Multiplex communications – Data flow congestion prevention or control
Reexamination Certificate
1998-09-21
2002-07-23
Patel, Ajit (Department: 2662)
Multiplex communications
Data flow congestion prevention or control
C370S232000, C370S235000, C370S395430, C370S400000
Reexamination Certificate
active
06424620
ABSTRACT:
BACKGROUNDS OF THE INVENTION
1. Field of the Invention
The present invention relates to a congestion control system, and more particularly to a congestion control system capable of detecting congestion occurring in an Asynchronous Transfer Mode (ATM) network for transferring connectionless traffic and autonomously avoiding the congestion.
2. Description of the Related Art
Recently, attention is being given to an ATM communication as a high-speed communication technique or a scalable wide-band transfer technique making good use of resources such as terminals introduce by a user on the basis of the communication technique of the existing LAN (Local Area Network) such as Ethernet. In this ATM communication, cell for dividing the transfer data with the transfer control information including the destination information attached thereto by the fixed length is defined as the unit of transfer and these cells are transferred to a network of the destination while passing on the respective ATM switches.
However, if using this ATM communication heavily in the field of the information communication, disadvantages such as abandonment of transfer data may occur due to the congestion caused by an increase of transfer information amount and overload on a node, thereby increasing the importance of technology for relieving the congestion.
In order to relieve the congestion, there is known a congestion control system for controlling traffic on a corresponding connection depending on the congestion state notified by the ATM network, at the entrance of receiving transfer packets for a network such as the ATM network. In this system, a virtual communication channel which is inevitably decided from a plurality of Virtual Path Identifiers (VPI) and Virtual Channel Identifiers (VCI) established on the identical transfer channel is defined as a connection group.
Since the ATM communication can establish a virtual communication channel inevitably decided from a plurality of VPIs and VCIs, within a physical line or a virtual path, it can make efficient use of the resources while restraining the cell abandonment at the minimum on a connection having the congestion occurrence.
FIG. 14
is a view for use in describing the principle of the conventional congestion control system. In this congestion control system, the respective transfer packets are transferred from a plurality of connections
201
a
,
201
b
, and
201
c
via a connection group
202
to a network
203
. Connection monitoring means
204
a
,
204
b
, and
204
c
are adopted to monitor the transfer packets flowing from the respective connections
201
a
,
201
b
and
201
c
to the connection group
202
and the flow amount of the transfer packets. A connection group monitoring means
205
is adopted to monitor the transfer packets transferred to the connection group
202
and monitor the flow amount of the transfer packets in every connection group defined by a connection group defining means
206
.
The control means
207
can switch the control between monitor mode and control mode, so to control the connection monitoring means
204
a
,
204
b
, and
204
c
and the connection group monitoring means
205
. The monitor mode is an operation mode for monitoring whether the flow amount of a transfer packet is beyond a predetermined threshold or not. The control mode is an operation mode for abandoning the extra packets when the flow amount of the transfer packets is beyond the threshold, and controlling the priority of abandonment by the cell loss priority (CLP) display.
In the non-congestion state, the connection monitoring means
204
a
,
204
b
, and
204
c
are operated in a monitor mode and the connection group monitoring means
205
is operated in a control mode. Namely, packets to be transferred from the connection group
202
to the network
203
are controlled and their flow amount is controlled by every connection group, so as not to cause the congestion within the network
203
.
In the congestion state, a connection on which the packet flow amount is beyond the threshold is recognized, based on the monitoring result from the connection monitoring means
204
a
,
204
b
, and
204
c
monitoring the flow amount of the respective packets of the respective connections
201
a
,
201
b
, and
201
c
. One of the connection monitoring means
204
a
,
204
b
, and
204
c
corresponding to the connection is switched to a control mode. In the other words, the packet flow amount is controlled only on a congested connection.
A congestion control technique for performing the flow control of traffic called polishing at the entrance of a network of the above-mentioned congestion control system is disclosed in, for example, Japanese Patent Publication Laid-Open (Kokai) No. Heisei 9-149046, “Packet Flow Amount Monitoring/Controlling Method”.
Further, a technique for performing the dynamic control of traffic within ATM switches dispersedly arranged in a network, instead of the flow control of the traffic at the entrance of a network, is disclosed in, for example, Japanese Patent Publication Laid-Open (Kokai) No. Heisei 8-204721, “Congestion Control Method in Asynchronous Transfer Mode Network”.
The conventional congestion control system is only to relieve congestion by monitoring the transfer flow only at the entrance of a network or within an ATM switch. It is not to make good use of resources of the whole network.
Namely, the technique disclosed in Japanese Patent Publication Laid-Open (Kokai) No. Heisei 9-149046, in which the flow control of traffic is performed at the entrance of a network, has to define every expected traffic as a connection group. Therefore, it is difficult to apply this technique to the traffic having the difficulty of defining the quality and having the dynamically changing volume like connectionless traffic. Even if applying this technique to such traffic, complicated processing will be required in order to assign the network resources efficiently.
The technique disclosed in Japanese Patent Publication Laid-Open (Kokai) No. Heisei 8-204721, in which the dynamic control of traffic is performed only within an ATM switch, requires complicated processing for the optimal control of the add-on device and ATM switches dispersedly arranged according to the transfer situation therebetween, in order to monitor traffic on the whole network and control congestion. It is difficult to apply the technique to the whole network.
The ATM forum recommends ABR (Available Bit Rate) regulation in an ATM network as a technique for dynamically assigning the resources of a network on a predetermined fixed channel to the respective traffic. This ABR regulation, however, requires the traffic control between terminals by the flow unit, thereby needing building a complicated network system and an edge device. Further, since the regulation includes neither a method of dynamically changing a channel nor condition of changing a channel, it cannot make use of the network resources dynamically and efficiently, or even if making use of the resources, complicated and sophisticated processing will be required.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a congestion control system capable of detecting congestion occurring in an ATM network, with respect to connectionless traffic, in a simple structure, so to relieve the congestion, thereby making use of the network resources efficiently.
A second object of the present invention is to provide a congestion control system capable of detecting congestion caused by outside blocking occurring on the boundaries of a user network and an ATM network for transferring connectionless data, with an easy operation, and further capable of autonomously relieving congestion caused by the outside blocking, in a simple structure.
A third object of the present invention is to provide a congestion control system capable of detecting congestion caused by inside blocking as second congestion when no congestion caused by the outside blocking is detected as the first congestion and autonomously relieving the co
NEC Corporation
Patel Ajit
Tsegaye Saba
Whitham Curtis & Christofferson, P.C.
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