JPH0750676A - Inter-node test system in atm exchange network - Google Patents

Abstract

PURPOSE:To economically realize a conduction recognition test including the quality test of nodes through the use of a monitoring cell even if a user cell is absent on an inter-node test system in an ATM exchange network provided with a monitoring cell generation part for quality monitor and a monitoring cell detection part in the node. CONSTITUTION:A dummy cell generation part 3 generating a dummy cell having VPI or VCI similar to that of an arbitrary logical path (VP) or logical channel (VC) is provided in the preceding stage of a calling node I monitoring cell generation part 4. When the cell which does not have VPI or VCI becoming the object of quality monitor is not generated or the number of the generated cells is small, the dummy cell is generated from the dummy cell generation part 3, the monitoring cell is given and transmitted from the monitoring cell generation part to the dummy cell or to the dummy cell and the user cell, and the cell is checked in the monitoring cell detection part 6 of a node 5 on an opposite side so as to conduct the inter-node test.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internode test system in an ATM switching network. In recent years, ATM (Asynchronous
Wideband ISDN (B-ISD) using Transfer Mode
N) is being researched for practical use. CCITT has issued various recommendations for this broadband ISDN. Among them, there is a function for maintenance and operation of communication networks (OAM function: Operation Administration and Mainten
ance) is defined.
In the OAM function, a technique of transmitting a monitoring cell from one node and detecting it at the other node is used in order to monitor the transmission quality of the network. Since this monitoring cell is to be added every time a fixed number of user cells are generated, it cannot be used unless user cells are generated. Therefore, improvement thereof is desired.

[0002]

2. Description of the Related Art VP or V in a section of an ATM switching network
When trying to monitor the quality of C, the following method can be considered. That is, a test cell generator is provided,
Alternatively, the test cell is inserted from the VC end point (transmission side node), and the test cell is extracted via the transmission line at the VP or VC end point (reception side node), and the number of test cells received, This is a method of monitoring the quality of VP and VC by bit check of test cells.

However, in this method, the test cell may be discarded in the portion where the test cell is multiplexed with the user cell. If this happens, the test cell is discarded before the original monitoring section and the measurement becomes meaningless. I will end up. Further, if the test cell is prioritized over the user cell, the user cell may be discarded, so that there is a problem that it is necessary to provide a sufficiently large buffer in the multiplex circuit for adjustment.

As a method for solving the problems of the above method,
There is a method described with reference to FIG. FIG. 3 is an explanatory diagram of an inter-node test method using a monitoring cell. Indicates a transmission path using a monitoring cell.

A. , 40 is a user terminal for generating and transmitting an ATM cell (user cell), 41 is a source node constituting an ATM switch, 42 is a user cell generated on the highway from the user terminal 40, and the user cell is fixed. Number (128, 256 in CCITT standard)
A monitoring cell generation circuit 43 for generating a monitoring cell including an error detection code (code having an error detection function of a plurality of bits) for each of the cells 512 and 1024) is a switching unit.

Further, 44 is a destination node (a destination termination point of VP or VC) which receives the cell transmitted from the source node 41 and transmits it to the user terminal of its own node, and 45 is a destination node 44.
Is a monitoring cell detection circuit that detects a monitoring cell from the received cell and detects an error, and 47 is a destination user terminal.

In the above configuration, the VP (Virtual Pat
h) and when performing a transmission quality test between nodes that specify VC (Virtual Channel) for VP or VC, when the user terminal 40 of the source node 41 transmits information to the user terminal 47 of the destination node 44, the user terminal A user cell (with a specific VPI and VCI set in the header) is transmitted from 40. This user cell normally passes through the monitoring cell generation circuit 42 of the source node 41, is sent to the destination node 44 through the exchange unit 43, passes through the exchange unit 45, and passes through the monitoring cell detection circuit 46. It is sent to the user terminal 47 of the other party.

When monitoring the transmission quality of the user cell between the source node 41 and the destination node 44, the monitoring cell generation circuit 42 generates a monitoring cell having the same VPI or VCI as the user cell. This monitoring cell is generated once for every fixed number of user cells,
According to CCITT, for example, it can be specified that it occurs every 1024 user cells. Therefore, the monitoring cell generation circuit 42 detects the number of generated user cells and
After the number of 24 user cells is reached, a monitoring cell is generated on the transmission path at the timing when the user cell becomes vacant.

The user cell and the monitoring cell are sent to the destination node 44 through the designated logical path (VP) and logical channel (VC) via the switching unit 43. When the data is input to the monitoring cell detection circuit 46 through the switching unit 45 of the destination node 44, the monitoring cell is extracted here, error detection is performed, and data of transmission quality such as an error rate of data is obtained. At this time, the monitoring cell is not transmitted to the partner user terminal 47.

The monitoring cell can be used not only between the source node and the destination node but also for testing between any nodes. Further, this monitoring cell is also used for confirming the continuity of the transmission line (transmission of the cell) by a specific VP or VC.

Referring to FIG. Shows an example of cells generated on the transmission path between nodes. In this example, the user cell is VCI
= 1, VC of the monitoring cell (MC)
Set "1" as I and display the monitoring cell (V
In the case of the C monitoring cell, a monitoring cell (MC) having a payload type identifier PTI in the header as a specific value and displayed) is generated. This monitoring cell is As shown in (1), when 1 to 1024 user cells occur, they are inserted immediately after that, and this is repeated.

[0012]

In the conventional inter-node test method using the monitoring cell shown in FIG. 3, a user cell is inserted into the transmission line every time a fixed number of user cells are generated.
On the other hand, an inter-node test using a monitoring cell is often executed by a user's declaration that there are many errors in data (there may also be periodical execution). The situation occurs where communication via VP or VC is avoided or only short information is transmitted. In this case, even if it is desired to perform an inter-node test for the user cell, there is a problem that the test cannot be substantially performed because the number of user cells for generating the monitoring cell is insufficient.

Further, when a new node is newly installed in the ATM switching network or a continuity test including transmission quality between nodes is desired when a VP or VC is opened, the user terminal is not connected (not operated). However, there is a problem that the test by the monitoring cell cannot be executed because of the state.

An object of the present invention is to provide an inter-node test system in an ATM switching network which can economically realize a continuity confirmation test including a quality test by using a monitoring cell even when there is no user cell.

[0015]

FIG. 1 is a block diagram showing the principle of the present invention. In FIG. 1, 1 is a source node, 2 is a multiplexer,
3 is a dummy cell generator, 4 is a monitoring cell generator,
Reference numeral 5 is a destination node, 6 is a monitoring cell detector, 7 is a highway in which a user cell from the transmitting side is generated, and 8 is a highway in which a user cell to the receiving side is generated.

According to the present invention, when the number of user cells is small or does not occur, the same VPI or V as the user cell to be tested is used.
By generating a dummy cell having CI, a test using a monitoring cell can be performed on a VP or VC to be tested.

[0017]

In FIG. 1, the VPI or VCI used by the user cell of the highway 7 is subjected to the test in the monitoring section from the source node 1 to the destination node 5. At this time, if the user cells on the highway 7 are constantly generated, the user cell is selected by the multiplexing unit 2 and a predetermined number (1024 in this example) of the user cells are selected.
The monitoring cell generating unit 4 adds a monitoring cell containing an error detection code for each transmission. However, in the case where only a small number of user cells are input within a fixed time, or no user cells are input at the time of node opening (including failure recovery), the dummy cell generation unit 3 in the multiplexing unit 2 Select the output of. The dummy cell generator 3 has the same VPI or VCI as the user cell under test.
A normal ATM cell structure in which is set (the information part has meaningless data, for example, a PN pattern) is output from the multiplexing part 2 and input to the monitoring cell generating part 4. The monitoring cell generation unit 4 counts dummy cells in the same manner as user cells, adds monitoring cells for each predetermined number, and transmits the cells.

At the destination node 5, a monitoring cell can be taken out from each cell input in the monitoring cell detector 6 and an error can be detected to monitor the quality.

The multiplexing unit 2 of the source node 1 preferentially selects a user cell as long as a user cell is generated, and selects the dummy cell from the dummy cell generation unit 3 only when there is no user cell.

[0020]

FIG. 2 is a block diagram of an embodiment of the present invention. Figure 2
In the figure, 20 is a calling side node, 21 to 27 are respective parts constituting the calling side node, and 21 is a subscriber line termination LU (LU: Li) to which an ascending and descending highway of the calling side user is connected.
ne Unit, line compatible device, 22 is a central control unit (CC
, 23 is a switch unit, and 24 is a switch (SW I) for switching cells output from inside the node to the outside.
N), 25 is a switch (represented by SW OUT) for switching a cell input from the outside to the node, 2
6 is a trunk line LU for accommodating a trunk line connected to another node,
27 is a dummy cell generator (represented by DCG: Damy Cell)
Generator), 28 is a source node 20 to a destination node 30
An upstream trunk line to the destination node 30 is a downstream trunk line from the destination node 30. Further, 30 is a destination node, 31 is a subscriber line termination LU to which the upstream and downstream highways of the destination user are connected, and 32 to 37 are respective parts 22 to 27 in the source node. Since it is the same device as, the description is omitted.

In the respective internal configurations of the subscriber line termination LUs 21 and 31 of the originating side node 20 and the destination side node 30,
210 and 310 are multiple circuits (represented by MX), 211 and 3
Reference numeral 11 is a monitoring cell addition circuit (represented by M1) corresponding to the monitoring cell generator 4 of FIG.
Is a monitoring cell check circuit (represented by M2) corresponding to the monitoring cell detection unit 6 in FIG.
Is a cell filter (F1
, 214, 314 are simple header conversion circuits (HC
(Represented by V).

In the configuration of this embodiment, the subscriber line termination LU
For the sake of convenience of explaining an example of communication originating from a subscriber of 21 and having a subscriber of the subscriber line termination LU 31 as a destination, different names are given to the originating side node 20 and the destination side node 30 for the sake of convenience. Each node has the same configuration. Further, there may be a plurality of nodes (not shown) between the nodes 20 and 30.

In the configuration of the embodiment, an example of the operation when performing the inter-node test from the source node 20 to the destination node 30 will be described in the order of the following operations (1) to (3). At the calling-side node 20, the cell having VCI = "a" and the VCI from the CC22 to the cell filter (F1) 213
= "B" and a cell with a dummy cell identification flag set (for example, PTI = "c", where PTI is the payload type identifier in the cell header) is instructed to be discarded. It should be noted that VCI = a is a special VCI reserved on the network, and the cell filter (F1) 213 that is not released to the user receives the cell with VCI = “a” and VCI = “b” among the cells to be input. "And PTI =
Only the cells of "c" are selectively discarded.

Next, in the calling-side node 20, the central controller (CC) 22 operates as a dummy cell generator (DCG) 2
7 is instructed to generate a cell with VCI = "a" and PTI = "c". Note that VCI = “a” is a special VCI reserved on the network and is a value that is not released to the user.

Dummy cell generator 2 of source node 20
The dummy cell generated from 7 is switched in SWOUT25 toward the target subscriber line termination LU21. In the subscriber line termination LU21, SW OUT
The multiplexed cell output from 25 passes through the downlink monitoring cell check circuit (M2) 212, and the simple header conversion circuit (HCV) 214 outputs the same VC as the user cell.
The I value is converted to VCI = “b” (however, PTI = “c”), the dummy cell is supplied to the multiplexing circuit (MX) 210, and is multiplexed with the user cell from the calling subscriber.
At this time, the multiplexing circuit (MX) 210 gives priority to the user cell from the calling subscriber and multiplexes the dummy cell when there is no user cell.

Monitoring cell addition circuit (M1) 211 for the dummy cell (when no user cell is generated at all) or the dummy cell and the user cell (when there is little user cell generation) output from the multiplexing circuit (MX) 210
In, an upstream monitoring cell is added, and SW
Switching to the trunk line LU26 connected to the destination LU by IN24. The cell filter (F1) 21
3, the cells generated by the dummy cell generator 27 are discarded and do not flow into the calling subscriber.

The trunk line LU26 transmits cells to the destination node 30 via the trunk line LU26 by the trunk line termination function. In the destination node 30, the target cell of VCI = "b" which is terminated in the trunk line LU36 and is sent to the destination subscriber is switched to the subscriber line termination LU31 by SW OUT35.

The monitoring cell check circuit (M2) 312 of the subscriber line termination LU 31 performs a check using the input monitoring cell, and the check result is notified to the central controller (CC) 32. In the destination node 30, the central control unit (CC) 32 sends VCI = to the monitoring cell check circuit (M2) 312 in advance.
The target cell having “b” is instructed to perform the check, and the cell filter (F1) 313 is instructed to discard the cell having VCI = “b” and PTI = “c”. As a result, only the dummy cell is discarded, and only the user cell is sent to the called subscriber.

By the above operation, the test by the monitoring cell is possible even when there is no subscriber line signal. By performing the same control in the opposite direction,
At the same time, it is possible to perform testing on the same upstream and downstream VCs.

[0030]

According to the present invention, in the ATM switching network,
The inter-node test using CCITT standard monitoring cells can be executed even when the subscriber is not connected or when the number of cells generated by the subscriber is small.

Further, generally, cells having a large number of VPIs and VCIs are multiplexed on the user highway, but cells having VPIs and VCIs other than the test object are not discarded by the multiplexing unit of the present invention. VP other than the test target,
Inter-node testing is possible even when the VC is in service. Furthermore, since the quality monitoring section extends from the monitoring cell generation part of the source node to the monitoring cell detection part of the destination node, the dummy cells are discarded in the source multiplexing part due to the burst arrival of user cells. Even if it occurs, quality monitoring is possible without any problems.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 1 Originating Node 2 Multiplexing Part 3 Dummy Cell Generating Part 4 Monitoring Cell Generating Part 5 Destination Node 6 Monitoring Cell Detecting Part 7 Highway where a user cell from the transmitting side is generated 8 Highway where a user cell to the receiving side is generated

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H04Q 11/04 9076-5K H04Q 11/04 L (71) Applicant 000005108 Hitachi, Ltd. Chiyoda, Tokyo 4-6, Surugadai, Kanda-ku (72) Toshio Shimoe, 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa, Fujitsu Limited (72) Inventor, Takafumi Kobayashi 1015, Kamikodanaka, Nakahara-ku, Kawasaki, Kanagawa, Fujitsu Limited (72) Inventor Kenji Miyabo 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Inventor Akira Nori 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (72) Inventor Hiroshi Ikeda 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (72) Inventor Yozo Oguri Yokohama, Kanagawa Mound Ward Totsuka-cho, 216 address Co., Ltd., Hitachi Information and Communications business unit

Claims (2)

[Claims] 1. A dummy cell having the same VPI or VCI as an arbitrary logical path (VP) or logical channel (VC) in an ATM switching network having a monitoring cell generation unit for quality monitoring and a monitoring cell detection unit in a node. A dummy cell generation unit for generation is provided in the preceding stage of the monitoring cell generation unit, and a VPI or V that is a target of quality monitoring is provided.
A node-to-node test method in an ATM switching network, wherein dummy cells are generated from the dummy cell generation unit to perform quality monitoring between nodes when there is no cell having CI or the number of cells is small. 2. The multiplexing unit according to claim 1, wherein the dummy cell generated from the dummy cell generating unit is multiplexed on a highway of a user cell, the multiplexing unit having a high priority of the user cell is provided. An inter-node test method in an ATM switching network in which a monitoring cell generated by the monitoring cell generating unit arranged in a subsequent stage is inserted into the cell output from the node to perform quality monitoring between nodes.