JPH10190663A - Cell copy device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the delay of a unicast call when the spacing of a multicast call is performed by writing the received cell into a unicast or multicast call buffer if the cell is related to the unicast or multicast call respectively and calculating the input load via the observation of the load caused by the reception of the cell. SOLUTION: A copy number extraction part 13 extracts the copy number (c) from the control information of a received cell. A write control part 14 writes the received cell into a unicast call buffer 11 or a multicast call buffer 12 if the cell is related to a unicast call or a multicast call, respectively. A spacing control part 15a finds the total sum of copy numbers (c) that are extracted at the part 13 in regard to the cells which are received at every time of a prescribed observation cycle T with the single cell time defined as a unit. The part 15a sends the total sum of numbers (c) to a read control part 16 as the input load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM switch for transferring cells related to a multicast call and a unicast call.
The present invention relates to a cell copy device used for a transmission device.

In recent years, a high-speed network using an ATM (asynchronous transfer mode) communication network has been attracting attention as a platform for realizing multimedia communication from voice to moving image.

In order to economically realize a broadcasting service such as CATV and a distribution service such as near VOD (Video on Demand) through an ATM communication network, an ATM exchange and the like are required.
It is effective to provide the transmission device with a multicast function and transmit only necessary minimum information. In order to realize the multicast function, ATM switching and transmission equipment includes:
A cell copy device that realizes a cell copy function for duplicating a cell carrying various information is required.

[0004]

2. Description of the Related Art Methods for realizing a cell copy function are roughly classified into a highway copy method and a highway copy method. FIGS. 7 to 9 show configuration examples in the vicinity of a switch section of an ATM switching / transmission apparatus having a multicast function.
Shown in

FIG. 7 shows a configuration of a copy trunk type. The switch 1 does not have a cell copy function, and the copy trunk 2 performs a copy within a highway to realize a multicast function. The cell from the highway (input side) is sent to the copy trunk 2, temporarily stored in the copy buffer 2a, copied by being read out a required number of times (the number of times of copying), and the destination is assigned by the destination assigning unit 2b. The signal is sent to the highway (output side) via the switch 1 again.

FIG. 8 shows a configuration of a switch and an outgoing line copy type.
Further, the outgoing line copy unit 3 provided on the output side performs in-highway copy. The cells from the highway (input side) are copied in the switch 1 and sent to the outgoing line copy unit 3, where the number of copies is assigned by the copy number assigning unit 3a based on the correspondence table and temporarily stored in the copy buffer 3b. Are copied by being read out only as many times as necessary (the number of times of copying), and sent to the highway (output side).

FIG. 9 shows an input and output line copy type configuration, in which the switch 1 has no copy function and
The in-line copy unit 4 provided on the input side performs the in-highway copy, and the out-line copy unit 3 provided on the output side performs the in-highway copy in the same manner as in FIG. is there.

The cells from the highway (input side) are sent to the incoming line copy unit 4, temporarily stored in a copy buffer 4a, read out only as many times as necessary (the number of times of copying), copied, and sent to a destination assigning unit 4b. Each destination is assigned and sent to the switch 1. The cell from the switch 1 is sent to the outgoing line copy unit 3 and the copy number assigning unit 3
In a, the number of copies is given based on the correspondence table, temporarily stored in the copy buffer 3b, read out by the required number of times (the number of copies), copied, and sent to the highway (output side).

The copy within the highway is realized by temporarily storing the cells to be copied in the copy buffers 3a and 4a and reading them out only as many times as necessary.
Here, since the outputs of the copy units 3 and 4 occur continuously (burst-wise) for the number of copies, there is a possibility of adversely affecting the subsequent apparatus. Pacing is performed to avoid this.

FIG. 10 shows an example of the configuration of a copy unit having a spacing function. The copy number extracting unit 5 extracts the number of copies set in the control information of the cell, and stores the cell in the copy buffer 6. The copy number c extracted by the copy number extraction unit 5 is sent to the load observation unit 7a and the read control unit 8 of the spacing control unit 7.

The load observing section 7a counts the sum N = の c of the copy numbers c of the cells written in the copy buffer 6 for each predetermined observation cycle T, and obtains an input load (use rate) ρ = N
/ T.

Here, since there is a possibility that N> T,
In that case, ρ = 1, and the excess (N−T) is carried over to the next observation window. The read interval calculation unit 7b calculates 1 / ρ based on the input load ρ from the load observation unit 7a, and passes it to the read control unit 8 as a read interval.

The read controller 8 can read cells at regular intervals at every observation cycle T by reading cells while copying them from the copy buffer 6 at the read interval 1 / ρ, thereby reducing burstiness of output traffic. can do.

For example, as shown in FIG.
Observation period (window size) in cell time units
Assuming that T = 16 (cell time) and the number of observed cells N in a certain observation window is N = 4, the input load (use rate) ρ = 1/4 and the readout interval is 1 / ρ = 4. Are transmitted at a rate of one cell.

When the number of observed cells N in the next observation window is N = 8, the input load ρ = １ ／ and the read interval is 1
/ Ρ = 2, and cells are transmitted at a rate of one cell every two cell times.

Since the read interval 1 / ρ is not always an integer, as shown in FIG. 12, the number of observed cells N is cumulatively added at each cell interval to become T or more. There is a case where a method of reading a cell at a predetermined timing and subtracting T from the sum of N at that time is adopted.

[0017]

By the way, in the copy trunk type as shown in FIG. 7, since the copy trunk 2 handles only the multicast call, the spacing processing does not affect the unicast call. .

However, as in the case of the switch and outgoing line copy type shown in FIG. 8 or the incoming and outgoing line copy type shown in FIG. When the spacing process is performed, a unicast call that is not copied and does not increase the burstiness of traffic is also subjected to the spacing process, so that there is a problem that the delay of the unicast call increases. .

Accordingly, an object of the present invention is to provide a cell copy apparatus which does not cause a delay of a unicast call even if a multicast call is spaced.

[0020]

A cell copying apparatus according to the present invention is used in an ATM switching / transmission apparatus for transferring cells relating to a unicast call and a multicast call, and the received cell is a cell relating to a multicast call. Is a device for copying and transmitting the same number of cells as the number of copies included in the control information of the cell, and is configured as follows.

That is, a unicast call buffer in which a plurality of cells relating to a unicast call are temporarily stored, a multicast call buffer in which a plurality of cells relating to a multicast call are temporarily stored, and a received cell And a copy number extracting unit for extracting the number of copies from the control information.

Further, when the received cell is a cell relating to a unicast call, the cell is written into the unicast call buffer, and when the received cell is a cell relating to a multicast call, the cell is referred to as the cell. A write control unit for writing to the multicast call buffer, a load observation control unit for observing a load accompanying the reception of the cell to obtain an input load, and a buffer for the unicast call based on an input load by the load observation control unit. A read control unit for selectively reading cells from the multicast call buffer and transmitting the cells.

According to the present invention, cells for a unicast call are stored in a buffer for a unicast call, and cells for a multicast call are stored in a buffer for a multicast call. It can be targeted only for cells.

Therefore, the transmission of the cell relating to the unicast call is performed during the idle time of the transmission of the cell relating to the multicast call, and the transmission of the cell relating to the unicast call is given priority over the transmission of the cell relating to the multicast call. It is possible to perform control such as transmitting the call and the multicast call equally, and to reduce the delay of the unicast call even if the spacing of the multicast call is performed.

The load monitoring unit monitors the input load for a plurality of lines (highways) through which the cells are transmitted, and the read control unit controls the read of a cell for a unicast call or a cell for a multicast call. Can be commonly performed between the lines.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION A cell copying apparatus according to each of the following embodiments is used for an ATM switching / transmission apparatus for transferring cells related to a multicast call and a unicast call.
If the received cell is a cell related to a multicast call, the apparatus duplicates and transmits the same number of cells as the number of copies included in the control information of the cell.

The cells to be transferred include a destination, an attribute,
Data to be transferred is set in control information such as the number of copies. The attribute is information indicating whether the cell is a unicast call or a multicast call, and the number of copies is information indicating the number to be copied by the cell copying apparatus when the cell is a multicast call. In addition,
Whether it is a unicast call or a multicast call,
The attribute can be omitted to determine whether the number of copies is 1 or not. However, since the order of cells may not be guaranteed,
Here, it is assumed that the attribute is provided separately from the number of copies.

(1) First Embodiment FIG. 1 is a block diagram showing a configuration of a cell copy apparatus according to a first embodiment of the present invention.

This cell copying apparatus includes a unicast call buffer 11, a multicast call buffer 12, a copy number extraction unit 13, a write control unit 14, a spacing control unit 15, a read control unit 16, and a selector 17. It is composed.

The unicast call buffer 11 is a buffer for temporarily storing a plurality of cells related to a unicast call, and the multicast call buffer 12 is a buffer for temporarily storing a plurality of cells related to a multicast call. It is. The unicast call buffer 11 and the multicast call buffer 12 are FIFO (first-in first-out) buffers, and are provided independently of each other.

The copy number extracting unit 13 extracts the copy number c from the control information of the received cell. The write control unit 14 writes the received cell to the unicast call buffer 11 when the received cell is a cell related to a unicast call, and writes the received cell to the multicast call buffer when the received cell is a cell related to a multicast call. Write to buffer 12.

The spacing control unit 15 includes a load observation unit 15
a and a reading interval calculation unit 15b. The load observing unit 15a observes the load accompanying the reception of the cell to obtain the input load, and the read interval calculating unit 15b calculates the cell sending interval according to the input load obtained by the load observing unit 15a.

The load observing section 15a uses one cell time as a unit, and for each predetermined observation cycle T (T cell time),
A sum N = Σc (including the number carried over from the previous observation) of the copy number c extracted by the copy number extraction unit 13 for the received cell is obtained, and as an input load (use rate) ρ, N ≦ T When ρ = N / T, when N> T, ρ =
1 and passes the input load ρ to the read interval calculation unit 15b. The read interval calculation unit 15b passes the reciprocal of the input load ρ, that is, 1 / ρ, to the read control unit 16 as a read interval.

The read controller 16 selectively reads cells from the unicast call buffer 11 or the multicast call buffer 12 based on the transmission interval 1 / ρ by the read interval calculator 15b. The selector 17 outputs the cell read by the read control unit 16 from the unicast call buffer 11 or the multicast call buffer 12 to the highway.

The control by the read control unit 16 to read out the cell from the unicast call buffer 11 or the multicast call buffer 12 can be performed, for example, as follows.

The read control unit 16 includes a read interval calculation unit 15b
Is smaller than 1, the multicast call buffer 12 according to the read interval 1 / ρ.
The cell can be read from the unicast call buffer 11 during a vacant time between the reading of the cell for one multicast call and the reading of the cell for the next multicast call.

When a cell is stored in the unicast call buffer 11, the read control unit 16 preferentially reads the cell from the unicast call buffer 11 and transfers the cell related to the unicast call. After that, the cell can be read from the multicast call buffer 12.

According to the first embodiment, since the unicast call buffer 11 and the multicast call buffer 12 are provided independently of each other, the spacing process is applied only to the cell related to the multicast call, The transmission of the cell relating to the cast call can be performed during the idle time of the transmission of the cell relating to the multicast call, or the transmission of the cell relating to the unicast call can be transmitted in preference to the transmission of the cell relating to the multicast call. Even if the spacing of the cell related to the multicast call is performed, the cell related to the unicast call is less affected and the delay of the cell related to the unicast call is less likely to occur.

(2) Second Embodiment FIG. 2 is a block diagram showing a configuration of a cell copy apparatus according to a second embodiment of the present invention.

This cell copying apparatus includes a shared buffer (cell buffer) 21, an empty address management FIFO 22, a unicast call address management FIFO 23, a multicast call address management FIFO 24, and a copy number extraction unit 2.
5, a writing control unit 26, a spacing control unit having a buffer amount management unit 27, a read control unit 28, a read pattern table 29, and a selector 30.

The shared buffer 21 is a buffer in which a plurality of cells for a unicast call and a plurality of cells for a multicast call are temporarily stored. This shared buffer 2
1 is a single random writable / readable buffer in hardware.

The empty address management FIFO 22 is a first-in first-out buffer for managing addresses of the shared buffer 21 where cells are not stored. In the empty address management FIFO 22, since the shared buffers 21 are all empty in the initial state,
All addresses of the shared buffer 21 are set.

Address management FIFO 2 for unicast calls
3 is a first-in-one for managing the address of the shared buffer 21 at which the cell related to the unicast call is stored.
First out buffer.

Address management FIFO for multicast call
Reference numeral 24 denotes a first-in first-out buffer for managing an address of the shared buffer 21 at which a cell related to the multicast call is stored. In the multicast call address management buffer 24, the number of copies is set together with the address.

The address management FIFOs 22, 2
By managing the address of the shared buffer 21 by 3 and 24, the single shared buffer 21 is logically used as a unicast call buffer and a multicast call buffer.

When a cell is received, the copy number extraction unit 25 extracts the number of copies from the control information of the received cell, the write control unit 26 extracts the address of the empty address management FIFO 22, and stores the received cell in the shared buffer 21. Write to the address.

Next, the write control unit 26 determines the attribute of the received cell, and if the cell is a cell related to a unicast call, writes the write address of the cell to the unicast call address management FIFO 23. Set to. Write control unit 2
6 sets the write address of the cell and the copy number of the cell extracted by the copy number extraction unit 25 in the multicast call address management FIFO 24 when the received cell is a cell related to the multicast call. .

The buffer amount management unit 27 obtains the input load ρ by observing the logical buffer length Q of the cell involved in the multicast call accompanying the acceptance of the cell. That is, the buffer amount management unit 27 sequentially adds the number of copies of the cell related to the received multicast call for each predetermined observation period T (T cell time) in units of one cell time, thereby making the logical buffer available. The length Q (including the number carried over from the previous observation) is obtained, and the input load to be obtained is ρ, and Q ≦ T
In this case, ρ = Q / T, and when Q> T, ρ = 1, and this input load ρ is passed to the read control unit 28.

The read pattern table 29 is a preset data table. As shown in FIG. 3, a read pattern corresponding to the range of the input load ρ is set. In the figure, the range of the input load ρ is divided into eight stages by dividing the range of 0 to 1 in units of 0.125, and the read pattern has a predetermined period τ (τ ≦ T; = 8) indicates whether or not cells can be transmitted in each of the time slots (0 to 7). In the figure, "1" indicates that cells are transmitted, and "0" indicates that cells are not transmitted.

The read control unit 28 refers to the read pattern table 29 based on the input load ρ from the buffer amount management unit 27 and extracts a corresponding read pattern. When the time slot corresponding to the read pattern is "0", the read control unit 28 extracts the address of the unicast call address management FIFO 23 according to the read pattern,
The cell is read from the corresponding address of the shared buffer 21.

The read control unit 28 has an address register for storing an address and a work variable register for storing a work variable, which are used for copying a cell related to a multicast call.

When the time slot corresponding to the read pattern is "1" and the work variable of the work variable register of the read control unit 28 is "0", the read control unit 28 controls the multicast call address management FIFO 24. Fetches the address and the number of copies from
The cell corresponding to the address in the shared buffer 21 is read, 1 is subtracted from the work variable in the work variable register, and 1 is subtracted from the logical buffer length Q managed by the buffer amount management unit 27.

When the time slot corresponding to the read pattern is "1" and the work variable of the work variable register of the read control unit 28 is not "0", the read control unit 28 The address is read (the contents are not changed), the cell corresponding to the address in the shared buffer 21 is read, 1 is subtracted from the work variable in the work variable register, and the logical buffer length Q managed by the buffer amount management unit 27 is Subtract 1 from. When the work variable in the work variable register becomes “0”, the address is returned to the empty address management FIFO 22.

According to the second embodiment, the address of the single shared buffer 21 is stored in the address management FIFO 2
2, 23, and 24, the cell for the unicast call and the cell for the multicast call are handled independently, and the spacing process is performed only for the cell for the multicast call. The transmission of the cell related to the call is performed during the idle time of the transmission of the cell related to the multicast call.

Therefore, even if the spacing of the cell related to the multicast call is performed, the cell related to the unicast call is less affected and the delay of the cell related to the unicast call is less likely to occur.

Further, since a single shared buffer 21 is used, the buffer can be used more effectively and the hardware can be reduced as compared with the first embodiment. (3) Third Embodiment FIG. 4 is a block diagram showing a configuration of a cell copy apparatus according to a third embodiment of the present invention.

In the cell according to the third embodiment, information indicating the priority (class 0, class 1) of the cell with respect to other cells is set as control information. This cell copying apparatus includes a shared buffer (cell buffer) 31,
Empty address management FIFO 32, first unicast call address management FIFO (class 0) 33a, second unicast call address management FIFO (class 1) 33b, first multicast call address management FIFO (class 0) 34a, 2 Multicast call address management FI
An FO (class 1) 34b is provided.

Further, this cell copying apparatus includes a copy number extracting unit 35, a writing control unit 36, and a buffer amount managing unit 37a.
And a spacing control unit having a load observation unit 37b, a read control unit 38, a read pattern table 39, and a selector 40.

The shared buffer 31 is a buffer in which a plurality of cells for a unicast call and a plurality of cells for a multicast call are temporarily stored. This shared buffer 3
1 is a single random writable / readable buffer in hardware.

The empty address management FIFO 32 is a first-in first-out buffer for managing addresses of the shared buffer 31 where cells are not stored. In the empty address management FIFO 32, since the shared buffer 31 is all empty in the initial state,
All addresses of the shared buffer 31 are set.

First Unicast Call Address Management FIF
O33a is a cell related to a unicast call in the shared buffer 31, and is a first-in first-out cell for managing an address where a class 0 is stored.
It is a buffer.

Second Unicast Call Address Management FIF
O33b is a cell related to a unicast call of the shared buffer 31, and is a first-in first-out cell for managing an address where a class 1 cell is stored.
It is a buffer.

First Multicast Call Address Management FI
The FO a is a first-in-first-out buffer for managing an address at which a class 0 cell is stored in the shared buffer 31 for a multicast call.

Second Multicast Call Address Management FI
The FO 34b is a first-in-first-out buffer for managing an address at which a class 1 cell is stored in the shared buffer 31 for a multicast call. In the first and second multicast call address management FIFOs 34a and 34b, the number of copies is set together with the address.

These address management FIFOs 32 and 33
a, 33b, 34a, and 34b manage the address of the shared buffer 31 so that a single shared buffer 3
1 is logically used as a unicast call buffer and a multicast call buffer.

The write control unit 36 has an empty address management FIFO.
Thirty-two addresses are taken out, and the received cell is written into the shared buffer 31 at the address. Next, the write control unit 3
6 determines the attribute of the received cell and determines the priority. If the cell is a class 0 cell in a unicast call, the write address of the cell is changed to the first unicast call. Set in the address management FIFO 33a. If the cell is a class 1 cell in a unicast call, the write control unit 36 sets the write address of the cell in the second unicast call address management FIFO 33b.

If the received cell is a cell related to class 0 in the multicast call, the write control unit 36 determines the write address of the cell and the copy number of the cell extracted by the copy number extraction unit 35. Is set in the first multicast call address management FIFO 34a. If the received cell is a cell relating to class 1 in a multicast call, the write control unit 36 determines the write address of the cell and the copy number of the cell extracted by the copy number extraction unit 35 as the second. Multicast call address management FIFO
34b.

The buffer amount management unit 37a obtains the input load ρ by observing the logical buffer length Q of the cell involved in the multicast call accompanying the acceptance of the cell. Load observation unit 37b
Counts the number N of cells related to a unicast call received at every predetermined observation period T.

The cell reading interval for a multicast call is determined in consideration of the minimum guaranteed bandwidth (minimum guaranteed transmission number) of the cell for a unicast call. For example, assuming that the minimum guaranteed bandwidth of the cell related to the unicast call is １ ／, the buffer amount management unit 37a sequentially adds the copy number of the cell related to the received multicast call for each observation cycle T, thereby obtaining the logical buffer. The length Q (including the number carried over from the previous observation) is determined, and the input load to be determined is ρ,
When Q ≦ TN / 2, ρ = Q / T, and when Q> TN / 2, ρ = (TN / 2) / T, and this input load ρ is passed to the read control unit 38. .

The read pattern table 39 is a preset data table, and as shown in FIG. 3, is a table in which read patterns corresponding to the range of the input load ρ are set. In the figure, the range of the input load ρ is divided into eight stages by dividing the range of 0 to 1 in units of 0.125, and the read pattern has a predetermined period τ (τ ≦ T; = 8) indicates whether or not cells can be transmitted in each of the time slots (0 to 7). In the figure, "1" indicates that cells are transmitted, and "0" indicates that cells are not transmitted.

The read control unit 38 includes a buffer amount management unit 37a.
Pattern table 39 based on the input load ρ
, And a corresponding read pattern is extracted. In accordance with the read pattern, if the time slot corresponding to the read pattern is "0", the read control unit 38 extracts the address of the first unicast call address management FIFO 33a and reads the first unicast call address management FIFO3.
If the address is not set in 3a, the address of the second unicast call address management FIFO 33b is taken out, and the cell is read out from the corresponding address in the shared buffer 31.

The read control unit 38 has an address register for storing an address and a work variable register for storing a work variable, which are used for copying a cell related to a multicast call.

When the time slot corresponding to the read pattern is "1" and the work variable in the work variable register of the read control unit 38 is "0", the read control unit 38 reads the first multicast call address. The address and the number of copies are extracted from the management FIFO 34a, and if no address is set in the first multicast call address management FIFO 34a, the address and the number of copies are extracted from the second multicast call address management FIFO 34b, and these are taken into the corresponding addresses. The data is fetched (overwritten) into the register and the work variable register, the cell corresponding to the address in the shared buffer 31 is read out, 1 is subtracted from the work variable in the work variable register, and the logical buffer length managed by the buffer amount management unit 37a. Subtract 1 from Q.

When the time slot corresponding to the read pattern is "1" and the work variable of the work variable register of the read control unit 38 is not "0", the read control unit 38 reads out the address register of its own. The address is read (the contents are not changed), the cell corresponding to the address in the shared buffer 31 is read, 1 is subtracted from the work variable in the work variable register, and the logical buffer length Q managed by the buffer amount management unit 37a is read. Subtract 1 from. When the work variable in the work variable register becomes “0”, the address is returned to the empty address management FIFO 32.

According to the third embodiment, as the unicast call address management FIFO, the first unicast call address management FIFO 33a and the second unicast call address management FIFO 33b are used as the multicast call address management FIFO. , A first multicast call address management FIFO 34a and a second multicast call address management FIFO 34b are provided corresponding to the cell priorities (class 0, class 1), respectively. Transmission is performed with priority over low (class 1) transmission.

Therefore, the delay associated with the transfer can be reduced according to the priority of the cell, and the transfer quality can be improved. In the third embodiment, the cell priority is set to two levels, class 0 and class 1.
Further, there can be a plurality.

The address of the single shared buffer 31 is stored in the address management FIFOs 32, 33a, 33b, and 34.
a and 34b, the cell for the unicast call and the cell for the multicast call are handled independently, and the spacing process is performed only for the cell for the multicast call. The transmission of such a cell guarantees a minimum guaranteed bandwidth in accordance with the input load of the cell related to the unicast call, and transfers the cell related to the unicast call.

Therefore, even if a cell for a multicast call is spaced, a cell for a unicast call is less affected and a delay of a cell for a unicast call is less likely to occur.

(4) Fourth Embodiment FIG. 5 is a block diagram showing a configuration of a cell copy apparatus according to a fourth embodiment of the present invention.

This cell copying apparatus includes a shared buffer (cell buffer) 41, an empty address management FIFO 42,
Unicast call address management FIFO (HW0) 43
a, the second unicast call address management FIFO (HW
1) 43b, first multicast call address management FI
An FO (HW0) 44a and a second multicast call address management FIFO (HW1) 44b are provided.

Further, the cell copying apparatus has a copy number extracting unit 45, a writing control unit 46, a spacing control unit having a load observation unit 47, a read control unit 48, a read pattern table 49, a selector 50, and a multiplexing unit 51. And separation unit 52
It has.

The shared buffer 41 is a buffer in which a plurality of cells related to a unicast call and a plurality of cells related to a multicast call are temporarily stored. This shared buffer 4
1 is a single random writable / readable buffer in hardware.

The empty address management FIFO 42 is a first-in first-out buffer for managing addresses of the shared buffer 41 where cells are not stored. In the empty address management FIFO 42, the shared buffer 41 is all empty in the initial state.
All addresses of the shared buffer 41 are set.

First Unicast Call Address Management FIF
O43a is a first-in, first-out buffer for managing an address at which a cell to be transferred to the highway 0 (HW0) is stored in the shared buffer 41 for a unicast call.

Second Unicast Call Address Management FIF
O43b is a first-in, first-out buffer for managing an address at which a cell to be transferred to the highway 1 (HW1) is stored in the shared buffer 41 for a unicast call.

First multicast call address management FI
The FO 44a is a first-in, first-out buffer for managing an address at which a cell to be transferred to the highway 0 (HW0) is stored in the shared buffer 41 for a multicast call.

Second multicast call address management FI
The FO 44b is a first-in, first-out buffer for managing an address at which a cell to be transferred to the highway 1 (HW1) is stored in the shared buffer 41 for the multicast call. First and second multicast call address management FIFO 44
In a and 44b, the number of copies is set together with the address.

These address management FIFOs 42 and 43
a, 43b, 44a, and 44b manage the address of the shared buffer 41 so that a single shared buffer 4
1 is logically used as a unicast call buffer and a multicast call buffer.

Highway 0 (HW0) or Highway 1
The cell transferred (HW1) is sent to the copy number extracting unit 45 via the multiplexing unit 51. When the cell is received, the copy number extracting unit 45 extracts the number of copies from the control information of the received cell, and the write control unit 46 sets the empty address management FIFO.
The address of 42 is taken out, and the received cell is written to the address of the shared buffer 41.

Next, the write controller 46 determines the attribute of the received cell, determines whether the highway to which the cell has been transferred is highway 0 or highway 1, and determines whether the cell is unicast. If the call is a cell related to the transfer of highway 0, the write address of the cell is set in the first unicast call address management FIFO 43a. When the cell is a cell related to the transfer of the highway 1 in the unicast call, the write address of the cell is set in the second unicast call address management FIFO 43b.

If the received cell is a cell related to the transfer of highway 0 in a multicast call, the write control unit 46 checks the write address of the cell and the cell number extracted by the copy number extraction unit 45. The number of copies is set in the first multicast call address management FIFO 44a.

If the received cell is a cell related to the transfer of the highway 1 in a multicast call, the write control unit 46 checks the write address of the cell and the cell number extracted by the copy number extraction unit 45. The number of copies is set in the second multicast call address management FIFO 44b.

The load observation unit 47 sets the initial value of the first work variable to 0, and sets a predetermined observation period T (W cell time) smaller than a predetermined window size W (W cell time) in units of one cell time. At every T cell time), a second work variable N is obtained by adding the sum of the number of copies in the observation cycle by the copy number extraction unit to the first work variable. The load observation unit 47 sets the input load to be obtained as ρ, sets ρ = N / W when N ≦ W, sets ρ = 1 when N> W, and transfers the input load ρ to the read control unit 48. Perform observation processing. Next, the value of the first work variable after the second time is calculated as N−N × T /
As W, the load observation processing is repeated. Here, the number of cells related to the multicast call read during the period T is n
At this time, the number N × T / W−n of cells that have been missed is further carried over to the next observation cycle.

FIG. 6 is a diagram specifically showing the load observing process, in which the input cell and the input load (use rate) ρ are calculated when the window size W = 8 and the observation period T = 2. , And input load ρ and output.

The read pattern table 49 is the same as that described with reference to FIG. 3 in the second embodiment. When addresses are set in the first unicast call address management FIFO 43a or the second unicast call address management FIFO 43b, the read control unit 48 first reads cells from the shared buffer 41 for these addresses. . The read cell is transmitted to the corresponding highway (HW0 or HW1) by the separation unit 52.

If no address is set in the first unicast call address management FIFO 43a or the second unicast call address management FIFO 43b, the read control unit 48 Referring to the read pattern table 49, the cell related to the multicast call is read out while being copied in the same manner as in the third embodiment according to the first multicast call address management FIFO 44a or the second multicast call address management FIFO 44b. The read cells are stored in the corresponding highway (HW0 or HW0) by the separation unit 52.
Sent to 1).

According to the fourth embodiment, the input load ρ can be observed with a large window size W while frequently updating the input load ρ at the observation period T. Also, the first unicast call address management FIFO 43a and the second unicast call address management FIFO 43b are used as the unicast call address management FIFO, and the first multicast call address management FIFO 44a and the second unicast call address management FIFO are used as the multicast call address management FIFO. 2 The address management FIFO 44b for multicast call is transferred to a plurality of highways (H
W0, HW1), and a plurality of highways can be handled by one cell copying apparatus, so that the configuration can be simplified in terms of hardware.

Further, since the transmission of the cell relating to the multicast call is performed after the transmission of the cell relating to the unicast call, the transfer delay of the unicast call accompanying the spacing processing of the cell relating to the multicast call is completely reduced. Can be eliminated.

In the fourth embodiment, the number of highways handled by the cell copying apparatus is two, but it goes without saying that more than two highways may be used.

[0100]

Since the present invention is configured as described above, it is possible to provide a cell copy apparatus which does not cause a delay of a unicast call even if a multicast call is spaced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a read pattern table.

FIG. 4 is a block diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a fourth exemplary embodiment of the present invention.

FIG. 6 is a diagram illustrating a specific example of a load observation process according to the fourth embodiment of this invention.

FIG. 7 is a diagram showing a configuration of a switch unit of the ATM switching / transmission device, which is a diagram showing a copy trunk type.

FIG. 8 is a diagram showing another configuration of the switch unit of the ATM switching / transmission device, showing a switch and an outgoing line copy type.

FIG. 9 is a diagram showing still another configuration of the switch unit of the ATM switching / transmission device, showing an incoming line and outgoing line copy type.

FIG. 10 is a diagram showing a configuration of a conventional technique.

FIG. 11 is a diagram illustrating an operation example of a spacing process.

FIG. 12 is a diagram illustrating a calculation example of a reading interval.

[Explanation of symbols]

 11 Unicast Call Buffer 12 Multicast Call Buffer 13 Copy Number Extraction Unit 14 Write Control Unit 15 Spacing Control Unit 15a Load Observation Unit 15b Read Interval Calculation Unit 16 Read Control Unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuo Kato 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Naoki Matsuoka 4-chome, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture No. 1 Fujitsu Limited (72) Inventor Kouji Amano 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture 1-1 Within Fujitsu Limited (72) Takashi Kurimoto 3-19 Nishishinjuku, Shinjuku-ku, Tokyo No. 2 Inside Nippon Telegraph and Telephone Corporation (72) Koichi Genda, inventor 3-19-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Naoaki Yamanaka 3-19, Nishi-Shinjuku, Shinjuku-ku, Tokyo No. 2 Nippon Telegraph and Telephone Corporation

Claims (11)

[Claims] 1. An ATM switching / transmission device for transferring cells related to a unicast call and a multicast call,
A cell copying apparatus for copying and transmitting the same number of cells as the number of copies included in the control information of a received cell when the received cell is a cell relating to a multicast call, wherein a plurality of cells relating to a unicast call are temporarily stored. A buffer for a unicast call that is temporarily stored, a buffer for a multicast call in which a plurality of cells related to a multicast call are temporarily stored, a copy number extraction unit that extracts the number of copies from control information of a received cell, If the received cell is a cell related to a unicast call, write the cell to the unicast call buffer,
When the received cell is a cell related to a multicast call, a write control unit that writes the cell to the multicast call buffer, and a load observation control unit that obtains an input load by observing a load accompanying the reception of the cell. And a read control unit for selectively reading and transmitting cells from the unicast call buffer or the multicast call buffer according to an input load by the load observation control unit. apparatus. 2. The cell copy apparatus according to claim 1, wherein the load observation control unit is configured to perform, for each predetermined observation cycle,
The logical buffer length of the multicast call buffer is observed, the logical buffer length is Q, the observation period is T, the input load to be obtained is ρ, and when Q ≦ T, ρ = Q / T, Q>
A cell copying apparatus wherein ρ = 1 at T, and the input load ρ is passed to the read control unit. 3. The cell copy apparatus according to claim 1, wherein the load observation control unit extracts the copy number as a first work variable for each predetermined observation cycle smaller than a predetermined window size. A second work variable obtained by adding the sum of the copy numbers in the observation cycle by the unit is obtained, and the second work variable is N, the window size is W, the observation cycle is T, and when N ≦ W, ρ = N / W, N> W, ρ =
1, the load observation process of passing the input load ρ to the read control unit is sequentially performed by setting the initial value of the first work variable to 0, and setting the second and subsequent values to N−N × T / W. A cell copying apparatus characterized by the following. 4. The cell copying apparatus according to claim 1, wherein the read control unit reads a cell related to a multicast call from the multicast call buffer based on a read interval from the load observation control unit, and then reads the cell. The cell copying apparatus according to claim 1, wherein the cell related to the unicast call is read from the unicast call buffer during an idle time until the cell related to the multicast call is read. 5. The cell copy device according to claim 1, wherein the load observation control unit monitors an input load for a unicast call, and the read control unit responds to an input load for a unicast. A cell copying apparatus for reading out a cell related to a unicast call or a cell related to a multicast call. 6. The cell copy apparatus according to claim 1, wherein the load observation control unit independently monitors an input load for a unicast call and an input load for a multicast call, and the read control unit A cell copy apparatus for reading a cell related to a unicast call or a cell related to a multicast call according to a ratio of an input load for a unicast call and an input load for a multicast call. 7. The cell copying apparatus according to claim 1, wherein the read control unit reads a cell from the unicast call buffer when the cell is stored in the unicast call buffer. A cell copying apparatus characterized in that when no cell is stored in the unicast call buffer, the cell is read from the multicast call buffer. 8. The cell copying apparatus according to claim 1, wherein a priority of the cell with respect to another cell is set as control information of the cell, and the unicast call buffer and the multicast call buffer are set. The write control unit writes the cell into the corresponding unicast call buffer or the multicast call buffer according to the priority of the received cell, and reads the cell. A cell copying apparatus, wherein the control unit is configured to preferentially read cells from the unicast call buffer or the multicast call buffer having a high priority. 9. The cell copying apparatus according to claim 1, wherein the unicast call buffer and the multicast call buffer are a single random writable / readable shared buffer commonly used. A cell copying apparatus wherein the shared buffer is logically used as the unicast call buffer and the multicast call buffer by managing the address of the shared buffer. 10. The cell copy apparatus according to claim 9, wherein the shared buffer is logically used for a plurality of lines by managing an address of the shared buffer. Copy device. 11. The cell copy apparatus according to claim 4, 5 or 6, wherein the load observation control unit observes an input load for a plurality of lines through which cells are transmitted, and the read control unit, A cell copying apparatus, wherein read control of a cell related to a unicast call or a cell related to a multicast call is commonly performed between the lines.