Electrical computers and digital processing systems: multicomput – Multiple network interconnecting
Reexamination Certificate
2000-06-27
2004-06-29
Geckil, Mehmet B. (Department: 2142)
Electrical computers and digital processing systems: multicomput
Multiple network interconnecting
C370S401000
Reexamination Certificate
active
06757743
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication control system and method, a communication system, and a recording medium. More particularly, this invention is concerned with a communication control system and method for dynamically managing connection or disconnection of equipment within a system, a communication system, and a recording medium.
2. Description of the Related Art
FIG. 1
shows an example of the configuration of a system for transferring data placed on a fast serial bus conformable to the standard 1394 stipulated by the Institute of Electrical and Electronics Engineers (IEEE) over an asynchronous transfer mode (ATM) network. A video camera
1
is connected to a bridge
3
-
1
over an IEEE 1394 bus
2
-
1
. Likewise, a monitor
4
is connected to a bridge
3
-
2
over an IEEE 1394 bus
2
-
2
. The bridge
3
-
1
and bridge
3
-
2
are interconnected with an ATM switch
5
between them. For connecting the bridges
3
-
1
and
3
-
2
to the ATM switch
5
, for example, an optical fiber is used.
Hereinafter, the IEEE 1394 buses
2
-
1
and
2
-
2
shall be generically referred to as an IEEE 1394 bus
2
unless they are required to be separated from each other. The same applies to the other components.
In the system shown in
FIG. 1
, an image produced by the video camera
1
is transmitted to the monitor
4
and then reproduced. At this time, the video camera
1
outputs image data to the bridge
3
-
1
at an isochronous channel
63
. The bridge
3
-
1
is designed (initialized) so that channel numbers (
0
to
63
) will be associated with virtual channel identifiers (VCIS) or virtual path identifiers (VPI), which are employed in ATM communication, on a one-to-one basis. Herein, the bridge
3
-
1
is pre-set so that when data is transmitted at the channel
63
, the bridge
3
-
1
starts transmitting the data in the ATM using an inherent virtual channel of an associated VCI or an inherent virtual path of an associated VPI. An ATM switch
5
selects the bridge
3
-
2
as a destination specified with the VCI or VPI, and transfers the data to the bridge
3
-
2
.
When a connection has been established between the bridges
3
-
1
and
3
-
2
, the connection is used to transfer image data. The bridge
3
-
2
converts received image data into data of a form acceptable by the monitor
4
, and transfers the resultant image data to the monitor
4
over the IEEE 1394 bus
2
-
2
.
As mentioned above, when the IEEE 1394 bus and ATM network is employed in a system, the permanent virtual connection (PVC) mode is adopted. According to the PVC mode, paths are determined relative to all remote terminals on a communication network, and a local terminal communicates with fixed remote terminals while being connected thereto all the time.
Equipment to be connected to other equipment over the IEEE 1394 bus, such as, the aforesaid video camera
1
and monitor
4
has an AV register incorporated therein. By changing values to be set in the AV register, isochronous channels at which data is transmitted or received can be switched. What is referred to as the AV register has a structure like the one shown in FIG.
2
.
FIG. 2A
to
FIG. 2D
show the structures of an output master plug register (oMPR), an output plug control register (oPCR), an input master plug register (iMPR), and an input plug control register (iPCR) constituting the AV register.
FIG. 2A
shows the structure of the OPCR,
FIG. 2B
shows the structure of the OPCR,
FIG. 2C
shows the structure of the iMPR, and
FIG. 2D
shows the structure of the iPCR. A code indicating a maximum transmission rate at which isochronous data transmissible or receivable by the equipment is transmitted is specified in a data rate capability field of the OMPR or iMPR to which two most-significant bits are assigned. A channel number used to broadcast data is specified in a broadcast channel base field of the oMPR.
A value representing the number of output plugs included in the equipment, that is, the number of oPCRs included therein is specified in a number-of-output plugs field of the OMPR to which five least-significant bits are assigned. A value representing the number of input plugs included in the equipment, that is, the number of iPCRs included therein is specified in a number-of-input plugs field of the iMPR to which five least-significant bits are assigned. A non-persistent extension field and a persistent extension field are defined for future functional expansion.
The used state of a plug is specified in an online field of the OPCR or iPCR. Specifically, when a bit assigned to the online field is 1, the plug is online. When the bit is 0, the plug is offline. A value specified in a broadcast connection counter of the OPCR or iPCR indicates whether a broadcast connection is present (1) or absent (0). A value specified in a point-to-point connection counter of the OPCR or iPCR that is 6 bits wide indicates the number of point-to-point connections accommodated by the plug.
A value specified in a channel number field of the OPCR or iPCR that is 6 bits wide indicates a number of an isochronous channel assigned to data that can be treated by the plug. A value specified in a data rate field of the OPCR that is 2 bits wide indicates an actual transmission rate adopted for transmission of a packet of isochronous data output through the plug. A code specified in an overhead identity (ID) field of the OPCR that is 4 bits wide indicates a bandwidth assigned to an overhead that is appended for isochronous communication. A value specified in a payload field of the OPCR that is 10 bits wide indicates a maximum value of data contained in an isochronous packet that can be treated by the plug.
A case where the video camera
1
and monitor
4
-transfer data on a point-to-point basis has been described so far. As shown in
FIG. 3
, a plurality of pieces of equipment may be interconnected over an IEEE 1394 bus subordinately to the bridge
3
, and multiple pieces of equipment may transfer data to or from multiple pieces thereof. This multi-points-to-multi-points communication will be described below. According to an example of a system configuration shown in
FIG. 3
, four video cameras
1
-
1
to
1
-
4
are connected to the bridge
3
-
1
over an IEEE 1394 bus (not shown), and four monitors
4
-
1
to
4
-
4
are connected to the bridge
3
-
2
over an IEEE 1394 bus.
In the system-configuration shown in
FIG. 3
, a connection has already been established between the video camera
1
-
1
and monitor
4
-
1
, and image data is transferred at the isochronous channel
63
. Furthermore, when image data is transmitted from the video camera
1
-
2
to the monitor
4
-
2
, the video camera
1
-
2
sets an isochronous channel. At this time, the same isochronous channel as that already used will not be set. For example, an isochronous channel
62
is set.
A connection is established between the bridge
3
-
1
and bridge
3
-
2
, and data transfer is started. The PVC mode is adopted as a communication mode. A VCI or VPI to be associated with the isochronous channel
62
is determined in advance. The bridge
3
-
2
determines an isochronous channel, at which received image data is transmitted, according to the VCI or VPI, and sets an AV plug. The bridge
3
-
2
selects, similarly to the bridge
3
-
1
, an isochronous channel (for example, isochronous channel
62
) that is not the same as an already used isochronous channel, converts the received data into data having the selected isochronous channel
62
, and transmits the resultant data. The monitor
4
-
2
reproduces input image data.
As mentioned above, an isochronous channel is set so that it will not be the same as an already used one. Multi-points-to-multi-points communication is thus achieved. However, equipment interconnected over an IEEE 1394 bus (within a system) may include equipment that does not have the ability to set an isochronous channel. Moreover, the bridge
3
itself may not have the ability to switch isochronous channels. The present applicant h
Kataoka Tomomichi
Nomura Takashi
Tamori Hirofumi
Geckil Mehmet B.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Sony Corporation
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