Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-03-02
2004-09-28
Vu, Huy D. (Department: 2665)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S395500, C370S354000
Reexamination Certificate
active
06798779
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a B-ISDN (Broadband ISDN) transmission device.
2. Description of the Related Art
In a public transmission network, telephony (speech) signals or various data information in an STM (Synchronous Transfer Mode) format are transmitted and handled within the infrastructure of an SDH (Synchronous Digital Hierarchy) or a SONET (Synchronous Optical NETwork). Service signals in the STM format are accessed by each transmission device at a level of an STS (Synchronous Transport Signal: 51.84 MHz) or of a VT (Virtual Tributary: 1.728 MHz), which are the frame formats of SONET. Additionally, an external interface uses a variety of signal formats such as OC-48 (optical signal: 2.4 GHz), OC-12 (optical signal: 600 MHz), OC-3 (optical signal: 150 MHz), DS3 (electric signal: 44.736 MHz), DS1 (electric signal: 1.544 MHz), etc.
Furthermore, data information services in an ATM (Asynchronous Transfer Mode) signal format have been made practical in recent years so as to effectively use the bandwidth of a transmission device or a transmission line. From the viewpoint of future network operations, it is demanded that terminal repeater equipment or an exchange not only carries ATM signals but also can access ATM signals as well as STM signals. That is, an ATM switching capability and diversified data interface capabilities such as 10Base-T, 100Base-T, FrameRelay, DS1-UNI, DS3-UNI, OC3UNI, etc. are required.
For an implementation, new services such as an ATM service, etc. are introduced in stages while using existing services, in most cases. Especially, in a data-service-related industry, devices are used in a variety of ways due to the entries of various service providers. Accordingly, the upgradability and the flexibility of the devices are demanded.
A conventional switching transmission device which can accommodate both the ATM and the STM is disclosed, for example, by the Japanese Patent Laid-Open Publication No. 1-148000. The STM/ATM hybrid switching transmission device disclosed by this publication will be briefly explained below.
FIG. 1
exemplifies the conventional network where the STM and the ATM are mixed.
In this figure, STM and ATM signals can be carried in STS-1×N units over a single optical fiber by an ADM (Add Drop Multiplexer) or by a SONET MUX (SONET Multiplexer), as long as the signals use the SONET frame format as a physical transmission medium. However, an ATM access capability is not included in the conventional network. When a communication between terminals using the ATM is attempted to be made, an ATM exchange must be passed through or an ATM MUX (ATM Multiplexer) must include an ATM switching capability. In this case, however, the bandwidth of a transmission line such as an optical fiber, etc. is wasted, and many terminals and multiplexing devices are required.
That is, when terminals
201
and
202
of
FIG. 1
, which are ATM terminals, attempt to make a communication, they can make a communication on a path from the terminal
201
—an ATM MUX
205
—the terminal
202
, if the ATM MUX
205
has a switching capability. However, if the ATM MUX
205
does not have a switching capability, the ATM cell transmitted from the terminal
201
must reach a BB exchange (BroadBand exchange)
203
which is an ATM exchange via the ATM MUX
205
and SONET ADM/MUXes
204
and
206
as indicated by a path (1) shown in FIG.
1
. The BB exchange switches the ATM cell, which is made to reach the terminal
202
again via the SONET ADM/MUXes
206
and
204
and the ATM MUX
205
.
As described above, in the conventional network where the ATM and the STM are mixed, a trunk transmission line must be used for the communication between the terminals
201
and
202
, which are connected to the single ATM MUX
205
, if the ATM MUX
205
does not have a switching capability. Therefore, the transmission bandwidth of the optical fiber of the trunk line is wasted. Additionally, if the ATM MUX
205
is equipped with the switching capability, its hardware configuration becomes complicated and the cost increases. Furthermore, since all ATM MUXes which accommodate ATM terminals must be equipped with this capability in a similar manner, the cost of the entire network rises.
Explained below is the outline of the conventional STM/ATM hybrid switching transmission device disclosed by the above described publication. For more details, please refer to this publication.
FIG. 2
is a block diagram exemplifying the configuration of the conventional STM/ATM hybrid switching transmission device.
In this figure,
191
indicates a highway and a plurality of highways
191
are arranged. In each of the plurality of highways
191
, STM and ATM information are multiplexed.
192
and
193
indicate time slot phase switching units.
195
indicates a time division slot switching device.
197
indicates a time-division switching device. The time-division switching device
197
includes the time slot phase switching units
192
and
193
, and the time-division slot switching device
195
.
Each of the time slot phase switching units
192
is arranged for each incoming highway
191
, while each of the time slot phase switching units
193
is arranged for each outgoing highway
191
. These time slot phase switching units
192
and
193
are intended to switch between the phases of time slots of each of the highways
191
.
The time-division slot switching device
195
is intended to switch between the time slots of the highways
191
.
This time-division slot switching device
195
separates the STM and ATM information, and switches between the time slots of the highways
191
for the STM information. Furthermore, the time-division slot switching device
195
has a capability for multiplexing and switching the STM and ATM information upon receipt of the output from an asynchronous transfer mode information switching device (ATM switching device).
196
indicates an ATM switching device which is intended to switch the ATM information separated by the time-division slot switching device
195
included in the time-division switching device
197
.
Since the capacity of the STM switch unit of each time slot phase switching unit
192
and the time-division slot switching device
195
, and the capacity of the ATM switch unit of the ATM switching device
196
are fixed in this configuration, the hardware size becomes larger as the respective capacities of the STM and the ATM switch units increase. At the same time, the efficiency decreases. If this configuration is used as an STM or an ATM dedicated machine, it is not cost-effective due to the inclusion of unnecessary portions. Additionally, because the minimum unit of switching is fixed in the STM switch unit, the hardware configuration becomes complicated if switching is attempted to be made also on a low level such as DS1 (1.544 MHz). Furthermore, if a redundant configuration is adopted, the entire hardware must be duplexed. As a result, the reliability degrades because the entire configuration is switched even at the time of the occurrence of a partial problem.
Conventionally, a terminal and an exchange which handle STM and ATM signals are respectively implemented as different devices. There are several methods for handling STM and ATM signal services by combining these devices, and for accessing/switching an STM signal by forcibly putting the STM signal into ATM cells, in the hardware which also accesses also ATM signals.
With the conventional methods, however, a node (device) within a network becomes redundant in order to realize both the coexistence with the network composed of an existing SONET ADM (Add-Drop Multiplexer) for an STM or of an ATM access node/exchange, and the support of various service interfaces of respective devices. As a result, an inefficient network is configured or a device configuration becomes complicated in order to convert an STM signal into ATM cells, which are signals of a different type. Therefore, it is impossible to reduce the size and cost of the device.
Additionally, w
Matsuno Noriyasu
Shimbashi Masahiro
Katten Muchin Zavis & Rosenman
Philpott Justin M.
Vu Huy D.
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