System and method for transferring data

A data transfer system comprises a first communication device, a second communication device connected thereto via a first line, a third communication device connected thereto via a second line, and a fourth communication device connected thereto via a third line. The first communication device has a data transmission condition reception section for receiving a data transmission condition value for the up channel of the first line transmitted by the second communication device and a data transmission section for enabling data to be transmitted according to the data transmission condition received by the data transmission condition reception section.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a system and method for transferring data, 
and, in particular, to a system and method for transferring data which can 
prevent lines from becoming busy and still transfer data efficiently in a 
digital network such as an ATM network, a frame relay network, a circuit 
switching network, or a private line network. 
2. Description of the Prior Art 
In these days, terminals, which are sources for generating transmitted 
information, have capabilities of processing data, images, and sounds in 
various manners, for example, integrating or separating them. That is, the 
multimedia traffic in a digital network comprises various formes of 
transmissions of data such as continuous data and burst data of a high or 
a low density. 
A large number of data transfer methods for digital networks as shown in 
the following (i) to (v) are being provided to address such transmission 
forms (see FIG. 38). 
(i) Bit string transfer in a private line network 
(ii) Bit string transfer in a circuit switching network (including the 
ISDN) 
(iii) Packet multiplex transfer (store and forward) in a packet exchange 
network 
(iv) Frame multiplex transfer in a frame relay network 
(v) Cell multiplex transfer in an ATM network 
The term "terminal device" in the following description and FIG. 21 and 
subsequent drawings means a host computer, a workstation, a personal 
computer, a CSMA/CD local area network (LAN), or a token ring LAN. 
All of the data transfer methods in (i) to (v) require information to be 
transferred efficiently and economically under both normal and abnormal 
traffic conditions. 
Communication and terminal devices perform the processing described in the 
following (1) and (2) to avoid the occurrence of a busy condition caused 
by abnormal traffic or to clear the busy condition promptly after its 
occurrence. 
(1) Avoidance of the occurrence of a busy condition 
(a) Terminal and communication devices that receive data (referred to as 
"receiving devices" below) provide a statistical peak or average traffic 
value to users as a service condition standard. 
Terminal and communication devices that transmit data (referred to as 
"transmitting devices" below) are set by users to operate within the range 
of service condition standards. 
(b) Receiving devices has a large amount of memory for receiving data to 
prevent the occurrence of a busy condition even if traffic exceeding the 
service condition is input instantaneously. Receiving devices usually have 
such performance to permit an instantaneous increase in traffic. 
(2) Clearance of a busy condition after its occurrence 
(a) A receiving device, when detecting the occurrence of a busy condition 
in itself, transmits to a transmission device information for simply 
informing that a busy condition is occurring (referred to as a "busy 
condition signalling" below). 
Although this conventional method informs the transmitting device that a 
busy condition is occurring, it does not provide a specific condition on 
the reduction of the amount of data which is required to clear the busy 
condition. The transmitting device is responsible for this reduction. 
(b) A transmitting device that has received a busy condition signal 
performs the processing described in the following 1) to 3). 
1) Stop the transmission of data. 
2) Reduce the amount of transmitted data based on its own determination. 
3) Not restrain the amount of transmitted data but retransmit data when the 
receiving device abandons it. 
As described above, since the prior art does not allow a receiving device 
to provide a transmitting device with a specific condition on the 
clearance of a busy condition (for example, phasing down of data), 
problems shown below may occur. 
A first problem is that a transmitting device may repeat processing such as 
deactivating data transmission or phasing transmitted data down until it 
is informed of the clearance of the busy condition. That is, the busy 
condition continues, and the transmitting device must execute wasteful 
processing. 
A second problem is that the busy condition will be cleared if a plurality 
of transmitting devices simultaneously stop transmitting data but that in 
this case, a busy condition may occur again if the receiving device 
informs the clearance of the busy condition and the transmitting devices 
simultaneously start transmitting data. 
In view of these problems, it is an object of this invention to provide a 
method and system for transferring data which prevents the occurrence of a 
busy condition and still enables lines to be used efficiently in the data 
transfer between a receiving device and a transmitting device. 
It is another object of this invention to provide a method and system for 
transferring data which enables a busy condition to be logically cleared 
in the data transfer between a receiving device and a transmitting device. 
SUMMARY OF THE INVENTION 
&lt;First data transfer system of this invention&gt; 
A first data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, this aspect is a data transfer system comprising a first 
communication device, a second communication device connected thereto via 
a first line (A), a third communication device connected thereto via a 
second line (B), and a fourth communication device connected thereto via a 
third line (C), 
wherein if the data transfer direction from the first communication device 
to the fourth communication device is defined as an up direction and the 
data transfer direction from the fourth communication device to the first 
communication device is defined as a down direction, 
the first communication device has: 
a data transmission condition reception section for receiving a data 
transmission condition (.sub.u d.sub.A, .sub.u t.sub.A) value for the up 
channel of the first line (A) which is transmitted by the second 
communication device; and 
a data transmitting section for enabling data transmission according to the 
data transmission condition (.sub.u d.sub.A, .sub.u t.sub.A) received by 
the data transmission reception section (corresponding to claim 1). 
As described, according to the first data transfer system of this 
invention, the data transmission condition reception section can receive 
the data transmission condition (.sub.u d.sub.A, .sub.u t.sub.A) value for 
the up channel of the first line (A) which is transmitted by the second 
communication device. The data transmitting section can transmit data 
according to the data transmission condition (.sub.u d.sub.A, .sub.u 
t.sub.A) received by the data transmission reception section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Before explaining specific embodiments, the approximate configuration of 
this invention is described according to the means for solving the 
problems. 
&lt;First data transfer system of this invention&gt; 
A first data transfer system of this invention has the following 
configuration to solve the above first and second problems. FIG. 1 is a 
block diagram showing the principle of the first data transfer system. 
That is, this aspect is a data transfer system comprising a first 
communication device (10), a second communication device (20) connected 
thereto via a first line (A), a third communication device (30) connected 
thereto via a second line (B), and a fourth communication device (40) 
connected thereto via a third line (C), 
wherein if the data transfer direction from the first communication device 
(10) to the fourth communication device (40) is defined as an up direction 
and the data transfer direction from the fourth communication device (40) 
to the first communication device (10) is defined as a down direction, 
the first communication device (10) has: 
a data transmission condition reception section (11) for receiving a data 
transmission condition (.sub.u d.sub.A, .sub.u t.sub.A) value for the up 
channel of the first line (A) which is transmitted by the second 
communication device (20); and 
a data transmitting section (12) for enabling data transmission according 
to the data transmission condition (.sub.u d.sub.A, .sub.u t.sub.A) 
received by the data transmission reception section (11) (corresponding to 
claim 1). 
According to the first data transfer system of this invention, the data 
transmission condition reception section (11) can receive the data 
transmission condition (.sub.u d.sub.A, .sub.u t.sub.A) value for the up 
channel of the first line (A) which is transmitted by the second 
communication device (20). The data transmitting section (12) can transmit 
data according to the data transmission condition (.sub.u d.sub.A, .sub.u 
t.sub.A) received by the data transmission reception section (11). 
A communication device in this invention means a data terminal equipment 
(DTE) or a communication control unit. This is applicable to a second to a 
thirty-eighth data transfer systems and a first to a sixteenth data 
transfer methods which are described below. 
In addition, the data transmission condition (d,t) in this specification is 
marked with the subscripts listed in the following 1) to 9) as required. 
1) Maximum: (d, t).fwdarw.(d.sub.m, t.sub.m) 
2) Up channel: (d, t).fwdarw.(u.sub.d, u.sub.t) 
3) Down channel: (d, t).fwdarw.(d.sub.d, d.sub.t) 
4) Actual case: (d, t).fwdarw.(d.sub.r, t.sub.r) 
5) Transmitted data less than the maximum amount: (d, t).fwdarw.(d.sub.s, 
t.sub.s) 
6) To line A: (d, t).fwdarw.(d.sub.A, t.sub.A) 
7) To line B: (d, t).fwdarw.(d.sub.B, t.sub.B) 
8) To line C: (d, t) (d.sub.C, t.sub.C) 
9) To, for example, arbitrary line A: (d, t).fwdarw.(d.sub.Ai, t.sub.Ai) 
A plurality of the subscripts in 1) to 9) can be included in the data 
transmission condition. For example, the maximum data transmission on the 
up channel of line A can be represented as (.sub.u d.sub.Am, .sub.u 
t.sub.Am). 
&lt;Second data transfer system of this invention&gt; 
A second data transfer system of this invention has the following 
configuration to solve the above first and second problems. FIG. 2 is a 
block diagram showing the principle of the second data transfer system. 
That is, this aspect is a data transfer system comprising a first 
communication device (10), a second communication device (20) connected 
thereto via a first line (A), a third communication device (30) connected 
thereto via a second line (B), and a fourth communication device (40) 
connected thereto via a third line (C), 
wherein if the data transfer direction from the first communication device 
(10) to the fourth communication device (40) is defined as an up direction 
and the data transfer direction from the fourth communication device (40) 
to the first communication device (10) is defined as a down direction, 
the second communication device (20) has a data transmission condition 
transmission section (1) for transmitting to the first communication 
device (10) a data transmission condition (.sub.u d.sub.A, .sub.u t.sub.A) 
value for the up channel of the first line (A) (corresponding to claim 2). 
According to the second data transfer system of this invention, in addition 
to the operation of the first data transfer system, the data transmission 
condition transmission section can transmit the data transmission 
condition (.sub.u d.sub.A, .sub.u t.sub.A) value for the up channel of the 
first line (A) to the data transmission condition reception section (1) of 
the first communication device (10). 
&lt;Third data transfer system of this invention&gt; 
A third data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the second data transfer system, the data transmission 
condition transmission section (1) of the second communication device (20) 
has a data transmission condition management table for storing the data 
transmission condition (.sub.u d.sub.A, .sub.u t.sub.A) value 
(corresponding to claim 3). 
According to the third data transfer system, in addition to the operation 
of the second data transfer system, the data transmission condition 
transmission section (1) can manage the data transmission condition 
(.sub.u d.sub.A, .sub.u t.sub.A) value transmitted to a plurality of 
communication devices (10) using the data transmission condition 
management table for storing the transmitted data transmission condition 
(.sub.u d.sub.A, .sub.u t.sub.A). 
&lt;Fourth data transfer system of this invention&gt; 
A fourth data transfer system of this invention has the following 
configuration to solve the above first and second problems. FIG. 3 is a 
block diagram showing the principle of the fourth data transfer system. 
That is, this aspect is a data transfer system comprising a first 
communication device (10), a second communication device (20) connected 
thereto via a first line (A), a third communication device (30) connected 
thereto via a second line (B), and a fourth communication device (40) 
connected thereto via a third line (C), 
wherein if the data transfer direction from the first communication device 
(10) to the fourth communication device (40) is defined as an up direction 
and the data transfer direction from the fourth communication device (40) 
to the first communication device (10) is defined as a down direction, 
the second communication device (20) has an actual data transmission 
condition acquisition section (2) for monitoring data transmitted on the 
up channel of the second line (B) using monitoring levels and obtaining an 
actual data transmission condition (.sub.u d.sub.Br, .sub.u t.sub.Br) 
value or obtaining an actual data transmission condition (.sub.u d.sub.Br, 
.sub.u t.sub.Br) value from a circuit for the up channel of the second 
line (B) of the communication device which recognizes digital signal, 
frame, and cell arrays to obtain the above value (corresponding to claim 
4). 
According to the fourth data transfer system of this invention, the actual 
data transmission condition acquisition section (2) can monitor data 
transmitted on the up channel of the second line (B) using monitoring 
levels and obtain the actual data transmission condition (.sub.u d.sub.Br, 
.sub.u t.sub.Br) value. 
&lt;Fifth data transfer system of this invention&gt; 
A fifth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fourth data transfer system, the data transmission 
condition acquisition section (2) of the second communication device (20) 
provides electric synchronization in layer 1 and detects and identifies 
digital signal arrays (corresponding to claim 5). 
According to the fifth data transfer system of this invention, the data 
transmission condition acquisition section (2) of the fourth data transfer 
system can provide electric synchronization in layer 1 and detect and 
identify digital signal arrays. 
&lt;Sixth data transfer system of this invention&gt; 
A sixth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fourth data transfer system, the actual data transmission 
condition acquisition section (2) of the second communication device (20) 
detects and identifies frame arrays by detecting a flag in each frame 
(corresponding to claim 6). 
According to the sixth data transfer system of this invention, the actual 
data transmission condition acquisition section (2) of the fourth data 
transfer system can detect and identify frame arrays by detecting a flag 
in each frame. 
&lt;Seventh data transfer system of this invention&gt; 
A seventh data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fourth data transfer system, the actual data transmission 
condition acquisition section (2) of the second communication device (20) 
detects and identifies cell arrays by detecting a header in each cell 
(corresponding to claim 7). 
According to the seventh data transfer system of this invention, the actual 
data transmission condition acquisition section (2) of the fourth data 
transfer system can detect and identify cell arrays by detecting a header 
in each cell. 
&lt;Eighth data transfer system of this invention&gt; 
An eighth data transfer system of this invention has the following 
configuration to solve the above first and second problems. FIG. 4 is a 
block diagram showing the principle of the eighth data transfer system. 
That is, in the fourth data transfer system, 
the second communication device (20) has a busy condition occurrence 
determination section (3) for comparing a maximum data transmission 
condition (.sub.u d.sub.Bm, .sub.u t.sub.Bm) value for the up channel of 
the second line (B) which is already stored in the communication device or 
the busy condition occurrence determination section (3) to an actual data 
transmission condition (.sub.u d.sub.Br, .sub.u t.sub.Br) value for the up 
channel of the second line (B) which is obtained by the actual data 
transmission condition acquisition section (2) to determine whether or not 
a busy condition is occurring on the up channel of the second line (B) and 
to obtain a value of the difference between the maximum data transmission 
condition (.sub.u d.sub.Br, .sub.u t.sub.Br) value and the actual data 
transmission condition (.sub.u d.sub.Br, .sub.u t.sub.Br) value 
(corresponding to claim 8). 
According to the eighth data transfer system, in the first data transfer 
system, the busy condition occurrence determination section (3) of the 
second communication device (20) can compare the maximum data transmission 
condition (.sub.u d.sub.Bm, .sub.u t.sub.Bm) value for the up channel of 
the second line (B) to the actual data transmission condition (.sub.u 
d.sub.Br, .sub.u t.sub.Br) value for the up channel of the second line (B) 
which is obtained by the actual data transmission condition acquisition 
section (2) to determine whether or not a busy condition is occurring on 
the up channel of the second line (B) and to obtain a value of the 
difference between the maximum data transmission condition (.sub.u 
d.sub.Br, .sub.u t.sub.Br) value and the actual data transmission 
condition (.sub.u d.sub.Br, .sub.u t.sub.Br) value. 
&lt;Ninth data transfer system of this invention&gt; 
A ninth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the eighth data transmission system, the busy condition 
occurrence determination section (3) of the second communication device 
(20) calculates equation (1), 
EQU .sub.u d.sub.Bm -.sub.u d.sub.Br =X (1) 
and if in equation (1), X is 0 or +j that is a value representing a margin 
until the occurrence of a busy condition, calculates equation (2), 
EQU (.sub.u d.sub.Bm +.sub.u t.sub.Bm)-(.sub.u d.sub.Br +.sub.u t.sub.Br)=Z(2) 
and if in equation (2), Z is 0 or +p that represents a margin until the 
occurrence of a busy condition, determines that a busy condition is not 
occurring, and if in equation (1), X is -k that represents a negative 
quantity, calculates equation (3), 
EQU (.sub.u d.sub.Bm, .sub.u t.sub.Bm)-(.sub.u d.sub.Br +.sub.u t.sub.Br)=Y(3) 
and if in equation (3), Y is 0 or +m that represents a margin until the 
occurrence of a busy condition, determines that a busy condition is not 
occurring, and if in equation (3), Y is -n that represents a negative 
quantity or if in equation (2), Z is -q that represents a negative 
quantity, determines that a busy condition is occurring (corresponding to 
claim 9). 
According to the ninth data transfer system of this invention, in the 
eighth data transfer system, the busy condition occurrence determination 
section (3) can determine a value of the difference between X and Y and Z 
to make comparison and to determine whether or not a busy condition is 
occurring using the following steps 1 to 6. 
Step 1! 
Calculate equation (1). 
EQU .sub.u d.sub.Bm -.sub.u d.sub.Br =X (1) 
Step 2! 
If in equation (1), X is 0 or +j that is a value representing a margin 
until the occurrence of a busy condition, calculate equation (2). 
EQU (.sub.u d.sub.Bm +.sub.u t.sub.Bm)-(.sub.u d.sub.Br +.sub.u t.sub.Br)=Z(2) 
Step 3! 
If in equation (2), Z is 0 or +p that represents a margin until the 
occurrence of a busy condition, determine that a busy condition is not 
occurring. 
Step 4! 
If in equation (1), X is -k that represents a negative quantity, calculate 
equation (3). 
EQU (.sub.u d.sub.Bm +.sub.u t.sub.Bm)-(.sub.u d.sub.Br +.sub.u t.sub.Br)=Y(3) 
Step 5! 
If in equation (3), Y is 0 or +m that represents a margin until the 
occurrence of a busy condition, determine that a busy condition is not 
occurring. 
Step 6! 
If in equation (3), Y is -n that represents a negative quantity or if in 
equation (2), Z is -q that represents a negative quantity, determine that 
a busy condition is occurring. 
&lt;Tenth data transfer system of this invention&gt; 
A tenth data transfer system of this invention has the following 
configuration to solve the above first and second problems. FIG. 5 is a 
block diagram showing the principle of the tenth data transfer system. 
That is, in the eighth data transfer system, the second communication 
device (20) has a data transmission condition determination section (4) 
for determining a data transmission condition (d.sub.A, t.sub.A) for the 
up channel of the first line (A) which allows data to be transferred 
efficiently without causing a busy condition in the data transfer on the 
up channel of the second line (B), based on the results output by the busy 
condition occurrence determination section (3) and using a specified 
allocation criteria, and sends this value to the data transmission 
condition transmission section (1) (corresponding to claim 10). 
According to the tenth data transfer system, the data transmission 
condition determination section (4) of the second communication device 
(20) can determine a data transmission condition (d.sub.A, t.sub.A) for 
the up channel of the first line (A) which allows data to be transferred 
efficiently without causing a busy condition in the data transfer on the 
up channel of the second line (B), based on the results output by the busy 
condition occurrence determination section (3) and using a specified 
allocation criteria. 
&lt;Eleventh data transfer system of this invention&gt; 
An eleventh data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the tenth data transfer system, the data transmission condition 
determination section (4) of the second communication device (20) uses 
instead of the maximum data transmission condition (.sub.u d.sub.Am, 
.sub.u t.sub.Am) a safe data transmission condition (.sub.u d.sub.Bs, 
.sub.u t.sub.Bs) with a larger margin on the safer side than the maximum 
data transmission condition (.sub.u d.sub.Am, .sub.u t.sub.Am) 
(corresponding to claim 11). 
According to the eleventh data transfer system, the data transmission 
condition determination section (4) of the tenth data transfer system can 
use instead of the maximum data transmission condition (.sub.u d.sub.Am, 
.sub.u t.sub.Am) the safe data transmission condition (.sub.u d.sub.Bs, 
.sub.u t.sub.Bs) with a larger margin on the safer side than the maximum 
data transmission condition (.sub.u d.sub.Am, .sub.u t.sub.Am). 
&lt;Twelfth data transfer system of this invention&gt; 
A twelfth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the tenth data transfer system, if data transmitted across the 
up channel of the first line (A) can occupy the up channel of the second 
channel (B), the data transmission condition determination section (4) of 
the second communication device (20) adopts as the specified allocation 
criteria, the relationship 
EQU .sub.u d.sub.Ai +.sub.u t.sub.Ai =.sub.u d.sub.Bs +.sub.u t.sub.Bs 
wherein .sub.u d.sub.Ai, .sub.u t.sub.Ai, .sub.u d.sub.Bs, and .sub.u 
t.sub.Bs are data length time in a data transmission condition for the up 
channel of the first line (A), a data transmission time interval in a data 
transmission condition for the up channel of the first line (A), data 
length time in a data transmission condition for the up channel of the 
second line (B), and a data transmission time interval in a data 
transmission condition for the up channel of the second line (B), 
respectively (corresponding to claim 12). 
According to the twelfth data transfer system, if data transmitted across 
the up channel of the first line (A) can occupy the up channel of the 
second channel (B), the data transmission condition determination section 
(4) of the tenth data transfer system adopts as the specified allocation 
criteria, the relationship 
EQU .sub.u d.sub.Ai +.sub.u t.sub.Ai =.sub.u d.sub.Bs +.sub.u t.sub.Bs. 
&lt;Thirteenth data transfer system of this invention&gt; 
A thirteenth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the tenth data transfer system, if data transmitted across the 
up channel of the (n) first lines (A) can occupy the up channel of the 
second line (B), the data transmission condition determination section (4) 
of the second communication device (20) adopts as the specified allocation 
criteria, the relationship 
EQU .SIGMA.(.sub.u d.sub.Ai +.sub.u t.sub.Ai)=.sub.u d.sub.Bs +.sub.u t.sub.Bs 
wherein .sub.u d.sub.Ai, .sub.u t.sub.Ai,.sub.u d.sub.Bs and .sub.u 
t.sub.Bs, are data length time in a data transmission condition for the up 
channel of the i-th first line (A), a data transmission time interval in a 
data transmission condition for the up channel of the i-th first line (A), 
data length time in a data transmission condition for the up channel of 
the second line (B), and a data transmission time interval in a data 
transmission condition for the up channel of the second line (B), 
respectively (corresponding to claim 13). 
According to the thirteenth data transfer system, if data transmitted 
across the up channel of the (n) first line (A) can occupy the up channel 
of the second line (B), the data transmission condition determination 
section (4) of the tenth data transfer system adopts as the specified 
allocation criteria, the relationship 
EQU .SIGMA.(.sub.u d.sub.Ai +.sub.u t.sub.Ai)=.sub.u d.sub.Bs +.sub.u t.sub.Bs. 
&lt;Fourteenth data transfer system of this invention&gt; 
A fourteenth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the thirteenth data transfer system, the sum of .sub.u d.sub.Ai 
and .sub.u t.sub.Ai is determined by the following uniform relationship, 
EQU (.sub.u d.sub.A1 +.sub.u t.sub.A1)=(.sub.u d.sub.A2 +.sub.u t.sub.A2)= . . 
. =(.sub.u d.sub.Ai +.sub.u t.sub.Ai)=(.sub.u d.sub.An +.sub.u t.sub.An). 
According to the fourteenth data transfer system, in the thirteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai is 
determined by the following uniform relationship, 
EQU (.sub.u d.sub.A1 +.sub.u t.sub.A1)=(.sub.u d.sub.A2 +.sub.u t.sub.A2)= . . 
. =(.sub.u d.sub.Ai +.sub.u t.sub.Ai)=(.sub.u d.sub.An +.sub.u t.sub.An). 
&lt;Fifteenth data transfer system of this invention&gt; 
A fifteenth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the thirteenth data transfer system, the sum of .sub.u d.sub.Ai 
and .sub.u t.sub.Ai is given in such a way that the ordinal relationship 
is reflected in .SIGMA.d.sub.Ai that is the sum of the amount of data bits 
transmitted per unit time (corresponding to claim 15). 
According to the fifteenth data transfer system, in the thirteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai is given 
in such a way that the ordinal relationship is reflected in 
.SIGMA.d.sub.Ai that is the sum of the amount of data bits transmitted per 
unit time. 
&lt;Sixteenth data transfer system of this invention&gt; 
A sixteenth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fifteenth data transfer system, the sum of udAi and utAi 
has its ordinal relationship established based on the performance of the 
first communication device (10) (corresponding to claim 16). 
The "performance" stated above means 1) the size of a data buffer for 
transmission and reception for the communication device and 2) the level 
of the capabilities of data transmission and reception (the speed at which 
the buffer can be emptied). 
According to the sixteenth data transfer system, in the fifteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai has its 
ordinal relationship established based on the performance of the first 
communication device (10). 
&lt;Seventeenth data transfer system of this invention&gt; 
A seventeenth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fifteenth data transfer system, the sum of .sub.u d.sub.Ai 
and .sub.u t.sub.Ai has its ordinal relationship established based on the 
operation of the first communication device (10) (corresponding to claim 
17). 
The "operation" stated above means a priority established for each 
communication device, and communication devices with a higher priority 
deal with information for which transfer should be completed promptly. 
According to the seventeenth data transfer system, in the fifteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai has its 
ordinal relationship established based on the operation of the first 
communication device (10). 
&lt;Eighteenth data transfer system of this invention&gt; 
An eighteenth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fifteenth data transfer system, the sum of .sub.u d.sub.Ai 
and .sub.u t.sub.Ai has its ordinal relationship established based on the 
performance of the fourth communication device (40) (corresponding to 
claim 18). 
The "performance" stated above means 1) the size of a data buffer for 
transmission and reception for the communication device and 2) the level 
of the capabilities of data transmission and reception (the speed at which 
the buffer can be emptied). 
According to the eighteenth data transfer system, in the fifteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai has its 
ordinal relationship established based on the performance of the fourth 
communication device (40). 
&lt;Nineteenth data transfer system of this invention&gt; 
A nineteenth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fifteenth data transfer system, the sum of .sub.u d.sub.Ai 
and .sub.u t.sub.Ai has its ordinal relationship established based on the 
operation of the fourth communication device (40) (corresponding to claim 
19). 
The "operation" stated above means a priority established for each 
communication device, and communication devices with a higher priority 
deal with information for which transfer should be completed promptly. 
According to the nineteenth data transfer system, in the fifteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai has its 
ordinal relationship established based on the operation of the fourth 
communication device (40). 
&lt;Twentieth data transfer system of this invention&gt; 
A twentieth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fifteenth data transfer system, the sum of .sub.u d.sub.Ai 
and .sub.u t.sub.Ai has its ordinal relationship established based on the 
performance of the first line (A) (corresponding to claim 20). 
The "performance" stated above means 1) the line speed, 2) the line 
propagation delay time, and 3) the magnitude of line bit errors. 
According to the twentieth data transfer system, in the fifteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai has its 
ordinal relationship established based on the performance of the first 
line (A). 
&lt;Twenty-first data transfer system of this invention&gt; 
A twenty-first data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fifteenth data transfer system, the sum of .sub.u d.sub.Ai 
and .sub.u t.sub.Ai has its ordinal relationship established based on the 
operation of the first line (A) (corresponding to claim 21). 
The "operation" stated above means a priority established for each line, 
and lines with a higher priority deal with information for which transfer 
should be completed promptly. 
According to the twenty-first data transfer system, in the fifteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai has its 
ordinal relationship established based on the operation of the first line 
(A). 
&lt;Twenty-second data transfer system of this invention&gt; 
A twenty-second data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fifteenth data transfer system, the sum of .sub.u d.sub.Ai 
and .sub.u t.sub.Ai has its ordinal relationship established based on the 
performance of the third line (C) (corresponding to claim 22). 
The "performance" stated above means 1) the line speed, 2) the line 
propagation delay time, and 3) the magnitude of line bit errors. 
According to the twenty-second data transfer system, in the fifteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai has its 
ordinal relationship established based on the performance of the third 
line (C). 
&lt;Twenty-third data transfer system of this invention&gt; 
A twenty-third data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fifteenth data transfer system, the sum of .sub.u d.sub.Ai 
and .sub.u t.sub.Ai has its ordinal relationship established based on the 
operation of the third line (C) (corresponding to claim 23). 
The "operation" stated above means a priority established for each line, 
and lines with a higher priority deal with information for which transfer 
should be completed promptly. 
According to the twenty-second data transfer system, in the fifteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai has its 
ordinal relationship established based on the operation of the third line 
(C). 
&lt;Twenty-fourth data transfer system of this invention&gt; 
A twenty-fourth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fifteenth data transfer system, the sum of .sub.u d.sub.Ai 
and .sub.u t.sub.Ai has its ordinal relationship established based on the 
operation of the second line (B) (corresponding to claim 24). 
The "performance" stated above means 1) the line speed, 2) the line 
propagation delay time, and 3) the magnitude of line bit errors. 
According to the twenty-fourth data transfer system, in the fifteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai has its 
ordinal relationship established based on the performance of the second 
line (B). 
&lt;Twenty-fifth data transfer system of this invention&gt; 
A twenty-fifth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fifteenth data transfer system, the sum of .sub.u d.sub.Ai 
and .sub.u t.sub.Ai has its ordinal relationship established based on the 
operation of the second line (B) (corresponding to claim 25). 
The "operation" stated above means a priority established for each line, 
and lines with a higher priority deal with information for which transfer 
should be completed promptly. 
According to the twenty-fifth data transfer system, in the fifteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai has its 
ordinal relationship established based on the operation of the second line 
(B). 
&lt;Twenty-sixth data transfer system of this invention&gt; 
A twenty-sixth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fifteenth data transfer system, the sum of .sub.u d.sub.Ai 
and .sub.u t.sub.Ai has its ordinal relationship established based on the 
data transmission time for the first communication device (10) 
(corresponding to claim 26). 
According to the twenty-sixth data transfer system, in the fifteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai has its 
ordinal relationship established based on the data transmission time for 
the first communication device (10). 
&lt;Twenty-seventh data transfer system of this invention&gt; 
A twenty-seventh data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the fifteenth data transfer system, the sum of .sub.u d.sub.Ai 
and .sub.u t.sub.Ai has its ordinal relationship established based on the 
data reception time for the fourth communication device (40) 
(corresponding to claim 27). 
According to the twenty-seventh data transfer system, in the fifteenth data 
transfer system, the sum of .sub.u d.sub.Ai and .sub.u t.sub.Ai has its 
ordinal relationship established based on the data reception time for the 
fourth communication device (40). 
&lt;Twenty-eighth data transfer system of this invention&gt; 
A twenty-eighth data transfer system of this invention has the following 
configuration to solve the above first and second problems. FIG. 6 is a 
block diagram showing the principle of the twenty-eighth data transfer 
system. 
That is, this aspect is a data transfer system comprising a first 
communication device (10), a second communication device (20) connected 
thereto via a first line (A), a third communication device (30) connected 
thereto via a second line (B), and a fourth communication device (40) 
connected thereto via a third line (C), 
wherein if the data transfer direction from the first communication device 
(10) to the fourth communication device (40) is defined as an up direction 
and the data transfer direction from the fourth communication device (40) 
to the first communication device (10) is defined as a down direction, 
the third communication device (30) has an actual data transmission 
condition acquisition section (21) for obtaining an actual data 
transmission condition (.sub.u d.sub.BR, .sub.u t.sub.Br) value from a 
circuit for the up channel of the second line (B) which monitors received 
data to detect the above value (corresponding to claim 28). 
According to the twenty-eighth data transfer system of this invention, the 
actual data transmission condition acquisition section (21) of the third 
communication device (30) can monitor data received from the up channel of 
the second line (B) to obtain the actual data transmission condition 
(.sub.u d.sub.Br, .sub.u t.sub.Br) value. 
&lt;Twenty-ninth data transfer system of this invention&gt; 
A twenty-ninth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the twenty-eighth data transfer system, the third communication 
device (30) has an actual data transmission condition transmission section 
(22) for transmitting to the second communication device (20) the actual 
data transmission condition (.sub.u d.sub.Br, .sub.u t.sub.Br) value 
obtained by the actual data transmission condition acquisition section 
(21) (corresponding to claim 29). 
According to the twenty-ninth data transfer system, in the twenty-eighth 
data transfer system, the actual data transmission condition transmission 
section (22) of the third communication device (30) transmits to the 
second communication device (20) the actual data transmission condition 
(.sub.u d.sub.Br, .sub.u t.sub.Br) value obtained by the actual data 
transmission condition acquisition section (21). 
&lt;Thirtieth data transfer system of this invention&gt; 
A thirtieth data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the eighth data transfer system, the second communication 
device (20) has instead of the actual data transmission condition 
acquisition section (2) an actual data transmission condition acquisition 
section (5) for receiving an actual data transmission condition (.sub.u 
d.sub.Br, .sub.u t.sub.Br) value transmitted from the actual data 
transmission control transmission section (22) of the third communication 
device (30) and outputting it to the busy condition occurrence 
determination section (3) (corresponding to claim 30). 
According to the thirtieth data transfer system, in the eighth data 
transfer system, the actual data transmission condition acquisition 
section (5) of the second communication device (20) can receive the actual 
data transmission condition (.sub.u d.sub.Br, .sub.u t.sub.Br) value 
transmitted from the actual data transmission control transmission section 
(22) of the third communication device (30) and output it to the busy 
condition occurrence determination section (3). 
&lt;Thirty-first data transfer system of this invention&gt; 
A thirty-first data transfer system of this invention has the following 
configuration to solve the above first and second problems. 
That is, in the eighth data transfer system, the second communication 
device (20) has instead of the actual data transmission condition 
acquisition section (2) an actual data reception condition output section 
(5a) for receiving the actual reception condition (.sub.u d.sub.Br, .sub.u 
t.sub.Br) of the up channel of the second line (B) which is monitored and 
measured by an externally installed management system and outputting it to 
the busy condition occurrence determination section (3) (corresponding to 
claim 31). 
According to the thirty-first data transfer system, in the eighth data 
transfer system, the actual data transmission condition output section 
(5a) of the second communication device (20) can receive the actual 
reception condition (.sub.u d.sub.Br, .sub.u t.sub.Br) of the up channel 
of the second line (B) which is monitored and measured by the externally 
installed management system and output it to the busy condition occurrence 
determination section (3). 
&lt;Thirty-second data transfer system of this invention&gt; 
A thirty-second data transfer system of this invention has the following 
configuration to solve the above first and second problems. FIG. 7 is a 
block diagram showing the principle of the thirty-second data transfer 
system. 
That is, this aspect is a data transfer system comprising a first 
communication device (10), a second communication device (20) connected 
thereto via a first line (A), a third communication device (30) connected 
thereto via a second line (B), and a fourth communication device (40) 
connected thereto via a third line (C), 
wherein if the data transfer direction from the first communication device 
(10) to the fourth communication device (40) is defined as an up direction 
and the data transfer direction from the fourth communication device (40) 
to the first communication device (10) is defined as a down direction, 
the second communication device (20) has a definite determination 
information output section (6) for receiving from an externally installed 
management system "the same information as output by the busy condition 
occurrence determination section (3) and which is determined definitely by 
the external management system" and outputting it to the data transmission 
condition determination section (4) (corresponding to claim 32). 
According to the thirty-second data transfer system, the definite 
determination information output section (6) of the second communication 
device (20) can receive from the externally installed management system 
"the same information as output by the busy condition occurrence 
determination section (3)" and which is determined definitely by the 
external management system and output it to the data transmission 
condition determination section (4). 
&lt;Thirty-third data transfer system of this invention&gt; 
A thirty-third data transfer system of this invention has the following 
configuration to solve the above first and second problems. FIG. 8 is a 
block diagram showing the principle of the thirty-third data transfer 
system. 
That is, in the eighth data transfer system, the second communication 
device (20) has a maximum data transmission condition output section (7) 
for "receiving from an externally installed management system a maximum 
data transmission condition (.sub.u d.sub.Bm, .sub.u t.sub.Bm) for the up 
channel of the second line (B)" instead of the maximum data transmission 
condition already stored in the communication device or the busy condition 
occurrence determination section (3) and "outputting it to the busy 
condition occurrence determination section (3)" (corresponding to claim 
33). 
According to the thirty-third data transfer system, the maximum data 
transmission condition output section (7) of the second communication 
device (20) can receive from the externally installed management system 
the maximum data transmission condition (.sub.u d.sub.Bm, .sub.u t.sub.Bm) 
for the up channel of the second line (B) and output it to the busy 
condition occurrence determination section (3). That is, this section can 
use this condition instead of the maximum data transmission condition 
stored in the communication device or the busy condition occurrence 
determination section (3). 
&lt;Thirty-fourth data transfer system according to this invention&gt; 
A thirty-fourth data transfer system according to this invention has the 
following configuration to solve the first and the second problems. FIG. 9 
is a block diagram showing the principle of the thirty-fourth data 
transfer system. 
That is, in the tenth data transfer system, the second communication device 
(20) has instead of the data transmission condition determination section 
(4) a first line data transmission condition determination section (8) for 
receiving from an externally installed management system "a data 
transmission condition (.sub.u d.sub.A, .sub.u t.sub.A) value for the up 
channel of an arbitrary first line (A) based on the specified allocation 
criteria used in any of the twelfth to twenty-seventh data transfer 
systems" and transmitting it to the data transmission condition 
transmission section (1) (corresponding to claim 34). 
According to the thirty-fourth data transfer system of this invention, the 
first line data transmission condition determination section (8) of the 
second communication device (20) can receive from the externally installed 
management system "the data transmission condition (.sub.u d.sub.A, .sub.u 
t.sub.A) value for the up channel of an arbitrary first line (A) based on 
the specified allocation criteria used in any of the twelfth to 
twenty-seventh data transfer systems" and transmit it to the data 
transmission condition transmission section (1). 
&lt;Thirty-fifth data transfer system according to this invention&gt; 
A thirty-fifth data transfer system according to this invention has the 
following configuration to solve the first and the second problems. FIG. 
10 is a block diagram showing the principle of the thirty-fourth data 
transfer system. 
That is, the functions of the data transmission condition transmission 
section (1), the actual data transmission condition acquisition section 
(2), the busy condition occurrence determination section (3), the data 
transmission condition determination section (4), the actual data 
transmission condition output section (5), the actual data reception 
condition output section (5a), the determined information output section 
(6), the maximum data transmission condition output section (7), and the 
first line data transmission condition determination section (8) are 
applicable to the down channel of the first line (A), the up and down 
lines of the second and the third lines (B) and (C) (corresponding to 
claim 35). 
According to the thirty-fifth data transfer system of this invention, the 
functions of the data transmission condition transmission section (1), the 
actual data transmission condition acquisition section (2), the busy 
condition occurrence determination section (3), the data transmission 
condition determination section (4), the actual data transmission 
condition output section (5), the actual data reception condition output 
section (5a), the determined information output section (6), the maximum 
data transmission condition output section (7), and the first line data 
transmission condition determination section (8) are applicable to the 
down channel of the first line (A), the up and down lines of the second 
and the third lines (B) and (C). 
&lt;Thirty-sixth data transfer system according to this invention&gt; 
A thirty-sixth data transfer system according to this invention has the 
following configuration to solve the first and the second problems. FIG. 
11 is a block diagram showing the principle of the thirty-sixth data 
transfer system. 
That is, in the thirty-fifth data transfer system, for better 
communications, the second communication device (20) connects to a 
plurality of communication devices (11) that provide a function similar to 
that of the first communication device (10), the third communication 
device (30) connects to a plurality of communication devices (41) that 
provide a function similar to that of the fourth communication device 
(40), and this is applicable to both up and down channels of each line. 
According to the thirty-sixth data transfer system of this invention, in 
the thirty-fifth data transfer system, for better communications, the 
second communication device (20) connects to a plurality of communication 
devices (11) that provide a function similar to that of the first 
communication device (10), the third communication device (30) connects to 
a plurality of communication devices (41) that provide a function similar 
to that of the fourth communication device (40), and this is applicable to 
both up and down channels of each line, as shown in FIG. 31. 
&lt;Thirty-seventh data transfer system according to this invention&gt; 
A thirty-seventh data transfer system according to this invention has the 
following configuration to solve the first and the second problems. 
That is, in the thirty-fifth data transfer system, if the second 
communication device (20) and the third communication device (30) uses a 
fixed virtual logical path instead of a call connection processing to set 
up and down channels in advance between the first communication device 
(10) and the fourth communication device (40), the functions of the data 
transmission condition transmission section (1), the actual data 
transmission condition acquisition section (2), the busy condition 
occurrence determination section (3), the data transmission condition 
determination section (4), the actual data transmission condition output 
section (5), the actual data reception condition output section (5a), the 
determined information output section (6), the maximum data transmission 
condition output section (7), and the first line data transmission 
condition determination section (8) are applicable to the up and down 
lines of the first, the second, and the third lines (A), (B), and (C) 
(corresponding to claim 37). 
According to the thirty-seventh data transfer system of this invention, if 
the second communication device (20) and the third communication device 
(30) uses a fixed virtual logical path instead of a call connection 
processing to set up and down channels in advance between the first 
communication device (10) and the fourth communication device (40), the 
functions of the data transmission condition transmission section (1), the 
actual data transmission condition acquisition section (2), the busy 
condition occurrence determination section (3), the data transmission 
condition determination section (4), the actual data transmission 
condition output section (5), the actual data reception condition output 
section (5a), the determined information output section (6), the maximum 
data transmission condition output section (7), and the first line data 
transmission condition determination section (8) are applicable to the up 
and down lines of the first, the second, and the third lines (A), (B), and 
(C) (corresponding to claim 37). 
&lt;Thirty-eighth data transfer system according to this invention&gt; 
A thirty-eighth data transfer system according to this invention has the 
following configuration to solve the first and the second problems. 
That is, in the first to thirty-seventh data transfer systems, if the use 
of the up and down channels of the first, the second, or the third lines 
(A), (B), and (C) is charged, the charge is based on the data transmission 
condition (d, t) value (corresponding to claim 38). 
According to the thirty-eighth data transfer system of this invention, in 
the first to thirty-seventh data transfer systems, if the use of the up 
and down channels of the first, the second, or the third lines (A), (B), 
and (C) is charged, the charge can be based on the data transmission 
condition (d, t) value. 
&lt;First data transfer method according to this invention&gt; 
A first data transfer method according to this invention has the following 
configuration to solve the first and the second problems. FIG. 12 is a 
flowchart showing the principle of the first data transfer method, and 
FIG. 20 shows data transfer on a line. 
That is, this invention is a data transfer method comprising a first 
communication device (10), a second communication device (20) connected 
thereto via a first line (A), a third communication device (30) connected 
thereto via a second line (B), 
wherein if the transmission time from the leading bit of continuous data to 
its trailing bit (referred to as "continuous data" below) is defined as 
data length time d.sub.A and the occurrence time interval of continuous 
data is referred to as t.sub.A when the continuous data is transmitted 
from the first communication device (10) to the second communication 
device (20) via the first line (A), 
and if the transmission time from the leading bit of continuous data to its 
trailing bit (referred to as "continuous data" below) is defined as data 
length time d.sub.B and the occurrence time interval of continuous data is 
referred to as t.sub.B when the continuous data is transmitted from the 
second communication device (20) to the third communication device (30) 
via the second line (B), the data transmission condition (.sub.u d.sub.A, 
.sub.u t.sub.A) for the first line (A) is set to the maximum data 
transmission condition (.sub.u d.sub.Bm, .sub.u t.sub.Bm)for the second 
line (B) (corresponding to claim 39). 
According to the first data transfer method of this invention, the data 
transmission condition (.sub.u d.sub.A, .sub.u t.sub.A) for the first line 
(A) can be set to the maximum data transmission condition (.sub.u 
d.sub.Bm, .sub.u t.sub.Bm)for the second line (B), thereby preventing a 
busy condition from occurring in the second communication device (20) and 
maximizing the data transfer efficiency of the up channel of the second 
line (B). 
The same effect can be produced on the down channel by using a means that 
inverses the relationship between the first communication device (10) and 
the second communication device (20). 
&lt;Second data transfer method according to this invention&gt; 
A second data transfer method according to this invention has the following 
configuration to solve the first and the second problems. FIG. 13 is a 
flowchart showing the principle of the second data transfer method, and 
FIG. 20 shows data transfer on a line. 
That is, this invention is a data transfer method comprising a first 
communication device (10) and a second communication device (20) connected 
thereto via a first line (A), wherein the second communication device (20) 
transmits a data transmission condition (d, t) to the first communication 
device (10), and wherein the first communication device (10) transmits 
data based on the data transmission condition (d, t) (corresponding to 
claim 40). 
According to the second data transfer method according to this invention, 
the second communication device (20) can transmit the data transmission 
condition (d, t) to the first communication device (10), and the first 
communication device (10) can transmit data based on the data transmission 
condition (d, t). 
That is, the receiver and the transmitter can control the amount of 
transmitted data according to the value of a specified amount. 
&lt;Third data transfer method according to this invention&gt; 
A third data transfer method according to this invention has the following 
configuration to solve the first and the second problems. 
That is, the data transfer method in the second data transfer method is 
used as required (corresponding to claim 41). 
According to the third data transfer method according to this invention, 
the second data transfer method is used as required. 
That is, this method can be switched to other data transfer methods. 
&lt;Fourth data transfer method according to this invention&gt; 
A fourth data transfer method according to this invention has the following 
configuration to solve the second problem. FIG. 14 is a flowchart showing 
the principle of the fourth data transfer method, and FIG. 20 shows data 
transfer on a line. 
That is, this invention is a data transfer method comprising a first 
communication device (10), a second communication device (20) connected 
thereto via a first line (A), a third communication device (30) connected 
thereto via a second line (B), and a fourth communication device (40) 
connected thereto via a third line (C), the first communication device 
(10) transferring data to the fourth communication device (40) via the 
second and the third communication devices (20) and (30), 
wherein if a busy condition occurs in the second communication device (20) 
during communications between the first communication device (10) and the 
fourth communication device (40), 
the second communication device (20) transmits to the first communication 
device (10) a data transmission condition (d.sub.A, t.sub.A) for the first 
line (A) which is set by any of the first to the thirty-fourth data 
transfer systems, and 
the first communication device (10) transmits data based on the data 
transmission condition (d.sub.A, t.sub.A) (corresponding to claim 42). 
According to the fourth data transfer method according to this invention, 
if a busy condition occurs in the second communication device (20) during 
communications between the first communication device (10) and the fourth 
communication device (40), the second communication device (20) can 
transmit to the first communication device (10) the data transmission 
condition (d.sub.A, t.sub.A) for the first line (A) which is set by any of 
the first to the thirty-fourth data transfer systems. 
The first communication device (10) transmits data based on the data 
transmission condition (d.sub.A, t.sub.A), thereby clearing the busy 
condition. 
&lt;Fifth data transfer method according to this invention&gt; 
A fifth data transfer method according to this invention has the following 
configuration to solve the second problem. FIG. 15 is a flowchart showing 
the principle of the fifth data transfer method, and FIG. 20 shows data 
transfer on a line. 
That is, this invention is a data transfer method comprising a first 
communication device (10), a second communication device (20) connected 
thereto via a first line (A), a third communication device (30) connected 
thereto via a second line (B), and a fourth communication device (40) 
connected thereto via a third line (C), the first communication device 
(10) transferring data to the fourth communication device (40) via the 
second and the third communication devices (20) and (30), 
wherein if a busy condition occurs in the third communication device (30) 
during communications between the first communication device (10) and the 
fourth communication device (40), 
the third communication device (30) transmits to the first communication 
device (10) a data transmission condition (dA, tA) for the first line (A) 
which is set by any of the first to the thirty-fourth data transfer 
systems, and 
the first communication device (10) transmits data based on the data 
transmission condition (d.sub.A, t.sub.A) (corresponding to claim 43). 
According to the fifth data transfer method according to this invention, if 
a busy condition occurs in the third communication device (30) during 
communications between the first communication device (10) and the fourth 
communication device (40), the third communication device (30) can 
transmit to the first communication device (10) the data transmission 
condition (d.sub.A, t.sub.A) for the first line (A) which is set by any of 
the first to the thirty-fourth data transfer systems. 
The first communication device (10) transmits data based on the data 
transmission condition (d.sub.A, t.sub.A) thereby clearing the busy 
condition. 
&lt;Sixth data transfer method according to this invention&gt; 
A sixth data transfer method according to this invention has the following 
configuration to solve the second problem. FIG. 16 is a flowchart showing 
the principle of the sixth data transfer method, and FIG. 20 shows data 
transfer on a line. 
That is, this invention is a data transfer method comprising a first 
communication device (10), a second communication device (20) connected 
thereto via a first line (A), a third communication device (30) connected 
thereto via a second line (B), and a fourth communication device (40) 
connected thereto via a third line (C), the first communication device 
(10) transferring data to the fourth communication device (40) via the 
second and the third communication devices (20) and (30), 
wherein if a busy condition occurs in the third communication device (30) 
during communications between the first communication device (10) and the 
fourth communication device (40), 
the third communication device (30) transmits to the fourth communication 
device (10) a data transmission condition (d.sub.C, t.sub.C) for the third 
line (C), and 
the fourth communication device (40) transmits data based on the data 
transmission condition (d.sub.C, t.sub.C) which is set by any of the first 
to the thirty-fourth data transfer systems (corresponding to claim 44). 
According to the sixth data transfer method according to this invention, if 
a busy condition occurs in the third communication device (30) during 
communications between the first communication device (10) and the fourth 
communication device (40), the third communication device (30) can 
transmit to the fourth communication device (40) the data transmission 
condition (d.sub.C, t.sub.C) for the third line (C) which is set by any of 
the first to the thirty-fourth data transfer systems. 
The fourth communication device (40) transmits data based on the data 
transmission condition (d.sub.C, t.sub.C), thereby clearing the busy 
condition. 
&lt;Seventh data transfer method according to this invention&gt; 
A seventh data transfer method according to this invention has the 
following configuration to solve the second problem. FIG. 17 is a 
flowchart showing the principle of the seventh data transfer method, and 
FIG. 20 shows data transfer on a line. 
That is, this invention is a data transfer method comprising a first 
communication device (10), a second communication device (20) connected 
thereto via a first line (A), a third communication device (30) connected 
thereto via a second line (B), and a fourth communication device (40) 
connected thereto via a third line (C), the first communication device 
(10) transferring data to the fourth communication device (40) via the 
second and the third communication devices (20) and (30), 
wherein if a busy condition occurs in the second communication device (20) 
during communications between the first communication device (10) and the 
fourth communication device (40), 
the second communication device (20) transmits to the fourth communication 
device (10) a data transmission condition (dC, tC) for the third line (C) 
which is set by any of the first to the thirty-fourth data transfer 
systems, and 
the fourth communication device (40) transmits data based on the data 
transmission condition (d.sub.C, t.sub.C) (corresponding to claim 45). 
According to the seventh data transfer method according to this invention, 
if a busy condition occurs in the second communication device (20) during 
communications between the first communication device (10) and the fourth 
communication device (40), the second communication device (20) can 
transmit to the fourth communication device (40) the data transmission 
condition (d.sub.C, t.sub.C) for the third line (C) which is set by any of 
the first to the thirty-fourth data transfer systems. 
The fourth communication device (40) transmits data based on the data 
transmission condition (d.sub.C, t.sub.C), thereby clearing the busy 
condition. 
&lt;Eighth data transfer method according to this invention&gt; 
An eighth data transfer method according to this invention has the 
following configuration to solve the second problem. FIG. 18 is a 
flowchart showing the principle of the eighth data transfer method, and 
FIG. 20 shows data transfer on a line. 
That is, this invention is a data transfer method comprising a first 
communication device (10), a second communication device (20) connected 
thereto via a first line (A), a third communication device (30) connected 
thereto via a second line (B), and a fourth communication device (40) 
connected thereto via a third line (C), the first communication device 
(10) transferring data to the fourth communication device (40) via the 
second and the third communication devices (20) and (30), 
wherein if a busy condition occurs in the second communication device (20) 
during communications between the first communication device (10) and the 
fourth communication device (40), 
the second communication device (20) transmits to the first communication 
device (10) a data transmission condition (d.sub.A, t.sub.A) for the first 
line (A) which is set by any of the first to the thirty-fourth data 
transfer systems, and p1 the first communication device (10) transmits 
data based on the data transmission condition (d.sub.A, t.sub.A) 
(corresponding to claim 46). 
According to the eighth data transfer method according to this invention, 
if a busy condition occurs in the second communication device (20) during 
communications between the first communication device (10) and the fourth 
communication device (40), the second communication device (20) can 
transmit to the first communication device (10) the data transmission 
condition (d.sub.A, t.sub.A) for the first line (A) which is set by any of 
the first to the thirty-fourth data transfer systems. 
The first communication device (10) transmits data based on the data 
transmission condition (d.sub.A, t.sub.A), thereby clearing the busy 
condition. 
&lt;Ninth data transfer method according to this invention&gt; 
A ninth data transfer method according to this invention has the following 
configuration to solve the second problem. FIG. 19 is a flowchart showing 
the principle of the ninth data transfer method, and FIG. 20 shows data 
transfer on a line. 
That is, this invention is a data transfer method comprising a first 
communication device (10), a second communication device (20) connected 
thereto via a first line (A), and a fourth communication device (40) 
connected thereto via a third line (C), the first communication device 
(10) transferring data to the fourth communication device (40) via the 
second communication devices (20) and (30), 
wherein if a busy condition occurs in the second communication device (20) 
during communications between the first communication device (10) and the 
fourth communication device (40), 
the second communication device (20) transmits to the fourth communication 
device (10) a data transmission condition (dC, tC) for the third line (C) 
which is set by any of the first to the thirty-fourth data transfer 
systems, and 
the fourth communication device (40) transmits data based on the data 
transmission condition (d.sub.c, t.sub.c) (corresponding to claim 47). 
According to the ninth data transfer method according to this invention, if 
a busy condition occurs in the second communication device (20) during 
communications between the first communication device (10) and the fourth 
communication device (40), the second communication device (20) can 
transmit to the fourth communication device (40) the data transmission 
condition (d.sub.C, t.sub.C) for the third line (C) which is set by any of 
the first to the thirty-fourth data transfer systems. 
The fourth communication device (40) transmits data based on the data 
transmission condition (d.sub.C, t.sub.C), thereby clearing the busy 
condition. 
&lt;Tenth data transfer method according to this invention&gt; 
A tenth data transfer method according to this invention has the following 
configuration to solve the first problem. 
That is, in the fourth data transfer method, even if a busy condition is 
not occurring in the second communication device (20), the second 
communication device (20) transmits to the first communication device (10) 
the data transmission condition (d.sub.A, t.sub.A) set by any of the first 
to the thirty fourth data transfer systems (corresponding to claim 48). 
According to the tenth data transfer method, even if a busy condition is 
not occurring in the second communication device (20), the second 
communication device (20) can transmit to the first communication device 
(10) the data transmission condition (d.sub.A, t.sub.A) set by any of the 
first to the thirty fourth data transfer systems, preventing a busy 
condition from occurring and still enabling lines to be used efficiently. 
&lt;Eleventh data transfer method according to this invention&gt; 
An eleventh data transfer method according to this invention has the 
following configuration to solve the first problem. 
That is, in the fifth data transfer method, even if a busy condition is not 
occurring in the third communication device (30), the third communication 
device (30) transmits to the first communication device (10) the data 
transmission condition (d.sub.A, t.sub.A) set by any of the first to the 
thirty fourth data transfer systems (corresponding to claim 49). 
According to the eleventh data transfer method, even if a busy condition is 
not occurring in the third communication device (30), the third 
communication device (30) can transmit to the first communication device 
(10) the data transmission condition (d.sub.A, t.sub.A) set by any of the 
first to the thirty fourth data transfer systems, preventing a busy 
condition from occurring and still enabling lines to be used efficiently. 
&lt;Twelfth data transfer method according to this invention&gt; 
A twelfth data transfer method according to this invention has the 
following configuration to solve the first problem. 
That is, in the sixth data transfer method, even if a busy condition is not 
occurring in the third communication device (30), the third communication 
device (30) transmits to the fourth communication device (40) the data 
transmission condition (d.sub.C, t.sub.C) set by any of the first to the 
thirty fourth data transfer systems (corresponding to claim 50). 
According to the twelfth data transfer method, even if a busy condition is 
not occurring in the third communication device (30), the third 
communication device (30) can transmit to the fourth communication device 
(40) the data transmission condition (d.sub.C, t.sub.C) set by any of the 
first to the thirty fourth data transfer systems, preventing a busy 
condition from occurring and still enabling lines to be used efficiently. 
&lt;Thirteenth data transfer method according to this invention&gt; 
A thirteenth data transfer method according to this invention has the 
following configuration to solve the first problem. 
That is, in the seventh data transfer method, even if a busy condition is 
not occurring in the second communication device (20), the second 
communication device (20) transmits to the fourth communication device 
(40) the data transmission condition (d.sub.C, t.sub.C) set by any of the 
first to the thirty fourth data transfer systems (corresponding to claim 
51). 
According to the thirteenth data transfer method, even if a busy condition 
is not occurring in the second communication device (20), the second 
communication device (20) can transmit to the fourth communication device 
(40) the data transmission condition (d.sub.C, t.sub.C) set by any of the 
first to the thirty fourth data transfer systems, preventing a busy 
condition from occurring and still enabling lines to be used efficiently. 
&lt;Fourteenth data transfer method according to this invention&gt; 
A fourteenth data transfer method according to this invention has the 
following configuration to solve the first problem. 
That is, in the eighth data transfer method, even if a busy condition is 
not occurring in the second communication device (20), the second 
communication device (20) transmits to the first communication device (10) 
the data transmission condition (d.sub.A, t.sub.A) set by any of the first 
to the thirty fourth data transfer systems (corresponding to claim 52). 
According to the fourteenth data transfer method, even if a busy condition 
is not occurring in the second communication device (20), the second 
communication device (20) can transmit to the first communication device 
(10) the data transmission condition (d.sub.A, t.sub.A) set by any of the 
first to the thirty fourth data transfer systems, preventing a busy 
condition from occurring and still enabling lines to be used efficiently. 
&lt;Fifteenth data transfer method according to this invention&gt; 
A fifteenth data transfer method according to this invention has the 
following configuration to solve the first problem. 
That is, in the ninth data transfer method, even if a busy condition is not 
occurring in the second communication device (20), the second 
communication device (20) transmits to the fourth communication device 
(40) the data transmission condition (d.sub.C, t.sub.C) set by any of the 
first to the thirty fourth data transfer systems (corresponding to claim 
53). 
According to the fifteenth data transfer method, even if a busy condition 
is not occurring in the second communication device (20), the second 
communication device (20) can transmit to the fourth communication device 
(40) the data transmission condition (d.sub.C, t.sub.C) set by any of the 
first to the thirty fourth data transfer systems, preventing a busy 
condition from occurring and enabling lines to be used efficiently. 
&lt;Sixteenth data transfer method according to this invention&gt; 
A sixteenth data transfer method according to this invention has the 
following configuration to solve the first and the second problem. 
That is, this invention is a data transfer method comprising a first 
communication device (10), a second communication device (20) connected 
thereto via a first line (A), a fifth communication device (50) connected 
thereto via a first trunk line (B.sub.1), a third communication device 
(30) connected thereto via a second trunk line (B.sub.2), and a fourth 
communication device (40) connected thereto via a third line (C) with data 
transferred bilaterally between the first communication device (10) and 
the second communication device (20), between the second communication 
device (20) and the fifth communication device (50), between the fifth 
communication device (50) and the third communication device (30), and 
between the third communication device (30) and the fourth communication 
device (40), 
wherein if the direction in which data is transferred from the first 
communication device (10) to the fourth communication device (40) is 
defined as an up direction and the direction in which data is transferred 
from the fourth communication device (40) to the first communication 
device (10) is defined as a down direction, 
the fifth communication device (50) 
transmits to the second communication device (20) a data transmission 
condition (.sub.u d.sub.B2, .sub.u t.sub.B2) for the up channel of the 
second trunk line (B.sub.2) which is set by any of the first to the 
thirty-fourth data transfer systems, 
transmits to the first communication device (10) a data transmission 
condition (.sub.u d.sub.B1, .sub.u t.sub.B1) for the up channel of the 
first trunk line (B.sub.1) which is set by any of the first to the 
thirty-fourth data transfer systems, 
transmits to the third communication device (30) a data transmission 
condition (.sub.d d.sub.B1, .sub.d t.sub.B1) for the down channel of the 
first trunk line (B.sub.1) which is set by any of the first to the 
thirty-fourth data transfer systems, and 
transmits to the fourth communication device (40) a data transmission 
condition (.sub.d d.sub.B2, .sub.d t.sub.B2) for the down channel of the 
second trunk line (B.sub.2) which is set by any of the first to the 
thirty-fourth data transfer systems (corresponding to claim 54). 
According to the sixteenth data transfer method according to this 
invention, the fifth communication device (50) can transmit to the second 
communication device (20) a data transmission condition (.sub.u d.sub.B2, 
.sub.u t.sub.B2) for the up channel of the second trunk line (B.sub.2) 
which is set by any of the first to the thirty-fourth data transfer 
systems. 
The fifth communication device can also transmit to the first communication 
device (10) a data transmission condition (.sub.u d.sub.B1, .sub.u 
t.sub.B1) for the up channel of the first trunk line (B.sub.1) which is 
set by any of the first to the thirty-fourth data transfer systems. 
The fifth communication device can also transmit to the third communication 
device (30) a data transmission condition (.sub.d d.sub.B1, .sub.d 
t.sub.B1) for the down channel of the first trunk line (B.sub.1) which is 
set by any of the first to the thirty-fourth data transfer systems, and 
Furthermore, the fifth communication device can transmit to the fourth 
communication device (40) a data transmission condition (.sub.d d.sub.B2, 
.sub.d t.sub.B2) for the down channel of the second trunk line (B.sub.2) 
which is set by any of the first to the thirty-fourth data transfer 
systems, thereby preventing busy condition from occurring and still 
enabling lines to be used efficiently. 
According to the first to third, and tenth to sixteenth data transfer 
methods and the first to thirty-eighth data transfer systems, before data 
transfer, a receiving device can transmit to a transmitting device a "data 
transmission condition" for quantitatively specifying the amount of 
transmitted data, thereby providing a data transfer method and system that 
prevents a busy condition from occurring and still enabling lines to be 
used efficiently. 
According to the fourth to ninth data transfer methods and the first to 
thirty-eighth data transfer systems, a data transmission condition that is 
a specific condition for causing a busy condition is transmitted from a 
transmitting device to a receiving device even if a busy condition 
actually occurs, thereby enabling the provision of a data transfer method 
and system capable of quantitatively clearing such a busy condition. 
Furthermore, once a network is established using the fourth to ninth data 
transfer methods and the first to thirty-eighth data transfer systems, the 
need to provide facilities (for example, alternate lines) for avoiding a 
busy condition due to an unpredictable abnormal traffic is obviated. 
The first to sixteenth data transfer methods and the first to thirty-eighth 
data transfer systems obviates the need of a "data reception buffer for 
terminal lines" and a "transmission/reception buffer memory for transit" 
provided in conventional communication devices. This minimizes the need of 
a buffer function for storing optical signals used in an optical 
communication device for transferring data using optical signals, so this 
invention is in particular expected to contribute substantially to optical 
communication devices. 
Embodiment! 
Embodiments 1 to 4 of this invention are described below with reference to 
the drawings. 
Embodiment 1! 
&lt;Overall configuration of Embodiment 1&gt; 
First, the overall configuration of Embodiment 1 is described, which is 
shown in FIG. 21. 
A switching device 20 connects a terminal 10 and a terminal 11 via a line A 
that is a first line. A switching device 30 is connected to the switching 
device 20 via a trunk line that is a second line (referred to as a "line 
B" below). The switching device 30 is connected to a terminal 40 via a 
receiving line C that is a third line (referred to as a "line C" below). 
The switching devices 20 and 30 are ATM switching devices that use user 
information and control information such as messages for call connection 
processing in units of cell. 
Call connections between each terminal and the switching device are 
processed according to the TTC standard-JT-Q981 (the Layer 3 protocol for 
user network interfaces). 
Call connections between the switching device 20 and the switching device 
30 are processed according to the TTC standard-JT-Q931-a (the Layer 3 
protocol for inter-PBX connections). 
&lt;Internal configuration of Embodiment 1&gt; 
Next, the internal configuration of Embodiment 1 is described, which is 
shown in FIG. 22. 
Terminal 10! 
The terminal 10 has a transmitter 15 and a receiver 16 both connected to 
the line A. In the line A, the direction in which information is 
communicated from the terminal 10 to the switching device 20 is called an 
up direction, while the direction in which information is communicated 
from the switching device 20 to the terminal 10 is called a down 
direction. 
A control section 17 is connected to both the transmitter 15 and the 
receiver 16. The control section 17 has a data transmission condition 
reception section 11 and a data reception section 12 therein, as shown in 
FIG. 23. 
The data transmission condition reception section 11 receives a data 
transmission condition for the up channel of the line A. 
The data transmission section 12 transmits data under the data transmission 
condition received by the data transmission condition reception section 11 
or a lower condition. 
Switching device 20! 
The switching device 20 has a transmitter 25a and a receiver 26a both 
connected to the line A. A switch 28 is connected to both the transmitter 
25a and the receiver 26a. The switch 28 is connected to both a transmitter 
25b and a receiver 26b. A line B is connected to both the transmitter 25b 
and the receiver 26b. In the line B, the direction in which information is 
communicated from the switching device 20 to the switching device 30 is 
called an up direction, while the direction in which information is 
communicated from the switching device 30 to the switching device 20 is 
called a down direction. 
A control section 27 is connected to both the transmitter 25a and the 
receiver 25b. The control section 27 has an actual data transmission 
condition acquisition section 2 therein, as shown in FIG. 24. The actual 
data transmission condition acquisition section 2 is connected to a busy 
condition occurrence determination section 3. The busy condition 
occurrence determination section 3 is connected to a data transmission 
condition determination section 4. The data transmission condition 
determination section 4 is connected to a data transmission condition 
transmission section 1. 
The actual data transmission condition acquisition section 2 monitors data 
transmitted on the up channel of the second line B to obtain actual data 
length time dr and actual data transmission interval time tr as actual 
data transmission conditions. The actual data transmission condition 
acquisition section 2 may be substituted by any of the following (i) to 
(ii). 
(i) An actual data transmission condition output section 5 for receiving an 
actual data transmission condition (.sub.u d.sub.Br, .sub.u t.sub.Br) 
transmitted by the actual data transmission condition transmission section 
22 and outputting it to a busy condition occurrence determination section 
3. 
(ii) An actual data reception condition output section 5a for receiving an 
actual data reception condition (.sub.u d.sub.Br, .sub.u t.sub.Br) for the 
up channel of the second line B which is monitored and measured by an 
externally installed management system and outputting it to the busy 
condition occurrence determination section 3. 
(iii) A maximum data transmission condition output section 7 for receiving 
a maximum data transmission condition (.sub.u d.sub.Bm, .sub.u t.sub.Bm) 
for the up channel from an externally installed management system and 
outputting it to the busy condition occurrence determination section 3. 
The busy condition occurrence determination section 3 determines whether or 
not a busy condition is occurring on the channel of the line B by 
comparing the maximum data length time dm and maximum data transmission 
interval time tm set for the up channel of the line B or obtained as in 
(iii) to the actual data length time dr and actual data transmission 
interval time tr obtained by the actual data transmission condition 
acquisition section 2. 
The busy condition occurrence determination section 3 may be replaced by a 
definitely determined information output section 6 for receiving the "same 
information as output by the busy condition occurrence determination 
section 3" which is determined definitely by an externally installed 
management system and outputting it to a data transmission condition 
determination section 4. 
The data transmission condition determination section 4 determines a data 
transmission condition for the up channel of the line A based on the 
results output by the busy condition occurrence determination section 3 
using a predetermined allocation criteria in such a way that data can be 
transferred efficiently on the up line of the line B without causing a 
busy condition thereon. 
The data transmission condition determination section 4 may be substituted 
by a first line data transmission condition determination section 8 (see 
FIG. 10) for "receiving a data transmission condition (.sub.u d.sub.A, 
.sub.u t.sub.A) for the up channel from an externally installed management 
system and outputting it to a data transmission condition transmission 
section 1. 
The data transmission condition section 1 transmits the data length time dA 
and data transmission interval time t.sub.A of transmitted data to the 
terminal 10 via the transmitter 2 as a data transmission condition for the 
up channel of the line A. 
Switching device 30! 
The switching device 30 has a transmitter 35b and a receiver 36b both 
connected to the line B. A switch 38 is connected to both the transmitter 
35b and the receiver 36b. The switch 38 is connected to both a transmitter 
35a and a receiver 36a. A line C is connected to both the transmitter 35a 
and the receiver 36a. 
In the line C, the direction in which information is communicated from the 
switching device 30 to a terminal 40 is called an up direction, while the 
direction in which information is communicated from the terminal 40 to the 
switching device 30 is called a down direction. 
A control section 37 is connected to both the transmitter 35a and the 
receiver 35b. The control section 27 has the actual data transmission 
condition acquisition section 2 therein, as shown in FIG. 24. The actual 
data transmission condition acquisition section 2 has the busy condition 
occurrence determination section 3 connected thereto. The busy condition 
occurrence determination section 3 has the data transmission condition 
determination section 4 connected thereto. The data transmission condition 
determination section 4 further has the data transmission condition 
transmission section 1 connected thereto. 
The actual data transmission condition acquisition section 2 monitors data 
transmitted on the down channel of the second line B to obtain actual data 
length time d.sub.dr and actual data transmission interval time d.sub.tr 
as actual data transmission conditions. 
The busy condition occurrence determination section 3 determines whether or 
not a busy condition is occurring on the channel of the line B by 
comparing the maximum data length time dm and maximum data transmission 
interval time tm set for the down channel of the line B or obtained as in 
(iii) to the actual data length time d.sub.r and actual data transmission 
interval time t.sub.r obtained by the actual data transmission condition 
acquisition section 2. 
The data transmission condition determination section 4 determines a data 
transmission condition for the down channel of the line C based on the 
results output by the busy condition occurrence determination section 3 
using a predetermined allocation criteria in such a way that data can be 
transferred efficiently on the up line of the line B without causing a 
busy condition thereon. 
The data transmission condition section 1 transmits the data length time 
d.sub.C and data transmission interval time t.sub.c of transmitted data to 
the terminal 40 via the transmitter 35a as a data transmission condition 
for the down channel of the line C. 
Terminal 40! 
The terminal 40 has a transmitter 45 and a receiver 46 both connected to 
the line C. In the line C, the direction in which information is 
communicated from the switching device 30 to the terminal 40 is called an 
up direction, while the direction in which information is communicated 
from the terminal 40 to the switching device 30 is called a down 
direction. 
A control section 47 is connected to both the transmitter 45 and the 
receiver 46. The control section 47 has the data transmission condition 
reception section 11 and the data reception section 12 therein, as shown 
in FIG. 23. 
The data transmission condition reception section 11 receives a data 
transmission condition for the down channel of the line C. 
The data transmission section 12 transmits data under the data transmission 
condition received by the data transmission condition reception section 11 
or a lower condition. 
&lt;Flow of processing in Embodiment 1&gt; 
Three processing flows shown in the following (i) to (iii) are described as 
processing flows in Embodiment 1 with reference to the drawings. 
(i) A flow of processing a "data transmission condition" from calling of 
the terminal 10 to a response of the terminal 40 (see FIGS. 27 and 28) 
(ii) A flow of updating a "data transmission condition" during the 
communication of the terminal 10 (see FIG. 29) 
(iii) A flow of processing a "data transmission condition" with a terminal 
11 and a terminal 41 added (see FIGS. 30 and 31) 
&lt;Flow of processing a "data transmission condition" from a call from the 
terminal 10 until a response from the terminal 40&gt; 
During this processing, the terminal 10 makes a call to request a 
connection to the terminal 40 and the switching devices 20 and 30 execute 
required connections. The determination of a "condition for transmissions" 
from the terminal 10 to the terminal 40 and the transmission and reception 
of a data transmission condition during this process are described. 
At step 1501, the terminal 10 specifies the address of the terminal 40 to 
communicate with, and makes a call by delivering a "call setup message". 
The switching device 20 receives the "call setup message" to detect the 
call. 
The call setup message passes from the control section 17 of the terminal 
10 through the control section 15, the up channel of the line A, and the 
receiver 26a of the switching device 20 to the control section 27 of the 
switching device 20. 
At step 1502, the switching device 20 analyzes the address to determine 
that this is a trunk line outgoing connection using the up channel of the 
line B. 
At step 1503, the data transmission condition determination section 4 of 
the control section 27 of the switching device 20 determines a "data 
transmission condition (.sub.u d.sub.A1, .sub.u t.sub.A1) value set by the 
terminal 10 for the up channel of the line A" for preventing a busy 
condition from occurring on the up channel of the line B and outputs it to 
the data transmission condition transmission section 1. 
The data transmission condition determination section 4 determines that 
other traffic that uses the up channel of the line B is not occurring and 
that the traffic of the terminal 10 can occupy the up channel of the line 
B, and sets the data transmission condition (.sub.u d.sub.A1, .sub.u 
t.sub.A1) for the up channel of the line A such that the terminal 10 
operates in such a manner that the condition meets Equation (4) 
EQU (.sub.u d.sub.A1, .sub.u t.sub.A1)=(.sub.u d.sub.Bs, .sub.u 
t.sub.Bs)=(.sub.u d.sub.Bm, .sub.u t.sub.Bm) (4) 
At step 1504, the data transmission condition transmission section 1 of the 
control section 27 of the switching device 20 stores the "data 
transmission condition (.sub.u d.sub.A1, .sub.u t.sub.A1)" in a "call 
setup acceptance message" that will be returned to the terminal 10. 
At step 1505, the switching device 20 returns a "call setup acceptance 
message" to the terminal 10 to inform it that the call has been accepted. 
The "data transmission condition" thus reaches the control section 17 of 
the terminal 10. The terminal 10 prepares for data transmission according 
to the data transmission condition (.sub.u d.sub.A1, .sub.u t.sub.A1). 
The call setup acceptance message passes from the control section 27 of the 
switching device 20 through the transmitter 25a, the up channel of the 
line A, and the receiver 16 of the terminal 10 to the control section 17 
of the terminal 10. 
At step 1506, the switching devices 20 attempts to establish a trunk line 
outgoing connection with the switching device 30. The switching device 20 
makes a call by sending a "call setup message" with an address stored 
therein to the switching device 30. 
At step 1507, the switching device 30 receives the "call setup message" and 
analyzes the address to determine that this is an incoming call to the 
terminal 40. The switching device 30 returns a "call setup acceptance 
message" to the switching device 20. 
At step 1508, the data transmission condition determination section 4 of 
the switching device 30 determines a "data transmission condition (.sub.d 
d.sub.c4, .sub.d t.sub.c4) value for preventing a busy condition from 
occurring on the down channel of the line B and outputs it to the data 
transmission condition transmission section 1. 
The data transmission condition determination section 4 determines that 
other traffic that uses the down channel of the line B is not occurring 
and that the traffic of the terminal 40 can occupy the down channel of the 
line B, and sets the data transmission condition (.sub.d d.sub.c4, .sub.d 
t.sub.c4) for the down channel of the line C such that the terminal 40 
operates in such a manner that the condition meets Equation (5) 
EQU (.sub.d d.sub.C4, .sub.d t.sub.C4)=(.sub.d d.sub.Bs, .sub.d 
t.sub.Bs)=(.sub.d d.sub.Bm, .sub.d t.sub.Bm) (5) 
wherein (ddBs, dtBs) is a "data transmission condition with a margin on the 
safer side" and (.sub.d d.sub.Bm, .sub.d t.sub.Bm) is a "maximum data 
transmission condition" value for the down channel of the line B. 
At step 1509, the data transmission condition transmission section 1 of the 
control section 37 of the switching device 30 stores the "data 
transmission condition (.sub.d d.sub.c4, .sub.d t.sub.c4)" in a "call 
setup message" that will be sent to the terminal 40. 
At step 1510, the switching device 30 calls the terminal 40 by returning a 
"call setup acceptance message" to it. The "data transmission condition" 
thus reaches the control section 47 of the terminal 40. The terminal 40 
prepares for data transmission according to the data transmission 
condition (.sub.d d.sub.c4, .sub.d t.sub.c4). 
At step 1511, the terminal 40 returns a "response message" to the switching 
device 30 to respond to the call. The switching device 30 receives the 
"response message" to determine that the terminal 40 has responded. 
At step 1512, the switching device 30 transmits a "response message" to the 
switching device 20. The switching device 30 also sets a logical path 
between the up and down channels of the line C connected to the terminal 
40 and the up and down channels of the line B. 
At step 1513, the switching device 20 receives the response message to 
determine that the terminal 40 has responded. It then sets a logical path 
between the up and down channels of the line A connected to the terminal 
10 and the up and down channels of the line B. 
At step 1514, the terminals 10 and 40 can transmit and receive data to and 
from each other by setting a logical path between the switching devices 20 
and 30. The terminal 10 transmits data on the up channel of the line A 
according to the "data transmission condition (.sub.u d.sub.A1, .sub.u 
t.sub.A1). On the other hand, the terminal 40 sends data on the down 
channel of the line C according to the "data transmission condition 
(.sub.d d.sub.c4, .sub.d t.sub.c4). 
&lt;Flow of updating a "data transmission condition" during the communication 
of the terminal 10&gt; 
If the usage of the up channel of the line B decreases to half its previous 
value while the terminal 10 is transmitting or receiving data, the 
switching device 20 needs to control the amount of data to be transmitted 
from the terminal 10. 
In this case, this process updates the "data transmission condition" value 
and outputs it to the terminal 10. 
The "data transmission condition" for the terminal 40 can also be updated 
as described below for the "down channel of the line B" and the "down 
channel of the line C" using the actual data transmission condition 
acquisition section 2, the busy condition occurrence determination section 
3, and the data transmission condition determination section 4 of the 
control section 37 of the switching device 30. 
Furthermore, updating can be performed only for the terminal 10 to enable 
data transfer between the terminal 10 and the terminal 40 with different 
line usages for the up and the down channels. 
At step 1701, the actual data transmission condition acquisition section 2 
of the control section 27 of the switching device 20 monitors via the 
transmitter 25b bit strings flowing on the up channel of the line B. It 
then detects an "actual data transmission condition (.sub.u d.sub.Br, 
.sub.u t.sub.Br) and outputs the transmission condition value to the busy 
condition occurrence determination section 3. 
1) N-th data length time: .sub.u d.sub.Br 
2) Occurrence interval time between N-th piece of data and N+1-th piece of 
data: .sub.u t.sub.Br 
At step 1702, the busy condition occurrence determination section 3 of the 
control section 27 of the switching device 20 compares the "actual data 
transmission condition (.sub.u d.sub.Br, .sub.u t.sub.Br) for the up 
channel of the line B according to a processing flow comprising the 
following steps 1 to 6. 
Step 1! 
It calculates Equation (1). 
EQU .sub.u d.sub.Bm -.sub.u d.sub.Br =X (1) 
Step 2! 
If in Equation (1), X is 0 or +j that is a margin until a busy condition 
occurs, it calculates Equation (2). 
EQU (.sub.u d.sub.Bm +.sub.u t.sub.Bm)-(.sub.u d.sub.Br +.sub.u t.sub.Br)=Z(2) 
Step 3! 
If in Equation (2), Z is 0 or +p that is a margin until a busy condition 
occurs, it determines that a busy condition is not occurring. 
Step 4! 
If in Equation (1), X is -k that represents a negative quantity, it 
calculates Equation (3). 
EQU (.sub.u d.sub.Bm +.sub.u t.sub.Bm)-(.sub.u +d.sub.Br +.sub.u t.sub.Br)=Y(3) 
Step 5! 
If in Equation (3), Y is 0 or +m that is a margin until a busy condition 
occurs, it determines that a busy condition is not occurring. 
Step 6! 
If in Equation (3), Y is -n that represents a negative quantity or if in 
Equation (2), Z is -q that represents a negative quantity, it determines 
that a busy condition is occurring. 
It finally determines whether or not a busy condition will not occur, 
obtains differential values (X, Y, Z), and outputs them to the data 
transmission condition determination section 4. 
The results of the above processing is shown in the following 1) to 3). 
1) (.sub.u d.sub.A1, .sub.u t.sub.A1)=(.sub.u d.sub.Bm, .sub.u t.sub.Bm) 
has been set and transmitted to the terminal 10. 
2) The terminal 10 has sent data on the up channel of the line A according 
to this value. Since the switching device 20 has relayed this data on the 
up channel of the line B, (.sub.u d.sub.A1, .sub.u t.sub.A1)=(.sub.u 
d.sub.Br, .sub.u t.sub.Br)=(.sub.u d.sub.Bm, .sub.u t.sub.Bm) has been 
established. 
3) Thus, as a result of the processing flow of the busy condition 
occurrence determination section 3, it has been determined that a busy 
condition will not occur and the differential values X, Y, and Z are as 
follows. 
X=.sub.u d.sub.Bm -.sub.u t.sub.A1 
X=0 . . . Thus, Y is not present. 
Z=(.sub.u d.sub.Bm +.sub.u t.sub.Bm)-(.sub.u d.sub.Br +.sub.u t.sub.Br) 
Z=0 
At step 1703, to reduce the usage of the up channel of the line B to half 
its current value, the data transmission condition determination section 4 
of the control section 27 of the switching device 20 performs the 
following updating processing to output to the data transmission condition 
transmission section 1 a "data transmission condition (.sub.u d.sub.A1-E2, 
.sub.u t.sub.A1-E2 ) value for the up channel of the line A" for reducing 
the usage of the up channel of the line B to half its current value. 
1) According to the results of processing by the busy condition occurrence 
determination section 3, the value of the "data transmission condition" 
during the current process is as follows. 
EQU (.sub.d d.sub.Br, .sub.d t.sub.Br)=(.sub.d d.sub.Bm, .sub.d 
t.sub.Bm)=(.sub.u d.sub.A1, .sub.u t.sub.A1) 
2) If the data length time (d) of transmitted data is fixed, the data 
transmission time interval (t) may be increased to reduce the usage of the 
up channel of the line B. Based on FIG. 25 showing the relationship 
between the data length time (d) and the data transmission time interval 
(t), Equations (6) and (7) are established. 
EQU .sub.u d.sub.A1-E2 =.sub.u d.sub.A1 (6) 
EQU .sub.u d.sub.A1-E2 =.sub.u t.sub.A1 +.sub.u d.sub.A1 +.sub.u t.sub.A1(7) 
At step 1704, the data transmission condition transmission section 1 of the 
control section 27 of the switching device 20 stores in a "call setup 
message" the updated "data transmission condition (.sub.u d.sub.A1-E2, 
.sub.u t.sub.A1-E2)" for the up channel of the line A, and sends the 
message to the terminal 10, thereby instructing the terminal 10 to follow 
the updated "data transmission condition". 
At step 1705, the terminal 10 transmits data according to the updated "data 
transmission condition (.sub.u d.sub.A1-E2, .sub.u t.sub.A1-E2)" for the 
up channel of the line A. 
&lt;Flow of processing a "data transmission condition" with the terminals 11 
and 41 added&gt; 
If the terminal 11 makes a call and data transfer between the terminal 11 
and the terminal 41 is enabled through connection processing by the 
switching devices 20 and 30, the up and down channels of the line B 
execute transmissions by multiplexing data "between the terminal 10 and 
the terminal 40" and data "between the terminal 11 and the terminal 41". 
FIG. 26 is a schematic FIG. of connections in this processing flow. 
The switching device 20 transfers data transmitted on the up channel of the 
line A and data sent on the up channel of the line B without causing a 
busy condition thereon. To do this, the switching device 20 controls the 
amount of data delivered from the terminal 10 so that data transmitted 
from the terminal 11 and data sent from the terminal 10 can be 
multiplexed. 
On the other hand, the switching device 30 transfers data transmitted on 
the down channel of the line C and data sent on the down channel of the 
line B without causing a busy condition thereon. To do this, the switching 
device 30 controls the amount of data delivered from the terminal 40 so 
that data transmitted from the terminal 41 and data sent from the terminal 
40 can be multiplexed. 
The amount of data transmitted and received between the terminal 10 and the 
terminal 40 and between the terminal 11 and the terminal 41 must be 
uniform per unit time. 
&lt;Call from the terminal 11&gt; 
The flow of processing wherein a call is made by the terminal 11 is 
described. 
At step 1801, the terminal 11 specifies the address of the terminal 41 to 
communicate with, and makes a call by delivering a "call setup message". 
The switching device 20 receives the "call setup message" to detect the 
call. 
At step 1802, the switching device 20 analyzes the address to determine 
that this is a trunk line outgoing connection using the up channel of the 
line B. 
At step 1803, the data transmission condition determination section 4 of 
the control section 27 of the switching device 20 performs the following 
processing in 1) to 3) to determine a "data transmission condition (.sub.u 
d.sub.A1-E2, .sub.u t.sub.A1-E2) value set by the terminal 10 for the up 
channel of the line A" and a "data transmission condition (.sub.u 
d.sub.A21, .sub.u t.sub.A21) value set by the terminal 11 for the up 
channel of the line A" for preventing a busy condition from occurring on 
the up channel of the line B and outputs them to the data transmission 
condition transmission section 1. 
1) The data transmission condition determination section 4 determines that 
the up channel of the line B has already been occupied by data transmitted 
by the terminal 10. It also determines that the up channel of the line B 
be shared evenly by the terminal 10 and 11. 
2) The data transmission condition determination section 4 determines a 
value for reducing the line usage to half its current value from Equations 
(8) and (9) based on the "data transmission condition (.sub.u d.sub.A1-E2, 
.sub.u t.sub.A1-E2)" set by the terminal 10 for the up channel of the line 
B. 
EQU .sub.u d.sub.A1-E2 =.sub.u d.sub.A1 (8) 
EQU .sub.u t.sub.A1-E2 =.sub.u t.sub.A1 +.sub.u d.sub.A1 +.sub.u t.sub.A1(9) 
3) The data transmission condition determination section 4 determines a 
value for reducing the line usage to half its current value from Equations 
(10) and (11) based on the "data transmission condition (.sub.u d.sub.A21, 
.sub.u t.sub.A21)" set by the terminal 11 for the up channel of the line A 
. 
EQU .sub.u d.sub.A21 =.sub.u d.sub.A1 (10) 
EQU .sub.u t.sub.A21 =.sub.u t.sub.A1 +.sub.u d.sub.A1 +.sub.u t.sub.A1(11) 
At step 1804, the data transmission condition transmission section 1 of the 
control section 27 of the switching device 20 stores in a "call setup 
message" the updated "data transmission condition (.sub.u d.sub.A1-E2, 
.sub.u t.sub.A1-E2)" value for the up channel of the line A from the 
terminal 10, and outputs the message to the terminal 10, thereby 
instructing the terminal 10 to follow the updated "data transmission 
condition". 
Furthermore, the data transmission condition transmission section 1 stores 
the "data transmission condition (.sub.u d.sub.A21, .sub.u t.sub.A21)" 
value in a "call setup acceptance message". 
At step 1805, the switching device 20 returns a "call setup acceptance 
message" to the terminal 11 to inform it that the call has been accepted. 
This causes the "data transmission condition" to be input to the control 
section (not shown) of the terminal 11. The terminal 11 prepares for data 
transmission according to the data transmission condition (.sub.u 
d.sub.A21, .sub.u t.sub.A21). 
At step 1806, the terminal 10 transmits data on the up channel of the line 
A according to the received "data transmission condition (.sub.u 
d.sub.A1-E2, .sub.u t.sub.A1-E2)" value for the up channel of the line A. 
&lt;Calling the terminal 41&gt; 
The flow of the operation of calling the terminal 41 is described. 
At step 1807, the switching device 20 attempts to establish a trunk line 
outgoing connection with the switching device 30 wherein the terminal 11 
can make a call. The switching device makes 20 a call by transmitting a 
"call setup message" with an address stored therein to the switching 
device 30. 
At step 1808, the switching device 30 receives the "call setup message" and 
analyzes the address to determine that this is an incoming call to the 
terminal 41. The switching device 30 returns a "call setup acceptance 
message" to the switching device 20. 
At step 1809, the data transmission condition determination section 4 of 
the control section 37 of the switching device 30 performs the following 
processing in 1) to 3) to determine a "data transmission condition (.sub.d 
d.sub.C4-E2, .sub.d t.sub.C4-E2) value set by the terminal 40 for the down 
channel of the line C" and a "data transmission condition (.sub.d 
d.sub.C24, .sub.d t.sub.C24) value set by the terminal 41 for the down 
channel of the line C" for preventing a busy condition from occurring on 
the down channel of the line B and outputs them to the data transmission 
condition transmission section 1. 
1) The data transmission condition determination section 4 determines that 
the down channel of the line B has already been occupied by data 
transmitted by the terminal 40. It also determines that the down channel 
of the line B be shared evenly by the terminal 40 and 41. 
2) The data transmission condition determination section 4 determines a 
value for reducing the line usage to half its current value from Equations 
(12) and (13) based on the "data transmission condition (.sub.u 
d.sub.C4-E2, .sub.u t.sub.C4-E2)" set by the terminal 40 for the down 
channel of the line C. 
EQU .sub.u d.sub.C4-E2 =.sub.u d.sub.A1 (12) 
EQU .sub.u t.sub.C4-E2 =.sub.d t.sub.A1 +.sub.u d.sub.A1 +.sub.u t.sub.A1(13) 
3) The data transmission condition determination section 4 determines a 
value for reducing the line usage to half its current value from Equations 
(14) and (15) based on the "data transmission condition (.sub.d d.sub.C24, 
.sub.d t.sub.C24)" set by the terminal 41 for the down channel of the line 
C. 
EQU .sub.u d.sub.C24 =.sub.u d.sub.A1 (14) 
EQU .sub.d t.sub.C24 =.sub.u t.sub.A1 +.sub.u d.sub.A1 +.sub.u t.sub.A1(15) 
At step 1810, the data transmission condition transmission section 1 of the 
control section 37 of the switching device 30 stores in a "call setup 
message" the updated "data transmission condition (.sub.d d.sub.C4-E2, 
.sub.d t.sub.C4-E2)" value for the down channel of the line C from the 
terminal 40, and outputs the message to the terminal 40, thereby 
instructing the terminal 10 to follow the updated "data transmission 
condition". 
Furthermore, the data transmission condition transmission section 1 stores 
the "data transmission condition (.sub.d d.sub.c24, .sub.d t.sub.c24)" in 
a "call setup acceptance message". 
At step 1811, the terminal 40 transmits data on the down channel of the 
line C according to the received "data transmission condition (.sub.d 
d.sub.C4-E2, .sub.d t.sub.C4-E2)" value for the down channel of the line 
C. 
At step 1812, the switching device 30 sends a "call setup message" to call 
the terminal 41. This causes the "data transmission condition (.sub.d 
d.sub.C24, .sub.d t.sub.C24)" to be output to the control means (not 
shown) of the terminal 41. 
At step 1813, the terminal 41 returns a "response message" to the switching 
device 30 to respond to the call. The switching device 30 receives the 
"response message" to determine that the terminal 40 has responded. 
At step 1814, the switching device 30 transmits a "response message" to the 
switching device 20. The switching device 30 also sets a logical path 
between the up and down channels of the line C connected to the terminal 
41 and the up and down channels of the line B. 
At step 1815, the switching device 20 receives the response message to 
determine that the terminal 41 has responded. It then sets a logical path 
between the up and down channels of the line A connected to the terminal 
11. 
At step 1816, the terminals 11 and 41 can transmit and receive data to and 
from each other by setting a logical path between the switching devices 20 
and 30. The terminal 10 transmits data on the up channel of the line A 
according to the updated "data transmission condition (.sub.u 
d.sub.A21-E2, .sub.u t.sub.A1-E2). On the other hand, the terminal 40 
sends data on the down channel of the line C according to the updated 
"data transmission condition (.sub.d d.sub.C4-E2, .sub.d t.sub.C4-E2). 
Furthermore, the terminal 11 transmits data on the up channel of the line A 
according to the updated "data transmission condition (.sub.u d.sub.A21, 
.sub.u t.sub.A21). On the other hand, the terminal 41 sends data on the 
down channel of the line C according to the "data transmission condition 
(.sub.d d.sub.C24, .sub.d t.sub.C24). 
&lt;Advantages of Embodiment 1&gt; 
By performing the above processing, data can be transferred between the 
terminal 10 and the terminal 40 and between the terminal 11 and the 
terminal 41 at the best channel usage without causing a busy condition on 
the up channel of the line B. 
Embodiment 2! 
&lt;Overall configuration of Embodiment 2&gt; 
Next, the overall configuration of Embodiment 2 is described, which is 
shown in FIG. 32. 
As is apparent from FIG. 32, Embodiment 2 has the same configuration as 
Embodiment 1 except that Embodiment 2 does not include the switching 
device 30 (thus, does not include the line B) and that the terminals 11 
and 41 are connected to the switching device 20. Only this difference is 
thus described; the like parts carry the same reference numerals and their 
description is omitted. 
&lt;Internal configuration of Embodiment 2&gt; 
Next, the internal configuration of Embodiment 2 is described, which is 
shown in FIG. 33. 
Switching device 20! 
The switching device 20 has the transmitter 25a and the receiver 26a both 
connected to the line A. Both the transmitter 25aand the receiver 26a are 
connected to the switch 28. The switch 28 is connected to both the 
transmitter 25b and the receiver 26b. Both the transmitter 25b and the 
receiver 26b are connected to the line C. 
In the line A, the direction in which information is communicated from the 
terminal 10 to the switching device 20 is called an up direction, while 
the direction in which information is communicated from the switching 
device 20 to the terminal 10 is called a down direction. On the other 
hand, in the line C, the direction in which information is communicated 
from the switching device 20 to the terminal 40 is called an up direction, 
while the direction in which information is communicated from the terminal 
40 to the switching device 20 is called a down direction. 
The control section 27 is connected to both the transmitters 25a, 25b and 
the receivers 26a, 26b. The control section 27 has the actual data 
transmission condition acquisition section 2 therein, as shown in FIG. 24. 
The actual data transmission condition acquisition section 2 is connected 
to the busy condition occurrence determination section 3. The busy 
condition occurrence determination section 3 is connected to the data 
transmission condition determination section 4. The data transmission 
condition determination section 4 is connected to the data transmission 
condition transmission section 1. 
The actual data transmission condition acquisition section 2 monitors data 
transmitted on the down channel of the line C to obtain actual data length 
time dr and actual data transmission interval time tr as actual data 
transmission conditions. 
The busy condition occurrence determination section 3 determines whether or 
not a busy condition is occurring on the down channel of the line C by 
comparing the maximum data length time dm and maximum data transmission 
interval time tm as the data transfer condition that prevents a busy 
condition from occurring on the up channel of the line C and is still 
efficient, to the actual data length time dr and actual data transmission 
interval time tr obtained by the actual data transmission condition 
acquisition section 2. 
The data transmission condition determination section 4 determines a data 
transmission condition for the up channel of the line A based on the 
results output by the busy condition occurrence determination section 3 
using a predetermined allocation criteria in such a way that data can be 
transferred efficiently on the up line of the line C without causing a 
busy condition thereon. 
The data transmission condition section 1 transmits the data length time 
(d) and data transmission interval time (t) of transmitted data to the 
terminal 10 as a data transmission condition for the up channel of the 
line A. 
&lt;Flow of processing in Embodiment 2&gt; 
The flow of processing in Embodiment 2 is the same as in Embodiment 1, so 
the description is omitted. 
Embodiment 3! 
&lt;Overall configuration of Embodiment 3&gt; 
Next, the overall configuration of Embodiment 3 is described, which is 
shown in FIG. 34. 
As is apparent from FIG. 34, Embodiment 3 has the same configuration as 
Embodiment 1 except that the switching device 20 in Embodiment 1 is 
substituted by an ATM communication device 20 and that the switching 
device 30 in Embodiment 1 is substituted by an ATM communication device 
30. Only this difference is thus described; the like parts carry the same 
reference numerals and their description is omitted. 
The ATM communication devices 20 and 30 do not involve call connection 
processing, and in this case, one or more permanent virtual channel (PVC) 
is set in advance between the terminals to enable communication between 
them. 
&lt;Flow of processing in Embodiment 3&gt; 
The flow of processing in Embodiment is described with reference to FIG. 
35. 
At step 2301, the switch 28 for the ATM communication device 20 and the 
switch 38 for the ATM communication device 30 set the following PVCs in 1) 
to 6). A known setting method is used. 
1) Up channel between the terminal 10 and the ATM communication device 20 
2) Down channel between the terminal 10 and the ATM communication device 20 
3) Up channel between the ATM communication devices 20 and 30 
4) Down channel between the ATM communication devices 20 and 30 
5) Up channel between the terminal 40 and the ATM communication device 30 
6) Down channel between the terminal 40 and the ATM communication device 30 
At step 2302, due to the lack of call connection processing, the ATM 
communication device 20 uses the actual data transmission condition 
acquisition section 2 of the control section 27 to monitor data bit 
strings on the up channel of the line B. It thus obtains the actual data 
transmission condition (.sub.u d.sub.Br, .sub.u t.sub.Br) of the up 
channel of the line B to output it to the busy condition occurrence 
determination section 3. 
On the other hand, the ATM communication device 30 uses the actual data 
transmission condition acquisition section 2 of the control section 37 to 
monitor data bit strings on the down channel of the line B. It thus 
obtains the actual data transmission condition (.sub.d d.sub.Br, .sub.d 
d.sub.Br) of the down channel of the line B to output it to the busy 
condition occurrence determination section 3. 
At step 2303, the busy condition occurrence determination section 3 of the 
control section 27 of the ATM communication device 20 determines whether 
or not the up channel of the line B will be busy, and determines the value 
of the difference between the actual data transmission condition of the up 
channel of the line B and the maximum data transmission condition for this 
channel to output it to the data transmission condition determination 
section 4. The busy condition occurrence determination section 3 of the 
control section 37 of the ATM communication device 30 determines whether 
or not the down channel of the line B will be busy, and determines the 
value of the difference between the actual data transmission condition of 
the down channel of the line B and the maximum data transmission condition 
for this channel to output it to the data transmission condition 
determination section 4. 
At step 2304, the data transmission condition determination section 4 of 
the control section 27 of the ATM communication device 20 determines a 
data transmission condition for the up channel of the line A from the 
terminal 10 to output this data transmission condition to the terminal 10. 
On the other hand, the data transmission condition determination section 4 
of the control section 27 of the ATM communication device 30 determines a 
data transmission condition for the down channel of the line C from the 
terminal 40 to output this data transmission condition to the terminal 40. 
Embodiment 4! 
&lt;Overall configuration of Embodiment 4&gt; 
Next, the overall configuration of Embodiment 4 is described, which is 
shown in FIG. 36. 
As is apparent from FIG. 36, Embodiment 4 has the same configuration as 
Embodiment 3 except that an ATM communication device 50 is provided 
between the ATM communication device 20 and 30 as a trunk device. Only 
this difference (the ATM communication device 50) is thus described; the 
like parts carry the same reference numerals and their description is 
omitted. 
The ATM communication device 50 is connected to the ATM communication 
device 20 via the line B.sub.1 and to the ATM communication device 30 via 
the line B.sub.2. The lines B.sub.1 and B.sub.2 are both trunk lines. In 
the line B.sub.1, the direction in which information is communicated from 
the ATM communication device 20 to the ATM communication device 50 is 
called an up direction, while the direction in which information is 
communicated from the ATM communication device 50 to the ATM communication 
device 20 is called a down direction. In the line B.sub.2, the direction 
in which information is communicated from the ATM communication device 50 
to the ATM communication device 30 is called an up direction, while the 
direction in which information is communicated from the ATM communication 
device 30 to the ATM communication device 50 is called a down direction. 
&lt;Flow of processing in Embodiment 4&gt; 
The flow of processing in Embodiment 4 is described with reference to FIG. 
37. 
At step 2501, the ATM communication device 50 monitors data bit strings on 
the up channel of the line B2. It thus obtains the actual data 
transmission condition (.sub.u d.sub.B2r, .sub.u t.sub.B2r) of the up 
channel of the line B2 to output it to the busy condition occurrence 
determination section 3 (having the same configuration as the busy 
condition occurrence determination section 3 of the switching device 20 in 
Embodiment 1) provided in the control section (not shown). 
The ATM communication device 50 also monitors data bit strings on the down 
channel of the line B.sub.1. It thus obtains the actual data transmission 
condition (.sub.d d.sub.B1r, .sub.d t.sub.B1r) of the down channel of the 
line B.sub.1 to output it to the busy condition occurrence determination 
section 3. 
At step 2502, the busy condition occurrence determination section 3 
determines whether or not the up channel of the line B.sub.2 will be busy, 
and determines the value of the difference between the actual data 
transmission condition of the up channel of the line B.sub.2 and the 
maximum data transmission condition for this channel to output it to the 
data transmission condition determination section 4. Furthermore, the busy 
condition occurrence determination section 3 determines whether or not the 
down channel of the line B.sub.1 will be busy, and determines the 
difference between the actual data transmission condition of the down 
channel of the line B.sub.1 and the maximum data transmission condition 
for this channel to output it to the data transmission condition 
determination section 4. 
At step 2503, the data transmission condition determination section 4 
determines a data transmission condition for the up channel of the line 
B.sub.1. The data transmission condition determined is sent by the data 
transmission condition transmission section 1 to the ATM communication 
device 20. The ATM communication device 20 determines a data transmission 
condition for the up channel of the line A based on the transmitted data 
transmission condition, and sends it to the terminals 10 and 11. 
The data transmission condition determination section 4 also determines a 
data transmission condition for the down channel of the line B.sub.2. The 
data transmission condition determined is sent by the data transmission 
condition transmission section 1 to the ATM communication device 30. The 
ATM communication device 30 determines a data transmission condition for 
the down channel of the line C based on the transmitted data transmission 
condition, and sends it to the terminals 40 and 41.