JP2624834B2 - Label conversion circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital electronic exchange, and in particular, exchanges communication information using a fixed-length packet (hereinafter, referred to as a "cell") comprising a header section and an information section. The present invention relates to a configuration of a label conversion circuit for rewriting the contents of a header portion and a reference number assignment circuit for assigning a reference number for identifying a call inside the exchange in a self-routing type exchange.

[Conventional technology]

A typical example of the conventional technology is the IEICE technical report (switching system workshop) SSE88-29 "ATM for wideband ISDN.
There is an exchange shown in "Prototype of exchange" (Kato, Hatsukano, Shimoe, Murakami). The label conversion method is shown in FIG. 3 of the above-mentioned document. According to this method, a label conversion table is provided in front of a switch, the conversion table is drawn using the call identifier of an input cell as an address, and routing information in the switch is obtained. And a new call identifier. The contents of the label conversion table are written by sending data from the control system of the exchange at the time of call setting.

[Problems to be solved by the invention]

In the above-mentioned prior art, there is a problem that a large-capacity label conversion table is required. The call identifier must have a bit length with sufficient margin for the communication volume.
In some cases, it is necessary to identify a path, which is a management unit of a transmission path, and a line corresponding to a call identifier, so that the bit length is considered to be 20 bits or more. Therefore, the memory used as the conversion table is only 2 addresses.
^Since the capacity is ²⁰ , a capacity of several tens of Mbits to several hundreds of Mbits per line is required. This is an unrealistic value, although the integration of the memory is increasing.

An object of the present invention is to provide a label conversion circuit that requires a relatively small storage capacity for a label conversion table. Another object of the present invention is to provide a reference number assigning circuit necessary for realizing the label converting circuit.

[Means for solving the problem]

The basic idea for achieving the above object is to decompose the call identifier, make it possible to use a plurality of conversion tables and realize it with one table memory device of one chip, make the conversion tables hierarchical, and The idea is to compress the address space when moving. Specific means will be described below.

First, in order to achieve the first object, a plurality of conversion tables for dividing a bit string of a call identifier included in a header portion into a plurality of parts and converting each of the divided parts into corresponding reference numbers, We have devised a label conversion circuit having a conversion table for converting a call identification number in a switch to which a number bit string is connected into an output terminal number of a switch and a new call identifier.

Further, in order to prevent a problem in circuit operation even if a signal cell used for communication of a signal for exchange control is input to the label conversion circuit, cell type information included in a header portion is detected, and Means for detecting whether the cell is a signaling cell for switching control and, if the signaling cell is a signaling cell, means for not converting the call identifier, and transmitting the contents of the cell to the control mechanism of the exchange. Means.

Next, in order to achieve the second object, a signal cell is used as input information, and a bit string of a call identifier included in a header portion of the signal cell is divided into a plurality of parts, and each of the divided parts is referred to by a corresponding reference numeral. We devised a reference number assignment circuit that has multiple conversion tables that convert to.

Further, in the reference number assignment circuit, in order to minimize the storage capacity of the conversion table, it is detected that the content of the conversion table for converting the divided call identifier into the reference number is a specific bit pattern (for example, all zeros). A comparison circuit that performs a comparison, a means for writing a new reference number to the conversion table when the result of the comparison is a specific bit pattern, and writing the bit pattern as an address when the result of the comparison is not a specific bit pattern, And a reference number management table that can be read, and means for detecting whether or not the content of the management table is zero, and rewriting the bit pattern in the conversion table to a specific bit pattern when the content is zero. Means for increasing or decreasing the content of the management table based on the signal identification information included in the signal cell. It has devised a number assignment circuit.

[Action]

In the information communication phase, the plurality of conversion tables of the label conversion circuit are extracted from the cell for information communication and convert the bit strings of the divided call identifiers into reference numbers each having a smaller number of digits. These multiple reference numbers,
The call is uniquely identified by the combined bit string. The bit length of this bit string may be any value as long as it can express a numerical value with a sufficient margin for the number of calls simultaneously communicated on one line.
Therefore, the present conversion table serves to reduce the bit length by converting the call identifier into the reference number, and to reduce the address space required for the call identification.

The reference number assignment circuit decomposes the bit string of the call identifier included in the signal cell in the call setting phase and converts the bit string into a reference number. The disassembled bit string may have the same value as the disassembled bit string in other call identifiers. In this case, the same reference number is assigned. However, when the same reference number is assigned, how many times the reference number is used is stored in a separately provided reference number management table. Since the bit length required for this storage can be even smaller than the bit length of the reference number itself, the amount of memory required for the entire table can be reduced.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, FIG. 2 is a schematic block diagram of a configuration example of a self-routing type exchange. In this exchange, one line is accommodated, and cell switching is performed by the self-routing switch 300. The line corresponding unit (input line side) 100 and the line corresponding unit (outgoing line side) 200 are circuits provided for each line. Among them, the line corresponding unit (input side) 100 is provided before the switch, one input line is input, and the input terminal of the switch is connected as an output. The line corresponding unit 100 has a label conversion function such as replacement of a call identifier of an input cell and addition of routing information in a switch. On the other hand, the line corresponding unit (outgoing line side) 200 is provided after the switch, and one of the outputs from the switch is connected as an input and the output line is connected as an output. The line corresponding unit 200 has a function of receiving a signal cell from the control mechanism 400 and rewriting the conversion table of the line corresponding unit (input side) 100. The control mechanism 400
One of the outputs of the switch is connected as an input, and one of the inputs of the switch is connected as an output.

Next, various cell formats are shown in FIG. Here, as an example, it is assumed that the call identifier is decomposed into two, I1 and I2. I1 and I2 may be, for example, meanings such as a path identifier and a line identifier, or may be simply divided bit strings. In the following description, the symbols in FIG. 5 may be used without any particular notice.

In the call setup phase of the self-routing type exchange shown in FIG. 2, a signal cell carrying call setup information (DN, I1, I2, etc.) arrives at the line corresponding unit (incoming side) 100, where control is performed. An output terminal number (DA ') and an input terminal number (SA) to be connected to the mechanism section 400 are added and sent out. The control mechanism unit 400 assigns the reference numbers (r1, r2) based on the reserved call identifiers (I1, I2) included in the call setting information of the signaling cell, and a new identifier used as the call identifier on the outgoing line side. (I1 ', I2') and the output terminal number (DA) of the switch are determined, and the signal cell carrying these pieces of information is sent to the line corresponding unit (outgoing line side) 200. The line corresponding unit (outgoing line side) 200 writes the received information in the conversion table of the line corresponding unit (incoming line side) 100. Here, the line corresponding section (input line side) 100 and the line corresponding section (outgoing line side) 200 are actually integrated as shown in FIG.

In the information transfer phase, the line handling section (incoming side)
The cell arriving at 100 is subjected to label conversion, added with an output terminal number and the like, and sent out to the self-routing switch 300. The switched cell has its output terminal number and the like removed in the line corresponding section (outgoing line side) 200 and is sent out to the output line.

FIG. 3 shows an example of the configuration of the control mechanism section 400. A plurality of reference number assignment circuits 4100 are provided for each line. The input signal cells are sorted by the sorting mechanism 4200 based on the input terminal number (SA). The output signal cells from each reference number assignment circuit 4100 are collected by the concentrator 4300 and sent to the self-routing switch 300.

Next, the label conversion circuit will be described in detail with reference to FIG.

First, the input line is connected to the input register 101 and the delay circuit 109.
Is connected to the output register 102 via the. Input register 1
From 01, extraction lines for I1 and I2 are provided and connected to the read address inputs of the conversion table 103 [TAB 1c] and the conversion table 104 [TAB 2c], respectively. The I1 extraction line is also connected to the signal cell detection circuit 106.
Each data output line of the conversion tables 103 and 104 is connected to a read address input of the conversion table 105 [TAB 3c]. The data output line of the conversion table 105 is connected to the output register 102 via the gate 107. Gate 1
07 is connected to the output of the signal cell detection circuit 106. The output of the input terminal number setting circuit 108 is output register 1
Connected to 02. The output of the output register 102 is connected to one of the input terminals of the self-routing switch 300.

On the other hand, one of the output terminals of the switch is
It is connected to the output register 203 via 1 and the delay circuit 205. From the input register 201, various extraction lines are connected to the transfer register 202. Transfer register 2
Of the various output lines 02, the call identifiers I1 and I2 are respectively connected to the write address inputs of the conversion tables 103 and 104 and the write address input of the conversion table 105, and the reference numbers r1 and r2 are connected to the data inputs of the conversion tables 103 and 104, respectively. ing. New identifiers (I1 ′, I2 ′) used as call identifiers on the outgoing line and output terminal numbers (DA) of the switches are connected to the data input of the conversion table 105. Note that the call identifier clear circuit 204 is a circuit for converting the received and used signal cells into empty cells.

The operation of the label conversion circuit will be described with reference to FIG. FIG. 6 shows a state of conversion by the conversion table. Call identifier I broken down into N and M bits
1 and I2 are converted to reference numbers r1 and r2 by pulling the conversion tables 103 and 104 using these as read addresses. Next, by reading a conversion table 105 as a read address, a numerical value obtained by combining r1 and r2 (for example, when r1 is the upper bit and r2 is the lower bit, abbreviated as “r1 + r2”), a new call is obtained. Identifiers (I1, I2) and output terminal numbers (D
A) is obtained. The incoming terminal number (SA) is uniquely determined by the physical location of the line. These are added to the header part of the cell, or the header part is converted, thereby forming a cell in the switch. When the input cell is a signal cell, the conversion is not performed, and the terminal number connected to the control mechanism is added as the output terminal number.

When the above conversion method is adopted, the bit length of r1 is
N may be shorter than I1, and the bit length of r2 may be m shorter than I2. This is because a call that makes full use of the bit length of the call identifier is not established on one line at a time.

Here, a specific example will be given for comparison. N = 1
In the case of 2, M = 16, U = 10 (bits), in the case of the conventional method, that is, conversion by one table, it is 2 ^{12 + 16} × 12 + 16 + 10, which is a memory capacity of about 10 G bits. On the other hand, n
If = m = 8, then 2 ¹² × 8 + 2 ¹⁶ × (12 + 16 + 10), which is about 2.5 Mbits. The former is an unrealistic setting, while the latter is a feasible value at present when a 1-Mbit class one-chip memory is available.

Next, the reference number assignment circuit will be described with reference to FIG.
The input line from the output terminal of the switch via the distribution mechanism 4200 shown in FIG.
Connected to An extraction line for call setting information and the like (signal information including call disconnection information and the like) is connected to a read address input of the conversion table 4111. At the same time, the I1 portion of the above information is connected to the read address input of the conversion table 4102. The data output of the conversion table 4111 is connected to the output register 4110. The data output of the conversion table 4102 is connected to the register 4104 and the comparison circuit 4103. Among the outputs of the comparison circuit, the output when it is not 0 is the enable input of the register 4104. On the other hand, when the output is 0, the reference number storage circuit 41
06 [FIF01] is the output enable input. The output of the register 4104 is connected to the output register 4110 via the reset circuit 4112. Further, the output is also an input of a read address of the reference number management table 4105 and an input of the reference number storage circuit 4106. The data output of the reference number storage circuit 4106 is connected to the comparison circuit 4107. The output of the comparison circuit 4107 is the reset input of the reset circuit 4112 and the input enable input of the reference number storage circuit 4106. From the input register 4101, a line for extracting J1 and signal type K, which are call identifier parts, is connected to a signal type detection circuit 4109, and the output thereof is connected to a data increment / decrement circuit 4108. The output of the data increment / decrement circuit 4108 is the data input of the reference number management table 4105.
The circuit corresponding to the remaining part of the call identifier, J2,
Since the configuration is the same as that of the circuit corresponding to J1, the details are omitted.

The operation of the above circuit is shown in FIG. Look up the conversion table for each of I1 and I2 included in the call setting information, and
Get 1, c2. (Hereinafter, only the I1 side will be described.) When c1 is a specific pattern, for example, 0, this I1 is used for the first time, and at this time, r1 is extracted from the reference number storage circuit as a new reference number, Replace with c1 on the conversion table. On the other hand, if c1 is not 0, since this I1 has already been used, the reference number management table is retrieved using the value of c1. Then, the number of times c1 is currently used is written as q1 there, and in the case of call setup, this value is further increased by one. In the case of a call disconnection, it is decremented by one. If q1 is 0, it means that all calls using r1 have been disconnected, and therefore r1 is returned to the reference number storage circuit. At the same time, the transfer to the output register is stopped.

From the call setting information (for example, the dial number: DN), the conversion table [TRANS] is used to obtain new call identifiers I1 'and I2'.
And the output terminal number DA. The contents of the inter-edge table are set by a control system (not shown) in a series of call setting procedures.

The conversion table of the present circuit also has the same configuration as the above-described label conversion table, and the memory capacity can be reduced by adopting this configuration. In the reference number management table, the bit width is smaller than n and m, and the number of words is 2 ⁿ to 2 ^m.
The amount of required memory is extremely small.

〔The invention's effect〕

As described above, the present invention provides a label conversion circuit,
Since the conversion table is divided and hierarchized, the required functions can be realized with an extremely small amount of memory compared to using a single conversion table.

In addition, in the reference number assigning circuit which is effective for hierarchizing the conversion table, the same division and hierarchization of the conversion table are performed, so that the same amount of memory can be reduced as in the label conversion circuit. As an example, when a conventional method requires a memory capacity of about 10 Gbits for a line, an equivalent function can be realized with a memory capacity of 2.5 Mbits, which is about 1/4000 of this.

[Brief description of the drawings]

FIG. 1 is a block diagram of a label conversion circuit according to an embodiment of the present invention, FIG. 2 is a block diagram of an exchange using the label conversion circuit of FIG. 1, and FIG. 3 is a part of FIG. FIG. 4 is a block diagram of a reference number assigning circuit according to an embodiment of the present invention, FIG. 5 is a structural diagram of a cell handled by the exchange of this embodiment, and FIG. 6 is a diagram of FIG. FIG. 7 is an explanatory diagram of the operation, and FIG. 7 is an explanatory diagram of the operation of FIG. 100: Line-corresponding section (incoming line side) 200: Line-corresponding section (outgoing line side) 300: Self-routing switch 400: Control mechanism section 103, 104, 105: Conversion table 4102: Conversion table 4105: Reference number management Table 4106 …… Reference number storage circuit

Claims (3)

(57) [Claims] 1. A self-routing type exchange for exchanging communication information using a fixed-length cell comprising a header section and an information section, wherein a bit string of a call identifier included in the header section is divided into a plurality of bits, and A plurality of conversion tables for converting the bit strings into corresponding reference numbers, and a conversion table for converting the in-switch call identification number obtained by combining the plurality of reference number bit strings into an outgoing terminal number of a switch and a new call identifier. A label conversion circuit, comprising: 2. A means for detecting the type information of the cell included in the header section and detecting whether the cell is a signaling cell for switching control, and a caller when the cell is the signaling cell. 2. The label conversion circuit according to claim 1, further comprising: means for converting the identifier to unconverted; and means for transmitting the contents of the cell to a control mechanism of the exchange. 3. When the cell type of the cell is a signal cell, the output terminal number to be added to the cell is set as the input terminal number of the control mechanism section, so that the contents of the signal cell are controlled by the control mechanism section of the exchange. 3. The label conversion circuit according to claim 2, wherein the signal is transmitted to the label conversion circuit.