Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Patent
1997-05-09
1999-04-27
Patel, Ajit
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
370410, H04J 116
Patent
active
058986723
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates generally to traffic control in telecommunication networks. More specifically, the invention relates to a method and an arrangement for preventing an overload in a telecommunication network.
The invention is intended especially for so-called Intelligent Networks (IN) that are being developed at present, but the same principle can be applied in any network wherein two or more nodes are interconnected in such a way that at least one of the nodes can be loaded by one or several other nodes.
BACKGROUND OF THE INVENTION
An Intelligent Network usually refers to a network comprising more intelligence (i.e. a better ability to utilize information stored in the network) than the present public (switched) networks. Another characteristic of the Intelligent Network is that the network architecture somehow draws a distinction between, on the one hand, the operations concerning the switching itself and, on the other hand, the stored data and its processing. Such a division makes it possible that, in principle, the organization providing network services can be different from the organization managing the physical network in which the services are provided. Conceptually, an Intelligent Network can be divided into three parts. The first part comprises the nodes switching traffic (performing connections), the second part contains the services provided by the network, and the third part consists of the internodal communication protocol, i.e. the "language" the machines use to communicate with one another. Since all services must be presented as a sequence of messages conforming with the protocol, the protocol defines the "intelligence" of the network.
In order to facilitate the understanding of the present invention, reference is first made to a simple basic situation illustrated in FIG. 1, wherein two machines (or network nodes) 1 and 2 are shown, the machines being interconnected by means of a signalling link 3. Machine 1 comprises a database DB, and machine 2 is a client asking questions from machine 1 by transmitting messages to machine 1 over the link 3. When machine 1 receives a question, it initiates a transaction resulting in an answer after a certain processing period. When the answer is ready, machine 1 transmits it to machine 2 over the link 3. Each answer costs machine 2 a certain sum.
A theoretical omnipotent machine 1 would answer each question immediately so that the correlation between the questions rate (questions per time unit) and the answering rate (answers per time unit) would look like the description in FIG. 2a. However, there is in practice a limit to how fast machine 1 can provide answers. Taking this into account, the response curve of the omnipotent machine 1 becomes like the one shown in FIG. 2b. When the questions rate exceeds a certain threshold Amax corresponding to the highest possible answering rate, the latter remains constant, i.e. some of the questions will not be answered. However, this situation does not correspond to a real situation, either. In practice, the situation is such that as the questions rate exceeds a certain threshold value for a long period of time, machine 1 becomes overloaded so that the increasing questions rate further reduces the answering rate. This situation is illustrated in FIG. 2c. The decreasing answering rate is due to the fact that the machine starts wasting its resources, for example in such a way that it reserves more and more free memory for storing the questions, so there will be correspondingly less and less memory available for computing the answers. The threshold value of the questions rate at which an overload situation occurs is not constant, but it depends on how much of the capacity of machine 1 is dedicated to answering. For example, the threshold value is lower than usual when the database DB of machine 1 is being updated.
The purpose of any overload prevention method is to make the curve (FIG. 2c) describing a real situation resemble as closely as possible the curve (FIG. 2b) describing an ideal
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Lee Chiho Andrew
Nokia Telecommunications Oy
Patel Ajit
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