JPH05268241A - Header conversion method in ATM exchange - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a communication technology capable of header conversion without requiring a large memory capacity for header exchange of ATM cells used in an ATM exchange system. [Structure] A first conversion table 4 for converting path information into more compressed intermediate path information is provided, and channel information (VCI) is provided corresponding to the intermediate path information (VPI).
Is provided and a second conversion table 5 in which new path information (new VPI) and new channel information (new VCI) are registered is provided,
The header 1 is rewritten by referring to the first conversion table 4 and the second conversion table 5 from the conversion control unit 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique effectively applied to header exchange of ATM cells used in an ATM exchange system.

[0002]

2. Description of the Related Art B-ISDN (Broad-band Integreated)
An ATM (Asynchronous Transfer Mode) exchange method has attracted attention as an exchange method for realizing Service Digital Network (Technology). This ATM switching technology is a technology for accommodating data such as voice or image in a fixed length packet called a cell and transferring it, and a conventional STM (Synchronous Transceiver) which allocates a band fixedly according to the amount of information.
It is expected as a technology that enables the transfer processing of enormous amounts of data such as image information that is difficult to handle with the fer mode) method.

The ATM cell 2 has a 5-byte header and a 4-byte header.
It is composed of an 8-byte information field, and path information (VPI: Virtual Path Identif) is included in the header.
ier) and channel information (VCI: Virtual Channel I)
It has an area called dentifier) in which route information is stored.

In the ATM exchange, the routing information, which is a call identification label, is assigned at the time of setting up a call, and is released at the time of releasing the call. Since a unique value is assigned to this routing information for each link between nodes, it is necessary to convert the routing information each time it passes through each node.

FIG. 11 shows an outline of the ATM switching system. In the figure, in the cell 2 transmitted from the calling terminal device 10 or the relay station through the input highway 8, the VCI and VPI in the header 1 are rewritten by a VC converter (VCC: VCI Convertor),
Intra-station switch (SRM: Self-routing module)
Receiving terminal device 1 through output highway 9 via
1 or another relay station. The VC converter (VCC) rewrites the channel information (VCI) and the path information (VPI) as well as the tag information (TA).
G) is added, but this description is omitted.

The VC converter (VCC) is specifically composed of a conversion table 12 including a memory as shown in FIG. That is, the input path information (VP
I) and rewriting data (TAGX, VPIX, VCIX) corresponding to the channel information (VCI) "X" are held in advance corresponding to all patterns. Then, here, the path information (V
PI) and channel information (VCI) are analyzed, and new path information (new VP) corresponding to this is analyzed from the conversion table 12.
I), new channel information (new VCI) and tag information (T
AG) was taken out and header 1 was rewritten.

[0007]

By the way, when the channel information (VCI) and the path information (VPI) are summed, a 24-bit area is required between the terminal and the exchange, and a 28-bit area is required between the exchanges. 6 for one VCI + VPI
Since the byte information must be stored, the size of the conversion table 12 is required to be 2 ²⁴ × 6 bytes, 96 Mbytes between terminal exchanges, and 2 ²⁸ × 6 bytes, 1.5 gigabytes) between exchanges. There was a problem that was bloated.

In the B-ISDN technology, a dedicated service using VP (Virtual Path) such as image broadcasting is expected, but in this case, the setting of channel information (VCI) is left to the user. In addition to the VC converter (conversion table 12), a VP switch or the like for converting only the path information (VPI) is necessary, and the memory enlargement becomes more serious.

The present invention has been made in view of the above problems, and an object thereof is to provide a communication technique capable of converting a header without requiring a large memory capacity.

[0010]

According to the present invention, there is provided a first conversion table 4 for converting path information into intermediate path information which is more compressed than the path information, and further, the intermediate path information (VP).
I), channel information (VCI) is allocated and new path information (new VPI) and new channel information (new VCI) are registered in the second conversion table 5, and the conversion controller 6 performs the first conversion. The header 1 is rewritten by referring to the table 4 and the second conversion table 5.

[0011]

According to the present invention, as shown in FIG. 1 which is a principle diagram, the cell 2 has its path information (VPI) rewritten into the intermediate path information (intermediate VPI) by the first conversion table 4, and then, In the second conversion table 5, the intermediate path information (intermediate VPI) and the channel information of the cell 2 (V
CI) and new path information (new VPI) and new channel information (new VCI) are determined. Then, the header 1 of the cell 2 is rewritten by these new path information and new channel information, and the exchange switch (SRM: Se) in the station is rewritten.
It is sent to the receiving terminal device 11 or another relay station through the output highway 9 via the lf-routing module).

[0012]

(Embodiment 1) FIG. 2 schematically shows the overall configuration of a communication system according to the present invention. The route from a transmitting terminal 10 to a receiving terminal device 11 is a switch provided in a switch network 18. It is set via the station 3.

On the path, the data output from the transmission terminal 10 is transmitted through the switching network 18 in the packet format called cell 2. Here, the format of the cell 2 in ATM will be described with reference to FIGS. 3 and 4.

FIG. 3 shows the header 1 portion of the cell 2 in the terminal-switching network, and FIG. 4 shows the header 1 portion of the cell 2 between the exchanges 3. The former includes 4-bit flow control information (GFC: Generic Flow).
Control), 8-bit path information (VPI), 12
Bit channel information (VCI) and 2-bit cell 2
Format information (PT: Payload Type) and reserved area (RE
S) and cell 2 discard priority information (CLP: Cell Loss Prio)
rity), and 8-bit header 1 control information (HEC:
Header Error Control).

The latter includes flow control information (GFC).
The path information (VPI) is assigned instead of. Then, both of them follow the header 1 and the information field 15
Is provided.

Cell 2 has path information (V
PI) and channel information (VCI) are sequentially rewritten for each switching center 3 and transmitted through the switching network 18, and finally reach the receiving terminal device 11.

Here, in each exchange 3, the exchange system shown in FIG. 11 described above is provided. The feature of the first embodiment lies in the configuration of the VC converter (VCC). FIG. 5 shows a specific configuration of this VC converter (VCC).

The VC converter (VCC) is provided with a first conversion table 4 and a second conversion table 5 which are controlled by the conversion control unit 6. These conversion tables are composed of a memory accessible from the conversion control unit 6, and the header 1 of the cell 2 is rewritten by both conversion tables to change the exchange switch (SRM: Self-rou
ting module).

First conversion table 4 and second conversion table 5
FIG. 6 shows the contents of the above. In this example,
The first conversion table 4 has a function of sequentially allocating the intermediate path information (intermediate VPI) mapped by 4 bits to the path information (VPI) having an 8-bit structure (assuming a terminal-switched network is assumed). ..

Here, for the first conversion table 4, intermediate path information (intermediate VP) corresponding to the path information (VPI).
An example of setting I) is shown in FIG. In the same figure, for simplification of description, the path information (VPI) is mapped in 4 bits and the intermediate path information (intermediate VPI) is mapped in 3 bits.

As shown in the figure, not all of the path information (VPI) is used at the same time, so the intermediate path information (intermediate VPI) can also be mapped with a small number of bits.

In the second conversion table 5, the tag information (TA) is added to the channel information (VCI) obtained by compressing the channel information (VCI) from 16 bits to 14 bits.
G), new path information (new VPI) and new channel information (new VCI) are respectively assigned, and further set in correspondence with the intermediate path information (intermediate VPI).

In the second conversion table 5, one intermediate path information (intermediate VPI) corresponds to four channel information (VCI). In this example, since the channel information (VCI) is compressed by 2 bits, four pieces of intermediate path information (intermediate VPI) correspond to one path information (VPI) channel. As described above, according to the present embodiment, the first conversion table 4 has 1 Kbit and the second conversion table 5 has 1.5 Mbytes, and it is possible to significantly reduce the memory amount as compared with 96 Mbytes in the above-described conventional technique. ..

In the present embodiment, for example, the transmitting terminal 10
When the cell 2 arrives, the conversion control unit 6 of the VC converter (VCC) first reads the path information (VPI) and the channel information (VCI) from the header 1 of the cell 2 and analyzes the contents. Here, the path information (VPI) is "
Assuming that the cell 2 having A "and the channel information (VCI) of" X "arrives, first, in the first conversion table 4, the intermediate path information (intermediate VPI) is transmitted to the" A "of the path information (VPI). Here, it is assumed that the intermediate path information (intermediate VPI) is determined to be “n” as an example.

Next, the conversion control unit 6 uses the second conversion table 5
Refer to. Then, in the intermediate path information (intermediate VPI)
For n ", the data whose channel information (VCI) is" X "is referred to, and based on the tag information, new path information (new VPI) and new channel information (new VCI) registered in this data. The header 1 is rewritten and the cell 2 is output to the exchange switch (SRM) in the office, and the cell 2 is sent from the exchange 3 to the next exchange 3 or the receiving terminal device 11 via the exchange switch (SRM). To be done.

In the example of FIG. 5, the case where the first conversion table 4 and the second conversion table 5 are accessed from the single conversion control unit 6 has been described, but as shown in FIG. The first conversion control unit 6a and the second conversion control unit 6b are divided, and the first conversion control unit 6a accesses the first conversion table 4 and the second conversion control unit 6b accesses the second conversion table 5 independently. You may do so. By providing the conversion control unit 6 for each conversion table in this manner, the efficiency of accessing the conversion table, that is, the memory can be improved by about 50%, and high-speed header 1 conversion processing can be performed. (Second Embodiment) In the example of FIG. 6, the intermediate path information (intermediate VP
Although the area of the second conversion table 5 used for each I) is separately provided, a plurality of intermediate path information (intermediate VPI) are grouped as shown in FIG. Part may be shared.

In FIG. 9, in the second conversion table 5, when the intermediate path information (intermediate VPI) is "3" and "1", the area of "0" is shared. In this case, even if the channel information (VCI) is not compressed and is used as it is in the original 8-bit configuration, the table is shared, so that the memory can be significantly saved.

In the figure, the path information (VPI) of the input cell 2 is "A" and the channel information (VCI) is "
If it is X ”,“ n ”is assigned as the intermediate path information (intermediate VPI) by the first conversion table 4. Then, in the second conversion table 5, this“ n ”is“ g ”of the path information group (VPI group). If you belong to
"X" in the group "g" is searched and the data is referred to. As a result, the tag information, the new path information (new VPI), and the new channel information (new VCI) are determined, and the header 1 is rewritten based on this.

In the second embodiment, the conversion control unit 6
May be a single unit as shown in FIG. 5, or may be a plurality of conversion control units composed of a first conversion control unit 6a and a second conversion control unit 6b as shown in FIG. (Embodiment 3) FIG. 10 shows an example of the configuration of a table for realizing a so-called VP switch that only converts path information (VPI) without converting channel information (VCI).

In this embodiment, the first conversion table 4 and the second conversion table 4
In addition to the conversion table 5, a third conversion table 7 is provided. Then, the path information (V
A VP registration unit 16 that indicates whether or not the conversion is only for (PI) (conversion additional information) is provided. For example, when "1" is registered in the VP registration unit 16, it indicates that the channel information (VCI) is not converted and only the path information (VPI) is converted.

The second conversion table 5 has the same structure as that of the first embodiment shown in FIG. 6, and therefore its explanation is omitted. In the third conversion table 7, a path information group (VPI group), channel information (VCI) corresponding thereto, tag information based on this, and new path information (new VPI) are registered as data. The third conversion table 7 is
In the VP registration unit 16 in the first conversion table 4,
Only the intermediate path information (intermediate VPI) in which "1" is registered is referred to and functions as a so-called VP switch.

In this embodiment, the first conversion table 4,
All the conversion tables of the second conversion table 5 and the third conversion table 7 may be accessed by the single conversion control unit 6, or the first conversion table 4 may be accessed by the first conversion control unit 6a and the second conversion table 6. The table 5 and the third conversion table 7 may be accessed by the second conversion control unit 6b.

Further, when only VP conversion is frequently used, a third conversion control unit for accessing only the third conversion table 7 may be provided. In FIG. 10, the path information (VP
Assuming that a cell 2 whose I) is “A” and whose channel information (VCI) is “X” arrives, “n” is assigned as the intermediate path information (intermediate VPI) in the first conversion table 4.

Next, the VP registration unit 16 will be referred to. Here, when the value stored in the VP registration unit 16 for the intermediate path information (intermediate VPI) is “0”, it means that the channel information (VCI) needs to be converted. When accessed, the tag information, the new path information (new VPI) and the new channel information (new VCI) are determined based on the channel information (VCI) of the second conversion table 5. Since the processing in the second conversion table 5 is the same as that in the second embodiment, detailed description will be omitted.

On the other hand, when the stored value of the VP registration unit 16 in the first conversion table 4 is "1", the cell 2
Since it is not necessary to convert the channel information (VCI) information, the third conversion table 7 is accessed. Figure 10
In the case of, the intermediate path information (intermediate VPI) is “n”,
This is the path information group (VPI
Group), it belongs to "g", so the data whose channel information (VCI) is "X" in this group "g" is referred to, and the tag information and new path information (VPI) are referred to.
Is decided. In this case, channel information (VC
I) (“X” in FIG. 10) is not rewritten, only the path information (VPI) is rewritten.

In the figure, the areas are shared for a plurality of intermediate path information (intermediate VPI) in the second conversion table 5 and the third conversion table 7.
As described above, individual intermediate path information (intermediate VPI)
Needless to say, the area may be set independently.

[0037]

According to the present invention, it is possible to efficiently perform the header conversion performed for each exchange without using a large capacity memory.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a schematic diagram showing the overall configuration of a communication system.

FIG. 3 is an explanatory diagram showing a cell format in ATM.

FIG. 4 is an explanatory diagram showing a cell format in ATM.

FIG. 5 is an explanatory diagram showing a configuration of a VC converter.

FIG. 6 is an explanatory diagram showing the contents of a conversion table in the first embodiment.

FIG. 7 is a diagram showing an example of setting intermediate path information.

FIG. 8 is a diagram showing an example in which a conversion control unit is divided.

FIG. 9 is a diagram showing an example of sharing a table.

FIG. 10 is a diagram showing a configuration example of a table for realizing a VP switch.

FIG. 11 is a schematic diagram of an inside of a switching center showing an outline of an ATM switching system.

FIG. 12 is a diagram showing a conversion table in the prior art.

[Explanation of symbols]

 1 ... Header 2 ... Cell 3 ... Switching station 4 ... First conversion table 5 ... Second conversion table 6 ... Conversion control unit 6a ... First conversion control unit 6b ... Second conversion control unit 7・ ・ 3rd conversion table 8 ・ ・ Input highway 9 ・ ・ Output highway 10 ・ ・ Sending terminal device 11 ・ ・ Reception terminal device 12 ・ ・ Conversion table 13 ・ ・ Transmission terminal 15 ・ ・ Information field 16 ・ ・ VP registration unit 18 ..Switching network VPI..Path information VCI..Channel information VCC..VC converter

Claims (5)

[Claims] 1. Path information (VPI) and channel information (V
In a communication system in which information is transmitted from a calling terminal to a receiving terminal device via a plurality of exchanges (3) using a cell (2) having route information including CI) stored in a header (1), Information (V) in the header (1) of the selected cell (2)
PI), and a first conversion table (4) that assigns intermediate path information (intermediate VPI) with a bit number reduced by a smaller number than that, and the input corresponding to the reduced intermediate path information (intermediate VPI). The second conversion table (5) in which the new path information (new VPI) and the new channel information (new VCI) are registered for each channel information by allocating the channel information (VCI) at the time, and the first conversion table (4). ) And a conversion control unit (6) for rewriting the header (1) of the cell (2) input with reference to the second conversion table (5), the conversion control unit (6) , Reading the path information (VPI) from the header (1) of the input cell (2),
By referring to the conversion table (4), intermediate path information (intermediate VP
After allocating I), the channel information (VCI) is read from the header (1) and the second conversion table (5) is referred to so as to identify the intermediate path information (intermediate VPI) and the channel information (VCI). Based on the combination, new path information (new VPI) and new channel information (new VCI) are determined, and the header (1) of the cell (2) is rewritten based on the determination. Conversion method. 2. In the second conversion table (5),
2. A header 1 exchange method in ATM exchange according to claim 1, wherein each channel information (VCI) is registered by reducing the capacity of the channel information (VCI) specified in the cell (2). .. 3. The conversion control unit (6) includes a first conversion control unit (6a) that references a first conversion table (4), and a second conversion control unit (6a).
Second conversion control unit (6b) that refers to the conversion table (5)
And the first conversion control unit (6a) includes the input cell (2)
The path information (VPI) is read from the header (1) of the above and the intermediate path information (intermediate VPI) is assigned by referring to the first conversion table (4), and the second conversion control unit (6b) is 1) The channel information (VCI) is read out, the second conversion table (5) is referred to, and the intermediate path information (intermediate VP) is read.
I) and the channel information (VCI) in combination, new path information (new VPI) and new channel information (new VCI)
2. The A according to claim 1, wherein the header (1) of the cell (2) is rewritten based on the determination.
Header conversion method in TM exchange. 4. In the second conversion table (5),
2. The header conversion method in ATM exchange according to claim 1, wherein a plurality of intermediate path information (intermediate VPI) is assigned to a fixed combination of channel information (VCI). 5. The first conversion table (4) includes path information (VPI) together with each intermediate path information (intermediate VPI).
An area for registering conversion additional information as to whether or not the cell (2) is only used for conversion, and assigns the channel information (VCI) at the time of input corresponding to the intermediate path information (intermediate VPI), A third conversion table (7) in which new path information (new VPI) is registered is provided for each channel information, and the conversion control unit (6) refers to the conversion additional information in the first conversion table (4). , The path information (VPI) and the channel information (VCI) need to be converted, the new path information (new V
PI) and new channel information (new VCI) are determined, and conversion of channel information (VCI) is not necessary, and path information (VP)
2. The header conversion method in ATM exchange according to claim 1, wherein when only I) is required to be converted, the new path information (new VPI) is determined by referring to the third conversion table (7). ..