JP3075551B2 - ATM multiplexer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM multiplexer for B-ISDN.

[0002]

2. Description of the Related Art B-ISDN stands for Broadband Integrated Services Digit.
al Network). ATM is B-ISDN
A communication mode in which communication information is divided into short-length bit strings (cells) as in the case of packet communication, and the header at the head of each bit string is attached with address information indicating its destination and the like, and is transferred. (Asynchronous Tra
nsfer Mode). First, the communication method of the ATM network will be described.

FIG. 2 shows a part of an ATM network. In the ATM network, users 21 and 22 who want to communicate first report their cell transfer peak speed and cell transfer average speed to the network node 23.
The cell transfer peak rate is the rate at which cells are transferred, that is, the highest value of the number of cells transferred per unit time, and the cell transfer average rate is the average value of the number of cells transferred per unit time. is there. The network node calculates the traffic volume of the user based on those declared values. Such a traffic amount may be, for example, simply the cell transfer peak speed as the traffic amount, or may be modified in consideration of the cell transfer average speed. Then, the network node accepts the user if the speed does not exceed the allowable traffic volume even if the speed accepts the traffic volume. Then the network node
The user constantly monitors whether or not the cell is transferred in violation of the declared value, and if the cell is transferred in violation of the declared value, the cell is discarded. UPC (Usage Parameter Control)
) Function.

In such an ATM network, a multiplexing device is provided to transfer cells from a plurality of users via one physical communication line. FIG. 3 is a block diagram showing a configuration of a conventional ATM multiplexer. The illustrated device includes a multiplexing function unit 301 and a spacing function unit 302. A cell is sent to the multiplexing function unit 301 from each of the input lines 1, 2, and 3. Here, it is assumed that the cells 11, 21, and 31 arrive at the same time as shown in the figure.
In this case, if the multiplexing function unit is cell 11, cell 21,
When multiplexing is performed in the order of the cells 31, the transmission time of the cell 31 is delayed by the time when the cells 11 and 21 are transmitted first. This fluctuation is caused by the multiplexing order (CDV: Cell
Delay Variation).

Due to this fluctuation, before multiplexing, cells 31
And the interval between cells 32 was Ta, but after multiplexing, T
b. At this time, if the interval Ta is a value close to the declared peak cell interval (the reciprocal of the cell transfer peak rate), the multiplexed interval Tb may be smaller than the peak cell interval Tp. When such a multiplexed cell is transferred to the network node 23, the UPC function unit 24 determines that the interval Tb has become shorter than the peak cell interval Tp because the user has violated the reporting violation. In other words, despite the fact that the user is transmitting cells according to the declared value, the interval Ta becomes the interval Tb due to fluctuation,
As a result of the interval Tb being shorter than the peak cell interval Tp, the cell 32 is regarded as a cell violating the declaration and is subjected to disposal or the like. Therefore, the following spacing function unit 302 is provided.

[0006] Spacing function unit 302 always monitors the cell spacing, when the interval of the cell is equal to or less than the peak cell <br/> interval reported value, widening the gap until the peak cell interval. This function allows the network node 23
Will not be determined to be a reporting violation.

[0007]

However, the above-mentioned prior art has the following problems. That is, as shown in FIG. 4, when the distance between the spacing function unit cell 31 by 302 and the cell 32 of the ATM multiplexer is extended to the peak cell <br/> interval Tp is inherently cell 32 is sent It is delayed by the time Td (= Tp-Tb) from the position to be performed. That is, the spacing function unit 302
Means that the cell delay has increased. Such an increase in the cell delay is a deterioration in the quality of the network, and is a serious problem. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide an ATM multiplexing device capable of suppressing occurrence of cell delay due to multiplexing.

[0008]

According to the present invention, communication information is divided.
A predetermined cell interval is used as the cell transfer rate of the divided cell.
ATM multiplexing equipment connected to the set communication system
Each cell input from a plurality of input lines.
A multiplexing function unit for multiplexing and outputting to the communication system;
Each cell is simultaneously transmitted from the plurality of input lines to the
When input, each input line is
Is the probability that cells will be input at intervals close to the cell interval.
The cells that have been input at the same time on the input line with a high probability.
The multiplexing function unit is controlled so that
And a priority control function unit for controlling the operation .

[0009]

In the ATM multiplexer of the present invention, when N cells arrive simultaneously from a plurality of input lines, cells are selected one by one from the N cells and multiplexed. First, the first when choosing a cell for each input line in the priority control function unit determine the probability that the next cell arrives within the peak cell interval +1 cell unit time. Then, Ru <br/> to multiplex the cell of the probability is the largest input line to the first. Then, when choosing the second cell from each input line, except the input line obtained by multiplexing, the priority control function section with the remaining input the next cell within the peak cell interval +2 cell unit time for line arrives in first Find the probability of doing. Then, Ru <br/> to multiplex the cell of the probability is the largest input line to the second. Thereafter, determine the probability that the next cell within the peak cell interval + N cell unit time for each input line, except the input line which is multiplexed to the N-1 th from 1 arrives, the cells of the input line that probability is maximum N multiplexing to second. This procedure is continued until all simultaneously arriving cells are multiplexed.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram of an embodiment of an ATM multiplexer according to the present invention. The illustrated device includes a multiplexing function unit 100 and a priority control function unit 120. The multiplexing function unit 100 multiplexes cells input from the plurality of input lines 1, 2, and 3, and outputs the multiplexed cells. This multiplexing function unit 100
Is controlled by the priority control function unit 120.

[0011] The priority control function unit 120 is a multiplexing function unit 1
When a plurality of cells 11, 21, 31 are simultaneously input from a plurality of input lines 1, 2, 3 at 00, each input line 1,
The probability that the next cell will be input within each predetermined time from that point on for 2 and 3 is determined. Details of how to determine this probability will be described later. Then, the cell of the input line having the highest probability is preferentially multiplexed. For example, as shown in FIG. 1, when cells 11, 21, and 31 are simultaneously input to the multiplexing function unit 100, if the cells 32 are input after a predetermined time Ta with a probability of 100%, the cells 31 It is multiplexed first. Therefore, no fluctuation occurs in the cell 31. Then, the cell 11 and the cell 21 are multiplexed next. Therefore, as shown on the output side of the multiplexing function unit 100 in FIG. 1, after the multiplexing, the cell 32 is output after a predetermined time Ta after the output of the cell 31, and as can be seen from FIG. The interval between the cells 31 and 32 is maintained at Ta.
Therefore, the spacing function does not work even after passing through the spacing function unit 130, and the cell 32 is not delayed.

FIG. 5 shows a detailed configuration of a multiplexing apparatus with priority control for multiplexing input lines 1 to N on an output line.
The input line 1 is connected to the input buffer 101,
The input buffer 101 is connected to the time division bus 110. Similarly, the input lines 2 to N also
02 to 10N, and the input buffers 102 to
10N is connected to the time division bus 110. The time division bus 110 is connected to the output buffer 111, and the output buffer 111
12 is connected. This spacing function unit 112
Are connected to the output line. Each input buffer 101
To 10N are connected to the priority control function unit 120 by signal lines 121 and 122.

A cell coming from the input line 1 is stored in the input buffer 101. The input buffer 101 notifies the priority control function unit 120 using the signal line 121 that the cell has been stored. The priority control function unit 120 controls the order of multiplexing of cells arriving at the same time. Thereby to suppress the occurrence of fluctuations of greater than declared peak cell interval. When a transmission permission is output from the priority control function unit 120 to, for example, the input buffer 101 via the signal line 122, the input buffer 101 transmits the cell to the time division bus 110. Then, the cell is sent from the time-division bus to the output buffer 111 and the spacing function unit 11
2 to the output line. Other input lines 2 to N
Is transmitted to the output line through the same procedure.

Here, it is assumed that cells have arrived simultaneously from m input lines. These m input lines are designated as K1, K
2 to Km, and the simultaneously arriving cells in each line are C1
1, C21 to Cm1. However, 1 <m ≦ N. The simultaneous arrival of cells from m input lines means that
The signal is transmitted to the priority control function unit 120 through the signal line 121. The priority control function unit 120 is connected to each of the input lines K1, K2
Determining the probability that the next arriving cell (next arriving come cells simultaneously arriving cell) arrives within fluctuation hours by multiplexing order + peak cell interval in miles. Then, the cells arriving simultaneously are multiplexed first in descending order of probability. Thus, it is possible to suppress the occurrence of fluctuations in excess of declared peak cell interval stochastically low.

Next, the priority control method will be specifically described with reference to FIGS. First, it is necessary to determine the cell to be multiplexed first from C11 and C21 to Cm1. Therefore, consider the case where the second multiplexing is inconvenient. As shown in FIG. 6 (a), the input line Ki, if the next arrival cell Ci2 simultaneous arrival cell Ci1 (1 ≦ i ≦ m) arrives at the peak cell interval Tpi, cell Ci1 are multiplexed into second and subsequent Then, it becomes inconvenient.
In other words, among the simultaneously arriving cells Ci1, the second and subsequent cells multiplexed by the multiplexing have fluctuations of one cell unit time Tc or more, and as shown in FIG. distance between Ci1 and cell Ci2 becomes shorter than <br/> interval Tpi between peak cell. As a result, the cell Ci2 is delayed by the spacing function unit 130.

Next, a case where multiplexing is not inconvenient will be described with reference to FIG. As shown in FIG. 7 (a), if the next cell Ci2 arrives after the peak cell interval Tpi + 1 cell unit time Tc, the cell Ci1 are multiplexed in the second, as shown in FIG. 7 (b), multiple cell interval after reduction is exactly equal to the peak cell interval Tpi.

[0017] From the above, in order to determine the cell to be multiplexed to the first, the peak cell for each input line Ki
The judgment is made based on the cell interval Tpi + 1 cell unit time Tc. In other words, the next arrival cell Ci2 peak cell interval Tp
The probability Pi of arrival within the (i + 1) -cell unit time Tc is obtained for each input line Ki. Then, the simultaneous arrival cell having the highest probability is multiplexed first. As a probability distribution function for determining the arrival probability Pi of the next arrival cell, as shown in FIG. 8, the peak cell interval is declared by the user Tpi
And an exponential distribution with an average interval Tvi. This exponential distribution function is represented by the following equation. P {T≤t} = 1-exp {-(t-Tpi) / Tvi} The use of the exponential distribution is an example, and another distribution function may be used.

The cells to be multiplexed in the second, as can be inferred from FIGS. 6 and 7, a peak next arriving cell cell interval Tp
The cell with the highest probability of arriving within the (i + 2) cell unit time (2 × Tc) is the cell with the highest probability. Similarly, the third multiplexed cell is
Probability that the next arriving cell arrives within the peak cell interval Tpi + 3 cells per unit time (3 × Tc) becomes the maximum cell.
Below, the same way the arrival probability Pi of the next arrival cell continue to multiplexing to choose the maximum of things. As a result, the multiplexing order is properly determined, and the peak due to the fluctuation due to the multiplexing is obtained.
The probability that cells multiplexed beyond the cell interval will occur can be reduced. As a result, the spacing function unit 1
Due to 30, the cell interval is hardly widened, and the occurrence of cell delay is extremely reduced.

FIG. 9 shows a priority control procedure by the apparatus of the present invention. First, in step S1, when cells arrive simultaneously from m input lines, the processing from step S2 is performed. In step S2, j is initialized, and after step S, j is processed m-1 times. That is, in step S4, the distribution probability Pi {T ≦ Tp + j × Tc} of the arrival of the next arrival cell is obtained for all the m input lines. Then, in step S5, the one with the largest Pi is selected. As a result, in step S6, simultaneously arriving cells of the input line i are multiplexed and transmitted. Next, in step S7, j is set to 1
Proceed to the tip.

In the above-described embodiment, the case where the spacing function unit 130 is provided in addition to the priority control function unit 120 has been described. However, the present invention is not limited to this. It may not be provided. That is, since the spacing function unit 130 hardly functions under the control of the priority control function unit 120, the spacing function unit 130 is omitted when there is no problem in disposing some cells. be able to.

[0021]

As described above, according to the ATM multiplexer of the present invention, the multiplexing order of simultaneously arriving cells is peaked.
Since so as to set, based on cell interval, cell interval after multiplexing by fluctuations due to the multiplexing can be suppressed to an extremely low probability of exceeding the peak cell <br/> intervals. Therefore, cell delay can be prevented, and network quality degradation can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of an ATM multiplexer according to the present invention.

FIG. 2 is an explanatory diagram of a part of an ATM network.

FIG. 3 is a diagram illustrating an example of a conventional ATM multiplexer.

FIG. 4 is an explanatory diagram of a problem of a conventional device.

FIG. 5 is a block diagram showing a detailed configuration of the device of FIG. 1;

FIG. 6 is an explanatory diagram of a multiplexing state when a cell interval exceeds a peak interval after multiplexing.

FIG. 7 is an explanatory diagram of a multiplexing state when a cell interval does not exceed a peak interval after multiplexing.

FIG. 8 is a graph showing an example of a probability distribution function.

FIG. 9 is a flowchart illustrating a priority control procedure performed by the apparatus of the present invention.

[Explanation of symbols]

 1, 2, 3 input lines 11, 21, 31, 32 cells 100 multiplexing function unit 120 priority control function unit 130 spacing function unit

Continuation of the front page (56) References JP-A-5-211519 (JP, A) JP-A-5-68047 (JP, A) JP-A-5-83284 (JP, A) Masanori Nozaki (three outside) Delay fluctuation control mechanism of ATM multiplexing equipment "IEICE Technical Report SS E93-110 (Heisei 5-12-16) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 12/28 H04L 12/56

Claims (1)

(57) [Claims] 1. Cell transfer of a cell obtained by dividing communication information
Connect to a communication system for which a predetermined cell interval is set as the speed.
An ATM multiplexer connected to a plurality of input lines for multiplexing each cell.
A multiplexing function unit that outputs to the communication system, and the multiplexing function unit receives the cells from the plurality of input lines.
When input at the same time, each input is
Cells are input at intervals close to the cell interval for each line
Obtain the probability, before the simultaneous input of the input line with the high probability
The multiplexing function for multiplexing with priority given to the cells in order.
An ATM multiplexing apparatus , comprising: a priority control function section for controlling the section .