Telephonic communications – Diagnostic testing – malfunction indication – or electrical... – Of centralized switching system
Reexamination Certificate
2000-10-19
2002-10-15
Kuntz, Curtis (Department: 2643)
Telephonic communications
Diagnostic testing, malfunction indication, or electrical...
Of centralized switching system
C379S012000, C379S014000, C379S016000, C379S032020, C379S112040, C379S112090
Reexamination Certificate
active
06466648
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a repetitive call control method, a switch using the method, and a recording medium storing repetitive call control program. More particularly, the present invention is concerned with detection and control of a repetitive call that occurs in a network including a switch.
2. Description of the Related Art
Recently, a switch network is constructed by mutual connections of common carriers. Each switch station included in the switch network performs setting of an outgoing path for determining a route through which a call passes. All switch stations in the switch network should be synchronized with each other with regard to the setting of outgoing paths.
In order to change the route through which the call passes, all the switch stations of different carriers are required to concurrently change the setting of outgoing paths. If the concurrent change does not take place, an asynchronous situation will occur in which the setting of outgoing paths does not match among the switch stations. When a bypass route is used to transmit the call, a complex procedure for setting of call outgoing paths must be performed in the switch stations of the carriers. Thus, there is a possibility that an error in setting of outgoing paths may occur. An error in setting of an outgoing path may cases a repetitive call in which a call occupies channels in an identical channel group in the switch network.
FIG. 1
is a diagram illustrating a mechanism of occurrence of a repetitive call. There is an error in setting of an outgoing path (channel) in a station (B)
14
. The station
14
erroneously sets a channel “be” with respect to a call directed to a station (C)
16
and initiated by a station (A)
12
. When a calling subscriber
10
calls a destination subscriber
22
, the station
14
erroneously sets the channel “be” although originally the station
14
should set an outgoing channel “bc”. A station (E)
20
determines that the call should be addressed to the station
16
, and sets an outgoing channel “eb”.
Thus, a group of channels “be” and “eb” are constantly used by a repetitive call, so that a congestion of channels “be” and “eb” occurs. If a station (D)
18
is available as a bypass route in a case where the channel “eb” is congested, channels “ed” and “db” will be congested by a repetitive call.
If an error in the setting of a bypass route, a repetitive call may occur in the switch network.
FIG. 2
shows another example of occurrence of a repetitive call. Referring to
FIG. 2
, it is assumed that a first outgoing channel for a call from the station
14
to the station
16
is “bc”, a second outgoing channel is “be” and that a first outgoing channel for a call from the station
20
to the station
16
is “ec” and a second outgoing channel is “eb”.
If the channels “bc” and “ec” are congested, the stations
14
and
20
will set the second outgoing channels as those for forming bypass routes. If the station
14
initiates a call directed to the station
16
, a group of channels “be” and “eb” is constantly used by a repetitive call until the channels “bc” and “ec” are recovered from the congested states. Thus, the channels “be” and “eb” will be congested.
FIGS. 3A and 3B
show a conventional method for resolving the problem of the repetitive call. A switch network shown in
FIG. 3A
includes a table shown in FIG.
3
B. For example, the station
14
is equipped with the table shown in FIG.
3
B. The table describes information indicating whether an outgoing channel is allowed to be connected to an incoming channel via which a call is transferred.
In a case where channel “eb” is an incoming channel of the station
14
and “be” is an outgoing channel thereof, the station
14
prevents the call from the channel “eb” to be output to the channel “be” again.
FIGS. 4A and 4B
show another conventional method for resolving the problem of the repetitive call. The station
14
in a network shown in
FIG. 4A
is equipped with a table shown in FIG.
4
B. The table shown in
FIG. 4B
describes information the ratio of occupation in an outgoing channel for each call type.
If the type of a call over incoming channel “ab” to the station
14
differs from that of a call over incoming channel “eb”, outgoing channel “be” is not occupied by one of the two incoming channels “ab” and “eb” even if a repetitive call occurs. Thus, even in a case where a loop is formed between the stations
14
and
20
, a group of the channels “be” and “eb
2
” is not occupied by the repetitive call, so that the channels “be” and “eb” can be prevented from being congested.
However, the methods for controlling the repetitive call shown in
FIGS. 3A
,
3
B and
FIGS. 4A and 4B
are not capable of detecting occurrence of a repetitive call in real time. That is, the maintenance person predicts occurrence of a repetitive call and takes measures against occurrence of a repetitive call and spreading of an unwanted situation. In practice, it is very difficult to seize a situation of occurrence of a repetitive call and look into a cause thereof.
More particularly, the repetitive call controlling method shown in
FIGS. 3A and 3B
does not cope with a repetitive call coming from a channel which is not registered in the table shown in FIG.
3
B. If information indicating whether a connection should be made is registered with respect to all incoming and outgoing channels, the switch stations will be needed to have increased inner resources such as a CPU and a memory. In addition, it is required to process a huge amount of data for setting outgoing channels so that maintenance cannot be performed reliably.
The repetitive call controlling method as shown in
FIGS. 4A and 4B
determines the ratio of occupation for each call type in advance. Thus, the method does not have wide applicability to various networks and does not utilize the channels efficiently.
As yet another means for controlling repetitive calls, it may be possible to integrally manage information concerning setting of outgoing channels and the current situation in real time. An intelligent network is equipped with means as described above. However, the means does not acknowledge, as a problem, a repetitive call resulting from a situation in which the setting of a bypass route is erroneously set, as shown in
FIG. 2
because information itself concerning setting of an outgoing channel does not have any problem.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide a repetitive call control method and a switch using the method.
A more specific object of the present invention is to provide a repetitive all control method and a switch using the method capable of automatically detecting and imposing a restriction on a repetitive call and preventing occurrence of a congested situation.
The above objects of the present invention are achieved by a switch comprises: a repetitive call detection unit which detects a repetitive call which occupies channels in an identical channel group; a release unit which releases the channels occupied by the repetitive call when the repetitive call is detected; a restriction unit which stores information concerning the repetitive call and imposes a restriction on a connection of a call having information identical to the information concerning the repetitive call; a test unit which determines whether a cause of the repetitive call has been removed; and a restriction release unit which releases the above restriction in accordance with a result of determination by the test unit.
The above objects of the present invention are also achieved by a method comprising the steps of: detecting a repetitive call which occupies channels in an identical channel group; releasing the channels occupied by the repetitive call when the repetitive call is detected; storing information concerning the repetitive call and imposing a restriction on a connection of a call having information identical to the information concerning the repetitive call; determining whether a cause of t
Honma Masaharu
Honma Masayuki
Ikeno Yasunori
Kobayashi Toshi-aki
Satoh Katsuhisa
Fujitsu Limited
Honma Masaharu
Katten Muchin Zavis & Rosenman
Kuntz Curtis
Tran Quoc D.
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