JP2845460B2 - Cell switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention particularly relates to a cell switch used in an ATM communication system for performing information communication using fixed-length short packets called cells.

(Prior Art) In recent years, a communication terminal has been required instead of a transfer mode called STM (Synchronous Transfer Mode) (used in an existing telephone network) which secures information transmission capability required for communication at the time of call setup. ATs sometimes use the information transmission capabilities of the communication network
Interest and expectations for M (Asynchronous Transfer Mode) are increasing.

ATM transmits information using short packets of fixed length called cells, and each communication terminal hands over cells to the communication network as needed, that is, the information transmission capacity of the communication network when the communication terminal is needed This is a transfer mode characterized by using.

Compared to STM, ATM can provide the communication terminal with any information transmission rate required by the communication terminal, and can improve communication efficiency by using the information transmission capacity of the communication network only when the communication terminal requires it There are advantages such as.

For this reason, ATM has been spotlighted as a basic technology for constructing a communication network capable of handling voice, data, moving images and the like in a unified manner, that is, a B-ISD network.

In order to make the ATM network applicable to communications with high demands such as voice and the like, the intra-network protocol inside the ATM communication network is, as disclosed in JP-A-62-85532, between each node. This is a simplified protocol that does not perform data packet delivery confirmation on a link-by-link basis, and a cell switch having a function of exchanging cells is configured by hardware.

However, as described above, the conventional intra-network protocol in the ATM communication network does not allow the link-by-link transmission confirmation of the data packet between the nodes, so that it is difficult to detect the failure of the cell switch, and as a public network, There was a problem that required reliability could not be secured.

(Problems to be Solved by the Invention) As described above, since the conventional intra-network protocol in the ATM communication network does not confirm the delivery of data packets on a link-by-link basis between each node, the failure detection of the cell switch is not performed. There is a problem that it is difficult to secure the reliability required as a public network.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to easily detect a failure of a cell switch constituted by hardware, thereby achieving an ATM communication network. An object of the present invention is to provide a cell switch capable of providing reliability required as a public network.

[Structure of the Invention] (Means for Solving the Problems) A first invention of the present application is directed to an output communication provided with at least one ATM cell input from at least one input communication path. A cell switch provided with switching means for switching and outputting to a desired output communication path among the paths, a maintenance cell inserting means provided for each of the input communication paths and inserting a maintenance cell between the ATM cells; and For each communication path, a maintenance cell detection means provided outside the exchange means and detecting the maintenance cell output from the exchange means to the output communication path, and inserted by the maintenance cell insertion means. When the maintenance cell is not detected from the maintenance cell detection means provided in the output communication path to which the maintenance cell is to be output even if a predetermined time has elapsed,
Control means for determining that a failure has occurred.

Further, the second invention of the present application is directed to a case where an ATM cell having routing information input from at least one input communication path is provided in a desired output communication path among at least one output communication path. In the cell switch that is exchanged and output, the routing information of the ATM cell that is actually exchanged and output to the output communication path, and the cell output to the output communication path should have, stored in advance. A comparison means for comparing routing information and a control means for determining that a failure has occurred when the two pieces of routing information are different as a result of the comparison by the comparison means.

(Operation) In the first invention, when a maintenance cell is input and a maintenance cell is not detected even after a predetermined time has elapsed, it is determined that a failure has occurred, so that the function can be achieved under easy conditions. In addition, since the maintenance cell detecting means is provided outside the output communication path, it is possible to surely detect a fault up to the output communication path as well as the exchange means.

According to the second aspect of the present invention, the cell switching unit monitors whether or not the cells passing through the cell switch are properly switched by the comparing means provided at the output unit of the cell switch. It can always be confirmed that the cell switching, which is the function of (1), is performed properly.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a cell switch according to an embodiment of the present invention.

The cell switch 20 shown in FIG.
so-called 4 accommodating a to 10d and four output communication paths 30a to 39d
It has a × 4 structure, and exchanges cells received from the input communication paths 10a to 10b with output communication paths 30a to 30d to which the cells should go.

The input cell handling means 201a to 201d
The signal format on 10a to 10d is matched with the signal format in the cell switch 20, the header of the cell is analyzed, the route in the cell switch of the cell is determined, and the information specifying the route in the cell switch for the cell is determined. The routing tag (routing information) is added, and the header of the cell is rewritten.

The maintenance cell insertion units 202a to 202d pass the cell strings received from the input cell handling units 201a to 201d to the input buffers 203a to 203d and, based on a command from a control unit (not shown) for controlling the cell switches. , A maintenance cell is inserted into a vacant part of the cell row received from the input cell handling means 201a to 201d.

The input buffers 203a to 203d include a maintenance cell insertion unit 202a.
This is to temporarily accumulate the cell strings received from .about.202d.

The unit switches 204a to 204d are provided in the cell switch 20 in order to realize a function of replacing the cell switch 20.

The comparing means 205a to 205d are connected unit switches.
While receiving the cell strings output from the cells 204a to 204d and passing them to the maintenance cell detecting means 206a to 206d, the cell switch 20 monitors whether the function of replacing the cells is properly performed.

The maintenance cell detectors 206a to 206d receive the cell arrays output from the connected comparators 205a to 205d, and select the maintenance cells inserted by the maintenance cell insertion units 202a to 202d from the cell arrays. This is detected and deleted and passed to output cell handling means 207a to 207d.

The output cell handling means 207a to 207d output the cell trains received from the maintenance cell detecting means 206a to 206d to an output communication path.
This is to match the signal format on 30a to 30d.

Incidentally, 2041a to 2041h are the buffers of the unit switches, 20
Reference numerals 42a to 2042d denote cell transfer control means for receiving cells from the input buffers of the unit switches and performing switching operations in accordance with the routing tags of the cells.

In the cell switch 20 having the above configuration, the input cell handling means 201a to 201d are replaced with the maintenance cell inserting means.
Input cells 203a to 203d when passing cells to input buffers 203a to 203d through 202a to 202d, and input buffers 203a to 203d when maintenance cell inserting means 202a to 202d insert maintenance cells into a cell row. When cells are output from the buffers 203a to 203d, the buffers 2041a to 2041h of the connected unit switches 204a to 204d of the input buffers 203a to 203d are further output.
The cell transfer means 2042a to 2042d of the unit switch 204a
When outputting cells from the buffers 2041a to 2041h to 204d, the buffer of the next unit switch or the comparing means 205a to 205d of the unit switch has an empty area for storing the cell when a new cell is received. Is checked, and cells are transferred only when there is a free area.

As a result, in the cell switch 20 of this embodiment, when congestion occurs, the input cell handling means 20
Cell discard occurs at the entrance of 1a to 201d, and it is guaranteed that no cell discard occurs inside the cell switch.

Next, a failure detection method in the cell switch 20 will be described in detail.

The cells input from the input communication paths 10a to 10d are output to the cell switches 20 by the output communication paths 30a to 3 to which the cells should be output.
Correct transfer to 0d is confirmed by the following method.

A cell input to the cell switch 20 is provided with a routing tag, which is information indicating a path inside the cell switch through which the cell should pass.

That is, the output communication paths 30a to 30d to which the cells are to be output are determined by the routing tags.

In the comparing means 205a to 205d provided corresponding to the output communication path of the cell switch, the bit pattern of the routing tag to be possessed by the cell passing through the comparing means is accumulated, and the comparing means 205a to 205d The bit patterns of the means 205a to 205d are compared with the routing tags of passing cells.

If the cell exchange is not performed properly, the bit patterns of the comparing means 205a to 205d and the comparing means 205a to 205d
It matches the routing tag of the cell passing through 205d.

If they do not match, the control unit (not shown) controlling the cell switch is notified that there is a failure in the cell switch 20, and the fact is notified.

The control means notified of the failure of the cell switch, for example, notifies the maintenance personnel of the failed cell switch,
It may be required to replace the failed cell switch.

Further, it is confirmed by the following method that the path from any input communication path accommodated in the cell switch 20 to any output communication path is not disconnected.

The control means for controlling the cell switch 20 is provided at regular intervals or when necessary for maintenance.
Maintenance cell insertion means 202a provided corresponding to the input communication path
To 202d to start checking the cell switch 20.

Upon receiving an instruction from the control means, the maintenance cell inserting means 20
2a to 202d insert a maintenance cell into a vacant part of the cell row received from the input cell handling means 201a to 201d.

As described above, when inserting a maintenance cell, it is confirmed that the input buffers 203a to 203d can store new cells.

In addition, the maintenance cell insertion means 202a to 202d pass through one of the paths so that the maintenance cell insertion means 202a to 202d can check all the paths that can pass from the corresponding input communication path. Maintenance cells having a routing tag are sequentially inserted into the cell row.

Maintenance cell insertion means 20 having maintenance cells inserted into cell rows
2a to 202d notify the control means of the routing tag attached to the inserted cell.

The control unit notified that the maintenance cell has been inserted detects the maintenance cell from the maintenance cell detection units 206a to 206d at the end of the path through which the maintenance cell passes for a predetermined time. Have notification that it is done.

If the maintenance cell detecting unit 206a to 206d does not receive a notification indicating that the maintenance cell has been detected during the predetermined time, the route that the maintenance cell has passed is disconnected. Judge that

By combining the information on the disconnected path, the position where the disconnection has occurred can be determined inside the cell switch.

Here, the predetermined time is the maximum cell delay time in the cell switch, and the maximum cell delay time is determined by the capacity of the buffer existing on each path inside the cell switch and the hardware of the cell switch. Can be determined by configuration.

It is also necessary to be able to distinguish maintenance cells from other types of cells, such as call setup cells used for call setup and data cells used for information transfer. There are various known methods for determining the cell type.
It has no effect on the effectiveness of the invention.

Further, the maintenance cell detection means 206a to 206d need to distinguish which maintenance cell insertion means the maintenance cell has been inserted.

Here, the maintenance cell insertion means 202a to 202d are provided with a number inside the cell switch, and when the maintenance cell insertion means inserts the maintenance cell, the number assigned to the maintenance cell insertion means is used. Is written in the maintenance cell to distinguish maintenance cells originating from different maintenance cell insertion means.

It should be noted that the present invention is not limited to the cell switch having the configuration shown in FIG. 1, but has a configuration capable of guaranteeing that no cell is discarded in the cell switch by, for example, increasing the cell transfer rate inside the cell switch. It is also applicable to cell switches.

The present invention is not limited to the cell switch having the same number of input communication paths and the same number of output communication paths, but also the cell switch having a different number of input communication paths and the number of output communication paths, particularly, the number of input communication paths or the number of output communication paths. Can be applied to a cell concentrator / deconcentrator in which either one is 1.

[Effects of the Invention] As described above, according to the first invention of the present application,
Since the maintenance cell detection means is provided outside the output communication path,
Not only the exchange means but also the failure to the output communication path can be reliably detected, and it is determined whether or not the path through which the cell inside the cell switch has been cut is determined by switching the maintenance cell to the cell switch. And the maintenance cell is not output from the cell switch even if a predetermined time has elapsed after the input.

Further, according to the second invention of the present application, it is confirmed by the comparing means provided at the output section of the cell switch whether or not the cells passing through the cell switch are being properly switched during the operation of the cell switch. Therefore, it can always be confirmed that the cell switching is performed properly.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a cell switch according to one embodiment of the present invention. 10a to 10d input communication path 20 cell switch 30a to 30d output communication path 201a to 201d input cell handling means 202a to 202d maintenance cell insertion means 203a to 203d input buffer 204a to 204d Unit switches 205a to 205d Comparison units 206a to 206d Maintenance cell detection units 207a to 207d Output cell handling units 2041a to 2041h Buffers of unit switches 2042a to 2042d Cell transfer control units

Claims (3)

(57) [Claims] 1. A cell comprising switching means for switching and outputting a plurality of ATM cells input from at least one input communication path to a desired output communication path among at least one output communication path. In the switch, a maintenance cell insertion means provided for each of the input communication paths and for inserting a maintenance cell between the ATM cells, and provided for each of the output communication paths, outside the exchange means,
A maintenance cell detection unit that detects the maintenance cell output from the exchange unit to the output communication path, and a maintenance cell inserted by the maintenance cell insertion unit, even if a predetermined time has elapsed. A cell switch comprising: control means for determining that a failure has occurred when the maintenance cell is not detected by the maintenance cell detection means provided on an output communication path to which the maintenance cell is to be output. 2. A buffer for temporarily storing the ATM cells to be output to an output communication path, detecting whether the buffer is empty, and transmitting the ATM cell to the buffer when the buffer is empty. The cell switch according to claim 1, wherein: 3. An ATM cell having routing information, which is input from at least one input communication path, is exchanged with a desired output communication path among at least one output communication path and output. In the cell switch, the routing information of the ATM cell that is actually exchanged and output to the output communication path is compared with the routing information stored in advance that the cell output to the output communication path should have. A cell switch comprising: comparing means; and control means for determining that a failure has occurred when the two pieces of routing information differ as a result of the comparison by the comparing means.