JPH06350644A - Call redirection function service system in non-operation of station accommodating called subscriber - Google Patents

Abstract

(57) [Abstract] [Purpose] Regarding the form in which a host and a terminal are connected by a virtual call (partner selection) method in a packet switching network,
It is intended to provide a call redirection (call transfer) function when the receiving subscriber accommodation station and the relay station are in a non-operational state. [Structure] Center station 5 has station data 7 owned by the station,
The redirect address of the sub-host 3 corresponding to the center host 2 is stored, the originating station 4 is provided with the first other-station subscriber redirect address 8, and the transfer station 6 is provided with the second other-station subscriber redirect address 9. The redirect address of the sub-host 3 corresponding to the redirector subscriber 2 is stored as the station 5 data, and it is determined when the call request packet detects that the relay to the destination subscriber accommodation station 5 is impossible,
Alternatively, before the call setup is completed, the call origination terminal 1 is determined at the time of notifying the recovery request packet of the network congestion, and the call redirection is performed to the sub-host 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a call redirection (call transfer) function in a form in which a host and a terminal are connected by a virtual call (partner selection) method in a packet switching network. There are two packet switching network connection modes, a virtual call partner selection (SVC) system and a permanent virtual circulate fixed selection (PVC) system. The terminal is connected.

A host and a terminal are SVCs in a packet switching network.
There is a growing demand for various types of services in the form of connection by the (partner selection method) as in the case of the conventional switching network. Among them, the user needs for using call redirection (call transfer) have increased in recent years. Is coming.

[0003] As the background, "Sunday banking" service support for financial business (usually, the weekday business host and the Sunday banking host often use different hosts depending on effective use of the host),
It is possible to switch from the center host to the sub-host in order to deal with a disaster at the center station.

However, when a call is redirected as a trigger for call redirection specified in CCITT Recommendation X.25, it is a failure of the terminating subscriber, a contract logical channel busy, or a prior application (planned redirection) of the subscriber. Even if the network including the center station is normal, call redirection is possible with the above trigger, but at the time of disaster of the center station (destination subscriber accommodation station) and relay station in the network, call redirection is not performed to the sub host, so connection is made. It is necessary to prevent deterioration of serviceability and serviceability.

[0005]

2. Description of the Related Art FIG. 6 shows an example of a conventional call redirection trigger connection configuration. In the figure, (a) shows an example of normal call redirection, and (b) shows an example of call redirection failure when the subscriber is out of service. In the figure, 11 is a calling terminal DTEaaa and 12 is a center host D.
TEbbb, 13 is the sub-host DTEccc, 14 is the source station a,
Reference numeral 15 is a center station b, 16 is a transfer station c, and 17 is station data held by the station b.

In the station data 17 held by the center station b, the subscriber address of the center host bbb is set with the redirect address DTEccc and with the first select, and in the case of normal call redirection FIG. When the line to DTEbbb fails, it is transferred to the sub-host DTEccc, and the call request packet CR (bbb) via the originating station a is converted to the call request packet CR (ccc) at the center station b. The transfer station c converts the incoming call request packet CN (ccc) into the incoming call to the sub-host DTEccc.

From the sub host DTEccc to the transfer station c
The incoming call acceptance packet CA (ccc) is returned to the terminal, the connection completion packet CC (ccc) is returned to the DTEaaa via the originating station a, and the connection between the calling terminal DTEaaa and the sub-host DTEccc is completed. This is the case for normal redirection.

In the case of a line failure to the center host DTEbbb, call redirection when the station data 17 held by the center station b is in a non-operational state due to a disaster or the like, in the case of FIG. 4 (b),
The call request packet CR (bbb) from the calling terminal DTEaaa to the center host DTEbbb is transferred to the transfer station c via the calling station a, and the call request packet CR between the transfer station c and the calling station a. (bbb) is returned, and the restoration request packet CQ / NC due to network congestion is returned from the transfer station c to the transmission station a when the number of relay stages is exceeded.

[0009]

[Problems to be Solved by the Invention] Conventional CCITT Recommendation
The call redirection triggers specified in X.25 are the failure of the terminating subscriber, the contract logical channel busy, and the subscriber's prior application (planned redirection), and it is judged by the subscriber's line status and line usage status. Therefore, there is a problem that connectivity and serviceability are deteriorated.

The present invention provides a service equivalent to the call redirection function at the time when a call request (CR) packet is not notified to the station where the called subscriber is accommodated. The purpose is to prevent deterioration of connectivity and serviceability in the event of a relay station disaster in the network.

[0011]

FIG. 1 is a block diagram showing the principle of the present invention. In the figure, 1 is a calling terminal DTEaaa, 2 is a center host DTEbbb, and 3 is a subhost DTEccc.
4, 4 is a transmitting station a, 5 is a center station b, 6 is a transfer station c,
Reference numeral 7 is station data held by station b, 8 is another station subscriber redirect address held by station a, and 9 is another station subscriber redirect address held by station c.

The station data 7 held by the station b is the redirect address DTEccc corresponding to the center host DTEbbb.
And the presence of the first select (short data CR, CQ, etc.) are stored, and the newly added other station subscriber redirect address 8 of station a corresponds to the redirect address source subscriber DTEbbb as the center station b data. The redirect address DTEccc is stored, and the other station subscriber redirect address 9 held by the station c is the sub host station c.
Redirect address source subscriber DTEbbb as data
It stores the redirect address DTEccc corresponding to.

A call request (C
R) There are the following two conditions as a condition for determining that the packet is not notified, and the means for providing the call redirection function under this condition will be shown below. (1) Judgment is made when a call request (CR) packet detects that the relay to the destination subscriber accommodating station b is impossible, and the call request (CR) packet has exceeded the number of relay stages or the route data has been registered to the called party. If all lines for persons with disabilities are in trouble. (Station b and DTEbbb
Between stations a and b, between stations b and c, and when station data owned by station b cannot be used. (2) Before the call setup is completed for the calling terminal DTEaaa, the cause of disconnection is network congestion (NC In the case where the judgment is made at the time of notifying the restoration request (CQ) packet of (1), and the call is disconnected by the calling subscriber accommodation station a when the call is disconnected due to the factor (1) above.

Here, the maximum number of relay stages exceeds the maximum number of relay stages of a packet in the network in order to prevent packet stray in the network, and the number of relay stages is the maximum number except the packet originating subscriber accommodation station a. When the station (c) which is (3) is not the receiving subscriber accommodation station (b), the packet cannot be relayed. (Set the maximum number of relay stages to 3)

[0015]

Therefore, the network configuration of (1) when relay is not possible and call redirection is performed is that the station a and the station c are provided with the direct addresses 8 and 9 of the subscribers of other stations and the redirect address corresponding to the subscriber DTEbbb of the redirector is provided. D
Refer to TEccc and perform call transfer in case of failure.

Further, the network configuration at the time of executing call redirection when the network congestion (NC) recovery request (CQ) is received due to the disconnection of (2) is such that the redirect source subscriber uses the direct address 8 of the other station subscriber of the station a. Referring to the redirect address DTEccc corresponding to DTEbbb,
Perform call forwarding in case of failure.

A sequence diagram in the above two cases is shown in FIG. Figure (a) shows the case of call redirection when relay is not possible and figure (b) shows the cause of disconnection is network congestion (NC).
Shows a case where call redirection is performed when the recovery request (CQ) packet is received.

In the case of performing call redirection without relaying as shown in FIG. 3A, a call request packet CR (bbb) is called from the DTEaaa to the calling station a. Calling request packet C from source station a to transfer station c
Transfer R (bbb). If the transfer station c determines that the call is not directed to the subscriber accommodated in itself, the call request packet CR (bbb) is sent to the call station a.
Will be returned. Call request packet CR between the calling station a and the transfer station c
If the exchange of (bbb) reaches the maximum number of relay stages of 3, it is determined that relay is not possible, the other station subscriber redirect address 9 of the transfer station c is referred to, and the direct address DTE corresponding to DTEbbb is referenced.
ccc is extracted, and incoming packet CN (c
cc) is connected. Incoming call acceptance packet CA (c) from DTEccc to station c
cc) is returned, and station c is relayed from station c to calling terminal DTE
By transferring the connection completion packet CC (ccc) to aaa, the calling process can be executed.

When call redirection is performed due to network congestion shown in FIG. 2B: A call request packet CR (bbb) is called from the DTEaaa to the calling station a. Calling request packet C from source station a to transfer station c
Transfer R (bbb). If the transfer station c determines that the call is not directed to the subscriber accommodated in itself, the call request packet CR (bbb) is sent to the call station a.
Will be returned. The call request packet CR (bbb) is again transferred from the caller station a to the transfer station c, and if it is judged that the network congestion occurs, the transfer station c sends to the caller station a a recovery packet CQ / N due to the network congestion.
C is returned, the calling station a refers to the subscriber redirect address 8 of another station, extracts the direct address DTEccc corresponding to DTEbbb, and sends a call request packet C to the station c.
R (ccc) is called, and an incoming packet CN (ccc) is connected from station c to DTEccc. Incoming call acceptance packet CA (c) from DTEccc to station c
cc) is returned, and station c is relayed from station c to calling terminal DTE
By transferring the connection completion packet CC (ccc) to aaa, the calling process can be executed.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a processing flow chart of a packet switch according to the present invention is shown in FIGS. FIG. 3 shows a processing flow in the case of performing call redirection without relaying, and FIG. 4 shows a processing flow in the case of performing call redirection at the time of receiving a recovery request for network congestion due to disconnection. Before describing the processing flow of the embodiment, the software block configuration in the packet switch and the network route data will be described with reference to FIG.

As shown in FIG. 5 (a), the software control block structure in the packet switch (PS) is such that the switching control unit performs the process of selecting the destination terminal / station of each packet, and the relay line control unit performs the inter-station control. The subscriber control unit controls communication between the packet switch and the subscriber terminal (provides communication suitable for subscriber data), and the line control unit controls the physical / electrical interface of the line and the link level. Take control.

Further, FIG. 5B shows in-network route data (network table). The figure shows the station selection data between the transfer source station and the transfer destination station. When transmitting packets from the transfer station source station to the transfer destination station, select the relay line for the station of the first selection and select the first selection. If the relay line for the station cannot be transferred, the Hackett is transferred by the relay line for the second selected station. For example, when the packet for the station b is transferred by the station a, the transfer is performed by the relay line for the station b of the first selected station.
When the relay line for the first selected station b cannot be transferred due to a line failure or the like, the transfer is performed on the medium-sized line for the second selected station c.

The processing flow at the time of carrying out call redirection without relaying shown in FIG. 3 is as follows: (1) whether a call request packet is received from the trunk line control unit,
When the call request packet is received from the subscriber control unit, the exchange control unit checks whether the destination address of the call request packet is a subscriber accommodated in another station, and if it is a subscriber accommodated in another station, the subscriber control unit issues a call. Perform call processing. (2) If the subscriber is not a subscriber accommodated in another station, it is checked whether the number of relay stages of the call request packet is the maximum stage number, and if it is the maximum stage number, it is detected that the relay is impossible. (7) (3) If it is not the maximum number of stages, 0 is set to the number of relay stages from the subscriber control unit, and 1 is added to the number of relay stages from the trunk line control unit. (4) The transfer station and the routing data are read from the destination address of the call request packet, (5) It is checked whether the first selection line for the accommodating station of the call request packet is normal, and if normal, the subscriber control unit Call processing is carried out in. (6) If the first selection line is not normal, it is checked whether the second selection line for the accommodating station of the call request packet is normal. If it is normal, the subscriber control unit executes the call processing. (7) If the second selected line is not normal, the relay failure is detected. In addition, even when the number of relay stages of the call request packet in (2) is the maximum number of stages, relay failure is detected. (8) If the relay failure is detected, it is checked whether or not the redirect source subscriber of the redirect address data of the other station has the incoming address, and if not, the trunk line control unit or the subscriber control unit performs the call disconnection process. (9) If there is a terminating address, the redirect address is detected from the terminating subscriber address, and (10) 0 is set to the number of relay stages, and the switching control unit executes the calling process.

The processing flow when the call redirection is performed when the disconnection cause in FIG.
(11) If the switching control unit responds to the call request (recovery request at the time of network congestion), the subscriber control unit checks whether the cause of disconnection of the recovery request is other than network congestion. ,
The line control unit sends a recovery request packet (disconnection-caused network congestion). (12) If network congestion is the cause, check whether there is an incoming address for the redirect source subscriber of the redirect address data of other station, and check if there is an incoming address. If there is no address, the line control unit sends a recovery request packet (disconnection-caused network congestion). (13) If there is an incoming address, the redirect address is read from the incoming subscriber address, and the switching control unit executes the calling process. To do.

The parts (8) to (10) of the exchange control unit in the process flow of FIG. 3 and the subscriber control units (11) to (13) in the process flow of FIG. 4 are added in the present invention. It is a part.

[0026]

EFFECTS OF THE INVENTION According to the present invention, the call redirection trigger is defined by CCITT Recommendation X.25, the failure of the called subscriber, the contract logical channel busy, and the called subscriber accommodation station of the subscriber's advance application (planned redirection). In addition, the call request (CR) packet cannot be relayed, or the cause of disconnection is the network congestion (NC) recovery request (C) before the call setup is completed.
Q) By adding the packet notification time, even if the subscriber accommodation station and the relay station are station disasters or maintenance, the calling subscriber can be provided with a call redirection function without being aware of it and connectable terminals. Incoming calls to the (host) become possible, and deterioration of connectivity and serviceability in the network can be prevented.

[Brief description of drawings]

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

FIG. 2 is a sequence diagram of the present invention.

FIG. 3 is a processing flowchart of the embodiment (No. 1)

FIG. 4 is a processing flowchart of the embodiment (part 2).

[Fig. 5] Software control block configuration and network route data

FIG. 6 is a connection configuration diagram of a conventional example.

[Explanation of symbols]

 1,11 Calling terminal 2,12 Center host 3,13 Sub host 4,14 Originating station 5,15 Center station 6,16 Transfer station 7,17 Station data held by station 8 1st other station subscriber redirect address 9th 2 other station subscriber redirect address

Claims (2)

[Claims] 1. A calling terminal (1) and a center host (2)
In a packet switch in a mode in which a sub-host (3) and a sub-host (3) are connected by a virtual call (partner selection) method, a center station (5) accommodating the host (2) has station-owned station data (7), The redirect address of the sub-host (3) corresponding to the center host (2) is stored in the station data (7), the first other-station subscriber redirect address (8) and the transfer station (6) are stored in the calling station (4). ) Is provided with a second other-station subscriber redirect address (9), and the other-station subscriber redirect addresses (8) and (9) correspond to the redirect-source subscriber (2) as center station (5) data. The redirect address of the sub-host (3) is stored, and it is judged when the call request packet detects that the call cannot be relayed to the destination subscriber accommodation station (5), and the call redirection to the sub-host (3) is performed. Call redirection function providing method when incoming subscriber accommodation station non operational and performing. 2. The calling station (4) according to the first aspect, wherein
The other station subscriber redirect address (8) is provided, and the other station subscriber redirect address (8) is provided with the redirect address of the sub-host (3) corresponding to the redirect source subscriber (2) as the center station (5) data. The call redirection is stored in the sub-host (3), which is stored in the sub-host (3) before the call setup (1) is completed and before the call setup is completed. The method of providing the call redirection function when the receiving subscriber accommodation station described in 1 is not operating.