JPH11355278A - Method for inserting alarm cell in atm network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for inserting a VC-AIS cell in an ATM network which can insert the VC-AIS cell in a short time and reduces a burden to software for a processor. SOLUTION: VPI/CI, CT and SON as of all connections in which the use is reserved on a transmission line of VCH are registered in a connection management table 2, it is discriminated by a cell discrimination part 32 whether a main signal cell arriving at the VCH is a user cell or a VP-AIS cell, the bit information of the discrimination result is recorded in an arrival management bit map 4 for every value of the VPI and a VC-AIS cell insertion part 5 inserts the VC-AIS cell to the all VCs in the case that the bit information in the arrival VP management bit map 4 corresponding to the VPI successively read out from the connection management table 2 is the VP-AIS cell and in the case of CT=0 and SON=1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of inserting a virtual channel alarm cell when a virtual path alarm cell is terminated by a virtual path terminating device in an ATM (Asynchronous Transfer Mode) network.

[0002]

2. Description of the Related Art ATM (Asynchronous Transfer Mode):
In an asynchronous transfer mode network, a single transmission line can be regarded as a plurality of virtual transmission lines. For this reason, in an ATM network, a communication channel that actually carries data is called a VC (Virtual Channel), and a path (path) in which a plurality of such communication channels are bundled is called a V (virtual channel).
It is called P (Virtual Path). A device corresponding to an exchange for relaying a VC communication channel set between user terminals is called a VC handling device (hereinafter, VCH).
, And generally called an ATM switch).
A device corresponding to a cross connector (a device that connects and switches paths) that relays a VP communication channel set between channels is called a VP handling device (hereinafter, referred to as a VPH).

[0003] Network devices (exchanges, transmission devices, etc.) constituting an ATM network are composed of the VPH and VCH.
are categorized. FIG. 6 shows a VP in an ATM network.
FIG. 3 is an explanatory diagram of the / VC connection, where a single circle of each connection in the figure indicates a connection point, and a double circle indicates a termination point. VC
In the case where communication is performed between users via, the user terminals at both ends are defined as termination points of a VC connection (VC communication channel). In a VP connection that bundles a plurality of VC connections on a network, VCHs on both sides connected to a user terminal are termination points of the VP connection.

The routing (communication path selection) of the ATM cell (transmission information unit composed of a total of 53 bytes of a 5-byte header and 48-byte user information) is temporarily given to the VC connection and the VP connection. VCI (Virtual Channel) which is a connection identification number
Identifier, virtual channel identifier) and VPI (Virtual
Path Identifier (virtual path identifier). In other words, in the ATM switching system, the identification number of the VP to be used is previously added to the header of the cell.
A PI and a VCI, which is an identification number of which VC in the VP is used to send data to the other party, are determined.
At the header conversion unit in the M exchange (VCH), the ATM cell is transmitted while sequentially converting the VCI, which is the destination information of the cell.

[0005] In the ATM standard protocol, packet data transmitted from a user terminal firstly receives AAL (AT
The M layer is divided into 48 bytes in a layer called an M adaptation layer, and a 53-byte cell is formed in the ATM layer by adding a 5-byte header including address information of the other party. An empty cell is added in the physical layer, and the SDH
(Synchronous Digital Hierarchy, international standard for transmission speed) A frame of the required number is packed in a frame and transmitted to the other side via a VCH (ATM exchange). In addition, in ATM, in addition to user cells in the same communication path, maintenance and operation (OAM: Operation and Maintena) having the same destination label information for monitoring and notification of failures and the like are performed.
nce) The cell can flow. One of the OAM functions is an alarm cell (AIS cell, Alarm Indication Signal cell). When a failure is detected, this AIS cell is generated and notified by inserting it into a transmission line.

When a failure in the physical layer is detected at the relay point of the VP connection and the VC connection, an alarm transfer cell in the ATM layer is generated and notified to the terminal point. In this alarm transfer cell, a VP-AIS cell and a VC-AIS cell are defined by the ITU-T (International Telecommunication Union / Telecommunication Standardization Sector) for the VP connection and the VC connection, respectively. FIG. 7 is an explanatory diagram of VC-AIS cell insertion in VCH of ATM, and FIG. 8 is an explanatory diagram of AIS cell format by ITU-T.

The payload of FIG. 8 is normally 48 bytes of user information, but in the case of an AIS cell, it becomes failure notification information as shown. In FIG. 7, the VPH at the relay point of the VP connection detects a failure, and the VP-AIS
The example when a cell is inserted is shown. In this case, the inserted VP-AIS cell is transferred to the VP connection, terminated (dropped) at the VCH that is the termination point of the VP, and the VPS is applied to all VC connections in this VP.
A C-AIS cell is generated and inserted into a communication path. Then, the VC-AIS cell is transferred to the user terminal which is the terminal point of the VC.

In the prior art, there are many systems for managing the VP / VC connection by software processing. In this system, the termination of the VP-AIS cell by the VCH which is the termination point of the VP is performed. , VC
The generation of the AIS cell (generation of the entire cell or generation of a part of the cell) is also performed by software, and the insertion of the VC-AIS cell is often performed via the processor interface.

[0009]

In the prior art for processing the generation and insertion of VC-AIS cells by software when the VP-AIS cells are terminated at the VP termination point in the ATM network, the software burden is increased. Because it is large, VC-
Since it takes time to generate AIS cells,
There was a problem that the insertion of the VC-AIS cell was delayed.

[0010]

According to the present invention, there is provided a method for inserting an alarm cell in an ATM network, comprising the steps of inserting a virtual channel alarm cell when a virtual path alarm cell is terminated by a virtual path terminating device in the ATM network. In the connection management, the type management information, the values of the virtual path identifier and the virtual channel identifier, and the information on whether or not the connection is currently being serviced for all connections reserved for use on the transmission path in the terminal device of the virtual path It is registered in a table, and it is determined whether the main signal cell arriving at the terminal device of the virtual path is a user cell in the virtual pulse layer or a virtual path alarm cell, and for each value of the virtual path identifier, Bit information is recorded in the arrival virtual path management bitmap, and If the connection information registered in the connection management table is sequentially read, and bit information of the arrival virtual path management bitmap corresponding to the value of the virtual path identifier in the read connection information is checked, and this is a virtual path alarm cell. When the type information in the connection information read at the same time is a virtual path connection and a connection currently being serviced, a virtual channel alarm cell is inserted for all virtual channels in the terminal device of the virtual path. is there. As a result, the virtual channel alarm cell can be inserted in a short time by hardware, and the load of software processing is reduced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The network operation and maintenance (OAM) function in an ATM network is described in IT
U.T. Recommendation I. 610. In the OAM function, it is specified that the physical layer and the ATM layer are managed in a hierarchical manner, and the ATM layer is managed in two layers of a VP layer and a VC layer. VCH (AT) that performs routing (communication path selection) for each VC among network devices constituting an ATM network
M exchange) terminates the VP connection. In the device (VCH) that terminates the VP in this manner, the VP-AIS
When a cell is received, the VP-AIS cell is dropped (terminated). Further, VC-AIS cells are generated for all VCs bundled in this VP connection and inserted into the communication path. And this VC-AIS cell is V
The data is transferred to the user terminal which is the terminal point of C. This operation is as described in FIG.

FIG. 1 shows a VC-AI according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of an S cell insertion device, FIG. 2 is a diagram showing a configuration example of a connection management table of FIG.
FIG. 3 is a diagram showing a configuration example of an arrival VP management bitmap of FIG. 1. The VC-AIS insertion device shown in FIG. 1 is a device for inserting a VC-AIS cell when a transmitted VP-AIS cell is terminated, and is mounted on a VCH (ATM exchange) or the like. 1, 1 is a cycle counter, 2 is a connection management table as shown in FIG. 2,
Reference numeral 3 denotes a cell identification unit, and reference numeral 4 denotes an arrival VP management bitmap generation unit, which generates an arrival VP management bitmap as shown in FIG. Reference numeral 5 denotes a VC-AIS cell insertion unit, an example of which is shown in FIG.

Generally, in a public network, various settings and monitoring of various devices constituting the network are performed by an operation center that manages the operation of the entire network. With this operation, the network provides various services to users. Generally, such an operation signal is transmitted through a network different from a network provided to the user. The following two services are provided by the user. (1) Connection setting is fixedly performed, (2) Connection is set on demand, and the connection as described in (1) above is set up at the time when the subscriber subscribes (the ATM network). VP
I / VCI setting, communication band setting, etc.). In the communication as in (2), a connection is set each time a communication request is issued from a subscriber.

In the ATM communication, the operation center considers the network congestion and the like based on the destination, band, and other call information of the call from the user according to the setting of (1) or (2). Then, a route (path) to the destination is determined, and if a band requested by the user exists on the route, V is set for each route.
The CI is determined and given to each device constituting the network. In this manner, the VCH is notified of the VPI / VCI values of the VP connection and the VC connection reserved for use on the transmission path of the VCH from the operation center. In the present invention, the VCCH is used by using these information.
-Registered in the connection management table 2 to generate an AIS cell. More specifically, each VCH has a control unit connected to a CPU bus (not shown). The control unit registers in the connection management table 2 according to instructions and settings notified from an operation center via an operation network. I do.

As shown in FIG. 2, the connection management table contains VPI / VCI values of the connections reserved for use on the VCH transmission line, and type information indicating whether the connection is a VP connection or a VC connection. CT bit (CT = 0 is VP connection, CT
= 1 indicates a VC connection) and SON of identification information indicating whether the service is currently provided or not.
Bit (SON = 1 indicates connection in service, SO
N = 0 indicates a connection not in service). In connection management table 2,
When the address is specified, the information of the VPI / VCI, CT, and SON registered in the specified area is output.

The cycle counter 1 counts up by a cell synchronization signal EN which is an input signal, and manages a one-second cycle by counting the number of input cells. FIG. 4 is a diagram showing the timing of the input cell flow and the synchronization signal. As shown in FIG. 4, the synchronization signal EN is input in synchronization with the rising edge of the header indicating the head of the input cell stream. Note that V in FIG.
A circuit for detecting cell synchronization is provided at a stage preceding the C-AIS insertion device, and a synchronization signal EN is generated by this circuit and supplied to the cycle counter 1. Then, the cycle counter 1 outputs an address signal that can make a round of all the addresses of the connection management table 2 based on the counted value during a one-second cycle obtained by counting the supplied synchronization signal EN.

For example, if the transmission speed is 155.52 Mbit / s,
If the cell length inside the device is 54 bytes, 360,
000 cells will be counted. Therefore, the cycle counter 1 can manage the one-second cycle by counting the number of cells. Therefore, the connection management table is accessed at regular intervals for the count value of the cycle counter 1. For example, if access is set every 100 cells, 1
It will be accessed 3600 times per second. For example, if the addresses of the connection management table 2 are 0 to 3599, all the addresses of the table 2 can be cycled in one second. Conversely, connection management table 2 per second
The access cycle is set so that all addresses of the address can be accessed. This access cycle is determined by a VC-AI described later.
This is the minimum interval for S cell generation.

As described above, the cycle counter 1 always performs a counting operation based on the input signal EN, and addresses 0, 1, and 1 accessing the connection management table 2 at a fixed cycle.
., And access the respective areas of the connection management table 2 in order. The connection management table 2 outputs the values of VPI, VCI, CT, and SON registered in the address area specified by the synchronization counter 1 to the VC-AIS cell insertion unit 5, and stores the VPI value in the arrival VP management bitmap. Output to the generation unit 4.

The cell identification unit 3 determines the VPI, VC of the input cell.
Based on the I value, whether the input cell is a VP-AIS cell or a user cell (a cell other than the VP-AIS cell) is identified, and the VP-AI
An identification signal indicating whether the cell is an S cell or a user cell and a VPI value are output. In the arriving VP management bitmap generation unit 4, the result of the cell identification unit 3 identifying the input cell at the VP level (identification signal of user cell or VP-AIS cell and VPI value)
Is written to the arrival VP management bitmap as follows.

The arrival VP management bitmap has a 1-bit area corresponding to each VPI value shown in FIG. 3 (the number in each box in FIG. 3). When a user cell arrives in this area, ""0" is written, and "1" is written when the VP-AIS cell arrives. The area corresponding to all the VPI values of the arrival VP management bitmap is as follows.
2. There is an area for ¹² bits, which is the VP in the cell header.
This is based on the fact that the area of I has 12 bits. That is, one bit is provided for each of the possible VPI values of the input cell.

On the other hand, an arrival VP management bitmap generator 4
Is the VPI input from the connection management table 2.
An area corresponding to the VPI value of the arrival VP management bitmap is searched by the value, and bit information of “1” or “0” written in the area (information indicated by an INS symbol in FIG. 1) is VC- Output to AIS cell insertion unit 5.

The VC-AIS cell insertion unit 5 receives VPI, VCI, and CT input from the connection management table 2.
And SON, and the bit information of the INS input from the arrival management bitmap generator 4 using the VC-AI
The insertion control of the S cell is performed. FIG. 5 is a diagram showing a configuration example of the VC-AIS cell insertion unit in FIG.
The cell insertion unit 5 includes a fixed value unit 11, an internal register 12, an insertion control unit 13, # 1, # 2 selectors 14, 15 and a CR.
C (Cyclic Redundancy Check) operation unit 1
6 is included.

The fixed value part 11 has PTI, CLP, OAM Type, and PTI shown in the AIS cell format of FIG.
The internal register 12 contains information on the type and location of the failure. Insert control unit 13
Determines whether VC-AIS cells need to be inserted, and if so, finds empty cells in the main signal cell stream,
The # 1 selector 14 is controlled to insert the VC-AIS cell into the empty cell, and has an INS buffer for temporarily storing INS information necessary for this control.

In the VC-AIS cell insertion unit 5,
The insertion control unit 13 determines whether or not to insert an AIS cell based on Table 1 below.

[0025]

[Table 1]

As shown in Table 1, the insertion control unit 13
When T = 0, SON = 1, INS = 1, an empty cell is detected from the main signal cell flow, and VC-AI is detected for this empty cell.
An S cell is inserted. FIG. 8 shows the format of the VC-AIS cell. The values output from the connection management table 2 are inserted into the VPI and VCI values of the inserted cell. Also, PTI, CLP, OAM of VC-AIS cell
Each value of Type and Function Type is inserted from the fixed value part 11, and information indicating a fault location and a fault type is set in the internal register 12 in advance. At present, there is no standardized bit indicating the fault location and the fault type. Therefore, the bit is externally set in the internal register 12 and the set value is inserted.

The insertion control unit 13 controls the signal selection operation of the # 1 selector 14 to allow the signals to be inserted to pass at predetermined timings of empty cells in the main signal cell flow, and to convert the signals into the AIS cell format shown in FIG. Generate a matching VC-AIS cell signal. The CRC calculation unit 16 calculates and generates a cyclic code for error detection, and the # 2 selector 15
Passes the cyclic code generated at a predetermined timing in the payload. In this way, the VC-AIS cell insertion unit 5 sends VC-AISs to all VCs in its own VP.
-Insert an AIS cell.

In this embodiment, as described above, when the VP-AIS cell is terminated at the termination point of the ATM network, the VC-AIS cell generation / insertion processing is performed not by software but by hardware as in the conventional case. Since the autonomous operation is performed by hardware, the VC-AIS can be generated in a shorter time than before, and the software processing can be reduced.

[0029]

As described above, according to the present invention, in a method for inserting a virtual channel alarm cell when a virtual path alarm cell is terminated by a virtual path terminal device in an ATM network, the virtual path terminal device The type information, the value of the virtual path identifier and the value of the virtual channel identifier for all the connections reserved for use on the transmission path in are registered in the connection management table, and information on whether the connection is currently being serviced, It is determined whether the main signal cell arriving at the terminal device of the virtual path is a user cell in the virtual pulse layer or a virtual path alarm cell, and the bit information of the determination result is received for each value of the virtual path identifier. Connection recorded in the bitmap and registered in the connection management table Information is sequentially read, and the bit information of the arrival virtual path management bitmap corresponding to the value of the virtual path identifier in the read connection information is checked, and when this is a virtual path alarm cell, the connection information in the connection information read at the same time is checked. When the type information is a virtual path connection and a connection currently in service, virtual channel alarm cells are inserted for all virtual channels in the terminal device of the virtual path. As a result,
The hardware allows for the insertion of virtual channel alarm cells in a short time and reduces software processing.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a VC-AIS insertion device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a connection management table in FIG. 1;

FIG. 3 is a diagram showing a configuration example of an arrival VP management bitmap of FIG. 1;

FIG. 4 is a diagram illustrating a timing relationship between an input cell flow and a synchronization signal in FIG. 1;

FIG. 5 is a diagram illustrating a configuration example of a VP-AIS cell insertion unit in FIG. 1;

FIG. 6 is an explanatory diagram of a VP / VC connection in an ATM network.

FIG. 7 is an explanatory diagram of VC-AIS cell insertion in VCH of ATM.

FIG. 8 is an explanatory diagram of an AIS cell format according to ITU-T.

[Explanation of symbols]

 Reference Signs List 1 cycle counter 2 connection management table 3 cell identification unit 4 arriving VP management bitmap generation unit 5 VC-AIS cell insertion unit 11 fixed value unit 12 internal register 13 insertion control unit 14 # 1 selector 15 # 2 selector 16 CRC calculation unit

Claims (2)

[Claims] 1. A method for inserting a virtual channel alarm cell when a virtual path alarm cell is terminated by a virtual path terminating device in an ATM network, wherein the virtual path alarm cell is reserved for use on a transmission path in the virtual path terminating device. Type information about all connections, values of virtual path identifiers and virtual channel identifiers, and information as to whether or not the connection is currently being serviced are registered in a connection management table. Discriminating whether the signal cell is a user cell or a virtual path alarm cell in the virtual pulse layer, and for each value of the virtual path identifier, records the bit information of the discrimination result in an arrival virtual path management bitmap, and the connection management table Sequentially read the connection information registered in the The bit information of the arriving virtual path management bitmap corresponding to the value of the virtual path identifier in the connection information is checked, and if this is a virtual path alarm cell, the type information in the connection information read at the same time is the virtual path connection. And a method of inserting an alarm cell in an ATM network, wherein a virtual channel alarm cell is inserted for all virtual channels in a terminal device of the virtual path in the case of a connection currently being serviced. 2. A method for sequentially reading connection information registered in the connection management table, wherein a signal synchronized with a main signal cell arriving at a terminal device of the virtual path is counted, and the counting is performed at predetermined intervals. A cycle counter for repeating the operation is provided, and all connection information registered in the connection management table is sequentially read within the predetermined cycle by an output signal based on the count value of the cycle counter. 2. The method for inserting an alarm cell in an ATM network according to claim 1, wherein