JP2002033744A - Atm communication relay time reduction system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ATM communication system accommodating terminals which conduct communication using a bit synchronization system protocol that is provided with a function of reducing a communication delay time between end-to-end terminals. SOLUTION: Upon the receipt of an ATM cell sent from an opposite communication node by a cell reception buffer 34, after a fluctuation control section 33 counts preset fluctuation absorbing times from the received cell, an assembly section 32 disassembles/assembles the cells, and a frame transmission control section 31 transmits frames to a terminal via a frame buffer. A buffer monitor section 36 monitors write/read timing of data to/from the frame buffer 3, instructs transmission of an abort to the frame transmission control section 31 on the occurrence of a frame transmission under-run, sequentially re-reads head data of the interrupted frame from the frame buffer 35 and retransmits the frames to the terminals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an HDLC (High Level
vel Data Link Control procedure) and other bit synchronous protocol data to ATM (Asynchronous Transfer Mode).
The present invention relates to a method for reducing a delay time at the time of assembling and disassembling an ATM cell in an ATM communication system for converting and transferring cells, and more particularly to an improvement for reducing a communication delay time between end-end terminals.

[0002]

2. Description of the Related Art An example of a conventional ATM communication system is described in Japanese Patent Application Laid-Open No. 5-56066. As shown in FIG. 5, in the conventional ATM communication system, the transmitting unit of the communication node performs cell assembly by the output of the means for detecting that the received data length has reached the cell length when receiving a frame from the terminal. A cell assembling control unit that starts and controls transmission to the partner communication node is provided.

When the head cell arrives from the transmitting side, the receiving unit of the communication node calculates the fluctuation absorbing time using the previously determined maximum network fluctuation time and the transmission time of one cell to the receiving terminal. A cell disassembly control unit is provided that starts cell disassembly after the fluctuation absorption time after the head cell arrives from the transmission side and transmits a frame assembled and created from the disassembled cells to the terminal.

[0004]

However, according to the technique described in the above publication, the fluctuation absorption time is calculated using the maximum fluctuation time in the network and the transmission time of one cell to the receiving terminal. Therefore, there is a disadvantage that the communication delay time is increased.

[0005] Further, since the route of the communication must be obtained in advance, the maximum delay time of the communication node on the route must be collected, and the maximum time of network fluctuation must be calculated. The processing is complicated.

Accordingly, an object of the present invention is to provide a function of reducing a communication delay time between end-to-end terminals in an ATM communication system accommodating terminals performing communication using a bit synchronization protocol such as HDLC. .

[0007]

According to the present invention, an ATM for transferring bit synchronous frame data by using ATM cells is provided.
The transmitting unit of the communication node of the communication system receives the frame data from the terminal and, when the length of the cell reaches one cell, starts disassembly of the frame and cell assembly, and transmits the frame to the partner communication node. An ATM cell assembling / disassembling system for performing a transmission delay time shortening operation characterized by starting cell disassembly and frame assembling after a fluctuation absorption time after a leading cell from the transmitting side arrives and transmitting a frame to a partner terminal. A receiving unit of the communication node detects that a head cell from a partner communication node transmitting unit has arrived, and a fluctuation control unit for notifying that a preset fluctuation absorption time has elapsed after the arrival of the cell; An assembly unit for receiving and outputting the received cell, disassembling the received cell, a buffer unit for storing cells output by the assembly unit, and a frame buffer. A buffer monitoring unit that detects a frame transmission underrun by monitoring the timing of writing and reading, and a frame transmission control unit that sends a frame read from the frame buffer to a terminal based on a transmission start instruction from the assembly unit. When a frame transmission underrun is detected by the buffer monitoring unit, an ABORT pattern is transmitted to the terminal, and then the frame buffer is sequentially read from the head data of the interrupted frame to retransmit the frame to the terminal. Thus, it is possible to obtain an ATM communication delay time reducing method characterized by the above. In setting the fluctuation absorption time, the average cell delay time between communication nodes may be used.

[0008] Also, instead of the fluctuation control unit, a received cell monitor for outputting an instruction to start cell disassembly by detecting the arrival of two cells, the first cell and the next intermediate cell, transmitted from the correspondent communication node. A unit may be provided to start disassembly and assembly of the received cell.

[0009]

Next, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG.
1 shows a communication node block diagram according to an embodiment of the present invention.

In FIG. 1, a transmitting unit 20 includes a frame receiving buffer 21 for receiving a frame from a terminal, a one-cell length detecting unit 22, 1 for detecting that one-cell-length data is stored in the frame receiving buffer 21. Cell length detector 22
And a cell transmission buffer 24 for temporarily storing the assembled cells.

The receiving unit 30 also includes a cell reception buffer 34 for temporarily storing cells transmitted by the opposite communication node.
A fluctuation control unit 33 that detects cell reception and counts a previously set fluctuation absorption time; an assembly unit 32 that starts disassembly of the cell and assembly of the frame after counting up the fluctuation absorption time; Buffer 35 for temporarily storing data, and a buffer monitor 36 for monitoring writing and reading to and from the frame buffer 35 and detecting a frame transmission underrun state.
And a frame transmission control unit 31 for transmitting the frame read from the frame buffer 35 to the terminal.

Further, the frame transmission control unit 31 transmits an abort to the terminal when a subsequent transmission cell is delayed for more than the fluctuation absorption time set by monitoring by the buffer monitoring unit 36 and a frame transmission underrun occurs. Then, it has a function of transmitting again from the head of the frame stored in the frame buffer 35. Upon receiving the abort, the terminal discards the incomplete frame received so far and receives the retransmitted frame.

The operation of the embodiment of the present invention will be described below in detail with reference to the drawings. Referring to FIG. 1, which is an embodiment of the communication node, the communication node 40 has a transmission unit 20 and a reception unit 30 roughly divided.

When receiving the frame transmitted by the terminal, the transmitting unit 20 inputs the received frame to the frame receiving buffer 21. The one-cell length detection unit 22 monitors the frame reception buffer 21, and when detecting that one-cell-length data is stored in the frame reception buffer 21, notifies the segmentation unit 23 of one-cell-length reception. In the segmentation unit 23, the received frame is decomposed and the cells are assembled, and sent to the cell transmission buffer 24. The cell transmission buffer 24 temporarily stores cells,
The cell is transmitted to the ATM communication network at an appropriate timing. In the same way, for the subsequent data in the frame,
Cell assembly is performed sequentially.

On the other hand, when the head cell transmitted by the opposite communication node is input to the cell reception buffer 34, the fluctuation control unit 33 detects cell reception and counts a predetermined fluctuation absorption time. Start. In the present embodiment, the average cell delay time between communication nodes is set as the set value of the fluctuation absorption time, and after the fluctuation absorption time is counted up, the assembly unit 32 is instructed to start cell disassembly.

The assembly unit 32 disassembles the cell, starts reproduction of the frame, writes the frame being reproduced in the frame buffer 35, and instructs the frame transmission control unit 31 to start transmission.

The frame buffer 35 stores the frame data output by the assembly unit 32 until the frame being reproduced is completely reproduced.

The frame transmission control unit 31 receives a transmission start instruction from the assembly unit 32 and
5 and starts transmission to the terminal. In the same procedure, the disassembly of the cell and the transmission of the frame are sequentially performed for the subsequent cells. Also, the assembly unit 32
Writes the last cell of the frame into the frame buffer 35, and notifies the frame transmission control unit 31 that it is the last data of the frame. Upon receiving the notification, the frame transmission control unit 31 performs a frame end process after transmitting the final data, and the transmission to the terminal ends. Here, when the data length excluding the frame flag has a length that can be assembled into a plurality of cells, the assembled cell needs information indicating whether it is the first cell, the intermediate cell, or the last cell. However, the method of storing this information is already known and will not be described.

Also, since cells are transferred between communication nodes via an ATM communication network, fluctuation delay occurs in the ATM communication network. When a cell arrives with the maximum delay, the fluctuation control unit 33 cannot absorb the fluctuation delay, so that the data of the transmission frame is lost from the frame transmission control unit 31 and a transmission underrun occurs. The following operation is performed to prevent this. The buffer monitoring unit 36
It monitors writing and reading to and from the frame buffer 35 and notifies the frame transmission control unit 31 of a frame transmission underrun state. When reading out the transmission frame from the frame buffer 35 and notifying the buffer empty state from the buffer monitoring unit 36 when reading the transmission frame from the frame buffer 35, the frame transmission control unit 31 immediately transmits the ABORT pattern and interrupts the frame transmission. The terminal receiving the ABORT pattern
Discard the frame currently being received. After that, the frame transmission control unit 31 reads out the frame data from the head of the frame buffer 35 and retransmits the frame to the terminal.

Next, FIG. 2 showing one embodiment of the data flow.
The flow of communication data in the ATM communication system according to the present invention will be described with reference to FIG.

When the communication node detects that the transmission frame (a) from the terminal has been received for one cell length, it decomposes the frame, assembles the cell, and transmits the cell. Thereafter, similar operations are sequentially performed, and in this example, one frame is divided into four cells and cell transmission is performed (b). The transmitted cell has a delay of Td while being transferred through the ATM network, and arrives at the opposite communication node (c). The communication node of the game which has received the cell starts disassembling the cell and assembling the frame after the preset fluctuation absorption time Tw has elapsed. The frame is in the state of being reproduced because not all cells have been received yet, but is transmitted to the terminal from the part where the frame assembly is completed. Thereafter, similar operations are sequentially executed, and in this example, the received four cells are reproduced into one frame and the frame is transmitted to the terminal (d).
In (c), the cell arrives with a delay of Td due to the fluctuation of the ATM network during the cell disassembly and the frame assembling, but since the fluctuation absorption time Tw> Td,
This indicates that the frame reproduction of the cell is in time for frame transmission.

Next, the flow of communication data when a frame retransmission operation occurs will be described with reference to FIG. At the communication node, disassembling the frame and assembling the cell;
The operations of disassembling the cell and assembling the frame are performed in the same manner as in FIG. In (c), during the cell disassembly and frame assembly, the cell becomes Td due to the fluctuation of the ATM network.
Since it arrives with a time delay and the fluctuation absorption time Tw <Td, it indicates that the frame reproduction of the cell is not in time for the frame transmission. At this time, the communication node immediately transmits the abort pattern immediately after transmitting a part of the frame reproduced from the cell, and invalidates the frame being transmitted (d). Thereafter, transmission is performed again from the beginning of the frame.
(E) As a result, since the cell arrives while the cell reproduced from the cell is being transmitted, the complete frame can be reproduced and transmitted.

As described above, in the above embodiment, even if the arrival time of the cell fluctuates, the transfer of the frame is guaranteed by retransmission.
Since the communication can be performed without waiting for the maximum fluctuation time of the ATM communication network, the effect of shortening the communication delay time can be obtained.

In another embodiment of the present invention, the basic configuration is as described above, but the method of absorbing fluctuations in the communication node receiving unit is further devised. The configuration is shown in FIG. In this figure, a received cell monitoring unit 100 is connected instead of the fluctuation control unit 33.

The reception cell monitoring unit 100 monitors cells input to the cell reception buffer 34. When detecting that two cells, the first cell and the next intermediate cell, have been input, the reception cell monitoring unit 100 instructs the assembly unit 32 to perform cell disassembly. To start. As a result, the communication node receiving unit starts transmitting frames after storing frames for two cells.

As a result, if the next cell arrives before the communication node receiving section transmits the frame of two cells, the frame transmission to the terminal can be made in time. Fluctuation delay can be absorbed.

As described above, in this embodiment, the fluctuation delay corresponding to the time for transmitting the frame for one cell can be absorbed, and the effect that the fluctuation time need not be set in advance can be obtained.

[0028]

As described above, according to the present invention, the fluctuation absorption time is determined using only the transmission time of one cell to the receiving terminal without considering the maximum fluctuation time in the network. -The communication delay time between end terminals can be reduced.

Further, since it is not necessary to consider the maximum time of network fluctuation, a process of obtaining the communication route in advance, collecting the maximum delay time of the communication node on the path, and calculating the maximum time of network fluctuation is performed. Since it is not performed, the method of determining the fluctuation absorption time can be simplified.

[Brief description of the drawings]

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

FIG. 2 is a timing chart showing a normal communication data flow in ATM communication according to the embodiment of the present invention;

FIG. 3 is a timing chart showing a flow of communication data accompanied by retransmission in ATM communication according to the embodiment of the present invention;

FIG. 4 is an apparatus block diagram showing an application configuration of the embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional ATM communication delay time reducing system.

[Explanation of symbols]

 Reference Signs List 20 communication node transmission unit 21 frame reception buffer 22 1 cell length detection unit 23 segmentation unit 24 cell transmission buffer 30 communication node reception unit 31 frame transmission control unit 32 assembly unit 33 fluctuation control unit 34 cell reception buffer 35 frame buffer 36 buffer monitoring unit 40 communication node 100 reception cell monitoring unit

Claims (3)

[Claims] 1. A transmitting unit of a communication node of an ATM communication system for transferring bit synchronous frame data in an ATM cell receives a frame data from a terminal and, when the length of the cell reaches one cell, disassembles the frame and performs cell disassembly. Start assembling and transmit to the partner communication node. The receiver of the communication node starts cell disassembly and frame assembly after fluctuation absorption time after the first cell from the sender arrives, and transmits the frame to the partner terminal. In the ATM cell assembling / disassembling method for performing the transmission delay time reducing operation, the receiving unit of the communication node detects that the head cell from the correspondent communication node transmitting unit has arrived, and is preset after the arrival of the cell. A fluctuation control unit that notifies that the fluctuation absorption time has elapsed,
An assembly unit for disassembling a cell received in response to the notification output, a buffer unit for storing cells output by the assembly unit, and a frame transmission underrun by monitoring timing of writing and reading to and from the frame buffer. And a frame transmission control unit for transmitting a frame read from the frame buffer to a terminal based on a transmission start instruction from the assembly unit. A frame transmission underrun is detected by the buffer monitoring unit. In this case, after transmitting the ABORT pattern to the terminal, the ATM buffer is sequentially read from the frame buffer from the head data of the interrupted frame, and the frame is retransmitted to the terminal. 2. The ATM communication delay time reducing system according to claim 1, wherein said fluctuation absorption time is an average cell delay time between communication nodes. 3. A transmitting section of a communication node of an ATM communication system for transferring bit synchronous frame data in an ATM cell receives frame data from a terminal and, when the length of the cell reaches one cell, disassembles the frame and performs cell disassembly. Start assembling and transmit to the partner communication node. The receiver of the communication node starts cell disassembly and frame assembly after fluctuation absorption time after the first cell from the sender arrives, and transmits the frame to the partner terminal. In the ATM cell assembling / disassembling method for performing a transmission delay time reducing operation, the receiving unit of the communication node detects that two cells of a head cell and a next intermediate cell transmitted from a partner communication node have arrived. A receiving cell monitoring unit that outputs a cell disassembly start instruction, and an assembly unit that disassembles the received cell based on the cell disassembly start instruction, A buffer unit that stores cells output by the assembly unit, a buffer monitoring unit that detects a frame transmission underrun by monitoring the timing of writing and reading to and from the frame buffer, and a transmission start instruction from the assembly unit. And a frame transmission control unit for transmitting a frame read from the frame buffer to the terminal based on the frame transmission control unit. If a frame transmission underrun is detected by the buffer monitoring unit, an ABORT pattern is transmitted to the terminal, An ATM communication delay time reducing method characterized by sequentially reading out the head data of the interrupted frame and retransmitting the frame to the terminal.