Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-10-20
2002-02-12
Hsu, Alpus H. (Department: 2662)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S401000, C370S410000, C370S467000, C370S522000
Reexamination Certificate
active
06347088
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technology for relaying calls on a line where a communication path is established through a cell transmission network by call setting control every time communications are needed.
2. Description of the Related Art
Lately, along with the spread of in-house LANs, etc., a WAN (Wide Area Network) node apparatus for integrating and accommodating conventional telephone audio traffic, low-speed data lines and LAN traffic, and dynamically securing relay bands for LAN traffic with a high burst characteristic, has been demanded.
For a technology for dynamically utilizing a relay band, an ATM (Asynchronous Transfer Mode) multiplex technology for transmitting each set of data after logically multiplexing a plurality of fixed length cells of data, has been examined mainly in a broad band field, and now this ATM multiplex technology has also come to be applied to a narrow band field.
In this case, for trunk lines, existing STM (Synchronous Transfer Mode) dedicated lines are used in which a multiplex access service is available, and a hybrid multiplex technology for transmitting ATM cells to be communicated between nodes using a predetermined one of or a plurality of time division channels of the STM dedicated line is being developed. By adopting such a configuration, an ATM multiplex technology capable of flexibly corresponding to traffic fluctuations and suitable for highly efficient transmissions, and a TDM (Time Division Multiplex) technology capable of guaranteeing transmission line quality, can be united.
In such a technological background, today an ATM-WAN node apparatus capable of terminating ATM dedicated lines or STM dedicated lines in which a multiplex access service is available, is being increasingly demanded.
Accordingly, a technology for relaying calls (SVC call: Switched Virtual Circuit call) on in-house lines where a communication path is established every time communications are needed using an ATM network comprised of ATM dedicated lines or STM dedicated lines as one function of such an ATM-WAN node (AWN) apparatus, such as an extension telephone network or ISDN (Integrated Services Digital Network), etc., becomes necessary.
For conventional technologies, in the case of relaying SVC calls on an ATM network, a technology called “network interwork” and a technology called “service interwork” are well known.
FIG. 1
shows the connection form of a path in a conventional network interwork system.
An ATM-WAN node
102
at site A (corresponding to a branch office) and an ATM-WAN node
102
at site B, are connected by an ATM trunk line
104
comprised of ATM dedicated lines or STM dedicated lines. At each site a Private Branch Exchange (PBX)
101
A accommodating N-ISDN (Narrow band Integrated services digital network) lines controlled by a common channel signalling system or a Private Branch Exchange (PBX)
101
B accommodating audio channels controlled by a channel associated signalling system, are accommodated in an interwork function unit (IWF)
103
in the ATM-WAN node
102
.
In a network interwork system, a path setting operation between the ATM-WAN nodes
102
varies depending on whether the signalling system of the line is a common channel signalling system or a channel associated signalling system.
First, when the signalling system of the line is a common channel signalling system, two kinds of ATM communication paths; an ATM communication path (D channel ATM-VCC) for relaying call setting N-ISDN signals (D channel signals), in which a call setting message specified by an N-ISDN common channel signalling system is stored, and an ATM communication path (B channel ATM-VCC) for communicating data (audio signals), are secured every time a communication request is issued from a terminal device (telephone set, etc.) connected to a PBX
101
A at one site to a terminal device (telephone set, etc.) connected to a PBX
101
A at the other site. Then, the call setting N-ISDN signal processed by the PBX
101
A is transparently transmitted in the D channel ATM-VCC.
On the other hand, when the signalling system of the line is a channel associated signalling system, only one kind of ATM communication path is secured between the ATM-WAN nodes
102
at each site every time a communication request is issued from a terminal device (telephone set, etc.) connected to the PBX
101
A at one site to a terminal device (telephone set, etc.) connected to the PBX
101
A at the other site. Then, both of the call setting channel associated signals in which the call setting message specified by a channel associated signalling system and the data (audio signals), are transmitted on the ATM communication path.
However, in the conventional network interwork system shown in
FIG. 1
, since the transfer methods of call setting messages between the ATM-WAN nodes
102
in the case where the signalling system of the line is a common channel signalling system and in the case where the system is a channel associated signalling system, are different from each other, there is a problem that communication cannot be performed between PBXs
102
accommodating lines of different signalling systems.
FIG. 2
shows the connection form of a path in a conventional service interwork system.
In a service interwork system, when a communication request is issued from a terminal device (telephone set, etc.) connected to a PBX
101
A at one site to a terminal device (telephone set, etc.) connected to a PBX
101
A at the other site, the IWF
103
of the ATM-WAN node
102
on a calling party side converts a call setting message in each call setting signal to a call setting message of a B-ISDN (Broad band Integrated Services Digital Network) format, regardless of whether a call setting N-ISDN signal is transmitted from a PBX
101
A or whether a call setting channel associated signal is transmitted from a PBX
101
B.
Then, the above-mentioned IWF
103
transmits a call setting B-ISDN signal in which a call setting message is in the above-mentioned B-ISDN format, to the IWF
103
of the ATM-WAN node
102
on a called party side using a specific ATM call setting path on an ATM trunk line
104
.
After extracting a call setting message in a B-ISDN format from the call setting B-ISDN signal, the IWF
103
of the ATM-WAN node
102
on the called party side converts the message to a call setting N-ISDN signal or a call setting channel associated signal, and transfers the signal to the PBX
101
A or PBX
101
B.
However, in the conventional service interwork system shown in
FIG. 2
, in the information elements of the call setting message set in the call setting N-ISDN signal of a common channel signalling system, there is an element which cannot be set by the call setting B-ISDN signal. Accordingly, the conventional service interwork system has a problem that there are some services which cannot be provided in the services supported by an N-ISDN signal.
FIG.
3
and
FIG. 4
show the data format of a SET-UP message in a B-ISDN format and the data format of a SET-UP message in an N-ISDN format, respectively.
Although in a SET-UP message in both the B-ISDN and N-ISDN formats, a plurality of information elements are transmitted following a protocol identifier, call reference and message class, for example, a display information element, key pad facility information element, signal information element, feature activation information element, feature indication information element, etc. transmitted in a SET-UP message in an N-ISDN format as shown in
FIG. 4
, cannot be transmitted in a SET-UP message of a B-ISDN format as shown in FIG.
3
.
SUMMARY OF THE INVENTION
The present invention was made in the above-mentioned background, and it is an object of the present invention to enable communications, even between PBXs accommodating lines of different signalling systems, and to enable the relay of information elements of a call setting message in all the signalling systems.
The present invention comprises a cell transmission apparatus (ATM-WAN node
502
) for re
Katou Junichi
Matsuo Shin-ichiro
Shibata Kenji
Watanabe Makoto
Fujitsu Limited
Hsu Alpus H.
Rosenman & Colin LLP
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