Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1996-08-06
2001-12-18
Chin, Wellington (Department: 2664)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S426000
Reexamination Certificate
active
06331982
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a connection control system and a method in a switch.
2. Description of the Related Art
Discussions about an ATM (Asynchronous Transfer Mode) switching technique are frequently made as a technique for implementing a broadband ISDN (Integrated Services Digital Network) of a next-generation switching system, in various organizations. An ATM switch exchanges contents of subscriber information (data, voice data, image data, etc.) using a fixed-length packet called a cell. The ATM switch identifies each connection according to a value of a VPI/VCI defined in a header of the cell, and makes the cell self-route to a target output line by adding routing information called a tag corresponding to a connection specified in the input cell at an entry point of the switch. This capability is one of the features of the ATM switching method.
A connection is normally a pair of an upward connection (from a subscriber at a source side to a subscriber at a destination side) and a downward connection (from the subscriber at the destination side to the subscriber at the source side). Therefore, if a connection is established between these two subscribers, an instruction for establishing the connection must be given to line response units at both sides where the subscribers are respectively accommodated. Accordingly, a timing when the subscriber information can be transferred in the upward connection is different from that in the downward connection, and a time for establishing the connection is expected to be longer. Therefore, it is vital to shorten the time for establishing the connection.
In a conventional switching control method, as shown in
FIG. 1
, a central control processor (CC)
101
which controls a call outputs an instruction for establishing a connection corresponding to each of microprocessors (&mgr;ps) in each of line response units
103
at source and destination sides, with an ATM switch
102
in between. Each of the microprocessors in each of the line response units
103
sets connection information for each piece of hardware in each of the line response units. Such hardware details a UPC (Usage Parameter Control) unit, an NPC (Network Parameter Control) unit, an accounting counter unit, a VCC (Virtual Channel Controller) table, etc.
With the conventional technique shown in
FIG. 1
, however, when a CC
101
transmits the instruction of establishing a connection to each of the line response units
103
at the source and destination sides, a process delay until an establishment of the connection becomes extended.
If a result of the process of establishing a connection in either of the line response units
103
is NG, an instruction for releasing the connection must be given to the other of the line response units
103
in which the result of the process of establishing the connection is OK. As a result, control of establishing a connection becomes complicated.
Even if the instruction for establishing the connection is transmitted respectively to the line response units
103
at the source and destination sides, it does not verify a proper exchange of cells between the line response units
103
at the source and destination sides via the ATM switch
102
. Accordingly, the cells may not flow properly when a subscriber starts a communication.
Furthermore, since the line response units
103
at the source and destination sides work both mutually and independently, it is difficult to examine the quality of the overall connection between the line response units
103
at the source and destination sides.
SUMMARY OF THE INVENTION
The present invention is made in order to overcome the above described problems, and aims at implementing a consistent control for line response units both at the source and destination sides, when a connection is established/released.
First of all, the first embodiment of the present invention is described below.
This embodiment assumes a method for controlling a connection for use in a switch where a fixed-length cell including connection identification information input via a first or a second line response unit from a first or a second line is transmitted to the second or the first line as opposed to the first or the second line, via the second or the first line response unit as opposed to the first or the second line response unit, by being self-switched according to routing information added to a header of the cell.
The first or the second line response unit transmits a connection control cell where connection identification information corresponding to a specified connection is set, routing information indicating a route to the second or the first line response unit as opposed to the first or the second line response unit is set in a header, connection control information identifying it as a connection control cell is set in an empty area of the header, and connection information for controlling the specified connection is stored, to a switch.
The second or the first line response unit then extracts the connection control cell which is transmitted from the first or the second line response unit as opposed to the second or the first line response unit, and input from the switch, according to the connection control information.
After that, the first and the second line response unit performs communication of the connection information using the connection control cell.
The above described first embodiment is made more specific by the following second and third embodiments of the present invention.
The second embodiment of the present invention is a mechanism related to a process of establishing a connection, and performs the following operations.
If an instruction for establishing a connection is given by a call control processor, etc., the first line response unit establishes a specified connection in a state where an inflow of subscriber cells corresponding to the specified connection from the first line is halted.
The first line response unit which establishes the specified connection then transmits a connection control cell where connection identification information corresponding to the specified connection is set, routing information indicating a route to the second line response unit as opposed to the first line response unit is set in a header, connection control information identifying it as a connection control cell is set in an empty area of the header, and connection information for establishing the specified connection is stored, to a switch.
Next, the second line response unit extracts the connection control cell which is transmitted from the first line response unit as opposed to the second line response unit and input from the switch, according to the connection control information.
The second line response unit establishes the specified connection according to the connection information included in the extracted connection control cell.
Then, the second line response unit starts an inflow of subscriber cells corresponding to the specified connection from the second line according to the connection information included in the extracted connection control cell.
The second line response unit transmits the connection control cell which includes the connection identification information corresponding to the specified connection, the routing information indicating a route to the first line response unit as opposed to the second line response unit in the header, the connection control information identifying it as the connection control cell in the empty area of the header, and the connection information indicating a result of establishing the specified connection, to the switch.
The first line response unit extracts the connection control cell which is transmitted from the second line response unit as opposed to the first line response unit and input from the switch, according to the connection control information.
Lastly, the first line response unit starts an inflow of subscriber cells corresponding to the specified connection from the first line, according t
Chin Wellington
Fujitsu Limited
Rosenman & Colin LLP
Yao Kwang B.
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