JPH0265343A - Call transfer control system - Google Patents

Abstract

PURPOSE:To switch a virtual call without disconnecting a logical link and to realize the efficient transfer control of the call by controlling a packet level. CONSTITUTION:When a recovery requesting packet 13 is received, a packet exchange network 10 confirms that the recovery request requires the transfer of the call according to transfer requesting information 14 added to the packet. The packet exchange network 10 reloads the corresponding relation of terminals on a storing means 11 without disconnecting a first terminal 8, disconnects a second terminal 9 and transfers the virtual call to a transfer destination terminal 17. By this operation, a communication opposite party is switched from the second terminal 9 (transfer source terminal) to the transfer destination terminal 17 without disconnecting a first terminal 8 but in a waiting condition. Accordingly, the fist terminal 8 can continue communication with the changed terminal without being conscious that which terminal the present communication opposite party is.

Description

[Detailed Description of the Invention] [Summary] Concerning a call transfer control method in a packet-switched network, the present invention provides efficient call transfer control by switching virtual calls without disconnecting logical links through packet-level control. With the purpose of
In a packet switching network in which terminals are associated with each other and a logical link is formed between the two terminals to perform packet communication, the second terminal includes the call transfer request information and the transfer destination in the call recovery request packet. The packet switching network, which receives the recovery request packet by adding designation information and transmitting it to the packet switching network, confirms the transfer request information and then determines the correspondence between the first and second terminals on the storage means. Attach the first
and the transfer destination terminal indicated by the transfer destination designation information, and is configured to transmit a disconnection confirmation packet to the second terminal and transfer the call to the transfer destination terminal.

[Industrial application field]

The present invention relates to a call transfer control method in a packet-switched network.

[Prior art] Packet switching is a data transmission method based on store-and-forward, in which data is transmitted in units called packets, and there is no need to set up a direct line between terminals. This method transmits packets to the other party's terminal based on the destination information added to the packet when the route is free, and it is possible to communicate with other parties with different transmission speeds and to easily convert protocols. Has characteristics. For this reason, it has become popular in various data networks including computer networks.

In the packet switching method, instead of setting up a direct physical line between terminals, a logical link is set up to send and receive packets, and packet communication is performed based on this. In this case, the originating terminal , by sending a call setup packet to the packet switch at the start of packet communication, the packet switch establishes a logical link for transmitting packets sent from the originating terminal to a specific destination terminal ( For example, to associate addresses, etc.), execute the following procedure. After this, free packet communication between terminals becomes possible. Then, at the time of disconnection, by sending a disconnection packet from one of the terminals, the packet switch executes a procedure for disconnecting the logical link set between the corresponding terminals. The call control operation of establishing and disconnecting a logical link between terminals in this manner is called a virtual call.

Now, consider a packet switching network as shown in FIG. In the figure, the terminal device 2 is accommodated in a packet switch 1-1, and the packet switch 1-1 includes a packet switch 1-2.
and packet switch 1-3 are connected. The packet switch 1-2 accommodates the information processing device 3, and the packet switch @1-3 accommodates the information processing device 4.

In the above packet switching network, for example, a terminal device that is a calling terminal! ! ! 2 is a personal computer, and it is assumed that the information processing device 3, which is a management center, is accessed through a virtual call. As a result, a logical link is established between the terminal device 2 and the information processing device 3 via the packet switches 1-1 and 1-2, and packet communication is started. Then, the information processing device 3 transmits, for example, a menu of information processing services to the terminal device 2, whereby the user of the terminal device 2 selects a desired service from the displayed menu.

Here, if the content (database) of the service (for example, database access) corresponding to the selected menu exists in the information processing device 4 instead of the information processing device 3, the information processing bag W3, which is the management center, After determining that, the packet switch 1-2 issues a request to the packet switch 1-1 to reconnect the terminal device 2 to the information processing device 4, so that the terminal device 2 can receive the service. It is necessary to perform call transfer (hereinafter simply referred to as call transfer).

FIG. 8 is a diagram showing a transfer control process according to a conventional example in which the above-described call transfer is performed in the packet switching network of FIG. 7. The following description will be made with reference to FIG. 7, with a focus on FIG.

Suppose that the information processing device 3 and the terminal device 2 are currently communicating (S1), and the terminal device 2 is a terminal that complies with CCTTT (International Telegraph and Telephone Consultative Committee, one of the United Nations organizations) Recommendation x, 28. .

The information processing device 3 sends the reselection PAD message 5 specified in CCITT Recommendation X, 29 to the packet switch 1-
2 (S2). The format of this message will be described later, but it is in the form of a data packet.

Packet switch 1 that received reselection PAD message 5
-2 sends it to packet switch 1-1 (S3
).

When the packet switch 1-1 receives the reselection PAD message 5, it transmits the disconnection instruction packet 1-CI to the packet switch 1.
-2 to the information processing device 3 (S4
, S5), gives a disconnection instruction to the terminal device 2 (S6)
.

When the packet switch 1-1 receives the disconnection/recovery confirmation packet CF from the information processing device 3 via the packet switch 12 (37, S8), the packet switch 1-1 sends a new message to the information processing device 4 via the packet switch 1-3. Incoming packet CN
(39.310).

Subsequently, the packet switch 1-1
When receiving the incoming packet CA from the information processing device 4 via the information processing device 3 (S11.512), the connection completion signal 7 is transmitted to the terminal device 2 (313).

Through the above operations, communication between the information processing device 3 and the terminal device 2 is switched to communication between the information processing device 4 and the terminal device 2. That is, the call is transferred from the information processing device 3 to the information processing device 4.

FIG. 9 shows the format of the reselection PAD message 5 transmitted from the information processing device 3 to the packet switch 1-2.1-1 in the transfer control process of FIG. 8. This format is a conventional data packet format,
Packet header HD (
dt), a message code Res indicating that it is a reselection PAD message, and an address code Add indicating a transfer destination address.

[Problem to be solved by the invention]

In the conventional transfer control method described above, the terminal device 2
The transfer source terminal issues a switching request for a specific packet that is limited to terminals transmitting in accordance with TTT Recommendations , disconnect the communication, and reconnect to the new destination terminal. Therefore, conventionally, the calling terminal side had to communicate while being aware of the current partner terminal, and if communication was interrupted in this way,
There were inconveniences such as the job on the sending terminal side being interrupted and having to be restarted from the beginning. Therefore, it has the problem that it is very difficult to handle for terminals using other high-performance packet transmission protocols, which have recently been standardized.

On the other hand, call forwarding control has already been put into practical use in telephone exchanges, but while telephone line switching is limited to physical control, packet switching methods allow transfer of packets without affecting the physical line. Calls, or virtual calls, need to be switched by level control; traditionally,
Since there is no efficient call transfer control protocol other than the conventional method described above, packet-level communication without disconnecting the other party's terminal and not limited to CCITT Recommendations X and 28 terminals is possible. The problem is that call transfer control cannot be performed by control alone.

An object of the present invention is to switch virtual calls without disconnecting logical links through packet-level control, and to realize efficient call transfer control.

[Means to solve the problem]

FIG. 1 is a block diagram of the present invention.

First, in the present invention, when a call from any one of the first terminal 8 and the second terminal 9, that is, a virtual call, the packet switching network 10 stores the first and second terminals on its internal storage means ll. The present invention is based on a packet exchange method in which two terminals 8 and 9 are associated as shown in FIG. 12, and a logical link is formed between the two terminals to perform packet communication. Here, the packet switching network 10 is actually a packet switching unit constituting, for example, a packet communication network, and the storage means 11 is stored in a packet switching unit related to the first and second terminals 8.9. Realized as a main storage device, etc.
Further, the correspondence relationship is realized as a line table indicating which terminal is currently communicating and a call control table storing the number of the communication partner connected to the terminal.

The present invention provides a call transfer control method when switching the logical link between the first terminal 8 and the second terminal 9 to the logical link between the first terminal 8 and the transfer destination terminal 17. , the call transfer request information 14 and transfer destination designation information 15 are added to the recovery request packet 13 corresponding to the call, and the packet is transmitted to the packet switching network 10 . Here, the recovery request packet 13 can be identified, for example, by packet type information added to the header portion of the packet.

Further, the transfer request information 14 and the transfer destination designation information 15 are added, for example, using a facility area normally provided in the recovery request packet 13.

Next, the packet/node switching network 10 (actually, for example, a packet switching device receives the recovery request packet 13) receives the recovery request packet 13.
After confirming the transfer request information 14, the information shown in FIG.
The correspondence between the first terminal 8 and the second terminal 9 shown in FIG. Correspondence 12 is deleted), and the connection is made to the second terminal 9 via the packet switch in which the second terminal 9 is accommodated.
[P! Send a packet.

Along with the above operation, the call, that is, the virtual call, is transferred to the transfer destination terminal 17. In this transfer operation, for example, the packet switch m10 transfers the incoming call instruction packet 1 corresponding to the call.
9, the call transfer notification information 20 and transfer source designation information 21
is added and transferred to the transfer destination terminal 17 via the packet switch in which the transfer destination terminal 17 is accommodated. In addition,
The transfer notification information 20 and the transfer source designation information 21 are added, for example, using a facility normally provided in the incoming call instruction packet 19.

Here, the packet switching network 10 receives the recovery request packet l-1.
3, it instructs the first terminal 8 to restrict 22 the input of packets to the packet switching network 10, and instructs the first terminal 8 to release the restriction 23 after the call transfer operation to the transfer destination terminal 17 is completed. Here, for example, when packet data is transmitted using the HDLC procedure, the input regulation 22 is RN R (
This is possible by the RR (Recieve NotReady) signal, and the restriction release 23 is possible by the RR (Recieve NotReady) signal.
This is possible with the EADY) signal.

[For production]

In the above means, when the packet switching network 10 receives the recovery request packet 13, it can recognize from the transfer request information 14 added thereto that the recovery request requests call transfer. Then, without disconnecting the first terminal 8, the packet switching network 10 rewrites the correspondence of the terminals on the storage means ll, disconnects the second terminal 9, and transfers the virtual call to the transfer destination terminal 17. do.

Through the above operation, the communication partner is switched from the second terminal 9 (transfer source terminal) to the transfer destination terminal 17 while the first terminal 8 is kept waiting without disconnecting. Therefore, the first terminal 8 can continue communicating with the changed terminal without being aware of which terminal is the current communication partner.

In this case, especially while the packet switching network 10 is performing the speed change control, input regulation 22 is performed on the first terminal 8,
By performing the restriction release 23 after the transfer control is completed, it is possible to prevent the first terminal 8 from outputting packet data and destroying the data during the transfer control.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail.

This embodiment is based on a packet switching network based on virtual calls, and its overall configuration is the same as that shown in FIG.

FIG. 2 is an internal configuration diagram of the packet switches 1-1 to 1-3 in FIG. 7.

A central control unit (CPU, hereinafter referred to as L/) 24 performs call control,
This is a control device that performs overall control of packet exchange operations, etc., and executes a control program (not shown) stored in a main memory (MM) 26 connected via a bus 25.

In addition to storing the program, the MM 26 also stores a line table (such as the area SD#2 corresponding to the terminal device 2 in FIG. 7).
SDT (the same applies hereinafter) 27, call control table (CDB,
The same applies hereafter) There are 28.

This means is used during call control operations of each terminal, as will be described later.

A communication control unit (CCU, hereinafter the same) 31 connected to the bus 25 is the terminal device 2 or information processing device 3.4 in FIG.
The communication line 32 is connected to the communication line 32, and controls the input/output of packet data etc. input/output via the communication line 32, and is composed of hardware and a line control program for controlling the hardware.

The input/output device (10, same hereinafter) 29 is a man-machine interface device during maintenance or testing, and is, for example, a terminal, a CRT display device, or the like. Furthermore, the input/output control device (10, the same applies hereinafter) 30 connected to the bus 25,
1029 and bus 25.

Note that since 1029 and 10C30 are not directly related to the present invention, their operations will be omitted.

The operation of controlling call transfer using the packet switches 1-1 to 1-3 having the configuration shown in FIG. 2 will be described below.

In the packet switching network shown in FIG. 7, as in the case of the conventional example, in order for the terminal device 2 (personal computer) that is the originating terminal to use the information processing service provided by the information processing device 3 that is the management center, In this case, when access is performed through a virtual call, the following operations are executed according to the operation flowchart of FIG. 3, which is executed as a control program within the packet switch 1-1. Further, an operation timing chart in this case is shown in FIG.

First, in 5TEP 1 of FIG. 3, a call is set up between the source terminal and the transfer source terminal.

That is, first, the terminal 2 transmits a call request signal 33 to the packet switch 11 (S15, see FIG. 4 below).

As a result, the packet switch 1-1 transmits an incoming call request inter-office bucket) CN'' to the packet switch 1-2 (516).
), the same packet is further transmitted to the information processing device 3 as a packet exchange [incoming call request bucket from 1-2] CN (S
17), although the functions of CN and CN' are the same, C
N' is different in that it is an inter-office packet between packet exchanges, so it is important to distinguish between them. CQr and CQr′ explained below
The same holds true for the relationships between CF and CF', CNr and CNr', and CA and CA'.

Subsequently, the information processing device 3 that has received the incoming call request packet CN returns the incoming call acceptance packet CA to the packet switch 1-2 (518), and further sends the incoming call request packet CN from the packet switch 1-2 to the packet switch 1. -1, the inter-receiving station bucket I-CA' is transmitted (S19).

As a result, the packet switching network 191-1 transmits the connection completion signal 34 to the terminal 2 (520), and from now on the terminal 2
A logical link is established between the information processing device 3 and the information processing device 3, and the two can communicate with each other (S21).

In this case, in the packet switch 1-1, C in FIG.
5DT (line table) 2 where PU24 is in MM26
In the terminal device 2 corresponding area SD#2 of No. 7, information indicating that the terminal device 2 is in a communication state is set. Further, the number N3 of the information processing device 3 of the communication partner is stored in the CDB (call control table) 28 coupled to the terminal device 2 corresponding area SD#2. Then, the CPU 24 allocates appropriate logical channels to the above table. From now on, terminal device 2
and information processing device 3, by simply setting a specific logical channel number in the data packet for communication, packet switching device 1
-1, etc. refer to the above table, thereby enabling communication with each other. That is, by setting the above table, a logical link is set between the terminal device 2 and the information processing device 3.

Here, in order to confirm the information processing service requested by the information processing device 3, predetermined guidance (menu) is transmitted to the terminal device 2, and the user of the terminal device 2 can then check the displayed menu. Select the desired service from among them. Here, if the content of the service (for example, database access) corresponding to the selected menu (its database) exists in the information processing device 4 instead of the information processing device 3, the information processing device 3 that is the management center
After recognizing this, in order to transfer the incoming call from the terminal device 2 to the information processing device 4, a recovery request bucket with the call switching facility FTa shown in FIG.
Qr is transmitted to the packet switch 1-2 (S22).

As shown in FIG. 5, the call switching facility FTa includes a facility type FD (La) indicating that the facility requests call transfer, and a transfer destination number Ntd.
The number N4 corresponding to the information processing device 4 is included as the transfer source number Nts, and the number N3 corresponding to the information processing device 3 is included as the transfer source number Nts. Note that HD(cqr) is a header indicating a recovery request packet.

The packet switch 1-2, which has received the recovery request packet CQr, further transmits a recovery request inter-office packet CQr'' with a similar call switching facility FTa to the packet switch 1-1 (S23). Third
It is received by the packet switch 1-1 by 5TEP 2 in the figure.

Next, according to 5TEP 3 in FIG.
When -1 identifies that the call switching facility FTa is attached to the received recovery request inter-office bucket (CQr), it sends an RNR signal to terminal 2 to notify that it is in a busy state (524), and terminal 2 prevents it from sending packets. Note that the RNR signal is an example of a signal allowed in the protocol of the HDLC procedure, but in other transmission protocols, it is sufficient to output a signal according to the protocol.Subsequently, the packet switch 1-1
transmits the disconnection 61i inter-certificate packet CF' to the packet switch 1-2 (525), and further transmits the packet CF' to the packet switch 1-2.
A disconnection confirmation packet CF is transmitted from the information processing device 2 to the information processing device 3 (S26), and the call to the information processing device 3 is released.

Along with the above operation, the packet switch 1-1 performs 5 in FIG.
At TEP 4, the called inter-station packet CNr' to which the call switching notification facility FD(tb) shown in FIG. 6 is added is transmitted (S25).

The call switching notification facility FTb includes the facility type FD (tb) indicating that it is a call switching notification facility FTb, the number N4 of the information processing device 4 as the transfer destination number Ntd, and the information processing device 3 as the transfer source number Nts. number N3 is included. In addition, HD (cnr)
is a header indicating a packet between called stations.Furthermore, at 5TEP5 in FIG.
C that stores the number N3 of the information processing device 3 as a communication partner connected to the terminal device 2 corresponding research area SD#2 in 27
The contents on the DB (call control table) 28 are changed to the number N4 of the information processing device 4, which is the transfer destination number Ntd included in the call switching facility FTa.

On the other hand, the packet switch 1-3 adds the call switching notification facility FD(tb) attached to the received inter-called packet CNr' to the called packet CNr and transmits it to the information processing device 4 ( 32B). The information processing device 4 that received this packet receives the incoming call acceptance packet CA.
is returned to the packet switch 1-2 (529), and the incoming call receiving inter-office packet CA' is transmitted from the bucket switch 1-2 to the packet switch 1-1 (330).

The above-mentioned incoming call reception inter-office connection) CA' is 5TEP in Figure 3.
At step 6, the packet is received by the packet switch 1-1. Along with this operation, the packet switch l-1 transfers the terminal 2
The busy state set by the 11JR signal is canceled by transmitting an RR multiplied signal indicating that reception is ready (S31). This RR multiplied signal, the R
Like the NR signal, this is an example in the transmission protocol of the HDLC procedure, and is not limited to this.

The above operations enable the terminal device 2 to communicate with the information processing device 4 (332).

As is clear from the above description, according to this embodiment, the information processing device 3 in FIG. 7 can transfer an incoming call from the terminal device 2 to the information processing device 4 without disconnecting the terminal device 2. Can be done. In this case, in this embodiment, the packet transmission control protocol is explained as being in accordance with CCITT Recommendation X, 28, but the present invention is not limited to this. That is, at least information representing call switching (transfer request information) and transfer destination number (transfer destination designation information) can be inserted into the recovery request packet, and at least call switching notification information (transfer notification information) can be inserted into the incoming call packet. Any transmission protocol that can insert a transfer source number (transfer source designation information) is applicable. Further, as described above, during the call transfer control operation of the packet switch 1-1,
The RNR signal and RR double signal used to regulate packets from terminal W2 follow the transmission protocol of the HDLC procedure, but similar signals are usually prepared for other transmission procedures as well. , it is possible to easily apply the present invention.

〔Effect of the invention〕

According to the present invention, it is possible to transfer a virtual call and switch the communication partner without disconnecting the logical link related to the terminal currently communicating. Efficient call transfer control can be realized without being aware of the change, and communication can be continued with the changed terminal.

In this case, in particular, while the packet switching network is performing call transfer control, it restricts input to the terminal that continues communication, and releases the restriction after the transfer control is completed, so that the terminal can receive packet data during the transfer control. It is possible to prevent the data from being destroyed by outputting the .

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the present invention, Fig. 2 is a configuration diagram of a packet switch, Fig. 3 is an operation flowchart of this embodiment, and Fig. 4 shows the transfer control process of this embodiment. 5 is a configuration diagram of a recovery request packet according to this embodiment. FIG. 6 is a configuration diagram of a packet between called stations according to this embodiment. FIG. 7 is an overall configuration diagram of a packet switching network. FIG. 8 is a diagram showing the transfer control process in the conventional example, and FIG. 9 is a diagram showing the transfer control process in the conventional example.
FIG. 2 is a configuration diagram of a D message. 8.. 9.. 10.. 11.. I2.. 13.. 14.. 15.. 16.. 17.. 18.. 19.. 20.. 21.. 22.. 23.. 1 terminal, ・Second terminal, ・Packet switching network, ・Storage means, ・Correspondence between the first terminal and second terminal, ・Recovery request packet, ・Transfer request information, ・Transfer destination designation information, ・Correspondence between the first terminal and the transfer destination terminal, - Transfer destination terminal, - Disconnection confirmation packet, - Incoming call instruction packet, - Transfer notification information, - Transfer source specification information, - Input restriction, - Restriction release,

Claims (1)

[Claims] 1) A virtual call, which is a call from the first or second terminal (8, 9), causes the packet switching network (10) to store the data on the storage means (11) it has internally. 1 and a second terminal (8, 9) are associated with each other (12), a logical link is formed between the two terminals, and packet communication is performed. Call recovery request packet (1
3) with the call transfer request information (14) and transfer destination designation information (15) added to the packet switching network (10), and the packet switching network (10) receiving the recovery request packet (13). 10) After confirming the transfer request information (14),
the first and second terminals (8) on the storage means (11);
, 9) to the first terminal (8) and the transfer destination terminal (17) indicated by the transfer destination designation information (15).
) to the mapping (16), and the second terminal (9)
A call transfer control system characterized by transmitting a disconnection confirmation packet (18) to the transfer destination terminal (17) and transferring the call to the transfer destination terminal (17). 2) To transfer the call to the transfer destination terminal, the packet switching network (10) includes the call transfer notification information (20) and transfer source designation information (2) in the call arrival instruction packet (19).
2. The call transfer control system according to claim 1, wherein the call is transferred to the transfer destination terminal (17) with the addition of 1). 3) When the packet switching network (10) receives the recovery request packet (13), the packet switching network (10) restricts the first terminal (8) from inputting packets to the packet switching network (10) (22). ), the call transfer control system according to claim 1 or 2, wherein the restriction is canceled (23) after the call transfer operation to the transfer destination terminal (17) is completed.