Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Utility Patent
1997-09-02
2001-01-02
Marcelo, Melvin (Department: 2739)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S236000
Utility Patent
active
06169727
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to an asynchronous transfer mode (ATM) network, and more particularly, relates to a device for notifying of congestion such as overflows in communication devices of the ATM network and a method for controlling such a congestion.
2. Related Art
Generally, ATM is a specific packet-oriented transfer mode using an asynchronous time division multiplexing technique where both line switching and packet switching are unified and many pieces of information, such as voice, data, and pictures, are organized in fixed-sized blocks, called cells. ATM can operate as both a packet exchange system and a circuit exchange system in one transmission mode for efficiently embodying both high speed and wide band communication networks. ATM is a target transfer mode solution for implementing a broadband integrated services digital network (B-ISDN) because it offers effective information channel management based upon virtual path and virtual channel identifiers (“VPI” and “VCI”) placed in a header of each cell in order to facilitate the use of a multiplexing, demultiplexing and exchange of digital information, and in order to decrease the costs of broad-band communication network facilities due to flexibility in bandwidth distribution.
An important consideration in ATM network operation is traffic control, i.e., the process of controlling the amount of information entering and traversing the network. Traffic control techniques are generally described, for example, in U.S. Pat. No. 5,253,247 for
Traffic Control Method And Traffic Control System For Controlling Cell Traffic In An Asynchronous Transfer Mode Communication Network
issued to Hirose et al., U.S. Pat. No. 5,280,483 for
Traffic Control System For Asynchronous Transfer Mode Exchange
issued to Kamoi et al., and U.S. Pat. No. 5,519,689 for
Traffic Control Apparatus And Method Of User-Network Interface Of Asynchronous Transfer Mode
recently issued to Kim and assigned to the same assignee of the present invention. Generally, the rate of data transmission between two points is regulated for flow control, or alternatively, traffic avoidance schemes are used to minimize conditions under which a sending node is unable to forward packets because no buffers are available in a receiving node along the transmission path.
One popular traffic control technique is congestion control which is to maintain the amount of information (e.g. the number of cells) within the ATM network below a level at which performance (e.g. delay, cell loss, etc.) becomes unacceptable. The objective of congestion control is to limit the fullness of buffers at nodes in the ATM network so as to avoid cell loss or delay. Contemporary congestion control systems for ATM networks are disclosed, for example, in U.S. Pat. No. 5,048,013 for
Transmission Congestion Control Method And Apparatus
issued to Eng et al, U.S. Pat. No. 5,062,106 for
ATM Exchange System
issued to Yamazaki et al., U.S. Pat. No. 5,067,127 for
Congestion Avoidance Control System
issued to Ochiai, U.S. Pat. No. 5,090,011 for
Packet Congestion Control Method And Packet Switching Equipment
issued to Fukuta et al., U.S. Pat. No. 5,167,033 for
Congestion Control In Computer Networks
issued to Bryant et al., U.S. Pat. No. 5,400,329 for
Packet Network And Method For Congestion Avoidance In Packet Networks
issued to Tokura et al., U.S. Pat. No. 5,463,620 for
Bandwidth Allocation Transmission Scheduling, And Congestion Avoidance In Broadband Asynchronous Transfer Mode Networks
issued to Sriram U.S. Pat. No. 5,574,720 for
Traffic Output Suppression Apparatus And Method For Preventing Congestion In Asynchronous Transfer Mode Network
issued to Lee, and U.S. Pat. No. 5,646,943 for
Method For Integrated Congestion Control In Networks
issued to Elwalid.
Generally, ATM networks use an explicit forward congestion notification (EFCN) method for controlling congestion in accordance with a recommendation from the Telecommunication Standardization Sector of International Telecommunication Union (ITU-T). A second bit of an ATM cell header payload type (PT) field is used for the explicit forward congestion indication (EFCI). In the congested ATM switch EFCI bits are set to ATM cells which are then output in a forward direction from a sending node to a receiving node. ATM cells containing EFCI bits inform all the ATM switches of a congestion state, while reaching the final destination, i.e., the receiving node. The receiving node returns the congestion notifying cell in a reverse direction so that all of the ATM switches and the sending and receiving nodes can be informed of the congestion state. Typically, the congestion notifying function is performed only when the congestion, such as buffer overflow, arises in interfaces of a switch unit. One problem that I have observed, however, is that the switch unit and control/maintenance unit must be provided with additional hardware in order to transfer such buffer overflow information through separate information channels. Another problem nota is that the processing time is delayed by information collection time, and as a result, the congestion control speed is slow. In addition, all interfaces of an ATM switch unit must administer and control the congestion states for every established connection. Since the number of connections available in the ATM network are 2
24
at the maximum in the case of a user network interface (UNI), congestion control and administration for every connection is practically impossible.
SUMMARY OF THE INVENTION
Accordingly, it is therefore an object of the present invention to provide a congestion notification device in an ATM network.
It is also an object to provide a congestion notification device installed in respective communication devices of an ATM network for notifying of congestion when overflow occurs in the communication devices of the ATM network.
It is another object to provide a method for preventing congestion notification delay resulting from congestion control within an ATM network.
It is still another object to provide a method for performing a congestion control function in advance before congestion occurs in an ATM network.
It is a further object to provide a device and a method for performing congestion control at every connection in an ATM network.
It is a further object to provide a simple circuit device for notifying of congestion resulting from buffer overflow and a method for rapidly and efficiently controlling the congestion notification procedure.
These and other objects of the present invention can be achieved by a congestion notifying device installed in individual communication units of an asynchronous transfer mode (ATM network, which comprises: a congestion indication signal generator for generating a congestion indication signal when congestion occurs within any one of the communication units; an explicit forward congestion indication (EFCI) bit set position detector for generating set position information to detect a prescribed bit set position of each incoming cell in response to a cell synchronization signal and a cell clock signal; and an explicit forward congestion indication (EFCI) bit set control unit for responding to the congestion indication signal and the set position information to set on the prescribed bit set position of each incoming cell an explicit forward congestion indication (EFCI) bit for notifying of occurrence of congestion in any one of the communication units.
The present invention is more specifically described in the following paragraphs by reference to the drawings attached only by way of example.
REFERENCES:
patent: 5048013 (1991-09-01), Eng et al.
patent: 5062106 (1991-10-01), Yamazaki et al.
patent: 5067127 (1991-11-01), Ochiai
patent: 5090011 (1992-02-01), Fukuta et al.
patent: 5167033 (1992-11-01), Bryant et al.
patent: 5280483 (1994-01-01), Kamoi et al.
patent: 5400329 (1995-03-01), Tokura et al.
patent: 5463620 (1995-10-01), Sriram
patent: 5570348 (1996-10-01), Holden
patent: 5574720 (1996-11-01), Lee
p
Marcelo Melvin
Robert E. Bushnell, Esq.
Samsung Electronics Co,. Ltd.
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