Automatic switching system

Details Automatic switching system Automatic switching system

1998-02-03

2001-06-26

Ton, Dang (Department: 2661)

Multiplex communications

Fault recovery

Bypass an inoperative switch or inoperative element of a...

C370S228000, C340S870030

Reexamination Certificate

active

06252846

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automatic switching system forming a communication network as a switching node, and more specifically to the automatic switching system having a redundant system configuration in order to improve a reliability of the communication network.
2. Description of the Related Art
As an automatic switching system having a redundant system configuration in order to improve a reliability of the communication network, which is composed of a plurality of automatic switching systems as switching nodes and inter connected by transmission lines to each other, there are known ones such as disclosed in Japanese Patent Laid-open Nos. Sho 63-276952 and Hei 5-244225, for example as the conventional technology.
FIG. 6
is a block diagram schematically showing a switching system disclosed in Japanese Patent Laid-open No. Sho 63-276952. As illustrated, a switching system
800
generally comprises a switching network
801
, a current-system control section (ACT)
802
and an auxiliary-system control section (STAND-BY)
803
.
The ACT system control section
802
comprises an ACT system central controller
811
connected to the switching network
801
through a signal line
831
, an ACT copy controller
812
connected to the ACT system central controller
811
through a signal line
832
and an ACT memory
813
connected to the ACT copy controller
812
through a signal line
833
. On the other hand, the STAND-BY system control section
803
comprises a STAND-BY central controller
821
connected to the switching network
801
through a signal line
841
, a STAND-BY copy controller
822
connected to the STAND-BY central controller
821
through a signal line
842
and a STAND-BY memory
823
connected to the STAND-BY copy controller
822
through a signal line
843
.
As described above, in this switching system
800
, the switching network
801
is separated from the control sections
802
,
803
, and the control sections
802
,
803
are forming a redundant configuration which provides a back up operation for each other in case of one section having a faulty condition. Then, a bus
851
is extended between the ACT central controller
811
and the STAND-BY central controller
821
, and a bus
852
also is extended between the ACT copy controller
812
and the STAND-BY copy controller
822
, whereby data to be written in the STAND-BY memory
823
is passing from the ACT central controller
811
through the bus
851
, the STAND-BY central controller
821
, the signal line
842
, the STAND-BY copy controller
822
and the signal line
843
when a bus trouble occurs between the ACT copy control apparatus
812
and the STAND-BY copy controller
822
, for example. Thus, there can be improved reliability against the bus trouble.
FIG. 7
is a block diagram schematically showing a communication system disclosed in Japanese Patent Laid-open No. Hei 5-244225, and illustrates connection relationships of its internal processing blocks. As illustrated, a communication system
900
generally comprises a current-system communication controller (ACT)
901
, an auxiliary-system communication controller (STAND-BY)
902
and a selector
903
, in which the communication controllers
901
,
902
for processing data communication control in accordance with a predetermined communication protocol are redundantly provided as the ACT system and the STAND-By system.
The ACT communication controller
901
comprises an ACT read/write control unit
911
and an ACT protocol processing section
912
connected to the ACT read/write control unit
911
through a signal line
951
. Further, the ACT protocol processing section
912
comprises a processor
921
connected to a bus
950
through a signal line
952
and a memory
923
connected to the bus
950
through a signal line
953
. Similarly, the STAND-BY communication controller
902
comprises a STAND-BY read/write control unit
931
and a STAND-BY protocol processing unit
932
connected to the STAND-BY read/write control UNIT
931
through a signal line
961
. Further, the STAND-BY protocol processing section
932
comprises a processor
941
connected to a bus
960
through a signal line
962
and a memory
942
connected to the bus
960
through a signal line
963
. Then, the ACT read/write control unit
911
and the STAND-BY read/write control unit
931
are connected to each other by means of a state information transfer bus
970
.
The ACT read/write control unit
911
reads out state information of layer
2
, which is necessary to the minimum to continue a layer
2
(data link layer) processing, from a memory
922
provided in the ACT protocol processing section
912
through the signal line
951
, the bus
950
and the signal line
953
, and transfers this state information of layer
2
from a state information transfer bus
970
to the STAND-BY read/write control unit
931
. The STAND-BY read/write control unit
931
writes the state information of layer
2
transferred through the state information transfer bus
970
in a memory
942
provided in the STAND-BY protocol processing unit
932
through the signal line
961
, the bus
960
and the signal line
963
.
The ACT communication protocol processing section
912
and the STAND-BY communication protocol processing section
932
are adapted to carry out a data communication control in accordance with a procedure of an HDLC (High level Data Link Control Procedure) as an example of a communication protocol. The selector
903
selects any one set of a reception line
971
and a transmission line
972
of the ACT communication controller
901
and a reception line
973
and a transmission line
974
of the STAND-BY communication controller
902
, and connects the selected set to an external reception line
975
and an external transmission line
976
.
FIG. 8
is a diagram used to explain the procedure in which the communication system
900
is operated, and illustrates a processing procedure executed when the redundant system (ACT and STAND-BY) is switched over in response to a command entered by an operator or the like. Assuming that there occurs a system switching factor at a timing shown by an open arrow X in the figure, then the ACT communication controller
901
, which has so far received a frame signal F from a communicated party, transmits a communication restriction frame signal RNR instructing a pause of a frame transmission to the communicated party, thereby controlling a data transmission of the communicated party (see
{circle around (1+L )} in FIG. 8).
Subsequently, the communication system executes a reception processing of the frame signal F which has been so far transmitted until the communicated party receives the frame signal RNR (see
{circle around (2+L )} in FIG. 8). Then, the ACT read/write control unit 911 transmits state information SS read out from the memory 922 to the STAND-BY read/write control unit 931 (see
{circle around (3+L )} in FIG. 8). After that, the STAND-BY read/write control unit 931 writes the received state information SS in the memory 942. Thus, the protocol processing states in the ACT protocol processing section 912 and the STAND-BY protocol processing section 932 become equivalent so that the STAND-BY protocol processing section 932 becomes able to continue the layer 2 processing.
Then, by exchanging a control signal CC between the ACT system and the STAND-BY system, the system is switched over (see
{circle around (4+L )} in FIG. 8), and a communication is resumed by using the STAND-BY communication controller 902 as a new ACT communication controller. Specifically, the STAND-BY communication controller 902, which became the new ACT communication controller, transmits a communication restriction releasing frame signal RR for instructing a resumption of a frame transmission to the communicated party (see
{circle around (5+L )} in FIG. 8), and receives the frame signal F continuously transmitted from the communicated party, thereby resuming a communication (see
{circle around (6+L )} in FI

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