Unit and method for duplex call control for SVC connection

Details Unit and method for duplex call control for SVC connection Unit and method for duplex call control for SVC connection

2000-01-06

2003-07-22

Vincent, David (Department: 2732)

Multiplex communications

Fault recovery

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

C370S250000

Reexamination Certificate

active

06597657

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a unit and a method for duplex call control for SVC (Switched Virtual Channel) connection, which is implemented as an ATM switch, an ATM subscriber line concentrator, etc. having duplex composition composed of an operating (working) system and a standby (protection) system.
Description of the Prior Art
In ATM (Asynchronous Transfer Mode) networks, three protocols are used as control protocols for establishing/releasing SVC (Switched Virtual Channel) connection. The first is a protocol according to ITU-T Q.2110 (hereafter, referred to as “SSCOP (Service Specific Connection Oriented Protocol)”). The second is a protocol according to ITU-T Q.2130 (hereafter, referred to as “SSCF (Service Specific Coordination Function)”). The third is a protocol for the signaling layer, according to ITU-T Q.2931, ITU-T Q.2971, ATM Forum Technical Committee UNI (User-Network Interface) Specification Version 3.1 (hereafter, referred to as “UNI3.1”), or ATM Forum Technical Committee ATM UNI Signaling Specification Version 4.0 (hereafter, referred to as “UNI4.0”). Each of the four standard specifications (ITU-T Q.2931, ITU-T Q.2971, UNI3.1, UNI4.0) for the signaling layer is hereafter referred to as “UNI signaling”.
FIG. 1
is a block diagram showing an example of the composition of a conventional duplex call control unit. The conventional duplex call control unit shown in
FIG. 1
is composed of an operating (working) system (including an ATM switch section
100
a
and a call control section
101
a
), a standby (protection) system (including an ATM switch section
100
b
and a call control section
101
b
), and line interface sections
102
a
,
102
b
, . . . ,
102
n
. The operating system ATM switch section
100
a
and the standby system ATM switch section
100
b
are connected to the line interface sections
102
a
,
102
b
, . . . ,
102
n
via buses
151
a
,
151
b
,
150
,
154
a
,
154
b
, . . . ,
154
n
. The standby system ATM switch section
100
b
can not receive ATM cells from the line interface sections
102
a
,
102
b
, . . . ,
102
n
via the buses
151
b
,
150
,
154
a
,
154
b
, . . . ,
154
n
until a switch-over from the operating system ATM switch section
100
a
occurs. The operating system ATM switch section
100
a
is connected to the operating system call control section
101
a
via a bus
152
a
, and the standby system ATM switch section
100
b
is connected to the standby system call control section
101
b
via a bus
152
b
. The operating system call control section
101
a
and the standby system call control section
101
b
are connected together via a bus
153
. The line interface sections
102
a
,
102
b
, . . . ,
102
n
transmit and receive ATM cells to/from ATM networks or subscriber terminals via ATM lines
155
a
,
155
b
, . . . ,
155
n
, respectively.
The operating system ATM switch section
100
a
receives ATM cells via the bus
151
a
, extracts call control cells for SVC connection (VPI=0, VCI=5) from the ATM cells, and sends the extracted call control cells to the operating system call control section
101
a
via the bus
152
a
. The operating system call control section
101
a
which received the call control cells executes call control according to the call control cells. In the call control, the operating system call control section
101
a
communicates UNI signaling messages of the signaling layer by use of the call control cells. The operating system call control section
101
a
first receives a UNI signaling message “SETUP” and transmits the UNI signaling message “SETUP” to the destination of the SVC connection. When a UNI signaling message “CONNECT” from the destination arrived, the operating system call control section
101
a
sets SVC connection information (as the result of the call control) to the operating system ATM switch section
100
a
, and thereby establishes the SVC connection. The operating system call control section
101
a
sends the SVC connection information of the established SVC connection only, to the standby system call control section
101
b
via the bus
153
. The standby system call control section
101
b
which received the SVC connection information sets the same SVC connection information to the standby system ATM switch section
100
b
and thereby establishes the same SVC connection (as the SVC connection which has been set to the operating system ATM switch section
100
a
) to the standby system ATM switch section
100
b
. When failure or maintenance occurred to the operating system ATM switch section
100
a
or the operating system call control section
101
a
, the bus
151
a
for connecting the operating system ATM switch section
100
a
and the bus
150
is disabled and the bus
151
b
for connecting the standby system ATM switch section
100
b
and the bus
150
is enabled, thereby the reception and transmission of ATM cells are thereafter executed by the standby system ATM switch section
100
b
. Thereafter, the standby system call control section
101
b
executes the call control.
However, in the conventional duplex call control unit which has been explained above, SSCOP link connections are necessitated to be disconnected when the switch-over from the operating system to the standby system is executed. Information concerning the SSCOP layer which is being operated is not communicated between the operating system call control section
101
a
and the standby system call control section
101
b
, therefore, mismatch of the SSCOP layer status occurs between the operating system call control section
101
a
and the standby system call control section
101
b
. Therefore, the SSCOP layer status of the standby system call control section
101
b
on the switch-over becomes different from peer protocol, that is, mismatch of the SSCOP layer status occurs between the standby system call control section
101
b
and an adjacent ATM switch or a subscriber terminal which has been linked with the operating system call control section
101
a
, and thus the SSCOP link connections are necessitated to be disconnected on the switch-over.
Due to the disconnection of the SSCOP link connections, some of signaling messages which should be communicated via the SSCOP link connections are missed or lost, and thereby a call during establishment/release of the SVC connection is necessitated to be interrupted.
SUMMARY OF THE INVENTION
It is therefore the primary object of the present invention to provide a duplex call control unit and a duplex call control method for SVC connection by which the disconnection of the SSCOP link connections on the switch-over from the operating system to the standby system is eliminated, information concerning established SVC connection can be held on the switch-over, and call control for a call during SVC connection establishment/release can also be continued and executed normally on the switch-over.
In accordance with a first aspect of the present invention, there is provided a duplex call control unit comprising a first ATM switch section, a second ATM switch section, a first call control section, a second call control section, a call control parameter database section, a control section, a first switch-over section and a second switch-over section. The first ATM switch section for switching ATM cells extracts call control cells for establishment/release of SVC connection from ATM cells which are supplied via ATM lines, and when call control cells as response are supplied thereto, inserts the call control cells in proper ATM cells and outputs the ATM cells including the call control cells so as to be transmitted to proper ATM lines. The second ATM switch section also executes the above operations of the ATM switch section similarly to the first ATM switch section. The first call control section receives call control cells which has been extracted by the first ATM switch section or the second ATM switch section, outputs call control cells as response to the first ATM switch section or the second ATM switch section, and when call control for an S

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