JP2714809B2 - Switch and congestion control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to an exchange and a congestion control method in a communication system based on an asynchronous transfer mode. In a communication system using an asynchronous transfer mode for performing information communication in a fixed-length cell, a congestion bit is provided in a header portion of the cell, and a network is transmitted from the congestion-occurring exchange to the terminal device using the congestion bit. It is configured to notify the occurrence of congestion.

[Industrial applications]

The present invention relates to an exchange and a congestion control method in a communication system using an asynchronous transfer mode.

The communication method using the asynchronous transfer mode incorporates the advantages of circuit switching and packet switching.
hronous Transfer Mode). In this method, a communication path is set at the time of call setting, and high-speed communication is possible because switching processing is not performed for each cell, and reception and reproduction quality can be obtained not only for data but also for a moving image signal and an audio signal. Can be multiplexed and transmitted without deteriorating.

In general, congestion in the ATM described above is classified into two types. One is call processor congestion and the other is ATM switch congestion. The congestion of the call processor is a phenomenon in which the call processor is overloaded as in a general telephone network, and the call cannot be processed smoothly.
The congestion of the ATM switch is a state in which when traffic is temporarily concentrated, a buffer in the ATM switch overflows and cells are discarded. Unless otherwise described below, congestion refers to congestion of the ATM switch. In order to minimize the deterioration of the channel quality due to the occurrence of congestion, it is necessary to notify the terminal device of the occurrence of congestion promptly, and a simple control method is demanded.

[Conventional technology]

FIG. 5 is an explanatory diagram of a conventional example, and shows terminal devices 31-1, 31-2.
Are connected via communication path switches 32-1 to 32-4 of each exchange and a communication line 34 between the exchanges, and a signal line is provided between central control units 33-1 to 33-4 of each exchange. The transmission information between the terminal devices 31-1 and 31-2 is transmitted as a fixed-length cell together with the transmission information between the other terminal devices and time-division multiplexed and transmitted to the communication line 34. . Various control signals between the exchanges are transmitted by a signal line 35 separated from the communication line 34 by a common channel signal system (CCITT standard No. 7CCS).

A cell in the asynchronous transfer mode includes, for example, as shown in FIG. 6, a header part H including a virtual call identifier VCI, a bearer service identifier BSI, a check bit CK, and an information part I. Is set to a fixed length that is an integral multiple of.

FIG. 7 shows the signal format of the significant signal unit in the common channel signal system (No. 7CCS). The flag F, the backward sequence number BSN, the backward display bit BIB, the forward sequence bit It comprises a number FSN, a forward indication bit FIB, a signal length indication LI, a priority indication PRI, a service indication SIO, signal information SIF, a check bit CK, and a flag F. Also, the signal information SIF is used as a status display, and the ring status signal unit or the signal information SIF and the service display S excluding the service display SIO and the priority display PRI are excluded.
A fill-in signal unit excluding IO and priority indication PRI is used.

In the common channel signal system, the signal unit is divided into four layers. The lowest level 1 is a physical level that matches transmission conditions such as a communication speed and a transmission code format, and the level 2 is a signal unit that is used for error checking and retransmission. Signal link level for error-free transfer, level 3 is a network level for analyzing outgoing routes, detour control, format confirmation, signal distribution to level 4, etc. Level 4 is signal editing, line number designation , Which is called a user unit for analyzing the receiving station.

The congestion is detected by monitoring the transmission queue corresponding to the outgoing route in the central control units 33-1 to 33-4 of each exchange. For example, when the central control device 33-3 identifies that the transmission queue length of the outgoing route to the exchange in which the terminal device 31-2 is accommodated is equal to or more than a predetermined value, the It is determined that the call is concentrated and congestion has occurred, and a congestion message is sent from the central control unit 33-3 via the signal line 35 to the originating station of the cell heading for the outgoing route using the significant signal unit.

Central control unit of the exchange that has received this congestion message
33-2 analyzes the contents at the level 4 described above and sends the congestion message via the signal line 35 to the central control unit 33-1 of the exchange in which the terminal device 31-1 is accommodated. Is sent by The central control device 33-1, which has received the congestion message, analyzes the content, notifies the terminal device 31-1 of the occurrence of congestion, reduces the amount of transmitted information, and prevents cell discard.

The congestion can be released by transmitting the message as a message from the central control unit 33-3 using a significant signal unit, or by automatically stopping the transmission from the occurrence of congestion to the congestion destination for a certain period of time and then automatically releasing the congestion.

[Problems to be solved by the invention]

As described above, even in the communication system using the asynchronous transfer mode, the congestion-occurring exchange transmits a congestion message via the signal line 35, and the relay exchange analyzes and transfers the congestion message. However, there has been a disadvantage that the time required from the occurrence of congestion to the notification to the terminal device becomes long.

An object of the present invention is to promptly notify a terminal device of the occurrence of network congestion.

[Means for solving the problem]

The switch of the present invention provides a virtual call identifier (VCI)
Using a fixed-length cell having a header portion (H) containing
The first device (terminal device 1-1) and the second device (terminal device 1-1-1)
2) The switch (switching station 2-1 to 2-n) that performs routing control of transmission information based on the virtual call identifier (VCI) in the header (H) detects the occurrence of congestion. And a notifying unit that detects congestion by the detecting unit and notifies the occurrence of congestion using the congestion bit (C) provided in the header (H). Or detecting means for detecting the release of congestion, and detecting the release of congestion by the detecting means and providing a congestion bit (C) provided in the header (H).
And notification means for notifying the congestion release by using.

Further, the congestion control method of the present invention uses a fixed-length cell having a header section (H) including a virtual call identifier (VCI) and a first device (terminal device 1-1) and a second device (terminal device). A step of detecting the occurrence of congestion in a communication system in an asynchronous transfer mode in which routing control of transmission information to and from the device 1-2) is performed based on the virtual call identifier (VCI) in the header (H). And the congestion bit (C) provided in the header portion (H) containing the virtual call identifier (VCI) of the cell, the device (terminal device 1-1, terminal device 1-1,
Notifying the occurrence of congestion to 1-2). Or detecting the release of congestion and using the congestion bit (C) provided in the header section (H) containing the virtual call identifier (VCI) of the cell (terminal device 1-
1, 1-2).

[Action]

A congestion bit (C) is provided in a header portion (H) of a cell comprising an information portion (I) and a header portion (H), and when the occurrence of congestion is detected by the detection portion, the congestion bit (C) is notified by the notification portion. For example, congestion occurrence notification is performed as "1", and when congestion release is detected, congestion release notification is performed with the congestion bit (C) set to "0". In this case, the exchange (transit exchange) on the relay route transfers the cell to the first and second devices (terminal devices 1-1 and 1-2) via the communication path. Therefore, the occurrence of congestion or the release of congestion can be notified to the first and second devices (terminal devices 1-1 and 1-2) without performing an analysis process or the like in the exchange (exchange center). That is, the occurrence of congestion can be promptly notified. Also, in this case, the occurrence of congestion or the release of congestion can be notified by the cell heading to the device on the transmission side (terminal device).

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is an explanatory diagram of a cell format according to an embodiment of the present invention. In the header portion H including a virtual call identifier VCI, a bearer service identifier BSI, and a check bit CK,
A congestion bit C is provided, and the information section I and the header section H constitute a fixed-length cell.

FIG. 3 is a block diagram of a main part of an exchange according to an embodiment of the present invention, wherein 11-1 to 11-n,..., 11-n1 to 11-nn are incoming lines, and 12-1 to 1-1.
2-n is a virtual call identifier converter (CNV), 13-1
13-n is a table (TB) having areas for outgoing virtual call identifiers, routing information and congestion indication for incoming lines,
14-1 to 14-n, 15-1 to 15-n, 16-1 to 16-n are self-routing channel units (SRMs) for setting a route based on routing information, 17-1 to 17-n, ... 17-n1 to 17-nn are outgoing lines,
18 is a bus, 19 is a congestion monitoring device, 20 is a call processing device, and 21 is a bus.

Tables 13-1 to 13-n in converters 12-1 to 12-n
For example, as shown in FIG. 4, for each of the n incoming call-corresponding (asynchronous transfer mode / channel-corresponding) virtual call identifiers IVCI (1) to IVCI (n), the outgoing virtual call identifier OVCI and the routing information A congestion display area is formed, and the outgoing virtual call identifier OVCI and the routing information are written from the call processing device 20 via the bus 21 at the time of call setting. Also, according to the congestion detection information from the congestion monitoring device 19, the call processing device 20 via the bus 21, the congestion occurrence outgoing virtual call identifier OVCI corresponding congestion display, for example,
Set to “1”, and set to “0” by releasing congestion.

For example, the virtual call identifier VCI of the cell from the terminal device A to the terminal device B corresponds to the incoming line 11-1, and is output by the outgoing virtual call identifier OVCI corresponding to the incoming line 11-1 in the table 13-1 of the converter 12-1. Line 17-nn is designated and the routing information is transmitted to the self-routing channel unit 14-1, 15-1,
16-n, and the virtual call identifier VCI of the cell from the terminal B to the terminal A corresponds to the incoming line 11-nn, and the outgoing virtual corresponding to the incoming line 11-nn in the table 13-n of the converter 12-n. The outgoing line 17-1 is specified by the call identifier OVCI, and the routing information is stored in the self-routing channel unit 14-n, 1.
When 5-n, 16-1 is indicated, the cell from the terminal device A is
The conversion of the virtual call identifier VCI of the cell is performed by referring to the table 13-1 in the converter 12-1, and the routing information is added.

That is, the outgoing virtual call identifier OVCI is read from the table 13-1 using the cell's virtual call identifier VCI as the incoming bar channel call identifier IVCI (1), and is used as the cell's virtual call identifier VCI. Each self-routing channel unit sets a transfer route of a cell in accordance with the added routing information. The cell from the terminal device A receives the self-routing channel in accordance with the routing information added in the converter 12-1. It is transmitted by the route of the units 14-1, 15-1, 16-n, and outgoing line 17-nn.

Similarly, the cell from the terminal device B is stored in the converter 12
-n → Self-routing channel unit 14-n → 15-n → 16-1
→ Sent out along the route of outgoing line 17-1.

As described above, the congestion monitoring device 19 monitors the transmission queue in each of the self-routing communication path units 14-1 to 16-nn via the bus 18, and when the length of the transmission queue becomes equal to or more than a predetermined value, congestion occurs. By making a judgment, the congestion occurrence self-routing communication path unit and the information on the exit side are notified to the call processing device 20.
For example, if congestion occurs on the exit side to the self-routing communication path unit 15-1 in the self-routing communication path unit 14-1 that processes cells of the terminal apparatus A from the terminal apparatus B, the information is subjected to call processing. The device 20 is notified. The call processing device 20 sets a channel from the self-routing channel unit 14-1 to the self-routing channel unit 15-1.
With reference to Table 13-1, the index is determined, and the channel corresponding thereto is determined. In this case, from the terminal device B to the terminal device A
When the call processing device 20 determines this channel, the congestion corresponding to the incoming virtual call identifier IVCI (n) in the table 13-n of the converter 12-n is performed via the bus 21. The display area is set to “1”.

When a cell from the terminal device B to the terminal device A passes, the converter 12-n converts the virtual call identifier VCI with reference to the table 13-n and adds routing information as described above. Since the congestion indicator corresponding to the incoming virtual call identifier IVCI (n) is "1", the congestion bit C is converted from "0" to "1". This cell is outgoing
Since the packet is transmitted from the terminal 17-1 and transferred to the terminal device A via another exchange or directly to the terminal device A, the terminal device A is congested in the route to the terminal device B by the congestion bit C of "1". Can be identified. Therefore, the amount of information transmitted to the terminal device B is reduced.

Also, when the congestion monitoring device 19 identifies that the length of the transmission queue in the self-routing communication channel unit 14-1 has become shorter than a predetermined value, the congestion is released and the call processing device 20 is notified. . The call processing device 20 changes the congestion indication corresponding to the incoming virtual call identifier IVCI (n) in the table 13-n from “1” to “0” via the bus 21. As a result, the congestion bit C of the next cell from the terminal device B to the terminal device A is transmitted as "0", and the terminal device A identifies the release of congestion and uses the original transmission information amount.

Also, as shown in FIG. 1, when the terminal devices are connected through a plurality of exchanges and congestion occurs in the plurality of exchanges,
The processing of the congestion bit C is performed by the logical sum of the contents of the congestion display in the table of each exchange. Therefore, when congestion occurs in a plurality of exchanges and the congestion bit C of the cell is set to "1", if all congestion is not released, the congestion bit C becomes "1" and the terminal device continues to be congested. Can be notified.

Although the embodiment shown in FIG. 3 described above shows a case of a three-stage configuration of the self-routing communication channel unit, the present invention is not limited to only such an exchange.
The present invention can be applied to an asynchronous transfer mode switching network having switching stations of other configurations.

〔The invention's effect〕

As described above, according to the present invention, the congestion bit C is provided in the cell in the asynchronous transfer mode, the occurrence of congestion or the release of congestion is detected by the detecting means such as the congestion monitoring device 19, and the call processing device 20 and the converter 12- By notification means including 1-12-n etc.
An exchange that sends a congestion occurrence notification or a congestion release notification using the congestion bit C to the first and second devices such as the terminal devices 1-1 and 1-2, and a congestion occurrence or a congestion release due to a transmission queue length or the like. And a step of performing a congestion occurrence notification or a congestion release notification using the congestion bit C based on the detection. In this case, the header H The congestion occurrence notification or the congestion release notification can also be performed using the congestion bit C of the above, without performing the analysis processing in the relay exchange, etc.
There is an advantage that congestion occurrence notification can be quickly performed to prevent the spread of congestion in the switching network.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention, FIG. 2 is a diagram illustrating a cell format according to an embodiment of the present invention, FIG. 3 is a block diagram of a main part of an exchange according to an embodiment of the present invention, and FIG. FIG. 5 is an explanatory diagram of a conventional example, FIG. 6 is an explanatory diagram of a cell format of a conventional example, and FIG. 7 is an explanatory diagram of a signal format of No. 7 CCS. 1-1 and 1-2 are terminal devices, 2-1 to 2-n are exchanges, H is a header part, I is an information part, VCI is a virtual call identifier, C is a congestion bit, BSI is a bearer service identifier, CK Is a check bit.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Eisuke Iwabuchi 1015 Uedanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Co., Ltd. 56) References JP-A-63-24742 (JP, A) JP-A-62-85532 (JP, A) JP-A-63-176045 (JP, A) JP-B-58-46899 (JP, B1)

Claims (10)

(57) [Claims] 1. A method for controlling routing of transmission information between a first device and a second device by using a fixed-length cell having a header portion including a virtual call identifier, comprising the steps of: In an exchange performed based on, a detecting means for detecting the occurrence of congestion, and a notifying means for detecting congestion by the detecting means and notifying the device of the occurrence of congestion using a congestion bit provided in the header section An exchange characterized by comprising: 2. The apparatus according to claim 1, wherein said notifying means notifies the occurrence of congestion detected by said detecting means by using a cell directed from the receiving apparatus to the transmitting apparatus. Exchange. 3. A method for controlling routing of transmission information between a first device and a second device by using a fixed-length cell having a header portion including a virtual call identifier. A switch for detecting the release of congestion, a notification for detecting the release of congestion by the detector and notifying the device of the release of congestion using a congestion bit provided in the header section. An exchange comprising: 4. The system according to claim 3, wherein said notifying means notifies the user of the release of the congestion detected by said detecting means by using a cell directed from the receiving apparatus to the transmitting apparatus. The exchange described. 5. A method for controlling routing of transmission information between a first device and a second device by using a fixed-length cell having a header portion including a virtual call identifier. In the exchange performed based on the following, detecting means for detecting the occurrence of congestion, detecting the congestion by the detecting means, using the congestion bit provided in the header portion, from the receiving-side device to the transmitting-side device An exchange comprising: a notification unit for notifying. 6. A method for controlling routing of transmission information between a first device and a second device by using a fixed-length cell having a header portion including a virtual call identifier. In the exchange performed on the basis of, the detecting means for detecting the release of congestion, detecting the release of congestion by the detection means, using the congestion bit provided in the header portion, from the receiving side device to the transmitting side An exchange comprising: a notification unit that notifies a device. 7. A method for controlling routing of transmission information between a first device and a second device by using a fixed-length cell having a header portion including a virtual call identifier, comprising the steps of: Detecting the occurrence of congestion in a communication system using an asynchronous transfer mode based on the following: and notifying the device of the occurrence of congestion using a congestion bit provided in a header portion including a virtual call identifier of the cell. A congestion control method, comprising: 8. The method according to claim 7, wherein the step of notifying the occurrence of congestion includes a step of notifying the source device using a cell from the destination device to the source device. Congestion control method. 9. A method for controlling routing of transmission information between a first device and a second device by using a fixed-length cell having a header portion including a virtual call identifier, wherein the virtual call identifier in the header portion is controlled. Detecting a release of congestion in a communication system using an asynchronous transfer mode based on the following: and notifying the device of the release of congestion using a congestion bit provided in a header portion including a virtual call identifier of the cell. A congestion control method, comprising: 10. The step of notifying the release of the congestion,
Using a cell from the called device to the calling device,
10. The congestion control method according to claim 9, further comprising the step of notifying the transmitting side device.