JP2000049822A - Atm switch and logical multiple address communication method for atm switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow an extension function section in a cell switch or at a post- stage of the cell switch conducting traffic processing or the like to conduct uni-cast, physical multicast and also logical multicast at the same time. SOLUTION: A data reference/control function 302 reads a VPI/VCI and refers to a routing table function 303 based thereon to obtain information 305 required for switching. A data copy function 307 discriminates uni-cast or multicast based on the obtained information 305 and copies data by a number for the multicast. An information conversion function 308 rewrites the VPI/VCI of the copied data and decides an output port based on the information 305 and a cell transfer function 309 transfers respective cells to each port. A cell switch or its extension section of the ATM switch realizes the functions above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM (asynchronous transfer mode) between a communication device, a terminal and other nodes.
AT that functions as an exchange when performing data communication by
The present invention relates to a method of logical broadcasting (also referred to as “logical multicast”, “logical multicast”, or “in-network multicast”) between an M switch and an ATM switch.

[0002]

2. Description of the Related Art Conventionally, logical multicast A
As disclosed in Japanese Patent Application No. Hei 7-231801, the TM switch is used for performing broadcast communication to a plurality of nodes in one communication network. In other words, communication channels (VCC: VirtualC) of a plurality of virtual channels set in one physical line.
channel connection). FIG. 7 shows a conventional ATM.
It is a block diagram of a block which performs logical multicast of a switch. The processing for the logical multicast is provided in a line interface (also referred to as a “network interface”) IF at a stage after the output port of the cell switch.

[0003] Of the cells output from the cell switch,
When the intra-network multicast cell Ce is provided, the header creating unit 11 uses the headers H1 and H1 including the VCI / VPI of the destination node based on the multicast identifier.
2. H3 is created. Each time the headers H1, H2, H3 are provided, the cell combining / sending unit 13
2 is read out. That is, the data part D is copied. Cell synthesis / transmission unit 13
Then, the headers H1, H2, H3 and the data part D are combined to create new cells Ce1, Ce2, Ce3, and sent out to the communication network.

[0004]

Problems to be Solved by the Invention Japanese Patent Application No. 7-23180
In the conventional technology described in Japanese Patent Application Laid-Open Publication No. 1 (1999), an electronic circuit for performing logical multicast is provided by:
It is necessary to newly add a line interface. Specifically, there is a problem that a data separation unit 10, a buffer 12, a header creation unit 11, its table memory 11a, a cell synthesis unit / extraction unit 13 and the like are newly required for the line interface, and the line interface becomes large. there were.

[0005] Further, in the above prior art, paragraph

As described in the above, since this is a network interface used for a cell including a multicast identifier in the network as the destination information, the cell does not include the multicast identifier in the network as the destination information, for example, a unicast cell or a physical multicast. A cell (also referred to as "physical multicast" or "multicast per line") must have a different network interface from the logical multicast, and at the same time, an intra-network multicast identifier between the cell switch and the network interface IF. For example, a processing block for determining whether or not to include the "?"

Further, when all cells are processed by a network interface as described in the above publication, data separation, header generation and cell combining are not originally required, and a multicast identifier in the network is not included as destination information. ,
For example, processing such as a unicast cell and a physical multicast is redundantly performed, and there is a problem that a transmission speed is reduced.

(Object of the Invention) It is an object of the present invention to provide an ATM switch and a logical broadcast communication method of the ATM switch which enable high-speed logical multicast processing without increasing the scale of the device configuration.

Another object of the present invention is to provide an ATM switch and an AT which enable logical multicast processing within a cell switch (for example, a routing processing section, a buffer control section, a section for referring to a cell header, a buffer section, etc.).
An object of the present invention is to provide a logical broadcast method for an M switch.

Another object of the present invention is to control traffic downstream of an output port of a cell switch (for example, priority control, shaping, congestion control, quality of service (QOS)).
rvice: ATM switch and AT that enable logical multicast processing in an extended function unit such as a block for performing service quality control processing and extended output buffering processing or a block for determining a physical line output port.
An object of the present invention is to provide a logical broadcast method for an M switch.

[0010]

The ATM switch for performing the logical multicast according to the present invention performs the logical multicast simultaneously with the unicast cell routing and the physical multicast routing in the cell switch. Further, in an ATM switch having an extension block for traffic control at a stage subsequent to the cell switch, logical control is performed simultaneously with performing traffic control. In addition, a function that enables logical multicasting without changing the hardware architecture of the original cell switch is realized.

The logical broadcast method for an ATM switch according to the present invention is a logical broadcast method for an ATM switch capable of outputting a unicast cell, a physical multicast cell and a logical multicast cell to an output port according to destination information. A cell switch in the ATM switch or an extended function unit for performing traffic processing at a stage subsequent to the cell switch extracts VPI / VCI or secondary information generated from the VPI / VCI from each cell and stores each cell data in a buffer memory. Then, referring to the table having the routing table function, the multicast cell copies data of the number of destination records, converts the header, and outputs the converted data to the destination.

(Operation) Information of a routing table (header conversion table) referred to for performing routing is prepared so that it can be determined whether it is unicast or multicast. In the case of multicast, only the number of records in the routing table indicating the multicast destination is provided. The data is copied and the header is converted, and then output to the destination port or destination buffer. Since these functional blocks are basically provided in the cell switch or an extended function unit for performing traffic processing at the subsequent stage of the cell switch, logical multicast can be realized in the cell switch or the like without any change of a line interface or the like. I do. Compared to ATM switches that cannot perform logical multicast, the hardware architecture does not change much,
Small increase in circuit scale.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Configuration of Embodiment) FIG. 1 is an example of a block diagram showing the entire configuration of an ATM switch to which the present invention is applied. The ATM switch 101 has a network interface (line interface) 1 on the data input side.
02. Similarly, the output side also has several network interfaces (line interfaces) IF. ATM cells sent from the circuit network pass through the circuit interface 102 and are routed by the cell switch 103.
The signal is switched, sent to the line interface IF, and output to the line network.

When the types of cell switches are roughly classified,
It can be divided into input buffer type switch, output buffer type switch, cross point buffer type switch, and common buffer type switch. The input buffer type switch has an input buffer and a self-routing switch (for example, Banyan Switch). The output buffer type switch is a system in which input cells are multiplexed once, the multiplexed cells are selected by a routing bit filter, and transferred to an output buffer. The crosspoint buffer type switch has a routing bit filter at each intersection of an input port and an output port and transfers the data to an output buffer. The common buffer type switch is a system in which cells are temporarily stored in a common buffer and routing is performed by controlling the order of reading.

An ATM cell input to the ATM switch is divided into a cell header portion and a payload portion. AT
A VPI (virtual) is added to the cell header of the M cell.
path identifier and VCI (virt
ual channel identifier) is included. VPI and VCI are information for determining what communication path the ATM cell selects. The ATM switch performs routing based on this information.

In the cell switch, the VPI and VCI of the cell
From the VPI, VCI or VPI, VC
There is a mechanism that refers to a routing table based on secondary information (such as a table reference pointer) generated from I. The cell switch refers to the routing table,
When control information (for example, routing bits) necessary for hardware processing is obtained, cells to be output to respective ports are determined and output.

FIG. 2 is a block diagram showing an example of the configuration of a common buffer type switch as an example of a cell switch to which the present invention is applied. Cells entering from the input port 201 are multiplexed by the cell multiplexing unit 202, and the routing process is sequentially performed. First, an input cell is divided into a header section and a payload section by a header separation section 203 and a payload separation section 204.

The VPI and V obtained by the header separation unit 203
The control unit 205 performs a routing process by referring to the routing memory 206 based on the information of the CI. Specifically, the cell is read from the common cell buffer memory 207 by the control information obtained from the routing memory 206, the header of the cell is rewritten to the new VPI and VCI by the header reading & conversion unit 208, and the cell distribution unit 2
10 to the output port 209.

(Operation of Embodiment) FIG. 3 is a flowchart showing processing of transfer data (cells) and control information according to the present embodiment in a cell switch. Arrow 301 indicates the flow of input cells. The data reference / control function 302 reads the header of the input cell, VPI / VCI. This block is a basic function block that the cell switch has together with the routing table (header conversion table) function 303 for the cell switch to perform routing.

An arrow 304 indicates the flow of the read VPI / VCI information. The routing table function 303 refers to the table based on the read VPI / VCI, and obtains information necessary for switching. For example, output port number, new VPI / VCI, cell routing information, routing bits in banyan switch,
The information includes control information, an identifier for a cell, a multicast / unicast discriminator, and the number of multicasts. Of course, it is not necessary to put all of this information in the routing table function 303, and if there is control information for determining each port to which a cell is finally output and a new cell header of each cell, Good. Arrow 305 indicates the flow of these information.

An arrow 306 indicates the flow of data whose header has been referred to. The data transmitted to the data copy function 307 may be the entire cell, or may be data excluding the header portion. Because the information of the header part is indicated by the arrow 305
This is because only the part which cannot be interpolated by this can be transmitted.

The data copy function 307 is based on information 305 obtained from the routing table function 303.
Data is copied as many times as necessary, in other words, as many times as physical multicast and logical multicast are performed for a certain cell. In the case of a unicast cell, a process of transmitting only one received data without making a copy is performed. That is, the data copy function 307 receives the number of cells to be output as control information and outputs data by that number.

This block is a basic functional block of a cell switch capable of performing physical multicast, and is not a kind of function newly added to realize logical multicast. In the case of a circuit in which data is simultaneously copied in parallel for each output port in physical multicast and the circuit up to cell transfer is configured in parallel, logical multicast cells are sequentially copied to the same port. In addition, as long as the data is held in the cell switch, the data copy function 3 can be extended by extending the function.
07 may be realized. For example, a configuration is such that a required number of data read controls are performed by a buffer unit that holds data and its buffer control.

The copied data is transferred to the header information conversion function 308. If the cell is a unicast cell that does not require copying, a configuration may be adopted in which the cell is transmitted to the header information conversion function 308 without passing through the data copy function 307.

A header information conversion function 308 rewrites or adds a header and VPI / VCI to each data based on the information 305 obtained from the routing table function 303, and transfers a cell by an arrow 310 to a cell transfer function 309. Transfer to At this time, control information 311 created from information 305 necessary for routing together with the cell,
For example, output destination port number etc. are also transferred at the same time.
09 to control cell transfer.

The control information 311 allows the cell transfer function 3
09 transfers each cell to each port or each output buffer. The header information conversion function 308 and the cell transfer function 309 are both basic functions of the cell switch.

FIG. 4 is a more specific block diagram showing how the functions and flow of FIG. 3 are realized in the example of the cell switch shown in FIG. The data reference / control function 302 is directed to a header separation 203 and a control 205 which are blocks for taking out a cell header in a cell switch. Routing table (header conversion table) 30
3 is made in the routing memory 206. This contains information for cell copy control, that is, information such as whether a cell to be transferred is a unicast cell, a multicast cell, and how many multicasts are performed.

In the case of the common buffer type cell switch shown in FIG. 4, the control unit 205 controls reading of the common cell buffer memory 207 based on this information. At this time, the data copy function 307 can be realized by buffer control such that reading is performed only once in the case of unicast, and the number of readings is performed in the case of multicast. The method of implementing the data copy function 307 can be changed depending on the switch configuration. For example, as another example of FIG. 4, cells may be copied by buffering control using cell copy control information in a buffer for data reading and header conversion included in the header reading & converting unit 208. Header information conversion function 308, cell transfer function 3
09 is realized by the header reading & conversion unit 208 and the cell distribution unit 210, respectively.

FIG. 5 shows a routing table (header conversion table) for implementing logical multicast.
FIG. 4 is a diagram showing an example of the above and an example of a reference method thereof. First, the data reference / control function 302 obtains the received port number and VCI / VPI included in the cell header. Based on this, 1
Calculate the address of the next conversion table memory. By referring to the reference destination record 503 in the primary conversion table 501, it can be determined whether it is unicast or multicast. In the case of unicast, control information 504 including an output port number and a new VPI / VCI attached to an output cell can be obtained from the record 503. In the case of multicast, a pointer to the secondary conversion table 502 can be obtained as in the control information 506. This is to increase the use efficiency of the routing memory by separating unicast or multicast. Another reason is that the area of the table for one cell in the memory can be changed by using a pointer to the secondary memory. In addition, an area indicating unicast or multicast (physical multicast or logical multicast) may be provided so that the type of casting can be understood only by referring to this area, and routing control may be performed. Alternatively, an area indicating the number of multicasts may be provided and used as an argument of a counter for performing copy control.

In the case of multicast, the record 505 can be referred to by the pointer to the secondary conversion table. 2
The next conversion table memory 502 may be prepared in another area of the same physical memory as the one-time conversion table memory 501, or may be physically different.

In the record 505, information on the number of each multicast destination is stored as many as the number to be broadcast. For example, the same output port (VPI,
Control information 507 indicating different VCIs can be obtained. In the case of physical multicast, control information 508 indicating different output ports (VPI and VCI are arbitrary) can be obtained.

In the case of the ATM switch of the present invention, one input cell can be simultaneously subjected to physical multicast and logical multicast. At this time, the number of pointers in the routing table may be increased to record 503 or record 505, and the table memory may be expanded so that physical multicast and logical multicast can be sequentially drawn. The logical multicast may be put into one record so that it can be pulled at a time.

The record 505 includes an output port, VPI,
An area indicating physical multicast or logical multicast may be provided in addition to the information indicating the VCI so that the type of the casting can be understood only by referring to the area to control the routing. Alternatively, an area indicating the number of multicasts may be provided and used as an argument to a counter for performing copy control.

The header information conversion function 308 rewrites or adds the header and VPI / VCI of each cell based on the information indicating the VPI and VCI thus obtained. The cell transfer function 30 based on the information indicating the output port number.
9 outputs a cell to each output port or output buffer.

As another form of FIG. 5, a record 503,
The record 505 may include other information necessary for routing, in addition to the output port number and the new VPI / VCI, which are information necessary for routing the cell. For example, a bit indicating whether the record itself is valid or invalid,
Control information, service class information, number of multicasts, multicast identifiers, cell identifiers for control, etc., bit information (bitmap table) that points to an output port for physical multicast and performs gate control, and other information It is a pointer for reference, shaping control information, and the like. The reference structure may have a hierarchical structure deeper than that of FIG. In FIG. 5, there are three stages of processing to obtain multicast information, but the number of stages can be made any number. However, considering the processing speed, it is desirable that the number of reference stages is not so large.

(Other Embodiment) FIG. 6 is a block diagram showing another embodiment of the present invention. Cell switch 103
In the case of the ATM switch 101 having the function extension unit 601 at the subsequent stage, instead of including the mechanism for performing the logical multicast in the cell switch 103, the function extension unit 60
In step 1, logical multicast may be performed. The function expansion unit 601 controls traffic at a stage subsequent to the output port of the cell switch, for example, priority control, shaping, congestion control, quality of service (QOS).
e: service quality) This block performs control processing, extended output buffering processing, and the like.

The function expansion unit 601 also performs traffic control on a cell-by-cell basis, so that the table reference is made to VPI or VCI or based on secondary information (cell-specific control information, etc.) generated from VPI or VCI. It basically has a block to perform, a block to perform processing for each cell, a block to input / output cells, and a block to control these.

Therefore, the data reference / control function 302 is used for a part for extracting VPI, VCI or secondary information and a block for performing table reference, a routing table function 303 is used for the table, a part for performing processing on each cell, and a buffer for the cell are used. And data copy function 3 in buffer controller
07, a header information conversion function 308, and a cell transfer function 309 for a cell output block. The routing table stores information shown in FIG. 5 and control information for the function expansion unit 601 to process each cell together. In this case, the arrow 301 input to the data reference / control unit 302 does not have to be in the cell format.

The data reference / control unit 302 is a VPI or VC
It is sufficient that secondary data (for example, a cell identifier) generated from I or VPI or VCI and uniquely specifying a cell and data to be transmitted are received. Further, the record 503 and the record 505 do not have to include the information of the output port. This is because the output port has already been determined by the cell switch. The function expansion unit may be a function block having a function of determining and outputting a plurality of physical line output ports at a stage subsequent to the output port of the cell switch. Information will always be included.

[0040]

According to the present invention, the function of the logical multicast can be performed only in the cell switch, so that the logical multicast can be realized without changing the line interface.

The respective blocks for performing the logical multicast can be arranged in various places in accordance with the architecture of the conventional cell switch, and the ATM switch can be constructed with almost the same architecture. The increase in the device scale is small for an ATM switch that cannot perform logical multicast up to this point.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an ATM switch according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration example of a cell switch unit in FIG. 1;

FIG. 3 is a diagram showing a flow of transfer data and control information.

FIG. 4 is a block diagram showing an example when a common buffer type cell switch is used.

FIG. 5 is a diagram illustrating an example of a routing table and a method of referring to the routing table.

FIG. 6 is a diagram showing an overall configuration of an ATM switch according to another embodiment of the present invention.

FIG. 7 is a diagram showing a conventional technique.

[Explanation of symbols]

302 data reference / control function 303 routing table function 307 data copy function 308 information conversion function 309 cell transfer function 504 unicast cell routing control information 506 multicast cell routing control information 507 logical multicast cell routing control information 508 physical multicast cell Routing control information

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Katsuho Hayashi Inventor F-term in Kyushu Nippon Telecommunication System Co., Ltd. 2-4-1 Hyakumichihama, Sawara-ku, Fukuoka, Fukuoka 5K030 GA05 HA10 HB14 KA03 KA05 KA15 KX11 KX18 KX28 LA19 LB07 LD04

Claims (8)

[Claims] An ATM switch for performing a logical multicast in an extended function unit for performing traffic processing in a cell switch or at a stage subsequent to the cell switch, wherein information for routing a unicast cell, a physical multicast cell, and a logical multicast cell is provided. An ATM switch comprising: a stored routing table; and routing means for performing a logical multicast in addition to a unicast cell and a physical multicast cell with reference to the routing table. 2. The method according to claim 1, wherein the routing table includes a VPI /
2. The ATM switch according to claim 1, wherein routing information derived from VCI or VPI / VCI is stored, and said routing means performs a transfer process by referring to said routing information and performs a logical multicast process. 3. The routing table has a different table reference structure between unicast and multicast.
The routing processing unit may perform a data copy process, a header rewrite process, and a cell output process performed by referring to the routing table in the same process in unicast, physical multicast, and logical multicast. Item 6. The ATM switch according to item 2. 4. The routing table includes destination port output information for a unicast cell, VPI / V
The primary conversion table in which pointer information to the secondary table for the CI and the multicast cell is stored, and the output port information of the destination for the physical multicast cell and the logical multicast cell, and the VPI / VCI are stored at the position designated by the pointer information. 4. The ATM switch according to claim 3, further comprising a stored secondary conversion table. 5. An ATM switch capable of outputting a unicast cell, a physical multicast cell, and a logical multicast cell to an output port according to destination information, wherein the ATM switch
A header information reading processing unit for reading header information, a routing processing unit for routing cells, and a copying process for duplicating data in an extended function unit that performs traffic processing in a cell switch or a subsequent stage of the cell switch in the M switch. An ATM switch, comprising: a unit, a header information rewriting processing unit for rewriting header information, and an output processing unit for outputting cells. 6. A logical broadcast communication method for an ATM switch capable of outputting a unicast cell, a physical multicast cell, and a logical multicast cell to an output port corresponding to destination information, comprising: a cell switch in the ATM switch or a subsequent stage of the cell switch. VPI / VCI or VPI / VC from each cell in an extended function unit for performing traffic processing and the like.
The secondary cell generated from I is taken out, the respective cell data is stored in the buffer memory, and the multicast cell copies the data of the number of destination records and converts the header by referring to the table having the routing table function. A logical broadcast communication method for an ATM switch, wherein the output is sent to a destination. 7. The routing table stores output port information of a destination, VPI / VCI, identification information of unicast or multicast, and the number of records indicating a multicast destination of a multicast cell. 7. The logical broadcast communication method for an ATM switch according to claim 6. 8. The routing table includes destination output port information for a unicast cell, VPI / V
Primary conversion table storing pointer information to a secondary table for CI and multicast cells, and secondary conversion storing physical multicast and logical multicast destination output port information stored at the pointer position and VPI / VCI 8. The method according to claim 7, wherein the routing table is referred to by unicast and multicast.
Logical broadcast method of TM switch.