JPH08331131A - Atm cell loop back system - Google Patents

Abstract

PURPOSE: To check a VPI conversion part and a switch part when connection is confirmed or a faulty part is specified by looping back a loop back cell (LB-OAM). CONSTITUTION: An LB-OAM cell detecting part 21 which discriminates whether or not a received cell is an LB-DAM cell, and an LB-OAM cell discrimination flag attaching part 12 which generates an LB-OAM discrimination flag when the received cell is the LB-OAM cell and attaches it on the cell are provided in an IF(interface) part 21. Also, a table 9 for LB-OAM cell conversion in addition to a routing table 8 is provided in the VPI conversion part 5, and VPI conversion is performed on the cell on which the LB-OAM cell discrimination flag is attached by using the table 9 for LB-OAM cell conversion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loopback system for confirming connection of an ATM network and specifying a fault location by using a loopback cell, and more particularly, whether the VPI converter and the cell switch are operating normally. The loopback method that can check whether

[0002]

2. Description of the Related Art In a network such as an ATM (Asynchronous Transfer Mode) network, cells are used for transmitting information. Then, when monitoring whether or not each device configuring such a network is operating normally, OAM (O
peram, administration and maintenance) cells or test cells are sent to the network, and OAM cells or test cells that are looped back (returned) from the network are detected (for example,
JP-A-5-30128, 4-207544, 4-157842, 4-127344
, Or US Pat. Nos. 5,251,204 and 5,257,311).

FIG. 6 is a block diagram showing the structure of a conventional loopback system for monitoring an ATM network. In this loopback method, a loopback cell (LB-OAM
Cell) is used for loopback and monitoring.

The IF (interface) units 1 ₁ to 1 _n are SW
It is connected to the (switch) unit 3. Here, the SW unit 3
With respect to the, IF section ₁ 1 to 1 _n from the SW unit 3 F toward the side of the R side, SW 3 IF unit ₁ 1 to 1 _n f toward the side from is defined as S side. In FIG. 6, each of the IF units 1 ₁ to 1 _n is illustrated as being divided into the R side, that is, the receiving side and the S side, that is, the transmitting side, but in reality, they are integrally configured. Each IF unit 1 ₁ to 1 _n is connected to another ATM terminal device or A
The cell input from the TM cross-connect device via the transmission path is received and input to the SW unit 3 as the R-side input cell.
The cell (S-side output cell) transferred from the W unit 3 is sent to another ATM terminal device or ATM cross-connect device. Figure 7 is a view for explaining the flow of data over configuration of the IF section 1 ₁ and the IF unit 1 _1. On the R side of each IF section 1 ₁ to 1 _n , receiving sections 6 _{a1 to} 6 _an for receiving cells from the transmission path and a cell header interpreting section 17 for interpreting the header of each cell are provided, and on the S side. Is S
Transmitting section 6 _b1 to 6 _bn for delivering the transmission path a cell transferred from the W portion 3 is provided. The cell header interpretation unit 17 and the transmission units 6 _{b1 to} 6 _bn are connected by the signal line 11.

The SW unit 3 has a routing table 8 and a VPI (virtual path identifier) included in the input cell.
A VPI conversion unit 4 that changes the number and the physical device number, and a cell SW unit 7 are provided. Hereinafter, this physical device number is called the HW number. In FIG. 6, the HW numbers are shown as 10 _a1 to 10 _an and 10 _b1 to 10 _bn , respectively.

For example, the IF unit 1 ₁ has a cell A 18 and a cell B.
When 19 is received, the cell header interpretation unit 17 interprets the cell header. Here, it is assumed that the cell A is an LB-OAM cell and the cell B is a normal cell (valid cell). When the cell header interpreting unit 17 identifies that the cell is LB-OAM, this cell is dropped, and the fact is transmitted to the transmitting unit 6 _b1 via the signal line 11 as an LB-OAM cell insertion request signal. Then, the transmission unit 6 _{b1 turns} to the SW unit 3
This LB-OAM cell is inserted into an empty cell (IDLE cell) in the cell (S-side output cell 16b) transferred further, and loops back. On the other hand, a normal cell is not dropped by the cell header interpreting unit 17, is input to the SW unit 3 as the R-side input cell 16a, and corresponds to the VPI number via the VPI converting unit 4 and the cell SW unit 7. It is output from the IF section.

In this conventional loopback system, LB-
Since the OAM cell is configured to be looped back in the IF section, the LB-OAM cell is folded back toward the opposite device without passing through the VPI conversion section or the cell SW section.

[0008]

As described above, the loopback method using the conventional LB-OAM cell is based on the VPI.
Since the loopback is performed in the IF unit without passing through the conversion unit and the cell SW unit, there is a problem that the VPI conversion unit and the cell SW unit cannot be checked.

An object of the present invention is to provide a loopback system capable of checking the VPI conversion unit and cell SW unit.

[0010]

The ATM cell loopback system of the present invention receives a cell input from another ATM terminal device or an ATM cross-connect device via a transmission line and interprets the header of the received cell. IF section and the I
The cell transferred from the F section is subjected to VPI conversion, and the converted cell is routed to the SW section.
In an ATM cell loopback system for looping back B-OAM cells, the IF unit receives a cell input from the transmission path, a cell header interpreter that interprets a header of each received cell, The received cell is the L
An LB-OAM cell detector that determines whether the cell is a B-OAM cell, and an LB-OAM that generates an LB-OAM cell identification flag and adds the cell to the cell when the received cell is the LB-OAM cell. A cell identification flag addition unit, wherein the SW unit has a routing table and an LB-OA.
The VPI conversion unit includes an M cell conversion table and performs the VPI conversion, and a cell SW unit that routes the cell after the VPI conversion.
The cells to which the B-OAM cell identification flag is added are converted by using the LB-OAM cell conversion table to loop back the LB-OAM cells.

In the present invention, in the LB-OAM cell conversion table, the physical device number of the routing destination and the VPI are set.
It is possible that the numbers match the physical device number of the transmission source and the VPI number, respectively. In addition, the IF unit may be provided with a transmission unit that sends out the cells transferred from the SW unit to the transmission path.

[0012]

In addition to the ordinary routing table, the VPI conversion unit is provided with a conversion table for LB-OAM cells.
When the LB-OAM cell is detected by the IF unit, the LB-OAM cell identification flag is added to the cell, so that the VP
When the I conversion unit performs conversion, the LB-OAM cell conversion table is used for cells to which the LB-OAM cell identification flag is added, whereby the LB-OAM cells are looped back. Since the LB-OAM cell is looped back via the VPI conversion unit and the cell SW unit, the VPI conversion unit and the cell SW unit can be checked.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows an LB-OA according to an embodiment of the present invention.
It is a block diagram which shows the structure of the loopback system using M cell. This loopback mode IF is of the substantially the same as the conventional loop-back method shown in FIG. 6, the internal configuration of each IF section 2 ₁ to 2 _n are connected to the SW unit 3 is shown in FIG. 6 This is different from the internal configuration of the unit, and is different in that an LB-OAM cell conversion table 9 is provided in the VPI conversion unit 5 in addition to the routing table 8.

Each IF unit 2₁~ 2_nHave the same configuration,
IF section 2 as a representative of₁The internal structure of the
It Other ATM terminal equipment or ATM cross connect
From the device, the HW number is 10_a1Input via the transmission line which is
Receiving unit 6 for receiving a cell _a1The output side of
Data interpretation unit 17 and LB-OAM cell identification flag addition unit 12
Are provided in series, and the receiving unit 6_1aOutput from R
The side input cell 16a and the cell header interpretation unit 17 and the LB
-SW sequentially passing through the OAM cell identification flag adding section 12
It is designed to be input to the section 3. Cell header interpreter 1
7 is a receiving unit 6 _1aOf the R side input cell 16a output from
It interprets the header part. Cell header interpreter 1
7 indicates whether the received cell is an LB-OAM cell.
The LB-OAM cell detection unit 21 for determining whether
If the cell is an LB-OAM cell, the LB-OA
Addition of LB-OAM cell identification flag from M cell detector 21
LB-OAM cell identification flag addition request signal to the unit 12
No. 22 is output. LB-OAM
Of the LB-OAM cell identification flag.
LB-OAM session when the request signal 22 is added.
Generate an identification flag and add it to the input cell on the R side
It is configured. Furthermore, the IF unit 2₁Is the SW section 3
The S-side output cell transferred from the_b1And
Transmission unit 6 for transmitting to a transmission line_b1It has.

As shown in FIG. 3, the VPI conversion unit 5 has a routing table 8 for use in normal VPI conversion and a conversion table for LB-OAM cells used for routing LB-OAM cells. Including 9 and. The VPI converter 8 receives the input R-side input cell 16a
If the LB-OAM cell identification flag is not added, the routing table 8 is used for VPI conversion, and if it is added, the LB-OAM cell conversion table 9 is used for VPI conversion. As shown in FIG. 3, in the LB-OAM cell conversion table 9, the HW number and VPI number of the routing destination (S-side output destination) are
The HW number and the VPI number of the transmission source (R-side input source) match.

Next, the operation of this embodiment will be described. The IF section 2 _1, and the cell B19 has entered a cell A18 and normal cells is LB-OAM cell. R side input cell 1
When 6a is the LB-OAM cell (when it is the cell A18), the fact is detected by the LB-OAM cell detection unit 21, and the LB-OAM cell detection unit 21 outputs the LB-OAM cell.
The OAM cell identification flag addition request signal 22 is output.
As a result, the LB-OAM cell identification flag addition unit 12
This R-side input cell is dropped to newly generate an LB-OAM cell to which LB-OAM cell identification flag (LB-OAM cell identification flag is set to "1") information is added, and SW
Transfer to part 3. When the R-side input cell is not the LB-OAM cell, the LB-OAM identification flag is set to "0" and transferred to the SW unit 3. As a method of adding the LB-OAM cell identification flag, for example, a method of adding the LB-OAM cell identification flag in the cell header or HEC (Header Error) after the ATM cell synchronization processing is performed.
Control; header error control) method using a byte, or LB-O in addition to the 53-byte cell as shown in FIG.
It is possible to use a method of separately adding AM cell identification flag information.

The R-side input cell output from the IF section is SW
When input to the unit 3, the VPI conversion unit 5 interprets the LB-OAM cell identification flag of the cell. And
In the case of a normal cell, that is, a cell that is not an LB-OAM cell, VPI conversion is performed by the routing table 8, and this cell is sent to the IF section corresponding to the specified VPI number via the cell SW section 7 and the S-side output cell. Is output as. On the other hand, for a cell that is interpreted as an LB-OAM cell, the LB-OAM cell conversion table 9 is used to make a VP.
I conversion is performed. In the LB-OAM cell conversion table 9, the HW number and VPI number of the routing destination are set to be equal to the HW number and VPI number of the transmission source, respectively, so this cell will eventually be looped back.

The flow of the LB-OAM cells described above is summarized in the LB-OAM cell transfer diagram shown in FIG.
The number of virtual paths (VP) is x.

For example, the cell A18 has the HW number = “# 1”,
VPI number = "VPI # a", LB-OAM cell identification flag = ""
1 "(cell type is LB-OAM cell) LB-OAM
Assume it is a cell. This cell A18 is the IF unit # 1.
When the data is transferred from the (R side) to the SW unit 3, the LB-OAM cell identification flag = “1”, so the LB-OAM cell conversion table 9 is used to determine the HW number and VP of the routing destination.
The I number is set equal to the source HW number and VPI number. Then, this cell is switched by the cell SW unit 7, and I with HW number = “# 1” and VPI number = “VPI # a”.
Reach F part # 1 (S side). Therefore, the SW unit 3
Loopback is realized via (VPI conversion unit 5 and cell SW unit 7).

On the other hand, the cell B has, for example, an HW number = “#
It is assumed that the valid cell has 1 ", VPI number =" VPI # a ", and LB-OAM cell identification flag =" 0 ".
Since it is not an LB-OAM cell, the HW number and VPI number are changed by the normal routing table 8.
As a result of being switched by the cell SW unit 7, the HW number = “# 2” and the VPI number = “VPI # b”, the IF unit # 2 (S side)
Reach. That is, normal routing is performed for cells other than the LB-OAM cell.

[0021]

As described above, according to the present invention, the VPI conversion unit has the LB-OAM in addition to the normal routing table.
A conversion table for cells is provided and LB-O is used in the IF section.
When an AM cell is detected, an LB-OAM cell identification flag is added to the cell, and a conversion table for the LB-OAM cell is added to a cell to which the LB-OAM cell identification flag is added when the VPI conversion unit performs conversion. By using, the LB-OAM cell is looped back via the VPI conversion unit and the cell SW unit, and the VPI conversion unit and the cell SW unit can be checked. There is.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a loopback system using an LB-OAM cell according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an IF unit in the loopback system of FIG.

FIG. 3 is a diagram showing an example of the contents of a table in a VPI conversion unit in the loopback system of FIG.

FIG. 4 is a diagram illustrating a 53-byte cell.

5 is an LB-OAM in the loopback system of FIG.
It is a figure explaining the flow of a cell.

FIG. 6 is a block diagram showing a configuration of a conventional loopback system using LB-OAM cells.

7 is a block diagram showing a configuration of an IF unit in the loopback system of FIG.

[Explanation of symbols]

_{1 1 ~1 n, 2 1 ~2} n IF unit 3 SW unit 4, 5 VPI conversion unit 6a1~6an receiver 6b1~6bn transmitter 7 cells SW 8 Routing Table 9 LB-OAM cell conversion table 10 _a1 ~ 10 _an R side HW number 10 _b1 to 10 _bn S side HW number 11 Signal line 12 LB-OAM cell identification flag addition part 16a R side input cell 16b S side output cell 17 Cell header interpretation part 18,19 cell 21 LB- OAM cell detection unit 22 LB-OAM cell identification flag addition request signal

Claims (3)

[Claims] 1. An IF unit for receiving a cell input from another ATM terminal device or an ATM cross-connect device via a transmission path and interpreting a header of the received cell;
And a SW unit that performs VPI conversion on the cell transferred from the unit and routes the converted cell.
In the ATM cell loopback method of looping back OAM cells, the IF unit receives a cell input from the transmission path, a cell header interpreter that interprets a header of each received cell, and a reception unit. An LB-OAM cell detector that determines whether the received cell is the LB-OAM cell, and LB-OAM when the received cell is the LB-OAM cell.
LB-O that generates a cell identification flag and adds it to the cell
An AM cell identification flag addition unit, and the SW unit includes a routing table and an LB-OAM cell conversion table to perform the VPI conversion.
An I conversion unit and a cell SW unit that routes the cell after the VPI conversion, and for the cell to which the LB-OAM cell identification flag is added, the VPI conversion unit converts the LB-OAM cell. By performing conversion using a table, the LB-
An ATM cell loopback system characterized in that OAM cell loopback is performed. 2. The ATM cell according to claim 1, wherein in the LB-OAM cell conversion table, the physical device number of the routing destination and the VPI number match the physical device number of the transmission source and the VPI number, respectively. Loopback method. 3. The ATM cell loopback system according to claim 1, wherein the IF unit is provided with a transmitting unit for transmitting the cells transferred from the SW unit to a transmission line.