Electrical computers and digital processing systems: multicomput – Computer network managing – Network resource allocating
Reexamination Certificate
2000-03-08
2004-05-18
Alam, Hosain (Department: 2155)
Electrical computers and digital processing systems: multicomput
Computer network managing
Network resource allocating
C709S223000
Reexamination Certificate
active
06738816
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication network composed of a plurality of nodes, each of which is provided with data transmission and reception functions conforming to IEEE 1394-1995 Serial Bus Standard (hereafter, referred to as IEEE1394) and, in particular, to a data communication method allowing data communication among these nodes according to communication protocols such as TCP/IP (Transmission Control Protocol/Internet Protocol).
2. Description of the Related Art
The IEEE 1394 standard defined in 1995 is an international standard for implementing a cost-effective and high-speed digital interface. The IEEE 1394 serial bus provides high-speed data transport of several hundreds of megabits per second and therefore enables real-time transport required for digital video data transmission. Therefore, the IEEE 1394 digital interface is caused to provoke widespread attention as a digital interconnect for both computer peripherals and consumer electronics including digital video cameras and digital television sets.
There has been known so-called “IP over 1394” defined by IETF (Internet Engineering Task Force), which can support the transport of Internet Protocol (TP) data over a communication network conforming to the IEEE1394 standard. The IP-over-1394 system provides necessary methods for transmitting and receiving IP unicast data, IP multicast data, and IP broadcast data. More specifically, in the case of IP unicast, Asynchronous packets of IEEE1394 are used for communication. In the cases of IP multicast and IP broadcast, an Asynchronous-Stream channel is used for communication.
Further, the IP-over-1394 system provides MCAP (Multicast Channel Allocation Protocol) which defines an allocation method of an Asynchronous Stream channel for multicast. More specifically, in the case of multicast channel allocation, a first node which intends sending data sends a message for querying whether the Asynchronous-Stream channel for multicast has been allocated in the network. When receiving no reply to the query message, the first node requests a new channel from IRM (Isochronous Resource Manager) defined in the IEEE 1394. After the channel has been allocated to the first node, the first node uses the allocated channel to send multicast data.
Thereafter, in the case where a second node starts sending or receiving multicast data, the second node sends a query message for querying whether the Asynchronous-Stream channel for multicast has been allocated in the network. When receiving the query message from the second node, the first node sends a message indicating correspondence information between multicast addresses and the allocated channel to the second node. When receiving the correspondence information message, the second node uses the designated channel for communication.
In the case where the first node completes the data sending, the first node sends a channel control transfer message including the correspondence information between the multicast addresses and the allocated channel. If a third node other than the first and second nodes which is sending data to nodes of the same multicast addresses is received the channel control transfer message, then the third node sends a message indicating the correspondence information between the multicast addresses and the allocated channel and inherits the channel control from the first node. In this case, the first node terminates the communication with doing nothing. If there is a no node inheriting the channel control like the third node, then the channel allocated to the first node is deallocated by the IRM before the first node terminates the communication.
As described above, the node that sends multicast packets has a channel allocated thereto by the IRM. However, a sufficient bandwidth for data communication is not always reserved. In the case of data communication requiring real-time processing such as voice and moving-picture transmission of a television conference system, it is difficult to transmit voice and moving-picture data in real time when the network falls into congestion.
In the system composed of a plurality of nodes such as a television conference system, there are possibly two cases: one case where only one of the nodes sends data at all times; and the other case where all the nodes can concurrently send data. In the former case, it is necessary to reserve the widest one of the bandwidths required for the nodes. In the latter case, it is necessary to reserve a total of bandwidths required for all the nodes.
In the television conference system, voice communication is an example of the former case because only one node talks when N nodes are in conversation. Therefore, the bandwidth required for voice communication of only one node may be reserved. In the case where the nodes have different voice qualities, it is necessary to reserve the widest one of the bandwidths required for the nodes. Moving-picture communication is an example of the latter case because video data is always transmitted from each of the nodes. Therefore, it is necessary to reserve a total of bandwidths required for video communications of all the nodes.
It is possible to provide a node with a means for reserving a bandwidth required for the node itself. However, such a means cannot cope with a case where two or more nodes send data with different required bandwidths and different uses of reserved bandwidths.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a data communication method allowing real-time communications among a plurality of nodes participating in a session even in the event of network congestion.
Another object of the present invention is to provide a data communication method allowing real-time communications among a plurality of nodes requiring different bandwidths and different uses of reserved bandwidths.
According to the present invention, in the case where a plurality of nodes participate in a session such that two or more nodes do not concurrently send data, a session management node which manages a channel and a bandwidth thereof for the session is determined and reserves a maximum bandwidth among bandwidths requested by the nodes participating in the session by accessing the Isochronous Resource Manager, to allow communications by sharing the maximum bandwidth among nodes which participate in the session and send data.
A first node which intends sending data in the session broadcasts a first query message for querying whether a channel and a bandwidth for the session have been reserved. When the first node is an initial node to send data, the first node receives no response to the first query message. In this case, the first node reserves a channel and a first bandwidth needed by the first node for the session. Thereafter, the first node becomes the session management node and sends data using an isochronous stream through the reserved channel.
When receiving a second query message for querying whether a channel and a bandwidth for the session have been reserved, from a second node other than the session management node, wherein the second query message includes a second bandwidth needed by the second node, the session management node compares the second bandwidth requested by the second node with a reserved bandwidth which has been reserved for the session in the network.
When the second bandwidth is broader than the reserved bandwidth, the session management node reserves a differential bandwidth between the second bandwidth and the reserved bandwidth accessing the Isochronous Resource Manger to reserve the maximum bandwidth among bandwidths requested by the nodes participating in the session. Then, the session management node broadcasts a report message including session identifying information and the maximum bandwidth which is sharable. In this manner, the maximum bandwidth which has been reserved is used as a shared bandwidth by all the nodes participating in the session.
As an example, in the case of a third node participating in th
Alam Hosain
Dickstein Shapiro Morin & Oshinsky LLP.
NEC Corporation
Tran Philip B.
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