JP2829255B2 - ATM switching equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an asynchronous transmission mode (As
The present invention relates to an ATM switching device that exchanges information in an asynchronous transfer mode (ATM).

[0002]

2. Description of the Related Art An ATM switching technique for exchanging data by placing user data in cells of fixed-length short packets involves a plurality of users even in a multimedia environment in which the amount of significant information given to a communication network by a user varies greatly. Exchange resources can be shared. As a result, the cost of the multimedia communication system can be reduced. Therefore, the ATM switching technology is regarded as the only solution of B-ISDN (Broadband Integrated Services Digital Network), and active research and development are currently being conducted.

[0003] A so-called AT that controls such ATM exchanges.
The M switching device is mainly composed of three functional blocks. The first is a cell switch for guiding cells input from a plurality of input terminals to a desired output terminal, which is generally realized by hardware to realize high speed.

[0004] The second is a cell processing apparatus that performs pre-processing for performing cell exchange processing in a cell switch and post-processing performed after the cell exchange processing. Specifically, the pre-processing unit refers to the header of the cell input from the interface point, grasps the connection to which the cell belongs, and provides information necessary for performing a cell routing tag on the cell with a cell switch. It has a function of adding a routing tag to the cell switch after attaching the routing tag. The post-processing unit has a function of deleting a routing tag added to the cell received from the cell switch and the like and transmitting the packet to the interface point.

The third is a control device for setting up connection information for the cell processing device, observing the operation status of the cell switch and the cell processing device, and transmitting hardware failure information to a maintenance person if necessary. is there.

[0006] Of these three functional blocks, the cell processing device in particular greatly affects the function of the ATM switching device, and requires only the number of terminals of the cell switch despite having relatively complicated functions. Most of the hardware cost of switching equipment.

[0007] On the other hand, a point-multipoint connection service is currently considered as one of the leading services in B-ISDN. As is well known, this is a function of making a copy of a cell input to a certain switching node to a plurality of terminals or nodes and transmitting the copy.

[0008] Many methods for implementing cell copy have been proposed so far. For example, Jonathan S. Turner, IEEE, Transactions on Communication, Vol. 36, no. 6 (1988, 6
In the copy network proposed in "Design of a Broadcast Packet Switch", the input switch of one input cell is divided into two as a function of a unit switch of a multistage multistage network well known as a banyan network. A function to send out to the output port is prepared, and cell copy is realized.

The cell copying apparatus proposed so far has a function of, for example, outputting copy cells one by one from any input terminal of a cell switch of any scale to all output terminals. have. Such a cell copy function is referred to herein as a full copy. In order to realize such a full copy function, it is necessary to separately create dedicated hardware for cell copy having a function different from the basic function of the cell processing apparatus described above.
This will further increase the cost of the switching equipment. Also, when increasing the scale of the cell switch, it is necessary to add more hardware.

Incidentally, the cell copy function is a redundant function for a point-to-point connection. Point-to-multipoint connections are an additional service for ATM switching equipment, and the central service is considered to be a point-to-point connection.
Nevertheless, realizing the full copy function as described above results in an increase in the cost of the entire ATM switching apparatus, and is not desirable.

[0011]

As described above, in the conventional cell copy technique in the ATM switching apparatus, since full copying is performed, new hardware is required for the cell copying, and the ATM switching apparatus is required. The drawback was that it resulted in increased body costs. SUMMARY OF THE INVENTION An object of the present invention is to provide an ATM switching device capable of realizing a cell copy without changing hardware of a cell processing device as much as possible.

[0012]

In order to achieve the above object, the present invention provides a virtual path identifier (VPI) indicating a connection of an input cell having a specific format at an interface point with an external device. ) Or virtual channel identifier (VCI) or less, and the length of the virtual channel identifier (VCI) or virtual path identifier (VPI), which indicates the number of copies of the cell. Copy tag addition means for adding and outputting a copy tag comprising the copy number information of the cell, receiving and temporarily holding the cell output from the copy tag addition means, and adding the copy number information of the cell. Overwrites the area with the copy number information indicating the number of the copy of the cell with the copy number information. Copy buffer means for outputting a number of cells, receiving the cells output from the copy buffer means, deleting the copy tag added by the copy tag addition means, and providing the copy connection identification information and the copy number information. Copy tag deleting means for accessing the first table with reference to the above, and overwriting the virtual path identifier / virtual channel identifier indicating the copied connection of the cell with the virtual path identifier / virtual channel identifier field of the cell and outputting the same. Wherein the copy tag deletion means diverts the first table using hardware for creating an address for accessing a second table used for rewriting the virtual path identifier / virtual channel identifier of the input cell. To access And generating an address.

[0013]

According to the present invention, copy number information and copy connection identification information equal to or shorter than the VPI / VCI length are used to specify the connection to which the copied cell is transferred. The function of rewriting the VPI / VCI of the selected cell can be substantially the same as the function of rewriting the VPI / VCI of the cell input from the interface point. This allows
A function of rewriting the VPI / VCI of the copied cell, and a function of rewriting the VPI / VCI of the cell input from the interface point.
The function of rewriting the CI can be easily realized with the same hardware, and the cost of the ATM switching device can be reduced.

[0014]

Embodiments of the present invention will be described below. FIG.
FIG. 2 is a diagram illustrating a configuration of a cell copy device in an ATM switching device according to an embodiment of the present invention and a cell format conversion process inside the cell copy device. This cell copying apparatus includes a copy tag adding unit (CTA) 301, a copy buffer (CPB)
302, copy tag deletion unit (CTD) 303, copy tag table (CTT) 304, copy cell new VPI /
It comprises a VCI table (CPT) 305.

The copy tag adding section 301 adds copy connection identification information and copy number information to an input cell and outputs the input cell. The copy buffer 302 stores the cell 3 to which the copy connection identification information and the copy number information are input.
The number of copy cells designated by the copy number information of No. 07 is created and output, and a copy indicating the number of the corresponding cell in a field where the copy number information of the output cell is written Overwrite number information.

The copy tag deletion unit 303 receives the cell output from the copy buffer 302, and uses the cell 308 that is input with the copy connection identification information and the copy number information to convert the copy connection identification information and the copy number information. At the same time, the connection to which the copied cell belongs is determined by referring to the copy connection identification information and the copy number information, and the VP indicating the connection is indicated.
The cell 309 is output by overwriting the I / VCI on the VPI / VCI field of the received cell.

The copy tag table 304 holds copy connection identification information and copy number information for each connection, and a copy cell new VPI / VCI table 305.
Holds a new VPI / VCI for each connection.

Hereinafter, the cell copy operation in this embodiment will be described. First, when a cell 306 having a format at the interface point with the external device (indicated as a UNI / NNI cell in FIG. 1) 306 is input to the copy tag adding unit 301, the copy tag adding unit 301 V
The connection to which the cell 306 belongs is grasped by referring to the PI / VCI, the copy tag table 304 is accessed, copy connection identification information is obtained, and these are added to the input cell 306 and output to the copy buffer 302. I do.

Next, in the copy buffer 302, when outputting the input cells, copies of the number of cells specified in the copy number information are made, and the copy tag deletion unit 303
Output to. At this time, the number of the field is incremented in order from 0 so that the field in which the copy number information is written retains the order in which the cell was copied (this is copy number information).

The copy tag deletion unit 303 deletes the copy connection identification information and the copy number information, and grasps the connection in which the copy cell is carried from the copy connection identification information and the copy number information.
The new VPI / VCI is obtained by accessing the copy cell new VPI / VCI table 305, and the VPI / V of the input cell is obtained.
The CI field is rewritten and output as the output cell 309.

FIG. 2 is a diagram showing how the connection is handled by the cell copy apparatus in the present embodiment. The number of connections set on the cell copy apparatus is one at the entrance of the copy tag addition unit, but is the number specified by the copy number information at the exit of the copy tag deletion unit CTD. Therefore, after the cell copy, information necessary for identifying the connection increases.

In this embodiment, at the exit of the copy tag adding unit CTA / the entrance of the copy buffer CPB, the connection is identified by the copy connection identification information, and the exit of the copy buffer CPB / the entrance of the copy tag deletion unit CTD. In this example, the identification is made by the copy number information added in the copy buffer CPB. The information that increases to identify the connection after copying is copy number information, but it is clear that the copy number information is easily created.

Here, the copy connection identification information is V
Equal to the PI length or shorter than the VPI length,
When the copy number information is equal to or shorter than the VCI length, the function of rewriting the VPI / VCI of the copied cell is changed to the VPI of the cell input from the interface point.
/ VCI rewriting function can be made almost the same configuration. The VPI / VCI rewriting function of the copied cell and the VPI / VCI
The function of rewriting the VCI can be easily realized with the same hardware. Specifically, in order to rewrite the VPI / VCI of the copied cell, the copy tag deletion unit CTD operates the copy cell new VPI / VCI table C.
As hardware for creating an address for accessing the PT, hardware for creating an address for accessing a table holding connection information (VPI / VCI) input from an interface point, which is usually included in the cell processing device, is diverted. It is possible to reduce the cost of the ATM switching device.

Here, the copy connection identification information is assumed to be equal to or shorter than the VPI length, and the copy number information and the copy number information are assumed to be equal to or shorter than the VCI length. Obviously, the information may be equal to or shorter than the VCI length, and the copy number information and the copy number information may be equal to or shorter than the VPI length. Optimum values of the respective lengths of the copy connection identification information, the copy number information, and the copy number information vary depending on an algorithm for creating an address for accessing a table holding the connection information.

[0025]

As described above, according to the present invention, the information for identifying the connection after being copied is made equal to or shorter than the connection information VPI / VCI, thereby retaining the connection information. The hardware for creating an address for accessing the table to be accessed can be configured in the same manner as the point-to-point connection, thereby reducing the development cost of the ATM switching equipment.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a cell copy device in an ATM switching device according to an embodiment of the present invention and a cell format conversion process inside the cell copy device;

FIG. 2 is an exemplary view showing how connections are handled in the cell copying apparatus according to the embodiment.

[Explanation of symbols]

301: Copy tag adding unit (CTA) 302: Copy buffer (CPB) 303: Copy tag deleting unit (CTD) 304: Copy tag table (CTT) 305: Copy cell new VPI / VCI table (CP)
T) 306: Input cell 307: Cell carrying copy connection identification information and copy number information 308: Cell carrying copy connection identification information and copy number information 309: Output cell

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasuo Masahata 1st Toshiba-cho, Komukai, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba R & D Center (72) Inventor Yoshinari Kumagi Toshiba, Koyuki-ku, Kawasaki-shi, Kanagawa No. 1 Toshiba Research & Development Center Co., Ltd. (72) Inventor Etsuyuki Tsuda No. 1 Komukai Toshiba Town, Koyuki-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba R & D Center Co., Ltd. No. 1, Komukai Toshiba, Toshiba R & D Center Co., Ltd. (72) Inventor Eiji Kamagata No. 1, Komukai Toshiba, Koyuki, Kawasaki, Kanagawa Prefecture, Toshiba R & D Center Co., Ltd. (72) Inventor, Takashi Kantake Kawasaki, Kanagawa 1 Toshiba-cho, Komukai-shi, Ichiko-ku Inside R & D Center, Toshiba Corporation (72) Inventor Shigeo Matsuzawa Sachi Kawasaki-shi, Kanagawa No. 1, Komukai Toshiba, Toshiba R & D Center Co., Ltd. (56) References JP-A-1-20050 (JP, A) JP-A-3-76450 (JP, A) JP-A-5-68045 (JP, A) JP-A-5-37547 (JP, A) JP-A-2-98246 (JP, A) JP-A-63-224445 (JP, A) JP-A-62-155648 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H04L 12/18

Claims (2)

(57) [Claims] 1. Specification at an interface point with an external device
Input cell with the format
Virtual path identifierHead ofLength less than
Connection identification information and the number of copies of the cell
Indicates the virtual channel identifierHead ofLess than
Add a copy tag consisting of copy number information and output
Copy tag adding means, and receiving the cell output from the copy tag adding means
Once, and the copy number information of the cell is added.
A copy indicating the number of the copy of the cell in the area
-Number information is overwritten and the number indicated by the copy number information is overwritten.
Copy buffer means for outputting a number of cells, receiving cells output from the copy buffer means
The copy tag adding meansAddedSaid copy
-Delete the tag and identify the copy connection.
Information and the copy number informationThe first tape
Access toIndicates the connection of the copied cell
Virtual path identifier / virtual channel identifier
Virtual path identifier / virtual channel identifier of the cell
Copy tag deletion method to overwrite and output the separate field
With steps, The copy tag deleting unit may be configured to perform virtual copy of the input cell.
For rewriting path identifier / virtual channel identifier
Address to access the second table
Divert the first table using the hardware
Generate an address to access Characterized by
ATM switching equipment. 2. An input cell having a specific format on an interface point with an external device, a virtual channel identifier indicating a connection before copying to which the cell belongs.
A copy connection identification information of length less the length of the, showing a number of copying the cell, virtual path identifier
And copying the tag adding means for outputting by adding a copy tag comprising a copy number information length less in length, temporarily receive and hold cell outputted from the copy tag adding means, the copy number of the cell Copy buffer means for overwriting copy number information indicating the number of the copy of the cell in the area where the information has been added and outputting the number of cells indicated by the copy number information; and receives the output cell, deletes the said copy tag attached by the copy tag adding means, the first table by referring to the copy connection identification information and the copy number information
Access the Le, a virtual path identifier / virtual channel identifier indicating the connection of the copied cells and a copy tag deleting unit to output the overwrite the virtual path identifier / virtual channel identifier field of the cell, deletes the copy tag Means for virtualizing the input cell
For rewriting path identifier / virtual channel identifier
Address to access the second table
Divert the first table using the hardware
An ATM switching device for generating an address for access .