Electrical computers and digital processing systems: multicomput – Computer network managing
Reexamination Certificate
1998-09-03
2001-11-20
Wiley, David (Department: 2155)
Electrical computers and digital processing systems: multicomput
Computer network managing
Reexamination Certificate
active
06321260
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a data communication method, and more particularly to a data communication method for satisfying a transfer rate requested by an information processor of a sender and transferring continuous media data such as voice data and moving picture data between two information processors connected via a plurality of information processors.
BACKGROUND OF THE INVENTION
As a communication method for transferring continuous media data such as voice data and moving picture data by satisfying the transfer rate requested by the information processor (hereinafter referred to as the sender node) sending the data, ST-II (RFC-1190) is known.
The procedure when continuous media data is to be transferred to an information processor (hereinafter referred to as a receiver node) performing one reception from one sender node in ST-II will be explained hereunder. It is assumed that continuous media data is relayed by an information processor (hereinafter referred to a router node) relaying a plurality of data while the continuous media data reaches the receiver node from the sender node.
Before starting transfer of continuous media data, the sender node sends the message CONNECT to the receiver node. While the message CONNECT reaches the receiver node from the sender node, it passes through a plurality of router nodes. In this case, the router nodes through which the message CONNECT passes are uniquely decided by the routing function of ST-II.
The message CONNECT contains the following information.
A) Hop ID
B) QoS parameter (QoS is an abbreviation for Quality of Service and means “quality of continuous media data”.)
C) Receiver node ID information
The hop ID is used to identify a logical connection between the sender node and the receiver node which is generated by the message CONNECT. This hop ID is decided by negotiation between a sender and a router node or a receiver node (hereinafter referred to as a next hop, a node previously receiving the message CONNECT is hereinafter called a previous hop) receiving the message CONNECT next. It is necessary to specify this ID so that it will be unique on the next hop. There is the possibility that the hop ID corresponding to the same logical connection may vary with the node. The QoS parameter specifies the required quality (for example, required network bandwidth, etc.) of continuous media data to be transferred on the aforementioned logical connection. In the receiver node ID information, sufficient information to uniquely decide the receiver node on the network is stored.
The router node receiving the message CONNECT performs the following.
1) Obtaining of Hop ID
A hop ID which is not used in the next hop is secured by negotiation with the next hop. The next hop uniquely decides the routing function of ST-II from the receiver node ID information included in the message CONNECT.
2) Generation of Routing Information to be Used for Continuous Media Data Transfer
From the hop ID included in the received continuous media data, routing information sufficiently enough to search for the hop ID and LAN address to be included in the continuous media data to be transferred to the next hop is generated.
3) Reservation of Resource Necessary for Continuous Media Data Transfer
The data buffer on the router node and the network bandwidth between the router node and the next hop are secured. ST-II does not specify a method for sending and receiving a control message to and from another node so as to secure the network bandwidth. Therefore, in a network occupying and using a logical transmission path (hereinafter a logical transmission path is abbreviated to a transmission path) such as an ATM network only by the self node, it can be guaranteed that the secured bandwidth can be used also during transfer of continuous media data. However, in a network sharing a transmission path such as Ethernet with another node, the aforementioned guarantee is impossible (the reason will be described immediately later).
4) Relay of the Message CONNECT to the Next Hop
The message CONNECT is relayed to the next hop uniquely decided by the routing function of ST-II.
The receiver node receiving the message CONNECT sends the message ACCEPT to the sender node when it accepts the logical connection establishment request from the sender node and the message REFUSE to the sender node when it rejects the logical connection establishment request.
The sender node receiving the message ACCEPT from the receiver node starts transfer of continuous media data. In the continuous media data sent from the sender node, the hop ID obtained by negotiation between the sender node and the next hop is included.
The continuous media data passes through a plurality of router nodes before it reaches the receiver node. The router nodes route the continuous media data using the routing information obtained in 2) mentioned above. Namely, the routing system for the control message such as the message CONNECT or ACCEPT is different from the routing system for continuous media data.
The data buffer and network bandwidth necessary for the continuous media data relay process are secured in 3) mentioned above. Therefore, it is impossible that the relay of continuous media data is delayed due to deficiency of the data buffer or deficiency of the bandwidth (in a network which can share the transmission path with the next hop) and the data transfer rate requested by the sender node is not satisfied.
Next, the procedure when the sender node transfers continuous media data to the receiver node in the CSMA/CD system (‘COMPUTER NETWORKS THIRD EDITION’ ANDREW S. TANENBAUM, PRENTICE HALL, pp 276-287, 1996) will be explained. In this case, it is assumed that the sender node and receiver node exist on the same LAN. Therefore, the sender node and receiver node communicate with each other without using router nodes.
In an LAN of the CSMA/CD system (that is, a network sharing the transmission path by a plurality of nodes), a transfer delay of continuous media data may occur due to another data transfer. Namely, even if the sender node attempts to transfer continuous media data at the transfer rate requested by the self node, the network is in use for another data transfer at transfer start time, so that the transfer of continuous media data may be delayed. As a result, the data transfer rate requested by the sender node will not be satisfied. To prevent it, it is necessary to control the total of bandwidths used on the LAN up to a fixed upper limit any time. When the total of bandwidths in use is a fixed upper limit or less, the probability of delay occurrence caused by that the network is in use reduces and the data transfer rate requested by the sender node can be satisfied.
As mentioned above, even if ST-II transfers continuous media data from the sender node to the receiver node via a plurality of router nodes, there is no possibility that the transfer rate requested by the sender node may not be satisfied due to deficiency of the data buffer on the router. When the network between the sender node and the receiver node comprises only networks which can occupy a transmission path such as ATM, there is no possibility that the transfer rate requested by the sender node may not be satisfied due to deficiency of the bandwidth of the network.
However, networks have recently speeded up and there is the possibility that the relay process for continuous media data to be performed by the router nodes or the receiving process for continuous media data to be performed by the receiver node may be delayed due to deficiency of the processing capacity of the router nodes or the receiver node. For example, it is assumed that continuous media data of 80 Mbps is to be relayed from the sender node to the receiver node. The intervening network comprises a 100-Mbps Fast Ethernet network and a 155-Mbps ATM network and the establishment of a logical connection by the message CONNECT in ST-II succeeds. However, when the intervening router node has only a relay capacity of 40-Mbps continuous media data, a
Iwasaki Masaaki
Nakano Takahiro
Takeuchi Tadashi
Tanaka Teruo
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Wiley David
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