JP3139412B2 - ATM cell loopback method and ATM cell switch device using the method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loopback method using a loopback cell for confirming the connection of an ATM network and identifying a faulty part, and checks whether the operation including a cell switch is normal. AT to check
The present invention relates to an M cell loopback method and an ATM cell switching device using the ATM cell loopback method.

[0002]

2. Description of the Related Art In an ATM network, a loop-back cell (LB-OA) is used for a preliminary connection test before starting a service or for specifying a failure point when a failure occurs.
(M cells).
As a prior art that discloses a loopback test method, for example, Japanese Patent Application Laid-Open No. 7-327031 discloses a method in which a part of a routing table is exclusively used for an LB-OAM cell. I have.

FIG. 3 is a block diagram showing a configuration of an ATM cell switch device having a routing table partially allocated for LB-OAM cells. As shown in the figure, the ATM cell switching device transmits cells 12 and 13 from an ATM terminal device and an ATM cross-connect device, respectively.
And interface units (IF units) 11-1n for sending out transmission cells to the respective transmission paths and a switch unit 22 for controlling the distribution of the reception cells to predetermined transmission paths. Each of the IF units 11 to 1n includes a receiving unit 31 for performing optical-to-electric conversion processing, synchronization processing, and the like when the transmission path is an optical transmission path.
-3n, an HW number adding section 41-4n for adding a highway number (HW number) to the cell, an LB-OAM cell discriminating section 51-5n for adding an LB-OAM cell identification flag, and a transmission cell to the transmission path. Transmitter 61 to perform processing
6n.

The switch section 22 includes an LB-OAM cell identification section 26 including an LB-OAM cell identification flag interpretation section 10 for determining whether or not the cell input from each of the IF sections 11 to 1n is an LB-OAM cell. A VPI conversion unit 27 that includes a table and performs VPI conversion, and performs cell allocation according to the HW number and the VPI (n × n)
The cell switch section 9 of FIG. Each output of the cell switch section 9 is supplied to transmission sections 61 to 6n of each of the IF sections 11 to 1n.

FIG. 4 is a block diagram showing the detailed configuration of each of the IF units 11 to 1n together with the switch unit 22. In addition,
Since each of the IF units 11 to 1n has the same configuration, they are represented as an IF unit 1 as a representative. Each block inside it also
Receiver 3, Transmitter 6, HW number adder 4, LB-OAM
Expressed as a cell determination unit 5. In the following description, the suffixes of the reference numerals will be omitted unless distinction is required.

As shown in FIG. 4, an LB-OAM cell discriminating section 5 adds an identification flag to an LB-OAM cell detecting section 14 for detecting whether or not a received cell is an LB-OAM cell. And an LB-OAM cell identification flag adding unit 17.

Next, the operation of the ATM cell switch shown in FIGS. 3 and 4 will be described.

Here, with reference to the switch section 22, the side of each of the IF sections 11 to 1n that sends cells to the switch section 22 is defined as the R side, and the side to which cells are sent from the switch section 22 is defined as the S side. When the receiving unit 3 receives a cell, the HW number adding unit 4 adds an HW number corresponding to the transmission lines 16a and 16b to the cell. The LB-OAM cell detection unit 14 interprets the header content in the cell and detects whether the cell is an LB-OAM cell. Upon detecting that the cell is an LB-OAM cell, the cell
This is sent to the B-OAM cell identification flag adding unit 17. Note that L
If the cell is not an LB-OAM cell, the B-OAM cell detector 14 transfers the cell to the switch 22 as it is.

LB-OAM cell identification flag adding section 17
Sets the LB-OAM cell identification flag. The LB-O with the LB-OAM cell identification flag added
The AM cell 16 is sent to the switch unit 22. In general, L
The B-OAM cell identification flag is added in the cell header. In this case, for example, an HEC area in the header which is an unused area after the cell synchronization processing as shown in FIG. 5 is used. Alternatively, an LB-OAM cell identification flag added separately from the 53-byte cell is used.

Note that the HW number adding unit 14 generally
The W number is set in the HEC area in the header after the cell synchronization processing, or set separately from the 53-byte cell. When the LB-OAM cell identification flag and the HW number are set in the HEC area, for example, the LB-OAM
One bit is allocated for the cell identification flag and seven bits for the HW number.

The VPI conversion unit 27 in the switch unit 22
In addition to the ordinary routing table area 37, a routing table area 38 for LB-OAM cell conversion is provided in the routing table. Each routing destination (S-side output destination) in the routing table area 38 for LB-OAM cell conversion includes the HW of each transmission source (R-side input source).
Numbers and those equal to the VPI number are set.
LB-OAM cell identification unit 26 in switch unit 22
If the input cell is an LB-OAM cell, that is, if the LB-OAM cell identification flag is set, the LB-OAM cell conversion flag is set based on the routing destination in the routing table area 38 for LB-OAM cell conversion. Control is performed so that switching is performed.

Since the routing destination in the routing table area 38 for LB-OAM cell conversion is set to be equal to the HW number and VPI of the transmission source, the switch unit 22 switches to loop back the cell to the transmission source. .

[0013]

In the conventional ATM cell loopback method, a routing table area 38 for LB-OAM cell conversion is required in addition to the normal routing table area 37.
There is a problem that the capacity of the buffer for storing the routing table setting value increases. For example, VP
Assuming that the number of I is 4096, an extra (4096 × the number of HWs) buffer area is required. Also, LB
Since registration and maintenance of the routing table area 38 for -OAM cell conversion are also required, there is also a problem that a heavy load is imposed on a maintenance person.

Accordingly, the present invention provides an ATM cell loopback method capable of reducing the buffer capacity required in the VPI conversion unit and reducing the load on maintenance personnel, and an ATM cell switch device using the method. The purpose is to:

[0015]

According to the present invention, there is provided an ATM cell loopback method comprising: a receiving unit for receiving a cell; a loopback cell determining unit for determining whether the cell is a user cell or a loopback cell; A VPI conversion unit that includes a routing table and performs VPI conversion
An ATM loopback method in a TM cell switch device, wherein when a cell determined by a loopback cell determination unit is a loopback cell, the cell is switched without performing VPI conversion by bypassing a VPI conversion unit. It is characterized by:

In the ATM cell switching device according to the present invention, when a cell input from the interface unit to the switch unit is a loopback cell, the cell is converted to a VP cell.
A loopback cell discriminating unit that supplies the signal to the switching unit without passing through the I conversion unit is provided.

FIG. 1 is a block diagram showing the configuration of an ATM cell switch device according to one embodiment of the present invention. As shown in the figure, the ATM cell switch device receives IFs 11 to 1n for receiving cells 12 and 13 from an ATM terminal device and an ATM cross-connect device and sending out a transmission cell to each transmission path, respectively, and transmits a reception cell to a predetermined cell. And a switch unit 2 for performing control for distributing to the transmission path. Each I
The configuration of the F sections 11 to 1n may be the same as the configuration shown in FIG. The switch unit 2 includes an LB-OAM cell identification unit 7 for determining whether a cell input from each of the IF units 11 to 1n is an LB-OAM cell, a VPI conversion unit 8 including a routing table 30 and performing VPI conversion, And VPI
And a (n × n) cell switch section 9 that sorts cells according to the following. The routing table 30 has LB-
There is no routing table area for OAM cell conversion.

Unlike the conventional switch unit 22, the LB-OAM cell identification unit 7 in the switch unit 2 determines whether or not the input cell is an LB-OAM cell.
In addition to the B-OAM cell identification flag interpreter 10, the cell
It has a cell output selection unit 11 for selecting whether to transfer to the PI conversion unit 8 or to the cell switch unit 9.

FIG. 2 is a block diagram showing the detailed configuration of each of the IF units 11 to 1n together with the switch unit 2. In FIG. 2 as well, the IF unit and each block in the IF unit include an IF unit 1, a receiving unit 3, a transmitting unit 6, an HW number adding unit 4, an LB-O
It is expressed as an AM cell discriminating unit 5.

Next, the operation of the ATM cell switch device shown in FIGS. 1 and 2 will be described.

The IF unit 1 operates in the same manner as in the conventional case. That is, when detecting that the cell is an LB-OAM cell, the LB-OAM cell detection unit 14 sends the cell to the LB-OAM cell identification flag adding unit 17 and, if the cell is not the LB-OAM cell, The cell is transferred to the switch unit 2 as it is. If the input cell is an LB-OAM cell, the LB-OAM cell 16 to which the LB-OAM cell identification flag is added is sent from the LB-OAM cell identification flag adding unit 17 to the switch unit 2. In the switch unit 2, the LB-OAM cell identification flag interpretation unit 10 in the LB-OAM cell identification unit 7 checks whether the LB-OAM cell identification flag added to the input cell is set. If the LB-OAM cell identification flag is not set, it is determined that the input cell is a normal user cell, and the cell output selection unit 11
Transfers the cell to the VPI conversion unit 8. For example, if the cell 12 is a user cell, the cell 12
The data is transferred to the I conversion unit 8. When the LB-OAM cell identification flag interpretation unit 10 detects that the LB-OAM cell identification flag has been set, the cell output selection unit 11
Transfers the cell to the cell switch unit 9. For example,
If cell 13 is an LB-OAM cell, cell 1
3 is transferred to the cell switch unit 9 without passing through the VPI conversion unit 8. In that case, the HW number and VPI of the cell
Is the source state. Therefore, the cell switch unit 9 performs switching so that the cell is transmitted to the transmission source (S-side output destination).

For example, HW number = “# 1”, VPI =
“VPI # b”, “LB-OAM cell identification flag = O
It is assumed that the cell 13 of "N" has been transferred from the IF unit 11 to the switch unit 2. Since the LB-OAM cell identification flag is set, the LB-OAM cell identification flag interpreter 10
Recognizes that the type of the cell 13 is an LB-OAM cell. In that case, the cell output selection unit 11
3 is transferred to the cell switch unit 9 without passing through the VPI conversion unit 8. The HW number and VPI of the cell 13 are #
1 and VPI # b, and the state of the transmission source. Therefore, the cell switch unit 9 performs switching so as to transfer the cell 13 to the transmission source. That is, as shown in FIG. 1, the cell 13 has the HW number = “# 1”,
Transmitter 6 of IF section 11 corresponding to PI = “VPI # b”
Output to 1. The transmitting unit 61 of the IF unit 11
To the transmission path 16b. Thus, LB-O
A loopback of the AM cell is realized.

HW number = “# 1”, VPI = “VPI #”
It is assumed that the cell 12 of “b” and “LB-OAM cell identification flag = OFF” has been transferred from the IF unit 11 to the switch unit 2. Since the LB-OAM cell identification flag is not set, the LB-OAM cell identification flag interpretation unit 10 recognizes that the type of the cell 12 is a user cell. In that case, the cell output selection unit 11 transfers the cell 12 to the VPI conversion unit 8. As shown in FIG. 1, in the routing table 30, the source HW number = “#
Assuming that the routing destination corresponding to “1” and VPI = “VPI # b” is HW number = “# 2” and VPI = “VPI # b”, the cell 12 receives the HW number = “VPI # b” from the cell switch unit 9. # 2 ”, VPI = IF corresponding to“ VPI # b ”
The signal is output to the transmitting section 62 of the section 12. The transmitting section 62 of the IF section 12 sends the cell 12 to the transmission path. In this way, normal cell routing is realized.

As described above, the cell output selection unit 11
-The cell with the OAM cell identification flag set is VP
If the data is transferred to the cell switch unit 9 without passing through the I conversion unit 8, a routing table area for LB-OAM cell conversion can be made unnecessary.

[0024]

As described above, the ATM cell loopback method and the ATM cell switch device are configured such that when an input cell is a loopback cell, the cell is switched without performing VPI conversion. As a result, the routing table area for loopback conversion is not required, and as a result, the buffer capacity in the VPI conversion unit is reduced, and the registration / maintenance of the routing table for loopback conversion becomes unnecessary. This has the effect of reducing the load on the user.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an ATM cell switch device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of each IF unit together with a switch unit.

FIG. 3 is a block diagram showing a configuration of a conventional ATM cell switch device.

FIG. 4 is a block diagram showing a detailed configuration of each IF unit together with a conventional switch unit.

FIG. 5 is an explanatory diagram showing a cell format.

[Explanation of symbols]

 1, 11 1 to 1n interface unit 2 switch unit 7 LB-OAM cell identification unit 8 VPI conversion unit 9 cell switch unit 10 LB-OAM cell identification flag interpretation unit 11 cell output selection unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 12/56 H04L 12/28 H04L 12/24 H04L 12/26 H04L 29/14

Claims (3)

(57) [Claims] 1. A receiving unit for receiving a cell , wherein the cell is a user cell or a loopback cell.
And a VPI that includes a routing table and performs VPI conversion
AT in ATM cell switch device having conversion unit
An M-loopback method, wherein when the cell determined by the loopback cell determination unit is a loopback cell, an ATM cell that switches the VPI conversion unit without performing VPI conversion for the cell. Loopback method. 2. A cell received via a transmission path is output with a highway number added thereto, and a transmission cell is transmitted to the transmission path. If the received cell is a loopback cell, an identification flag is set. An interface unit for outputting, and a VP for performing VPI conversion of cells from the interface unit
An ATM cell switch device comprising: an I conversion unit; and a switch unit having a switching unit that routes a cell from the VPI conversion unit and outputs the cell to the interface unit, wherein the cell input from the interface unit to the switch unit is If the cell is a loopback cell, a loopback cell discriminator for supplying the cell to the switching unit without passing through the VPI converter is provided.
TM cell switch device. 3. A loopback cell determining unit includes: an identification flag interpreting unit that determines whether an identification flag is set in a cell from an interface unit; and the identification flag interpreting unit detects that the identification flag is set. 3. The ATM cell switching device according to claim 2, further comprising: a cell output selecting unit that transfers a cell to the cell switching unit in the case where the cell switching is performed.