KR19980020892A - Multicasting Connection Method in ATM Switching System - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Asynchronous Transfer Mode (ATM) exchange for multicasting cells. The present invention relates to a method for dynamically changing a multicasting connection when the number of communication counterparts is increased or decreased during an exchange operation. The present invention relates to a multicasting connection method in an ATM exchange system that enables stable service without affecting a currently communicating subscriber.

In the prior art, since there are two or more tables required for one connection, and there are cells being processed in the copy network CN and the transport network RN, when a new output port is added or an existing output port is removed from the connection. There was a problem that temporary data loss occurred.

According to the present invention, the present invention provides a subscriber station that is dynamically changing a multicasting connection by allocating a new logical channel identifier used for channel identification within the exchange to have all the table contents before and after the connection change. Stable service is possible without affecting Therefore, the present invention can stably provide a connection even when the number of subscribers to be connected is dynamically changed when the multicasting connection is performed to subscribers, for example, video conferencing, distance education, and the like.

Description

Multicasting Connection Method in ATM Switching System

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Asynchronous Transfer Mode (ATM) exchange for multicasting cells. In particular, the multicasting connection is dynamically changed when the number of communication partners increases or decreases during the exchange operation. The present invention relates to a multicasting connection method in an ATM exchange which enables stable service without affecting subscribers currently communicating.

In general, when an ATM switcher connects broadcasting information such as CATV to a subscriber, the subscriber watching the broadcast may change according to time, and the new subscriber may watch the broadcast at any point in time or may have previously watched the broadcast. When the subscriber stops broadcasting and the subscriber to be connected changes, the subscriber should be efficiently multicasted to provide the broadcasting service without affecting the existing broadcasting subscriber.

As shown in Fig. 1, the ATM switch for multicasting includes a plurality of input port processors (IPP0 to IPPn), a copy network (CN), a plurality of broadcast / group converters (BGT0 to BGTn), a transport network (RN), and a plurality of An output port processor OPP0 to OPPn and a control processor CNP are provided. The input port processor (IPP0 to IPPn) converts the input data cells into internal packets for exchange and outputs them to the copy network CN. The output cells indicate the number of packets to be copied from the copy network CN. Contains information about the branch number (FO). The cells copied from the copy network CN are output to the broadcast / group converters BGT0 to BGTn, and the broadcast / group converters BGT0 to BGTn assign a destination address, that is, an output port number, to a cell to be exchanged. By outputting to the (RN) side, the transmission network RN is exchanged with the output port processors OPP0 to OPPn of the corresponding destination. Therefore, in the input port processors IPP0 to IPPn, the broadcast / group converters BGT0 to BGTn, and the output port processors OPP0 to OPPn, there is a table having the number of branches and the destination address of the cell to be processed.

An example of a procedure in which an input ATM cell is exchanged via an internal copy network (CN) and a transport network (RN) is shown in FIG. That is, the input port processor (IPP0 to IPPn) is provided with a table (IPT) for converting input cells into internal cells, and the broadcast / group converters (BGT0 to BGTn) provide destination addresses to cells copied from the copy network CN. A table BTT is provided, and an output port processor OPP0 to OPPn includes an output VPI / VCI (Virtual Path Identifier / Virtual Channel Identifier) value for reconverting the exchanged cell into an ATM cell. Is provided. In addition, when establishing a connection to a cell, the control processor (CNP) requests that required values be recorded in each table.

In Fig. 2, the table IPT records allocation / unassigned bits (AU), copy number (FO), and logical channel number (LCN) corresponding to the VPI / VCI values of the input cells. When an internal cell configured according to the present invention is input to the copy network CN, the copy network CN copies the corresponding number of cells based on the copy branch number FO of the corresponding cell. The allocation / non-allocation bit (AU) recorded in the table IPT is used to distinguish whether the input cell is a valid data cell or an empty cell, and the logical channel number LCN is used for internal exchange. It is used to identify the channel, and in particular, the logical channel number LCN is used to distinguish the channel to which the cell processed in the table BTT and the table OPT belongs.

The cell converted by the input port processor (IPP) is assigned to the copy network (CN) with the assigned / unassigned bit (AU), copy number (FO) and logical channel number (LCN) values by referring to the table (IPT). do. In the copy network CN, the corresponding number of cells is copied based on the number of copy branches FO of the corresponding cell. For example, when the input ATM cell is exchanged with three output ports, the value of the copy branch number (FO) is set to 3 so that the copy network (CN) copies three cells and broadcast / group converter (BGT). ) And the BGT sends a destination address (DA) to the corresponding cell by referring to the logical channel number (LCN) value of the table (BTT) provided therein. Output Then, the transmission network RN refers to the destination address DA assigned by the broadcast / group converter BGT, and delivers it to the corresponding output port processor OPP, and the output port processor OPP transfers the corresponding cell to the VPI. It converts to ATM cell based on / VCI value and outputs it. In this case, depending on the type of connection, in case of virtual path, VCI value keeps VCI value of input ATM cell as it is. OPT) is provided with a virtual path termination identifier (VPT) for identifying the type of connection.

An example of connecting a cell to multicasting will be described with reference to FIG. 3 as follows. In FIG. 3, a case in which cells input through the sixth input port I6 are output to the second, third, and eighth output ports O2, O3, and O8 is illustrated. This should be recorded in BTT, OPT). That is, the input port processor (IPP) records the copy branch number (FO) as 3 in its table (IPT), and the broadcast / group converter (BGT) records O2, as a destination address (DA) for the copied corresponding cell. The values corresponding to O3 and O8 should be recorded in its own table (BTT), and the output port processor (OPP) records in the table (OPT) to have the appropriate output VPI / VCI values.

In the prior art, since there are two or more tables required for one connection, and there are cells being processed in the copy network CN and the transport network RN, a new output port is added or an existing output port is removed from the connection. In this case, there is a problem that temporary data loss occurs. This is common in broadcast services. For example, if a current subscriber is watching through a channel while a new subscriber is watching the channel in the middle, the number of subscribers increases to four. Therefore, the number of copy branches (FO) of the table (IPT) provided in the input port processor (IPP) is converted from 3 to 4, and the output port to which the new subscriber is connected to the table (BTT) of the broadcast / group converter (BGT). The cell must be reflected so that it can be transmitted. However, two or more tables cannot be changed at the same time, and even if they are changed at the same time, it is not known whether the cell being processed in the copy network is data when the number of subscribers is 3 or whether the data when the number of subscribers is 4 because new subscribers are added. .

This problem will be described in more detail with reference to FIGS. 4 and 5. 4 shows an example in which a new subscriber connected to the fifth output port O5 is added in the connection of FIG. At this time, the number of copy branches FO of the table IPT provided in the input port processor IPP should be changed from 3 to 4, and the destination address DA is shown in the table BTT of the broadcast / group converter BGT. It should be changed to have a value corresponding to O5. If the table IPT and the table BTT are changed, the cells having a copy number FO of 3 are copied from the copy network CN as a ratio and output to the broadcast / group converter (BGT). The packet is output to only three ports of O2, O3, O5, and O8. For example, if three copied packets are outputted as O2, O3, or O5, the packet is not output to O8 and data loss occurs. If the lost data is video data, the subscriber who is watching is temporarily You will not be able to watch the screen.

In addition, FIG. 5 is an example in which an existing subscriber connected to the eighth output port of the connection of FIG. 3 is excluded from the connection, and the copy number of branches FO of the table IPT should be changed from 3 to 2. In the table BTT, the copied cells should be output as O2 and O3. At this time, after changing the contents of the table (IPT) and the table (BTT), the input cell is copied when the copy branch number (FO) is 3 in the copy network (CN). Since it is input to the broadcast / group converter BGT, one packet is duplicated and output as O2 or O3 because the table BTT has a value output only to O2 and O3. Even in this case, the ATM treats the error, and therefore, the error occurs when the existing subscriber is removed as well as the addition of the new subscriber described above, causing problems for the existing subscriber.

The present invention has been made to solve the conventional problems as described above, so that the logical channel identifier used to identify the channel in the exchange is newly assigned during the change of the connection so as to have all the contents of the table before and after the change of the connection. Therefore, it is an object of the present invention to provide a multicasting connection method in an ATM exchange system that dynamically changes a multicasting connection to enable stable service without affecting a subscriber in communication.

The present invention for achieving the above object is, in the multicasting connection method in the ATM switch, due to the addition of a new subscriber or removal of an existing subscriber during the multicasting connection operation for connecting a cell to a plurality of subscribers. When the number of subscribers to be connected varies, the broadcast / group converter records the assigned / unassigned bits and destination addresses corresponding to the logical channel identifiers of the existing connection, and the assigned / unassigned bits and destinations corresponding to the logical channel identifiers of the new connection. Recording the address in its own table, and outputting the VPI / VCI value corresponding to the logical channel identifier of the existing connection and the logical channel identifier of the new connection into its own table by the output port processor; A second step of, after the first step, the input port processor assigns a logical channel identifier for a new connection to a newly input cell and outputs it to a copy network; After the second process, the broadcast / group converter assigns a destination address for the existing connection and the new connection to the cell based on its table and outputs the cell to the delivery network, and the output port processor transmits the existing address to the cell authorized through the delivery network. And converting into an ATM cell by granting VPI / VCI and converting into an ATM cell by granting VPI / VCI for a new connection.

With such a configuration, the present invention dynamically changes the multicasting connection by allocating a new logical channel identifier used for channel identification within the exchange to have all the table contents before and after the change in the connection. Stable service is possible without affecting subscribers in communication.

1 is a block diagram of an ATM switch for a multicasting connection.

2 is a diagram illustrating a cell processing procedure in a conventional ATM switch.

3 is a diagram illustrating a process of connecting cells.

4 is a diagram illustrating a cell connection process when a new subscriber is added.

5 is a diagram illustrating a cell connection process when an existing subscriber is removed;

6 is a flowchart illustrating a multicasting connection procedure in an ATM switch according to the present invention.

Fig. 7 is a diagram showing an example of creating a conversion table in the present invention.

Explanation of symbols on the main parts of the drawings

IPP: Input Port Processor CN: Copy Network

BGT: Broadcast / Group Converter RN: Transport Network

OPP: Output Port Processor

In the present invention, when a connection change occurs while an ATM exchange performs a cell connection operation, a new logical channel identifier (LCN) used to identify a channel is newly allocated to have a table content before and after the connection change. The multicasting connection can be dynamically changed by simultaneously processing the cell of the connection and the cell of the newly changed connection.

The multicasting connection operation in the ATM switch according to the present invention is performed in the order shown in FIG.

First, when performing the multicasting connection operation of connecting a cell to a plurality of subscribers (step ST10), if the number of subscribers to be connected changes due to the addition of new subscribers or removal of existing subscribers (step ST11), the broadcast / group converter (BGT) records the allocation / deallocation bits (AU) and destination address (DA) corresponding to the logical channel identifier (LCN) of the existing connection, and at the same time, the allocation / deallocation corresponding to the logical channel identifier (LCN) of the new connection. The bit (AU) and the destination address (DA) are written in its own table (BTT) to change the contents of the table (BTT), and the output port handler (OPP) changes the logical channel identifier (LCN) of the existing connection and the new connection. The VPI / VCI value corresponding to the logical channel identifier LCN is recorded in its own table OPT to change the contents of the table OPT (step ST12). After that, the input port processor (IPP) assigns a logical channel identifier (LCN) for the new connection corresponding to the newly input cell and outputs it to the copy network (step ST13). Cell linking processing for linking is performed (step ST14).

The multicasting connection operation will be described in more detail as follows. In step ST10, while the ATM switch performs an operation of connecting a cell to the output ports O2, O3 and O8 as shown in FIG. 3, a new subscriber is added to the output port O5 as shown in FIG. When the subscriber of the output port O8 is removed as shown in FIG. 5 and the number of subscribers to be connected varies, in step ST12, the broadcast / group converter (BGT) sets the logical channel identifier (LCN) of the existing connection and the logical channel identifier (LCN) of the new connection. Change the contents of the table (BTT) by recording the assigned / unassigned bit (AU) and destination address (DA) corresponding to the table in its own table (BTT). When a new subscriber is added as shown in Fig. 4, the destination address (DA) values O2, O3, and O8 corresponding to the logical channel identifier (LCN) value 100 for the existing connection are recorded as shown in FIG. Logical Channel Identifier (LCN) value for If the destination address (DA) values O2, O3, O5, and O8 corresponding to 0 are recorded in its table (BTT), and the subscriber is removed as shown in FIG. 5 in the connection operation state as shown in FIG. As shown in B), the destination address (DA) values O2, O3, O8 corresponding to the logical channel identifier (LCN) value 100 for the existing connection and the destination address (DA) values 200 for the logical channel identifier (LCN) value 200 for the new connection. ) Record the values O2 and O3 in your table (BTT). At the same time, in step ST12, the operation of changing the table OPT of the output port processor OPT is performed. The VPI corresponding to the logical channel identifier LCN of the existing connection and the logical channel identifier LCN of the new connection is performed. Change the contents of the table (OPT) by writing the / VCI value to its own table (OPT).

Then, in step ST13, the input port processor IPP assigns and outputs the logical channel identifier LCN for the new connection to the cell to be applied. For example, when the logical channel identifier LCN for the existing connection is 100, Give a logical channel identifier (LCN) of 200 for the connection. Accordingly, in step ST14, the copy network CN performs a cell copy operation on an existing connection and a cell copy operation on a new connection, and the broadcast / group converter BGT is applied to its table BTT. In response to the recorded logical channel identifier (LCN), a destination address (DA) for an existing connection is given, and a destination address (DA) for a new connection is assigned to output a cell to the transport network (RN). The processor (OPP) assigns a VPI / VCI value corresponding to the logical channel identifier (LCN) recorded in its table (OPT), converts it into an ATM cell, and outputs it to the subscriber. (CN) and transport network (RN) have a function of temporarily storing a cell, so when a cell having a logical channel identifier (LCN) value of 100 and 200 is simultaneously stored, the broadcast / group converter (BGT) Own tei According to (BTT), if the logical channel identifier (LCN) is 100, the cell is treated as the cell of the previous connection. If the logical channel identifier (LCN) is 200, the cell is treated as the cell of the new connection, the correct destination address ( DA) can be allocated, resulting in no loss of data cells or duplication of data, resulting in a dynamic multicasting connection.

As described above, the present invention dynamically changes the multicasting connection by allocating a new logical channel identifier used for identifying a channel within the exchange so as to have all the contents of the table before and after the change in the connection. Stable service is possible without affecting subscribers in progress. Therefore, the present invention can stably provide a connection even when the number of subscribers to be connected is dynamically changed in the case of multicasting a video conference, a distance education, etc. to a subscriber in addition to broadcasting, for example.

Claims (1)

In the multicasting connection method in an ATM switch, when the number of subscribers to be connected is changed due to the addition of a new subscriber or the removal of an existing subscriber while performing a multicasting connection operation connecting a cell to a plurality of subscribers, a broadcast / group The translator records the assigned / unassigned bits and destination addresses corresponding to the logical channel identifiers of the existing connection, and at the same time records the assigned and unassigned bits and destination addresses corresponding to the logical channel identifiers of the new connection, in its own table. A first step of the processor writing a VPI / VCI value corresponding to the logical channel identifier of the existing connection and the logical channel identifier of the new connection in its table; A second step of, after the first step, the input port processor assigns a logical channel identifier for a new connection to a newly input cell and outputs it to a copy network; After the second process, the broadcast / group converter assigns a destination address for the existing connection and the new connection to the cell based on its table and outputs the cell to the delivery network, and the output port processor transmits the existing address to the cell authorized through the delivery network. And a third process of converting to an ATM cell by granting VPI / VCI and converting it into an ATM cell, and converting the result into an ATM cell by giving VPI / VCI for a new connection.