JPH0738610A - Packet transmission system - Google Patents

Abstract

PURPOSE:To avoid congestion in a transmission line by allowing each receiver of a couple of communication nodes to use a multiplexer means so as to send signals of plural transmission lines to one output transmission line and selecting only the sender side transmission lines when congestion takes place in the transmission lines thereby switching the transmission line instantaneously. CONSTITUTION:N-sets of transmission lines 24-26 between a transmitter 10 and a receiver 11 are connected to one output transmission line 2 confluently with the receiver 11 to obtain an output path. The same configuration is adopted for both vertical directions. The transmitter 10 or 12 sends a monitor packet periodically to the transmission lines 24-26 and outputs a path switching command signal when a detection rate of a congestion signal detected by a detection circuit 30 of the receiver 11 or 13 reaches a predetermined rate or over. Furthermore, relay nodes 14-19 insert a signal to a packet in the opposite direction to inform it to the transmitters 10, 12 when the detection circuit 32 detects congestion. Then the transmission line in the reverse direction opposite to the path not in congestion is selected. Thus, the outputs are converged to one and the transmission line is selected by the input side only to select the line instantaneously.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is used in digital communications. In particular, it relates to a transmission path switching technology for digital communication using packets.

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIG. Figure 6
FIG. 4 is a conceptual diagram showing a configuration of a conventional example. In the transmitting device 1 and the receiving device 2, communication is normally performed using the working transmission line 4. When congestion is detected in the relay node 3, the congestion notification signal 8 is transmitted via the common line 9 to the transmission device 1
And to the receiving device 2. The transmitter 1 and the receiver 2 switch from the working transmission line 4 to the backup transmission line 5 by the congestion notification signal 8. When the spare transmission line 5 is congested, it can be switched to another spare transmission line. In this case, opposite communication switching control is required between the transmission device 1 and the reception device 2.

[0003]

According to this conventional method, since the congestion notification signal is transferred from the relay node which has detected the congestion to the transmitting / receiving device by using the common line, the time from the detection of the congestion to the line switching. Becomes longer. Also, line switching requires switching at the transmitter and receiver,
When there are a plurality of spare transmission lines, it is necessary to communicate the spare transmission line number information to be switched between the transmission / reception devices, so that the opposite communication switching control is required. Further, it is difficult to match the switching time of the transmitting device with the switching time of the receiving device. Even if they match, packet switching and packet order inversion due to line switching will occur.

The present invention has been made against such a background, and an object of the present invention is to provide a packet transmission system in which transmission paths are switched instantaneously and packet discarding, packet reversal, etc. do not occur.

[0005]

According to the present invention, there are provided a pair of communication nodes, which are provided in opposition to each other for transmitting and receiving packets, and a plurality of N pairs of bidirectional transmission paths are provided between the opposition communication nodes. This is a packet transmission method in which a relay node is inserted in each pair of bidirectional transmission paths.

Here, a feature of the present invention is that each of the receiving devices of the pair of communication nodes comprises a multiplexing means for transmitting the signals arriving at the plurality of N transmission paths to one output transmission path. The relay node sends a congestion notification signal to each of the means for detecting congestion of a passing signal bidirectionally and to the opposite transmission line corresponding to the detected congestion according to the detection result of the detecting means. And a means for detecting the congestion notification signal in the receiving device of the communication node, the congestion is detected in the subsequent transmission line according to the output of the detecting device in the transmitting device of the communication node. There is a means to switch to a non-transmission line.

The switching means includes a buffer circuit which gives a delay time equal to or more than a difference between a transmission path delay time of a switching source and a transmission path delay time of a switching destination, and a transmission path having a large delay time to a transmission path having a small delay time. It is desirable to provide means for passing the buffer circuit when switching is performed.

The N transmission paths may be virtual paths (VP) or virtual channels (VC).

[0009]

The N transmission lines which are set bidirectionally and which are connected to one transmission line at the reception unit are provided between the transmission device and the reception device. The transmission path input to the transmitter is
Usually, one of the N transmission lines or m (≦ N) of the N transmission lines is used for transmission. Therefore, since the working transmission line in use is constantly connected to the remaining spare transmission line on the receiving side, only the transmitting side needs to switch the transmission line. That is, the switching of the transmission line can be controlled independently by using the reverse direction congestion notification signal sent from the relay node which has detected the congestion to the transmitting device. Therefore, the transmission path can be switched quickly.

Furthermore, when switching from a transmission path with a small transmission delay to a transmission path with a large transmission delay, even if it is switched as it is, it will be a switch without interruption. When switching from a transmission line with a large transmission delay to a transmission line with a small transmission delay, the transmission delay difference is temporarily absorbed by the buffer circuit before switching.
It is possible to switch without interruption. As a result, packet loss and order reversal do not occur in the transmission path.
Further, since the packet output rate from the buffer circuit is controlled to prevent the packet rate from increasing more than necessary, it is possible to prevent congestion induction at the intermediate relay node by switching the transmission path.

It is sufficient if this buffer circuit is arranged in the transmitter of the communication node. A buffer circuit may be prepared in advance so that the respective delay times of the plurality of N transmission lines are equal. This buffer circuit can be deleted when the signal is interrupted after switching the transmission path.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of the first embodiment of the present invention. FIG. 2 is a conceptual diagram of the first embodiment of the present invention. FIG. 2 is a diagram in which the upstream direction and the downstream direction are shown separately. The communication node 50 shown in FIG. 1 is shown as the transmitter 10 and the receiver 13, and the communication node 51 is shown as the receiver 11.
And as transmitter 12. The relay nodes 14 and 17, the relay nodes 15 and 18, and the relay nodes 16 and 19 are the same node, respectively. In addition, the transmission line 24
And 27, the transmission lines 25 and 28, and the transmission lines 26 and 29 are the same path route.

According to the present invention, a pair of communication nodes 50 and 51 provided facing each other for transmitting and receiving packets, and a plurality of N pairs of bidirectional transmission paths 24 to 29 are provided between the communication nodes 50 and 51 facing each other. The N pairs of bidirectional transmission lines 24
No. 29 is a packet transmission system in which relay nodes 14 to 19 are inserted.

Here, the feature of the present invention is that the receiving devices 11 and 13 of the communication nodes 50 and 51 send the signals arriving on the transmission lines 24 to 29 to one output transmission line 21 and 23, respectively. The relay nodes 14 to 19 are provided with a multiplexing circuit 36 as a multiplexing unit for detecting the congestion of the passing signals in both directions, and the congestion detection circuit 32 detects the congestion in both directions. Transmission line 2 in the opposite direction corresponding to when detected
4 to 29 are provided with a congestion notification signal insertion circuit 33 as a means for transmitting a congestion notification signal, and the congestion notification signal detection circuit 30 is provided as a means for detecting the congestion notification signal in the receiving devices 11 and 13 of the communication nodes 50 and 51. The transmission devices 10 and 12 of the communication nodes 50 and 51 are provided with a transmission path 24 for subsequent transmission according to the output of the congestion notification signal detection circuit 30.
The switch control circuit 35 is provided as a means for switching the transmission lines 24-29 to the transmission lines 24-29 in which congestion is not detected. In the first embodiment of the present invention, the transmission paths 24 to 29 are path paths of virtual paths (VP).

Next, the operation of the first embodiment of the present invention will be described. N transmission lines 24 to 26 having different routes are set between the transmission device 10 and the reception device 11 in the upstream direction, and the transmission lines 24 to 26 are connected to one output transmission line 21 in the reception device 11. They are joined together to form an upstream output path.
The downstream direction has the same configuration. Since the N transmission lines 24 to 26 are connected to each other on the receiving device 11 side, only the transmitting device 10 side needs to perform path switching.

The network congestion monitoring packet generating circuit 31 of the transmitter 10 or 12 periodically sends the network congestion monitoring packet to the transmission lines 24 to 29. This network congestion monitoring packet is extracted by the receiving device 11 or 13 and input to the congestion notification signal detection circuit 30. Congestion notification signal detection circuit 3
In 0, the detection rate of the packet including the congestion notification signal within a fixed time is constantly monitored, and when the value is equal to or higher than the fixed value, the path using the opposite transmission lines 24 to 29 is being used. The switching instruction signal of is output.

Here, the packet configuration will be described with reference to FIG. FIG. 3 is a diagram showing a packet structure. The header area 60 is composed of a path identification number 61, a line identification number 62, and a congestion notification signal insertion area 63, and the information area 66 is
It is composed of a packet type identification number 64 and information 65.
The network congestion monitoring packet is the same as the packet flowing in from the input transmission line 20 or 22, but the line identification number uses a specific number. As a result, the packet can be distinguished from the normal packet in the path, so that the receiving device 11 or 13 can extract only the network congestion monitoring packet.

The relay nodes 14 to 19 constantly monitor the congestion state from the Q length of the buffer or the usage rate of the transmission lines 24 to 29. When the congestion detection circuit 32 detects the congestion, the congestion monitoring packet is transferred. The congestion notification signal is inserted into the congestion notification signal insertion area 63 of all packets or only network congestion monitoring packets flowing in the reverse transmission lines 24-29 at a time period equal to or longer than the cycle.

Next, a path switching procedure due to congestion will be shown. In FIG. 2, the input transmission line 20 is connected to the transmission line 24 at the transmission device 10, and the input transmission line 20 becomes the output transmission line 21 by the confluent connection of the transmission lines 24 to 26 at the reception device 11. In this state, when the congestion detection circuit 32 of the relay node 14 detects congestion, the congestion notification signal insertion circuit 33 of the relay node 17 inserts the congestion notification signal into the backward packet. In the congestion notification signal detection circuit 30 indicated by the receiver 13, the path switching instruction signal is output when the detection rate of packets including the congestion notification signal within a certain time exceeds a certain value. As shown by this, the congestion notification signal within a certain period of time is used for the path using the transmission path 24 in the opposite direction opposite to the transmission line 27 whose detection rate of the packet including the congestion notification signal within a certain period exceeds a certain value. The transmission path 25 is switched to the opposite transmission path 25 that faces the path path in which the detection rate of packets including the packet does not exceed a certain value.

When the congestion notification signal detecting circuit 30 of the receiving device 13 does not detect the network congestion monitoring packet for a certain period of time or longer, the reverse transmission lines 24 to 26 facing the transmission lines 27 to 29 are used. In the reverse path, the network congestion monitoring packet is detected in the middle path within a certain time interval and the detection rate of the packet including the congestion notification signal within the certain time does not exceed a certain value. Road 24
Switch to ~ 26. This is because when the network congestion monitoring packet does not arrive at the receiving device 13 side, the transmission path 24 in the reverse direction is
This is because it cannot be determined whether or not ~ 26 are congested.

Further, in FIG. 2, the transmission line 24 due to congestion
Before switching the path from 25 to 25, the network congestion monitoring packet arriving from the transmission path 27 in the receiving device 13 is sent as it is to the output transmission path 23 without being terminated by the congestion notification signal detection circuit 30, and after switching the path, it is replaced with this. Then, the network congestion monitoring packet arriving from the transmission line 28 may be transmitted to the transmission line 23. As a result, even if the path switching occurs, the congestion states of the relay nodes 14 to 19 can be transmitted to the terminal. Furthermore, all transmission lines 27 to
When the detection rate of the packet including the congestion notification signal within the fixed time exceeds the fixed value in the congestion notification signal detection circuit 30 corresponding to 29, the receiving device 13 outputs the packet including the network congestion notification signal to the output transmission path 23. It can also be configured to deliver.

Further, the congestion notification signal detection circuit 30 replaces the method of outputting the path switching instruction signal when the detection rate of the packets including the congestion notification signal within a certain time is equal to or more than a certain value, A path switching instruction signal is set when the detection rate of packets including a congestion notification signal is a constant value Th1 or more, and the switching instruction signal is reset when the detection rate is a constant value Th2 (<Th1) or less, and the switching instruction signal is In the set state, the path switching instruction signal may be output. This is effective in preventing unnecessary path switching by providing a hysteresis for detecting the congestion notification signal.

Further, in the above description, the transmitting devices 10 and 1
2 periodically sends a network congestion monitoring packet, and the relay nodes 14 to 19 insert a congestion notification signal into the packet, so that the congestion of the relay nodes 14 to 19 is transmitted to the transmitter 10.
12, but relay nodes 14 to 19 that detected congestion
Causes a packet including a congestion notification signal to be newly generated and inserted into the transmission lines 24 to 29 in the reverse direction.
The congestion of the relay nodes 14 to 19 may be transmitted to 0 and 12. In this case, the line identification number 62 of the newly generated packet uses a specific number. A specific number is used as the packet type identification number 64. This makes it possible to distinguish between a normal packet and a packet containing a congestion notification signal.

It should be noted that instead of outputting a path switching signal due to congestion to switch paths, it is also possible to switch to select the transmission paths 24 to 29 with a smaller transmission delay even when congestion does not occur. .

A second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a conceptual diagram of the second embodiment of the present invention. In the second embodiment of the present invention, the N that joins and connects on the side of the receivers 11 and 13
The example of line switching using a line route of a book can be directly replaced. However, in this case, the packet is transferred by the line identification number 62.

In FIG. 4, the lines within the same path of the input transmission lines 20 and 22 are distributed to the transmission lines 24-26 and 27-29 for each line in the transmitter 10 or 12. The handling of the packets in the transmission lines 24-29 is performed by the path identification number 61.

Switching by congestion is similar to that of the first embodiment of the present invention, except that switching is performed for each virtual channel (VC) corresponding to a line. FIG. 4 shows an example of line switching of the VCb 41 when the congestion detection circuits 32 of the relay nodes 14 to 19 detect congestion. In the case of FIG. 4, compared with the case of FIG. 2, the transmission paths 24 to 29 of the switching destinations can be selected for each virtual channel (VC), so that the traffic can be more dispersed.

In switching the transmission lines 24 to 29 due to congestion in the first and second embodiments of the present invention, the transmission lines 24 to 29 having a small transmission delay to the transmission line 2 having a large transmission delay.
Switching to 4-29 can be performed without interruption. However, in switching from the transmission paths 24-29 having a large transmission delay to the transmission paths 24-29 having a small transmission delay, the order of the packets is reversed. A method for preventing this will be described with reference to FIG.
FIG. 5 is a diagram showing a method of switching without interruption from the transmission lines 24-29 having a large transmission delay to the transmission lines 24-29 having a small transmission delay. In FIG. 5, when the input transmission line 46 is switched from the current transmission line 48 having a large transmission delay to the backup transmission line 49 by the switching signal 53, the input transmission line 46 is first connected to the buffer circuit 52. This buffer circuit 52 delays the packet input to the buffer circuit 52 by a transmission delay difference between the current transmission path 48 and the backup transmission path 49 and then starts the output, and the packet in the buffer circuit 52 disappears. At this point, the buffer circuit 52 is disconnected from the spare transmission line 49. In this case, when the packets in the buffer circuit 52 are continuously output, the packet speed of the output of the buffer circuit 52 increases, and the subsequent relay nodes 14 to
19 causes congestion induction, which is not desirable. In order to prevent this, as disclosed in Japanese Patent Application No. 3-163499 (unpublished at the time of filing this application), packet intervals are compressed by periodically removing empty packets from the packet stream input to the buffer circuit 52. The output packet stream is output from the buffer circuit 52. As a result, the buffer circuit 5
The increase amount of the output packet rate of 2 compared with the input packet rate can be made minute, and congestion induction due to switching can be prevented. In the first and second embodiments of the present invention, the buffer circuit 52 is provided on the transmission device 10, 12 side.

When the relay nodes 14 to 19 predict the future packet rate from the present packet rate and send out the congestion predicting signal, the method of switching without interruption described in FIG. 5 cannot be applied. This is because, in the method shown in FIG. 5, in the relay nodes 14 to 19 on the transmission lines 24 to 29 of the switching destination, the packet speed suddenly increases due to the switching of the transmission lines 24 to 29.
This is because congestion cannot be predicted. In order to solve this, at the time of switching the transmission lines 24-29, the packet flow in the transmission lines 24-29 to be switched is guided to the buffer circuit 52, and the switching is performed from the transmission lines 24-29 having a large delay to the small one. In the case of switching to the transmission lines 24 to 29, the packet flow is delayed by the buffer circuit 52 by the transmission delay difference or more, and the transmission lines 24 to 2 having a small delay.
In the case of switching from 9 to the large transmission lines 24-29, the output of the packet from the buffer circuit 52 is immediately started. As for the packet output from the buffer circuit 52, there is no packet in the buffer circuit 52 from the initial rate at which the output packet rate is constant, or the transmission lines 24 to 29 to be switched are switched.
The packet speed is controlled so that the packet speed increases up to a fixed multiple of the specified maximum speed, which is the acceleration that is the time change rate of the packet speed or the constant acceleration ratio that is the time change ratio. As a result, the packet speed immediately after the switching gradually increases, so that the relay nodes 14 to 19 can predict the future packet speed from the present packet speed and can send the congestion prediction signal.

[0030]

As described above, according to the present invention,
Transmission lines are switched instantly, and packet discard and packet inversion do not occur. Further, since the packet output rate from the buffer circuit is controlled to prevent the packet rate from increasing more than necessary, it is possible to prevent congestion induction at the intermediate relay node by switching the line or path.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a first embodiment of the present invention.

FIG. 2 is a conceptual diagram of the first embodiment of the present invention.

FIG. 3 is a diagram showing a packet structure.

FIG. 4 is a conceptual diagram of a second embodiment of the present invention.

FIG. 5 is a diagram showing a method of instantaneously switching from a transmission line having a large transmission delay to a transmission line having a small transmission delay.

FIG. 6 is a conceptual diagram showing a configuration of a conventional example.

[Explanation of symbols]

 1, 10, 12 Transmission device 2, 11, 13 Reception device 3, 3 ', 14-19 Relay node 4,5, 24-29 Transmission line 6, 20, 22, 46 Input transmission line 7, 21, 23, 47 Output transmission path 8 Congestion notification signal 9 Common line 10, 12, 44 Transmitter 11, 13, 45 Receiver 30 Congestion notification signal detection circuit 31 Network congestion monitoring packet generation circuit 32 Congestion detection circuit 33 Congestion notification signal insertion circuit 41 VCb 50 , 51 communication node 60 header area 61 path identification number 62 line identification number 63 congestion notification signal insertion area 64 packet type identification number 65 information 66 information area

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04L 29/00 9371-5K H04L 13/00 S

Claims (4)

[Claims] 1. A pair of communication nodes provided opposite to each other for transmitting and receiving packets, and a plurality of N pairs of bidirectional transmission paths are provided between the opposing communication nodes, and the N pairs of bidirectional transmission paths are provided. In a packet transmission system in which relay nodes are respectively inserted, each receiving device of the pair of communication nodes includes a multiplexing unit that sends out signals arriving at the plurality of N transmission lines to one output transmission line, respectively. The relay node, means for respectively detecting the congestion of the passing signal bidirectionally, and means for transmitting a congestion notification signal to the corresponding opposite direction transmission line when congestion is detected according to the detection result of this detecting means, The receiving device of the communication node is provided with means for detecting the congestion notification signal, and the transmitting device of the communication node is configured to transmit subsequent signals according to the output of the detecting means. A packet transmission method comprising means for switching a signal transmission line to a transmission line in which congestion is not detected. 2. A buffer circuit for giving a delay time equal to or greater than a difference between a transmission path delay time of a switching source and a transmission path delay time of a switching destination, and the switching means, from a transmission path having a large delay time to a transmission having a small delay time. The packet transmission system according to claim 1, further comprising means for passing through the buffer circuit when switching to the path. 3. The packet transmission system according to claim 1, wherein the N transmission paths are virtual paths (VP). 4. The N transmission paths are virtual channels (V
The packet transmission system according to claim 1, which is C).