JPH0248847A - Data transmittal confirming method - Google Patents

Abstract

PURPOSE:To prevent a resident transmission wait FL by decreasing a timer value in the case of the succeeding 1FL if timeout takes place until an 1FL from an opposite station is not received after the transmission of one frame (FL) from its own station. CONSTITUTION:The 1FL including a message of its own station user is sent from its own station to an opposite station and a timer is started to monitor the time till the reception of the 1FL from the opposite station. Before the reception of the 1FL from the opposite station, if timeout of the timer takes place, an SFL is sent from its own station to the opposite station and the transmittal of the 1FL sent from its own station is confirmed by using the sequence number of the SFL from the opposite station as the reply to the SFL. Then the timer value is decreased in the range while the timer value of the timer is not decreased from the minimum limit.

Description

[Detailed Description of the Invention] [Summary] Regarding a data delivery confirmation method for data transmitted from a local station to a partner station using an HDLC procedure, after an I frame is transmitted from the local station, but before one frame from the partner station is received. When the timer times out, the timer value when transmitting the next I frame from the local station is shortened, so that the S frame delivery 1+
In order to shorten the time required for first acknowledgment processing and to prevent frames waiting to be sent from being accumulated, in data communication in the asynchronous balanced mode (A B M) of the HDLC procedure, 1 frame containing a user's message from the local station is transmitted. A timer is started at the same time as sending the 1 frame to the partner station, and the time until the reception of the 1 frame sent from the partner station is monitored.If the 1 frame is received from the partner station before the timer times out, the reception The L frame confirms the delivery of the L frame sent from the local station to the remote station, and the transmission of the next L frame from the local station and the operations after starting the timer are repeated until the L frame is received from the remote station. When the timer times out, the local station sends data link monitoring and control S to the other station.
By transmitting a frame and receiving a response S frame from the partner station in response to the S frame, it is possible to confirm the delivery of the transmission frame from the own station to the partner station, and to keep the timer value of the timer below the minimum value. It is configured to repeat the transmission of the next frame from the local station and the operations after the timer activation.

[Industrial application field]

The present invention relates to a communication control system in data communication, and more particularly to a data delivery confirmation method for data transmitted from a local station to a partner station using an HDLC procedure.

[Conventional technology]

In data communications, HDLC is a protocol equivalent to the data link layer that smoothly transfers data between adjacent devices and provides error detection and recovery functions.
(High Level Data Link Control) procedures are currently becoming widespread.

In this HDLC procedure, multiple stations that have equal responsibility for data link control and that transmit and receive both commands and responses are always in asynchronous balanced mode (ABM).
Composite stations set to this ABM can send commands or responses to each other without permission from the other station.

In the HDLC procedure, frames as a unit of data transfer exchanged between stations include an l frame containing messages exchanged between users, and an S frame for monitoring and controlling a link. and asynchronous balanced mode (AB
In M), one of the following two methods is used to confirm whether the l-frame data transmitted by the local station has been delivered to the other station.

In the first method, confirmation is made using the sequence number N added to the I frame or S frame received from the partner station. Here, N indicates the sequence number of the next l frame expected to be received, and is used to notify that frames up to N, -1° have been accurately received.

In the second method, after a certain set time has elapsed after transmitting the l frame, the local station transmits the S frame, prompts the other station to send an S frame as a response, and uses the sequence number of the received response S frame. N, by i
I approve. In this method, the set time after sending the R frame until sending the S frame is usually the time until either of the two timers of the device times out. One of the timers is an l-frame response monitoring timer that stops and starts, or restarts, every time an l-frame is transmitted from the local station.
The other one is a no-communication monitoring timer that is restarted every time a frame is received from the partner station.

Here, the timer value of the l-frame response monitoring timer is generally much shorter than the timer value of the non-communication monitoring timer.

[Problem to be solved by the invention]

In communication in the asynchronous balanced mode as described above,
In the case of a business configuration in which only one station actually transmits l frames, or in a business configuration in which the local station transmits l frames continuously while the other station only transmits intermittently. In this case, it is difficult to confirm the delivery of the l frame transmitted from the own station to the other station using the first method described above because the number of l frames transmitted from the other station is small.

Therefore, confirmation will inevitably be performed using the second method, but in this method, the communication control program DLCP (data There is a problem in that frames waiting to be transmitted tend to remain in the link control program (link control program).

In the present invention, after the I frame is transmitted from the own station, the timer times out before receiving the frame from the other station.
When a failure occurs, shorten the timer value when requesting the next I frame from the local station, thereby shortening the time until S frame delivery TIILW processing and preventing frames waiting to be transmitted from remaining. The purpose is to

[Means and operations for solving the problems] A functional block diagram of the present invention is shown in FIG. In the figure, at 1, an I frame containing a message from the user of the own station is transmitted from the own station to the other station, and at the same time, a timer, for example, an I frame response monitoring timer, is started, and at 2, a ■ frame from the other station is sent. The time until reception is monitored.

■When an I frame from the other station is received before the frame response monitoring timer times out, the sequence number of the received I frame is set to 3, and the transmission 1 from the own station is
Delivery of the frame is confirmed, and the next I frame transmission from the local station 1 and the operations after the timer activation are repeated.

On the other hand, if the I frame response monitoring timer times out before receiving an I frame from the other station, the local station transmits an S frame to the other station in step 4, and the other station sends an S frame as a response. Delivery of the I frame transmitted from the local station is confirmed by the sequence number of the S frame. Next, in order to shorten the time required for the delivery confirmation process for the next ■ frame to be transmitted from the own station, that is, the time required to send the S frame, the timer value of the 1-frame response monitoring timer is shortened at 5 to the extent that it does not fall below the minimum value. be destroyed. Here, the minimum limit value of the timer value is set in advance based on the line speed, maximum transmission/reception frame length, etc. Thereafter, the next I frame transmission from the local station 1 and the operations after the timer activation are repeated.

Note that if the other station starts transmitting I frames continuously, there is no need to perform delivery confirmation processing by sending and receiving S frames. The timer value is returned to the initial value at the time when the delivery of the transmitted I frame from the local station is confirmed.

As described above, according to the present invention, the communication control program (
It is possible to prevent frames from remaining waiting to be transmitted in the DL CP.

〔Example〕

FIG. 2 shows an example of setting/changing the frame response monitoring timer. In the figure, a communication control program (DLC) is executed by commands from write 0 to write n from the own host.
P) sends a frame to the other host (S open'lf
Do 3. I-frames are generally written in the form 1 (n, m), where m is the transmission sequence number and n
indicates the next expected reception sequence number.

First, DL'CP starts an I frame response monitoring timer (T1) at the same time as transmitting the first frame (0,0). In FIG. 2, Tl5 (V) activates the T1 timer, and ■ in parentheses represents the initial value of the timer. Here, as a prerequisite, the window size, that is, the number of I frames that can be transmitted per - degree, is set to '3'', so DLCP transmits the next I frame 1 (0, 1) and restarts the T1 timer. ).TIR(V) indicates restart.

The DLCP then transmits the third frame I (0,2) and restarts the timer.

Having sent a number of I-frames matching the window size, DLCP waits for a response from the other host. If an I frame is not received from the other host before the TI timer times out, the S frame for link monitoring control, RR (0)
, P are sent to the other host. This frame is called an S frame command with P bit and generally has the format RR(n), P. Here, n is the next expected reception sequence number, and P indicates P bit, that is, with a poll bit. Between complex stations, a command of P=1 solicits a response with an F bit whose final bit (F bit) is "1" from the other complex station.

Response S frame RR (3), F from the other host
By receiving this, DLC'P indicates that the next sequence number that the other host expects to receive is 3, that is, that the write data of frames with sequence numbers 0 to 2 have been delivered. Then, after cutting the timer value of the response monitoring timer (T1) to, for example, half of the initial value V, ■ -, transmit the next I frame I (0, 3) and start the timer. I (0,4) and 1 (0,5) are transmitted within the range of the window size, and the timer T1 is restarted each time.

After sending r frame r (0,5), if the response monitoring timer with a timer value of 1 times out before the ■ frame from the other host is received, the S frame command RR with a ball bit for supervisory control is sent in ■ in Figure 2. (0), P
is sent to the other host side, and S frames with final bits RR (6), F as responses thereto are sent to the other host side.
is received, and the DLCP confirms that write data 3 to 5 have been delivered because the next expected reception sequence number of the destination host is 6'. Here, the timer value of the response monitoring timer is shortened again, for example, to 1/4 of the initial value, and then the next frame I
As soon as (0,6) is transmitted, the timer is started. It is assumed here that the negative timer value is also larger than the timer limit value V min, which is preset based on the line speed, maximum transmission/reception frame length, etc.

If a frame I (7, O) is received from the other host as shown in Figure 2 before the response monitoring timer times out and the timer value becomes -, the I frame causes the DLCP to proceed to the next step. It is confirmed that the sequence number that the other host expects to receive is "7" and that up to write data 6 has been delivered.

D due to receiving an I frame from the other host.
The LCP assumes that the other host has started the continuous transmission of ■ frames, returns the timer value of the response monitoring timer to the initial value ■, and then transmits the next I frame I (1, 7). Here, "1" in parentheses is the next frame number expected to be received from the other host.

DLCP is! At the same time as transmitting frame I (1,7), start the l frame response monitoring timer whose timer value is returned to V, and continue transmitting the next I frame I (1,0) and restarting the timer, etc. To go. Here, I (1
, 7), the next I frame is I (1°0) because
This is because the modulo indicating the total number of sequence numbers of ■ frames sent from the host is set to 8 as a prerequisite.

Next, the effect of reducing the time required for transmission when the present invention is implemented will be explained with reference to FIG. 3, taking as an example the case where write data O to 9 are sent to the other host as 10 I frames.

As in FIG. 2, the prerequisites are that the window size is "3", the modulo is "8", and one-eighth of the timer initial value, - is larger than the timer limit value V min.

FIG. 3 (al shows the case where the present invention is not implemented, and (b) shows the case where it is implemented. In the same figure (a), three one-frame I (
After transmitting 0,0), I (0,1), I (0,2>), the timer times out and the S frame with P bit RR (0), the transmission of P and the S frame R with F bit
Delivery is confirmed by receipt of R(3) and F.

Then I frames I (0,3), I (0,4
), I (0, 5) is sent, and when the timer times out, the delivery of the frame is confirmed by sending RR (0), P and receiving RR (6), F, but the timer value at this time is remains at V, and the time from ■ frame transmission to S frame delivery confirmation processing is not shortened.

After that ■ Frame I (0,6), I (0,7)
, J (0,0) transmission, timer timeout, R
Delivery confirmation and processing by sending R(0), P and receiving RR(1), F further includes sending I(0,1), timer timeout, sending RR(0), P, and receiving RR(2). ),
A delivery confirmation process is performed upon reception of F, and all data transmission and delivery confirmation are completed.

In the case of FIG. 3(b) to which the present invention is applied, the time it takes from the own host to send the S frame RR (0), P after sending the ■ frame + (0,5) -, In addition, I frame ■ (wholesale 0) is sent (f7 & s frame RR ■ (0), the time until sending P is -1, and after sending r frame I (0,1), S frame RR (0) is sent.

The same figure (
As in case a), all data is transmitted and its delivery confirmation process is performed.

Here, the time required to transmit the i-th T frame is Ti,,I
Frame response monitoring timer timeout occurs. Let Tr be the time it takes to send an S frame command with eP bit and confirm delivery by receiving an S frame response with F bit, and let V be the initial value of the timer.
The total transmission time Ta in the case of fbl in the same figure is as follows.

The first and second terms of both equations are the same, and the third term is the time reduction when the delivery 6 upbringing method of the present invention is implemented.

In the above description, the embodiment has been described on the assumption that the timer value of the I frame response monitoring timer is successively shortened by half, but it goes without saying that the method of shortening the timer value is not limited to this.

FIG.

[Effects of the Invention] As described above, according to the present invention, I frames waiting to be transmitted do not remain in the data link control program, and data flow is improved. As a result, data throughput can be improved for users, and the data communication system can be operated efficiently.

Claims (1)

[Claims] In data communication in asynchronous balanced mode (ABM) of the HDLC procedure, a timer is started (
1), and monitors the time until reception of the I-frame sent from the partner station (2), and when the I-frame from the partner station is received before the timer times out, the received I-frame Confirm the delivery of the transmitted I frame from the station to the partner station (3), repeat the transmission of the next I frame from the local station and start the timer (1), and repeat the operation before receiving the I frame from the partner station. When the timer times out, the own station transmits an S frame for data link monitoring and control to the other station, and receives a response S frame from the other station to the S frame, thereby preventing the transmission from the own station. Confirm the delivery of the I frame to the other station (4), shorten the timer value of the above-mentioned timer within a range that does not fall below the minimum value (5), and transmit the next I frame from the local station and start the timer (1). ) A data delivery confirmation method characterized by repeating the following operations.