Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus access regulation
Reexamination Certificate
1999-01-19
2001-07-24
Beausoleil, Robert (Department: 2781)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus access regulation
C710S120000, C710S016000, C710S009000
Reexamination Certificate
active
06266728
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a network system incorporating a plurality of buses each of which is constituted by connecting a plurality of nodes to one another with communication-control signal lines each of which is capable of transmitting a control signal and an information signal in a mixed manner, and to a bridge apparatus for connecting the buses to one another.
2. Related Background Art
Network systems have been widely used that are constituted by connecting a multiplicity of computers, peripheral equipment or AV apparatuses to one another. Each of the apparatuses which are connected as described above is called a “node” which includes an interface for establishing the connection with the other apparatuses.
The structure of the conventional network system is shown in FIG.
1
. The network system shown in
FIG. 1
is constituted by connecting eleven buses
100
to
110
, each of which is formed by connecting a plurality of nodes to one another with communication-control signal lines, to one another by bridges
90
and
91
for example.
The communication-control signal lines may be signal lines of a type based on IEEE1394 which is a standard for serial interfaces. Not more than sixty three nodes can be connected to one bus because of the regulation of IEEE1394. If a larger number of nodes must be connected, a plurality of buses must be prepared to connect the buses to one another with the bridges
90
,
91
and so forth. IEEE1394 defines a fact that a large-scale network system can be constituted by not more than 1023 buses. Moreover, IEEE1394 defines a fact that determination of states of the connection among the buses and assignment of identification (ID) numbers for the buses are automatically performed. The process for assigning the ID for the bus is called a configuration process. The configuration process is performed when a bus is added or omitted, the configuration process being performed in the overall network system.
If the number of the buses is increased, addition and omission of the buses are performed frequently. Whenever the addition or the omission is performed, the configuration process must be performed in the overall network system. Therefore, interruption of data communication frequently occurs. What is worse, there is apprehension that the apparatus is operated incorrectly or data is eliminated. Since the computer and peripheral equipment must have significant reliability, frequent configuration processes undesirably cause the operations of the apparatuses to be unstable.
In a case of a large-side network system having a multiplicity of buses, there is a possibility of using, to connect the buses to one another, a line connection type communication passage, such as the public telephone network, or a wireless communication. The communication passages of the above-mentioned types suffer from unstable connection and easily encounter occurrence of unintentional connection and disconnection. In the above-mentioned case, there is a possibility that configuration is frequently repeated. Thus, there is apprehension that the network system becomes unstable.
If the apparatus, for example, the node or the bridge, breaks down or becomes defective, the network system cannot always be operated in conformity with the foregoing standard. Also the foregoing fact causes the operation of the network system to be unstable.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a network system and a bridge apparatus each of which can stably be operated by reducing a frequency of configuration processes which occur in the overall system.
According to one aspect of the present invention, there is provided a network system constituted by connecting a plurality of buses to one another by bridges so that a tree structure is formed having a bus in which a network manager, serves as a center and is arranged to perform configuration so as to sequentially assign numbers to the buses, wherein only when the number of the identification numbers which have been previously reserved is smaller than the number of buses which are newly added, a configuration demand is communicated to an upper level, and a configuration process of a lower tree structure is performed in other cases.
Specifically, a number of buses which is larger than the number of buses which is included in a tree structure in which the bridge serves as the top of the tree structure is previously reserved. If a cause of configuration occurs in the tree structure and a configuration demand is received, the configuration demand is not communicated to the upper level of the tree structure if the number is not larger than the number of buses which have previously been reserved. A means disposed in the tree structure and arranged to perform the configuration process solves the above-mentioned problem.
Therefore, if a cause to perform re-configuration occurs in the tree structure having the bus which serves as the top of the tree structure, the configuration demand is not communicated to the upper level if a sufficiently large number of buses are reserved. Thus, a frequency of the configuration in the overall network can be reduced.
Other objects, features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.
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Shima Hisato
Sugita Takehiro
Beausoleil Robert
Maioli Jay H.
Phan Raymond N
Sony Corporation
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