JP3106426B2 - EPD control method - 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 (Asynchr
In the case where a packet is divided into a plurality of cells (cells) and transferred using an onous transfer mode (network), when the network is congested, an EPD (E) that performs cell discarding in packet units is performed.
In particular, the present invention relates to an EPD control method that can reduce the transmission of invalid cells to a receiving side and improve transmission efficiency.

[0002]

2. Description of the Related Art ATM (Asynchronous Transfer Mod)
e) The communication network is a high-speed packet exchange in a broad sense. Data is divided into fixed-length cells instead of variable-length packets and transferred in cell units. Is a promising communication network in the multimedia society. When the amount of information transmitted in the ATM communication network increases, the network becomes congested and cell loss occurs,
Invalid cells are transmitted to the receiving side, and the effective transmission efficiency deteriorates.
An EPD (Early Packet Discard) control method is known as a cell discarding method for reducing transmitted invalid cells.

In order to effectively discard an invalid cell, it is necessary to recognize the packet to which the cell belongs. Therefore, means for identifying a packet from a cell will be described. Here, AAL type 5 is used. For AAL type 5, EOP (End Of P
The AUU (ATM layer User to User) parameter of the "Acket" cell is set to "1", and the others are set to "0". Therefore, it is possible to identify that the cell from the cell next to the cell whose AUU parameter is “1” to the next cell whose AUU parameter is “1” constitutes the same packet.

Next, a conventional EPD (Early Packet Di)
scard) The control method will be described. In the conventional EPD control method, when it is determined that the network is in a congested state when the first cell constituting a packet arrives, all cells constituting the same packet as the arriving cell are forcibly discarded except for EOP cells. I do. That is, in the example of FIG.
When the first cell of the packet # 1 arrives, the network is not congested, so that input of all cells is permitted. If the network is congested when the first cell of packet # 2 arrives,
Cells other than the EOP cell of packet # 2 are forcibly discarded. When the first cell of packet # 3 arrives, the network is not congested and all cells of packet # 3 are allowed to be input.

When it is determined that the network is not in a congested state when the first cell constituting a packet arrives,
Allows cells that constitute the same packet as the arriving cell to be input to the network, and discards when a cell that has been permitted to be input is input to the network and a cell in the middle of the packet is discarded. By forcibly discarding cells from the cell to the cell immediately before the EOP cell, cell discarding is performed in packet units. That is, in the example of FIG.
No. 1 allows all cells to be input as in the case described above. When the first cell of packet # 2 arrives, it is determined that the network is not congested, and input of all cells is permitted. However, if the second cell is dropped in the network, EO
The cells up to the cell immediately before the PCell (third cell) are discarded.

[0006]

The conventional EOP control method has the following problems. (Problem 1) Even when the network is congested, EOP cells are to be input as long as there is free space in the buffer, so that only a large number of invalid EOP cells are continuously received during congestion. Side, the transmission efficiency of the network deteriorates. In the conventional example of FIG. 8, the EOP cell of the packet # 2 is an invalid cell. (Problem 2) If the EOP cell of the packet whose input is permitted is discarded, a large number of cells are wasted because the next packet cannot be distinguished from the previous packet even if it is completely transmitted. In the conventional example of FIG.
2 are discarded, so that even if all cells of packet # 3 are completely transmitted, packet # 2 and packet # 2
3 cannot be identified, so that all cells of the packet # 3 also become invalid cells. SUMMARY OF THE INVENTION An object of the present invention is to provide an EPD control method capable of improving the above problems and reducing the number of invalid cells transmitted to the receiving side as compared with the conventional EPD control method, thereby improving the transmission efficiency of the network. Is to do.

[0007]

According to the EPD control method of the present invention, when the first cell constituting a packet arrives, the same VPI / VCI (virtual path ID) as the arriving cell arrives.
ntifier / virtual channel identifier (EOP) is a cell input to the network most recently.
It is determined whether the cell is a cell or not. If the result of the determination is that the cell is not an EOP cell, regardless of the congestion state of the network,
Forcibly discard cells other than all EOP cells constituting the same packet as the arriving cell, and forcibly discard all cells including the EOP cells if the result of the above determination indicates that the cells are EOP cells and the network is congested. Discarded, and as a result of the judgment,
If the cell is determined to be an OP cell and the network is not congested, E
All cells including OP cells are input, and when a cell loss occurs in the middle of a packet, subsequent cells other than EOP cells are forcibly discarded.

[0008]

FIG. 1 is an example of the configuration of an EPD control system for implementing an EPD control method according to the present invention.
In the figure, 1 is a cell identification unit, 2 is a management table, 3
Denotes a congestion determination unit, 4 denotes a processing unit, and 5 denotes a state monitoring unit. The cell identification unit 1 determines the VPI / VCI, AUU of the arriving cell.
It identifies the parameter. Management table 2
It stores and manages “AUU parameters”, “packet status”, and “information on whether or not an EOP (End Of Packet) cell has been input” for each VPI / VCI. The congestion determination unit 3 determines whether or not the network is congested. The processing unit 4 according to the information from the management table 2,
The cell is input to the network or discarded. The state monitoring unit 5 monitors whether a cell has been input to the network.

Here, the AU managed by the management table 2
The U parameter and the packet status will be described. A
The UU parameter is 1 when the cell is an EOP cell, and is 0 when the cell is not an EOP cell. The packet status indicates the status of the packet.
1 "," 10 ", and" 11 ". A packet state “00” means that a cell having the same VPI / VCI as the arriving cell that has been input to the network most recently is an EOP cell,
Since the network is not in a congested state, it indicates the state of a packet in which all cells are permitted to enter. The packet state “01” is the same VP as the arriving cell that was input to the network most recently.
A cell having an I / VCI is not an EOP cell, but indicates a state of a packet in which a cell other than the EOP cell has been forcibly discarded. A packet state “10” is the same VPI as the arriving cell input to the network most recently. The cell having / VCI is an EOP cell. Since the network is in a congested state, it indicates the state of a packet in which all cells including the EOP cell are forcibly discarded. The input cell having the same VPI / VCI as the arriving cell is an EOP cell. Since the network is not in a congested state, all the cells have been permitted to be input. This indicates the state of the packet in which the cells subsequent to the discarded cells other than the EOP cell are forcibly discarded because they have been discarded.

Next, the operation of the EPD control system shown in FIG. 1 will be described. 2 to 5 are processing flowcharts of the EPD control method according to the present invention. Hereinafter, the EPD control method of the present invention will be described in detail with reference to the configuration diagram of FIG. 1 and the flowcharts of FIGS. When the cell arrives (step 1
0), the cell identification unit 1 determines the VPI / VC of the arriving cell.
I, AUU parameters are identified, and the information is notified to the management table 2. The management table 2 includes a cell identification unit 1
Knows where the information corresponding to the arriving cell is managed by the VPI / VCI notified from the AUU parameter and the AUU parameter of the notified AUU parameter and the AUU parameter of the management table 2 (corresponding to the AUU parameter of the cell arriving most recently). Is compared.

As a result of comparison and comparison, if the notified AUU parameter is 0 and the AUU parameter in the management table 2 is 0, the process proceeds to step 20. If the notified AUU parameter is 0 and the AUU parameter in the management table is 1, the process proceeds to step 20. If the notified AUU parameter is 1 and the AUU parameter in the management table 2 is 0, the process proceeds to step 40. If the notified AUU parameter is 1 and the AUU parameter in the management table 2 is 1, the process proceeds to step 50.

(1) When the notified AUU parameter is 0 and the AUU parameter in the management table 2 is 0 (step 20): Next, referring to the packet status in the management table 2, it is determined whether the packet status is 00. (Step 21), if not 00, the processing unit 4 is notified that the cell is discarded (Step 22). If the packet status is 00, the processing unit 4 is notified that the cell is input (Step 23). (See below).

(2) When the notified AUU parameter is 0 and the AUU parameter in the management table is 1 (step 30): Next, as shown in FIG. 3, whether or not an EOP cell in the management table 2 has been input Information was "entered"
It is determined whether or not (step 31). If it is not "input", the AUU parameter of the management table 2 is set to 0
Then, after updating the packet state to 01 (step 3
2) The processing unit 4 is notified of discard (step 33).

The result of the determination in step 31 is the management table 2
If the information as to whether or not the EOP cell has been input is "input", information about whether or not the network is congested is obtained from the congestion determining unit 3 (step 34). If the network is in a congested state, the AUU parameter in the management table 2 is updated to 0, and the packet state is updated to 10 (step 35), and the processing unit 4 is notified of discard (step 36). If the network is not in a congestion state, the AUU parameter in the management table 2 is set to 0.
Then, after updating the packet state to 00 (step 3
7), the input is notified to the processing unit 4 (step 38), and FIG.
(See below).

(3) When the notified AUU parameter is 1 and the AUU parameter in the management table 2 is 0 (step 40): Next, after updating the AUU parameter in the management table 2 to 1 (step 41), the management is performed. Referring to the packet status in Table 2, it is determined whether or not the packet status is 10 (Step 42). If it is 10, the processing unit 4 is notified that the cell is discarded (Step 43), and the packet status is 1
If it is not 0, the processing unit 4 is notified of the input (step 4
4), perform the processing shown in FIG. 5 (described later).

(4) When the notified AUU parameter is 1 and the AUU parameter in the management table 2 is 1 (step 50): Next, as shown in FIG. 4, information as to whether or not an EOP cell has been input is received. It is determined whether or not "input" has been made (step 51). If the information on whether or not the EOP cell has been input is “input”, then the congestion determination unit 3
To obtain information on whether or not the network is congested (step 5
2). If the network is in a congested state, the processing unit 4 is notified of the discard (step 53). If the network is not in a congestion state, after notifying the processing unit 4 of the input (step 54), the processing shown in FIG. 5 is performed (described later). If it is determined in step 51 that the information indicating whether or not the EOP cell has been input is not “input”, the processing unit 4 is notified of the input (step 55), and the processing shown in FIG. (Described later).

Next, the processing when the processing unit 4 is notified of the input will be described with reference to the flowchart of FIG. Processing unit 4
After that, the status monitoring unit 5 is requested to notify whether or not the cell has been input into the network (step 61), and it is determined whether or not the notification from the status monitoring unit 5 is discarded (step 6).
2) If discarded, it is next determined whether or not the AUU parameter of the management table 2 is 0 (step 63). If the AUU parameter in the management table 2 is 0, the packet status is updated to 11 (step 64). If the AUU parameter in the management table 2 is not 0, the information as to whether or not an EOP cell has been input is "not input". (Step 65).

If it is determined in step 62 that the notification from the state monitoring unit 5 is not discarded, it is determined whether the AUU parameter in the management table 2 is 1 and the packet state is 01 (step 66). The information on whether or not the EOP cell has been input is updated to "input" (step 67).

Next, the EPD control method of the present invention will be specifically described with reference to the packet / cell configuration diagram of FIG. 6 and the above-mentioned flowchart (indicated by step numbers). In this case, the user has VPI = “10”, VCI =
Assume that you are using "10". First, packet # 1
Will be described. When the first cell of the packet # 1 arrives (step 10), the VPI / VC is stored in the management table 2.
Information of I / AUU = “10” / “10” / “0” is notified. The value of the management table 2 corresponding to the notified VPI / VCI at that time is AUU = “1”, packet status =
It is assumed that “00” and “EOP cell has been input” are set. When the information is notified, the notified AUU is "0" and the AUU parameter of the management table 2 is "1" (step 30), and therefore, the information on whether or not the EOP cell is input is checked (step 31). Now, since "EOP cell has been input", it is next obtained from the congestion determination unit 3 whether or not the network is congested (step 34). When the information of "not congested" is notified, the AUU of the management table 2 is updated from "1" to "0", the packet status is updated to "00" (step 37), and "input" is sent to the processing unit 4. Is notified (step 38). Next, a request is made to the state monitoring unit 5 to notify information on whether or not a cell has been input (step 61). Entered (Step 62; NO)
Is notified. In this case, since the condition of step 66 is not satisfied, the process waits until the next information is notified from the cell identifying unit 1.

When the second cell of packet # 1 arrives (step 10), the VPI / VCI
Information of / AUU = “10” / “10” / “0” is notified. The value of the management table 2 corresponding to the notified VPI / VCI at that time is AUU = "0", packet status =
"00", "EOP cell has been input".
When the information is notified, the notified AUU is “0” and the AUU of the management table is “0” (step 20).
Check the packet status (step 21). Now, since the packet state is "00", "input" is notified to the processing unit 4 (step 23). Next, a request is made to the state monitoring unit 5 to notify information on whether or not a cell has been input (step 61). It is notified that it has been input (step 62; NO). In this case, since the condition of step 66 is not satisfied, the process waits until the next information is notified from the cell identifying unit 1.

The operation of the third cell of packet # 1 is exactly the same as that of the second cell. When the fourth cell (EOP cell) of packet # 1 arrives (step 1
0), VPI / VCI / AUU = “1” in the management table 2
Information of “0” / “10” / “1” is notified. Current management table 2 corresponding to the notified VPI / VCI
Are AUU = “0”, packet status = “00”, “E
The OP cell has been input. " When the information is notified, the notified AUU parameter is "1" and the AUU of the management table is "0" (step 40), so that the AUU parameter of the management table is updated to "1" (step 41), and the packet status is updated. Is checked (step 42).
Since the packet state is "00", the processing unit 4 is notified of "input" (step 44). Next, a request is made to the state monitoring unit 5 to notify information on whether or not a cell has been input (step 61). Entered (Step 6
2; NO). In this case, since the condition of step 66 is not satisfied, the process waits until the next information is notified from the cell identifying unit 1.

Next, packet # 2 will be described. When the head cell of packet # 2 arrives (step 10),
In the management table 2, VPI / VCI / AUU = “10” /
Information of “10” / “0” is notified. Notified VP
The value of the management table 2 corresponding to the I / VCI at that time is A
It is assumed that UU = “1”, packet status = “00”, and “EOP cell has been input”. When the information is notified, the notified AUU parameter is "0" and the AUU parameter in the management table 2 is "1" (step 3).
0), it is checked whether an EOP cell has been input (step 31). Now, since "EOP cell has been input", it is next obtained from the congestion determination unit 3 whether or not the network is congested (step 34). When the information of "congested" is notified (step 34; YES), the AUU parameter of the management table 2 is updated from "1" to "0", and the packet state is updated to "10" (step 35). The processing unit 4 is notified of "discard" (step 36).

When the second cell of the packet # 2 arrives (step 10), the VPI / VCI
Information of / AUU = “10” / “10” / “0” is notified. The value of the management table 2 corresponding to the notified VPI / VCI at that time is AUU = "0", packet status =
"10", "EOP cell has been input".
When the information is notified, the notified AUU parameter is "0" and the AUU parameter in the management table 2 is "0" (step 20), so the packet status is checked (step 21). Since the packet state is "10" (step 21; NO), the processing unit 4 is notified of "discard" (step 22).

The operation of the third cell of packet # 2 is exactly the same as the operation of the second cell. When the fourth cell (EOP cell) of packet # 2 arrives (step 1)
0), VPI / VCI / AUU = “1” in the management table 2
Information of “0” / “10” / “1” is notified. The values of the management table at that time corresponding to the notified VPI / VCI are AUU = “0”, packet status = “10”, and “EO”.
The P cell has been input. " When the information is notified, the notified AUU parameter is "1" and the AUU parameter in the management table 2 is "0" (step 4).
0), the AUU parameter in the management table 2 is updated to “1” (step 41), and the packet status is checked. Now, the packet state is “10” (step 4
2; YES), the processing unit 4 is notified of "discard" (step 43). The operation of packet # 3 is exactly the same as the operation of packet # 1.

Comparing the embodiment shown in FIG. 6 with the conventional example shown in FIG. 8, EOP cells in which cells other than the EOP cells were discarded and became invalid cells existed in the conventional example (packet # 2). In this embodiment, the EOP cell is discarded, and it can be seen that the number of invalid cells transmitted to the receiving side is reduced. Thereby, the transmission efficiency in the ATM network can be improved.

Next, the EPD control method of the present invention will be specifically described with reference to the packet configuration diagram of FIG. 7 and the above-mentioned flowchart (indicated by step numbers). In this case, it is assumed that the user is using VPI = “10” and VCI = “10”. First, packet # 1 will be described. The operation of packet # 1 is exactly the same as the operation of packet # 1 in FIG. Next, packet # 2 will be described. When the first cell of packet # 2 arrives (step 10), VPI / VCI / AUU =
Information of “10” / “10” / “0” is notified. The values of the management table 2 corresponding to the notified VPI / VCI at that time are AUU = “1”, packet status = “00”,
"EOP cell has been input". When the information is notified, the notified AUU parameter is "0" and the AUU parameter in the management table 2 is "1" (step 30), so it is checked whether an EOP cell is input (step 31). Now, since "EOP cell has been input", it is next obtained from the congestion determination unit 3 whether or not the network is congested (step 34). "Not congested"
Is notified (step 34; NO), the AUU parameter of the management table 2 is changed from “1” to “0”,
The packet status is updated to "00" (step 37), and "input" is notified to the processing unit 4 (step 38). Next, a request is made to the state monitoring unit 5 to notify information on whether or not a cell has been input (step 61). It is notified that it has been input (step 62; NO). In this case, since the condition of step 66 is not satisfied, the process waits until the next information is notified from the cell identifying unit 1.

When the second cell of the packet # 2 arrives (step 10), the VPI / VCI
Information of / AUU = “10” / “10” / “0” is notified. The value of the management table 2 corresponding to the notified VPI / VCI at that time is AUU = "0", packet status =
"00", "EOP cell has been input".
When the information is notified, the notified AUU parameter is "0" and the AUU parameter in the management table 2 is "0" (step 20), so the packet status is checked (step 21). Now, since the packet state is "00", "input" is notified to the processing unit 4 (step 23).
Next, a request is made to the state monitoring unit 5 to notify information on whether or not a cell has been input (step 61). It is notified that it has been discarded (step 62; YES). Since AUU = “0” (step 63; YES), the packet state is set to “11”.
(Step 64), and waits until the next information is notified from the cell identification unit 1.

When the third cell of packet # 2 arrives (step 10), the VPI / VCI
Information of / AUU = “10” / “10” / “0” is notified. The value of the management table 2 corresponding to the notified VPI / VCI at that time is AUU = "0", packet status =
"11", "EOP cell has been input".
When the information is notified, the notified AUU parameter is "0" and the AUU parameter in the management table is "0" (step 20; YES), so the packet status is checked (step 21). Since the packet state is "11" (step 21; NO), the processing unit 4 is notified of "discard" (step 22).

When the fourth cell (EOP cell) of the packet # 2 arrives (step 10), the management table 2
VPI / VCI / AUU = “10” / “10” /
The information of “1” is notified. Notified VPI / VCI
At that time, the value of the management table 2 is AUU =
“0”, packet status = “11”, and “EOP cell has been input”. When the information is notified, the notified AUU parameter is “1”, and the AUU in the management table is set.
Since the parameter is "0" (Step 40; YES), the AUU parameter in the management table 2 is updated to "1" (Step 41), and the packet status is checked (Step 4).
2). Now, the packet status is "11",
The processing unit 4 is notified of "input" (step 44). Next, a request is made to the state monitoring unit 5 to notify information on whether or not a cell has been input (step 61). "Discarded" is notified (step 62; YES), and since AUU = "1" (step 63; NO), it is updated to "EOP cell was not input" (step 65), and the cell identification unit 1 Wait for the following information:

Next, packet # 3 will be described. When the first cell of packet # 3 arrives (step 1
0), VPI / VCI / AUU = “1” in the management table 2
Information of “0” / “10” / “0” is notified. The values of the management table at that time corresponding to the notified VPI / VCI are AUU = “1”, packet status = “11”, and “EOP
The cell has not been entered. " When the information is notified, the notified AUU parameter is "0" and the AUU parameter in the management table is "1" (step 30; YES), so it is checked whether an EOP cell has been input (step 31). Now, since "EOP cell has not been input", the AUU parameter in the management table 2 is updated from "1" to "0", the packet state is updated to "01", and the processing unit 4 outputs "discard". Notify.

When the second cell of packet # 3 arrives (step 10), the VPI / VCI
Information of / AUU = “10” / “10” / “0” is notified. The value of the management table 2 corresponding to the notified VPI / VCI at that time is AUU = "0", packet status =
"01", "EOP cell was not input". When the information is notified, the notified AUU parameter is “0” and the AUU parameter in the management table 2 is “0” (Step 20; YES), so the packet status is checked (Step 21). Now, the packet status is “01”
Therefore, the processing unit 4 is notified of "discard".

The operation of the third cell of packet # 3 is exactly the same as the operation of the second cell. When the fourth cell (EOP cell) of packet # 3 arrives (step 1
0), VPI / VCI / AUU = “1” in the management table 2
Information of “0” / “10” / “1” is notified. Current management table 2 corresponding to the notified VPI / VCI
Are AUU = “0”, packet status = “01”, “E
No OP cell was input ". When the information is notified, the notified AUU parameter is “1”,
Since the AUU parameter of the management table 2 is "0" (step 40; YES), the AUU parameter of the management table 2 is updated to "1" (step 41), and the packet status is checked (step 42). Now, the packet status is “01”
Therefore, the processing unit 4 is notified of “input”. Next, a request is made to the state monitoring unit 5 to notify information on whether or not a cell has been input (step 61). "Entered"
(Step 66; NO), and since AUU = “1” and the packet status is “01” (step 66; YES),
Update to “EOP cell has been input” (step 6
7) Wait until the next information is notified from the cell identification unit 5.

Comparing the present embodiment shown in FIG. 7 with the conventional example shown in FIG. 9, in this embodiment, cells other than the EOP cell of packet # 3 existing in the conventional example are discarded. It can be seen that the number of invalid cells transmitted to the prior art is smaller than in the conventional example. Thereby, the transmission efficiency in the ATM network can be improved.

[0034]

As described above, according to the EPD control method of the present invention, the transmission of invalid cells to the receiving side can be reduced as compared with the prior art, and the transmission efficiency in the ATM network is improved. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is an example of a system configuration for implementing an EPD control method according to the present invention.

FIG. 2 is a flowchart (part 1) of a process of the EPD control method of the present invention.

FIG. 3 is a processing flowchart (part 2) of the EPD control method of the present invention.

FIG. 4 is a flowchart (part 3) of the EPD control method according to the present invention;

FIG. 5 is a flowchart (part 4) of the EPD control method according to the present invention;

FIG. 6 is a packet / cell configuration diagram (part 1) for explaining the EPD control method of the present invention.

FIG. 7 is a packet / cell configuration diagram (part 2) for describing the EPD control method of the present invention.

FIG. 8 is a diagram illustrating a packet / cell configuration (part 1) for describing an EPD control method according to the related art.

FIG. 9 is a packet / cell configuration diagram (part 2) for describing an EPD control method in the related art.

[Explanation of symbols]

1: cell identification unit, 2: management table, 3: congestion determination unit,
4: processing unit, 5: status monitoring unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-233077 (JP, A) Proceedings of the 1996 IEICE General Conference B-912 IEICE Technical Report SSE 96-88 Electronic Information Technical report of IEICE SSE 94-94 (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 12/28 H04L 12/56

Claims (1)

(57) [Claims] 1. When the first cell constituting a packet arrives, the same VPI / VCI (virtual) as the cell that arrived.
(Path Identifier / Virtual Channel Identifier)
The cell that was most recently entered into the network with
f Packet) cell, and if it is determined that the cell is not an EOP cell, regardless of the congestion state of the network, other than all EOP cells constituting the same packet as the arriving cell. The cell is forcibly discarded, and as a result of the determination, it is determined that the cell is an EOP cell, and when the network is in a congested state, all cells including the EOP cell are forcibly discarded. If the cell is not in the congestion state, input all cells including the EOP cell, and if a cell loss occurs in the middle of the packet,
An EPD control method characterized by forcibly discarding cells other than cells.