JP3011850B2 - Cell frame transfer reception method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for dividing an information frame into a plurality of cells having shorter lengths and transferring the divided cells, or a cell applied to a system for relaying, multiplexing or exchanging cells. It relates to a method of accepting frame transfer.

[0002]

2. Description of the Related Art Conventionally, an apparatus for dividing an information frame (hereinafter, referred to as a PDU) into a plurality of cells and transferring the divided data to a plurality of cells has a new P-type frame.
When the first cell constituting the PDU arrives, the reception determination of the DU is performed based on the P included in the first cell frame.
The sum of the number of cells constituting the DU and the number of untransmitted cells of the PDU currently being transmitted is compared with the number of empty buffers. If the former is larger, each cell constituting the PDU is discarded. A method of transmitting each cell constituting a PDU has been adopted.

FIG. 4 is a block diagram showing an embodiment of the prior art. Here, 10 is an input line, 11 is a transmission line of an output line, 12 is a transmission buffer for accumulating cells, 13 is a counting unit for counting empty buffers in the transmission buffer 12,
Numeral 14 denotes a cell admission judgment circuit for judging cell admission, 15 denotes a cell information extraction / discard control circuit for controlling information extraction and cell discard from a cell frame, and 16 holds a PDU identifier indicating discarding in PDU units. It is a frame list.

[0004] Next, with reference to FIG. 5, a description will be given of a processing procedure of a prior art cell frame transfer acceptance.

When a cell frame arrives from the input line 10, the cell information extraction / discard control circuit 15 outputs a PDU identifier, a cell type identifier,
Is extracted and passed to the cell reception determining circuit 14.

[0006] The cell acceptance determination circuit 14 determines the PD of the cell.
It is determined whether the U identifier is in the frame list 16 (step 501). If not, it is determined whether the cell type identifier is the first cell (step 502).
The cell number s of the PDU to which the cell belongs is calculated from the U length (step 503), and the judgment formula (number of untransmitted cells + s) × (prediction tolerance)> (number of empty buffers) (1) where the prediction tolerance is a constant It is determined whether or not the condition is satisfied (step 504). If the determination formula (1) is satisfied, the PDU to which the cell belongs
After registering the identifier in the frame list 16 (step 5
05), the cell reception determination circuit 14 notifies the discard information to the cell information extraction / discard control circuit 15, and the cell information extraction / discard control circuit 15 discards the input cell frame (step 506).

If the judgment formula (1) is not satisfied in step 504, the cell reception judgment circuit 14 adds s to the number of untransmitted cells (step 507), and decreases the number of untransmitted cells by 1 (step 507). 508), the reception information is notified to the cell information extraction / discard control circuit 15, and the cell information extraction / discard control circuit 15 receives the input cell frame and buffers it in the transmission buffer 12 (step 50).
9). If the input cell frame is not the head cell in step 502, the input cell frame is accepted and buffered in the transmission buffer 12 (step 50).
9).

On the other hand, if the PDU identifier has already been registered in the frame list 16 in step 501, it is determined whether the cell type identifier is the last cell (step 510). Notify the discard information to the cell information extraction / discard control circuit 15,
The cell information extraction / discard control circuit 15 discards the input cell frame (step 511). If it is the last cell, after deleting the PDU identifier from the frame list 16 (step 510), the input cell frame is discarded (step 506).

The counting unit 13 counts empty buffers.
Decreases every time a cell is input to the transmission buffer 12, and increases by one each time a cell is output from the transmission buffer 12. The cell reception determining circuit 14 recognizes the number of empty buffers from the count value of the counting unit 13.

[0010]

In the above-mentioned conventional cell frame transfer accepting method, when the first cell frame constituting a new PDU arrives, the number of succeeding cells of the PDU is determined.
Since this is compared with the number of untransmitted cells belonging to the PDU being transmitted and the number of empty buffers, there is a problem in that the amount of processing for determining whether to accept or discard cells increases.

An object of the present invention is to provide an information frame (PDU).
In the cell frame transfer in which the cells divided from the above are queued and transmitted in the transmission buffer, the processing amount and processing procedure for judging cell acceptance / discarding are simplified to reduce the hardware amount and increase the processing speed. It is to plan.

[0012]

In order to achieve the above object, the present invention manages the number of PDUs being transmitted and the number of empty or used buffers in a transmission buffer, so that when the first cell frame constituting a new PDU arrives, In the transmission PDU
The number of received buffers is multiplied by a predetermined acceptance coefficient and compared with the number of empty or used buffers in the transmission buffer.
That is, acceptance / discard of cells constituting a DU is determined.

[0013]

According to the present invention, reception and reception of a cell group constituting a PDU are performed.
When the first cell frame constituting the PDU arrives, the product of the number of PDUs currently being simultaneously transmitted and the acceptance coefficient is discarded.
Determined by comparing with the number of free or used buffers. This eliminates the need for a process of counting the number of cells constituting a newly accepted PDU and the number of unsent cells of each PDU currently being transmitted, thereby simplifying the cell acceptance process, reducing the amount of hardware, and reducing the processing speed. Can be speeded up.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. The configuration of this embodiment is basically the same as that of FIG.
The difference is that the cell information extraction / discard control circuit 15 does not need to extract the number of cells (PDU length) constituting the newly accepted PDU. As will be described later with reference to FIG. 3, when the first cell frame constituting the new PDU arrives, the cell reception determining circuit 14 adds the number of cells constituting the PDU to the number of untransmitted cells to determine the number of free buffers. This is because the comparison process is not required.

In this embodiment, it is assumed that a plurality of PDUs are divided into cells and arrive in a cell multiplexed manner. In addition, the cell frames constituting an arbitrary PDU are the same PDU.
It is assumed that the identifier is guaranteed uniqueness. It is also assumed that cells constituting a PDU have a cell type identifier indicating the first cell frame, the last cell, etc. of the PDU.

FIG. 2 shows ITU-T Recommendations I.361 and I.T.
AAL3 / 4 described in TU-T Recommendation I.363
Is used to show a configuration example of a cell frame in ATM communication. The meaning of each field is as follows.

(1) Regarding ATM-PDU (Cell) This is described in ITU-T Recommendation I.361. GFC (Generic Flow Control): General flow control When a LAN or the like is connected, it is used to prevent cells from colliding on a bus. VPI (Virtual Path Identifier): a virtual channel identifier is a number assigned to distinguish each VP. VCI (Virtual Channel Identifier): A virtual channel identifier is a number for distinguishing each VC, and cells are sorted based on this number. PT (Payload Type): Indicates how the payload type information field is used. CLP (Cell Loss Priority): Cell loss priority indicator Displayed when a cell is to be transmitted without loss. HEC (Header Error Control): Header error control Used to accurately transmit and receive cells. (2) Regarding AAL314, this is described in ITU-T Recommendation I.363. ST (Segment Type): Segment type Indicates the beginning, middle, end, or sole frame. SN (Sequence Number): Sequence number A number is assigned in order so that even if there is a cell loss, it can be recognized. MID (Multiplexing Identity): Multiple identifier Used as a frame identifier when a plurality of frames are multiplexed and transmitted.

Here, PPI is obtained by VPI / VCI / MID.
The DU can be identified and the ST in the SAR header can be identified.
(Start / Middle / Last / Single cell) can identify a PDU break. In FIG. 1, the PDU identifier corresponds to VPI / VCI / MID, and the cell type identifier corresponds to ST.

Next, a processing procedure for accepting cell frame transfer in the embodiment of FIG. 1 will be described with reference to FIG.

When a cell frame arrives from the input line 10, the cell information extraction / discard control circuit 15 sends a PDU identifier (VPI / VCI / MID in FIG. 2) from the cell frame.
Etc.) and a cell type identifier (ST in FIG. 2) are extracted and passed to the cell reception determination circuit 14. The cell reception determination circuit 14
It is determined whether the PDU identifier of the cell is in the frame list 16 (step 301). Here, if present, the cell is a cell constituting the PDU to be discarded, and if not, it is a cell of the PDU to be accepted.

If the PDU identifier of the input cell frame is not registered in the frame list 16, the cell reception determining circuit 14 determines whether or not the input cell frame is the first cell from the cell type identifier (step 302). , Determination formula, (untransmitted PDU + 1) × (acceptance coefficient)> (number of empty buffers) (2) It is determined whether or not (2) is satisfied (step 303). Here, the acceptance coefficient is (average number of cells constituting a PDU) × (0 to 1)
) And is determined in advance by empirical rules or the like.

In step 303, the judgment formula (2)
If the above condition is satisfied, the cell reception determination circuit 14 determines that there is no room in the transmission buffer 12 and determines the PDU of the cell frame.
The identifier is registered in the frame list 16 (step 30).
4), the discard information is notified to the cell information extraction / discard control circuit 15, and the cell information extraction / discard control circuit 15 discards the input cell frame (step 305). Step 30
3 satisfies the determination formula (2), the transmission buffer 12
Means that there is room, and the cell reception determination circuit 14
The number of PDUs being transmitted is increased by 1 (step 306), and the reception information is notified to the cell information extraction / discard control circuit 15, and the cell information extraction / discard control circuit 15 receives the input cell frame and buffers it in the transmission buffer 12. (Step 307).

If the input cell frame is not the first cell in step 302, the cell acceptance judgment circuit 14
Determines whether or not the cell is the last cell (step 308). If the cell is not the last cell, the reception information is simply notified to the cell information extraction / discard control circuit 15. In response to this, the cell information extraction / discard control circuit 15 The input cell frame is buffered in the transmission buffer 12 (step 307). If the cell is the last cell, the transmission of the PDU is terminated. Therefore, the cell reception determining circuit 14 decreases the number of PDUs being transmitted by 1 (step 308), and then returns the reception information to the cell information extraction / discard control circuit 15 , And buffer the last cell (step 307).

On the other hand, if the PDU identifier of the input cell frame is found in the frame list 16 in step 301, the cell acceptance determining circuit 14 determines whether the input cell frame is the last cell (step 310). If the cell is not the last cell, the discard information is immediately notified to the cell information extraction / discard control circuit 15. If the cell is the last cell, the corresponding PDU identifier is deleted from the frame list 16 (step 311), and the discard information is notified. I do. In response to the notification of the discard information, the cell information extraction / discard control circuit 15 discards the input cell frame (step 10).
5).

The counting unit 13 decrements by one each time a cell is input to the transmission buffer 12 (buffering), and decrements by one each time a cell in the transmission buffer 12 is output to the transmission transmission line 11.
to add. The cell reception determination circuit 14 manages the number of empty buffers in the transmission buffer 12 by fetching the contents of the counting unit 13 from time to time, and the number of PDUs being transmitted is increased or decreased by 1 in step 106 or 109 as an initial value. Thus, the number of PDUs currently being accepted (transmitted) is managed.

Although the embodiment manages the number of empty buffers in the transmission buffer, the same applies to the number of in-use buffers.

[0028]

As described above, according to the present invention,
Since it is not necessary to add the number of cells of a newly received PDU and the number of untransmitted cells of a PDU being transmitted during the process of accepting / discarding a cell constituting a PDU, hardware can be simplified and downsized. It is economical. Further, since the processing can be simplified, the BI
It can be applied to high-speed communication such as SDN.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an example of a cell frame format.

FIG. 3 is a diagram showing a flow of a cell frame reception process in FIG. 1;

FIG. 4 is a configuration diagram of one embodiment of the prior art.

FIG. 5 is a diagram showing a flow of a cell frame receiving process in FIG. 4;

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 input line 11 transmission transmission line 12 transmission buffer 13 counting unit 14 cell acceptance judgment circuit 15 cell information extraction / discard control circuit 16 frame list

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 12/28 H04L 12/56

Claims (1)

(57) [Claims] An information frame (hereinafter, referred to as a PDU) is divided into a plurality of cells.
It manages the number of DUs and the number of empty or used buffers in the transmission buffer, and when the first cell frame constituting a new PDU arrives, multiplies the number of PDUs being transmitted by a predetermined acceptance coefficient and determines whether the number of DUs in the transmission buffer is empty or not. A method for accepting a cell frame transfer, comprising determining accepting / discarding of cells constituting the new PDU by comparing the number of used buffers with the number of used buffers.