ATM exchange

Details ATM exchange ATM exchange

1997-11-24

2003-02-11

Rao, Seema S (Department: 2661)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C379S209010

Reexamination Certificate

active

06519258

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ATM exchange used in an ATM communications system, and more particularly to an ATM exchange capable of performing camp-on registration.
2. Description of the Related Art
An ATM (Asynchronous Transfer Mode) communications system comprises a network in which a plurality of ATM exchanges are connected by transmission lines, and terminals connected to each ATM exchange.
In a common ATM communications system, a terminal notifies an ATM exchange of the desired band, quality, and other connection requirements when a call connection is requested. The ATM exchange investigates whether or not sources that satisfy these connection requirements can be found, performs the call connection when this can be offered, and notifies this terminal that the connection is denied when this cannot be offered. A terminal whose call request has been accepted performs communication, whereas a terminal that has been notified of a connection refusal repeats its requests for a call connection until it is accepted.
There are also ATM communications systems that use ATM exchanges capable of camp-on request registration. In such ATM communications systems, a terminal that has been notified of a connection refusal can issue a camp-on request, and the ATM exchange that has received the camp-on request monitors an empty band value and grants permission to communicate to the terminal that has issued the camp-on registration when the empty band value exceeds the band value required for the camp-on request.
The structure and operation of a conventional ATM exchange capable of performing camp-on registration will now be described in further detail with reference to FIG.
50
.
As shown in the figure, a conventional ATM exchange
100
comprises a subscriber's line circuit
30
, a switching unit
20
, an output buffer
40
, a control device
200
, and a storage device
300
as its main constituent elements. The subscriber's line circuit
30
is a circuit for providing an interface with terminals T
1
through Tn; the switching unit
20
identifies the addresses from the headers of the cells (fixed-length data that constitute a portion of the communications content) that have been inputted via the subscriber's line circuit
30
, and presents the address to the output buffer
40
. The output buffer
40
temporarily accumulates the cells and sends them out over a transmission line
50
.
The control device
200
monitors the operating condition (empty band value #
0
) of the transmission line
50
and changes the empty band value #
0
in accordance with the used or released band value when a call connection or disconnection occurs. The empty band value #
0
and the required band value are compared with each other and connection receipt management is performed when a call connection has been requested. For example, the requested call is connected and the empty band value #
0
is reduced by #Ti when a call connection requiring a band value #Ti (<#
0
) has been made from a terminal Ti. Meanwhile, a terminal Tj is notified of a refusal to connect when a call connection requiring a band value #Tj (>#
0
) has been made from the terminal Tj.
In addition, when a camp-on request have been issued from a terminal, the control device
200
registers the content thereof in the storage device
300
. Every time a band value is released due to disrupted communication, it is determined whether or not the empty band value #
0
exceeds the band value required for the registered camp-on request, and a call that corresponds to this camp-on request is established on the transmission line
50
when the empty band value #
0
has exceeded the required band value.
As described above, in a conventional ATM exchange it is determined whether or not a connection request has been received based on the empty band value #
0
. The determination as to whether or not permission has been granted with respect to a camp-on request is also performed based on the empty band value #
0
. In a conventional ATM exchange, therefore, when a request is received for a call connection that uses a band below the empty band value after a camp-on request has been registered, a long time is often needed to finally establish a call in accordance with this connection request. For example, a long time is often needed before a camp-on request that requires a substantial band value is executed, as when television images are transmitted.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an ATM exchange in which a permission for a camp-on request is issued in a short time.
The first ATM exchange pertaining to the present invention receives from terminals call connection requests and camp-on requests in which the band values being used are specified, and establishes on a transmission line calls for which the specified band values can be used, wherein this ATM exchange comprises a band value storage unit, a camp-on request storage unit, a connection request response unit, a camp-on request registration unit, a band value setting unit, a band value updating unit, a camp-on request response unit, and a post-processing unit.
The band value storage unit divides the unused band value of the transmission line into a empty band value and temporarily saved band value, and stores them. The camp-on request storage unit stores the contents of camp-on requests issued by each terminal, in correlation with the processing rank of these contents.
The connection request response unit establishes on the transmission line the call requested by a connection request when the connection request received from a terminal is one for which the use of a band value below the empty band value stored in the band value storage unit has been specified, and notifies the terminal of a refusal to connect when the connection request is such that the use of a band value exceeding the empty band value has been specified. In addition, the camp-on request registration unit, upon receipt of a camp-on request from a terminal, establishes the processing rank of this camp-on request and performs registration in the camp-on request storage unit in correlation with the processing rank that identifies the camp-on request data that represent the contents of this camp-on request. The band value setting unit adds the empty band value stored in the band value storage unit to the temporarily saved band values stored in the band value storage unit, and setting zero for the empty band value in the band value storage unit, when the registration of camp-on request data by the camp-on request registration unit is performed with respect to a camp-on request storage unit in which no camp-on request data have been registered.
The band value updating unit adds a band value released by a disconnected call to a temporarily saved band value stored in the band value storage unit when camp-on request data have been registered in the camp-on request storage unit upon detection of the disconnected call in the transmission line. In addition, the band value updating unit adds a band value released by a disconnected call to an empty band value stored in the band value storage unit when no camp-on request data have been registered in the camp-on request storage unit upon detection of a disconnected call in the transmission line.
The camp-on request response unit establishes a call that corresponds to camp-on request data in the transmission line when the temporarily saved band value stored in the band value storage unit exceeds the band value specified for use by the camp-on request data that are stored in the camp-on request storage unit and that are assigned the highest processing rank. The post-processing unit reduces the temporarily saved band value stored in the band value storage unit by the band value used to set up a call when it is set up by the camp-on request response unit, and erases the camp-on request data that is stored in the camp-on request storage unit an

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