JPH08130542A - Exchange network control system - Google Patents

Abstract

PURPOSE: To reduce influence to be exerted upon a terminal/logical path having high priority and to control congestion in an exchange network control system capable of executing efficient routing processing corresponding to the priority of the terminal/logical path at the occurance of congestion. CONSTITUTION: Nodes NOD00, NOD01 are respectively provided with priority tables 2-0, 2-1 setting up the priority of terminals DTEa to DTEf stored in themselves. The nodes NOD00 to NOD02 are respectively provided with routing tables 1-0 to 1-2 setting up 1st and 2nd routes (a reference repeating route and a 2nd repeating route) corresponding to respective opposite nodes and a routing processing part for by-passing a terminal/logical path having low priority to the 2nd repeating route at the time of generating congestion in the reference repeating route, canceling a frame connected to a transmission queue from the low priority terminal, and when the congestion is restored, returning terminals/logical paths to the reference repeating route in the descending order of priority.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching network control system which enables efficient routing processing even when congestion occurs. A node in a switching network in which nodes are connected via a relay route selects a relay route based on a routing table, and when congestion occurs in the relay route, it is diverted to another relay route. It is a thing. In that case, congestion may occur again in the bypass route on the bypass side. Therefore, there is a demand for efficient control when congestion occurs.

[0002]

2. Description of the Related Art FIG. 7 is an explanatory diagram of a conventional example.
OD00, NOD01, NOD02 are connected via relay routes RUT01, RUT02, RUT03, respectively, and the nodes DTEa, DTEb, DT are connected to the node NOD00.
Ec is accommodated, and the terminals DTEd and D are connected to the node NOD01.
TEe, DTEf are accommodated, and each node NOD00, N
OD01 and NOD02 are routing tables RT
The case where 0, RT1 and RT2 are provided is shown.

Each node NOD00, NOD01, NOD
02 is a routing table RT0, RT1, RT2
Refer to the relay routes RUT01, RUT02, RUT0
Select 3. For example, from terminal DTEa to terminal DTEd
When sending data to the node NOD00, the node NOD00 refers to the routing table RT0, and the first path to the node NOD01 in which the terminal DTEd is accommodated is RUT0.
Since it is 1, the route RUT01 is selected.

In this case, when congestion occurs in the relay route RUT01, the node NOD00 refers to the routing table RT0 and selects the second route RUT02 for the node NOD01. That is, the bypass route via the node NOD02 is selected. Thereby, even if congestion occurs, communication between the terminals DTEa and DTEd can be continued.

In the congestion state, the communication load increases and the processing load of the processor for performing the routing processing becomes large.
Normal control becomes difficult, or frames before processing are accumulated in the buffer and the line connected to the buffer cannot communicate, or waiting for more than the specified number of routes in the queue waiting for transmission. Shows the case of being connected, and it is necessary to perform control to regulate before such a congestion state occurs.

Therefore, the processing state of the processor is monitored, the inflow amount of frames from the terminal is regulated, and the call from the network is disconnected to restore the congestion in the network. For terminals, transmission restrictions are applied to terminals with low priority, and transmission restrictions are applied to all terminals.

FIG. 8 is an explanatory diagram of the priority exchange processing. For example, in the node NOD00 accommodating the terminals DTEa, DTEb and DTEc, the transmission waiting queues PR1Q, PR2Q and PR3Q corresponding to the priorities are provided. Assuming the case, the priority of the terminal DTEa is 1, the priority of the terminal DTEb is 2, and the priority of the terminal DTEc is 3, the terminal DT
Ea is connected to the transmission waiting queue PR1Q of priority 1,
The terminal DTEb is connected to the transmission waiting queue PR2Q of priority 2, and the terminal DTEc is connected to the transmission waiting queue PR of priority 3.
Connected to 3Q, each terminal DTEa, DTEb, DTE
As for the frames a, b, and c of frame c, the frame a of the transmission waiting queue PR1Q of priority 1 is first transmitted to the relay route RUT01, and then the frame b of the transmission waiting queue PR2Q of priority 2 is transmitted. Queue queue PR3 with priority 3
Frame Q of Q is transmitted. That is, it is possible to set a priority for each terminal and preferentially transmit a frame from a terminal having a high priority.

[0008]

In the conventional control at the time of congestion occurrence, for example, by transmitting a non-reception code to a terminal having a low priority, the frame inflow amount to the node is regulated and the priority is given. Regardless of the degree, all terminals are switched from the first route to the second route, and the method of discarding frames from terminals with low priority is known. There is a large possibility that congestion will occur even in the second route when switching from the second route to the second route.

If the amount of frame transmission from the terminal is increased for a long time even after the congestion of the first route is restored and the second route is switched back to the first route, There is a problem that congestion is likely to occur again on the road. If congestion is repeated in this way, communication of terminals with high priority will be greatly affected. Further, when the frame discarding process is performed, there is a problem that the processing load on the terminal and the processing delay for performing the processes such as the retransmission process and the transmission order control increase. An object of the present invention is to perform congestion control in consideration of the priority of a terminal or a logical path and reduce the influence on a terminal having a high priority.

[0010]

The switching network control system of the present invention includes (1) a plurality of nodes NOD00, NOD01, NOD02, ... Connected via a relay route.
.. each node NOD in switching network having
00, NOD01, NOD02, ... Are terminals DTEa, DTEb, DTEc, DT accommodated in the node.
Ed, DTEe, DTEf, ... Set a priority in units or logical path units, and according to this priority, a routing table 1-0, for determining a relay route for each logical path,
1-1, ..., When the congestion occurs in the standard relay route, the routing table is referenced to detour to the second relay route in ascending order of priority, and when the congestion is restored, the standard relay is performed from the second relay route. And a routing processing unit that restores routes in descending order of priority. Further, 2-0 and 2-1 indicate the priority table of the terminal.

(2) Nodes NOD00, NOD01,
When the congestion occurs in the standard relay route, the NOD02, ... Divert the low priority logical path to the second relay route, and the priority of the queue connected to the transmission waiting queue of the standard relay route. A configuration may be provided in which frames of a low logical path are discarded and a plurality of standard relay routes are relaxed to a preset first congestion regulation value m.

(3) Nodes NOD00, NOD01,
When the congestion occurs in the standard relay route, NOD02, ... Diverts the low priority logical path to the second relay route, and the usage rate of the standard relay route becomes the first congestion regulation value m. When the second congestion regulation value n, which is a smaller value, is reduced to the second
It is possible to provide a configuration for notifying the terminal corresponding to the logical path detoured to the relay route of the instruction to lower the communication rate.

(4) Nodes NOD00, NOD01,
When the congestion occurs in the standard relay route, NOD02, ... Diverts the low priority logical path to the second relay route, and the usage rate of the standard relay route becomes the first congestion regulation value m. When the value decreases to the second congestion regulation value n which is a smaller value, the second
After notifying the communication path lowering instruction to the terminal supporting the logical path detoured to the relay route and confirming that the communication rate of this terminal has fallen to the preset threshold, congestion recovery in the header part of the frame The notification identification code is added and transmitted, and the subsequent frames from this terminal are accumulated in the buffer.

(5) The node accommodating the destination terminal sends a reception confirmation notification to the node which added the congestion recovery notification identification code and sent it when the reception identification of the congestion recovery notification identification code is performed. Can be provided.

(6) Nodes NOD00, NOD01,
When the reception confirmation notification of the congestion recovery notification identification code from the node accommodating the destination terminal cannot be received within a predetermined time, the NOD02, ... Send out a frame with the congestion recovery notification identification code added to the header portion again. It can be configured.

[0016]

[Action]

(1) The routing processing in the nodes NOD00, NOD01, NOD02 is performed by the routing table 1-0,
1-1 and 1-2. For example, as shown in the priority table 2-0, the priority of the terminal DTEa accommodated in the node NOD00 is 1, and the priority of the terminal DTEb is 2. , The terminal DTEc has a priority of 3, and the node N
The relay route RUT01 between OD00 and NOD01 is used as a standard relay route, and the relay route RUT is used for this standard relay route.
02 as the second relay route, and terminals DTEa, DTEb, D
When the frames a, b, and c (logical paths) from the TEc are being sent to the standard relay route RUT01 as shown by the arrow (see FIG. 1), priority is given when congestion occurs on the standard relay route RUT01. The frame c of the terminal DTEc having a low frequency is diverted to the second relay route RUT02 as indicated by an arrow. If the congestion of the standard relay route RUT01 is not alleviated by this also, the frame b of the terminal DTEb having the next priority is diverted to the second relay route RUT02. Further, when the second relay route RUT02 is restored to the standard relay route RUT01, the restoration is performed in the descending order of priority.

(2) When congestion occurs in the standard relay route,
For example, when congestion occurs in the standard relay route RUT01 of the node NOD00, the logical path of the terminal DTEc having a lower priority is diverted to the second relay route RUT02, and the node DTEc is connected to the transmission waiting queue of the standard relay route RUT01. Terminal DT
Discard the Ec frame. By this processing, when the congestion is not relieved to the first congestion regulation value m, the logical path of the terminal DTEb of the next priority is bypassed and the frame connected to the transmission waiting queue is discarded.

(3) When congestion occurs in the standard relay route,
For example, when congestion occurs in the standard relay route RUT01 of the node NOD00, the logical path of the terminal DTEc having a lower priority is diverted to the second relay route RUT02, and the usage rate of the standard relay route RUT01 is Congestion control value n (n <
m), the terminal DTEc is notified of a communication rate reduction instruction, and preparations are made for switching back from the second relay route RUT02 to the standard relay route RUT01.

(4) When congestion occurs in the standard relay route,
For example, when congestion occurs in the standard relay route RUT01 of the node NOD00, the logical path of the terminal DTEc having a lower priority is diverted to the second relay route RUT02, or the standard relay route RUT01, as in the above case. Usage rate of the second
Of the terminal DT when the congestion control value n (n <m) of
When the Ec is notified of a communication rate lowering instruction, and preparations for switching back from the second relay route RUT02 to the standard relay route RUT01 are made, and it is confirmed that the second congestion regulation value n has been reduced. , After sending the frame with the congestion recovery notification identification code added to the header part and notifying the node accommodating the destination terminal of the congestion recovery, do not send the frame of the terminal DTEc with the low priority to the second relay route RUT02. Then, the data is accumulated in the buffer, and preparations for switching back to the standard relay route RUT01 are made.

(5) A node accommodating the destination terminal, for example,
The node NOD01 sends the reception confirmation notification to the node NOD00 by an in-network control frame or the like.

(6) If the congestion recovery notification identification code is added to the header of the node, for example, the node NOD00 cannot receive the reception confirmation notification from the node NOD01 within a predetermined period of time, the node may be damaged or an error may occur. When NOD01 determines that the congestion recovery notification identification code cannot be received and identified, the congestion recovery notification identification code is sent again, and the second relay route RUT02 returns to the standard relay route RUT0.
Prepare to switch back to 1.

[0022]

1 is an explanatory view of an embodiment of the present invention, in which nodes NOD00, NOD01, NOD02 are connected to a relay route RU.
The case of a switching network connected via T00, RUT01, and RUT02 is shown, 1-0 to 1-2 are routing tables, 2-0 and 2-1 are priority tables, 1
0 indicates a frame structure. This frame shows a case having a header part for inter-network control including a source node number, a destination node number, and a congestion recovery notification identification code, and a user data part. The header portion of the frame between the terminals can be configured to include the calling terminal number, the called terminal number, the calling node number, and the called node number.

In the routing table 1-0 in the node NOD00, the first one-way (standard relay route) to the node NOD01 is RUT01, the second one (second relay route) is RUT02, and the first route to the node NOD02 is the node NOD02. The case where the one-way (standard relay route) is RUT02 and the second route (second relay route) is RUT01 is shown.
Routing table 1-1 and node N in 01
Similarly, for the routing table 1-2 in OD02, the first one-way (standard relay route) and the second one (second relay route) are set.

The priority table 2-0 in the node NOD00 shows the case where the logical paths of the terminals DTEa, DTEb and DTEc are one and the priorities are 1, 2 and 3, respectively, and the node NOD01. The priority table 2-1 in FIG. 2 shows a case where the respective logical paths of the terminals DTEd, DTEe, and DTEf are one and the priorities are 1, 2, and 3. When there are a plurality of logical paths for one terminal, different or the same priority can be given to each logical path.

FIG. 2 is an explanatory view of a main part of a node according to the embodiment of the present invention, showing a main part of the node NOD00 in FIG. 1, 1-0 is a routing table, 2-0 is a priority table, and 3 is a table. Is a routing processing unit, 4-1 and 4-2 are transmission queues corresponding to relay routes, and 5 are terminals DTEa and DT.
An interface unit for Eb and DTEc, 6-1 is an interface unit for the relay route RUT01, 6-2 is an interface unit for the relay route RUT02, and 7 is a buffer. Further, a case where frames are transmitted from the terminals DTEa, DTEb, and DTEc is shown, and the frame receiving configuration is not shown.

Further, P1 of the transmission waiting queues 4-1 and 4-2
P2 and P3 denote transmission waiting queues corresponding to the priorities of the terminals, and refer to the priority according to the priority table 2-0 and the routing table 1-0 to refer to the terminals DTEa and DT.
Frames from Eb and DTEc wait for transmission 4-
1, 4-2 are connected.

The terminals DTEa, DTEb, DTEc accommodated in the node NOD00 and the node NOD in FIG.
In the communication with the terminals DTEd, DTEe, DTEf accommodated in 01, the node NOD00 refers to the routing table 1-0, the first one-way route RUT01 becomes the standard relay route, and the priority is given. Referring to Table 2-0, the frame from terminal DTEa waits for transmission queue 4-
1, a frame from the terminal DTEb is connected to P2 of the transmission waiting queue 4-1 and a frame from the terminal DTEc is connected to P3 of the transmission waiting queue 4-1. Then, as described with reference to FIG. 8, priority exchange processing is performed in which frames are transmitted in the order of terminals or logical paths having a high priority.

For example, when congestion occurs due to the number of transmission waiting frames connected to the transmission waiting queue 4-1 corresponding to the standard relay route RUT01 of the node NOD00 exceeding a predetermined number, the transmission waiting queue 4-1 outputs The routing processing unit 3 is notified, and the routing processing unit 3 notifies the frame connected to P3 of the transmission waiting queue 4-1 having a low priority,
That is, the frame from the terminal DTEc having the priority 3 is discarded. Then, referring to the routing table 1-0,
The second relay route for the standard relay route RUT01 is searched, and the logical path of the terminal DTEc having a low priority is detoured to the second relay route RUT02. Frames a, b, and c are sent from the node NOD00 to the node NOD01 as indicated by the arrows on the standard relay route RUT01 in FIG.
Due to the occurrence of congestion in the standard relay route RUT01, the frame c of the terminal DTEc having a low priority is transferred to the second relay route RUT.
Detour as indicated by the arrow at 02.

In this state, it is judged whether or not the usage rate of the standard relay route RUT01 has dropped to a preset first congestion regulation value m [%]. The logical path of the terminal DTEb is diverted to the second relay route RUT02, and the frame connected to P2 of the transmission waiting queue 4-1 is discarded. By such processing, the logical path of the terminal DTEa having a high priority is the standard relay route RU.
It is continuously set to T01, and there is no need to detour to the second relay route RUT02. That is, the communication of the terminal with high priority will not be interrupted even when congestion occurs, and it is possible to provide a highly reliable switching network for terminals requiring real-time or important terminals.

FIGS. 3, 4 and 5 are flowcharts of the embodiment of the present invention. First, in each node, a priority (1 to k) is set for each terminal / logical path (a). .
The priority tables 1-0 and 1-1 in FIGS. 1 and 2 show the case where k = 3. Then, in response to the communication request from the terminal, the node refers to the routing table and selects the relay route. Then, when communication is started (b) and congestion occurs in the relay route (c), the congestion is notified from the transmission waiting queue to the routing processing unit 3 (d). For example, when the number of transmission waiting frames in the transmission waiting queue 4-1 of the node NOD00 reaches or exceeds a predetermined number, the congestion notification is given to the routing processing unit 3. Below this node NOD0
The description will focus on 0.

The routing processing unit 3 searches for the terminal / logical path having the lowest priority (e). Then, it is judged whether or not the frame of the terminal / logical path having the lowest priority is connected to the transmission waiting queue 4-1 of the relay route RUT01 (f). In this case, the terminal D with the lowest priority
Frames from TEc (priority 3) are queued for transmission 4
-1 is determined to be connected to P3, and if not connected, the process proceeds to step (h). If connected, the frame connected to P3 of the transmission waiting queue 4-1 is discarded. (G).

Further, the routing processing section 3 refers to the routing table 1-0 to obtain the second route RUT02 for the first one route RUT01, and performs the detouring process of the logical path of the terminal DTEc (h). In that case, the frame from the terminal DTEc is connected to P3 of the transmission waiting queue 4-2, and the second relay route RU is connected via the interface unit 6-2.
It is sent to T02. Then, it is determined whether the usage rate of the standard relay route, which is the first one-way route, has dropped to the first congestion regulation value m [%] (i). If the first congestion regulation value m
If it does not decrease to [%], the process returns to step (e), and for the terminal DTEb (priority 2) having the next lowest priority, steps (f), (g), (h), and (i) are performed. Perform processing.

When the usage rate drops to the first congestion regulation value m [%], the standard relay route RUT01 in which congestion has occurred
(J) (see FIG. 4), and determines whether the usage rate has dropped to the second congestion regulation value n [%] (n <m) (k). If it drops, send queue 4
The congestion recovery notification is sent from -1 to the routing processing unit 3 (l). Then, the terminal having the highest priority among the terminals in the congestion detour is requested to suppress the communication rate (m).
In this case, if the terminal in the congestion detour is only DTEc,
The terminal DTEc is instructed to lower the communication rate, and if the terminals in the congestion detour are DTEb and DTEc, the terminal DTEb having the higher priority is instructed to lower the communication rate.

Then, it is judged whether or not the communication rate has decreased to a preset threshold value h [%] (n), and if it does not decrease, an instruction to decrease the communication rate is issued again. In this case, not only the terminal with the highest priority but also the terminal with the next highest priority can be instructed to lower the communication rate.

When the communication rate is reduced to the threshold value h [%], the congestion recovery notification identification code is generated as shown in the intra-network control header part of one frame from the switchback target terminal, that is, the header part of the frame 10 in FIG. With node NOD0
It is sent to 2 (o). And the terminal DT after that
The frame from Ec is accumulated in the buffer 7 without being sent to the bypass route (p). Although the buffer 7 in this case is provided in the routing processing unit 3, it may be provided in another portion.

The frame with the congestion recovery notification identification code added to the header is sent to the destination node N via the node NOD02.
It is transferred to OD01. Each node has a function of monitoring the header part of the frame to identify the source node and the destination node, and at the destination node, the function of receiving and identifying the congestion recovery notification identification code added to the header part. When the recovery notification identification code is received and identified, the frame with the reception confirmation notification added to the in-network control header is sent to the source node. In that case, the user data section becomes empty.

The node NOD00 is the destination node NOD01.
It is judged whether or not the reception confirmation notification of the congestion recovery notification identification code from (q) is received, and when the reception confirmation notification is received,
The frames accumulated in the buffer 7 are sequentially sent to the first one-way route (standard relay route RUT01) (r) (see FIG. 5).
In this case, in step (o), after the congestion recovery notification identification code is added to the header and sent out, if the reception confirmation notification from the destination node cannot be received even after a predetermined time has elapsed due to timer activation, etc. , The frame in which the congestion recovery notification identification code is added to the header is sent to the destination node.

Then, the route, that is, the standard relay route R
The usage rate of UT01 is monitored (s), and the usage rate is p [%]
It is determined whether or not (n <p <m) is reached (t), and when the value becomes p [%] which is larger than the second congestion regulation value n and smaller than the first congestion regulation value m, the next priority is given. For each terminal, the switchback processing is performed in the same manner as the above-described switchback processing (u).

As described above, when congestion occurs, the detour control is performed based on the priority, so that it is possible to avoid the interruption of the communication of the terminal having the high priority, and the reliability of the exchange network for the important terminal. It is possible to improve the property.

FIG. 6 is an explanatory diagram of the ATM cell, showing the format of the user-network interface (UNI).
It consists of a 5-byte header part and a 48-byte information field. The GFC of the header part is a general flow control part, a VP.
I is a virtual path identifier, VCI is a virtual channel identifier, P
T is the payload type, CLP is the cell loss priority indicator,
HEC is a header error control unit.

The present invention is an ATM (Asynchronous Trans)
The present invention is also applicable to an exchange network of fer mode), and the priority of a terminal or a logical path is the required communication quality QOS (Quality of Service),
In combination with the cell loss priority display portion CLP, for example, QO
S = 4, CLP = 1 has priority 1, QOS = 4, CLP =
0 is priority 2, QOS = 3, CLP = 1 is priority 3, QOS
OS = 3, CLP = 0 is priority 4, QOS = 2, CLP
= 1 for priority 5, QOS = 2, CLP = 0 for priority 6,
QOS = 1, CLP = 1 is priority 7, QOS = 1, CL
P = 0 can be the priority 8. The priority of the terminal or the logical path can be set by combining other conditions.

The detection of the congestion state is performed either when the usage rate of the transmission queue of each node rises above a predetermined value, or by the congestion indication by the payload type PT in the cell header portion, or a combination thereof. In addition, the communication rate decrease instruction notification may be sent to, for example, a specific VP
By allocating the I / VCI cell for suppressing the communication rate, it is possible to notify the terminal of the decrease in the communication rate using this cell. Further, the transmission of the congestion recovery notification identification code to the destination node assigns a cell of a specific VPI / VCI to the transmission and reception of the control information between the nodes in advance, and uses this cell to notify the congestion recovery notification from the source node to the destination node. Also, the reception confirmation notification can be sent from the destination node to the source node.

The present invention is not limited to the above-mentioned respective embodiments, but can be variously added and changed, and not only when all terminals or logical paths are assigned different priorities. The case where the same priority is assigned is included, and the case where the second route (second relay route) is provided as a bypass route for the first one route (standard relay route) is shown. It also includes the case of a configuration in which multiple relay routes such as a route can be selected.In this case, the selection of the utilization ratio of other relay routes at the occurrence of congestion on the first route It can be performed based on the prediction of rise, etc.

[0044]

As described above, according to the present invention, when congestion occurs with respect to the standard relay route, the detour processing is performed in order of the terminal having the lower priority or the logical path unit. Communication will not be interrupted for the logical path, and terminals / logical paths with low priority will be bypassed, but communication will not be stopped, so the impact at the time of congestion will be reduced, The congestion can be recovered.

When the congestion is restored, the standard relay route is restored in the order of the terminal / logical path having the highest priority, and the transmission delay of the terminal / logical path having the high priority can be reduced. Further, by reducing the communication rate of the bypassed terminal and then switching back to the standard relay route, it is possible to avoid the occurrence of congestion again. In addition, by communicating between the originating node and the terminating node at the time of congestion recovery, there is an advantage that the switchback at the time of congestion recovery can be smoothly performed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a main part of a node according to the embodiment of this invention.

FIG. 3 is a flowchart of an embodiment of the present invention.

FIG. 4 is a flowchart of an embodiment of the present invention.

FIG. 5 is a flowchart of an embodiment of the present invention.

FIG. 6 is an explanatory diagram of an ATM cell.

FIG. 7 is an explanatory diagram of a conventional example.

FIG. 8 is an explanatory diagram of priority exchange processing.

[Explanation of symbols]

 1-0,1-1 Routing table 2-0,2-1 Priority table NOD00-NOD02 Node DTEa-DTEf Terminal RUT01-RUT03 Relay route

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichiro Nomura 3-2-1 Sakado, Takatsu-ku, Kanagawa Fujitsu Network Engineering Co., Ltd. (72) Minoru Yamaguchi 3-2-1 Sakado, Takatsu-ku, Kanagawa Within Fujitsu Network Engineering Limited

Claims (6)

[Claims] 1. Each node in a switching network having a plurality of nodes connected via a relay route,
A priority is set for each terminal accommodated in the node or for each logical path of the terminal, and a routing table for determining a relay route for each logical path according to the priority, and congestion occurrence in the standard relay route A routing processing unit that sometimes refers to the routing table to detour to the second relay route in order of low priority, and restores from the second relay route to the standard relay route in order of high priority when congestion is restored. A switching network control system comprising: 2. The node diverts the low priority logical path to the second relay route and transmits the standard relay route when congestion occurs in the standard relay route of the node. It is characterized in that the frame of the low priority logical path connected to the waiting queue is discarded and the congestion of the standard relay route is alleviated to a preset first congestion regulation value m. The switching network control system according to claim 1. 3. The node diverts the low priority logical path to the second relay route when congestion occurs in the standard relay route of the node, and the usage rate of the standard relay route is increased. However, when the second congestion regulation value n is smaller than the first congestion regulation value m, an instruction to lower the communication rate is given to the terminal corresponding to the logical path bypassed to the second relay route. The device for providing notification is provided.
Or the switching network control system according to item 2. 4. The node diverts the low priority logical path to the second relay route when congestion occurs in the standard relay route of the node, and the usage rate of the standard relay route is increased. However, when the second congestion regulation value n is smaller than the first congestion regulation value m, an instruction to lower the communication rate is given to the terminal corresponding to the logical path bypassed to the second relay route. After notifying and confirming that the communication rate of the terminal has decreased to a preset threshold value, the frame with the congestion recovery notification identification code added to the header is sent, and the subsequent frames from the terminal are buffered. 4. The exchange according to claim 3, further comprising a configuration for sequentially storing the frames stored in the buffer and transmitting the frames stored in the buffer to the standard relay route when the reception confirmation notification for the congestion recovery notification identification code is received. Net Network control system. 5. The node accommodating the destination terminal sends a reception confirmation notification to the node which added the congestion recovery notification identification code and sent out, when the reception identification of the congestion recovery notification identification code is performed. The switching network control system according to claim 4, further comprising a configuration. 6. The node adds the congestion recovery notification identification code to the header portion again when the node cannot receive a reception confirmation notification of the congestion recovery notification identification code from the node accommodating the destination terminal within a predetermined time. 6. The switching network control system according to claim 4, further comprising a structure for transmitting a frame.