Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
1998-08-31
2002-07-09
Ton, Dang (Department: 2732)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
Reexamination Certificate
active
06418119
ABSTRACT:
TECHNICAL FIELD
This invention relates to a data transmission apparatus and a method thereof for use in a physical layer apparatus that handles a circuit for transmitting data between a plurality of communication nodes pursuant to the frame relay (FR) architecture. The invention prevents an LMI (Local Management Interface) frame stored with communication controlling data from being discarded when there occurs abandshortage/congestion, thereby to prevent an occurrence of any disorganized communication control between communication nodes. More specifically, this invention relates to a data transmission apparatus and a method thereof for use in such a data transmission system, which are capable of effectively performing congestion control between communication nodes without violating a communication protocol of the frame relay architecture even if there occurs a band shortage/congestion.
BACKGROUND OF THE INVENTION
The frame relay (FR) architecture, characterized by using a packet switching technique with a simplified processing scheme and by establishing a virtual circuit (PVC: Permanent Virtual Circuit) via a data communication network, has been practically used in the art to transmit data between communication nodes to each other. To implement the frame relay architecture, it is necessary that a frame relay switching equipment, a frame relay multiplexer and a router support an LMI for sharing data (LMI data) indicating the status of a virtual circuit between them and used for communication control.
In such frame relay architecture, however, if data traffic increases and results in a band shortage of a transmission path, FR data may be randomly discarded. That is, in case of shaping a frame relay circuit (i.e., decreasing a data amount of FR data in line with a transmission capacity of a transmission path), LMI data required for communication control may be discarded at the time of an occurrence of congestion, which may cause the virtual circuit to be disabled and lead to an undesirable situation where no data transmission is possible.
Japanese Patent Publications, PUPA (publication of unexamined patent application) H8-163177, PUPA H9-64916, PUPA H7-73291, PUPA H9-93284 and PUPA H7-15436 (References 1 to 5), disclose congestion control schemes in the frame relay architecture. However, none of the congestion control schemes disclosed in these References is adapted for solving a problem of the frame relay architecture that LMI data may be discarded at the time of an occurrence of congestion and consequently any further data transmission may become impossible. Nor do they satisfy the requirement of performing effective congestion control between data terminals.
In view of the aforementioned problem of the prior art, it is an object of this invention to provide a data transmission apparatus and a method thereof for use in a communication system, which are capable of transparently transmitting data required for communication control between communication nodes even if there occurs a band shortage/congestion. More particularly, it is another object of this invention to provide a data transmission apparatus and a method thereof for use in a communication system configured to perform a data transmission pursuant to the frame relay architecture, which are capable of transmitting all data required for supporting an LMI necessarily used for communication control between communication nodes even if there occurs a band shortage/congestion.
It is yet another object of this invention to provide a data transmission apparatus and a method thereof for use in an apparatus configured to perform a data transmission pursuant to the frame relay architecture, which are capable of effectively performing congestion control between data terminals with a simple process by noting a result of operation made by said apparatus with respect to congestion controlling data (CN bits) within a data transmitting frame (FR frame).
SUMMARY OF THE INVENTION
In order to accomplish said objects of this invention, there is provided a data transmission apparatus for connecting a plurality of communication nodes to transmit data via circuits established between said communication nodes, said plurality of communication nodes transmitting control data for use in controlling the data transmission and communication data other than said control data to each other, comprising: control data queuing means for queuing said control data from at least a first one of said communication nodes transmitting data to each other (first communication node); and data transmission means for transmitting all of said queued control data and at least a portion of said communication data from said first communication node to another one of said communication nodes (second communication node) in accordance with a transmission capacity between said communication nodes.
Preferably, said communication nodes store said control data or said communication data into certain frames and transmit the said frames to each other; said certain frames contain identification data for indicating whether or not at least said control data is stored therein; said control data queuing means comprises: separation means, responsive to said identification data contained in said frames received from said first communication node, for separating said frames stored with said control data from said frames stored with said communication data; a control data queue for queuing said separated frames stored with said control data; and a communication data queue for queuing said separated frames stored with said communication data; and said data transmission means transmits all of said queued frames stored with said control data and at least a portion of said queued frames stored with said communication data to said second communication node in accordance with a transmission capacity between said communication nodes transmitting data to each other.
Preferably, said data transmission means comprises: congestion detection means for detecting an occurrence of congestion between said first communication node and said second communication node when a data amount of said queued frames stored with said control data and/or said queued frames stored with said communication data exceeds a certain threshold value; and sending means, responsive to detection of the congestion between said first communication node and said second communication node, for sending all of said queued frames stored with said control data and at least a portion of said queued frames stored with said communication data, which is within the rest of the transmission capacity between said first communication node and said second communication node, to said second communication node.
Preferably, said plurality of communication nodes store said control data and said communication data into said frames (FR frames) pursuant to the frame relay architecture and transmit the said FR frames to each other in such a manner that in case of storing said control data into the said FR frames, addresses (DLCIs) therein used as said identification data are set to have certain values, whereas in case of storing said communication data into the said FR frames, said DLCIs are set to have values other than said certain values; and said separation means separates said FR frames stored with said control data and said DLCIs having said certain values from said FR frames stored with said communication data and said DLCIs having values other than said certain values.
Preferably, said sending means sets congestion controlling data (CN bits) of said FR frames to values indicating an occurrence of congestion while there is occurring congestion between said first communication node and said second communication node and sends the said FR frames to said second communication node; and each of said plurality of communication nodes is responsive to said CN bits of received FR frames indicating the occurrence of congestion for performing congestion control pursuant to said frame relay architecture.
The data transmission apparatus of this invention may ta
Hatta Tomoaki
Kashimura Hideaki
Herndon Jerry W.
Ton Dang
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