JP3704953B2 - Distributed switching system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a distributed switching system in which a plurality of switching devices that can operate independently are connected.
[0002]
[Prior art]
A conventional example in which a small-sized exchange device is connected to construct a large capacity exchange system will be described with reference to FIGS. FIG. 2 and FIG. 3 are both an exchange system constituted by a plurality of exchange apparatuses and a coupling mechanism for connecting these exchange apparatuses.
[0003]
FIG. 2 shows a small switching device (20a, 20b, 20c) provided as a coupling mechanism for coupling a plurality of switching devices (10a, 10b, 10c) that accommodate subscriber lines, trunk lines, and the like. Lines are connected so that a route can be secured from each small switching device (20a, 20b, 20c) constituting the coupling mechanism to all the switching devices (10a, 10b, 10c). The small switching device is composed of a speech path switch 21a and a processing processor 22a. As such a system, there is a disclosure in “Configuration of software for large-scale time-division switching system” SE83-18, IEICE / Exchange Research Group SE83-18. In this system, in order to reduce a call loss that is blocked internally and cannot be set up even though the input / output line 13 is free, every time there is a call request, the outgoing link (coupled with the outgoing switching equipment) is reduced. A free channel is selected between the free channel of the link between the mechanisms and the incoming link (link between the terminating switching apparatus and the coupling mechanism).
[0004]
FIG. 3 shows a case where a large single-stage switch 25 controlled by the processing processor 26 is used as a coupling mechanism for coupling a plurality of switching devices (10a, 10b, 10c). This is disclosed in ISS92 [International Switching Symposium], A3.2 An ATM Switching System Architecture for First Generation of Broadband Services. In this configuration, if the input / output line 13 has a free space, an internal link can be selected without fail, so that a non-blocking system that does not cause a call loss when a channel is selected by a coupling mechanism is achieved.
[0005]
[Problems to be solved by the invention]
In the conventional method using the above coupling mechanism, in FIG. 2, a process for managing free block information on all links from the originating switching device (originating switching device) to the terminating switching device (incoming switching device) and finding a free channel on the incoming / outgoing link. Must be performed for each call. In FIG. 3, such complicated processing for each call is unnecessary, but it is the same in that it is necessary to terminate the control information for controlling the link and perform channel assignment processing for each call. Therefore, in the prior art, the coupling mechanism, which is a common part of the system, has intelligence, and there is a problem in terms of reliability. Further, in FIG. 2 and FIG. 3, an increase in cost is caused by incorporating the coupling mechanism.
[0006]
An object of the present invention is to provide a distributed switching system without using a coupling mechanism.
[0007]
[Means for Solving the Problems]
Each of a plurality of line interfaces connected to a subscriber line, a plurality of line interfaces connected to an extension link, a speech path switch connected to the plurality of line interfaces, and a control terminated at the line interface A plurality of switching devices having a switching processor for controlling the speech path switch in response to a signal, wherein the plurality of switching devices are directly connected to any two switching devices by the extension link; A distributed exchange system is provided.
[0008]
In a distributed switching system comprising a plurality of switching devices, (1) the originating switching device checks the status of the line connected to the called switching device, and if there is an empty channel, selects that channel; If all the lines to the switching device are in use, the state of the line connected to the other switching device is checked, and if there is an empty channel, the channel is selected. The channel between this switching device and the destination switching device is supplemented, and the other switching device controls the communication path switch to connect the calling switching device and the destination switching device, and between the calling switching device and the other switching device. A return path that connects the internal link channel between the other switching device and the internal switching channel and simultaneously activates the called switching device, and (4) between the relay switching device and the terminating switching device. All lines For blocked, via a plurality of switching devices, as well as incoming and outgoing exchange device to connect.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0010]
(1) Configuration of switching system FIG. 1 shows a configuration of a distributed switching system according to the present invention. In the present invention, a plurality of switching devices (10a, 10b, ---, 10n) are used to operate as one switching system. This exchange system operates as one exchange node (switch office). Each switching apparatus 10 is connected by an internal link (inter-switching apparatus line) 14 which is a line between the switching apparatuses. The connection method is a mesh type in which any two switching devices 10 (10a, 10b,..., 10n) are directly connected to each other via a line. Therefore, the internal link is configured to form a mesh network. Each switching device 10 is connected to a communication path switch 11, an input / output line 13 that is a relay line to a subscriber line or another exchange, or an internal link 14, and terminates control information such as a call, response, and disconnection request. The line interface 15 performs signal processing, and the switching processor 12 performs processing control according to control information terminated at the line interface. It should be noted that the function for terminating control information such as a call, response, and disconnection request does not necessarily have to be realized by the line interface unit. What is the means for obtaining such control information if it can be obtained via the line interface unit? Also good. For example, it may be a signal device that terminates a control signal in the line interface unit, or a signal device that is connected to the line interface unit, receives a control signal from the line interface unit, and terminates the received control signal. Good. The switching processor 12 controls the communication path switch 11 in accordance with the control signal, and connects the input / output line interfaces, the extension link line interfaces, or the input / output line interface and the extension link line interfaces. The exchange processor 12 includes a memory, a processing device, an I / O device that sets and reads various data with an external device (not shown), and the like. Each of the plurality of switching devices of this switching system has a subscriber line and a trunk line to another switching system, which is different from the small switching devices and switches used in the conventional coupling mechanism.
[0011]
The thick line portion in FIG. 1 shows a configuration diagram in which the originating switching apparatus 10a and the terminating switching apparatus 10n are connected via one relay switching apparatus 10b. Here, the communication path switch of the exchange device 10b connects the extension link line interfaces.
[0012]
(2) Exchange processing operation The exchange processing operation will be described with reference to FIGS. 4, 5, and 6. FIG. Here, the operation to be described can be realized, for example, by being stored in a memory in the exchange processor 12 in the form of a program and executed by a processing device in the exchange processor.
[0013]
First, the calling process will be described with reference to FIG.
[0014]
FIG. 4 shows the operation of the outgoing call processing in the outgoing exchange device (outgoing exchange device). Here, the call switching apparatus receives the call setting signal including the incoming number for identifying the call / communication partner (destination) from the input / output line 13 (any information that can identify the other party) is received by the line interface 15. It is an exchange device. The originating switching apparatus determines the terminating switching apparatus number by the “incoming number-incoming switching apparatus number conversion table” of FIG. 11 based on the incoming call number indicating the communication destination in the received call setting signal (step 101). The incoming call number-reception switching apparatus number conversion table of FIG. 11 is a table showing the correspondence between the incoming call number and the incoming call exchange apparatus number of the exchange apparatus in which the line interface related to the incoming call number is accommodated in the exchange system. Yes, the switching device having the incoming call switching device number is connected to the receiving line interface having the incoming call number or the line interface to the trunk line to another switching node. This table is stored in the memory of the exchange processor 12. The incoming switching apparatus number is a number used in the switching system (in the switching node), and is used to identify the switching apparatus in the switching system. Note that the information need not be a number as long as the information can identify the exchange device.
[0015]
Next, the originating switching device checks whether or not the own switching device is the terminating switching device, based on the called switching device number, that is, determines whether or not the call is a failure of the own switching device (step 112). In this check, each switching device stores its own switching device number in advance in the memory of the switching processor, and compares this with the previously obtained incoming switching device number. This can be determined by using an exchange device. If the local exchange apparatus is an incoming call exchange apparatus, it activates the incoming subscriber from the incoming call number (step 113). If the local switching device is not a terminating switching device, a line (internal link 14) connected to the terminating switching device is selected, and multiplexed channels (time-division time slots or packet multiplexing) on the internal link are selected. The free blockage of the logical channel being checked is checked in a free block table managed separately (step 102). The empty block table can be managed, for example, by setting that the used channel is used every time the channel is used and resetting the used state every time the use is completed.
[0016]
As a result of the check (step 103), if the channel to the incoming call switching apparatus is free, the channel is captured (step 104). For example, the inter-station signal No. of ITU-T shown in FIG. 7 is transmitted as an activation signal from the originating exchange to the terminating exchange via the line interface 15 on the internal link side (step 105). This IAM message includes a message type indicating that the message is an IAM message, and an incoming number indicating the destination.
[0017]
Further, there are a method for setting the incoming call exchange number output using FIG. 11 in the IAM message in the area of the destination station code of the IAM message and a method for not setting it. When setting the incoming switching apparatus number, the switching apparatus that has received this message can use the incoming switching apparatus number to determine whether or not its own switching apparatus is the incoming switching apparatus. If not set, the incoming call number in the message will be used. When the switching device number is put on the IAM message that is the activation signal, the activation switching device needs time to carry it, but the switching device that receives the IAM message can use the switching device number as it is, and the incoming call number There is an advantage that the number conversion in the incoming call switching apparatus is not required compared to the case where only the message is transmitted. In particular, when the number of switching devices constituting the switching system increases, it is expected that the number of relay switching devices will increase. In this case, the fact that number conversion at the called switching device is not required has a great merit. This incoming call exchange number is a number used in the exchange system.
[0018]
On the other hand, if all the channels directly connected from the originating switching apparatus to the terminating switching apparatus are in use, the channel for connecting to another switching apparatus is checked for blockages (step 106). If there is an empty channel (step 107), the channel to the relay switching apparatus is captured (step 108), and an activation signal is transmitted to the relay switching apparatus (step 109). If there is no vacancy (step 107), it goes to search for vacancy in another channel (step 110). With the above operation, even when there is no channel directly connected from the originating switching device to the terminating switching device, it becomes possible to request relay connection to another switching device, and the call loss rate can be lowered. If all the channels are blocked, block processing, that is, information indicating that connection cannot be established is transmitted to the originating exchange or subscriber without connection (step 111).
[0019]
With the operation of FIG. 5, when there are two or more lines from the originating switching device to the terminating switching device, the route directly connected from the originating switching device to the terminating switching device is preferentially selected as the first candidate route. , Efficient connection becomes possible.
[0020]
Next, incoming call processing will be described.
[0021]
FIG. 5 shows the incoming call process 1. A switching device that receives an activation signal from an internal link (channel) uses an activation signal (input signal) to identify whether the received call is for its own switching device or another switching device. The incoming call exchange number or the incoming call number of the destination station code area of an IAM message is extracted (step 121).
[0022]
When extracting the incoming call number from the IAM message, the incoming call exchange apparatus number is obtained from the incoming call number-incoming exchange apparatus number conversion table shown in FIG. 11, and it is checked whether or not the own exchange apparatus has been dropped (step 122). This check is performed by comparing with the exchange device number held by the own exchange device. If the result of the comparison is that the own switching device has failed, the called subscriber is activated from the called number (step 128). When the switching device number is extracted from the signal station code area of the IAM message, the switching device number is used as it is to check whether or not the own switching device has been dropped (step 122). The subsequent operation is the same as when the incoming call number is extracted.
[0023]
If the local switching device is not down, the line connected to the incoming switching device (incoming switching device) indicated by the incoming call number is checked for blockage (step 123). If there is a free channel, the channel is captured (step 125). The activation signal is transmitted to the new incoming call exchange device (step 126). As described above, the switching apparatus that executes the incoming call processing determines that the call received by the IAM message is a call to be relayed to the called switching apparatus when the incoming switching apparatus number does not match the own switching apparatus number. Can be processed. When a channel to the switching device is found, the switching device connects a channel from the originating switching device to the switching device, and a channel from the local switching device found this time to the terminating switching device using a speech path switch. On the other hand, if all the channels are in use, block processing is performed (step 127).
[0024]
FIG. 6 shows an incoming call process 2 which is another incoming call process.
[0025]
Upon receiving the activation signal from the internal link (channel), the switching apparatus extracts the called switching apparatus number or the called number in the receiving station code area in the activation signal (input signal) (step 141). When extracting the incoming call number, the incoming call exchange apparatus number is obtained from the incoming call number-incoming exchange apparatus number conversion table shown in FIG. Thereafter, the switching device compares the incoming switching device number with the number of the own switching device stored in advance, and checks whether the call received from the internal link is dropped or not (step 142). If there is a failure in the own switching device, activation is performed on the called subscriber from the called number (step 153).
[0026]
On the other hand, if there is no failure in the local switching device, it checks whether the line connected to the called switching device indicated by the called number is closed (step 143), and if there is a free channel to the called switching device, the channel is captured (step). 145), an activation signal is transmitted to the incoming call exchange device (step 146). If all channels to the terminating switching device are in use, the channel to another switching device is selected. In selecting another switching device, a switching device that has never passed is selected from the number of the passing switching device included in the activation signal. As a result, it is possible to prevent ping-pong transfer of calls between the two switching devices. Specifically, for example, this can be realized by inserting the own switching device number into the activation signal, and using this as the passing exchange device number. In addition, an exchange system having two or more middle cost routes can be configured. It checks whether the channel of the line connected to the selected switching device is full (steps 147 and 148). If there is a vacancy, the channel is acquired (step 149), and an activation signal is transmitted to the relay switching apparatus (step 150). If there is no vacancy, go to search for vacancy in another line (step 151). If all lines are blocked, block processing is performed (step 152).
[0027]
As described above, this switching device has a function of finding a line to the target switching device via another switching device when the direct line (channel) to the target switching device is blocked. Therefore, the call loss rate is smaller than when the direct line is blocked and the block is used.
[0028]
(3) Connection of speech paths FIGS. 7 to 9 show an exchange system composed of four switching devices, and the connections in this figure show the connection status of the speech paths between the incoming and outgoing switching devices. For simplification of the figure, individual internal links that connect the exchanges are not shown. Here, it is assumed that the switching device 201 is a calling switching device that accepts a call from a calling subscriber or another switching system. Further, the switching device 204 is a terminating subscriber that receives the call or a terminating switching device having a trunk line to another switching system. FIG. 7 shows a case where an internal link is directly connected from the originating switching device to the terminating switching device. FIG. 8 shows one relay switching device (202), and FIG. 9 shows two relay switching devices (202, 203). This shows a case where the call path is connected via Here, in FIG. 9, for example, the function of the incoming call processing 2 (particularly to the switching device that has been passed so far using the passing switching device number is used so that the relay switching device 203 does not send an activation signal to the originating switching device. It is necessary to stop issuing the activation signal again). In the case of FIGS. 7 and 8, a call can be set to the incoming call exchange apparatus using the incoming call processing 1, but a call path can be set even if the incoming call processing 2 is installed. However, the state of the channel between switching devices is constantly changing, that is, the connection from the calling switching device to the called switching device cannot always be connected by a direct link or a single relay. It is desirable to have it.
[0029]
【The invention's effect】
In the configuration of the present embodiment, since a mesh connection in which two switching apparatuses are directly connected by a line is used, a conventionally used coupling mechanism becomes unnecessary. Therefore, the overall cost is reduced by the cost of the coupling mechanism.
[0030]
Next, the cost is compared with this system and the conventional switching system (FIGS. 2 and 3). In comparison, a system capacity of 64 k lines, a capacity of 16 k lines of one switching device, a switch in the coupling mechanism shown in FIG. 2 is the same as the switching device (16 k lines), and the cost is proportional to the number of lines. The number proportional part is assumed to be 70% of the entire switching system (30% is a common part).
[0031]
Based on the above assumptions and evaluation, the results are as follows.
[0032]
・ Application method: 16k line (switching device) x 4
-Figure 2 method: 16k line (switching device) x 4 + 16k line (coupling device) x 2
-Figure 3 method: 16k line (switching device) x 4 + 64k line (coupling device) x 1
From the above, regarding the line proportional portion, if this method is 1, the cost is 1.5 at the rate of 1.5 in FIG. 2 and 2 at the rate of FIG. Therefore, in consideration of the common part, this method can reduce the cost by 26% compared with the method of FIG. 2 and 41% compared with the method of FIG.
[0033]
Therefore, when constructing a large-capacity exchange system by connecting a small exchange (in this embodiment, an exchange device is supported), it is more effective at a lower cost than a configuration using a coupling mechanism that cannot accommodate a subscriber line. realizable.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an exchange system to which the present invention is applied.
FIG. 2 is a configuration diagram of an exchange system using a small-capacity switch as a coupling device.
FIG. 3 is a configuration diagram of an exchange system using a large-capacity single-stage switch as a coupling device.
FIG. 4 is a flowchart showing call processing in the call exchange device.
FIG. 5 is a flowchart showing incoming call processing 1 in the relay exchange apparatus or the incoming call exchange apparatus.
FIG. 6 is a flowchart showing an incoming call process 2 in the relay exchange apparatus or the incoming call exchange apparatus.
FIG. 7 is a diagram showing a case where the arrival / departure switching apparatus is directly connected.
FIG. 8 is a diagram showing a case where the arrival / departure switching apparatus is connected via one relay switching apparatus.
FIG. 9 is a diagram showing a case where the arrival / departure switching apparatus is connected via two relay switching apparatuses.
FIG. 10: ITU-T No. The figure which shows the IAM message of 7 signal systems.
FIG. 11 is a diagram showing an incoming number-incoming exchange number conversion table;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Switching apparatus, 11 ... Switch, 12 ... Processor, 13 ... Input line, 14 ... Inter-switching apparatus line, 15 ... Line interface, 20, 25 ... Coupler, 21 ... Switch, 22, 26 ... Processor, 101-111 ... Call processing, 121-128 ... Call processing 1, 141-153 ... Call processing 2, 201-204 ... Switching device, 205, 215, 216, 225, 226, 227 ... Call path.

Claims (9)

Each is obtained via a plurality of line interfaces connected to subscriber lines, a plurality of line interfaces connected to extension links, a speech path switch connected to the plurality of line interfaces, and the line interfaces. A plurality of switching devices having a switching processor for controlling the speech path switch in response to the control signal;
Here, the plurality of switching devices are a distributed switching system characterized in that any two of the switching devices are directly connected by the extension link,
A first means for connecting the call using the extension link that directly connects the originating switching device that accepts the call and the terminating switching device that receives the call;
Using the originating switching device, the terminating switching device, and another switching device, the extension link between the originating switching device and the other switching device, and between the other switching device and the terminating switching device the distributed switching system that having a second means for connecting the call using the extension link. A distributed switching system of claim 1 wherein using said first means in preference to the second means. Each of the plurality of switching devices stores identification information for identifying the switching device,
The distributed switching system according to claim 1, wherein an incoming switching apparatus that receives the call is specified by using the identification information in an activation signal of an extension link between the switching apparatuses. A plurality of switching devices having a call path switch, a line interface, a call processing processor for performing call processing control, and a mesh network in which any two switching devices are directly connected;
Here, when there is no vacancy in the line directly connecting the originating switching apparatus and the destination switching apparatus, the originating switching apparatus selects the first vacant line connected to the relay switching apparatus, and then A distributed switching system in which the relay switching device selects a second line connected to the destination switching device and connects the first line and the second line at a switch in the relay switching apparatus. A plurality of switching devices having a call path switch, a line interface, a call processing processor for performing call processing control, and a mesh network in which any two switching devices are directly connected;
Here, when there is no vacancy in the line directly connecting the originating switching apparatus and the destination switching apparatus, the originating switching apparatus selects the first vacant line connected to any first switching apparatus. Then, when the first relay exchange device selects a line to be connected to the destination exchange device, if it detects that all of the lines are blocked, a free space connected to the second relay exchange device A distributed switching system that selects a second line and connects the first line and the second line at the switch of the first relay switching apparatus. The selected relay switching apparatus selected if there is a space in the line connected to the destination switching device, according to claim 4, wherein selecting a line connected to the relay switching apparatus free is not over even once unless Distributed switching system. A plurality of switching devices having a call path switch, a line interface, a call processing processor for performing call processing control, and a mesh network in which any two switching devices are directly connected;
Here, when there is no vacancy in the line directly connecting the originating switching apparatus and the destination switching apparatus, the originating switching apparatus selects the first vacant line connected to the relay switching apparatus, and then A distributed switching system in which a call loss occurs when all of the second lines connected to the relay switching apparatus are in use. A plurality of switching devices having a call path switch, a line interface, and a call processor for performing call processing control;
A mesh network in which any two switching devices are directly connected;
Means for converting an incoming call number information into an incoming exchange number when receiving an activation signal from a line interface connecting a subscriber or a trunk, and transmitting an activation signal including the incoming exchange number to another exchange; and
A distributed switching system having means for performing an incoming call processing by using the incoming call exchange device number when an activation signal is received from another exchange device. A plurality of switching devices having a call path switch, a line interface, and a call processor for performing call processing control;
A mesh network in which any two switching devices are directly connected;
Means for transmitting an activation signal including the called number to another switching device when the activation signal is received from a line interface connecting a subscriber or a trunk; and
A distributed switching system having means for performing an incoming call processing by an incoming call number in an activation signal when an activation signal is received from another switching apparatus.

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