the present embodiment will be described.
(1) Normal operation In normal time when there is no system switching, the output destination selection unit 13 selects a short-distance system based on an instruction from the control unit 14 in order to reduce the delay. In normal times, a packet input from the interface unit 11 (IF_R1) and written in the memory 121 is immediately read out and passed to the output destination selection unit 13. Then, the output destination selection unit 13 sends the packet to the short-distance system interface unit 16 (IF_S2) which is a system selected based on an instruction from the control unit 14. As a result, the packet is sent from the interface unit 12 (IF_S2) to the short-distance transmission path and reaches the transmission apparatus 20 on the receiving side via the short-distance transmission path.
(2) Operation 1 at the time of switching (short distance system ⇒ long distance system)
When the control unit 14 receives a switching instruction to switch the selected system from the short-distance system to the long-distance system from the operation system 30 or the like in response to planned construction, the control unit 14 has a packet being read from the memory 121. If there is a packet being read out, the packet transmission process is performed before switching. That is, this packet is sent out to a short-distance transmission path.

  Thereafter, the control unit 14 issues a system switching instruction to the output destination selection unit 13, and the output destination selection unit 13 switches the selection system from the short distance system to the long distance system. After switching from the short-distance system to the long-distance system, the packet input from the interface unit 11 (IF_R1) is passed to the output destination selection unit 13 in the same way as in normal operation, and is output from the output destination selection unit 13. The data is sent to the interface unit 15 (IF_S1) of the distance system, and sent to the transmission line of the long distance system from the interface unit 15 (IF_S1).

  FIG. 2 shows a packet timing diagram when switching from the short-distance system to the long-distance system. "Transmission side reception" shown in (a) indicates the timing at which the transmission apparatus 10 receives a packet from the upstream side, and "short-range arrival" in (b) indicates that the packet sent from the transmission apparatus 10 is The timing of arrival at the transmission device 20 on the receiving side via the short-distance transmission path is shown. “Long-distance system arrival” shown in (c) indicates that the packet sent from the transmission device 10 is a long-distance system. Shows the timing of arrival at the transmission device 20 on the receiving side via the transmission line, and “reception side transmission” shown in (d) shows the timing at which the transmission device 20 on the receiving side sends packets downstream. .

As shown in FIG. 2, when there is an instruction to switch from the short distance system to the long distance system between the packet 6 and the packet 7 shown in FIG. Since the system is switched in step 1, the packet 6 is transmitted in the short distance system, and the packet 7 and subsequent packets are transmitted in the long distance system. Further, as shown in (c) and (d), since the packet 7 and later arrives at the receiving side transmission apparatus 20 with a delay due to the delay of the long distance transmission line, the packet 6 and An interval corresponding to the delay difference X between the long-distance system and the short-distance system is left between the packets 7, but no burst, order reversal, or frame loss occurs.
(3) Switching operation 2 (Long distance system ⇒ Short distance system)
After the planned construction is completed, switching from the long-distance system to the short-distance system (switchback) is performed in order to resume operation in the short-distance system with a small delay. Hereinafter, the switching operation from the long-distance system to the short-distance system will be described along the procedure of the flowchart of FIG.

  There is a possibility that the path length of the short-distance system has changed due to the construction of the short-distance system. Therefore, before switching, the control unit 14 first updates the delay difference between the long-distance system and the short-distance system. Here, for example, the operation system 30 transmits an update command including the latest delay difference to the control unit 14, and the control unit 14 holds the latest delay difference in the storage unit. Note that, in this embodiment and other embodiments, even when not specifically described, the delay difference is updated as necessary.

  When the control unit 14 receives a switching instruction from the outside of the operation system 30 or the like (step 1), the control unit 14 checks whether there is a packet being read from the memory 121, and there is a packet being read. In this case, the packet transmission process is performed before switching (step 2).

  Thereafter, the control unit 14 issues a system switching instruction to the output destination selecting unit 13 and executes system switching (step 3). Thereby, the selection system in the output destination selection unit 13 is switched from the long distance system to the short distance system.

  After switching the system (that is, after the previous packet is output from the memory 121), the control unit 14 does not immediately read the packet from the memory 121, but after the lapse of X time as a delay difference from the switching point of the system. The packet reading is started (steps 4 and 5). The control unit 14 maintains the current selection system state (short-distance system selection) and updates the delay difference X to the latest information. Thereafter, normal processing is performed.

  FIG. 4 shows a packet timing chart when switching from the long distance system to the short distance system. As shown in FIG. 4A, when there is a switching instruction between the packet 6 and the packet 7, the output destination selection unit 13 switches the system there, but the reading of the packet 7 is delayed by X time. , (B) and (c), the packet 7 passing through the short-distance transmission path arrives at the receiving-side transmission apparatus 20 after the last packet 6 passing through the long-distance transmission path. As a result, as shown in (d), switching can be performed without causing packet order reversal. However, after switching to the short-distance system, packets are accumulated in the memory 121 for a time during which reading from the memory 121 is stopped, and the accumulated packets are sent together, so a burst occurs and the bandwidth increases.

  In order to make it easy to understand the effect of the switching method from the long-distance system to the short-distance system in the present embodiment, FIG. 5 shows a timing diagram when not waiting for a packet at the time of switching. As shown in FIG. 5, after switching, a packet (packet 5 or the like) transmitted in a long-distance system arrives at the receiving side after a packet (packet 7 or the like) transmitted in a short-distance system, and the order is reversed. Will occur. On the other hand, in this embodiment, as described above, order inversion does not occur.

  In the above-described example, when switching from the long-distance system to the short-distance system, the packet reading is stopped after X hours, which is the delay difference time after stopping the packet reading, but the packet reading start time may be X + α. That is, a margin of α may be provided. This margin α is a value stored in the storage means of the control unit 14 and is a value that is greater than or equal to the assumed transmission path delay fluctuation amount. As a result, even if there is fluctuation fluctuation in the delay time of the transmission line, it is possible to prevent the occurrence of order reversal.

  Further, in the above-described example, the transmission device 20 on the reception side can receive any packet that passes through the switched transmission channel when the transmission channel is switched by the transmission device 10 on the transmission side. For example, when the transmission apparatus 20 on the reception side needs to switch the interface in accordance with the transmission path switching, the configuration shown in FIG. 6 can be adopted.

  In the example illustrated in FIG. 6, the transmission device 10 includes a packet generation unit 17. When the packet generation unit 17 receives a system switching instruction from the control unit 14, the packet generation unit 17 transmits a system switching instruction packet before the system switching. The transmission apparatus 20 on the receiving side can promptly switch the interface by receiving the system switching instruction packet.

  Furthermore, in the above example, the delay difference X is used only when switching from the long-distance system to the short-distance system (that is, switching back), but the delay difference X is set to X = max (0, ((selected System delay time) − (deselection system delay time))), and the control unit 14 calculates the delay difference X based on this definition, so that the direction of switching is shown in FIG. A switching operation can be performed based on the operation.

  The above max (A, B) is a function that returns the larger value of A and B. For example, the selection system (before switching) is a short distance system and the non-selection system (switching destination) is a long distance. In the case of a system, since the value of ((delay time of selected system) − (delay time of non-selected system)) is negative, X is 0. Therefore, in the process shown in FIG. 3, the packet is read from the memory 121 without performing the waiting in step 4. On the other hand, if the selected system (before switching) is a long-distance system and the non-selected system (switching destination) is a short-distance system, the value of ((delay time of selected system) − (delay time of non-selected system)) It becomes positive and becomes the value of X. In this case, the process as described with reference to FIG. 3 is performed.

  The first embodiment described above is the basis of each embodiment described below.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. The configuration of the transmission apparatus 10 in the second embodiment is the same as the configuration of the transmission apparatus 10 in the first embodiment, as shown in FIG. However, the present embodiment differs from the transmission device 10 in the first embodiment in the information and operations held by the transmission device 10. In the following, a description will be given focusing on differences from the transmission apparatus 10 according to the first embodiment.

  In the first embodiment, when switching from the long-distance system to the short-distance system, the rate at which packets are read from the memory is used as the wire rate, so as shown in FIGS. 4 (c) and 4 (d) A burst has occurred.

  Therefore, in the present embodiment, the control unit 14 holds the packet reading interval time β in advance. When switching from the long-distance system to the short-distance system, the control unit 14 waits for reading from the memory 121 for X time or X + α time which is a delay difference, and then waits for waiting when reading from the memory 121. Each packet is read at the read interval time β until the packet accumulated in the memory 121 becomes empty, and is sent to the output destination selection unit 13. After the packet stored in the memory 121 becomes empty, the packet written in the memory 121 is immediately read out as in the normal case.

  FIG. 7 shows a packet timing chart in the second embodiment. As shown in FIGS. 7B and 7D, in the second embodiment, the burst property after the start of reading from the memory 121 is relaxed compared to the case of FIG.

(Modification)
The above example is a method suitable for the case where the length of each packet is constant because the packet is read from the memory 121 at a predetermined read interval time β. Hereinafter, an example that can be applied when the length of the packet is variable (for example, when the packet is an Ethernet (registered trademark) frame or the like) will be described as a modification of the second embodiment. In the following, the description will focus on differences from the transmission apparatus 10 in the first embodiment.

  In this modification, the control unit 14 holds the read rate R (bps) from the memory 121 after switching from the long distance system to the short distance system. The read rate R is, for example, a value notified in advance from the operation system 30 to the control unit 14, and is a value equal to or higher than the line speed at which packets are transmitted.

  In this modification, the control unit 14 obtains the length L (byte) of the packet immediately before reading from the memory 121 from the header information included in the packet, and the packet reading interval time from L and R. A function of calculating a certain 8L / R value, holding this value, and controlling reading of the next packet using this value is provided. This process is performed for each read packet until the packet stored in the memory 121 becomes empty.

  The packet reading process in this modification will be described with reference to the flowchart shown in FIG. The process shown in FIG. 8 corresponds to the details of the packet read process in step 5 shown in FIG. Further, in the reading process shown in FIG. 8, the above-described process of calculating the 8L / R value for each packet is performed in parallel.

  First, the control unit 14 reads the data of the first packet stored in the memory 121 at the read rate R (step 11). If the memory 121 is not empty (No in step 12), it is checked whether or not (8L / R) time corresponding to the packet has elapsed since the start of reading the packet (step 13). Then, when the time has elapsed, the next packet is read out. Such a process is repeated until the memory 121 becomes empty. With this operation, even when the packet length is variable, packets stored in the memory after switching can be gradually read out.

<Third Embodiment>
Hereinafter, a third embodiment of the present invention will be described. First, the outline of the processing in the present embodiment will be described with reference to FIG. 9 which is a timing chart corresponding to the operation based on the first embodiment. In the example shown in FIG. 9, when there is an instruction to switch from the long distance system to the short distance system between the packet 2 and the packet 3, the packet transmission to the short distance system is started after waiting for the delay difference X. However, as described above, this method can prevent the packet order from being reversed, but a burst occurs.

  Now, in general, the packet transmission interval is not constant. For example, as shown in FIG. 9A, it frequently occurs when there is an interval greater than the delay difference.

  Thus, if such a vacancy between packets is detected, switching from the long-distance system to the short-distance system causes the vacancy time itself to have the same effect as the waiting time in the memory 121, and the memory Switching from the long-distance system to the short-distance system can be performed without performing 121 waiting. In the example of FIG. 9, after the switching instruction, for example, if actual switching is performed at the time indicated by A, transmission is performed in the short distance system after the packet 6 transmitted in the long distance system. Packets after packet 7 to be received arrive at the receiving side, and neither order reversal nor burst occurs. This embodiment is a system based on this principle.

  The configuration of the transmission apparatus 10 in the third embodiment is the same as the configuration of the transmission apparatus 10 in the first embodiment, as shown in FIG. However, the present embodiment differs from the transmission device 10 in the first embodiment in the information and operations held by the transmission device 10. In the following, a description will be given focusing on differences from the transmission apparatus 10 according to the first embodiment.

  In the present embodiment, the storage means of the control unit 14 in the transmission apparatus 10 holds the time interval Ta. The value of the time interval Ta is notified in advance from the operation system 30 or the like to the control unit 14 and is held by the control unit 14. Ta is a value larger than the delay difference X. In addition, the control unit 14 has a function of holding, for each packet, the time when the packet reading is completed as the packet transmission time T.

  The operation at the time of switching from the long distance system to the short distance system in the present embodiment will be described with reference to the flowchart of FIG.

  When the control unit 14 receives a switching instruction from the outside of the operation system 30 or the like (step 21), the control unit 14 checks whether there is a packet being read from the memory 121, and if there is a packet being read. Performs transmission processing of the packet (step 22).

  When the packet is read from the memory 121, the control unit 14 acquires and holds the packet transmission time T of the packet (step 23). Then, the control unit 14 monitors whether or not the next packet is written in the memory 121 within the Ta time from the packet transmission time T (step 24), and is written into the memory 121 within the Ta time. In step S25, the packet is read (step 25), and the process returns to step 23.

  In the monitoring in step 23, when the next packet is not written in the memory 121 within the time Ta from the previous packet transmission time T, that is, when no packet is written and Ta has elapsed from T, the control unit 14 performs switching by issuing an output destination switching instruction to the output destination selection unit 13 (step 26). After the system is switched, the process proceeds to normal processing.

  FIG. 11 shows a packet timing chart when switching from the long-distance system to the short-distance system in the third embodiment. As shown in FIG. 11, when there is a switching instruction between the packet 2 and the packet 3, the time interval between the subsequent packets 3 to 6 is less than Ta. In this period, as shown in (c), a packet that has passed through the long-distance system arrives at the transmission device 20 on the receiving side.

  As shown in FIG. 11A, since the control unit 14 detects that the packet is not written in the memory 121 within the Ta time after the packet 6 is transmitted, the control unit 14 performs switching, and then the upstream Packets after packet 7 received from are sent in a short-distance system. As shown in (b) to (d), the packet transmission to the short-distance system is delayed due to the space between the packets, so that the packet order is not reversed. Further, since the packet is not waited in the memory 121, no burst occurs.

  In the above example, a value larger than the delay difference X is used as Ta, but a value equal to or smaller than X may be used as Ta. However, in this case, in order to prevent the order reversal, the readout of the packet after switching is waited for (X-Ta) time in the same manner as the processing in step 4 shown in FIG.

(Modification)
In the above example, it is detected by monitoring the packet writing that a time interval of Ta or more is left between packets. However, the delay can be determined by identifying the packet type without monitoring such time. Switching may be performed when it is detected (predicted) that an empty space of difference X or more is generated.

  As an example, FIG. 12 shows an example of TCP communication between a client and a server. As shown in FIG. 12, in the case of a TCP packet in which the PSH flag is set in the header, the transmission distance corresponding to twice the distance between the ground and the distance between the transmission of the specific byte in the packet and the transmission of the next PSH data. It can be predicted that it will take a long transmission time. This time can be considered to be at least the delay difference X or more.

  Based on such a principle, the transmission apparatus 10 according to the present embodiment performs switching when detecting an input of a predetermined specific type of packet. The above example is merely an example, and any type may be used as long as it is a type that can predict a vacancy.

  In this example, as illustrated in FIG. 13, the transmission apparatus 10 identifies the type of packet written in the memory 121 and detects a packet of a predetermined type that can be predicted to be free. A packet monitor unit 18 for notifying the control unit 14 is provided.

  Hereinafter, the operation of the transmission apparatus 10 when switching from the long-distance system to the short-distance system in this example will be described with reference to the flowchart of FIG.

  When the control unit 14 receives a switching instruction from the outside such as the operation system 30 (step 31), the control unit 14 instructs the packet monitoring unit 18 to monitor a packet (step 32). For each input packet, the packet monitor 18 checks whether the packet is a predetermined type of packet (step 33). When a packet of a predetermined type is not detected, the control unit 14 performs packet transmission processing as usual without performing switching (step 34). When a predetermined type of packet is detected, the packet monitor unit 18 notifies the control unit 14 that a predetermined type of packet has been detected (step 35).

  Then, after step 35, the control unit 14 performs the switching by issuing a switching instruction to the output destination selection unit 13 after performing the transmission process of the packet detected by the packet monitoring unit 18 (step 36) (step 36). Step 37).

  Since the packet next to the packet detected by the packet monitor unit 18 should be input to the transmission apparatus 10 after a delay of the delay difference X or more, the packet transmitted in the long-distance system before step 36, For packets transmitted in the short-haul system after step 36, no order reversal or burst occurs in the transmission apparatus 20 on the receiving side.

<Fourth embodiment>
Next, a fourth embodiment will be described. The fourth embodiment is an example generalized so that the number of transmission paths is not two but three or more. Further, in this example, it is not necessary to distinguish between “short distance” and “long distance”, such as a short distance system to a long distance system and a long distance system to a short distance system. The basic configuration and operation of the fourth embodiment are the same as those of the first embodiment, and the following description will focus on differences from the first embodiment.

(Device configuration)
FIG. 15 shows a configuration diagram of the transmission apparatus 10 according to the present embodiment. The configuration of the transmission apparatus 10 of the present embodiment is basically the same as the configuration of the transmission apparatus 10 of the first embodiment, but the number of paths may be three or more in the transmission apparatus 10 of the present embodiment. As an example showing this, the interface unit 19 (IF_S3) is provided to cope with the case where the number of paths is three.

  In the present embodiment, the control unit 14 holds the delay amount (d1, d2, d3) of each path in advance according to an instruction from the outside such as the operation system 30 and the selected system n (n = 1, 2, ...)). Further, the control unit 14 determines the delay difference between the paths Xnm = max (0, ((the delay time of the selected system) − (the delay time of the non-selected system))) (n ≠ m) based on the delay amount. Is calculated and stored in the storage means. When the number of paths is three, Xnm held in the control unit 14 can be shown in a table format in FIG. 16, for example.

(Operation of Transmission Device 10)
Hereinafter, the operation of the transmission apparatus 10 in the present embodiment will be described.
(1) Normal operation In a normal time when there is no system switching, the control unit 14 writes the arrived packet in the memory 121 and immediately reads it. The read packet is sent to the transmission path of the path n selected by the output destination selection unit 13.
(2) Operation at the time of switching Next, the operation at the time of switching such as switching for planned construction and switching back will be described with reference to the flowchart of FIG.

  When the control unit 14 receives a switching instruction (including information on the switching-destination system m) from outside the operation system 30 or the like (step 41), the control unit 14 determines whether there is a packet being read from the memory 121. If there is a packet that is being read and is being read, the packet transmission process is performed before switching (step 42).

  Thereafter, the control unit 14 issues a system switching instruction to the output destination selecting unit 13 and executes system switching (step 43). That is, switching from the system n to the system m is performed.

  After switching the system (that is, after the previous packet is output from the memory 121), the control unit 14 starts reading the packet after the Xnm time as the delay difference has elapsed from the switching point of the system (step 44, 45). Thereafter, the control unit 14 holds the current selection system state (system m selection), and thereafter, normal processing is performed. In the above process, if Xnm is 0 (that is, in the case of switching from the short distance system to the long distance system), the packet is transmitted without waiting in step 44.

<Fifth embodiment>
Next, a fifth embodiment will be described. In the embodiments so far, the delay control unit 12 uses the memory 121 and adjusts the packet read timing from the memory 121 to insert a delay. However, in the present embodiment, the delay control unit 12 As a control means, a PAUSE frame defined in IEEE802.3x is used. In the present embodiment, the “packet” is an Ethernet (registered trademark) frame.

  IEEE 802.3x defines a MAC control method for flow control that is full-duplex communication. In this system, by transmitting the PAUSE frame to the sending station (upstream communication device), it becomes possible to stop the transmission for the time specified by the PAUSE frame. When receiving the switching instruction, the transmission apparatus 10 according to the present embodiment generates a PAUSE frame and transmits the PAUSE frame to the transmission station, thereby controlling the packet transmission interval from the transmission station. As a result, a time for absorbing the delay difference of the route is secured, and switching without packet order reversal is realized. For reference, FIG. 18 shows a frame structure of a PAUSE frame. As shown in FIG. 18, the interruption time is expressed in bits, and a desired interruption time is given by bit information. In the example shown, the interruption time is 512 bit times. Also, for example, the 1-bit time is 1 ns for the 1G interface.

(Device configuration)
FIG. 19 shows a configuration of transmission apparatus 10 according to the present embodiment. The basic configuration of the transmission apparatus 10 of this embodiment is the same as that of the first embodiment, but in this embodiment, the PAUSE frame generation unit 122 is used as the delay control unit 12 instead of the memory 121. Prepare. Also, FIG. 19 shows an interface unit 51 (IF_S0) for sending a PAUSE frame to the transmission station 60 side. In addition, the transmission apparatus 10 according to the present embodiment includes a merging unit 52 for merging the PAUSE frame and the frame transmitted to the upstream side (transmission station side). Further, FIG. 19 shows an interface unit 53 (IF_R1) and an interface unit 54 (IF_R2) that receive frames from the transmission apparatus 20. The control unit 14 in the present embodiment holds a delay difference X similar to that in the first embodiment.

  In this embodiment, a memory functioning as a buffer is also provided. However, in this embodiment, the memory is not shown because it does not function as a delay control unit.

(Operation of Transmission Device 10)
The normal operation and the switching operation from the short-distance system to the long-distance system are the same as those in the first embodiment. The operation at the time of switching from the long distance system to the short distance system will be described with reference to the flowchart of FIG.

  When the control unit 14 receives a switching instruction from outside the operation system 30 or the like (step 51), the control unit 14 transmits information indicating the time of the delay difference X and a PAUSE frame transmission instruction to the PAUSE frame generation unit 122. (Step 52). Upon receiving the instruction, the PAUSE frame generation unit 122 generates a PAUSE frame including information indicating that frame transmission to the transmission apparatus 10 is stopped for the time of the delay difference X, and transmits it to the transmission station 60 (step 53). ).

  After step 53, the control unit 14 waits for the time U + 2Z, and then issues a system switching instruction to the output destination selecting unit 13 to execute system switching (step 54). Here, Z is a transmission time between the transmission station 60 and the transmission apparatus 10, and U is a processing time until the transmission station 60 stops sending a packet after receiving the Pause frame.

  Packets (frames) are transmitted in the same manner as in the normal state from when the switching instruction is received until before switching at step 54. By executing the switching, the selection system in the output destination selection unit 13 is switched from the long distance system to the short distance system. Thereafter, the control unit 14 holds the current selection system state (short-distance system selection).

  The transmitting station 60 that has received the PAUSE frame resumes the packet transmission after the elapse of the time X, which is the delay difference, after the time U has elapsed, and the transmission apparatus 10 selects the arriving packet in the same manner as normal. Send out from the system (short distance system) (step 55).

  Although the PAUSE frame is used in this example, the switching wait control in the present embodiment may be performed using a packet having the same function in addition to the PAUSE frame.

<Effect of Embodiment>
According to the transmission apparatus 10 in the embodiment of the present invention, order reversal due to system switching can be eliminated. Also, bursts can be suppressed by a method of gradually reading packets from the memory 121 or a method of not waiting for packets in the memory 121.

  Further, since the short-distance system is selected during normal operation of the transmission apparatus 10, it is possible to reduce the delay during normal operation. In addition, when signal transmission is performed in a plurality of sections, only a route with planned construction or the like becomes a long distance system, and end-to-end delay can be suppressed.

  In addition, since the method in the present embodiment is a switching method on the transmission side, it is only necessary to transfer a packet to only one path, and the occupied bandwidth is less wasted compared to the prior art, and the bandwidth is effectively utilized. Is possible. Further, since the switching method is performed on the transmission side, it is not necessary to provide as many buffer memories and the like as the number of paths as the configuration on the reception side. Therefore, the function of the transmission apparatus 10 according to the present embodiment can be easily implemented in a packet transfer device such as a router or a switch.

Hereinafter, the configurations disclosed in this specification are listed as examples.
(Section 1)
A transmission device that receives a packet from an upstream device and transmits the packet to a transmission device on the reception side via one transmission path of a selection system among a plurality of transmission paths,
Delay control means for temporarily holding packets received from the upstream device;
Output control means for sending a packet read from the delay control means to at least one transmission line of a selection system of the first transmission line and the second transmission line;
Storage means for holding a delay difference between the delay of the first transmission path and the delay of the second transmission path having a delay smaller than the delay;
When switching the transmission line of the selection system from the first transmission line to the second transmission line, a predetermined time based on the delay difference has elapsed after switching the selection system for the output control means Control means for reading a packet held in the delay control means at a time point and sending it out through the output control means;
A transmission apparatus comprising:
(Section 2)
The transmission apparatus according to claim 1, wherein the predetermined time is the time of the delay difference or a time obtained by adding a predetermined time to the time of the delay difference.
(Section 3)
The storage means holds a predetermined readout interval time,
The control means reads out each packet held in the delay control means at the read interval time when a predetermined time based on the delay difference has elapsed. The transmission apparatus described in 1.
(Section 4)
The storage means holds a predetermined read rate,
When the predetermined time based on the delay difference has elapsed, the control means reads the length of the packet to be read first when reading each packet held in the delay control means at the read rate. The transmission apparatus according to claim 1 or 2, wherein the next packet is read out at a time interval obtained by dividing by.
(Section 5)
A transmission device that receives a packet from an upstream device and transmits the packet to a transmission device on the reception side via one transmission path of a selection system among a plurality of transmission paths,
Output control means for sending a packet received from the upstream device to at least one transmission line of the selection system out of the first transmission line and the second transmission line;
Storage means for holding a predetermined threshold time;
When switching the transmission line of the selection system from the first transmission line to the second transmission line having a delay smaller than the delay of the first transmission line, a packet is received from the upstream device. A control means for switching the selection system for the output control means when it is detected that the next packet has not been received before the threshold time elapses after being sent through the output control means; ,
A transmission apparatus comprising:
(Section 6)
A transmission device that receives a packet from an upstream device and transmits the packet to a transmission device on the reception side via one transmission path of a selection system among a plurality of transmission paths,
Output control means for sending a packet received from the upstream device to at least one transmission line of the selection system out of the first transmission line and the second transmission line;
Packet identification means for determining whether the type of packet received from the upstream device is a predetermined type;
When switching the transmission line of the selection system from the first transmission line to the second transmission line having a delay smaller than the delay of the first transmission line, the packet identification means Control for switching the selection system for the output control means after sending the packet through the output control means when it is determined that the packet received from the apparatus is the predetermined type of packet Means,
A transmission apparatus comprising:
(Section 7)
A transmission device that receives a packet from an upstream device and transmits the packet to a transmission device on the reception side via one transmission path of a selection system among a plurality of transmission paths,
Delay control means for sending an instruction packet to temporarily stop sending packets to the upstream device;
Output control means for sending a packet received from the upstream device to at least one transmission line of the selection system out of the first transmission line and the second transmission line;
Storage means for holding a delay difference between the delay of the first transmission path and the delay of the second transmission path having a delay smaller than the delay;
Instructing the upstream device to interrupt packet transmission for a predetermined time based on the delay difference when switching the selected transmission line from the first transmission line to the second transmission line. Control means for switching the selection system for the output control means after sending the packet to the delay control means;
A transmission apparatus comprising:
(Section 8)
A program for causing a transmission device to realize the function of the control means in the transmission device according to any one of items 1 to 7.
(Section 9)
A transmission path switching method executed by a transmission apparatus that receives a packet from an upstream apparatus and transmits the packet to a transmission apparatus on the reception side via one transmission path of a selection system among a plurality of transmission paths. There,
The transmission apparatus is
Delay control means for temporarily holding packets received from the upstream device;
Output control means for sending a packet read from the delay control means to at least one transmission line of a selection system of the first transmission line and the second transmission line;
Storage means for holding a delay difference between the delay of the first transmission path and the delay of the second transmission path having a delay smaller than the delay;
With
When switching the transmission line of the selection system from the first transmission line to the second transmission line, a predetermined time based on the delay difference has elapsed after switching the selection system for the output control means A transmission path switching method characterized by reading a packet held in the delay control means at the time and sending it out through the output control means.
(Section 10)
A transmission path switching method executed by a transmission apparatus that receives a packet from an upstream apparatus and transmits the packet to a transmission apparatus on the reception side via one transmission path of a selection system among a plurality of transmission paths. There,
The transmission apparatus is
Output control means for sending a packet received from the upstream device to at least one transmission line of the selection system out of the first transmission line and the second transmission line;
Storage means for holding a predetermined threshold time;
With
When switching the transmission line of the selection system from the first transmission line to the second transmission line having a delay smaller than the delay of the first transmission line, a packet is received from the upstream device. And switching the selection system for the output control means when it is detected that the next packet has not been received before the threshold time elapses after being sent through the output control means. A transmission line switching method.
(Section 11)
A transmission path switching method executed by a transmission apparatus that receives a packet from an upstream apparatus and transmits the packet to a transmission apparatus on the reception side via one transmission path of a selection system among a plurality of transmission paths. There,
The transmission apparatus is
Output control means for sending a packet received from the upstream device to at least one transmission line of the selection system out of the first transmission line and the second transmission line;
Packet identification means for determining whether the type of packet received from the upstream device is a predetermined type;
With
When switching the transmission line of the selection system from the first transmission line to the second transmission line having a delay smaller than the delay of the first transmission line, the packet identification means When it is determined that the packet received from the apparatus is the packet of the predetermined type, after the packet is transmitted through the output control unit, the selection system for the output control unit is switched. A transmission line switching method characterized by the above.
(Section 12)
A transmission path switching method executed by a transmission apparatus that receives a packet from an upstream apparatus and transmits the packet to a transmission apparatus on the reception side via one transmission path of a selection system among a plurality of transmission paths. There,
The transmission apparatus is
Delay control means for sending an instruction packet to temporarily stop sending packets to the upstream device;
Output control means for sending a packet received from the upstream device to at least one transmission line of the selection system out of the first transmission line and the second transmission line;
Storage means for holding a delay difference between the delay of the first transmission path and the delay of the second transmission path having a delay smaller than the delay;
With
Instructing the upstream device to interrupt packet transmission for a predetermined time based on the delay difference when switching the selected transmission line from the first transmission line to the second transmission line. A transmission path switching method, wherein after the packet is sent to the delay control means, the selection system is switched to the output control means.

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

10, 20 Transmission device 30 Operation system 11, 15, 16, 19, 51, 53, 54 Interface unit 12 Delay control unit 13 Output destination selection unit 14 Control unit 121 Memory 17 Packet generation unit 18 Packet monitoring unit 52 Junction unit 122 PAUSE Frame generator

Claims (5)

A transmission device that receives a packet from an upstream device and transmits the packet to a transmission device on the reception side via one transmission path of a selection system among a plurality of transmission paths,
Output control means for sending a packet received from the upstream device to at least one transmission line of the selection system out of the first transmission line and the second transmission line;
Packet identification means for determining whether the type of packet received from the upstream device is a predetermined type;
When switching the transmission line of the selection system from the first transmission line to the second transmission line having a delay smaller than the delay of the first transmission line, the packet identification means When it is determined that a packet received from the device is a packet of the predetermined type, and when it is detected that a vacant space of a predetermined time length is generated until the next packet is received , the packet is Control means for switching the selection system for the output control means after sending it through the output control means;
A transmission apparatus comprising: A transmission device that receives a packet from an upstream device and transmits the packet to a transmission device on the reception side via one transmission path of a selection system among a plurality of transmission paths,
Delay control means for sending an instruction packet to temporarily stop sending packets to the upstream device;
Output control means for sending a packet received from the upstream device to at least one transmission line of the selection system out of the first transmission line and the second transmission line;
Storage means for holding a delay difference between the delay of the first transmission path and the delay of the second transmission path having a delay smaller than the delay;
Instructing the upstream device to interrupt packet transmission for a predetermined time based on the delay difference when switching the selected transmission line from the first transmission line to the second transmission line. Control means for switching the selection system for the output control means after sending the packet to the delay control means;
A transmission apparatus comprising: The function of the control means in the transmission apparatus according to claim 1 or 2, a program for implementing on the transmission device. A transmission path switching method executed by a transmission apparatus that receives a packet from an upstream apparatus and transmits the packet to a transmission apparatus on the reception side via one transmission path of a selection system among a plurality of transmission paths. There,
The transmission apparatus is
Output control means for sending a packet received from the upstream device to at least one transmission line of the selection system out of the first transmission line and the second transmission line;
Packet identification means for determining whether the type of packet received from the upstream device is a predetermined type;
With
When switching the transmission line of the selection system from the first transmission line to the second transmission line having a delay smaller than the delay of the first transmission line, the packet identification means When it is determined that a packet received from the device is a packet of the predetermined type, and when it is detected that a vacant space of a predetermined time length is generated until the next packet is received , the packet is A transmission path switching method characterized by switching the selection system for the output control means after sending it through the output control means. A transmission path switching method executed by a transmission apparatus that receives a packet from an upstream apparatus and transmits the packet to a transmission apparatus on the reception side via one transmission path of a selection system among a plurality of transmission paths. There,
The transmission apparatus is
Delay control means for sending an instruction packet to temporarily stop sending packets to the upstream device;
Output control means for sending a packet received from the upstream device to at least one transmission line of the selection system out of the first transmission line and the second transmission line;
Storage means for holding a delay difference between the delay of the first transmission path and the delay of the second transmission path having a delay smaller than the delay;
With
Instructing the upstream device to interrupt packet transmission for a predetermined time based on the delay difference when switching the selected transmission line from the first transmission line to the second transmission line. A transmission path switching method, wherein after the packet is sent to the delay control means, the selection system is switched to the output control means.

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