JPH057223A - Physical channel reselection method - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a physical channel reselection method, which enables channel selection again when a user selects an unusable physical channel, thereby improving call connectivity and network serviceability. The purpose is to do. [Structure] The ISDN exchange 3 sends a call packet X. Physical channel information setting means 5 for searching and managing available physical channel information when 25CR4 is received, and referring to the physical channel information, the usable physical channel information is coded in the call setup message 6. Call setting message transmitting means 7 for transmitting to the destination user 2
Then, if the communication capacity can be secured from the physical channel selected by the called user 2 in the response message 8 in which the called user 2 receives the call setup message 6 and responds, the channel is established and the packet X. When 25CN10 is transmitted and the communication capacity cannot be secured, the call setup message transmitting means 7 is restarted, and the response message processing means 9 for transmitting the call setup message 6 again to reselect the channel is configured.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a physical channel reselection system. More specifically, in the ISDN packet switching service that supports the incoming call providing procedure that enables the called user to select a communication channel, if the channel selected by the called user is unavailable, the channel can be selected again. The present invention relates to a physical channel reselection method.

[0002]

2. Description of the Related Art In many cases, an ISDN packet switching service supports an incoming call providing procedure. To user X.
If there are 25 incoming call packets, the exchange sends a call setup message SETUP to the user, and X. 25 Ask the physical channel for sending the incoming call packet to be selected.

FIG. 8 is an explanatory diagram of a conventional communication procedure in the ISDN packet switching service supporting the incoming call providing procedure. When the calling user 81 tries to send a packet to a called user 82, a network 83 exists between them and a process for connecting the calling user 81 and the called user 82 is executed.

First, the calling user 81 sends a call setup request packet X. 25CR (X.25 call request) is transmitted (S81). The network 83 receives this, and the network 83 transmits a call setup message SETUP to the destination user 82 (S82). This call setup message SETUP includes a channel that can be selected by the called user and a channel identifier information element that is information indicating whether or not the channel can be changed.

The channel identifier information element is a selectable B
B channel display showing the channel name, channel change designation showing the possibility of changing the channel, D showing the presence or absence of the D channel
It is composed of channel indications, the contents of which are decided by the network 83 and coded in the call setup message SETUP. Here, it is assumed that a certain empty B channel Bi is displayed as the B channel display, changeable as the channel change designation, and present as the D channel display.

The destination user 82 receives the call setup message SETUP from the network 83 and returns a response message CONN to the network 83 (S83). This response message CONN
Contains the physical channel name specified by the user. now,
It is assumed that the user has designated the already established B channel (Old Bch).

The network 83 receives the response message CONN, analyzes the content of the response message CONN, and executes appropriate processing. If the channel designated by the user is available, the packet transmission processing by the channel is executed. Now, it is assumed that the established B channel designated by the destination user 82 cannot be used because the logical channel is busy or the total throughput is exceeded.
The total throughput over is managed for the purpose of guaranteeing the throughput for each packet call generated on the physical channel. For example, the threshold of the throughput that can be provided for each physical channel is set in advance by a maintenance command or the like, and the throughput of the call is added for each transmission / reception direction every time a packet call is generated. Exceeds the threshold, it can be managed by not connecting the packet call to the physical channel.

Since the incoming call packet cannot be sent to the physical channel selected by the user, the network 83 sends the call disconnection message X. 25CI (X.25 Clear
(indicate) is sent (S84), and a release message REL (release) including an indication that the channel is unavailable is sent to the destination user 82 (S85). And X. 25 Disconnect the virtual call. On the other hand, the calling user 81 determines that the call disconnection message X. 25 CI
Packet X. 25CF (X.2
5 clear confirmation) (S86), and the destination user 82 sends a release completion message REL COM (release complete) indicating that the release message has been received (S87).

[0009]

However, in the conventional method, when it is determined that the physical channel designated by the called user cannot be used due to the logical channel being busy or the total throughput being exceeded, the current time is determined. Then, there is a problem that the call is disconnected and the communication ends. Many users manage the logical channels that can be used for each physical channel, but there are few users who manage the total throughput of each physical channel and are used for the logical selection of physical channels. In many cases, the user selects. In such a case, call connectivity is significantly deteriorated and network serviceability is also degraded.

According to the present invention, when the destination user selects a physical channel that cannot be used, the physical channel that can be used again can be selected, so that the call connectivity can be improved and a better service can be provided. With the goal.

[0011]

FIG. 1 is a functional block diagram of the present invention. First, the ISDN exchange 3 has a physical channel information setting means 5. The physical channel information setting means 5 uses the call setting request packet X. 25
When CR4 is received, a physical channel that can be used with the destination user 2 is searched, and whether or not there is a usable D channel, whether or not there is an unused B channel, and whether or not there is a B channel that has already been established. Set and hold physical channel information for.

Next, the ISDN exchange 3 has a call setup message transmitting means 7. Call setting message transmitting means 7
Is created by coding the physical channel information usable by the destination user 2 in the call setup message 6 as a channel identifier information element based on the physical channel information held by the physical channel information setting means 5. The call setup message 6 is transmitted to the called user 2.

Finally, the ISDN exchange 3 has a response message processing means 9. The response message processing means 9
First, the physical channel selected by the called user 2 included in the response message 8 sent by the called user 2 in response to the call setting message 6 sent by the call setting message sending means 7 is analyzed. If the physical channel is inconsistent with the channel identifier information element created by the call setup message transmitting means 7, the call is disconnected and the communication is terminated.
If there is no contradiction, if the selected physical channel can be used, the channel is established and the incoming packet X. 25C
Send N10. On the other hand, if the selected physical channel cannot be used, the physical channel information held by the physical channel information setting means 5 is changed, the call setting message transmitting means 7 is activated, and the call setting message 6 is generated again. , To the destination user 2.

[0014]

When the calling user 1 wants to send a packet to a certain called user 2, the call setting packet X. 25CR
(X.25 call request) 4 is transmitted to the ISDN exchange 3. In this packet, in addition to the data you want to send,
Control information such as the name of the destination user 2 is included.

The ISDN exchange 3 receives the call setup packet X. 25CR4 is received, and the process for setting the channel between the ISDN exchange 3 and the destination user 2 is started. First, the physical channel information setting means 5 searches for a currently usable channel among nB + D channels of ISDN communication, and creates and holds physical channel information. That is, it is determined whether or not the throughput of the D channel is sufficient, and information on the availability of the D channel is created. As for the B channel, ISDN exchange 3-destination user 2 has already been used.
The presence / absence of a channel (existing B channel) established between them and the presence / absence of an empty B channel (new B channel) are checked and held as physical channel information.

Next, the call setting message transmitting means 7 is activated. The call setup message sending means 7 sends a message (call setup message 6) indicating a call setup request to the destination user 2. In this call setup message 6,
The call setup message transmitting means 7 includes a channel identifier information element that is information of a channel that the destination user 2 can select.
Code this in the call setup message 6.

First, referring to the physical channel information held by the physical channel information setting means 5, a channel identifier consisting of availability / impossible of D channel, presence / absence of new B channel, and possible / impossible of channel change. Code information elements. At this time, if there is no channel that can be selected by the called user, the call is disconnected and the communication ends.
If there is even one channel that the user can select, the call setup message 6 including the channel identifier information element is transmitted to the destination user 2.

The destination user 2 receives the call setup message 6 and selects a physical channel to be used as a reference for channel selection by using the channel identifier information element therein. Then, the response message 8 including the selected physical channel information is I
Return to SDN exchange 3.

The ISDN exchange 3 receives the response message 8 from the destination user 2 and activates the response message processing means 9. The response message processing means 9 first determines whether or not the physical channel selected by the destination user 2 is consistent with the usable physical channel information held in the physical channel information setting means 5, and if there is a conflict. To disconnect the call and terminate the communication. On the other hand, if there is no contradiction, whether or not the selected channel can be actually used is determined from the viewpoints of logical channel busy, total throughput over, and the like. If available, the call is established and packet X. Two
5CN (X.25 incoming call) is transmitted. If the channel cannot be used, the physical channel information held in the physical channel information setting means 5 is changed. That is, the availability / inability of the D channel, the presence / absence of a new B channel, and the presence / absence of an existing B channel are changed so as to match the state at that time. Then, the call setup message sending means 7 is activated, and the call setup message 6 including the channel identifier information element at that time is sent to the called user 2 again.

This allows the destination user 2 to select the channel again. The destination user 2 includes the selected channel in the response message 8 and transmits it to the ISDN exchange 3. The response message processing means 9 analyzes the response message 8 and disconnects or establishes the channel, and retransmits the call setup message 6.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is an ISD according to an embodiment of the present invention.
It is a system configuration diagram of an N exchange.

First, each user, that is, the calling user 1
There is an ISDN terminal 10 owned by the destination user 2 and is connected to the ISDN exchange unit via the basic / primary group interface 11. For example, this ISDN communication system has nB
It shall have a communication capacity of + D. That is, n B
It has a channel and one D channel.

The ISDN switching unit 12 comprises a circuit switching unit 13 and a packet switching unit 14. The circuit switching unit 13
It is a part that accommodates users and realizes the ISDN circuit switching service and also realizes the ISDN packet switching service in cooperation with the packet switching unit 14. The line switching unit 13 is composed of line corresponding units 15 and 16 and a line switching processing unit 17. The line-corresponding units 15 and 16 accommodate the users, and the Q. Perform link level control using the 921 procedure. In addition, in order to realize the ISDN packet switching service, the packet switching unit 14 and the internal interface 18 are connected.

On the other hand, the line switching processing unit 17 sends the Q. 931 messages are transmitted and received, and the B channel is switched. When the user desires to realize the B channel / packet switching service or the D channel / packet switching service, the packet switching unit 14 and the user are used for packet communication via the packet switching unit 14 and the internal interface 18. Set the logical path of.

The circuit switching processing section 17 uses the Q. 931 message transmitter 19, Q.I. 931 message receiving unit 20,
Q. 931 message analysis unit 21, Q.I. A 931 message editor 22 is included. Q. 931 message transmitter 1
9 to the user or the packet switching unit 14. 931 message is transmitted, and Q. The 931 message receiving unit 20 receives the Q. 931 message from the user or the packet switching unit 14. The process of receiving the 931 message is executed. In addition, Q. 931 message analysis unit 21 receives the Q. 931 message from the user or the packet switching unit 14. The 931 message and various information elements in the message are analyzed. If the user wants to communicate in packet switched mode,
Q. 931 to the packet switching unit 14 via the message transmitting unit 19. 931 message is transmitted. Finally, Q. 931 message editing unit 22 sends a Q. 931 Message edit processing is executed.

On the other hand, the packet switching unit 14 is the line interface unit 2
3 and a packet switching processing unit 24. Since the line interface 23 realizes the ISDN packet switching service,
The line interface 16 is connected to the line interface 16 of the line switching unit 13. If the packet communication is the B channel, the X. 25 layer 2 procedure, Q. Link level control is performed using the 921 procedure.

The packet switching processing unit 24 realizes a B channel packet switching service or a D channel packet switching service in cooperation with the circuit switching unit 13. The packet exchange processing unit 24 uses the Q. 931 message receiver 25, Q. 931 message transmitter 26, Q. 931 message analyzer 27, Q. 931 message editor 2
8, channel consistency check processing unit 29, channel capacity check processing unit 30, physical channel management unit 31, capacity management unit 32, path control unit 33, X. 25 procedure controller 34.

First, Q. 931 message receiver 25
Q. from the user. 931 Message reception processing is executed. Specifically, Q. 931 Message analysis unit 27
Is activated to request checking of various information elements including the channel identifier information element. If the channel matching check processing unit 29 determines that the channel designated by the user is unusable, the Q.Q. The 931 message transmission unit 26 is requested to retransmit the call setup message. Q. 931 message transmitter 26 sends the Q. 931 A message transmission request is sent to the circuit switching unit 13.

Q. 931 message analysis unit 27 receives the Q. The 931 message and various information elements in the message are analyzed. The channel matching check processing unit 29 is requested to check the channel identifier information element set by the user. In addition, Q. 931 message editing unit 28 sends a Q. 931 Message edit processing is performed. At this time, regarding the channel identifier information element, the channel identifier information element is coded with reference to the information managed by the physical channel management unit 31. When transmitting the first call setup message to the destination user, the channel capacity check processing unit 30 is activated.

The channel consistency check processing unit 29 checks whether or not there is a contradiction in the coding of the channel identifier information element designated by the destination user, based on the information managed by the physical channel management unit 31. Further, the capacity check of the channel designated by the destination user is executed based on the information managed by the capacity management unit 32. When it is determined that the capacity is insufficient, the physical channel management unit 31 is notified that the channel designated by the destination user is unavailable. Also, the channel capacity check processing unit 30
When sending the first call setup message to the called user,
Check available capacity on each channel.

The physical channel management unit 31 executes processing for managing information on physical channels available to the called user each time the presence of an incoming call packet to the user is detected.
In addition, the capacity management unit 32 is configured to allow the user to exchange packets with the packet switching unit 14.
The logical channel and the total throughput are managed for each logical communication path for packet communication that should be established during. In addition, the path control unit 33 includes the circuit switching unit 13
And the control / setting of the logical communication path set between the packet switching unit 14 and the packet switching unit 14. And finally, X. The 25 procedure control unit 34 controls the X.25. 25 Layer 3 procedures are used for packet level control.

The operation of this system will be described with reference to the communication procedure diagram between the calling user, the network and the called user according to the embodiment of FIG. Now, it is assumed that the calling user 1 has established a logical communication path for packet communication with the packet switching unit on the B channel or the D channel. The calling user 1 receives the incoming packet X. 25CR is sent to the destination user 2. At this time, the packet passes through the ISDN switching unit 12 existing in the network 35 and is subjected to various kinds of processing.

First, the X.15 transmitted by the ISDN terminal 10 of the calling user 1 is transmitted. The 25CR packet reaches the ISDN switching unit 12 of the network 35 (S1). Then, it flows on the logical communication path for packet communication set with the packet switching unit and is sent to the packet switching unit 14. That is, the line interface 15-line interface 16-internal interface 18-
It is sent to the packet switching processing unit 24 via the line interface unit 23. In the packet switching processing unit 24, the X. 25. The procedure control unit 34 is activated, and the received X. The originating / terminating DTE address of the 25CR packet is analyzed. In this analysis, X. It can be seen that the request is 25 virtual call setup request.

Therefore, first, the physical channel management unit 31 is activated to execute information management of the physical channels available to the called user. This process is performed according to the operation flow chart of the capacity check which the network processes when the first call setup message is transmitted to the called user in FIG. That is, a usable channel is searched for, and physical channel information 51 indicating usable / unusable is created. FIG. 5 is a configuration diagram of physical channel information to be created.

The physical channel information 51 is constructed as data having a width of about 1 byte. Then, each bit is assigned to each channel, and “0” is inserted when it is not selectable, and “1” is inserted when it is selectable. For example, the first bit is D
The channel selectable display 52, the second bit is a new B channel selectable display 53, and the third bit is an existing B channel selectable display 54. The other bits (4th to 8th bits) are reserved bits 55.

The selectable display of each channel is determined according to the flowchart of FIG. First, the physical channel information 51 is initialized (S41). That is, the first to third bits of the physical channel information shown in FIG. 5 are set to "1" so that all channels can be selected. Next, the channel capacity check processing unit 30 is activated and it is determined whether or not the throughput of the D channel is sufficient (S42). If the throughput is not sufficient (No), the value of the D channel selectable display 52 of the physical channel information 51 is set to "0" to indicate that selection is not possible (S43). When the throughput is sufficient (Yes), the value of the D channel selectable display 52 remains "1", and the value becomes selectable.

Next, in the case of Yes in S42, and in S4
After the processing of 3, it is determined whether or not there is an unused B channel (S44). When there is no unused B channel (No), the value of the new B channel selectable display 53 of the physical channel information 51 is set to "0" to indicate that selection is not possible (S45). When there is an unused B channel (Yes), the initial value of the physical channel information 51 is "1".
, And the new B channel becomes selectable.

In the case of Yes in S44 and after the processing of S45, it is determined whether or not there is an already established B channel (S46). When there is no existing B channel (No), the value of the existing B channel selectable display 54 in the physical channel information 51 is set to "0" so that the existing B channel cannot be selected (S47). If there is an existing B channel (Yes), the value of the existing B channel selectable display 54 remains '1', and it becomes selectable.

With the above processing, the setting of the physical channel information 51 is completed, and thereafter, the physical channel management unit 31 manages this information. Next, the packet switching unit 14 sends the Q. 931 message editing unit 28 is activated, a call setup message to be sent to the called user is edited, and the edited call setup message SETUP is sent to 931 message transmitter 26-line interface 23-internal interface 18-line interface 16
-Q. 931 Message transmission unit 19-Sends to destination user 2 via line interface 15 (S2 in FIG. 3). A channel identifier information element is written in the call setup message SETUP, and the destination user 2 is informed of the information on whether or not each channel can be selected. The channel identifier information element includes the presence / absence of a usable D channel, the presence / absence of a selectable new B channel and the channel name, and the possibility of changing the channel.
It consists of two elements.

These call setting message editing and transmitting processes are executed according to the process flow chart when the call setting message is transmitted from the network to the called user. First, the call setting message editor 28 is activated. The call setup message editor 28 checks the channel selectability and codes the channel identifier information element. First, the physical channel information 5 managed by the physical channel management unit 31
1 is checked to determine whether the D channel can be selected (S51). If it is selectable (Yes), the D channel display of the channel identifier information element is coded as "present" (S52), and if not selectable (No), it is coded as "none" (S53).

Next, the possibility of selecting a new B channel is determined by referring to the physical channel information 51 (S54). If the new B channel can be selected (Yes), "empty B channel (Bi)" is coded in the new B channel display of the channel identifier information element, and "changeable" is coded in the channel change designation display (S55). On the other hand, if the new B channel cannot be selected (No), then the existing B channel selectability is determined by referring to the physical channel information 51 (S56). If the existing B channel can be selected (Yes), "no channel" is coded in the new B channel display of the channel identifier information element, and "changeable" is coded in the channel change designation display (S57). If the existing B channel cannot be selected (No), "no channel" is coded in the new B channel display of the channel identifier information element, and "unchangeable" is coded in the channel change designation display (S58).

When the coding of all three items of the channel identifier information element is completed (S55 or S5
7, after the end of S58), referring to the coded channel identifier information element, whether or not all the channels are not selectable, that is, D channel display “none”, new B channel display “no channel”, It is determined whether the channel change designation display is "unchangeable" (S5).
9). If all channels are not unselectable (N
o), Q. The 931 message transmitter 26 is activated, and the call setup message SETUP including the coded channel identifier information element is sent to the destination user 2 (S6).
0). On the other hand, if all the channels cannot be selected (Yes), it has turned out that it is difficult to secure the channels at this point. 25. The procedure control unit 34 is started, and X.25. X.25 to originating user 1 to disconnect the 25 virtual call. 25 CI packet (X.25 clear
send an indicate packet) (S61).

With the above processing, the processing (S2) of sending the call setting message SETUP to the destination user 2 is completed. Now, in the procedure shown in FIG. 3, it is assumed that the channel identifier information element included in the call setup message SETUP is set as follows. That is, "new B channel Bi" is displayed on the B channel, "changeable" is displayed on the channel change display, and "present" is displayed on the D channel display.

The destination user 2 receives the call setup message SET.
Response message CONN that receives UP and responds to it
Is returned to the network 35 (S3). Response message CON
N includes information on the channel selected by the destination user 2.
Here, it is assumed that the existing B channel (Old Bch) is designated.

The ISDN switching unit 12 of the network 35 receives the response message CONN from the destination user 2. Then, this message is the line interface 15-Q. 931 message receiver 20 (Q.931 message analyzer 21) -Q. 9
31) The message is sent to the packet switching unit 14 via the message sending unit 19-line interface 16-internal interface 18.
In the packet switching unit 14, the Q.Q. 9
31 The message receiving unit 25 receives this message,
Perform the process corresponding to the message. This process is shown in Figure 7.
The processing is performed according to the network processing flowchart when the response message CONN from the destination user is received.

First, Q. The 931 message analysis unit 27 analyzes the message and activates the channel consistency check processing unit 29 to check whether the channel selected by the destination user 2 is consistent. The channel consistency check processing unit 29 refers to the physical channel information 51 managed by the physical channel information management unit 31 and checks the correspondence with the channel selected by the destination user 2 (S70). Then, it is determined whether the channel selected by the destination user 2 is consistent with the content of the physical channel information 51 (S71). If there is a contradiction (Yes), that is, if the destination user 2 selects the D channel even though the D channel selectable display 52 of the physical channel information 51 is “0” and the selection is not possible, for example, the selection is made. It is determined that there is a contradiction, and processing for disconnecting the call is executed (S72). A release message REL (release) for releasing the call is sent to the called user 2, and X. 25. Disconnect virtual call X. 25CI (X.25 Clear indicat
send e). With the above processing, the X. The 25 virtual call is disconnected and the communication ends in failure.

On the other hand, if it is determined in the check in S71 that there is no contradiction (No), Q. The processing proceeds according to the type of physical channel selected by the destination user 2 analyzed by the 931 message analysis unit 27. First, it is determined whether the selected channel of the destination user 2 is the existing B channel (S7).
3) If it is not the existing B channel (No), then it is determined whether the selected channel is the D channel (S74). If it is not the D channel (No), the channel selected by the destination user 2 is the new B channel. When the new B channel is selected, it is already confirmed that the designated channel of the destination user 2 is consistent with the physical channel information (S71), so that the packet communication can be unconditionally started. Therefore, the path control unit 33 and the X. 25
The procedure control unit 34 is activated to establish the link of the selected channel, and X. A process of transmitting 25 incoming call packets is executed (S75).

If it is determined in S74 that the selected channel of the called user 2 is the D channel (Yes), the channel consistency check processing unit 29 is activated and the D channel designated by the called user 2 has sufficient capacity. It is determined whether or not (S7
6). At this time, the logical channel busy information and the total throughput information for each logical communication path managed by the capacity management unit 32 are referred to. If neither logical channel busy nor total throughput over, it is judged that there is sufficient capacity (No in S76), and S75.
Then, the packet switching process is executed. on the other hand,
If the logical channel is busy or the total throughput is exceeded, it is determined that the capacity is insufficient (S7
6), and notifies the physical channel management unit 31 that the channel cannot be selected. Then, the physical channel management unit 31 disables selection of the D channel from the physical channel information 51, and the Q. The 931 message editing unit 28 is activated, and a release message accompanied by a reason display indicating that the channel cannot be used is transmitted to the destination user 2 (S77). Then, the process (FIG. 6) of transmitting the call setting message to the called user 2 is executed again (S7).
8).

On the other hand, suppose that the selected channel of the called user 2 is determined to be the existing B channel in S73 (Yes). This corresponds to the example of the communication procedure diagram of FIG. Also in this case, as in the case of the D channel, the channel consistency check processing unit 29 is activated and the information of the capacity management unit 32 is referred to, and it is determined whether or not the designated channel has sufficient capacity (S79). And if there is sufficient capacity (N
In o), the process of S75 is executed, and the packet switching process is executed. On the other hand, when there is not sufficient capacity, that is, when the logical channel is busy or the total throughput is exceeded (Yes), the channel consistency check processing unit 29 cannot select the channel from the physical channel management unit 31. Notify that The physical channel management unit 31 disables the existing B channel from the physical channel information 51, The 931 message editing unit 28 is activated, and a release message accompanied by a display indicating that the channel is unavailable is transmitted to the destination user 2 (S8).
0). Then, the process (FIG. 6) of transmitting the call setting message to the called user 2 is executed again (S78).

In the communication procedure diagram of FIG. 3, the destination user 2 selects the existing B channel (S3), and the ISDN exchanging unit 12 executes the processing in accordance with the processing flow chart for receiving the response message in FIG. is doing. In this case, since it is assumed that the existing B channel is busy with the logical channel or the total throughput is exceeded, it is determined in S79 that the capacity is insufficient (Yes). As a result, Q. 931 message editor 2
8 creates a release message REL (release) with indication () that the channel is unavailable, 9
31 message transmitter 26-line interface 23-internal interface 18-line interface 16-Q. 931 Message transmission unit 19-Sends to the called user 2 via the line interface 15 (S80, S4 in FIG. 3). Receiving user 2 receives this release message and notifies that the release is approved.
L COMP (release complete) to ISDN exchange unit 1
Return to 2 (S5).

On the other hand, on the ISDN exchange section 12 side, the release message REL is transmitted and the physical channel management section 31 is activated to disable the information of the existing B channel in the physical channel information 51 (S80). . And Q. 931 message editing unit 28 is started, the processing is executed according to the processing flow chart of the call setting message transmission in FIG. 6, the call setting message is recreated, and Q. 9
31 is transmitted to the destination user 2 via the message transmission unit 26 (S78, S6 in FIG. 3). In this case, referring to the physical channel information 51, the D channel can be selected (Fig. 6 S5).
1) and new B channel can be selected (S54 Y)
es), the existing B channel cannot be selected (No in S56). The 931 message editing unit 28 sets the channel identifier information element in the call setup message to a new B channel display “channel Bi”, a channel change display “no change”, and a D channel display “present”.

The destination user 2 receives the call setup message, selects a channel with reference to the channel identifier information element, and returns a response message CONN (connect) (S7). In this case, the destination user 2 receives the ISDN exchange unit 12
The new B channel (New
Bch) is selected. ISDN exchange section 12
Receives this response message, and executes the processing again according to the processing flowchart for receiving the response message in FIG. The physical channel designated by the destination user 2 is consistent with the content of the physical channel information 51 (No in S71), and the selected channel is the new B channel (No in S74). 931 The message editing unit 28 is activated, and the CONN A that reports the receipt of the response message CONN
CK (connect acknowledge) is created, and Q. It is sent to the destination user 2 via the 931 message transmitting unit 26 (S8).
Further, the path control unit, X. 25 control unit 34 to activate the link of the new B channel (S9), and the incoming packet X.25. 25CN (X.25 incomming call) is sent to the destination user 2 (S10, S75 in FIG. 7). Destination user 2
Incoming packet X. 25CN can be accepted, the incoming call acceptance packet X. 25CA (X.25 call accept) is sent to the network 35 (S11), and in response to this, the ISDN exchange unit 12 sends the X.25 call to the calling user 1. Packet X.25 which notifies that the connection of the virtual call is completed. 25 CC
(X.25 call confirmation) is sent (S12).

By the above processing, the physical channel reselection of the destination user 2 becomes possible.

[0054]

[Table 1]

Table 1 is a table showing the channel identifier information element coded in the call setup message and the pattern of the channel selected by the called user. First, when a call request packet from the calling user 1 is generated, the network side checks the physical channel information that can be used by the called user 2 at that time, expresses it as a channel identifier information element in the call setup message, and sends it to the called user 2. . This is the first network → SETU for the user
P. There are five possible channel identifier information elements (1) to (3) in combination with the new B channel display, the channel change display, and the D channel display.

On the other hand, the destination user 2 returns a response message CONN including information on the selected channel. For each channel identifier information element from network to user, the destination user can select several channels. That is, for example, for a destination user who already has a packet-switching configured B channel, the network has a new B channel
SET the channel identifier information element "D channel present"
When transmitted as UP, the destination user 2 can select three types of channels: new B channel-1, existing B channel-2, and D channel-3. Further, when the channel identifier information elements of new B channel, channel changed, and no D channel are transmitted to the called user 2 as SETUP, the called user 2 selects either the new B channel-1 or the existing B channel-2. It is selectable. Hereinafter, it is possible to select a channel by the destination user 2 in two ways for the channel identifier information element and one way for each of the channel identifier information element and.

When the destination user 2 selects the channel, the network side executes the process (FIG. 7) when the response message is received. Here, if the destination user selects a new channel (-1
And -1), a channel can be established and packet switching processing is executed. Further, if only the existing B channel can be selected by the channel identifier information element () and the called user 2 selects the existing B channel (-1), the existing B channel of the existing B channel is processed by the process when the response message is received (FIG. 7). When the capacity is sufficient (No in S79), the packet switching process is executed (S75), and when the capacity is insufficient (Yes in S79).
Since communication cannot be performed in s), the call is disconnected when the next call setup message is created (S61 in FIG. 6). Also, only the D channel can be selected with the channel identifier information element (),
The same applies when the destination user selects the D channel (-1), and if the capacity is sufficient, packet switching processing is executed (S75), and if the capacity is insufficient, the call is disconnected (FIG. 6).
S61).

On the other hand, -2, -3, -2, -1,
-2, the second call setup message is the destination user 2
May be sent to. That is, if the destination user 2 designates the existing B channel at -2, but the capacity of the existing B channel is not sufficient (Yes in S79),
The call setup message is recreated by disabling the existing B channel of the physical channel information 51 (FIG. 6). in this case,
The channel identifier information element of the next call setup message allows selection of a new B channel or D channel-
2 '. In addition, the destination user 2 selects the D channel,
If the capacity is not sufficient (Yes in S76), the D channel of the physical channel information 51 is disabled and the call setup message is recreated (FIG. 6). In this case, the channel identifier information element of the new call setup message is -3 ', which allows selection of a new B channel or channel change.

For -2 ', the destination user 2 has a new B channel (-2'-1) or D channel (-2'-).
There is a possibility to select 2). In the case of -2'-1, since it is a new B channel, packet switching processing is executed (S
75). On the other hand, in the case of -2'-2, if the D channel has sufficient capacity (No in S76), the packet switching process is executed (S75), and if the capacity is insufficient (Yes in S76).
s) makes the D channel of the physical channel information unselectable and creates a call setup message three times (FIG. 6). In this case, the channel identifier information element of the created call setup message allows only the new B channel to be selected-2'-
2 '. In this case, the destination user 2 can select only the new B channel (-2'-2'-1).

For -3 ', the destination user 2 can select two channels (-3'-1 and-).
3'-2). In the case of -3'-2, the call setup message may be sent three times. The channel identifier information element in this case is -3'-2-1.

By retransmitting the call setup message twice or three times by the above method, it becomes possible to allow the destination user to reselect the usable channel.

[0062]

According to the present invention, even if the destination user selects an unusable channel once or twice, by transmitting the call setup message including the reusable physical channel information, It allows the user to select a channel. As a result, X.X.X. is set for users who do not manage capacity such as logical channels or total throughput. The probability that 25 incoming call packets can be transmitted is improved, and the network connectivity can be improved. This also improves the serviceability of the network.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the principle of a physical channel reselection system of the present invention.

FIG. 2 is a system configuration diagram of an ISDN exchange section according to an embodiment.

FIG. 3 is a communication procedure diagram between a calling user, a network, and a called user according to an embodiment.

FIG. 4 is an operation flowchart of a capacity check performed by the network when transmitting a first call setup message to a called user.

FIG. 5 is a configuration diagram of physical channel information.

FIG. 6 is a processing flowchart when a call setup message is transmitted from the network to a destination user.

FIG. 7 is a processing flowchart of a network when a response message is received from a called user.

FIG. 8 shows a conventional communication procedure.

[Explanation of symbols]

1 user Second user 3 ISDN exchange 4 X. 25CR 5 Physical channel information setting means 6 Call setup message 7 Call setup message sending means 8 response message 9 Response message processing means 10 X. 25CN

Claims (6)

[Claims] 1. A call originated by a calling user (1) in an ISDN exchange (3) that supports a called call providing procedure that enables a called user (2) to select a switching channel in an ISDN packet switching service. Packet X. 25C
A physical channel information setting means (5) for receiving and receiving an R (X.25 call request) (4) and creating and managing information indicating a physical channel selectable by the destination user (2), and the physical channel information setting means. Call setup message sending means for creating a call setup message (6) containing physical channel information selectable by the called user based on the physical channel information managed by (5) and sending it to the called user (2). (7),
The called user (2) receiving the call setting message (6) sent by the call setting message sending means (7) and included in the response message (8) sent to the call setting message (6) by the called user (2). 2) analyzes the selected physical channel, and if it is a selectable channel, connects the call and realizes packet switching, and if it is a non-selectable channel,
A response message processing means for activating the call setup message sending means (7) so that the called user (2) can select the physical channel again and sending the call setup message (6) to the called user (2) again ( 9) A physical channel reselection method comprising: 2. The physical channel information setting means (5) according to claim 1, for an nB + D physical channel of ISDN communication, whether or not there is still room for communication in the D channel, and whether or not there is an unused B channel. 2. The physical channel reselection method according to claim 1, wherein information about whether or not to do so and whether or not there is an existing B channel that has already established a route is set as binary information. 3. The call setup message transmitting means (7) according to claim 1 is the physical channel information setting means (5) according to claim 2.
Refer to the physical channel information set by, and appropriately set the items of "D channel display", "new B channel display", and "channel change designation display" of the channel identifier information element included in the call setup message (6). The physical channel reselection method according to claim 1, which is provided. 4. The call setup message sending means (7) according to claim 1 is the physical channel information setup means (5) according to claim 1.
Refer to the physical channel information set by, and if the D channel is selectable, D of the channel identifier information element
Code the channel display to "Yes", while if the D channel cannot be selected, code it to "No", and if a new B channel can be selected, add one empty B channel to the new B channel display. , "Changeable" is coded in the channel change designation display, if the new B channel cannot be selected and the existing B channel can be selected, "No channel" is displayed in the new B channel display and "No channel" is displayed in the channel change designation display. Changeable "is coded, and when neither a new B channel nor an existing B channel can be selected," no channel "is added to the new B channel display and" unchangeable "is added to the channel change designation display. 1. The physical channel reselection method described in 1. 5. The call setup message sending means (7) according to claim 1 is the physical channel information setup means (5) according to claim 1.
If the D channel, the existing B channel, or the new B channel cannot be selected by referring to the physical channel information set by the X. The physical channel reselection method according to claim 1, wherein the 25 virtual call is disconnected and the communication is terminated. 6. The response message processing means (9) according to claim 1, wherein the answering user (2) is included in the answering message (8) to which the answering user (2) responds in response to the call setup message (6). It is determined whether or not the selected channel is inconsistent with the physical channel information set by the physical channel information setting means (5) according to claim 2, and when it is inconsistent, the X. Two
5 If the virtual call is disconnected and the communication is terminated and there is no contradiction, then it is judged whether the channel selected by the destination user (2) is the logical channel busy or the total throughput is exceeded, and the logical channel is determined. -If at least one of busy and total throughput is exceeded, the physical channel information of the channel set by the physical channel information setting means (5) of claim 1 is changed to unselectable, and then If the call setup message (6) is sent again by the call setup message sending means (7), and neither the logical channel busy nor the total throughput is exceeded,
Establishing the channel, X. X.25 incoming call packet.
25CN (10) is transmitted to the destination user (2).
The physical channel reselection method described.