Multiplex communications – Fault recovery – Bypass an inoperative switch or inoperative element of a...
Reexamination Certificate
1999-11-19
2003-09-16
Vincent, David (Department: 2732)
Multiplex communications
Fault recovery
Bypass an inoperative switch or inoperative element of a...
C370S395300
Reexamination Certificate
active
06621788
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ATM (asynchronous transfer mode) network technology, and in particular, to a dual SVC (switched virtual connection) system for an ATM device.
This application is based on Japanese Patent Application No. Hei 10-330369, the contents of which are incorporated herein by reference.
2. Description of the Related Art
In an ATM device, VPI (virtual path identifier) logically allows establishment of 256 ATM connections per line, and VCI (virtual channel identifier) logically allows establishment of 65536 ATM connections per VPI. The maximum number of SVCs (switched virtual connections) depends on the call processing performance and the storage capacity for the internal resources of the ATM device, and has increased recently as the performance of ATM devices has improved.
While ATM devices, such as ATM switching devices and ATM concentrators, handle a number of connections per line, and provide ATM communication service using a number of lines, various dual SVC systems are implemented in the ATM devices. The conventional dual SVC systems have the problems described below.
FIG. 8
is a diagram showing an ATM device using a conventional dual SVC system, and
FIG. 9
is a diagram showing the sequence operation of the conventional dual SVC system for handling the SVC protocol.
Referring to
FIGS. 8 and 9
, the ATM device
200
which includes the conventional dual SVC system is connected to ATM members
10
and
11
through the SVC connection.
The ATM member
10
is connected to the ATM device
200
through a line
12
, and the ATM member
11
is connected to the ATM device
200
through a line
13
.
The ATM device
200
comprises: line terminating devices
7
and
8
; active and standby switches
201
a
and
201
b;
and an information exchange device
206
between the active system and the standby system. The active and standby switches
201
a
and
201
b
comprise: signaling terminating functions
202
a,
202
b,
204
a,
and
204
b;
call process control functions
203
a
and
203
b;
and internal information management functions
205
a
and
205
b.
The call process control functions
203
a
and
203
b
hold routing setting information in the switches
201
a
and
201
b.
The ATM device
200
using the dual SVC system operates as follows.
SVC signaling information from the line
12
is sent by the line terminating device
6
to the active signaling terminating function
202
a,
and is processed by the active signaling terminating function
202
a
and the active call process function
203
a.
In this process, the signaling terminating function
202
a
and the call processcontrol function
203
a
continuously communicate with the active internal information management function
205
a,
obtain the internal resource information (B in
FIG. 9
) to execute the protocol procedure, and refer to the protocol information (A and A′ in FIG.
9
).
Further, the call process control function
203
a
performs routing in the active switch
201
a
based on the result of the above process, and sends this routing information to the active internal information management function
205
a
as the ATM connection information B.
The active internal information management function
205
a
periodically transmits the internal resource information which is updated when processing the SVC protocol, the SVC connection information (B in FIG.
9
), and the SVC protocol information (A and A′ in
FIG. 9
) to the standby internal information management function
205
b
through the information exchange device
206
as information for executing routing setting procedure.
This information is received by the standby internal information management function
205
b.
The standby signaling terminating function
202
b
and the call process control function
203
b
communicate with the standby internal information management function
205
b
in a manner similar to the active system, to execute the protocol process.
Based on the result of the process, the standby call process control function
203
b
performs routing in the standby switch
201
b.
Thus, the same SVC connection is established in both active and standby systems.
FIG. 10
is a diagram showing the second example of the ATM device using the conventional dual SVC system.
Referring to
FIG. 10
, ATM members
10
and
11
are connected via an ATM device
300
through the SVC connection. The ATM member
10
is connected to the ATM device
300
through a line
12
, and the ATM member
11
is connected to the ATM device
300
through a line
13
.
The ATM device
300
comprises: line terminating devices
7
and
8
; and active and standby switch
301
a
and
301
b.
The active and standby switches
301
a
and
301
b
comprise: signaling terminating functions
302
a,
302
b,
304
a,
and
304
b;
and call process control functions
303
a
and
303
b.
The call process control functions
303
a
and
303
b
hold routing setting information in the switches
301
a
and
301
b.
The ATM device
300
using the conventional dual SVC system operates as follows.
SVC signaling information from the line
12
is sent to both active and standby switches
301
a
and
301
b
by the line terminating device
7
. The signaling information is simultaneously processed by active and standby signaling terminating functions
302
a
and
302
b
and by the call process control functions
303
a
and
303
b.
As the result, the active and standby call process control functions
303
a
and
303
b
simultaneously perform routing in the active and standby switches
301
a
and
301
b.
Thus, the active and standby systems have the same SVC connection information.
However, the first example of the conventional dual SVC system, explained with reference to
FIG. 8
, has the following problems.
The first problem is that, as the number of SVC connections increases, the normal process performance including the call process by the active system is degraded.
The reason for this is that the amount of transferred data is increased because the information periodically exchanged between the active system and the standby system contains the internal resource information, which includes all the SVC connection information of the established and running connections, and the SVC protocol information.
The second reason is that, when the information transfer rate between the active and standby systems is increased, the possibility of inconsistencies in the internal information between the active and standby systems is increased.
The reason for this is that the time lag, between the establishment of the connection in the standby system based on the internal information from the active system and the occurrence of a problem in the active system, is increased, and that the information of the established or released SVC connection may be lost due to the time lag.
The second example of the conventional dual SVC system, explained with reference to
FIG. 10
, has the following problems.
The first problem is that, while, when an accident occurs in one of the two systems, the parts where the accident occurred are exchanged and the recovered system is registered as the standby system, the synchronization in setting between the active systems and the recovered standby system cannot be achieved.
The reason for this is that the information of the ATM connection, which is established or terminated in the time period from the occurrence of the accident to the registration of the recovered standby system, cannot be exchanged between the active and standby systems because the information exchange device is not prepared.
FIG. 11
is a diagram showing the third example of the ATM device
400
using the conventional dual SVC system (disclosed in Japanese Patent Application, First Publication No. Hei 10-084354).
Referring to
FIG. 11
, ATM members
10
and
11
are connected via an ATM device
400
through the SVC connection. The ATM member
10
is connected to the ATM device
400
through a line
12
, and the ATM member
11
is connected to the ATM de
NEC Corporation
Vincent David
Whitham Curtis & Christofferson, PC
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