JP3438111B2 - Shaping control method - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to an asynchronous transfer mode (A
TM: Asynchronous Transfer Mode) The present invention relates to a shaping control method in a network. The ATM network employs a policing control method that monitors traffic for each user, discards user cells that exceed the declared value at call setup, and does not discard user cells that are within the declared value. Has been done. This policing control method uses the usage parameter control (UPC; Usage Par).
It is also called amater control. By the way, the interval between cells may fluctuate due to multiplexing processing or overhead insertion processing in the network during the transfer of cells. Therefore, as a policing method, it is recommended to use a leaky bucket method in consideration of this delay variation (CELL DELAY VARIATION; CDV).
When performing UPC by this leaky bucket method,
The output cell flow includes an arbitrary cell delay fluctuation (CDV), which is less than a certain fixed amount, but the network accommodation design is difficult. Therefore, it has been proposed to provide a shaper after the UPC. In the shaper,
Reduce CDV of UPC output.

[0002]

2. Description of the Related Art FIG. 7 is a diagram for explaining a shaping operation of a conventional example. (A) and (c) show input cells, (b) and (d) show output cells, and fluctuations as shown in (a). When a certain user cell is input, as shown in (b), the cell is output after the minimum cell interval T0 from the output time of the cell immediately before.

Further, as shown in (c), the user cell and OA
M (Operation, Administration and Maintenance)
When cells are mixed, if the OAM (maintenance operation) cell is subjected to shaping control to output cells after the minimum cell interval T0 from the output time of the immediately preceding cell, as in the case of user cells, (d) ). In this case, the delay of the user cell becomes large. A leaky bucket algorithm and a virtual scheduling algorithm are known as algorithms for such shaping control.

FIG. 8 is an explanatory diagram of the leaky bucket algorithm. Initial values are X = 0 and LCT = ta.
(k), when a cell is input at time ta (k) (a), the arrival time ta (k) of this cell, the arrival time LCT of the previous cell, and the count content X of the bucket counter X Based on and, X'is calculated by the calculation of X '= X- (ta (k) -LCT) (b). Then, it is determined whether or not X '<0 (c). When X'<0, X '= 0 is set (d), and the process proceeds to step (f). That is, this corresponds to the case where the cell arrives later than the scheduled arrival time.

If X '<0 is not satisfied, the cell arrives earlier than the estimated arrival time, and it is determined whether the accumulated time of the earlier arrival times is larger than the threshold value L (e). Then, when the threshold L is not exceeded, the process proceeds to step (f). In step (f), X = X '+ I and LCT = ta (k). In addition, I shows a cell interval.
When X ′> L, the cell arrives earlier than the expected arrival time, and when the cumulative time earlier than the scheduled time exceeds the threshold value L, it corresponds to the case where the user's declared value is exceeded, and it is regarded as a nonconforming cell. Process (g).

FIG. 9 is an explanatory diagram of the virtual scheduling algorithm, which is the same as the above-mentioned case at time ta.
The cell arrives at (k) (1) and it is determined whether TAT <ta (k) (2). If TAT <ta (k), that is, the cell arrival time ta (k) is scheduled to arrive. If it is later than the time, TA
Set T = ta (k) (3), and move to step (5).
If TAT <ta (k) is not satisfied, that is, the cell arrival time t
If a (k) is earlier than the estimated arrival time, TAT> ta
(4) It is judged whether or not it is + L (4). That is, if the arrival time ta (k) of the cell is earlier than the estimated arrival time even if the threshold value L is taken into consideration, it corresponds to the case where it exceeds the user-reported value, and it is processed as a nonconforming cell (6). If the cell arrival time ta (k) can be tolerated earlier than the estimated arrival time, TAT =
TAT + I (5), next scheduled arrival time is cell interval I
Is the time added.

FIG. 10 is a diagram for explaining a cell structure, showing a cell structure of a user-network interface (UNI) in ATM, which shows a general flow control GFC of 4 bits, a virtual path identifier VPI of 8 bits, and a 16 bit of Virtual channel identifier VCI, 3-byte payload type PT, 1-bit cell loss priority display CLP, 8-bit header error control HEC consisting of 5-byte header section and 2-byte information field 48-byte information including header And fields. The network structure of the network node interface (NNI) is
The above-mentioned general flow control GFC is used for the virtual path identifier VPI to make a virtual path identifier of 12 bits in total.

Although the above-mentioned VCI indicates a connection number, it is also used in the VP connection to distinguish between a user cell and an OAM cell. It is possible to set a certain threshold and indicate a user cell when the VCI value is equal to or more than the threshold, and indicate an OAM cell when the VCI value is less than the threshold. Further, in the case of a VC connection, the above-mentioned payload type PT is used to distinguish a user cell and an OAM cell, and for example, 3-bit "000" to "01".
1 "indicates a user cell, and" 100 "to" 110 "
Can indicate an OAM cell.

[0009]

When the user cell and the OAM cell are transferred, the above-described leaky bucket algorithm or virtual scheduling algorithm does not consider the OAM cell, so that the shaping control is performed for all the user cells. When done, the result is as shown in FIG. That is, there arises a problem that the delay of the user cell becomes large. An object of the present invention is to solve the problem of user cell delay by performing shaping control by distinguishing between user cells and OAM cells.

[0010]

A shaping control system of the present invention will be described with reference to FIG. 1. A cell type determination unit 1 for determining whether an input cell is a user cell or a maintenance operation (OAM) cell, and an input The cell type is provided with a shaping memory 2 for outputting cells at specified cell intervals based on a user-reported value, and a control unit 3 for controlling the shaping memory 2 based on the arrival time of an input cell and the user-reported value. When the user cell judged by the judging means 1 arrives at an interval shorter than the specified cell interval based on the user-reported value from the arrival time of the immediately preceding cell, the ideal transmission time of the immediately preceding cell is reached. A user cell is output from the shaping memory 2 with a cell transmission time being a time later than the specified cell interval, and a cell arrival time being a cell transmission time otherwise.
Maintenance operation (OAM) judged by the cell type judging means 3
At least 1 from the ideal transmission time of the previous cell for the cell
The control for transmitting the maintenance operation (OAM) cell from the shaping memory is performed with the cell transmission time being the time after the cell.

For the OAM cell judged by the cell type judging means 1, the time after one cell of the ideal transmission time of the user cell is compared with the current time, and the time after one cell is compared. Shows a large value, the time is set as the cell sending time, and if the current time shows a larger value, the current time is set as the cell sending time, and the shaping memory 2 is controlled and the maintenance which arrives before and after is performed. Operation (OAM) cell
When the same cell transmission time is set for
Cells in the order in which they are sent out first
It is provided with a means for controlling transmission.

Further, when the same cell transmission time is set for a plurality of cells corresponding to the virtual path VP, it is possible to control the cells that have arrived first in the order of transmitting them first.

Further, the time when the decimal point of the cell transmission time obtained after the specified cell interval based on the user-declared value is rounded down can be set as the transmission time of the cell.

[0014]

The cell type determining means 1 determines whether the cell is a user cell or an OAM cell according to the payload type of the header of the arriving cell. The control unit 3 obtains the specified cell interval based on the user-reported value, determines whether the user cell arrives at an interval shorter than the specified cell interval for the ideal transmission time of the previous cell, and arrives at the short interval. Controls the shaping memory 2 with the cell transmission time at which the user cell is transmitted after the specified cell interval from the ideal transmission time of the preceding cell, and otherwise the cell arrival time as the cell transmission time. In the case of an OAM cell, the shaping memory 2 is controlled with the cell transmission time being at least one cell after the ideal transmission time of the preceding cell.

For the OAM cell, the time after one cell of the ideal transmission time of the previous cell is compared with the current time, and when the time after one cell shows a larger value, that is, with respect to the current time. When the time one cell after the ideal transmission time of the previous cell is late, the time is set as the cell transmission time. Also, when the current time shows a larger value, that is, when the time one cell after the ideal transmission time of the previous cell is earlier than the current time, the time cannot be traced back to the cell transmission time. , The current time is the cell transmission time

When the same cell transmission time is set as a result of performing the shaping control for the cells corresponding to the plurality of virtual paths VP, the cell that arrived first is transmitted first by means of a queue or the like. Thus, the order of cells corresponding to the virtual path VP is saved.

Further, the prescribed cell interval calculated based on the user-reported value often includes a value after the decimal point, and when the cell transmission time is calculated on the basis of the value, the value after the decimal point is included. Therefore, the fractional part is truncated to obtain an integer cell transmission time.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is an explanatory view of the essential parts of a first embodiment of the present invention, in which 11 is a shaping memory, 12 is a header extraction unit, 13 is a cell type determination unit, and 14 is a bucket counter compatible with virtual paths. A parameter memory that sets the count value Cp, the arrival time LT of the previous cell and the specified cell interval T0, 15 is a register that indicates the current time ta, 16 is a register that sets the count value Cp of the bucket counter,
17 is a register for setting the arrival time LT of the previous cell, 1
8 is a register for setting the specified cell interval T0, 19, 2
3 is an adder, 20 and 22 are subtractors, 21 and 25 are comparison units, 24 is an adder for adding +1, 26, 27 and 28 are selectors, and 29 is an adder.

The arriving cell has the shaping memory 11
In addition, the header extraction section 12 extracts the header section of the cell, and the cell type determination section 13 extracts the user cell based on the VCI value in the header section or the payload type PT (see FIG. 10). Or maintenance operation (O
AM) cell is determined. The cell sending time is controlled from the shaping memory 11 based on the determination. In this embodiment, the cell output time of the OAM cell is one cell later than the scheduled output time of the immediately previous user cell.

The arrival time of the cell is ta, and in the case of the user cell, the arrival time LT of the previous cell, the count value Cp of the bucket counter (not shown) and the specified cell interval T0 are set in correspondence with the virtual path VP. Is the parameter memory 14
Read out from and is set in registers 16, 17, and 18.

FIG. 3 is a flow chart of the first embodiment of the present invention. Referring to FIG. 2, each step (A1)-
(A14) will be described. Registers 16, 17, 1
8 is initialized (A1), and the current time is ta,
Cp = 0 and LT = ta. Then, when the cell arrives at time ta (A2), the cell type determination unit 13 determines whether or not the cell is the OAM cell based on the payload type PT in the header portion extracted by the header extraction unit 12 (A2).
3).

If it is not an OAM cell, that is, if it is a user cell, as described above, the count value Cp of the bucket counter corresponding to the virtual path VP, the arrival time LT of the previous cell, and the specified cell interval T0 are calculated from the parameter memory 14. It is read and set in the registers 16, 17, and 18, and C
The process of p '= max (0, Cp- (ta-LT)) is performed (A4). That is, Cp + LT is added by the adder 19, and (Cp + LT) −ta is processed by the subtractor 20 to obtain Cp ′. If it is negative, it is set to 0, and if it is positive,
Let that value be Cp '.

The comparison unit 21 determines whether Cp 'is larger than 0 (A5). If Cp'<0, the adder 29
The selector 26 is controlled to select the side. Therefore,
The cell transmission time t0 is t0 added by the adder 29.
= Cp '+ ta (A6). The cell transmission time t0 in this case corresponds to giving a delay of Cp '.

When Cp '<0 is not satisfied, the selector 26 is controlled so that t0 = ta (A7). Then, Cp ′ = 0 is set (A8), Cp = Cp ′ + T0 and LT = ta are set (A9), and the cell is transmitted from the shaping memory 11 at time t0. Since the cell transmission time t0 in this case does not delay the cell arrival time ta, the cell is immediately transmitted from the shaping memory 11.

In the case of an OAM cell, the selector 28 is controlled to select the selector 27 side, and the subtractor 22 subtracts Cp '= Cp'-T0 (A
10), this Cp 'is added to the comparison unit 25, and 0 <C
It is determined whether it is p '(A11). When Cp 'is 0, it means that the cell immediately before was not delayed, and therefore the cell is transmitted without delay.
That is, the selector 27 is controlled so that t0 = ta (A
13).

If Cp 'is larger than 0, it means that a delay is given to the previous cell. Therefore, a value obtained by adding 1 to LT + Cp' which is the transmission time of the previous cell is added to the cell transmission time t0.
(A12). That is, the adder 23 causes Cp '+ L
T is calculated, the adder 24 performs +1 and the selector 27 is controlled so that this is the cell transmission time t0, and the shaping memory 11 outputs the cell at time t0 (A14). In this case, +1 indicates the time for one cell.

As shown in FIG. 4A, the user cell and O
When an AM cell is input, as shown in (B), the first user cell is immediately output without delay, and when the next user cell arrives at an interval less than the specified cell interval T0, the specified cell is It is output with a delay so that the interval becomes T0. That is, the user cell has a specified cell interval T0.
Is output with. The OAM cell is transmitted at a time one cell after the transmission time t0 of the user cell. Therefore, the user cell has less delay than the conventional example shown in FIG.

FIG. 5 is an explanatory view of the essential portions of the second embodiment of the present invention. The same symbols as those in FIG. 2 indicate the same portions, 30 is a decoder, and 31 is a comparing portion. This embodiment considers a case where an OAM cell arrives after a considerable time interval after the user cell, and FIG. 6 shows a flowchart thereof.

Steps (B1) to (B1) in FIG.
1) performs the same processing as steps (A1) to (A11) shown in FIG. 3, and a duplicate description will be omitted.
When it is determined in step (B3) that the arriving cell is an OAM cell, the subtractor 22 calculates Cp '= Cp-T0 (B10), and the comparison unit 25 determines whether 0 <Cp'. (B11) If 0 <Cp ', the comparing unit 31 determines whether ta> LT + Cp' + 1 (B12).

The decoder 30 is for controlling the selector 27 based on the outputs of the comparison units 25 and 31. For example, when the output signal of the comparison unit 25 is 0 <Cp ', it is "1", and other than that. Is “0”, the output signal of the comparison unit 31 is
If ta> LT + Cp ′ + 1 is “1” and otherwise is “0”, if the output signal of the comparison unit 25 is “0”, it is related to the output signals “1” and “0” of the comparison unit 31. Instead, the decoder 3 sets the cell transmission time t0 to ta.
The selector 27 is controlled by 0. That is, since no delay was given to the previous cell, t0 = ta.

When the output signal of the comparison unit 25 is "1",
If the output signal of the comparison unit 31 is "1", the current time ta
Indicates after LT + Cp ′ + 1, the cell transmission time t
The decoder 27 controls the selector 27 so that 0 is set to ta. The output signal of the comparison unit 25 is "1".
Then, when the output signal of the comparison unit 31 is “0”, the current time ta indicates before LT + Cp ′ + 1, so that the cell transmission time t0 is set to LT + Cp ′ + 1, that is, the selector 27 is set by the decoder 30 by the decoder 27. It is controlled to select the output signal of the adder 24.

For example, the user cell and the OAM cell are shown in FIG.
If the OAM cell is input again as shown in (C) of FIG. 1 and arrives again at a time interval next to the OAM cell, the last OAM cell is one cell after the user cell, as shown in (D). Since it is the transmission time, the transmission time is the same as the OAM cell before that. That is, as indicated by the dotted arrow, the transmission time of the last OAM cell becomes the same as the transmission time of the immediately previous OAM cell. In such a case, O
By connecting AM cells to a queue, the order of OAM cells is preserved and sent out.

In the above embodiment, the step (A1
2) or t0 = LT + C in step (B13)
“1” of p ′ + 1 can be set to “n” indicating a plurality of cells. In this case, it can be selected within the range of n = 1 to (T0-1). That is, when the specified cell interval T0 is relatively large, the selection range of the transmission time t0 of the OAM cell becomes wide. It is also possible to change the value of "n" in consideration of the relationship with the user cell.

[0034] In the above-mentioned shaping control, for a plurality of virtual paths VP, when shaping in control that is effected line to the respective virtual path VP corresponding Re their, cell transmission <br/> out time of conflict May occur. In that case, as described above, the cells having the same transmission time are connected to the queue, and the cell that arrived first is controlled to be transmitted first, so that the cell order is saved corresponding to the virtual path VP. can do.

If the traffic value declared by the user is, for example, a value represented by the number of cells per second, the prescribed cell interval T0 of the parameter based on it is a value including a decimal, and therefore, the ideal Even when the sending time is calculated, a decimal number will be included. However, since the actual cell transmission time is represented by an integer, for example, processing such as rounding up, rounding down, or rounding off is required. Whichever is adopted, the influence on the output traffic is small, so that, for example, the truncation whose control is relatively easy can be adopted.

The present invention is not limited to the above-mentioned embodiments, but various additions and modifications can be made. For example, in FIGS. 2 and 5, each part except the shaping memory 11 can be modified. The function can be realized by the arithmetic processing function of the processor. Further, the shaping memory 11 may be a buffer memory for buffering cells.

[0037]

As described above, according to the present invention, when the cell type determination means 1 determines that the user cell is a user cell, the user cell is at an interval shorter than the specified cell interval T0 from the arrival time of the immediately preceding cell. When the cell arrives, the cell transmission time t0 is a time later than the ideal cell transmission time by the specified cell interval T0, and in other cases, the cell arrival time ta is the cell transmission time t0. Further, when it is determined that the cell is the OAM cell, the cell transmission time t0 is one cell or a plurality of cells later than the ideal transmission time of the preceding cell, whereby the user cell and the OAM cell are transferred. There is an advantage that shaping control can be performed without increasing the delay of the user cell.

For the OAM cell, the time T one cell after the ideal transmission time of the preceding cell is compared with the current time ta,
When the time T after one cell shows a larger value, the time T is set to the cell sending time t0, and when the current time ta shows a larger value, the current time ta is set to the cell sending time t0. Specified cell interval T of user cell of OAM cell
It can be set within 0 so as not to overlap with the transmission time t0 of the user cell.

Further, when performing shaping control for a plurality of cells corresponding to the virtual path VP, a queue or the like is provided so that the cell arriving first is output first for the cells set at the same cell transmission time. By using the control method, there is an advantage that the ordering of cells can be maintained for the virtual path VP and the shaping control can be performed.

Further, the specified cell interval T0 based on the user-reported value
Includes a decimal point, and thus the calculated cell transmission time often includes a decimal point. Therefore, the shaping memory 2 is rounded down to the integer cell transmission time.
The control of truncation after the decimal point has an advantage that control is simple.

[Brief description of drawings]

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

FIG. 2 is an explanatory view of a main part of the first embodiment of the present invention.

FIG. 3 is a flowchart of the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of shaping operation according to the first and second embodiments of the present invention.

FIG. 5 is an explanatory view of a main part of a second embodiment of the present invention.

FIG. 6 is a flow chart of a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a shaping operation of a conventional example.

FIG. 8 is an explanatory diagram of a leaky bucket algorithm.

FIG. 9 is an explanatory diagram of a virtual scheduling algorithm.

FIG. 10 is an explanatory diagram of a cell structure.

[Explanation of symbols]

1 Cell type determination means 2 shaping memory 3 control unit

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kan Toyoshima 1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Yoichi Sato 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Japan (56) Reference JP-A-7-135503 (JP, A) JP-A-6-338904 (JP, A) JP-A-6-37790 (JP, A) JP-A-7-95211 ( JP, A) JP-A-8-79264 (JP, A) JP-A-7-250071 (JP, A) 1994 Autumn Fall Conference, B-723 (58) Fields investigated (Int.Cl. ⁷ , DB name) ) H04L 12/28 H04L 7/00

Claims (3)

(57) [Claims] 1. A cell type determining means for determining whether an input cell is a user cell or a maintenance cell, a shaping memory for outputting the input cell at a prescribed cell interval based on a user declared value, and the input cell. And a control unit that controls the shaping memory based on the user-declared value, and the user cell determined by the cell type determination means is the user cell from the arrival time of the immediately preceding user cell. when we arrive at an interval shorter than the specified cell interval based on the declared value
Is a cell transmission time that is later than the ideal transmission time of the previous user cell by the specified cell interval, and at other times , the cell arrival time is the cell transmission time, and the user cell is stored from the shaping memory. Output and multiple
Sending the same cell to the user cell supporting the virtual path
When the departure time is set, the user cell that arrived first is
Cell transmission control in the order of transmission to the
The maintenance operation cell determined by
At least one cell time after the ideal sending time of Zacell
From the shaping memory as the cell transmission time.
It outputs the maintenance operation cell and the maintenance operation that arrives before and after
If the same cell transmission time is set for the
Sending cells in the order of sending out the maintenance cells that arrived at
A shaping control method comprising means for controlling. 2. The maintenance operation cell determined by the cell type determination means is compared with a time one cell after the ideal transmission time of the user cell and the current time, and the time one cell later is determined. 2. The shaping memory is controlled when the time is a large value, the cell sending time is set to the current time, and when the current time is large, the current time is set to the cell sending time to control the shaping memory. The described shaping control method. 3. A specified cell interval based on the user-reported value
When the cell transmission time obtained according to
The time is the transmission time of the cell.
The shaping control method according to Item 1 or 2 .