JP2920225B2 - Cell loss measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an asynchronous transfer mode (Asyn
It is used for information transfer in a chronous transfer mode (hereinafter referred to as "ATM"). In particular, connections in which cell loss has occurred, for example, VP (Virtual Path) or VC
(Virtual Channel) as a unit.

[0002]

2. Description of the Related Art In an ATM exchange, even if a call setting request from a user is accepted, if the call quality is determined to be protected from the current network usage status even if the call is accepted, the probability of the user is reduced. Band allocation is performed in connection units such as VCs or VPs, and statistical multiplexing is performed to realize effective use of the network. However, the capacity of buffers provided for a plurality of output lines is finite, and there is a possibility of cell loss due to buffer overflow.

[0003] The cell loss rate in the output line buffer is:
It can be measured from the number of cells arriving at the output line buffer and the number of cells lost due to buffer overflow.

[0004]

SUMMARY OF THE INVENTION In an ATM network,
Communication is performed by setting a connection such as VC or VP between users. Therefore, from the viewpoint of verifying whether or not the communication quality promised between the user and the network is guaranteed, VC or VP or the like is used. It is necessary to know the cell loss rate for each connection.

However, A which multiplexes many connections
In order to measure the cell loss rates of all the connections multiplexed in the TM exchange, it is necessary to store and manage all the connection identifiers in the cell header in a memory. VPI (VP identifier) as connection identifier
Alternatively, assuming that VCI (VC identifier) is used, the field in the cell header is UNI (User Network).
rk Interface), 24 bits, NNI (Network Node I)
nterface) with 28 bits, so that V
To manage PI / VCI numbers in memory, a maximum of 2
You need an entry table for ²⁸ words. Further, for example, the number of lost cells counted is 10 ³ (10 bits).
If a cell loss ratio of 10 ⁻³ is to be measured, 30 bits per word are required, including 10 ⁶ (20 bits) of the counted number of arriving cells. If this is converted into a memory amount, a capacity of about several tens of Gbits is required, and the hardware scale becomes enormous.

For this reason, conventionally, it has been general to count arrival cells and lost cells on a connection basis, but not on an output line buffer basis. Therefore, there is a problem that the quality of each connection is not known, and it is not possible to detect the quality-degraded connection reported by the user.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cell loss measuring apparatus which can solve such problems and detect a lost cell connection and grasp the quality of each connection with a small-scale hardware. .

[0008]

A cell loss measuring device according to the present invention reads a connection identifier of a cell immediately before arriving at a buffer and identifies a connection to which the cell belongs, and detects a cell loss in the buffer. Means,
Storage means for holding lost cell information including the number of cells arriving at the buffer, the number of lost cells, and the time of occurrence of lost cells in connection units; an identification output of identification means; that is, an address of the storage means corresponding to the connection; Means for setting the lost cell information of the set address according to the output of the detecting means, and the occurrence of the lost cell based on the lost cell occurrence time and the current time held in the storage means. Means for selecting the oldest connection, wherein the address means determines whether or not the lost cell information for the connection identified by the identifying means has already been registered in the storage means. If it is determined, the address corresponding to the connection is output, and an empty address is stored in the storage unit although it is not registered. Means for outputting the address if there is a scan, lost cell information about the identified connection means for identifying has not been registered in the storage means,
In addition, there is provided a means for rejecting lost cell information relating to the connection selected by the selecting means when there is no free address in the storage means.

[0009]

[Operation] Instead of performing quality measurement for all connections, a lost cell is detected by detecting a connection in which a lost cell has occurred and counting the arrival cell and the lost cell of the connection. The number of cell losses is measured for the existing connection. As a result, it is possible to detect the connection in which a lost cell occurs and to grasp the quality of each connection with a small-scale hardware.

[0010]

FIG. 1 is a block diagram showing an embodiment of the present invention.

The apparatus of this embodiment is roughly divided into a buffer controller 101, a search processing unit 102, and a replacement processing unit 1.
03, a registration processing unit 104 and a measurement table unit 105, and further includes a timer 106 and a timer value holding register 107.

The measurement result storage memory 145 of the measurement table section 105 stores lost cell information for each connection for which a lost cell has occurred previously. The search processing unit 102 calculates the VPI / VCI of the lost cell information registered in the measurement result storage memory 145.
Manage numbers.

The buffer controller 101 identifies the VPI / VCI number of the cell that should arrive at the output line buffer, and monitors the queue length of the output line buffer to determine whether a cell is lost. The search processing unit 102 searches the management table 122 and determines whether a VPI / VCI number corresponding to the cell is registered.

If the registered and lost cell, that is, the VPI / VCI number of the cell that should arrive, is registered in the management table 122 and it is determined that the cell is lost,
The registration processing unit 104 adds “1” to the number of arrived cells and the number of lost cells in the corresponding connection column of the measurement result storage memory 145, and supplies a time stamp from the timer 106 via the timer value holding register 107. A time stamp overflow flag (hereinafter referred to as “O”) indicating whether or not the timer 106 has made one or more rounds from the time at which the last time stamp was registered is updated while updating the timer value at the current time.
F ”) to“ 0 ”.

If it is determined that the cell has been registered and that the cell has not been lost, the registration processing unit 104
“1” is added only to the number of arrival cells in the corresponding connection column of No. 5.

If it is determined that the cell is unregistered and lost, the search processing unit 102 determines whether or not the measurement result storage memory 145 has a free space based on the registration status of the management table 122. If there is a free space in the measurement result storage memory 145, the VPI / VCI number is registered at a free address of the management table 122, and the number of arrived cells, the number of lost cells, and the time stamp are registered at the same address of the measurement result storage memory 145.
OF is set to “0”. If there is no free space in the measurement result storage memory 145, the replacement processing unit 103 compares the time stamps of all the connections already registered in the measurement result memory 145 with the timer 106 indicating the current time, and checks the latest of each registered connection. The period length from the lost cell occurrence time to the current time is calculated. At this time, it is determined from the calculated time and the time stamp overflow flag whether or not a timer period has elapsed since the lost cell occurrence time, and a connection having the longest period length is selected. The replacement processing unit 103 also notifies the registration processing unit 104 of a replacement candidate address corresponding to the selected connection. In response to this notification, the registration processing unit 104 causes the VPI / VCI number to be registered at the same address in the management table 122, and registers the number of arriving cells and the number of lost cells as “1” at the same address in the measurement result storage memory 145, respectively. The timer value of the time is registered as a time stamp, and OF is set to “0”.

Hereinafter, the operation of each unit will be described in more detail.

FIG. 2 is a block diagram showing details of the buffer controller 101. As shown in FIG.

The buffer controller 101 includes a queue length management section 111, a VPI / VCI identification section 121, and a lost cell detection section 131. The loss cell detection section 131 includes a queue length threshold value holding register 141 and a comparator 151.
It consists of. Queue length threshold holding register 1
In 41, a queue length to be treated as a buffer overflow is set in advance.

The queue length management unit 111 constantly manages the queue length of the output line buffer. VPI / VCI identification unit 1
21 extracts the VPI / VCI number from the header of the cell immediately before arriving at the output line buffer, and
The information (information of a cell that should arrive at the output line buffer) is output to the search processing unit 102, and the comparator 151 in the lost cell detection unit 131 is operated at that time. The comparator 151 of the lost cell detection unit 131 holds the queue length and the register 141 that are always output from the queue length management unit 111 at the output timing of the VPI / VCI information from the VPI / VCI identification unit 121. The threshold value is compared with the queue length threshold value, and if it is within the threshold value, it is determined that there is no cell loss, and if it exceeds the threshold value, it is determined that a lost cell has been detected. The output of the comparator 151 is supplied to the registration processing unit 104 as a control signal of “0” when no lost cell is detected and “1” when a lost cell is detected.

FIG. 3 is a block diagram showing details of the measurement table unit 105. As shown in FIG.

The measurement table unit 105 includes a control unit 11
5, "+1" adder 125 for counting the number of arrived cells, "+1" adder 135 for counting the number of lost cells, measurement result storage memory 1
45 and a counter 155.

As described above, the measurement result storage memory 145 stores the number of lost cells of the lost cell connection, the number of arrived cells after the detection of the lost cell, the time stamp indicating the latest lost cell occurrence time, and the time stamp value. Holds OF indicating that the timer has completed one or more rounds. The VPI / VCI number of the connection for which the lost cell information is registered in the measurement result storage memory 145 is simultaneously registered at the same address position as the measurement result storage memory 145 in the management table 122 of the search processing unit 102.

The control unit 115 stores the measurement result memory 14
In the case where a lost cell has occurred from an unregistered connection in a state where there is no free address in 5, the deletion information from the replacement processing unit 103 indicates that the connection history of the connection whose registration history has been determined to be the oldest among registered connections is determined. The measurement result storage memory 145 is controlled so that all address positions are reset to “0”. The “+1” adder 125
When the arrival cell information is received from the registration processing unit 104, the count value is incremented by “1”, and the new value is added to the measurement result storage memory 145.
In the corresponding address field. "+1" adder 13
5 receives the lost cell information from the registration processing unit 104, adds “1” to the count value, and registers the new value in the corresponding address field of the measurement result storage memory 145. Each time the lost cell number registration process is performed, the measurement result storage memory 145
, The current time is registered as the lost cell occurrence time, and the OF is updated to “0”. Timer 10
If the time stamp 6 is one or more rounds from the registered time stamp value, the OF is registered as “1” based on the information output from the replacement processing unit 103.

FIG. 4 is a block diagram showing details of the search processing unit 102.

The search processing unit 102 includes an address search counter 112, a management table 122, a VPI / VCI number registration unit 132, and a VPI / VCI number holding register 14.
2. It includes a collator 152 and an address output circuit 162.

The management table 122 stores the measurement result memory 1
45 of the connection whose lost cell information is registered in
The PI / VCI number and the free address of the measurement result storage memory 145 are held. The counter 112 specifies a read address of the management table 122 in order from the first address, and outputs a VPI / VCI number. VPI / V
The CI number registration unit 132 registers the VPI / VCI number of the connection in which the lost cell has occurred in the management table 122. The register 142 temporarily holds the VPI / VCI number output from the buffer controller. The collator 152 determines whether the VPI / VC stored in the register 142
It is determined whether the I number is registered in the management table 122 or not. The address output circuit 162 outputs an address at which the VPI / VCI number collated by the collator 152 is registered or a free address that can be registered.

Upon receiving the VPI / VCI information from the buffer controller 101, the search processing unit 102 searches whether or not the VPI / VCI number of the cell which should arrive at the output line buffer is registered in the management table 122. This operation will be described below.

The VPI / VCI number output from the buffer controller 101 is stored in a register 142 in the search processing unit 102. At this time, the counter 112 operates in response to an enable signal from the buffer controller 101, and the VPI / VCI numbers of the connections in which the lost cell information is registered in the measurement result storage memory 145 are read out sequentially from the first address of the management table 122. It is. The collator 152 collates the VPI / VCI number held in the register 142 with the VPI / VCI number sequentially read from the first address of the management table 122, and the cell in which the buffer controller 101 identifies the VPI / VCI number. Is searched for in the management table 122. When there is a matching VPI / VCI number, the address output circuit 162 outputs the address on the management table 122 to the registration processing unit 104.

Here, the address output circuit 162 determines that the management table 122 has an empty address and the register 142
/ VCI number and management table 1 held in
If there is no match between the VPI / VCI number registered in the management table 122 and the VPI / VCI number, the free address of the management table 122 is output to the registration processing unit 104. There is no free address in the management table 122 and the register 142
/ VCI number and management table 1 held in
If there is no match with the VPI / VCI number registered in 22, an enable signal is output from collator 152 to replacement processing section 103.

When registering lost cell information of a new connection in the measurement result storage memory 145, the VPI
The / VCI number registration unit 132 stores the VPI / VCI number held in the register 142 based on the enable signal output from the lost cell occurrence notification signal generation unit of the registration processing unit 104 when a lost cell is generated. Overwrite At this time, the old lost cell information registered at the address on the measurement result storage memory 145 corresponding to the address overwritten and registered in the management table 122 is deleted, and then new lost cell information is registered.

FIG. 5 is a block diagram showing details of the replacement processing unit 103, and FIG. 6 is a flowchart showing the operation thereof.

The replacement processing unit 103 stores the lost cell information of the connection which has no free address in the measurement result storage memory 145 and is not registered in the measurement result storage memory 145. A connection in which a lost cell occurs at the oldest time is extracted from a registered connection in one cell time slot. [Timer period-1] Value holding register 113, comparator 123, subtractor 133, comparator 1
43, a subtraction result maximum value holding register 153, an address output circuit 163, and an address holding register 173.

The register 113 holds a timer value smaller by one count than the timer cycle counter. Comparator 12
3 compares the value held in the register 113 with the difference between the timer value indicating the current time and the time stamp value registered in the measurement result storage memory 145 (the output of the subtractor 133). The subtractor 133 calculates the difference between the timer value indicating the current time and the time stamp value registered in the measurement result storage memory 145. Comparator 143
Is the value held in the register 153 and the value of the subtractor 13
3 is compared with the output. The register 153 is
Timer value indicating current time and measurement result storage memory 145
Holds the maximum value with the time stamp value registered in. The address output circuit 163 outputs a replaceable address to the registration processing unit 104. The register 173 holds the connection address corresponding to the maximum value of the subtraction result held in the register 153.

In the register 153 for holding the maximum value of the subtraction result and the register 173 for holding the address, "0" is set as an initial value.

The OF value of the first address is input from the measurement result storage memory 145 of the measurement table unit 105,
When the F value is “1”, the corresponding address is held in the register 173. When the OF value is “0”, the subtractor 133 calculates the time stamp TS ₁ registered at the first address of the measurement result storage memory 145 and the timer value TIM indicating the current time inputted from the timer. Difference TIM-
TS ₁ is calculated, and the comparator 113 outputs
T that is one count less than the timer period held by
Compare with IM (MAX) -1. At this time, the comparator 123
Is larger is better for TIM-TS _1, the timer is determined to have one rotation from the time stamp value, the OF of the measurement result storage memory 145 and outputs the OF information to "1".
On the other hand, the comparator 143 compares the TIM-TS ₁ with the maximum value of the subtraction result held in the register 153,
TI in the register 153 when TIM-TS ₁ is greater
M-TS ₁ is written, and the first address is written to the register 173. When the OF of the first address is set to “1”, the processing of the subsequent second address and thereafter is not performed, and when the enable signal is input from the search processing unit 102, the first address is stored in the registration processing unit 104. Is output and the replacement process ends. The above processing is sequentially executed for the first address and thereafter.

By repeating this operation within one cell time slot, the address holding register 173 stores, as a replaceable address in the measurement result storage memory 145, the address of the connection that the timer has made one or more rounds from the time stamp value. Alternatively, the address of the connection having the largest difference between the time stamp value in the timer cycle and the current timer value is held. This address is notified to the registration processing unit 104 when the enable signal from the search processing unit 102 is received.

FIG. 7 is a block diagram showing a detailed configuration of the registration processing unit 104.

The registration processing unit 104 registers a VPI / VCI number in the management table 122 based on information input from the buffer controller 101, the search processing unit 102, and the replacement processing unit 103, and stores it in the measurement result storage memory 145. The control signal output unit 114 outputs an enable signal for counting the number of arriving cells and the number of lost cells, and a registration signal output unit 124 operated by the enable signal. The registration signal output unit 124 outputs an enable cell notification signal generating unit 134 that outputs an enable signal to the “+1” adder 125 of the measurement table unit 105, the “+1” adder 135 of the measurement table unit 105, and the search processing unit 102. A lost cell occurrence notifying signal generating unit 144 that outputs an enable signal to the VPI / VCI number registering unit 132 and the timer value holding register, and a search processing unit 102 and a replacement processing unit 103 determine their output destinations.
And an output control unit 154 that performs control based on the address information output from the CPU.

The control signal output unit 114 is capable of registering control information a output from the lost cell detection unit 131 of the buffer controller 101 and indicating the presence or absence of a loss, and registering lost cell information from the search processing unit 102 or the replacement processing unit 103. The enable signal is output to the registration signal output unit 124 by calculating the logical sum with the enable signal output simultaneously with the address information. More specifically, when an enable signal for registration processing is received from search processing section 102, an enable signal is output to arrival cell notification signal generating section 134, information indicating that a lost cell is present is received from buffer controller 101, and search processing is performed. When the enable signal is received from the unit 102 or the replacement processing unit 103, the enable signal is output to both the arrival cell notification signal generation unit 134 and the lost cell generation notification signal generation unit 144.

Therefore, the buffer controller 101
When the information indicating that there is no lost cell is received from the search processing unit 102, the enable signal is supplied to the arrival cell notification signal generation unit 143 when the registration processing enable signal is received from the search processing unit 102. At this time, the arrival cell notification signal generation unit 13
4 is the search processing unit 10 under the control of the output control unit 154.
With respect to the registrable address of the measurement result storage memory 145 searched in 2, the “+1” adder 1 for counting the number of arriving cells is used.
25 to output an enable signal.

When information indicating that there is a lost cell is received from the buffer controller 101 and an enable signal for registration processing is received from the search processing unit 102, the arrival cell notification signal generation unit 134 and the lost cell generation notification signal generation unit 144
And an enable signal is supplied. Arrival cell notification signal generator 134 and lost cell occurrence notification signal generator 144
Indicates “+” for each of the registerable addresses in the measurement result storage memory 145 searched by the search processing unit 102.
1 "An enable signal is output to the adders 125 and 135. “+1” adder 125 receiving the enable signal,
135 adds 1 to the number of arriving cells and the number of lost cells of the address. Further, in the measurement table unit 105, the value of the timer 106 connected to the measurement table unit 105 is set as the current time based on the enable signal output from the lost cell occurrence notification signal generation unit 144, and is registered as a time stamp. Also, OF is updated to “0”.

When information indicating that there is a lost cell is received from the buffer controller 101 and an enable signal for replacement registration processing is received from the replacement processing unit 103, the lost cell occurrence notification signal generation unit 144 sends the VP of the search processing unit 102.
An enable signal is output to I / VCI number registration section 132. With this enable signal, the VPI / VCI number registration unit 132 registers the VP / VCI number of the newly detected lost cell in the corresponding address of the management table 122. In addition, the arrival cell notification signal generation unit 134 and the lost cell generation notification signal generation unit 144
The same measurement result storage memory 14 as the address registered in
For the 5 registerable addresses, an enable signal is output to “+1” adders 125 and 135 for counting the number of arrival cells and counting the number of lost cells. The “+1” adders 125 and 135 that have received the enable signal record “1” in the number of arrived cells and the number of lost cells of the corresponding address. Further, the value of the timer 106 connected to the measurement table unit 105 is set as a current value, and the current value is registered as a time stamp. Also, OF is updated to “0”.

OF is always updated to "0" when a control signal for counting the number of lost cells is output. Also, the addresses of the management table 122 and the measurement result storage memory 145 correspond one-to-one.

The overall flow of the operation of the embodiment described above is shown in the flowchart of FIG.

FIG. 9 shows an execution time chart within one cell time.

As described above, in this embodiment, the buffer controller 101 controls the VP within the time of one cell time slot.
The I / VCI identification process and the lost cell detection process are performed. The search processing unit 102 performs a search process for the presence / absence of registration of the cell identified by the VPI / VCI number. The number of arriving cells and the number of lost cells, the time stamp and its overflow are registered, and the replacement processing unit 103 updates the OF within one cell time slot and replaces the measurement result storage memory 145 for lost cell information. A replacement candidate search process for selecting a candidate address is performed. By such processing, the detection of the lost cell occurrence connection and the measurement of the cell loss number of the lost cell occurrence connection can be realized with a small amount of hardware.

In the above embodiment, VC is used as the connection.
Although the description above mainly deals with the case where the target is a VP, the detection of the lost cell connection and the measurement of the cell loss rate are possible by the same processing when the VP is the target or when the VC and the VP are mixed. .

[0049]

As described above, the cell loss measuring apparatus according to the present invention can detect a connection in which a lost cell has occurred and measure the latest cell loss rate of a connection in which a lost cell occurs frequently. There is an effect that can be realized by the hardware configuration of FIG.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a cell loss measuring device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing details of a buffer controller.

FIG. 3 is a block diagram showing details of a measurement table unit.

FIG. 4 is a block diagram showing details of a search processing unit.

FIG. 5 is a block diagram showing details of a replacement processing unit.

FIG. 6 is a flowchart illustrating an operation example of a replacement processing unit.

FIG. 7 is a block diagram showing details of a registration processing unit.

FIG. 8 is a flowchart showing the overall operation of the embodiment.

FIG. 9 is a time chart for explaining the operation of this embodiment.

[Explanation of symbols]

 Reference Signs List 101 buffer controller 111 queue length management unit 121 VPI / VCI identification unit 131 lost cell detection unit 141 queue length threshold value holding register 151 comparator 102 search processing unit 112 address search counter 122 management table 132 VPI / VCI number registration unit 142 VPI / VCI number holding register 152 Collator 162 Address output circuit 103 Replacement processing unit 113 [Timer period-1] Value holding register 123 OF information output comparator 133 Subtractor 143 Subtraction result size comparison comparator 153 Subtraction Result maximum value holding register 163 Address output circuit 173 Address holding register 104 Registration processing unit 114 Control signal output unit 124 Registration signal output unit 134 Arrival cell notification signal generation unit 144 Lost cell generation notification signal generation unit 15 4 Output Control Unit 105 Measurement Table Unit 115 Erasing Control Unit 125 "+1" Adder for Counting Arrived Cells 135 "+1" Adder for Counting Lost Cells 145 Measurement Result Storage Memory 155 Measurement Table Address Search Counter 106 Timer 107 Timer value holding register

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-329733 (JP, A) JP-A-5-191429 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04L 12/28 H04L 12/56 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A cell loss measuring device for measuring the number of cell losses due to overflow of a buffer for storing cells in an asynchronous transfer mode for each output line, comprising: reading a connection identifier of a cell immediately before arriving at the buffer; Means (121) for identifying the connection to which it belongs, and means (111, 1
31); storage means (145) for holding the lost cell information including the number of cells arriving at the buffer, the number of lost cells, and the lost cell occurrence time in connection units; and a storage means (145) corresponding to the identification output of the identification means. Address means (102) for setting an address of the storage means, and means (104, 1) for updating lost cell information of the set address in accordance with the output of the detecting means.
25, 135, 106, 107) and means (103) for selecting a connection with the oldest lost cell occurrence from the lost cell occurrence time and the current time held in the storage means. Means (112, 122, 132, 142, 1) for determining whether or not lost cell information for the connection identified by the identifying means has already been registered in the storage means.
52) means for outputting an address corresponding to the connection when it is determined that the connection has already been registered, and outputting the address if the storage means has not been registered but has an empty address. If lost cell information for the connection identified by the identifying means is not registered in the storage means and there is no free address in the storage means, the lost cell information for the connection selected by the selecting means (132, 115). A cell loss measuring device comprising: