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Claims  |
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What is claimed is:
1. A data communication apparatus for a first data communication station
connectable to a second data communication station with a plurality of
modes served by a ISDN network, comprising:
data communication control means for performing data communication in a
selected one of said plurality of modes;
inquiring means for inquiring of the second station subjected to the data
communication whether a changeover from said selected one of said modes to
another mode can be performed in response to a changeover request of the
first station; and
changeover means for controlling said data communication control means so
as to changeover from said selected one of said modes to said another mode
without breaking continuity of the data communication in response to an
affirmative response from the second data communication station.
2. A data communication apparatus for a first data communication station
connectable to a second data communication station with a plurality of
modes served by an ISDN network, comprising:
data communication control means for performing data communication in a
selected one of said plurality of modes;
notifying means for notifying the second data communication station whether
a changeover from said selected one of said modes to another mode is
enabled or disabled, in response to an inquiry from the second station;
and
changeover means for controlling said data communication control means so
as to changeover from said selected one of said modes to said another mode
without breaking continuity of the data communication in case that said
notifying means notify an affirmative
3. The data communication apparatus as claimed in claim 1, further
comprising:
user interfacing means for accepting an operation request of a changeover
of modes from a user, and for informing said inquiring means that the
request has occurred.
4. The data communication apparatus as claimed in claim 1, further
comprising:
level-of-data supervision means for supervising a level of data produced
between the first data communication station and the second data
communication station, and for requesting said inquiring means to inquire
according to a variation in the level of said produced data.
5. The data communication apparatus as claimed in claim 1, wherein said
data communication control means can carry out the data communication in
line and packet switching modes defined as said plurality of modes.
6. The data communication apparatus for a first data communication station
connectable to a second data communication station with a plurality of
modes served by a ISDN network, comprising:
data communication control means for performing data communication in a
selected one of said plurality of modes;
inquiring means for inquiring of the second station subjected to the data
communication whether a changeover from said selected one of said modes to
another mode can be performed in response to a changeover request of the
first station; and
changeover means for controlling said data communication control means so
as to changeover from said selected one of said modes to said another mode
without breaking continuity of the data communication in response to an
affirmative response from the second data communication station;
wherein said data communication control means comprises a plurality of
inputting means provided in association with said plurality of modes, a
receiving buffer for storing therein received data from one of said
plurality of inputting means, a plurality of outputting means provided in
association with said plurality of modes, and a transmitting buffer for
storing therein data to be transmitted to one of said plurality of
outputting means, said changeover means synchronously selects said one
inputting means and said one outputting means.
7. The data communication apparatus as claimed in claim 2, wherein said
data communication control means can carry out the data communication in
line and packet switching modes defined as said plurality of modes.
8. The data communication apparatus for a first data communication station
connectable to a second data communication station with a plurality of
modes served by an ISDN network, comprising:
data communication control means for performing data communication in a
selected one of said plurality of modes;
notifying means for notifying the second data communication station whether
a changeover from said selected one of said modes to another mode is
enabled or disabled, in response to an inquiry from the second station;
and
changeover means for controlling said data communication control means so
as to changeover from said selected one of said modes to said another mode
without breaking continuity of the data communication in case that said
notifying means notify an affirmative response;
wherein said data communication control means comprises a plurality of
inputting means provided in association with said plurality of modes, a
receiving buffer for storing therein received data from one of said
plurality of inputting means, a plurality of outputting means provided in
association with said plurality of modes, and a transmitting buffer for
storing therein data to be transmitted to one of said plurality of
outputting means, said changeover means synchronously selects said one
inputting means to said one outputting means.
9. The data communication apparatus for a first data communication station
connectable to a second data communication station with a plurality of
modes served by a ISDN network, comprising:
data communication control means for performing data communication in a
selected one of said plurality of modes;
inquiring means for inquiring of the second station subjected to the data
communication whether a changeover from said selected one of said modes to
another mode can be performed in response to a changeover request of the
first station; and
changeover means for controlling said data communication control means so
as to changeover from said selected one of said modes to said another mode
without breaking continuity of the data communication in response to an
affirmative response from the second data communication station;
wherein said changeover means serves to stop data from being transmitted to
the second station at a time when said changeover request is made, and to
resume the transmission of data from a time when said changeover has been
completed or when a negative response is received from the second station.
10. The data communication apparatus as claimed in claim 6, further
comprising communication data supervising means for being notified by
information indicating final data transferred up to a specific point of
time between the two stations in said selected one of said modes from said
second station, and performing the transfer of undelivered data again
between the two stations in another mode after completion of said
changeover.
11. The data communication apparatus as claimed in claim 10, further
comprising data communication data control table for storing therein
packet numbers transferred between the two in case that stations data
communication is made in a packet switching mode as said selected one of
said modes.
12. The data communication apparatus for a first data communication station
connectable to a second data communication station with a plurality of
modes served by a ISDN network, comprising:
data communication control means for performing data communication in a
selected one of said plurality of modes;
inquiring means for inquiring of the second station subjected to the data
communication whether a changeover from said selected one of said modes to
another mode can be performed in response to a changeover request of the
first station; and
changeover means for controlling said data communication control means so
as to changeover from said selected one of said modes to said another mode
without breaking continuity of the data communication in response to an
affirmative response from the second data communication station;
wherein said changeover means is activated in such a manner that when the
changeover is made from said selected one of said modes, the data
communication between the two stations is continued in said another mode,
and when undelivered data to the second station are present at the time of
the changeover, said undelivered data are transmitted to the second data
communication station in said selected one of said modes in parallel with
said another mode.
13. The data communication apparatus for a first data communication station
connectable to a second data communication station with a plurality of
modes served by a ISDN network, comprising:
data communication control means for performing data communication in a
selected one of said plurality of modes;
inquiring means for inquiring of the second station subjected to the data
communication whether a changeover from said selected one of said modes to
another mode can be performed in response to a changeover request of the
first station;
changeover means for controlling said data communication control means so
as to changeover from said selected one of said modes to said another mode
without breaking continuity of the data communication in response to an
affirmative response from the second data communication station; and
means for calculating a time at which a charge for use of a public line
shall increase from a date of the data communication and an address of the
second data communication station, in case that the data communication is
performed in a line switching mode as said selected one of said modes, and
wherein said changeover means is so activated that the data communication
is continuously made in said line switching mode up to said calculated
time, without regard to the time of occurrence of said changeover request.
14. A method of data communication linked between first and second data
communication stations with an ISDN network in a plurality of kinds of
modes, comprising the steps of:
transmitting a changeover inquiry command to the second data communication
station from the first data communication station for inquiring of the
second data communication station whether a changeover of one of said
modes to another of said modes is enabled, when a request of the
changeover is made in the first data communication station;
setting a second data communication call with said another of said modes in
addition to an existing first data communication call with said one of
said modes;
transmitting a permission command to the first data communication station
from the second data communication station in response to said changeover
inquiry command, in case that said changeover is enabled;
transmitting a reject command to the first data communication station from
the second data communication station in response to said changeover
inquiry command, in case that said changeover is disabled;
starting the data communication with said second data communication call
when the first data communication station accepts said permission command;
and
continuing the data communication with said first data communication call
when the first data communication station accepts said reject command.
15. A method of data communication linked between first and second data
communication stations with an ISDN network in a plurality of kinds of
modes, comprising the steps of:
transmitting a changeover inquiry command to the second data communication
station from the first data communication station for inquiring of the
second data communication station whether a changeover of one of said
modes to another of said modes is enabled, when a request of the
changeover is made in the first data communication station;
setting a second data communication call with said another of said modes in
addition to an existing first data communication call with said one of
said modes;
transmitting a permission command to the first data communication station
from the second data communication station in response to said changeover
inquiry command, in case that said changeover is enabled;
transmitting a reject command to the first data communication station from
the second data communication station in response to said changeover
inquiry command, in case that said changeover is disabled;
starting the data communication with said second data communication call
when the first data communication station accepts said permission command;
continuing the data communication with said first data communication call
when the first data communication station accepts said reject command; and
stopping the data communication with said first data communication call
when said first data communication station accepts aid permission command,
and cancelling the data communication with said second data communication
call when said first data communication accepts said reject command.
16. A method of data communication linked between first and second data
communication stations with an ISDN network in a plurality of kinds of
modes, comprising the steps of:
transmitting a changeover inquiry command to the second data communication
station from the first data communication station for inquiring of the
second data communication station whether a changeover of one of said
modes to another of said modes is enabled, when a request of the
changeover is made in the first data communication station;
setting a second data communication call with said another of said modes in
addition to an existing first data communication call with said one of
said modes;
transmitting a permission command to the first data communication station
from the second data communication station in response to said changeover
inquiry command, in case that said changeover is enabled;
transmitting a reject command to the first data communication station from
the second data communication station in response to said changeover
inquiry command, in case that said changeover is disabled;
starting the data communication with said second data communication call
when the first data communication station accepts said permission command;
continuing the data communication with said first data communication call
when the first data communication station accepts said reject command; and
transmitting said changeover inquiry command to the second data
communication station from the first data communication station again when
the first data communication station accepts said reject command.
17. A method of data communication as claimed in claim 14, wherein the
first and second data communication stations are capable of performing
data communication in line and packet switching modes defined as said
plurality of kinds of modes.
18. A method of data communication as claimed in claim 16, further
comprising the steps of:
cancelling the data communication with said second data communication call
when said first data communication station accepts said reject command a
predetermined number of times after said second data communication call
has been set.
19. A method of data communication linked between first and second data
communication stations with an ISDN network in a plurality of kinds of
modes, comprising the steps of:
transmitting a changeover inquiry command to the second data communication
station from the first data communication station for inquiring of the
second data communication station whether a changeover of one of said
modes to another of said modes is enabled, when a request of the
changeover is made in the first data communication station;
setting a second data communication call with said another of said modes in
addition to an existing first data communication call with said one of
said modes;
transmitting a permission command to the first data communication station
from the second data communication station in response to said changeover
inquiry command, in case that said changeover is enabled;
transmitting a reject command to the first data communication station from
the second data communication station in response to said changeover
inquiry command, in case that said changeover is disabled;
starting the data communication with said second data communication call
when the first data communication station accepts said permission command;
and
continuing the data communication with said first data communication call
when the first data communication station accepts said reject command;
wherein said changeover inquiry command, said accept command and said
reject command are incorporated into user to user information elements in
call control primitives. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION AND RELATED ART
The present invention relates to a data communication apparatus connectable
to an ISDN network and capable of performing data communication in a
plurality of communication modes such as line switching and packet
switching, and to a method of data communication between data
communication stations having communication-mode changeover function.
In the ISDN network, data communications can be carried out in two
communication modes comprised of line switching and packet switching in
the same network. This is one of the communication services which have not
been realized in a conventional public communication network.
Data communication using the line switching is an effective means where
large amounts of data are transmitted and/or received at high speed. In
the public communication network, accounts or charges are made for the
time required for data communication. On the other hand, data
communication using the packet switching is an effective method in a case
where low-speed data communications are made and small amounts of data
generated or created in a discrete manner are transmitted and/or received.
In this data communication, charges are made for the amount of data
transmitted.
When the level or density of generation of data varies between the two
stations which perform data communications continuously over a long period
of time, the execution of data communication in a communication mode
suitable for the density of generation of the data is most effective. It
is necessary to change over the communication mode from the line switching
to the packet switching or vice versa under data communication in order to
realize this.
However, when it is desired to perform a highspeed data communication,
there has heretofore been used a digital dedicated line of such a type
that a fixed rate charged for data communication is paid for each month.
It was therefore unnecessary to take into consideration variations in the
density of generation of the data. As disclosed in Japanese Patent
Publication Laid-Open No. 62(1987)-290242, this disclosure describes a
conventional data communication apparatus of a type wherein the amount of
information processed in a central processing unit is supervised, and when
its amount exceeds 80% of the information-processing amount, which is
defined as the threshold value, the data receiving rate is reduced,
whereas when it is below 80%, the data receiving rate is raised, without
changing the communication mode from the line switching to the packet
switching or vice versa. On the other hand, when it is desired to change
the communication rate, this has been realized by performing the data
transfer, i.e., data transmission/reception in a escape sequence form
between communication terminal apparatus.
Further, Japanese Patent Publication Laid-Open No. 61(1986)-158244
discloses a facsimile apparatus capable of performing data communications
in the two communication modes described above. However, the disclosure
cannot perform the communication-mode changeover under data communication
because the communication-mode changeover is simply performed in hardware
form in advance of the data communication.
The above-described prior art has a problem that it is used to change the
communication rate according to the amount of the generated data
corresponding to the processing rate in the CPU and it does not take into
consideration a system of such a type that the accounts or charges are
made for the time required for the data communication as in the public
communication line, thus the more the communication rate being reduced,
the more the amount of accounts or charges increasing. In addition, the
prior art also has another problem that all the data are needed to be
supervised in the data communication apparatus because the communication
rate is varied and the data transmission/reception is performed in the
escape sequence form, thus increasing processing overhead time.
OBJECT AND SUMMARY OF THE INVENTION
A first object of the present invention is to make it possible to change
over a plurality of communication modes such as line switching and packet
switching between data communication apparatus with a view toward reducing
the amount of accounts as small as possible without causing generated data
to be in waiting upon execution of data communication using an ISDN and
raising, as much as practicable, the efficiency in use of information
channels inclusive of other communication as well as the data
communication.
More specifically, high-speed data can be transmitted during a period in
which the density of transmit/receive data is high. In addition, the data
communication to be accounted according to the time required for data
communication is carried out in the line switching form. On the other
hand, the data communication can be performed in the packet switching form
during a period in which the density of the transmit/receive data is low
and the data communication can be performed even at the data transmission
rate based on the packet switching.
A second object of the present invention is to select a most suitable
communication mode out of a plurality of communication modes according to
variations in the density of generation of data under data communication
to thereby automatically perform a communication-mode changeover process.
A third object of the present invention is to perform a communication-mode
changeover process without breaking the continuity of the flow of transmit
and receive data even upon changeover of the communication mode.
A fourth object of the present invention is to continuously perform data
communication based on line switching until the time immediately before
the amount of accounts is varied upon changing the communication mode from
line switching to packet switching, thereby realizing the high efficiency
of data transmission with respect to the amount of accounts.
In order to achieve the above first object, there is provided a data
communication apparatus comprising changeover inquiring means for
enquiring of a receiving station or a called party subjected to data
communication whether or not the changeover of one of data communication
modes to another can be performed, and changeover control means activated
in such a manner that when a communication-mode changeover enable response
is received from the receiving station, the data transmit-receive transfer
of from one of two data communication calls to the other thereof is
effected between said two data communication calls created between a
transmitting station and said receiving station. In addition, there are
provided, in a data communication system linked between the data
communication apparatus, a changeover inquiring command for making an
inquiring as to whether or not the communication mode can be changed from
a first data communication apparatus to a second data communication
apparatus, a changeover acceptance command delivered from a second data
terminal apparatus in response to the changeover inquiring command when
the communication-mode changeover is enabled, and a changeover reject
command delivered from the second data terminal apparatus when the
communication-mode changeover is disabled.
Further, in order to achieve the second object, there is provided a data
communication control apparatus comprising density-of-generation-of-data
supervising means for supervising the level or density of creation of data
under data communication, which is activated in such a manner that a
process for changing the present communication mode to another
communication mode is initiated where a situation of the density of
creation of the data meets a condition for the communication-mode
changeover.
Furthermore, in order to achieve the third object of the present invention,
the transfer of undelivered data is performed by the changeover control
means upon changing one of the two data communication calls corresponding
to two communication modes to the other.
Still further, in order to achieve the fourth object of the present
invention, there is provided a data communication apparatus comprising
means for calculating the date of communication and the time at which the
rate of accounts varies according to the difference in distance between
the transmitting and receiving stations, and a communication call control
means activated in such a manner that data communication is made by means
of a data communication call based on the line switching up to the time at
which the rate of the accounts varies.
When a data communication terminal received with a request for the data
communication-mode changeover from a user under data communication makes
an inquiry as to whether or not the communication-mode changeover can be
performed, so as to receive a communication-mode changeover enable
response from a called party, i.e., a receiving station, the data
transmit-receive transfer of from one of two data communication calls to
the other thereof is performed between the two data communication calls
produced between the transmitting and receiving stations. More
specifically, the changeover inquiring command is used to make an
inquiring as to whether on not the communication mode can be changed from
the first data communication apparatus to the second data communication
apparatus, in a data communication system linked between the data
communication apparatus. The changeover acceptance command is delivered
from the second data terminal apparatus in response to the changeover
enquiry command and used to transmit a communication-mode changeover
enable response to the first data communication apparatus. The changeover
reject command is delivered from the second data terminal apparatus and
used to transmit a communication-mode changeover disable response to the
first data communication apparatus. The first data communication apparatus
performs the communication-mode changeover processing in response to the
changeover acceptance command.
Still further, the density-of-generation-of-data supervising means in the
data communication apparatus serves to supervise the density of production
of data under data communication. The data communication apparatus makes a
judgment as to in which kinds of communication modes the data
communication should be performed suitably, thereby determining a desired
communication mode for performing the data communication.
Still further, the changeover control means is used to control
communication-mode changeover timing and the undelivered data upon
changeover of the communication mode in order to prevent data from being
undelivered.
Still further, the above calculating means calculates the date of
communication and the time at which the rate of accounts varies according
to the difference in distance between the transmitting and receiving
stations. The changeover control means is so activated that the data
communication is performed by means of the data communication call based
on the line switching up to the time at which the rate of the accounts
varies, thereby making it possible to make the best use of the time
necessary for data communication, which can be used in the same charge,
and to carry out data communication in the minimum charge.
According to the present invention, since the communication-mode changeover
can be carried out between the data communication modes without
discontinuing the data communication on the basis of the changeover
request from the user, it is possible to perform economically-effective
data communications corresponding to the amount of the generated data. In
addition, the data communication-mode changeover request can automatically
be made even though no changeover request is made from the user.
Therefore, the communication mode corresponding to the amount of the
generated data can be selected even when the user does not supervise the
conditions of generation of the data at all times.
In addition, the interconnection of data between a call-before-changeover
and a call-after-changeover can be held by means of interconnection of
communication buffers to be used, upon changeover of the communication
mode. Therefore, the data communication can be performed without breaking
the continuity of the data even when the data communication-mode is
changed from the line switching to the packet switching or vice versa.
Furthermore, upon changing the communication mode from the line switching
to the packet switching, the data communication based on the line
switching can be carried out up to a straight line from which the rate of
accounts made under the line switching increases, thereby making it
possible to perform an economically-effective data communication-mode
changeover.
The above and other objects, features and advantages of the present
invention will become apparent from the following description and the
appended claims, taken in conjunction with the accompanying drawings in
which a preferred embodiment of the present invention is shown by way of
illustrative example.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing a data communication control unit
according to one embodiment of the present invention;
FIG. 2 is a block diagram depicting the structure of a communication
control apparatus according to one embodiment of the present invention;
FIG. 3 is a functional block diagram of the communication control apparatus
according to said one embodiment of the present invention;
FIG. 4 is a diagram illustrating a modification of the communication
control apparatus according to said one embodiment of the present
invention;
FIG. 5 is a diagram showing a table for control of data communication
calls;
FIG. 6 is a diagram depicting a format of messages for communication mode
changeover;
FIGS. 7 and 18 are diagrams showing the structure of transmitting/receiving
buffers employed in the communication control apparatus according to said
one embodiment of the present invention;
FIGS. 8, 12 and 19 are diagrams each depicting a message sequence used in
said one embodiment of the present invention;
FIG. 9 is a diagram showing the relationship of transmission between a
changeover reject and a request for reissuance of changeover request;
FIGS. 10, 11, 13, 14, 20, 21, 22 and 23 are flowcharts for performing
processes for control of data communication modes;
FIG. 15 is a diagram showing a table for control of accounting period used
for each line switching call;
FIG. 16 is a diagram depicting a table for retrieval of accounting period;
FIG. 17 is a flowchart of a process for supervising accounts changed;
FIG. 24 is a diagram showing the structure of a table for supervising the
amount of creation of data based on a data communication call;
FIG. 25 is a flowchart for describing a routine procedure performed at a
communication-mode changeover request generating unit; and
FIG. 26 is a diagram for describing an overall outline of a communication
network to which said one embodiment of the present invention is applied.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A preferred embodiment of the present invention will hereinafter be
described with reference to the accompanying drawings. FIG. 2 is a diagram
showing the structure of a communication control apparatus 200 according
to one embodiment of the present invention. The communication control
apparatus 200 comprises a ROM 201, a RAM 202, a processor 203, a layer-3
type control processor 204, a data communication control processor 205,
terminal interface units 206, 207 and a key interface 208. The ROM 201
serves to store therein a program executed by each of the processors of
the apparatus. The RAM 202 is used as a control table and data
transmitting and receiving buffers. The processor 203 separates a signal
inputted from an ISDN subscriber's line 211 into respective signals used
for a B channel 106 and a D channel 212, and performs processes for the
improper control of a frame of the D channel signal, or the like. Namely,
the processor 203 performs layer-1-plus-2 type control in an OSI7
layer-type model. The processor 204 performs control for connection of
calls in both communication modes indicative of line and packet switching.
The data communication control processor 205 carries out data
communications in the communication modes indicative of the line and
packet switching, and performs control for data communication made between
a data terminal connected to the data communication control apparatus and
a receiving station, i.e., a party called. The terminal interface units
206, 207 communicate between the data terminal and the party called
through terminal connecting cables 209, 210. The key interface 208 detects
a state of a key operated by a user with respect to the communication
control apparatus 200 and notifies the result of its detection to
corresponding or intended units.
FIG. 3 is a functional block diagram of the communication control
apparatus. The layer-3 type control unit 204 comprises a line switching
protocol control unit 310 and a packet switching protocol control unit
320. Data are transferred, i.e., transmitted to and received from a host
communication software 370 through an interface unit 360 for the
communication control apparatus at a data terminal 350.
FIG. 4 is a diagram showing a modification in which each of the
communication control apparatus 200 shown in FIGS. 2 and 3 is built in a
data terminal 400 as an ISDN interface board 410 The data communication
control apparatus 420 may be provided outwardly of the ISDN interface
board. A request for the changeover of the communication mode to be
performed at the data terminal 400 is made inside the data terminal 400,
and thereafter notified to the data communication control apparatus 420
through the host communication software 370.
FIG. 26 shows an overall outline of a communication network to which one
embodiment of the present invention is applied. An ISDN 880 as seen from
the side of the communication control apparatus 200 comprises subscriber's
exchangers 2600 which accommodate subscriber's lines therein, tandem
exchangers 2630 each for connecting a line switching network 2650 to each
of the subscriber's exchangers 2600, and packet switching units 2640 each
for connecting a packet switching network 2660 to each of the subscriber's
exchangers 2600. More specifically, as viewed from the communication
control apparatus 200, an ISDN subscriber's line 211-a is accommodated in
an interface service module (hereinafter called merely "ISM") 2610-a of a
subscriber's exchanger 2600-a. Each of the ISM 2610 performs line
switching service of ISDN, line switching connection, and connection to a
packet handling module (hereinafter called merely "PHM") 2620 for handling
a packet call. When the content of communication received at the ISM
2610-a is a request for the line switching, the ISM 2610-a is connected to
a tandem exchanger 2630-a. Thereafter, the ISM 2610-a is connected to a
tandem exchanger 2630-b connectable to an ISDN subscriber's line 211-b on
the side of the called party through the line switching network 2650.
Thus, the ISM 2610-a is finally connected to a communication control
apparatus 200-b in a communication path opposite to the above path. On the
other hand, when the content of communication received at the ISM 2610-a
is a request for the packet switching, the ISM 2610-a is connected to a
PHM 2620-a. Further, the PHM 2620-a is connected to a packet exchanger
2640-b connectable to the ISDN subscriber's line 211-b on the called party
side through a packet exchanger 2640-a and a packet switching network
2660. Thus, the PHM 2620-a is finally connected to the communication
control apparatus 200-b in a communication path opposite to the above
path. When it is desired to make a dial in line switching form in such a
process described above, the communication control apparatus 200 performs
communication control between the communication control apparatus 200 and
the ISM 2610 by making use of the protocol for the line switching so as to
be connected to the line switching network 2650. On the other hand, when
it is desired to make a dial in packet switching form, the communication
control apparatus 200 performs communication control between the
communication control apparatus 200 and the PHM 2620 through the ISM 2610
by making use of the protocol for the packet switching so as to be
connected to the packet switching network 2660. When an incoming call is
received under the line switching form, the communication control
apparatus 200 performs communication control under the line switching
protocol in the same manner as when dialing. When an incoming call is
received under the packet switching form, the ISM 2610 inquires of the
communication control apparatus 200 whether or not interconnection made in
the packet switching form can be performed in accordance with the line
switching protocol. If it is determined to be positive, then the
communication control is made between the PHM 2620 and the communication
control apparatus 200 by making use of the packet switching protocol.
FIG. 1 is a diagram showing the structure of software operated in a data
communication control unit 100 according to one embodiment of the present
invention. The data communication control unit 100 receives data
transferred through a B channel 106, a message delivered from the layer-3
type control processor 204, and data supplied from a terminal interface
206 through a terminal interface control processing unit 103. The data
communication control unit 100 comprises a data transmit/receive
processing unit 101, a data communication mode control processing unit
102, a terminal interface control processing unit 103, a change-in-account
supervisory processing unit 104, and a data transmission level supervisory
processing unit 105. The data transmit/receive processing unit 101
receives data relative to a corresponding call so as to process the same,
and thereafter transmits the thus-processed data therefrom. The data
communication mode control processing unit 102 enters data communication
calls onto a table 500 for control of data communication calls shown in
FIG. 5 at the time of appearance of the data communication calls, and
delete the same therefrom at the time of disappearance thereof. When a
data communication-mode changeover request is made, the data communication
mode control processing unit 102 performs a process necessary for the data
communication-mode changeover. Assuming that a data communication call in
line switching form is made, the change-in-account supervisory processing
unit 104 changes counted values entered on a table 1500 for control of
accounting periods used for line switching calls, and notifies a variation
in accounts or charges relative to a corresponding call to the data
communication mode control processing unit 102 before such an account
variation takes place. When it is desired to automatically change one of
data communication modes to another instead of a changeover request from a
user, the data transmission level supervisory processing unit 105
supervises in a regular manner whether or not a data communication-mode
changeover condition is met. If it is judged to be positive, the data
transmission level supervisory processing unit 105 makes a demand of the
data communication-mode changeover on the data communication mode control
processing unit 102. The terminal interface control processing unit 103
controls the terminal interface 206 and transmits data and commands
delivered from the data terminal to each of the data transmit/receive
processing unit 101 and the data communication mode control processing
unit 102.
FIG. 5 shows the table 500 for control of the data communication calls,
which is used to control all the data communication calls with the data
communication control unit 100 and the layer-3 type control unit 204 and
to register or enter the same therein. The data communication call control
table 500 includes the following elements. Namely, it has call
identification numbers 501 dedicatedly assigned to all the calls, between
the layer-3 type control unit 204 and the data communication control unit
100, a call classification 502 used to identify whether data communication
is made in the line switching form or in the packet switching form,
numbers 503 of stations or parties called used for storage of addresses on
the side of the called parties as the parties subjected to data
communication and of subaddresses, a transmit packet number 504 as an area
and a receive packet number 505 as an area used to store serial numbers of
transmit and receive data packets, respectively, when the data
communication is made in the packet switching form, addresses 506 for a
transmitting buffer and addresses 507 for a receiving buffer, both of
which are used to store addresses, i.e., data of buffers arranged in
transmitting and receiving directions for every calls when the data
communication is performed, numbers 508 of calls connected, which are used
to store data about the correlation between
calls-before-communication-mode-changeover and
calls-after-communication-mode-changeover when it is desired to change one
communication mode to another, busy flags 509 used to show the calls
registered in the numbers 508 as storage areas, which are present in the
level below the level of a layer 3, changeover flags 510 used to show
calls-before-communication-mode-changeover during the communication-mode
changeover, and changeover COMPLETE flags 511 used to represent calls
subjected to completion of the communication-mode changeover and not
subjected to the data communication.
FIG. 6 shows the structure of data as a message 600 for the
communication-mode changeover, which is transferred between a transmitting
side of a changeover request and its receiving side when it is desired to
change one communication mode to another. The message 600 is loaded into a
user/user information area 611 in a primitive 610 for control of line
switching calls and into a user data area for CALL REQUEST packets at the
request of a packet switching call. Then, the message 600 is transferred
between the transmitting side and the receiving side. The message 600
comprises the following elements. Namely, it includes a command's name
area 601 used to show a message about the communication-mode changeover,
an operation indicating area 602 in which an operation about a
communication-mode changeover request at the time that the
communication-mode changeover is made and an operation about a changeover
request such as a changeover REJECT request are written as data, a
changeover mode indicating area 603 used to indicate whether or not the
transfer of from the line switching to the packet switching is made upon
the communication-mode changeover or whether or not the transfer of from
packet switching to the line switching is made thereupon, and a transmit
data packet number notifying area 604, and a receive data packet number
notifying area 605 used to notify a transmit data packet number and a
received data packet number, respectively, to the receiving side when a
data communication mode prior to that at the time of the
communication-mode changeover is represented in the form of packet
switching.
FIG. 7 is a diagram showing the relationship between transmitting/receiving
buffers 701, 702 and calls at the time that the transmitting buffer 701
and the receiving buffer 702 are each used in common between two calls
subjected to the communication-mode changeover when it is desired to
perform the changeover of the data communication mode. When a data
communication call is changed from a call K to a call L with the
changeover of the data communication mode, the transmitting buffer 701
receives incoming data through the terminal interface unit 207, and
transmits the data stored therein as transmit data 703 of a call K before
completion of the data communication-mode changeover, whereas it transmits
the data as transmit data of a call L after completion of the data
communication-mode changeover. The receiving buffer 702 writes th | | |
