JPH06268663A - Cell frame transfer system - Google Patents

Abstract

PURPOSE:To reduce the rate of abandonment by transmitting the cell of a specified information frame when the number of waiting cells in a transmission queue exceeds a threshold level and the cell abandonment is generated. CONSTITUTION:When the frame identifier of the arriving cell is not existent in a frame list 13 and the number of waiting cells in a transmission queue 71 applied from a counting part 72 does not exceed the threshold level, the arriving cell is piled into the queue 71. When the number exceeds the threshold level a cell abandonment judging circuit 12 controls registration onto the list 13. First of all, when the arriving cell from a cell class identifier is a leading cell, the frame identifier of the arriving cell is registered on the list 13, and the arriving cell is abandoned. Afterwards, the following cell provided with the same frame identifier as that cell is preferentially abandoned. When the arriving cell is not the leading cell, the circuit 12 judges whether the queue 71 is full or not. When there is any space in the queue 71, the arriving cell is piled into the queue 71 but when there is no space, the arriving cell is abandoned. Thus, the abandonment rate of information frame can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cell frame transfer system applied to a device for dividing an information frame into cells having a length shorter than that of the cell for transmission, or a system for relaying, multiplexing, or exchanging cells. Regarding

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing a configuration of a conventional cell frame transfer system. In the figure, 71 is a transmission queue for waiting for cells to be sent to the transmission transmission path 70, 72 is a counting unit for counting the number of waiting cells in the transmission queue 71, and 73 is a number corresponding to the number of waiting cells counted by the counting unit 72. Then, the control unit determines whether the arrived cell is loaded into the transmission queue 71 or discarded.

The conventional cell frame transfer operation will be described below. When a cell to be transmitted arrives on the transmission line 70, the control unit 73 checks whether or not the transmission queue 71 has a free space based on the number of waiting cells supplied from the counting unit 72. Then, if there is a vacancy, the cell is loaded in the transmission queue 71. That is, if the number of waiting cells in the transmission queue 71 is smaller than the queue length (capacity) of the transmission queue 71, the arrived cells are loaded into the transmission queue 71. On the other hand, if the number of waiting cells in the transmission queue 71 has reached the queue length of the transmission queue 71, the arrived cell is discarded.

[0004]

Since the conventional cell frame transfer method is performed as described above, when a plurality of information frames are cell-multiplexed, the transmission line 70 is congested and many cells are discarded. In such a situation, there is a high possibility that the information frames formed by the discarded cells will be different.

On the other hand, when even one of the cells forming one information frame is lost, the cell is generally lost in the receiving side switching device and the terminal device, and the information frame including the cell is discarded. . That is, randomly discarding cells belonging to different information frames increases the discard rate of information frames, which causes a decrease in communication efficiency.

According to the present invention, when a plurality of information frames are respectively divided into cells and cells are multiplexed and arrive,
An object of the present invention is to provide a cell frame transfer method that can reduce the discard rate of information frames on the receiving side even if the transmitting side discards cells according to the congestion state of the transmission path.

[0007]

According to the cell frame transfer method of the invention described in claim 1, when the number of waiting cells in the transmission queue exceeds a predetermined threshold value, cells belonging to a specific information frame are given priority. It is equipped with a judgment means for discarding.

The cell frame transfer system according to the second aspect of the present invention has a frame list that specifies the information frames to be discarded, and includes a determination means that discards the arriving cell according to the registration information and transmits the others. It is a thing. When registering in the frame list, the arrival cell is the first cell,
If the number of waiting cells in the transmission queue exceeds a predetermined threshold value, the information frame is to be discarded.

The cell frame transfer system of the invention described in claim 3 has a frame list for specifying an information frame to be transmitted, and comprises a judging means for transmitting an arriving cell according to the registration information and discarding the other. It is a thing. When registering in the frame list, the arrival cell is the first cell,
If the number of waiting cells in the transmission queue does not exceed the predetermined threshold value, the information frame is targeted for transmission.

The cell frame transfer system according to the invention of claim 4 has a frame list for specifying information frames to be discarded and transmitted, and is provided with a judging means for discarding or transmitting the arriving cell according to the registration information. It is a thing. To register in the frame list, if the arrival cell is the head cell and the number of waiting cells in the transmission queue exceeds a predetermined threshold, the information frame is discarded,
If it does not exceed the threshold value, it is a transmission target.

According to a fifth aspect of the present invention, there is provided a cell frame transfer system having a frame list for identifying information frames to be discarded, transmitted and waited, and determining whether to discard or transmit an arriving cell according to the registration information. It is equipped with means. For registration in the frame list, if the arriving cell is not the final cell and the number of waiting cells in the transmission queue exceeds a predetermined threshold, the information frame is discarded and if not, the transmission is targeted. It is a thing.

The cell frame transfer system of the invention described in claim 6 is the judgment means described in any one of claims 1 to 5,
Means for determining whether or not the arriving cell is a single cell that constitutes an information frame with one cell, and if it is a single cell, sends it to the transmission queue even if the number of waiting cells in the transmission queue exceeds a predetermined threshold value. including.

[0013]

The judging means of the present invention judges whether the number of waiting cells in the transmission queue exceeds the threshold value when the head cell of the divided information frames arrives. If the threshold is not exceeded, the cell is loaded in the transmission queue. On the other hand, if the number of waiting cells exceeds the threshold, the cells belonging to the information frame are controlled so as to be preferentially discarded. As a result, only cells belonging to a specific information frame are subject to discarding, so that it is possible to prevent the discard rate of information frames from increasing for discarded cells over many information frames.

Alternatively, if the number of waiting cells does not exceed the threshold value when the leading cell arrives, then the cells belonging to the information frame are preferentially transmitted and the other cells are discarded. As a result, only cells belonging to a specific information frame are targeted for transmission, so that the information frame in which the leading cell is transmitted can reliably transmit all cells, and the discard rate of information frames can be reduced.

[0015]

FIG. 1 is a block diagram showing the configuration of an embodiment of a cell frame transfer system of the present invention. In the figure, 71 is a transmission queue for waiting for cells to be sent to the transmission transmission path 70, 72 is a counting unit for counting the number of waiting cells in the transmission queue 71, 10 is the number of waiting cells received from the counting unit 72, and arrived. It is a judgment means for judging whether to load or discard cells in the transmission queue 71, and which cells to discard when further discarding.

The judging means 10 comprises a cell information extraction / discard control circuit 11, a cell discard judgment circuit 12 and a frame list 13. Cell information extraction / discard control circuit 1
1 extracts the frame identifier and the cell type identifier from the information of the arrived cell and gives them to the cell discard determination circuit 12,
According to the discard information received from the cell discard determination circuit 12, the cell is loaded into the transmission queue 71 or discarded.
The cell discard determination circuit 12 receives the frame identifier and the cell type identifier from the cell information extraction / discard control circuit 11, receives the number of waiting cells from the counting unit 72, and further discards the cell together with the information in the frame list 13. Then, the discard information is given to the cell information extraction / discard control circuit 11.

The algorithm of the judging means 10 will be described below by taking as an example the case of applying it to an ATM communication system in which an information frame is divided into cells and transmitted. First, AAL
Three algorithms applied to the system using the type 3/4 will be described with reference to the flowcharts shown in FIGS.

In the case of AAL type 3/4, a virtual path identifier (VPI), a virtual channel identifier (VCI) and a multiplex identifier (MID) described in the cell are used as frame identifiers for associating cells with information frames. To use. Further, the segment type (ST) is used as a cell type identifier for identifying cells in the same frame, and the beginning cell (BOM), intermediate cell (COM), final cell (EOM) or single cell (SSM) of the information frame is identified. To do.

In FIG. 2, the frame list 13 is "discarded".
An algorithm for registering a frame identifier of (claim 1,
It is a flowchart explaining (corresponding to claim 2). When the cell arrives, the cell discard determination circuit 12 determines whether the frame identifier is registered in the frame list 13 (S21). If there is a frame identifier in the frame list 13 that matches the frame identifier of the arriving cell, the arriving cell is the last cell (E
OM) is determined (S22). If it is the last cell, the frame identifier of the arriving cell is set to the frame list 13
The cell is deleted (S23) and the arriving cell is discarded (S24). If it is not the final cell, only the arrival cell is discarded (S2
Four).

If the frame identifier of the arriving cell is not in the frame list 13, it is judged whether or not the current number of waiting cells in the transmission queue 71 given from the counting section 72 exceeds a threshold value (S25). If the number of waiting cells does not exceed the threshold, the arriving cells are loaded in the transmission queue 71 (S26). It should be noted that this threshold value is set to a value smaller than the queue length of the transmission queue 71, and loading is performed with a margin.

If the number of waiting cells exceeds the threshold,
The cell discard determination circuit 12 controls registration in the frame list 13. First, it is determined from the cell type identifier whether the arriving cell is the head cell (BOM) (S27). If it is the first cell, the frame identifier of the arriving cell is registered in the frame list 13 (S28), and the arriving cell is discarded (S2).
Four). After that, the subsequent cells having the same frame identifier as that cell (cells belonging to the same information frame) are S21.
~ Priority is discarded according to the procedure of S24.

If the arriving cell is not the head cell, the cell discard determination circuit 12 determines whether the number of waiting cells has reached the queue length of the transmission queue 71, as in the conventional transfer control.
That is, it is determined whether the transmission queue 71 is full (S2).
9). If there is a space in the transmission queue 71, the arrival cell is loaded in the transmission queue 71 (S26). If there is no free space, the arrival cell is discarded (S24).

In FIG. 2, the order of the judgment as to whether the number of waiting cells exceeds the threshold value (S25) and the judgment as to whether the arriving cell is the head cell (S27) can be interchanged.

In FIG. 3, the frame list 13 is "transmitting".
4 is a flowchart illustrating an algorithm (corresponding to claim 3) for registering the frame identifier of FIG. When the cell arrives, the cell discard determination circuit 12 determines whether the frame identifier is registered in the frame list 13 (S31). Then, if there is a frame identifier in the frame list 13 that matches the frame identifier of the arriving cell, it is determined from the cell type identifier whether the arriving cell is the last cell (EOM) (S32). If it is the last cell, the frame identifier of the arriving cell is deleted from the frame list 13 (S33), and the arriving cell is loaded into the transmission queue 71 (S3).
Four). If it is not the final cell, only the arrival cell is loaded (S34).

If the frame identifier of the arriving cell is not in the frame list 13, it is judged from the cell type identifier whether the arriving cell is the head cell (BOM) (S35).
If it is not the first cell, the arriving cell is discarded (S36).

If the arriving cell is the head cell, the cell discard determination circuit 12 sends the transmission queue 7 supplied from the counting section 72.
It is determined whether the current number of waiting cells of 1 exceeds the threshold value (S37). If the number of waiting cells exceeds the threshold, the arriving cells are discarded (S36).

If the number of waiting cells does not exceed the threshold value, the frame identifier of the arriving cell is registered in the frame list 13 (S38), and the arriving cell is loaded in the transmission queue 71 (S34). After that, the subsequent cells having the same frame identifier as that cell (cells belonging to the same information frame) are
The cells are preferentially loaded in the transmission queue 71 according to the procedure of S31 to S34, and the other cells are discarded.

FIG. 4 is a flow chart for explaining an algorithm (corresponding to claim 4) for registering the "transmitting" and "discarding" frame identifiers in the frame list 13. When the cell arrives, the cell discard determination circuit 12 determines from the cell type identifier whether the arriving cell is the head cell (BOM) (S41). If the arriving cell is the leading cell, the cell discard determination circuit 12 determines whether or not the current number of waiting cells in the transmission queue 71 given from the counting section 72 exceeds a threshold value (S42). If the number of waiting cells does not exceed the threshold, the frame list 13 of the frame identifier of the arriving cell is rewritten to "transmitting" (S43), and the arriving cell is loaded into the transmission queue 71 (S).
44).

If the number of waiting cells exceeds the threshold,
Frame list of arriving cell Frame list 13
Is rewritten to "discarding" (S45) and the arriving cell is discarded (S46).

If the arriving cell is not the first cell, the cell discard determination circuit 12 determines whether the frame identifier is registered in the frame list 13 as "transmitting" or "discarding".
It is determined whether or not is registered as (S47). If the frame identifier of the arriving cell is "transmitting", the arriving cell is loaded in the transmission queue 71 (S44). If the frame identifier of the arriving cell is "discarding", the arriving cell is discarded (S
46).

As described above, in the present algorithm, the frame identifier is set to "transmitting" according to the state of the transmission queue 71 (whether the number of waiting cells exceeds the threshold value) when the leading cell arrives. Or "discard" is set. Therefore, when the leading cell is loaded in the transmission queue 71, subsequent cells having the same frame identifier (cells belonging to the same information frame) are loaded with priority by following the procedure of S47 and S44. On the other hand, when the head cell is discarded, subsequent cells having the same frame identifier (cells belonging to the same information frame) are preferentially discarded according to the procedures of S47 and S46.

Next, an algorithm applied to a system using AAL type 5 will be described with reference to the flowchart shown in FIG. 5 (corresponding to claim 5). AAL
In the case of type 5, a virtual path identifier (VPI) and a virtual channel identifier (VCI) are used as the frame identifier,
The payload type (PT) is used as the cell type identifier to identify the final cell (EOM).

Here, the frame identifier is registered in the normal frame list 13 as "standby", and is registered as "transmitting" or "discarding" according to a predetermined condition. When the cell arrives, the cell discard determination circuit 12 determines that the frame identifier is “transmitting” in the frame list 13,
It is determined whether the content is "discard" or "standby" (S51).

If the frame identifier of the arriving cell is "waiting", the cell discard judging circuit 12 judges whether or not the current number of waiting cells in the transmission queue 71 given from the counting section 72 exceeds a threshold value. Yes (S52). If the number of waiting cells exceeds the threshold, it is determined from the cell type identifier whether the arriving cell is the final cell (PT = 1) (S53). If it is not the final cell, the frame list 13 of the frame identifier of the arriving cell is rewritten to "discarding" (S54), and the arriving cell is discarded (S55). If it is the last cell, only the arrival cell is discarded (S55). If the number of waiting cells does not exceed the threshold value, it is similarly determined whether or not the arrival cell is the final cell (S56). If it is not the final cell, the frame list 13 is rewritten to "transmitting" for the frame identifier of the arriving cell (S57), and the arriving cell is loaded into the transmission queue 71 (S58). If it is the final cell, only the arrival cell is loaded (S58).

If the frame identifier of the arriving cell is "transmitting", it is similarly judged whether or not the arriving cell is the final cell (S59). If it is the last cell, the frame list 13 is rewritten to "standby" for the frame identifier of the arriving cell (S60), and the arriving cell is loaded into the transmission queue 71 (S58). If it is not the final cell, only the arrival cell is loaded (S58).

If the frame identifier of the arriving cell is "discarding", it is similarly determined whether or not the arriving cell is the final cell (S61). If it is the last cell, similarly, the frame list 13 is rewritten to "standby" (S62), and the arriving cell is discarded (S55). If it is not the final cell, only the arrival cell is discarded (S55).

As described above, in this algorithm, when an arriving cell is loaded into the transmission queue 71, subsequent cells having the same frame identifier (cells belonging to the same information frame) are loaded with priority until the final cell. On the other hand, when the arrival cell is discarded, the subsequent cells having the same frame identifier (cells belonging to the same information frame) are preferentially discarded until the final cell.

By the way, in the algorithm shown above,
Since the loading of cells into the transmission queue 71 is controlled by a threshold value smaller than the queue length, the cells are discarded even if the transmission queue 71 is not full. For example, in FIG.
In the algorithm shown in FIG. 5, when the number of waiting cells in the transmission queue 71 exceeds the threshold value, the cell that is “transmitting” in the frame list 13 is preferentially transmitted to the transmission queue 71.
And other cells are discarded. The difference between the queue length of the transmission queue 71 and the threshold is a priority area for surely transmitting all cells belonging to the same information frame, and contributes greatly to the reduction of the discard rate of information frames. ing.

However, a single cell (S
In the case of SM), there is no problem even if it interrupts this priority area. Rather, it is possible to reduce the discard rate of information frames by preferentially handling individual cells without discarding them. Therefore, in the algorithms shown in FIGS. 3 to 5, it is determined whether or not the arriving cell is a single cell, and if it is a single cell, it is preferentially loaded in the transmission queue 71. As an example thereof, a flowchart (corresponding to claim 6) when applied to the algorithm shown in FIG. 3 is shown in FIG.

Since the frame identifier of the single cell is not in the frame list 13, the process moves from S31 to S37. Here, it is determined from the cell type identifier of the arriving cell whether the arriving cell is a single cell (SSM) (S39). If it is a single cell, the arrival cell is loaded in the transmission queue 71 (S34). If it is not a single cell, the process proceeds to the judgment whether the arriving cell is the first cell (S35), and the same processing is performed thereafter.

The determination as to whether the cell is a single cell may be made between S35 and S36 before S31 in the algorithm shown in FIG. 6 (FIG. 3). Further, in the algorithm shown in FIG. 4, it may be before S41 or between S41 and S47.

Further, in the algorithm shown in FIG. 2, since the individual cells are certainly loaded in the transmission queue 71, it can be said that it is unnecessary to judge whether or not the individual cells are the individual cells.
The determination process may be performed at an appropriate place in order to improve the processing efficiency.

In the embodiment described above, the counting unit 72 detects the number of waiting cells in the transmission queue 71,
The configuration in which the determination unit 10 uses the number of waiting cells as congestion information is shown. As the congestion information, it is also possible to use information obtained by comparing cell arrival intervals and transmission intervals, congestion information notified from the network side, or a combination thereof.

[0044]

As described above, according to the cell frame transfer method of the present invention, when it is expected that the number of waiting cells in the transmission queue exceeds the threshold value and cell discard occurs, cells belonging to a specific information frame are transferred. Discard preferentially or preferentially transmit cells belonging to a specific information frame. As a result, since the information frames to which the discarded cells belong are concentrated on a specific one, it is possible to reduce the probability that the receiving side becomes an incomplete frame and is discarded as an information frame.

Since a single cell does not have a succeeding cell, even if the number of waiting cells in the transmission queue exceeds a predetermined threshold value, the single cell is preferentially handled without being discarded, and the discard rate of the information frame is reduced. Can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a cell frame transfer system of the present invention.

FIG. 2 is a flowchart showing an algorithm (claim 2) for registering a “discard” frame identifier in the frame list.

FIG. 3 is a flowchart showing an algorithm (claim 3) for registering a “transmitting” frame identifier in the frame list.

FIG. 4 is a flowchart showing an algorithm (claim 4) for registering “transmitting” and “discarding” frame identifiers in the frame list.

[Fig. 5] "Transmitting", "Discarding",
The flowchart which shows the algorithm (Claim 5) which registers the frame identifier of "waiting".

FIG. 6 is a flowchart showing an algorithm (claim 6) suitable for processing a single cell.

FIG. 7 is a block diagram showing a configuration of a conventional cell frame transfer system.

[Explanation of symbols]

 10 determination means 11 cell information extraction / discard control circuit 12 cell discard determination circuit 13 frame list 70 transmission channel 71 transmission queue 72 counting unit 73 control unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Miki Hirano 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (6)

[Claims] 1. A cell frame transfer method for waiting a cell into which an information frame has been divided in a transmission queue and transmitting the cell to a transmission line, when a number of waiting cells in the transmission queue exceeds a predetermined threshold value. A cell frame transfer system comprising a determination means for preferentially discarding cells belonging to an information frame. 2. In a cell frame transfer system in which a cell into which an information frame is divided is waited in a transmission queue and transmitted to a transmission channel, an arriving cell is the head cell and the number of waiting cells in the transmission queue is predetermined. If it exceeds the threshold value, the arriving cell is discarded and the information frame to which it belongs is registered in the frame list as a discard target, and the cells belonging to the information frame registered in the frame list among the subsequent cells are discarded, and other A cell frame transfer system comprising a determination means for transmitting a cell to the transmission queue. 3. A cell frame transfer method in which a cell obtained by dividing an information frame is waited in a transmission queue and transmitted to a transmission transmission line, wherein an arriving cell is the head cell and the number of waiting cells in the transmission queue is predetermined. If the threshold is not exceeded, the arrival cell is transmitted to the transmission queue and the information frame to which it belongs is registered in the frame list as a transmission target,
A cell frame transfer system comprising a determination means for transmitting only cells belonging to information frames registered in a frame list among subsequent cells to the transmission queue and discarding other cells. 4. A cell frame transfer method for waiting a cell into which an information frame is divided in a transmission queue and transmitting the cell to a transmission channel, wherein an arriving cell is the head cell and the number of waiting cells in the transmission queue is predetermined. If it exceeds the threshold, the arriving cell is discarded and the information frame to which it belongs is registered in the frame list as a discard target, and if the number of waiting cells in the transmission queue does not exceed the predetermined threshold,
A cell provided with a judging means for transmitting an arriving cell to the transmission queue, registering an information frame to which the cell belongs to a frame list as a transmission object, and discarding or transmitting a subsequent cell according to the registered contents of the frame list. Frame transfer method. 5. A cell frame transfer method in which a cell into which an information frame is divided is waited in a transmission queue and transmitted to a transmission transmission line. If the number of waiting cells in the transmission queue exceeds a predetermined threshold, an arriving cell is reached. If it is not the final cell, the information frame to which the cell belongs is registered in the frame list as a discard target, and if the number of waiting cells in the transmission queue does not exceed a predetermined threshold, the arrival cell is transmitted. If it is not the final cell, it is sent to the queue, the information frame to which it belongs is registered in the frame list as the transmission target, and subsequent cells are discarded or transmitted according to the registered contents of the frame list. If there is a self-checker, it is equipped with a judgment means to clear the registration information of the frame list. Beam transfer system. 6. The cell frame transfer method according to claim 1, wherein the determining means determines whether or not the arriving cell is a single cell that constitutes an information frame with one cell. A cell frame transfer system, which is characterized in that it includes means for sending to a transmission queue even if the number of waiting cells in the transmission queue exceeds a predetermined threshold in the case of a single cell.