JPH11331250A - Line switching network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relay a packet having a transmission control protocol-Internet protocol(TCP-IP) address via a synchronous transfer mode(STM) network. SOLUTION: Any of local switches LS-1, LS-2 that contains a destination terminal based on a TCP-IP address in a TCP-IP packet is identified, time slot switch information that is route information in an STM network up to the local switch is generated and a packet is transferred in the STM network according to the time slot switch information. In this case, when no idle time slot is in existence, the packet is temporarily stored till an idle slot is available.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an STM (Synchronous
Transfer Mode) Used for communication networks. The present invention relates to TCP-
IP (Transmission Control Protocol-Internet Protocol)
ol) A technology for transferring data having an address via an STM connection.

[0002]

2. Description of the Related Art The operation and problems of a conventional circuit switching network based on STM will be described with reference to FIGS. FIG.
FIG. 1 is a diagram showing a main part configuration of a conventional circuit switching network based on STM. FIG. 9 is a diagram showing a main part configuration of a conventional subscriber exchange. In the STM communication network, since signals on physical channels are multiplexed into time slots and circuit-switched, the delay time during communication is extremely short, and an ATM (Asynchronous Transfer Mode) header using virtual paths and cells is used. There is no overhead. Also, no cell loss or the like occurs during communication.

For example, if the voice of a telephone has a delay of 20 to 30 ms or more, there is a problem in quality, and an echo canceller is required. In general, not only telephone calls but also two-way video conferences should have a small delay. From the above points, STM is a transfer mode suitable for the digital telephone network.

As shown in FIG. 8, in a conventional circuit switching network based on STM, a user inputs a telephone number of a destination to a CCITT.
No. defined in the Recommendation The transmission in the STM mode by transmitting to the exchange through the common line signaling network allows the physical transmission to be independent of the E.7. 164 addresses (ITU
-T is mapped to an ISDN address standardized by -T for communication. That is, ST in the STM network
The MTM connection is established, and the user data is transferred to the E.M. 164 addresses and transferred to the destination exchange.

In such a conventional circuit switching network based on STM, switching is performed by exchanging time slots of information multiplexed by 8 bytes on a frame. This operation is realized by, for example, sequential write random read as shown in FIG. That is, the sequential counter CT
R writes data to the data buffer memory DBM at sequential addresses with a sequential address, and the address control memory ACM changes the reading order to perform time slot conversion.

[0006]

SUMMARY OF THE INVENTION Such a conventional ST
As described above, the circuit switching network based on M has the advantages that the delay time is extremely short and that there is no overhead as compared with the ATM network or the like. However, in such a conventional circuit switching network using STM, it is necessary to set up an STM connection in advance from a terminal of a calling user to a terminal of a called user, and transfer data via the STM connection. It is.

FIG. 10 shows an image of a dedicated STM connection. Therefore, as shown in FIG. 10, there is a problem that the application is used only as a data dedicated line between large-scale offices.

On the other hand, regarding data communication performed by the TCP-IP architecture, a TCP-IP address, which is an identification number of a terminal, is written in a header of a packet and sent to a communication network such as the Internet that supports the TCP-IP. Each router such as an exchange searches for the existence of the address and transfers the datagram without having to set up a connection between two terminals with which communication is desired.
Thus, a dedicated connection is not required, and data can be transferred by a very simple procedure.
However, in this case, the delay time is longer than that of the circuit switching network based on STM, and overhead is required.

The inventors have considered constructing a new circuit switching network having both the advantages of the circuit switching network using the STM and the advantages of data communication using the TCP-IP address.

The present invention has been made in such a background, and can be provided only as a mere dedicated line by providing a relay network by STM based on a TCP-IP address used for data communication. Missing S
An object of the present invention is to provide a circuit switching network capable of dynamically providing a TM circuit. SUMMARY OF THE INVENTION It is an object of the present invention to provide a circuit switching network having a small delay time and a small overhead. SUMMARY OF THE INVENTION It is an object of the present invention to provide a circuit switching network that can reduce the number of packets discarded due to congestion of an output line.

[0011]

According to the present invention, TCP-I
Further, a route to a subscriber exchange accommodating a terminal serving as a destination indicated by the TCP-IP address is set in advance in the originating exchange to add a header to the packet having the header in which the P address is written. As a result, the packet is transferred to a desired destination terminal via the STM network. At this time, the transit exchange exchanges the packet in the time slot based on the time slot information described in the header of the arriving packet, thereby setting the exchange receiving the packet without setting up a dedicated connection in the STM network in advance. By connecting the time slot for carrying the packet at that time each time, it is as simple as data communication performed by the TCP-IP architecture as described above, as if the entire network is a huge router, High-speed data transfer can be performed.

At this time, if there is no vacancy in the desired time slot for loading the packet, it is necessary to temporarily store the packet and wait for the vacancy of the desired time slot. The present invention is characterized in that the vacancy of a desired time slot is monitored at predetermined time intervals, and when a vacancy is made in a desired time slot, a packet is placed in that time slot with priority according to reservation. . Further, a means for storing packets is provided for each input line.

That is, the present invention relates to a circuit switching network,
A plurality of subscriber exchanges accommodating one or more terminals, and a transit exchange for connecting the subscriber exchanges to each other, wherein the subscriber exchange and the transit exchange are connected via an STM network; The exchange includes means for receiving a packet having a header in which a TCP-IP address coming from the terminal is written, a table in which route information in the STM network corresponding to the TCP-IP address is recorded, This TCP- obtained by referring to the table
Means for adding a header in which the route information corresponding to the IP address is written to the header, and means for referring to the added header and transferring the packet in a time slot corresponding to the route information, The transit exchange includes means for referring to a header in which the route information of the packet written in the time slot is written, and a route in which the packet is newly written in the header according to a reference result of the referencing means. Means for transferring the packet to a time slot corresponding to the information, and when the time slot does not have a vacancy, a means for temporarily storing the packet until a vacancy occurs in the time slot. is there.

Here, a feature of the present invention is that the means for temporarily storing includes means for searching for the presence or absence of the time slot at predetermined time intervals.

Alternatively, the means for temporarily storing is:
When there is no free space in the time slot, there is provided a means for making a reservation for placing the packet preferentially in the time slot when a free space occurs in the time slot.

[0016] This makes it possible to prevent packets from being discarded even when there is no empty time slot.

Further, the means for temporarily storing may be provided for each input line.

This makes it possible to avoid a situation in which there is no available line for transferring packets from the input line to the means for temporarily storing packets. further,
Unbalanced packet transfer traffic from one input line to the temporary storage means does not prevent packet transfer from another input line to the temporary storage means.

Preferably, the route information is time slot exchange information.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a configuration of a circuit switching network according to an embodiment of the present invention. FIG. 2 is a block diagram showing a main part block configuration of the local exchange according to the embodiment of the present invention. FIG. 3 is a diagram showing a block configuration of a main part of the transit exchange according to the embodiment of the present invention. FIG. 4 is a diagram showing a block configuration of a main part of the transit exchange according to the first embodiment of the present invention. FIG. 5 is a diagram showing a time slot management table of the control circuit according to the first embodiment of the present invention. FIG. 6 is a diagram showing a time slot management table of the control circuit according to the second embodiment of the present invention. FIG. 7 is a diagram showing a main part block configuration of a transit exchange according to a third embodiment of the present invention.

The present invention relates to a circuit switching network, as shown in FIG. 1, which includes local exchanges LS-1 and LS-2 accommodating terminals TE-1 and TE-2, and the local exchanges L and L2.
Transit exchange TS for connecting between S-1 and LS-2
-1 and TS-2, and the local exchanges LS-1 and LS-2 and the transit exchanges TS-1 and TS-2.
Are connected via the STM network 1, and as shown in FIG.
The local exchanges LS-1 and LS-2 are connected to the terminal TE-1.
And a receiving unit 2 for receiving a packet having a header in which a TCP-IP address coming from TEP-2 and TE-2 is written, and an ST corresponding to the TCP-IP address.
And a table 3 in which route information in the M network 1 is recorded. The receiving unit 2 stores a header in which the route information corresponding to the TCP-IP address obtained by referring to the table 3 is written. A transmission unit 4 which is a means for transferring the packet in a time slot corresponding to the route information by referring to the added header in addition to the header, and as shown in FIG. 3, FIG. 4, FIG. The exchanges TS-1 and TS-2 provide a header reference unit 5 as a means for referring to a header in which the route information of the packet written in the time slot is written, and a reference result of the header reference unit 5. A relay unit 6 for reloading the packet to a time slot corresponding to the route information written in the header again, and when there is no free space in the time slot, The serial packet circuit switched network having a time slot management table T1 of the burst buffer 7 and the control circuit 9 is a means for temporarily storing until empty occurs in the time slot.

Here, the feature of the present invention is that, in the first embodiment of the present invention, as shown in FIG. 4, the burst buffer 7 stores the data in the time slot management table T1 shown in FIG. It includes a timer 30 which is means for searching for the presence or absence of the time slot.

In the second embodiment of the present invention, as shown in FIG. 6, when there is no empty time slot, the time slot management table T1 gives priority to the packet when an empty time slot occurs. A reservation table T2, which is a means for making a reservation for placing in the time slot, is included.

In the third embodiment of the present invention, as shown in FIG. 7, a burst buffer 7 is provided for each input line.

The route information is time slot exchange information, and is information on the order in which time slots are exchanged when packets are transferred in the STM network 1. This reordering sequence indicates the reordering sequence of the time slots performed for each of the transit exchanges TS-1 and TS-2 or for each of the subscriber exchanges LS-2 accommodating the terminal TE-2.

Here, in order to make the explanation easy to understand, the subscriber exchanges LS-1, LS-2 and the transit exchange T
Although S-1 and TS-2 are expressed as devices having different configurations, each switch is actually configured as a device having both the function of the local exchange and the function of the transit exchange. That is, the embodiment describes a case where the terminal TE-1 transmits a packet to the terminal TE-2. Accordingly, in order to receive the packet transferred from the transit exchange TS-2, the subscriber exchange LS-2 needs to have the transit exchanges TS-1 and TS-2 shown in FIGS.
Must also have the configuration shown as.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The local exchanges LS-1, LS according to the embodiment of the present invention.
-2 and the relay exchanges TS-1 and TS-2 will be generally described with reference to FIGS. The TCP / IP packet transferred from the terminal TE-1 is transmitted to the local exchange LS.
-1, time slot exchange information as route information is added. That is, in the STM network 1, refer to Table 3 to search for time slot exchange information that is route information to the local exchange LS-2 in which the terminal TE-2 serving as the destination of the TCP-IP address is accommodated. I do. Table 3 contains TCP-
Time slot exchange information corresponding to the IP address is recorded.

In this way, the TCP / IP packet I
The header in which the time slot exchange information is written is added to the P header, and the header is input to the transmitting unit 4. At the same time, the information on the route sent from the local exchange LS-1 is transferred to the control circuit 9. The control circuit 9 transfers data according to the route information. The basic operation at this time is the same as the operation of the conventional time slot exchange shown in FIG. 9, but the apparatus according to the embodiment of the present invention temporarily stores packets when no time slot is available. And a burst buffer 7 for storing.

The control circuit 9 includes a data buffer memory DBM
Is monitored to determine the availability of a time slot, and if there is no available time slot, a packet to be written to that time slot is temporarily stored in the burst buffer 7. Thereafter, when a vacancy occurs in a desired time slot, the packet temporarily stored in the burst buffer 7 is again input to the data buffer memory DBM via the delay circuit 10. The delay circuit 10 compensates for the control delay of the control circuit 9 and places the packet in a desired time slot.

As shown in FIG. 3, the relay exchanges TS-1 and TS-2 copy the packet for each time slot by the data copying unit 11 and input the copied packet to the header reference unit 5.
The header reference unit 5 virtually reproduces the input packet to search for a header in which the time slot exchange information included in the packet is written. The retrieved time slot exchange information is transferred to the control circuit 9.
The subsequent operations are the same as those of the local exchange LS-1, such as setting the address control memory ACM and temporarily storing the packets in the burst buffer 7 if there is no free space. Also, in the local exchange LS-2 accommodating the destination terminal TE-2, the transit exchanges TS-1 and TS
-2 is performed, and the packet is transferred to the terminal TE-2.

Thus, the transit exchanges TS-1 and T-1
The time slot exchange information is read from the packet by the S-2 and the local exchange LS-2, and the packet is reloaded into a predetermined time slot, so that the packet is received without the need for a preset dedicated line. When the transit exchanges TS-1 and TS-2 and the local exchange LS-2 transfer bursts, data is transferred on a link-by-link basis by temporarily holding a time slot carrying the packet. Can be. Therefore, it is possible to hold the line only during the data transfer and release the line when the transfer is completed.

As a result, a link can be established at a high speed, network resources can be occupied only during a data transfer period, and released during other periods. Therefore, A
When data transfer by TM is used as a comparative example, ATM
In this case, one cell has 53 bytes, of which 5 bytes have overhead, but this embodiment does not require this overhead. In addition, since there is no fear of fluctuation and no cell loss, it is easy to assemble a packet on the receiving side.

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. Although the general description of the transit exchanges TS-1 and TS-2 has been made with reference to FIG. 3, in practice, as shown in FIG. -1 and TS-
2 housed. Here, four input lines # 1 to # 4
Assume # 4 and output lines # 1 to # 4. Input line #
The packets transferred on the time slots on 1 to # 4 are copied by the data copying unit 11, input to the header reference unit 5, and input to the multiplexer 20 to be multiplexed. Here, four output lines # 1 to #
Since four are assumed, four time slots are transferred to each of the input lines # 1 to # 4, and 16 time slots are output from the multiplexer 20. The subsequent operation is as described above. The packet output from the relay unit 6 is divided into four output lines # by the demultiplexer 21.
1 to # 4.

In the first embodiment of the present invention, the output for the output line # 4 is connected to the input of the burst buffer 7, and the output of the burst buffer 7 is connected to the input line # 4 of the multiplexer 20. As a result, if there is no vacancy in the time slot, packets destined for output lines # 1 to # 3 are allocated to output line # 4 and temporarily stored in burst buffer 7. In the burst buffer 7, the output line # 1
To # 3 are stored in buffers B1 to B3 assigned to output lines # 1 to # 3, respectively.

As shown in FIG. 5, the control circuit 9 is provided with a table T1. The control circuit 9 monitors the data buffer memory DBM to grasp the time slot vacancy status. Record the situation.

The timer 30 in the burst buffer 7 inquires of the control circuit 9 about the availability of time slots at predetermined time intervals. The control circuit 9 returns an answer to the inquiry with reference to the table T1. As a result, if a desired time slot is vacant, the packets stored in the buffers B1 to B3 and destined for the vacant time slot are output to the input line # 4 of the multiplexer 20. The output packet is processed in the same manner as a newly input packet, and is output in a time slot corresponding to a desired output line # 1 to # 4.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. In the second embodiment of the present invention, a reservation table T2 is added to the table T1 of the control circuit 9. The configuration of the second embodiment of the present invention is a configuration in which the timer 30 is omitted from the configuration shown in FIG.

In the first embodiment of the present invention, the control circuit 9 simply records the time slot availability in the table T1, and the timer 30 of the burst buffer 7 sends the status to the control circuit 9 every predetermined time. However, in the second embodiment of the present invention, the control circuit 9 records in the reservation table T2 which time slot the packet temporarily stored in the burst buffer 7 is a desired packet. Grasp by doing.

In this way, when a vacant time slot is generated, the control circuit 9 promptly gives a transmission permission to the buffer storing the packets waiting for the vacant time slot. Can be.

Third Embodiment A third embodiment of the present invention will be described with reference to FIG. The third embodiment of the present invention is an example in which burst buffers 7 are provided for input lines # 1 to # 4, respectively. FIG. 7 shows the burst buffer 7 provided for the input line # 1, but the burst buffer 7 is similarly provided for the other input lines # 2 to # 4.

In the structure of the first and second embodiments of the present invention,
Although the output of the output line # 4 is connected to the input of the burst buffer 7, if the traffic of packets to be written to the burst buffer 7 is concentrated on the output line # 4, there is a possibility that discarded packets may occur. . When traffic from a specific input line is overloaded, packets from another input line are sent to a burst buffer 7.
It becomes difficult to write to.

However, according to the configuration of the third embodiment of the present invention, the burst buffers 7 can be provided independently for each of the input lines # 1 to # 4. It is possible to avoid cell discard due to concentration of traffic to the expected burst buffer 7.

The control circuit 9 monitors the vacant state of the time slot. If the input packet is a packet addressed to the time slot corresponding to the vacant output line, the selector 22 switches the selector 22 so that the packet is stored in the burst buffer 7. Enter If a desired time slot of the packets stored in the burst buffer 7 is available, the control circuit 9 switches the selector 23 to output the packets in the burst buffer 7.

In the third embodiment of the present invention, similarly to the first embodiment of the present invention, the control circuit 9 stores the time slot management table T
1, a timer 30 is provided in the burst buffer 7 to control the transfer of packets temporarily stored in the burst buffer 7, and, similarly to the second embodiment of the present invention, a time slot is provided in the control circuit 9. A reservation table T2 may be provided in addition to the management table T1 to control the transfer of packets temporarily stored in the burst buffer 7.

[0045]

As described above, according to the present invention,
Based on the TCP-IP address used for data communication,
By providing a transit network by TM,
An STM line that could only be provided as a mere dedicated line can be dynamically provided. As a result, a circuit switching network with a small delay time and a small overhead can be realized. Further, the number of packets discarded due to congestion of the output line can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a circuit switching network according to an embodiment of the present invention.

FIG. 2 is a diagram showing a block configuration of a main part of the local exchange according to the embodiment of the present invention.

FIG. 3 is a diagram showing a main block configuration of a transit exchange according to the embodiment of the present invention.

FIG. 4 is a diagram showing a main part block configuration of the transit exchange according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a time slot management table of the control circuit according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a time slot management table of a control circuit according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a main block configuration of a transit exchange according to a third embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a main part of a conventional circuit switching network based on STM.

FIG. 9 is a diagram showing a configuration of a main part of a conventional subscriber exchange.

FIG. 10 is a diagram showing an image of a dedicated STM connection.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 STM network 2 Receiving part 3 Table 4 Transmitting part 5 Header reference part 6 Relay part 7 Burst buffer 9 Control circuit 10 Delay circuit 11 Data copying part 20 Multiplexer 21 Demultiplexer 22, 23 Selector 30 Timer ACM Address control memory CTR Sequential counter DBM data buffer memory LS-1, LS-2 local exchange T1 time slot management table T2 reservation table TS-1, TS-2 transit exchanges TS # i, TS # j, TS # k time slot exchange information TE- 1, TE-2 terminal

Claims (4)

[Claims] A plurality of subscriber exchanges accommodating one or more terminals, and a transit exchange for connecting the subscriber exchanges to each other, wherein the subscriber exchange and the transit exchange comprise:
The subscriber exchange is connected via an STM (Synchronous Transfer Mode) network, and receives a TCP
−IP (Transmission Control Protocol-Internet Prot
ocol) means for receiving a packet having a header in which an address is written, a table in which route information in the STM network corresponding to the TCP-IP address is recorded,
Means for adding a header in which the route information corresponding to the TCP-IP address obtained by referring to the table is written to the header, and a time slot corresponding to the route information by referring to the added header. Means for transferring the packet at, the transit exchange, the means for referring to the header in which the route information of the packet written in the time slot is written, according to the reference result of the means for referring, Means for re-loading the packet in a time slot corresponding to the route information written in the header, and when there is no empty time slot, temporarily store the packet until an empty time slot is generated. In the circuit switching network provided with a means for temporarily storing, the means for temporarily storing, A circuit switching network including means for searching for the presence or absence of a slot. 2. A local exchange comprising a plurality of local exchanges accommodating one or more terminals, and a transit exchange connecting between the local exchanges, wherein the local exchange and the transit exchange comprise:
The subscriber exchange is connected via an STM (Synchronous Transfer Mode) network, and receives a TCP
−IP (Transmission Control Protocol-Internet Prot
ocol) means for receiving a packet having a header in which an address is written, a table in which route information in the STM network corresponding to the TCP-IP address is recorded,
Means for adding a header in which the route information corresponding to the TCP-IP address obtained by referring to the table is written to the header, and a time slot corresponding to the route information by referring to the added header. Means for transferring the packet at, the transit exchange, the means for referring to the header in which the route information of the packet written in the time slot is written, according to the reference result of the means for referring, Means for re-loading the packet in a time slot corresponding to the route information written in the header, and when there is no empty time slot, temporarily store the packet until an empty time slot is generated. In the circuit switching network provided with a means for temporarily storing, the means for temporarily storing is empty in the time slot. A circuit switching network comprising means for making a reservation for placing the packet in the time slot preferentially when the time slot becomes empty when there is no available time. 3. A local exchange comprising a plurality of local exchanges accommodating one or more terminals, and a transit exchange for connecting the local exchanges, wherein the local exchange and the transit exchange comprise:
The subscriber exchange is connected via an STM (Synchronous Transfer Mode) network, and receives a TCP
−IP (Transmission Control Protocol-Internet Prot
ocol) means for receiving a packet having a header in which an address is written, a table in which route information in the STM network corresponding to the TCP-IP address is recorded,
Means for adding a header in which the route information corresponding to the TCP-IP address obtained by referring to the table is written to the header, and a time slot corresponding to the route information by referring to the added header. Means for transferring the packet at, the transit exchange, the means for referring to the header in which the route information of the packet written in the time slot is written, according to the reference result of the means for referring, Means for re-loading the packet in a time slot corresponding to the route information written in the header, and when there is no empty time slot, temporarily store the packet until an empty time slot is generated. In the circuit switching network having means for temporarily storing, the means for temporarily storing is provided for each of the input lines. A circuit-switched network characterized by the following. 4. The circuit switching network according to claim 1, wherein said route information is time slot switching information.