JPH1056456A - Multi-point aal5 communication trunk and atm switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a storage capacity required for a terminal equipment by allowing a reception terminal equipment to receive a packet from a plurality of transmission terminal equipments with one virtual circuit(VC) and to decrease the number of VCs stored by the reception terminal equipment in the AAL5 communication using a high order layer having a function of describing an identifier of the terminal equipment. SOLUTION: An input of a trunk 11 and an optional output port of a switch 10, and the output of the trunk 11 and the optional input port of the switch 10 are connected respectively. When a cell transferred by multi-point multiplex asynchronous transfer mode(ATM) is given to the switch 10, the switch 10 rewrites a label value of the cell, the port at switch input, a label value at the time of an input to the trunk 11 corresponding to the label value, the trunk 11 transfers the cell to the connected port, and the trunk 11 rewrites the label value of the cell into a label value at output from the trunk 11 corresponding to the port and label value when the cell is outputted finally from the switch 10 and gives the cell again to the switch 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM (Asyn)
The present invention relates to an ATM trunk and an ATM switch for transmitting information between one or a plurality of data terminals by means of a transfer (chronous transfer mode), and more particularly to an ATM trunk and an ATM switch for multipoint AAL5 communication.

[0002]

2. Description of the Related Art ATM transfer is based on ITU-TI. This is a data transfer method internationally recommended by the ITU-T Recommendation 361 ("ATM Layer" of ITU-TI.361). In the ATM transfer, data transfer is performed in units of fixed-length packets (called cells). Each cell is provided with a label, and the terminal uses the label to identify the communication partner terminal, and the relay node (switch) identifies the data transfer destination. The cell transfer path from the transmitting terminal to the receiving terminal identified by the label value is
It is called VC (Virtual Circuit). Also,
An input identified by a combination of a port and a label value is called an input system, and an output identified by a combination of a port and a label value is called an output system. Note that the label value is VPI (Virtual Pass Identity) / VC
I (Virtual Circuit Identification). A relay node (switch) is an input port (terminal)
And a plurality of output ports, and holds a table (routing table) for specifying the correspondence between the port and label value at the time of cell input and the port and label value at the time of cell output. Therefore, when a cell is input, the relay node refers to the routing table to check an output system corresponding to the input system, and outputs the cell to the specified output system. In this case, the routing table associates one input system with a plurality of output systems, associates a plurality of input systems with one output system, and associates one or more input systems with one or more output systems. This allows the relay node to change the input-to-output relationship not only for one-to-one transfers but also for one-to-N
(N is an integer exceeding 1), M to 1 (M is an integer exceeding 1), and M to N can be transferred.

[0003] In the following description, in the above description, the ATM transfer performed by associating a plurality of input systems with one or a plurality of output systems in a routing table is performed by multipoint multiplexing A.
This will be referred to as TM transfer. When communicating data,
The transmitting terminal performs a process of dividing data to be transmitted into one or a plurality of cells and transmits the cells, and the receiving terminal performs a process of assembling and reproducing data from the received one or a plurality of cells. In general, in data communication, ITU-TI. 363-5 ("ATM A
A method called AAL5 recommended in daptation Layer Type 5 ") is used.
It is characterized in that a certain bit in the header of the ATM cell is used to indicate the division of one AAL5 frame. That is, ITU-TI. Recommendation 361 includes PTI
AAL5 uses the third bit of the PTI as a bit indicating this purpose, that is, a frame delimiter, in the cell header. Of the cells forming one AAL5 frame, this bit, that is, the bit indicating the delimiter, is set to 1 for the last cell of the AAL5 frame, and this bit is set to 0 for the other cells. In the following, P
A cell in which the third bit of the TI is 1 is called a cell with an end flag.

[0004]

Here, as in the case where an IP packet is transferred in an AAL5 frame, an AA using an upper layer having a function of writing a terminal identifier is used.
Consider the L5 communication. In this case, since the receiving terminal does not need to identify the transmitting terminal by the label value, communication is possible even if packets from a plurality of transmitting terminals are received with one label value, that is, one VC. As a result, the number of VCs that the receiving terminal should hold simultaneously can be reduced. However, according to the conventional technique, the receiving terminal sends one V to the transmitting terminal even in the above-described communication for the following reason.
C was set. That is, in the case of the communication as described above, the switch needs to perform multipoint multiplex ATM transfer in order to multiplex cells transmitted by a plurality of transmitting terminals and transfer the cells to a certain receiving terminal. When performing multipoint ATM multiplex transfer, the switch performs different AAL5 transmissions from a plurality of different input systems to perform transfer processing for each cell.
If cells forming a frame are input to the switch at the same time, cells forming different AAL5 frames will be mixed in the output of the switch before and after. When communication is performed using AAL5, the receiving terminal sets 1 from the cell next to the cell with the end flag to the next cell with the end flag.
Since the cells are regarded as cells constituting one AAL5 frame, the above-mentioned phenomenon makes it impossible for the receiving terminal to normally reproduce the AAL5 frame.

FIG. 2 is a diagram showing a conventional transfer by an ATM switch. Normally, the label value in an ATM cell is 2 bits of a 12-bit VPI value and a 16-bit VCI
In FIG. 2, the label value is represented by a single numerical value for simplicity. The numerical value (40) in the box is the label value. As described above, conventionally, in the receiving terminal, AAL
Reproduction of 5 frames could not be performed normally. Therefore, as one method of solving this, when the switch performs cell transfer, cell transfer is performed for a certain input system until a cell with an end flag is transferred, and during that time cells from other input systems are transferred. A back pressure method of performing a process of not performing the process is conceivable. However, the use of the back pressure method causes a problem of blocking in which the transfer of all cells arriving at the port having the input system whose transfer is stopped is stopped. An object of the present invention is to solve such a problem and to provide a different AA when a switch performs multipoint multiplex ATM transfer.
A multipoint AAL capable of preventing the cells constituting the L5 frame from being mixed up and down, and preventing other cell transfer from being blocked at that time.
(5) To provide an ATM trunk and an ATM switch for communication.

[0006]

To achieve the above object, a multipoint AAL5 communication trunk and ATM switch of the present invention multiplex a plurality of cells input from a plurality of input systems having different input ports or label values. AAL transmitted by a plurality of different transmitting terminals on a VC in which one or a plurality of receiving terminals exist using multipoint multiplex ATM transfer for transferring to one or a plurality of output systems
AT that performs cell switching in multipoint AAL5 communication that receives information based on a five-frame structure
The M switch (10 in FIG. 5) and the ATM switch (1
0) has its input connected to any output port (D), and its output is connected to any input port (D) of the ATM switch (10). A one-to-one relationship between a trunk device (11 in FIG. 5) that rewrites and outputs a label value and a port and label value when a cell is input to an ATM switch and a label value when the cell is input to the trunk device. The first decided to be
Of the routing table (FIG. 5 (b)) and the correspondence between the port and the label value at which the cell is to be finally output from the ATM switch and the label value at the time of output from the trunk device are in a one-to-one relationship. The ATM switch (10) is provided with a second routing table (FIG. 5 (c)) so that when a cell to be subjected to multipoint multiplex ATM transfer is inputted, the label value of the cell is inputted. Is rewritten to the label value at the time of input to the trunk device (11) corresponding to the port and label value at the time of inputting the ATM switch, and transferred to the port (D) to which the trunk device (11) is connected. The trunk device (11) outputs the label value of the cell at the time of output from the trunk device corresponding to the port and label value when the cell is finally output from the ATM switch. Rewrite the bell value, the ATM
It is characterized by inputting again to the switch (10).
Further, the trunk device (11) holds a second routing table (FIG. 5 (c)) for specifying a correspondence between a label value at the time of input of a cell and a label value at the time of output of the cell. A first memory (27 in FIG. 4) for temporarily storing input cells, the number of which is equal to the number of labels at the time of input, and a cell in which the third bit of the PTI is 1 in the stored cells Is stored in the second memory (26 in FIG. 4) for a flag indicating 1 if it is included, and 0 otherwise.
A separating unit (23 in FIG. 4) for separating cells according to the label value of the input cell and storing the cells in the storing unit (25) corresponding to the label value;
The cell in the storage means (25) whose flag is 1 is set to P
Continue reading until the cell where the third bit of TI is 1;
A multiplexing means (22 in FIG. 4) for rewriting and outputting the label value in accordance with the second routing table (21 in FIG. 4) is also characterized.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle and embodiments of the present invention will be described below in detail with reference to the drawings. First, the principle of the present invention will be described. In the present invention, this is realized by the connection configuration between the trunk and the switch, the routing setting process, and the configuration inside the trunk. FIG. 1 is a diagram illustrating the configuration of a switch and an operation from a switch input to an output of a cell according to an embodiment of the present invention. Hereinafter, a connection configuration between the trunk and the switch will be described. In FIG. 1, 10 is A
TM switch, 11 is a trunk for multipoint AAL5 communication, 12 is the label value of the cell at the time of input to the first switch, 14 is the label value of the cell at the time of output from the second switch, and 13 is the label value of the cell from the trunk. The label value of the cell at the time of output (at the time of input to the second switch), 15 is the label value of the cell at the time of input to the trunk (at the time of output from the first switch), and 17 is the input value to the first switch Cell port at the time, 18 is the output port of the switch to which the output of the trunk is connected, 19 is the port of the cell at the time of output from the second switch, and 20 is the output port of the switch to which the input of the trunk is connected It is. In the connection configuration between the trunk and the switch, a routing table that specifies the correspondence between label values at the time of cell input and label values at the time of output is maintained, the input cells are stored once, and the label values are rewritten according to the routing table. A trunk 11 having a function of outputting the data is prepared. Next, the input port of the trunk 11 is connected to the output port 20 having the switch 10, and the output port is connected to the input port 18 having the switch 10. And the switch 10
When a cell to be subjected to multipoint multiplex ATM transfer is input, the cell is transferred to the port to which the trunk 11 is connected once.

According to the configuration, multipoint multiplex AT
After the cell to be subjected to the M transfer is first input to the switch 10, the cell is input from the switch 10 to the trunk 11, re-input from the trunk 11 to the switch 10, and finally output from the switch 10. At this time, the port 17 and the label value 12 at the time of the first switch input of the cell are set to P SW
IN, L SW IN, port 20 and label value 15 at the time of trunk input (at the time of first switch output) are PT
R IN and L TR IN, and port 18 and label value 13 at the time of trunk output (at the time of second switch input) are P
TR IN, L TR OUT, last (2nd time)
The port 19 and the label value 14 at the time of the switch output of the
W OUT, L SW OUT. For cells to which a plurality of final output systems correspond, P SW OU
T, L SW OUT is a set of a plurality of ports and label values. In this case, the switch 10 is configured to perform multicast (AT in which a plurality of output systems correspond to the input system 1).
M transfer) function. Of the cell to be subjected to the multipoint multiplex ATM transfer by the trunk 1
Since the cells are once detoured to one, it is possible to prevent cells from performing normal transfer by these cells.

FIG. 3 is a diagram showing a routing table setting procedure according to an embodiment of the present invention. Hereinafter, the routing setting processing will be described. Given input port PSW IN, label value L SW IN, output port P
SW OUT, label value L SW OUT
The setting of the routing table of the switch 10 and the trunk 11 is performed as follows. As in procedure 2 of FIG. 3, (P
SW IN, L SW IN) and L TR IN have a one-to-one relationship, and the value of L TR IN is assigned, and (P SWIN, L SW IN) and L TRI
The correspondence of N is determined. In addition, (P SW OUT, L
SW OUT) and L TR OUT are one-to-one.
Assign the value of L TR OUT so that
(PSW OUT, LSW OUT) and LTRO
Define the correspondence with the UT. Then, as in step 3 of FIG. 3, the cell input to (P SW IN, L SW IN) is output to (PTR IN, L TR IN) and input to (P TR OUT, L TR OUT). The routing table of the switch 10 is set so that the changed cell is output to (PSW OUT, LSW OUT). Further, the routing table of the trunk 11 is set so that the cell input at L TR IN is output at L TR OUT. In the embodiment shown in FIG. 3, as shown in Procedure 1, the input (P SW IN1, L
SW IN1) and (P SW IN2, L SW IN
The cells input from 2) are multiplexed and (PSW OU)
T1, L SW OUT1) and input (P SW
IN3, L SW IN3) and (P SW IN4,
The figure shows a case where the cells input from L SW IN4) are multiplexed and transferred to (P SW OUT2, L SW OUT2). After the first switch input of the cell, the cell is transferred from the switch 10 to the trunk 11 with a different label value due to the difference in the input system, and then the cell is transferred from the trunk to the switch 10 by the difference in the system from which the cell is to be output. Can be re-input with a different label value.

Hereinafter, the definitions of terms used in the present invention will be described. The label value is a VPI / VCI value, the input system is an input identified by an input port and a label value at the time of input, and the output system is identified by an output port and a label value at the time of output. Output. Further, the multipoint AAL5 communication is communication for receiving information based on the AAL5 frame structure issued by a plurality of different transmitting terminals in a VC where one or a plurality of receiving terminals are present, and the multipoint multiplex ATM transfer is This is an ATM transfer in which a plurality of cells input from a plurality of input systems are multiplexed and transferred to one or a plurality of output systems. The cell with an end flag is a cell in which the third bit of the PTI is “1”. Note that P SW IN and L SW IN are cell ports (P
SW IN) and a label value (L SW IN).
TR IN is the output port of the switch to which the input of the trunk is connected, and P TR OUT is the input port of the switch to which the output of the trunk is connected. L TR IN is a label value of a cell at the time of input to the trunk (at the time of output from the first switch),
L TR OUT is defined as the time of output from the trunk (from the time of output from the second switch to the port (PSW) of the cell.
OUT) and a label value (L SW OUT).

FIG. 4 is a configuration diagram of a trunk showing an embodiment of the present invention. Hereinafter, the configuration of the trunk will be described. As shown in FIG. 4, the trunk 11 includes a routing table 21 for specifying a correspondence relationship between a label value at the time of input of a cell and a label value at the time of output, and a plurality of memory units which are provided by the number of labels at the time of input. 25, an input separation unit 23 that sorts cells according to the label value of the input cell and stores the cells in the memory unit 25 corresponding to the label value, and ends the cells in the memory unit 25 whose flag is 1 A multiplex output unit 22 is provided for continuously reading out the cells with flags and rewriting and outputting the label values in accordance with the routing table 21. Note that one memory unit 25 indicates a memory 27 for temporarily storing input cells, and indicates 1 if a cell with an end flag is included in the stored cells. If not, a memory 26 for a flag indicating 0 is provided. With the configuration described above, the trunk 11 can multiplex and output cells input with different label values in units of AAL5 frames. As described above, by simultaneously providing the above configuration, cells to be subjected to multipoint multiplex ATM transfer input to the switch 10 are multiplexed in units of AAL5 frames without blocking other ATM transfers and output. To the output system (port, label value) to be performed.

FIG. 5A is an operation diagram of the whole switch showing an embodiment of the present invention, FIG. 5B is a diagram of a switch body routing table, and FIG. 5C is a diagram of a trunk routing table. FIG. In FIG. 5A,
The combination of (port, label value) is (A, 40),
A plurality of cells input from three input systems (B, 40) and (C, 40) are multiplexed, and (A, 40), (B, 4)
2 shows an example of simultaneous distribution to three output systems of (C) and (C, 40). The input of the trunk 11 is connected to the output port D of the switch 10, and the output of the trunk 11 is connected to the input port D of the switch 10. As shown in FIG. 5B, (A, 4)
The cells input at (0), (B, 40), (C, 40) are transferred to (D, 50), (D, 51), (D, 52), and input at (D, 60). Cell (A, 4)
0), (B, 40), and (C, 40). As shown in FIG. 5C, the routing table of the trunk 11 has label values 50,
It is specified that the cells input at 51 and 52 are rewritten to the label value 60 and output. That is, in the present invention, the cell input from the input port is converted from the label value 40 to 50, 51, 52 by the switch 10, and is input to the multipoint AAL5 communication trunk 11 from the output port at the crossing position. So the label values 50,5
By converting 1, 52 to a label value 60 and inputting it again to the switch 10, the switch 10 converts it to the label value 40.

FIG. 6 is a diagram illustrating the operation of a trunk according to an embodiment of the present invention. The trunk 11 includes a routing table 21, a multiplexing unit 22, a separating unit 23, and a memory unit 25. After the cell is input to the switch 10 for the first time, the cell is transferred to the port (D) to which the trunk 11 is connected. At this time, based on the routing table of the switch 10, the label value of the cell input from (A, 40) is 50, and the label value of the cell input from (B, 40), (C, 40) is respectively Rewritten to 51 and 52.
The trunk 11 recognizes the difference of the input system of the cell to the switch 10 by the difference of the label value, multiplexes the cells input from the different input systems in units of AAL5 frame, and based on the routing table 21 of the trunk 11, the label value. Is rewritten to 60 and output. The output cell is input to the switch 10 from the port D again. The switch 10 converts the cell input second time into (A, 4) based on the routing table of the switch 10.
0), (B, 40), and (C, 40).

[0014]

As described above, according to the present invention,
In AAL5 communication using an upper layer having a function of writing terminal identifiers, a receiving terminal can receive packets from a plurality of transmitting terminals with one VC. As a result, the number of VCs to be held by the receiving terminal can be reduced, and the required storage capacity of the terminal can be reduced, thereby facilitating the line setting of the terminal when performing communication.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a switch and a path of a cell from a switch input to an output according to an embodiment of the present invention.

FIG. 2 is a diagram showing transfer by a conventional ATM switch.

FIG. 3 is a diagram illustrating a routing setting procedure according to an embodiment of the present invention;

FIG. 4 is a configuration diagram of a trunk showing one embodiment of the present invention.

FIG. 5 is an explanatory diagram of the operation of the entire switch showing one embodiment of the present invention.

FIG. 6 is an explanatory diagram of an operation of a trunk showing one embodiment of the present invention.

[Explanation of symbols]

10: ATM switch, 11: Multipoint AAL5
Communication-supporting trunk 12 ... Cell label value at the time of input to the first switch 13 ... Cell label value at the time of output from the trunk (input to the second switch) 14 ... Input to the first switch Cell port at time 15: Cell label value at the time of input to the trunk (at the time of output from the second switch) 17: Port of the cell at the time of input to the first switch 18 ... Output of the trunk is connected Input port 19 of the switch that is present 19 Port number of the cell from the time of output from the second switch 20 ... Label value of the cell at the time of input to the trunk (at the time of output from the first switch) 11 ... Trunk, 22 ... Multiplexer, 23 ... separator, 24 ...
Memory unit group 25: memory unit, 26: memory for flag, 27: memory for cell storage.

Claims (2)

[Claims] 1. A multipoint multiplex ATM for multiplexing a plurality of cells input from a plurality of input systems having different input ports or label values and transferring the multiplexed cells to one or more output systems.
VC with one or more receiving terminals using forwarding
In a multipoint AAL5 communication that receives information based on an AAL5 frame structure transmitted by a plurality of different transmitting terminals, an ATM switch that performs cell switching, and an input of the ATM switch is connected to an arbitrary output port of the ATM switch. The output is connected to an arbitrary input port of the ATM switch, and the input cell is stored once,
A trunk device that rewrites and outputs a label value, and a correspondence relationship between a port and a label value when a cell is input to the ATM switch and a label value when the cell is input to the trunk device is determined to be a one-to-one relationship. The first routing table, and the correspondence between the port and the label value at which the cell is to be finally output from the ATM switch and the label value at the time of output from the trunk device are determined so as to have a one-to-one relationship. A second routing table, wherein, when a cell to be subjected to multipoint multiplex ATM transfer is input, the ATM switch changes the label value of the cell to the port and label value corresponding to the port at the time of inputting the ATM switch. The trunk device rewrites the label value at the time of input to the trunk device and transfers the label value to the port to which the trunk device is connected. The value is rewritten to the label value at the time of output from the trunk device corresponding to the port and label value at the time when the cell is finally output from the ATM switch, and re-input to the ATM switch. Multipoint AAL5 communication trunk and ATM switch. 2. The trunk device holds the second routing table for specifying a correspondence between a label value at the time of input of a cell and a label value at the time of output, and the number of labels at the time of cell input. And a first memory for temporarily storing the input cell, and 1 if the third bit of the PTI is 1 in the stored cells. If not, a storage means having a second memory for a flag indicating 0; a separation means for separating the cell according to the input label value of the cell and storing the cell in the storage means corresponding to the label value The cell in the storage means whose flag is 1 is continuously read out until the cell in which the third bit of the PTI is 1;
And multiplexing means for rewriting and outputting the label value according to the routing table of (1).
2. A multipoint AAL5 communication trunk and ATM switch according to item 1.