Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1997-05-09
2002-03-19
Rao, Seema S. (Department: 2738)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S217000, C370S389000, C370S524000, C370S469000, C370S410000
Reexamination Certificate
active
06359909
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to switch devices, and more particularly to a switch device of a communication system which provides services of relaying cells or packets on demand.
A switch device of this type provides an on-demand cell relay service or a switched virtual call service (SVC service) which is an on-demand frame relay service.
In the SVC service, a call set-up/release process is carried out between a calling terminal and a called terminal by a pre-event/post-event signaling control according to a layer-
3
communication protocol. In this case, there is no problem when the call set-up/release process is normally performed. If a fault occurs in a user terminal, a line (channel) or a switch device, the call process will no longer controlled and managed normally, and an incompatibility of the state of the call will occur between the user terminal and the switch device. It is thus desired that a switch device be provided which can easily release the incompatibility of the call state.
2. Description of the Related Art
FIG. 1
is a block diagram of a conventional ATM (Asynchronous Transfer Mode) switch system, which includes user terminals
1
a
and
1
b
, line (channel) termination equipments
2
a
and
2
b
, an ATM switch (ATMSW)
3
, a signaling controller
4
which terminates a signaling link, and a main controller
5
. An ATM switch device includes the line termination devices
2
a
and
2
b
, the signaling controller
4
and the main controller
5
.
The user terminals
1
a
and
1
b
and the ATM switch device are coupled together via physical links, via which logical data paths are set and released between the user terminals
1
a
and
1
b
and the ATM switch device. The setting and releasing of the data paths are carried out by a signaling control using the signaling links. The signaling control is realized by providing the ATM switch device and the user terminals
1
a
and
1
b
with a layer-
3
communication control function which conforms with respective specific layer-
3
communication protocols.
The main controller
5
includes a processor part CC, and a main memory part MM. The processor part CC has a main function of realizing various communication services. The main memory part MM stores various pieces of data for controlling. The processor part CC includes a layer-
3
communication controller
6
. The main memory part MM includes a connection management table, a subscriber (user) data table, a line termination equipment information (identification number) table, and a call process management table.
The subscriber data table includes, for each subscriber, the telephone number and information concerning various communication services. The line termination equipment information table includes translation information used to obtain a number of the related line termination equipment
2
from a number SN of the signaling controller
4
and a port number PN of the corresponding signaling link. The translation information is generated by a command when a user terminal request the SVC service, and is stored in the line termination equipment information table. Further, the translation information is sent to the signaling controller
4
when it is generated, and is stored in a memory (not shown) therein.
When the SVC service is presented, the information concerning the connection used as a signaling link is presented in the same manner as the translation information, and the connection for the signaling link is supplied between the user terminal and the ATM switch device. The connection information for the signaling link is managed by specific data so that it can be searched for by the signaling controller number SN and the part number PN.
The information concerning a connection (data path) used in the SVC service is managed, for each service application, using the connection management table of the layer-
3
communication controller
6
. The service application includes a permanent virtual circuit (PVC) and a switched virtual call (SVC). When an inquiry request for the connection information is generated within the ATM switch device or from the outside thereof, the request source can be notified of the connection information VPI/VCI for each service application PVC/SVC. The above connection management process can inform the service application PVC/SVC by receiving the connection information VPI/VCI.
With the above structure, when a data path is set between the user terminals on demand, the signaling controller
4
of the ATM switch device receives information concerning a signaling related to the SVC service and sent by the user terminal. The received information is modified so that the signaling controller number SN and the port number PN which terminates the signaling link are added thereto, and is sent to the layer-
3
communication controller
6
.
The layer-
3
communication controller
6
searches the line termination equipment table by referring to the signaling controller number SN and the part number PN, and obtains the corresponding line termination equipment number CN presented to the subscribers, and refers to the subscriber data table by using the obtained line termination equipment number CN. Then, the controller
6
obtains subscriber data of the subscriber accommodated in the ATM switch device, and controls the SVC service according to the subscriber information in the subscriber data.
However, the above conventional scheme has the following disadvantages. There is a possibility that a fault may occur in the ATM switch device while the service is provided. Examples of such a fault are faults occurring the line, the signaling link, the signaling controller
4
, the ATM switch, the processor part CC/main memory part MM (which may require a restart of the ATM switch), and a controller which specifically deals with the protocol such as the layer-
3
communication controller. If a fault as described above occurs, a communication between the ATM switch device and the user terminal will be interrupted. Even if the fault is removed and the system restarts, the control of the correct SVC service will not be ensured. If a fault which does not ensure the restarting or the call process in a defective device occurs in the ATM switch device, the ATM switch device releases the relating call by itself. However, there is no method to ensure that the user terminal will be correctly notified of the call releasing procedure carried out in response to the occurrence of a fault. Hence, there is a possibility that an incompatibility may occur between the call process in the ATM switch device and the call process in the user terminal. Such a situation may occur if a fault occurs in the user terminals.
SUMMARY OF THE INVENTION
It is a general object of the present invention to eliminate the above disadvantages.
A more specific object of the present invention is to provide a switch device which efficiently eliminate an incompatibility regarding the call process which occurs between the user terminals and the switch device.
The above objects of the present invention are achieved by a switch device in a communication system in which a relay service of a cell or packet is provided on demand, the switch device comprising: a layer-
3
communication controller which performs a signaling control of a call set-up/release requested by a user terminal in accordance with a layer-
3
communication protocol; and a layer-
3
communication restart controller which can be connected to the user terminal in accordance with the layer-
3
communication protocol and is connected to controllers in the switch device via a given interface. The layer-
3
communication restart controller perform a call release process for a call managed by the layer-
3
communication controller in accordance with a restart request for a call from the user terminal, and requests a call restart process to the user terminal in accordance with a call release process issued in the switch device.
The switch device may be configured so that: the layer-
3
commu
Ito Jun
Moriyama Shigetaka
Ogawa Tomomi
Fujitsu Limited
Rao Seema S.
Rosenman & Colin LLP
Tsegaye Saba
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